The dense integration of residential distributed photovoltaic(PV)systems into three-phase,four-wire low-voltage(LV)distribution networks results in reverse power flow and three-phase imbalance,leading to voltage viola...The dense integration of residential distributed photovoltaic(PV)systems into three-phase,four-wire low-voltage(LV)distribution networks results in reverse power flow and three-phase imbalance,leading to voltage violations that hinder the growth of rural distributed PV systems.Traditional voltage droop-based control methods regulate PV power output solely based on local voltage measurements at the point of PV connection.Due to a lack of global coordination and optimization,their efficiency is often subpar.This paper presents a centralized coordinated active/reactive power control strategy for PV inverters in rural LV distribution feeders with high PV penetration.The strategy optimizes residential PV inverter reactive and active power control to enhance voltage quality.It uses sensitivity coefficients derived from the inverse Jacobian matrix to assign adjustment weights to individual PV units and iteratively optimize their power outputs.The control sequence prioritizes reactive power increases;if the coefficients are below average or the inverters reach capacity,active power is curtailed until voltage issues are resolved.A simulation based on a real 37-node rural distribution network shows that the proposed method significantly reduces PV curtailment.Typical daily results indicate a curtailment rate of 1.47%,which is significantly lower than the 15.4%observed with the voltage droop-based control method.The total daily PV power output(measured every 15 min)increases from 5.55 to 6.41 MW,improving PV hosting capacity.展开更多
As an indispensable part of modern buildings,centralized central air conditioning systems play an important role in maintaining the comfort and air quality of the indoor environment.However,with the increasing energy ...As an indispensable part of modern buildings,centralized central air conditioning systems play an important role in maintaining the comfort and air quality of the indoor environment.However,with the increasing energy consumption,how to improve the energy efficiency ratio of air conditioning systems and reduce energy consumption has become an important issue in research and practice.The purpose of this paper is to discuss the impact of humidity control strategies on energy saving in centralized central air conditioning systems,with a view to providing a theoretical basis and practical guidance for realizing building energy efficiency.展开更多
As the development of new power systems progresses,the inherent inertia of power systems continues to diminish.Centralized frequency regulation,which relies on rapid communication and real-time control,can enable inve...As the development of new power systems progresses,the inherent inertia of power systems continues to diminish.Centralized frequency regulation,which relies on rapid communication and real-time control,can enable inverter-based thermostatically controlled load(ITCL)clusters to provide virtual inertia support to the power grid.However,ITCL clusters exhibit significant discrete response characteristics,which precludes the direct integration of load-side inertia support into the synchronous unit side.To address this issue,this paper elaborates on the existing technical framework and analyzes the underlying causes of the problem.It proposes a timestamp allocation mechanism for ITCL cluster control instructions,ensuring that many ITCL terminals can be triggered at staggered times,thereby allowing the load cluster power to adhere to the inertia analog control law at any moment.Building on this foundation,the paper further examines the impact of the inertia response delay of ITCL clusters,which is based on centralized frequency regulation,on the stability of the power system.A design scheme for inertia analog control parameters is proposed,taking into account dual constraints,frequency stability and load cluster regulation capacity.Finally,the feasibility and applicability of the proposed mechanism and parameter design scheme are investigated through simulations conducted via MATLAB/Simulink.展开更多
With the rapid development of Virtual Private Network (VPN), many companies and organizations use VPN to implement their private communication. Traditionally, VPN uses security protocols to protect the confidentiality...With the rapid development of Virtual Private Network (VPN), many companies and organizations use VPN to implement their private communication. Traditionally, VPN uses security protocols to protect the confidentiality of data, the message integrity and the endpoint authentication. One core technique of VPN is tunneling, by which clients can access the in- ternal servers traversing VPN. However, the tunneling technique also introduces a concealed security hole. It is possible that if one vicious user can establish tunneling by the VPN server, he can compromise the internal servers behind the VPN server. So this paper presents a novel Application-layer based Centralized Information Access Control (ACIAC) for VPN to solve this problem. To implement an efficient, flexible and multi-decision access control model, we present two key techniques to ACIAC—the centralized management mechanism and the stream-based access control. Firstly, we implement the information center and the constraints/events center for ACIAC. By the two centers, we can provide an abstract access control mechanism, and the material access control can be decided dynamically by the ACIAC’s constraint/event mechanism. Then we logically classify the VPN communication traffic into the access stream and the data stream so that we can tightly couple the features of VPN communication with the access control model. We also provide the design of our ACIAC prototype in this paper.展开更多
The interference reduction capability of cell sectoring and power control algorithms have been considered separately as means to decrease the interference in Code Division Multiple Access (CDMA) cellular systems. In t...The interference reduction capability of cell sectoring and power control algorithms have been considered separately as means to decrease the interference in Code Division Multiple Access (CDMA) cellular systems. In this paper, we present Switched-Beam (SB) and Rotatable Equal Sectoring (RES) techniques for CDMA cellular systems in a 2D urban environment. In the SB technique by using a number of fixed, independent, or directional antennas we increase the downlink capacity of the CDMA systems. Also in the RES method, the equal sectors of the base stations are rotating together to decrease the inter-cell and intra-cell interferences. Also in this paper we use centralized power control to overcome the near-far problem. Simulation results indicate that the proposed techniques considerably increase the capacity of the CDMA cellular systems compared to ordinary Equal Sectoring (ES) method.展开更多
