lecture_notes_cluster_2
下课了,同们在教室里做什么英语作文
下课了,同们在教室里做什么英语作文全文共3篇示例，供读者参考篇1The bell has just rung, signaling the end of another grueling class. As the teacher wraps up their lecture and dismisses us, a palpable sense of relief washes over the classroom. Some of my classmates let out an audible sigh, while others eagerly pack up their belongings, eager to escape the confines of the four walls that have held us captive for the past hour.But for many of us, the true adventure begins once the teacher has left the room. The classroom transforms from a sterile environment of learning into a vibrant hub of social interaction and recreational activities. It's a chance for us to shed the shackles of academic rigor and indulge in the simple joys of adolescence.As I scan the room, I can't help but marvel at the diverse tapestry of behaviors unfolding before my eyes. In one corner, a group of friends has formed a tight circle, engrossed in animated conversation. Their laughter reverberates through the air, echoing the carefree spirit of youth. I can't help but envy theirability to find humor in the most mundane of topics, a skill that seems to elude me more often than not.Across the room, a cluster of students has gathered around a desk, huddled over their smartphones. Their faces are illuminated by the soft glow of their screens, engrossed in the virtual worlds that have become an inextricable part of our lives. Some are engaged in heated gaming battles, their fingers deftly maneuvering virtual characters across pixelated landscapes. Others scroll mindlessly through social media feeds, their eyes glazed over as they consume an endless stream of content.In one corner, a small group of students has formed an impromptu study session. Their heads are bent over textbooks and notebooks, their brows furrowed in concentration. They exchange ideas and clarify concepts, their voices a low murmur amidst the cacophony of activity. It's a testament to their dedication and drive, a reminder that even in these fleeting moments of respite, the pursuit of knowledge remains a driving force for some.Near the window, a solitary figure sits, eyes closed and headphones firmly in place. They seem to have found solace in the realm of music, escaping the chaos of the classroom throughthe melodic compositions that fill their ears. Their foot taps rhythmically, a silent dance that only they can perceive.Amidst this tapestry of activity, I can't help but feel a sense of belonging. This classroom, once a sterile environment for learning, has become a microcosm of our lives, a snapshot of the diverse interests and personalities that make up our generation.As the minutes tick by, the energy in the room begins to shift. Some students start to trickle out, eager to embrace the freedom that lies beyond the classroom walls. Others linger, savoring these precious moments of camaraderie before the next class beckons.For me, these moments are a cherished respite from the rigors of academia. They remind me that life is not merely a series of lectures and assignments, but a rich tapestry woven from the threads of friendship, laughter, and shared experiences.As I gather my belongings and prepare to depart, I can't help but feel a twinge of sadness. These fleeting moments of freedom will soon give way to the next class, and the cycle will begin anew. But in the depths of my heart, I know that these memories will linger, a testament to the enduring bonds that form within the walls of our beloved classroom.篇2The bell rings loudly, signaling the end of another long class period. Mr. Johnson dismisses us with a reminder about the homework assignment due next week. As he gathers his materials and heads out the door, the room erupts into a chorus of voices and commotion. Welcome to the after-class chaos in a typical high school classroom!For many students, the real action begins once the teacher has left the room. It's a chance to let loose, socialize, and engage in activities that were off-limits during the structured lesson. As I look around, I see a diverse array of behaviors unfolding around me.In the front row, a group of diligent overachievers immediately turns to each other, comparing notes and clarifying concepts from the lecture. Ava, the resident brainiac, holds court as she patiently explains the finer points of quadratic equations to her peers. Her meticulous color-coded notebook lies open, serving as a reference for the study group.Just behind them, the class clowns are already up to their usual antics. Ryan is balancing a pencil on his nose, much to the amusement of his gaggle of admirers. Chloe, never one to beoutdone, attempts to one-up him by spinning her pen between her fingers, only to have it slip from her grasp and go clattering across the floor. Their infectious laughter fills the air, momentarily drowning out the other conversations.In the back corner, the athletes congregate, their boisterous voices carrying across the room. They rehash the highlights of last night's game, analyzing each play with the intensity of professional coaches. Occasionally, one of them will mimic a spectacular dunk or tackle, prompting cheers and high-fives from their teammates.The artistic souls of the class have already begun to doodle and sketch in their notebooks, their creativity flowing freely now that the constraints of the lesson have been lifted. Sophie, a talented painter, is working on a vibrant landscape, while her friend Ethan experiments with intricate calligraphy styles.Scattered throughout the room are the tech-savvy students, their eyes glued to their smartphones or laptops. Some are messaging friends, making plans for after school, while others are sneaking in a few rounds of their favorite mobile game before the next class begins.Near the windows, a small group of drama enthusiasts has already launched into an impromptu performance. They act outscenes from their favorite plays or movies, complete with exaggerated gestures and accents. Their improvisational skills are both impressive and entertaining, drawing a captive audience from nearby classmates.As the minutes tick by, the classroom transforms into a microcosm of teenage life, with its diverse interests, social dynamics, and energy levels on full display. Some students take advantage of the lull to catch up on homework or review notes, while others see it as an opportunity to recharge their batteries through socializing and engaging in preferred activities.Amidst the controlled chaos, I find myself drawn into various conversations and activities. One moment, I'm helping a friend proofread an essay; the next, I'm being roped into a heated debate about the latest blockbuster movie release. Theafter-class period is a delightful reprieve from the structured learning environment, allowing us to explore our interests and connect with our peers in a more relaxed setting.Of course, not all classrooms are created equal. Some are more subdued, with students opting to spend the time quietly reading, listening to music, or simply resting their minds after an intense lesson. Others are a whirlwind of activity, with groupsconstantly shifting and merging as new conversations and games emerge.Regardless of the specific dynamics, these after-class moments serve an important function in our lives as students. They provide a much-needed outlet for socializing, creativity, and stress relief. In a world where academic pressures can sometimes feel overwhelming, these pockets of unstructured time allow us to recharge and reconnect with our authentic selves.As the minutes wind down, a collective groan rises from the room as the next period's bell sounds, reminding us that it's time to transition back into student mode. Reluctantly, we gather our belongings and prepare to move on to the next class, carrying with us the memories and energy from the after-class escapades.Looking back on these moments, I realize that they are an integral part of the high school experience. They remind us that education is about more than just academic achievement; it's also about personal growth, social connections, and finding joy in the journey. So, the next time the bell rings and the teacher exits the room, embrace the chaos, the laughter, and the unscripted moments that make the after-class experience so uniquely memorable.篇3What Happens When the Bell RingsThe shrill ringing of the bell cuts through the classroom, signaling the end of another lecture. Mr. Thompson's voice trails off mid-sentence as we all perk up, the sudden jolt of sound stirring us from our varying degrees of attentiveness. That familiar brrring triggers an immediate chain reaction as chairs screech backwards and backpacks are hastily zipped up.But there's always a hesitant pause before the mass exodus, a fleeting moment where we all glance around, scoping out what the rest of the class is doing. Despite the teacher's valiant efforts to dismiss us with a "See you all next time!", more than a few of us linger behind.The first groups to stake their claim are the gamers and the studious ones. You can hear the shuffling of chairs and desks being dragged across the floor as they rearrange the classroom geography to suit their needs. The gamers cluster around the battered smart board, jostling for prime position as they fire up their contraband Switches and phones in preparation for an epic multiplayer showdown.Across the room, the bookworms have formed their own study coalition. They pull nutrition bars and thermoses of tea from their bags, hunkering down with notebooks and textbooks splayed out in front of them. The distinctive scramble of pen hitting paper fills the air as they begin comparing notes and quizzing each other.Meanwhile, the social nomads wander the aisles aimlessly, gravitating towards friends' desks for animated chatter and big gestures. The classroom is a cauldron of laughter and shouting as they catch up on the latest gossip and inside jokes. I swear Jessie's laugh gets more raucous and cackling each week.Front and center are the performers, reveling in their temporary stage. Someone produces a beat-up guitar from under their seat, and before you know it, an impromptu jam session has sprung up. Half-remembered chord progressions and botched lyrics ricochet through the space as theself-appointed frontman serenades their captive audience with angsty teen anthems.Not to be outdone, the content creators stake out their territory, usually nestled in the back corner. Tripods and ring lights are carefully arranged as they prep for filming another oneof their quirky skits or makeup tutorials. Cue the near-deafening giggles and countless re-takes.Over by Mr. Thompson's cluttered desk, the teacher's pets try to make themselves useful by sorting handouts and reorganizing the sprawling bookshelves. I guess they're hoping a little brown-nosing might bump up their participation grade.As the ACs kick in to battle the mounting humidity, the jocks emerge from the hallway like a pack of rambunctious hyenas, fresh from sports practice. They pound each other on the backs, comparing athletic feats and war stories as they collapse into the plastic seats, uniform jerseys sweat-stained and grass-streaked.Not everyone joins the social free-for-all though. The quiet ones slip out to the library or an empty corridor to seize a few tranquil moments away from the chaos. Headphones on, they immerse themselves in music, books, or mobile games, their own own private oases amid the bustle.Then there's those of us who float between groups - the social butterflies dodging rogue paper airplanes and stray backpack straps as we flutter from cluster to cluster, one ear turned towards the latest teen drama, the other monitoring the card game emerging in the corner.At some point, Mr. Thompson will attempt to corral the madness, his pleas for order drowned out by the rising decibel levels. We'll grudgingly heed his warnings, but not before a few more rogue Nerf darts are flung and the last echoes of thatoff-key jam session finally fade away.That's how it goes in the pause between periods. A chaotic kaleidoscope of energy, impatience, and creativity unleashed during that hazy pocket of time when the school day's rigid structure gives way, however briefly, to our own youthful pursuits and whims. Who knows what kind of shenanigans may unfurl before the tone-deaf bell inevitably wails once more, dragging us back to reality.。
