The influence of process concurrency on project outcomes in productdevelopment: an empirical study of cross-functional teams

This study examines the practice of concurrent engineering (CE) in terms of process concurrency, and the impact of concurrency on success of product development projects. The study is based on 50 cross-national projects from companies in Australia, Canada, Denmark, Finland, United Kingdom, and the United States in the aerospace, automobile, chemical, computer, electronics, shipbuilding, and telecommunications industries. Four dimensions of process and behaviors of engineering/R&D and manufacturing members of cross-functional product development teams were reliably operationalized: (1) two-way communication, (2) overlapping problem solving, (3) readiness to make decisions on the basis of uncertain and ambiguous information, and (4) readiness to release uncertain and ambiguous information. These dimensions of process concurrency were found to be reliable predictors of development projects' success, as measured by product cost and quality, project schedule and budget performance, and project team satisfaction. The paper offers implications for theory and practice and models of CE management for future research     

Examining the relationship between electronic marketplace strategy and structure

The contribution of market structure to the success of an electronic marketplace (e-marketplace) is an issue that has not received a great deal of attention in the literature. Although, researchers have given some attention to the antecedents of successful e-marketplace participation by organizations,there has been relatively little attention given to the e-marketplace structures. In this paper, the issue of e-marketplace strategy and its relationship withe-marketplace structure is examined. A classification of e-marketplace strategies is presented. The market structures of intermediary, hierarchy, consortium,and large group ownership structures are mapped onto this classification using four case studies to explain the relationship between structure and strategy. Each structural model has a range of implications for market participants. These include the economic and service benefits from intermediaries, economic benefits, and the potential to deliver improved levels of service for hierarchies,the relational benefits from the strong network ethos of consortia, and large group ownership structures which have potential for regional community or industry sector development.     

PLC与变频器的串行通讯设计

介绍了PLC和变频器的串行通讯技术，分析并讨论了系统的结构、工作原理、硬件组成和软件设计，实践证明该系统结构简单，运行可靠，易于调整，便于推广和应用。     

The relationship between just-in-time purchasing techniques and firm performance

Just-in-time purchasing (JITP), as a process technology, is an important component of supply chain management in managing inventory flows throughout the chain. Thus far, a detailed examination of JITP relating to firm performance has not been conducted. This study fills this void in the current literature by investigating the relationships among JITP techniques and their relation to firm performance. The hypotheses based on the research model presented are tested by using data from a broader cross-sectional mail study than is reported here. The sample in this study consists of 214 organizations operating in the US and encompasses various sizes of firms and a large variety of industries. Structural equation modeling is used to test the hypotheses. JITP techniques positively and directly related to firm performance are: (1) supplier value-added, a concept that melds supplier-buyer cooperation and increased supply of quality materials and (2) quantities delivered, which refers to frequent and timely delivery of supplied materials in the right quantities. The finding that top management commitment to JITP is directly or indirectly related to other techniques of JITP underscores the importance of leadership in implementing change in organizations.     

Note on the relationship between the domain-transit frequency and the cavity-controlled frequency of thin Gunn devices

Some measurements on thin Gunn devices mounted in cavities covering the range 7?20GHz are reported. For any particular device, it has been found that VBf is approximately constant, where VB is the bias voltage which gives maximum r.f. output at the frequency f. This observation has been related to the domain-transit frequency.     

修改麦克斯伟分布律以定量理解异质结的频率—电导谱

通过测量频率—电导谱,可以确定异质结的界面态密度。由此、通过数学更好地理解异质结的频率—电导谱手段之一是由频率能够预测电导。由观察典型的异质结的频率—电导谱并与麦克斯伟气体分子速率分布函数比较,本文通过麦克斯伟分布律参数化,得到了能够定量描述异质结的电导同频率关系的四参数模型。当将这个数学关系应用于三个异质结的频率—电导谱时,所得理论结果非常好的同实验结果相吻合。此外、本文还成功地推导出(pyronine-B)/p-Si 结构中界面态密度同能量的关系。     

同步通信中的软件鉴频与锁相技术

本文介绍了一种利用软件产生同步通信中同步时钟信号的方法,论述了软件鉴频与锁相技术的基本思想,论证了软件鉴频与锁相技术的可靠性,并以实例说明了软件鉴频与锁扣技术的实际应用.软件鉴频与锁相技术较之硬件实现具有适应性强,经济性好,实现简便等优点.     