BACKGROUND Post-hepatectomy liver failure(PHLF),represents a serious complication after liver resection,significantly impacting the long-term outcomes for patients who undergo such surgeries.There exists a strong corr...BACKGROUND Post-hepatectomy liver failure(PHLF),represents a serious complication after liver resection,significantly impacting the long-term outcomes for patients who undergo such surgeries.There exists a strong correlation between intraoperative hemorrhage and transfusion requirements with the development of PHLF.Presently,a combination of hepatic portal occlusion techniques alongside con-trolled low central venous pressure(CLCVP)methodologies is extensively em-ployed to mitigate intraoperative bleeding.Nonetheless,limited studies have analyzed the risk factors for PHLF under CLCVP.AIM To develop and validate a nomogram that predicts the risk factors associated with the development of PHLF patients undergoing liver resection with CLCVP.METHODS We conducted a retrospective analysis of 285 patients who underwent hepatectomy for the first time and had no history of prior non-index abdominal surgeries,with hepatic inflow occlusion combined with CLCVP from January to December 2019 in Hunan Provincial People’s Hospital.Univariate and multivariate regression analyses were used to identify preoperative and intraoperative risk factors for PHLF.Eligible patients were randomly divided into training and validation groups in a 7:3 ratio,and a nomogram prediction model was constructed.RESULTS The incidence of PHLF in these patients was 22.46%.Multiple logistic analysis showed that preoperative serum albumin level,causes of liver resection(cancer or others),and cirrhosis were independent preoperative risk factors for PHLF(P<0.05)and that only post-blocking blood potassium concentration was an independent intraoperative risk factor for PHLF(P<0.05).Least absolute shrinkage and selection operator regression analysis revealed that preoperative serum albumin level,direct bilirubin level(DBIL),platelet count,causes of liver resection(cancer or others),and cirrhosis were significant predictors of PHLF.The nomogram risk prediction model based on preoperative serum albumin level,DBIL,platelet count,causes of liver resection(cancer or others),cirrhosis and post-blocking blood potassium concentration can better predict the occurrence of PHLF.CONCLUSION For patients undergoing liver resection with CLCVP,serum albumin level,DBIL,platelet count,causes of liver resection(cancer or others),and cirrhosis are independent preoperative risk factors for PHLF.展开更多
How to control the dynamic behavior of large-scale artificial active matter is a critical concern in experimental research on soft matter, particularly regarding the emergence of collective behaviors and the formation...How to control the dynamic behavior of large-scale artificial active matter is a critical concern in experimental research on soft matter, particularly regarding the emergence of collective behaviors and the formation of group patterns. Centralized systems excel in precise control over individual behavior within a group, ensuring high accuracy and controllability in task execution. Nevertheless, their sensitivity to group size may limit their adaptability to diverse tasks. In contrast, decentralized systems empower individuals with autonomous decision-making, enhancing adaptability and system robustness. Yet, this flexibility comes at the cost of reduced accuracy and efficiency in task execution. In this work, we present a unique method for regulating the centralized dynamic behavior of self-organizing clusters based on environmental interactions. Within this environment-coupled robot system, each robot possesses similar dynamic characteristics, and their internal programs are entirely identical. However, their behaviors can be guided by the centralized control of the environment, facilitating the accomplishment of diverse cluster tasks. This approach aims to balance the accuracy and flexibility of centralized control with the robustness and task adaptability of decentralized control. The proactive regulation of dynamic behavioral characteristics in active matter groups, demonstrated in this work through environmental interactions, holds the potential to introduce a novel technological approach and provide experimental references for studying the dynamic behavior control of large-scale artificial active matter systems.展开更多
When the vehicle is on a split-μramp and is restricted by the differential's torque-equalizing characteristic,a sig-nificant functional conflict may occur between the driving force limitation requirement of the a...When the vehicle is on a split-μramp and is restricted by the differential's torque-equalizing characteristic,a sig-nificant functional conflict may occur between the driving force limitation requirement of the acceleration slip regulation(ASR)control strategy for low-adhesion side wheels and the driving force enhancement demand of the entire vehicle during hill starting.Aiming at this problem,this paper proposes an ASR control strategy for the start-up of the electric vehicle on the split-μramp based on the combined control architecture of the service brake system and the parking brake system.First,the relationship between the driving force,braking force,and road adhesion at the slip moment is analyzed,and the ground adhesion estimation algorithm based on the dynamic equation of the driving wheel slip moment is proposed.Second,a service braking torque control model is constructed,and an ASR controller method based on the super-twisting sliding mode control(STSMC)algorithm is proposed to study the hill start assist(HSA)control strategy of electric vehicles on split-μroads.Finally,the proposed control strategy is si-mulated in this paper.The simulation results show that the proposed strategy can accurately estimate the ground adhesion of the driving wheel on the low-adhesion side effectively preventing the vehicle from slipping back,and improving the dynamic performance of the vehicle under harsh conditions.展开更多
Isolated operation of hydropower stations on Wujinag River was seen disadvantages of low rate of water utilization and much loss of electricity caused by abandoned water during low load periods. To tackle the problem,...Isolated operation of hydropower stations on Wujinag River was seen disadvantages of low rate of water utilization and much loss of electricity caused by abandoned water during low load periods. To tackle the problem, centralized control over cascade hydropower stations is practiced with a considerable economic benef it gained.展开更多
