Abstract UbiHand A Wearable Input Device for 3D Interaction
复杂适应系统与分布式卫星系统自主运行
第23卷第9期计算机仿真2006年9月文章编号：1006-9348（2006）09-0023-04复杂适应系统与分布式卫星系统自主运行张健，戴金海（国防科技大学航天与材料工程学院，湖南长沙410073）摘要：以复杂适应系统理论为指导，探讨了基于Agent技术实现分布式卫星系统（DSS）自主运行的研究方法和主要步骤。
目前国内外关于DSS自主运行技术的研究尚处于起步阶段，缺乏系统的理论指导。
该文试图运用复杂适应系统（CAS）理论的思想和方法来指导DSS自主运行技术的研究，并以此扩展CAS理论的应用领域。
首先介绍CAS理论的基本概念和核心思想，然后分析自主运行DSS的控制需求和特征，指出CAS理论用于指导DSS自主运行的必要性和可行性，并给出基于Agent 实现DSS自主运行的整体框架。
关键词：复杂适应系统；智能体；分布式卫星系统；自主运行中图分类号：TP391.9；V423 文献标识码：AComplex Adaptive System and Autonomy of Distributed Satellite SystemsZHANG Jian，DAI Jin-hai（Coiiege of Astronautics&Materiai Engineering，NUDT，Changsha Hunan410073，China）ABSTRACT：Under the instruction of CompieX Adaptive System（CAS）theory，the methods and main steps of Agent-based autonomy of Distributed Sateiiite Systems（DSS）are discussed.Tiii now，study on spacecraft autonomy is stiii in the eariy stage，and is in great need of theoreticai instruction.We try to adopt the ideas and methods of Com-pieX Adaptive System（CAS）theory to research autonomy of DSS，and thereby eXtend the appiication domain of CAS theory.Basic concepts and kernei thoughts of CAS are introduced.Then the controi demands and characteristics of autonomous DSS are anaiyzed.The necessity and feasibiiity of instruction of CAS theory is pointed out.In the end，generai frameworks of Agent-based autonomy of DSS are discussed.KEYWORDS：CompieX adaptive system（CAS）；Agent；Distributed sateiiite system（DSS）；Autonomy引言航天器的自主运行是指利用人工智能等现代控制技术，实现由地面系统到航天器系统的智能移位，使航天器在无人干涉的情况下，实现自我管理并完成各种任务。
四下第二单元作文我的发明
四下第二单元作文我的发明英文回答：I am thrilled to share with you my exceptional invention that has the potential to revolutionize the world of innovation and technology. This extraordinary device, which I have named the "Omni-Versal Quantum Nexus," is a testament to my unwavering passion for pushing the boundaries of human ingenuity.The Omni-Versal Quantum Nexus (OVQN) is a groundbreaking invention that harnesses the untapped potential of quantum mechanics to create a groundbreaking platform for computational power. This remarkable device operates at the atomic and subatomic level, leveraging the principles of superposition and entanglement to perform calculations at an unprecedented speed and accuracy.One of the most significant advantages of the OVQN is its ability to solve complex problems that are currentlyimpossible to address with existing computational methods. By harnessing the power of quantum computing, the OVQN can accelerate scientific discoveries, facilitate medical breakthroughs, and optimize financial models with unparalleled precision.Furthermore, the OVQN is designed to be highly versatile and adaptable to a wide range of applications. This innovative device can be integrated into various fields, including artificial intelligence, cryptography, and materials science, enabling users to explore new frontiers of knowledge and technological advancements.Beyond its practical applications, the OVQN also has the potential to inspire future generations of scientists, engineers, and inventors. This exceptional creation serves as a beacon of possibility, demonstrating that anything is possible with relentless determination and a thirst for innovation.In recognition of its transformative potential, I am eager to collaborate with leading experts in academia,industry, and government to develop the OVQN further and unleash its full potential to shape the future of technology and human progress.中文回答：我的发明，全能量子网络（Omni-Versal Quantum Nexus），是一项具有革命性意义的发明，它将彻底改变创新和技术领域。
全息投影手环的作文英语
全息投影手环的作文英语Title: The Revolutionary Holographic Projection Wristband。
In recent years, technology has advanced by leaps and bounds, bringing forth innovations that redefine the way we perceive and interact with the world around us. Among these remarkable advancements stands the holographic projection wristband, a groundbreaking invention poised to revolutionize the realm of wearable technology. In this essay, we delve into the myriad capabilities and implications of this cutting-edge device.At its core, the holographic projection wristband integrates state-of-the-art holographic technology into a sleek, wearable form factor. Unlike traditional displays, which are confined to flat screens, this wristband projects three-dimensional holograms into the surrounding space, creating an immersive visual experience for the user and those around them.One of the most notable features of the holographic projection wristband is its versatility. Whether it's for entertainment, communication, education, or productivity, the wristband offers a wide range of applications limited only by imagination. Imagine being able to watch your favorite movies or concerts in full 3D, with holographic images appearing as if they were right in front of you. Furthermore, the wristband could serve as a communication tool, allowing users to engage in holographic video calls with friends, family, or colleagues from anywhere in the world.In the realm of education, the holographic projection wristband holds immense potential to revolutionize learning experiences. Imagine students being able to visualize complex concepts in three dimensions, bringing subjectslike biology, physics, and history to life in ways never before possible. With interactive holographic simulations, learning becomes not only more engaging but also more effective, as students gain a deeper understanding of abstract concepts through immersive experiences.Moreover, the wristband could significantly enhance productivity in various fields. For professionals such as architects, engineers, and designers, being able tovisualize and manipulate 3D models directly in front ofthem could streamline the design process and foster greater creativity. In business settings, presentations could become more dynamic and engaging, as speakers use holographic visuals to convey their ideas with impact.Beyond its practical applications, the holographic projection wristband also has the potential to reshape entertainment and social interactions. Imagine attendinglive events where holographic performers interact with the audience in real-time, blurring the lines between thevirtual and the physical worlds. Additionally, thewristband could enable new forms of social media, where users share holographic experiences and engage with each other in immersive virtual environments.Of course, with any new technology, there are also considerations regarding privacy, security, and ethical use.As holographic projections become more commonplace in everyday life, it will be essential to establish clear guidelines and regulations to protect users' privacy and prevent misuse of the technology.In conclusion, the holographic projection wristband represents a paradigm shift in wearable technology, offering a glimpse into a future where interactions with digital content are no longer confined to screens but seamlessly integrated into our surroundings. With its vast potential for entertainment, education, productivity, and social interaction, the wristband heralds a new era of immersive experiences limited only by our imagination. As we continue to push the boundaries of technological innovation, the possibilities presented by the holographic projection wristband are truly limitless.。
华为突破技术封锁自主研发芯片英语作文
