JTRAS/OSTBC系统在莱斯信道下的性能分析

在莱斯衰落信道下,研究了使用联合发射/接收天线选择(JTRAS)和正交空时分组码(OSTBC)的多输入多输出(MIMO)系统的平均符号误码率(ASEP)性能。基于标量加性高斯白噪声(AWGN)信道的方法,推导出了分别使用频移键控调制(FSK)和脉冲幅度调制(PAM)的ASEP性能的精确闭合表达式。数值仿真结果与理论分析结果相吻合,验证了分析结果的正确性。仿真结果表明：随着发射天线或接收天线数的增加,JTRAS/OSTBC系统的ASEP性能得到了很好的改善,当使用2FSK调制,信噪比为8 dB时,(4,4;2)系统的误码率是1×10-2,(6,6;6)系统的误码率是2×10-4;莱斯因子对JTRAS/OSTBC系统的ASEP性能有显著影响,当使用2FSK调制,信噪比为10 dB时,在莱斯因子为0时,(4,4;4)系统的误码率是7×10-4;在莱斯因子为4时,(4,4;4)系统的误码率是1.5×10-4;在莱斯因子为100时,(4,4;4)系统的误码率是8×10-5。     

多基站协作传输中的宽带OSTFDM-MIMO系统

在多基站协作传输中,由于发射天线分布在不同基站而导致接收信号具有内在的时间异步特性.基于现有MIMO系统同步环境下应用的正交空时分组码,提出了能适应多基站协作环境的一种异步空时分组码构造方法,并给出了相应的宽带OSTFDM-MIMO系统发射端编码结构和接收端译码实现.该系统在多基站协作传输中对信号异步传输具有鲁棒性,较传统的其它系统结构能提供更高的空间分集度和更高的数据传输速率,但同时不会增加系统接收机的译码复杂度.     

一种新的CDMA系统空时分组码结构

本文提出了一种新的采用空时分组码的CDMA系统上行链路的结构。发射端每个用户对发送信号先进行扩频,再对扩频后的信号进行空时分组编码后送至发射天线。同时本文还相应提出了接收端对接收信号的处理方法。仿真结果表明,该结合空时分组码的CDMA系统的误码率优于一般CDMA系统的误码率。     

最优天线选择空时分组码的性能分析

空时分组码(Spce—Time Block Coding)是目前研究发送分集(Transmit Diversity)技术的一个热点。针对TD—SCDMA系统的MIMO(Multiple-Input Multiple-Output)信道，将天线子集选择技术与空时分组码(Spce—Time Block Coding)相结合，进一步提升了发送分集的误码率性能。通过理论分析对此方案的进行了性能评估，表明天线选择技术对空时分组码(STBC)的性能有较大的改善。     

匙孔信道容量及中断概率分析

在某些多输入多输出(MIMO)衰落环境下,虽然发射或者接收信号不相关,但是系统的信道容量依然很低,这种现象称之为匙孔(Keyhole)效应.针对匙孔衰落MIMO信道,在任意的收发天线数目下,分析了Keyhole信道容量以及中断概率.研究结果表明,匙孔信道的最大分集增益由发射或接收天线数目的最小值决定.     

最优天线选择的空时分组编码

本文针对TD－SCDMA系统的MIMO（Multiple-Input Multiple-Output)信道，采用天线选择技术来提高空时分组码（Space-Time Block Coding)的分集性能。其依据是利用TDD系统上、下行信道的互易性，将系统对上行信道的估计直接应用于行链路。仿真结果表明，将天线选择技术与空时分组码（STBC）相结合对系统的误码率性能有较大的改善。     

不同约束对MMSE软干扰消除Turbo均衡器性能的影响

在MIMO空时编码系统中寻求一种有效的抑制等信道干扰（CCI）的方法是无线通信系统中的关键。基于最小均方差（MMSE）的软干扰消除Turbo均衡器能有效地消除系统共信道干扰与多用户干扰，在频率选择信道下的是一种非常有效的均衡接收技术。它在多天线系统中应用时，需要通过MMSE的方法得到优化的滤波系数；但在不同的约束条件下，会得到不同的滤波系数。本文比较研究了不同的约束方法对系统性能的影响。通过仿真得出了发射天线约束对系统性能起主要作用的结论。     

