Showing papers by "Robert M. Edwards published in 2003"
01 Jan 2003
22 citations
TL;DR: In this article, the authors performed thermal performance analyses for some proposed modifications in the Three Mile Island Nuclear Power Plant auxiliary systems, including: auxiliary-condenser circulating-water (ACCW) flow reduction, ACCW discharge diversion to the main condenser, and feedwater heater drain recycling.
Abstract: Thermal performance analyses have been performed for some proposed modifications in the Three Mile Island Nuclear Power Plant auxiliary systems, including: 1) auxiliary-condenser circulating-water (ACCW) flow reduction; 2) ACCW discharge diversion to the main condenser; and 3) feedwater heater drain recycling. Analysis shows that the secondary-system thermal efficiency can be improved by reducing circulating-water (CW) flow to the auxiliary condensers at high CW temperatures. This improvement decreases as CW temperature decreases. No benefit can be obtained from ACCW flow reduction at low CW temperatures. It is also shown that electricity output can be increased by diverting ACCW discharge to the main condenser instead of directly to cooling towers as in the current practice. This increase, though also varying with CW temperature, is consistently positive within the considered CW temperature range. For feedwater heater drain recycling, thermal efficiency improvement is significant for the two lowest-pressure stages.
15 citations
TL;DR: In this paper, the first harmonic mode of the neutron spectrum in a boiling water reactor (BWR) is approximated as a linear combination of the fundamental and first harmonic modes, and these two modes are studied applying reduced order modal models.
Abstract: The study of the first harmonic mode of the neutron spectrum in a boiling water reactor (BWR) yields the capability to assess the decay ratio for the harmonic mode and anticipate the impact on the fundamental mode when an out-of-phase oscillation is about to take place. In this work, the neutron spectrum for a BWR is approximated as a linear combination of the fundamental and first harmonic modes, and these two modes are studied applying reduced order modal models. A stability estimator is constructed to monitor the development of the harmonic mode instability through the calculation of the decay ratio. To achieve an estimation of the decay ratio for each mode, the estimator requires the separation of both modes from the neutron spectrum, and a method to obtain these modes based on a bare homogeneous reactor is presented. The Reduced Order Modal Estimator is tested with computer-generated data and with data from the Ringhals Stability Benchmark.
9 citations
20 Mar 2003
TL;DR: The delay cost function is used in solving the capacity assignment of a single link and is also applicable to large-size multi-link and multi-hop networks, and could be extended to generic data networks with asymmetric links.
Abstract: Bluetooth is a typical short-range radio packet ad-hoc technique that is attractive in the rapid formation of a personal area network and inter-connection of different portable mobile devices. Compared with many high-speed wireless LAN techniques, Bluetooth provides a moderate link speed because each link is only allocated with 1 MHz bandwidth. In order to increase the link utilization, Bluetooth introduces the flexible usage of asymmetric link capacity allocation. It means different speeds are allowed in two directions of a link that flow from the master to the slave and from the slave to the master. Because of this, it is possible for Bluetooth to adaptively adjust the link capacity distribution to increase the link performance with lower latency. In this paper, we use the delay cost function to analyse the capacity assignment for a Bluetooth link. Although it only focuses in solving the capacity assignment of a single link, it is also applicable to large-size multi-link and multi-hop networks. It could be extended to generic data networks with asymmetric links.
5 citations
22 Apr 2003
TL;DR: This paper proposes a novel and topical partial solution which focuses on the slow lossy link and not on the large scale Internet, and retransmitted packets are prioritised over originally transmitted ones, resulting in reduced recovery times.
Abstract: Existing TCP recovery schemes for lost packets are not optimised for wireless environments and consequently are subject to overall performance degradation and channel underutilisation. In slow lossy links the long recovery cycles associated with lost packets result in significant loss of TCP performance. Causes are related to slow packet drop detection, spurious timeouts, and erroneous congestion avoidance triggering that have a cumulatively adverse effect on throughput. In this paper we propose a novel and topical partial solution which focuses on the slow lossy link and not on the large scale Internet. Retransmitted packets are prioritised over originally transmitted ones, resulting in reduced recovery times. This proposed architecture involves only minor modifications to end nodes.
