Lithium iron phosphate batteries have been increasingly utilized in recent years because their higher safety performance can improve the increasing trend of recurring thermal runaway accidents.However,the safety perfo...Lithium iron phosphate batteries have been increasingly utilized in recent years because their higher safety performance can improve the increasing trend of recurring thermal runaway accidents.However,the safety performance and mechanism of high-capacity lithium iron phosphate batteries under internal short-circuit challenges remain to be explored.This work analyzes the thermal runaway evolution of high-capacity LiFePO_(4) batteries under different internal heat transfer modes,which are controlled by different penetration modes.Two penetration cases involving complete penetration and incomplete penetration were detected during the test,and two modes were performed incorporating nails that either remained or were removed after penetration to comprehensively reveal the thermal runaway mechanism.A theoretical model of microcircuits and internal heat conduction is also established.The results indicated three thermal runaway evolution processes for high-capacity batteries,which corresponded to the experimental results of thermal equilibrium,single thermal runaway,and two thermal runaway events.The difference in heat distribution in the three phenomena is determined based on the microstructure and material structure near the pinhole.By controlling the heat dissipation conditions,the time interval between two thermal runaway events can be delayed from 558 to 1417 s,accompanied by a decrease in the concentration of in-situ gas production during the second thermal runaway event.展开更多
Ultrasonic assisted GMAW （U-GMAW） method is a novel process, which combines the ultrasonic wave with gas metal arc welding to improve the process stability and weld quality. The U-GMAW system is developed and the ul...Ultrasonic assisted GMAW （U-GMAW） method is a novel process, which combines the ultrasonic wave with gas metal arc welding to improve the process stability and weld quality. The U-GMAW system is developed and the ultrasonic wave is applied by means of acoustic radiation. The arc characteristics and metal transfer modes are studied in comparison with conventional GMAW process. The arc plasma is compressed and the arc length is shorter than that in conventional GMAW process after the ultrasonic is applied onto the arc. The parameter range of short-circuiting mode is extended and the range of unstable transfer is minimized. The changes in arc characteristics are responsible for changes in metal transfer modes.展开更多
When laser ablation is subjected to supersonic flow, the influence mechanism of airflow on laser ablation behavior is still unclear. A coupled thermal-fluid-structure model is presented to investigate the influence of...When laser ablation is subjected to supersonic flow, the influence mechanism of airflow on laser ablation behavior is still unclear. A coupled thermal-fluid-structure model is presented to investigate the influence of supersonic airflow on the development of a laser ablation pit. Results show that the aerodynamic convection cooling effect not only reduces the ablation velocity but also changes the symmetry morphology of the ablation pit due to the non-uniform convective heat transfer. Flow mode transition is also observed when the pit becomes deeper, and significant change in flow pattern and heat transfer behavior are found when the open mode is transformed into the closed mode.展开更多
Using Xenon lamp lights to overcome the strong interference from the welding arc, a computer-based system is developed to sense and visualize the metal transfer in GMAW. This system combines through-the-arc sensing of...Using Xenon lamp lights to overcome the strong interference from the welding arc, a computer-based system is developed to sense and visualize the metal transfer in GMAW. This system combines through-the-arc sensing of the welding current and arc voltage with high speed imaging of the metal transfer. It can simultaneously display the metal transfer processes and waveforms of electrical welding parameters in real-time The metal transfer videos and waveforms of electrical welding parameters can be recorded. Metal transfers under various welding conditions have been investigated with the system developed.展开更多
Elastic heat transfer tube bundles are widely used in the field of flow-induced vibration heat transfer enhancement. Two types of mainly used tube bundles, the planar elastic tube bundle and the conical spiral tube bu...Elastic heat transfer tube bundles are widely used in the field of flow-induced vibration heat transfer enhancement. Two types of mainly used tube bundles, the planar elastic tube bundle and the conical spiral tube bundle were comprehensively compared in the condition of the same shell side diameter. The natural mode characteristics, the effect of fluid-structure interaction, the stress distribution, the comprehensive heat transfer performance and the secondary fluid flow of the two elastic tube bundles were all concluded and compared. The results show that the natural frequency and the critical velocity of vibration buckling of the planar elastic tube bundle are larger than those of the conical spiral tube bundle, while the stress distribution and the comprehensive heat transfer performance of the conical spiral tube bundle are relatively better.展开更多
