Discrete storage processes and their Poisson flow and fluid flow approximations

Consider discrete storage processes that are modulated by environmental processes. Environmental processes cause interruptions in the input and/or output processes of the discrete storage processes. Due to the difficulties encountered in the exact analysis of such discrete storage systems, often Poisson flow and/or fluid flow models with the same modulating environmental processes are proposed as approximations for these systems. The analysis of Poisson flow and fluid flow models is much easier than that of the discrete storage processes. In this paper we give sufficient conditions under which the content of the discrete storage processes can be bounded by the Poisson flow and the fluid flow models. For example, we show that Poisson flow models and the fluid flow models developed by Kosten (and by Anick, Mitra and Sondhi) can be used to bound the performance of infinite (finite) source packetized voice/data communication systems. We also show that a Poisson flow model and the fluid flow model developed by Mitra can be used to bound the buffer content of a two stage automatic transfer line. The potential use of the bounding techniques presented in this paper, of course, transcends well beyond these examples.Supported in part by NSF grant DMS-9308149.     

老年抑郁症患者预后相关因素研究

目的探讨影响老年抑郁症患者预后的相关因素。方法收集住院或门诊就诊的87例老年抑郁症患者的一般资料,并进行生活事件量表（LES）、艾森克人格问卷（EPQ）、简易智力状态检查表（MMSE）和社会支持评定量表（SSRS）等因子评定,采用大体功能评定量表（GAS）评定老年抑郁症患者的预后疗效,并根据GAS分值分组,GAS≤60分视为预后差,作为研究组;GAS＞60分视为预后好,作为对照组。通过logistic回归分析,探讨影响老年抑郁症患者预后的相关因素。结果87例老年抑郁症患者中疗效差者占37.9%。两组患者在起病形式、治疗是否恰当、治疗依从性、合并慢性躯体疾病、负性生活事件值、对社会支持的利用度、EPQ的N维度分值及MMSE总分等因子方面的差异均有统计学意义（均P＜0.05）,经多元logistic回归分析发现,影响老年抑郁症预后的主要因素为：治疗依从性、慢性躯体疾病、EPQ标准N维度分值、合并精神病症状及对支持的利用度。结论老年抑郁症患者的预后可能受精神病理学、神经心理学和家庭社会等多种因素的影响,应从多方位着手,降低复发率,提高生活质量。     

Adverse Effects of Environmental Noise on Acoustic Voice Quality Measurements

An accurate analysis of voice quality is imperative when using acoustic measurements to diagnose vocal pathologies. It is known that noise has a significant effect on the reliability and validity of acoustic voice measurements, but the precise relationship has not been established. The purpose of this study was to investigate the influence of noise on the accuracy, reliability, and validity of acoustic voice quality measurements while balancing for gender, age, intersubject and intrasubject variability, microphones, computer hardware, analysis software, and type of noise. Level of noise was precisely controlled. The specific focus of interest was to determine the critical levels of noise that can invalidate voice quality measurements and to generate practical recommendations. Results suggest that the recommended, acceptable, and unacceptable levels of noise in the acoustic environment are above 42 dB, above 30 dB, and below 30 dB signal-to-noise ratio, respectively.