An opportunistic maintenance model is presented for a continuously deteriorating series system with economical de-pendence. The system consists of two kinds of units, which are respectively subjected to the deteriorat...An opportunistic maintenance model is presented for a continuously deteriorating series system with economical de-pendence. The system consists of two kinds of units, which are respectively subjected to the deterioration failure described by Gamma process and the random failure described by Poisson process. A two-level opportunistic policy defined by three decision parameters is proposed to coordinate the different maintenance actions and minimize the long-run maintenance cost rate of the system. A computable expression of the average cost rate is established by using the renewal property of the stochastic process of the maintained system state. The optimal values of three deci- sion parameters are derived by an iteration approach based on the characteristic of Gamma process. The behavior of the proposed policy is illustrated through a numerical experiment. Comparative study with the widely used corrective maintenance policy demonstrates the advantage of the proposed opportunistic maintenance method in significantly reducing the maintenance cost. Simultane- ously, the applicable area of this opportunistic model is discussed by the sensitivity analysis of the set-up cost and random failure rate.展开更多
Background:Our goal is to build a multi-unit ocular biometric system based on the fusion of left and right corneal shapes for identity authentication.Methods:Ocular biometrics such as iris,periocular,retina,sclera and...Background:Our goal is to build a multi-unit ocular biometric system based on the fusion of left and right corneal shapes for identity authentication.Methods:Ocular biometrics such as iris,periocular,retina,sclera and eye movement have become established biometric traits,primarily due to extensive efforts made by the biometrics community in the field of iris recognition.In this work,we propose an ocular biometric trait based on the 3D shape of the cornea to improve biometric authentication.We show how the fusion of the left and right corneas can be used as a biometric trait for person recognition.First,we started by realizing our own cornea database by using a Pentacam Topographer(Oculus)which contains 288 corneal topographies of both eyes captured from 36 different people of different ages.For each eye,data acquisition was done during two different sessionsto establish the repeatability of the measurements over time.The time interval between the two sessions was equal or greater than one month.In each session;8 acquisitions(4 left eyes end 4 right eyes)were taken.Then,features were extracted by modeling the shape of the left and right corneas with a Zernike polynomial expansion.The fusion of the left and right shapes of cornea was performed at the matching score level using the weighted-sum rule.Results:For each individual,we had eight feature vectors(eight measures in two sessions)of size 36(Zernike polynomial coefficients)from their corneal topographies.The experimental results on our cornea database constructed for this study showed encouraging performance of the proposed ocular biometric system with Equal Error Rate decreasing to 1.38%with the weighted-sum rule compared to the analysis of the left(4.5%)or right(3.7%)cornea alone.Conclusions:The objective of this work was to investigate corneal topographyas an accurate biometric modality using shape discriminating features.Our idea was to propose an ocular multi-unit system based on the fusion of the left and right corneal shapes.The corneal feature extraction was done by Zernike polynomial decomposition.Multi-unit cornea fusion was performed at the matching score level to generate a unique score.This allowed a significative decrease of the EER to 1.38%.展开更多
Auction was widely used to tackle spectrum allocation and sharing in the secondary market under the condition of spectrum scarcity. In real communication system, such as broadband communication, the utilization of spe...Auction was widely used to tackle spectrum allocation and sharing in the secondary market under the condition of spectrum scarcity. In real communication system, such as broadband communication, the utilization of spectrum resource is various because of different requirements and complex application scenarios. So, these schemes cannot be directly applied to the above wireless communication system. To solve this problem, a new model where sellers/buyers can sell/buy multi-unit for heterogeneous spectrum was proposed and a truthful multi-unit double auction framework was designed for heterogeneous spectrum trading. A valuation function is first applied to represent the buyer's true valuation of the sub-band and reflect the buyer's satisfaction degree and a novel concept termed ‘virtual player' was introduced. Then the buyer group was constructed based on the conflict graph to reuse the same spectrum among interference-free buyers in both spatial and temporal domains. The winner determination strategy and algorithm of clearing price were designed elaborately. According to the theoretical analysis, the scheme can satisfy three critical economic properties: truthfulness, individual rationality, and budget balance. Finally, simulation results show that the proposed scheme can achieve better user satisfaction, auction efficiency and spectrum reuse rate for the real communication system. The proposed auction framework is practical and effective.展开更多
现有用户画像方法缺乏不同粒度文本信息表示,且特征提取阶段存在噪声,导致构建画像不够准确。针对以上问题,提出一种融合多粒度信息的用户画像生成方法(user profile based on multi-granularity information fusion,UP-MGIF)。首先,该...现有用户画像方法缺乏不同粒度文本信息表示,且特征提取阶段存在噪声,导致构建画像不够准确。针对以上问题,提出一种融合多粒度信息的用户画像生成方法(user profile based on multi-granularity information fusion,UP-MGIF)。首先,该方法在嵌入层融合字粒度、词粒度表示向量以扩充特征内容;其次,在改进双向门控循环单元网络基础上,结合降噪自编码器和注意力机制设计一种特征提取混合模型Bi-GRU-DAE-Attention,实现特征降噪和语义增强;最后,将鲁棒性强的特征向量输入到分类器中实现用户画像生成。实验表明,该用户画像生成方法在医疗和互联网两个画像数据集上的分类准确率高于其他基线方法,并通过消融实验验证了各个模块的有效性。展开更多
基金supported by the National Natural Science Foundation of China(6090400271201166)
文摘An opportunistic maintenance model is presented for a continuously deteriorating series system with economical de-pendence. The system consists of two kinds of units, which are respectively subjected to the deterioration failure described by Gamma process and the random failure described by Poisson process. A two-level opportunistic policy defined by three decision parameters is proposed to coordinate the different maintenance actions and minimize the long-run maintenance cost rate of the system. A computable expression of the average cost rate is established by using the renewal property of the stochastic process of the maintained system state. The optimal values of three deci- sion parameters are derived by an iteration approach based on the characteristic of Gamma process. The behavior of the proposed policy is illustrated through a numerical experiment. Comparative study with the widely used corrective maintenance policy demonstrates the advantage of the proposed opportunistic maintenance method in significantly reducing the maintenance cost. Simultane- ously, the applicable area of this opportunistic model is discussed by the sensitivity analysis of the set-up cost and random failure rate.