Huawei's Breakthrough in Self-Developed Chips: Overcoming Technological BlockadesHuawei has emerged as a global leader in the technology sector, particularly in telecommunications and consumer electronics. However, the company has faced significant challenges due to geopolitical tensions and subsequent technological blockades imposed by various countries. In response to these hurdles, Huawei has made remarkable strides in self-developing its own chips, showcasing its resilience and innovation. This essay explores the significance of Huawei's breakthrough in chip development and its implications for the global tech industry.The imposition of technological blockades on Huawei, particularly by the United States, has created substantial obstacles for the company. These restrictions have limited Huawei's access to critical components and technologies, especially those involving semiconductors and advanced chipsets. As a result, Huawei faced the daunting task of maintaining its competitive edge and ensuring the continuity of its product lines without relying on foreign suppliers.In response to these challenges, Huawei embarked on an ambitious journey towards self-reliance. The company invested heavily in research and development, allocating significant resources to its semiconductor subsidiary, HiSilicon. This strategic move aimed to reduce Huawei's dependence on external suppliers and establish a robust in-house capability for chip design and manufacturing.The breakthrough came with the development of Huawei's Kirin series of processors, which are used in the company’s smartphones and other devices. These chips, designed by HiSilicon, demonstrated competitive performance and efficiency, positioning Huawei as a formidable player in the semiconductor industry. The latest iterations of Kirin chips have showcased advanced features, including artificial intelligence capabilities and 5G compatibility, further cementing Huawei's technological prowess.Huawei's successful development of its own chips has significant implications for the global tech industry. Firstly, it highlights the potential for companies to innovate and overcome external pressures through substantial investment in research and development. Huawei's achievements can serve as an inspiration for other firms facing similar challenges, encouraging them to pursue self-reliance and innovation.Secondly, Huawei's breakthrough underscores the shifting dynamics of the global semiconductor market. Traditionally dominated by a few key players,the market is now witnessing the rise of new contenders from diverse regions. This increased competition can drive further innovation and potentially lead to more affordable and advanced technologies for consumers worldwide.Furthermore, Huawei's advancements in chip technology can contribute to the development of a more resilient global supply chain. By diversifying sources of critical components, the tech industry can reduce vulnerabilities and mitigate the risks associated with geopolitical tensions and trade restrictions.In conclusion, Huawei's breakthrough in self-developing chips represents a significant milestone in the face of technological blockades. Through substantial investment in research and development, the company has demonstrated its resilience and capability to innovate independently. This achievement not only strengthens Huawei's position in the global tech industry but also has broader implications for innovation, competition, and supply chain resilience. As Huawei continues to push the boundaries of technology, it serves as a powerful example of how challenges can be transformed into opportunities for growth and advancement.。
英语抽象类作文模板范文
英语抽象类作文模板范文Abstract Class Essay Template。
An abstract class is a concept in object-oriented programming that serves as a blueprint for other classes. It cannot be instantiated on its own and is meant to be extended by other classes. In this essay, we will discuss the characteristics of an abstract class, its purpose, and its role in the development of software applications.An abstract class is a class that cannot be instantiated, meaning you cannot create an object of the abstract class itself. Instead, it serves as a base for other classes to inherit from. It can contain both abstract and non-abstract methods. An abstract method is a method that is declared but not implemented in the abstract class. It is meant to be implemented by the subclasses that inherit from the abstract class. On the other hand, a non-abstract method is a method that has an implementation in the abstract class itself.The purpose of an abstract class is to provide a common interface for its subclasses. It allows you to define a set of methods that must be implemented by all the subclasses, ensuring that they have a consistent behavior. This is useful when you have a group of classes that share some common characteristics but also have their own unique behavior. By using an abstract class, you can define the common methods in the abstract class and leave the specific implementation to the subclasses.Another important role of an abstract class is to provide a level of abstraction in the design of a software application. Abstraction is a fundamental concept in object-oriented programming that allows you to focus on the essential features of an object while hiding the unnecessary details. By using an abstract class, you can define the essential methods and properties that are common to a group of related classes, while hiding the implementation details from the outside world. This makes the design of the software application more modular and easier to maintain.In addition, an abstract class can also be used to enforce a specific contract on its subclasses. By defining abstract methods in the abstract class, you can require that all thesubclasses provide an implementation for those methods. This ensures that the subclasses adhere to a certain set of rules and guarantees a consistent behavior across the different subclasses.To create an abstract class in a programming language such as Java or C#, you use the "abstract" keyword in the class definition. For example, in Java, you would declare an abstract class like this:```java。
协同过滤算法英语作文
协同过滤算法英语作文Title: Exploring Collaborative Filtering Algorithm。
Introduction:Collaborative filtering algorithm, a cornerstone in recommendation systems, plays a pivotal role in predicting user preferences and providing personalized recommendations. This essay delves into the intricacies of collaborative filtering, its variants, applications, and the challengesit faces.Understanding Collaborative Filtering:Collaborative filtering operates on the principle of leveraging collective user behavior to make recommendations. It doesn't rely on explicit descriptions of items butrather on historical data on user interactions. There are two primary approaches:1. User-Based Collaborative Filtering (UBCF):UBCF recommends items to a target user based on the preferences of similar users. It identifies users with similar tastes through similarity metrics such as cosine similarity or Pearson correlation coefficient.This approach is intuitive and easy to implement. However, it suffers from the "sparsity" problem when dealing with large datasets, where finding similar users becomes challenging.2. Item-Based Collaborative Filtering (IBCF):IBCF recommends items similar to those previously rated highly by the user. It calculates item similarity based on user ratings and suggests items that are most similar to those the user has liked in the past.Compared to UBCF, IBCF often performs better with sparse data, and it is computationally less expensive. However, it requires precomputing item-item similaritymatrices, which can be resource-intensive.Applications of Collaborative Filtering:Collaborative filtering finds applications across various domains:1. E-commerce: Platforms like Amazon and eBay use collaborative filtering to recommend products based on users' browsing and purchasing history.2. Media Streaming: Netflix and Spotify utilize collaborative filtering to suggest movies, TV shows, and songs tailored to users' preferences.3. Social Media: Platforms like Facebook and Twitter employ collaborative filtering to recommend friends, pages, or tweets based on users' interactions