采用次谐波混频技术的毫米波超宽带混频器研制

提出了一种次谐波混频技术结合宽带匹配滤波电路的设计方法,能有效降低本振源的制作难度,并可扩展中频带宽。应用高频场仿真软件以及谐波平衡仿真软件,研制了两个频段的超宽带次谐波混频器。测试结果：K频段混频器,固定本振频率15 GHz,射频频率在18～26.5 GHz的频带内变化时,变频损耗小于10.7 dB,最小变频损耗为7.5 dB;Ka频段混频器,固定本振频率22 GHz,射频频率在26.5～40 GHz的频带内变化时,变频损耗小于11.5 dB,最小变频损耗为8 dB。测试结果指标与传统的双平衡混频器指标相当,证明了电路设计方案的正确性。     

0.1～4 GHz达林顿-共射共基结构的增益模块

提出了一种新型电路拓扑结构的增益模块,该增益模块为达林顿-共射共基结构,对 其工作原理进行了分析。基于AWR Microwave Office软件的仿真结果表明：达林顿晶体管共 射放大电路具有较强的电流放大能力,能有效提高增益;共基放大电路能抑制电路密勒效应 ,改善电路高频响应。设计了增益模块的版图,用2 μm InGaP/GaAs HBT工艺成功流片 ,测试结果表明：在01～4 GHz频率范围内,该增益模块最大增益为25 dB,最小 增益大于13.5 dB,在900 MHz工作频率时,该增益模块的P1dB为20 d Bm。     

3 kW微波源传导电磁干扰测试及分析

微波源工作时内部的电磁干扰可以通过电源输入线耦合出来,干扰其他电力电子设备。研究三相输入电源线的传导干扰文献很多,但分离的共模（CM）和差模（DM）电流局限于相线之间,缺少对中线上干扰的分析。使用电流探头测试3 kW磁控管微波源输入线的传导干扰,利用矢量网络分析仪校准电流探头,从而获得150 kHz~30 MHz频带内相线和中线的传导干扰电流,并分离出CM电流与DM电流。通过对比DM电流和中线上干扰的频谱,分析了中线上传导干扰成分。测试数据表明,在150 kHz~8 MHz频带内差模干扰电流比共模干扰电流大10 dB以上;中线上的干扰与DM干扰幅值一致,表明中线上的干扰主要是差模成分。该干扰分布规律有助于提出有效的干扰抑制手段。     

靶场毫米波信号高灵敏度接收与测试新方法

基于靶场毫米波测试中微弱信号（低至-128 dBm）检测的实际需求,通过信噪比分析 ,采用外差式宽带多通道快速扫频复合信道化技术,在W频段实现了-128 dBm接收灵敏 度的测 试系统。同时,设计了毫米波信标源并利用空间衰减理论,提出了一种W频段高灵敏度（- 128 dBm）测试的新方法。理论分析表明,测试距离为290 m、相应的衰减值约为-1 21.5 dB时,可提供一个功率最小达到-128 dBm的W频段毫米波信号源。利用标定后的 毫米波信号源进行外场实际测量,证明了该测试方法的可行性。     

同步轨道卫星四站时差统计定轨精度分析

基于卫星通信信号的多站时差测轨是一种重要的新型无源测轨方法,分析其定轨精度对系统 应用具有重要意义。介绍了四站时 差测轨原理与系统组成,提出了基于四站时差测量数据的自校准统计定轨策略,采用计算机 仿真了同步轨道卫星的统计定轨精度。仿真结果表明：当无系统误差时,24 h观测数据统计定轨位置误差约为11 m,预报1周位置误差约100 m;当存在系统 误差时,可用自校准方法同步估计系统误差,系统误差估计精度约为4 m,位置误差约 为120 m,预报1周的位置误差约为200 m。     

一种Ku频段机载同轴双工器设计

为实现Ku频段双工器的小型化,以便适于对体积和重量有严格要求的机载环境使用, 提出了一种Ku频段机载同轴双工器设计方法。该方法使用两个同轴带通滤波器构成双工器实 现小体积,采用等效电路对带通滤波器进行设计,采用群时延拟合法利用仿真软件对T型接 头尺寸进行优化设计,并给出了详细设计过程。实物测试结果表明,所设计的Ku频段同轴双 工器体积仅为70 mm×29 mm×12 mm,插损小于0.9 dB,隔离大于80 dB  ,已在多个工程中得以应用。     

