Predicting 1-year outcome following acute myocardial infarction: physicians versus computers

Whether decision rules derived statistically from patient data can produce better decisions than an expert clinician or a model of the expert clinician (expert system) is controversial. We examined this issue in the context of predicting cardiac death by 1 year for patients discharged from the hospital following acute myocardial infarction. Decision rules were derived from a base sample of 781 patients. These decision rules and three experienced cardiologists then estimated probability of death by 1 year for each patient in a separate test sample (n = 400). In our evaluation of the performance of the decision rules and physicians, we detected no differences, although the decision rules and physicians tended to classify the patients somewhat differently. Further multivariate analyses on the physicians' predictions showed that two of the physicians paid attention to somewhat different variables than the third physician. Lack of agreement among expert cardiologists would complicate modeling of a consensual decision-making process within the framework of an expert system.     

NBCC:一种数据流上变化的挖掘算法

针对数据流上变化的挖掘问题,提出了算法NBCC,首先利用精确抽样的方法对数据流构建概要数据结构,然后借鉴经典朴素贝叶斯分类方法的思想,将训练样本集分成Ci类,i=1,2,…,m。对测试样本集设定一个阈值!:当P(Ci｜X)相似文献   

中央加密系统在动态密钥分存方案中的应用研究*

在单齿加密－解密算法基础上,提出了一种基于单齿中央加密系统的动态密钥分存方案。研究指出：任意K个系统成员B={B1,B2,…,Bk},它们各自选择无规则分布的正整数集合XBi={xi1,xi2,…,xim}。其中i=1,2,…,k,并公开XBi。利用P〈G, X,X′〉,任意l个(或更多)Bi能够重构共享密钥。其中k,l∈N,l≤k。研究结果表明,该方案具有良好的保密性和安全性。     

Mathematical models of quantum computation

In this paper, we introduce two mathematical models of realistic quantum computation. First, we develop a theory of bulk quantum computation such as NMR (Nuclear Magnetic Resonance) quantum computation. For this purpose, we define bulk quantum Turing machine (BQTM for short) as a model of bulk quantum computation. Then, we define complexity classes EBQP, BBQP and ZBQP as counterparts of the quantum complexity classes EQP, BQP and ZQP, respectively, and show that EBQP=EQP, BBQP=BQP and ZBQP=ZQP. This implies that BQTMs are polynomially related to ordinary QTMs as long as they are used to solve decision problems. We also show that these two types of QTMs are also polynomially related when they solve a function problem which has a unique solution. Furthermore, we show that BQTMs can solve certain instances of NP-complete problems efficiently. On the other hand, in the theory of quantum computation, only feed-forward quantum circuits are investigated, because a quantum circuit represents a sequence of applications of time evolution operators. But, if a quantum computer is a physical device where the gates are interactions controlled by a current computer such as laser pulses on trapped ions, NMR and most implementation proposals, it is natural to describe quantum circuits as ones that have feedback loops if we want to visualize the total amount of the necessary hardware. For this purpose, we introduce a quantum recurrent circuit model, which is a quantum circuit with feedback loops. LetC be a quantum recurrent circuit which solves the satisfiability problem for a blackbox Boolean function includingn variables with probability at least 1/2. And lets be the size ofC (i.e. the number of the gates inC) andt be the number of iterations that is needed forC to solve the satisfiability problem. Then, we show that, for those quantum recurrent circuits, the minimum value ofmax(s, t) isO(n ²2 ^n/3). Tetsuro Nishino, D.Sc.: He is presently an Associate Professor in the Department of Information and Communication Engineering, The University of Electro-Communications. He received the B.S., M.S. and D.Sc degrees in mathematics from Waseda University, in 1982, 1984 and 1991 respectively. From 1984 to 1987, he joined Tokyo Research Laboratory, IBM Japan. From 1987 to 1992, he was a Research Associate of Tokyo Denki University, and from 1992 to 1994, he was an Associate Professor of Japan Advanced Institute of Science and Technology, Hokuriku. His main interests are circuit complexity theory, computational learning theory and quantum complexity theory.     

