Analysis of the deformation structures in the West Kunlun-Tarim basin-range junction belt indicates that sediments in the southwestern Tarim depression were mainly derived from the West Kunlun Mountains and that with ...Analysis of the deformation structures in the West Kunlun-Tarim basin-range junction belt indicates that sediments in the southwestern Tarim depression were mainly derived from the West Kunlun Mountains and that with time the region of sedimentation extended progressivdy toward the north. Three north-underthrusting （subducting）, steep-dipping, high-velocity zones （bodies） are recognized at depths, which correspond to the central West Kunlun junction belt （bounded by the Kiida-Kaxtax fault on the north and Bulungkol-Kangxiwar fault on the south）, Quanshuigou fault belt （whose eastward extension is the Jinshajiang fault belt） and Bangong Co-Nujiang fault belt. The geodynamic process of the basin-range junction belt generally proceeded as follows： centering around the magma source region （which largely corresponds with the Karatag terrane at the surface）, the deep-seated material flowed and extended from below upward and to all sides, resulting in strong deformation （mainly extension） in the overlying lithosphere and even the upper mantle, appearance of extensional stress perpendicular to the strike of the orogenic belt in the thermal uplift region or at the top of the mantle diapir and localized thickening of the sedimentary cover （thermal subsidence in the upper crust）. Three stages of the basin- and mountain-forming processes in the West Kunlun-southern Tarim basin margin may be summarized： （1） the stage of Late Jurassic-Early Cretaceous rampingrapid uplift and rapid subsidence, when north-directed thrust propagation and south-directed intracontinental subduction, was the dominant mechanism for basin- and mountain-building processes; （2） the stage of Late Cretaceous-Paleogene deep-level detachment-slow uplift and homogeneous subsidence, when the dominant mechanism for the basin- and mountain-forming processes was detachment （subhorizontal north-directed deep-level ductile shear） and its resulting lateral propagation of deep material; and （3） the stage of Neogene-present compression-rapid uplift and strong subsidence, when the basin- and mountain-forming processes were simultaneously controlled by north-vergent thrust propagation and compression. The authors summarize the processes as the “ramping-detachment-compression basin- and mountain-forming dynamic model”. The basin-range tectonics was initiated in the Late Jurassic, the Miocene-Pliocene were a major transition period for the basin- and mountain-forming mechanism and the terminal early Pleistocene tectonic movement in the main laid a foundation for the basin-and-mountain tectonic framework in the West Kunlun-southern Tarim basin margin.展开更多
To analyze and reduce the impact of Machine-to-Machine (M2M) Devices (MDs) on the traditional Human-to-Human (H2H) users for the blending scenario, where both M2M and H2H services coexist in the current Universal Mobi...To analyze and reduce the impact of Machine-to-Machine (M2M) Devices (MDs) on the traditional Human-to-Human (H2H) users for the blending scenario, where both M2M and H2H services coexist in the current Universal Mobile Telecommunication System (UMTS) and perform the Random Access (RA) procedure simultaneously, a comprehensive RA analysis model of RA is proposed in this paper. Further, a power ramping strategy based on the logarithm for M2M is proposed. The efficiency of both the existing and proposed scheme is assessed through a simulation across several metrics, including average target power, throughput, blocking probability, and delay statistics. Numerical results show that the proposed algorithm can ensure a minimal impact on H2H communication while maintaining the throughput of the M2M communication. Meanwhile, because of its low energy consumption, this algorithm has a significant guide value for real-world applications.展开更多
This paper proposes an improved optimal operation planning method for residential PEFC-CGS (Polymer Electrolyte Fuel CellCo-Generation System). Residential PEFC-CGS has recently been gathering attention as one of the ...This paper proposes an improved optimal operation planning method for residential PEFC-CGS (Polymer Electrolyte Fuel CellCo-Generation System). Residential PEFC-CGS has recently been gathering attention as one of the distributed power sources with high efficiency and low environmental impacts. Previous research pointed out that the output variations of PEFC adversely affect the durability. It can be surmised that smaller output variations will be desired to extend durability years. However, in this field, ramping rate have not been sufficiently considered. For local search and tabu search, ramping rate constraint makes our operation planning difficult because it restricts the search for feasible neighborhood solutions. Therefore, the authors proposed a method to deal with typical and harsher ramping rate constraints in comparison with conventional methods. There are two key points for the improvement. One is the reinforcement of the search along the output power axis;the other is to make use of the strategy of tabu search which avoids the local optimal solutions. The simulation results show the effectiveness of the proposed method in the daily operation planning. Furthermore, in the case using typical ramping rate parameter, it is confirmed that tabu search doesn’t contribute the reduction of daily operational cost due to the above stated restriction of the search area.展开更多
