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38648 results in Cambridge Textbooks

Page 1333 of 1933

  • 21 - Mobile Cloud Computing and The Internet of Things

  • Sandeep Bhowmik
  • Book:
    Cloud Computing
    Published online:
    31 August 2020
    Print publication:
    17 April 2017, pp 375-383

  • Summary

    The introduction of cloud computing has revolutionized the way of computing as it was being done. The impact of cloud computing technology has reached every corner of the world. It has introduced a new era where innovative technological advancements are emerging based on the strength and utility of cloud computing. Cloud computing may take some time to attain its full maturity but it has appeared as the biggest thing after the Internet. With its fast adoption in different domains and businesses, researchers are working on several issues of cloud computing. This concluding chapter of the book discusses such topics.

    This chapter briefly introduces two topics which are emerging as subjects of attraction after cloud computing. Mobile cloud computing is a technology that has opened the scope for overcoming the limitations of mobile computing through effective utilization of cloud computing. This makes mobile computing attractive and more useful for users, especially for billions of smart phone users.

    The most remarkable happening in the connectivity domain, after cloud computing is the ‘internet of things’. It promises to bring a revolution in human civilization by connecting living and non-living objects, and simplifying the act of collecting different information about them. All these digital innovations are propelling us towards a smarter planet.

    MOBILE CLOUD COMPUTING

    Mobile cloud computing (MCC) refers to the computing facility introduced by combining three fascinating technologies together: mobile computing, cloud computing and wireless communication. The emergence of MCC is followed by the explosive growth in uses of mobile devices, especially smart phones where cloud computing acts as a potential technology enabler for mobile services. The actual objective of MCC is to provide rich experience to users by offering cutting edge applications over a variety of mobile devices.

    The popularity of mobile devices which facilitates trouble-free communication and instant availability of information has made them an integral part of modern age human civilization. As a consequence, mobile cloud computing has emerged as an advanced step in the process of enriching mobile computing.

    Mobile Computing

    In simple words, mobile computing is a technology where computing-capable devices can transmit data without being connected to any device or network physically, even when in transit.

  • 19 - Cloud Management and a Programming Model Case Study

  • Sandeep Bhowmik
  • Book:
    Cloud Computing
    Published online:
    31 August 2020
    Print publication:
    17 April 2017, pp 327-350

  • Summary

    Cloud computing does not imply any single technology. In short, a combination of multiple methodologies defines its architecture. The management of various aspects associated with this computing facility thus becomes very important case for successful outcome during its real-life implementations. Be it business delivery, or technical foundation of system development, the ‘service’ takes center stage in cloud computing. Consequently, cloud service management has become another important issue to be discussed in a new context.

    Most management activities in cloud are automated and SLA-driven. The service level agreement (SLA) thus plays an important role in the success of cloud computing. This chapter represents the lifecycle of SLA, apart from discussing the lifecycle of cloud service. Cloud management standards, tools and responsibilities of providers and consumers have also been discussed.

    This chapter also focuses on various programming models which are implemented on cloud. For this purpose a case study is represented with Aneka cloud platform which has a special feature of supporting multiple programming models. In this context, the chapter tries to revisit the cloud computing architecture once more and represents its design characteristics and few non-functional features as well from different angles.

    CLOUD ARCHITECTURE: REVISITED

    In very broad sense, the cloud computing system can be viewed as composition of two elements:

  • ▪ Client application at the front end

  • ▪ The cloud as the back end.

    • This is a very simple description as the backend comprises of several layers and abstractions. In most cases, the ‘client application’ at the frontend is a web browser through which cloud service interfaces (i.e. the portals) are accessed. Consumers can access the backend ‘cloud’ from any simple electronic device capable of running web browsers. Only prerequisite is the availability of network or Internet service. Quality of cloud service accessibility often depends on the speed of the network. But with advancements in the field of internet technology, speed is the least worrying factor nowadays.

    At the backend, the ‘cloud’ resides at some remote location generally being managed by some service providers. Reputed providers develop cloud service infrastructure at their own data centers. A provider can have multiple data centers at different geographic locations. As shown in Figure 19.1, this backend part can be seen as composition of two broad components: a cloud building platform and the cloud services.