Syntactic decision rules for recognition of spoken words and phrases using a stochastic automaton

This study deals with the design of a syntactic decision rule for recognizing an unknown utterance from a set X. The decision rule is expressed as a function of the character string (CS) derived from the test utterance. To obtain the CS, the waveform of the utterance is divided into a large number of frames of roughly equal duration numbered 1, 2,...,n. The ith symbol in the CS is the phonemic symbol obtained by subjecting the ith frame of the waveform to a relatively simple phoneme decision rule, the number of symbols in the CS being n. All the available nonacoustic information such as the lexicon of words in the set X, the possibility of confusion between different phonemes as seen by the phoneme decision rule, etc. is used in the design of the decision rule. The syntactic decision rule can be implemented by a stochastic finite state automaton involving limited memory and computation. The decision rule can also be interpreted as yielding the phrase x which minimizes a distance measure D(x, z) between the phrase x X and the observed CS z. We wili compare this approach with the other approaches such as the Viterbi methods, the distance approaches involving various types of distances, etc.     

出栈序列的性质及其求解新算法

设集合N=｛1,2,3,…,n｝,N中的元素按次序1、2、3、…、n入栈,所有不同的出栈序列的集合记为S[1,2,3,…,n]。论文讨论了出栈序列的性质,通过新的计数方法证明了｜S[1,2,3,…,n]｜=n+112n!"n,并给出了求S[1,2,3,…,n]中所有元素的一种新算法。新计数方法与传统的方法相比简单直观,且易于理解。求所有出栈序列的新算法的时间复杂度为O(n+112n!"n),较传统算法速度更快、效率更高。用C语言程序验证了新算法的有效性。     

Collaborative multimedia systems: synthesis of media objects

When a group {/1,..., l_n} of individuals wishes to collaboratively construct a complex multimedia document, the first requirement is that they be able to manipulate media-objects created by one another. For instance, if individual L_j wishes to access some media objects present at participant l_k's site, he must be able to: 1) retrieve this object from across the network, 2) ensure that the object is in a form that is compatible with the viewing/editing resources he has available at his node, and 3) ensure that the object has the desired quality (such as image size and resolution). Furthermore, he must be able to achieve these goals at the lowest possible cost. In this paper, we develop a theory of media objects, and present optimal algorithms for collaborative object sharing/synthesis of the sort envisaged above. We then extend the algorithms to incorporate quality constraints (such as image size) as well as distribution across multiple nodes. The theoretical model is validated by an experimental implementation that supports the theoretical results     

Some Indices of Alphabet Overlap Graph

The undirected de Bruijn graph is often used as the model of communication network for its useful properties,such as short diameter,small maximum vertex degree.In this paper,we consider the alphabet overlap graph G(k,d,s): the vertex set V = {v|v = (v1 ...vk);vi ∈ {1,2,...,d},i = 1,2,...,k};they are distinct and two vertices u = (u1 ...uk) and v = (v1 ...vk) are adjacent if and only if us+i = vi or vs+i = ui (i = 1,2,...,k s).In particular,when s = 1,G(k,d,s) is just an undirected de Bruijn graph.First,we give a formula to calculate the vertex degree of G(k,d,s).Then,we use the corollary of Menger’s theorem to prove that the connectivity of G(k,d,s) is 2ds 2d2s k for s k/2.     

量子网络中多用户量子密钥共享协议

设计了基于多用户的量子密钥共享协议，该协议在多个用户组成的3个簇中共享多串光子和多个GHZ态。在S簇中，S1, S2, …, Sn-1利用多串光子直接编码，生成包含mN元的量子态，传输给Sn。Sn通过M簇中任选的一个用户Mj，传递给D簇中每一个用户D1, D2,…, Dn。该协议利用现有的手段可以实现。     

Ontology driven decision support for the diagnosis of mild cognitive impairment

In recent years, mild cognitive impairment (MCI) has attracted significant attention as an indicator of high risk for Alzheimer's disease (AD), and the diagnosis of MCI can alert patient to carry out appropriate strategies to prevent AD. To avoid subjectivity in diagnosis, we propose an ontology driven decision support method which is an automated procedure for diagnosing MCI through magnetic resonance imaging (MRI). In this approach, we encode specialized MRI knowledge into an ontology and construct a rule set using machine learning algorithms. Then we apply these two parts in conjunction with reasoning engine to automatically distinguish MCI patients from normal controls (NC). The rule set is trained by MRI data of 187 MCI patients and 177 normal controls selected from Alzheimer's Disease Neuroimaging Initiative (ADNI) using C4.5 algorithm. By using a 10-fold cross validation, we prove that the performance of C4.5 with 80.2% sensitivity is better than other algorithms, such as support vector machine (SVM), Bayesian network (BN) and back propagation (BP) neural networks, and C4.5 is suitable for the construction of reasoning rules. Meanwhile, the evaluation results suggest that our approach would be useful to assist physicians efficiently in real clinical diagnosis for the disease of MCI.     