and interests.Challenges and Limitations:Despite its effectiveness, collaborative filteringfaces several challenges:1. Cold Start Problem: It struggles to make accurate recommendations for new users or items with limited data.2. Scalability: As the user and item base grows, the computational complexity and storage requirements of collaborative filtering algorithms increase significantly.3. Sparsity: In large datasets, the number of items users interact with is relatively small compared to the total number of items, resulting in sparse user-item matrices.4. Data Privacy: Collaborative filtering relies heavily on user data, raising concerns about privacy and data security.Future Directions:Researchers are actively exploring techniques to address the limitations of collaborative filtering andenhance its performance:1. Hybrid Approaches: Integrating collaborativefiltering with other recommendation techniques likecontent-based filtering or matrix factorization to overcome the shortcomings of individual methods.2. Context-Aware Recommendations: Incorporating contextual information such as time, location, and device to make more relevant and timely recommendations.3. Deep Learning Models: Applying deep learning architectures like neural collaborative filtering to learn intricate user-item interactions and improve recommendation accuracy.4. Privacy-Preserving Mechanisms: Developing techniques to enable personalized recommendations while preserving user privacy through methods like differential privacy or federated learning.Conclusion:Collaborative filtering stands as a cornerstone in recommendation systems, empowering businesses to deliver personalized experiences to users. Despite its challenges, ongoing research and advancements continue to refine collaborative filtering algorithms, making them more effective and adaptable to evolving user preferences and needs.。
美国赛写作模版模板
CONTENTSAbstract (1)Ⅰ Introduction (2)ⅡGeneral Assumptions (3)ⅢKey Terminology (3)ⅣModel Development.......................................................................... (3)4.1 (4)4.1.1 (4)4.1.2 (4)4.1.3 (4)4.2 (5)4.2.1 (5)4.2.2 …………………………………................................................................ .64.2.3 (9)4.3 (9)4.3.1 (9)4.3.2 (10)4.3.3 (10)4.4 (10)4.4.1 (10)4.4.2 (10)4.4.3 (10)4.5 (13)4.5.1 (13)4.5.2 (13)4.5.3 (13)ⅤStrengths and Weakness (14)ⅥConclusion (15)ⅦReferences (16)ⅧAppendix (16)TITLEAbstract♦In our essay, we first develop a basic model to account for the fundamental but important phenomena in baseball game and then three improved models for some details. When developing the basic model, in order to analyze overall hitting process clearly, we focus on simplifying the practical problem into a mechanical model.We resolve basic model through three steps, each step considering one important part of the model that greatly impacts our searching for the “sweet spot”. After resolving the basic model, we begin to revise the model to make it more practical.♦Before resolving the basic model, we establish a criteria for evaluation-the proportion of effective energy transmission r, a criteria used to determine at which spot of the bat the maximum proportion of energy output by human is transferred to the ball. Our three steps are designed as follows:⑴In our first step, we mainly investigate the action process between the simplified baseball bat andbaseball. Ignoring other influencial factors, we find one “sweet spot”.⑵In our second step, our focus moves to the relationship between the hand and the bat. Ignoringother influencial factors, we find another “sweet spot”.⑶In our last step, we integrate merits of each “sweet spot ” in above two steps so that we find out a“sweet spot zone”. Then we figure out the variation of r in “sweet spot zone”and find the maximum r.♦After resolving the basic model, we revise our model in three aspects to make it more practical.⑴In our first improvement, we restore the simplified line and particle with objects of different shapeand find out the “sweet spot”after revision.⑵In our second improvement, we consider the shape change of the baseball bat when the bat hits theball and also calculate the lost energy consumed by the shape change of bat made of different material.After revision, we find that the position of the practical “sweet spot”should be a bit more closely than that of “sweet spot”calculated in basic model to the thin end of the bat.⑶In our last improvement, we take into account the vibration that might also impact our searchingfor the “sweet spot”.After detailed analysis, we calculated the lost energy consumed by vibration when the ball hits different spot on the bat and figure out that the position of the practical “sweet spot”should also be a bit more closely than that of “sweet spot”calculated in basic model to the thin end of the bat.♦ⅠIntroductionOn the softball field, hitters usually attempt their best to hit the baseball.In addition to the physical strength the player applied to the baseball, the hitting spot also has great influence on our searching for the sweet spot. Usually, according to the moment of momentum theorem, it seems that the fat end of the baseball bat should be the best hitting spot. However, this is known to be empirically incorrect. Experienced player usually chooses a spot called “sweet spot”to be the best hitting spot, at which the maximum power is transferred to the baseball, thus the hit ball travelling the longest distance. Howard Brody(1989) conducted a series of experiments and investigated that vibration of the baseball would affect the choice of the best hitting spot. Rod Cross(1998) proved that both center of percussion and vibration of the bat affect the searching for the sweet spot through a series of experiment. However, none of scientistshas given a theoretical method to find out the solution. In our essay, we attempt to find out and explain that the sweet spot does not lies on the end of the bat.ⅡGeneral Assumption♦The baseball and baseball bat are assumed to move at uniform velocity. Air friction and gravity can be neglected♦The direction of the velocity of the particle is assumed to collinear that of the linear veloc ity of the action point.♦Baseball bats made of different materials are assumed to attain identical energy after accelerated by human.ⅢKey TerminologyTable 1.Symbols.Symbols Description UnitsⅣModel Development4.1 Simplifying the situationIn order to address the problem, we need to simplify the hitting process. It is reasonable to abstract the process as follows: replacing the baseball bat with a single line, on which the mass is distributed uniformly, and substituting a particle for the baseball; fixing one end of the line so that the line can oscillate on the smooth ground freely; using the process that a baseball hits an oscillating rod to simulate the process that a baseball hits a bat.This is the basic and simplest model that we can extract from hitting process, based on which we can analyze the most basic motion of these two objects. However, we cannot ignore the importance of the elasticity, the vibration and the antihunt action, which might also have impact on our searching for the sweet spot.4.1.1 Basic ModelWe analyze the whole hitting process:Step oneAt the beginning of hitting, the particle moves at a fixed velocity to the line that is oscillating at a fixed angular velocity and linear velocity. The moment of the momentum of the overall system with respect to o is:1112o L m v d J ω=-+, (1) After the hitting, the particle and the line separate and move respectively. The moment of the momentum ofthe overall system with respect to o is2112o L m v d J ω''=+As exterior impulsive moment vanishes, we can then get:12o o L L =that is112112m v d J m v d J ωω''-+=+ (2) Given the material of the line