  • 12 - Partially and Completely Periodic Potentials

  • Ravinder R. Puri
  • Book:
    Non-Relativistic Quantum Mechanics
    Published online:
    16 July 2025
    Print publication:
    17 April 2017, pp 225-242

  • Summary

    A problem of considerable interest is the theory of motion of electrons in a bulk or in a nano sized crystalline solid. Whereas the potential in a bulk solid may be considered to be periodic in entire space, that in a nano sized solid is periodic in a finite region of space. In this chapter, we develop the formalism to study the motion of a particle in a one-dimensional potential which is periodic in a finite part of the space, and the one which is periodic in entire space. In the limit of the potential extending from −1to1, the results for the potentials periodic in the finite part of space reproduce those for the potentials periodic in entire space. We will see that completely periodic potentials can also be treated invoking symmetry considerations.

    Potential Periodic in a Finite Region of Space

    Consider a potential V(x) which is periodic with period a in the finite region of space 0 ≤ x ≤ Na such that

    whereas on the remaining part of the x-axis,

    The solution of the Schrödinger equation corresponding to the potential defined in (12.1) and (12.2) is obtained by solving it in different regions and matching the solutions at the boundaries of the adjoining regions.

    We find first the solution in the region 0 ≤ x ≤ Na in which the potential is periodic. Consider the interval na ≤ x ≤ (n + 1)a which we call the nth interval. Since, due to (12.1), the potential in nth interval is same as that in (0, a), the linearly independent solutions of the Schrödinger equation in nth interval are same as those in (0, a).

  • 12 - Service-Oriented Architecture

  • Sandeep Bhowmik
  • Book:
    Cloud Computing
    Published online:
    31 August 2020
    Print publication:
    17 April 2017, pp 207-223

  • Summary

    Management of any large system turns out to be a complex task if the architecture of the system is not flexible enough. It becomes difficult to deploy new functionalities, alter existing functionalities and integrate interoperability when an immovable system grows. As a solution, any large system should be decomposed into functional primitives for efficient and flexible management and this philosophy perfectly applies to cloud computing systems too.

    Clouds are generally heterogeneous and large in volume by their own nature. Hence, the flexible architecture (or flexible application architecture) is an essential criterion for making the computing system agile and capable of adjusting to quick changes in business strategy to take advantage in a competitive business market.

    The conventional application architectures are not designed to take advantage of infrastructural agility and diversity like a cloud. In cloud computing, applications perform best when they are built based on the paradigm called as ‘service-oriented architecture’ or SOA. This new architectural paradigm makes cloud applications flexible and specially shows its ability when the system grows over time. This chapter focuses on the philosophy of the service orientation, discusses its advantages and indicates how business application becomes agile with SOA implementation.

    THE PRE-SOA ERA

    Conventional computing systems were based on centrally-administrated architecture. But, such architecture was not appropriate for quick application development, neither was it designed to support rapid changes in functionality. Moreover, the processes of developing a new application system used to become complex, time-consuming and expensive.

    Then the concept of component based application development (CBD) model emerged. It had many goals similar to SOA. A component is a software object which is meant to interact with other components. Components are used to represent basic system functionalities, those which collaborate with other components. CBD promotes decomposition and reusability. It also increases productivity, quality and decreases the time-to-market. But interoperability is the issue that could not be handled with this system development model.

    With the widespread adoption of heterogeneous distributed systems, the need for application interoperability appeared. Heterogeneous system refers to the ability of integrating multiple type (cross architecture and/or cross vendor) of one or more computing resources (like processor) into a single computing environment. Cloud computing system is the ultimate outcome of heterogeneity.

  • 1 - History of Quantum Mechanics

  • Ravinder R. Puri
  • Book:
    Non-Relativistic Quantum Mechanics
    Published online:
    16 July 2025
    Print publication:
    17 April 2017, pp 1-30

  • Summary

    History is the most fundamental science, for there is no human knowledge which cannot lose its scientific character when men forget the conditions under which it originated, the questions it answered, and the functions it was created to serve.Astudent of quantum mechanics can ignore these words of Benjamin Farrington, often quoted by Schrödinger [1], only at his own peril. For, without their historical perspective, the counter-intuitive nature of the physical laws of the quantum theory may appear to be mystic. Indeed, the laws of quantum mechanics exhibit their distinctive character on a scale which is out of reach of our everyday experience. This is in contrast with the intuitive appeal of the Newton's laws and their conformity with our common experience. However, the inability of the then known theories, referred to now as the classical theories, to explain certain physical phenomena led to the search for a new theory. It culminated with the advent of the quantum theory. The true scientific character of the quantum theory cannot be appreciated without understanding the conditions under which it originated, the questions it answered, and the functions it was created to serve. Such an understanding can even motivate one to ponder whether there can be any other description of the laws of nature which is free from the conceptual and philosophical inconsistencies which are often pointed out in the present-day quantum theory. This chapter outlines brie_y how the ideas leading to the birth of quantum mechanics took shape.