文摘Background:Our goal is to build a multi-unit ocular biometric system based on the fusion of left and right corneal shapes for identity authentication.Methods:Ocular biometrics such as iris,periocular,retina,sclera and eye movement have become established biometric traits,primarily due to extensive efforts made by the biometrics community in the field of iris recognition.In this work,we propose an ocular biometric trait based on the 3D shape of the cornea to improve biometric authentication.We show how the fusion of the left and right corneas can be used as a biometric trait for person recognition.First,we started by realizing our own cornea database by using a Pentacam Topographer(Oculus)which contains 288 corneal topographies of both eyes captured from 36 different people of different ages.For each eye,data acquisition was done during two different sessionsto establish the repeatability of the measurements over time.The time interval between the two sessions was equal or greater than one month.In each session;8 acquisitions(4 left eyes end 4 right eyes)were taken.Then,features were extracted by modeling the shape of the left and right corneas with a Zernike polynomial expansion.The fusion of the left and right shapes of cornea was performed at the matching score level using the weighted-sum rule.Results:For each individual,we had eight feature vectors(eight measures in two sessions)of size 36(Zernike polynomial coefficients)from their corneal topographies.The experimental results on our cornea database constructed for this study showed encouraging performance of the proposed ocular biometric system with Equal Error Rate decreasing to 1.38%with the weighted-sum rule compared to the analysis of the left(4.5%)or right(3.7%)cornea alone.Conclusions:The objective of this work was to investigate corneal topographyas an accurate biometric modality using shape discriminating features.Our idea was to propose an ocular multi-unit system based on the fusion of the left and right corneal shapes.The corneal feature extraction was done by Zernike polynomial decomposition.Multi-unit cornea fusion was performed at the matching score level to generate a unique score.This allowed a significative decrease of the EER to 1.38%.
文摘为考虑颗粒群碰撞过程中时间效应对非堆积型多颗粒阻尼器(non-packed particle damper, NPPD)减振性能的影响,在现有考虑惯容的等效单颗粒力学模型(equivalent inertia single-particle model, EISM)研究基础上,提出了基于接触单元法的等效单颗粒力学模型(equivalent inertia single-particle model based on contact element method, EISM-CE),并基于Runge-Kutta算法建立了NPPD单自由度结构运动状态求解算法。设计进行附加NPPD单层钢框架结构振动台试验,探究不同填充率对结构顶层位移频响曲线的影响规律,提出了EISM-CE参数取值原则,进而进行力学模型试验验证及模型对比分析。在模型验证合理性基础上,基于EISM-CE依次进行了自由振动、简谐激励及记录强震动下减振性能及能量变化规律分析。研究结果表明,与现有EISM相比,提出的基于接触单元法的EISM-CE模型及参数取值原则更加合理有效。减振性能数值分析结果表明,不同激励下NPPD均具有较好的减振性能;考虑碰撞时间效应后EISM-CE与EISM对应减振性能及机理分析结果存在一定的差异。
基金supported by the National Natural Science Foundation of China(61531007,51877010)
文摘Auction was widely used to tackle spectrum allocation and sharing in the secondary market under the condition of spectrum scarcity. In real communication system, such as broadband communication, the utilization of spectrum resource is various because of different requirements and complex application scenarios. So, these schemes cannot be directly applied to the above wireless communication system. To solve this problem, a new model where sellers/buyers can sell/buy multi-unit for heterogeneous spectrum was proposed and a truthful multi-unit double auction framework was designed for heterogeneous spectrum trading. A valuation function is first applied to represent the buyer's true valuation of the sub-band and reflect the buyer's satisfaction degree and a novel concept termed ‘virtual player' was introduced. Then the buyer group was constructed based on the conflict graph to reuse the same spectrum among interference-free buyers in both spatial and temporal domains. The winner determination strategy and algorithm of clearing price were designed elaborately. According to the theoretical analysis, the scheme can satisfy three critical economic properties: truthfulness, individual rationality, and budget balance. Finally, simulation results show that the proposed scheme can achieve better user satisfaction, auction efficiency and spectrum reuse rate for the real communication system. The proposed auction framework is practical and effective.
文摘现有用户画像方法缺乏不同粒度文本信息表示,且特征提取阶段存在噪声,导致构建画像不够准确。针对以上问题,提出一种融合多粒度信息的用户画像生成方法(user profile based on multi-granularity information fusion,UP-MGIF)。首先,该方法在嵌入层融合字粒度、词粒度表示向量以扩充特征内容;其次,在改进双向门控循环单元网络基础上,结合降噪自编码器和注意力机制设计一种特征提取混合模型Bi-GRU-DAE-Attention,实现特征降噪和语义增强;最后,将鲁棒性强的特征向量输入到分类器中实现用户画像生成。实验表明,该用户画像生成方法在医疗和互联网两个画像数据集上的分类准确率高于其他基线方法,并通过消融实验验证了各个模块的有效性。
