Optimal Scheduling of Utility Electric Vehicle Fleet Offering Ancillary Services

Vehicle‐to‐grid presents a mechanism to meet the key requirements of an electric power system, using electric vehicles (EVs) when they are parked. The most economic ancillary service is that of frequency regulation, which imposes some constraints regarding the period and duration of time the vehicles have to be connected to the grid. The majority of research explores the profitability of the aggregator, while the perspective of the EV fleet owner, in terms of their need for usage of their fleet, remains neglected. In this paper, the optimal allocation of available vehicles on a day‐ahead basis using queuing theory and fuzzy multi‐criteria methodology has been determined. The proposed methodology is illustrated on the daily scheduling of EVs in an electricity distribution company.     

Screw dislocation in nonlocal anisotropic elasticity

Based on Eringen’s model of nonlocal anisotropic elasticity, new solutions for the stress fields of screw dislocations in anisotropic materials are derived. In the theory of nonlocal anisotropic elasticity the anisotropy is twofold. The anisotropic material behavior is not only included in the anisotropy of the elastic stiffness properties, but also in the anisotropy of the nonlocality which is expressed by the anisotropy of the length scale parameters, which is incorporated in the anisotropy of the nonlocal kernel function. Particularly, a new two-dimensional anisotropic kernel which is the Green function of a linear differential operator with three length scale parameters is derived analytically. New solutions for the stresses of straight screw dislocations in anisotropic (monoclinic and hexagonal) materials are found. The stresses do not have singularities and possess interesting features of anisotropy, which are presented and discussed.     

Peroxisome proliferator-activated receptor gamma activators inhibit gene expression and migration in human vascular smooth muscle cells

Mesenchymal hamartomas of the liver are the second most common benign liver tumor of childhood. The experience with this tumor at Egleston's Children Hospital at Emory University from 1989 to 1994 is reviewed. Eight patients presented with abdominal distention or an upper abdominal mass. Six patients presented at a mean age of 8 months, and two patients presented at 17 and 23 years of age, respectively. Four patients displayed normal alpha-fetoprotein levels, whereas one patient had an elevated level. Liver function studies were normal in all patients. Abdominal ultrasonography and CT scans revealed a cystic, septated mass within the liver or on a pedicle in all patients. Five patients had simple excision of the tumor, and two had major hepatic resections. The cysts were multiloculated and lined with cuboidal bile duct epithelium surrounded by stroma containing proliferating bile ducts, blood vessels, and compressed liver tissue with no calcifications. In one patient, some pathologists favored the diagnosis of malignant myxoid fibrous histiocytoma because of similar-appearing stroma. Follow-up (mean, 35 months) revealed one symptomatic recurrence after initial resection was incomplete. There were no other recurrences and no malignant transformations. A septated, noncalcified, cystic hepatic mass in an infant with normal liver function studies and characteristic ultrasound or CT is likely a benign mesenchymal hamartoma that can be cured by total local excision.     

Ruptured pseudoaneurysm of the splenic artery. A complication of chronic pancreatitis

HISTORY AND FINDINGS: A pale looking 33-year-old man with a history of perforated gastric ulcer and pancreatitis with surgically drained pseudocyst was admitted because of painless anal bleeding. Heart rate was 100/min, blood pressure 90/60 mm Hg. INVESTIGATIONS: Haemoglobin concentration (6.3 g/dl) and RBC count (2.4 mill./microliters) indicated anaemia due to bleeding. Sonography and computed tomography demonstrated chronic calcifying pancreatitis and thrombosis of splenic and mesenteric veins. There were grade 1 oesophageal varices on endoscopy. The source of bleeding was found by coloscopy to be a submucous pulsating tumour in the region of the left flexure, which on angiography was an aneurysm of the splenic artery. TREATMENT AND COURSE: The pseudoaneurysm of the splenic artery, which had perforated into the colon, was resected together with a partial pancreas excision and splenectomy. There were no complications and the patient was discharged symptom-free after 15 days, and there had been no further bleeding 6 months later. CONCLUSION: Pseudoaneurysm of a visceral artery is a rare, but life-threatening, complication of pancreatitis. Treatment options are operation and/or interventional catheter embolisation.     

