Aggregator-based demand response mechanism for electric vehicles participating in peak regulation in valley time of receiving-end power grid

With the increase in the power receiving proportion and an insufficient peak regulation capacity of the local units, the receiving-end power grid struggles to achieve peak regulation in valley time. To solve this problem while considering the potential of the large-scale charge load of electric vehicles(EVs), an aggregator-based demand response(DR) mechanism for EVs that are participating in the peak regulation in valley time is proposed in this study. In this aggregator-based DR mechanism, the profits for the power grid’s operation and the participation willingness of the EV owners are considered. Based on the characteristics of the EV charging process and the day-ahead unit generation scheduling, a rolling unit commitment model with the DR is established to maximize the social welfare. In addition, to improve the efficiency of the optimization problem solving process and to achieve communication between the independent system operator(ISO) and the aggregators, the clustering algorithm is utilized to extract typical EV charging patterns. Finally, the feasibility and benefits of the aggregator-based DR mechanism for saving the costs and reducing the peak-valley difference of the receiving-end power grid are verified through case studies.

Combined hybrid energy storage system and transmission grid model for peak shaving based on time series operation simulation

This study proposes a combined hybrid energy storage system(HESS) and transmission grid(TG) model, and a corresponding time series operation simulation(TSOS) model is established to relieve the peak-shaving pressure of power systems under the integration of renewable energy. First, a linear model for the optimal operation of the HESS is established, which considers the different power-efficiency characteristics of the pumped storage system, electrochemical storage system, and a new type of liquid compressed air energy storage. Second, a TSOS simulation model for peak shaving is built to maximize the power entering the grid from the wind farms and HESS. Based on the proposed model, this study considers the transmission capacity of a TG. By adding the power-flow constraints of the TG, a TSOS-based HESS and TG combination model for peak shaving is established. Finally, the improved IEEE-39 and IEEE-118 bus systems were considered as examples to verify the effectiveness and feasibility of the proposed model.

Mapping winter wheat using phenological feature of peak before winter on the North China Plain based on time-series MODIS data

By employing the unique phenological feature of winter wheat extracted from peak before winter （PBW） and the advantages of moderate resolution imaging spectroradiometer （MODIS） data with high temporal resolution and intermediate spatial resolution, a remote sensing-based model for mapping winter wheat on the North China Plain was built through integration with Landsat images and land-use data. First, a phenological window, PBW was drawn from time-series MODIS data. Next, feature extraction was performed for the PBW to reduce feature dimension and enhance its information. Finally, a regression model was built to model the relationship of the phenological feature and the sample data. The amount of information of the PBW was evaluated and compared with that of the main peak （MP）. The relative precision of the mapping reached up to 92% in comparison to the Landsat sample data, and ranged between 87 and 96% in comparison to the statistical data. These results were sufficient to satisfy the accuracy requirements for winter wheat mapping at a large scale. Moreover, the proposed method has the ability to obtain the distribution information for winter wheat in an earlier period than previous studies. This study could throw light on the monitoring of winter wheat in China by using unique phenological feature of winter wheat.

Trans-Thoracic Echocardiographic Aortic Blood Flow Peak Velocity Variation, Distance Minute, Aortic Velocity Time Integral and Postoperative Outcome in Pediatric Surgical Patients—An Observational Pilot Study Protocol

Background: A Randomized Controlled Trial (RCT) has been elaborated where goal directed fluid and hemodynamic therapy (GDFHT) will be realized with trans-thoracic echocardiographic aortic blood flow peak velocity variation (ΔVpeak) and distance minute (DM) to guide fluid therapy and hemodynamics in high risk pediatric surgical patients. This RCT will clarify the impact of GDFHT with ΔVpeak and DM on postoperative outcome in terms of morbidity, length of stay in the intensive care unit (LOSICU), length of mechanical ventilation (LMV) and length of hospital stay (LOS) in children. To determine values of ΔVpeak, DM and VTI predictive of these postoperative outcomes, an observational pilot study will be realized. This pilot study is described here. The primary objective of this study is to determine values of ΔVpeak, DM and ITV predictive of postoperative outcome in children in terms of morbidity. The secondary objectives are to determine values of ΔVpeak, DM and ITV predictive of LOSICU, LMV, LOS, intraoperative, postoperative fluid administration and vasoactive-inotropic therapy. Methods: 500 - 1000 children aged less than 18 years will be included prospectively. Statistic analysis will be realized with XLSTAT 2019.4.2 software or plus. Results and Conclusions: This trial protocol will determine values of ΔVpeak, DM and ITV with echocardiography predictive of postoperative outcome in children.