吴恩达深度学习第二课第一周编程作业_regularization（正则化）
吴恩达深度学习第⼆课第⼀周编程作业_regularization（正则化）Regularization 正则化声明本⽂作业是在jupyter notebook上⼀步⼀步做的，带有⼀些过程中查找的资料等（出处已标明）并翻译成了中⽂，如有错误，欢迎指正！参考Kulbear 的和和，以及的，以及，欢迎来到本周的第⼆次作业。
深度学习模型有很⼤的灵活性和容量，如果训练数据集不够⼤，过拟合可能会成为⼀个严重的问题。
当然，它在训练集上做得很好，但学习过的⽹络不能推⼴到它从未见过的新例⼦!（也就是训练可以，⼀到实战测试就拉胯。
） 第⼆个作业的⽬的： 2. 正则化模型： 2.1：使⽤⼆范数对⼆分类模型正则化，尝试避免过拟合。
2.2：使⽤随机删除节点的⽅法精简模型，同样是为了尝试避免过拟合。
您将学习:在您的深度学习模型中使⽤正则化。
让我们⾸先导⼊将要使⽤的包。
# import packagesimport numpy as npimport matplotlib.pyplot as pltfrom reg_utils import sigmoid, relu, plot_decision_boundary, initialize_parameters, load_2D_dataset, predict_decfrom reg_utils import compute_cost, predict, forward_propagation, backward_propagation, update_parametersimport sklearnimport sklearn.datasetsimport scipy.io #scipy是构建在numpy的基础之上的，它提供了许多的操作numpy的数组的函数。
scipy.io包提供了多种功能来解决不同格式的⽂件的输⼊和输出。
from testCases import * #from XXX import*是把XXX下的所有名字引⼊当前名称空间。
文印室英文
文印室英文篇一：科室牌中英文对比标识标牌中医院科室牌中英文对比（五）心理询问 Psychology Consulting佝偻病专科 Rachitis Dept.神经、脊柱 Neurology Rachitis神经科Neurology贵宾（特需）门诊 VIP Clinic体检中心风湿专科挂号须知请便后冲水请勿吸烟未经批准不得进入严禁吸烟医患沟通园地在此候诊暂停服务急诊部急救分中心办公室急救中心抢救室急诊诊疗室急诊化验室急诊收费急诊药房输液室抢救监护室急诊仪器室医师办公室观看区医技科室药剂科药剂科办公室药剂科会议室制剂讨论室 Physical Examination Center Rheumatism Notes for Registration Please Flush After Use Please No Smoking No Admittance No Smoking Patient-Doctor Communication Grounds Waiting Aera Service Suspended Office of Branch Emergency Center Emergency Center Emergency Treatment Room Emergency Room Emergency Laboratory Emergency Cashier Emergency Pharmacy Infusion Room First-aid Care Room Emergency Instrument Room Physician’s Office Observation Ward Pharmacy Dept.Pharmacy Office Meeting Room of Pharmacy Preparation Research Room西药调剂室 Prescription Room of Medicine中药调剂室 Prescription Room of TCM一般制剂室 General Preparation Room中药制剂室 Preparation Room for TCM西药库Medicine Store中药库TCM Store一次性物品库 DisposabLe Storage Room无菌室Asepsis Room无菌制剂室 Aseptic Preparation Room口服液灌封间 Filling Enveloping Room for Orally Liquid灌封间Filling Enveloping Room灯检包装间 Packing Room of Light Examination配制间Confecting Room工作人员休息室 Staff’s Rest Room中药制剂产前处理 TCM Preparation Processing片剂调剂室 Dispensary Room for Tablet针剂调剂室 Dispensary Room for Injection输液库Infusion Store小型仪器室 small- scale instrument room大型仪器室 large -scale instrument room 纯水制备室 pure water preparation room无菌操作室 asepsis operation room药品贮存室 physic storeroom玻璃器械室 glass appliance room更衣室 locker room中心化验室 laboratory center room总经理室 general manager room副总经理室 vice general manager room会议室 meeting room接待室 reception room楼层牌 floor厕所 toilet董事长室 president room服务台information desk急诊室 emergency room抢救室 rescue room换药室re-dressing room观看室observation room输液室1 observation room (1)检验中心lab center传染病检验室 epidemiology laboratory room病理检验室pathology laboratory room 细菌室bacteriology room心电图室ECG roomb超室（一）B-ultrasonic room（1）供应室provide room接收室receive room发放处extend locate粗洗间ordinarily washing room精洗间earnest washing room清洁间cleaning room消毒间disinfected room综合门诊 out-patient integrate内科中心mdeicine center外科中心surgery center肝病中心liverish center呼吸内科respiratory medicine神经内科neurology心血管内科cardiovasology消化内科gastroenterology胃镜室gastroscopy lab room内分泌室endocrinology room免疫科immunology儿科pediatrics Dept.普外科general surgery伤骨科orthopedic surgery伤骨科治疗室treatment room for orthopedic肛肠科colorecta dept.肛肠科治疗室treatment room for colorecta皮肤科（一）dermatology(1)中医科traditional chinese medicine肿瘤科medical oncology肝病科(一）liverish dept.(1)门诊部办公室out-patient office医学美容中心medicine for hairdressing center 询问处consult医生办公室doctor’s office手术室operating room妇科中心gynecology center妇科（一）gynecology dept.(1)妇科治疗区treatment area for gynecology冲洗室（一）washing room(1)微波室（一）microwave room(1)激光室(一）laser room(1)方案生育室Spcoialist Clinic检查室examination room泌尿科中心urology center泌尿外科(一）urology surgery眼耳鼻喉科中心ophthalmologyENT center 口腔科(一）stomatology （1）耳鼻喉科（一）ENT dept. 1眼科ophthalmology预备室preparation room内儿科病区pediatrics medicine area外科病区surgery area妇科病区gynecology area院长室 affair AD院办公室director of the hospital医务科clinic AD护理部nursing dept.经营部manage dept.企划部layout dept.总务科general affair dept.文印室printing room财务科financial dept.卫生间toilet男卫生间men toilet女卫生间women toilet饮水间drinking room程控室procedure control room护士站nurse station导医台enquiryct线诊断室 ct scan test roomx线诊断室 x-ray test room餐厅 dining hall警卫室gatehouse泌尿科治疗区treatment area for urologyb超、心电图、生化、消毒b-ultrasonic、ECG、biochemistry lab、disinfected 放射科radiology dept 收费处cashier行政办公室 administratve office院长办公室President’s Office职能科室 function dept.图书阅览室reading room病理室（1）pathology dept.1卫生间toilet药剂主任办pharmacy director’s office药剂财会科pharmacy financial dept.遗传检验室genetic exanine room西药库房medicine store理疗室physiotherapy多功能会议室multi-function meeting room乳腺科口腔科（1）oral medicine 1眼科ophthalmology口腔科（2）oral medicine 2针灸理疗室acupuncture massagephysical therapy 暗室darkroom病理室（2）pathology dept.2病理室（3）pathology dept.3B超室B ultrasonic room耳鼻喉科ENT dept.胃镜gastroscopy lab心电图室ECG lab超声诊断室（1）ultrasonic diagnostic room1超声诊断室（2）ultrasonic diagnostic room2白带检验科特别检验科exceptional lab dept.放免室radiological innunology room细菌室bacteriology room临床检验室 laboratory medicine room血液分析室 clinic chemistry blood篇二：学校功能室门牌英语翻译请把下面的中文翻译成英文：1、美术室 Art Room2、休息室 Lounge3、音乐室 Music Room4、老师办公室Teachers Office5、体育室 Sports Room6、综合活动室 Multi-functional Hall7、文学社 Literary Association8、语文辅导室Chinese Office9、数学辅导室 Mathematics Office10、英语辅导室 English Office11、综合活动室 Multi-functional Hall12、活动室 Activity Room13、名师工作室Distinguished Teacher Workshop14、德育工作室Moral Education Workshop15、档案室Files Room16、会议室 Meeting Room17、校长室Principal’s Office18、副校长室 Vice-principal’s Office19、小会议室 Small Meeting Room20、少先队队部室 Young Pioneers Committee21、德育处Moral Education Office22、教导处Teaching Affair Office23、卫生室 School Clinic24、总务处General Maintenance Office25、后勤部Logistics Department26、文印室Printing Room27、舞蹈室 Dancing Room28、管乐训练室Wind Training Room29、电脑3室Computer Room 330、演播室Studio31、电脑2室Computer Room 232、电脑1室Computer Room 133、仪器室Instrument Room34、科学试验室Science Lab35、阶梯室Stairs Hall36、心理辅导活动室Psychological Consultation Room37、图书馆 Library38、书法室 Calligraphy Room39、书法展厅Exhibition Hall篇三：学校办公室门牌英语翻译1.校长室(Principal’s Office)2.副校长室(Deputy Principal’s Office)3.教务处(Teaching Affairs Department)4.总务处(General Affairs Department)5.同学处(Student Affairs Department) 政教处6.财务处(Financial Department)7.团委(CYL Committee)8.工会(Teachers’Union)9.教学楼(Teaching Building)10.行政楼(Administrative Building)11.试验楼(Laboratory Building)12.食堂(Canteen)13.图书馆(Library)14.学校语文组(Junior High Chinese Teachers Office)15.学校数学组(Junior High Math Teachers Office)16.学校英语组(Junior High English Teachers Office)17.学校科学组(Junior High Science Teachers Office)18.学校___组(Junior High Politics, History and Geography Teachers Office)19.高中语文组(Senior High Chinese Teachers Office)20.高中数学组(Senior High Math Teachers Office)21.高中英语组(Senior High English Teachers Office)22.高中物理组(Senior High Physics Teachers Office)23.高中生化组(Senior High Biology and Chemistry Teachers Office)24.高中政史地组(Senior High Politics, History and Geography Teachers Office)25.信息与技术教研组(IT Teachers Office)26.艺术教研组(Art Teachers Office)27.体育教研室(PE Teachers Office)28.学校老师办公室(Junior A Teachers Office)29.高中老师办公室(Senior A Teachers Office)30.物理试验室(Physics Lab)31.物理试验预备室(Physics Experiment Preparation Room)32.生物试验室(Biology Lab)33.生物试验预备室(Biology Experiment Preparation Room)34.化学试验室(Chemistry Lab )35.化学试验预备室(Chemistry Experiment Preparation Room)36.音乐教室(Music Classroom)37.美术教室(Art Classroom)38.电脑教室/ 微机室 (Computer Cluster)39.阶梯教室(Lecture Hall)40.高A(b)班(Class b Senior A )41.初A(b)班(Class b Junior A)42.阅览室(Reading Room)43.期刊室(Periodical Room)44.外文阅览室(Foreign Book Journal Reading Room)45.广播室(Broadcasting Studio )46.洗手间(Lady’s / Gentlemen’s)47.医务室(Clinic)48.文印室(Copy Center)49.会议室(Meeting Room)50、远程训练室：Distance education room51、老师阅览室：Teachers reading room52、同学阅览室：Students reading room53、心理询问室：Psychological consultation room54、柳编室：Willow room55、平安办公室：Safety Office56、电教器材室：Electronic equipment room57、思品组：Moral teacher’s office58、历史组：History teachers Office59、地理组：Geography teachers Office60、教科室：The teaching research61、器材室：Equipment room62、综治办：Comprehensive management office63、七班级一班： Class 1 Grade 7 (班1 班级 7) 依据班级换数字就行64、贮存室 storeroom65、仪器室 Instrument room66、多媒体教室 Multi-media classroom67、舞蹈室、Dancing room68、学前一班、Pre-School One舞蹈室、Dancing Room葫芦丝教室、 Hulus Classroom古筝教室、Zithers Classroom钢琴教室、 Piano Classroom美术教室、 Art Classroom书法室、 Handwriting Classroom图画室、 Picture Room跆拳道室、Taekwondo room围棋室、Chess Room奇妙英语室 Magic English room小一班、 Pre-kindergarten One中三班、Kindergarten Three大一班、Senior Class One园长办公室、Principal’s Office钢琴室、Piano Classroom美术室、Art Classroom保健室、Health Clinic舞蹈室、Dancing Room资料室、 Reference Room科学发觉室、Scientific discovery room 图书阅览室 Library《文印室英文》由：创业找项目整理转载请保留,感谢!。
δ-Pu态密度的动力学平均场理论研究
