• Journal of information and communication convergence engineering
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• v.12 no.3
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• pp.181-185
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• 2014

The lifetime of a solid-state drive (SSD) is limited because of the number of program and erase cycles allowed on its NAND flash blocks. Data cannot be overwritten in an SSD, leading to an out-of-place update every time the data are modified. This result in two copies of the data: the original copy and a modified copy. This phenomenon is known as write amplification and adversely affects the endurance of the memory. In this study, we address the issue of reducing wear leveling through efficient handling of write requests. This results in even wearing of all the blocks, thereby increasing the endurance period. The focus of our work is to logically divert the write requests, which are concentrated to limited blocks, to the less-worn blocks and then measure the maximum number of write requests that the memory can handle. A memory without the proposed algorithm wears out prematurely as compared to that with the algorithm. The main feature of the proposed algorithm is to delay out-of-place updates till the threshold is reached, which results in a low overhead. Further, the algorithm increases endurance by a factor of the threshold level multiplied by the number of blocks in the memory.

• IE interfaces
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• v.16 no.3
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• pp.332-343
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• 2003

This paper deals with pre-erection scheduling and erection scheduling in shipbuilding. Among shipbuilding scheduling, the ship erection scheduling in a dock is one of the most important since the dock is the most critical resource in a shipyard. However, it is more reasonable to consider pre-erection scheduling and erection scheduling as unified because they compete with the common constrained resources such as labor, crane, space, and so on. It is very hard to consider two scheduling problems simultaneously, and hence, we approach them sequentially. At first, we propose space resource leveling heuristics in pre-erection scheduling given erection date. And then, considering the manpower resource determined by pre-erection scheduling, we also propose manpower resource leveling heuristics in erection scheduling. Various experimental results with real world data show that the proposed heuristics have good performance in terms of scheduling quality and time.

• Journal of Ship and Ocean Technology
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• v.10 no.2
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• pp.37-44
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• 2006

The erection in shipbuilding is the process to assemble all the blocks one by one in certain order and requires more leveled and efficient schedule than other processes do. However, erection schedule includes too many constraints to be systemized with simple programs and constraints are changed frequently. These difficulties make it rare to find automatic erection schedule generation system with load leveling ability. In this paper, a CSP (Constraint Satisfaction Problem)-based load leveling algorithm using a maximum load diminution technique is proposed and applied to the block erection scheduling of a dock in a shipyard. The result shows that it performs better than currently used scheduling method based on empirical logics. The maximum load of welding length and crane usage are reduced by 31.63% and 30.00% respectively. The deviation of resource usage amount also decreases by 8.93% and 7.51%.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2004.11a
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• pp.575-578
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• 2004

Since a construction project is a series of works that utilizes resources to accomplish the project goal for a given time period, efficient resource management is a prerequisite for the success of the project. Two major areas of resource management are resource constrained scheduling focusing on the limited resource availability and resource leveling focusing on smoothing resource usage pattern on the fixed project completion time. It is not available, however, to apply both techniques to a project at the same time. This paper proposes a model to enhance the minimum moment algorithm of resource leveling, aiming to find an efficient usage of resources and an appropriate project completion time. A survey is performed to evaluate the major five factors using the AHP.

• IEMEK Journal of Embedded Systems and Applications
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• v.12 no.3
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• pp.185-192
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• 2017

Due to the characteristics of low power, high durability and high density, NAND flash memory is being heavily used in various type of devices such as USB, SD card, smart phone and SSD. On the other hand, because of another characteristic of flash cell with the limited number of program/erase cycles, NAND flash memory has a short lifetime compared to other storage devices. To overcome the lifetime problem, many researches related to the wear leveling have been conducted. This paper presents a method called a TCB (Tracking Cold Blocks) using more reinforced constraint conditions when classifying cold blocks than previous works. TCB presented in this paper keeps a MCT (Migrated Cold block Table) to manage the enhanced classification process of cold blocks, with which unnecessary migrations of pages can be reduced much more. Through the experiments, we show that TCB reduces the overhead of wear leveling by about 30% and increases the lifetime up to about 60% compared to BET and BST.

• IEMEK Journal of Embedded Systems and Applications
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• v.12 no.3
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• pp.149-157
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• 2017

In this paper, we propose BCMR (Block Classification with Monitor and Restriction) to ensure the isolation and to reduce the interference of blocks between a garbage collection and a wear leveling. The proposed BCMR monitors an endurance variation of blocks during the garbage collection and detects hot blocks by making a restriction condition based on this information. The proposal induces a block classification by its update frequency for the garbage collection and the wear leveling, so we will get a prolonged lifetime of NAND flash memory systems. In a performance evaluation, BCMR prolonged the lifetime of NAND flash memory systems by 3.95%, on average and reduced a standard deviation per block by 7.4%, on average.

