Ground state and thermal transitions in Field Induced spin-Supersolid Phase

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可靠性基础

可靠性基本概念

可靠性定义
产品在规定的条件下和规定的时间内完成规定功能的能力。产品
指零件，元器Байду номын сангаас，部件，设备或系统。

规定的条件
工作条件：电压，负载，使用方法，维修方法，输出功率等。环境条件：温度，湿度，压力，振动，冲击，电场，磁场等。储存条件：运输，保管等。

规定的时间
失效分析
失效的分类
MTBF计算及评估

MTBF---Mean Time Between Failure
平均无故障间隔时间, MTBF是衡量一个产品（尤其是电器产品）的可靠性指针, 单位为“小时”。它反映了产品的时间质量，是体现产品在规定时间内保持功能的一种能力。具体来说，是指相邻两次故障之间的平均工作时间，也称为平均故障间隔。它仅适用于可维修产品。 MTTF—Mean Time to Failure,表示不可维修产品的平均寿命,称为失效前的平均工作时间
MTBF计算及评估
阿氏计算公式参考:
资料参考:
思考:我们目前使用的OP-02-205中的计算方式是否合理?

可靠性测试

HALT & HASS & ORT
HASS – Highly Accelerated Stress Screening 高加速应力
筛选 -（用在生产制造量产阶段）

目的是在极短的时间内发现量产成品是否有工艺品质上的不良存在
ORT – On-going Reliability Test 可靠性测试（用于大量生产制造阶段）

通过试验发现产品潜在失效模式 (Failure Mode) 探求失效机理 (Failure Mechanism) 优化研发设计，工艺流程 (Optimize design and process) 监控原材料，工艺流程的改变 (Monitor raw material and process)

循迹算法原理

循迹算法原理The principle of the line-following algorithm is to use sensors to detect the line on the ground and make adjustments to keep the robot on track.循迹算法的原理是利用传感器检测地面上的线路，并做出调整以保持机器人在轨道上。

There are several different types of line-following algorithms, including the proportional-integral-derivative (PID) algorithm, the Bang-bang algorithm, and the state machine algorithm.有几种不同类型的循迹算法，包括比例-积分-微分（PID）算法，Bang-bang算法和状态机算法。

The PID algorithm uses feedback from the sensors to calculate the robot's position relative to the line and adjust the motors accordingly.PID算法利用传感器的反馈来计算机器人相对于线路的位置，并相应调整电机。

The Bang-bang algorithm, also known as on-off control, simply switches the motors on or off depending on the sensor input.Bang-bang算法，也称为开关控制，根据传感器输入简单地打开或关闭电机。

The state machine algorithm uses a predefined set of states and transitions to determine how the robot should behave based on sensor input.状态机算法使用预定义的状态和转换集来确定机器人应根据传感器输入如何行为。

热力学的英语

热力学的英语Thermodynamics is a branch of physical science that deals with the relationships between heat, work, and energy. It is a fundamental concept that is crucial in understanding the behavior of systems and processes in various fields such as physics, chemistry, engineering, and biology. In this article, we will explore the key principles of thermodynamics and their significance in different applications.The first law of thermodynamics, also known as the law of energy conservation, states that energy cannot be created or destroyed in an isolated system. It can only be transformed from one form to another. This principle is essential in understanding the concept of internal energy, which is the sum of the kinetic and potential energies of the particles within a system. The first law of thermodynamics also introduces the concept of heat and work as forms of energy transfer. Heat is the transfer of energy due to a temperature difference, while work is the transfer of energy due to a force acting over a distance.The second law of thermodynamics introduces the concept of entropy, which is a measure of the disorder or randomness of a system. It states that in an isolated system, the entropy will either remain constant or increase over time. This principle has profound implications in various processes, such as heat engines, refrigerators, and chemical reactions. For example, the second law of thermodynamics sets a limit on the efficiency of heat engines, known as the Carnot efficiency, which depends on the temperature difference between the heat source and the heat sink.Thermodynamics also encompasses the concept of thermodynamic equilibrium, which is the state in which a system's properties do not change over time. It is crucial in understanding the behavior of systems in thermal, mechanical, and chemical equilibrium. For instance, in thermal equilibrium, two systems are in thermal contact with each other, and there is no net heat transfer between them. In mechanical equilibrium, the forces acting on a system are balanced, resulting in no net force or acceleration. In chemicalequilibrium, the rates of the forward and reverse reactions are equal, leading to a constant composition of the system.The laws of thermodynamics have wide-ranging applications in various fields. In physics, thermodynamics is essential in understanding the behavior of gases, liquids, and solids, as well as the principles of heat engines and refrigerators. In chemistry, it is crucial in the study of chemical reactions, phase transitions, and the behavior of solutions. In engineering, thermodynamics is fundamental in the design and operation of power plants, engines, refrigeration systems, and HVAC (heating, ventilation, and air conditioning) systems. In biology, it plays a significant role in understanding the energy transformations in living organisms and ecosystems.In conclusion, thermodynamics is a fundamental concept that underpins our understanding of energy, heat, and work. The laws of thermodynamics, including the conservation of energy, the increase of entropy, and the concept of equilibrium, have profound implications in various fields and applications. A solid grasp of thermodynamics is essential for scientists, engineers, and researchers to develop innovative technologies and solutions to address the challenges of the modern world.。

Physics and Astronomy Classification Scheme

01.40.gb 01.40.gf 01.40.Ha
Curricula and evaluation Teaching methods and strategies Theory of testing and techniques
Learning theory and science teaching
07.78.+s
07.81.+a
Computers in experimental physics Data analysis: algorithms and implementation; data management Display and recording equipment Transducers Servo and control equipment; robots Mechanical instruments and equipment Thermal instruments and apparatus Cryogenics, refrigerators, low temperature detectors Vacuum apparatus High-pressure apparatus; shock tubes; diamond anvil cells Electrical and electronic instruments and components Magnetic instruments and components Infrared spectrometers, auxiliary equipment, techniques Optical instruments and equipment Photography, photographic instruments; xerography Mass spectrometers Atomic, molecular, and charged-particle sources and detectors Electron, positron, and ion microscopes; electron diffractometers Electron and ion spectrometers

常见材料表征技术

常见材料表征技术Materials characterization refers to the techniques and methods used to study and analyze the structure, properties, and composition of materials. Understanding the characteristics of materials is essential for various fields such as chemistry, physics, engineering, and materials science.材料表征是指用于研究和分析材料结构、性质和成分的技术和方法。

了解材料的特性对于化学、物理、工程和材料科学等各个领域都是至关重要的。

One common technique for materials characterization is microscopy, which allows researchers to visualize materials on a microscopic scale. This includes techniques such as optical microscopy, electron microscopy, and scanning probe microscopy. Microscopy provides valuable insights into the morphology, crystal structure, and defects of materials.一种常见的材料表征技术是显微镜技术，这使得研究人员能够在微观尺度上观察材料。

这包括光学显微镜、电子显微镜和扫描探针显微镜等技术。

显微镜技术为材料的形貌、晶体结构和缺陷提供了宝贵的见解。

Spectroscopy is another important technique for materials characterization. It involves the interaction of materials with different forms of radiation, such as light or X-rays, to study their chemical composition and electronic structure. Spectroscopic techniques, including infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy, provide valuable information about the molecular and electronic properties of materials.光谱学是材料表征的另一个重要技术。

关于冰块实验的作文英语

关于冰块实验的作文英语Title: The Ice Cube Experiment: Unveiling the Secrets of Science。

Introduction:Science, with its endless mysteries and intriguing phenomena, often beckons us to explore and unravel its secrets. Among the many fascinating experiments that captivate both young minds and seasoned scientists alike is the timeless ice cube experiment. This experiment, seemingly simple yet profoundly insightful, unveils the principles of physics, chemistry, and thermodynamics. In this essay, we delve into the intricacies of the ice cube experiment, exploring its underlying principles, applications, and significance in scientific inquiry.Understanding the Experiment:At its core, the ice cube experiment involves observingthe process of ice melting in various environmental conditions. It serves as a practical demonstration of concepts such as heat transfer, phase transitions, and equilibrium. By subjecting ice cubes to different temperatures, pressures, and mediums, researchers can investigate the factors influencing the rate of melting and the final equilibrium state.Key Concepts:1. Heat Transfer: Heat transfer plays a central role in the ice cube experiment. When an ice cube is exposed to a warmer environment, such as room temperature air or water, heat energy flows from the surroundings to the ice cube. This influx of heat causes the ice cube to absorb thermal energy, leading to a rise in temperature and ultimately melting.2. Phase Transitions: The transition of water from a solid (ice) to a liquid state exemplifies a phase transition. As heat is absorbed by the ice cube, thekinetic energy of its molecules increases, eventuallysurpassing the threshold for maintaining a solid structure. Consequently, the bonds holding the water molecules in a rigid lattice break, resulting in the formation of liquid water.3. Equilibrium: Throughout the melting process, the system strives to reach equilibrium, where the rate of ice melting equals the rate of heat absorption. At equilibrium, the temperature remains constant, and the ice-water mixture coexists in a delicate balance. Understanding the concept of equilibrium is crucial for interpreting experimental results and predicting the behavior of complex systems.Experimental Variations:The versatility of the ice cube experiment allows for a myriad of variations, each offering unique insights into physical phenomena. Some common variations include:1. Temperature Variation: Altering the temperature of the surroundings can significantly impact the rate of ice melting. By placing ice cubes in environments of differenttemperatures, researchers can observe how heat transfer influences the melting process.2. Pressure Variation: Pressure also affects the melting point of ice, albeit to a lesser extent than temperature. High-pressure environments, such as those found deep underwater or in pressurized containers, can lower the melting point of ice, causing it to melt more rapidly.3. Medium Variation: The medium surrounding the ice cube, whether air, water, or another substance, can influence the rate of melting. For instance, ice melts more slowly in cold water than in warm water due to differences in thermal conductivity.Significance and Applications:Beyond its educational value, the ice cube experiment has practical applications in various fields:1. Climate Science: Studying the melting behavior ofice cubes provides insights into the processes driving glacial melting and sea-level rise, crucial considerations in climate change research.2. Engineering: Understanding heat transfer and phase transitions is essential for designing efficient cooling systems, refrigeration units, and thermal insulation materials.3. Food Science: Food preservation techniques oftenrely on controlling temperature and phase transitions to extend the shelf life of perishable goods.Conclusion:In conclusion, the ice cube experiment serves as a gateway to understanding fundamental principles of physics and chemistry. Its simplicity belies the depth of knowledge it offers, making it a timeless educational tool and a cornerstone of scientific inquiry. By unraveling the mysteries hidden within the humble ice cube, we gain valuable insights into the workings of the natural worldand pave the way for technological advancements that benefit society as a whole.。

Parity-even and Parity-odd Mesons in Covariant Light-front Approach

0
–
–
fsu¯ (160)
22 (210) −186
11
–
–
fcu¯ (200)
86 (220) −127
45
130
−36
fcs¯ (230)
71 (230) −121
38
122
−38
fbu¯ (180) 112 (180) −123
68
140
−15
From Table 1 we see that the decay constants of light scalar resonances are sup-
for form factors in B → D, D∗, D∗∗ (D∗∗ denoting generic p-wave charmed mesons) transitions agree with those in the ISGW2 model.4 Relativistic eﬀects are mild in
B → D transition, but they could be more prominent in heavy-to-light transitions,
especially at maximum recoil (q2 = 0). For example, we obtain V0Ba1 ay constants and form factors
Consider the decay constants for mesons with the quark content q1q¯2 in the 2S+1LJ = 1S0, 3P0, 3S1, 3P1, 1P1 conﬁgurations. In the SU(N)-ﬂavor limit (m1 = m2) the decay constants fS(3P0) and f1P1 should vanish.6 In the heavy quark limit (m1 → ∞), it is more convenient to use the LjJ = P23/2, P13/2, P11/2 and P01/2 basis as the heavy quark spin sQ and the total angular momentum of the light