  • Preface

  • Ravinder R. Puri
  • Book:
    Non-Relativistic Quantum Mechanics
    Published online:
    16 July 2025
    Print publication:
    17 April 2017, pp xv-xviii

  • Summary

    This book is the outcome of my belief, shared undoubtedly by many that, like classical mechanics is taught starting with Newton's laws, so should the teaching of quantum mechanics be based on its postulates, and that since, in contrast with the intuitive appeal of Newton's laws, the quantum laws appear counter-intuitive, therefore, introduction of the postulates of quantum mechanics must be preceded by narrating the fascinating story of their birth. The understanding of the thought process that led to seemingly puzzling but remarkably accurate formulation of the laws of nature can arguably provide greater appreciation and grasp of the essence of radically different and counter-intuitive ideas of the theory. Furthermore, I find that some mathematical techniques, which can significantly simplify the algebra, are generally overlooked in the standard quantum mechanics literature.

    The subject is generally introduced by glancing through those phenomena which historically necessitated search for a new theory and by providing the motivation and justification of the new ideas by examples. Making a departure from that approach, drawing upon the papers that formed the foundations of quantum mechanics, this book opens by providing an account of how the new theory took shape. It describes, for example, how Planck came up with the law of black-body radiation. How Heisenberg came up with the idea of representing a dynamical variable x by the set of quantities [xmnm] labelled by two indices and how he arrived at the law of their multiplication, not knowing that his was the matrix representation of the classical dynamical variables.

  • 2 - Evolution and Enabling Technologies

  • Sandeep Bhowmik
  • Book:
    Cloud Computing
    Published online:
    31 August 2020
    Print publication:
    17 April 2017, pp 19-37

  • Summary

    Cloud computing is not an abrupt innovation. Rather, it is a series of developments that have taken place over past few decades. Progresses in computing technology, starting from its early days, has slowly metamorphosed into cloud computing in this advanced era. Although the idea of cloud computing originated long ago, the concept could not materialize due to lack of necessary technological elements.

    Documentary evidence can be traced back to the 1960s, when John McCarthy (who coined the term ‘artificial intelligence’) wrote that ‘computation may someday be organized as a public utility.’ Since then, computing technology has gone through phases of development. Hardware and communication technology have been progressed, Internet has changed the world and at the same time, the web-based software architecture has also matured.

    As advancements in all associated fields have slowly overcome the limitations of earlier approaches, it has been possible to realize the dream of computing as the new measure of public utility. This chapter focusses on the evolution of cloud computing and discusses how generations have developed through stages like centralized computing, client server computing, distributed computing and grid computing on to cloud computing.

    THE EVOLUTION OF CLOUD COMPUTING

    Cloud computing is not an isolated development. Cloud technology has been matured over the years with constant advancements in the field of computing. The beginning can be traced back to a time when remote access to time-shared computing system became a reality. The realization of cloud computing has been closely linked with several other subsequent developments in the domain.

    Several decades of research, particularly in the domain of parallel and distributed computing, have paved the way for cloud computing.

    A thorough discussion about the development of cloud computing can never overlook the continuous innovations in the field of electronic and computing hardware. As the hardware technology evolved, so did the software. Beside these, with the advancements in communication protocols, network communication technology as well as Internet also played a vital role in this process. This section focusses on different phases of developments in the field of computing starting from the mainframe age and discusses how those progresses have contributed towards the growth of cloud computing.

  • C - Riccati Equation

  • Ravinder R. Puri
  • Book:
    Non-Relativistic Quantum Mechanics
    Published online:
    16 July 2025
    Print publication:
    17 April 2017, pp 425-426

  • Summary

    The non-linear equat

    where the coefficients p(t), b(t), q(t) are functions of the real variable t, is known as the Riccati equation. The solution of (C.1) is known only for some special forms of the coefficients in it.