δ-Pu态密度的动力学平均场理论研究刘以良;肖培【摘要】利用局域密度近似结合动力学平均场理论研究了δ-Pu的态密度. 借助赫伯德模型下的多体哈密顿量, 并使用赫伯德 I方法进行杂质求解. 计算结果很好的呈现出了强关联电子体系的低赫伯德带以及高赫伯德带, 并可以呈现出费米能级处的准粒子Kondo共振峰.【期刊名称】《西南民族大学学报（自然科学版）》【年(卷),期】2010(036)006【总页数】4页(P1014-1017)【关键词】态密度;赫伯德模型;赫伯德;I近似【作者】刘以良;肖培【作者单位】西南民族大学电气信息工程学院,四川成都,610041;西南民族大学电气信息工程学院,四川成都,610041【正文语种】中文【中图分类】O56钚是一种剧毒的、人造的强放射性锕系元素, 在能源、军事、航天等领域有极为广泛的应用.其在固态下与元素周期表中其他元素相比, 显示出复杂而反常的属性：钚有6种晶体结构, 低温下(273-373 K)以α相的形式存在, α相晶胞中有16个原子, 随着温度的升高, 会经历一系列的相过渡, 最终形成结构相对简单的面心立方δ相(573 –723 K)和体心立方ε相(~773 – 923 K), 温度再高就会融化; 晶体中钚原子的体积与温度的关系反常, 在从α 向δ相的过渡中原子体积扩展明显, 大约增加了25%, 而在δ相内部呈现一热膨胀的负增长, 并且从α相向更高温度的ε相过渡中原子体积大约减少了5%; 反常的电磁行为, 与其他的重费米体系类似, 钚呈现反常的电阻行为, 但是它的6个相都是没有磁性的, 磁化系数非常的小, 并且相对而言与温度无关; 反常的光谱特征, 从钚的光子发射谱可以看到在费米能级处有一个较强且窄的类Kondo峰存在, 这个现象与钚具有较大的线性比热系数一致[1-2].这些奇特的性质主要是由Pu的5f电子引起的, 5f电子同时具有定域和离域的特征.这种情况下, 电子处于强关联状态, 尽管传统的密度泛函理论(DFT)基础上的第一性原理可以成功计算很多实际材料的电子结构, 而对于强关联电子体系,例如存在未满壳层的d电子或者f电子的体系, 电子运动受到的限制明显, 轨道较窄, 电子之间的库仑相互作用较大与其带宽数值相差不大, 甚至超过电子的动能.DFT/LDA得出的结果将不再可靠, 这是因为局域密度近似(LDA)建立在弱关联电子模型基础上, 对于强关联电子体系, 电子空间密度变化剧烈, 电子局域密度是一个常数的假设不再成立, 并且电子之间相互作用明显, 单电子不能再被看成在一个静态的平均场中运动, 因此DFT通常只能处理非定域的弱关联的电子体系.例如DFT会将绝缘体CoO和La2CuO错误的计算成为导体.鉴于强关联电子体系的重要性, 其处理仍是是当今凝聚态物理发展的一个重要方向, 找到一个就像DFT解决弱关联体系一样成功的解决强关联电子体系的第一性原理方法就显的尤为重要.典型的强关联电子体系第一性原理解决方法有LDA+U、LDA++以及Local GW等的方法[3-7], 然而这些方法相对比较粗糙.作为20世纪90年代发展起来的一种非微扰多体技术, 动力学平均场理论DMFT[8-9]及其团簇扩展CDMFT[10-11]可以同时考虑电子的能带特性和类原子特性, 为研究强关联电子体系提供了新的有效途径.尤其是将DFT/LDA与DMFT结合起来,用DFT/LDA 处理模型哈密顿量的若关联部分, 用DMFT处理体系的强关联部分的LDA+DMFT方法正逐渐被越来越多的科研人员认同并发展起来[12-13].LDA+DMFT方法已经被成功的用来解决一些过渡金属氧化物, 磁过渡金属以及Ce和Pu等稀土金属的光谱、传输以及热力学等的性质[14-17].本文首先简要介绍了DMFT方法的本质、物理思想、基本条件以及对应的哈密顿量的形式.然后在653K下,利用赫伯德模型和LDA+DMFT方法计算了δ-Pu的态密度(DOS), 其中使用了赫伯德 I近似解决杂质问题, 最后将计算结果与其他的理论以及实验结果进行了比较.DMFT的本质就是用一个单位量子杂质模型替代原来的晶格模型, 这个单位量子杂质模型镶嵌在一个自洽的有效媒介中, 并且自洽条件满足平移不变性和连贯性效应, 其根本的物理思想就是对于某个确定的晶格位,其动力学可以看成是位上的自由度与一个外部“浴室”的相互作用, 这个“浴室”是由给定晶格位周围其它位所有自由度产生的.具体而言, 就是除了某个特定晶格位外, 其他的晶格位上的库仑相互作用都用自能来代替, 而这个特定位上的电子之间有相互作用并可以在整个晶格中运动, 但是电子在其他的位上传播是通过自能产生的媒介而不是通过电子间的相互作用, DMFT引入的“单位问题”与安德森杂质问题是等价的, 而且安德森杂质问题需要通过自能与格林函数的关系(Dyson方程)自洽求解.杂质模型为量子多体问题的局域动力学提供了直观的图像, 鉴于杂质问题迄今已经历四十几年的发展并得到一系列可用的解法[5][8][12][17-20], 杂质模型问题成为 DMFT方法中非常重要的一环.空间的纬数越大, DMFT方法就越精确, 近似说来, 也就是晶格的配位数越高计算结果就越精确,达到无限纬极限时最精确[8-9][13], 所以DMFT方法迄今难以进行表面电子态的计算.对于具有强关联f电子的体系, DMFT计算是将哈密顿量进行如下的分解[17]:多带周期安德森模型的非相互作用部分描述库仑相互作用的局域贡献, 用一个关联项来补充上面的公式如下：为了避免双重计算, 需要将 LDA 哈密顿量中的库仑关联减去.LDA 哈密顿量中的库仑关联可以近似用库仑相互作用能的平均值给出.新的非相互作用哈密顿量如下:右边第一项可以用LDA方法计算, 右边第二项可以用DMFT方法计算.如上所示, 关联电子的哈密顿量虽然可以精确写出, 但是非常复杂无法精确求解, 甚至高于 10个晶格位时已经不能够得出数值解, 因此需要用到近似的方法, 这里DMFT就是一种强有力的考虑了电子关联的近似方法, 在DMFT中, 库仑关联的效应由局域近似的自能算符来表示, 自能Σ(iωn)和格林函数G(iωn)在虚 Matsubara频率iωn=iπ(2n+1)/ β 下得到.如果要计算光谱性质就需要实轴上的格林函数.为了进行LDA+DMFT计算, 我们用密度泛函理论的局域密度近似结合量子杂质求解模型完成一个完整的LDA+DMFT循环.首先DFT Code 用以产生δ-Pu在k空间哈密顿量矩阵, δ-Pu为面心立方结构, 在653K下的实验晶格参数为8.759 a.u.[21], 使用LDA作为交换关联势, 电子的波函数基矢使用线性响应muffin-tin 轨道(LMTO)和原子球近似(ASA), 鉴于δ-Pu处于顺磁性态, 实际自旋的数目为1, 并且在未考虑S-O耦合的情况下, 在6×6×6四面体网格分割的k空间, 哈密顿量在spdf的LMTO下写成16×16的矩阵.并得到满足7s6p6d5f上的总电子数为14的化学势为8.875 eV.其次, 使用了赫伯德-I近似来解决杂质问题, 赫伯德-I方法相对比较近似, 但是使用的计算时间比较短, 更加趋于反应Pu的原子特性, 因此其得到的结果可以为其他的杂质求解器提供参考, 取库仑相互作用的平均值U＝F0=4.0 eV, 杂质能级为9.025 eV, 温度为653 K(0.0562 eV), 考虑自旋量子数, f 轨道的兼并度取14, 结合解析四面体方法求解格林函数, 并最终使用Pade近似将Matsubara频率下的格林函数和自能转化到实频下.得出δ-Pu的DOS,如图1所示.计算的结果与文献[16]吻合的很好, 并且呈现出强关联电子体系的一个典型的特征,即低赫伯德带以及高赫伯德带的存在, 将费米能级处态密度与实验光电谱进行比较, 如图 2所示.计算结果与实验测得的光电谱[22]有一定的吻合, 可以看到在费米能级处一个较强的准粒子Kondo共振峰的存在.然而由于赫伯德 I方法比较适宜计算顺磁Mott绝缘子的光电谱, 因此计算中并未得到费米能级处的连贯峰.由于DMFT方法的相对不成熟性, 以及其不是完整意义上的ab initio计算方法,需要半经验的参数, 使得各种计算结果以及与实验的吻合度有所差异[2][14-16][22].利用局域密度近似结合动力学平均场理论研究了653K下δ-Pu的态密度, 使用赫伯德模型下的多体哈密顿量,以及使用赫伯德 I近似进行杂质模型求解.计算结果很好的呈现出了强关联电子体系的低赫伯德带以及高赫伯德带, 并可以看到在费米能级处较强的准粒子 Kondo共振峰的存在.然而由于赫伯德 I方法不够精确, 并且更适宜计算顺磁Mott绝缘子的光电谱, 所以要想得到更加符合实验结果的光电谱就需要量子Monte Carlo(QMC)方法、精确对角化方法(ED)等相对精确的杂质解决器, 而且需要进一步考虑 f轨道的电子占有数、经过 DMFT循环后电荷密度改变对哈密顿量的影响、平均库仑相互作用、能级的兼并度、自旋轨道耦合、强关联指数等因素对计算结果的影响.【相关文献】[1] SAVRASOV S Y.Spectral density functionals for electronic structure calculations[J].Phys Rev B, 2004, 69:245101-245105.[2] ZHU J X, MCMAHAN A K, JONES M D, et al.Spectral properties of δ-plutonium: Sensitivity to 5f occupancy[J].Phys Rev B, 2007,76:145118-145123.[3] SAVRASOV S Y, KOTLIAR G.Ground State Theory of δ-Pu[J].Phys Rev L, 2000, 84: 3670-3675.[4] BOUCHET J, SIBERCHICOT B, JOLLET F, et al.Equilibrium properties of δ-Pu: LDA + U calculations (LDA ≡ local density approximation)[J].J Phys: Condens Matter, 2000, 12: 1723-1727.[5] ANISIMOVY V I, ARYASETIAWANZ F, LICHTENSTEIN A I.First-principles calculations ofthe electronic structure and spectra of strongly correlated systems: the LDA +Umethod[J].J Phys Condens Matter, 1997,9: 767-772.[6] LICHTENSTEINA I, KATSNELSON M I.Ab initio calculations of quasiparticle band structure in correlated systems: LDA++approach[J].Phys Rev B, 1998, 57: 6884-6889. [7] ZEIN N E, ANTROPOV V P.Self-Consistent Green Function Approach for Calculation of electronic Structure in Transition MetalS[J].Phys Rev L, 2002, 89: 126402-126407.[8] GEORGES N, KOTLIAR G, KRARTH W, et al.Dynamical mean-field theory of strongly correlated fermion systems and the limit of infinite dimensions[J].Rev Mod Phys, 1996, 68: 13-19.[9] KOTLIAR G, SAVRASOV S Y, HAULE K, et al.Electronic structure calculations with dynamical mean-field theory[J].Rev Mod Phys, 2006, 78: 865-871.[10] MAIER T, JARRELL M, HETTLER M H.Quantum cluster theory[J].Rev Mod Phys, 2005, 77: 1027-1033.[11] TREMBLAY A-M S, KYUNG B, SÉNÉCHAL D.Pseudogap and high-temperature superconductivity from weak to strong coupling.Towards a quantitative theory (Review Article) [J].Low Temperature Physics, 2006, 32: 424-428.[12] HELD K, NEKRASOV I A, KELLER G, et al.The LDA+DMFT Approach to Materials Strong Electronic Correlations, Quantum Simulations of Complex Many-Body Systems: From Theory to Algorithms[J].Lecture Notes, NIC Series, 2002(10): 175-181.[13] HELD K, ANDERSEN O K, FELDBACHERM, YAMASAKI A, et al.Bandstructure meets many-body theory: the LDA + DMFT method[J].J Phys: Condens.Matter, 2008, 20: 064202-064207.[14] SAVRASOV S Y, KOTLIAR G, ABRAHAMS E.Correlated electrons in δ-plutonium withina dynamicalmean-field picture[J].Nature, 2001, 410: 793-797.[15] SHIM J H, HAULE K, KOTLIAR G.Fluctuating valence in a correlated solid and the anomalous properties of δ-plutonium[J].Nature, 2007, 446: 513-519.[16] ZHU J X, JONES M D.Electronic Structure Calculations with Dynamical Mean Field Theory in δ-Pu[M].CONDENSED MATTER,MATERIALS SCIENCE, 2005.[17] NEKRASOV I A, HELD K.Calculation of photoemission spectra of the doped Mott insulator La1-xSrxTiO3 using LDA+DMFT(QMC) [J].Eur Phys J B, 2000, 18: 55-61.[18] ZOLFL M B, PRUSCHKE bining density-functional and dynamical-mean-field theory for L a1ÀxSrxTiO3[J].Phys Rev B,2000, 61: 12810-12815.[19] Haule k.Quantum Monte Carlo impurity solver for cluster dynamical mean-field theory and electronic structure calculations with adjustable cluster base[J].Phys Rev B, 2007, 75: 155113-155117.[20] WERNER P, COMANAC A, MEDICI L D, et al.Continuous-Time Solver for Quantum Impurity Models[J].Phys Rev B, 2006, 97:076405-076409.[21] ARKO A J, JOYCE J J, MORALES L, et al.Electronic structure of α- and δ-Pu from photoelectron spectroscopy[J].Phys Rev B 2000, 62: 1773-1778.。
Lecture 2 (new)
Design of Survey Research
• 1. Choose an appropriate mode of response - Reliable primary modes
*Personal interview *urvey
- Less reliable self-selection modes (not appropriate for making inferences about the population) • TV survey • Internet survey • Printed survey • Product or service questionnaires
Discrete variable
A discrete variable can only take individually separated values that usually occur through the process of counting, and not any value in between two given values For example, number of children in a family could take values such as 0, 1, 2, 3, etc., thus is a discrete variable. Data collected on a discrete variables is called …………. Discrete data are numeric data that have a finite number of possible values. Discrete random variables yield numerical response that arise from a counting process
createnccmodel的参数说明
createnccmodel的参数说明createnccmodel是一个用于创建NCC（Neural Collaborative Filtering）模型的函数，该模型常用于推荐系统中。
下面将对createnccmodel的参数进行详细说明。
1. 参数一：user_num参数名：user_num参数类型：整数参数含义：用户数量说明：该参数表示参与推荐的用户数量，需要根据实际情况设定。
用户数量越多，模型的训练和推荐效果可能会更好，但也会增加计算和存储的成本。
2. 参数二：item_num参数名：item_num参数类型：整数参数含义：物品数量说明：该参数表示参与推荐的物品数量，需要根据实际情况设定。
物品数量越多，模型的训练和推荐效果可能会更好，但也会增加计算和存储的成本。
3. 参数三：latent_dim参数名：latent_dim参数类型：整数参数含义：潜在因子维度说明：该参数表示模型中潜在因子的维度，用于表示用户和物品的特征。
潜在因子维度越大，模型能够更好地捕捉用户和物品的特征，但也会增加模型的复杂度和训练时间。
4. 参数四：layers参数名：layers参数类型：列表参数含义：神经网络层数和每层的隐藏单元数说明：该参数表示神经网络的结构，列表中的元素依次表示每一层的隐藏单元数。
例如，[64,32,16]表示神经网络有3层，第一层隐藏单元数为64，第二层隐藏单元数为32，第三层隐藏单元数为16。
神经网络的结构可以根据实际情况进行调整，以提高模型的表达能力。
5. 参数五：num_classes参数名：num_classes参数类型：整数参数含义：分类数量说明：该参数表示推荐结果的分类数量，用于多分类问题。
例如，如果推荐结果分为10个类别，则num_classes为10。
如果是二分类问题，则num_classes为2。
6. 参数六：dropout_rate参数名：dropout_rate参数类型：浮点数参数含义：丢弃率说明：该参数表示在训练过程中随机丢弃神经元的比例，用于防止过拟合。
Lecture_2
Economics2010a Fall2003Edward L.Glaeser Lecture22.Choice and Utility Functionsa.Choice in Consumer Demand Theory and Walrasian Demandb.Properties of demand from continuity and properties from WARPc.Representing Preferences with a Utility Functiond.Demand as Derived from Utility Maximizatione.Application:Fertilityx i denotes commodities,continuous numbersx x 1,x 2,....x Lvector of discretecommodities p p 1,p 2,....p L vector of prices w wealth available to be spentThe budget constraint p x i 1Lp i x iwMWG Definition2.D.1The Walrasian Budget SetB p,w x L:p x wis the set of all feasible consumption bundles for the consumer faces market prices p and has wealth w.Note:We will be treating all prices and consumption levels as being weakly positive.Prices are treated as exogenous–as they will be in the production case.While neither consumer nor producer chooses prices(generally)prices are the extra parameter in each side’s problem that ensures that demand and supply are equal.Non-linear prices are certainly possible(example2.D.4).The Walrasian Demand Function is the set C B p,w which is defined for all p,w ,or at least for a full dimensional subsetp,w L 1We generally assume that C B p,w has a single element(for convenience)but it doesn’t need to.We writeC B p,w x p,w x1 p,w ,...x L p,wWe will also generally assume that demand is continuous and differentiable. MWG Definition2.E.1:The Walrasian Demand Function ishomogeneous of degree zero ifx p, w x p,w for any p,w and 0.This property follows from the fact that choice is only a function of the budget set and B p,w x L:p x w is the same set asB p, w x L: p x wThis fairly obvious claim is in many ways the underlying intellectual basis for the economic bias that the price level doesn’t matter.Differentiating x p, w x p,w totally with respect to gives us the following equation:i 1L x k p ,w p i p i x k p ,w ww 0 i 1L x k p ,w p i p i x k x k p ,w w w x k i 1L pi k w k 0This tells you that for any commodity,the sum of own and cross price elasticities equals -1times the income elasticity.MWG Definition2.E.2Walras’Law:The Walrasian Demand correspondence x p,w satisfies Walras’law if for every p 0and w 0,we have p x w for all x x p,w .This just says that the consumer spends all of his wealth.Looking ahead,Walras’law will come about as long as consumers are not “satiated”in at least one of the goods.Walras’Law and differentiability give us two convenient equalities.Differentiating p x w with respect to w yields:i 1Lp i x i p ,w w 1or manipulating this slightly yields:i 1L x i p ,w w w x i p i x i w i 1Lw i i0,where i p i x i w ,the budget share of good i .This means that income elasticities (when weighted by budget shares)sum to one.All goods can’t be luxuries,etc.Sometimes this is known as Engel aggregation (income effects are after all drawn with Engel curves).Differentiating p x w with respect to p k yields:i 1Lp i x i p ,wp k x k 0or multiplying