1,721,212 research outputs found
Indexing range sum queries in spatio-temporal databases
No full textAlthough spatio-temporal databases have received considerable attention recently, there has been little work on processing range sum queries on the historical records of moving objects despite their importance. Since the direct access to a huge amount of data to answer range sum queries incurs prohibitive computation cost, materialization techniques based on existing index structures are suggested. A simple but effective solution is to apply the materialization technique to the MVR-tree known as the most efficient structure for window queries with spatio-temporal conditions. Aggregate structures based on other index structures such as the HR-tree and the 3DR-tree do not provide satisfactory query performance. In this paper, we propose a new index structure called the Adaptively Partitioned Aggregate R-Tree (APART) and query processing algorithms to efficiently process range sum queries in many situations. Our experimental results show that the performance of the APART is typically 1.3 times better than that of its competitor for a wide range of scenarios. (c) 2006 Elsevier B.V. All rights reserved.This research was supported by the Agency for Defense
Development, Korea, through the Image Information Research
Center at Korea Advanced Institute of Science &
Technology
Improved luminance and luminous efficiency of AC plasma display panel
No full textThe effect of applying auxiliary pulses to the address electrode during the sustain period on the discharge characteristics of, an AC plasma display panel was investigated. When auxiliary pulses of 100 V and 250kHz were applied to the address elec ' trode during the sustain period, the maximum sustain voltage was found to decrease by 14%, while the minimum sustain voltage increased by 15% when compared to the case of a grounded address. It was also found that higher frequency auxiliary pulses resulted in a higher luminance in the sustain discharge. Consequently, the application of a pulse of 100V and 250kHz to the address electrode during the, sustain period improved the luminous efficiency by 12%
Exploring the prognostic value of ultra-low-pass whole-genome sequencing of circulating tumor DNA in hepatocellular carcinoma
Full text linkAn efficient and scalable approach to CNN queries in a road network
Full text linkInternational Conference on VLDB(Trondheim, Norway from August 30 to September 2, 2005)Image Information Research Center and Information Technology Research Cente
The effects of several growth parameters on the formation behavior of point defects in Czochralski-grown silicon crystals
No full textVariation of growth parameters such as the crystal rotation rate, the crucible rotation rate and the configuration of cusp magnetic fields results in the increase or the decrease of critical growth rate V*, transition from interstitial to vacancy, of Czochralski (CZ)-grown silicon crystals. It can also make axially asymmetric distributions of grown-in microdefect regions. V* is remarkably increased in some range of the crystal rotation rate and the crucible rotation rate, which are likely to depend on crucible shape, size and melt volume. The crystal rotation rate as well as the crucible rotation rate affects the incorporation of point defects into the growing crystal through modification of the melt convection. Variation of the configuration of cusp magnet also can increase V* since it affects the melt temperature field. Significant results of interstitial-rich region at crystal center and vacancy-rich region at crystal edge are given in the minority carrier life-time map. These effects are directly caused by the change of heat flow in the melt, controlled with the crystal rotation rate, the crucible rotation rate and the magnetic configuration. The axial temperature gradient in the crystal near the crystal-melt interface is indirectly affected by heat flow through the crystal-melt interface. In addition, the novel technique, the unbalanced magnetic technique, is proposed to control heat transfer and oxygen transfer separately. (c) 2006 Elsevier B.V. All rights reserved
An adaptive indexing technique using spatio-temporal query workloads
No full textMany spatio-temporal access methods, such as the HR-tree, the 3DR-tree, and the MV3R-tree, have been proposed for timestamp and interval queries. However, these access methods have the following problems: the poor performance of the 3DR-tree for timestamp queries, the huge size and the poor performance of the HR-tree for interval queries, and the large size and the high update cost of the MV3R-tree. We address these problems by proposing an adaptive partitioning technique called the Adaptive Partitioned R-tree (APR-tree) using workloads with timestamp and interval queries. The APR-tree adaptively partitions the time domain using query workloads. Since the time domain of the APR-tree is automatically fitted to query workloads, the APR-tree outperforms the other access methods for various query workloads. The size of the APR-tree is on the average 1.3 times larger than that of the 3DR-tree which has the smallest size. The update cost of the APR-tree is on the average similar to that of the 3DR-tree which has the smallest update cost. (C) 2003 Elsevier B.V. All rights reserved
Time-to-go weighted optimal guidance with impact angle constraints
No full textIn this paper, the optimal guidance law with terminal constraints of miss distance and impact angle is presented for a constant speed missile against the stationary target. The proposed guidance law is obtained as the solution of a linear quadratic optimal control problem with the energy cost weighted by a power of the time-to-go. Systematic selection of guidance gains and trajectory shaping are possible by adjusting the exponent of the weighting function. A new time-to-go calculation method taking account of the trajectory curve is also proposed for implementation of the proposed law. Nonlinear and adjoint simulations are performed to investigate the performance of the proposed guidance law and time-to-go calculation method
Heuristic approach for early separated filter and refinement strategy in spatial query optimization
No full textRecently, we proposed an optimization strategy for spatial and non-spatial mixed queries. In the strategy, the filter step and the refinement step of a spatial operator are regarded as individual algebraic operators, and are early separated at the algebraic level by the query optimizer. By doing so, the optimizer using the strategy could generate more diverse and efficient plans that the traditional optimizer. We called this optimization strategy the Early Separated Filter And Refinement (ESFAR). In this paper, we improved the cost model of the ESFAR optimizer considering the real life environment such as the LRU buffer, the clustering of the dataset, and the selectivity of the real data distribution. And we conducted a new experiment for ESFAR by comparing the optimization result generated by the new cost model and the actual execution result using real data. The experimental result showed that our cost model is accurate and our ESFAR optimizer estimates the costs of execution plans well. Since the ESFAR strategy has more operators and more rules than the traditional one, it consumes more optimization time. In this paper, we apply two existing heuristic algorithms, the iterative improvement (11) and the simulated annealing (SA), to the ESFAR optimizer. Additionally we propose a new heuristic algorithm to find a good initial state of 11 and SA. Through experiments, we show that the 11 and SA algorithms in the ESFAR strategy find a good sub-optimal plan in reasonable time. Mostly the heuristic algorithms find a lower cost plan in less time than the optimal plan generated by the traditional optimizer. Especially the 11 algorithm with the initial state heuristic rapidly finds a plan of a high quality. (C) 2001 Elsevier Science Inc. All rights reserved.This research was supported by the Basic Research Program
grant number 99-2-315-001-3) of the Korea Science and
Engineering Foundation
Asymmetric distributions of grown-in microdefects in Czochralski silicon
No full textThe axial temperature gradient in the CZ-Si melt near the crystal-melt interface was increased by controlling the crucible and crystal rotation rate. For the crystal grown under the increased temperature gradient in the melt with a very low crucible rotation rate, asymmetric distributions of grown-in microdefects were formed. This result has never been reported, and cannot be explained simply by any theory such as Voronkov's theory. In addition, it is shown that the shape of the crystal-melt interface is not the parameter determining the dominant type of point defects. Therefore, a new aspect of the formation behavior of point defects is discussed in terms of asymmetry of the melt temperature distributions. (c) 2006 Elsevier B.V. All rights reserved
Remediation of Groundwater contaminated with nitrate and phosphate using Micellar-Enhanced Ultrafiltration
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