智慧树知到《学术英语写作(本科)》章节测试答案

5、学术英语写作中的一般文本特征包括：
答案：sentence、heading、sub-title、paragraph、title、phrase
第2章单元测试
1、在细化主题时，需要考虑你的写作目的是什么以及预期读者是谁。
答案：对
2、My Most Embarrassing Moment是一个可以写的论文题目。
答案：错
2、The negative effects of GM crops have been shown on animals in many studies. 不属于 common knowledge.
答案：错
3、There have been about 400 cancer deaths among 100,000 Japanese nuclear bomb survivors. 属于common knowledge.
4、A good literature review, especially a self-contained review, is composed of four parts: a introduction, a body ， a discussion and a conclusion.
答案：错
答案：错
3、选题不一定是自己感兴趣的和好奇的。
答案：错
4、1. 在本章中，提到的四个写作技巧是：
答案：Research Log、Work Schedule、Mental Inventory、Brainstorming
5、计划书包含下面哪些内容？
答案：your topic and your thesis、the kinds of sources you plan to consult、the problems you anticipate、any special aspects of your project

激发三重态（Excitedthreestates）

激发三重态（Excited three states）At most temperatures, most molecules are at the lowest vibrational level of the ground state. Molecules absorbed in the ground state absorb energy (electric energy, thermal energy, chemical energy, or light energy, etc.) and are excited to be excited. The excited state is very unstable,It will release energy quickly and re jump back to the ground state. When the molecules return to the ground state, the energy is emitted in the form of emission of electromagnetic radiation (light), known as luminescence". If the molecules of matter absorb light energy, they are stimulatedThe electromagnetic radiation emitted by the transition back to the ground state, known as fluorescence and phosphorescence. The mechanism of fluorescence and phosphorescence is discussed in terms of molecular structure theory.Each molecule has a series of strictly separated energy levels, called electron energy poles, and each electron energy level contains a series of vibrational energy levels and rotational energy levels. The state of motion of electrons in moleculesIn addition to the energy levels, the electrons contain multiple states of electrons. In M=2S+1, S is the sum of the quantum numbers of each electron spin quantum, with a value of 0 or 1. According to the principle of Pauli incompatibility, the same orbital in the moleculeThe two electrons occupied must have opposite spin directions, namely spin pairing. If all electrons in the molecule are spinpaired, then S=0, M=1, the molecule is in a singlet state (or a single line), expressed in symbolic S.The ground states of most organic compounds are in the singlet state. When the ground state molecules absorb energy, if the electron does not change in the direction of spin during the transition, it is still M=1, and the molecules are excited at a single weightIf the electron is accompanied by a change in the spin direction during the transition, then the molecule has two spin unpaired electrons, S=1, M=3, and the molecule is in the excited three state, expressed in symbolic T.Fig. 14.1 is a schematic diagram of electronic states.Fig. 14.1 sketch of excitation of three heavy states in a singlet stateThe unpaired electrons in discrete orbits are more stable than spin pairs (especially the rules), so in the same excited state, the energy levels of the three states are always slightly lower than those of the singlet state.Fig. 14.2 is a diagram of energy levels and transitions, in which S0, S1 and S2 represent the ground states of the molecules, the first and second electron excited singlet states, respectively, and T1 and T2 represent the three and second electron excited states of the molecule respectively. V=0, 1, 2, 3,... Represents the vibrational level of theground state and excited state.Fig. 14.2 energy level diagram of fluorescence and phosphorescence systemThe molecules in the excited state are very unstable, which may be activated by means of radiative transitions and nonradiative transitions (de excitation), releasing excess energy and returning to the ground state.Radiation transitions are mainly related to fluorescence, delayed fluorescence or phosphorescence emission; nonradiative transition is the release of excess energy in the form of heat, including vibrational relaxation, internal transfer, intersystem crossing and external transferCheng. Fig. 14.2 represents the energy transfer process of molecular excitation and deactivation:(1) vibrational relaxation (Vibration, relaxation, abbreviated as VR) - the transition from the lowest vibrational energy level (V=0) of the ground state to the excited singlet state may be possible when the molecules absorb the radiation of light (as shown in lambda 1, lambda 2 in Fig. 14.2)Higher vibrational levels of Sn (as shown in S1 and S2). Then，In the gas phase where the liquid phase or the pressure is high enough, the collision probability between molecules is large, and the molecules may pass excess vibrational energy to the surrounding region in the form of heatEnvironment, and its transition from the high vibrational energy level of the excited state to the lowest vibrational level of the electron energy level, this process is called vibrational relaxation. The vibrational relaxation time is 10 - 12s orders of magnitude.(2) internal transfer (Internal, conversion, abbreviated as IC) - when the low vibrational energy levels in the high electron levels overlap with the high vibrational energy levels in the lower electron levels, electrons frequently occur from the high electron energy levelsThe transition from nonradiative to low electron levels. As shown in Fig. 14. and 2, the low vibrational kinetic energy levels in S2 and T2 overlap with the high vibrational kinetic energy levels in S1 and T1, and electrons can transition from S2 to S1 through the superposition of vibrational levels, or fromT2 transition to T1. This process is called internal transfer. Time transfer for 1011s ~ 1013s magnitude. The rate of vibrational relaxation and internal transfer is much faster than the direct emission of photons by a highly excited state,Therefore, no matter which excited singlet state excited by the radiation energy, the molecules can jump to the lowest vibrational level via vibrational relaxation and internal transfer to the lowest (first) excited singlet state.(3) fluorescence emission (Fluorescence, emission, FE) - afterthe vibrational relaxation and internal transfer of electrons in the excited singlet state, reach the lowest vibrational level (V=0) of the first excited singlet (S1),The vibrational levels of the ground state (S0) transition in the form of radiation. The process is fluorescence emission with a fluorescence wavelength of. The energy loss due to vibrational relaxation and internal transfer, and hence the fluorescence emission energyThe energy is smaller than the molecular absorption, and the wavelength of fluorescence emission is longer than the wavelength of molecular absorption. The average lifetime of the lowest vibrational level in the first excited singlet state is about 10-9 - 10 - 4S, so the fluorescence lifetime is also in the rangeThis order of magnitude.(4) department (Intersystem Crossing, ISC Kuayue) - between leap refers to the non radiative transition process between different multiplets, it relates to the electronic excited spin state change.Such as the transition from the first excited singlet state S1 to the first excited three heavy state T1, so that the two spin pairs of electrons are no longer paired. This transition is prohibited (not in conformity with the spectral selection rule),But if the two energy layers have a large overlap, the minimumvibrational level of S1 in Figure 14.2 overlaps with the higher vibrational levels of T1, and it is possible to achieve this transition by spin orbit coupling.Between leap slower and experience a long time.(5) (Phosphorescence emission, PE luminescence emission) - the electronic excited state by the Department after three leap reach the excited state, after the rapid relaxation of vibrational relaxation and the transition to the first excited state threeThe lowest vibrational energy levels are then converted in the form of radiation back to the vibrational levels of the ground state, which are emitted by phosphorescence. The transition of the phosphorescence emission is still the spin forbidden, so the light speed is very slow.The life of 10-4 ~ 100s phosphor. Therefore, after the external light source is stopped, phosphorescence remains a short time. After the system vibration leap and T1 lost a part of the energy relaxation,So the phosphorescence wavelength is longer than the fluorescence wavelength, that is, the wavelength is longer than the wavelength of the phosphor.It must be pointed out that T1 may also be re excited by thermal excitation back to S1, i.e., T1S1, and then converted back to S0 by radiation from S1, S1S0, which emits fluorescence, which is called delayed fluorescence,Its lifetime is similar to that of phosphorescence, but its wavelength is shorter than phosphorescence.(6) external transfer (External, convertion, EC) - excited state molecules collide with solvent molecules or other solute molecules, and the process of energy transfer is called external transfer.External transfer can weaken or even weaken the intensity of fluorescence or phosphorescence. This phenomenon is called quenching or quenching.。

高中英语新教材译林必修件Integrated Skills Writing

02
Key points of writing skill training
Writing Skills and Strategies
Understanding writing prompts and requirements
Students should learn to analyze writing prompts, identify key information, and understand the requirements of different writing tasks
Applicable objects and usage scenarios
Applicable objects
The Yilin Edition High School English Textbook and its Integrated Skills Writing section are suitable for high school students in China who are learning English as a foreign language
Ways to improve language proficiency
• Vocabulary building: Students should actively expand their vocabulary by reading broadly, learning new words, and practicing their usage in context
• Emphasis on practical language skills: The Yilin Edition High School English Textbook focuses on developing students' practical language skills, including listening, speaking, reading, and writing

O电介质物理程序册[1]

