基于工艺过程的AGV空时响应调度机制研究

依据生产工艺过程在组织模式及AGV运送路径的自身特点,提炼串行、并行、交叉、空过作业等典型的生产作业模型。在生产作业时间及AGV小车运送时间做分解及相应的预设的基础上,估算投入系统运行的AGV数量。提出AGV小车编号及服务优先级设定方法,分析工艺节点与AGV小车物料运送在时间上的错配的影响因素,采用历史记录预设方法及统一协调的实时空时响应机制,趋近或者达到AGV运送整体最优效果。

Effects of axial static stress on stress wave propagation in rock considering porosity compaction and damage evolution

A wave equation of rock under axial static stress is established using the equivalent medium method by modifying the Kelvin-Voigt model.The analytical formulas of longitudinal velocity,space and time attenuation coefficients and response frequency are obtained by solving the equation using the harmonic method.A series of experiments on stress wave propagation through rock under different axial static stresses have been conducted.The proposed models of stress wave propagation are then verified by comparing experimental results with theoretical solutions.Based on the verified theoretical models,the influences of axial static stress on longitudinal velocity,space and time attenuation coefficients and response frequency are investigated by detailed parametric studies.The results show that the proposed theoretical models can be used to effectively investigate the effects of axial static stress on the stress wave propagation in rock.The axial static stress influences stress wave propagation characteristics of porous rock by varying the level of rock porosity and damage.Moreover,the initial porosity,initial elastic modulus of the rock voids and skeleton,viscous coefficient and vibration frequency have significant effects on the P-wave velocity,attenuation characteristics and response frequency of the stress wave in porous rock under axial static stress.

Responses of Spatial-temporal Variation of Karst Ecosystem Service Values to Landscape Pattern in Northwest of Guangxi,China

The responses of spatiotemporal variation of ecosystem service values (ESVs) to landscape pattern from 1985 to 2005 in a typical Karst area of the northwest Guangxi Zhuang Autonomous Region,China,were examined us-ing remote sensing and geographic information system techniques in this paper.The total ecosystem service values de-clined significantly from 1985 to 1990,and then increased slowly from 1990 to 2005,almost equaled to the 1985 level.The ecosystem service values tended to decline from the west to the east and from mountainous regions to peak-cluster depression areas in 1985,1990,2000 and 2005 respectively.During the period from 1985 to 2005,the ecosystem ser-vice values have increased in the middle and eastern parts of the study area.Landscape pattern indices,such as total area,largest patch index,contagion,aggregative index,effective mesh and proportion of like adjacencies,are significantly correlated with ecosystem service values.This suggests that ecosystem service values tend to increase with the growth of patch area and patch connectivity.However,there are negative correlations between ecosystem service values and landscape pattern indices,such as division index and patch richness.It indicates that ecosystem service values decrease with patch fragmentation and patch size shrinkage.The ecosystem conditions in the typical Karst area have been improved because of the control measures of rocky desertification.It is important to protect key landscape types,such as woodland,shrub and grassland,and to increase patch size and connectivity to avoid further fragmentation.Furthermore,it is necessary to reduce disturbances to ensure the growth of ecosystem service values and to facilitate the sustainable development in this region.

Laser Induced Breakdown of Poly （Methyl Methacrylate （PMMA）） in Air

In the present work, Laser induced Breakdown spectroscopy technique is used to investigate the laser induced plasma of PMMA in air. The optical emission of PMMA plasma is found quite intense and dominated by vibrational band of CN molecules （violet band, B^2∑^＋ - X^2∑^＋） at 388.4 nm. The temporal response of the CN band emission is studied and found decay time 22 ns. The low decay time and small laser spot （34 × 32 μm^2） conf＇n-ms good thermal stability of PMMA. To get structural fingerprint of PMMA, Raman spectrum is recorded prior to the exposure to laser. Several sharp Raman peaks have been observed along with a very intense peak at 2,957 cm1 attributed to C-H stretching vibration. Post exposure Raman spectrum is also recorded to analyze the heating effect and re-deposition of ablated material.

Analyzing the service availability of mobile cloud computing systems by fluid-flow approximation

Mobile cloud computing （MCC） has become a promising technique to deal with computation- or data-intensive tasks. It overcomes the limited processing power, poor storage capacity, and short battery life of mobile devices. Providing continuous and on-demand services, MCC argues that the service must be available for users at anytime and anywhere. However, at present, the service availability of MCC is usually measured by some certain metrics of a real-world system, and the results do not have broad representation since different systems have different load levels, different deployments, and many other random factors. Meanwhile, for large-scale and complex types of services in MCC systems, simulation-based methods （such as Monte- Carlo simulation） may be costly and the traditional state-based methods always suffer from the problem of state-space explosion. In this paper, to overcome these shortcomings, fluid-flow approximation, a breakthrough to avoid state-space explosion, is adopted to analyze the service availability of MCC. Four critical metrics, including response time of service, minimum sensing time of devices, minimum number of nodes chosen, and action throughput, are def＇med to estimate the availability by solving a group of ordinary differential equations even before the MCC system is fully deployed. Experimental results show that our method costs less time in analyzing the service availability of MCC than the Markov- or simulation-based methods.