With the simultaneous rise of energy costs and demand for cloud computing, efficient control of data centers becomes crucial. In the data center control problem, one needs to plan at every time step how many servers t...With the simultaneous rise of energy costs and demand for cloud computing, efficient control of data centers becomes crucial. In the data center control problem, one needs to plan at every time step how many servers to switch on or off in order to meet stochastic job arrivals while trying to minimize electricity consumption. This problem becomes particularly challenging when servers can be of various types and jobs from different classes can only be served by certain types of server, as it is often the case in real data centers. We model this problem as a robust Markov decision process(i.e., the transition function is not assumed to be known precisely). We give sufficient conditions(which seem to be reasonable and satisfied in practice) guaranteeing that an optimal threshold policy exists. This property can then be exploited in the design of an efficient solving method, which we provide.Finally, we present some experimental results demonstrating the practicability of our approach and compare with a previous related approach based on model predictive control.展开更多
The Adaptive Quality Control Phantom (AQCP) is a computer-controlled phantom which positions and moves a radioactive source in the Field of View (FOV) of an imaging nuclear medicine device on a definite path to produc...The Adaptive Quality Control Phantom (AQCP) is a computer-controlled phantom which positions and moves a radioactive source in the Field of View (FOV) of an imaging nuclear medicine device on a definite path to produce a spatial distribution of gamma rays to perform QC Tests such as the Collimator Hole Angulation (CHA) and the Center of Rotation (COR) of Single Photon Emission Computer Tomography (SPECT). The collimator hole angulation for six collimators was measured using a point source and a computer-controlled cylindrical positioning system. In this method, the displacement of the image of a point source was examined as the AQCP was moving point source vertically away from the collimator face. The results of the high-accuracy measurement method of CHA show that the measurement accuracy for absolute angulation errors is better than ±0.024°. The Root Mean Square (RMS) of CHA for LEHR, LEHS and LEUHR collimators of SMV dual heads camera and LEGP, MEGP and HEGP of GE Millennium MG were evaluated to be 0.290°, 0.292°, 0.208°, 0.154°, 0.220° and 0.202°, respectively. It is to be added in this connection that the evaluated RMS of CHA for LEHR collimator with the distance variation from the collimator’s surface ±1 mm has been varied ±0.04 degree. A new method for the center of rotation assessment by AQCP is introduced and the results of this proposed method as compared with the routine QC test and their differences are discussed in detail. We defined and measured a new parameter called Dynamic Mechanical Error (DME) for applying the gantry motion correction.展开更多
目的通过对汕头市、区二级疾控中心的人力资源相关数据进行比较分析,了解疾控中心人力资源配置现状,为汕头市各级疾控中心人才资源配置及专业队伍建设提供参考。方法通过标准表格收集汕头市2022年12月—2023年5月1个市级和7个区(县)疾...目的通过对汕头市、区二级疾控中心的人力资源相关数据进行比较分析,了解疾控中心人力资源配置现状,为汕头市各级疾控中心人才资源配置及专业队伍建设提供参考。方法通过标准表格收集汕头市2022年12月—2023年5月1个市级和7个区(县)疾控中心的人力资源数据,采用描述性方法对疾控中心人员的性别、年龄、职称、学历学位和专业背景等情况进行分析。使用Excel和GraphP ad Prism软件进行数据统计及差异比较分析。结果汕头市、区二级疾控中心人员性别构成较均衡,男女比例分别为48.1%和51.9%,差异无统计学意义(χ^(2)=0.66,P=0.42)。市级疾控中心35岁以下人员占比较区(县)级CDC高(分别为35.5%和18.9%),二级疾控中心人员年龄构成差异有统计学意义(χ^(2)=16.68,P<0.001)。市级疾控中心人员学历以本科、硕士为主,占77.6%;但区(县)疾控中心职工学历严重失衡,以本科、大专为主,硕士人员比例仅为1.7%,二者学历构成差异有统计学意义(χ^(2)=87.43,P<0.001);市级疾控中心人员职称集中在中级、高级职称,占比为55.2%,无职称人员占比为10.3%;区(县)疾控中心人员职称主要集中在中、初级,占比为71.4%,无职称人员占比为21.0%,二者专业技术职称构成差异有统计学意义(χ^(2)=33.99,P<0.001);二级疾控中心职工专业背景均以卫生专业为主(77.4%),二者专业背景构成差异无统计学意义(χ^(2)=1.35,P=0.24)。结论汕头市、区二级疾控中心在编人员总量不足,其中区(县)疾控中心职工总体学历偏低,人才配置不平衡,高层次人才总体缺乏;当地政府应当重视疾控人才队伍建设,提高已有专业人员的专业水平,积极引进高层次人才,切实做好本市各级疾控中心的人力资源规划。展开更多
