• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.8
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• pp.2032-2041
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• 1998

In this work, we propose a novel bit allocation method that is to minimize overall distortions subject ot the bit rate constraint. We partition the original bitallocation problem into 'macroblock level bit allocation' problems that can be solved by conventional Lagrangian mutiplier methods and a 'frame level bit allocation' problem. To tackle the frame level problem, 'two-phase optimization' algorithm is used with iter-frame dependency model. While the existing approaches are almost impossible to find the macroblock-unit result for the moving picture coding system due to high computational complexity, the proposed algorithm can drastically reduce the computational loads by the problem partitioning and can obtain the result close to the optimal solution. Because the optimally allocated results can be used as a benchmark for bit allocation methods, the upper performance limit, or a basis for approximation method development, we expect that the proposed algorithm can be very useful for the bit allocation related works.

• The KIPS Transactions:PartD
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• v.14D no.6
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• pp.675-688
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• 2007

Memory access errors are frequently occurred in C programs. A number of tools and research works have been trying to detect the errors automatically. However, they have one or more of the following problems: inability to detect all memory errors, changing the memory allocation mechanism, incompatibility with libraries, and excessive performance overhead. In this paper, we suggest a new method to solve these problems, and then present a result of comparison to the previous research works through the experiments. Our approach consists of two phases. First is to transform source code at compile time through inserting instrumentation into the source code. And second is to detect memory errors at run time with a bitmap that maintains information about memory allocation. Our approach has improved the error detection abilities against the binary code analysis based ones by using the source code analysis technique, and enhanced performance in terms of both space and time, too. In addition, our approach has no problem with respect to compatibility with shared libraries as well as does not need to modify memory allocation mechanism.

• The Transactions of the Korea Information Processing Society
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• v.4 no.6
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• pp.1625-1635
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• 1997

An extension of the weighted buddy system, called the extended-weighted buddy system, for dynamic memory allocation in an object-oriented computer is presented. The extended-weighted buddy system allows block sizes of $2^k,\;3*2^k,\;5*2^k,\;7*2^k$, whereas the original weighted buddy system allowed block sizes of $2^k\;and\;3*2^k$. This extension is achieved at only the cost of additional 3 bits per block for memory management unit. Simulation results are presented which compare our method with the weighted buddy system. These results indicate that, for uniform request distributions, our system has less internal memory fragmentation than the weighted buddy system(approximately 60%). And, for exponential request distributions, it has less internal memory fragmentation than the weighted buddy method (approximately 50%). The external fragmentation is greater for this system than the weighted buddy system. But, our system has less total memory fragmentation for exponential request distributions, and two systems take a similar total memory fragmentation for uniform request distributions, so we can substitutes the extended-weighted buddy system for weighted buddy system.

• Journal of KIISE:Databases
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• v.36 no.5
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• pp.374-385
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• 2009

Flash memory becomes increasingly popular as data storage for various devices because of its versatile features such as non-volatility, light weight, low power consumption, and shock resistance. Flash memory, however, has some distinct characteristics that make today's disk-based database technology unsuitable, such as no in-place update and the asymmetric speed of read and write operations. As a result, most traditional disk-based database systems may not provide the best attainable performance on flash memory. To maximize the database performance on flash memory, some approaches have been proposed where only the changes made to the database, i.e., logs, are written to another empty place that has born erased in advance. In this paper, we propose an efficient log management scheme for flash-based database systems. Unlike the previous approaches, the proposed approach stores logs in specially allocated blocks, called log blocks. By evenly distributing logs across log blocks, the proposed approach can significantly reduce the number of write and erase operations. Our performance evaluation shows that the proposed approaches can improve the overall system performance by reducing the number of write and erase operation compared to the previous ones.