Discovering causality in large databases

A causal rule between two variables, X M Y, captures the relationship that the presence of X causes the appearance of Y. Because of its usefulness (compared to association rules), techniques for mining causal rules are beginning to be developed. However, the effectiveness of existing methods (such as the LCD and CU-path algorithms) are limited to mining causal rules among simple variables, and are inadequate to discover and represent causal rules among multi-value variables. In this paper, we propose that the causality between variables X and Y be represented in the form X M Y with conditional probability matrix M Y|X . We also propose a new approach to discover causality in large databases based on partitioning. The approach partitions the items into item variables by decomposing "bad" item variables and composing "not-good" item variables. In particular, we establish a method to optimize causal rules that merges the "useless" information in conditional probability matrices of extracted causal rules.     

Structural stability of ternary D8m–Ti5Sb2X (X=Al,Ga, In,Si, Ge,Sn) compounds

The crystal and electronic structures of Ti₅Sb₂X (X=Al, Ga, In, Si, Ge, Sn) ternary compounds in the Nb₅Sn₂Si-type structure (ternary-D8_m) have been investigated by means of first principles calculations. The calculated structural parameters are in good agreement with the experimental data. The total electronic densities of states as well as the Bader charges of the atoms have been computed. Both electronic and size effects allow to explain the stability of the Ti₅Sb₂X (X=Al, Ga, In, Si, Ge, Sn) ternary compounds in the ternary D8_m structure. The enthalpies of formation of the ternary D8_m compounds have been obtained. The off-stoichiometry domains of D8_m–Ti₅Sb₂Ga and D8_m–Ti₅Sb₂Si are discussed.     

大规模无线网络中(X,S)-Bottleneck 区域性能分析

基于二层QBDs(quasi birth-death models),提出了一个(X,S)-bottleneck区域性能分析模型,(X,S)-bottleneck区域的特征通过第1层QBD模型描述,而经过(X,S)-bottleneck区域的每条流的特征由第2层QBD模型描述.基于该性能分析模型,对(X,S)-bottleneck区域的性能进行了一些概率分析,如(X,S)-bottleneck区域的平衡状态概率、经过该区域通信流的成功转发概率和吞吐量等,确定了上述概率及吞吐量的取值范围,仿真实验结果表明了该性能分析模型对于分析(X,S)-bottleneck区域性能的有效性.结论有助于无线网络通信性能的改进和管理.     

基于多传感器的发动机故障诊断模糊专家系统

本文介绍了采用多传感器综合监测技术的汽车发动机故障诊断专家系统。总结了汽车发动机常见故障,建立了汽车发动机典型故障集。介绍了汽车发动机的故障征兆提取方法,建立了汽车发动机故障征兆集。提出了一种基于模糊规则汽车发动机故障诊断方法。设计了基于模糊规则的发动机故障诊断专家系统,并通过实例证明了该诊断系统的有效性。     

Lower bounds for Bayes error estimation

We give a short proof of the following result. Let (X,Y) be any distribution on N×{0,1}, and let (X₁,Y₁),...,(X_n,Y_n) be an i.i.d. sample drawn from this distribution. In discrimination, the Bayes error L*=inf_gP{g(X)≠Y} is of crucial importance. Here we show that without further conditions on the distribution of (X,Y), no rate-of-convergence results can be obtained. Let φ_n(X₁,Y₁,...,X_n,Y_n ) be an estimate of the Bayes error, and let {φ_n(.)} be a sequence of such estimates. For any sequence {a_n} of positive numbers converging to zero, a distribution of (X,Y) may be found such that E{|L*-φ_n(X₁,Y ₁,...,X_n,Y_n)|}⩾a_n often converges infinitely     

利用ODBC API函数编写CGI程序的研究与实现

本文以数据库的查询操作为例，详细介绍了ＣＧＩ的编程的四个关键步骤，这是企业Ｂ／Ｓ／Ｄ即浏览器／服务器／数据库开发的核心技术。这为希望尽快掌握ＣＧＩ技术者提供一种行之有效的方法。     