The Prediction of the Peak Time of People Taking School Bus Based on Martingale Process

As the main tool for students and professors to come and go to different districts in-campus, the school bus is of great importance. In order to improve its efficiency and convenient students and professors, a rational schedule of departure is badly needed. A model is established to predict the peak time of people taking school bus based on martingale process, and it is solved according to stopping time of martingale. Then it is applied to Wuhan University of Technology. A large amount of data is collected and the peak time for each day is predicted combined with the actual situation of the college. In doing so, suggestions are given for those who are in charge of the school buses.

Simultaneous Prediction of Retention Times and Peak Shapes of Sulfonamides in Reversed-Phase High-Performance Liquid Chromatography

In this paper, we propose a novelmethod based on the plate theory to simultaneously predict retention times and peak shapes under gradient elutions and different flow rates by reversed-phase high-performance liquid chromatography. The proposed method yielded excellent retention prediction results in experiments with 16 common sulfonamides under 18 gradient conditions and four different flow rates, including 0.7, 1.0, 1.3, and 1.5 mL/min. The mean absolute deviation was 0.70%, which indicates accurate prediction. Moreover, the proposed method predicts the change wellin peak shapes caused by the expansion or compression ofpeaks under different gradient conditions.

Electric Vehicle Charging Load Optimization Strategy Based on Dynamic Time-of-Use Tariff

Electric vehicle(EV)is an ideal solution to resolve the carbon emission issue and the fossil fuels scarcity problem in the future.However,a large number of EVs will be concentrated on charging during the valley hours leading to new load peaks under the guidance of static time-of-use tariff.Therefore,this paper proposes a dynamic time-of-use tariff mechanism,which redefines the peak and valley time periods according to the predicted loads using the fuzzy C-mean(FCM)clustering algorithm,and then dynamically adjusts the peak and valley tariffs according to the actual load of each time period.Based on the proposed tariff mechanism,an EV charging optimization model with the lowest cost to the users and the lowest variance of the grid-side load as the objective function is established.Then,a weight selection principle with an equal loss rate of the two objectives is proposed to transform the multi-objective optimization problem into a single-objective optimization problem.Finally,the EV charging load optimization model under three tariff strategies is set up and solved with the mathematical solver GROUBI.The results show that the EV charging load optimization strategy based on the dynamic time-of-use tariff can better balance the benefits between charging stations and users under different numbers and proportions of EVs connected to the grid,and can effectively reduce the grid load variance and improve the grid load curve.

基于TimeSVD++与DPC的推荐算法研究

针对使用奇异值分解(SVD)方法时需要填充矩阵的内容较多以及K-means算法受到K值的影响且数据集形状限制等问题,提出一种将TimeSVD++与改进的密度峰值聚类结合的方法。首先在SVD++的基础上引入参数时间因子,构建TimeSVD++模型;其次,采用将相似系数引入高斯核函数的方法,对密度峰聚类算法中的局部密度公式进行修正;引入信息熵确定最优截断距离,最后在数据集MovieLens-1M和MovieLens-100k上验证,并将实验结果与其它算法进行对比。结果表明:所提出的方法在MAE,RMSE,Recall和F1值指标上均优于其它的算法。