This paper introduces a method to realize digital television transmission based on asynchronous transfer mode (ATM), a technology based on fast packet switching. Choosing the integral multiple length of an ATM cell pa...This paper introduces a method to realize digital television transmission based on asynchronous transfer mode (ATM), a technology based on fast packet switching. Choosing the integral multiple length of an ATM cell payload to equal to the length of an MPEG transport stream packet, an MPEG transport stream packet can be inextenso loaded by several ATM cells and trans-formed into ATM cells. Using ATM virtual connection technology and B-ISDN, the interoperability between ATM and DTV may be realized, and DTV signal transmission may also be realized finally.展开更多
Digital TV (DTV) video signal transmission over ATM network is emphasized on.Some important problems are introduced about TV video signals asynchronous transfer to network application client, and the idea of video tra...Digital TV (DTV) video signal transmission over ATM network is emphasized on.Some important problems are introduced about TV video signals asynchronous transfer to network application client, and the idea of video transfer design is discussed. The contents mainly include the DTV video streams asynchronous transfer topology, compressed coding adopted ATM network, asynchronous transfer efficiency and some problems of DTV video transmission in ATM network .展开更多
Objective: To explore the clinical value of safe transfer nursing model in hospital transfer of critically ill patients in emergency department. Methods: 850 critically ill patients admitted to the emergency departmen...Objective: To explore the clinical value of safe transfer nursing model in hospital transfer of critically ill patients in emergency department. Methods: 850 critically ill patients admitted to the emergency department of the central hospital were selected as the observation group (the implementation of safe transport care model), 660 critically ill patients admitted to the emergency department of the central hospital from April to December 2019 were selected as the control group (the use of regular car escort), and the occurrence of adverse events, transit time and satisfaction of patients' families were compared between the two groups. Results: the total incidence rate of adverse events in the observation group was 1.76%, which was significantly lower than that in the control group (10.00%) (P < 0.05). The time taken for external examination, including ultrasound, CT and X-ray, in the observation group was (26.12±3.11) min, time taken for transfer to specialized department (21.18±3.13) min and time taken for transfer to interventional room (5.32±1.19) min, which were significantly shorter than those in the control group (34.25±4.27), (25.33±3.07) min and (6.16±1.32) min, with statistical significance (P < 0.05). The scores of nurse-patient communication, care in transit, and treatment in the department and the total score in the observation group were (21.52±5.32), (34.56±7.13), (25.34±6.32) and (76.35±11.26) respectively, which were significantly higher than those in the control group (20.33±4.78), (32.33±6.25), (22.33±6.41) and (73.62±11.09), with statistical significance (P < 0.05). Conclusion: the safe transfer nursing model has high clinical value in the hospital transfer of critically ill patients in emergency department, which can effectively reduce the risk of adverse events, shorten the transfer time and improve the satisfaction of patients' families.展开更多
The heat exchanger,a crucial device facilitating heat transfer between different temperature media,finds extensive application across diverse industries such as chemical,metallurgy,electric power,and construction,play...The heat exchanger,a crucial device facilitating heat transfer between different temperature media,finds extensive application across diverse industries such as chemical,metallurgy,electric power,and construction,playing a pivotal role in energy conservation.It encompasses various structural configurations including tubular,shell-and-tube,and plate heat exchangers,and operates through different heat transfer modes including convection,radiation,and composite convection-radiation mecha nisms.This study focuses on experimentation with a plate heat exchanger to ascertain optimal heat transfer parameters via manipulation of heat transfer mode and flow rate.The findings underscore the significant enhancement in heat transfer efficiency achievable through judicious adjustments in working medium flow rate and heat transfer mode.展开更多
The ultrasonic assisted GMAW （U-GMAW） method is proposed to achieve a more stable welding process and better weld quality. Tbe U-GMA W system is dereloped, which consists of power supplies, ultrasonic vibration syst...The ultrasonic assisted GMAW （U-GMAW） method is proposed to achieve a more stable welding process and better weld quality. Tbe U-GMA W system is dereloped, which consists of power supplies, ultrasonic vibration system and specially designed u＇elding torch. The U-GMA W process and eonventional GMA W process are compared through bead-on-plate welding. The weld beads arc continuous and well protected, while the weld surface appearances by GMA W and U-GMA W are apparently diffierent. The metal transfe ,node changes from globular transfer to short-circuiting transfer after ultrasonic wave is applied onto the arc.展开更多