An improved algorithm for implication testing involving arithmeticinequalities

Implication testing of arithmetic inequalities has been widely used in different areas in database systems and has received extensive research as well. Klug and Ullman (A. Klug, 1988; and J.D. Ullman, 1989) proposed an algorithm that determines whether S implies T, where T and S consist of inequalities of form (X op Y), X and Y are two variables, and opϵ {=<, ⩽, ≠, >, ⩾}. The complexity of the algorithm is O(n³), where n is the number of inequalities in S. We reduce the problem to matrix multiplication, thus improving the time bound to O(n^2.376). We also demonstrate an O(n² ) algorithm if the number of inequalities in T is bounded by O(n). Since matrix multiplication has been well studied, our reduction allows the possibility of directly adopting many practical results for managing matrices and their operations, such as parallel computation and efficient representation of sparse matrices     

A medical decision support system for disease diagnosis under uncertainty

This paper presents a decision support system (DSS) modeled by a fuzzy expert system (FES) for medical diagnosis to help physicians make better decisions. The proposed system collects comprehensive information about a disease from a group of experts. To this aim, a cross-sectional study is conducted by asking physicians’ expertise on all symptoms relevant to a disease. A fuzzy rule based system is then formed based on this information, which contains a set of significant symptoms relevant to the suspected disease. Linguistic fuzzy values are assigned to model each symptom. The input of the system is the severity level of each symptom reported by patients. The proposed FES considers two approaches to account for uncertain inputs from patients. Two case studies on kidney stone and kidney infection were conducted to demonstrate how the proposed method could be used. A group of patients were used to validate the effectiveness of the proposed expert system. The results show that the proposed fuzzy expert system is capable of diagnosing diseases with a high degree of accuracy and precision comparing to a couple of machine learning methods.     

嫁接决策树用于相似疾病诊断研究

对于相似性疾病的区别诊断,年青医师可能缺乏经验,经验丰富的医师可能由于经验而容易忽视。如何利用数据挖掘领域中的决策树方法对相似性疾病的诊断给予辅助是本文的目的。本文基于疾病的诊断规则表通过嫁接决策树方法,实现在一棵决策树上对多种相似疾病进行诊断,使医师快速找到疾病判别的分界点,尽早确定较有针对性的诊断方案,避免误诊和医疗资源的浪费,以及缩短病人就诊周期,减轻患者病痛和经济负担。嫁接决策树也可以提高医师对患者可能同时患有多种疾病或存在最可能演化的另一种病种的警觉性,有助于尽早检查或做好预防。     

Validation of biochemical laboratory results using the DNSev expert system

In a modern hospital biochemical laboratory, the efficiency and quality of the analysis result production process are fundamental. With respect to quality, an important step in the process is validation. In this step, laboratory physicians, who are physicians specialized in laboratory work, check the analysis result reports in order to verify that no error has occurred during their production. The application described in this paper is an expert system named DNSev. DNSev has been developed in order to improve the quality of the validation process performed by a specific laboratory information system (LIS), called ITALAB C/S, a system used in about thirty percent of Italian hospital laboratories. Objectives achieved by DNSev are: analysis result validation support (medical laboratory expertise in the process is translated into rules and automatically applied by DNSev), help for laboratory automation (checks that are usually manually executed are now automatically executed), clarity (reasoning performed by DNSev in issuing alarms is documented in order to explain it to laboratory physicians), flexibility (new types of reasoning can be easily added to the system by simply upgrading its knowledge base), reliability (checks may be tailored, based on patient characteristics) and time saving and cost reduction. During the development of DNSev, the knowledge acquisition and elicitation task was performed by interviewing laboratory physicians, and also by using available documents and laboratory guidelines. In order to conduct a significant trial test, we installed DNSev in the centralized biochemical laboratory of ‘Sant'Orsola-Malpighi’ Hospital in Bologna (Italy). This is one of the largest Italian biochemical laboratories, managed entirely by ITALAB C/S LIS. During this test we achieve a time saving of around 63% for each analysis request and a reduction on the overall number of analysis requests to be manually examined by laboratory physicians by around 20–25%. About performance of DNSev checks we achieved good accuracy and sensibility levels and a very low false normal level. These results demonstrate that an expert system may be a valid solution for improving quality and efficiency of well-defined medical tasks.