Internetwork handover performance analysis in a GSM-satelliteintegrated mobile communication system

This paper evaluates the internetwork handover performance in a GSM and satellite integrated mobile communication system. The performance evaluation is based on an analytical model developed for internetwork handover. The handover performance parameters considered are the handover position, unnecessary handover probability, and call-dropping probability. Handover initiation is based on the signal level and distance measurement. The results are compared with those of the GSM handover performance. The analysis shows that the performance achieved in internetwork handover can be similar to those of the GSM handover with the considered handover initiation scheme     

Empirical relationship between communication costs and the channel bit rate for large computer networks

The primary trade-off in a large computer-communication network (CCN) is the balance between computation processing capability and communication capability. Essentially, a CCN model should utilize operational optimization (rather than mathematical optimization) allowing the user (mostly a non-programme network expert) to call upon his experience and insight in dealing with real-life networks to decide upon proper direction for modifications. We propose, in this paper, a unified approach which will hopefully allow an on-line user to make real-time modifications to CCNs to obtain operationally optimal system trade-offs in such areas as network overall reliability, communication response, computation response, and optimum channel capacities etc.     

总监理工程师胜任力与绩效关系研究

总监理工程师是监理企业的一个重要的职位,工程师的强胜任力能够帮助其建立起很好的竞争力,不断地促使监理企业建立起人才开发功能权力。在现如今的环境之下,对于总监理工程师胜任力和业绩关系的研究相对较少,所以针对于此本研究分析总监理工程师胜任力和绩效关系,希望能够为相关领域提供有价值的参考。     

A study on the relationship between DWDM transmission performance and chromatic dispersion

In this letter, we numerically study the relationship between 40-Gb/s-based dense wavelength-division-multiplexing (DWDM) transmission performance and chromatic dispersion in two different transmission lines. We show that the optimum chromatic dispersion region for improving the DWDM transmission performance varies with the type of transmission line. We also show that a hybrid transmission line has a greater potential to resist any change in the dispersion slope compensation characteristics than a single fiber transmission line with a dispersion compensation fiber module. Finally, we show that chromatic dispersion of more than 12 ps/nm/km in a hybrid transmission line is optimum for a 40-Gb/s-based DWDM transmission system by taking the design of a dispersion compensating fiber into account.     

Contradictory relationship between Hurst parameter and queueing performance (extended version)

Long Range Dependent (LRD) network traffic does not behave like the traffic generated by the Poisson model or other Markovian models. From the network performance point of view, the main difference is that LRD traffic increases queueing delays due to its burstiness over many time scales. LRD behavior has been observed in different types and sizes of networks, for different applications (e.g., WWW) and different traffic aggregations. Since LRD behaviour is not rare nor isolated, accurate characterization of LRD traffic is very important in order to predict performance and to allocate network resources. The Hurst parameter is commonly used to quantify the degree of LRD and the burstiness of the traffic. In this paper we investigate the validity and effectiveness of the Hurst parameter. To this end, we analyze the UCLA Computer Science Department network traffic traces and compute their Hurst parameters. Queueing simulation is used to study the impact of LRD and to determine if the Hurst parameter accurately describes such LRD. Our results show that the Hurst parameter is not by itself an accurate predictor of the queueing performance for a given LRD traffic trace.     

Call performance in a frequency reuse digital portable radio system

A discrete-event stochastic simulation of many concurrent calls was used to generate signal-to-interference ratio (S/I) time histories and statistics on a time-division multiple-access (TDMA) uplink. The simulation integrates portable radio multiple access, uplink/downlink signal modeling, and the traffic process. Calls were held to completion, enabling observation of the effects of cochannel interference on time-dependent S/I statistics. It was found that the improvement obtained from measurement-based time-slot assignment in uplink S/I at access partially erodes over the life of a call, if it retains the time-slot assigned at the start. The amount and speed of erosion of S/I at the first percentile suggests that good transmission quality can be maintained for stationary users, with low overhead in the fixed radio network     