the whole expression by p k w : i 1L x i p ,w p k p k x i p i x i w p k x k w i 1Lp k ii k0,where again i p i x i wThis means that cross price elasticities sum to-1times the budget share of the relevant good.Overall,these elasticities have to sum to a negative number.MWG Definition2.F.1The Walrasian Demand function satisfies the weak axiom of revealed preference if the following property holds for any two price-wealth situations p,w and p ,w : If p x p ,w w and x p ,w x p,wthen p x p,w w .In words–if the goods that are chosen with budget set(a)are affordable at budget set (b),and not the same as the goods that are chosen at budget set(b),then the goods that are chosen at budget set(b) are not affordable at budget set(a).Just like in the last lecture,WARP meansthat if bundle(b)is preferred to bundle(a) in one setting,it will be preferred in all other settings.A property that follows from WARP:price changes that are fully income compensated make consumers weakly better off.Take any p,w and let p p p Compensate the consumer with an income change so that the old bundle is exactly affordable at the new prices,i.e.:w w w x p,w pThe consumer’s new consumption level atp ,w satisfies the WARP condition:p x p,w w ,which then implies thatp x p ,w w,and this holds with strict equality whenx p ,w x p,wGiven that the consumer could have chosen the old bundle,the consumer must have weakly preferred the new bundle.MWG Proposition2.F.1:WARP implies the law of compensated demand.If the Walrasian demand function x p,w satisfies Walras’Law and is homogeneous of degree zero,then x p,w satisfies the weak axiom if and only if the following property holds.For any compensated price change from an initial situation p,w to a new price wealth pair p ,w p ,p x p,x ,then p p x p ,w x p,x 0,and this equality holds strictly whenx p ,w x p,x .We are now interested only in the weakaxiom- law of demand part of the proposition.First,note that if x p ,w x p,w we’re done,so consideronly the case where x p ,w x p,w . In that case,Walras’law gives us:p x p ,w w ,and we havedefined w so that w p x p,w Together,this gives us thatp x p ,w x p,w 0But we also know that as p ,w satisfies theWARP condition:p x p,w w andx p ,w x p,wit follows that p x p ,w w.Using p x p,w w(again by Walras’Law),this gives us that:p x p ,w x p,w 0Subtraction then yields:p p x p ,w x p,w 0 Change in prices times change in quantities is negative.Since p x 0for all compensated price changes,this also holds in the limit for very small price changes and dp dx 0.We can use matrix notation and write:dx D p x p ,w dp D w x p ,w dwwhich just means:dxi 1L x 1 p i dp i x 1 w dw ,.., i 1L x L p i dp i x L w ordx D p x p ,w dp D w x p ,w x p ,w dp ordxD p x p ,w D w x p ,w x p ,wT dpThe D p x p ,w D w x p ,w x p ,wTterm is a matrix where the element in row i ,column j of the matrix isx ip k x i w xkx 1 p 1 x 1 w x 1....x 1 p L x 1w x L.............x L p 1 x L w x 1.... x L p L x Lw xLand thendpD p x p ,w D w x p ,w x p ,wT dp 0The term in brackets is the Slutsky matrix.MWG Proposition2.F.2:If a differentiable Walrasian demand function x p,w satisfies Walras’law, homogeneity of degree zero and WARP, then at any p,w the Slutsky matrix is negative semi-definite,i.e.v Sv 0for any v L.MWG Proposition2.F.3:Suppose that the Walrasian demand function x p,w is differentiably homogeneous of degree zero,and satisfies Walras’Law.Then p S p,w 0 and S p,w p 0for any p,wUtility Functions–Finally getting to the basic tool of99%ofeconomics.Back to preferences.We want fourattributes:(1)completeness and(2)transitivityThese were defined in lecture1and we refer to preferences with these attributes as being rational.Definition3.B.2.:The preference relation on X is monotone if x,y X,and y x impliesy x.It is strongly monotone if y x and y x implies y x.In many cases,we won’t naturally have monotonicity,but then a little redefinition of variables does the trick(turn a bad into a good by multiplying by-1).A slight twist(I mentioned this earlier):Definition3.B.3:The preference relation on Xis locally nonsatiated if for every x,y X,and every0,there exists a ysuch that y x and y x.This means that there exists a y vector that is arbitrarily close to x that is strictly preferred to x.One last property:Definition 3.C.1.:The preference relation on X is continuous if it is preserved under limits.That is,for any sequence of pairs x n ,y n n 1 with x n y n for all n ,x lim n x n and y lim n y n we have x y .The famous counterexample islexicographic preferences,where more of good 2is preferred to less,but unless the bundles have thesame amount good 1,then the bundle with more good 1is always preferred.Consider sequence 1,with no units of good 2and 1/n units of good 1,and sequence 2with no units of good 1,and1 1/n units of good2.For all finite n,sequence1is preferred to sequence1,but in the limit sequence1 yields zero unit of either good and sequence2yields1unit of good2and is therefore preferred.Lexicographic preferences are a famous example,but hardly amainstay of either theory or empirical work.MWG Definition1.B.2:A functionu:X is a utility function representing preference relation if for all x,y X, x y if and only if u x u y Proposition3.C.1:If the rational preference relation on L is continuous, then there is a continuous utility functionu x that represents .The proof in MWG requires monotonicity–a slight variant is toto take a probability measure on L that has positive density everywhere,and then letu x 1 prob y y x .By construction,if x y then u x u y and if u x u y then x y.Now we’ve gotten to a utility function and we know that it is continuous.MWG Definition3.B.4:The preference relation is convex if for every x X the upper contour sety Y:y x is convex,that is if y x and z x then y 1 z x for every 0,1 .MWG Definition3.B.5:The preference relation is strictly convex if for every x X if y x and z x andy z implies that y 1 z x for every 0,1 .Convex preferences imply that u . is quasi-concave,i.e.the sety L:u y u xis concave(equivalentlyu y 1 x Min u x ,u y for any x,y and all 0,1 .Strict convexity implies strictquasi-concavity.The utility maximization problem is to maximize u x subject to theconstraint p x 0.MWG Proposition3.D.1:If p 0and u . is continuous then the utility maximization problem has a solution. The proof relies on the fact that a continuous function always has a maximum on a compact set,so you just need to show that the budget set is closed and bounded,pact.Proposition3.D.2:Suppose that u . is a continuous utility functionrepresenting a locally non-satiated preference relation defined on the consumption set X L.Then the Walrasian demand correspondence has the following properties:(1)x p,w is homogeneous of degree zero in prices and wealth,i.e.x p,w x p, w for every 0(2)Walras’law p x p,w w(3)If is convex so that u . isquasi-concave,then x p,w is a convex set.Moreover if is strictly convex,so that u . is strictly quasi-concave,then x p,w consists of a single element.In practice,we write down a Langrangianmax x, U x1,x2,...x Lwi 1Lp i xiwhich yields us a system of first order conditions:U x1,x2,...x Lx ip iThese are L equations and we have L 1 unknowns,so we need to use the budget set as well to solve the problem.An application:fertility decisions.Many empirical puzzles:(1)Why does fertility drop with income so substantially across countries?(2)Why is fertility below replacement in all of Europe,but not in the U.S.?How would we capture this:Begin with U C,N –utility over consumption and kids.Assume that kids have both a cash cost(k),and a time cost(t)Assume that you have a time budget that can either be used producing kids or making money.Write down the total budget constraintWT Y C k tW NSolving C from the budget set the agent’s maximization problem reduces toU WT Y k tW N,NmaxNWhich in turn produces a F.O.C.k tW U1 WT Y k tW N,NU2 WT Y k tW N,N 0 where U1is the partial w.r.t.the1st argumentof U and similarly for U2.The marginal utility of another kid is weighed off against the marginal cost in terms of time and money.Comparative statics can be derived by (1)Using the implicit function theorem to define N Z ,where Z is a vectorrepresenting all of the parameters in this equation(i.e.,Z t,T,Y,W,k )and(2)Totally differentiating the F.O.C.to findNZ.LetF N,Z k tW U1 WT Y k tW N,NU2 WT Y k tW N,Nso that the F.O.C is F N Z ,Z 0.Differentiation w.r.t parameter Z then gives us:F1 N Z ,Z NZF2 N Z ,Z 0 from whichN Z F2 NZ ,ZF1 N Z ,Z.In this caseF1 N ,Z k tW 2U11 C ,N U22 C ,NU22 C ,N 2 k tW U12 C ,N and C WT Y k tW N .We generally assume that terms likeF1 N Z ,Z are negative(Why?)so thesign of Ndepends entirely on the sign ofZF2 N ,Z F N ,Z.ZIn the case of Z Y for example:Y k tW U1 WT Y k tW N ,N U2 WT Y k tW N ,Nk tW U11 WT Y k tW N ,N U12 WT Y k tW N ,NWhat can we say about this?Does this give us any intuition about anything?In the case of W:W k tW U1 WT Y k tW N ,N U2 WT Y k tW N ,Nk tW T tN U11 WT Y k tW N ,N T tN U12 WT Y k tW N ,NtU1 WT Y k tW N ,NIt’s the same as the unearned incomeeffect expect for the third term.What doesthat third term represent?Now let’s get a little more fancy and assume that parents care about both quantity and quantity,i.e.U C,Q,N .For simplicity assume utility is a separableand quasi-linear in consumption,soU C,Q,N C V Q,Z Q W N,Z N . Assume children cost WtQN.Then the first order conditions are:V Q,Z QWtNQandW N,Z NWtQNIf a parameter increases the marginal return to quality–this will have the following effect2V Q,Z QQ2 QZ Q2V Q,Z QQ Z QWt NZ Qand2W N,Z NN2 NZ QWt QZ Qor QZ Q2V Q,Z QQ Z Q2V Q,ZQQ2Wt 22W N,Z NN2and NZ Q2V Q,Z QQ Z Q2V Q,ZQQ22W N,Z NN2Wt 2How can we sign these two things?Each equation also tells you that the price per child rises as the quality of each child increases,and the price of quality rises as the number of children rises.Through the budget set there is an inherent substitutability between quantity and quality of children.。
chatgpt学术手册
chatgpt学术手册
ChatGPT学术手册主要包括以下内容：
1. ChatGPT简介：介绍ChatGPT的概念、发展历程、主要功能和特点，以及在学术领域的应用前景。
2. 安装与配置：指导用户如何安装和配置ChatGPT，包括软件环境、网络
设置等。
3. 基本操作：介绍如何使用ChatGPT进行基本的学术交流，包括提问、回
答问题、写论文等。
4. 高级应用：介绍如何使用ChatGPT进行更高级的学术研究，如文献综述、实验设计、数据分析和解释等。
5. 常见问题与解答：列举并解答使用ChatGPT时可能遇到的问题，如语言
选择、个性化设置等。
6. 学术道德与规范：强调在使用ChatGPT进行学术研究时需要遵守的道德
和规范，如避免抄袭、尊重知识产权等。
7. 案例分析：选取一些成功的ChatGPT在学术领域应用的案例，进行分析
和评价，为用户提供参考和借鉴。
8. 未来展望：分析ChatGPT在学术领域的发展趋势和前景，提出建议和展望。
此外，ChatGPT学术手册还可以根据不同学科的特点，介绍ChatGPT在该学科领域的应用方法和技巧。
例如，在物理学领域，可以使用ChatGPT进行物理实验的设计和数据分析；在文学领域，可以使用ChatGPT进行文学创作和语言学研究等。
总之，ChatGPT学术手册旨在帮助用户更好地使用ChatGPT进行学术研究，提高研究效率和成果质量。
lecture 2
VII. Thesis statement
A thesis statement, also called the statement of the
problem, or the thesis sentence, usually states or suggests the research subject or the main topic. Making the thesis statement will help you to focus on the research topic and to avoid reading unrelated materials and writings that are of little or no relevance to your research topic.