全膝关节置换前膝关节伸屈肌肌肉力量与置换后步态功能的关系

背景:步态功能障碍是导致全膝关节置换后患者不满的重要原因之一,临床研究中发现术前股四头肌和腘绳肌的肌肉力量与术后步态功能障碍有关,但其相关性目前尚不完全清楚。目的:探讨全膝关节置换前以股四头肌为主的伸肌、以腘绳肌为主的屈肌肌肉力量与置换后步态功能等的相关性。方法:回顾性分析70例接受单侧初次全膝关节置换患者的纵向数据,术前测量伸屈肌的峰力矩、峰力矩体质量比、总功数据,术后6个月测量起立-步行计时测试结果和步态速度。使用岭回归分析确定术后步态功能的影响因素。结果与结论:①术前伸肌峰力矩、峰力矩体质量比、总功以及屈肌峰力矩、总功与术后步态速度呈非常强正相关(P<0.001),术前屈肌峰力矩体质量比与术后步态速度呈强正相关(P<0.001);术前伸肌、屈肌峰力矩、峰力矩体质量比、总功与术后起立-步行计时测试结果呈非常强负相关(P<0.001);②岭回归分析中,94.2%可能性可说明术前伸肌峰力矩、峰力矩体质量比、总功及屈肌峰力矩、总功对全膝关节置换后患者的步态速度具有正向影响(P<0.001),术前屈肌峰力矩体质量比对术后步态速度具有负向影响(P<0.001);87.7%可能性说明术前伸肌峰力矩、峰力矩体质量比、总功及屈肌峰力矩、总功对术后起立-步行计时测试具有负向影响(P<0.05),而屈肌峰力矩体质量比对术后起立-步行计时测试无影响(P>0.05);③提示全膝关节置换前股四头肌、腘绳肌肌肉力量的大小与置换后步态速度、起立-步行计时测试结果相关,可预测术后步态功能结果;加强置换前膝关节肌肉锻炼可能是减缓全膝关节置换后步态障碍发生的途径。

基于flushing time的春季水库优化调度可行性研究

针对三峡水库支流库湾春季水华问题,通过建立三维水动力模型,探讨了利用调峰调度和潮汐式调度促进干支流水体交换的可行性。研究表明,当4月水库实施调峰调度时,整个库湾水体的flushing time较常规调度有所缩短,尤其是库湾上游至中上游区域;当5月水库开始实施潮汐式调度时,水体体积较大的库湾下游区域的flushing time较常规调度方案有所缩短。可见,两种水库优化调度方案对增大干支流水体交换均具有可行性。当水库实施调峰调度和潮汐式调度联合调度时,整个库湾水体的平均flushing time较常规调度方案有不同程度的缩短,表明该联合调度方案更能促进干支流水体的交换。研究成果可为支流库湾水环境问题的防治提供借鉴。

Time derivative of earthquake acceleration

Unlike acceleration, velocity, and displacement, the time derivative ofacceleration (TDoA) of ground motion has not been extensively studied. In this paper, the basiccharacteristics of TDoA are evaluated based on records from the 1999 Chi-Chi, earthquake (Mw 7.6)and one of its aftershocks (Mw 6.2). It is found that the maximum TDoA at a free-field station wasover 31,200 cm/s3 (31.8 g/s); and the duration of 'strong' TDoA, between the first and the last timepoints exceeding 2,000 cm/s3 (2 g/s), was almost one minute near the epicenter area. Since groundTDoA sensors are not commonly available, the time series are calculated by direct numericaldifferentiation of acceleration time series. Relative error analysis shows that the error isnon-transitive and total error is within 4%. The density function of TDoA amplitude, frequencycontent and spatial distribution of peak ground jerk (PGJ) are evaluated. The study also includesexamination of some TDoA responses from a seven-story building and comparison of ground TDoA withthe limit TDoA used in the transportation industry for ride comfort. Some potential impacts of TDoAon humans have also been reviewed.

Peak earthquake response of structures under multi-component excitations

Accurate estimation of the peak seismic responses of structures is important in earthquake resistant design. The internal force distributions and the seismic responses of structures are quite complex, since ground motions are multidirectional. One key issue is the uncertainty of the incident angle between the directions of ground motion and the reference axes of the structure. Different assumed seismic incidences can result in different peak values within the scope of design spectrum analysis for a given structure and earthquake ground motion record combination. Using time history analysis to determine the maximum structural responses excited by a given earthquake record requires repetitive calculations to determine the critical incident angle. This paper presents a transformation approach for relatively accurate and rapid determination of the maximum peak responses of a linear structure subjected to three-dimensional excitations within all possible seismic incident angles. The responses can be deformations, internal forces, strains and so on. An irregular building structure model is established using SAP2000 program. Several typical earthquake records and an artificial white noise are applied to the structure model to illustrate the variation of the maximum structural responses for different incident angles. Numerical results show that for many structural parameters, the variation can be greater than 100%. This method can be directly applied to time history analysis of structures using existing computer software to determine the peak responses without carrying out the analyses for all possible incident angles. It can also be used to verify and/or modify aseismic designs by using response spectrum analysis.

