99mTc-MIBI used for diagnosis of portal hypertension: an experimental study

The authors investigated the relationship between portal-systemic shunting and portal pressure in 16 CCl4-induced cirrhotic wistar rats by 99mTc-MIBI photography of heart and liver. Based on radio-counts taken at 30 minutes after 99mTc-MIBI was given per rectum 8 rats or medial clonic vein 8 rats, heart radio-counts/liver radio-counts (H/L) and portal-systemic shunting index (SI) were recorded. It was shown that 1. H/L and SI of the two cirrhotic groups were greater than those of normals (P < 0.001); 2. H/L in cirrhotic rats by rectum 99mTc-MIBI administration was more closely related to free portal pressure (FPP, r = 0.83, P < 0.01) than in those by venous route (r = 0.74, P < 0.05) and its regressive formation FPP (kPa) = 0. 24 + 4.06 (H/L) was deduced and used to calculate portal pressure of cirrhotic rats. The very good relationship between the calculated and measured portal venous pressure was shown in a group of 12 cirrhotic rats (r = 0.85, P < 0.01). These findings suggested that the rectum administration of 99mTc-MIBI may be a useful method in calculating portal pressure and portal-systemic shunting in portal hypertensive patients.     

集散控制系统在选煤生产中的应用

介绍了太原选煤厂新建的集散控制系统的结构和功能.     

Notes on interval estimation of risk difference in stratified noncompliance randomized trials: A Monte Carlo evaluation

When comparing an experimental treatment with a standard treatment in a randomized clinical trial (RCT), we often use the risk difference (RD) to measure the efficacy of an experimental treatment. In this paper, we have developed four asymptotic interval estimators for the RD in a stratified RCT with noncompliance. These include an asymptotic interval estimator based on the weighted-least-squares (WLS) estimator of the RD, an asymptotic interval estimator using tanh⁻¹(x) transformation with the WLS optimal weight, an asymptotic interval estimator derived from Fieller’s Theorem, and an asymptotic interval estimator using a randomization-based approach. Based on Monte Carlo simulations, we have compared these four asymptotic interval estimators with the asymptotic interval estimator recently proposed elsewhere. We have found that when the probability of compliance is high, the interval estimator using a randomization-based approach is probably more accurate than the others, especially when the stratum size is not large. When the probability of compliance is moderate, the interval estimator using tanh⁻¹(x) transformation is likely to be the best among all interval estimators considered here. We note that the interval estimator proposed elsewhere can be of use when the underlying RD is small, but lose accuracy when the RD is large. We also note that when the number of patients per assigned treatment is large, the four asymptotic interval estimators developed here are essentially equivalent; they are all appropriate for use. Finally, to illustrate the use of these interval estimators, we consider the data taken from a large field trial studying the effect of a multifactor intervention program on reducing the mortality of coronary heart disease in middle-aged men.     

CBL VDL和CCL测井技术在检测套管脱扣方面的应用

套管在井下发生脱扣失效事故之后通常要采用测井方法确定失效位置和失效形式。经过对多口井CBL、VDL和CCL套管测井结果进行了调查研究和分析,发现API接箍式偏梯形螺纹接头套管、接箍式特殊螺纹接头套管和直连型特殊螺纹接头套管接头部位在测井图像中均有不同各自的特征,不正常的CCL和CBL曲线和VDL波形位置表明了套管损坏位置和损坏形式。根据CCL、CBL和VDL波形测井结果,可以判断套管接头从现场端脱扣或工厂端脱扣。     

热泵干燥系统在纺织行业的应用

在分析对比热泵干燥系统的几种空气循环方式后,结合纺织干燥工艺的特点,提出一种新的干燥循环方式-物料流动准封闭式循环干燥系统,通过对这种循环方式的运行过程分析,说明该系统具有较好的节能效果.     

BYS91─1多机系统存储器频带的分析

ＢＹＳ９１－１是基于ＲＩＳＣｉ８６０ＸＰ设计的具有局部存储和共享存储的多机系统。本文以排队论为工具，建立了该系统存储器的排队模型，给出了存储器使用频带的解析式，并结合具体的设计参数，分析了系统中处理机个数、存储空间配置对存储器有效频带的影响。     

Analysis of distribution time of multiple files in a P2P network

Peer-to-Peer (P2P) file sharing attracts much attention due to its scalability and robustness. One important metric in measuring the performance of a P2P file sharing system is the amount of time required for all peers to get the files. We refer this time as the file distribution time. Researchers have proposed protocols to minimize the file distribution time under different situation. However, most works are based on the single-file scenario. On the other hand, there are studies showing that in a file sharing application, users may download multiple files at the same time. In this paper, we analyze the minimum time needed to distribute multiple files. We develop an explicit expression for the minimum amount of time needed to distribute multiple files in a heterogeneous P2P fluid model. Unlike the single-file scenario, we demonstrate that the theoretical lower bound in multi-file is not always achievable. With a comprehensive consideration of all the configurations, we elaborate how to partition the bandwidth capacities of both seeds and leechers for a particular file such that the finish time is optimal.     

Chaos-based joint compression and encryption algorithm for generating variable length ciphertext

Here we modify a chaos-based joint compression and encryption algorithm previously proposed by us. Two modifications are suggested for improving the compression performance and generating ciphertext with variable length, respectively. The first goal is achieved by counting the number of distinct symbols visited by the chaotic search orbit, rather than the total number of iterations of the chaotic map. The second objective is realized by introducing a user-chosen parameter to determine the ratio between the search and the mask modes. The performance of the modified algorithm is justified by simulation results using standard test files.     

An efficient partitioning algorithm for distributed virtualenvironment systems

Distributed virtual environment (DVE) systems model and simulate the activities of thousands of entities interacting in a virtual world over a wide area network. Possible applications for DVE systems are multiplayer video games, military and industrial trainings, and collaborative engineering. In general, a DVE system is composed of many servers and each server is responsible to manage multiple clients who want to participate in the virtual world. Each server receives updates from different clients (such as the current position and orientation of each client) and then delivers this information to other clients in the virtual world. The server also needs to perform other tasks, such as object collision detection and synchronization control. A large scale DVE system needs to support many clients and this imposes a heavy requirement on networking resources and computational resources. Therefore, how to meet the growing requirement of bandwidth and computational resources is one of the major challenges in designing a scalable and cost-effective DVE system. In this paper, we propose an efficient partitioning algorithm that addresses the scalability issue of designing a large scale DVE system. The main idea is to dynamically divide the virtual world into different partitions and then efficiently assign these partitions to different servers. This way, each server will process approximately the same amount of workload. Another objective of the partitioning algorithm is to reduce the server-to-server communication overhead. The theoretical foundation of our dynamic partitioning algorithm is based on the linear optimization principle. We also illustrate how one can parallelize the proposed partitioning algorithm so that it can efficiently partition a very large scale DVE system. Lastly, experiments are carried out to illustrate the effectiveness of the proposed partitioning algorithm under various settings of the virtual world