O电介质物理分会负责人：刘俊明、金奎娟、王春雷分会地点：会场待定邀请报告时间20分钟，讨论5分钟；口头报告10分钟，讨论5分钟。

9月16日下午墙报专场主持人：曹光旱、金奎娟、王春雷、刘俊明9月17日上午主持人金奎娟(中科院物理所)时间报告人题目08:30-08:55 李晓光(中国科大) BiFeO3纳米单晶的自旋团簇玻璃态动力学特性及交换偏置效应研究08:55-09:20 戴吉岩(香港理工) Field effect of 2DEG at LaAlO3/SrTiO3 interface and its application as ionic molecule sensor09:20-09:45 赵永刚(清华大学) 典型多铁体系磁电耦合效应的研究09:45-10:00 姚晓燕(东南大学) 圆锥自旋序导致多铁态的失措调制10:00-10:15 休息主持人李晓光(中国科大)时间报告人题目10:15-10:40 段纯刚(华东师大) Electric-field control of magnetic ordering in the tetragonal BiFeO310:40-11:05 陈万平(武汉大学) BiFeO3的电导机理及其可能实现的最高电阻率11:05-11:20 贺树敏(山东大学) BiFeO3单晶薄膜的微观结构和性能研究11:20-11:35 李美亚(武汉大学) 多铁复合同轴纳米管线的制备与性能研究11:35-11:50 曹高龙(物理所) 多铁材料Bi1-x Ca x FeOδ的微结构与物性研究9月17日下午主持人王雨(香港理工)时间报告人题目14:00-14:25 周益春(湘潭大学) 铁电场效应晶体管保持性能的应变调控14:25-14:50 江安全(复旦大学) 极化调制铁电半导体存储器及其测量技术14:50-15:05 谭秋红(湘潭大学) Polar ZnO Thin-Film Nonvolatile Transistors with (Bi,Nd)4Ti3O12 Gate Insulators15:05-15:20 阚益(南京大学) 扫描探针显微镜铁电畴工程技术15:20-15:35 李雷(浙江大学) 高损耗介质材料微波介电性能的评价方法15:35-15:50 葛琛(物理所) 金属/铁电/金属结构反转二极管效应的理论研究15:50-16:05 休息主持人周益春(湘潭大学)时间报告人题目16:05-16:30 王雨(香港理工) 磁电复合材料微观结构对其耦合行为的影响16:30-16:55 万建国(南京大学) 多铁复合薄膜的磁电耦合效应调控16:55-17:05 樊慧庆(西北工大) 铌镁酸铅铁电体的介电弛豫与V-F特性研究17:05-17:20 范润华(山东大学) Ag/Al2O3复合材料的高频介电性能研究17:20-17:35 杨文露(扬州大学) 植入方法制备Bi5Fe1-x Co x Ti3O15陶瓷的磁电性能17:35-17:50 张溢(湘潭大学) 铁电薄膜翻转动力学9月18日上午主持人万建国(南京大学)时间报告人题目08:30-08:55 孙学峰(中国科大) 多铁性单晶材料的低温热传导与磁转变08:55-09:20 杨怀馨(物理所) Fe2OBO3中的纳米极化畴和强磁电耦合效应09:20-09:35 曹坤(中国科大) 对多铁性材料RMn2O5中电磁子的分子-自旋动力学研究09:35-09:50 陈宏波(浙江大学) 螺旋自旋序多铁材料中键弯曲效应的研究09:50-10:05 仲崇贵(南通大学) 应变作用下量子顺电材料EuTiO3的磁电性质10:05-10:20 休息主持人杨怀馨(物理所)时间报告人题目10:20-10:45 于浦(清华大学) Interface control of bulk ferroelectric polarization10:45-11:10 陆成亮(华中科大) Electric field driven phase transition and phase-dependent magnetism in BiFeO311:10-11:35 吕笑梅(南京大学) SrTiO3的制备及改性研究11:35-11:50 胡古今(上海技物所) 极性缺陷复合体Ti3+-VO¨的产生与解离9月18日下午主持人陈万平(武汉大学)时间报告人题目14:00-14:25 郑仁奎(上海硅所)钙钛矿锰氧化物薄膜材料应变和物理性能的原位调控研究14:25-14:50 赵昆(石油大学) Photovoltaic effects in La-doped manganite films14:50-15:05 颜志波(南京大学) High-Performance Programmable Memory Devices Based on Co-doped BaTiO315:05-15:20 秦霓(中山大学) M/Mg x Zn1-x O(MZO)/M薄膜器件的单极型电阻开关性质及阻变机理15:20-15:35 师玉军(南京大学) La1-x Sr x MnO3覆盖层对LaAlO3/SrTiO3界面二维电子气载流子浓度的调控15:35-15:50 休息主持人赵昆(石油大学)时间报告人题目15:50-16:15 吴勇军(浙江大学) Ti部分置换Fe对钇铁石榴石陶瓷的介电性能和磁介电性能的影响16:15-16:40 朱俊(电子科大) Modulation effect on electrical transportation characteristics of AlGaN/GaN by epitaxial LiNbO3 ferroelectric film16:40-16:55 王大威(西安交大) 钙钛矿结构铁电材料的分子动力学模拟16:55-17:10 郭艳艳(南京大学) Suppression of ferroelectricity and quantum fluctuations in Ru-doped TbMnO317:10-17:25 汪春昌(安徽大学) IsCaCu3Ti4O12 a new relaxor?17:25-17:40 莫忠(中山大学) 有机柔性衬底上室温脉冲激光沉积法制备Er掺杂Bi4Ti3O12薄膜及其介电特性研究墙报展讲报告清单：1.The magnetic training effect of PZT/CFO/PZT composited films, Bo Chen, Jianguo Wan,Junming Liu, and Guanghou Wang, 南京大学2.取向Bi5Fe0.5Co0.5Ti3O15薄膜的制备及性能，毛翔宇，杨文露，王伟，陈小兵，扬州大学3.Co掺杂对Bi6Fe2Ti3O18铁电材料性能的影响，陈春燕，杨文露，武鑫华，毛翔宇，陈小兵，扬州大学4.Eu、Co双掺杂对Bi5FeTi3O15铁电和铁磁性能的影响，武鑫华，王伟，毛翔宇，陈小兵，扬州大学5.Tuning the polarization and magnetism in BiCoO3 by strain and oxygen vacancy effect: afirst-principle study, Xing-Yuan Chen, and Yu-Jun Zhao, South China University ofTechnology6.高能球磨法低温制备微波介电陶瓷，程琳，刘鹏，陈晓明，陕西师范大学7.锰氧化物中相分离态介电电泳机制的模拟，储鹏，董帅，刘俊明，南京大学、东南大学8.Hf掺杂浓度对电子型掺杂锰氧化物La1-x Hf x MnO3(0.05≤x≤0.3)的磁学和电学特性的影响，郭尔佳，王乐，吕惠宾，何萌，金奎娟，汪琳，吴真平，高矩，北京凝聚态物理国家实验室、香港大学物理系9.Nonstoichiometry-induced ferroelectricity and ferromagnetism in bulk SrTiO3, Y. Y. Guo,H. M. Liu, and J. –M. Liu, Nanjing University10.不同晶粒尺寸BaTi0.995Mn0.005O3陶瓷的时效效应，郭艳艳，南京大学11.基于压电材料的超声微流筛选芯片的制备与表征，李思晢，邓宇亮，国世上，赵兴中，武汉大学12.NiFe2O4薄膜电致电阻开关性能研究，胡伟，秦霓，伍广亨，包定华，中山大学13.Significant polarization variation near room temperature of Ba0.65Sr0.35TiO3 thin films forpyroelectric energy harvesting, K. Huang, J. B. Wang, X. L. Zhong, B. L. Liu, and Y. C.Zhou, Xiangtan UniversityTO/环氧树脂复合材料的力学及介电性能，黄旭，郑兴华，汤德平，杨小炳，陈凤英，福州大学15.铁电半导体Pb(Fe1/2Nb1/2)1-x Ti x O3单晶的非线性电学性能，贾艳敏，罗豪甦，浙江师范大学、中国科学院上海硅酸盐研究所16.Size dependent domain configuration and electrocaloric properties in BaTiO3 constrainedferroelectric system: A phase field investigation, B. Li, J. B. Wang, Xiangtan University 17.Recent progress in experimental study on the deformation and fracture of ferroelectricceramics/single crystals, Yingwei Li, Faxin Li, Hairong Cai, Peking University, Dalian University of Technology, Institute of Acoustics, Chinese Academy of Sciences18.基于压电材料的超声微流筛选芯片的制备与表征，李思晢，邓宇亮，国世上，赵兴中，武汉大学19.循环电场调制多铁CoFe2O4/Pb(Zr0.53Ti0.47)O3异质薄膜，李子威，万建国，宋凤麒，王广厚，南京大学20.Eu3+/Y3+共掺杂ZrO2薄膜的介电及发光性能，梁立容，周洪，伍广亨，包定华，中山大学21.Mn缺失与Fe掺杂的Ca3CoMnO6的多铁性研究，林林，郭云均，谢云龙，董帅，颜志波，刘俊明，南京大学、江苏教育学院、东南大学22.Great improvement of electricaloric in BST compositional graded films, B. L. Liu, J. B.Wang, Xiangtan University23.xBST-(1-x)(LMT-LNT)陶瓷中的异常介电非线性与介电弛豫行为，刘成，刘鹏，陕西师范大学24.基于地磁扰动的磁性目标静态检测，刘国希，董蜀湘，北京大学25.铁电体中光辅助极化反转的动态研究，朱美玲，刘宏德，梁启锐，孔勇发，许京军，南开大学26.Role of Ti-richness in SrTiO3, H. M. Liu, Y. Y. Guo, and J. –M. Liu, Nanjing University27.Fragile magnetic ground state and metal-insulator transitions in CaCrO3: thefirst-principles calculations, H. M. Liu, C. Zhu, C. Y. Ma, S. Dong, and J. –M. Liu,Nanjing University28.Spin order induced ferroelectricity in DyMnO3: doping effects, N. Zhang, S. Dong, Z. B.Yan, K. F. Wang, and J. –M. Liu, Nanjing University29.镍锌铁氧体 Ni0.37Zn0.63Fe2O4和铁电体PZT多铁复合陶瓷的介电性能和磁性能，刘倩，周剑平，陈晓明，刘鹏，王燕，肖瑞娟，杨若琳，陕西师范大学30.First Principles Study of Improper Ferroelectricity with Cyclocial Order DyMnO3 , ChunYang Ma, Nanjing University31.球磨时间对Al-Sn物相的影响，马海燕，陈晓明，刘鹏，周剑平，陕西师范大学32.Zn掺杂BiFeO3陶瓷的制备及其性能，马志洪，郑兴华，汤德平，陈培津，高琳珊，福州大学33.Si83Ge17/Si压应变衬底上HfO2栅介质薄膜的电学性能，涂雅婷，周广东，张守英，邱晓燕，西南大学34.Si83Ge17/Si衬底上HfAlO x栅介质薄膜的电学性能，张守英，周广东，涂雅婷，邱晓燕，西南大学35.无磁性掺杂HfAlOx薄膜的室温弱铁磁各向异性，周广东，张守英，涂雅婷，邱晓燕，西南大学36.Bi5Fe0.5Co0.5Ti3O15薄膜的磁与铁电性研究，孙慧，吕笑梅，朱劲松，南京大学37.Two nonspiral spin orders induced spiral spin order in the RMnO3: Monte Carlosimulations, Yong Mei Tao, Nanjing University38.R-site substitution induced coexistence of two cycloid-phases in multiferroic RMnO3:Monte Carlo simulations, Yong Mei Tao, Nanjing University39.Ca2TiMnO6低温介电性能研究，王国景，汪春昌，黄守国，雷长梅，孙晓红，李腾，梅既云，安徽大学40.多铁超晶格界面诱导巨磁电耦合效应，王宏伟，何力新，中国科技大学41.The magnetic phase transition in Cu-doped ZnO: From bulk to nanocluster, Qianjin Wang,Qiuhong Tan, Jinbin Wang, Xiangli Zhong, Yichun Zhou, Xiangtan University42.准二维多铁性材料CuFeO2的热输运性质研究，王新明，范诚，赵志颖，张发宝，柯文炮，刘旭光，孙学峰，中国科学技术大学43.Sol-gel方法制备BiFeO3薄膜的漏导特性，王秀章，骆文锦，周双，蒋西西，湖北师范学院44.多铁Er1-x Yb x Fe2O4的荧光光谱研究，武睿，王瑞，杨槐馨，秦元斌，董斌，李建奇，赵继民，中国科学院物理研究所45.微波调谐Ba0.5Sr0.5TiO3-MgO-Mg2TiO4的介电性能研究，赵静媛，吕超，徐业彬，华中科技大学0.7Sr0.3MnO3薄膜电致电阻效应的研究，徐中堂，金奎娟，王灿，吕惠宾，王聪，王乐，杨国桢，中国科学院物理研究所47.Ca(1-x)Ce0.5x Cu3Ti4O12(x=0,0.1,0.25,0.5,1)陶瓷介电性能研究，闫妍，刘鹏, 杨锋莉,王亚娟，陕西师范大学48.CaCu3Ti4O(12-x)Cl x(x=0,0.2,0.4,0.6,1)陶瓷介电性能研究，杨锋莉，吴俊林, 闫妍,刘鹏，陕西师范大学49.EuTiO3薄膜漏电机制研究，赵润，李伟伟，孟庆权，杨军，汤如俊，杨浩，苏州大学50.First principle study of polarization-strain coupling in SrBi2Ta2O9 and Bi4Ti3O12, Q. Yang,Y. C. Zhou, J. X. Cao, Y. Ma, Xiangtan University51.交流电压老化下聚酰亚胺薄膜的红外和介电性质研究，杨阳，尹镝，熊锐，石兢，田付强，王暄，雷清泉，武汉大学、北京交通大学、哈尔滨理工大学52.Cu位掺Fe对CaCu3Ti4O12电学性能的影响，杨芝，张悦，熊锐，石兢，武汉大学53.磁场对PbZr0.52Ti0.48O3/La3/8Ca5/8MnO3多铁复合薄膜中介电和铁电性质的影响，姚一平，刘愉快，董思宁，李晓光，中国科学技术大学54.Dielectric Properties of CaCu3Ti4O12 at High Temperatures, Mei-Ni Zhang, Chun-ChangWang, Ke-Biao Xu, Guo-Jing Wang, Chen-Chen Yin, Anhui University55.Z型铁氧体中的磁介电效应，张鑫，赵永刚，崔永锋，王嘉维，张森，张慧云，朱美红，清华大学56.Retention loss in the ferroelectric (SrBi2Ta2O9) - insulator (HfO2) - silicon structurestudied by piezoresponse force microscopy, Z. H. Zhang, X. L. Zhong, Y. Zhang, J. B.Wang, and Y. C. Zhou, Xiangtan University57.烧结温度对Pb0.7Ti0.3Nb2O6介电陶瓷电学性能的影响，赵小刚，刘鹏，陈晓明，陕西师范大学58.Magnetoelectric Coupling of (Pb0.99Nb0.02)(Zr0.85Sn0.13Ti0.02)O3/Co Heterostructural Film,Mingxiu Zhou, Ziwei Li, Jian-guo Wan, and Guanghou Wang, Nanjing University59.铋掺杂TbMnO3陶瓷磁与介电性能研究，张超，吕笑梅，朱劲松，南京大学、河南科技大学60.外延NiO/Nb(0.7%):SrTiO3异质结的电阻变换效应，朱永丹，李美亚，赵兴中，武汉大学。

