Bandwidth estimation: metrics, measurement techniques, and tools

In a packet network, the terms bandwidth and throughput often characterize the amount of data that the network can transfer per unit of time. Bandwidth estimation is of interest to users wishing to optimize end-to-end transport performance, overlay network routing, and peer-to-peer file distribution. Techniques for accurate bandwidth estimation are also important for traffic engineering and capacity planning support. Existing bandwidth estimation tools measure one or more of three related metrics: capacity, available bandwidth, and bulk transfer capacity. Currently available bandwidth estimation tools employ a variety of strategies to measure these metrics. In this survey we review the recent bandwidth estimation literature focusing on underlying techniques and methodologies as well as open source bandwidth measurement tools.     

On the dimensionality of optical absorption, gain, andrecombination in quantum-confined structures

The purpose of this paper is to explore the dimensionality of the optoelectronic properties of quantum-well and dot systems by expressing carrier distributions in the confinement directions in terms of envelope functions rather than assuming that carriers are localized to the geometrical extent of the confining potential. The conclusions apply to an ideal two-dimensional (2-D) system or a structure where only the n=1 electron and hole subbands are populated. We show that optical absorption normal to the plane of a QW cannot be expressed as an absorption coefficient but should be specified as a fraction of light transmitted or absorbed per well. The modal gain for light propagating along the plane of a QW does not scale with well width and the variation of the material gain inversely proportional to the well width is a consequence of the definition of the confinement factor and has no independent physical significance. Coupling to the optical mode can be specified as a mode width without the need to assume the gain medium is localized in the well. Optical absorption and gain by quantum dots should be expressed as a cross section per dot. The radiative recombination current should be expressed in terms of a two-dimensional recombination coefficient and use of an equivalent three-dimensional coefficient introduces an artificial dependence on well width which can lead to errors in the comparison of QW systems. We provide an analysis of experimental data for optical absorption in GaAs wells and show that, using the correct dimensional forms, it is straightforward to use this to estimate modal gain and the recombination coefficient     

Convex relaxations in circuits, systems, and control

It is well known that a large variety of systems and control problems can be formulated as optimization problems. The classical approach pursued in typical contexts is to look for a closed form solution to the specific optimization problem at hand. The last decade has seen a noticeable shift in the meaning of "closed form" solution. The formidable increase of computational power has dramatically changed the feeling of theoreticians as well as of practitioners about what is meant by "tractable" and "untractable" problems. One of the main issues is convexity. While from a mathematical viewpoint there has been a large amount of work in the direction of "convexifying" nonconvex problems and studying structural features of convex problems, considerable advances on techniques for recognizing convexity and algorithms for solving convex problems have been made mainly in the last 15 years [1, 2]. Efforts in this direction are motivated by the recognition that a large number of engineering problems can be formulated as convex problems.     

可靠性、维修性、保障性参数指标体系探讨

研究了可靠性、维修性、保障性指标体系,将参数指标划分为战术、技术、工程设计三个层次,阐述了可靠性、维修性、保障性各种组合参数与单项参数之间存在的主从层次和相互关系,可靠性、维修性、保障性指标的顶层到现场更换模块之间的相互关系.为军用装备可靠性、维修性、保障性指标论证奠定基础,为可靠性、维修性、保障性总体方案的优化设计创...     

Writing research article introductions in software engineering: howaccurate is a standard model?

A standard model for describing the structure of research article introductions, the CARS (Create A Research Space) model, is evaluated in terms of how well it can be applied to 12 articles which have received “best paper” awards in the field of software engineering. The results indicate that, although the model adequately describes the main framework of the introductions, a number of important features are not accounted for, in particular: an extensive review of background literature, the inclusion of many definitions and examples, and an evaluation of the research in terms of application or novelty of the results     