THE Chinese Government released a range of reform and opening up policies, as is custom- ary. ahead of the Third Plenary Session of the 18th Central Committee of the Communist Party of China （CPC）, which ran from No...THE Chinese Government released a range of reform and opening up policies, as is custom- ary. ahead of the Third Plenary Session of the 18th Central Committee of the Communist Party of China （CPC）, which ran from November 9 to 12. This year. the corporate registration system was included in the reform package.展开更多
In northern China,thermal power units(TPUs)are important in improving the penetration level of renewable energy.In such areas,the potentials of coordinated dispatch of renewable energy sources(RESs)and TPUs can be bet...In northern China,thermal power units(TPUs)are important in improving the penetration level of renewable energy.In such areas,the potentials of coordinated dispatch of renewable energy sources(RESs)and TPUs can be better realized,if RESs and TPUs connected to the power grid at the same point of common coupling(PCC)are dispatched as a coupled system.Firstly,the definition of the coupled system is introduced,followed by an analysis on its characteristics.Secondly,based on the operation characteristics of deep peak regulation(DPR)of TPUs in the coupled system,the constraint of the ladder-type ramping rate applicable for day-ahead dispatch is proposed,and the corresponding flexible spinning reserve constraint is further established.Then,considering these constraints and peak regulation ancillary services,a day-ahead optimal dispatch model of the coupled system is established.Finally,the operational characteristics and advantages of the coupled system are analyzed in several case studies based on a real-world power grid in Liaoning province,China.The numerical results show that the coupled system can further improve the economic benefits of RESs and TPUs under the existing policies.展开更多
High penetration of renewable energy generation(REG)in the distribution system increases both the power uncertainty at a given interval and the power variation between two intervals.Reserve markets addressing power un...High penetration of renewable energy generation(REG)in the distribution system increases both the power uncertainty at a given interval and the power variation between two intervals.Reserve markets addressing power uncertainty have been widely investigated.However,there is a lack of market mechanisms regarding the power variation of the load and REGs.This paper thus defines a planned ramping(PR)product to follow the net load variation and extends the local energy market to include the trading of PR products.Players are economically compensated for their PR products.Bidding models of dispatchable generators and flexible load aggregators in the joint market are investigated.To solve the market problem in polynomial time,a distributed market clearing method is developed based on the ADMM algorithm.The joint market is tested on a modified IEEE 33-bus system.It verifies that introducing the PR market can encourage flexible loads to provide more PR service to accommodate the net load variation.As such,the ramping cost of dispatchable generators is reduced by 29.09%in the test case.The planned energy curtailment from REG is also reduced.The computational efficiency of the proposed distributed clearing method is validated by comparing it with a centralized method.展开更多
The high penetration of wind energy sources in power systems has substantially increased the demand for faster-ramping thermal units participating in the frequency regulation service.To fulfill the automatic generatio...The high penetration of wind energy sources in power systems has substantially increased the demand for faster-ramping thermal units participating in the frequency regulation service.To fulfill the automatic generation control(AGC)and compensate the influence of wind power fluctuations simultaneously,ramping capacity should be considered in the dispatch model of thermals.Meanwhile,conventional methods in this area do not take the impact of transmission loss into the dispatch model,or rely on offline network model and parameters,failing to reflect the real relationships between the wind farms and thermal generators.This paper proposes an online approach for AGC dispatch units considering the above issues.Firstly,the power loss sensitivity is online identified using recursive least square method based on the real-time data of phasor measurement units.It sets up power balance constraint and results in a more accurate dispatch model.Then,an improved multi-objective optimization model of dispatch is proposed and a connection is established between the thermal units with fast ramping capacity and the wind farms with rapid fluctuations.Genetic algorithm is used to solve the dispatch model.The proposed method is compared with conventional methods in simulation case in the IEEE 30-bus system.Finally,simulation results verify the validity and the feasibility of identification method and optimization model.展开更多
The layer-wound coil has a great potential in nuclear magnetic resonance and magnetic resonance imaging owing to the better spatial homogeneity of the magnetic field.However,high-temperature superconducting(HTS)coil w...The layer-wound coil has a great potential in nuclear magnetic resonance and magnetic resonance imaging owing to the better spatial homogeneity of the magnetic field.However,high-temperature superconducting(HTS)coil wound by no-insulation(NI)layer-wound technique has been verified with a long field delay time.A new method named the intra-layer no-insulation(LNI)winding technique has been proposed to reduce the charging delay time of the coil.This paper is mainly to study and compare the ramping loss and mechanical characteristics of the layer-wound coil and LNI coil.The results indicate that the total ramping loss can be significantly reduced by using the LNI winding method.The effects of the ramping rate of power supply current and the contact resistivity on the ramping loss are also discussed in the paper.Furthermore,the stress distributions in the layer-wound coil and LNI coil are compared,where the cooling process and Lorentz force are both considered.It can be found that the copper sheet of the LNI coil experiences relatively higher stress than its(RE)Ba;Cu;O;(REBCO)conductor layer.Meanwhile,the magnitude of stress generated in the REBCO conductor of the LNI coil is slightly different from that of the layer-wound coil.展开更多