A Method for Improving Power Distribution Characteristics of Space Time Block Codes

Improving power distribution characteristics of space time block codes(STBCs),namely peak to average power ratio(PAPR),average to minimum power ratio(Ave/min),and probability of transmitting"zero"by antenna,makes easier their practical implementation.To this end,this study proposes to multiply full diversity STB C with a non-singular matrix in multiple input multiple output(MIMO)or multiple input single output(MISO)systems with linear or maximum likelihood(ML)receivers.It is proved that the obtained code achieves full diversity and the order of detection complexity does not change.The proposed method is applied to different types of STBCs.The bit error rate(BER)and power distribution characteristics of the new codes demonstrate the superiority of the introduced method.Further,lower and upper bounds on the BER of the obtained STBCs are derived for all receivers.The proposed method provides trade-off among PAPR,spectral efficiency,energy efficiency,and BER.

The determination of the relative permittivity of periodic stratified media based on the iterative time-reversal method

In this paper, we present a new method to determine the relative permittivity of periodic stratified media using the iterative time-reversal method. Based on transmission line theory, the focal peak value of iterative time-reversal electro- magnetic waves, which contain information about the periodic stratified medium, is computed in pulse-echo mode. Using the relationship between the focal peak value and the relative permittivity of the periodic stratified medium, the relative permittivity can be obtained by measuring the focal peak value. Numerical simulations are conducted, and the results demonstrate the feasibility of the proposed approach to the measurement of the relative permittivity of a periodic stratified medium.

Hydration Heat Evolution of Cement and Its Relation With Setting Time

In order to veritably measure the first peak of hydration heat evolution that has been illustrated important in indicating cement behavior in early hydration, an improved way of water addition into cement in isothermally calorimetric experiment is put forward. The experimental results indicated that: the magnitude of first peak of heat evolution varies from sample to sample, correlation between heat evolution during first peak of heat evolution and initial (as well as final) setting time is unsatisfactory when samples are not classified; while groups of sample classified based on strength grade represent satisfactory correlations, which indicating the existence of close relation between hydration heat evolution in much earlier hydration age and setting property of cement in rather later age. Importance of first peak in hydration heat evolution for understanding cement setting property and reasons for sample classification are also discussed in this paper.

高频超声联合血流灌注参数Peak、Tp、MTT对甲状腺肿瘤的临床诊断价值

目的探讨高频超声联合血流灌注参数Peak、Tp、MTT用于诊断甲状腺肿瘤的临床价值。方法收集进行手术治疗的甲状腺肿瘤患者126例,根据1988年WHO甲状腺组织学分类标准进行分类,即恶性组(n=64)、良性组(n=62),观察2组血流灌注参数如峰值强度(Peak)、达峰时间(Tp)、平均通过时间(MTT)。采用高频超声、血流灌注参数单一及联合检查,观察各项误诊和漏诊率、诊断准确率。采用ROC曲线分析高频超声、血流灌注参数单一及联合检查的诊断效能,记录AUC、截断值、截断值敏感度、截断值特异度、置信区间等。结果恶性组CEUS血流灌注参数Peak[(12.65±3.31)%]显著低于良性组,Tp[(40.32±8.15)s]、MTT[(59.62±3.04)s]显著高于良性组,差异均具有统计学意义(P<0.05)。高频超声联合CEUS血流灌注参数误诊和漏诊率(5.56%)均显著低于单独检测,且诊断准确率(93.65%)显著高于单独检测,差异均具有统计学意义(P<0.05)。高频超声联合CEUS血流灌注参数的AUC为0.889、敏感度86.35%、特异度81.65%,均显著高于高频超声及CEUS血流灌注参数单一检测。结论良恶性甲状腺肿瘤CEUS血流灌注参数Peak、Tp、MTT间差异显著。高频超声联合血流灌注参数Peak、Tp、MTT诊断甲状腺肿瘤准确率高,能够作为临床上鉴别诊断以及治疗甲状腺肿瘤的参考依据。

Time Step Issue in Unit Hydrograph for Improving Runoff Prediction in Small Catchments