A QoS-aware input-queued scheduling algorithm, called Smallest Timestamp First (STF), is proposed, which is improved upon iSLIP and can allocate bandwidth among inputs sharing a common output based on their reservatio...A QoS-aware input-queued scheduling algorithm, called Smallest Timestamp First (STF), is proposed, which is improved upon iSLIP and can allocate bandwidth among inputs sharing a common output based on their reservation by assigning suitable finishing tiniest-amps to contending cells. STF can also provide isolation between flows that share a common output, link. Misbehaving flows will be restricted to guarantee the behaving flows' bandwidth. Simulations prove the feasibility of our algorithm.展开更多
To enhance the fidelity and accuracy of the simulation of communication networks,hardware-in-the-loop（HITL） simulation was employed.HITL simulation methods was classified into three categories,of which the merits an...To enhance the fidelity and accuracy of the simulation of communication networks,hardware-in-the-loop（HITL） simulation was employed.HITL simulation methods was classified into three categories,of which the merits and shortages were compared.Combing system-in-the-loop（SITL） simulation principle with high level architecture（HLA）,an HITL simulation model of asynchronous transfer mode（ATM） network was constructed.The throughput and end-to-end delay of all-digital simulation and HITL simulation was analyzed,which showed that HITL simulation was more reliable and effectively improved the simulation credibility of communication network.Meanwhile,HLA-SITL method was fast and easy to achieve and low-cost during design lifecycle.Thus,it was a feasible way to research and analyze the large-scale network.展开更多
ECFD （erroneous cell tail drop）, a buffer management optimization strategy is suggested which can improve the utilization of buffer resources in satellite ATM （asynchronous transfer mode） networks. The strategy, i...ECFD （erroneous cell tail drop）, a buffer management optimization strategy is suggested which can improve the utilization of buffer resources in satellite ATM （asynchronous transfer mode） networks. The strategy, in which erroneous cells caused by satellite channel and the following cells that belong to the same PDU （protocol data Unit） are discarded, concerns non-real-time data services that use higher layer protocol for retransmission. Based on EPD （early packet drop） policy, mathematical models are established with and without ECTD. The numerical results show that ECTD would optimize buffer management and improve effective throughput （goodput）, and the increment of goodput is relative to the CER （cell error ratio） and the PDU length. The higher their values are, the greater the increment. For example, when the average PDU length values are 30 and 90, the improvement of goodput are respectively about 4% and 10%.展开更多
Admission control is an important strategy for Quality of Service (QoS) provisioning in Asynchro- nous Transfer Mode (ATM) networks. Based on a control-theory model of resources on-Demand Allocation (DA) protocol, the...Admission control is an important strategy for Quality of Service (QoS) provisioning in Asynchro- nous Transfer Mode (ATM) networks. Based on a control-theory model of resources on-Demand Allocation (DA) protocol, the paper studies the effect of the protocol on the statistical characteristics of network traffic, and proposes a combined connection admission control algorithm with the DA protocol to achieve full utiliza- tion of link resources in satellite communication systems. The proposed algorithm is based on the cross-layer-design approach. Theoretical analysis and system simulation results show that the proposed algo- rithm can admit more connections within certain admission thresholds than one that does not take into account the DA protocol. Thus, the proposed algorithm can increase admission ratio of traffic sources for satellite ATM networks and improve satellite link utilization.展开更多
In this paper, an extended Kendall model for the priority scheduling input-line group output with multi-channel in Asynchronous Transfer Mode （ATM） exchange system is proposed and then the mean method is used to mod...In this paper, an extended Kendall model for the priority scheduling input-line group output with multi-channel in Asynchronous Transfer Mode （ATM） exchange system is proposed and then the mean method is used to model mathematically the non-typical non-anticipative PRiority service （PR） model. Compared with the typical and non-anticipative PR model, it expresses the characteristics of the priority scheduling input-line group output with multi-channel in ATM exchange system. The simulation experiment shows that this model can improve the HOL block and the performance of input-queued ATM switch network dramatically. This model has a better developing prospect in ATM exchange system.展开更多
