Evolution of superpeer topologies — An analytical perspective

In superpeer based networks, resourceful peers (having high bandwidth and computational resources) are discovered through the process of bootstrapping, whereby they get upgraded to superpeers. However, bootstrapping is influenced by several factors like limitation on the maximum number of connections a peer can have due to bandwidth constraints, limitation on the availability of information of existing peers due to cache size constraints and also by the attachment policy of the newly arriving peers to the resourceful peers. In this paper, we derive closed form equations that model the effect of these factors on superpeer related topological properties of the networks. Based on the model, we show that existing bootstrapping protocols can lead to a situation where only a small fraction of the resourceful peers gets converted to superpeers, i.e., a large fraction of them remain underutilized; we later validate this statement using real Gnutella snapshots. We observe that as a node attachment policy, newly arriving peers must use a combination of random and preferential attachment strategy so as to ensure proper utilization of the resourceful peers. We also show that the cache parameters must also be suitably tuned so as to increase the fraction of superpeers in the network. Finally, we show that in real Gnutella networks the degree distribution generated using our models suitably fits the corresponding empirical values.     

降低用棉单耗的生产体会

探讨降低净用棉单耗的途径和措施。以JC 9.7tex纱为例,通过在各项专业及生产技术管理工作方面采取一系列措施,结果获得了良好的降耗效果。认为,降低净用棉单耗是一项全面系统的管理工作,首先应发挥各职能部门专业管理作用,做好原棉采购、收付检验、配棉、混棉、拣花间回花、落棉、下脚的管理以及月末盘存和数据统计工作。各生产工序在稳定成纱质量的前提下,以减少落棉、回花,提高制成率为主线,做好工艺、设备、操作等各方面的基础管理工作,最终能够取得良好的降耗效果。     

Komplementäre Modellierung in der Fluidverfahrenstechnik

Optimization of technological processes depends on the relevant process design, properly selected column internals and sufficient understanding of the process behavior. This can only be achieved with the help of accurate and reliable process models. Along these lines, the present article suggests a new modelling concept – complementary modeling – for a large class of fluid engineering processes. Due to diversity of process conditions and criteria, it is impossible to develop a unified modelling approach. Instead, an efficient combination of different modeling approaches is advantageous. The complementary modeling is discussed in detail and illustrated with several case studies.     

Physiological workload reactions to increasing levels of task difficulty

The sensitivity of physiological measures to mental workload was investigated in a flight simulator. Twelve pilots had to fly through a tunnel with varying levels of difficulty. Additionally, they had to perform a memory task with four levels of difficulty. The easiest memory task was combined with the easiest tunnel task and the most difficult memory task with the most difficult tunnel task. Between the tunnel tasks, subjects had to fly a pursuit task in which a target jet had to be followed. Rest periods before and after the experiment were used as a baseline for the physiological measures. Mental workload was measured with heart period, continuous blood pressure, respiration and eye blinks. Several respiratory parameters, heart rate variability, blood pressure variability and the gain between systolic blood pressure and heart period (modulus) were scored. All measures showed differences between rest and flight, and between the pursuit and the tunnel task. Only heart period was sensitive to difficulty levels in the tunnel task. Heart rate variability increased when respiratory activity around 0.10 Hz increased, which occurred often. The modulus was hardly influenced by respiration and therefore appears to be a better measure than heart rate variability. Among the respiratory parameters, the duration of a respiratory cycle was the most sensitive to changes in workload. The time in between two successive eye blinks (blink interval) increased and the blink duration decreased as more visual information had to be processed. Increasing the difficulty of the memory task led to a decrement in blink interval, probably caused by subvocal activity during rehearsal of target letters. The data show that physiological measures are sensitive to mental effort, whereas rating scales are sensitive to both mental effort and task difficulty.     