and the particle, we can achieve the coefficient of the restitution between the line and the particle, a coefficient that will help us to achieve the relationships of the linear velocity of the line and the particle.1212v v k v v ''-=+ (3)22v d ω= , 22v d ω''= (4)Putting .Eq (1),(2),(3)and (4) together, we have junctions()221122121221233d m v l m v k v v v m d m l-+++⎡⎤⎣⎦'=+ (4) ()22111222222123133d k m v d km L m d m l m ωωω-+-+'=+ (5)When considering at which spot of the line the maximum power is transferred to the particle, we attempt to work out a spot at which the hit particle reaches the fastest velocity. Differentiating 1v 'with respect to d , we will achieve that when123d m ω=(6)the hit particle reaches the fastest velocity. We just define this spot as the spot of moment(SOM).Step twoIt is necessary for us to take the function of the hands into account if we want to simulate the hitting process exactly. At the instant of hitting the particle, the impulse of the particle will rotate the line unless the particle hits a specified spot on the line-the center of percussion(COP) at which the impulse will only move the translationally with no rotation. According to the momentum theorem()22221111122ox I m l m l m v v ωω''=--+ (7)If the particle hits the COP exactly, the momentum theorem o x I should be 0. Inserting .Eq (4) and (5) into .Eq (7)leads to equation:()()()1212212132062w k d l lm mvd d m l m ω+-+=+ (8)Because all of the parameters in .Eq (8)are greater than 0, only under condition that 320d l -= can the .Eq (8) result in a proper solution. Then we can know the position of the COP:23C O P d l =(9)Step threeAccording to the investigation of ……..(), if viewing hand as soft tissue, we can get the relationship between the force pressed on the tissue and the degree at which the hands ’ shape changes012aseF a-= (10)where♦ 0F represents the force pressed on hands♦ s denotes the relative displacement of the point on palm♦ b and c are constants which have been discussed in !!!!!!!!!!!!!!!!!!!!!!!!!文献As the the force pressed on palm generates the relative displacement, the hand apply negative force on the line, thereby absorbing part of the energy transferred from our arms to the particle. We can easily figure out the lost energy through definite integral:100s w F ds =⎰(11)212ase asa-+-=At the instant of hitting, the energy transferred from the line to the particle is:22222221126w J m l ωω== (12)The energy achieved by the particle is:22011111122w m v m v '=- (13) To transfer the maximum proportion of power output from the human body to the particle, we define this proportion as12w p w w =+ (14)Plugging .Eq (4),(5),(10),(11),(12),(13) into .Eq (14),we have()()()2222211121222112222122231122310.3672as m d m v K l m v dl m K m v d m l mp easaωω-+++-++=-+-+空As the value of p varies when the hitting spot on the rod changes, the variation of p with respect to0d and K is pictured in Fig.14.1.2 Improvement ⅠWith the purpose of improving the practicability, we have to restore the single line and the particle with bodies of axisymmetry (In effect, both the baseball and the bat are axisymmetry). In this way, our model more closely resembles the real hitting process. In this situation, we regard the two bodies as rigid bodies. Unlike the moment of inertia of a line, the moment of inertia of the bat has to be calculated through definite integral. Since we cannot attain the equation of the generating line of the equation, here is an example to compute the moment of inertia of a circular cone to illustrate our methods.In practice, the motion state of an axisymmetrical body, the mass of which is distributed uniformly, is usually equivalent to that of its axis line, on which the mass of the body concentrates. However, the mass is unevenly distributed on the axis line. By computing the moment of inertia of the axis line, we will reach the same result as calculating the moment of inertia of the circular cone. Like circular cone, all of the axisymmetrical bodies can also be figured out in this way.4.1.4 Improvement ⅡAssume that the ball is completely elastic and the energy dissipation mainly stems from the deformation of the bat. As suggested by Adair (2002), the hitting between the bat and the baseball can be reasonably modeled by a ball and a flat without introducing large error. This collision can be simply described as Figure 1. Denoting by R the radius of the ball and by δ the depth of the indentation, the equation of the sphere, on the surface of contact, is[]222()r z R R δ++-= (14)Figure 1. The indentation by a baseball.For shallow indentations /1R δ and /1z R , where in the second inequality the coordinate z is meant to be on the indented surface. According to Asaro and Lubarda (2006), the distributed force takes theform1/2202()1r q r q a ⎛⎫=- ⎪⎝⎭ (15)The total hitting force is1/22200202213a r P q rdr a q a ππ⎛⎫=-=⎪⎝⎭⎰(16)The displacement of the indented surface is given as22212a r w R a ⎛⎫=- ⎪⎝⎭r a ≤ (17) or alternatively, in terms of the depth δ of the indentation,22rw Rδ=-r ≤ (18)Consequently, the energy bat E absorbed by the bat can be expressed as4200232d 55a bat q a a P E qwr r RRππ==⎰(19)4.1.4 Improvement ⅢBy employing the d ’Alembert ’s Principle, one gets the equilibrium equation:()()22,s s s F y x dx F F dx f x t dx t x ρ∂∂⎛⎫=-++ ⎪∂∂⎝⎭(20)where()x ρdenotesthe quality of the unit lengths F is shear force(),f x t is external excitation.Here the shear deformation and the rotation of the cross section are neglected. The small element satisfies the momentum balance which requires(),02s Mdx M dx M F dx f x t dxx ∂⎛⎫+---= ⎪∂⎝⎭(21)Droping the high order small quantity yieldss M F x∂=∂ (22)According to the mechanics of materials, the moment relates the deflection by:()()()2,,y x tM x t E I x x∂=∂ (23) Inserting .Eq (22) and (23) into (21) leads to:()()()()()222222,,,y x t y x t EI x x f x t x x t ρ⎡⎤∂∂∂+=⎢⎥∂∂∂⎣⎦(24)The dynamic equation (24) provides unified theoretical framwork for considering the vibration arbitrayrod or beam. When the rod is uniform, in both quality and shape, the .Eq (24) reduces to()()()4242,,,y x t y x t EIfx t xtρ∂∂+=∂∂ (25)Under our current interest, namely, the hitting between the baseball and the rod, the impulse reads()(),,0F x d tfx t δ⎧-=⎨⎩(26)Where F represents the impulse force By writing()()(),y x t x q t φ=we have()()()2200qt q t E I x ωφωρφ⎧+=⎪⎨''''-=⎪⎩(27) ()()()440x x φβφ-= (28)Obiviously, the solution of ()q t is()()sin q t A t ωθ=+ (29)The homogeneous solution of (27)is()1234cos sin cosh sinh x c x c x c x c x φββββ=+++ (30) Where ()1,2,3,4i c i =are constants which are yet to be determined by following boundary conditions:()()()()()00, 000EI K l l φφφφφ'''=-=⎧⎪⎨'''''==⎪⎩(31) From .Eq (31),we obtain the frequency equation()()()()()()c o s h s i n c o s s i n h 0K l K c o n s l E I l E I l l βββββββ+⋅+-= (32)If 0K =, .Eq (32) reduces tot a n t a n h l l ββ=(33)Normalizing .Eq (32)as:()()()()()00cosh cos sin cos sinh 0K l K l l l l βββββ++-=⎡⎤⎣⎦ (34)with 0K K EI β=Assigning K with a certain value ranged from 0 to 1, we attempt to find out the numerical solution offrequency.The variation of .Eq (34) with respect to l β is illustrated in Fig.1. As can be seen from the figure, the first two-oder frequencies are 3.87701 and 7.01587, respectively, when 0.1K =.重画图4.2 Model ⅡBecause wood has been removed from the bat and replaced by some substance with a s maller density than the wood, not only is the bat lighter, but the center of the gravity of the bat moves closer to the thin end. Since center of percussion(COP) and is relavant to the center of the gravity , the COP also movesJ M α=212t t ωαϕα=⎧⎪⎨=⎪⎩22αϕω⇒= We can get the mechanical energy of the bat:212E J ω=122E J J αϕαϕ=⋅=E Mϕ=4.2.14.2.24.2.34.3 Model Ⅲ4.3.14.3.24.3.34.44.4.14.4.24.4.34.54.5.14.5.24.5.3ⅤStrengths and WeaknessesStrengths♦Our basic model’s strength is that we consider the whole process of energy transmission, energy from hand to bat to baseball.♦We view the palm of the hand as soft tissue and consider the shape change of the hand so that we can model the strengths the hand press on the bat.♦The improvement in basic model take into account the energy loss from vibration, and we develop the “simple support and spring” model to model the function of human hand.♦We consider and compute the lost energy consumed by the shape change of the bat.WeaknessesSince neglecting the data of several parameters in the model, we have difficulty in deducing a perfect solution. We introduce some examples so as to illustrate our method.ⅥConclusionⅦReferencesⅧAppendix。