正交空时分组码在OFDM系统中的性能估计

在宽带OFDM系统中对正交空时分组码方案进行了研究，根据Almouti方案的译码原理给出了在正交空时分组码传输的频率选择性衰落信道条件下接收机输出瞬时信噪比的一般表达式，同时分两种情况进一步分析了其最小距离球界的符号差错性能。结果表明，在系统发送天线数、接收天线数及多径数目乘积较小的情形下，系统可以达到最大的分集增益。     

基于多种调制方式的空时OFDM系统多用户检测技术

建立了基于空时分组码的多输入多输出(MIMO)-正交频分复用(OFDM)系统模型,研究 了基于最小均方误差的串行干扰消除（MMSE-SIC）多用户检测算法,通过优化排序迭代结构 ,使得接收算法具有较好的性能。仿真结果表明,该算法在误码率方面能够取得优于常规线 性MMSE算法的性能,而且得出星座图中映射点间距也影响着检测算法的性能,随着间距的缩 小,误码概率会上升。     

MIMO技术的发展与应用

给出了多输入多输出(MIMO)技术的概念,详细叙述了MIMO技术的研究现状,阐述了MIMO的关键技术和MIMO技术的应用,研究和分析表明无线移动通信领域智能天线技术的重大突破就是多MIMO技术,它能在不增加带宽的情况下成倍地提高通信系统的容量和频谱利用率,是下一代移动通信系统中最富有竞争力的技术之一。文章最后给出了MIMO技术今后的研究方向。     

基于MMSE横式滤波器和PIC联合的MUD算法

新制度经济学认为,资源、资本和技术等因素只是经济发展的必要条件,但还不是经济发展的充要条件。从根本上讲,只有当经济制度和经济组织是有效率的,资源、资本和技术这些因素才会发挥作用,经济发展才会出现。在现实中,人们必须受到激励才会去从事符合社会需要的活动。为此,就需要设计某种制度或者进行制度改革,以达到激励的作用。制度因素对一国的经济发展具有决定性的作用。这一命题同样适用于中国经济问题的研究,尤其适用于我国国有经济改革的研究。     

一种机载地面侦察雷达多机动目标跟踪方法

加拿大经济学家巴伯(C.L.Barber)提出的有效保护率概念是对整个产业征税后实际保护程度的一个有效分析工具。但一些不符合现实的假设条件限制了有效保护理论的适用范围。一些著作也就这方面的问题作过探讨,本文在综合一些学者观点的基础上逐步放宽了其所假设的限制条件,使这一理论更加完善,更具现实指导意义。并在此基础上对中国关税结构的优化问题进行简要的分析。     

凝胶渗透色谱净化高效液相色谱-串联质谱法检测辛辣蔬菜中咪鲜胺等7种农药残留

建立了辛辣蔬菜基质中咪鲜胺、异菌脲、虫酰肼、噻螨酮、涕灭威、涕灭威亚砜和涕灭威砜7种农药残留量的凝胶渗透色谱-分散固相萃取技术相结合净化高效液相色谱串联质谱检测法。样品经乙腈提取,氮气吹干,环己烷-乙酸乙酯(1＋1)溶液溶解后,凝胶渗透色谱与分散固相萃取法相结合进行净化,反相高效液相色谱柱分离后,采用液相色谱-串联质谱法在分时段多反应监测模式下进行测定,外标法定量。结果表明：7种农药在0.005-2.0μg/mL范围内线性关系均良好(r2在0.995-0.999),且所有农药检出限和定量限均低于国际限量要求;在定量限、5倍和10倍定量限的添加水平下,辛辣蔬菜中7种农药的平均回收率介于60％-120％,相对标准偏差不大于5.0％。该方法定性、定量准确,干扰小,能用于辛辣蔬菜基质中7种农药残留的检测,能很好的满足我国进出口辛辣蔬菜中这7种农药限量的严格要求。     

Investigation of pedestrian crashes using multiple correspondence analysis in India

Abstract

Pedestrian safety is of growing concern with an increasing number of traffic accidents, especially in developing economies like India. In 2017, there were 20,457 pedestrian fatalities in India. Pedestrian crashes have also become a key concern in the state of Tamilnadu, India, due to the high percentage of deaths. If the available datasets are large and complex, identifying key factors is a challenging task. In this study, Multiple Correspondence Analysis (MCA), an exploratory data analysis technique was used to explore the roadway, traffic, crash, and pedestrian-related variables influencing pedestrian crashes. This study used the data from Government of Tamilnadu Road Accident Traffic Management System (RADMS) database, to analyse accident data of nine years (2009–2017) related to pedestrian crashes. The results of the study show that crashes occurring on the express highways on a multilane road are often associated with hit-and-run behaviour among drivers. Factors such as lighting conditions, location, pedestrian behaviour, crossings, and physical separation are also significantly contributing to pedestrian crashes. The key advantage of MCA is that it identifies a possible association between various contributing factors. The findings from this study will be useful for state transport authorities to improve countermeasures for mitigating pedestrian crashes and fatalities.     

