• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2010년도 추계학술대회
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• pp.434-437
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• 2010

시그니처 기반 필터링(Signature based filtering)은 이미 알려진 공격으로부터 방어하는 방법으로, 침입방지 시스템을 통과하는 패킷의 페이로드와 시그니처라 불리는 공격 패턴들과 비교하여 같으면 그 패킷을 폐기한다. 그러나 시그니처의 개수가 증가함에 따라 하나의 들어온 패킷에 대하여 요구되는 패턴 매칭 시간은 증가하게 되어 패킷의 지연현상이 발생한다. 고성능 침입방지 시스템을 위해서는 보다 효율적인 패턴 매칭 알고리즘이 필요하며, 패턴 매칭의 수행 성능 향상을 위해 가장 중요한 부분은 처리해야 하는 패킷이 도착했을 때, 해당 패킷의 데이터를 룰의 시그니처와 비교하는 횟수를 줄이는데 있다. 이에 본 논문에서는 고성능 침입방지 시스템의 개발을 위해 기존의 제안된 시그니처 해싱 기반의 침입방지 시스템에 패킷 분류를 위한 다차원 검색을 튜플 공간이라는 이차원 공간을 이용하여 검색하는 튜플 공간 패킷 분류 알고리즘과 블룸 필터를 적용한 패턴 매칭 방법을 제안한다.

• 한국산업융합학회 논문집
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• 제27권2_2호
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• pp.475-485
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• 2024

In many regions of Korea, including the Four Major Rivers, the seriousness of the problem of algal blooms due to eutrophication of water quality is being raised.In this study, in order to solve these social problems, we manufactured a filter using natural mineral fusion (red illite, zeolite, germanium ceramic, selenium ceramic, carbon ceramic) and independently developed a tank system for green algae experiments to observe and determine the stages of change in water quality. In order to study ways to improve water quality through quantitative analysis, 1 ton of severely polluted green algae water from the Nak dong River region was stored in a water tank and exposed to ultraviolet rays in the same environment as the Nak dong River. Then, the same environment as the Nak dong River was created. The results were derived from a 5-week water quality test. The results of this experiment confirmed that green-colored cyano bacteria were significantly reduced just by the turbidity results. The results were obtained through a request to the Korea Testing & Research Institute located in Changwon-si, Gyeong sang nam-do. CI-(chlorine ion) and NH3-N(ammonia nitrogen) had the effect of saving every week. The device used in this study was made of natural minerals free of heavy metals that are harmless to the human body and nature through long-term consideration and exploration to kill and prevent various strains living in water. Green purification system using natural hydrogen generating mineral filter were effective a non-chemical and physical methods. The results of this study are one way to contribute to the serious problems caused by green algae in many countries, and will contribute to the water quality environment by preventing the waste of environmental resources, improving the health of the people, and increasing the ability to purify environmental water quality at home and abroad.

• 생태와환경
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• 제41권3호
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• pp.367-373
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• 2008

유해남조의 생물학적 제어를 위한 연구의 일환으로 북한강수계(가평)에 서식하는 이매패 말조개(Unio douglasiae)의 섭식특성을 조사하였다. 섭식실험은 크게 시간별, 개체크기, 동물밀도, 먹이밀도 (엽록소-a 농도) 등에 따라 패류의 여과율 및 배설물 생산량을 각각 측정하였다. 말조개의 여과율은 섭식 후 적용 7시간째 (0.21 L $g^{-1}h^{-1}$, 0.54 mg $g^{-1}h^{-1}$), 크기 5 cm보다 작은 개체에서 최고 여과율 및 배설물 생산량 (5.89 L $g^{-1}h^{-1}$, 16.38 mg $g^{-1}h^{-1}$)을 각각 나타냈다. 또한 가장 낮은 먹이밀도 (엽록소-a 88.5 ${\mu}gL^{-1}$)에서 0.41 L $g^{-1}h^{-1}$로 최고 여과율을 보였으며, 일정 먹이농도 이상에서는 배설물 생산량이 증가하지 않는 것으로 나타났다. 또한 패류의 조류 제어효과는 개체 밀도가 증가할수록 뚜렷한 효과를 나타냈다. 결국 이상의 결과들은 북한강에 서식하는 이매패 말조개가 부영양호수의 남조류 제어의 유용생물로서 적용 가능성을 입증하였다.

