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Anomaly detection of user behavior based on DTMC with states of variable-length sequences

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The Journal of China Universities of Posts and Telecommunications 2011年第6期18卷 106-115页

作者： xiao xi xiA Shu-tao TIAN xin-guang ZHAI Qi-bin Graduate School at Shenzhen Tsinghua University Shenzhen 518055 China State Key Laboratory of Information Security Graduate University of Chinese Academy of Sciences Beijing 100049 China Key Laboratory of Network Science and Technology Institute of Computing Technology Chinese Academy of Sciences Beijing 100190 China

In anomaly detection, a challenge is how to model a user＇s dynamic behavior. Many previous works represent the user behavior based on fixed-length models. To overcome their shortcoming, we propose a novel method based on discrete-time Markov chains （DTMC） with states of variable-length sequences. The method firstly generates multiple shell command streams of different lengths and combines them into the library of general sequences. Then the states are defined according to variable-length behavioral patterns of a valid user, which improves the precision and adaptability of user profiling. Subsequently the transition probability matrix is created. In order to reduce computational complexity, the classification values are determined only by the transition probabilities, then smoothed with sliding windows, and finally used to discriminate between normal and abnormal behavior. Two empirical evaluations on datasets from Purdue University and AT＆T Shannon Lab show that the proposed method can achieve higher detection accuracy and require less memory than the other traditional methods.

关键词： intrusion detection anomaly detection shell command discrete-time Markov chain (DTMC)

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回流焊机过炉速度对温度曲线的影响研究

数学的实践与认识 2024年第9期54卷 248-256页

作者：杨宝男刘金东田怀谷章培军惠小健王震陕西省可控中子源应用技术国际联合研究中心西京学院理学院陕西西安710123

回流焊机的温度对于电子产品的焊接至关重要,理想的回流焊机温度曲线可以提升焊接质量.利用定积分思想以及一维热传导方程,研究了过炉速度对于温度曲线和受热量的影响.同时在固定温区温度的情况下确定了最优过炉速度范围.并在限制受热... 详细信息

回流焊机的温度对于电子产品的焊接至关重要,理想的回流焊机温度曲线可以提升焊接质量.利用定积分思想以及一维热传导方程,研究了过炉速度对于温度曲线和受热量的影响.同时在固定温区温度的情况下确定了最优过炉速度范围.并在限制受热量和平滑降低温度曲线的条件下,确定了提升焊接质量最优过炉速度.仿真结果表明,通过研究传输带过炉最优速度,实现对于回流焊机温度曲线的控制,对焊接质量的提升有很大帮助.

关键词：回流焊机温度曲线过炉速度热传导方程

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催产素在甲基苯丙胺使用障碍中的研究进展

中国药物依赖性杂志 2024年第4期33卷 286-289页

作者：王艳艳赵小溪赵天舒向小军中南大学湘雅二医院精神卫生研究所长沙410011

甲基苯丙胺在世界范围内被广泛滥用,但目前还没有针对甲基苯丙胺使用障碍的药物治疗方法。催产素是一种内源性神经肽,其在甲基苯丙胺成瘾过程中的重要作用逐渐被发现,研究表明催产素系统有望成为治疗甲基苯丙胺使用障碍的新靶点。本文... 详细信息

甲基苯丙胺在世界范围内被广泛滥用,但目前还没有针对甲基苯丙胺使用障碍的药物治疗方法。催产素是一种内源性神经肽,其在甲基苯丙胺成瘾过程中的重要作用逐渐被发现,研究表明催产素系统有望成为治疗甲基苯丙胺使用障碍的新靶点。本文从甲基苯丙胺渴求、戒断及复发三方面综述了催产素对啮齿类动物及人体甲基苯丙胺使用障碍的影响及可能机制,为甲基苯丙胺使用障碍的药物治疗提供新的思路。

关键词：甲基苯丙胺催产素物质使用障碍渴求戒断复吸

Modified strict sperm morphology threshold aids in the clinical selection of conventional in vitro fertilization(IVF)or intracytoplasmic sperm injection(ICSI)

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Asian Journal of Andrology 2022年第1期24卷 62-66页

作者： Yong Zhu Feng Zhang Hua Cheng xiao-xi Sun Feng Jiang Obstetrics and Gynecology Hospital Fudan UniversityShanghai 200011China Shanghai Ji Ai Genetics and IVF Institute Obstetrics and Gynecology HospitalFudan UniversityShanghai 200011China

For infertility treatment,the selection of in vitro fertilization(IVF)or intracytoplasmic sperm injection(ICSI)is decided by multiplying indicators(including fallopian tube factors,semen count,and semen motility),except for sperm *** this study,we conducted a retrospective analysis,from implantation to birth,over a period of 5 years.A total of 1873 couples with primary or secondary fallopian tube factors and an increased defective sperm morphology rate(DSMR)were divided into different groups to receive IVF or ICSI *** comparing the outcomes,we found that the F1 group(DSMR98%,IVF group 3;P98%,ICSI group 3)had higher cleavage rate(P<0.001),biochemical pregnancy rate(P<0.05),clinical pregnancy rate(P<0.05)and live birth rate(P<0.05)than the F3 ***,the ICSI subgroup had a lower two pronuclei fertilization rate than the IVF subgroup(P<0.05).Our data suggest that the sperm morphology should also be considered when selecting IVF or ICSI combined with other semen parameters before the first assisted reproductive technologies(ART)cycle,especially for males with severe sperm defects.

