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AN ESTIMATE ON THE DISTRIBUTION AND MOMENTS OF THE LAST EXIT TIME OF AN ELLIPTIC DIFFUSION PROCESS
Let LB be the last exit time from a compact set B of an elliptic diffusion process X. A moderate estimate for the distribution of LB is obtained, and the sufficient and necessary condition for Ex (LkB) ＜∞ is proved....
2020-11-22 17:58:37浏览：62
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A hierarchical algorithm for cyberspace situational awareness based on analytic hierarchy process
The existing network security management systems are unable either to provide users with useful security situation and risk assessment, or to aid administrators to make right and timely decisions based on the current state of network. These disadvantages always put the whole network security management at high risk. This paper establishes a simulation environment, captures the alerts as the experimental data and adopts statistical analysis to seek the vulnerabilities of the services provided by the hosts in the network. According to the factors of the network, the paper introduces the two concepts: Situational Meta and Situational Weight to depict the total security situation. A novel hierarchical algorithm based on analytic hierarchy process (AHP) is proposed to analyze the hierarchy of network and confirm the weighting coefficients. The algorithm can be utilized for modeling security situation, and determining its mathematical expression. Coupled with the statistical results, this paper simulates the security situational trends.Finally, the analysis of the simulation results proves the algorithm efficient and applicable, and provides us with an academic foundation for the implementation in the security situation....
2020-11-22 17:58:37浏览：69
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Toxicity Reduction of Municipal Wastewater by Anaerobic-anoxic-oxic Process
Objective This study was conducted to optimize the operational parameters of anaerobic-anoxic-oxic (A2/O) processes to reduce the toxicity of municipal wastewater and evaluate its ability to reduce toxicity. Methods A luminescent bacterium toxicity bioassay was employed to assess the toxicity of influent and effluent of each reactor in the A2/O system. Results The optimum operational parameters for toxicity reduction were as follows: anaerobic hydraulic retention time (HRT) = 2.8 h,anoxic HRT = 2.8 h, aerobic HRT = 6.9 h, sludge retention time (SRT) = 15 days and internal recycle ratio (IRR) = 100%. An important toxicity reduction (%) was observed in the optimized A2/O process, even when the toluene concentration of the influent was 120.7 mg.L-1. Conclusions The toxicity of municipal wastewater was reduced significantly during the A2/Oprocess. A2/O process can be used for toxicity reduction of municipal wastewater under toxic-shock loading....
2020-11-22 17:58:37浏览：61
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Simulation analysis of construction process of high rock slope's stabilization
A self-developed elasto-plastic finite element program was used to analyze the construction sequence of high rock slope' s stabilization in a coal-coking plant, and the result was compared with that employing the ultimate equilibrium method. Based on the results of finite element analysis, the stress contour graphs and dis-placement vector graphs at different construction steps were obtained, and the behavior of the slope during stabi-lization construction process was analyzed quantitatively. Based on the analysis of safety factors of three different schemes of stabilization and two different construction schemes, the assessment of stability and bracing design of the construction process were performed. The results show that the original reinforcement design is improper;the stability of the rock slope is controlled by a developed structural plane, the stability factor after excavation is less than 1, and the free surface should be braced in time ; for stability, the construction sequence should adopt that bracing follows excavation step by step up to down; the local slide occurred during the construction process agrees with the dangerous slide determined by the numerical analysis, which proves the validity and rationality of the adopted method....
2020-11-22 17:58:37浏览：64
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Preparation of Hydroxyapatite/Polylactide Bicomposites by Absorption Process in Liquid Phase
The hydroxyapatite/polylactide biocomposites were prepared by absorption process in liquid phase. The method avoided many disadvantages, such as interfusion of chemical impurity substances, nonuniformity dispersal of HA in PLA, low molecular weight of PLA. HA particles were uniformly dispersed in PlA matrix,and shawed well adhesion with PLA matrix. The biocomposites have the higher mechanical properties and suitable decomposable capability....