The alternative energy resources, like solar, are always complementary due to environmental changes. Energy generation with the sources such as solar and wind is gaining importance and of that photovoltaic conversion ...The alternative energy resources, like solar, are always complementary due to environmental changes. Energy generation with the sources such as solar and wind is gaining importance and of that photovoltaic conversion is the main focus of researches due to its promising potential as the electrical source. This paper presents the constant voltage method of control where the output of the converter is maintained constant irrespective of the variations in the irradiance with the high step-up isolated efficient single switch DC-DC converter for the solar PV systems. Constant voltage method of control uses the array of photovoltaic systems as its energy source. The output of the Solar PV systems is nonlinear and has its dependency on temperature and irradiance by which the panel voltage and current varies with the variation in irradiance. Constant voltage control method always operates in such a way that the converter voltage is tried to be maintained constantly to the reference voltage which is set by the user. The system used here utilizes high step single switch isolated DC-DC converter and monitors the voltage continuously by varying the duty cycle to maintain the converter voltage always constant. As a way of improving the performance, both the open and closed loop analysis is done where the closed loop analysis uses the PI controller for its performance. The model is implemented in MATLAB and it accepts the irradiance as the input and outputs the constant voltage from the converter and the feasibility of the proposed converter topology is confirmed with experimental results of the prototype model.展开更多
This paper introduces the upgrading process and application effect of centralized control of water treatment system in 850 rolling line. At the beginning of the design, the water treatment system of Delong Iron and St...This paper introduces the upgrading process and application effect of centralized control of water treatment system in 850 rolling line. At the beginning of the design, the water treatment system of Delong Iron and Steel 850 rolling line was composed of four parts, including the primary tank system, laminar flow pump room system, central pump room system and high-pressure water system. The design was all operated by the machine side operation box. In order to meet the requirements of automatic operation, the whole water treatment system was upgraded and reformed in combination with NARI company. NARI PCS control system is used for centralized control. Through upgrading, all the control modes in the above areas are centralized to the control console, and unified centralized operation is carried out through PLC. This paper provides a reference for the upgrading of water treatment system and the design and application of control system in steel rolling plant.展开更多
In recent years, with the rapid development of society, the demand for electric energy in the production field and life field is increasing, and the power supply quality is directly related to the performance of centr...In recent years, with the rapid development of society, the demand for electric energy in the production field and life field is increasing, and the power supply quality is directly related to the performance of centralized control operation steam turbine in power plant. Once there is an operation problem, it will lead to the reduction of smooth power supply, poor quality, and even affect the production and life of society, damage to the benefits of the power plant. Based on this, the author studies and discusses the centralized control operation of steam turbine, analyzes the existing shortcomings, and puts forward relevant operation optimization measures, in order to lay a solid foundation for improving the power generation quality and production efficiency of power plant.展开更多
One of the key tasks of centralized control operation of thermal power plant is to pre-control dangerous points, which ensures the safety of the whole thermal power plant. Therefore, it is necessary to understand the ...One of the key tasks of centralized control operation of thermal power plant is to pre-control dangerous points, which ensures the safety of the whole thermal power plant. Therefore, it is necessary to understand the main dangerous points and causes of centralized control operation, so as to take effective solutions, implementing preventive pre-control, and ensuring the safety of thermal power plant.展开更多
Under the background of rapid development of science and technology, people's quality of life continues to improve. In the actual life and production of modern people, there is almost no way to separate from the a...Under the background of rapid development of science and technology, people's quality of life continues to improve. In the actual life and production of modern people, there is almost no way to separate from the actual application of energy. Therefore, it is crucial to ensure normal and stable power generation. A normal power plant requires hard work from the staff. In the power plant, centralized control personnel are responsible for the normal production, delivery of facilities, design planning, inspection and maintenance. This paper will analyze and explain the training measures for the centralized control operation personnel of the newly-built power plant, hoping to provide some suggestions and ideas for the corresponding personnel.展开更多
The stable operation of thermal power plants is the core condition to ensure the stable power supply. Therefore, the application of unit centralized control technology around the three parts of the electromechanical f...The stable operation of thermal power plants is the core condition to ensure the stable power supply. Therefore, the application of unit centralized control technology around the three parts of the electromechanical furnace system layout, system principle, fixed value parameters, operation mode, logic and operation procedures control can improve the power generation stability of thermal power plants. Based on this, this paper first summarizes the concept of centralized control of thermal power plants and generating units, and then focuses on the principles and technical solutions of the application of centralized control technology of generating units.展开更多
The coronavirus disease 2019(COVID-19)pandemic increased the burden on many healthcare systems and in the process,exposed the need for medical resources and physical space.While few studies discussed the efficient uti...The coronavirus disease 2019(COVID-19)pandemic increased the burden on many healthcare systems and in the process,exposed the need for medical resources and physical space.While few studies discussed the efficient utilization of medical resources and physical space so far.Therefore,this study aimed to summarize experiences related to facilities used for centralized isolation for medical observation and treatment during the COVID-19 pandemic in China and to provide suggestions to further improve the management of confirmed cases,suspected cases,and close contacts.In China,three types of facilities for centralized isolation(Fangcang shelter hospitals,refitted non-designated hospitals,and quarantine hotels)underwent retrofitting for the treatment and isolation of confirmed and suspected cases.These facilities mitigated the immediate high demand for space.Moreover,in order to minimize infection risks in these facilities,regulators and governmental agencies implemented new designs,management measures,and precautionary measures to minimize infection risk.Other countries and regions could refer to China’s experience in optimally allocating social resources in response to the COVID-19 pandemic.As a conclusion,government should allocate social resources and construct centralized isolation and quarantine facilities for an emergency response,health authorities should issue regulations for centralized isolation facilities and pay strict attention to the daily management of these facilities,a multidisciplinary administration team is required to support the daily operation of a centralized isolation facility,in-depth studies and international collaboration on the centralized isolation policy are encouraged.展开更多
