带启动期的多级适应性休假M~x/G/1队长的瞬态解

本文研究了带启动时间的多级适应性休假Mx/G/1排队系统模型,在LS和L变换下得到了队长瞬态分布的L变换递推式.     

Finite time-horizon Markov model for IEEE 802.11e

We model wireless local area network channel utilization over a finite interval through a finite time-horizon Markov （FTHM） model. By accurately capturing time-varying utilization, the FTHM model allows for generally distributed transmission-opportunity （TXOP） duration, which most existing models do not account for. An absorbing state is introduced to limit the lifetime of the counting process, resulting in a non-ergodic Markov chain that is solved via transient analysis. The model predictions for time-varying utilization are validated by simulation with errors of no more than 0.1% after eight beacon intervals. Moreover, we show that the FTHM model prediction error is below 4% for Poisson distributed and uniformly distributed TXOP durations.     

The Roles of Fibroblast Growth Factor (FGF)-23, α-Klotho and Furin Protease in Calcium and Phosphate Homeostasis : A Mini-Review

The roles of calcitonin, parathormone and calcitriol in the regulation of plasma calcium and phosphate are well-established. However, in autosomal-dominant hypophosphatemic rickety patients, studies have revealed normal plasma levels of calcium, associated with normal thyroid and parathyroid functions, but decreased levels of phosphate and calcitriol despite adequate reserves of vitamin D. Also, in tumoral calcinosis, persistent hyperphosphatemia with increased levels of 1,25(OH)₂D₃ have been observed. These studies indicate the involvement of factors other than the ones already known. The first decade of this century/millennium has led to the discovery of the involvement of fibroblast growth factor-23, furin protease and α-klotho in the homeostasis of calcium and phosphate, which is the subject of this mini-review.     

瞬变电磁法发射机装置及参数对关断时间的影响研究

本文对多匝重叠小回线装置不同的线圈参数和发射机参数进行了同点关断时间的实验,对比分析了同点同参数的关断时间随时间的变化规律、发射机数据采集时参数设置对关断时间的影响,以及不同线圈匝数和发射磁矩对关断时间的影响。结果表明,同一装置及参数的关断时间受线圈电阻影响较大;发射机叠加次数的设置和时间序列的选择对关断时间基本无影响;线圈匝数与其关断时间呈正比线性关系;线圈的发射磁矩与其关断时间在线圈匝数不变的情况下呈正比线性关系。     

车用汽油机瞬态燃烧的研究

本文对汽油机瞬态工况燃烧特性的研究意义和研究现状进行了概述,介绍了进行瞬态燃烧研究的实验方案,提出了一种研究内燃机瞬态信号的方法——符号时间序列方法。     

Optimal location and controller design of STATCOM for power system stability improvement using PSO

The optimal location of a static synchronous compensator (STATCOM) and its coordinated design with power system stabilizers (PSSs) for power system stability improvement are presented in this paper. First, the location of STATCOM to improve transient stability is formulated as an optimization problem and particle swarm optimization (PSO) is employed to search for its optimal location. Then, coordinated design problem of STATCOM-based controller with multiple PSS is formulated as an optimization problem and optimal controller parameters are obtained using PSO. A two-area test system is used to show the effectiveness of the proposed approach for determining the optimal location and controller parameters for power system stability improvement. The nonlinear simulation results show that optimally located STATCOM improves the transient stability and coordinated design of STATCOM-based controller and PSSs improve greatly the system damping. Finally, the coordinated design problem is extended to a four-machine two-area system and the results show that the inter-area and local modes of oscillations are well damped with the proposed PSO-optimized controllers.     

先天性胆管囊状扩张症术后的护理体会

先天性胆管囊状扩张症是一种少见病,儿童多见,本病的典型临床表现为腹痛、黄疸和腹部包块,但临床上具有典型的三联征者非常少见。此病保守治疗效果差,一经确诊尽早手术治疗是本病唯一有效的治疗方法。术后严密观察病情变化,及时发现和处理异常情况可避免严重并发症的发生。应做好患儿的心理护理、饮食护理及各种引流管的护理,指导患儿及早下床活动,提高手术疗效。     

A Socio-cognitive Approach to How Children with Deafblindness Understand Symbols

Children with congenital deafblindness are a population of learners who may need intervention in order to develop symbolic understanding. They experience a combination of vision and hearing impairments that can affect how they make sense of the world, develop relationships, and understand symbols. In this article, the author reviewed a socio-cognitive framework of symbolic understanding and suggested it as one way to organise the extant research on symbolic development of children with deafblindness. A socio-cognitive framework describes the development of children’s individual skills and how their abilities are supported by active participation in social and cultural experiences. Symbolic understanding is not an isolated cognitive skill, but rather a complex socio-cognitive developmental process that is intimately supported by meaningful interactions. A socio-cognitive framework may help teachers to support the symbolic understanding of school-aged children with deafblindness. Teachers of children with deafblindness can use the framework to understand their students’ individual socio-cognitive abilities and their social interactions. In other words, a socio-cognitive framework may support teachers of children with deafblindness to understand the abilities and environments that are critical to the development of symbolic understanding.