• Korean Journal of Geomatics
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• v.5 no.1
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• pp.43-49
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• 2005

It is well known that GPS technique can be used for high accuracy leveling positioning if a precise geoid model is available to use at a surveying point. In this study, KOGD2003 geoid model was developed in and around Korean peninsula and this geoid model could be achieved by combining GPS/leveling data with the formerly developed KOGD2002. To this end, the software for orthometric height obtaining and geodetic datum transformation has been implemented with the visual C++ language, what we called GPS-GeoL v.1.0. In order to evaluate the performance and the accuracy of the software, GPS field tests were carried out in the Korean second-order leveling network over Chollabukdo area. Results of the tests have shown that the mean value of the differences between outputs of the software developed in this research and officially announced orthometric heights by NGII (National Geographic Information Institute) was 0.0221 m and also those of RMS was 0.0332 m. Therefore, it was possible to conclude that the KOGD2003 and GPS-GeoL v.1.0 software could be used to determine orthometric heights for civil construction field applications with cm-level accuracy.

• Proceedings of the Korean Information Science Society Conference
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• 2007.06b
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• pp.321-326
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• 2007

최근 휴대전화 디지털 카메라, 랜 스위치, 디지털 셋톱박스, 휴대용 MP3 플레이어, 노트북용 PC 카드, 내장 기기의 펌웨어 등 플래시 메모리의 활용이 증가하고 있다. 하지만 기존 저장 장치와 달리 플래시 메모리는 특정 블록에 쓰기 연산을 하기 전에 해당 블록은 미리 소거(erase-before-write)되어 있어야 하는 제약이 있으며, 각 블록은 소거될 수 있는 횟수가 제한적이다. 이런 단점들은 플래시 메모리가 대용량화됨에 따라 중요한 문제로 대두되고 있다. 이런 각 블록에 대한 소거 횟수의 제한을 해결하기 위하여 소거 횟수 평준화 기법(wear-leveling) 기법이 필수적이다. 본 논문에서는 블록의 소거 횟수의 한계를 극복하기 위한 새로운 소거 횟수 평준화 기법으로 전체 블록에 대한 소거 횟수 레벨을 두어 소거 횟수 평준화를 이루는 KM-평준화(KM-leveling)를 제안한다. KM-평준화는 소거 횟수 평준화를 위한 전체 블록의 계산 비용을 최소화하고 블록에 대한 소거 레벨을 두어 적은 공간을 사용하는 효율적인 기법이다. 본 논문은 M값 범위 이내에 각 블록의 소거 횟수들이 존재하도록 보장하는 KM-평준화를 제안한다.

• Journal of the Korea Institute of Military Science and Technology
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• v.23 no.5
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• pp.502-515
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• 2020

To identify the dynamic characteristics of the Auto-leveling system applied to the Tractor-Trailer type Transporter for mounting a large scale precision equipment, Dynamics Modeling & Simulation were performed using general Dynamics Analysis Program - RecurDyn(V9R2). The axial load data, transverse load data and pad trace data of leveling actuators were obtained from M&S. And they were analyzed and compared with each other by parameters, i.e. friction coefficients on the ground, landing ram speed of actuators, and direction & quantity of ground slope. It was observed that ground contact friction coefficients affected to transverse load and pad trace; the landing ram speed of actuators to both amplitude of axial & transverse load, and this phenomena was able to explain from the frequency analysis of the axial load data; the direction of ground slope to driving sequence of landing ram of actuators. But the dynamic behaviors on the two-directional slope were very different from them on the one-directional slope and more complex.

• Journal of the Korea Institute of Building Construction
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• v.7 no.4
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• pp.125-132
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• 2007

The use of Self-Leveling material is increasing recently. This paper assesses the quality of surface layer of concrete floor when Self-Leveling material is defective. The paper shows how to predict the defect of SL material before construction begins. The relationship between the quality of surface layer of concrete floor and the defect of SL material was determined and the quality of surface layer of concrete floor was then estimated. The relations between the quality of surface layer and the defect of SL material were determine considering surface strength, moisture, and consistency of surface layer. Absorbing amount was used as the indicator of consistency and the absorbing amount of test material was measured. Then the relations between the test material and surface strength were determined. Generally concrete floor with greater consistency has greater surface strength, however in this study, we hound that high impact concrete floor could have lower surface strength as the consistency gets bigger. The relations between the level of defect occurred in SL material and the quality of surface layer were examined and we clarified that the surface layer with lower consistency gets higher possibility to occur exfoliation in early stage, one or two weeks after constructing SL material. When the consistency is sufficient, the occurring situation of defect depends upon the moisture of surface layer. Little amount of moisture gets higher possibility not to occur the defect. As the amount increases, fissure generates and early exfoliation may occur. In addition, the level of fissure is highly related with the surface strength.