As a typical rhythmic movement, human being＇s rhythmic gait movement can be generated by a central pattern generator （CPG） located in a spinal cord by self- oscillation. Some kinds of gait movements are caused by g...As a typical rhythmic movement, human being＇s rhythmic gait movement can be generated by a central pattern generator （CPG） located in a spinal cord by self- oscillation. Some kinds of gait movements are caused by gait frequency and amplitude variances. As an important property of human being＇s motion vision, the attention selection mechanism plays a vital part in the regulation of gait movement. In this paper, the CPG model is amended under the condition of attention selection on the theoretical basis of Matsuoka neural oscillators. Regulation of attention selection signal for the CPG model parameters and structure is studied, which consequentially causes the frequency and amplitude changes of gait movement output. Further, the control strategy of the CPG model gait movement under the condition of attention selection is discussed, showing that the attention selection model can regulate the output model of CPG gait movement in three different ways. The realization of regulation on the gait movement frequency and amplitude shows a variety of regulation on the CPG gait movement made by attention selection and enriches the controllability of CPG gait movement, which demonstrates potential influence in engineering applications.展开更多
Taking the tight oil of the Zhongnan sag in the Ordos Basin,Jimusar sag in the Junggar Basin and Qingxi sag in the Jiuquan Basin as study objects,based on field survey,dissection of tight oil reservoirs,sample test,mo...Taking the tight oil of the Zhongnan sag in the Ordos Basin,Jimusar sag in the Junggar Basin and Qingxi sag in the Jiuquan Basin as study objects,based on field survey,dissection of tight oil reservoirs,sample test,modeling experiment and comprehensive analysis,this study reveals that the tight oil accumulates at start-up pressure,advances under differential pressure,diffuses at alternating fast and low speeds,charges in stepped large area and migrates rapidly through fractures,and enriches in dominant fractures and pores.The root cause of ladder-like charge is the multiple scales of pores.The widespread source rock with high hydrocarbon generation intensity is the material basis for tight oil enrichment;the dominant source reservoir assemblage is the basic unit for tight oil enrichment;fractures and beddings are conducive to local rapid migration of tight oil;fractures and pores work together to control the enrichment of tight oil.Two typical accumulation models of tight oil are established,namely"source reservoir in coexistence,four optimal factors controlling enrichment around central area,and large-scale continuous distribution"for a large freshwater lake clastic rock basin and"source reservoir integration,four optimal factors controlling enrichment,central area distribution,small in size but high in enrichment degree"for a small saline lake diamictite depression.展开更多
Extensive studies on aerosol chemistry have been carried out in megacities in China,however,aerosol characterization in Central China Plain(CCP)is limited.Here we conducted real-time measurements of fine particle comp...Extensive studies on aerosol chemistry have been carried out in megacities in China,however,aerosol characterization in Central China Plain(CCP)is limited.Here we conducted real-time measurements of fine particle composition with a time-of-flight aerosol chemical speciation monitor in Kaifeng,Henan province in October 2019.Our results showed that nitrate and organics constituted the major fraction of non-refractory PM_(2.5)for the entire study,on average accounting for 34%and 33%,respectively.However,aerosol composition was substantially different among four periods due to different meteorological conditions and chemical processing.For instance,nitrate presented the lowest contribution during the first period due to evaporative loss associated with high temperature(T),and then rapidly increased during polluted periods as a function of relative humidity(RH).Positive matrix factorization analysis showed the dominance of secondary organic aerosol(SOA)in OA,and also the changes in OA composition under different T and RH levels.In addition,this study is unique with two periods of local emission controls.Back trajectory and coefficient of divergence analysis showed that air pollution in CCP was overall homogeneously distributed.As a result,the effectiveness of local emission controls in this region was strongly affected by meteorological conditions and regional transport.We found that one of the periods with emission control even showed the highest concentrations for the entire study.Our results point towards the limited effect of local emission controls in mitigating air pollution in CCP,and highlight the importance of joint emission controls under unfavorable meteorological conditions.展开更多
Sandi Arabia is renown for its rich oil and gas Mesozoic.However,the discovery of Paleozoic fields in resources with the bulk of the reserves reservo/red in the the late 1980s has encouraged further exploration in the...Sandi Arabia is renown for its rich oil and gas Mesozoic.However,the discovery of Paleozoic fields in resources with the bulk of the reserves reservo/red in the the late 1980s has encouraged further exploration in the Paleozoic.This paper reviews the salient features of the Paleozoic petroleum geology in central Saudi Arabia and discusses the main factors controlling hydrocarbon accumulation in the Paleozoic.The Lower Silurian Qusaiba hot shale is the principal source rock for the hydrocarbons discovered in the Ordovician to Permian reservoirs.Of them,the Permo-Carboniferous Unayzah and Upper Ordovician Sarah Formations have the best exploration potential.The key factors controlling hydrocarbon accumulation in the Unayzah Formation are migration pathways and reservoir petrophysics.The key factors controlling hydrocarbon accumulation in the Sarah Formation are reservoir petrophysics and the development of structural traps.展开更多
基金supported by the Provincial Industrial Science and Technology Project of State Grid Jiangsu Electric Power Co.,Ltd.of China,grant number JC2024118.
