• Patent21
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• s.54
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• pp.20-30
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• 2004

• The KIPS Transactions:PartD
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• v.11D no.1
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• pp.23-30
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• 2004

In order to approximate the spatial query result size we partition the input rectangles into subsets and estimate the query result size based on the partitioned spatial area. In this paper we examine query result size estimation in skewed data. We examine the existing spatial partitioning techniques such as equi-area and equi-count partitioning, which are analogous to the equi-width and equi-height histograms used in relational databases, and examine the other partitioning techniques based on spatial indexing. In this paper we propose a new spatial partitioning technique based on the Hilbert space filling curve. We present a detailed experimental evaluation comparing the proposed technique and the existing techniques using synthetic as well as real-life datasets. The experiments showed that the proposed partitioning technique based on the Hilbert space filling curve achieves better query result size estimation than the existing techniques for space query size, bucket numbers, skewed data, and spatial data size.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.8 s.350
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• pp.35-43
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• 2006

In the paper, we propose a new method for power optimization that uses path balancing based on stochastic estimation of glitch in Statistical Static Timing Analysis (SSTA). The proposed method estimates the probability of glitch occurrence using tightness probability of each node in timing graph. In addition, we propose efficient gate sizing technique for glitch reduction using accurate calculation of sizing effect in delay considering probability of glitch occurrence. The efficiency of proposed method has been verified on ISCAS85 benchmark circuits with $0.16{\mu}m$ model parameters. Experimental results show up to 8.6% of accuracy improvement in glitch estimation and 9.5% of optimization improvement.

• Journal of the Korea Society of Computer and Information
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• v.19 no.4
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• pp.17-24
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• 2014

Detecting data races is important for debugging shared-memory programs with nested parallelism, because races result in unintended non-deterministic executions of the program. It is especially important to detect the first occurred data races for effective debugging, because the removal of such races may make other affected races disappear or appear. Previous dynamic detection tools for first race detecting can not guarantee that detected races are unaffected races. Also, the tools does not consider the nesting levels or need support of other techniques. This paper suggests a post-mortem tool which collects candidate accesses during program execution and then detects the first races to occur on the program after execution. This technique is efficient, because it guarantees that first races reported by analyzing a nesting level are the races that occur first at the level, and does not require more analyses to the higher nesting levels than the current level.

• The Transactions of the Korea Information Processing Society
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• v.6 no.6
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• pp.1468-1480
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• 1999

In database systems, join operations are the most complex and time consuming ones which limit performance of such system. Many parallel join algorithms have been proposed for the systems. However, they did not consider data skew, such as attribute value skew (AVS) and join product skew (JPS). In the skewness environments, performance of framework for a uniform load distribution and an efficient parallel join algorithm using the framework to handle AVS and JPS. In our algorithm, we estimate data distributions of input and output relations of join operations using the sampling methodology and evaluate join cost for the estimated data distributions. Finally, using the histogram equalization method we distribute data among nodes to achieve good load balancing among nodes in the local joining phase. For performance comparison, we present simulation model of our algorithm and other join algorithms and present the result of some simulation experiments. The results indicate that our algorithm outperforms other algorithms in the skewed case.

• The Transactions of the Korea Information Processing Society
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• v.5 no.5
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• pp.1151-1161
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• 1998

In this paper, we are considering a heterogeneous processor system in which each processor may have different performance and reliability characteristics. In other to fully utilize this diversity of processing power it is advantageous to assign the program modules of a distributed program to the processors in such a way that the execution time of the entire program is minimized. This assignment of tasks to processors to maximize performance is commonly called load balancing, since the overloaded processors can perform their own processing with the performance degradation. For the task assignment problem, we propose a new objective function which formulates this imbalancing cost. Thus the task assignment problem is to be carried out so that each module is assigned to a processor whose capabilities are most appropriate for the module, and the total cost is minimized that sum of inter-processor communication cost and execution cost and imbalance cost of the assignment. To find optimal assignment is known to be NP-hard, and thus we proposed an efficient heuristic algorithm with time complexity $O(n^2m)$ in case of m task modules and n processors.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.11C
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• pp.140-147
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• 2001

In this paper, we propose a scheme of calculating resources\` costs for precomputation in QoS routing schemes. This scheme is effective in respect to the g1oba1 network utilization and the balanced use of network resources. We also propose a QoS routing scheme for transit and intra traffic in a large scale of domain-based network. For a domain in the network, the routing scheme first precomputes multiple paths between all pairs of ingress and egress border routers while considering balancing of the expected load and then selects paths with the probability of path selection. We, therefore, expect that the paths are better than any other paths in respect to reserving the network resources on paths. The routing scheme combines inter and intra domain routings seamlessly and uses the same cost calculation scheme. And for analysis of a load balancing cost calculation proposed a simulation is done.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.9
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• pp.1048-1057
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• 2012

In this paper, a new compact dual-band unequal power divider is suggested. Instead of the quarter wavelength transmission line(TX-line)s for the branches of the conventional Wilkinson's power divider, we use composite right- and left-handed(CRLH) phase-shift lines and can reduce the physical length. With the non-linear dispersion of the meta-meterial, each branch in the proposed divider is designed to have $+90^{\circ}$ and $-90^{\circ}$ at $f_1$ and $f_2$ respectively. To validate the proposed method, the performances of the circuit and full-wave simulation results are shown with the CRLH dispersion curve. The measurement results are compared with the simulation results. Also, the size reduction effect by the proposed scheme is addressed.

• Journal of the Korea Society of Computer and Information
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• v.19 no.6
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• pp.71-80
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• 2014

Employing PTAS to building minimum spanning tree for a large number of equal distribution input terminal nodes can be a effective way in execution time. But applying PTAS to building minimum spanning tree for tremendous unequal distribution node may lead to performance degradation. In this paper, a partial PTAS reflecting the scheme into specific node dense area is presented. In the environment where 90% of 50,000 input terminal nodes stand close together in specific area, approximate minimum spanning tree by our proposed scheme can show about 88.49% execution time less and 0.86%tree length less than by existing PTAS, and about 87.57%execution time less and 1.18% tree length more than by Prim's naive scheme. Therefore our scheme can go well to many useful applications where a multitude of nodes gathered around specific area should be connected efficiently as soon as possible.

• Geophysics and Geophysical Exploration
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• v.15 no.1
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• pp.23-32
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• 2012

The comparison between time-lapse seismic datasets is the most popular method in the reservoir monitoring. The method of extracting the changes only due to the change in the reservoir is the essential technique in the comparison of time-lapse seismic datasets. In the paper, the conventional cross-equalization approaches and an enhanced optimized approach have been tested and compared each other. As conventional approaches, the bandwidth equalization and phase rotation methods have been tested in frequency, time and mixed domains, respectively and their results were compared each other. In order to overcome the limit of the conventional approaches, which loses high frequency components, a new constrained optimum filtering method was proposed and experimented. The new constrained filtering method has shown the improvement in broadening the bandwidth of the components of reservoir changes by acquiring optimized match filter.