The roll-out of a flexible ramping product provides independent system operators(ISOs)with the ability to address the issues of ramping capacity shortage.ISOs procure flexible ramping capability by committing more gen...The roll-out of a flexible ramping product provides independent system operators(ISOs)with the ability to address the issues of ramping capacity shortage.ISOs procure flexible ramping capability by committing more generating units or reserving a certain amount of headrooms of committed units.In this paper,we raise the concern of the possibility that the procured flexible ramping capability cannot be deployed in realtime operations due to the unit shut-down in a look-ahead commitment(LAC)procedure.As a solution to the issues of ramping capacity shortage,we provide a modified ramping product formulation designed to improve the reliability and reduce the expected operating cost.The trajectories of start-up and shutdown processes are also considered in determining the ramping capability.A new optimization problem is formulated using mixed integer linear programming(MILP)to be readily applied to the practical power system operation.The performance of this proposed method is verified through simulations using a small-scale system and IEEE 118-bus system.The simulation results demonstrate that the proposed method can improve the generation scheduling by alleviating the ramping capacity shortages.展开更多
High penetration level of renewable energy has brought great challenges to operation of power systems,and use of flexible resources(FRs)is becoming increasingly important.Flexibility of power systems can be improved b...High penetration level of renewable energy has brought great challenges to operation of power systems,and use of flexible resources(FRs)is becoming increasingly important.Flexibility of power systems can be improved by changing generation arrangements,but the interests of some market participants may be harmed in the process.This study proposes a stochastic economic dispatch model with trading of flexible ramping products(FRPs).To calculate changes in revenue and reasonably compensate units that provide FRs,multisegmented marginal bidding for energy is simulated by linearizing generation cost,and an optimal market clearing strategy for FRPs is developed according to changes in clearing energy and marginal clearing price.Then,the correlation between prediction errors of wind speeds among different wind farms is determined based on a joint distribution function modeled by the copula function,and quasi-Monte Carlo simulation(QMC)is used to generate wind power scenarios.Finally,numerical simulations of modified IEEE-30 and IEEE-118 bus systems is performed with minimum comprehensive cost as the objective function.This verifies the proposed model could effectively deal with wind variability and uncertainty,stabilize the marginal clearing price of the electricity market,and ensure fairness in the market.展开更多
Ramping a physical parameter is one of the most common experimental protocols in studying a quantum system, and ramping dynamics has been widely used in preparing a quantum state and probing physical properties. Here,...Ramping a physical parameter is one of the most common experimental protocols in studying a quantum system, and ramping dynamics has been widely used in preparing a quantum state and probing physical properties. Here, we present a novel method of probing quantum many-body correlation by ramping dynamics. We ramp a Hamiltonian parameter to the same target value from different initial values and with different velocities, and we show that the first-order correction on the finite ramping velocity is universal and path-independent, revealing a novel quantum many-body correlation function of the equilibrium phases at the target values. We term this method as the non-adiabatic linear response since this is the leading order correction beyond the adiabatic limit. We demonstrate this method experimentally by studying the Bose-Hubbard model with ultracold atoms in three-dimensional optical lattices.Unlike the conventional linear response that reveals whether the quasi-particle dispersion of a quantum phase is gapped or gapless, this probe is more sensitive to whether the quasi-particle lifetime is long enough such that the quantum phase possesses a well-defined quasi-particle description. In the BoseHubbard model, this non-adiabatic linear response is significant in the quantum critical regime where well-defined quasi-particles are absent. And in contrast, this response is vanishingly small in both superfluid and Mott insulators which possess well-defined quasi-particles. Because our proposal uses the most common experimental protocol, we envision that our method can find broad applications in probing various quantum systems.展开更多
本研究旨在深入探索RAMP(Range of Motion,Activation,Mobility,Potentiation)热身系统在初中体育教学中的应用效果,通过一个学期的对比实验,评估其对初中生体能水平、运动技能掌握、运动损伤预防以及体育课堂参与度的综合影响。研究选...本研究旨在深入探索RAMP(Range of Motion,Activation,Mobility,Potentiation)热身系统在初中体育教学中的应用效果,通过一个学期的对比实验,评估其对初中生体能水平、运动技能掌握、运动损伤预防以及体育课堂参与度的综合影响。研究选取某初中二年级2个班级共80名学生作为研究对象,采用随机对照试验设计,实验组采用RAMP热身系统,对照组沿用传统热身方式。结果表明,RAMP热身系统在提升体能、促进技能掌握、降低运动损伤风险及提高课堂参与度方面均表现出显著优势。本研究为初中体育教学提供了科学依据,建议推广RAMP热身系统以优化体育课堂结构,促进学生全面发展。展开更多
