• 전기학회논문지
• /
• 제65권3호
• /
• pp.371-381
• /
• 2016

This paper presents a study on reliability assessment and new contribution function development of power system including Wind Turbine Generator(WTG) combined with Battery Energy Storage System(BESS). This paper develops and proposes new reliability contribution function of BESS installed at wind farms. The methodology of reliability assessment, using Monte Carlo Simulation(MCS) method to simulate sample state duration, is proposed in detail. Forced Outage Rate(FOR) considered probabilistic approach for conventional generators is modelled in this paper. The penetration of large wind power can make risk to power system adequacy, quality and stability. Although the fluctuation of wind power, BESS installed at wind farms may smooth the wind power fluctuation. Using small size system as similar as Jeju island power system, a case study of reliability evaluation and new proposed contribution function of power system containing WTG combined with BESS is demonstrated in this paper, which would contributes to BESS reliability contribution and assessment tools of actual power system in future.

• Journal of Communications and Networks
• /
• 제16권4호
• /
• pp.397-406
• /
• 2014

Radio frequency (RF) jamming is a denial of service attack targeted at wireless networks. In resource-hungry scenarios with constant traffic demand, jamming can create connectivity problems and seriously affect communication. Therefore, the vulnerabilities of wireless networks must be studied. In this study, we investigate a particular type of RF jamming that exploits the semantics of physical (PHY) and medium access control (MAC) layer protocols. This can be extended to any wireless communication network whose protocol characteristics and operating frequencies are known to the attacker. We propose two efficient jamming techniques: A low-data-rate random jamming and a shot-noise based protocol-aware RF jamming. Both techniques use shot-noise pulses to disrupt ongoing transmission ensuring they are energy efficient, and they significantly reduce the detection probability of the jammer. Further, we derived the tight upper bound on the duration and the number of shot-noise pulses for Wi-Fi, GSM, and WiMax networks. The proposed model takes consider the channel access mechanism employed at the MAC layer, data transmission rate, PHY/MAC layer modulation and channel coding schemes. Moreover, we analyze the effect of different packet sizes on the proposed jamming methodologies. The proposed jamming attack models have been experimentally evaluated for 802.11b networks on an actual testbed environment by transmitting data packets of varying sizes. The achieved results clearly demonstrate a considerable increase in the overall jamming efficiency of the proposed protocol-aware jammer in terms of packet delivery ratio, energy expenditure and detection probabilities over contemporary jamming methods provided in the literature.

• Spatial Information Research
• /
• 제19권1호
• /
• pp.107-116
• /
• 2011

최근 무선 인터넷 환경의 발달로 실시간 교통정보안내와 지도를 통해 목적지까지의 경로 안내를 해주는 차량 항법 서비스 등 공간 데이터를 활용한 위치기반서비스가 증가되고 있다. 하지만, 현재 시스템 환경에서는 대용량의 공간 데이터를 파일 시스템 기반으로 관리하기 때문에 실시간적인 데이터 저장과 관리측면에서 많은 제약을 가진다. 이를 보완하기 위해 임베디드 데이티베이스를 바탕으로 대용량의 공간 데이터를 구조적으로 관리할 수 있는 연구가 요구된다. 이에 본 연구는 임베디드 시스템에서 대용량의 공간 데이터의 효율적인 저장을 위해 데이터베이스에 적용 가능한 바이트패킹과 Lempel-Ziv 압축기법을 혼합 개선한 무손실 압축 기법을 제시하고자 하였다. 이렇게 제시된 공간 데이터 압축 기법을 실제 대도시권 데이터(서울 인천)에 적용하여 실험해 보고 농일 데이터에 대하여 실험을 통해 재구성이 되기까지의 질의 처리 시간을 분석을 통해 선행 연구에서 제시한 방법을 적용한 결과와 비교 하였다. 연구결과로 본 연구에서 제시된 압축 방법이 높은 위치 정확도를 요구하는 데이터에 대해 더 나은 성능을 보이는 것을 획인 할 수 있었다.