• 한국수자원학회논문집
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• 제55권4호
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• pp.301-308
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• 2022

조류는 수생태계에서 소비자의 에너지를 공급하여 생태계 내 없어서는 안 될 1차 생산자로서 크게 녹조류, 남조류, 규조류로 나뉘어진다. 남조류의 경우 수온이 상승하여 여름철 발생하여 과대 증식하여 녹조현상의 주원인이 되며, 최근 기후 변화로 인해 녹조현상의 발생시기의 변화와 빈도수가 늘고 있는 추세이다. 기존의 조류 조사 방식은 채수 및 센서를 통한 측정으로 이루어지고 있으며 시간, 비용 및 인력의 한계가 나타난다. 이러한 기존 모니터링 방법의 한계를 극복 하기위해 위성영상이나 무인항공기(Unmanned Aearial Vehicles, UAV), 등 탑제체를 운용한 다중분광 및 초분광과 같은 분광기기를 이용하여 원격 모니터링을 수행하는 연구가 진행되어 왔다. 본 연구에서는 조류 배양액 및 하천수 채수를 통한 실험실 규모의 실험을 통해 원격 모니터링의 종 구분에 대한 가능성에 대하여 확인 해보고자 하였다. 초분광 영상을 취득하기 위해 400-1000 nm에서 분석할 수 있는 초분광 센서를 활용하였다. 채수한 하천수의 조류 종 구분을 위한 분광특성을 추출하기 위해 GF/C필터를 이용하여 여과를 진행하여 시료를 제조하여 영상을 수집하였다. 수집된 영상을 방사보정 및 Base (하천수 및 배양보존액 통칭) 제거를 진행하였고 조류의 분광 정보 추출 과정을 통해 시료별 분광 정보를 추출, 분석하여 조류의 분광특성을 파악, 비교분석하여 하천·호소에서의 초분광영상 기반 원격탐사 모니터링의 적용성을 검토하고자 하였다.

• 상하수도학회지
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• 제27권4호
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• pp.439-444
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• 2013

Excessive phosphorus in aquatic systems causes algal bloom resulting in eutrophication, DO depletion, decline in recreational value of water and foul tastes. To treat wastewater containing phosphorus including effluent of wastewater treatment plant, the continuous experiments were performed by using electrochemical way. The spherical ZVI and silica sand which act as physical filter are packed at appropriate volume ratio of 1:2. Electric potential is applied externally which can be changed as per the operational requirement. The results indicate that optimum hydraulic retention time of 36 minutes (10 mL/min at 1 L reactor) was required to meet the effluent standards. Lower concentrations of phosphorus (<10 mg/L as phosphate) were removed by precipitation by contact with iron. Thus, additional electric potential was not required. In order to remove high concentration phosphorus around 150 mg/L as phosphate, external electric potential of 600 V was applied to the reactor.

• 한국인터넷방송통신학회논문지
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• 제20권2호
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• pp.179-185
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• 2020

DRAM은 메인 메모리 시스템을 구성하는 주요한 요소로서 운영체제의 발전, 응용 프로그램의 복잡도와 용량의 증가에 맞추어 DRAM의 용량과 속도 역시 증가하는 추세이다. DRAM은 주기적으로 저장된 값을 읽은 후 다시 저장하는 리프레시 동작을 수행해야 하며, 이에 수반되는 성능 및 파워/에너지 오버헤드는 용량이 증가할수록 더 악화되는 특성을 내재하고 있다. 본 연구는 전하의 보존 시간이 가장 낮은 셀들에 대해서 블룸 필터를 사용하여 64ms, 128ms 이내에 리프레시를 수행해야 하는 로우들을 효율적으로 저장하여 선택적 리프레시를 수행하는 에너지 효율 향상 기법을 제안한다. 실험 결과에 따르면 제안 기법을 통하여 평균 5.5%의 성능 향상이 있었으며, 리프레시 에너지는 평균 76.4% 절감되었고, 평균 EDP는 10.3% 절감된 것으로 나타났다.