A multi-layered dual-band on-body conformal integrated antenna for WBAN communication

This article presents a dual-band, multi-layered on-body conformal metamaterial (MTM) integrated antenna for Wireless Body Area Network (WBAN) communication. The frequency bands range from 3.2 GHz to 3.5 GHz and 3.9 GHz to 4.3 GHz. A zero-reflection-phase based MTM comprises of the 2 × 2 array of H-shaped unit-cell is installed beneath the monopole antenna to suppress the back radiations, and enhance the gain. The characterization of the unit-cell is done in terms of its reflection and transmission characteristics, refractive index, and material characteristics. The integration of the MTM brings down the peak 1-g-averaged SAR to 0.174 W/kg and 0.207 W/kg at the respective bands of the conformal configuration for a body-antenna separation of 1 mm. The proposed configuration proffers peak realized antenna gain of 4.54 dBi and 4.71 dBi, and Front to Back Ratio (FBR) of 11.79 dB and 12.98 dB at the respective frequency bands. The performance of the proposed antenna is rigorously analyzed against structural deformation, operating frequency, gain, and FBR. The measured performance of antenna agrees well with that of simulated results.     

Degradation of the antimicrobial triclocarban (TCC) with ozone

Triclocarban (TCC) has been used as an antimicrobial compound for many decades due to its sanitising properties. Recent studies showed that TCC is toxic and causes disruption to the endocrine system. In this work, ozone oxidation of TCC was studied in 70% acetonitrile:30% water solutions. Ozone degraded TCC effectively and the reaction rates increased substantially with ozone gas concentration, pH and temperature. Second-order-reaction kinetics was suitable to describe the chemical reaction. The effect of temperature was described by the Arrhenius equation and the activation energy was found equal to 31.0 kJ/mol. The stoichiometry of the reaction was one and the value of the rate constant at pH 7 was 5 × 10³ M⁻¹ s⁻¹.     

短波通信中基于自适应帧长的数据速率变化改进算法

为解决传统数据速率变化（DRC）传输算法中因速率震荡造成的高误码率（BER）问题，提出一种基于自适应帧长（AFL）的DRC改进传输算法。首先，在初始化阶段，根据当前信道的参数和以往经验值信息确定初始传输的帧长和传输速率，并进行数据传输。然后，当检测到传输过程中连续两个相同长度帧发送成功后，开始增加帧长；若出现重发帧连续两次重传失败的情况，则在下次传输时将帧长减半。最后，结合当前的帧长计算误帧率，若该值小于预设的阈值，则提高数据传输速率。与RapidM DRC算法相比，该算法的链路平均BER降低了个1.8百分点，链路连通率提高了11个百分点。实验结果表明，所提算法基本消除了速率震荡的现象，能够提高短波通信系统的通信能力。     

恩斯林装置的改进及吸水率影响因素分析

吸水率是球团用膨润土的重要指标,直接影响造球效应和生球质量的稳定。研究表明,恩斯林装置中市售毛细管内径的差别,对膨润土吸水率的测定带来较大的误差。测定方法参照《非金属矿物化性能测试规程》。对恩斯林装置进行改进,使用2 ml的移液管代替毛细管,测试体积直读;并对试验装置进行固定、水平检测,试验条件进行优化,并分析了影响膨润土吸水率的几个因素。实验测试可以达到准确、简便检测的目的。     

倾斜式太阳能烟囱强化自然通风理论研究

倾斜式太阳能烟囱利用太阳辐射增加烟囱内空气温度,烟囱内外空气温差形成的密度差提供了自然通风所需的驱动力。根据质量守恒和能量守恒方程给出倾斜式太阳能烟囱通风量计算方法,并将计算结果与文献试验测试值进行了对比,分析了烟囱长度、宽度、深度及倾角对通风量的影响,计算了倾斜式太阳能烟囱用于乌鲁木齐地区的通风量,并与竖直式烟囱进行对比,计算结果表明,相同结构尺寸下增加50°倾角可使通风量增加11.52%,是一种值得进一步研究的自然通风方式。     

Gamma rate theory for causal rate control in source coding and video coding

The rate distortion function in information theory provides performance bounds for lossy source coding. However, it is not clear how to causally encode a Gaussian sequence under rate constraints while achieving R–D optimality. This problem has significant implications in the design of rate control for video communication. To address this problem, we take distortion fluctuation into account and develop a new theory, called gamma rate theory, to quantify the trade-off between rate and distortion fluctuation. The gamma rate theory implies that, to evaluate the performance of causal rate controls in source coding, the traditional R–D metric needs to be replaced by a new GRD metric. The gamma rate theory identifies the trade-off between quality fluctuation and bandwidth, which is not known previously. To validate the gamma rate theory, we design a rate control algorithm for video coding; our experimental results demonstrate the utility of the gamma rate theory in video coding.