A separation principle between scheduling and admission control forbroadband switching

A framework for joint scheduling and admission control in broadband switching systems based on a principle of separation between these two levels of control is developed. It is shown that an admission control strategy can be tailored to a particular mix of traffic by using high-level information from the scheduler. This principle is presented in the context of asynchronous time-sharing (ATS) in which explicit guarantees of cell-level and call-level quality of service (QOS) are given to several traffic classes. The separation principle allows the formulation of an optimal admission control policy that maximizes the expected system utility and maintains all QOS guarantees. Several heuristic admission control policies are considered and compared with the optimal policy. The admissible load region is introduced as a means of quantifying the capacity of a switch under the QOS constraints at the cell and call levels. Numerical calculations for a single MAGNET II switching node carrying two classes of real-time traffic are used to illustrate the effects of different scheduling and admission control policies on both the expected utility and the admissable load region     

The first decade of continuous progress in retinal transplantation

In recent months, neural fetal retina has been transplanted into blind human patients affected by Retinitis Pigmentosa. Initial success, as documented by improved visual activity, has been reported (del Cerro et al., Neuroscience Abstract, 1996). With the rapid progress in human patients, additional questions are arising concerning transplantation issues. Additional answers and further success in treating clinical disease will necessarily come from new laboratory research in animal models as well as in vitro systems. This increases the need for evaluation of the data already gathered over the first decade of retinal transplantation. The extensive experimental background work that preceded the current wave of human retinal transplants is reviewed in this paper, with particular emphasis given to the work dealing with the transplantation of neural retina.     

MAGNET: Columbia's Integrated Network Testbed

Fundamental issues arising in the design and implementation of architectures and protocols for integrated local area networks (ILAN's) supporting video, voice, graphics, data, and facsimile, are addressed, and open questions are identified. To characterize the performance of ILAN's, a set of performance evaluation guidelines is established. A class of conceptual solutions for ILAN's is proposed, and its expected performance is obtained by means of simulation. The class includes priority assignment schemes, parametrized sequential and simultaneous scheduling algorithms, and centralized and decentralized access control mechanisms. Our analysis, based upon simulations, shows that the bandwidth freed up by the video and voice calls during periods of little movement in the images and silence periods in the speech signals can be efficiently utilized for graphics and data transmission. The optimal priority mechanism among the different user classes depends on the traffic mix. Finally, it is argued that additional experimentation providing empirical data is imperative for understanding the real-time behavior of ILAN's. Consequently, a network testbed (NTB) called MAGNET is proposed for evaluating the performance of the proposed theoretical systems. It consists of an adaptive ILAN whose mediaaccess protocol is controlled by an Expert System.     

A probabilistic approach to fault diagnosis in linear lightwavenetworks

The application of probabilistic reasoning to fault diagnosis in linear lightwave networks (LLNs) is investigated. The LLN inference model is represented by a Bayesian network (or causal network). An inference algorithm is proposed that is capable of conducting fault diagnosis (inference) with incomplete evidence and on an interactive basis. Two belief updating algorithms are presented which are used by the inference algorithm for performing fault diagnosis. The first belief updating algorithm is a simplified version of the one proposed by Pearl (1988) for singly connected inference models. The second belief updating algorithm applies to multiply connected inference models and is more general than the first. The authors also introduce a t-fault diagnosis system and an adaptive diagnosis system to further reduce the computational complexity of the fault diagnosis process     

An architecture for managing virtual circuit and virtual path services in ATM networks

ATM networks rely on the Virtual Circuit (VC) and Virtual Path (VP) concepts to provide unicast connection-oriented services with Quality of Service (QoS) guarantees. This paper presents a model for managing the configuration and performance of the VC and VP services in these networks. The model consists of a connection management architecture that provides the services and is instrumented for network management purposes, and a network management architecture that uses the OSI management model to provide access to the appropriate service monitoring and control functions. The network management architecture proposes complete managed object definitions that achieve a variety of monitoring and control objectives: service configuration, service performance at the call and cell level, and service control. The latter includes the capability to establish VPs and control their allocated networking capacity and also control parameters of the signaling system that affect the performance of the VC service. The architecture was implemented in its entirety on the Xunet ATM testbed, and several experiments were conducted to illustrate the trade-off between the throughput of the VC service and the allocation of capacity to VPs. The experiments further demonstrated that the signaling system can create throughput bottlenecks in the absence of VPs in the network, and therefore, the network operator can increase performance by controlling the VP distribution.     

Objective-driven monitoring for broadband networks

An approach to sensor configuration, installation, and activation for real-time monitoring of broadband networks for performance management is presented. An objective-driven measurement strategy for establishing the dynamic and statistical databases of the network is described. Objective driven monitoring allows the activation of sensors for data collection and abstraction based on a set of objectives. The objectives are derived from the quality of service requirements for real-time traffic control and operator submitted queries. The methodology of objective-driven monitoring for selective activation of sensors is implemented as a set of rules in the knowledge base of the monitor