• Journal of environmental and Sanitary engineering
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• v.14 no.3
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• pp.39-53
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• 1999

This thesis is to analyze and assess a new refuse collection system that was based on the term of discharge based quantity and collection of refuse from the beginning on January 1, 1995.In the case study for the refuse collection policy of metropolitan Taegu city based on the year of operation, ie, before 1994, after 1995 and as of 1998, the refuse collection policy analyzed from current position and actual condition. The results of analysis as follows. In case of discharged refuse quantity was show 20.4% reduction than the operation was begun and more 5.8% reduction as of 1998.Under the operation of the refuse collection system, therefore, management of refuse and garbage, the reduction of discharged refuse, activation of refuse collection, Recycling and expansion of financial self-reliance increased efficiency of refuse collection system. In the conclusion, more perfect refuse collection system should be developed of implemented in the near future.

• Journal of Digital Contents Society
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• v.14 no.1
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• pp.51-57
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• 2013

Storage device based on Flash Memory have many attractive features such as high performance, low power consumption, shock resistance, and low weight, so they replace HDDs to a certain extent. An Storage device based on Flash Memory has FTL(Flash Translation Layer) which emulate block storage devices like HDDs. A garbage collection, one of major functions of FTL, effects highly on the performance and the lifetime of devices. However, there is no de facto standard for new garbage collection algorithms. To solve this problem, we propose File Clustering Algorithm. File Clustering Algorithm respect to update page from same file at the same time. So, these are clustered to same block. For this mechanism, We propose Page Allocation Policy in FTL and use MIN-MAX GAP to guarantee wear leveling. To verify the algorithm in this paper, we use TPC Benchmark. So, The performance evaluation reveals that the proposed algorithm has comparable result with the existing algorithms(No wear leveling, Hot/Cold) and shows approximately 690% improvement in terms of the wear leveling.

• Proceedings of the Korean Information Science Society Conference
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• 2006.06a
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• pp.202-204
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• 2006

최근 임베디드 시스템 개발이 활발히 진행되면서 비휘발성 메모리 요구가 커지고 있다. 이에 휴대가 용이하고, 접근시간이 빠르고, 전력소비가 적은 플래시 메모리가 많이 사용되고 있으나 상대적으로 느린 지움 시간과 지움 횟수의 한계, 플래시 메모리의 대용량화로 인한 느린 마운트 속도, 예상치 못한 파워차단으로 인한 데이터 손실 등 극복해야할 문제점이 있다. 본 논문에서는 이러한 문제점을 해결하기 위해 개발된 RFFS 파일 시스템에서 연산을 줄일 수 있는 GC(Garbage Collection) 수행 방법을 제안한다. RFFS 파일 시스템을 분석하고, 예상되는 연산시간을 토대로 한 GC 수행 부하를 줄이는 방법을 제안한다.

• Journal of KIISE:Computing Practices and Letters
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• v.13 no.6
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• pp.422-426
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• 2007

Personal mobile devices equipped with non-volatile storage such as MP3 player, PMP, cellular phone, and USB memory require safety for the stored data on the devices. One of the safety requirements is secure deletion, which is removing stored data completely so that the data can not be restored illegally. In this paper, we study how to design the secure deletion on Flash memory, commonly used as storage media for mobile devices. We consider two possible secure deletion policy, named zero-overwrite and garbage-collection respectively, and analyze how each policy affects the performance of Flash memory file systems. Then, we propose an adaptive file deletion scheme that exploits the merits of the two possible policies. Specifically, the proposed scheme applies the zero-overwrite policy for small files, whereas it employs the garbage-collection policy for large files. Real implementation experiments show that the scheme is not only secure but also efficient.

• Journal of Korea Multimedia Society
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• v.24 no.8
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• pp.1192-1201
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• 2021

This study focused on how to analyze the ICT policy formation process using social big data. Specifically, in this study, a method for quantifying variables that influenced policy formation using the concept of a policy triggering mechanism and elements necessary to present the analysis results were proposed. For the analysis of the ICT policy triggering mechanism, variables such as 'Scope', 'Duration', 'Interactivity', 'Diversity', 'Attention', 'Preference', 'Transmutability' were proposed. In addition, 'interpretation of results according to data level', 'presentation of differences between collection and analysis time points', and 'setting of garbage level' were suggested as elements necessary to present the analysis results.