AC loss is one of the critical issues for designing REBCO fast‐ramping magnets operating at cryogenic temperatures.There are many ways to reduce AC loss for coil windings.However,it is not clear which method is the m...AC loss is one of the critical issues for designing REBCO fast‐ramping magnets operating at cryogenic temperatures.There are many ways to reduce AC loss for coil windings.However,it is not clear which method is the most effective way to minimize AC loss in the coil windings for a given Ampere‐turns.In this work,we numerically studied coil configurations of several small superconducting magnets constructed from 12 mm SuperPower REBCO coated conductors,for fast‐ramping application with the same Ampere‐turns to identify the lowest AC loss among them.The HTS magnets have a total turn number of 50 and inner diameter of 30 cm,carrying AC current operating in the temperature range of 20–40 K at 25 Hz.We incorporated several existing loss reduction strategies including spacing between the turns for single pancake coils,grading Ic values for the solenoid configuration,and applying flux diverters to shape the magnetic field around the coil windings.The simulation was implemented using a homogenized H‐formulation.Across all studied loss reduction methods,the use of flux diverters has the largest impact in AC loss reduction.The AC loss values in the solenoid winding comprising a stack of five single pancake coils with 0.1 mm turn‐to‐turn gap with the flux diverters agree well with those in the single pancake coil for 2 mm turn‐to‐turn gap with the flux diverters.Solenoid type coil configurations with flux diverters generate much smaller AC loss than the single pancake type with flux diverters when they generate the same center magnetic field.展开更多
[目的]比较关节镜下缝合钩和Fast-fix缝合Ⅳ型半月板Ramp区损伤的临床疗效。[方法]回顾性分析2016年1月—2020年10月45例前交叉韧带(anterior cruciate ligament, ACL)损伤合并Ⅳ型半月板Ramp损伤患者的临床资料。所有患者均取自体腘绳...[目的]比较关节镜下缝合钩和Fast-fix缝合Ⅳ型半月板Ramp区损伤的临床疗效。[方法]回顾性分析2016年1月—2020年10月45例前交叉韧带(anterior cruciate ligament, ACL)损伤合并Ⅳ型半月板Ramp损伤患者的临床资料。所有患者均取自体腘绳肌腱行ACL重建,依据术前医患沟通结果,21例应用缝合钩缝合Ramp损伤,24例应用Fast-fix缝合。对比患者围手术期、随访及影像学结果。[结果]所有患者均顺利完成手术,术中未出现血管、神经损伤等并发症。缝合钩组手术时间[(91.2±10.6) min vs (62.5±8.4) min, P<0.001]、切口总长度[(5.9±0.5) cm vs (5.1±0.6) cm, P<0.001]均显著长于Fast-fix组,但前者住院费用显著少于后者[(3.4±0.3)万元vs (4.3±0.7)万元, P<0.001]。两组Ramp撕裂长度、缝合针数、下地行走时间、切口愈合、住院时间比较差异均无统计学意义(P>0.05)。所有患者均获36~72个月随访。两组完全负重活动时间的差异无统计学意义(P>0.05)。术后1年及末次随访时,两组膝间隙压痛、麦氏征,轴移征、膝关节屈伸ROM、IKDC评分及Lysholm评分较术前均显著改善(P<0.05)。同一时间点,两组上述指标的差异均无统计学意义(P>0.05)。影像方面,与术前相比,术后1年,两组半月板损伤分级及胫骨平台后侧骨髓水肿均显著改善(P<0.05),相应时间点,两组上述指标的差异均无统计学意义(P>0.05)。术后1年MRI显示缝合钩组愈合率为90.5%、Fast-fix组为87.5%,差异无统计学意义(P>0.05)。[结论]关节镜下缝合钩和Fast-fix缝合半月板Ramp区Ⅳ型损伤均可获得满意疗效。展开更多
The influence of ramps on the transient rolling contact characteristics and damage mechanisms of switch rails remains unclear,presenting substantial challenges to the safety of railway operations.To this end,this pape...The influence of ramps on the transient rolling contact characteristics and damage mechanisms of switch rails remains unclear,presenting substantial challenges to the safety of railway operations.To this end,this paper constructs a transient rolling contact finite element model of the wheel-rail in switch under different ramps using ANSYS/LSDYNA method,and analyzes the tribology and damage characteristics when the wheel passes through the switch at a uniform speed.Our research findings reveal that the vibration induced in the switch rail during the wheel load transfer process leads to a step-like increase in the contact force.Moreover,the interaction between the wheel and the rail primarily involves slip contact,which may significantly contribute to the formation of corrugations on the switch rail.Additionally,the presence of large ramps exacerbates switch rail wear and rolling contact fatigue,resulting in a notable 13.2%increase in switch rail damage under 40‰ramp conditions compared to flat(0‰ramp)conditions.Furthermore,the large ramps can alter the direction of crack propagation,ultimately causing surface spalling of the rail.Therefore,large ramps intensify the dynamic interactions during the wheel load transfer process,further aggravating the crack and spalling damage to the switch rails.展开更多
胰腺癌是公认的最具侵袭性和致命性的恶性肿瘤之一,其中约20%的病例为胰体尾部癌症。由于该类型癌症生长迅速且早期缺乏明显症状,许多患者在诊断时已经错过了最佳治疗时机。手术是唯一可能治愈的手段,但传统的远端胰腺切除术和脾切除术...胰腺癌是公认的最具侵袭性和致命性的恶性肿瘤之一,其中约20%的病例为胰体尾部癌症。由于该类型癌症生长迅速且早期缺乏明显症状,许多患者在诊断时已经错过了最佳治疗时机。手术是唯一可能治愈的手段,但传统的远端胰腺切除术和脾切除术存在较高的阳性切缘率、较低的淋巴结清扫率和较差的总体生存率,已发表的证据表明经过传统手术治疗的病人,其五年生存率介于8%至22%之间。2003年,Strasberg等人提出了一种新的手术方法——根治性顺行模块化胰脾切除术(Radical Antegrade Modular Pancreatosplenectomy, RAMPS),旨在提供更好的肿瘤切除效果、提高R0切除率并改善患者的长期预后。RAMPS的五年总体生存率可高达30%~40%。随着腹腔镜技术的不断进步,腹腔镜下根治性顺行模块化胰脾切除术(Laparoscopic Radical Antegrade Modular Pancreatosplenectomy, L-RAMPS)作为一种微创手术,具有术后恢复快等优势,逐渐获得越来越多外科医师的关注。文章总结了这种手术的现状,并展望其未来发展。Pancreatic cancer is widely recognized as one of the most aggressive and lethal malignant tumors, with approximately 20% of cases occurring in the body and tail of the pancreas. Due to the rapid growth of this cancer and the lack of obvious symptoms in its early stages, many patients miss the opportunity for optimal treatment by the time of diagnosis. Surgery remains the only potentially curative option;however, traditional distal pancreatectomy and splenectomy are associated with high positive margin rates, low lymph node dissection rates, and poor overall survival. Published evidence shows that the five-year survival rate for patients treated with traditional surgery ranges from 8% to 22%. In 2003, Strasberg et al. proposed a new surgical technique—Radical Antegrade Modular Pancreatosplenectomy (RAMPS)—designed to improve tumor resection, increase the R0 resection rate, and enhance long-term prognosis. The five-year overall survival rate for RAMPS can reach 30%~40%. With the continuous advancement of laparoscopic technology, Laparoscopic Radical Antegrade Modular Pancreatosplenectomy (L-RAMPS), as a minimally invasive procedure, offers advantages such as faster postoperative recovery and is gradually gaining more attention from surgeons. This article provides an overview of the current status of this surgery and discusses its potential future development.展开更多