用MFSK调制实现水声远程信息传输

研究了一种基于多进制频移键控(MFSK)调制的水声远程信息传输技术，介绍了通过谱分析进行解调的方法。初步的海试结果表明，该技术可以实现80km距离、4bit／s数据率的信息可靠传输。     

移动通信中的空分多址技术

在信息时代，人们对通信业务的需求不断增加，这对通信技术提出了更高的要求，空分多址（SDMA）技术由于其在提高系统容量和频谱利用率方面的独特优势而引起了人们的广泛关注。本文从基本概念、信道模型、系统实现和对通信系统的性能改善等几个方面对空分多址技术进行了较为全面的论述。     

A decision support model for buying battery electric vehicles considering consumer learning and psychological behavior

Developments in battery electric vehicles (BEVs) have received more and more attentions in the last decades due to alleviating carbon emissions and energy crisis. Consequently, how to rank alternative BEVs to assist consumers make better purchasing decisions is a worthy research study. However, there are still some defects in the existing studies for ranking of BEVs: 1) the evaluation index system of BEVs is not comprehensive; 2) the determination of criteria weights cannot be well applied to the actual purchase scenarios; and 3) the psychological behavior of consumers is ignored. To address those shortcomings, this paper proposes a decision support model to assist with consumers to buy BEVs. First, a systematic evaluation criteria system of BEVs including quantitative and qualitative indicators from parameter configurations and online reviews is constructed. Then, a weight algorithm considering consumer learning is proposed to determine the criteria weights. Furthermore, a decision support process considering consumers' regret avoidance behavior is proposed. Finally, an actual BEV purchase case is given to illustrate the practicability of the decision support model. This can be seen in case studies the proposed support model can be well applied to consumers with different regret avoidance behaviours.     

Analysis of multiple response in marketing research: Estimating the degree of association

Researchers often are forced to analyze nominally-scaled multiple response questions for which respondents have provided more than one response. A Multiple Index of Predictive Association (MIPA) is derived for estimating the effect of the independent variable on the dependent variable when one or both variables have multiple responses. MIPA is illustrated using demographic and preference data. The relevance of the Multiple Index of Predictive Association to marketing and its implications are discussed.     

美国国际贸易法院判定美国商务部对河北兴茂轮胎有限公司非公路用轮胎“双反”措施不当案评述

美国进口商和中国出口商不满美国商务部对来自中国的某些非公路用轮胎实施反倾销和反补贴税的裁定,向美国国际贸易法院提出起诉。美国国际贸易法院裁定,美国法律没有明确规定反倾销税法是否可适用于非市场经济国家;本案中美国商务部做的"双反"裁定,在方法上不合理。本文在介绍该案的基本案情、归纳法院推理和判决的基础上,对该案涉及的法律问题做了简要评论。     

How do economic,cultural, and global-connectedness distances moderate the effect of customers’ experiences on their intention to revisit non-indigenous restaurants? Evidence from Korean restaurants

In this study, we evaluate how the effect of customers' experiences on revisit intention for non-indigenous restaurants can be moderated by economic distance (ED), cultural distance (CD) and global-connectedness distance (GD) between the country of origin for a given non-indigenous restaurant and the customer’s resident country. Surveys were conducted in seven countries across three continents, and the levels of ED, CD and GD between Korea and the seven countries were used as moderators. The findings suggest that the types of food and staff are two elements that should be emphasized in countries that are relatively close to Korea. Conversely, elements like the atmosphere of the restaurant and word of mouth should be emphasized in countries that have greater distances from Korea. Of the three distances considered in the study, GD had the strongest moderating effect on the relationship between customers’ experiences and their intentions to return to the restaurant. As a whole, the results imply that ED, CD and GD are important points of reference when considering prior experience while selecting a target country based on the strength of the restaurant’s experience management.