城市有线电视网的探讨（上）

本文简要介绍了有线电视的发展，并从有线电视的传输手段、网络功能，结构、工程，以及邻频与双向传输等各个方面，研究探讨了城市有线电视网的技术问题，以供同行参考。     

Electrical engineering education and certification, validation, and licensing

Evidence is accumulating that legislative actions will result in new requirements for practicing electrical engineers and electrical engineering educators. These requirements will include registraction and licensing as professional engineers for both groups as well as proof of up-to-date competence before relicensing. Such requirements will provide problems as well as opportunities for electrical engineering educators. The problems are associated with responding to the new require ments while retaining some degree of control over and responsibility for the educational programs. The opportunities are available because continuing education will play an important role in the relicensing of practitioners as well as their career development. This paper will dis cuss the many ramifications of the interface between government, the public, practicing electrical engineers and electrical engineering educators.     

Hydrophobized Hydrogels: Construction Strategies,Properties, and Biomedical Applications

Hydrogels, as 3D networks containing huge amount of water, display similarity to soft tissues, and thus they are of wide interest in tissue engineering. Hydrogels, due to biocompatibility and porous structure, are valuable therapeutic platforms for hydrophilic drugs. Over the last decade, there has been a strong emphasis on the development of hydrogel platforms with the ability to increase the solubility of hydrophobic drugs. However, the pronounced discrepancy between the hydrophilic character of hydrogels and the hydrophobic nature of numerous pharmacologically active compounds is problematic. In recent years, different strategies are applied using special polymer constructs or composite materials exploiting the advanced scientific knowledge in the area of polymer and lipid-based nano- and microcarriers hydrophobization of the hydrogel turns out to be not only valuable in terms of achieving the ability to dissolve poorly soluble drugs in water, but also proves to be crucial in obtaining bioadhesion in wet conditions, but also, unexpected abnormal water swelling behavior, as well as in mechanical properties such as the dissipation mechanism and self-healable hydrogel properties. This review is mainly focused on recent advances in the usage of hydrophobized hydrogels in biomedical applications.     

Coding method for vector representation of engineering drawings

Many engineering drawings exist today that are still subject to change yet do not have the benefit of computer-aided design and drafting because of the cost and difficulties associated with placing them into automated graphics systems. This paper describes a new efficient vector coding method which extracts vector information in real time from raster data acquired by optically scanning and digitizing. The resultant representation of the engineering drawing can be displayed on a CRT terminal or on a plotter as a hard copy, can be rapidly edited or revised to reflect future changes and facilitates fast transfer of drawings over telephone lines to other locations enabling remote viewing and changing. Experimental results in terms of data compaction are presented for a variety of engineering drawings, including one of the CCITT standard test documents.     

Side-Chain Engineering of Aggregation-Induced Emission Molecules for Boosting Cancer Phototheranostics

The ingenious construction of versatile cancer phototheranostics involving fluorescence imaging (FLI) and photodynamic and photothermal therapies (PDT, PTT) concurrently has attracted great interest. By virtue of their inherent twisted structures and plentiful motion moieties, aggregation-induced emission luminogens (AIEgens) have been proven to be perfect templates for the development of multimodal phototheranostic systems as their diverse energy consumption pathways can be flexibly regulated through tuning the intramolecular motions. Side-chain engineering is generally accepted as a useful regulation strategy for intramolecular motions through altering the side-chain structure of the molecule, but has rarely been reported for the construction of AIE-active multimodal phototheranostics. Herein, by taking full advantage of the side-chain engineering strategy, an AIE-active multifunctional phototheranostic system (TBFT2 nanoparticles) is successfully constructed by intentionally manipulating the length of side chains. Bearing the longest alkyl chain, all of those three energy dissipation pathways including radiative decay, nonradiative thermal deactivation, and intersystem crossing process of TBFT2 are retained simultaneously and controllably in the aggregate state. In vitro and in vivo evaluations verify that TBFT2 nanoparticles perform well in terms of FLI-guided PDT and PTT synergistic cancer therapy. This study thus provides new insight into the exploration of superior versatile phototheranostics through side-chain engineering.     