4 citations
TL;DR: Hybrid Reactor Simulation (HRS) of boiling water reactor (BWR) instabilities, including in-phase and out-of-phase (OOP) oscillations, has been implemented on The Pennsylvania State University TRIGA reactor as mentioned in this paper.
Abstract: Hybrid reactor simulation (HRS) of boiling water reactor (BWR) instabilities, including in-phase and out-of-phase (OOP) oscillations, has been implemented on The Pennsylvania State University TRIGA reactor. The TRIGA reactor's power response is used to simulate reactor neutron dynamics for in-phase oscillation or the fundamental mode of the reactor modal kinetics for OOP oscillations. The reactor power signal drives a real-time boiling channel simulation, and the calculated reactivity feedback is in turn fed into the TRIGA reactor via an experimental changeable reactivity device. The thermal-hydraulic dynamics, together with first harmonic mode power dynamics, is digitally simulated in the real-time environment. The real-time digital simulation of boiling channel thermal hydraulics is performed by solving constitutive equations for different regions in the channel and is realized by a high-performance personal computer. The nonlinearity of the thermal-hydraulic model ensures the capability to simulate the oscillation phenomena, limit cycle and OOP oscillation, in BWR nuclear power plants. By adjusting reactivity feedback gains for both modes, various oscillation combinations can be realized in the experiment. The dynamics of axially lumped power distribution over the core is displayed in three-dimensional graphs. The HRS reactor power response mimics the BWR core-wide power stability phenomena. In the OOP oscillationmore » HRS, the combination of reactor response and the simulated first harmonic power using shaping functions mimics BWR regional power oscillations. With this HRS testbed, a monitoring and/or control system designed for BWR power oscillations can be experimentally tested and verified.« less
4 citations
01 Jan 2003
TL;DR: In this article, a dual band planar inverted F antenna is designed for the specific application of gathering data on seals at sea, and a mobile phone module with the above antenna is encased in epoxy resin and affixed to a seal for transmission of sensor data via the short message service over GSM in both European frequency bands.
Abstract: In this paper a novel encapsulated dual band planar inverted F antenna is presented designed for the specific application of gathering data on seals at sea. A mobile phone module with the above antenna is encased in epoxy resin and affixed to a seal for transmission of sensor data via the short message service over GSM in both European frequency bands. Results are presented for a prototype both in anechoic facilities and affixed to a seal at sea. Finite element software is used for optimisation.
2 citations
02 Apr 2003
TL;DR: An enhancement scheme is presented by introducing the predictive link capacity assignment plus the multi-slot framing, which lead to a possible practical design of a new scheduler that exploits a better performance of a Bluetooth piconet.
Abstract: Unlike most wireless techniques, Bluetooth uses time division duplex (TDD) to arrange the transmission slots so that it can avoid the collisions. In a Bluetooth piconet, a master node coordinates up to seven active slave nodes, which implies up to fourteen different active virtual links. The schedulers of the devices, especially the one in the master node, are in charge of all the transmission disciplines. Therefore, the policy of the scheduler will affect the networks performance of the piconet, like delay and throughput. Currently the Bluetooth scheduler uses a round robin policy to distribute the slots for different links. An enhancement scheme is presented by introducing the predictive link capacity assignment plus the multi-slot framing. The advantages of the corresponding methods is discussed, which lead to a possible practical design of a new scheduler that exploits a better performance of a Bluetooth piconet.
1 citations
02 Apr 2003
TL;DR: An RA protocol based on S-ALOHA with data as a session for mobile TDMA cellular networks is researched and an analytical framework is derived based on equilibrium-point-analysis (EPA) and is novel and topical.
Abstract: Research into mixed services in mobile cellular networks is highly topical However, to date, the analytical facility has been limited by the absence of closed forms for the random access (RA) protocols that are pervasive in mixed voice and data systems with a finite number of sessions We research an RA protocol based on S-ALOHA with data as a session for mobile TDMA cellular networks and present an analytical framework The paper begins with a general model description of a voice and data subsystem in which admission protocols are explained An analytical framework is derived An algorithm is then formulated that complements the analytical framework The analysis is based on equilibrium-point-analysis (EPA) and is novel and topical Numerical results are corroborated using a simulation in OPNET