关键词： clinical outcome in vitro fertilization intracytoplasmic sperm injection sperm morphology

Duration-Distribution-Based HMM for Speech Recognition

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Frontiers of Electrical and Electronic Engineering in China 2006年第1期1卷 26-30页

作者： WANG Zuo-ying xiao xi Department of Electronic Engineering Tsinghua UniversityBeijing 100084China

To overcome the defects of the duration modeling in the homogeneous Hidden Markov Model(HMM)for speech recognition,a duration-distribution-based HMM(DDBHMM)is proposed in this paper based on a formalized definition of a left-to-right inhomogeneous Markov *** has been demonstrated that it can be identically defined by either the state duration or the state transition *** speaker-independent continuous speech recognition experiments show that by only modeling the state duration in DDBHMM,a significant improvement(17.8%error rate reduction)can be achieved compared with the classical *** ideal properties of DDBHMM give promise to many aspects of speech modeling,such as the modeling of the state duration,speed variation,speech discontinuity,and interframe correlation.

关键词： duration speech recognition DDBHMM

Nonadiabatic Geometric Quantum Computation with Asymmetric Superconducting Quantum Interference Device

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Communications in Theoretical Physics 2002年第9期37卷 285-291页

作者： HAO San-Ru HOU Bo-Yu xi xiao-Qiang YUE Rui-Hong Institute of Modern Physics Northwest University Xi''an 710069 China Galculating Physics Division Department of Computer Teaching Hunan Normal University Changsha 410081 China Institute of Modern Physics Northwest University Xi''an 710069 China Institute of Modern Physics Northwest University Xi''an 710069 China Institute of Modern Physics Northwest University Xi''an 710069 China

We propose a method of controlling the dc-SQUID (superconducting quantum interference device) system by changing the gate voltages, which controls the amplitude of the fictitious magnetic fields B-z, and the externally applied current that produces the piercing magnetic flux Phi(x) for the dc-SQUID system. We have also introduced a physical model for the dc-SQUID system. Using this physical model, one can obtain the non-adiabatic geometric phase gate for the single qubit and the non-adiabatic conditional geometric phase gate (controlled NOT gate) for the two qubits. It is shown that when the gate voltage and the externally applied current of the dc-SQUID system satisfies an appropriate constraint condition, the charge state evolution can be controlled exactly on a dynamic phase free path. The non-adiabatic evolution of the charge states is given as well.

关键词： non-adiabatic geometric phase gate dc-SQUID quantum computation

Four-quadrant Force Control with Minimal Ripple for Linear Switched Reluctance Machines

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CES Transactions on Electrical Machines and Systems 2020年第1期4卷 27-34页

作者： Xuanrui Huang Zechuan Lin xi xiao Department of Electrical Engineering Tsinghua UniversityBeijing 100084China

Linear switch reluctance machine(LSRM)has been tried to act as an alternative generator for direct drive linear wave energy converter(WEC).Many researchers have proposed new topologies of LSRM to improve the power density,efficiency and ***,the control methods for LSRM applied in direct drive WEC have been paid little attention,especially control methods considering the wave energy generator operating *** this paper,according to the generator control requirements of the direct drive WEC,force control algorithm for LSRM operating in four quadrants without a speed closed loop is put *** force ripple of LSRM is suppressed using force sharing function *** four-quadrant control is easy to realize requiring only phase currents *** results validate the proposed method and indicate that LSRM is able to be used as the generator for direct drive WEC.

关键词： Linear switched reluctance machine direct drive wave energy converter force ripple suppression four-quadrant operation.

Excess Molar Volume of Binary Mixtures of Methylheptenone+Alkanols at 298.15 K

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Chemical Research in Chinese Universities 2002年第4期18卷 427-429页

作者： xiao xi LI Hao-ran WANG Cong-min WANG Qi HAN Shi-jun Department of Chemistry Zhejiang UniversityHangzhou310027P.R.China

Excess molar volume(V E) data on binary liquid mixtures of methylheptenone (MHO) with methanol, ethanol, n-propanol or n-butanol have been determined from the density measurements at 298.15 K and atmospheric pressure. The values of V E in all the systems over the entire composition range are quantified by the Redlich-Kister equation. The effects of the chain length of alkanols on V E are discussed.

关键词： Excess molar volume Binary mixtures Methylheptenone Alkanol Density

Optimal Conclusive Teleportation of an Arbitrary d-Dimensional N-Particle Unknown State via a Partially Entangled Quantum Channel

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Communications in Theoretical Physics 2003年第2期39卷 157-166页

作者： Hao San-Ru Hou Bo-Yu xi xiao-Qiang Yue Rui-Hong Calculating Physics Division Department of Computer Teaching Hunan Normal University Changsha 410081 China Institute of Modern Physics Northwest University Xi'an 710069 China

In the paper we generalize the standard teleportation to the conclusive teleportation case which can teleportan arbitrary d-dimensional N-particle unknown state via the partially entangled quantum channel. We show that onlyif the quantum channel satisfies a constraint condition can the most general d-dimensional N-particle unknown state beperfect conclusively teleported. We also present a method for optimal conclusively teleportation of the N-particle statesand for constructing the joint POVM which can discern the quantum states on the sender's (Alice's) side. Two typicalexamples are given so that one can see how our method works.

关键词： N-粒子态量子隧道光学远距传物