一种多信道的分簇式短波令牌协议

传统的短波令牌协议（HFTP）调度方式单一,在没有数据传送时,信道资源会被各节点间的令牌传递所占用,且令牌在通信质量较差时易丢失。基于此,提出一种多信道的分簇式短波令牌协议（CHFTP）,通过以通信质量评估为标准的分簇算法和基于预约的动态令牌调度,减小了令牌丢失的概率和令牌传递、处理的开销,并给出了仿真分析。仿真结果表明,该协议的端到端平均时延和网络吞吐量明显优于短波令牌协议,CHFTP的平均时延最多可减少75%,网络吞吐量最多可增加66.7%,适合在短波通信网络中使用。     

新型Koch岛分形耦合微带线带通滤波器

为抑制平面带通滤波器的二次谐波,实现高选择性和低插入损耗,提出了一种新型 Koch岛分形结构,并将其应用到平面耦合微带线带通滤波器的设计中。仿真及测试结果表明 ：所设计的新型Koch岛分形耦合微带线带通滤波器的中心频率为3 GHz,3 dB通带 宽度为10%;与传统的耦合微带线带通滤波器相比,该新型滤波器的二次谐波降低了1 1.5 dB,选择特性提高了5 dB/GHz,通带内最大回波损耗降低了4.7 dB,尺寸缩 小了近5%。该新型滤波器具有尺寸小、重量轻、成本低且性能好等优点。     

毫米波线性化固态功放的研制

研制了工作于Ka频段的10 W线性化固态功放。采用预失真技 术的线性化单元主要由一个肖特基二极管和一个电容并联构成,具有增益扩展和相位延迟的 特性, 并且其增益和相位特性具有可调性。将其应用于工作频率为30 GHz、输出功率为10 W 的功放,双音激励信号频率间隔为5 MHz,三阶互调（IMD3）可以改善15 dBc。     

具有谐波抑制特性的LTCC带通滤波器新设计

提出了一种新型的具有多次谐波抑制功能的低温共烧陶 瓷(LTCC)微型带通滤波器,该滤波器电路由电感耦合的四阶谐振腔组成。在一般抽头式梳状线滤波器 设计的基础上,引入了交叉耦合,通过改进其结构,形成了多个传输零点,并结合电路仿真 以及三维电磁场仿真,辅之以DOE(Design of Experiment)的设计方法,设计出了一种尺寸 小、频率选择性好、阻带宽的滤波器。实际测试结果与仿真结果吻合较好,中心频率为13 .4 GHz,其3 dB带宽为200 MHz,在15.5～35 GHz频率上的衰减均优于 20 dB,体积仅为3.2 mm×1.6 mm×1.2 mm。所提方法对滤波器谐波抑制 的设计具有指导作用。     

GPS_GPRS定位系统车载终端的应用设计与实现

介绍了一种将GPRS应用于GPS定位数据传输的GPS—GPRS定位系统。该系统以GPRS、GPS及CPU(77E58)为核心构成，涉及到控制、协议解析、无线技术的应用等各方面，车载终端具有安装简单、功能强大、极具实用性等特点。     

物联网燃气表系统的设计与实现

针对现有远程抄表系统的不足，结合计算机及通信领域的最新科技成果，提出了一种基于LoRa(Long Range)和GPRS(General Packet Radio Service)相结合的网络化远程抄表系统。其无线智能燃气表终端采用超低功耗微处理器MSP430进行智能化设计，完成气表数据采集与处理；采用LoRa技术进行测控组网；集中器和管理中心通过GPRS无线通信网络实现数据的远程交互。最后，给出了抄表系统的可靠性解决方案。实验结果表明，该系统比传统的远程抄表系统能耗低，且更快捷、可靠、方便，可广泛应用于无线远程抄表领域。     

Improving Group Attention: An Experiment with Synchronous Brainstorming

In this paper we address the problem of information overload in synchronous group work: the large quantity of information, multiple information sources, and the need to sustain reciprocal interdependence have a negative impact on the capacity to attend to the group. We propose a group attention model characterizing the dynamic coupling between the group members and the mediating technology. Based on that model, we developed a compensation mechanism capable to estimate the most adequate time to raise the users?? attention to the group. We describe how this compensation mechanism was applied to synchronous brainstorming and present results from a laboratory experiment. The obtained results indicate that groups using the compensation mechanism produced 9.6% more ideas when compared to the control groups. A detailed post-hoc analysis of the data obtained in the experiment also indicates that users using the compensation mechanism had 7.5 s of extra uninterrupted time to think about and type an idea, which they began to write 6.4 s sooner, and completed in 4.2 s less time.     