Compared with a conventional single section two-phase closed thermosyphon （TPCT） wellbore, a two-section TPCT wellbore has better heat transfer performance, which may improve the temperature distribution of fluid in...Compared with a conventional single section two-phase closed thermosyphon （TPCT） wellbore, a two-section TPCT wellbore has better heat transfer performance, which may improve the temperature distribution of fluid in wellbores, increase the temperature of fluid in wellheads and even more effectively reduce the failure rate of conventional TPCT wellbores. Heat transfer performance of two-section TPCT wellbores is affected by working medium, combination mode and oil flow rate. Different working media are introduced into the upper and lower TPCTs, which may achieve a better match between the working medium and the temperature field in the wellbores. Interdependence exists between the combination mode and the flow rate of the oil, which affects the heat transfer performance of a two-section TPCT wellbore. The experimental results show that a two-section TPCT wellbore, with equal upper and lower TPCTs respectively filled with Freon and methanol, has the best heat transfer performance when the oil flow rate is 200 L/h.展开更多
Recent efforts to add new services to the wide-band code division multiple accesses （WCDMA） system have increased interest in network processor （NP）-based routers that are easy to extend and evolve. In this paper,...Recent efforts to add new services to the wide-band code division multiple accesses （WCDMA） system have increased interest in network processor （NP）-based routers that are easy to extend and evolve. In this paper, an application of NPs in routing engine module （REM） of radio network controller （RNC） in WCDMA system is proposed. The measuring results show that NPs have good performance and efficiency in routing traffic of the communication network and the simulation verifies the fast forwarding function of NPs.展开更多
The present paper attempts to design an adaptive multi-model predictive control strategy for strongly nonlinear or switched systems with various operating points.The proposed control system guarantees the feasibility ...The present paper attempts to design an adaptive multi-model predictive control strategy for strongly nonlinear or switched systems with various operating points.The proposed control system guarantees the feasibility and the asymptotic stability of the closed-loop system,considering various challenges such as inherent uncertainties in the local models constituting the model bank,limited prediction/control horizons,and set point changes.To this end,four fundamental challenges in this area,namely guaranteeing feasibility throughout the region assigned to each subspace,ensuring asymptotic stability in each subspace considering the inherent uncertainties of the local models,guaranteeing feasibility and asymptotic stability during changes in the set point and switching between the subspaces,are addressed.By introducing transferring mode concept,this paper presents a novel method for guaranteeing the feasibility and stability of the switched systems without the need for increasing the prediction/control horizons or decreasing the size of the feasibility region.The proposed control structure uses a supervisor algorithm along with a soft-switching technique.The supervisor algorithm is responsible for determining the suitable local model/controller pair,determining the operational mode of the control system,managing the soft switching,and specifying the control objectives in accordance with the defined set point.The efficiency of the proposed control strategy is demonstrated by simulating a Continuous Stirred Tank Reactor(CSTR)as the controlled system.Based on the results,the proposed controller is able to guarantee the feasibility and stability of highly nonlinear and switched systems in a wide operating region under set point changes and uncertainties in the local models.展开更多
基金supported by the National Key R&D Program of China(2021YFB2402001)the China National Postdoctoral Program for Innovative Talents(BX20220286)+1 种基金the China Postdoctoral Science Foundation(2022T150615)supported by the Youth Innovation Promotion Association CAS(Y201768)。
文摘Lithium iron phosphate batteries have been increasingly utilized in recent years because their higher safety performance can improve the increasing trend of recurring thermal runaway accidents.However,the safety performance and mechanism of high-capacity lithium iron phosphate batteries under internal short-circuit challenges remain to be explored.This work analyzes the thermal runaway evolution of high-capacity LiFePO_(4) batteries under different internal heat transfer modes,which are controlled by different penetration modes.Two penetration cases involving complete penetration and incomplete penetration were detected during the test,and two modes were performed incorporating nails that either remained or were removed after penetration to comprehensively reveal the thermal runaway mechanism.A theoretical model of microcircuits and internal heat conduction is also established.The results indicated three thermal runaway evolution processes for high-capacity batteries,which corresponded to the experimental results of thermal equilibrium,single thermal runaway,and two thermal runaway events.The difference in heat distribution in the three phenomena is determined based on the microstructure and material structure near the pinhole.By controlling the heat dissipation conditions,the time interval between two thermal runaway events can be delayed from 558 to 1417 s,accompanied by a decrease in the concentration of in-situ gas production during the second thermal runaway event.