文摘The dense integration of residential distributed photovoltaic(PV)systems into three-phase,four-wire low-voltage(LV)distribution networks results in reverse power flow and three-phase imbalance,leading to voltage violations that hinder the growth of rural distributed PV systems.Traditional voltage droop-based control methods regulate PV power output solely based on local voltage measurements at the point of PV connection.Due to a lack of global coordination and optimization,their efficiency is often subpar.This paper presents a centralized coordinated active/reactive power control strategy for PV inverters in rural LV distribution feeders with high PV penetration.The strategy optimizes residential PV inverter reactive and active power control to enhance voltage quality.It uses sensitivity coefficients derived from the inverse Jacobian matrix to assign adjustment weights to individual PV units and iteratively optimize their power outputs.The control sequence prioritizes reactive power increases;if the coefficients are below average or the inverters reach capacity,active power is curtailed until voltage issues are resolved.A simulation based on a real 37-node rural distribution network shows that the proposed method significantly reduces PV curtailment.Typical daily results indicate a curtailment rate of 1.47%,which is significantly lower than the 15.4%observed with the voltage droop-based control method.The total daily PV power output(measured every 15 min)increases from 5.55 to 6.41 MW,improving PV hosting capacity.
文摘As an indispensable part of modern buildings,centralized central air conditioning systems play an important role in maintaining the comfort and air quality of the indoor environment.However,with the increasing energy consumption,how to improve the energy efficiency ratio of air conditioning systems and reduce energy consumption has become an important issue in research and practice.The purpose of this paper is to discuss the impact of humidity control strategies on energy saving in centralized central air conditioning systems,with a view to providing a theoretical basis and practical guidance for realizing building energy efficiency.
基金supported by the Key Scientific and Technological Projects(2024KJGG27)of Tianfu Yongxing Laboratorythe Experimental Platform Open Innovation Funding(209042025003)of Sichuan Energy Internet Research Institute,Tsinghua University.
文摘As the development of new power systems progresses,the inherent inertia of power systems continues to diminish.Centralized frequency regulation,which relies on rapid communication and real-time control,can enable inverter-based thermostatically controlled load(ITCL)clusters to provide virtual inertia support to the power grid.However,ITCL clusters exhibit significant discrete response characteristics,which precludes the direct integration of load-side inertia support into the synchronous unit side.To address this issue,this paper elaborates on the existing technical framework and analyzes the underlying causes of the problem.It proposes a timestamp allocation mechanism for ITCL cluster control instructions,ensuring that many ITCL terminals can be triggered at staggered times,thereby allowing the load cluster power to adhere to the inertia analog control law at any moment.Building on this foundation,the paper further examines the impact of the inertia response delay of ITCL clusters,which is based on centralized frequency regulation,on the stability of the power system.A design scheme for inertia analog control parameters is proposed,taking into account dual constraints,frequency stability and load cluster regulation capacity.Finally,the feasibility and applicability of the proposed mechanism and parameter design scheme are investigated through simulations conducted via MATLAB/Simulink.
基金Project (No. 60373088) supported by the National Natural ScienceFoundation of China
文摘With the rapid development of Virtual Private Network (VPN), many companies and organizations use VPN to implement their private communication. Traditionally, VPN uses security protocols to protect the confidentiality of data, the message integrity and the endpoint authentication. One core technique of VPN is tunneling, by which clients can access the in- ternal servers traversing VPN. However, the tunneling technique also introduces a concealed security hole. It is possible that if one vicious user can establish tunneling by the VPN server, he can compromise the internal servers behind the VPN server. So this paper presents a novel Application-layer based Centralized Information Access Control (ACIAC) for VPN to solve this problem. To implement an efficient, flexible and multi-decision access control model, we present two key techniques to ACIAC—the centralized management mechanism and the stream-based access control. Firstly, we implement the information center and the constraints/events center for ACIAC. By the two centers, we can provide an abstract access control mechanism, and the material access control can be decided dynamically by the ACIAC’s constraint/event mechanism. Then we logically classify the VPN communication traffic into the access stream and the data stream so that we can tightly couple the features of VPN communication with the access control model. We also provide the design of our ACIAC prototype in this paper.