One thing should be pointed out is that as your writing progresses, your thesis statement may change, it can change in one way or another when you try to narrow down or broaden your research topic.
Secondary research is often called documentary or library research. It is a kind of study that makes use of data in documents, books, and journals. These data have been collected by other people for their own purposes. Therefore, secondary research consists of summarizing previous studies, reviewing the literature in a given area, and synthesizing the research undertaken by others.
高教版大学英语泛读教程2(第三版)电子教案-Review 01
Review 01-p.38
B Multiple Matching
Look at the four paragraphs(A-D) that deal with the deniers claims. In which paragraph does the author mention …
__D___ 1. a claim that focuses on a really small percentage? __A___ 2. two different parts of one continent? __C___ 3. a hope that may be unrealistic? __A___ 4. a measurement of weight?
பைடு நூலகம்
c. Science is about agreement.
d. Skepticism is an important part of science. B 2. Why does the author say “it seems fair to be skeptical of the skeptics”? Detail
B? Inference
a. confusion
Lecture2
Illustration of some typical asymptotic running time functions
We can see:The linear algorithm is obviously slower than the quadratic one
and faster than logarithmic one,
Don’t care
N n0
Ω-notation
Informal definition of Ω(.) :
If an algorithm’s running time t(n) is bounded blow by a function g(n), to within a constant multiple c, for n > n0, we say that the running time of the algorithm is Ω(g(n)).
Lecture 2 The Time Complexity
An example to illustrate the importance of analyzing the running time of an algorithm
The Sorting Problem: Input(实例): An array of n elements A[1…n], Output(询问): Sort the entries in A in non-decreasing order.
Time
c· g(n)
t(n)
Don’t care
N n0
Obviously, O-notation is used to bound the worst-case running time of an algorithm
SequencetoSequenceLearningwithNeuralNetworks（。。。
SequencetoSequenceLearningwithNeuralNetworks（。
1. Introduction本⽂提出了⼀种端到端的序列学习⽅法，并将其⽤于英语到法语的机器翻译任务中。
使⽤多层LSTM将输⼊序列映射为固定维数的表⽰向量，然后使⽤另⼀个多层LSTM从该向量解码得到⽬标序列。
作者还提出，颠倒输⼊序列的单词序列可以提⾼LSTM的性能，因为这在源和⽬标序列之间引⼊了许多短期依赖性。
之前的DNN只能将源序列和⽬标序列编码为固定维数的向量，⽽许多问题需⽤长度不是先验已知的序列表⽰，例如语⾳识别、机器翻译。
本⽂的想法是，使⽤⼀个LSTM读取源序列逐步得到固定维数的表⽰向量，然后⽤另⼀个LSTM从该表⽰向量中得到⽬标序列，第⼆个LSTM本质上是⼀个RNN语⾔模型，只是它以输⼊序列为条件。
由于输⼊与输出之间有很⼤的时间延迟，所以使⽤具有学习长时间依赖关系的数据能⼒的LSTM（如下图）。
测试结果表明，该模型在机器翻译任务中可以得到不错的BLEU score，显著地优于统计机器翻译基线（SMT baseline）。
令⼈惊讶的是，LSTM在长句⼦的训练上也没有什么问题，原因是颠倒了输⼊序列单词的顺序。
另外，编码的LSTM将变长序列映射为维数固定的向量，传统的SMT⽅法倾向于逐字翻译，⽽LSTM能够学习句⼦的含义，具有相似含义的句⼦在表⽰向量中距离近，不同含义的句⼦则距离远。
⼀项评估表明，该模型可以学习到单词的顺序，并且对主动和被动语态具有不变性。
2. The modelRNN是前馈神经⽹络的⼀种⾃然泛化。
给定⼀个输⼊序列{ \left( x\mathop{{}}\nolimits_{{1}},...,x\mathop{{}}\nolimits_{{T}} \right) }，RNN通过以下公式迭代计算出输出：{\begin{array}{*{20}{l}} {h\mathop{{}}\nolimits_{{t}}= \sigma \left(W\mathop{{}}\nolimits^{{hx}}x\mathop{{}}\nolimits_{{t}}+W\mathop{{}}\nolimits^{{hh}}h\mathop{{}}\nolimits_{{t-1}} \right) }\\{y\mathop{{}}\nolimits_{{t}}=W\mathop{{}}\nolimits^{{yh}}h\mathop{{}}\nolimits_{{t}}} \end{array}}只要事先知道输⼊与输出之间的对齐⽅式，RNN就可以将序列映射到序列。
描述自己和同桌上学的一天英语作文
描述自己和同桌上学的一天英语作文全文共3篇示例，供读者参考篇1A Day at School with My DeskmateThe shrill ringing of my alarm clock jolts me awake at 6:30 am. I groan and hit the snooze button, trying to steal a few more precious minutes of sleep. But my mom's voice soon rings out from the kitchen. "Andy! Time to get up for school!"Reluctantly, I drag myself out of the warm cocoon of my blankets and into the bathroom to get ready. After splashing some water on my face and brushing my teeth, I feel a bit more awake. I throw on my uniform - a white collared shirt, navy blue sweater vest, and khaki pants. A glance in the mirror confirms that my brown hair is sticking up in all directions as usual. Oh well, good enough.Downstairs, I grab a granola bar and my backpack before dashing out the door. The crisp autumn air makes me shiver a bit as I hurry down the street towards the looming brick building of Roosevelt Middle School. As I approach the entrance, I see afamiliar figure waiting under the flagpole - my deskmate and best friend, Jessica."Hey Jess!" I call out with a wave. Jessica turns and her face breaks into a huge smile, making her green eyes crinkle at the corners."Andy! I was wondering if you were going to make it on time for once," she teases. Her red hair is pulled back into its usual neat ponytail.I roll my eyes good-naturedly. "Yeah, yeah. You know Mom would never let me be late."We link arms and head inside, joining the flow of students streaming through the doors. Our first class is English Literature with Mr. Hendricks. Jessica and I slide into our usual desks near the back corner and unpack our books and notebooks."Did you finish reading the chapters for today?" Jessica whispers as Mr. Hendricks starts writing vocabulary words on the board.I grimace slightly. "I may have...fallen asleep before finishing last night." Jessica just shakes her head in mock disappointment.The class period is spent discussing the symbolism in the chapters we were assigned from To Kill A Mockingbird. I try tofollow along and take notes, but Jessica has to occasionally nudge me when my attention starts wandering. Mr. Hendricks calls on me at one point to analyze a quotation, and I stumble through an answer while Jessica not-so-discreetly slides her notes toward me. I shoot her a grateful look.Finally, the bell rings for our next period - Math with Mrs. Thompson. As we shuffle out of English, Jessica links arms with me again."You owe me for saving you back there," she says with a grin. "I'll take your dessert at lunch as payment.""What? No way! You know I live for Mom's chocolate chip cookies," I protest. But I'm smiling too, knowing she's only teasing. This kind of playful banter is just how we operate.Math class seems to drag on forever as we p篇2A Typical School Day with My DeskmateThe shrill beeping of my alarm jolts me awake at 6:30 AM. I groan and hit the snooze button, trying to steal a few more precious minutes of sleep. But my deskmate Emily is alreadyposting on our class group chat, reminding everyone to get up and get ready for another day at Franklin High School.Emily has been my assigned deskmate since the beginning of freshman year. We ended up being total opposites - she's an overachiever who lives for her color-coded schedules and curriculum, while I'd rather spend my time daydreaming about becoming a famous YouTuber. But over the years, we've formed an unlikely friendship built on shared commiseration over tough classes and way too much homework.I finally drag myself out of bed at 7:00 and hurriedly get dressed, scarfing down a granola bar as I race out the door. Emily is already waiting at our usual meeting spot, neatly put together as always with her hair in a perfect ponytail."Cutting it a bit close today, aren't we?" she teases as we start the 10 minute walk to school. I just roll my eyes. This is pretty typical for us.When we get to our lockers, Emily is already rattling off a list of everything that's due today - a history essay, a stack of algebra problem sets, and a presentation for English class that we're partnering on. I try not to let the overwhelming wave of anxiety and dread show on my face. Somehow she always gets itall done with time to spare, while I'm always scrambling at the last minute.The morning flies by in a blur of lectures and notes and quizzes. I have a hard time focusing through my usual morning grogginess. Thankfully, Emily is meticulous about taking detailed notes that she lets me borrow to copy later. I don't know what I'd do without her.Finally, it's time for lunch, and we make our way to the cafeteria to meet up with our friends. I get my usual greasy slice of pizza while Emily opts for a salad, raising her eyebrows disapprovingly at my poor nutritional choices. We squeeze in at the lunch table with our other friends - Josh, Samantha, David, and Brianna. The conversation quickly turns to the latest rants and gossip circulating around school."Did you hear that Mr. Robertson actually got fired for being wasted during his 4th period class?" Josh asks through a mouthful of fries.Emily groans. "That's just a rumor. He's out on family leave to deal with some personal issues. Don't spread misinformation."I can't help but laugh at the disparity between Josh's insatiable need for high school drama and Emily's dedication to truth and facts above all else.As the lunch period winds down, I start to get that familiar pit of dread in my stomach, realizing I'm totally unprepared for our English presentation later. I'll have to beg Emily for a copy of her notes and talking points. She'll definitely give me a hard time about leaving everything to the last minute again, but she always comes through for me in the end.The rest of the afternoon is a blur - more classes, more due dates looming. Finally, the final bell rings at 3:15, signaling freedom...for about four hours until I'll have to hit the books again. Emily is all ready to go straight to the library to get a headstart on homework, but I beg her to come with me to grab a coffee first. I need a pick-me-up after this crazy day.We end up spending a couple hours at the coffee shop, Emily tutoring me through the algebra problem sets I didn't understand while I shamelessly take advantage of her knowledge and work ethic. In between equations, we laugh and chat about everything from weekend plans to where we hope to go to college in a couple years.As stressful as days at Franklin High can be, I'm grateful to have Emily by my side through it all. Yeah, she can be an uptight, annoying brainiac at times. But she's fiercely loyal, always looking out for me even when I don't particularly deserve it. I've got no idea how I would survive the constant barrage of tests and assignments without her guidance and meticulous preparation. She pushes me to be better and holds me accountable.Finally, we pack up our books and laptop around 5:30. I groan, realizing I still have at least 4 more hours of homework ahead of me tonight. Emily gives me an encouraging pat on the back - she knows I'll inevitably end up sliding into her DMs around midnight frantically asking for her English notes whenI've procrastinated too long."One step at a time," she says with a smile. "We've got this...well, I'VE got this. Not sure about you!"I playfully punch her arm, but I'm smiling too. For all our differences, I know Emily will always have my back. That's what makes getting through the daily grind of homework, tests, and never-ending academic stress at Franklin High bearable. I'm lucky to have a deskmate like her.