针对丘陵山区单边制动农用履带车辆路径跟踪精度低、控制次数多、转向偏差大等问题,本文开展不同负载条件下履带车辆路径跟踪控制研究。首先,对履带车辆的转向运动学进行理论分析,并建立履带车辆运动学模型;其次,根据履带车辆单边制动...针对丘陵山区单边制动农用履带车辆路径跟踪精度低、控制次数多、转向偏差大等问题,本文开展不同负载条件下履带车辆路径跟踪控制研究。首先,对履带车辆的转向运动学进行理论分析,并建立履带车辆运动学模型;其次,根据履带车辆单边制动转向特性,提出一种基于瞬时旋转中心(Instantaneous center of rotation, ICR)的大角度转向控制算法,该算法能够根据规划路径的转向点位置与履带车辆转向瞬心,规划出最优的转向目标点,并控制履带车辆在该转向目标点一次性转向到所需航向,与此同时,完成转向控制器设计;最后,开展履带车辆在3种不同负载条件下的仿真试验与田间试验。仿真结果表明,大角度转向控制算法产生的跟踪路径平均误差面积与平均转向控制次数分别降低68.95%、68.77%;田间试验结果表明,大角度转向控制算法产生的跟踪路径平均横向偏差均值、平均转向控制次数与转向点处平均最小偏差分别减少57.27%、33.93%、62.29%,且路径跟踪效果更优,验证了大角度转向控制算法的有效性。试验结果满足履带车辆路径跟踪的要求,为实现农用履带车辆的路径跟踪提供理论基础与参考。展开更多
为研究设备可用度对列车控制中心(TCC,Train Control Center)的影响和预测TCC的剩余使用寿命(RUL,Remaining Useful Life),降低TCC的故障发生率,确保车辆安全运行,构建TCC动态故障树模型。通过引入Markov理论,将其转化为Markov模型,设计...为研究设备可用度对列车控制中心(TCC,Train Control Center)的影响和预测TCC的剩余使用寿命(RUL,Remaining Useful Life),降低TCC的故障发生率,确保车辆安全运行,构建TCC动态故障树模型。通过引入Markov理论,将其转化为Markov模型,设计了TCC可用度评估与RUL预测方法;考虑了TCC的失效率和共因失效,利用D-S(Dempster-Shafer)证据理论对失效数据作数据融合处理,得到TCC设备初始故障区间概率;在此基础上,采用超椭球模型约束设备初始故障区间概率,得到更加精确的底事件故障区间概率;画出Markov状态转移图,用矩阵推导出TCC可用度和RUL的函数关系式,且对可用度的计算还考虑了维修因素。以兰州—乌鲁木齐客运专线某TCC数据作为分析案例,用该方法计算TCC及其各设备的可用度,并预测TCC的RUL。结果表明:与通用方法相比,评估结果相同,但评估信息更丰富。展开更多
文摘With the simultaneous rise of energy costs and demand for cloud computing, efficient control of data centers becomes crucial. In the data center control problem, one needs to plan at every time step how many servers to switch on or off in order to meet stochastic job arrivals while trying to minimize electricity consumption. This problem becomes particularly challenging when servers can be of various types and jobs from different classes can only be served by certain types of server, as it is often the case in real data centers. We model this problem as a robust Markov decision process(i.e., the transition function is not assumed to be known precisely). We give sufficient conditions(which seem to be reasonable and satisfied in practice) guaranteeing that an optimal threshold policy exists. This property can then be exploited in the design of an efficient solving method, which we provide.Finally, we present some experimental results demonstrating the practicability of our approach and compare with a previous related approach based on model predictive control.
文摘The Adaptive Quality Control Phantom (AQCP) is a computer-controlled phantom which positions and moves a radioactive source in the Field of View (FOV) of an imaging nuclear medicine device on a definite path to produce a spatial distribution of gamma rays to perform QC Tests such as the Collimator Hole Angulation (CHA) and the Center of Rotation (COR) of Single Photon Emission Computer Tomography (SPECT). The collimator hole angulation for six collimators was measured using a point source and a computer-controlled cylindrical positioning system. In this method, the displacement of the image of a point source was examined as the AQCP was moving point source vertically away from the collimator face. The results of the high-accuracy measurement method of CHA show that the measurement accuracy for absolute angulation errors is better than ±0.024°. The Root Mean Square (RMS) of CHA for LEHR, LEHS and LEUHR collimators of SMV dual heads camera and LEGP, MEGP and HEGP of GE Millennium MG were evaluated to be 0.290°, 0.292°, 0.208°, 0.154°, 0.220° and 0.202°, respectively. It is to be added in this connection that the evaluated RMS of CHA for LEHR collimator with the distance variation from the collimator’s surface ±1 mm has been varied ±0.04 degree. A new method for the center of rotation assessment by AQCP is introduced and the results of this proposed method as compared with the routine QC test and their differences are discussed in detail. We defined and measured a new parameter called Dynamic Mechanical Error (DME) for applying the gantry motion correction.