文摘Analysis of the deformation structures in the West Kunlun-Tarim basin-range junction belt indicates that sediments in the southwestern Tarim depression were mainly derived from the West Kunlun Mountains and that with time the region of sedimentation extended progressivdy toward the north. Three north-underthrusting （subducting）, steep-dipping, high-velocity zones （bodies） are recognized at depths, which correspond to the central West Kunlun junction belt （bounded by the Kiida-Kaxtax fault on the north and Bulungkol-Kangxiwar fault on the south）, Quanshuigou fault belt （whose eastward extension is the Jinshajiang fault belt） and Bangong Co-Nujiang fault belt. The geodynamic process of the basin-range junction belt generally proceeded as follows： centering around the magma source region （which largely corresponds with the Karatag terrane at the surface）, the deep-seated material flowed and extended from below upward and to all sides, resulting in strong deformation （mainly extension） in the overlying lithosphere and even the upper mantle, appearance of extensional stress perpendicular to the strike of the orogenic belt in the thermal uplift region or at the top of the mantle diapir and localized thickening of the sedimentary cover （thermal subsidence in the upper crust）. Three stages of the basin- and mountain-forming processes in the West Kunlun-southern Tarim basin margin may be summarized： （1） the stage of Late Jurassic-Early Cretaceous rampingrapid uplift and rapid subsidence, when north-directed thrust propagation and south-directed intracontinental subduction, was the dominant mechanism for basin- and mountain-building processes; （2） the stage of Late Cretaceous-Paleogene deep-level detachment-slow uplift and homogeneous subsidence, when the dominant mechanism for the basin- and mountain-forming processes was detachment （subhorizontal north-directed deep-level ductile shear） and its resulting lateral propagation of deep material; and （3） the stage of Neogene-present compression-rapid uplift and strong subsidence, when the basin- and mountain-forming processes were simultaneously controlled by north-vergent thrust propagation and compression. The authors summarize the processes as the “ramping-detachment-compression basin- and mountain-forming dynamic model”. The basin-range tectonics was initiated in the Late Jurassic, the Miocene-Pliocene were a major transition period for the basin- and mountain-forming mechanism and the terminal early Pleistocene tectonic movement in the main laid a foundation for the basin-and-mountain tectonic framework in the West Kunlun-southern Tarim basin margin.
基金supported in part by the National Natural Science Foundation of Chinaunder Grants No.60971125, No.61121001Major National S&T Project under Grant No. 2012ZX03005010 the project under Grant No.201105
文摘To analyze and reduce the impact of Machine-to-Machine (M2M) Devices (MDs) on the traditional Human-to-Human (H2H) users for the blending scenario, where both M2M and H2H services coexist in the current Universal Mobile Telecommunication System (UMTS) and perform the Random Access (RA) procedure simultaneously, a comprehensive RA analysis model of RA is proposed in this paper. Further, a power ramping strategy based on the logarithm for M2M is proposed. The efficiency of both the existing and proposed scheme is assessed through a simulation across several metrics, including average target power, throughput, blocking probability, and delay statistics. Numerical results show that the proposed algorithm can ensure a minimal impact on H2H communication while maintaining the throughput of the M2M communication. Meanwhile, because of its low energy consumption, this algorithm has a significant guide value for real-world applications.
文摘This paper proposes an improved optimal operation planning method for residential PEFC-CGS (Polymer Electrolyte Fuel CellCo-Generation System). Residential PEFC-CGS has recently been gathering attention as one of the distributed power sources with high efficiency and low environmental impacts. Previous research pointed out that the output variations of PEFC adversely affect the durability. It can be surmised that smaller output variations will be desired to extend durability years. However, in this field, ramping rate have not been sufficiently considered. For local search and tabu search, ramping rate constraint makes our operation planning difficult because it restricts the search for feasible neighborhood solutions. Therefore, the authors proposed a method to deal with typical and harsher ramping rate constraints in comparison with conventional methods. There are two key points for the improvement. One is the reinforcement of the search along the output power axis;the other is to make use of the strategy of tabu search which avoids the local optimal solutions. The simulation results show the effectiveness of the proposed method in the daily operation planning. Furthermore, in the case using typical ramping rate parameter, it is confirmed that tabu search doesn’t contribute the reduction of daily operational cost due to the above stated restriction of the search area.
文摘THE Chinese Government released a range of reform and opening up policies, as is custom- ary. ahead of the Third Plenary Session of the 18th Central Committee of the Communist Party of China （CPC）, which ran from November 9 to 12. This year. the corporate registration system was included in the reform package.
基金supported in part by the National Key Research and Development Program of China(No.2019YFB1505400).
