令人困惑的a=*a

“指向二维数组的指针和指针变量”是C语言程序设计中的难点,对于初学者来说有些概念难以理解,容易产生混淆;在实际编程时,也容易错误地加以应用。本人在教学实践中经过摸索发现,从容易理解的一维数组出发,循序渐进地学习与理解此部分内容,就会收到良好的学习效果。     

Optimizing a damped system – a case study

We consider a second-order damped-vibrational system described by the equation M ?+C(v) [xdot]+K x=0, where M, C(v), K are real, symmetric matrices of order n. We assume that the undamped eigenfrequencies (eigenvalues of (λ² M+K) x=0) ω₁, ω₂, …, ω _n , are multiple in the sense that ω₁=ω₂, ω₃=ω₄, …, ω _n?1=ω _n , or are given in close pairs ω₁ ≈ ω₂, ω₃ ≈ ω₄, …, ω _n?1 ≈ ω _n . We present a formula which gives the solution of the corresponding phase space Lyapunov equation, which then allows us to calculate the first and second derivatives of the trace of the solution, with no extra cost. It can serve for the efficient trace minimization.     

Is a Semantic Web Agent a Knowledge-Savvy Agent?

The issue of knowledge sharing has permeated the field of distributed AI and, in particular, its successor, multiagent systems. Through the years, many research and engineering efforts have tackled the problem of encoding and sharing knowledge without the need for a single, centralized knowledge base. The proposed solutions to this problem are based, more or less, on stringent assumptions, such as static, shared ontological models, or the existence of a common blackboard (or "Linda Space") environment where entities can share knowledge. However, the uptake of the World Wide Web and the emergence of modern computing paradigms, such as distributed, open systems, have highlighted the importance of sharing distributed and heterogeneous knowledge on a larger scale-possibly on the scale of the Internet.     

Implementing a Serializer Using a Java XML Schema API

W3C XML （Extensible Markup Language） Schema defines a set of abstract components, which carry the core semantics of document structure definition. There has been no standard API for accessing these components or their structures yet. The MARKUP Technology Company has specified a Java API for accessing XML Schema and submitted it to the W3C as a possible basis for standard Schema API. An overview of the schema API is provided and then XML schema serializer is implemented using this API in this paper.     

走进802.11a

在现在的工作(家庭)环境中,您是否感觉需要无线设备给我们提供更加便捷的网络连接了么?以往当我们提起网络连接设备,通常人们所想到的是网卡、集线器、交换机以及各种网络线缆。从     

Living in a bubble? Toward a unified bubble theory

We generalise the notion of a bubble beyond the financial domain, by showing how a single social mechanism, based on an information feedback-loop, explains both financial bubbles and other seemingly disparate social phenomena, such as the recognition of academic articles, website popularity, and the spread of rumours.

We discuss examples of phenomena explained by this bubble mechanism, as well as other phenomena that exhibit certain bubble characteristics, yet are not bubbles according to our model. Finally, we present mathematical mechanisms for two phenomena that conform with our model, and show by computer simulation how they exhibit bubble behaviour.     

Does a back support have a positive biomechanical effect?

Back supports, or lifting belts, are widely used. Subjects, free of low back pain, lifted in a simulated task, meeting the 1993 NIOSH guidelines. The back support reduced the electromyographic signal in the dorsal muscles. The back support also reduced the height loss as measured by a stadiometer. In most subjects the support also gave a subjective impression of increased support and increased lifting capacity.     

H ∞ control of a suspension with a magnetorheological damper

This research work presents an H _∞ controller based on a Takagi–Sugeno (T–S) fuzzy model for a two-degrees-of-freedom (2-DOF) one-quarter-vehicle semi-active suspension with a magnetorheological damper where the actuator dynamics are included in the control synthesis. These dynamics enclose nonlinear damper phenomena, avoided in many other studies, and that can improve the suspension system by means of a more accurate model. The objective is to obtain a semi-active suspension that considerably improves the passive suspension efficiency based on some frequency domain performance criteria. The advantage of having the T–S system as a reference is that each piecewise linear system can be exposed to the well-known control theory. Besides, the proposed solution is compared with the recent reported work to highlight its advantages. A case of study is included and simulation work supports the results. The methodology applied herein can be extended to a half-vehicle model, and to the four wheels to have a global chassis control in order to maximise passenger comfort and vehicle stability.     

File distribution using a peer-to-peer network––a simulation study

As the Internet became widespread, people saw it as a way of distributing content. But while the average bandwidth capacity is increasing, users around the world are trying to share more data. Although the servers are able to acquire more bandwidth, they cannot keep up with the rapidly increasing requests of the users. Several systems appeared that alleviate the server from the dissemination process. But such systems are not always suitable for disseminating highly anticipated files of considerable size. The evolution of peer-to-peer systems gave a new way of attacking this problem. Each user can assist the dissemination process by acting as a server as well. In this paper the way traditional systems meet users' demands is demonstrated, and simulation results of a peer-to-peer approach based on a mobile agent platform are presented. Our focus is on how different parameters can affect the dissemination process of a highly anticipated file in this network.     

Velocity planning for a mobile robot to track a moving target — a potential field approach

Potential field method has been widely used for mobile robot path planning, but mostly in a static environment where the target and the obstacles are stationary. The path planning result is normally the direction of the robot motion. In this paper, the potential field method is applied for both path and speed planning, or the velocity planning, for a mobile robot in a dynamic environment where the target and the obstacles are moving. The robot’s planned velocity is determined by relative velocities as well as relative positions among robot, obstacles and targets. The implementation factors such as maximum linear and angular speed of the robot are also considered. The proposed approach guarantees that the robot tracks the moving target while avoiding moving obstacles. Simulation studies are provided to verify the effectiveness of the proposed approach.     