文摘Ultrasonic assisted GMAW （U-GMAW） method is a novel process, which combines the ultrasonic wave with gas metal arc welding to improve the process stability and weld quality. The U-GMAW system is developed and the ultrasonic wave is applied by means of acoustic radiation. The arc characteristics and metal transfer modes are studied in comparison with conventional GMAW process. The arc plasma is compressed and the arc length is shorter than that in conventional GMAW process after the ultrasonic is applied onto the arc. The parameter range of short-circuiting mode is extended and the range of unstable transfer is minimized. The changes in arc characteristics are responsible for changes in metal transfer modes.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11332011 and 11472276the Project of the Chinese Academy of Sciences,and the Defense Industrial Technology Development Program
文摘When laser ablation is subjected to supersonic flow, the influence mechanism of airflow on laser ablation behavior is still unclear. A coupled thermal-fluid-structure model is presented to investigate the influence of supersonic airflow on the development of a laser ablation pit. Results show that the aerodynamic convection cooling effect not only reduces the ablation velocity but also changes the symmetry morphology of the ablation pit due to the non-uniform convective heat transfer. Flow mode transition is also observed when the pit becomes deeper, and significant change in flow pattern and heat transfer behavior are found when the open mode is transformed into the closed mode.
基金supported by the Opening Project Foundation of MOE Key Laboratory of Liquid Structure and Heredity of Materials and Natural Science foundation of Shandong Province(Grant NO.Y20002F24).
文摘Using Xenon lamp lights to overcome the strong interference from the welding arc, a computer-based system is developed to sense and visualize the metal transfer in GMAW. This system combines through-the-arc sensing of the welding current and arc voltage with high speed imaging of the metal transfer. It can simultaneously display the metal transfer processes and waveforms of electrical welding parameters in real-time The metal transfer videos and waveforms of electrical welding parameters can be recorded. Metal transfers under various welding conditions have been investigated with the system developed.
基金Projects(xjj2013104,08143063)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(2011CB706606)supported by the National Basic Research Program of China
文摘Elastic heat transfer tube bundles are widely used in the field of flow-induced vibration heat transfer enhancement. Two types of mainly used tube bundles, the planar elastic tube bundle and the conical spiral tube bundle were comprehensively compared in the condition of the same shell side diameter. The natural mode characteristics, the effect of fluid-structure interaction, the stress distribution, the comprehensive heat transfer performance and the secondary fluid flow of the two elastic tube bundles were all concluded and compared. The results show that the natural frequency and the critical velocity of vibration buckling of the planar elastic tube bundle are larger than those of the conical spiral tube bundle, while the stress distribution and the comprehensive heat transfer performance of the conical spiral tube bundle are relatively better.
基金Project (No. zk043093) supported by the Introduced Talent Founda-tion of Southwest University of Science and Technology, China
文摘This paper introduces a method to realize digital television transmission based on asynchronous transfer mode (ATM), a technology based on fast packet switching. Choosing the integral multiple length of an ATM cell payload to equal to the length of an MPEG transport stream packet, an MPEG transport stream packet can be inextenso loaded by several ATM cells and trans-formed into ATM cells. Using ATM virtual connection technology and B-ISDN, the interoperability between ATM and DTV may be realized, and DTV signal transmission may also be realized finally.
文摘Digital TV (DTV) video signal transmission over ATM network is emphasized on.Some important problems are introduced about TV video signals asynchronous transfer to network application client, and the idea of video transfer design is discussed. The contents mainly include the DTV video streams asynchronous transfer topology, compressed coding adopted ATM network, asynchronous transfer efficiency and some problems of DTV video transmission in ATM network .
