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计算不同调制方式下的信道容量对实际通信系统的信道编译码设计具有重要的理论意义。首先从Shannon信息论出发,介绍了平稳无记忆连续信道与加性白高斯噪声信道容量的定义。接着利用互信息与微分熵的相互关系,推导了几种常用的不同调制方式下高斯信道的容量,并给出了相应的信道容量闭合计算表达式。通过将电力卫星通信信道模拟为高斯信道,对采用无速率信道编码联合不同调制方式的卫星通信进行了数值仿真。仿真结果显示,通过推导得到的闭合表达式计算信道容量,能对实际卫星通信的编码速率、译码启动条件的确定起到很好的理论指导作用。 相似文献
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Michael S. Garver 《Journal of Business Logistics》2019,40(1):30-43
To increase the relevance of logistics and supply chain academic research, this paper recommends the development and testing of middle‐range theory and practice‐level theory. Yet, there are a number of research issues that arise when academic researchers test middle‐range and practice‐level theory, both in measuring constructs and in testing theoretical relationships between constructs. Concerning the measurement of constructs, this paper recommends that academic researchers pay more attention to content validity and undertake rigorous processes to ensure content validity. In addition, academic researchers need to more explicitly define constructs as either reflective or formative. If the construct is defined as formative, then the traditional statistical approaches to validate these measurement scales are not recommended. The appropriate use of employing single‐item measures for concrete constructs is discussed. In regard to conducting hypothesis tests, research issues associated with multicollinearity and omitted variable bias are discussed. Relative weight analysis is ideal for testing theoretical models and research hypotheses when survey data are obtained, multicollinearity is present, and there are a large number of independent variables predicting a dependent variable. Thus, relative weight analysis is ideal for testing research hypotheses in logistics and supply chain management. 相似文献
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Protecting Innovation Through Patents and Trade Secrets: Evidence for Firms with a Single Innovation
Dirk Crass Francisco Garcia Valero Francesco Pitton 《International Journal of the Economics of Business》2019,26(1):117-156
AbstractThis paper analyzes the use and effectiveness of patents and trade secrets designed to protect innovation. While previous studies have usually considered patents and trade secrets as substitutes for one another, we investigate to what extent and in what situations the two protection methods are used jointly. We identify protection strategies for single innovation firms and hence overcome the assignment problem of existing empirical studies, that is, whether firms using both protection methods do so for the same innovation or for different innovations. Employing firm panel data from Germany, we find fairly few differences between the determinants for choosing secrecy and patenting. Single innovators that combine both strategies, 39% of the group, tend to aim at a higher level of innovation and act in a more uncertain technological environment. Firms combining both protection methods yield significantly higher sales with new-to-market innovations, providing some evidence for a complementarity of the two protection methods. 相似文献
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