文摘In northern China,thermal power units(TPUs)are important in improving the penetration level of renewable energy.In such areas,the potentials of coordinated dispatch of renewable energy sources(RESs)and TPUs can be better realized,if RESs and TPUs connected to the power grid at the same point of common coupling(PCC)are dispatched as a coupled system.Firstly,the definition of the coupled system is introduced,followed by an analysis on its characteristics.Secondly,based on the operation characteristics of deep peak regulation(DPR)of TPUs in the coupled system,the constraint of the ladder-type ramping rate applicable for day-ahead dispatch is proposed,and the corresponding flexible spinning reserve constraint is further established.Then,considering these constraints and peak regulation ancillary services,a day-ahead optimal dispatch model of the coupled system is established.Finally,the operational characteristics and advantages of the coupled system are analyzed in several case studies based on a real-world power grid in Liaoning province,China.The numerical results show that the coupled system can further improve the economic benefits of RESs and TPUs under the existing policies.
文摘High penetration of renewable energy generation(REG)in the distribution system increases both the power uncertainty at a given interval and the power variation between two intervals.Reserve markets addressing power uncertainty have been widely investigated.However,there is a lack of market mechanisms regarding the power variation of the load and REGs.This paper thus defines a planned ramping(PR)product to follow the net load variation and extends the local energy market to include the trading of PR products.Players are economically compensated for their PR products.Bidding models of dispatchable generators and flexible load aggregators in the joint market are investigated.To solve the market problem in polynomial time,a distributed market clearing method is developed based on the ADMM algorithm.The joint market is tested on a modified IEEE 33-bus system.It verifies that introducing the PR market can encourage flexible loads to provide more PR service to accommodate the net load variation.As such,the ramping cost of dispatchable generators is reduced by 29.09%in the test case.The planned energy curtailment from REG is also reduced.The computational efficiency of the proposed distributed clearing method is validated by comparing it with a centralized method.
基金This work is supported in part by Major State Basic Research Development Program of China(No.2012CB215206)National Natural Science Foundation of China(No.51107061).
文摘The high penetration of wind energy sources in power systems has substantially increased the demand for faster-ramping thermal units participating in the frequency regulation service.To fulfill the automatic generation control(AGC)and compensate the influence of wind power fluctuations simultaneously,ramping capacity should be considered in the dispatch model of thermals.Meanwhile,conventional methods in this area do not take the impact of transmission loss into the dispatch model,or rely on offline network model and parameters,failing to reflect the real relationships between the wind farms and thermal generators.This paper proposes an online approach for AGC dispatch units considering the above issues.Firstly,the power loss sensitivity is online identified using recursive least square method based on the real-time data of phasor measurement units.It sets up power balance constraint and results in a more accurate dispatch model.Then,an improved multi-objective optimization model of dispatch is proposed and a connection is established between the thermal units with fast ramping capacity and the wind farms with rapid fluctuations.Genetic algorithm is used to solve the dispatch model.The proposed method is compared with conventional methods in simulation case in the IEEE 30-bus system.Finally,simulation results verify the validity and the feasibility of identification method and optimization model.
基金supported by the National Natural Science Foundation of China(Grant Nos.11872195,11472120)the Fundamental Research Funds for the Central Universities(Grant No.lzujbky-2020-1)。
文摘The layer-wound coil has a great potential in nuclear magnetic resonance and magnetic resonance imaging owing to the better spatial homogeneity of the magnetic field.However,high-temperature superconducting(HTS)coil wound by no-insulation(NI)layer-wound technique has been verified with a long field delay time.A new method named the intra-layer no-insulation(LNI)winding technique has been proposed to reduce the charging delay time of the coil.This paper is mainly to study and compare the ramping loss and mechanical characteristics of the layer-wound coil and LNI coil.The results indicate that the total ramping loss can be significantly reduced by using the LNI winding method.The effects of the ramping rate of power supply current and the contact resistivity on the ramping loss are also discussed in the paper.Furthermore,the stress distributions in the layer-wound coil and LNI coil are compared,where the cooling process and Lorentz force are both considered.It can be found that the copper sheet of the LNI coil experiences relatively higher stress than its(RE)Ba;Cu;O;(REBCO)conductor layer.Meanwhile,the magnitude of stress generated in the REBCO conductor of the LNI coil is slightly different from that of the layer-wound coil.
基金This work was supported by a Research Grant of Pukyong National University(2020).
文摘The roll-out of a flexible ramping product provides independent system operators(ISOs)with the ability to address the issues of ramping capacity shortage.ISOs procure flexible ramping capability by committing more generating units or reserving a certain amount of headrooms of committed units.In this paper,we raise the concern of the possibility that the procured flexible ramping capability cannot be deployed in realtime operations due to the unit shut-down in a look-ahead commitment(LAC)procedure.As a solution to the issues of ramping capacity shortage,we provide a modified ramping product formulation designed to improve the reliability and reduce the expected operating cost.The trajectories of start-up and shutdown processes are also considered in determining the ramping capability.A new optimization problem is formulated using mixed integer linear programming(MILP)to be readily applied to the practical power system operation.The performance of this proposed method is verified through simulations using a small-scale system and IEEE 118-bus system.The simulation results demonstrate that the proposed method can improve the generation scheduling by alleviating the ramping capacity shortages.
基金supported by the National Natural Science Foundation of China 51937005the Natural Science Foundation of Guangdong Province 2019A1515010689.