• 대한조선학회논문집
• /
• 제55권5호
• /
• pp.371-378
• /
• 2018

Internal detonation of a warhead inside a compartment of naval vessel can result in serious blast damages including plastic deformation and rupture of the structural members especially bulkhead due to the huge explosive impact pressure, fragments and high temperature flame. To secure watertight integrity and to prevent the domino-type flooding of neighbouring compartments caused by the rupture of bulkheads, it is necessary to develop the structural design technology of Blast Hardened Bulkheads(BHB) which can resist the blast impact pressure of threatening weapons to increase the survivability of naval vessels. This study dealt with the simplified structural response analysis of BHB under impact pressure of confined explosion and aimed to develop the efficient and rational design method of BHB and joint structures which can be applied at initial design stage. The present 1st report dealt with the phenomena of explosive detonation surveying the preceding experimental/theoretical research and the characteristics of time history of blast pressure including the peak value and duration time were examined. And to predict the large plastic deformation behaviors of BHB by the huge blast pressure reasonably, the plastic hinge method including the membrane effects was formulated. It was applied to the simplified structural design equations. The following report will deal with the application and adjustment process of the structural scantling equations to the actual BHB design and verification of validity of them.

• 한국건축시공학회지
• /
• 제13권4호
• /
• pp.341-350
• /
• 2013

본 연구에서는 창호철물 공사의 하자발생 원인을 제도(System), 설계, 시공 3가지 측면에서 제도 미비(공사시방서 작성능력 부족등), 창호철물의 중요성에 대한 사회적 인식부족, 설계도면 작성 기술력 부족, 설계비 저가등 7가지를 도출하였다. 도출된 7가지 원인 중 창호철물 공사의 하자 발생에 높은 영향을 미치는 원인은 제도 미비(공사시방서 작성능력 부족), 설계도면 작성 기술력 부족이 각각 1순위, 2순위로 나타났다. 또한 이러한 하자발생 원인이 실제 프로젝트에서 건축사사무소와 시공사의 규모에 따라 어떻게 분포하는지와 시공품질에 미치는 영향을 분석 제시함으로써 향후 창호철물공사 하자방지 방안 마련을 위한 기초 연구를 수행하였다.

• 한국건설관리학회논문집
• /
• 제19권4호
• /
• pp.61-69
• /
• 2018

원도급계약에서의 공기연장 추가간접비에 대한 연구는 지속되어왔다. 그러나 하도급계약에서의 공기연장 추가간접비 산정방식에 대한 연구는 거의 없는 실정이다. 본 연구는 기존 현장에서 사용되고 있는 공기연장 추가간접비 산정방식과 선행연구에서 제안된 공기연장 추가간접비 산정방식에 대해 고찰하고 모형사례를 분석하여 산정방식을 비교하였다. S-curves형태의 간접비 발생을 반영한 모형사례의 발생상황을 사례별로 제시하여 선행연구에서 제시된 공기연장 추가간접비 산정방식별 산출결과를 비교하였다. 산정방식의 문제점을 고찰하는 과정에서 원사업자의 공기연장 추가간접비 산정방식으로 타당한 것으로 연구된 바 있는, 지연기간 평균실비산정방법이 수급사업자의 공기연장 추가간접비 산정에도 타당하다는 결론을 도출하여 보편적으로 적용될 수 있음을 입증하였다.

• Smart Structures and Systems
• /
• 제12권2호
• /
• pp.97-119
• /
• 2013

This paper presents numerical and experimental results on the use of guided waves for structural health monitoring (SHM) of crack growth during a fatigue test in a thick steel plate used for civil engineering application. Numerical simulation, analytical modeling, and experimental tests are used to prove that piezoelectric wafer active sensor (PWAS) can perform active SHM using guided wave pitch-catch method and passive SHM using acoustic emission (AE). AE simulation was performed with the multi-physic FEM (MP-FEM) approach. The MP-FEM approach permits that the output variables to be expressed directly in electric terms while the two-ways electromechanical conversion is done internally in the MP-FEM formulation. The AE event was simulated as a pulse of defined duration and amplitude. The electrical signal measured at a PWAS receiver was simulated. Experimental tests were performed with PWAS transducers acting as passive receivers of AE signals. An AE source was simulated using 0.5-mm pencil lead breaks. The PWAS transducers were able to pick up AE signal with good strength. Subsequently, PWAS transducers and traditional AE transducer were applied to a 12.7-mm CT specimen subjected to accelerated fatigue testing. Active sensing in pitch catch mode on the CT specimen was applied between the PWAS transducers pairs. Damage indexes were calculated and correlated with actual crack growth. The paper finishes with conclusions and suggestions for further work.