篇3A Typical School Day with My DeskmateThe shrill ringing of my alarm clock jolts me awake at 6:30 AM sharp. As my eyes slowly adjust to the harsh morning light filtering in through the curtains, I let out a long yawn and stretch my arms above my head. Another school day has begun.I groggily make my way to the bathroom to brush my teeth and splash some cold water on my face in an attempt to fully wake up. After getting dressed in my uniform, I head downstairs where mom has prepared a simple but nourishing breakfast of oatmeal and fresh fruit."Good morning, sleepyhead," she chirps in an overly cheery voice. How she can be so energetic this early is beyond me. I mumble a half-hearted "morning" in return as I shuffle over to the kitchen table.By 7:15, I've wolfed down my breakfast and am out the door, backpack slung lazily over one shoulder. The short walk to school is a blur as I stumble along the quiet neighborhood streets, still not fully awake.I arrive at the front gates just as the first bell rings at 7:30. A cluster of students decked out in the same navy blazers and grayslacks milling about the courtyard. I spot my deskmate, Alex, standing with a group of friends and give him a wave."Cutting it a bit close again, I see," Alex says with a sly grin as I approach. His messy blonde hair sticking up in every direction makes it obvious he just rolled out of bed himself."You're one to talk," I shoot back with a playful nudge of his arm. We've been deskmates since the first year of secondary school and have developed a sort of unspoken competition to see who can show up latest without actually being tardy.The warning bell rings out, signaling we have five minutes to get to our first class. Alex and I say goodbye to our friends and head inside, our beaten up trainers squeaking against the tiled floors.We slide into our usual desks just as the teacher calls the class to order. Mrs. Patterson dives right into her lecture on algebraic equations, her voice a dull drone in the background as I doodle absently in my notebook. Alex has his head cocked back, eyes closed, already nodding off. Typical.The rest of the morning passes by in a blur - fumbling through a French vocabulary quiz, taking notes on the Napoleonic Wars in history, attempting to balance chemicalequations in science. My brain feels fried by the time the bell for lunch rings at noon.Alex and I make our way to the cafeteria and get in the queue for today's somewhat questionable special - cottage pie, by the looks and smell of it. We grab a sandwich from the cold bar as well, knowing the main course likely won't be enough to fuel us through the afternoon."Hey, did you finish the English essay that's due today?" Alex asks as we scan the cafeteria for an empty table.I feel my stomach drop. "The essay? Uh, no? That was due today?" I rack my brain but have no recollection of such an assignment.Alex lets out an exasperated sigh. "Dude, how could you forget? We've had two weeks to do it! Mrs. Robertson is going to kill you."We find a spot and I immediately pull out my English notebook and flip through it frantically. Sure enough, the essay prompts and requirements are scribbled there, mocking me. How could I have spaced on this so badly?I start frantically trying to formulate a basic outline in my head, then pause. "Yo, Alex...you wouldn't happen to have youressay on you, would you?" I give him a sheepish grin and my best attempt at puppy dog eyes. "Just to, you know...reference?"He narrows his eyes at me suspiciously for。
claude2 训练参数
claude2 训练参数在使用claude2进行训练时，我们需要关注一些重要的参数。
首先是学习率（learning rate），学习率决定了模型在每次迭代中对参数进行调整的程度。
较高的学习率可以加快收敛速度，但可能会导致模型在最优点附近震荡；较低的学习率则可能会导致模型收敛速度过慢。
因此，选择一个合适的学习率是非常重要的。
另一个重要的参数是批量大小（batch size），批量大小决定了每次迭代中参与训练的样本数量。
较大的批量大小可以加快训练速度，但可能会导致内存消耗过大；较小的批量大小则可能会导致模型训练不稳定。
因此，在选择批量大小时需要综合考虑计算资源和模型性能的平衡。
正则化（regularization）也是一个常用的训练参数。
正则化可以帮助防止模型过拟合，提高模型的泛化能力。
常见的正则化方法包括L1正则化和L2正则化。
选择合适的正则化参数可以在一定程度上平衡模型的拟合能力和泛化能力。
还有一个重要的参数是网络结构（network architecture），网络结构决定了模型的拟合能力。
不同的任务可能需要不同的网络结构。
在使用claude2进行训练时，可以根据具体的任务需求选择合适的网络结构，如使用不同的层数、不同的神经元个数等。
除了上述提到的参数外，还有一些其他的训练参数也需要我们关注。
例如，优化算法（optimization algorithm）可以影响模型的训练速度和效果；初始化方法（initialization method）可以影响模型的初始状态；训练迭代次数（number of iterations）可以影响模型的收敛程度等等。
选择合适的训练参数是一个综合考虑多个因素的过程，需要根据具体问题和数据集的特点进行调整。
claude2训练参数的选择对于模型的性能和效果具有重要影响。
在使用claude2进行训练时，我们需要关注学习率、批量大小、正则化、网络结构等参数，并根据具体问题和数据集的特点进行调整。
(高级版)机器学习全套教程
(高级版)机器学习全套教程机器研究是现在最热门的领域之一，它让机器能够通过研究、探索来实现人工智能的目标。
如果你想在机器研究领域深入研究，那么这份全套教程就是为你准备的。
第一章：机器研究基础在这一章节中，我们将介绍机器研究的基础知识，包括机器研究的基本原理、常用算法和应用场景等。
第二章：数据分析与数据预处理机器研究需要大量数据来训练模型。
在这一章节中，我们将介绍如何对数据进行分析和预处理，以便更好地应用机器研究算法。
第三章：监督研究与非监督研究在这一章节中，我们将深入研究机器研究的两种主要类型：监督研究和非监督研究。
我们将分别介绍这两种类型的算法，并且提供大量的代码实例。
第四章：神经网络神经网络是机器研究中最重要的技术之一。
在这一章节中，我们将介绍神经网络的基本结构和原理。
此外，我们还将介绍如何使用Python和TensorFlow等工具来构建和训练神经网络。
第五章：深度研究深度研究是机器研究中最前沿的技术之一。
在这一章节中，我们将深入探讨深度研究的原理和应用。
此外，我们还将提供大量的代码实例，以帮助你更好地理解深度研究的实现过程。
第六章：自然语言处理自然语言处理是机器研究的一个重要应用领域。
在这一章节中，我们将介绍如何使用机器研究算法来处理自然语言。
我们将涵盖从预处理到算法选择再到应用的整个过程。
第七章：机器研究平台机器研究平台可以帮助企业快速部署和管理机器研究模型。
在这一章节中，我们将介绍几个流行的机器研究平台，并演示如何使用它们来构建机器研究应用。
结束语这份机器学习全套教程覆盖了机器学习的基础知识和前沿技术，是机器学习学习者的必备指南。
希望这份教程能帮助你更好地入门和掌握机器学习领域的知识。
触觉听觉 等细节描写 校园环境英语作文
触觉听觉等细节描写校园环境英语作文全文共3篇示例，供读者参考篇1The Pulse of Campus LifeThe alarm blares, jarring me from a dreamless sleep. As my eyes flutter open, I'm greeted by the familiar sight of my dorm room walls, plastered with posters and photos chronicling my college journey. Reluctantly, I peel off the covers, my feet making contact with the worn, slightly scratchy carpet. Through the open window, I catch the first whiffs of the brisk morning air, tinged with the earthy aroma of freshly mown grass.After a quick shower, I grab my backpack and head out, joining the stream of students making their way across campus. The pathways are already alive with chatter and laughter, a symphony of voices in different pitches and cadences. My sneakers crunch against the gravel as I navigate the winding paths, flanked by neatly trimmed hedges and bursts of vibrant flowers.Up ahead, the clock tower chimes, its rich baritone tones reverberating through the air. I quicken my pace, not wanting tobe late. The main quad opens up before me, a vast expanse of perfectly manicured lawns dotted with towering oak trees that provide welcome pockets of shade. Students lounge on the grass, textbooks and laptops scattered around them, taking advantage of the pleasant morning to study al fresco.As I approach the stately brick buildings, the cacophony of campus life crescendos. The air is thick with the mingled scents of freshly brewed coffee, dusty tomes from the library, and the faint tang of whiteboard markers. Clusters of students hover around bulletin boards, fingers tracing along flyers advertising club meetings, social events, and study groups.I weave through the throngs, climbing the broad steps leading up to the main lecture hall. The heavy wooden doors groan as I push them open, and I'm enveloped in the hall's familiar ambiance. The lofty ceilings amplify the dull roar of hundreds of murmuring voices, punctuated by the occasional burst of laughter or the squeak of chairs being dragged across tile.Finding my usual spot, I sink into the snug contours of the well-worn seat, the faux leather creaking beneath me. As the professor strides to the podium, her sensible heels click-clacking against the polished floor, a hush gradually descends upon theroom. I flip open my notebook, the crisp pages whispering as they're riffled by the draft wafting through the open windows. The lecture begins, and I'm lost in a whirlwind ofthought-provoking concepts, scribbling furiously to capture every pearl of wisdom.The hours blur by, and soon it's lunchtime. I make my way to the dining hall, pushing through the heavy double doors. A wall of scents – sizzling burgers, tangy marinara sauce, and freshly baked bread – washes over me. The din of clattering trays and boisterous conversation is near-deafening as I navigate the labyrinth of tables occupied by boisterous groups of friends catching up between classes.Out on the sun-drenched patio, I settle at a quiet table, savoring the gentle breeze that carries the faint strains of music from a student band performing nearby. I unwrap my sandwich, the crunch of the crisp lettuce and tomato mingling with the crunchy baguette. A sip of iced tea, sweetened with a hint of lemon, refreshes my palate.The afternoon stretches on, a blur of lectures, study sessions in the library, and casual meetings with professors during their office hours. The library's hushed ambiance is a stark contrast to the lively campus buzz, a sanctuary of soft rustles and theoccasional squeak of a chair or murmured whisper. Pages rasp asI turn them, and my pencil scratches against my notepad, leavinga trail of graphite in its wake.As the sun sinks lower in the sky, I find myself back in the quad, basking in the tranquility of the fading afternoon light. A gentle breeze stirs the branches overhead, and the leaves whisper in a language only they can understand. Patches of sunlight dapple the ground around me, and I bask in their warmth, allowing my mind to wander.The day draws to a close with the evening campus rituals. Sports teams take to the fields for practice, the air reverberating with the thwack of lacrosse sticks, the thud of soccer balls, and the grunts of exertion. In the theater, the muffled strains of rehearsals leak through the doors as the drama club prepares for their next production. The scents of charred burgers and sizzling fries waft from the student union as hungry scholars gather for a late dinner.As night falls, the campus takes on an enchanting new persona. Lampposts cast puddles of golden light across the pathways, their soft glow reflecting off the dew-kissed foliage. Clusters of fireflies wink in and out of existence, dancing their mystical courtship ritual. A solitary owl's haunting call echoesthrough the still air, a reminder of the natural world that coexists alongside this vibrant scholastic community.Finally, I return to my dorm, weary but content. I sink onto my bed, savoring the comforting familiarity of the worn sheets and plump pillows. As I drift off to sleep, the muted soundtrack of campus life – distant laughter, the grumble of a lawn mower in the distance, the chirping of crickets in the shrubbery outside –lulls me into peaceful slumber. Tomorrow, this vibrant cycle will begin anew, and I will once again be immersed in the multisensory tapestry that is the essence of college life.篇2The Rhythms of Campus LifeAs I walk across the main quad on my way to class, the sounds and sensations of campus life envelop me. The gentle breeze carries the aroma of freshly cut grass mingling with the sweet fragrance of blossoms from the flowering trees lining the paths. Beneath my feet, the bricks feel smooth and warm from the morning sun. Birds chirp melodically from the branches above, accompanying the ambient murmurs of students chatting and laughing together.Rounding the corner of the English building, I pass by a cluster of students seated on the steps, books open in their laps and backpacks strewn casually around them. The energy is studious yet relaxed as they discuss course readings with thoughtful tones. I catch snippets of their conversation analyzing metaphors and debating literary interpretations. Their voices mingle into an academic bassline underlying the high-pitched trills of songbirds flitting among the ivy climbing the building's aged stone facade.I pull open the heavy wooden door, and the atmosphere shifts. The vaulted entry hall is blessedly cool as the air conditioning counteracts the warmth of the late spring day outside. My footsteps echo hollowly as I cross the tiled floor towards the stairwell. Voices ricochet through the open space as students shuffle between classrooms, a constant fluid stream of motion and chatter.Climbing the stairs, the wooden handrail is smooth and polished from thousands of hands that have traced its contours over the decades. At the landing, I pause and gaze out the window at the panoramic view - the grassy expanse of the quad, the stone clock tower standing sentinel in the distance, studentslounging on blankets or tossing frisbees. It's a quintessential collegiate scene saturated in nostalgia and vitality.My next class is down the narrow corridor, its high arched ceilings and tall windows letting in shafts of buttery light that pool on the hardwood floors. The wooden doors lining the hallway are closed but not soundproof; snippets of lectures filter through in muffled tones. English romantic poetry, microeconomic principles, French pronunciation drills – the murmured voices and cadences provide an auditory preview of the diverse subjects unfolding inside.Ducking into my classroom, I grab a seat near the airy window. The professor's voice is melodious yet substantial as she delves into analyzing Toni Morrison's iconic novel. I revel in the rustle of pages turning, the scratch of pencils scribbling notes, the hum of the projector whirring as she sequences through PowerPoint slides. These are the sounds that form the soundtrack to our scholarly endeavors.When class concludes, the atmosphere regenerates into a effervescent buzz. Students gather their belongings, chatting about plans for the afternoon – catching a movie at the campus