英语抽象类作文模板
英语抽象类作文模板Abstract Class Essay Template。
Introduction。
An abstract class is a concept in object-oriented programming that serves as a blueprint for other classes. It cannot be instantiated on its own and often contains abstract methods that must be implemented by its subclasses. In this essay, we will explore the features and uses of abstract classes, as well as their advantages and disadvantages.Definition and Purpose。
An abstract class is a class that cannot be instantiated, meaning you cannot create an object of that class. It is designed to be a base class for other classes to inherit from. The main purpose of an abstract class is to provide a common interface for its subclasses. It can contain both abstract and non-abstract methods, and it may also have member variables.Features of Abstract Classes。
英语作文-虚拟现实技术应用于游戏开发,打造沉浸式体验
英语作文-虚拟现实技术应用于游戏开发，打造沉浸式体验The advent of virtual reality (VR) technology has revolutionized the gaming industry, offering players an unprecedented level of immersion. By simulating as many senses as possible, such as vision, hearing, touch, and even smell, VR games transport players into vivid virtual worlds where they can interact with the environment in a way that was once the stuff of science fiction.The core of VR's allure lies in its ability to create a sense of presence, the feeling that one is actually "inside" a digital environment. This is achieved through the use of head-mounted displays (HMDs), which track the user's movements and adjust the perspective accordingly, creating a 360-degree sphere of perception. When combined with spatial audio and haptic feedback devices, the illusion of reality is enhanced, tricking the brain into believing the virtual experiences are real.Game developers are leveraging VR to craft experiences that are not just games but journeys. For instance, adventure games in VR can include climbing virtual mountains, exploring deep-sea environments, or navigating through fantasy landscapes. The player's physical actions, such as reaching out to grab objects or ducking to avoid obstacles, become part of the gameplay, making the experience more engaging and interactive.One of the challenges in VR game development is creating intuitive user interfaces that can be operated within the VR environment without breaking the sense of immersion. Developers are experimenting with gesture-based controls, voice commands, and even eye-tracking to create a seamless interaction between the player and the game.Another significant aspect of VR gaming is the social experience. Multiplayer VR games allow players to interact with each other in a shared virtual space, providing a platform for collaborative and competitive play. This social dimension adds a layer of complexity to game design, as developers must create virtual spaces that facilitate natural and intuitive interactions among players.The potential applications of VR in gaming are vast and varied. From educational games that can simulate historical events to therapeutic applications that can help people overcome phobias, the possibilities are as limitless as the imagination of the developers. As VR technology continues to evolve, with improvements in graphics, latency, and affordability, it is poised to become an integral part of the gaming landscape.In conclusion, VR technology is not just enhancing the gaming experience; it is redefining it. By offering an immersive experience that engages the senses and blurs the line between the virtual and the real, VR is setting a new standard in interactive entertainment. As the technology matures, we can expect to see even more innovative uses of VR in game development, further solidifying its role in the future of gaming.。
全息投影手环的作文英语
全息投影手环的作文英语英文：As a tech enthusiast, I have always been fascinated by the idea of holographic technology. And when I first got my hands on a holographic projection bracelet, I wasabsolutely blown away by its capabilities. The holographic projection bracelet, or "hologram wristband" as some people call it, is a revolutionary piece of technology that hasthe potential to change the way we interact with the world around us.One of the most amazing things about the holographic projection bracelet is its ability to project 3D images and videos right onto the user's wrist. This means that you can literally have a holographic display right in front of your eyes, without the need for any bulky screens or devices. Imagine being able to watch a holographic movie or play a holographic game, all from the comfort of your own wrist.It's like something straight out of a science fiction movie!But the holographic projection bracelet isn't just about entertainment. It also has practical applicationsthat can make our lives easier and more convenient. For example, imagine being able to project a virtual keyboard onto your wrist, allowing you to type and send messages without needing a physical keyboard or touchscreen. Or imagine being able to project a map or directions right onto your wrist, making it easier to navigate and find your way around.Of course, the holographic projection bracelet is still in its early stages, and there are some limitations to its capabilities. For example, the quality of the holographic images and videos is not yet as high as traditional displays, and the battery life of the bracelet can be quite limited. However, as technology continues to advance, these limitations are likely to be overcome, and we may soon see holographic projection bracelets becoming a common and indispensable part of our daily lives.In conclusion, the holographic projection bracelet isan incredibly exciting piece of technology that has the potential to revolutionize the way we interact with the world around us. Its ability to project 3D images andvideos right onto the user's wrist is truly mind-blowing, and its practical applications are endless. I can't wait to see how this technology develops in the future, and I'm excited to be a part of the holographic revolution.中文：作为一个科技爱好者，我一直对全息技术的概念深感着迷。
抽象类英语作文
抽象类英语作文Abstract ClassAbstract class is a concept in object-oriented programming that allows us to create a class which cannotbe instantiated on its own. It serves as a base for other classes to inherit and provides a common interface for all the derived classes.The main purpose of an abstract class is to define a blueprint for other classes to follow. It contains abstract methods, which are methods with no implementation, and concrete methods, which have an implementation. Theabstract methods must be implemented by the derived classes, while the concrete methods can be used as they are or overridden.One key feature of an abstract class is that it cannotbe instantiated. This means we cannot create an object ofan abstract class directly. Instead, we need to create a subclass that extends the abstract class and theninstantiate the subclass.Another important aspect of abstract class is that itcan have member variables just like a regular class. These member variables can be inherited by the subclasses andused as per their requirements.In Java, we use the "abstract" keyword to declare an abstract class. Any class that contains at least oneabstract method must be declared as an abstract class. We also use the "extends" keyword to create a subclass that inherits from the abstract class.In conclusion, abstract class is a powerful tool inobject-oriented programming that allows us to define a common interface for a group of related classes. It helpsin achieving abstraction and reusability in our code, making it easier to maintain and extend our software system.抽象类抽象类是面向对象编程中的一个概念，允许我们创建一个不能单独实例化的类。
