我国煤炭类上市公司折旧政策的选择——基于企业所得税效率

本文探讨了固定资产折旧政策选择与企业所得税效率之间的关系。并在此基础上,以我国煤炭类上市公司为例,分析了这些企业无一例外地选择年限平均法计提折旧背后的动机,并为如何使企业选择适合的固定资产折旧政策提出了相关建议。     

Sequential point estimation of normal mean under LINEX loss function

A sequential point estimation of the mean of a normal distribution is considered under LINEX loss function. The regret of sequential procedures are obtained. Furthermore, it is shown that a sequential procedure with the sample mean as an estimate is asymptotically inadmissible. An accerelated stopping time is also considered. Received: December 1999     

Performance of methods to conduct mediation analysis with time-to-event outcomes

Previous studies have discouraged the use of the Cox proportional hazards (PH) model for traditional mediation analysis as it might provide biased results. Accelerated failure time (AFT) models have been proposed as an alternative for Cox PH models. In addition, the use of the potential outcomes framework has been proposed for mediation models with time-to-event outcomes. The aim of this paper is to investigate the performance of traditional mediation analysis and potential outcomes mediation analysis based on both the Cox PH and the AFT model. This is done by means of a Monte Carlo simulation study and the illustration of the methods using an empirical data set. Both the product-of-coefficients method of the traditional mediation analysis and the potential outcomes framework yield unbiased estimates with respect to their own underlying indirect effect value for simple mediation models with a time-to-event outcome and estimated based on Cox PH or AFT.     

Expected termination times of progressively Type-I censored step-stress accelerated life tests under continuous and interval inspections

A step-stress accelerated life test is a special life test where test units are subjected to higher stress levels than normal operating conditions so that the information on the lifetime parameters of a test unit can be obtained more quickly in a shorter period of time. Also, progressive Type-I censoring is a generalized form of time censoring where functional test units are withdrawn successively from the life test at some prefixed nonterminal time points. Despite its flexibility and efficient utilization of the available resources, progressively censored sampling has not gained much popularity due to its analytical complexity compared to the conventional censoring schemes. In particular, understanding the mean completion time of a life test is of great practical interest in order to design and manage the life test optimally under frequent budgetary and time constraints. In this work, the expected termination time of a general k-level step-stress accelerated life test under progressive Type-I censoring is derived using a recursive relationship of the stochastic termination time based on the conditional block independence. To be comprehensive, two different modes of failure inspections are considered: continuous inspection, where the exact failure times are observed, and interval inspection, where the exact failure times are not available but only the number of failures that occurred.     

802.11n高线性功率放大器的设计与实现

为了扩大802.11n无线产品的覆盖范围，设计了一款符合802.11n标准的2.4 GHz高线性 功率放大器。在该功率放大器的设计中采用了双路均衡功率合成技术和差异化加速开关技术 ，在提供高功率输出的同时满足了802.11n的误差向量幅度（EVM）的要求，尤其是实际应用 中的动态EVM。测试结果表明，该功率放大器回退7 dB后的线性输出功率为27 dBm，此 时的EVM为-30 dB，合成功率输出为29.5 dBm。该功率放大器可广泛用于无线局域 网中，与各种类型的无线AP直接匹配使用，提高其覆盖范围。     

Multi-sample simple step-stress experiment under time constraints

In the context of accelerated life testing, a step-stress model allows for testing under different conditions at various intermediate stages of the experiment. The goal is to develop inference for the mean lifetime at each stress level. The maximum likelihood estimates (MLEs) exist only when some (at least one) failures are observed at each stress level. This limitation can be tackled by a multi-sample step-stress model, which imposes a weaker condition for the existence of the MLEs, i.e. at each stress level, some failures (at least one) must be observed in at least one of the samples. The step-stress experiment with multiple samples at the same stress levels was introduced by Kateri et al. ( Journal of Statistical Planning and Inference, 139 , 2009a ). In this article, we focus on the likelihood inference under such a multi-sample set-up for the case of a simple step-stress experiment under exponentially distributed lifetimes when time constraints are in place in the experimentation.     

Sequential estimation of means of linear processes

First the minimum risk point estimation as well as the fixed-width confidence interval problems for the mean parameter of a linear process are addressed under the framework of Fakhre-Zakeri and Lee (1992). The accelerated versions of their full sequential methodologies are introduced in order to achieve operational savings. Next, multi-sample analogs are discussed along the lines of Mukhopadhyay and Sriram (1992) both under full sequential as well as accelerated sequential sampling. In either setup, the first-order asymptotic characteristics are highlighted.     

航空惯导系统核心器件寿命测定方法

本文采用一种新方法对航空惯导系统核心器件进行加速寿命试验,试验中采用的加速电流超过了一般加速寿命试验所选取的加速电流,通过对试验数据的分析讨论了该方法的可行性,在加速寿命试验中,对加速电流的上限进行了确定。     

加速寿命试验在车用电子喇叭质量改进中的应用

针对车用电子喇叭产品在质量改进中的可靠性特征数据难于获取问题,采用加速寿命试验方法缩短试验时间,达到快速获取失效时间数据的目的。本文通过实例,对应用背景、加速寿命试验条件、样本选取及数据处理进行了分析和说明。同时,针对车用电子喇叭产品的特殊性,试验中不仅采用了提高工作电压的加速失效方法,同时采用了包括机械结构变更、工作方式调整在内的其它加速失效方法。