Excitons, Biexcitons and Trions

9Excitons,Biexcitons and TrionsIn Chap.8we deﬁned the bandstructure for electrons and holes as the solu-tions to the(N±1)-particle problem and later we saw that the number of electrons in a band can be increased or decreased by donors and acceptors,re-spectively(Sect.8.14).In contrast,the number of electrons remains constant in the case of optical excitations with photon energies in the eV or band gap region.What we can do,however,is to excite an electron from the valence to the conduction band by absorption of a photon.In this process,we bring the system of N electrons from the ground state to an excited state.What we need for the understanding of the optical properties of the electronic system of a semiconductor an insulator or even a metal is therefore a description of the excited states of the N particle problem.The quanta of these excitations are called“excitons”in semiconductors and insulators.We can look at this problem from various points of view.The ground state of the electronic system of a perfect semiconductor is a completelyﬁlled valence band and a completely empty conduction band. We can deﬁne this state as the“zero”energy or“vacuum”state.In addition it has total momentum K=0,angular momentum L=0and spin S=0. From this point E=0,K=0we will start later on to consider the dispersion relation of the excitons in connection with Fig.9.1b.Another point of view is the following.If we start from the above-deﬁned groundstate and excite one electron to the conduction band,we simultaneously create a hole in the valence band(Fig.9.1a).In this sense an optical excitation is a two-particle transition.The same is true for the recombination process.An electron in the conduction band can return radiatively or non-radiatively into the valence band only if there is a free place,i.e.,a hole.Two quasiparticles are annihilated in the recombination process.This concept of electron–hole pair excitation is also used successfully in other disciplines of physics.If one excites,e.g.,an electron in a(larger)atom or a neutron or proton in a nucleus from a deeper lying occupied state into a higher,empty one,a quantitative description concerning the transitions energies is obtained only if one takes into account both the particle in the2429Excitons,Biexcitons and Trionsexcited state and the hole left behind.This is even true if one excites an electron in a metal from a state in the Fermi sea with an energy below the Fermi energy E F to an empty state above.Excitons can be described at various levels of sophistication.We present in the next sections the most simple and intuitive picture using the eﬀective mass approximation.Other approaches are described in[57E1,62N1,63K1, 63P1,77B1,78U1,79E1,79R1,79S1,81F1,81K1,85H1]or[82M1,86U1,93P1, 96Y1,98E1,98R1,04O1]of Chap.1and references therein.In Chap.27we shall also see how excitons are described in semiconductor Bloch equations.The concepts of Wannier and Frenkel excitons were introduced in the second half of the1930s[31F1,37W1].There is some controversy concerning theﬁrst experimental observations.The author does not wish to act as the referee to settle this point.Instead we give some references to early work [50H1,52G1,56G1,58N1,62N1]and to Fig.13.9and leave the decision to the reader.9.1Wannier and Frenkel ExcitonsUsing the eﬀective mass approximations,Fig.9.1a suggests that the Coulomb interaction between electron and hole leads to a hydrogen-like problem with a Coulomb potential term–e2/(4π 0 |r e−r h|).Indeed excitons in semiconductors form,to a good approximation,a hy-drogen or positronium like series of states below the gap.For simple parabolicFig.9.1.A pair excitation in the scheme of valence and conduction band(a)in the exciton picture for a direct(b)and for an indirect gap semiconductor(c)9.1Wannier and Frenkel Excitons243 bands and a direct-gap semiconductor one can separate the relative motion of electron and hole and the motion of the center of mass.This leads to the dispersion relation of excitons in Fig.9.1b.E ex(n B,K)=E g−Ry∗1n2B+2K22M(9.1a)withn B=1,2,3...principal quantum number,Ry∗=13.6eVµm01ε2exciton Rydberg energy,(9.1b)M=m e+m h,K=k e+k h translational mass andwave vector of the exciton.(9.1c) For the moment,we use a capital K for the exciton wave vector to distinguish this two-particle state from the one-particle states.When we are more familiar with the exciton as a new quasi-particle we shall return to k.µ=m e m hm e+m hreduced exciton mass,(9.1d)a ex B=a H Bεm0µexcitonic Bohr radius.(9.1e)The radii of higher states can be considered on various levels of complexity.If one only takes into account the exponential term exp{Zr/na HB }in the radialpart of the wave function of the hydrogen problem appearing as the envelope function in(9.4a)and deﬁnes the(excitonic)Bohr radius by the decrease of this term to1/e,one obtains with Z=1for excitonsa B(n B)=a H Bεm0µn B,(9.2a)i.e.,a linear increase with n B.If,on the other hand,one takes the full radial function into account,i.e., also including the factorρl L2l+1n B+l(ρ)(9.2b)where l is the angular quantum number andρ=2Z r/n B·a H B and L2l+1n0B+l are the Laguerre polynomials and calculates the average distance between electron and proton or hole,respectively,one obtains[55S1,94L1]r(n B) =a B23n2B−l(l+1)(9.2c)i.e.,for the n B S states(i.e.l=0)a quadratic dependence starting with3a B/2 for n B=1.2449Excitons,Biexcitons and TrionsThe series of exciton states in(9.1a)has an eﬀective Rydberg energy Ry∗modiﬁed by the reduced mass of the electron and hole and the dielectric “constant”of the medium in which these particles move;n B is the principal quantum number.The kinetic energy term in(9.1a)involves the translational mass M and the total wave vector K of the exciton.The radius of the exciton equals the Bohr radius of the H atom again modiﬁed byεandµ.Using the material parameters for typical semiconductors oneﬁnds1meV≤Ry∗≤200meV E g(9.3a) and50nm a B≥1nm>a lattice.(9.3b) This means that the excitonic Rydberg energy Ry∗is usually much smaller than the width of the forbidden gap and the Bohr radius is larger than the lattice constant.This second point is crucial.It says that the“orbits”of electron and hole around their common center of mass average over many unit cells and this in turn justiﬁes the eﬀective mass approximation in a self-consistent way.These excitons are called Wannier excitons[37W1].In this limit,excitons can usually also be described in the frame of semicon-ductor Bloch equations,butﬁner details or corrections to this simple model, which we shall treat in Sect.9.2and which are necessary to understand optical spectra,are usually not incorporated in the semiconductor Bloch equations of Chap.27.It should be mentioned that in insulators like NaCl,or in organic crys-tals like anthracene,excitons also exist with electron–hole pair wavefunctions conﬁned to one unit cell.These so-called Frenkel excitons[31F1]cannot be described in the eﬀective mass approximation.As a rule of thumb,one can state that in all semi-conductors the inequalities(9.3a,b)hold,so that we always deal with Wannier excitons.A series of conferences devoted both to excitons in anorganic semicon-ductors and in organic ones as well as in anorganic and organic insulators is EXCON(excitonic process in condensed matter).The proceedings have been published in[94E1]To get an impression of the wavefunction,we form wave packets for elec-trons and holesφe,h(r e,h)in the sense of the Wannier function of(8.10)and obtain schematically for the exciton wavefunction(r e−r h),(9.4a)φ(K,n B,l,m)=Ω−1/2e i K·Rφe(r e)φh(r h)φenvn B,l,mwith the center of mass RR=(m e r e+m h r h)/(m e+m h),(9.4b) whereΩ−1/2is the normalization factor.The plane-wave factor describes the free propagation of a Wannier exciton through the periodic crystal similarly as9.1Wannier and Frenkel Excitons245 for the Bloch waves of Sect.8.1,and the hydrogen-atom-like envelope function φenv describe the relative motion of electron and hole.The quantum numbers l and m,with l<n B and−l≤m≤l have the same meaning as for the hydrogen atom in the limit that the angular momentum is a good quantum number in a solid(see Chap.26).As for the H atom,the exciton states converge for n B→∞to the ioniza-tion continuum,the onset of which coincides with E g.Excitons features are especially strong for regions of the electron and hole dispersions,where the group velocities of electrons and holesυe g andυh g are equal e.g.zero.See e.g.[96Y1]of Chap.1.This means,that in direct gap semiconductors excitons form preferentially around K=0if the direct gap occurs at theΓpoint.In indirect gap semiconductors exciton states form preferentially with the hole around k h=0and the electron in its respective minimum,as shown in Fig.9.1c schematically e.g.for Ge where the conduction band has minima at k e=0and k e=0.Electrons and holes with diﬀerent group velocities still“see”their mutual Coulomb interaction,but the dashed continuation of exciton dispersion from the indirect to the direct gap is an oversimpliﬁcation, among others because the states away from the band extrema are strongly damped and their binding energy varies.See e.g.again[96Y1]of Chap.1.The discrete and continuum states of the excitons will be the resonances or oscillators which we have to incorporate into the dielectric function of Chaps. 4and5.For direct semiconductors with dipole allowed band-to-band transitions, oneﬁnds an oscillator strength for excitons in discrete states with S(l=0) envelope function proportional to the band-to-band dipole transition matrix element squared and to the probability ofﬁnding the electron and hole in the same unit cell.For the derivation of this relation see[57E1].This lattercondition leads to the n−3B dependence of the oscillator strength for three-dimensional systems.f nB∝|H D cv|21n3B.