仿生假肢英语作文
仿生假肢英语作文Bionic prostheses, also known as bionic limbs, are artificial limbs that are designed to mimic the function and movement of natural limbs. These advanced prostheses are a result of the rapidly advancing field of bionics, which combines biology and electronics to create innovative solutions for people with limb loss.Bionic prostheses are a significant advancement in the field of prosthetics, as they offer a level offunctionality and natural movement that was previously unattainable with traditional prosthetic limbs. These bionic limbs are equipped with sensors and microprocessors that enable them to detect and respond to the user's movements, allowing for a more natural and fluid range of motion.One of the key features of bionic prostheses is their ability to provide sensory feedback to the user. This means that the user can feel and control the movement of theprosthesis in a way that closely resembles the sensation of using a natural limb. This sensory feedback is made possible through the use of advanced technologies such as myoelectric sensors, which detect the electrical signals produced by the muscles in the residual limb and translate them into movement commands for the prosthesis.In addition to providing enhanced functionality, bionic prostheses also offer a more natural appearance. The use of advanced materials and design techniques allows for the creation of prosthetic limbs that closely resemble the shape and texture of natural limbs. This not only helps to improve the user's self-esteem and confidence but also reduces the stigma associated with using a prosthetic limb.Furthermore, bionic prostheses are constantly evolving, with ongoing research and development leading to new and improved designs. For example, recent advancements in the field of bionics have led to the development of bionic limbs that can be controlled using brain-computer interfaces, allowing for even greater levels of control and functionality.The impact of bionic prostheses on the lives of amputees cannot be overstated. These advanced prosthetic limbs have the potential to significantly improve thequality of life for individuals with limb loss, enabling them to regain independence and participate in activities that were previously out of reach. Whether it's walking, running, or engaging in sports and recreational activities, bionic prostheses empower users to live life to the fullest.In conclusion, bionic prostheses represent a groundbreaking advancement in the field of prosthetics, offering enhanced functionality, natural appearance, and a potential for greater independence for individuals withlimb loss. As the field of bionics continues to advance, we can expect to see even more impressive innovations in the development of bionic prostheses, further improving thelives of those in need.。
全自动智能笔这篇英语作文
全自动智能笔这篇英语作文英文回答：The Full-Automated Intelligent Pen.Intelligent pens are the latest advancement in the realm of writing technology. They are designed to provide a seamless and enhanced writing experience by incorporating advanced features and functionalities. One of the most notable innovations in this category is the full-automated intelligent pen. This pen takes automation to a whole new level, offering a range of capabilities that streamline the writing process and make it more efficient and enjoyable.Key Features:Real-Time Translation: The pen is equipped with abuilt-in translation engine that can instantly translate handwritten text into over 100 different languages. This feature is particularly useful for individuals who workwith multiple languages or frequently travel to different countries.Voice Recording and Transcription: The pen features a voice recording function that allows users to capture audio notes while they write. The pen then automatically transcribes the audio recordings into text, saving users the time and effort of manually typing out their notes.Digital Note-Taking: The pen can be connected to a smartphone or tablet, allowing users to seamlessly transfer their handwritten notes to digital format. This eliminates the need for manual transcription and makes it easy to organize, search, and share notes with others.Smart Search Function: The pen has a built-in search function that enables users to quickly search for information related to their writing. This feature is powered by an advanced AI engine that provides relevant results from various online sources.Gesture Control: The pen supports gesture control,allowing users to perform various actions such as scrolling, zooming, and selecting text with simple hand gestures. This feature enhances the overall user experience and makes the writing process more intuitive.Benefits:Enhanced Productivity: The full-automated intelligent pen significantly improves productivity by eliminating the need for manual translation, transcription, and note-taking. This allows users to focus more on the content they are writing and less on the mechanics of writing.Increased Accuracy: The pen's built-in translation and transcription features ensure high levels of accuracy, reducing the risk of errors and misunderstandings. This is particularly important for individuals who work with sensitive or confidential information.Improved Collaboration: The digital note-taking capabilities of the pen make it easy for users to sharetheir notes with others, fostering collaboration andknowledge sharing within teams or organizations.Time Savings: The pen's automation features save users a substantial amount of time by eliminating tedious and repetitive tasks. This allows them to dedicate more time to other important activities and projects.Enhanced Writing Experience: Overall, the full-automated intelligent pen provides a more convenient, efficient, and enjoyable writing experience. It empowers users to write with confidence, knowing that their words are being accurately translated, transcribed, and storedfor future reference.Conclusion:The full-automated intelligent pen is a revolutionary tool that transforms the writing process. Its advanced features and functionalities offer a range of benefits that enhance productivity, accuracy, collaboration, and time savings. By leveraging the power of technology, this pen empowers users to write with greater efficiency andconfidence, enabling them to focus on the substance of their work rather than the mechanics of writing.中文回答：全文自动化智能笔。
纳米多功能手环作文
