Voltage-dependent P-Q Reserve Capacity Evaluation for TSO-DSO Interface Considering Uncertainties of DGs and FLs

Increasing distributed generators(DGs)and flexible loads(FLs)enable distribution systems to provide both active and reactive power reserves(P-Q reserves)in supporting the frequency and voltage regulations of transmission systems.However,such requirements at the interface between the transmission system operator(TSO)and distribution system operator(DSO)affect the distribution system operation security,considering the uncertainties of DGs and FLs.To exploit the reserve potential of distribution systems,this paper investigates the voltagedependent P-Q reserve capacity(V-PQRC)of such types of distribution systems.V-PQRC reflects the feasible space of PQ reserves that the DSO can provide to the TSO taking the voltage deviation limit at TSO-DSO interface into consideration,while ensuring the distribution system operation security under uncertainties of DGs and FLs.An evaluation method for VPQRC at the TSO-DSO interface is proposed.To improve the robust performance of the evaluation method,the DG uncertainty is captured by a generalized ambiguity set and the FL uncertainty is addressed by designing a constrained sliding mode controller(CSMC).Three objectives are considered in the evaluation,i.e.,P reserve capacity,Q reserve capacity,and the voltage deviation limit at the TSO-DSO interface.Then,a multiobjective optimization model integrating the generalized robust chance-constrained optimization and CSMC(GRCC-CSMC)is established for V-PQRC evaluation to obtain the Pareto optimal reserve schemes.Finally,a non-approximated selecting(NAS)method is proposed to build up a simplified V-PQRC linear model,which can be convenient to apply in the transmissiondistribution system coordination.Simulation results reveal that the V-PQRC evaluation method can achieve a good performance of accuracy and robustness against uncertainties.

Cerebral perfusion in corresponding blood supply areas of transient ischemic attack patients with intracranial stenosis Seven cases of diamox-perfusion verified by magnetic resonance-perfusion-weighted imaging

BACKGROUND： Due to collateral circulation and cerebrovascular reserve, arterial stenosis and reduced cerebral blood flow may not necessarily indicate impaired cerebral peffusion. Therefore, according to degree of stenosis and clinical symptoms, interventional surgery to relieve arterial stenosis in transient ischemic attack （TIA） patients with major intracranial stenosis is imprudent. Rather, cerebral perfusion and reserve capacity are direct indicators for the assessment of degree and presence of cerebral ischemia. OBJECTIVE： To evaluate cerebral perfusion and reserve in TIA patients with major intracranial stenosis or occlusion using magnetic resonance-perfusion-weighted imaging （MR-PWl） data prior to and following diamox administration. DESIGN, TIME AND SETTING： A self-comparative, neuroimaging observation was performed at the Neurological Department and Radiological Center of the First Affiliated Hospital of Jinan University between December 2007 and April 2009. PARTICIPANTS： Seven acute TIA patients, who were admitted to the Neurological Department of the First Affiliated Hospital of Jinan University between December 2007 and April 2009, were enrolled in the present study. Magnetic resonance imaging confirmed that no acute cerebral infarction happened, nor did bleeding exist. Magnetic resonance angiography, transcranial Doppler ultrasound, and/or digital subtraction angiography confirmed the presence of major intracranial arterial stenosis. Clinical symptoms corresponded to blood supplying regions of the arterial stenosis. METHODS： Baseline MR-PWI was performed on seven patients with intracranial stenosis or occlusion. Two grams of acetazolamide （diamox） were orally administered after 2 days. A second PWl was performed after 2 hours to compare cerebral perfusion parameters prior to and following diamox administration. MAIN OUTCOME MEASURES： PWI results of cerebral perfusion prior to and following diamox administration. RESULTS： The baseline PWl from five patients indicated decreased cerebral perfusion areas. Following oral administration of diamox, cerebral perfusion significantly decreased in those areas. Moreover, new areas of decreased cerebral perfusion were observed in two out of the five patients. In one patient, no significant decrease in cerebral perfusion was found. In another patient, baseline PWl indicated decreased cerebral perfusion in the left hemisphere. However, normal perfusion was observed in both cerebral lobes following diamox administration. CONCLUSION： TIA patients with intracranial stenosis, who are diagnosed by PWI and exhibited decreased cerebral perfusion and reserve, might require further treatment such as intervention by angioptasty.

A Subsection Shared Restoration Method for Long-Haul WDM Networks

A novel restoration scheme, Parted Path Shared Restoration (PPSR), was proposed. The major idea of PPSR is the strategy of ‘parted disposal’. PPSR keeps the advantage of Path Based Shared Restoration (PBSR) in utilization of capacity. In addition, the restoration time of PPSR is much less than that of PBSR. Furthermore, a satisfaction function was proposed to estimate the performance of PPSR. This function takes the utilization of capacity and restoration time into a harmonious and uniform frame. Through theoretical analysis and computer simulation, the performance of PPSR was demonstrated.

Changes of Some Capacities and Failure Mode of Ni/MH Batteries During Cycling

The changes of capacities of positive and negative electrodes, reserve capacities of charging and discharging, and the weight of batteries during cycling have been determined. The increase of the discharging reserve capacity due to the conjugated electrochemical reactions of the oxidation of hydrogen storage alloy is estimated. The results show that the failure mode of Ni/MH batteries developed is as follows: during the increase of cycles, the hydrogen storage alloy is oxidized continuously and the charging reserve capacity is decreased rapidly while the discharging reserve capacity is increased gradually, thus the internal pressure is increasing, first H 2 leaks out from the battery, then the mixture of H 2 and O 2. The leakage of gases and the total reaction of oxidation of the alloy consume H 2O, and the surface oxides on the alloy increase, so that the internal resistance of the battery increases.

Sourcing Decisions with Capacity Reservations under Supply Disruptions

Firms employing both offshore outsourcing and nearshore sourcing strategies may face supply disruption,demand uncertainty,and quality risks simultaneously.Sourcing decisions become inevitably important and complicated when both profit and the customer-service level are taken into consideration.In this paper,we model a scenario where a manufacturer who faces stochastic demand procures major modules from an overseas supplier and two local suppliers.The overseas supplier offers quality products while being susceptible to disruption risks;if the local suppliers,who are completely reliable and serve as a backup,offer products that are of inferior quality,it may result in lower market acceptance and a bad experience for the final customers.The manufacturer has to reserve capacity with backup suppliers before urgent orders are placed,when the primary source experiences a shortfall.We explicitly derive the manufacturer’s optimal order quantities and reservation quantities,which are functions of the heterogeneous suppliers’wholesale prices,reservation prices,and other parameters.The impacts of the fill-rate constraint and customer-experience quality constraint on the manufacturer’s purchasing decisions are investigated.Interesting managerial insights on the merits of backup sourcing with capacity reservations for managing demand uncertainties and supply disruption risks are also discussed.

Centralized Decisions for a Two-Stage Supply Chain with Price-Discount Dependent Demand

In this paper,we study a centralized supply chain for a two-stage with selling price discount.This supply chain consists of a supplier and a retailer. Based on the feature that the product’s selling season is short and the supply chain faces great demand uncertainty. We consider a two-stage scenario where,at the beginning of stage 1,the supplier reserves production capacity based on historic data in advance,stage 2 comes to us after some leadtime,both the supplier and the retailer update the demand information,the retailer then places an order not exceeding the reserved capacity based on the selling-pricing discount dependent demand. We make optimal decisions on the reserved capacity in stage 1,selling price discount and order quantity in stage 2. In this supply chain,the pattern in stage2 is figured out first,and then stage 1 is cleared as well. Then we present a numerical example to give some insights. Finally we get some conclusions.