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Copyright of Systems Engineering & Electronics is the property of Journal of Systems Engineering & Electronics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

As the rapid deployment of low earth orbit (LEO) mega-constellations and the swift growth of satellite Internet unfolds, distributed satellite systems composed of a large number of LEO satellites become a significant feature of the space-air-ground integrated networks. In satellite networks, low-cost, high-precision time synchronization technology is one of the core technologies.The distributed timing synchronization problem of LEO communication constellations, influenced by the high dynamics and temporally varying topological structures of low orbit satellites was focused on. Considering the communication delay characteristics in the LEO satellite scenario, and addressing the deficiencies in synchronization accuracy and convergence speed of existing methods in dynamic network topologies, a timing synchronization method based on maximum likelihood estimation for LEO satellites was proposed. This method effectively solves the problem of unpredictable random communication delays and asymmetric inter-satellite distances in distributed dynamic networks. The simulation results show that the synchronization error of the time synchronization method based on maximum likelihood estimation is less than 5 ns under the dynamic scenario and topology of LEO satellites.

Aiming at the traditional accelerated life test only considering the single stress and single failure cause, the inference method of double stress accelerated competing risks data is studied under the adaptive type-Ⅱ progressively censored and the life of test units follow Weibull distribution. The maximum likelihood estimations and the asymptotic confidence intervals of unknown parameters are obtained by using the Newton-Raphson iteration and asymptotic likelihood theory. A Gibbs sampling combining with Metropolis-Hasting algorithm method is developed to obtain Bayes estimations, and the Monte Carlo method is employed to construct the HPD credible intervals. The simulated results show that the present method has good statistical inference performance, meanwhile the failure sample size and the expected experimentation time have significant effect on the estimations.

The use of structural durability analysis technology can effectively improve the economic efficiency of aircraft structures while ensuring their reliability. This paper utilizes the structural durability analysis technique to study the initial fatigue quality (IFQ) of a typical fatigue structure of 7B04-T651 high-strength aluminum alloy under the action of flight load spectrum of a certain type of aircraft. Firstly, the maximum likelihood estimation method is applied to the parameter estimation problem of crack initiation time distribution based on three-parameter Weibull distribution. The Monte Carlo method is used to verify the correctness of this approach. Secondly, fatigue tests under three different stress levels are carried out on the flight load spectrum. The logarithmic sample moment approach is proposed to process the equivalent initial flaw size distribution to obtain its general model. In addition, the initial fatigue quality model describing the typical structure is established, which verifies that the equivalent initial flaw size (EIFS) is less than the allowable 0.125 mm. By analyzing the initial fatigue quality of the typical structure, the correctness and practicability of the generalization method is demonstrated, and the life estimation model of this typical structure is built under different stress zones, different specified crack sizes and different reliability levels. [ABSTRACT FROM AUTHOR]

Zero-and-one-inflated geometric distribution model was investigated, the conditional distribution of latent variables were constructed, and a sampling algorithm was designed. On the basis of data expansion, the maximum likelihood estimation, expectation maximization (EM) algorithm and Bayesian method were employed to estimate the model parameters. Different sample sizes and parameter true values were setted, and the performance of these methods were evaluated through numerical simulations. Finally, the Detroit traffic accident deaths dataset in 1994 of United States were analyzed, the results indicate that zero-and-one-inflated geometric distribution model can fit the dataset better. [ABSTRACT FROM AUTHOR]

Copyright of Telecommunications Science is the property of Beijing Xintong Media Co., Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Nanchang University (Engineering & Technology) is the property of Nanchang University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Nanchang University (Engineering & Technology) is the property of Nanchang University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Jilin University (Science Edition) / Jilin Daxue Xuebao (Lixue Ban) is the property of Zhongguo Xue shu qi Kan (Guang Pan Ban) Dian zi Za zhi She and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Guangxi Normal University - Natural Science Edition is the property of Gai Kan Bian Wei Hui and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Guangxi Normal University - Natural Science Edition is the property of Gai Kan Bian Wei Hui and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Guangxi Normal University - Natural Science Edition is the property of Gai Kan Bian Wei Hui and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to explore the widespread applications of Odd Log-Logistic Generalized Gompertz （OLLGG） distribution in fields such as biology, sociology, computer science and marketing, this paper studies a multi-parameter regression model for OLLGG distribution under left-truncated and right-censored data, and estimates the parameters using maximum likelihood thinking. Through numerical simulation, the effectiveness of the estimation method is verified, and the Akaike information criterion is used to select the appropriate distribution form. Finally, the regression model proposed in this article is applied to the channing house dataset to demonstrate its good fitting performance. [ABSTRACT FROM AUTHOR]

The strategy of population migration towards the mean point in heuristic optimization algorithms is investigated, and the strategy is found that it has significant impact on the algorithm’s performance and has both physical and mathematical implications. By using the maximum likelihood estimation method, the parameters of the ground state wave function are estimated, and the connection between the probability density function of the optimal solution when the quantum system reaches the ground state and the population mean point is established. The physical significance of the population mean point is explained from a dynamic perspective. The operations that utilize the information of the mean point’s position is added to several classical optimization algorithms and a comparative experiment is carried out on the CEC2013 test set and the engineering application of camera layout optimization. Experimental results show that reasonable use of the mean point position information can effectively improve the performance of the algorithm. [ABSTRACT FROM AUTHOR]

