Motives behind retailers’ post-entry expansion - Evidence from the Chinese luxury fashion market

This study aims to examine the motives behind retailers’ post-entry expansion in foreign markets. Through case studies of eleven participating luxury fashion retailers in China, qualitative data was collected from twenty-two executive interviews. Although their initial market entry was driven by both reactive (push) and proactive (pull) factors, the motives behind their post-entry expansion have become predominantly proactive, especially long-term growth strategies, the ambition to extend their brands and retail formats to more cities, and the experiences gained in entry markets. The desire to optimize the retail store portfolio through multiple channel strategies have slowed down the expansions of physical stores.     

黄浦江下游吴淞口站低潮位重现期研究

黄浦江为感潮河流,低潮位重现期的确定对黄浦江航道的设计具有重要意义。为了准确估计黄浦江低潮位的重现期,以黄浦江下游吴淞口站年最低潮位序列为例,在对样本进行三性审查的基础上,分别采用传统的数理统计方法和时变矩方法进行水文频率分析。结果表明:吴淞口站年最低潮位序列在1996年发生了变异;还现修正后的序列服从位置参数线性时变的GEV模型,低潮位存在缓慢的上升趋势;一致性条件下百年一遇低潮位约为0.261 m,在非一致性条件下其重现期增大为150 a。非一致性条件下的重现期增大说明黄浦江现有的航道设计标准偏安全,航道通航保证率提高。     

Stock market volatility forecasting: Do we need high-frequency data?

The general consensus in the volatility forecasting literature is that high-frequency volatility models outperform low-frequency volatility models. However, such a conclusion is reached when low-frequency volatility models are estimated from daily returns. Instead, we study this question considering daily, low-frequency volatility estimators based on open, high, low, and close daily prices. Our data sample consists of 18 stock market indices. We find that high-frequency volatility models tend to outperform low-frequency volatility models only for short-term forecasts. As the forecast horizon increases (up to one month), the difference in forecast accuracy becomes statistically indistinguishable for most market indices. To evaluate the practical implications of our results, we study a simple asset allocation problem. The results reveal that asset allocation based on high-frequency volatility model forecasts does not outperform asset allocation based on low-frequency volatility model forecasts.     

基于AD9361的掌上型LTE RRU设计与开发

当前小体积远端射频单元（Remote Radio Unit,RRU）主要是皮站级别的Pico-RRU，其重量和体积仍然难以满足掌上型的要求。为此，采用高集成度的AD9361芯片来实现长期演进（Long Term Evolution，LTE）宽带收发信机功能，配合时钟同步模块、放大器模块和控制接口电路等一起构建低成本的掌上型RRU。主要解决了基于AD9516的时钟同步、低相位噪声设计和高灵敏度接收机设计三个技术难点，成功实现了掌上型、高性能、低成本的设计目标。整个RRU样机尺寸为18 cm×10 cm×2 cm，质量约500 g，量产成本千元以内。测试表明，该RRU下行误差向量幅度（Error Vector Magnitude，EVM）小于3%，优于3GPP要求的8%；10 MHz带宽时上行接收机灵敏度优于3GPP要求的-93.5 dBm。     

珠江河口区水环境整体数学模型研究

根据珠江河口区的特点，建立了珠江河口区水流，泥沙及含氟度的整体联解数学模型，探讨了联解的计算模式；利用珠江三角洲和河口区水流泥沙、含氟度连续条件，把珠江三角洲网河区一维水沙、含氟度输移数学模型和河口区二维水沙、含氟度输移数学模型进行联解。同时采用最新的地形资料并选用洪、中、枯水及大、中、小潮等多种水文组合条件对该模型进行分区验证和整体验证，模型验证成果满足精度要求。     

Expanding the analytical potential of channel locational probability maps using cellular statistics

The planimetric shifts in channel location of large alluvial rivers are a critical component in the creation of diverse structures and functions in riverine habitats. Engineered management schemes must also compensate for this type of channel change to protect resources and maintain navigation channels. The stability of the Lower Mississippi River channel was assessed through an analysis of historical records of channel position produced and archived by the United States Army Corps of Engineers. Channel location was recorded for the years 1765, 1820, 1881, 1915, 1930, 1937, 1960 and 1970. Channel stability was measured by two introduced metrics on a cell‐by‐cell basis: (1) the standard deviation of Euclidean distance to a channel cell for the entire period of record, and (2) the rate of Euclidean distance change between years in the period of record. At a coarse spatial scale, channel instability increased in the downstream direction. The variability of channel stability also increased in the downstream direction. Analysis of this variability identified alternating areas of high and low stability occurring with greater frequency as distance downstream increased. These findings are validated by past studies of channel stability along the Lower Mississippi River. As a result, the proposed metrics provide a consistent, quantitative, efficient and cost‐effective means of identifying areas of channel instability at several spatial scales. Copyright © 2006 John Wiley & Sons, Ltd.     

利用黄河泥沙加固下游大堤

黄河是一条举世闻名的多泥沙河流，善淤、善决、善徒给沿河人民带来对过深重灾难，防洪问题一直是国家的心腹之患。泥沙问题是黄河防洪问题的症结所在。在总结固大堤经验的基础，进行挖河疏浚，淤筑“相对地下河”，已作为黄河治理的一项重大决策付诸实施。     

永定新河治理工程几个关键问题的研究

永定新河是天津市防洪的北部防线。由于受海相来沙淤积 ,河道行洪能力大幅度下降。针对永定新河治理工程设计中涉及到的河道淤积治理方案、闸位比选、防潮闸结构型式及施工方法、闸下减淤清淤措施等诸多问题进行了分析和研究 ,提出了相应的措施和建议     

佛山市中心组团桥梁群对河道影响的数值分析

在不同频率流量和阻水程度条件下,采用一维明渠非恒定流网河数学模型,分析规划中的佛山市桥梁群对区间河道洪季行洪、枯季水环境的影响,计算洪季不同频率洪峰流量下规划桥梁群对区间河道行洪洪水位、分流比的影响,枯季时规划桥梁群对区间河道过流量、分流比的影响,结果表明,利用一维网河数学模型计算佛山市中心组团规划桥梁群对区间河道断面平均水位、流量和流速的影响,结果有足够的数值精度,是可信的。     

明渠断面水流流速与边界剪切应力横向分布模型

天然河流的横断面多为由主槽和漫滩组成的复式断面,水流在这种断面中比在单一断面中受到更多因素影响,流态也更加复杂。通过将明渠横断面上微元体在水流方向的N-S控制方程沿水深积分,得出描述垂线平均流速和边界剪切应力横向分布的模型,并通过对实验数据的验证,确定了模型的实用性。