• 한국컴퓨터정보학회논문지
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• 제22권3호
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• pp.9-16
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• 2017

In recent computing systems, LRU replacement policy has been widely used because it can be simply implemented and applicable to most programs. However, if the working set size of the program is bigger than the actual cache size, LRU replacement policy may occur thrashing problem. Thrashing problem means that cache blocks are consistently replaced without re-referencing in the cache. This paper proposes a new cache management scheme to solve the thrashing problem in the second-level cache. The proposed scheme measures per set reuse frequency using EAF structure to find thrashing sets. When the cache miss occurs, it tests whether the address of the missed block is stored or not. If the address of the missed block is stored, it means that the recently evicted block is re-requested, so the reuse frequency is predicted high. In this case, the corresponding counter of the set is increased. When the counter value is bigger than the threshold value, we assume that the corresponding set shows high reuse frequency. The proposed scheme assigns the set with high reuse frequency to the additional small size cache to keep the blocks in the cache for a long time. Our experimental results show that the proposed scheme improves the IPC by 3.81% on average.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권7호
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• pp.2512-2531
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• 2014

We propose a new Distributed Denial of Service (DDoS) defense mechanism that protects http web servers from application-level DDoS attacks based on the two methodologies: whitelist-based admission control and busy period-based attack flow detection. The attack flow detection mechanism detects attach flows based on the symptom or stress at the server, since it is getting more difficult to identify bad flows only based on the incoming traffic patterns. The stress is measured by the time interval during which a given client makes the server busy, referred to as a client-induced server busy period (CSBP). We also need to protect the servers from a sudden surge of attack flows even before the malicious flows are identified by the attack flow detection mechanism. Thus, we use whitelist-based admission control mechanism additionally to control the load on the servers. We evaluate the performance of the proposed scheme via simulation and experiment. The simulation results show that our defense system can mitigate DDoS attacks effectively even under a large number of attack flows, on the order of thousands, and the experiment results show that our defense system deployed on a linux machine is sufficiently lightweight to handle packets arriving at a rate close to the link rate.

• 한국물환경학회지
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• 제25권4호
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• pp.597-605
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• 2009

Algae bloom occurred in reservoir in summer can cause taste and odor in water and disturb the flocculation and sedimentation processes in water treatment plant and cause sand filter plugging. It was also reported that microcystins, anatoxin and saxitoxin released from cyanobacteria had acute toxic effects on liver and nervous system. For these reasons, many advanced countries inclusive of WHO set the guideline for these toxins and cyanotoxins have been managed with regular monitoring in Korea as well. However, complex sample preparation steps such as a solid phase extraction (SPE) and derivatization are required with an existing analysis method with HPLC. We needed to improve an analysis method for low extraction efficiency and long sample preparation time. In this study, we have established a new LC/MS/MS method which can simultaneously determine 6 cyanotoxins (Microcystins-LR, Microcystins-RR, Microcystins-YR, Anatoxin-a, Saxitoxin, Neosaxitoxin) with only simple filtration step. When $75{\mu}L$ filterated sample was injected onto the LC-MS/MS, the recovery ranged from 86% to 112% and the MDL was $0.025{\sim}0.581{\mu}g/L$. We can make the MDL be lower than the guideline ($1{\sim}3{\mu}g/L$) of advanced countries with simple preparation.

• Journal of Communications and Networks
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• 제13권2호
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• pp.187-200
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• 2011

We present the design and implementation of a novel anti-malware system called SplitScreen. SplitScreen performs an additional screening step prior to the signature matching phase found in existing approaches. The screening step filters out most non-infected files (90%) and also identifiesmalware signatures that are not of interest (99%). The screening step significantly improves end-to-end performance because safe files are quickly identified and are not processed further, and malware files can subsequently be scanned using only the signatures that are necessary. Our approach naturally leads to a network-based anti-malware solution in which clients only receive signatures they needed, not every malware signature ever created as with current approaches. We have implemented SplitScreen as an extension to ClamAV, the most popular open source anti-malware software. For the current number of signatures, our implementation is $2{\times}$ faster and requires $2{\times}$ less memory than the original ClamAV. These gaps widen as the number of signatures grows.