文摘Objective: To explore the clinical value of safe transfer nursing model in hospital transfer of critically ill patients in emergency department. Methods: 850 critically ill patients admitted to the emergency department of the central hospital were selected as the observation group (the implementation of safe transport care model), 660 critically ill patients admitted to the emergency department of the central hospital from April to December 2019 were selected as the control group (the use of regular car escort), and the occurrence of adverse events, transit time and satisfaction of patients' families were compared between the two groups. Results: the total incidence rate of adverse events in the observation group was 1.76%, which was significantly lower than that in the control group (10.00%) (P < 0.05). The time taken for external examination, including ultrasound, CT and X-ray, in the observation group was (26.12±3.11) min, time taken for transfer to specialized department (21.18±3.13) min and time taken for transfer to interventional room (5.32±1.19) min, which were significantly shorter than those in the control group (34.25±4.27), (25.33±3.07) min and (6.16±1.32) min, with statistical significance (P < 0.05). The scores of nurse-patient communication, care in transit, and treatment in the department and the total score in the observation group were (21.52±5.32), (34.56±7.13), (25.34±6.32) and (76.35±11.26) respectively, which were significantly higher than those in the control group (20.33±4.78), (32.33±6.25), (22.33±6.41) and (73.62±11.09), with statistical significance (P < 0.05). Conclusion: the safe transfer nursing model has high clinical value in the hospital transfer of critically ill patients in emergency department, which can effectively reduce the risk of adverse events, shorten the transfer time and improve the satisfaction of patients' families.
文摘The heat exchanger,a crucial device facilitating heat transfer between different temperature media,finds extensive application across diverse industries such as chemical,metallurgy,electric power,and construction,playing a pivotal role in energy conservation.It encompasses various structural configurations including tubular,shell-and-tube,and plate heat exchangers,and operates through different heat transfer modes including convection,radiation,and composite convection-radiation mecha nisms.This study focuses on experimentation with a plate heat exchanger to ascertain optimal heat transfer parameters via manipulation of heat transfer mode and flow rate.The findings underscore the significant enhancement in heat transfer efficiency achievable through judicious adjustments in working medium flow rate and heat transfer mode.
文摘The ultrasonic assisted GMAW （U-GMAW） method is proposed to achieve a more stable welding process and better weld quality. Tbe U-GMA W system is dereloped, which consists of power supplies, ultrasonic vibration system and specially designed u＇elding torch. The U-GMA W process and eonventional GMA W process are compared through bead-on-plate welding. The weld beads arc continuous and well protected, while the weld surface appearances by GMA W and U-GMA W are apparently diffierent. The metal transfe ,node changes from globular transfer to short-circuiting transfer after ultrasonic wave is applied onto the arc.
基金Supported by National Natural Science Foundation of China under Grant No.69896246
文摘A QoS-aware input-queued scheduling algorithm, called Smallest Timestamp First (STF), is proposed, which is improved upon iSLIP and can allocate bandwidth among inputs sharing a common output based on their reservation by assigning suitable finishing tiniest-amps to contending cells. STF can also provide isolation between flows that share a common output, link. Misbehaving flows will be restricted to guarantee the behaving flows' bandwidth. Simulations prove the feasibility of our algorithm.
基金Supported by the National Natural Science Foundation of China (61101129)Specialized Research Fund for the Doctoral Program of Higher Education(20091101110019)
文摘To enhance the fidelity and accuracy of the simulation of communication networks,hardware-in-the-loop（HITL） simulation was employed.HITL simulation methods was classified into three categories,of which the merits and shortages were compared.Combing system-in-the-loop（SITL） simulation principle with high level architecture（HLA）,an HITL simulation model of asynchronous transfer mode（ATM） network was constructed.The throughput and end-to-end delay of all-digital simulation and HITL simulation was analyzed,which showed that HITL simulation was more reliable and effectively improved the simulation credibility of communication network.Meanwhile,HLA-SITL method was fast and easy to achieve and low-cost during design lifecycle.Thus,it was a feasible way to research and analyze the large-scale network.
文摘ECFD （erroneous cell tail drop）, a buffer management optimization strategy is suggested which can improve the utilization of buffer resources in satellite ATM （asynchronous transfer mode） networks. The strategy, in which erroneous cells caused by satellite channel and the following cells that belong to the same PDU （protocol data Unit） are discarded, concerns non-real-time data services that use higher layer protocol for retransmission. Based on EPD （early packet drop） policy, mathematical models are established with and without ECTD. The numerical results show that ECTD would optimize buffer management and improve effective throughput （goodput）, and the increment of goodput is relative to the CER （cell error ratio） and the PDU length. The higher their values are, the greater the increment. For example, when the average PDU length values are 30 and 90, the improvement of goodput are respectively about 4% and 10%.
