飞行器射频隐身技术及发展思路

射频隐身是武器平台对抗无源探测设备的重要技术手段,与雷达、红外隐身一起构成 作战平台的隐身能力。飞行器射频隐身性能是其作战能力和生存能力达成的重要因素。在对 飞行器典型有源传感器的使用和面临的威胁分析基础上,分析了飞行器射频隐身主要技术手 段,概括了飞行器射频隐身主要技术特点,提出了飞行器射频隐身技术的发展思路。     

New Technologies And The Demand For Heterogeneous Labor: Firm-Level Evidence For The German Business-Related Service Sector

This paper investigates the impact of modern information and communication technologies on the demand for heterogeneous labor. It starts with an interrelated factor demand system. The ‘desired’ level of employment which is needed in such models, is derived from a Generalized Leontief cost function with quasi-fixed factors. Firm-level, cross-sectional data taken from an innovation survey in the service sector are used in the empirical analysis. The model is estimated by a trivariate ordered probit model. Evidence in favor of skill-biased technological change in the fast-growing German business-related services sector is found. ‘Ibe paper suggests a new method of calculating skill-specific and firm-specific labor cost from information on total labor cost and the share of each skill group in total employment only.     

Option smiling when investors’ estimates of asset volatility disagree

This study sheds light on why heterogeneous beliefs in volatility manifest the smile effect of options and how the degree of belief disagreement influences option-implied volatility. It is found that when investors’ level of heterogeneous beliefs increases, agents who over estimate volatility raise their subjective probability about those outer dividend states and hence increase more consumption to those states. As a result, an increase of consumption causes a decrease of their marginal rate of transformation in outer states. The raising subjective probability increases the prices of outer states, while the lower marginal rate of transformation decreases the prices of that. However, the influence of the former dominates the latter, causing a fatter tail of the state-price density. As a consequence, the values increase for those call options with high strike prices and put options with low strike prices, leading to a U-shaped implied volatility and hence causes a smell effect.     

How time horizons and arbitrage cost influence the turnover premium?

There are multiple theories for the causal relation between stock turnover and expected return. The risk theory argues that stocks with high turnover generally have high information uncertainty, and thus high subsequent returns are required to compensate for the increased risk. By contrast, the theory of heterogeneous beliefs considers that high-turnover stocks have high speculative values and tend to be overpriced. We find that the information contained in stock turnover is multidimensional and controlling time horizons and arbitrage cost contributes to the reconciliation of the theories of risk compensation and heterogeneous beliefs. Our result shows that expected return is positively correlated with short-term turnover, and negatively correlated with long-term one. The premium on short-term turnover is consistent with the explanations based on transaction cost and liquidity risk. The premium on long-term turnover is much more pronounced among stocks with high arbitrage cost and can be largely explained by the mispricing theory and heterogeneous beliefs.     

Book review

The paper develops a general equilibrium model of international production and trade. Technology is carried across borders by multinational producers and the set of technologies being used in a particular country is endogenous. Production locations are chosen based on the costs of production and getting the product to market. A producer may manufacture its product in its home country, target market country, or a third country. Estimated model parameters describe the states of technology in different countries, barriers to international investment, and trade costs. It is found that the barriers to international trade and investment are highly correlated. The model is used to measure the extent of technology diffusion across countries, study the relationship between international production and trade, investigate the effects of free-trade agreements (FTAs) on offshoring, and to quantify the welfare effects of international production and trade.     

Industry concentration and optimal discriminatory commercial policies

We derive the characteristics of firm-specific strategic trade policies when industries consist of heterogenous firms, and show how the informational requirements for policy design are thereby expanded. A knowledge of the Herfindahl index of concentration of the foreign industry is required for the design of optimal protection for domestic firms. It is shown that optimal firm-specific tariffs reduce the degree of foreign concentration, thus shifting rents to domestic firms.     

Aircraft safety analysis using clustering algorithms

In recent years, there have been many cost-benefit studies on aviation safety, which deal mainly with economic issues, omitting some strictly technical aspects. This study compares aircraft accidents in relation to the characteristics of the aircraft, environmental conditions, route, and traffic type. The study was conducted using a database of over 1500 aircraft accidents worldwide, occurring between 1985 and 2010. The data were processed and then aggregated into groups, using cluster analysis based on an algorithm of partition binary ‘Hard c means.’ For each cluster, the ‘cluster representative’ accident was identified as the average of all the different characteristics of the accident. Moreover, a ‘hazard index’ was defined for each cluster (according to annual movements); using this index, it was possible to establish the dangerousness of each ‘cluster’ in terms of aviation accidents. Obtained results allowed the construction of an easy-to-use predictive model for accidents using multivariate analysis.     

区域企业异质性特征、节能减排与碳排放强度——基于中国省市工业企业面板数据的研究

选取中国各省市2007—2010年面板数据对工业企业异质性特征与地区碳排放强度关系进行实证研究,结果显示,工业企业的规模和技术水平对碳排放强度具有显著的抑制作用,从业人员规模对碳排放强度具有正向作用,而企业效益与碳排放强度关系不显著。进一步研究后发现,企业规模和技术水平通过降低能源排放强度、产生减排效果来降低碳排放强度;单位工业企业从业人员的减少可以降低能源消耗强度和能源排放强度,通过节能与减排双重方式降低碳排放强度;工业企业效益提高了单位资产期望经济产出,没有很好地抑制非期望碳排放产出,无法降低碳排放强度。     

从飞机与高铁的瑜亮之争看交通工具的替代品威胁

针对高速铁路开通后对相应飞机航线产生冲击,导致航线萎缩、停飞的现象,本文从消费者角度出发,选择了价格、速度、载客量、每日开行班次、安全性、准点率、机场/车站环境与服务、机/车内环境与服务、购退票方式、机场/车站交通接驳便利度等10个指标,并按照重要程度为各指标赋予权重,以京沪线为例,对两种交通工具进行了比较。结果是高铁以相对优势胜出。从而得出结论：在运行时间5-6小时区间内,高铁在性价比上占优,飞机只能立足于更远程的运输市场。同时对飞机运输提出了开辟海岛航线和加大中西部航线等发挥自身优势的建议。     

波音B737-300飞机电源故障分析

本文主要对B737-300飞机运行中出现的典型电源故障进行分析检测,从故障现象并结合以往经验入手,对可能出现此故障的地方进行逐一排查,发现问题所在。更换部件之后,并按手册对其进行综合测试。最后对故障隔离进行了分析总结。