文摘The interference reduction capability of cell sectoring and power control algorithms have been considered separately as means to decrease the interference in Code Division Multiple Access (CDMA) cellular systems. In this paper, we present Switched-Beam (SB) and Rotatable Equal Sectoring (RES) techniques for CDMA cellular systems in a 2D urban environment. In the SB technique by using a number of fixed, independent, or directional antennas we increase the downlink capacity of the CDMA systems. Also in the RES method, the equal sectors of the base stations are rotating together to decrease the inter-cell and intra-cell interferences. Also in this paper we use centralized power control to overcome the near-far problem. Simulation results indicate that the proposed techniques considerably increase the capacity of the CDMA cellular systems compared to ordinary Equal Sectoring (ES) method.
基金Supported by the Natural Science Foundation of Hunan Province,No.2018JJ3291the Scientific Research Project of the Hunan Provincial Health Commission,No.202104111288.
文摘BACKGROUND Post-hepatectomy liver failure(PHLF),represents a serious complication after liver resection,significantly impacting the long-term outcomes for patients who undergo such surgeries.There exists a strong correlation between intraoperative hemorrhage and transfusion requirements with the development of PHLF.Presently,a combination of hepatic portal occlusion techniques alongside con-trolled low central venous pressure(CLCVP)methodologies is extensively em-ployed to mitigate intraoperative bleeding.Nonetheless,limited studies have analyzed the risk factors for PHLF under CLCVP.AIM To develop and validate a nomogram that predicts the risk factors associated with the development of PHLF patients undergoing liver resection with CLCVP.METHODS We conducted a retrospective analysis of 285 patients who underwent hepatectomy for the first time and had no history of prior non-index abdominal surgeries,with hepatic inflow occlusion combined with CLCVP from January to December 2019 in Hunan Provincial People’s Hospital.Univariate and multivariate regression analyses were used to identify preoperative and intraoperative risk factors for PHLF.Eligible patients were randomly divided into training and validation groups in a 7:3 ratio,and a nomogram prediction model was constructed.RESULTS The incidence of PHLF in these patients was 22.46%.Multiple logistic analysis showed that preoperative serum albumin level,causes of liver resection(cancer or others),and cirrhosis were independent preoperative risk factors for PHLF(P<0.05)and that only post-blocking blood potassium concentration was an independent intraoperative risk factor for PHLF(P<0.05).Least absolute shrinkage and selection operator regression analysis revealed that preoperative serum albumin level,direct bilirubin level(DBIL),platelet count,causes of liver resection(cancer or others),and cirrhosis were significant predictors of PHLF.The nomogram risk prediction model based on preoperative serum albumin level,DBIL,platelet count,causes of liver resection(cancer or others),cirrhosis and post-blocking blood potassium concentration can better predict the occurrence of PHLF.CONCLUSION For patients undergoing liver resection with CLCVP,serum albumin level,DBIL,platelet count,causes of liver resection(cancer or others),and cirrhosis are independent preoperative risk factors for PHLF.
基金Project supported by the National Natural Science Foundation of China (Grant No. 12174041)China Postdoctoral Science Foundation (CPSF)(Grant No. 2022M723118)the seed grants from the Wenzhou Institute,University of Chinese Academy of Sciences (Grant No. WIUCASQD2021002)。
文摘How to control the dynamic behavior of large-scale artificial active matter is a critical concern in experimental research on soft matter, particularly regarding the emergence of collective behaviors and the formation of group patterns. Centralized systems excel in precise control over individual behavior within a group, ensuring high accuracy and controllability in task execution. Nevertheless, their sensitivity to group size may limit their adaptability to diverse tasks. In contrast, decentralized systems empower individuals with autonomous decision-making, enhancing adaptability and system robustness. Yet, this flexibility comes at the cost of reduced accuracy and efficiency in task execution. In this work, we present a unique method for regulating the centralized dynamic behavior of self-organizing clusters based on environmental interactions. Within this environment-coupled robot system, each robot possesses similar dynamic characteristics, and their internal programs are entirely identical. However, their behaviors can be guided by the centralized control of the environment, facilitating the accomplishment of diverse cluster tasks. This approach aims to balance the accuracy and flexibility of centralized control with the robustness and task adaptability of decentralized control. The proactive regulation of dynamic behavioral characteristics in active matter groups, demonstrated in this work through environmental interactions, holds the potential to introduce a novel technological approach and provide experimental references for studying the dynamic behavior control of large-scale artificial active matter systems.
基金Supported by the National Natural Science Foundation of China(Grant No.52172369).