纳米多功能手环作文英文回答：A nanotechnology multifunctional bracelet is a wearable device that is equipped with various advanced features and capabilities. It is designed to enhance our daily lives by providing convenience, health monitoring, and communication functions.Firstly, the nanotechnology multifunctional bracelet serves as a personal assistant. It can sync with our smartphones and provide notifications for incoming calls, messages, and social media updates. This feature allows us to stay connected with our friends and family without constantly checking our phones. For example, when I am in a meeting, I can discreetly glance at my bracelet to see if there are any urgent messages or calls that require my attention.Secondly, the bracelet incorporates health monitoringfeatures. It can track our heart rate, sleep patterns, and even blood pressure. This information is valuable for maintaining a healthy lifestyle. For instance, if my heart rate is consistently high during exercise, the bracelet can alert me to take a break and avoid overexertion. Additionally, the bracelet can remind me to stand up and stretch if I have been sitting for too long, promoting better posture and reducing the risk of sedentary-related health issues.Furthermore, the nanotechnology multifunctional bracelet can also function as a mobile payment device. With the integration of near-field communication (NFC) technology, it allows us to make contactless payments at various stores and establishments. This feature eliminates the need to carry multiple cards or cash, making shopping more convenient and secure. For example, I can simply tap my bracelet on the payment terminal to complete a transaction, without the hassle of searching for my wallet or entering a PIN.In addition to its practical functions, the braceletcan also be customized to suit our personal style and preferences. It comes in various designs and colors,allowing us to express our individuality. Moreover, the bracelet can be paired with different bands and accessories to match different outfits and occasions. This versatility makes it a fashionable accessory that complements ouroverall look.中文回答：纳米多功能手环是一种可穿戴设备，具备各种先进的功能和能力。
英语作文设计一款可穿戴设备作文
英语作文设计一款可穿戴设备作文English: Wearable devices have become increasingly popular in recent years due to their convenience and functionality. As a response to this trend, I would design a wearable device that combines the features of a smartwatch and a fitness tracker. This device would not only track the user's daily activities such as steps taken, calories burned, and heart rate, but also provide smartwatch functions such as notifications for calls, messages, and calendar events. In addition, it would have a sleek and stylish design with customizable straps to suit different styles and preferences. Another unique feature of this wearable device would be the integration of a GPS system for accurate location tracking during outdoor activities. Overall, this innovative wearable device aims to seamlessly blend fashion and functionality to enhance the user's daily life.中文翻译: 近年来，由于其便利性和功能性，可穿戴设备变得越来越受欢迎。
超凡智能笔作文
超凡智能笔作文The concept of superintelligent writing with an AI pen has sparked both excitement and concern among people around the world.超级智能书写与AI笔的概念在全世界引起了人们的兴奋和关注。
On one hand, the idea of having a tool that can instantly generate well-written essays, articles, and other forms of content is incredibly appealing.一方面，拥有一种可以立即生成写作文章、论文和其他形式内容的工具的想法非常吸引人。
Imagine the time and effort that could be saved by simply speaking or typing out your ideas and having them transformed into polished, articulate pieces of writing in a matter of seconds.想象一下，通过简单的讲话或打字表达出你的想法，然后将它们在几秒钟内转化为完整、清晰的文字，可以节省多少时间和精力。
However, there are also valid concerns about the potential consequences of relying too heavily on AI for writing tasks.然而，对于过度依赖AI进行写作任务可能带来的潜在后果也存在着合理的担忧。
Firstly, there is a fear that the use of such technology could lead to a decline in the overall quality of writing and communication skills.首先，人们担心使用这种技术可能导致写作和沟通技能整体质量的下降。
人工智能时代的真实和虚假英语作文素材
人工智能时代的真实和虚假英语作文素材英文回答：In the age of artificial intelligence (AI), discerning between reality and falsehood becomes increasingly crucial. As AI-powered tools proliferate, they present both opportunities and challenges in terms of authenticity and accuracy.One primary concern is the spread of "deepfakes" —highly realistic videos or images that have been manipulated to deceive viewers. These can be used to create false narratives, damage reputations, or spread misinformation. With AI systems able to generate convincing text and audio, the boundaries between truth and fiction become even more blurred.However, AI can also be harnessed to combat these challenges. Natural language processing (NLP) algorithms can identify patterns and inconsistencies in text, helpingto detect fraudulent content. Image analysis techniques can expose deepfakes by detecting subtle anomalies or inconsistencies.But beyond technological solutions, it is essential to foster critical thinking skills and media literacy in society. Individuals need to be equipped to evaluate information critically, considering its source, context,and potential biases. They should also be aware of the capabilities and limitations of AI systems.By embracing a nuanced approach that combines technological advancements with human judgment, we can navigate the complexities of the AI era and ensure thattruth prevails.中文回答：在人工智能时代，辨别真实与虚假变得越来越重要。
电子不能替代手写的英语作文 范文模板
电子不能替代手写的英语作文范文模板In today's digital age, the allure of electronic devices is undeniable. From smartphones to tablets to laptops, these gadgets have become ubiquitous in our daily lives, offering convenience and efficiency at our fingertips. However, amidst this technological revolution, one question remains contentious: can electronics truly replace the art of handwriting in English composition?At first glance, the idea of electronic devices replacing handwriting seems plausible. After all, typing on a keyboard is faster and more convenient than painstakingly forming each letter by hand. With spell checkers and grammar correction tools readily available, the likelihood of making errors diminishes significantly. Additionally, the ability to easily edit and revise text on a digital platform provides a level of flexibility that traditional pen and paper cannot match.Yet, despite these advantages, there are inherent qualities to handwritten English compositions that electronic devicescannot replicate. One such quality is the personal touch that handwriting imparts. When we write by hand, our unique penmanship reflects our individuality, adding a personal flair to our compositions. Each stroke of the pen carries with it a piece of our identity, making handwritten texts feel more intimate and authentic.Moreover, the act of handwriting engages differentcognitive processes than typing. Studies have shown that writing by hand stimulates areas of the brain associated with creativity and critical thinking. The tactile feedback of pen on paper fosters a deeper connection to the words being written, allowing for greater concentration and retention of information. In contrast, typing on a keyboard can feel mechanical and detached, lacking the sensory richness of the handwritten experience.Furthermore, handwriting plays a crucial role in the learning process, especially for language acquisition. When students write by hand, they are forced to actively engage with the language, processing and internalizing the words and grammar rules as they write. This process aids inmemory retention and comprehension, leading to a deeper understanding of the English language.Additionally, handwriting promotes better motor skills and hand-eye coordination, particularly in young learners. The physical act of forming letters and words helps develop fine motor skills, which are essential for tasks such as writing, drawing, and even typing. By neglecting handwriting in favor of electronic devices, we risk depriving students of this fundamental aspect of their development.Furthermore, there is a nostalgic charm to handwritten English compositions that cannot be replicated by electronic means. The sight of a handwritten letter or essay evokes a sense of warmth and authenticity that is often lost in the digital realm. In an age dominated by screens and pixels, the handwritten word serves as a tangible reminder of our humanity, preserving a connection to our past and traditions.In conclusion, while electronic devices offer undeniableadvantages in terms of speed and efficiency, they cannotfully replace the art of handwriting in English composition. Handwriting adds a personal touch, engages different cognitive processes, aids in language acquisition, promotes motor skills development, and preserves a sense of authenticity and tradition. Therefore, while technology has its place in the modern world, we must not overlook the enduring value of pen and paper in the realm of English writing.。