文摘High penetration level of renewable energy has brought great challenges to operation of power systems,and use of flexible resources(FRs)is becoming increasingly important.Flexibility of power systems can be improved by changing generation arrangements,but the interests of some market participants may be harmed in the process.This study proposes a stochastic economic dispatch model with trading of flexible ramping products(FRPs).To calculate changes in revenue and reasonably compensate units that provide FRs,multisegmented marginal bidding for energy is simulated by linearizing generation cost,and an optimal market clearing strategy for FRPs is developed according to changes in clearing energy and marginal clearing price.Then,the correlation between prediction errors of wind speeds among different wind farms is determined based on a joint distribution function modeled by the copula function,and quasi-Monte Carlo simulation(QMC)is used to generate wind power scenarios.Finally,numerical simulations of modified IEEE-30 and IEEE-118 bus systems is performed with minimum comprehensive cost as the objective function.This verifies the proposed model could effectively deal with wind variability and uncertainty,stabilize the marginal clearing price of the electricity market,and ensure fairness in the market.
基金supported by Beijing Outstanding Young Scholar Programthe National Key Research and Development Program of China (2021YFA0718303, 2021YFA1400904, and 2016YFA0301501)+1 种基金the National Natural Science Foundation of China (91736208, 11974202, 61975092, 11920101004,61727819, 11934002, 11734010, and 92165203)the XPLORER Prize。
文摘Ramping a physical parameter is one of the most common experimental protocols in studying a quantum system, and ramping dynamics has been widely used in preparing a quantum state and probing physical properties. Here, we present a novel method of probing quantum many-body correlation by ramping dynamics. We ramp a Hamiltonian parameter to the same target value from different initial values and with different velocities, and we show that the first-order correction on the finite ramping velocity is universal and path-independent, revealing a novel quantum many-body correlation function of the equilibrium phases at the target values. We term this method as the non-adiabatic linear response since this is the leading order correction beyond the adiabatic limit. We demonstrate this method experimentally by studying the Bose-Hubbard model with ultracold atoms in three-dimensional optical lattices.Unlike the conventional linear response that reveals whether the quasi-particle dispersion of a quantum phase is gapped or gapless, this probe is more sensitive to whether the quasi-particle lifetime is long enough such that the quantum phase possesses a well-defined quasi-particle description. In the BoseHubbard model, this non-adiabatic linear response is significant in the quantum critical regime where well-defined quasi-particles are absent. And in contrast, this response is vanishingly small in both superfluid and Mott insulators which possess well-defined quasi-particles. Because our proposal uses the most common experimental protocol, we envision that our method can find broad applications in probing various quantum systems.
文摘本研究旨在深入探索RAMP(Range of Motion,Activation,Mobility,Potentiation)热身系统在初中体育教学中的应用效果,通过一个学期的对比实验,评估其对初中生体能水平、运动技能掌握、运动损伤预防以及体育课堂参与度的综合影响。研究选取某初中二年级2个班级共80名学生作为研究对象,采用随机对照试验设计,实验组采用RAMP热身系统,对照组沿用传统热身方式。结果表明,RAMP热身系统在提升体能、促进技能掌握、降低运动损伤风险及提高课堂参与度方面均表现出显著优势。本研究为初中体育教学提供了科学依据,建议推广RAMP热身系统以优化体育课堂结构,促进学生全面发展。
基金supported in part by New Zealand Ministry of Business,Innovation and Employment(MBIE)by the Strategic Science Investment Fund“Advanced Energy Technology Platforms”under Contract RTVU20042020 Google Excellence Research University ProgramUS DOE Ernst Courant Traineeship in Accelerator Sciences and Engineering,the educational program of next generation of accelerator physicists and engineer,US Department of Energy,HEP office.
文摘AC loss is one of the critical issues for designing REBCO fast‐ramping magnets operating at cryogenic temperatures.There are many ways to reduce AC loss for coil windings.However,it is not clear which method is the most effective way to minimize AC loss in the coil windings for a given Ampere‐turns.In this work,we numerically studied coil configurations of several small superconducting magnets constructed from 12 mm SuperPower REBCO coated conductors,for fast‐ramping application with the same Ampere‐turns to identify the lowest AC loss among them.The HTS magnets have a total turn number of 50 and inner diameter of 30 cm,carrying AC current operating in the temperature range of 20–40 K at 25 Hz.We incorporated several existing loss reduction strategies including spacing between the turns for single pancake coils,grading Ic values for the solenoid configuration,and applying flux diverters to shape the magnetic field around the coil windings.The simulation was implemented using a homogenized H‐formulation.Across all studied loss reduction methods,the use of flux diverters has the largest impact in AC loss reduction.The AC loss values in the solenoid winding comprising a stack of five single pancake coils with 0.1 mm turn‐to‐turn gap with the flux diverters agree well with those in the single pancake coil for 2 mm turn‐to‐turn gap with the flux diverters.Solenoid type coil configurations with flux diverters generate much smaller AC loss than the single pancake type with flux diverters when they generate the same center magnetic field.