文摘When the vehicle is on a split-μramp and is restricted by the differential's torque-equalizing characteristic,a sig-nificant functional conflict may occur between the driving force limitation requirement of the acceleration slip regulation(ASR)control strategy for low-adhesion side wheels and the driving force enhancement demand of the entire vehicle during hill starting.Aiming at this problem,this paper proposes an ASR control strategy for the start-up of the electric vehicle on the split-μramp based on the combined control architecture of the service brake system and the parking brake system.First,the relationship between the driving force,braking force,and road adhesion at the slip moment is analyzed,and the ground adhesion estimation algorithm based on the dynamic equation of the driving wheel slip moment is proposed.Second,a service braking torque control model is constructed,and an ASR controller method based on the super-twisting sliding mode control(STSMC)algorithm is proposed to study the hill start assist(HSA)control strategy of electric vehicles on split-μroads.Finally,the proposed control strategy is si-mulated in this paper.The simulation results show that the proposed strategy can accurately estimate the ground adhesion of the driving wheel on the low-adhesion side effectively preventing the vehicle from slipping back,and improving the dynamic performance of the vehicle under harsh conditions.
文摘Isolated operation of hydropower stations on Wujinag River was seen disadvantages of low rate of water utilization and much loss of electricity caused by abandoned water during low load periods. To tackle the problem, centralized control over cascade hydropower stations is practiced with a considerable economic benef it gained.
文摘The alternative energy resources, like solar, are always complementary due to environmental changes. Energy generation with the sources such as solar and wind is gaining importance and of that photovoltaic conversion is the main focus of researches due to its promising potential as the electrical source. This paper presents the constant voltage method of control where the output of the converter is maintained constant irrespective of the variations in the irradiance with the high step-up isolated efficient single switch DC-DC converter for the solar PV systems. Constant voltage method of control uses the array of photovoltaic systems as its energy source. The output of the Solar PV systems is nonlinear and has its dependency on temperature and irradiance by which the panel voltage and current varies with the variation in irradiance. Constant voltage control method always operates in such a way that the converter voltage is tried to be maintained constantly to the reference voltage which is set by the user. The system used here utilizes high step single switch isolated DC-DC converter and monitors the voltage continuously by varying the duty cycle to maintain the converter voltage always constant. As a way of improving the performance, both the open and closed loop analysis is done where the closed loop analysis uses the PI controller for its performance. The model is implemented in MATLAB and it accepts the irradiance as the input and outputs the constant voltage from the converter and the feasibility of the proposed converter topology is confirmed with experimental results of the prototype model.
文摘This paper introduces the upgrading process and application effect of centralized control of water treatment system in 850 rolling line. At the beginning of the design, the water treatment system of Delong Iron and Steel 850 rolling line was composed of four parts, including the primary tank system, laminar flow pump room system, central pump room system and high-pressure water system. The design was all operated by the machine side operation box. In order to meet the requirements of automatic operation, the whole water treatment system was upgraded and reformed in combination with NARI company. NARI PCS control system is used for centralized control. Through upgrading, all the control modes in the above areas are centralized to the control console, and unified centralized operation is carried out through PLC. This paper provides a reference for the upgrading of water treatment system and the design and application of control system in steel rolling plant.
文摘In recent years, with the rapid development of society, the demand for electric energy in the production field and life field is increasing, and the power supply quality is directly related to the performance of centralized control operation steam turbine in power plant. Once there is an operation problem, it will lead to the reduction of smooth power supply, poor quality, and even affect the production and life of society, damage to the benefits of the power plant. Based on this, the author studies and discusses the centralized control operation of steam turbine, analyzes the existing shortcomings, and puts forward relevant operation optimization measures, in order to lay a solid foundation for improving the power generation quality and production efficiency of power plant.
文摘One of the key tasks of centralized control operation of thermal power plant is to pre-control dangerous points, which ensures the safety of the whole thermal power plant. Therefore, it is necessary to understand the main dangerous points and causes of centralized control operation, so as to take effective solutions, implementing preventive pre-control, and ensuring the safety of thermal power plant.
文摘Under the background of rapid development of science and technology, people's quality of life continues to improve. In the actual life and production of modern people, there is almost no way to separate from the actual application of energy. Therefore, it is crucial to ensure normal and stable power generation. A normal power plant requires hard work from the staff. In the power plant, centralized control personnel are responsible for the normal production, delivery of facilities, design planning, inspection and maintenance. This paper will analyze and explain the training measures for the centralized control operation personnel of the newly-built power plant, hoping to provide some suggestions and ideas for the corresponding personnel.
文摘The stable operation of thermal power plants is the core condition to ensure the stable power supply. Therefore, the application of unit centralized control technology around the three parts of the electromechanical furnace system layout, system principle, fixed value parameters, operation mode, logic and operation procedures control can improve the power generation stability of thermal power plants. Based on this, this paper first summarizes the concept of centralized control of thermal power plants and generating units, and then focuses on the principles and technical solutions of the application of centralized control technology of generating units.
文摘The coronavirus disease 2019(COVID-19)pandemic increased the burden on many healthcare systems and in the process,exposed the need for medical resources and physical space.While few studies discussed the efficient utilization of medical resources and physical space so far.Therefore,this study aimed to summarize experiences related to facilities used for centralized isolation for medical observation and treatment during the COVID-19 pandemic in China and to provide suggestions to further improve the management of confirmed cases,suspected cases,and close contacts.In China,three types of facilities for centralized isolation(Fangcang shelter hospitals,refitted non-designated hospitals,and quarantine hotels)underwent retrofitting for the treatment and isolation of confirmed and suspected cases.These facilities mitigated the immediate high demand for space.Moreover,in order to minimize infection risks in these facilities,regulators and governmental agencies implemented new designs,management measures,and precautionary measures to minimize infection risk.Other countries and regions could refer to China’s experience in optimally allocating social resources in response to the COVID-19 pandemic.As a conclusion,government should allocate social resources and construct centralized isolation and quarantine facilities for an emergency response,health authorities should issue regulations for centralized isolation facilities and pay strict attention to the daily management of these facilities,a multidisciplinary administration team is required to support the daily operation of a centralized isolation facility,in-depth studies and international collaboration on the centralized isolation policy are encouraged.