Cobol: a historic past, a vital future?

One of the strangest stories in the software world centers around the programming language Cobol. Academics have reviled it for decades; its demise has been predicted since the 1960s; industry gurus have suggested that programmers who know only Cobol are committing career suicide. You would think, based on all this bad press, that Cobol was not long for this software world. Yet the giant lumbers on. In poll after poll, it is either the most-used or the second-most-used programming language in industry. In fact, in one industry poll, each year those contacted predict that Cobol's use will diminish by the next poll, and each year the findings are that Cobol is the only language whose use has actually increased. The devil refuses to die. What's with Cobol? I give my Loyal Opposition answer to that question and then give some input on the subject from a Cobol expert who is tracking Cobol's future directions     

Such a Beautiful Disease

奈奈是一家网络游戏公司的小MM。有句话叫做“命悬一线”，像我这样一天超过12个小时面对电脑的人，工作、生活就寄托在那根小小的网线上。     

Building a domain-specific compiler for emerging processors with a reusable approach

High-performance computing and deep learning domains have been motivating the design of domain-specific processors.Although these processors can provide promising computation capability,they are notorious for exotic programming paradigms.To improve programming productivity and fully exploit the performance potential of these processors,domain-specific compilers(DSCs) have been proposed.However,building DSCs for emerging processors requires tremendous engineering efforts because the commonly used...     

Approximating a helix segment with a rational Bézier curve

From a differential geometric point of view a helix segment can be considered as a spatial generalization of a circular arc. Thus for problems of shape preservation and geometric modelling an approximate rational representation of a helix segment is of interest. In this paper rational Bézier curves of degree 4, 5 and 6 are presented that approximate a helix segment. The approximants fulfill certain geometric constraints. A generalized degree elevation for rational polynomials in Bézier representation is discussed and used for the construction.     

Towards a parallel component in a GPU–CUDA environment: a case study with the L-BFGS Harwell routine

Modern graphics processing units (GPUs) have been at the leading edge of increasing parallelism over the last 10 years. This fact has encouraged the use of GPUs in a broader range of applications, where developers are required to lever age this technology with new programming models which ease the task of writing programs to run efficiently on GPUs. In this paper, we discuss the main guidelines to assist the developer when porting sequential scientific code on modern GPUs. These guidelines were carried out by porting the L-BFGS, the (Limited memory-) BFGS algorithm for large scale optimization, available as Harwell routine VA15. The specific interest in the L-BFGS algorithm arises from the fact that this is the computational module with the longest running time of a Oceanographic Data Assimilation application software, on which some of the authors are working.     

Maximum power tracking of a generic photovoltaic system via a fuzzy controller and a two-stage DC–DC converter

This study presents a new two-stage DC–DC converter for maximum power point tracking (MPPT) and a voltage boost of a generic photovoltaic (PV) system. An intelligent MPPT of PV system based on fuzzy logic control (FLC) is presented to adaptively design the proposed fuzzy controlled MPPT controller (FC-MPPTC) while a voltage boost controller (VBC) is used to fix the output voltage to a voltage level that is higher than the required operating voltage to the back-end grid impedance. Modeling and simulation on the PV system and the DC–DC converter circuit are achieved by state-space and the software Powersim. The PV string considered has the rated power around 600?VA under varied partial shadings. The FC-MPPTC and VBC are designed and realized by a DSP module (TMS320F2812) to adjust the duty cycle in the two-stage DC–DC converter. A special FLC algorithm is forged to render an MPPT faster and more accurate than conventional MPPT technique, perturb and observe (P&O). The simulations are intended to validate the performance of the proposed FC-MPPTC. Experiments are conducted and results show that MPPT can be achieved in a fast pace and the efficiency reaches over 90?%, even up to 96?%. It is also found that the optimized tracking speed of the proposed FC-MPPTC is in fact more stable and faster than the general P&O method with the boost voltage capable of offering a stable DC output.     

Simulation of a mannequin’s thermal plume in a small room

Simulation results are presented for the buoyancy-driven flow in a small room containing a seated mannequin that is maintained at a constant temperature. The study was motivated, in part, by a published experimental study of the thermal plume around a human subject. The results presented are a step toward the goal of using DNS to develop a more detailed understanding of the nature of the flow in the thermal plume created by humans modeled here as heated mannequins. The results were obtained without using sub-grid scale modeling and are helpful in establishing the resolution requirements for accurate simulations. It is seen that the results for the highest resolution grid are in reasonable quantitative agreement with a published experimental study of a human subject’s thermal plume. The results for the velocity field are used to compute the trajectories of small particles in the room. Results are presented for the trajectories of five-micrometer solid particles that are initially dispersed near the floor in front of the mannequin. The simulation results show that the buoyancy-driven flow around the mannequin is effective at dispersing the particles over a large portion of the room.     

Geometric phase as a determinant of a qubit�C environment coupling

We investigate the qubit geometric phase and its properties in dependence on the mechanism for decoherence of a qubit weakly coupled to its environment. We consider two sources of decoherence: dephasing coupling (without exchange of energy with environment) and dissipative coupling (with exchange of energy). Reduced dynamics of the qubit is studied in terms of the rigorous Davies Markovian quantum master equation, both at zero and non–zero temperature. For pure dephasing coupling, the geometric phase varies monotonically with respect to the polar angle (in the Bloch sphere representation) parameterizing an initial state of the qubit. Moreover, it is antisymmetric about some points on the geometric phase-polar angle plane. This is in distinct contrast to the case of dissipative coupling for which the variation of the geometric phase with respect to the polar angle typically is non-monotonic, displaying local extrema and is not antisymmetric. Sensitivity of the geometric phase to details of the decoherence source can make it a tool for testing the nature of the qubit–environment interaction.