• 한국조경학회지
• /
• 제14권2호
• /
• pp.43-68
• /
• 1986

It is necessary that children's actual activities in the playgrounds should be analyzed for the study on the children's playgrounds. The purpose of this study is to establish the design principles for the improvement of the children\`s playgrounds in apartment complex by means of the various methods ; behavior mapping, questionaires and photo simulations. For the purpose of data collection, children are divided into three groups-infants(0 to 4 years), young children(pre ; 5 to 8 years, post ; 9 to 11 years), teenagers(7.2 to 14 years). The study results are as follows; 1) Analysis of behavior mapping : (a) Approximately 70 percent of the children observed stayed in the playground less than 20 minutes. (b) Playing time for each play apparatus was less than 5 minutes. (c) As a result of the observation, the duration time in the attic was 1 hour or more (d) The swing was the most frequently used apparatus as children's first and last choice. (e) Most of the users were young children(46.5%). 2) Analysis of questionaires : (a) Children considered that the existing playgrounds were lack of shadows and the play apparatuses are not interesting. (b) They felt danger and crowding at the multi-used wooden apparatus. 3) Suggestions for the playground design : It is necessary that the playgrounds are divided into the infants, the young children's and the teenagers'playground. (a) The infants'playground needs about 50 square meters and needs to be located in the apartment court. (b) The young children's playground needs about 330 to 660 square meters and needs to be located adjacent to the pedestrian road. (c) The teenagers'playground needs about 660 to 1000 square meters, which is needed for various ball games.

• 한방안이비인후피부과학회지
• /
• 제30권4호
• /
• pp.75-96
• /
• 2017

Objectives : The purpose of this study was to investigate the treatment trend for allergic rhinitis in Korean Medicine. Methods : We conducted an online survey for Korean Medicine Doctors who were registered in the association of Korean Medicine. The questionnaire was consisted of patient characteristics, diagnosis status, treatment status, and future research needs. Results : Data from total of 396 respondents were analyzed. More than 70% of the patient came to the Korean Medicine Clinic after visiting the Western Medicine Clinic in 43.9% of the respondents. 55.6% of the respondents performed combination therapy. History taking, nasal examination, x-ray, and Korean Medicine diagnostic test were used for diagnosis. The mean duration of treatment ranged from $4.9{\pm}2.91$ to $15.2{\pm}8.45$ for pediatric and early childhood patients and from $17.5{\pm}16.15$ to $5.3{\pm}3.85$ weeks for adolescents and adult patients. The mean number of treatment times was from $9.8{\pm}7.00$ to $33.5{\pm}24.45$ for pediatric and early childhood patients and from $10.8{\pm}11.55$ to $40.4{\pm}48.18$ times for adolescents and adult patients. 64.5%, 48.0%, and 91.2% of the respondents used herbal medication in national health insurance coverage, herbal medication uninsured in health insurance and herbal prescription filled at each medical institution, respectively for pediatric and early childhood patients and 67.6%, 42.8% and 86.1% for adolescents and adult patients. 36.9% and 36.4% of respondents answered that the study of acupuncture and herbal medicine are needed preferentially. Conclusions : The results of this survey will be used to develop clinical practice guideline that reflect actual clinical practice.

• 동력기계공학회지
• /
• 제6권1호
• /
• pp.20-26
• /
• 2002

The purpose of this study is preventing the stick, scuffing, scratch between piston and cylinder in advance, and obtaining data for duration test in actual engine operation. The temperature gradient in cylinder bore according to coolant temperature were measured using $1.5{\ell}$ class diesel engine. 20 thermocouples were installed 2mm deep inside from cylinder wall near top ring of piston in cylinder block, at which points major thermal loads exist. It is suggested as proper measurement points for engine design by industrial engineers. Under full load and $70^{\circ}$, $80^{\circ}C$ and $90^{\circ}C$ coolant temperature conditions, the temperature in cylinder block and engine oil increased gradually according to the increase of coolant temperature, the siamese side temperature of top dead center is $142^{\circ}C$ in peripheral distribution, that is about $20^{\circ}C$ higher than that at thrust, anti-thrust, and rear side temperature, respectively. The maximum pressure of combustion gas in $70^{\circ}C$ coolant temperature is about 2 bar lower than those of $80^{\circ}C$ and $90^{\circ}C$ coolant temperature. The engine torque in $80^{\circ}C$, $90^{\circ}C$ coolant temperature condition is about 4.9Nm higher than that of $70^{\circ}C$ coolant temperature.