基金supported by the National Natural Science Foundation of China(Nos.11232005 and11472104)the Doctoral Fund of Ministry of Education of China(No.20120074110020)
文摘As a typical rhythmic movement, human being＇s rhythmic gait movement can be generated by a central pattern generator （CPG） located in a spinal cord by self- oscillation. Some kinds of gait movements are caused by gait frequency and amplitude variances. As an important property of human being＇s motion vision, the attention selection mechanism plays a vital part in the regulation of gait movement. In this paper, the CPG model is amended under the condition of attention selection on the theoretical basis of Matsuoka neural oscillators. Regulation of attention selection signal for the CPG model parameters and structure is studied, which consequentially causes the frequency and amplitude changes of gait movement output. Further, the control strategy of the CPG model gait movement under the condition of attention selection is discussed, showing that the attention selection model can regulate the output model of CPG gait movement in three different ways. The realization of regulation on the gait movement frequency and amplitude shows a variety of regulation on the CPG gait movement made by attention selection and enriches the controllability of CPG gait movement, which demonstrates potential influence in engineering applications.
基金Supported by the National Natural Science Foundation of China(41672118)Strategic Cooperation Science and Technology Project Between China University of Petroleum and Petro China(ZLZX2020-01-06)。
文摘Taking the tight oil of the Zhongnan sag in the Ordos Basin,Jimusar sag in the Junggar Basin and Qingxi sag in the Jiuquan Basin as study objects,based on field survey,dissection of tight oil reservoirs,sample test,modeling experiment and comprehensive analysis,this study reveals that the tight oil accumulates at start-up pressure,advances under differential pressure,diffuses at alternating fast and low speeds,charges in stepped large area and migrates rapidly through fractures,and enriches in dominant fractures and pores.The root cause of ladder-like charge is the multiple scales of pores.The widespread source rock with high hydrocarbon generation intensity is the material basis for tight oil enrichment;the dominant source reservoir assemblage is the basic unit for tight oil enrichment;fractures and beddings are conducive to local rapid migration of tight oil;fractures and pores work together to control the enrichment of tight oil.Two typical accumulation models of tight oil are established,namely"source reservoir in coexistence,four optimal factors controlling enrichment around central area,and large-scale continuous distribution"for a large freshwater lake clastic rock basin and"source reservoir integration,four optimal factors controlling enrichment,central area distribution,small in size but high in enrichment degree"for a small saline lake diamictite depression.
基金supported by the National Key Research and Development Program of China(No.2019YFC0214200)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA23020301)。
文摘Extensive studies on aerosol chemistry have been carried out in megacities in China,however,aerosol characterization in Central China Plain(CCP)is limited.Here we conducted real-time measurements of fine particle composition with a time-of-flight aerosol chemical speciation monitor in Kaifeng,Henan province in October 2019.Our results showed that nitrate and organics constituted the major fraction of non-refractory PM_(2.5)for the entire study,on average accounting for 34%and 33%,respectively.However,aerosol composition was substantially different among four periods due to different meteorological conditions and chemical processing.For instance,nitrate presented the lowest contribution during the first period due to evaporative loss associated with high temperature(T),and then rapidly increased during polluted periods as a function of relative humidity(RH).Positive matrix factorization analysis showed the dominance of secondary organic aerosol(SOA)in OA,and also the changes in OA composition under different T and RH levels.In addition,this study is unique with two periods of local emission controls.Back trajectory and coefficient of divergence analysis showed that air pollution in CCP was overall homogeneously distributed.As a result,the effectiveness of local emission controls in this region was strongly affected by meteorological conditions and regional transport.We found that one of the periods with emission control even showed the highest concentrations for the entire study.Our results point towards the limited effect of local emission controls in mitigating air pollution in CCP,and highlight the importance of joint emission controls under unfavorable meteorological conditions.
文摘Sandi Arabia is renown for its rich oil and gas Mesozoic.However,the discovery of Paleozoic fields in resources with the bulk of the reserves reservo/red in the the late 1980s has encouraged further exploration in the Paleozoic.This paper reviews the salient features of the Paleozoic petroleum geology in central Saudi Arabia and discusses the main factors controlling hydrocarbon accumulation in the Paleozoic.The Lower Silurian Qusaiba hot shale is the principal source rock for the hydrocarbons discovered in the Ordovician to Permian reservoirs.Of them,the Permo-Carboniferous Unayzah and Upper Ordovician Sarah Formations have the best exploration potential.The key factors controlling hydrocarbon accumulation in the Unayzah Formation are migration pathways and reservoir petrophysics.The key factors controlling hydrocarbon accumulation in the Sarah Formation are reservoir petrophysics and the development of structural traps.