基因检测英语作文
基因检测英语作文题目：Personalized Medicine Unfolded: The Power of Genetic TestingGenetic testing, a remarkable advancement in modern medical science, is transforming healthcare with its ability to delve into the intricate blueprint of life encoded in our DNA. This innovative technology enables us to peek into the biological foundation of who we are and how we may respond to various health challenges.Imagine untying the mystery of life from a single drop of blood. Genetic testing does precisely that—it extracts the DNA from cells, decodes the complex genetic sequences, and pinpoints variations that can potentially influence our health. These tests provide a wealth of information, ranging from identifying inherited conditions, predicting the likelihood of developing certain diseases, to guiding personalized treatment plans for illnesses like cancer or even lifestyle choices to mitigate disease risks.Take, for instance, a scenario where a family with a history of breast cancer undergoes genetic testing. By analyzing specific genes such as BRCA1 and BRCA2, experts can determine if an individual is a carrier of mutations linked toincreased risk. This knowledge empowers them to make informed decisions about preventive measures, including early screening and possibly prophylactic surgery.Moreover, genetic testing is pivotal in prenatal care, allowing parents-to-be to understand the genetic makeup of their unborn child, thereby detecting chromosomal abnormalities or inherited disorders early on. It aids in preparing families and healthcare providers for necessary interventions and support.In the realm of pharmacogenomics, genetic testing helps tailor drug prescriptions according to an individual's genetic makeup. This means doctors can now predict how well a patient will respond to a medication, minimizing adverse reactions and maximizing therapeutic benefits.Despite its groundbreaking potential, genetic testing raises ethical and privacy concerns. It is crucial to ensure that results are handled sensitively, with appropriate counseling provided to interpret and cope with the outcomes. The dissemination of accurate information and guidelines for genetic testing, as well as establishing robust regulations, are essential to protect patients' rights and prevent misuse.genetic testing represents a profound shift towardsprecision medicine, where prevention and treatment strategies are customized to the unique genetic makeup of each person. It's a powerful tool that, when wielded responsibly, can illuminate the path to healthier futures and contribute significantly to the ongoing evolution of personalized healthcare. Through this lens, we witness not just the science of genetics, but the art of crafting a future where healthcare is as individualized as the very genomes it serves to understand.。
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UbiHand:A Wearable Input Device for3D InteractionFarooq Ahmad∗University of Alberta Edmonton,CanadaPetr Musilek†University of Alberta Edmonton,CanadaAbstractIncreasing interest in virtual and augmented reality is encouraging the development of unobtrusive,intuitive input interfaces for ges-ture recognition and3D interaction.Current approaches require the user to wear instrumented gloves,or rely onfixed cameras that lack precisefinger tracking.The UbiHand is an input device that uses a miniature wrist-worn camera to trackfinger position,provid-ing a natural and compact wearable input interface.A hand model is used to generate a3D representation of the hand,and a gesture recognition system can interpretfinger movements as commands. 1IntroductionHand gesture interface development has followed two paths:data-glove based approaches which require the user to wear instru-mented gloves;and machine vision based approaches that use a fixed camera placed in front of the user to segment the hands and determine hand position using a kinematic model.Glove based ap-proaches incorporate severalflex sensors to provide accurate mea-surements of the bending of eachfinger joint,but are cumbersome and expensive.On the other hand,vision based approaches do not require the user to wear any special equipment.However,video based motion capture using afixed camera generally provides less precisefinger tracking,and restricts the users movement to the cam-eras’field of view.The approach described here is a fusion of the two approaches;a wrist-worn camera is used to determine the position of eachfin-ger using skin color segmentation,and thefinger tracking data is used to generate a3D model of the hand.The system can record 10degrees of freedom of motion,corresponding to theflexion and abduction of fourfingers(8DOF),and wrist pitch and yaw(2DOF). The device can be trained to recognize hand gestures to switch be-tween modes;for example,object selection and manipulation,and drawingmodes.Figure1:The prototype system and kinematic hand model.BendB=1.5∗e-mail:farooq@ualberta.ca†e-mail:musilek@ece.ualberta.caFigure2:Hand Motion Capture and Generated Model2System OverviewIn[Ahmad and Musilek2006],a text input device based on a wristworn camera is described.The work described here extends the ap-proach to include a hand model and3Dfinger pose estimation,foruse within virtual and augmented reality environments.The proto-type system is shown infigure1.A wireless color camera is wornunder the users’wrist and continuously tracksfinger motion.Thehand contour is extracted from the images by skin color discrim-ination.After applying morphological operators to remove noise,the peaks and valleys of the hand contour are recorded,correspond-ing to the fourfingertips and metacarpal joints visible within thecameras’field of view.Finger motion constraints allow the deter-mination of the abduction angle(side-to-sideflexion)of eachfinger,as well as the most likely bend angles of the metacarpophalangeal(MCP),proximal interphalangeal(PIP)and distal interphalangeal(DIP)joints.More specifically,the hand model illustrated on theright side offigure1illustrates the relative bending constraints ofeach joint,and considers bend angles to be directly proportionalto the image distance v between the metacarpal joint andfingertip.Using this model,thefinger pose is determined and used to controla virtual hand model as shown infigure2.In addition tofinger tracking,a2D marker integrated into the wrist-band allows hand tracking in three dimensions using an additionalcamera.The second camera can be static,or integrated into a headmounted display,allowing use of the system as a3D input devicefor augmented reality applications.Gesture recognition allows the user to input discrete data such astext and commands.Thefingers are tracked continuously,and rapidfinger movements that exceed a threshold distance from a rest po-sition are detected as keystrokes.When a keystroke is detected,the position and speed of eachfinger is recorded.During a brieftraining phase,keystrokes are mapped to commands.For example,keystroke gestures can be used to select among several interfacetools,such as a paintbrush,eraser,or selection tools which can beused to perform actions in the virtual environment.ReferencesA HMAD,F.,AND M USILEK,P.2006.A keystroke and pointercontrol input interface for wearable computers.In Proceedingsof Fourth IEEE International Conference on Pervasive Comput-ing and Communications(PerCom’06),IEEE,2–11.。