Copyright of Computer Measurement & Control is the property of Magazine Agency of Computer Measurement & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Experimental Technology & Management is the property of Experimental Technology & Management Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A channel-fixed delay error estimation method was proposed to tackle the performance degradation of digital beamforming caused by the channel-fixed delay error of wideband digital array radar.First, the integer part of the fixed delay of the channel was estimated through the correlation integral peak of the baseband transmitted signal and the baseband received signal containing unknown delay parameters.Then, the fractional part of the fixed delay of the channel was estimated with parabolic interpolation by using the correlation peak and its adjacent two points.Finally, the multi-channel fixed delay error was calculated and compensated.The simulation results show that the multi-channel fixed delay estimation of wideband digital array radar can be realized on Xilinx xcku115.The estimative precision can reach 0.001～0.014 times the sampling gap when the signal-to-noise ratio of the input signal is 10～30 dB.The proposed method can meet the engineering application requirements and improve the performance of digital beamforming in wideband digital array radar.

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The purpose of this paper was to introduce five key techniques and the multi-directional decomposition methods of effect components in the analysis of causal mediation effects. The contents of the five key technologies were as follows： ① identification of causal mediation effect； ② regression method of causal mediation effect analysis； ③ maximum likelihood estimation； ④ estimation of total effect and various component effects； ⑤ estimation by bootstrap method. The multi-directional decomposition methods included 3 bidirectional decompositions， 2 three-directional decompositions and 1 four-directional decomposition. Through an example， a causal mediation effect analysis model including covariates and interaction terms was constructed with the help of SAS， bidirectional decomposition， three-directional decomposition and four-directional decomposition were carried out for the total effect in the causal mediation effect analysis， and the output results were explained.

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal on Communication / Tongxin Xuebao is the property of Journal on Communications Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Guangdong University of Technology is the property of Journal of Guangdong University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to alleviate the huge amount of calculation when using the continuous domain ant colony optimization (ACO) algorithm to handle the maximum likelihood (ML) estimation problem, we propose a maximum likelihood direction of arrival (ML-DOA) estimation method based on modified ant colony optimization (MACO) algorithm. Firstly, MACO algorithm adopts the elite reverse learning strategy to obtain a better initial solution group. Secondly, the optimization method of ant colony is conducted by combining global cross-neighborhood search and local search of Gaussian kernel function to expand the algorithm search space and accelerate the convergence speed. Finally, the nonlinear global optimal solution of ML estimation method is obtained. Simulation results show that, compared with ML estimation methods based on particle swarm optimization (PSO) algorithm and ACO algorithm, the convergence speed of the ML-MACO algorithm is 4 times faster than that of the ML-ACO algorithm, the computational load is 1/3 that of the ML-ACO algorithm, the resolution success rate is higher than the ML-PSO algorithm and the ML-ACO algorithm, and the estimation error is less than the ML-PSO algorithm and the ML-ACO algorithm. The ML-MACO algorithm maintains the excellent estimation performance of the ML algorithm with lower computational effort, better convergence performance, and higher estimation accuracy. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Test & Measurement Technology is the property of Publishing Center of North University of China and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

OBJECTIVE : To assess the validity and effectiveness of parameter estimation using a time-dependent Weibull proportional hazards model for survival analysis containing partly interval censored data and explore the impact of different covariates on the results of analysis. METHODS : We established a time-dependent Weibull proportional hazards model using the Weibull distribution as the baseline hazard function of the model which incorporated time-varying covariates. Maximum likelihood estimation was employed to estimate the model parameters, which were obtained by optimization of the likelihood function. RESULTS AND CONCLUSION : Numerical simulation results showed that with higher proportions of precise observations across different sample sizes and parameter settings, the proposed model resulted in improved accuracy of parameter estimation with coverage probabilities approximating the theoretical expectation of 95%. As the sample sizes increased, the parameter biases of the model tended to decrease. Experiments with empirical data further validated the effectiveness of the model. Compared with the failure time data for each precisely observed individual, additional interval-censored data helped to obtain more effective estimates of the regression parameters. Comparison with the Cox model that included time-varying covariates further demonstrated the effectiveness of the time-dependent Weibull proportional hazards model for parameter estimation in survival analysis with partly interval censored data.

Aiming at the life data information of multiple types of testing sources for the same product, a mixed base distribution constructed to achieve three-source data fusion, and at the same time, the overall distribution density function of the life data source was estimated. And the iterative formula of the maximum likelihood estimation of each unknown parameter in the parameter vectors of the mixed basis distribution density function was obtained based on the EM algorithm. At the same time, the estimated value of each parameter was given by using the sample weighted by Bootstrap method, the density function analysis of the mixed basis distribution was determined, and the product reliability analysis was completed. The calculation example verified the feasibility and effectiveness of this type of model.