• The Transactions of the Korea Information Processing Society
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• v.6 no.4
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• pp.1098-1105
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• 1999

The caches in distributed shared memory systems enhance the performance by reducing memory access latency and communication overhead, but they must solve the cache coherence problem. This paper proposes a new directory protocol to solve the cache coherence problem and to improve the system performance in distributed shared memory systems. To maintain the cache coherence of shared data, processors within a limited distance reduce the communication overhead by using a bit-vector like the full directory scheme. Processors over a limited distance store pointers in a directory pool. Since the bit-vector and the directory pool remove the unnecessary cache invalidations, the proposed scheme reduces the communication traffic and improves the system performance. The dynamic limited directory scheme reduces the communication traffic up to 66 percents compared with the limited directory scheme and the number of directory access up to 27 percents compared with the dynamic pointer allocation scheme.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.4
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• pp.642-648
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• 2006

In this paper, I have proposed a secure dynamic ID allocation protocol using mutual authentication on the RFID tag. Currently, there are many security protocols focused on the low-price RFID tag. The conventional low-price tags have limitation of computing power and rewritability of memory. The proposed secure dynamic ID allocation protocol targets to the high-performance RFID tags which have more powerful performance than conventional low-price tag by allocating a dynamic ID to RFID using mutual authentication based on symmetric encryption algorithm. This protocol can be used as a partial solution for ID tracing and forgery.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.15 no.6
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• pp.49-58
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• 2005

In this paper, we have proposed a secure dynamic ID allocation protocol using mutual authentication on the RFID tag. Currently, there are many security protocols focused on the low-price RFID tag. The conventional low-price tags have limitation of computing power and rewritability of memory. The proposed secure dynamic ID allocation protocol targets to the high-performance RFID tags which have more powerful performance than conventional low-price tag by allocating dynamic ID to RFID using mutual authentication based on symmetric encryption algorithm. This protocol can be used as a partial solution for ID tracing and forgery.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.2
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• pp.1-6
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• 2017

Due to the recent advances in IoT technologies, reducing power consumption in battery-based IoT devices becomes an important issue. An IoT device is a kind of real-time systems, and processor voltage scaling is known to be effective in reducing power consumption. However, recent research has shown that power consumption in memory increases dramatically in such systems. This paper aims at combining processor voltage scaling and low-power NVRAM technologies to reduce power consumption further. Our main idea is that if a task is schedulable in a lower voltage mode of a processor, we can expect that the task will still be schedulable even on slow NVRAM memory. We incorporate the NVRAM memory allocation problem into processor voltage scaling, and evaluate the effectiveness of the combined approach.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.10B
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• pp.1648-1664
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• 2000

This paper proposes a real-time dynamic storage allocation algorithm QSHF(quick-segregated-half-fit) that provides various memory allocation policies. that manages a free block list per each word size for memory requests of small size good(segregated)-fit policy that manages a free list per proper range size for medium size requests and half-fit policy that manages a free list per proper range size for medium size requests and half-fit policy that manages a free list per each power of 2 size for large size requests. The proposed algorithm has the time complexit O(1) and makes us able to easily estimate the worst case execution time(WCET). This paper also suggests two algorithm that finds the proper free list for the requested memory size in predictable time and if the found list is empty then finds next available non-empty free list in fixed time. In order to confirm efficiency of the proposed algorithm we simulated the memory utilization of each memory allocation policy. The simulation result showed that each policy guarantees the constant WCET regardless of memory size but they have trade-off between memory utilization and list management overhead.

• Journal of the Korea Computer Graphics Society
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• v.14 no.1
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• pp.27-33
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• 2008

Mobile systems have relatively limited resources such as low memory, slow CPU, or low power comparing to desktop systems. In this paper, we present a new 3D mesh connectivity coding algorithm especially optimized for mobile systems(i.e., mobile phones). By using adaptive octree data structure for vertex positions, a new distance-based connectivity coding is proposed. Our algorithm uses fixed point arithmetic and minimizes dynamic memory allocation, appropriate for mobile systems. We also demonstrate test data to show the utility of our mobile 3D mesh codec.