Additive Manufacturing Approaches for Hydroxyapatite‐Reinforced Composites

Additive manufacturing (AM) techniques have gained interest in the tissue engineering field, thanks to their versatility and unique possibilities of producing constructs with complex macroscopic geometries and defined patterns. Recently, composite materials—namely, heterogeneous biomaterials identified as continuous phase (matrix) and reinforcement (filler)—have been proposed as inks that can be processed by AM to obtain scaffolds with improved biomimetic and bioactive properties. Significant efforts have been dedicated to hydroxyapatite (HA)‐reinforced composites, especially targeting bone tissue engineering, thanks to the chemical similarities of HA with respect to mineral components of native mineralized tissues. Herein, applications of AM techniques to process HA‐reinforced composites and biocomposites for the production of scaffolds with biological matrices, including cellular tissues, are reviewed. The primary outcomes of recent investigations in terms of morphological, structural, and in vitro and in vivo biological properties of the materials are discussed. The approaches based on the nature of the matrices employed to embed the HA reinforcements and produce the tissue substitutes are classified, and a critical discussion is provided on the presented state of the art as well as the future perspectives, to offer a comprehensive picture of the strategies investigated as well as challenges in this emerging field of materiomics.     

SiC power MOSFETs performance,robustness and technology maturity

Relatively recently, SiC power MOSFETs have transitioned from being a research exercise to becoming an industrial reality. The potential benefits that can be drawn from this technology in the electrical energy conversion domain have been amply discussed and partly demonstrated. Before their widespread use in the field, the transistors need to be thoroughly investigated and later validated for robustness and longer term stability and reliability. This paper proposes a review of commercial SiC power MOSFETs state-of-the-art characteristics and discusses trends and needs for further technology improvements, as well as device design and engineering advancements to meet the increasing demands of power electronics.     

What is engineering management?

The question, “what is engineering management?” has certainly been addressed before in both professional articles and textbooks. However, it seems appropriate to again address this question because of the renewed interest in engineering management. This renewed interest comes in many forms, but two stand out. The first is the increasing trend to give engineering management assignments earlier and earlier in a new engineering graduate's career. The second is the emphasis of engineering management skills in ABET 2000 in the undergraduate engineering program. Both of these initiatives seem to be led by industry and may be a direct result of industry's interest in engineering management skills as a competitive advantage as well as their downsizing practices, which have resulted in the more experienced engineers retiring early and their responsibilities being pushed down to the more junior engineers. If you believe, as does this author, that before you can become a good engineering manager you should first be a good engineer, then the trend of giving management assignments before engineers have had an opportunity to become well grounded in their engineering disciplines should be disturbing. This could eventually affect a company's ability to continue to play a leadership role in introducing new technologies. Hence, the question “what is engineering management?” is an important question. This article attempts to answer the question by addressing when engineering management skills are needed in an engineer's career     

Multiproject strategy, design transfer, and project performance: asurvey of automobile development projects in the US and Japan

Large manufacturers usually need to manage multiple projects in order to leverage their financial and engineering resource investments on new technologies and designs. The purpose of this paper is to explore the relationship between different multiproject strategies and project performance measured by lead time and engineering hours. The multiproject strategy in this study focuses on different ways of transferring core technologies and designs from one project to another within the firm. First, this paper proposes a typology of different multiproject strategies, which categorizes new product development projects into four types: new design, rapid design transfer, sequential design transfer, and design modification. Second, using survey results on 103 different new product projects at 10 automobile firms in Japan and the US, this study concludes that projects using the rapid design transfer strategy are the most efficient in terms of engineering hours. Only through rapid design transfer can a preceding design be transferred from a base project to a new project with effective task sharing among engineers and mutual adjustments between the two projects. This paper also discusses organizational requirements for managing rapid design transfer projects. Neither a pure project-team approach nor a functional approach seem appropriate for the management of concurrent multiple projects     

Electrode Engineering by Atomic Layer Deposition for Sodium‐Ion Batteries: From Traditional to Advanced Batteries