Copyright of Sichuan Mental Health is the property of Sichuan Mental Health Center and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Systems Engineering & Electronics is the property of Journal of Systems Engineering & Electronics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Telecommunication Engineering is the property of Telecommunication Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Signal Processing is the property of Journal of Signal Processing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Control Theory & Applications / Kongzhi Lilun Yu Yinyong is the property of Editorial Department of Control Theory & Applications and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Guangxi Normal University - Natural Science Edition is the property of Gai Kan Bian Wei Hui and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Jilin University (Science Edition) / Jilin Daxue Xuebao (Lixue Ban) is the property of Zhongguo Xue shu qi Kan (Guang Pan Ban) Dian zi Za zhi She and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Engineering for Thermal Energy & Power / Reneng Dongli Gongcheng is the property of Journal of Engineering for Thermal Energy & Power and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of China University of Petroleum is the property of China University of Petroleum and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper applies the method of learning to rank to the research of component retrieval. Firstly, the facet description method is used to describe the components comprehensively, and the features of the facet described components are extracted through the Word2vec model and the weight setting method. Secondly, the component semantics analysis and cosine similarity calculation are performed on the component feature description information to obtain the component training data set. Finally, the component training data set and the component data set are used to train the model parameters of the improved Plackett-Luce probabilistic ranking model through the maximum likelihood estimation method, so as to obtain a component ranking model. The component ranking model is applied to the component retrieval to realize a component retrieval method. Experiments show that the method has better effect iveness, recall, precision and efficiency are bet ter than the traditional componen tretrieval methods. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin University of Science & Technology is the property of Journal of Harbin University of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of China University of Petroleum is the property of China University of Petroleum and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Zhejiang University (Science Edition) is the property of Journal of Zhejiang University (Science Edition) Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Electric Power Automation Equipment / Dianli Zidonghua Shebei is the property of Electric Power Automation Equipment Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Basic Sciences Journal of Textile Universities / Fangzhi Gaoxiao Jichu Kexue Xuebao is the property of Basic Sciences Journal of Textile Universities and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To accurately locate hidden damage in welded joints, a metal magnetic memory (MMM) gradient model was present based on maximum likelihood estimation (MLE) optimized by particle swarm optimization (PSO). Tabular welded Q235 specimens were subjected to fatigue tensile experiments. Using electron microscope scanning and X-ray detection, it is found that MMM gradient K is sensitive to the location of early hidden damage and decreases with an increase in distance from it. A nonlinear function is then presented between the position parameter and the MMM gradient. MLE is introduced to establish the nonlinear objective function. Furthermore, considering the nonlinear objective function is easy to get into the local rather than the global extremum, the PSO is adopted to optimize the objective function for a global search ability. The results show the location error of the model is 3.48%, therefore MMM provides a new tool for the identification and accurate location of early hidden damage in welded joints.

This paper proposes a kind of method considering the corrosion pipelines phased degradation model and the remaining useful life (RUL) prediction method under imperfect maintenance. Firstly, the total number of imperfect maintenance in the whole life should be set to 3 times, then the degradation process is divided into 4 stages. Secondly, under the theoretical framework of nonlinear staged random diffusion process with the intervention of maintenance activities, the failure law should be modeled, on the basis of the first time, the probability distribution of remaining useful life (RUL) is derived, and the real-time remaining useful life (RUL) estimation of the corrosion pipelines is realized. Then, the parameters in the degradation model are estimated by maximum likelihood estimation (MLE) and Bayesian updating strategy based on the condition monitoring (CM) data and the maintenance data of the corroded pipelines. Finally, the effectiveness of the model is verified by case studies. The results show that the degradation model can well describe the staged degradation process of corrosion pipelines under the imperfect maintenance intervention, and it can provide the credible results of the reliability assessment, which makes the corroded pipelines have a higher level of safe operation, thus overcoming the adverse effects of the over maintenance or under-repair resulted by traditional method and reducing the maintenance cost. [ABSTRACT FROM AUTHOR]

Copyright of Telecommunication Engineering is the property of Telecommunication Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Aiming at node localizations of wireless sensor network(WSN)， a semi-definite programming(SDP)optimization algorithm based on the maximum likelihood estimation(MLE)was proposed. Combining the effective anchor node position selection and ratio range setting， the SDP algorithm was used to relax the non-convex constraints， effectively reduce the impact of errors and get the actual position of measurement nodes. Changing the position of the anchor node can effectively solve the problem of inaccurate estimation of nodes outside the convex hull of the anchor node. The simulation results showed that the proposed SDP algorithm achieves high-precision in the position estimation of unknown nodes， and improves the convex optimization method. [ABSTRACT FROM AUTHOR]

Copyright of Experimental Technology & Management is the property of Experimental Technology & Management Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of National University of Defense Technology / Guofang Keji Daxue Xuebao is the property of NUDT Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The MLE of geometric distribution are studied by ML method and EM algorithm under a particular random censoring test. The proof of existence and uniqueness of MLE and EM iterative formula of the parameter are given. The asymptotic variance of EM estimation is obtainde by Louis algorithm. Random simulation results show that the MLE and EM estimation are both fairly accurate,and make little difference.