(9.5)These f nBresult in corresponding longitudinal–transverse splitting as shown in connection with(4.26).Equation((9.5))holds for so-called singlet excitons with antiparallel electron and hole spin.Triplet excitons involve a spin ﬂip,in their creation which signiﬁcantly reduces their oscillator strength(spin ﬂip forbidden transitions).Since the singlet and triplet pair or exciton states will play some role in later chapters(see,e.g.,Chaps.13to16)we give some simpliﬁed information on this topic here.The crystal ground state,i.e.,completelyﬁlled valence bands and com-pletely empty conduction bands,has,as already mentioned above,angular momentum L,spin S and total angular momentum J equal to zero.If we excite optically an electron from the valence band to the conduction band,2469Excitons,Biexcitons and Trionse.g.,by an electric dipole transition,the spin of the excited electron does not change because the electricﬁeld of the light does not act on the spin. Consequently,the simultaneously created hole has a spin opposite to the one of the excited electron and the total spin S of the electron–hole pair state is still zero.Consequently,the electron–hole pair,and likewise the ex-citon,is said to be in a spin singlet state.The spin S=1of the photon is accommodated by the spatial part of the band-to-band matrix element in ((9.5))or by the envelope function of the exciton(see(9.4a)and[96Y1]of Chap.1).If the spinﬂips in the transition,e.g.,by interaction with the magnetic component of the lightﬁeld,one ends up with a total spin S=1corresponding to spin triplet(exciton)state.The triplet state is situated energetically below the singlet state and the splitting is due to a part of the electron–hole exchange interaction,essentially the so-called short-range or analytic(for K→0)part of the exchange interaction.There are names other than triplet and singlet used for certain materials like para and ortho exciton(e.g.,for Cu2O)or dark and bright excitons(in quantum dots).The last pair of names reﬂects the fact that triplet excitons have small oscillator strength because they are“spin-ﬂip forbidden.”Since spin and angular momentum are,strictly speaking,no good quantum numbers in a crystal(see Chap.26)it is not obligatory that the triplet exciton is threefold degenerate and the singlet is not degenerate.There are cases where the triplet or para exciton is nondegenerate,as in Cu2O, and the singlet is threefold degenerate,as in many zinc-blende type crystals like CuCl or ZnSe or GaAs.This is possibly the reason that in some older, especially French,literature the names singlet and triplet exciton states are interchanged.The oscillator strength of the continuum states is inﬂuenced by the so-called Sommerfeld enhancement factor.We come back to this point later in (9.3)and in Chaps.13and15,when we discuss the optical properties.In the picture of second quantization,we can deﬁne creation operators for electrons in the conduction band and for holes in the valence bandα+keandβ+kh ,respectively.The combination of both gives creation operators for elec-tron hole pairsα+ke β+kh.The exciton creation operator B+can be constructedvia a sum over electron–hole pair operators(see[81K1]or[93H1]of Chap.1).B+K=k e k h δ[K−(k e+k h)]αke,k hα+keβ+kh;(9.6)the expansion coeﬃcients a ke,k h correspond,in principle,to those also used inan(slightly old-fashioned)expansion into Slater determinantes of the manyparticle problem,which contains either all valence band statesϕkh (r i,h)forthe ground state or always has one line being replaced by a conduction band state[63K1].It can be shown that the B+K,B K,obey Bose commutation relations with a density-dependent correction term which increases with the number9.2Corrections to the Simple Exciton Model247of electrons and holes contained in the volume of one exciton4π(a exB )3/3[77H2,81K1].This has two consequences:in thermodynamic equilibrium for low densities and not too low temperatures,the excitons can be well described by Boltz-mann statistics with a chemical potential ruled by their density and temper-ature similar to(8.43).For higher densities they deviate more and more from ideal bosons until they end up in an electron–hole plasma made up entirely from fermions(see Sect.20.5).This makes the creation of a Bose-condensed state of excitons(or of biexcitons)a very complicated problem.Though the-ory predicts a region in the temperature density plane where an excitonic Bose–Einstein condensed state could occur[77H2],there are currently many hints but no generally accepted,clearcut observation of a spontaneous Bose condensation of excitons.There are some experiments that prove the Bose character of excitons[76L1,83H1,83M1,83P1,84W1,87F1].We come back to this problem in Sect.20.5where we shall discuss also more recent results. 9.2Corrections to the Simple Exciton ModelThe simple model outlined in the preceeding section is,as already mentioned, adequate for non-degenerate,parabolic bands.We keep these assumptions for the moment and inspect aﬁrst group of corrections which are relevant for the parametersεandµentering in(9.1a–e).We already know from Chaps.4–7 thatεis a function ofω,resulting in the question of which value should be used.As long as the binding energy of the exciton E b ex is small compared to the optical phonon energies and,consequently,the excitonic Bohr radius((9.1e)) larger than the polaron radius(8.16)E b ex< ωLO;a B>a Pol⇒ε=εs,(9.7a) we can use for the static valueεs below the phonon resonances and the polaron masses and polaron gap.This situation is fulﬁlled for some semi-conductors for all values of n B, e.g.,for GaAs where Ry∗ 5meV andωLO 36meV.In many other semiconductors including especially the wide gap semicon-ductors(see Fig.9.3)the inequality(9.7a)holds only for the higher states n B≥2,while for the ground state exciton(n B=1)weﬁndE b ex ωLO;a B a Pol−→εs≥ε≥εb.(9.7b)Examples are CdS,ZnO,CuCl or Cu2O.In this situation a value forεbetweenεs andεb seems appropriate,because the polarization of the lattice can only partly follow the motion of electron and hole.A useful approach is the so-called Haken potential[55H1]which interpolates betweenεs andεb depending on the distance between electron2489Excitons,Biexcitons and Trionsand hole,where r eh,r p e and r h p are the distances between electron and hole, and the polaran radii of electron and hole,respectively:1ε(r e,h)=1εb−1εb−1εs1−exp(−r eh/r p e)+exp(−r eh/r ph)2.(9.8)The next correction concerns the eﬀective masses.The polarization cloudsof the polarons(Sect.8.6)have diﬀerent signs for electron and hole.If bothparticles are bound together in an exciton state fulﬁlling(9.7b)the polaronrenormalization is partly quenched,with the consequence that values for theeﬀective masses will lie somewhere between the polaron values and the onesfor a rigid lattice.The gap“seen”by the exciton in the1S state will likewisebe situated between the two above extrema.Fortunately,the above eﬀectstend to partly compensate each other.A transition from the polaron gap tothe larger rigid lattice gap shifts the exciton energy to larger photon energies.A transition fromεs toεb and a increase of the eﬀective masses increasesthe binding energy and shift the1S exciton to lower photon energies.Asa consequence oneﬁnds,even for many semiconductors for which inequality(9.7b)holds,that the1S excitonﬁts together with the higher exciton statesreasonably well into the hydrogen-like series of(9.1).We shall use this ap-proach in the future if not stated otherwise.In other cases like Cu2O or CuCl,the higher states with n B≥2follow a hydrogen-like n−2B series converging to the polaron gap,but the1S exciton shows,with respect to the polarongap,a binding energy E b ex,which diﬀers from and is generally larger thanthe excitonic Rydberg energy deduced from the higher states.We call theexperimentally observed energetic distance between the1S exction and thepolaron gap the exciton binding energy E b ex,in contrast to Ry∗in(9.1).Thisdiscrepancy introduces some ambiguity when comparing theoretical resultswith experimental data,since in theory one often normalizes energies withthe excitonic Rydberg energy Ry∗,but the1S exciton has a diﬀerent valuefor E b ex.There is a general trend of the material parameters m eﬀandεwith E gwhich results in an increase of the exciton binding energy with increasing E gas shown in Fig.9.3.This is an analogous consequence of increasing the band width or in otherwords decreasing eﬀective mass with decreasing width of the gap as described,e.g.,in the band structure model of Sect.8.5.The next complication comes from the band structure.If the bands aredegenerate,as is theΓ8valence band in T d symmetry,it is no longer possibleto separate the relative and the center of mass motion–they are coupledtogether.Similar eﬀects stem from k-linear terms and other sources.We getlight-and heavy-hole exciton branches and splittings,e.g.,between the2Sand2P exciton states partly induced by the envelope function.An examplefor Cu2O will be given in Sect.13.2.Furthermore it should be mentioned,without going into details,that thesplitting between singlet and triplet excitons∆st and the splitting of the9.2Corrections to the Simple Exciton Model249 singlet state into a transverse and a longitudinal one∆LT,are both due to exchange interaction between electron and hole caused by their Coulomb in-teraction[73D1,88F1,03G1]if we consider the N-electron problem in the form of Slater’s determinant where the ground state consists only of valence-band states and the excited state of a sum of determinants in each of which one valence-band state is replaced by a conduction-band state.This aspect is treated in detail in[73D1]or in[93H1,93P1]of Chap.1.Usually the following relation holds for Wannier excitons∆st ∆LT with0.1meV ∆LT 15meV.