基金Supported by the National Natural Science Foundation of China (No.60472027).
文摘Admission control is an important strategy for Quality of Service (QoS) provisioning in Asynchro- nous Transfer Mode (ATM) networks. Based on a control-theory model of resources on-Demand Allocation (DA) protocol, the paper studies the effect of the protocol on the statistical characteristics of network traffic, and proposes a combined connection admission control algorithm with the DA protocol to achieve full utiliza- tion of link resources in satellite communication systems. The proposed algorithm is based on the cross-layer-design approach. Theoretical analysis and system simulation results show that the proposed algo- rithm can admit more connections within certain admission thresholds than one that does not take into account the DA protocol. Thus, the proposed algorithm can increase admission ratio of traffic sources for satellite ATM networks and improve satellite link utilization.
文摘In this paper, an extended Kendall model for the priority scheduling input-line group output with multi-channel in Asynchronous Transfer Mode （ATM） exchange system is proposed and then the mean method is used to model mathematically the non-typical non-anticipative PRiority service （PR） model. Compared with the typical and non-anticipative PR model, it expresses the characteristics of the priority scheduling input-line group output with multi-channel in ATM exchange system. The simulation experiment shows that this model can improve the HOL block and the performance of input-queued ATM switch network dramatically. This model has a better developing prospect in ATM exchange system.
基金the financial support from the National Natural Science Foundation of China (No. 50674096)PetroChina Scientific & Technological Risk Innovation Project (No. 060511-2-1)
文摘Compared with a conventional single section two-phase closed thermosyphon （TPCT） wellbore, a two-section TPCT wellbore has better heat transfer performance, which may improve the temperature distribution of fluid in wellbores, increase the temperature of fluid in wellheads and even more effectively reduce the failure rate of conventional TPCT wellbores. Heat transfer performance of two-section TPCT wellbores is affected by working medium, combination mode and oil flow rate. Different working media are introduced into the upper and lower TPCTs, which may achieve a better match between the working medium and the temperature field in the wellbores. Interdependence exists between the combination mode and the flow rate of the oil, which affects the heat transfer performance of a two-section TPCT wellbore. The experimental results show that a two-section TPCT wellbore, with equal upper and lower TPCTs respectively filled with Freon and methanol, has the best heat transfer performance when the oil flow rate is 200 L/h.
文摘Recent efforts to add new services to the wide-band code division multiple accesses （WCDMA） system have increased interest in network processor （NP）-based routers that are easy to extend and evolve. In this paper, an application of NPs in routing engine module （REM） of radio network controller （RNC） in WCDMA system is proposed. The measuring results show that NPs have good performance and efficiency in routing traffic of the communication network and the simulation verifies the fast forwarding function of NPs.
文摘The present paper attempts to design an adaptive multi-model predictive control strategy for strongly nonlinear or switched systems with various operating points.The proposed control system guarantees the feasibility and the asymptotic stability of the closed-loop system,considering various challenges such as inherent uncertainties in the local models constituting the model bank,limited prediction/control horizons,and set point changes.To this end,four fundamental challenges in this area,namely guaranteeing feasibility throughout the region assigned to each subspace,ensuring asymptotic stability in each subspace considering the inherent uncertainties of the local models,guaranteeing feasibility and asymptotic stability during changes in the set point and switching between the subspaces,are addressed.By introducing transferring mode concept,this paper presents a novel method for guaranteeing the feasibility and stability of the switched systems without the need for increasing the prediction/control horizons or decreasing the size of the feasibility region.The proposed control structure uses a supervisor algorithm along with a soft-switching technique.The supervisor algorithm is responsible for determining the suitable local model/controller pair,determining the operational mode of the control system,managing the soft switching,and specifying the control objectives in accordance with the defined set point.The efficiency of the proposed control strategy is demonstrated by simulating a Continuous Stirred Tank Reactor(CSTR)as the controlled system.Based on the results,the proposed controller is able to guarantee the feasibility and stability of highly nonlinear and switched systems in a wide operating region under set point changes and uncertainties in the local models.