文摘[目的]比较关节镜下缝合钩和Fast-fix缝合Ⅳ型半月板Ramp区损伤的临床疗效。[方法]回顾性分析2016年1月—2020年10月45例前交叉韧带(anterior cruciate ligament, ACL)损伤合并Ⅳ型半月板Ramp损伤患者的临床资料。所有患者均取自体腘绳肌腱行ACL重建,依据术前医患沟通结果,21例应用缝合钩缝合Ramp损伤,24例应用Fast-fix缝合。对比患者围手术期、随访及影像学结果。[结果]所有患者均顺利完成手术,术中未出现血管、神经损伤等并发症。缝合钩组手术时间[(91.2±10.6) min vs (62.5±8.4) min, P<0.001]、切口总长度[(5.9±0.5) cm vs (5.1±0.6) cm, P<0.001]均显著长于Fast-fix组,但前者住院费用显著少于后者[(3.4±0.3)万元vs (4.3±0.7)万元, P<0.001]。两组Ramp撕裂长度、缝合针数、下地行走时间、切口愈合、住院时间比较差异均无统计学意义(P>0.05)。所有患者均获36~72个月随访。两组完全负重活动时间的差异无统计学意义(P>0.05)。术后1年及末次随访时,两组膝间隙压痛、麦氏征,轴移征、膝关节屈伸ROM、IKDC评分及Lysholm评分较术前均显著改善(P<0.05)。同一时间点,两组上述指标的差异均无统计学意义(P>0.05)。影像方面,与术前相比,术后1年,两组半月板损伤分级及胫骨平台后侧骨髓水肿均显著改善(P<0.05),相应时间点,两组上述指标的差异均无统计学意义(P>0.05)。术后1年MRI显示缝合钩组愈合率为90.5%、Fast-fix组为87.5%,差异无统计学意义(P>0.05)。[结论]关节镜下缝合钩和Fast-fix缝合半月板Ramp区Ⅳ型损伤均可获得满意疗效。
基金Project(2023YFB2604304)supported by the National Key R&D Program of ChinaProjects(52122810,51978586,51778542,U23A20666,52472458)supported by the National Natural Science Foundation of China+1 种基金Project(K2022G034)supported by the Technology Research and Development Program of China National Railway Group Co.Ltd.Projects(2020JDJQ0033,2023NSFSC0884)supported by Sichuan Province Science and Technology Support Program,China。
文摘The influence of ramps on the transient rolling contact characteristics and damage mechanisms of switch rails remains unclear,presenting substantial challenges to the safety of railway operations.To this end,this paper constructs a transient rolling contact finite element model of the wheel-rail in switch under different ramps using ANSYS/LSDYNA method,and analyzes the tribology and damage characteristics when the wheel passes through the switch at a uniform speed.Our research findings reveal that the vibration induced in the switch rail during the wheel load transfer process leads to a step-like increase in the contact force.Moreover,the interaction between the wheel and the rail primarily involves slip contact,which may significantly contribute to the formation of corrugations on the switch rail.Additionally,the presence of large ramps exacerbates switch rail wear and rolling contact fatigue,resulting in a notable 13.2%increase in switch rail damage under 40‰ramp conditions compared to flat(0‰ramp)conditions.Furthermore,the large ramps can alter the direction of crack propagation,ultimately causing surface spalling of the rail.Therefore,large ramps intensify the dynamic interactions during the wheel load transfer process,further aggravating the crack and spalling damage to the switch rails.
文摘胰腺癌是公认的最具侵袭性和致命性的恶性肿瘤之一,其中约20%的病例为胰体尾部癌症。由于该类型癌症生长迅速且早期缺乏明显症状,许多患者在诊断时已经错过了最佳治疗时机。手术是唯一可能治愈的手段,但传统的远端胰腺切除术和脾切除术存在较高的阳性切缘率、较低的淋巴结清扫率和较差的总体生存率,已发表的证据表明经过传统手术治疗的病人,其五年生存率介于8%至22%之间。2003年,Strasberg等人提出了一种新的手术方法——根治性顺行模块化胰脾切除术(Radical Antegrade Modular Pancreatosplenectomy, RAMPS),旨在提供更好的肿瘤切除效果、提高R0切除率并改善患者的长期预后。RAMPS的五年总体生存率可高达30%~40%。随着腹腔镜技术的不断进步,腹腔镜下根治性顺行模块化胰脾切除术(Laparoscopic Radical Antegrade Modular Pancreatosplenectomy, L-RAMPS)作为一种微创手术,具有术后恢复快等优势,逐渐获得越来越多外科医师的关注。文章总结了这种手术的现状,并展望其未来发展。Pancreatic cancer is widely recognized as one of the most aggressive and lethal malignant tumors, with approximately 20% of cases occurring in the body and tail of the pancreas. Due to the rapid growth of this cancer and the lack of obvious symptoms in its early stages, many patients miss the opportunity for optimal treatment by the time of diagnosis. Surgery remains the only potentially curative option;however, traditional distal pancreatectomy and splenectomy are associated with high positive margin rates, low lymph node dissection rates, and poor overall survival. Published evidence shows that the five-year survival rate for patients treated with traditional surgery ranges from 8% to 22%. In 2003, Strasberg et al. proposed a new surgical technique—Radical Antegrade Modular Pancreatosplenectomy (RAMPS)—designed to improve tumor resection, increase the R0 resection rate, and enhance long-term prognosis. The five-year overall survival rate for RAMPS can reach 30%~40%. With the continuous advancement of laparoscopic technology, Laparoscopic Radical Antegrade Modular Pancreatosplenectomy (L-RAMPS), as a minimally invasive procedure, offers advantages such as faster postoperative recovery and is gradually gaining more attention from surgeons. This article provides an overview of the current status of this surgery and discusses its potential future development.