    By transforming to the variable x(t) defined by

    the Riccati equation transforms to the second-order ordinary linear differential equation for x(t):

    The solution of the Riccati equation may thus be used to solve (C.3).

    A solvable case of (C.1) arises when the coefficients in it are independent of t. Assuming that to be the case, rewrite (C.1) as

    Substitute (C.5) in (C.4) and integrate the resulting equation to obtain

    On rearranging the terms, the expression for y(t) reads

    The same result can be arrived at by solving the linear equation (C.3) corresponding to (C.1) (see Ex. C.2)

    Ex. C.1. Show that even though x(t) in (C.2) is the linear combination of two linearly independent solutions x1(t) and x2(t) of (C.3), y(t) is determined only by its initial value.

    Ex. C.2. Assuming the coefficients in (C.1) to be independent of t, solve the associated linear equation (C.3) for x(t) and show that the solution y(t) so obtained is the same as (C.8).

  • 9 - Schrödinger Equation in One Dimension

  • Ravinder R. Puri
  • Book:
    Non-Relativistic Quantum Mechanics
    Published online:
    16 July 2025
    Print publication:
    17 April 2017, pp 165-176

  • Summary

    This chapter summarizes some qualitative properties of the solutions of the one-dimensional Schrödinger equation. The one-dimensional equation represents not only the idealized situations but is of interest also for solving the Schrödinger equation for three-dimensional central potentials as in that case the problem reduces to solving one-dimensional equations. The study of the qualitative properties enables one to extract useful physics information without solving the equation which more often than not is a formidable task. The question of identification of exactly solvable one-dimensional potentials and their explicit solutions is addressed in subsequent chapters.

    Asymptotic Behaviour

    Consider a particle of mass m constrained to move in one dimension in a time-independent potential V(x). Its wave function of definite energy E solves the Schrödinger equation

    where U(x) and are the scaled potential and energy defined by

    We study first the asymptotic properties of the solutions of (9.1) under the condition as , where V± are constants. The solution of (9.1) as is then given by

    where. It is real for. In that case, as we will see in Section 10.1, the first term in (9.3) represents the particle moving freely in the direction, whereas the second one represents the one moving freely in the −x direction.

    However, if E < V+m, then k+ is imaginary and (9.3) reads

  • A - Delta Function

  • Ravinder R. Puri
  • Book:
    Non-Relativistic Quantum Mechanics
    Published online:
    16 July 2025
    Print publication:
    17 April 2017, pp 409-412

  • Summary

    As a function of the variable x the Dirac delta function, or simply the delta function, denoted by δ(x), is defined as follows:

    The condition on the ei's means that the limit of integration in (A.1) should include origin. The ϵ1, ϵ2 in (A.1) can have any positive value and may even be infinitesimally close to zero. It then follows that for f (x) continuous at the origin (a, b, ϵ > 0, ϵ ½ 0),

    The second equation above follows by the use of the first part of (A.1), and the third from the fact that, due to continuity of f (x) at x = 0, the value of f (x) for x 2 (−ϵ, ϵ) can be taken to be f (0) as ϵ → 0. In general

    The derivative of the delta function is defined as follows:

    The higher derivatives can be defined in similar manner.

    The defining relations of the delta function and its derivative may be written symbolically as follows:

    where prime denotes the derivative with respect to x.

    We may similarly define the three-dimensional delta function δ(3)(r−r), where r, rÌ are the position vectors, by the equation

    where the integral is over the volume containing r. Let us express δ(3)(rÌ − r) in terms of one-dimensional delta functions. We will see that the said expression depends on the coordinate system.

  • 18 - Portability and Interoperability Issues

  • Sandeep Bhowmik
  • Book:
    Cloud Computing
    Published online:
    31 August 2020
    Print publication:
    17 April 2017, pp 307-326

  • Summary

    Cloud computing is about using services provided by cloud vendors. When consumers invest effort and capital to develop their computing setup on some provider's service, one major concern for them is whether they can move to other cloud service in future, if necessary, with minimal disruption and effort. Can things once built over one cloud service be moved to another cloud service? This question arises since there are possibilities of vendor-lock-in, a situation where a consumer using one cloud service cannot easily move to a similar service delivered by a competitor company or service provider. All investments by a consumer may be in stake if computing setup created on one provider's service cannot be moved to other provider's service in future.

