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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal DOI :
Electronics and Telecommunications Research Institute
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Volume & Issues
Volume 16, Issue 3 - Oct 1994
Volume 16, Issue 2 - Jul 1994
Volume 16, Issue 1 - Apr 1994
Volume 15, Issue 3 - Jan 1994
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MAXIMUM TOLERABLE ERROR BOUND IN DISTRIBUTED SIMULATED ANNEALING
Hong, Chul-Eui ; McMillin, Bruce M. ; Ahn, Hee-Il ;
ETRI Journal, volume 15, issue 3, 1994, Pages 1~1
Simulated annealing is an attractive, but expensive, heuristic method for approximating the solution to combinatorial optimization problems. Attempts to parallel simulated annealing, particularly on distributed memory multicomputers, are hampered by the algorithm's requirement of a globally consistent system state. In a multicomputer, maintaining the global state S involves explicit message traffic and is a critical performance bottleneck. To mitigate this bottleneck, it becomes necessary to amortize the overhead of these state updates over as many parallel state changes as possible. By using this technique, errors in the actual cost C(S) of a particular state S will be introduced into the annealing process. This paper places analytically derived bounds on this error in order to assure convergence to the correct optimal result. The resulting parallel simulated annealing algorithm dynamically changes the frequency of global updates as a function of the annealing control parameter, i.e. temperature. Implementation results on an Intel iPSC/2 are reported.
A SPATIAL PREDICTION THEORY FOR LONG-TERM FADING IN MOBILE RADIO COMMUNICATIONS
Yoo, Seong-Mo ;
ETRI Journal, volume 15, issue 3, 1994, Pages 27~27
There have been traditional approaches to model radio propagation path loss mechanism both theoretically ad empirically. Theoretical approach is simple to explain and effective in certain cases. Empirical approach accommodates the terrain configuration and distance between base station and mobile unit along the propagation path only. In other words, it does not accommodate natural terrain configuration over a specific area. In this paper, we propose a spatial prediction technique for the mobile radio propagation path loss accommodating complete natural terrain configuration over a specific area. Statistical uncertainty analysis is also considered.
APPROXIMATION OF THE QUEUE LENGTH DISTRIBUTION OF GENERAL QUEUES
Lee, Kyu-Seok ; Park, Hong-Shik ;
ETRI Journal, volume 15, issue 3, 1994, Pages 35~35
In this paper we develop an approximation formalism on the queue length distribution for general queueing models. Our formalism is based on two steps of approximation; the first step is to find a lower bound on the exact formula, and subsequently the Chernoff upper bound technique is applied to this lower bound. We demonstrate that for the M/M/1 model our formula is equivalent to the exact solution. For the D/M/1 queue, we find an extremely tight lower bound below the exact formula. On the other hand, our approach shows a tight upper bound on the exact distribution for both the ND/D/1 and M/D/1 queues. We also consider the
queue and compare our formula with other formalisms for the
and M+D/D/1 queues.
A CAPACITY EXPANSION STRATEGY ON PROJECT PLANNING
Joo, Un-Gi ;
ETRI Journal, volume 15, issue 3, 1994, Pages 47~47
A capacity expansion planning problem with buy-or-lease decisions is considered. Demands for capacity are deterministic and are given period-dependently at each period. Capacity additions occur by buying or leasing a capacity, and leased capacity at any period is reconverted to original source after a fixed length of periods, say, lease period. All cost functions (buying, leasing and idle costs) are assumed to be concave. And shortages of capacity and disposals are not considered. The properties of an optimal solution are characterized. This is then used in a tree search algorithm for the optimal solution and other two algorithms for a near-optimal solution are added. And these algorithms are illustrated with numerical examples.
THE EFFECT OF DOPANT OUTDIFFUSION ON THE NEUTRAL BASE RECOMBINATION CURRENT IN Si/SiGe/Si HETEROJUNCTION BIPOLAR TRANSISTORS
Ryum, Byung-R. ; Kim, Sung-Ihl ;
ETRI Journal, volume 15, issue 3, 1994, Pages 61~61
A new analytical model for the base current of Si/SiGe/Si heterojunction bipolar transistors(HBTs) has been developed. This model includes the hole injection current from the base to the emitter, and the recombination components in the space charge region(SCR) and the neutral base. Distinctly different from other models, this model includes the following effects on each base current component by using the boundary condition of the excess minority carrier concentration at SCR boundaries: the first is the effect of the parasitic potential barrier which is formed at the Si/SiGe collector-base heterojunction due to the dopant outdiffusion from the SiGe base to the adjacent Si collector, and the second is the Ge composition grading effect. The effectiveness of this model is confirmed by comparing the calculated result with the measured plot of the base current vs. the collector-base bias voltage for the ungraded HBT. The decreasing base current with the increasing the collector-base reverse bias voltage is successfully explained by this model without assuming the short-lifetime region close to the SiGe/Si collector-base junction, where a complete absence of dislocations is confirmed by transmission electron microscopy (TEM).The recombination component in the neutral base region is shown to dominate other components even for HBTs with a thin base, due to the increased carrier storage in the vicinity of the parasitic potential barrier at collector-base heterojunction.