Sodium‐ion batteries (SIBs) have emerged as one of the most promising and competitive energy storage systems due to abundant sodium resources and its environmentally friendly features. However, further improvements in the engineering of the SIB electrode/electrolyte interphase—which directly determines the Na‐ion transfer behavior, material structure stability, and sodiation/desodiation property—are highly recommended to meet the continuously increasing requirements for secondary power sources. Reasonably speaking, to promote SIBs, the advanced and controllable interphase/electrode engineering approach exhibits promise by rationally designing the bulk electrode and generating a well‐defined interphase. Atomic layer deposition (ALD) technology, with atomic‐scale deposition, superior uniformity, excellent conformality, and a self‐limiting nature, is thus expected to address the current challenges facing SIBs in terms of low energy density, limited cycling life, and structural instability, and to promote innovations such as multifunctional electrodes and nanostructured materials for advanced SIBs. This review summarizes and discusses the most recent advancements in the interphase engineering of SIBs by ALD via modifying traditional electrodes and designing advanced electrodes (such as 3D, organic, and protected sodium metal electrodes). Furthermore, based on the recent critical progress and current scientific understanding, future perspectives for the engineering of next‐generation SIB electrodes by ALD can be provided.     

非电类专业"自动控制原理"课程教学实践

为了提高工科非电类专业"自动控制原理"课程的教学水平,从多方面介绍了笔者的教学实践:选用将经典控制理论与实际自控系统相结合而编写的学本教材;根据专业的特点和实际需要合理组织教学内容,重点讲授基本概念、基本原理和基本方法;采用启发式的教学方法;使用答疑和质疑相结合的辅导方式;采用将传统板书与现代化多媒体相结合的教学手段;开设着眼于基本技能训练的实验项目;采取将平时成绩与期末考试相结合的考核方式.实践表明,这些措施取得了良好的教学效果.     

人体快转向运动自适应卡尔曼跟踪算法

穿墙雷达对人体目标进行跟踪探测面临一系列技术难点,包括墙体反射产生的虚警、射频干扰、定位误差和目标丢失等。针对上述问题,文中基于多目标数据关联和自适应的卡尔曼滤波算法,提出一种适用于穿墙雷达探测的快转向运 动人体轨迹跟踪综合处理算法,重点解决快转向运动人体目标的跟踪及多运动人体目标的轨迹交叉等问题。实验结果验证了该算法具有虚警较少、轨迹平滑、计算量小、易于工程实现、定位误差可减小50% 等优点。对于反向运动的人体目标, 算法也可进行有效跟踪。     

Comparative analysis of design concepts of mechatronics systems with a CAD tool for system architecting

In mechatronics systems design, designers need to deal with complexity derived from the integration of subsystems with various engineering disciplines. In particular, while developing product architecture for the next generation systematically, the present generation systems in the market should be reviewed in terms of their functional overview as well as module structure. This paper proposes a method for developing product architecture by a comparative analysis of the functional overview as well as physical decomposition of existing mechatronics systems. The method employs function–behaviour–state modelling and a computer-aided design (CAD) system for system architecting (SA-CAD) as a modelling scheme and modelling environment, respectively. The paper describes the application of the proposed method in the development of product architecture of autonomous vacuum cleaning robots.     

Engineering notion of mean-residual-life and hazard-rate for finitepopulations with known distributions

This article overviews some foundation issues in reliability and argues that generally it does not make sense to use classical notions of the hazard rate (HR) and mean residual life (MRL) to describe the HR and MRL of a device (the HR and failure rate are interchangeable terms). It provides a new methodology, using engineering notions of HR and MRL, to describe the HR and MRL of a device. and discusses the relevance of these methods in comparison to existing methods. In practice, the engineering notions of HR and MRL can be more complicated and more difficult to compute than the classical notions of these functions. Nevertheless, one should adhere to the procedures in this paper insofar as feasible because, as the examples indicate, the engineering notions of these functions dramatically differ from the classical notions. The finite populations have specified joint distributions