• Proceedings of the Korean Information Science Society Conference
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• 2008.06b
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• pp.361-365
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• 2008

낸드 플래시 메모리를 저장매체로 사용하기 위해서는 제자리 덮어쓰기가 불가능하고 블록의 지움 횟수가 제한된다는 문제점을 해결해야 한다. 이러한 문제점을 해결하기 위해 지움 횟수 평준화를 지원하는 다양한 가비지 컬렉션 정책들이 연구되고 있다. 하지만 기존 정책들은 지움 횟수 평준화를 지원하기 위해 가비지 컬렉션이 수행될 때마다 전체 블록에 대해 지움 대상 블록을 선정하기 위한 클리닉 지표를 구하는 연산을 수행하여야 하고 이 연산들은 시스템의 성능을 저하시킨다. 본 논문은 블록당 지움 횟수의 분산과 블록들의 최대 지움 횟수에 따라 변경되는 임계값을 이용하여 전체 블록에 대한 클리닉지표를 구하는 연산을 수행하지 않으면서 지움 횟수 평준화를 제공한다. 가비지 컬렉션 시 분산이 임계값 보다 작을 때에는 Greedy 정책을 이용하여 지움 비용을 최소화하고, 분산이 임계값 보다 클때에는 최대 지움 횟수를 가진 블록을 지움 대상에서 제외하여 지움 횟수를 평준화시킨다. 제안된 방법은 전체 블록에 대한 클리닉 지표를 연산하는 과정을 제거하여 가비지 컬렉션 속도를 향상시킨다.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.04a
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• pp.647-650
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• 2009

IPTV(Internet Protocol Television)는 차별화된 초고속 광대역 네트워크를 기반으로 기존 TV의 단점을 보완하여 차세대 DTV 시장을 주도할 것으로 예상된다. IPTV의 저장용량이 증가하는 추세에 따라 SSD(Solid State Disk)가 NAND 플래시 메모리를 대체 할 것으로 예상된다. 본 논문에서는 IPTV의 저장장치인 SSD의 수명을 증가시키고 플래시메모리의 특성인 마모도 제한을 고려하지 않은 지움 정책(Garbage-Collection)을 사용하는 YAFFS(Yet Another Flash FileSystem)의 문제점을 해결하기 위해 블록을 내용기반 리스트로 관리하고 블록스왑을 사용하는 내용기반 지움 정책을 제안한다. 기존 파일시스템 보다 수명을 향상 시키는 내용기반 파일시스템을 설계 및 구현하여 성능을 분석하였다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.574-577
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• 2007

While disk can be overwritten on updating data, because flash memory can not be overwritten on updating data, new data are updated in new area. If data are frequently updated, garbage collection, which is achieved by erasing blocks, should be performed to reclaim new area. Hence, because the number of erase operations is limited due to characteristics of flash memory, every block should be evenly written and erased. However, if data with access locality are processed by cost benefit algorithm with separation of hot block and cold block, though the performance of processing is high, wear-leveling is not even. In this paper, we propose CB-MB (Cost Benefit between Multi Bank) algorithm in which hot data are allocated in one bank and cold data in another bank, and in which role of hot bank and cold bank is exchanged every period. CB-MB showed that its performance was similar to that of others for uniform workload, however, the method provides much better performance than that of others for workload of access locality.

• International journal of advanced smart convergence
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• v.10 no.1
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• pp.142-150
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• 2021

Open-channel SSD is a new type of Solid-State Disk (SSD) that improves the garbage collection overhead and write amplification due to physical constraints of NAND flash memory by exposing the internal structure of the SSD to the host. However, the host-level Flash Translation Layer (FTL) provided for open-channel SSDs in the current Linux kernel consumes host memory excessively because it use page-level mapping table to translate logical address to physical address. Therefore, in this paper, we implemente a selective mapping table loading scheme that loads only a currently required part of the mapping table to the mapping table cache from SSD instead of entire mapping table. In addition, to increase the hit ratio of the mapping table cache, filesystem information and mapping table access history are utilized for cache replacement policy. The proposed scheme is implemented in the host-level FTL of the Linux kernel and evaluated using open-channel SSD emulator. According to the evaluation results, we can achieve 80% of I/O performance using the only 32% of memory usage compared to the previous host-level FTL.

• Journal of the Korea Organic Resources Recycling Association
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• v.5 no.1
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• pp.53-61
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• 1997

This study was conducted to analysis citizen's attitude and style to the foodwaste from l0th Sept. to 30th Sept. in 1996. The research was used questionare method and analysis was used prequency analysis and cross table method by SPSS (scientific statistics). The foodwaste of householdwaste account for 24.8%, and the magnitude by the kinds of garbage were waste from pre-cocking stage, fruitshell, foodwaste remained after eating, septic foodwaste during storage. The more the housewives'age are young, foodwaste volumne were much. Most remained foodwaste after eating were soup and pot stew. The main cause of foodwaste production was overvolumne cooking. 88.8% of answers think that a menu can be useful to reduce foodwaste. The survey showed that 87.3% of answers put into the meter-rate bag after removed wetness of garbage. 84.1% of answers thought that the recycling of foodwaste needed, but the practical housewife was only 21%. For the suitable treatment of foodwaste, Survey showed that the consistent policy of goverment and continuous publicity was needed essentially, and that the public notice of TV or radio was effective. All of answers would like to participate in recycling of foodwastes whether public-posting or personal-posting. To set up vessel of posting at household, the proper purchase price and space of institution are needed, also the solution of sanitory & aesthetic problem and the collection of composting-product must be achieved smoothly.