(9.9)For the AΓ5-excitons in CdS or ZnO oneﬁnds,e.g.,∆CdSLT =1.8meV,∆CdSst =0.2meV and∆ZnOLT=1.2meV,∆ZnOst=0.17meV.Since theshort range interaction increases with decreasing exciton radius as a−3B thesituation begins to change for1S excitons with a value of a exB exceeding onlyslightly the lattice constant,and leading thus also to the limit of the conceptWannier excitons.Oneﬁnds,e.g.,for CuCl or Cu2O,∆CuCLLT =5.5meV,∆CuClst =2.5meV,∆Cu2OLT≈50µeV,∆Cu2Ost=12meV(see[85H1]).Theextremely low value of∆LT in Cu2O comes from the fact,that the band-to-band transition is parity forbidden and the1S singlet or ortho exciton is only allowed in quadrupole approximation(see Sect.13.2).The singlet-triplet splitting is even enhanced by the compression of the excitonic wave function in quantum wells and especially in quantum dots(see, e.g.,[98F1,03G1]).We come back to this aspect in Sect.9.3and Chap.15.Fig.9.2.The splitting of the1S exciton with the notation of the various contri-butions to exchange splitting for bulk samples(a)and in a quantum dot(b).The abreviations have the following meanings:S=singlet,T=triplet,∆lr=long range or nanoanalytic(for k→0)part of the exchange interaction,∆sr=short range or analytic part of the exchange interaction[03G1]2509Excitons,Biexcitons and TrionsFig.9.3.The exciton bind-ing energy E b ex as a functionof the band-gap for various di-rect gap semiconductors([82L1,93H1,93P1]of Chap.1) It should be mentioned that the excitation of an optically(dipol-)allowedexciton is accompanied by a polarization as detailed in Chaps.5and27onpolaritons and on(semiconductor)Bloch equations,respectively.The concept of exciton-phonon boundstates has been introduced in[68T1,72K1,02B1].Finally we mention that excitons can also be formed with holes in deepervalence bands.These so-called“core-excitons”are usually situated in the VUVor X-ray region of the spectrum and have a rather short lifetime.An exampleand further references are given in Sect.13.1.7and[87C1,88K1].9.3The Inﬂuence of DimensionalityIf we consider the exciton again as an eﬀective mass particle with parabolicdispersion relations,as given by(9.1),we expect aﬁrst inﬂuence of the di-mensionality on the density of states analogous to the situation shown in Fig.8.20for every exciton branch n B=1,2,3...Another eﬀect of the dimensionality manifests itself in the binding energy,the Rydberg series and the oscillator strength.We consider an exciton,forwhich the motion of electron and hole is restricted to a two-dimensional plane,but the interaction is still a3d one,i.e.,proportional to e2/|r e−r h|and ﬁnd(9.10a),(9.10b)in comparison to the3d case of(9.1)(see e.g.[93H1]ofChap.1):3d:E(K,n B)=E g−Ry∗1n2B+2(K2x+K2y+K2z)2M(9.10a)and for the oscillator strength f for the principal quantum number n B in the limit of(9.2a):f(n B)∝n−3B;a B∝a H B n B;n B=1,2,3....(9.10b)9.3The Inﬂuence of Dimensionality2512d:E(K,n B)=E g+E Q−Ry∗1(n B−12)2+2(K2x+K2y)2M(9.10c)with E Q quantization energyf(n B)∝n B−12−3;a B∝a H Bn B−12,n B=1,2,3....(9.10d)Essentially n B has to be replaced by n B−1/2when going from3d to 2d systems and the quantization energies E Q of electrons and holes must be considered.Actually E Q diverges for conﬁnement in a mathematically2d plane,see Sect.8.10.The excitonic Rydberg Ry∗is the same in both cases with the consequence that the binding energy of the1S exciton is Ry∗in three,and 4Ry∗in two dimensions.The oscillator strength increases and the excitonic Bohr radius decreases when going from three-to two-dimensional systems.The usual realization of quasi-2d excitons is via(M)QW of type I.In this case the motion in the z-direction is quantized,but the width of the quantum well l z is non-zero.In Fig.9.4we show the exciton binding energy for GaAs as a function of l z for inﬁnitely high barriers,where the curve reaches4Ry∗for l z=0and for ﬁnite barrier height,where the binding energy converges to the value of the barrier material for l z=0passing through a maximum of about2to3times Ry∗depending on the material parameters.It is possible to describe the binding energy of the exciton in the quasi two-dimensional case of a QW in terms of an“eﬀective”dimensionality d eﬀthat ranges between three and two and interpolates thus between the limiting cases of(9.10a)and(9.10c)by[91H1,92M1].E b ex(1S)=Ry∗1+d eff−322(9.10e)with d eﬀ=3−exp−L W2aβ(9.10f)where aβis the three-dimensional excitonic Bohr radius and L W the width of the quantum well increased by the penetration depth of electron and hole into the barrier.The increase of the oscillator strength of the1S exciton comes from the fact that the quantization in the z-direction increases both the overlap between electron and hole and their attraction,which results in turn in a reduction of the two-dimensional Bohr radius.The Sommerfeld factor F,which describes the enhancement of the os-cillator strength of the continuum states and which arises from the residual electron–hole correlation,depends also on the dimensionality[66S1,91O1]. It reads3d:F3d=πW1/2eπW1/2sinh(πW1/2)with W=(E−E g)Ry∗−1;(9.11a)2529Excitons,Biexcitons and TrionsFig.9.4.The calculated bind-ing energy of n z=1hh excitonsin AlGaAs/GaAs quantum wellsas a function of the well thick-ness l z([81M1,84G1,88K2])2d:F2d=eπW1/2cosh(πW1/2)with W=(E−E g+E Q)Ry∗−1.(9.11b)In the three-dimensional case it has a square-root singularity at E g and decreases gradually to unity for E>E g.In two dimensions it decays only from two to one with increasing energy and in a one-dimensional system it is even below unity above the gap quenching thus the singularity in the(combined) density of states.We shall see the consequences in Chap.13.The corrections which we mentioned in Sect.9.2hold partly also in the quasi-2d case.The2d valence band structure may be even more complex, than the3d one,comparing e.g.Figs.8.17and Fig.8.24.However,it should be noted that the most widely investigated(M)QW are based on AlGaAs and InGaAs,which fulﬁll the inequality(9.6).The most striking feature of excitons in quasi-two-dimensional systems and in systems of even lower dimensionality,however,are the facts,that ex-citon series(n B=1...∞)exist for every combination of electron-and hole subband,though partly with small or vanishing oscillator strength and that the exciton splits into light-and heavy-hole excitons which results from the corresponding splitting of the valence-band states(Figs.8.23and8.24).To describe the exciton states we thus need more quantum numbers.Apart from the principal quantum number n B in(9.1)or(9.10a),we must state which of the quantized conduction-and valence-band states are involved.The sim-9.3The Inﬂuence of Dimensionality253 plest optical interband selection rule is∆n z=0,so that we shall see in optical spectra mainly excitons which obey this rule.Finally we must specify whether we are speaking of the light-or the heavy-hole plete information might thus be the n h z=2hh,n e z=2,n B=1exciton ually one uses the abbreviation n z=2hh exciton involving the above selection rule and the fact that excitons in MQW with n B>1are usually diﬃcult to resolve due to broadening eﬀects.For examples see Sect.15.1.As already discussed with one particle states in Sect.8.10,minibands also form for excitons in superlattices.In type II structures,the Coulomb interaction is decreased due to the spa-tial separation of electrons and holes in the two materials with wave function overlap reduced to the interface region.Excitons in such structures are also said to be indirect in real space.In strictly one-and zero-dimensional cases the binding energy for the ex-citon diverges.So it is not possible to give general formulas like(9.10c)for these situations.One is always limited to numerical calculations which have to explicitly include theﬁnite dimensions of the quantum wire or quantum dot.The various possibilities to produce quantum wells,superlattices,quan-tum wires and dots have been discussed already in Sects.8.11to8.13.In the following,we give some information relevant for approximately spherical quan-tum dots,as they occur frequently for semiconductor nanocrystals in glass or organic matrices.For details see e.g.[93B1,97W1,98G1,98J1]of Chap.1.Three regimes of quantization are usually distinguished in quantum dots in which the crystallite radius R is compared with the Bohr radius of the excitons or related quantities:weak conﬁnement:R a B,E Q<Ry∗;(9.12a) medium or intermediate conﬁnement:a e B≥R≥a h B;E Q≈Ry∗,(9.12b)with a e,hB =a H Bεm0m e,hstrong conﬁnement:R≤a h B;E Q>Ry∗.(9.12c) In theﬁrst case(9.12a)the quantum dot(QD)is larger than the exciton.Asa consequence the center-of-mass motion of the exciton,which is described in(9.1a)and(9.4a)by the term e i K·R,is quantized while the relative motionof electron and hole given by the envelope functionφnB,l,m (r e−r h)is hardlyaﬀected.This situation is found,e.g.,for the Cu halides where a B is small,or for CdSe QD with R≥10nm.In the second case(9.12b)R has a value be-tween the radii of the electron orbit and the hole orbit around their common center of mass.As a consequence,the electron state is quantized and the hole moves in the potential formed by the dot and the space charge of the quan-tized electron.This case is the most demanding from the theoretical point of view since Coulomb eﬀects and quantization energies are of the same order of magnitude.However,it is often realized for QD of II–VI semiconductors.The regime given by(9.12c)becomes easier again.The Coulomb energy increases。