theater, grabbing lunch at the dining hall, heading to club meetings or study groups. Their voices intermingle into a joyfulclamor as they spill out into the hallway, the energy amplifying as it funnels into the open space.Outside once more, I meanderdown the tree-lined paths, my shoes crunching slightly on the occasional fallen twig or pine cone. Squirrels scamper across the branches above, scolding with territorial territoriality. In the distance, I can hear the rhythmic thump of music from someone's car speakers, hip hop or house pulsing through the open windows in staccato beats.Turning onto the main promenade, the scents intensify into an olfactory overload – french fries and pizza wafting from the food trucks clustered on the plaza, freshly brewed coffee mingling with clouds of vape smoke, the unmistakable aroma of Hopkins' famous Husky Dogs searing on the grills outside the student center. As I approach, dozens of tables stretch across the paved expanse, students eating and socializing al fresco.I grab a shady spot and unpack my lunch, savoring each bite of my turkey sandwich while observing the swirling currents of campus life. A capella groups gather in circles, harmonizing vocal warmups before their rehearsals. Hacky sack circles form impromptu as cleats join bare feet in the ritualized rhythms of the footbag. Clusters of students sprawl on the grass, somecontentedly studying, others animatedly debating the latest TED talk or political issue.The hours drift by languidly until the gentle lull of campus begins to intensify once more into an effervescent surge. It's late afternoon now, and everywhere there is motion as the day's grand finale commences. Lacrosse players stride purposefully towards the athletics fields, their sticks clutched resolutely overhead, sneakers squeaking against the pavement. Dancers in stylized warmup wear sashay by, hair tightly secured, earbuds pulsing with choreographed beats. Wafts of chlorine emanate from the doors of the recreation center as swimteams depart morning practices.As dusk falls, the ambience transitions yet again as the evening crowd emerges. Greek life members filter onto porches and lawns, laughing and chatting over the dull thud of bass lines leaking from houses. The scent of barbecue merges with the smoky tang of cigarettes into a heady bouquet. Across campus, auditoriums and concert halls come alive in glowing entrances as gowned crowds stream inside for lectures, recitals, and performances.In this perpetual rhythm, each cycle repleting the last, the cadences of academia ebb and flow. It's a choreographedsymphony of sounds, aromas, textures, and scenes – frenzied yet harmonious, dynamic yet eternal. This is the very essence of the collegiate experience, a multi-sensory phenomenon to be absorbed and savored. I wouldn't have it any other way.篇3The Sensory Tapestry of Campus LifeAs I make my way across the bustling academic quad, a rich tapestry of sights, sounds, and sensations envelops me, reminding me why I love being on this vibrant campus. The first thing that greets me is the reassuring crunch of gravel beneath my well-worn sneakers, that familiar sound resonating with each purposeful stride. I can't help but smile as I feel the warmth of the spring sun kissing my face, its rays filtering through the gently swaying branches of the majestic oaks that line the walkway.My nose is tantalized by a delightful medley of scents wafting through the air – the earthy aroma of freshly trimmed grass mingling with the sweet fragrance of newly blossomed flowers. In the distance, I catch an enticing whiff of sizzling burgers from the student union grill, making my mouth water in anticipation of lunchtime.As I approach the grand stone archway that marks the entrance to the main academic building, my fingers trace the intricate carvings etched into the aged masonry, feeling the grooves and ridges that generations of students have worn smooth over time. The heavy wooden doors groan in protest as I pull them open, ushering me into the climate-controlled sanctuary within.The hushed ambiance of the library instantly embraces me, a stark contrast to the lively energy outside. My footsteps are muffled by the plush carpeting as I wind my way through the towering shelves, running my fingertips along the spines of countless volumes. The scent of aged paper and leather bindings is heady and comforting, like a warm embrace from a dear friend.I settle into a cozy nook, the soft fabric of the overstuffed armchair cradling my body as I crack open my textbook. The gentle whisper of turning pages mingles with the occasional creak of a chair or the muted tapping of keyboards, creating a soothing symphony that aids my concentration.After hours of focused study, I emerge back into the sunshine, squinting against the brightness as my eyes readjust. The quad is now abuzz with activity, a vibrant kaleidoscope of sights and sounds. Laughter and chatter fill the air as groups ofstudents lounge on the lush green lawns, their voices mingling with the melodic trills of birds nesting in the nearby trees.As I make my way towards the residence halls, the rhythmic pounding of a bass line draws my attention to a group of students gathered around a makeshift dance floor. The pulsating beat resonates in my chest as I watch their bodies move in perfect synchronicity, their feet stomping and shuffling in intricate patterns. The energy is electric, and I can't resist tapping my foot in time to the infectious rhythm.Evening falls, and the campus takes on a whole new ambiance. The soft glow of antique lampposts casts a warm, inviting hue over the brick pathways, creating a cozy atmosphere perfect for leisurely strolls. The cool night air carries the tantalizing aroma of freshly baked cookies wafting from the campus bakery, tempting my sweet tooth.As I retreat to my dorm room, the familiar squeak of the ancient springs in my mattress greets me as I sink into its comforting embrace. The faint hum of the air conditioning unit and the distant laughter of friends in the hallway create a soothing white noise that lulls me into a restful slumber, ready to awaken and experience the sensory delights of campus life anew.。
描述同学们的课间活动的英语作文
描述同学们的课间活动的英语作文全文共3篇示例，供读者参考篇1Life Between Classes: A Vibrant Tapestry of Extracurricular ActivitiesAs the bell chimes, signaling the end of another grueling lecture, a palpable sense of relief washes over the classroom. For a fleeting moment, the weight of academic responsibilities lifts from our shoulders, and we are reminded of the vibrant tapestry of extracurricular activities that awaits us during our cherished breaks.The hallways come alive with a cacophony of voices and laughter, as students eagerly spill out from their classrooms, their minds already drifting towards the myriad of pursuits that lie ahead. It is during these precious pockets of time that we truly come into our own, exploring our passions, forging new friendships, and discovering the depths of our talents.For some, the call of the stage beckons, and they make their way to the auditorium, where the drama club holds its rehearsals. Here, aspiring thespians shed their inhibitions and immersethemselves in the world of make-believe, breathing life into characters that transcend the confines of the classroom. With each line delivered and every emotion conveyed, they hone their craft, preparing for the day when the spotlight will shine upon them.Others find solace in the rhythm of their footsteps, as they lace up their sneakers and head to the basketball courts or football fields. The sound of rubber soles against the pavement echoes through the air, accompanied by the unmistakable thud of a ball being dribbled or kicked. In these moments, the boundaries between teammates blur, and a sense of camaraderie takes root, forged through the shared pursuit of victory and the thrill of friendly competition.Yet, for those whose hearts beat to a different tune, the music room beckons. Here, melodies and harmonies intertwine, as the members of the school band and choir pour their souls into their instruments and vocal cords. Whether it's the soaring notes of a trumpet or the rich timbre of a cello, each contribution adds depth and beauty to the tapestry of sound that fills the air.Nearby, the art studio bustles with creativity, as budding artists wield brushes and sculpting tools, transforming blank canvases and formless lumps of clay into masterpieces thatspeak to the human condition. With each stroke and each sculpted curve, they express their innermost thoughts and emotions, leaving an indelible mark on the world around them.In the depths of the library, the literary club gathers, engaging in spirited discussions and debates that challenge the boundaries of intellectual discourse. Here, words take on a life of their own, as aspiring writers and poets share their works, seeking feedback and inspiration from their peers. The rustling of pages and the scribbling of pens create a symphony of their own, a testament to the enduring power of the written word.Meanwhile, in the computer labs, the coding club convenes, their fingers dancing across keyboards as they delve into the intricacies of programming languages. With each line of code they write, they unlock new realms of possibility, harnessing the power of technology to solve complex problems and bring their innovative ideas to life.And yet, amidst this tapestry of activities, there are those who choose to simply bask in the company of their friends, exchanging stories and laughter over a shared meal or a game of cards. For them, these breaks serve as a respite from the demands of academia, a chance to forge bonds that will endure long after the final bell has rung.As the minutes tick by, the corridors remain a vibrant mosaic of activity, each student contributing their own unique thread to the rich tapestry of extracurricular life. It is in these moments that we truly come to understand the depth and breadth of our passions, and the limitless potential that lies within each and every one of us.For when the final bell tolls, signaling the end of another day, we carry with us the memories and experiences forged during these precious breaks. They serve as a reminder that education extends far beyond the confines of the classroom, and that true growth and fulfillment are found in the pursuit of our dreams, no matter how diverse or unconventional they may be.So, let us cherish these moments, these fleeting interludes between classes, for they are the living, breathing embodiment of our spirits, a testament to the boundless creativity and passion that lies within the hearts of students everywhere.