直通放行中基于RFID的智能电子检锁监控系统设计与实现

为解决直通放行中进出境货物检验检疫过程中出现的区域分离性监管缺失问题,有效避免待检货物运输过程中逃漏检现象的发生,加强监控的有效性,本系统以主动式RFID和GPS技术搭建待检货物运输车辆及其实时位置信息采集体,借助GPRS网络实现信息的无线通讯,开发了以RFID后台软件系统和WebGIS为信息融合表达手段的智能电子检锁监控系统。其信息集成平台主要有车载电子检锁模块、固定式无线RFID阅读器模块、控制中心模块和手持智能终端PDA模块四个组成部分。监控系统信息发布采用B/S结构。系统实际运行结果表明本系统采用的解决方法正确可行,达到了预期监管效果。     

Customer complaining: The role of tie strength and information control

We examine the impact of two key constructs, information control and tie strength, on consumers’ likelihood of complaining following service failures. We report convergent results from three types of studies—an experiment, a survey, and secondary data. In the first study, tie strength and information control were systematically varied in an experiment using a restaurant scenario. In a second study, survey data from patients who experienced dissatisfactory service was collected. The third study used field data from 1,470 customers of an HMO. Results from all three studies showed that, following service failure, complaining is more likely when the tendency for information control is stronger and ties are weaker.     

基于GPRS的LED显示屏的无线数据更新系统

针对市场上出现的带大容量存储器的LED显示屏,设计了一种基于GPRS业务的无线数据更新系统。该系统能实现对LED显示屏16Mbit以上存储器中数据的无线更新。介绍了该系统的设计方案和软硬件的实现。目前,该系统已成功应用于显示屏的无线数据更新,并取得了良好的效果。     

ZigBee和GPRS技术在无线监控系统中的应用

为了使家居系统摆脱各种线缆的羁绊,设计了一种基于ZigBee和GPRS技术的智能家居系统。采用MSP430单片机和无线射频模块CC2420搭建了一个符合ZigBee规范的星型传感器网络,对温度、煤气、人体入侵进行实时采集,并通过GPRS网络对系统进行实时监控。实验结果表明,系统功耗小、可靠性高,是一种理想的智能家居实现方式。     

Forecasting Methods and Seasonal Adjustment for a University Foodservice Operation

ABSTRACT

Considering the unique seasonal pattern in university dining environments, this study attempts to determine the degree of improvement in accuracy of each forecasting method tested when seasonally adjusted data is employed. This study also seeks to identify the most accurate forecasting method of the six forecasting methods used in this study: naïve, moving average, simple exponential smoothing, Holt's method, Winter's method, and linear regression. Accuracy is measured using Mean Squared Error, Mean Absolute Percentage Error, and Mean Percentage Error. Results show that Winter's method outperforms the other five methods when raw data is used, while Moving Average method, when used with seasonally adjusted data, is the most accurate forecasting technique. Seasonally adjusted data is found to greatly improve forecasting accuracy in most of the methods. The findings of this study indicate that seasonally adjusted data is more effective in forecasting customer counts in the university foodservice operations than raw data, so the adjusted data help control costs and increase customer satisfaction.     

Understanding the role of situational factors on online grocery shopping among older adults

This paper seeks to identify the situational factors that drive the adoption of online grocery shopping among older adults. A two-step research process is employed. First, exploratory qualitative research is carried out to identify situational factors that older adults take into account when deciding whether to buy groceries online. This is followed by a conjoint experiment to determine which situational factors are considered most important when making such a decision. The sample consisted of 9 participants in the in-depth individual interviews and 206 respondents in the conjoint experiment. The findings indicate that health, mobility issues, and distance to a store are the most important situational factors driving older adults to buy groceries online. Moreover, the findings confirm that the adoption of online grocery shopping among older adults is a result of a complex trade-off of situational variables. The findings contribute to managerial practice by providing online grocery retailers with insight that can be applied when designing promotional programs targeted at older adults.     

An Analysis of Data Quality: Professional Panels,Student Subject Pools,and Amazon's Mechanical Turk

Data collection using Internet-based samples has become increasingly popular in many social science disciplines, including advertising. This research examines whether one popular Internet data source, Amazon's Mechanical Turk (MTurk), is an appropriate substitute for other popular samples utilized in advertising research. Specifically, a five-sample between-subjects experiment was conducted to help researchers who utilize MTurk in advertising experiments understand the strengths and weaknesses of MTurk relative to student samples and professional panels. In comparisons across five samples, results show that the MTurk data outperformed panel data procured from two separate professional marketing research companies across various measures of data quality. The MTurk data were also compared to two different student samples, and results show the data were at least comparable in quality. While researchers may consider MTurk samples as a viable alternative to student samples when testing theory-driven outcomes, precautions should be taken to ensure the quality of data regardless of the source. Best practices for ensuring data quality are offered for advertising researchers who utilize MTurk for data collection.