2020-11-22 17:58:37浏览：59
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Surface alloying of Cu with Ti by double glow discharge process
The surface of pure copper alloyed with Ti using double glow discharge process was investigated. The morphology, structure and forming mechanism of the Cu-Ti alloying layer were analyzed. The microhardness and wear resistance of the Cu-Ti alloying layer were measured, and compared with those of pure copper. The results indicate that the surface of copper activated by Ar and Ti ions bombardment is favorable to absorption and diffusion of Ti element. In current experimental temperature, as the Ti content increases, the liquid phase occurs between the deposited layer and diffused layer, which makes the Ti ions and atoms easy to dissolve and the thickness of Cu-Ti alloying layer increase rapidly. After cooling, the structure of the alloying layer is composed of CuTi, Cu4 Ti and Cu(Ti) solid solution. The solid solution strengthening and precipitation strengthening effects of Ti result in high surface hardness and wear resistance....
2020-11-22 17:58:37浏览：55
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Quality Stability of Multi-Station Assembly Process Based on Variation Stream
To analyze the physical structure of assembly process and assure product quality, the quality stability of multi-station assembly process was investigated. First, the assembly process was modeled as a one-dimensional discrete variant system by state space equation based on variation stream. Then, the criterion to judge whether the process is stable or not and the index, stability degree, to show the level of stability were proposed by analyzing the bounded-input bounded-output(BIBO) stability of system. Finally, a simulated example of a sheet metal assembly process with three stations, was provided to verify the effectiveness of the proposed method....
2020-11-22 17:58:37浏览：51
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Virtual Mold Technique in Thermal Stress Analysis during Casting Process
It is important to analyse the casting product and the mold at the same time considering thermal contraction of the casting and thermal expansion of the mold. The analysis considering contact of the casting and the mold induces the precise prediction of stress distribution and the defect such as hot tearing. But it is difficult to generate FEM mesh for the interface of the casting and the mold. Moreover the mesh for the mold domain spends lots of computational time and memory for the analysis due to a number of meshes. Consequently we proposed the virtual mold technique which only uses mesh of the casting part for thermal stress analysis in casting process. The spring bar element in virtual mold technique is used to consider the contact of the casting and the mold. In general, a volume of the mold is much bigger than that of casting part, so the proposed technique decreases the number of mesh and saves the computational memory and time greatly. In this study, the proposed technique was verified by the comparison with the traditional contact technique on a specimen. And the proposed technique gave satisfactory results....
2020-11-22 17:58:37浏览：61
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Coordination-theoretic approach to modelling grid service composition process
A grid service composite process is made up of complex coordinative activities.Developing the appropriate model of grid service coordinative activities is an important foundation for the grid service composition.According to the coordination theory,this paper elaborates the process of the grid service composition by using UML 2.0,and proposes an approach to modelling the grid service composition process based on the coordination theory.This approach helps not only to analyze accurately the task activities and relevant dependencies among task activities,but also to facilitate the adaptability of the grid service orchestration to further realize the connectivity,timeliness,appropriateness and expansibility of the grid service composition....
2020-11-22 17:58:37浏览：65
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Intelligent prediction model of matte grade in copper flash smelting process
Due to the importance of detecting the matte grade in the copper flash smelting process, the mechanism model was established according to the multi-phase and multi-component mathematic model. Meanwhile this procedure was a complicated production process with characteristics of large time delay, nonlinearity and so on. A fuzzy neural network model was set up through a great deal of production data. Besides a novel constrained gradient descent algorithm used to update the parameters was put forward to improve the parameters learning efficiency. Ultimately the self-adaptive combination technology was adopted to paralleled integrate two models in order to obtain the prediction model of the matte grade. Industrial data validation shows that the intelligently integrated model is more precise than a single model. It can not only predict the matte grade exactly but also provide optimal control of the copper flash smelting process with potent guidance....