文摘目的通过对汕头市、区二级疾控中心的人力资源相关数据进行比较分析,了解疾控中心人力资源配置现状,为汕头市各级疾控中心人才资源配置及专业队伍建设提供参考。方法通过标准表格收集汕头市2022年12月—2023年5月1个市级和7个区(县)疾控中心的人力资源数据,采用描述性方法对疾控中心人员的性别、年龄、职称、学历学位和专业背景等情况进行分析。使用Excel和GraphP ad Prism软件进行数据统计及差异比较分析。结果汕头市、区二级疾控中心人员性别构成较均衡,男女比例分别为48.1%和51.9%,差异无统计学意义(χ^(2)=0.66,P=0.42)。市级疾控中心35岁以下人员占比较区(县)级CDC高(分别为35.5%和18.9%),二级疾控中心人员年龄构成差异有统计学意义(χ^(2)=16.68,P<0.001)。市级疾控中心人员学历以本科、硕士为主,占77.6%;但区(县)疾控中心职工学历严重失衡,以本科、大专为主,硕士人员比例仅为1.7%,二者学历构成差异有统计学意义(χ^(2)=87.43,P<0.001);市级疾控中心人员职称集中在中级、高级职称,占比为55.2%,无职称人员占比为10.3%;区(县)疾控中心人员职称主要集中在中、初级,占比为71.4%,无职称人员占比为21.0%,二者专业技术职称构成差异有统计学意义(χ^(2)=33.99,P<0.001);二级疾控中心职工专业背景均以卫生专业为主(77.4%),二者专业背景构成差异无统计学意义(χ^(2)=1.35,P=0.24)。结论汕头市、区二级疾控中心在编人员总量不足,其中区(县)疾控中心职工总体学历偏低,人才配置不平衡,高层次人才总体缺乏;当地政府应当重视疾控人才队伍建设,提高已有专业人员的专业水平,积极引进高层次人才,切实做好本市各级疾控中心的人力资源规划。
文摘针对丘陵山区单边制动农用履带车辆路径跟踪精度低、控制次数多、转向偏差大等问题,本文开展不同负载条件下履带车辆路径跟踪控制研究。首先,对履带车辆的转向运动学进行理论分析,并建立履带车辆运动学模型;其次,根据履带车辆单边制动转向特性,提出一种基于瞬时旋转中心(Instantaneous center of rotation, ICR)的大角度转向控制算法,该算法能够根据规划路径的转向点位置与履带车辆转向瞬心,规划出最优的转向目标点,并控制履带车辆在该转向目标点一次性转向到所需航向,与此同时,完成转向控制器设计;最后,开展履带车辆在3种不同负载条件下的仿真试验与田间试验。仿真结果表明,大角度转向控制算法产生的跟踪路径平均误差面积与平均转向控制次数分别降低68.95%、68.77%;田间试验结果表明,大角度转向控制算法产生的跟踪路径平均横向偏差均值、平均转向控制次数与转向点处平均最小偏差分别减少57.27%、33.93%、62.29%,且路径跟踪效果更优,验证了大角度转向控制算法的有效性。试验结果满足履带车辆路径跟踪的要求,为实现农用履带车辆的路径跟踪提供理论基础与参考。
文摘为研究设备可用度对列车控制中心(TCC,Train Control Center)的影响和预测TCC的剩余使用寿命(RUL,Remaining Useful Life),降低TCC的故障发生率,确保车辆安全运行,构建TCC动态故障树模型。通过引入Markov理论,将其转化为Markov模型,设计了TCC可用度评估与RUL预测方法;考虑了TCC的失效率和共因失效,利用D-S(Dempster-Shafer)证据理论对失效数据作数据融合处理,得到TCC设备初始故障区间概率;在此基础上,采用超椭球模型约束设备初始故障区间概率,得到更加精确的底事件故障区间概率;画出Markov状态转移图,用矩阵推导出TCC可用度和RUL的函数关系式,且对可用度的计算还考虑了维修因素。以兰州—乌鲁木齐客运专线某TCC数据作为分析案例,用该方法计算TCC及其各设备的可用度,并预测TCC的RUL。结果表明:与通用方法相比,评估结果相同,但评估信息更丰富。