美国国家自然科学基金

AwardTitle Collaborative Research: Investigation of Odor-triggered Neuronal Dynamics and Experience-induced Ol GOALI/Collaborative Research: Deciphering the Mechanisms of Wear to Enable High Performance Tip-Bas EAGER: Multifunctional devices based on coupled phase transitions in antiferromagnetic semiconducto Ultra-precise Coordinate Metrology of Three-dimensional Objects at Micrometer and Nanometer Scales GOALI/Collaborative Research: Deciphering the Mechanisms of Wear to Enable High Performance Tip-Bas GOALI/Collaborative Research: Deciphering the Mechanisms of Wear to Enable High Performance Tip-Bas GOALI/Collaborative Research: Deciphering the Mechanisms of Wear to Enable High Performance Tip-Bas GOALI/Collaborative Research: Deciphering the Mechanisms of Wear to Enable High Performance Tip-Bas

东华大学材料学专业英语翻译高分子方向

Graft copolymerization is an efficient method to modify polymers .Various vinyl monomers have been investigated to graft onto starch ,and the starch graft copolymers have been used as flocculating agents , superabsorbents,ion exchanges and matrix or filler of thermo plastics. In this paper,mo dified starch paste by grafting with butylacrylate(BA) is firstly investigated as rubber-reinforcing filler. Three types of natural rubber(NR)/starch composites are prepared . Properties and morphology of these composites and corresponding starch powders are examined .The observed reinforcement effect of modified starch powder on NR/starch composites is interpreted.NO20this exploratory investigation examined the structural mechanism accounting for the enhanced compressive properties of heat-treated Kevlar-29 fibers . A novel theory was set forth that hydrogen-bond disruption and concurrent misorientation of crystallites may account for the observed augmentation of compressive properties. To examine the said theory ,as-received Kevlar-29 fibers were characterized by themogravimetric analysis and differential scanning calorimetry in an effort to determine if crosslinking and/or hydrogen disruption was responsible for the improved behavior in compression.NO21to prevent the loss of fiber strength , ultrahigh-molecular-weight polyethylene (UHMWPE) fibers were treated with an ultraviolet radiation technique combined with a corana-discharge treatment .the physical and chemical changes in the fiber surface were examined with scanning electron microscopy and Fourier transform infrared/attenuated total reflectance .the gel contents of the fibers were measured by a standard device .the mechanical properties of the treated fibers and the interfacial adhesion properties of UHMWPE-fiber-reinforced vinyl ester resin composites were investigated with tensile testing .NO22bicomponent fiber were wet-spun from soybean protein and poly(vinyl alcohol). the protein core of spun bicomponent fiber was brittle .our effort was then to study the soybean protein solution ,with the aim of trying to understand the cause for fiber brittleness and to determine the optimum solution conditions for fiber spinning . the effectsof alkali ,urea ,and sodium sulfite on the viscosity of the soybean protein solution were examined. the hydrolytic stability of the soybean protein solution was examined at various pH values at two temperatures .NO13a novel natural polymer blend ,namely ,a semi-interpenetrating polymer network (semi-IPN)composed of crosslinked chitosan with glutaraldehyde and silk fibroin was prepared .the FTIR spectra of the semi-IPN manifested that the chitosan and silk fibroin had a strong hydrogen-bond interaction and formed an interpolymer complex . the semi-IPN showed good pH sensitivity and ion sensitivity, and could also act as an "artificial muscle" because its swelling-shrinking behavior exhibited a fine reversibility.a number of papers have been published on the structure of PAN using X-ray diffraction ,infrared spectroscopy ,nuclear resonance ,and molecular simulations .based on the scattering pattern ,PAN is considered either orthorhombic with 3D,or hexagonal with 2D order . it has been proposed that hexagonal packing ,of PAN chains in dry samples becomes orthorhombic due to co-crystallization of PAN with polar solvent molecules .in this study ,we use in still XRD measurements, and draw upon these earlier publication ,to understand the deformation process on microscopic scale in PAN and its nanocompositeNO15new organic-inorganic hybrids based on PS/TiO2 hybrid membranes were prepared by sol-gel and phase inversion process. the membranes were characterized in terms of morphology, structure ,hydrophlicity, UF ,performance and thermal stability .the results showed that macrovoids were nearly suppressed with formation of sponge like membrane structure .the TiO2 particles were uniformly dispersed in membrane . the nanodispersed morganic network formed after sol-gel process and the strong interaction between inorganic network and polymeric chains led to the improvement of porosity and thermal stability.NO16polymers carrying a hydrolyzable ester function and bactericidal quaternary ammonium salts were successfully synthesized in two steps . the first one was the modification of hydroxyl functions of poly(vinyl alcohol) by chloroacetic anhydride . the structure of synthesized polymers was confirmed by infrared ,1H-,and 13C- nuclear magnetic resonance .the kinetic results were consistent with a 1-order reaction ,and the activation energy in the case of total modification was found to be 16.8(J/Mol) . the second step was the quaternization of the pendant chlorine atom with a long alkyl chain or aromatic tertiary amines.NO17blending homopolymers with block copolymers has been proved to be another interesting approach to modify the morphology of the block copolymer self-assembly. by blending homopolymer of identical chemical structure with one block in the copolymer , the dimension of the domains in the final phase separation has been adjusted , by changing either the volume fraction or the molecular weight of the homopolymer .at low volume fraction of the block copolymers , the structure formation is analogous to micelle formation of surfactant molecules in solutions, and the interfacial tension between the copolymer and the homopolymer is a critical factor.NO18differential scanning calorimetry and dynamic mechanical zhermal analysis techniques have been used to characterize different Kevlar/epoxy composites. tetra-functional aliphatic amine and anhydride/diglycidyl epoxy have been used as matrix and different quantities of continuous Kevlar fibers as reinforcement .Kevlar fibers had different effects on curing kinetics and final thermal properties depending on epoxy matrix type . a significant decrease in the glass transition temperature(Tg)was observed as Kevlar content increased when anhydride matrix was used .NO10the electrostatic spinning technique was used to produce ultrafine polyamide-6 fibers. the effects of solution conditions on the morphological appearance and the average diameter of as-spun fibers were investigated by optical scanning and scanning electron ,microscopy techniques . it was shown that the solution properties (i.e. viscosity , surface tension and conductivity) were important factors characterizing the morphology of the fibers obtained .among these three properties ,solution viscosity was found to have the greatest effect . solutions with high enough viscosities were necessary to produce fibers without beads.NO11ternary blend fibers (TBFs) ,based on melt blends of poly(ethylene 2,6-naphthalate) , poly(ethylene terephthalate ), and a thermotropic liquid-crystal polymer (TLCP), were prepared by a process of melt blending and spinning to achieve high performance fibers . the reinforcement effect of the polymer matrix by the TLCP component the fibrillar structure with TLCP fibrils of high aspect ratios and the development of more ordered and perfect crystalline structures by an annealing process resulted in the improvement of the tensile strength and modulus for the TBFs .NO12an amphiphilic AB block copolymer composed of poly(N-isopropylacrylamide) as a hydrophilic segment and poly (10-undecenoic acid) as a hydrophobic segment was synthesized . the lower critical solution temperature (LCST) of the copolymer was 30.8 ..,as determined by the turbidity method . the block copolymer forms micells in an aqueous medium. transmission electron microscopy images showed that these nanoparticles were regularly spherical in shap . the micelle size determined by size analysis was around 160 nm .NO7this work examines the PBT/PET sheath/core conjugated fiber with reference to melt spinning, fiber properties and thermal bonding . regarding the rheological behaviors in the conjugated spinning , PET and PBT show the smallest difference between their melt -viscosity at temperatures of 290 and 260 respectively , which has been thought to represent optimal spinning conditions . the effect of processing parameters on the crystallinity of core material-PET was observed and listed . in order of importance , these factors are the draw ratio, the heat-set temperature , and the drawing temperature.NO8thermoresponsive shape memory fibers were prepared by melt spinning form a polyester polyol-based polyurethane shape memory polymer and were subjected to different postspinning operations to modify their structure . the effect of drawing and heatsetting operations on the shape memory behavior , mechanical properties , and structure of the fibers was studied . in contrast to the as-spun fibers , which were found to show permanent shape , the drawn and heat-set fibers showed significantly higher stresses and complete recovery.NO9the dry-jet-wet spinning process was employed to spin poly(lactic acid) fiber by the phase inversion technique using chloroform and methanol as solvent and nonsolvent ,respectively , for PLA . the as-spun fiber was subjected to two-stage hot drawing to study the effect of various process parameters , such as take-up speed ,drawing temperature , and heat-setting temperature on the fiber structural propertics . the take-up speed speed had a pronounced influence on the maximum draw ratio of the fiber . the optimum drawing temperature was observed to be 90 to get a fiber with the tenacity of 0.6 GPa for the draw ratio of 8 .NO1the purpose of this work is to examine zhe changes in thermal properties and zhe crystallization behavior of polyamide 6(PA6) when filled with multi-walled carbon nanotubes (MWCNT). the composites were produced by melt mixing starting from an industrial available masterbatch containing as produced MWCNT . the focus of this article is a detailed discussion of results obtained by differential scanning calorimetry (DSC) ,X-ray ,diffraction (XRD) dynamic mechanical thermal analysis (DMTA), and water sorption . the influence of CNT on zhe thermal transitions (glass transition temperature ,melting ,and crystallization) of PA6 is investigated .NO2the effects of nucleating agents (NAs) on fracture toughness of injection-molded isotactic poly(propylene)/ethylene-diene terpolymer (PP/EPDM) were studied in this work . compared with PP/EPDM blends without any NA,EP/EPDM/NA blends show very small and homo geneous PP sphernlites . as we expected ,PP/EPDM blends nucleated with B-phase NA(TMB-5) present not only a significant enhancement in toughness but also a promotion of brittle-ductile transition . however ,the addition of A-phase NA(DMDBS) has no apparent affect on the toughness of the blends . the impact-fractured surface morphologies of such samples were analyzed via scanning electronic microscope(SEM).NO3solutions of poly(ethylene-co-vinyl alcohol) or EVOH ,ranging in composition from 56 to 71 wt% vinyl alcohol ,can be readily electrospun at room temperature from solutions in 70% 2-propanol/water . the solutions are prepared at 80 and allowed to cool to room temperature .interestingly, the solutions are not stable at room temperature and eventually the polymer precipitates after several hours . however prior to precipitation , electrospinning is extensive and rapid ,allowing coverage of fibers on various substrates . fiber diameters of ca. 0.2-8.0 um were obtained depending upon the solution concentration .NO4the use of macromonomers is a convenient method for preparing branched polymers . however graft copolymers obtained by conventional radical copolymerization of macromonomers often exhibit poorly controlled molecular weights and high polydispersities as well as large compositional heterogeneities from chain-to-chain . in contrast , the development of "living"/controlled radical polymerization has facilitated the precise synthesis of well-defined polymers with lowpolydispersities in addition to enabling synthetic chemists to prepare polymers with novel and complex architectures .NO5the thermal and electrical conductivities in nanocomposites of single ,walled carbon nanotubes (SWNT) and polyethylene (PE) are investigated in terms of SWNT loading the degree of PE crystallinity , and the PE alignment . isotropic SWNT/PE nanocomposites show a significant increase in thermal conductivity with increasing SWNT loading , having 1.8 and 3.5 W/m K at a SWNT volume fraction of ———0.2 in low-density PE(LDPE) and high-density PE (HDPE), respectively . this increase suggests a reduction of the interfacial thermal resistance . oriented SWNT/HDPE nanocomposites exhibit higher thermal conductivities , which are attributed primarily to the aligned PE matrix .NO6we previously discovered that isotropic monomer solution show birefringence due to its anisotropic structure after gelation in the presence of a small amount of rod-like polyelectrolyte. here ,we focus on what mechanism is responsible for the formation of anisotropic structure during gelation .various optical measurements are perfected to elucidate the structure change during gelation . it is found that the existence of a large-size structure in monomer solution with the rod-like polyelectrolyte is essentially important to induce birefringence during gelation .。

升压和SEPIC控制器LM5022-Q1说明书

ProductFolderSample &BuyTechnicalDocumentsTools &SoftwareSupport &CommunityReferenceDesignLM5022-Q1ZHCSES8–MARCH2016 LM5022-Q1适用于升压和SEPIC的2.2MHz、60V低侧控制器1特性•具有符合AEC-Q1001级标准的下列结果：–器件温度等级1：-40°C至125°C的环境运行温度范围–器件人体放电模式(HBM)静电放电(ESD)分类等级2–器件组件充电模式(CDM)ESD分类等级C5•内部60V启动稳压器•峰值电流为1A的金属氧化物半导体场效应晶体管(MOSFET)栅极驱动器•V IN范围：6V至60V（启动后，最低可以在3V下工作）•占空比限值为90%•可编程欠压锁定(UVLO)与滞后•逐周期电流限制•可通过单个电阻设置振荡器频率•可调节开关频率范围达2.2MHz•外部时钟同步•斜率补偿•可调节软启动•10引脚超薄小外形尺寸(VSSOP)封装2应用•升压转换器•SEPIC转换器3说明LM5022-Q1是一款高压、低侧N沟道MOSFET控制器，非常适合升压稳压器和SEPIC稳压器。

该器件包含实现单端一次侧拓扑所需的全部功能。

输出稳压基于电流模式控制，这不仅简化了环路补偿的设计，同时还能够提供固有输入电压前馈。

LM5022-Q1包含一个启动稳压器，该稳压器在6V至60V的宽输入电压范围内工作。

PWM控制器专为高速性能而设计，振荡器频率范围高达2.2MHz，总传播延迟不到100ns。

其他功能包括误差放大器、精密基准、线路欠压锁定、逐周期电流限制、斜率补偿、软启动、外部同步功能以及热关断。

LM5022-Q1采用10引脚VSSOP封装。

器件信息(1)器件型号封装封装尺寸（标称值）LM5022-Q1VSSOP(10) 3.00mm x3.00mm(1)要了解所有可用封装，请见数据表末尾的可订购产品附录。

三价铁离子在四氯化碳中的颜色

三价铁离子在四氯化碳中的颜色英文回答：The color of trivalent iron ions in carbontetrachloride is pale yellow. When trivalent iron ions are dissolved in carbon tetrachloride, they absorb light in the blue-green region of the electromagnetic spectrum and reflect light in the yellow region. This absorption and reflection of specific wavelengths of light result in the observed pale yellow color.To understand why trivalent iron ions appear pale yellow in carbon tetrachloride, we need to consider the concept of electronic transitions. When light interacts with a substance, it can be absorbed by the electrons in the atoms or ions present. This absorption of light causes the electrons to move to higher energy levels or orbitals. The energy difference between these levels determines the wavelength of light that is absorbed.In the case of trivalent iron ions, the absorption of light occurs in the blue-green region of the spectrum. This means that the energy difference between the ground state and the excited state of the electrons corresponds to the wavelengths of light in the blue-green region. As a result, the trivalent iron ions appear yellow because they reflect or transmit light in the yellow region of the spectrum, while absorbing light in the blue-green region.It is important to note that the color of a substance can be influenced by various factors, such as the concentration of the ions, the solvent used, and the presence of other substances. In the case of trivalent iron ions in carbon tetrachloride, the specific color observed may vary depending on these factors.中文回答：三价铁离子在四氯化碳中的颜色是淡黄色。