    An other concern comes in mind when consumers think about linking applications of two different cloud services together or, when it is required to link some on-premises non-cloud or cloud computing setup with a public cloud service. Such linking brings forth the issue of interoperability. Can applications of two different cloud environments be linked in such a way? This concern may worry the consumers.

    Consumers should have a clear understanding regarding these issues before moving into cloud. Such understanding enables one to take informed decisions when choices have to be made concerning technology, application or platform.

    Cloud adoption among the consumers also depends on how a cloud environment can address users’ concerns regarding portability and interoperability, apart from the issue of security.

    CHALLENGES IN THE CLOUD

    Although the cloud service offerings present a simplistic view of computing services to consumers, there are few critical issues to consider while moving into cloud. As already discussed, the prime challenges among these are the challenges associated with information security, privacy and compliance. The other vital challenges are related to issues of:

  • ▪ Portability and

  • ▪ Interoperability

    • These two issues arise while moving a system into cloud. The primary concerns during such initiatives are whether the system components are portable into a new environment or not. And then, there are concerns about the interoperability of the components of the existing system too.

  • 15 - Symmetry in Quantum Mechanics

  • Ravinder R. Puri
  • Book:
    Non-Relativistic Quantum Mechanics
    Published online:
    16 July 2025
    Print publication:
    17 April 2017, pp 281-304

  • Summary

    Whether classical or quantum, solving the equations of motion analytically exactly is often a formidable task. Some properties of the motion may, however, be inferred without solving the equations of motion. One such important property is the symmetry of the Hamiltonian under some transformation. The interesting and practically useful aspect of symmetry is that it characterizes the constants of the motion. The symmetry may be under some transformation of space and time, called the geometrical symmetry, or it may be in some abstract space resulting from particular functional form of the Hamiltonian, called the dynamical symmetry. This chapter investigates the consequences of such symmetries on the quantum mechanical description of the motion of a particle.

    Symmetry Transformation

    Consider a system whose state for some observer is. If the observer performs the measurement of an observable on the system, we know that the probability of observing an eigenvalue corresponding to an eigenstate as an outcome is. Now, let the same experiment be described in a coordinate system transformed with respect to the first one. Since the result of a measurement is not expected to depend on the coordinate system used, the probability of observing certain eigenvalue as the outcome should not change. Generalizing the arguments above, we expect the transition probability between the states to be independent of the coordinate system. This chapter is concerned with investigating the consequences of the invariance of the probabilities under linear transformation of the coordinate system.

  • 6 - Security Reference Model

  • Sandeep Bhowmik
  • Book:
    Cloud Computing
    Published online:
    31 August 2020
    Print publication:
    17 April 2017, pp 95-110

  • Summary

    Security is one of the topmost concerns of any computing model and cloud computing is no exception. Consumers or enterprises moving into cloud need to feel secure about their computing facilities and more importantly about the data they are disclosing to service providers. This is a critical choice for enterprises accustomed to safeguarding data sitting in their own centers in the traditional way of computing. Cloud computing promotes the concept of working on proprietary data and applications outside their jurisdiction.

    It is often said that, ‘cloud computing is an excellent idea, but cloud security is not good’. The common perception is that the cloud services are not inherently secure. Cloud computing creates scope for scores of possibilities although like any other technology, there are some risks associated with it which can be overcome if understood correctly.

    A cloud computing environment can be formed in different ways and there can be several ‘cloud formations’. Each form is not suitable for every kind of business operations. Consumers must first understand which among these forms which is best-suited for their purpose. This little judgment can make the security of cloud computing even better than that of traditional in-house computing environments. This chapter focusses on these important aspects.

    If studied and designed appropriately, cloud computing causes no more threat to security than what exist in traditional computing.

    THE SECURITY CONCERN IN CLOUD

    Traditional computing systems used to create a security boundary by placing firewalls at the gateways through which the network used to communicate with the outer world. Firewall blocks unwanted traffic trying to access the network it protects and thus only authenticated accesses are allowed into the system. Thus, malicious accesses get blocked at firewalls in the traditional data centers in order to keep the system protected from outside threats.

    But this strategy only makes sense when all applications and data reside within one network of security perimeter. Traditional data centers allow perimeterized (i.e. within organization's own network boundary or perimeter) access to computing resources. But, the de-perimeterization (to open-up the interaction with outer network) and erosion of trust boundaries that was happening in enterprise applications, have been amplified and accelerated by cloud computing.

Page 1333 of 1933