信息通信行业的ICT项目管理模式研究

文章主要针对ICT项目进行分析,在分析其特点的基础上解析项目建设内容,最后对ICT项目管理模式进行分析。     

On the performance of DQPSK communication systems impaired bytiming error, mixer imbalance, and frequency nonselective slow Rayleighfading

In this paper, the error performance of the differential detection scheme is assessed for differentially encoded quaternary-phase-shift-keying (DQPSK) and π/4-shifted-DQPSK signals, It is assumed that the receiver suffers from mixer imbalance and timing error impairments. Expressions for the system bit-error rate (BER) are obtained when the channel is free of fading and when the channel suffers from frequency nonselective (flat) slow Rayleigh fading in the face of additive white Gaussian noise. To arrive at the desired expressions, the probability density function (pdf) of the phase angle between a pair of Gaussian random vectors is used to obtain the probability of bit error conditioned on the channel fading and timing error. The resulting expressions are then averaged over the nonnegligible timing error and the channel fading to arrive at the desired expressions for the system BER. Finally, with the aid of numerical analysis and in the presence of the aforementioned impairments, a number of conclusions are drawn and the performance of differential receivers for DQPSK and π/4-shifted-DQPSK modulation schemes are compared. It is shown here that the performance of a DQPSK receiver in the absence of fading and timing error is substantially impaired by mixer imbalance for BERs less than 10^-4. In the presence of fading, the performance is noticeably degraded due to mixer imbalance when a nonzero timing error is present     

Research on the system error performance of coherent orthogonal frequency division multiplexing system with M-distribution in satellite-to-ground laser communication

In order to alleviate the influence of atmospheric turbulence on the performance of satellite-to-ground laser communication system,based on the M-distribution atmospheric channel model,a multi-carrier coherent orthogonal frequency division multiplexing (OFDM) modulation system was proposed for uplink and downlink in the satellite-to-ground laser communication.The closed-form expression of bit error rate (BER) of coherent OFDM modulation system was derived.The relationship between the zenith angle,receiving aperture,signal-to-noise ratio (SNR),optimal beam divergence angle,and optimal transmission radius and the BER were studied under weak,and strong atmosphere turbulence,and compared with binary coherent differential phase shift keying (DPSK) modulation.Both the theory and the simulation results show that compared with coherent DPSK modulation,the bit error performance of the coherent OFDM modulation system in the satellite-to-ground laser communication system is better.     

通信系统中一种频响补偿技术的研究与设计

依据通信系统内基带信号成形FIR滤波器的原理,结合频谱叠加、傅立叶变换等数学模型,研究出了一种对系统引入的频率响应误差进行纠正的技术,着重讨论了如何将误差频率响应叠加到FIR滤波器频谱之中得到修正的FIR滤波因子,并给出了一个补偿CIC频率响应的完整设计实例,实验结果验证了该设计思想的可行性、灵活性及实用性.     

太赫兹频段星地通信信道建模与仿真

太赫兹频段作为至今尚未被完全开发的超高通信频段,具有超大带宽等优点,将其应用于第五代（the 5th Generation,5G）、后五代（Beyond 5G,B5G）移动通信系统,除实现更高速率传输外,还可实现地面移动网络与卫星网络频谱资源的共享,有利于推动新一代空天地一体化通信网络建设.文章提出了一种适用于星地通信系统的太赫兹信道建模与仿真方法,分析了自由空间损耗、分子吸收损耗、云雾衰减、雨衰减及多普勒频移等太赫兹信道的影响因素,构建了星地太赫兹通信信道建模流程,并给出了分步骤信道参数的生成方法.通过数值仿真,对不同天气状况下传输距离和频率对传输信号的影响进行了分析,并基于所生成的信道响应对误码率进行评估,从而验证了所提出模型和方法的可用性.所提建模方法能够提供不同传输条件下的动态太赫兹信道响应数据,从而为今后太赫兹频段无线通信系统的设计与开发提供评估与测试依据.     

卫星通信抗干扰设计考虑及性能分析

提出了直接序列扩频和自适应调零天线相结合的卫星通信抗干扰设计思路,针对不同干扰条 件和不同卫星转发方式,进行了系统抗干扰性能的理论分析,结果表明,直接序列扩频和自 适应调零天线相结合,经星上再生处理转发可有效提高系统抗干扰能力。相关分析与结论对 工程应用具有一定的参考意义。