2020-11-22 17:58:37浏览：57
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Simulating the vegetation-producing process in small watersheds in the Loess Plateau of China
Small watersheds are the basic composition unit of the Loess Plateau in China.An accurate estimation of vegetation net primary productivity (NPP) is of great significance for eco-benefit evaluation in small watershed management in this region.Here we describe the development and testing of a vegetation-producing process model (VPP) of a small watershed in the Loess Plateau.The model couples three modules:radiation adjustment;soil hydrological processes; and vegetation carbon assimilation.Model validation indicates that the VPP model can be used to estimate the NPP of small watersheds in the region.With the VPP model,we estimated the spatial NPP distributions in the Yangou watershed for 2007.The results show that in the Yangou watershed the NPP is relatively low,averaging 168 g C/(m2·a).Trees and shrubs have a higher NPP than crops and grasses.The NPP is larger on the partly shaded and shaded slopes than on the partly sunny and sunny slopes.The NPP on the slopes increases gradually on 0-20° slopes and decreases slightly on slopes steeper than 20°.Our simulation indicates that the vegetation type is the most important factor in determining the NPP distribution in small watersheds in the Loess Plateau....
2020-11-22 17:58:37浏览：53
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Responses of distribution pattern of desert riparian forests to hydrologic process in Ejina oasis
By using the theories and methods of landscape ecology and the technology of GIS and RS, a study has been carried out on the responses of distribution pattern of desert riparian forest to hydrologic process on the basis of the hydrologic data from 1990 to 2000 and the TM image of 2001 year. The results showed that: (1) there appears an even distribution pattern for the relative forest area in oasis, however, the degenerated forest diaplays an increasing tendency from west to east; (2) the desert riparian forest in Ejina is in completely degenerated process at the patch scale; (3) the number of patch is influenced not only by hydrologic process,but also by agricultural activity such as cultivation. The severe deterioration of the degraded vegetation in whole oasis initiates from lower reaches, and gradually impels to upstream; the fragmentation of landscape in the terminal site is more obvious, which is influenced by river shape and decreasing flux of water. It is found that the influence of surface hydrologic process to the ground hydrologic process of desert riparian forest in Ejina oasis is little for the recent ten years. The relative area of the degenerated forest increased with increasing ground water depth in the direction of parallel to river channel. On the contrary, in the direction perpendicular to river channel, there is a decreasing tendency for the average patch area of the forest and the degenerated forest with increasing ground water depth....
2020-11-22 17:58:37浏览：57
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Numerical simulation and process optimization for producing large-sized castings
3-D velocity and temperature fields of mold filling and solidification processes of large-sized castings were calculated, and the efficiency and accuracy of numerical calculation were studied. The mold filling and solidification processes of large-sized stainless steel, iron and aluminum alloy castings were simulated by using of new scheme; their casting processes were optimized, and then applied to produce castings....
2020-11-22 17:58:37浏览：62
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Research about Process Archive of Computerized Surgery Navigation Based on PACS
Since the process of the surgery navigation is an operation-sensitive process, it is important to record and archive the whole process. In this paper, some key technologies are introduced to accomplish process archive of computerized surgery navigation based on the picture archiving and communication system (PACS). Firstly, the images and track data are acquired by the screen captured tool and the navigation software. Secondly, these image and data files are converted to the digital imaging and communications in medicine (DICOM) files supported by PACS and transferred into the database in PACS. The process of surgery navigation is recorded and archived. Finally, the original data of process archive is acquired from PACS, and this data is used to play back and restore the process of surgery navigation....
2020-11-22 17:58:37浏览：66
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Impact of Modal Parameters on Milling Process Chatter Stability Lobes
Modals of the machine/tool and machine/part system are the principal factors affecting the stability of a milling process. Based on the modeling of chatter stability of milling process, the influence of modal parameters on chatter stability lobes independently or jointly has been analyzed by simulation. Peak-to-valley specific value, lobe coefficient and the corresponding calculation formula have been put forward. General laws and steps of modal simplification for multimodality system have been summarized....
2020-11-22 17:58:37浏览：60
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