Unit hydrograph is a very practical tool in runoff prediction which has been used since decades ago and to date it remains useful. Unit hydrograph method is applied in Way Kuala Garuntang, an ungauged catchment in Lampung Province, Indonesia. To derive an observed unit hydrograph it requires rainfall and water level data with fine time scale which are obtained from automatic gauges. Observed unit hydrograph has an advantage that it is possible to derive it for various time steps including those with time step less than an hour. In order to get a more accurate unit hydrograph, it is necessary to derive a unit hydrograph with small time step for a small catchment such as those used in this study. The study area includes Way Kuala Garuntang and its tributaries, i.e. Way Simpur, Way Awi with areas are 60.52 km2, 3.691 km2, and 9.846 km2 respectively. The results of this study highlight the importance of time step selection on unit hydrograph, which are shown to have a significant impact on the resulting unit hydrograph’s variables such as peak discharge and time to peak.

A Time-Based Framework for Evaluating Hydrologic Routing Methodologies Using Wavelet Transform

In this study we explore a method which provides an insight into the effectiveness of various hydrologic models’ routing components based on their ability to accurately represent flood peak times and shapes. The method is based on using Cross-Wavelet Transforms to estimate the phase (time) difference between the time series of the observed and the simulated discharges. In this article we evaluate two routing components, the Routing Application for Parallel Computation of Discharge (RAPID), which is based on the simplified Muskingum routing method, and the routing component of the non-linear Hillslope-Link hydrologic Model (HLM) produced in the Iowa Flood Center (IFC). Both routing components are driven by the same source of runoff and used the same channel network to ensure that the discrepancies between the simulated stream discharges are due to channel routing alone. We also explore the suitability of different wavelet shapes for our application, and how the difference in wavelet shape can affect our evaluation results. Unlike the conventional statistical skill scores used to evaluate model performance (e.g. Root Mean Squared Error, correlation coefficient, and Nash Sutcliff efficiency index), which give an estimate of the overall hydrograph performance, our method conveniently provides time-localized information with higher resolution at peak location. We perform our evaluation at multiple stream gauge locations, covering a wide range of scales (700 to 16,862 km2), located in the eastern part of the state of Iowa. Our results show that the proposed wavelet method is effective in evaluating the performance of the routing components in simulating peak times across spatial scales. Generally, the non-linear routing method employed in the HLM outperformed the Muskingum based method employed in RAPID. In addition, our results suggest that the Paul wavelet is more effective in detecting and separating individual peaks than the Morlet wavelet, which in turn leads to a more accurate evaluation of the routing components.

Time-Series Characteristics of Wind Power and Its Impact on Jilin Power Grid

With the rapid development of wind power, the large-scale wind power integration brings a new range of issues in dispatching operation. In order to gain a better grasp of the influence caused by wind power combined to the grid, the paper first establishes the impact characteristic indexes, and then analyzes the regularity of wind power time series in different spatial and temporal scales. At last, according to the analysis results, this paper assesses the impact of time-series characteristics of wind power on power grid, such as the frequency regulation, peak load regulation, which can provide the reference for wind power optimal dispatching of Jilin Power Grid.

Patient Peak Skin Dose and Dose Area Product from Interventional Cardiology Procedures

Information about the peak skin dose and Dose Area product (DAP) from percutaneous transluminal coronary angioplasty (PTCA) and coronary angiography (CA) was collected from three catheter application rooms. The range of maximum photon energy was 50 - 125 kVp and the fluoroscopy time was 0.6 - 52 seconds. Values of up to 143 Gy·cm2 for DAP and 0.752 mGy for cumulative dose (CD) were found in CA procedures. Otherwise the DAP and CD for PTCA were found to be 143 Gy·cm2 and 2.287 mGy respectively in 3rd Quartile. The relation between the fluoroscopy time and the DAP is also considered. Objectives: The objective of this study is to obtain information about patient peak skin doses (PSD), dose area product (DAP), Fluoroscopy Time (FT) and Cumulative Dose (CD) from PTCA and CA which is the most predominant with respect to high skin doses in addition to other procedures. The aim of this study is also to assess the radiation dose received by patients undergoing interventional radiology procedures, by identifying the procedures that deliver the highest doses. This study is also helpful to establish the reference dose level for adult patients undergoing interventional procedure, and to provide recommendations on how to reduce dose on selected procedures that have been identified to deliver patient dose values near the ICRP (International Commission on Radiological Protection) threshold values.