篇2A Bustling Campus During BreaksAs the bell rings, signaling the end of another grueling class, a collective sigh of relief echoes through the hallways. The brief respite between lessons is a much-anticipated time for studentsto recharge, socialize, and engage in various activities that provide a welcome distraction from the academic rigors. Our campus comes alive during these breaks, transforming into a vibrant hub of energy and camaraderie.The courtyard is a popular gathering spot, where friends converge to catch up on the latest gossip or discuss the intricacies of their favorite video games or TV shows. Laughter and animated conversations fill the air, creating a lively atmosphere that is a stark contrast to the quiet classrooms we've just left behind. Some students prefer to seek solace in quieter corners, immersing themselves in books or scrolling through their phones, savoring these moments of solitude amidst the bustling campus.For the more athletically inclined, the various sports facilities become hives of activity during breaks. The basketball courts are always abuzz with the sound of squeaking sneakers and the rhythmic thump of bouncing balls. Friendly rivalries are forged as teams compete in impromptu matches, cheered on by enthusiastic spectators. The soccer field is another popular destination, where skilled footwork and strategic passes are showcased in pickup games that often draw quite a crowd.The cafeteria is a hub of culinary delights, where the tantalizing aromas of freshly baked goods and sizzling snacks waft through the air. Students eagerly line up to indulge in their favorite treats, whether it's a warm, gooey slice of pizza or a refreshing fruit smoothie. The cafeteria is not just a place to refuel but also a social gathering spot, where friends cluster around tables, exchanging tales of their day while savoring their chosen delicacies.For those with artistic inclinations, the art rooms become sanctuaries of creativity during breaks. The sound of brushes against canvas and the scratching of pencils on paper fills the air as students lose themselves in their artistic endeavors. Some prefer to work collaboratively, bouncing ideas off one another and offering constructive critiques, while others relish the solitude of their own creative process.The library is a haven for the studious, offering a quiet escape from the hubbub of the campus. Here, students can be found hunched over books or laptops, furiously typing away at research papers or catching up on assigned readings. The gentle hush of turning pages and the occasional whispered conversation create a serene atmosphere conducive to focused study.Outside, the school gardens provide a tranquil oasis for those seeking a connection with nature. Students can be found tending to the various plants and flowers, nurturing them with care and attention. Others simply bask in the sun, enjoying the fresh air and the peaceful surroundings, perhaps even engaging in a bit of meditation or journaling to clear their minds.As the minutes tick by, the campus buzzes with a multitude of activities, each student finding their own unique way to spend these precious moments of freedom. Whether they're engaging in physical pursuits, indulging in creative expression, or simply savoring the company of friends, these breaks are an essential part of our school experience. They provide a much-needed respite from the academic demands, allowing us to recharge and rejuvenate before diving back into the next round of classes.As the final moments of the break wind down, a collective reluctance settles over the campus. Students slowly make their way back to classrooms, their laughter and chatter gradually fading into the familiar hush of lessons resuming. But the memories of these lively interludes linger, a reminder of the vibrancy and camaraderie that make our school community truly special.篇3Surviving the School Day: A Guide to Making the Most of Free PeriodsLet's face it, being a student is tough. We spend hours upon hours sitting in classrooms, trying to absorb information that seems endless. Lectures drag on, notes blur together, and by the time the bell rings for a break, we're ready to pull our hair out. But fear not, my friends, for those precious free periods between classes offer a chance to recharge, have fun, and make it through another grueling day.As I stroll through the hallways during a free period, the first thing that hits me is the buzz of activity. Students are everywhere, some hurriedly heading to their next class, others lounging against the lockers chatting animatedly. The din of voices fills the air, a cacophony of laughter, gossip, and the occasional frustrated groan over a failed test or impossible homework assignment.For many, free periods are a chance to catch up on work or study for upcoming exams. You'll find them huddled in quiet corners of the library, textbooks and notebooks spread out before them. The serious looks on their faces are a testament to their dedication, but also a reminder of the relentless academic pressure we all face.Then there are the socializers, those for whom free periods are a welcome opportunity to kick back and swap stories with friends. They congregate in the cafeteria or on the sun-drenched quads, sipping from water bottles and munching on snacks from the vending machines. The topics of conversation range from the mundane to the profound, from dissecting the latest drama between classmates to debating the great philosophical questions of our time.Of course, no discussion of free periods would be complete without mentioning the athletes. For them, these breaks are a chance to get some exercise and blow off steam. You'll find them on the basketball courts, engaged in fierce pick-up games, or jogging around the track, earbuds in and music blasting. Their energy and competitive spirit are truly inspiring, even if the rest of us are content to simply watch from the sidelines.But perhaps the most intriguing group during free periods are the creators and artists. These are the students who use their free time to unleash their creative talents, be it through sketching in notebooks, strumming guitars, or writing poetry and short stories. They can be found in secluded corners of the school, lost in their own little worlds of imagination andself-expression.As I continue my stroll, I can't help but feel a sense of camaraderie and community among my fellow students. Despite our diverse interests and pursuits, we're all united in our quest to make the most of these fleeting moments of freedom. And who knows, maybe during one of these free periods, we'll stumble upon our true passions or forge friendships that will last a lifetime.Of course, not every free period is a blissful escape from the rigors of academia. There are times when the stress and pressure seem overwhelming, when the weight of assignments and impending deadlines threatens to crush us. During those moments, free periods can feel like a cruel tease, a brief respite before being plunged back into the fray.But even then, there is solace to be found in the company of our peers. We commiserate over shared struggles, offer words of encouragement, and remind each other that we're all in this together. After all, that's what makes our school community so special – the unbreakable bonds forged through shared experiences, both triumphs and tribulations.As the bell signals the end of yet another free period, I can't help but feel a twinge of sadness. These precious moments of freedom, however fleeting, have become an integral part of ourdaily routines, a lifeline amidst the chaos of academia. But as we reluctantly gather our belongings and head off to our next classes, there's a sense of renewed determination, a newfound resilience born of the laughter, camaraderie, and self-expression we've just experienced.So, to my fellow students, I say this: embrace these free periods, cherish them, and make the most of them. For it is during these stolen moments that we truly come alive, forging friendships, discovering passions, and finding the strength to tackle whatever challenges lie ahead. After all, surviving the school day is about more than just academics – it's about finding joy, solace, and growth in the unexpected pockets of freedom that punctuate our lives.。
S t e r e o M a t c h i n g 文 献 笔 记
立体匹配综述阅读心得之Classification and evaluation of cost aggregation methods for stereo correspondence学习笔记之基于代价聚合算法的分类，主要针对cost aggregration 分类，20081.?Introduction经典的全局算法有：本文主要内容有：从精度的角度对比各个算法，主要基于文献【23】给出的评估方法，同时也在计算复杂度上进行了比较，最后综合这两方面提出一个trade-off的比较。
2?Classification?of?cost?aggregation?strategies?主要分为两种：1)The?former?generalizes?the?concept?of?variable?support?by? allowing?the?support?to?have?any?shape?instead?of?being?built?u pon?rectangular?windows?only.2)The?latter?assigns?adaptive?-?rather?than?fixed?-?weights?to?th e?points?belonging?to?the?support.大部分的代价聚合都是采用symmetric方案，也就是综合两幅图的信息。
（实际上在后面的博客中也可以发现，不一定要采用symmetric的形式，而可以采用asymmetric+TAC的形式，效果反而更好）。
采用的匹配函数为（matching?(or?error)?function?）：Lp distance between two vectors包括SAD、Truncated SAD [30,25]、SSD、M-estimator [12]、similarity?function?based?on?point?distinctiveness[32] 最后要指出的是，本文基于平行平面（fronto-parallel）support。
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Web Based Information Architectures 课程之----文本聚类部分的内容第4节 基于划分的文本聚类方法1．对包含n 个文档的文本集合，划分将生成k 个分组，k<=n ，每一个分组代表一个聚类。
聚类的准则函数通常选用平方误差准则：21||i k i i p C E p =∈=−∑∑m 典型的划分方法（Partitioning methods ）:k-平均方法、 k-中心点方法2． k-平均算法step1. 任意选择k 个点作为初始的类的中心step2. repeatstep3. 根据类中文档的平均值,将每个文档(重新)赋给最相近的类step4. 更新类的平均值，step5. until 不再发生变化，即没有对象被进行重新分配时过程结束。
3. 举例： 在ppt 上4． 特点：该算法试图找出使平方误差值最小的k 个划分。
当结果簇是密集的，而簇与簇之间区分明显时，它的效果较好。
算法复杂度O （nkt ），其中 t 是迭代次数。
因此其可扩展性较好，对大数据集处理有较高的效率。
算法常以局部最优结束。
全局最优要穷举所有可能的划分。
缺点： 不适合发现非凸面状的簇。
不适合大小差别较大的簇。
对于噪声和孤立点是敏感的，由于少量的该类数据对平均值产生较大的]影响。
5．k-平均方法有多种变形形式：不同改进在于：初始k个平均值的选择，相异度的计算、计算类平均值。
6．产生较好聚类结果的一个有趣策略：首先用层次聚类方法决定结果簇的个数，并找到初始的聚类，然后用迭代重定位来改进聚类结果。
==================k-中心点（k-modoid）方法1． PAM（partitioning around medoid）是最早提出的k-中心点方法之一。
它选用簇中位置最靠近中心的对象作为代表对象（中心点），试图对n个对象给出k个划分。
最初随机选择k个对象作为中心点，该算法反复用非代表对象（非中心点）代替中心点，试图找出更好的中心点，以改进聚类结果的质量。
在每次迭代中，所有可能的对象对被分析，每个对中的一个对象是中心点，而另一个是非中心点。
对所有可能的组合，估算聚类结果的质量。
一个对象O i被可以使最大平方误差减少的对象代替。
在一次迭代中产生的最佳对象集合成为下次迭代的中心点。
2．判定一个对象O h是否是当前一个代表对象O i的好替代，对每一个非代表对象O j需要分情况考虑替换的代价。
对非代表对象O j来说，上图给出了O h替代O i所化的代价。
遍历所有j即得到总交换代价TC ih。
该代价函数反映了替换前后平方误差值之间的差别。
若总代价为负，O h可以替代O i，否则说明当前的中心点是可接受的，在本次迭代中不发生变化。
3． k-中心点（k-modoid）算法step1. 任意选择k个对象作为初始的类的中心点step2. repeatstep3. 指派每个剩余对象给离它最近的中心点step4. 随机选择一个非中心点O hstep5. 计算用O h代替中心点O i的总代价 Sstep6. if S<0, then O h代替中心点O i形成新的k个中心点集合until 不再发生变化。
4. 算法执行实例5. 算法性能分析有效消除了对孤立点数据的敏感性。
比k-means方法更健壮，不易受极端数据的影响。
PAM对小数据集非常有效（如100个对象聚成5类），但对大数据集效率较低。
可扩展性差。
========PAM算法的改进:CLARA（Cluster LARger Application）: 基于k-medoid类型的算法，能处理较大的数据集合。
首先进行随机抽样，用PAM方法从样本中选择中心点。
如果样本是以非常随机的方式选取的，它应该足以代表原来的数据集合。
从中选出的中心点很可能与从整体集合中选出的非常近似。
1．CLARA可以抽取多个样本，对每个样本应用PAM算法，返回最好的聚类结果。
2．复杂度是O（ks2+k(n-k)）,其中s是样本大小。
3．如果样本发生倾斜，基于样本的一个好的聚类不一定代表整个数据集合的一个好的聚类。
特别地，如果任何取样得到的中心点不包含最佳的中心点，CLARA算法不能得到最佳聚类。
第5节自组织映射 (SOM)S O M的基础:尽管大脑具有大量的细胞，但生物学研究表明作用并不同。
在空间中处于不同位置的脑细胞控制着人体不同部位的运动。
同样，处于不同区域的脑细胞对来自某一方面的刺激信号的敏感程度也不一样。
这种特定细胞对特定信号的特别反映能力似乎是由后来的经历和训练形成的。
Kohonen根据人脑的这一原理提出了自组织映射。
1. 自组织映射 (SOM)SOM（self-organizing map）神经网络是一种基于模型的聚类方法。
SOM是由芬兰赫尔辛基大学神经网络专家Kohonen教授在1981年提出的竞争式神经网络，它模拟大脑神经系统自组织特征映射的功能，在训练中能无监督地进行自组织学习。
由于它的强大功能， 多年来，网络在数据分类、知识获取、过程监控、故障识别等领域中得到了广泛应用。
SOM神经网络由输入层和竞争层组成。
输入层由N个神经元组成，竞争层由M个神经元组成。
竞争层每个神经元与输入层的N个神经元间建立连接；竞争层各个神经元之间按某种方式（网格、六角形、随机拓扑）建立连接。
为可视化表示结果，常将M表示为一个二维平面阵列M=s*t ，当然, 一维或多维也是允许的。
典型的SOM聚类算法步骤可归纳如下：1 初始化，用较小的随机数对竞争层各个神经元的每一个权向量赋初值。
2．用文本集合中选择选择一个训练向量X i 进行输入3．比较竞争层中所有神经元，寻找神经元j ，使它的突融权重向量W j 最接近X i ，即 |X i --W j |=min {|X i –W k |, k=1，…，M}。
4. 修改神经元j 及其邻居神经元，更新它的突融权重(1)()(())k k i k w t w t t X W t α+=+−其中，a(t)为训练参数, 0<a(t)<1，t 为训练次数5．如果训练次数t 的值达到预设次数T ，则停止训练，否则减少a(t)的值，重复2—4步。
注：在训练过程中，随着训练次数t 的增加，a(t)和领域都不断变小。
==============神经元间的不同拓扑结构：1． 矩形结构（网格结构）2．六角形结构3 随机拓扑结构: 具有随机形式分布的神经元拓扑结构神经元之间的距离： 欧几里德距离、位置向量之间距离、Manhattan距离等。
一个例子:m a t l a bp=rands(2,1000);plot(p(1,:),p(2,:), '+r');net=newsom([0 1; 0 1],[5 6] );hold on;net.trainParam.epochs=1;net=train(net, p);plotsom(net.iw{1,1}, yers{1}.distances)hold off;一个具体应用:SOM文档信息地图：把语义相近的文档聚集在一起，并为每个类目自动地分配一个标签来说明这个类目的主题。
X i a L i n（1991）在论文A S e l f-o r g a n i z i n g S e m a n t i c M a p f o r I n f o r m a t i o n R e t r i e v a l中的实例.另一个文档集的结果Kohonen Feature Maps (Lin 92, Chen et al. 97）SOM类似于大脑的信息处理过程。
它能把任意维的输入信号变换到一维或二维的离散网格上，并保持一定的拓扑有序性。
SOM通过对输入向量的反复学习，其权向量的空间分布能反映输入向量的统计特征。
训练结束后，状态相同或相近的输入向量在竞争层网络上所处位置相邻近，采用距离映射法在二维平面上得到的映像点也相邻近，因此，该方法可以正确显示SOM的聚类训练结果。
不足：网络连接权向量初值的选取对网络收敛性影响很大。
第6节聚类结果的评价因为没有训练文档集合，所以评测聚类效果是比较困难的。
常用的方法是：选择人工已经分好类或者做好标记的文档集合作为测试集合，聚类结束后，将聚类结果与已有的人工分类结果进行比较。
文档关联评测及其指标所谓文档关联，是指属于同一个类别的任意两个文档之间所形成的“文档对”关系。
基于文档关联的聚类评测方法，其考察的基本对象就是“文档对”。
各种不同情况下的“文档对”数据主要有：P t: 文档集合中所有可能的文档对的数量。
设文档总数为n，则P t=C n2=n*(n-1)/2. T m: 人工分类中所有可能的文档对的数量。
T a: 聚类结果中所有可能的文档对的数量。
E i: 错误关联，指在聚类结果中出现，而在人工分类中没有出现的文档对的数量。
E m: 遗漏关联，指在人工分类中出现，而在聚类结果中没有出现的文档对的数量。
评测指标：1）。
聚类错误率CE=(错误关联+遗漏关联)/ 文档集合中所有可能的文档对的数量=( E a + E m )/ P t2). 聚类全面率CR=正确关联数/人工分类中文档对的数量=（T a-- E i）/ T m3). 聚类准确率CP=正确关联数/聚类结果中文档对的数量=（T a-- E i）/ T a上述2).和3)对应IR的recall and precision.,他们分别反映聚类方法发现文档间关联的能力和关联的准确程度。