氢原子光谱按频率展开的谱线

氢原子光谱按频率展开的谱线英文回答：Hydrogen atom spectrum can be expressed as a series of spectral lines according to their frequencies. These spectral lines are the result of transitions between different energy levels of the hydrogen atom. Each line corresponds to a specific energy difference between two energy levels. The frequencies of these lines can be calculated using the Rydberg formula:1/λ = R_H (1/n_1^2 1/n_2^2)。

where λ is the wavelength of the spectral line, R_H is the Rydberg constant for hydrogen, and n_1 and n_2 are the principal quantum numbers of the initial and final energy levels, respectively.The hydrogen spectrum consists of several series of spectral lines, including the Lyman series, Balmer series,Paschen series, Brackett series, and Pfund series. Each series corresponds to transitions starting or ending at a specific energy level. The Lyman series corresponds to transitions starting from the ground state (n_1 = 1), while the Balmer series corresponds to transitions starting from the first excited state (n_1 = 2).The spectral lines in each series have different frequencies and can be observed in different regions of the electromagnetic spectrum. For example, the Lyman series consists of ultraviolet lines, the Balmer series consists of visible lines, and the Paschen, Brackett, and Pfund series consist of infrared lines.The hydrogen atom spectrum is of great importance in astronomy and spectroscopy. By analyzing the frequencies and intensities of the spectral lines, scientists can determine the composition, temperature, and other properties of celestial objects. It also provides valuable insights into the quantum nature of atoms and the behavior of electrons in different energy levels.中文回答：氢原子光谱可以按照频率展开成一系列谱线。

bohr单位

bohr单位Bohr's units are a system of natural units used in atomic physics, named after the Danish physicist Niels Bohr. These units are based on fundamental constants of nature, such as the speed of light, Planck's constant, and the electron mass. They provide a way to express physical quantities in a way that simplifies calculations and enhances understanding of atomic phenomena.One important Bohr unit is the Bohr radius, denoted by "a_0". It represents the average distance between the electron and the nucleus in a hydrogen atom in its ground state. Its value is approximately 0.52918 angstroms or 5.2918 × 10^(-11) meters. The Bohr radius plays a crucial role in the atomic structure and energy levels of hydrogen-like atoms.Another significant Bohr unit is the Bohr momentum, denoted by "p_0". It is the product of the electron mass and the Bohr velocity, which is the velocity of the electron in a hydrogen atom in its ground state. The Bohr momentum is equal to the reduced Planck constant divided by the Bohr radius. Its value is approximately 5.2918 × 10^(-24) kilogram meters per second.The Bohr energy, denoted by "E_0", is the energy of the electron in a hydrogen atom in its ground state. It is equal to minus the Rydberg constant times the speed of light divided by the Bohr radius. The Bohr energy is approximately -13.6 electron volts or -2.1799 × 10^(-18) joules.The Bohr frequency, denoted by "ν_0", is the frequency of the radiation emitted or absorbed when an electron transitions betweenenergy levels in a hydrogen atom. It is equal to the Bohr energy divided by Planck's constant. Its value is approximately 6.5797 ×10^(15) hertz.The Bohr magneton, denoted by "μ_B", is a unit of magnetic moment for electrons orbiting around a nucleus. It is equal to the electron charge multiplied by the reduced Planck constant divided by twice the electron mass. The Bohr magneton has a value of approximately 9.2740 × 10^(-24) ampere square meters per tesla.In addition to these units, there are several other Bohr units used in atomic physics, such as the Bohr kinetic energy, Bohr angular momentum, and Bohr electric field. These units provide a framework for understanding and calculating atomic phenomena and are widely used in quantum mechanics and atomic theory.It is important to note that while Bohr's units were groundbreaking in their time and provided insight into atomic structure, they are not commonly used in modern scientific research. Instead, the International System of Units (SI) is now the standard system for expressing physical quantities. However, the concepts and principles behind Bohr's units remain fundamental to the study of atomic physics.。

Advanced Materials Characterization

Advanced Materials CharacterizationAdvanced materials characterization is a crucial aspect of material science and engineering, as it provides valuable insights into the structure, properties, and performance of various materials. This field encompasses a wide range of techniques and methods that enable researchers and engineers to analyze and understand the behavior of materials at the atomic, molecular, and macroscopic levels. From determining the composition and microstructure of a material to evaluating its mechanical, thermal, and electrical properties, advanced materials characterization plays a pivotal role in the development of new materials and the improvement of existing ones. One of the key aspects of advanced materials characterization is the use of advanced imaging techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM). These techniques allow researchers to visualize and analyze the surface and internal structure of materials with high resolution, providing detailed information about features such as grain boundaries, dislocations, and defects. This level of insight is invaluable for understanding the mechanical and physical properties of materials, as well as for identifying potential areas for improvement or optimization. In addition to imaging techniques, advanced materials characterization also involves the use of spectroscopic methods such as X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), and Raman spectroscopy. These techniques are used to analyze the chemical composition and bonding characteristics of materials, providing information about elemental composition, chemical states, and molecular structures. By understanding the chemical properties of materials, researchers can gain a deeper understanding of their reactivity, stability, and compatibility with other materials, which is essential for applications in fields such as catalysis, electronics, and biomaterials. Furthermore, advanced materials characterization encompasses a wide range of mechanical testing and analysis techniques, including tensile testing, hardness testing, and fatigue testing. These methods are used to evaluate the mechanical behavior and performance of materials under various loading conditions, providing data on parameters such as strength, ductility, toughness, and fatigue resistance. This information iscrucial for designing materials with specific mechanical properties tailored to their intended applications, whether in structural engineering, aerospace, or biomedical devices. Another important aspect of advanced materialscharacterization is the use of thermal and electrical analysis techniques to evaluate the thermal and electrical properties of materials. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and thermal conductivity measurements are commonly used to assess the thermal stability, phase transitions, and heat transfer characteristics of materials. Similarly, techniques such as electrical conductivity measurements and dielectric spectroscopy provide insights into the electrical conductivity, resistivity, and dielectric properties of materials, which are essential for applications in electronics, energy storage,and insulation materials. Moreover, advanced materials characterization also involves the use of advanced analytical techniques such as X-ray diffraction (XRD), neutron diffraction, and electron paramagnetic resonance (EPR) spectroscopy. These methods are used to analyze the crystal structure, phase composition, and magnetic properties of materials, providing valuable information about their structural stability, magnetic behavior, and potential applications in fields such as magnetic storage, spintronics, and magnetic resonance imaging. In conclusion, advanced materials characterization is a multidisciplinary field that encompassesa wide range of techniques and methods for analyzing and understanding the structure, properties, and performance of materials. From imaging andspectroscopic techniques to mechanical, thermal, and electrical analysis methods, advanced materials characterization plays a crucial role in the development of new materials with tailored properties and improved performance. By leveraging these advanced characterization techniques, researchers and engineers can gain valuable insights that drive innovation and advancement in various industries, ultimately leading to the development of new materials with enhanced functionality and capabilities.。

我最喜欢的英语作文

Writing an essay in English is one of my favorite activities.It allows me to express my thoughts and ideas in a structured and coherent manner.Heres how I approach writing my favorite English essay:1.Choosing a Topic:First,I select a topic that interests me.It could be anything from a personal experience to a social issue or a historical event.2.Research:I conduct thorough research on the topic to gather relevant information and facts.This helps in providing a solid foundation for my essay.3.Outlining:Before I start writing,I create an outline to organize my thoughts.This includes an introduction,body paragraphs,and a conclusion.4.Introduction:In the introduction,I present the topic and provide some background information.I also state my thesis statement,which is the main argument or point I will be making in the essay.5.Body Paragraphs:Each body paragraph focuses on one main idea that supports my thesis.I use evidence,examples,and logical reasoning to develop each point.6.Transitions:I make sure to use smooth transitions between paragraphs to maintain the flow of my essay.7.Conclusion:In the conclusion,I summarize the main points and restate my thesis.I also provide a final thought or a call to action that leaves a lasting impression on the reader.8.Revising and Editing:After writing the first draft,I revise and edit my essay to improve clarity,coherence,and grammar.I also check for consistency in tense and point of view.9.Proofreading:The final step is proofreading to catch any typos,grammatical errors,or inconsistencies that may have been missed during editing.10.Enjoyment:Throughout the process,I enjoy the challenge of articulating my thoughts in English and the satisfaction of producing a wellwritten essay.Writing an essay not only helps in improving my language skills but also enhances my critical thinking and analytical abilities.Its a creative process that allows me to explore different perspectives and deepen my understanding of various subjects.。

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a r X i v :0802.0458v 1 [c o n d -m a t .s t r -e l ] 4 F eb 2008Nj,ke −i q ·(r j −r k ) S z j S zk ,Q =(π,π,π),(2)and the spin stiffness,ρs ,deﬁned as the response of the system to a twist in the boundary conditions.S zz (Q )measures the extent of diagonal (Ising like)long-range order (LRO)at the ordering wave vector Q =(π,π,π),while the stiffness (su-perﬂuid density in particle language [8]),indicates the pres-ence of XY (off-diagonal)LRO (this is not true for D <3).In 3D,the superfulid density is identical to the condensate fraction.In the simulations,the stiffness is obtained from the winding numbers of the world lines along the three axes:ρs = W 2x +W 2y +W 2z /3β[9].Ground state (GS)phases As the ﬁeld,B ,is varied,the GS of (1)goes through a succession of phases,including spin-gapped Ising-ordered (IS)and gapless XY -ordered (XY )states.The IS phase is marked by a diverging value of S zz (Q )∝N in the thermodynamic limit,whereas a ﬁnite ρs characterizes the gapless XY ordered phase.A spin SS phase is identiﬁed by a ﬁnite value of both S zz (Q )/N and ρs [10].Both quantities are always ﬁnite for ﬁnite size sys-tems and estimates for N →∞are obtained from ﬁnite-size scaling.Fig.1shows the quantum phase diagram as a function of magnetic ﬁeld,B ,for D =3.0and ∆=6.0–it is qualita-tively similar to that obtained in 2Ds[6].The m z (B )curve features two prominent plateaus corresponding to different ISphases.For small B ,the GS is a gapped AFM solid (IS1)with no net magnetization.The stiffness,ρs ,vanishes in the thermodynamic limit,while S zz (Q )/N ≈1with the spins primarily in the S z i =±1states in the two sublattices.At a critical ﬁeld,B c 1,there is a second order transition to a state with a ﬁnite fraction of spins in the S z i =0state.These S z =0“particles”Bose-Einstein condense (BEC)to give the2spins on abilayer[13].The melting of the SS phase proceeds via two steps–the super-ﬂuid order disappears at a lower temperatute whereas the solid order persists up to a higher temperature.In2Ds,the contin-uos U(1)symmetry cannot be broken at T>0and the SS has only a quasi long-range off-diagonal order for T<T KT.The vanishing of the spin stiffness occurs via a KT transition.In contrast,true long-range off-diagonal order in the SS persists toﬁnite temperatures in3Ds and the melting of the superﬂuid order belongs to the XY universality class.The solid order disappears at a higher temperature via an Ising-like transition. The results of simulations of thermal transitions associated with the SS phase are shown inﬁg.2.The top panel shows the variation of the solid and superﬂuid order parameters as a function of temperature.At low temperatures,both order parameters areﬁnite.With increasing T,the SS“melts”into a pure solid.The disappearence of SF order is marked by an ρSSzz(Q)/NT/JCvFIG.2:(Color online)Two-step melting of the SS for parameters in Fig.1and B/J=16.5(solid line in Fig.1).The top panel shows the vanishing of the two orders at different temperatures.The disappear-ance of superﬂuidity is accompanied by an unusual increase in the solid order parameter.The lower panel shows the signatures in the speciﬁc heat at the two transitions.enhancement in the solid order.This apparently anomalous behavior reﬂects the fact that in the SS phase,the solid order is partially suppressed by the co-existing SF order.The lon-gitudinal component of the SSF is accessible experimentally by neutron scattering and its non-monotonic behavior at the onset of superﬂuid order can serve as an important signature of the SS phase.The three dimensionality of the model im-plies that the two transitions should be accompanied by spe-ciﬁc heat anomalies at the corresponding temperatures.The XY transition will manifest itself as aλ-anomaly while the Ising-like solid melting will be marked by a cusp.Indeed we ﬁnd clear signatures of the two transitions in the calculated speciﬁc heat(lower panel ofﬁg.2).While both the peaks are rounded byﬁnite-size effects,their positions coincide unam-biguously with the melting of the superﬂuid and Ising orders. Since it is one of the most readily measurable observables, having clear signatures in the speciﬁc heat is of great experi-mental relevance.Next we discuss the relevance of these results forﬁnding a SS phase in real magnets.The magnetic properties of spin compunds with spin-orbit interaction much smaller than the crystalﬁeld splitting can be adequately described by a U(1) invariant model(although this invariance is never perfect)[10]. The transition metal magnetic ions belong to this class.On the other hand,the exchange anisotropy is typically very small in these compunds.The above model with large∆is not di-rectly applicable to this class of real quantum magnets.We。