• Structural Engineering and Mechanics
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• 제84권1호
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• pp.85-100
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• 2022

The updated Turkish Building Earthquake Code has been significantly renovated and expanded compared to previous seismic design codes. The use of earthquake ground motion levels with different probabilities of exceedance is one of the major advances in structural mechanics with the current code. This study aims to investigate the earthquake performance of steel structure in settlements with different seismic hazards for various earthquake ground motion levels. It is focused on earthquake and structural parameters for four different ground motion levels with different probabilities of exceedance calculated according to the location of the structure by the updated Turkish Hazard Map. For this purpose, each of the seven different geographical regions of Turkey which has the same seismic zone in the previous earthquake hazard map has been considered. Earthquake parameters, horizontal design elastic spectra obtained and comparisons were made for all different ground motion levels for the seven different locations, respectively. Structural analyzes for a sample steel structure were carried out using pushover analysis by using the obtained design spectra. It has been determined that the different ground motion levels significantly affect the expected target displacements of the structure for performance criteria. It is noted that the different locations of the same earthquake zone in the previous code with the same earthquake-building parameters show significant variations due to the micro zoning properties of the updated seismic design code. In addition, the main innovations of the updated code were discussed.

• ETRI Journal
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• 제43권2호
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• pp.184-196
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• 2021

The research domain of underwater communication has garnered much interest among researchers exploring underwater activities. The underwater environment differs from the terrestrial setting. Some of the main challenges in underwater communication are limited bandwidth, low data rate, propagation delay, and high bit error rate (BER). As such, this study assessed the underwater acoustic (UWA) aspect and explored the expression of error performance based on t-distribution noise. Filter orthogonal frequency-division multiplexing refers to a new waveform candidate that has been adopted in UWA, along with turbo and polar codes. The empirical outcomes demonstrated that the noise did not adhere to Gaussian distribution, whereas the simulation results revealed that the filter applied in orthogonal frequency-division multiplexing could significantly suppress out-of-band emission. Additionally, the performance of the turbo code was superior to that of the polar code by 2 dB at BER 10-3.

• 정보보호학회논문지
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• 제19권5호
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• pp.189-194
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• 2009

버퍼오버플로 악성코드 탐지를 위해 대부분의 안티바이러스 프로그램은 공격코드의 시그너처만 비교 탐지하고 있어 알려지지 않은 공격코드에 대해 탐지하지 못하는 문제점이 있다. 본 논문에서는 공격코드에서 필수적으로 사용하는 API의 메모리 실행영역 추적기법을 이용하여 알려지지 않은 공격코드에 대한 탐지기법을 제안한다. 제윤기법 검증을 위해 7개의 샘플 공격코드를 선정하여 8개의 안티바이러스 프로그램과 비교 실험한 결과, 대부분의 안티바이러스 프로그램은 Stack영역만 감시하고 Heap영역은 감시하지 않아 제안적인 탐지만 가능하였다. 이에 대부분의 안티 바이러스 프로그램에서 탐지할 수 없는 공격코드를 제안 기법을 이용하여 탐지할 수 있음을 시뮬레이션 하였다.

• Nuclear Engineering and Technology
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• 제51권8호
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• pp.1939-1950
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• 2019

The MELCOR code useful for a plant-specific hydrogen risk analysis has inevitable limitations in prediction of a turbulent flow of a hydrogen mixture. To investigate the accuracy of the hydrogen risk analysis by the MELCOR code, results for the turbulent gas behavior at pipe rupture accident were compared with CFX results which were verified by the American National Standard Institute (ANSI) model. The postulated accident scenario was selected to be surge line failure induced by station blackout of an Optimized Power Reactor 1000 MWe (OPR1000). When the surge line failure occurred, the flow out of the surgeline was strongly turbulent, from which the MELCOR code predicted that a substantial amount of hydrogen could be released. Nevertheless, the results indicated nonflammable mixtures owing to the high steam concentration released before the failure. On the other hand, the CFX code solving the three-dimensional fluid dynamics by incorporating the turbulence closure model predicted that the flammable area continuously existed at the jet interface even in the rising hydrogen mixtures. In conclusion, this study confirmed that the MELCOR code, which has limitations in turbulence analysis, could underestimate the existence of local combustible gas at pipe rupture accident. This clear comparison between two codes can contribute to establishing a guideline for computational hydrogen risk analysis.

• 한국기계가공학회지
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• 제17권4호
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• pp.150-159
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• 2018

The present research deals with a finite element analysis and fatigue evaluation of a steam separator of a high-pressure evaporator for the Heat Recovery Steam Generator (HRSG). The fatigue during the expected life of the HRSG was evaluated according to the ASME Boiler and Pressure Vessel Code Section VIII Division 2 (ASME Code). First, based on the eight transient operating conditions prescribed for the HRSG, temperature distribution of the steam separator was analyzed by a transient thermal analysis. Results of the thermal analysis were used as a thermal load for the structural analysis and used to determine the mean cycle temperature. Next, a structural analysis for the transient conditions was carried out with the thermal load, steam pressure, and nozzle load. The maximum stress location was found to be the riser nozzle bore, and hence fatigue was evaluated at that location, as per ASME Code. As a result, the cumulative usage factor was calculated as 0.00072 (much less than 1). In conclusion, the steam separator was found to be safe from fatigue failure during the expected life.

• 한국화재소방학회논문지
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• 제25권1호
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• pp.1-6
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• 2011

고층건축물에서의 피난효율과 수용인원 산정기준의 문제점을 확인하기 위하여 피난 시뮬레이션을 수행하였다. 지상 39층 주상복합 건축물의 계단폭이 각각 1.2m, 1.5m, 1.8m일 때, 피난시간과 피난자수를 Simulex로 계산하였다. 소방법 기준으로 산정한 총수용인원은 실거주자의 2.3배, NFPA 101 인명구조코드 기준의 2.6배였다. 소방법 기준의 경우, 계단폭이 작을수록 증간층에서의 병목현상으로 인해 피난효율이 낮았지만, 실거주나 NFPA 기준에서는 피난효율이 높고 계단폭이 피난효율에 미치는 영향이 미미함을 확인하였다. 소방법 기준을 적용할 때 계단폭이 1.8m에서도 병목현상이 일어나지만, 실거주 또는 NFPA 기준을 적용할 때는 계단폭 1.2m에서도 안전한 것으로 나타 남에 따라 수용인원 산정관련 소방법 기준의 완화가능성에 대한 추가연구가 필요하다.

• Journal of Mechanical Science and Technology
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• 제19권5호
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• pp.1182-1193
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• 2005

The capability of TRAC-M code to predict downcomer boiling effect during reflood phase in postulated PWR LOCA is evaluated using the results of downcomer effective water head and Cylindrical Core Test Facility (CCTF) experiments, which were performed at JAERI. With a full height downcomer simulator, effective water head experiment was carried out to investigate the applicability of the TRAC-M best estimate LOCA code to evaluate the effective water head with superheated wall temperature in downcomer. In order to clarify the effect of the initial superheat of the downcomer wall on the system and the core cooling behaviors during the reflood phase, two sets of analysis were also performed with a CCTF. Results show that TRAC­M code tends to under-predict downcomer effective water head and core differential pressure. However, the code results show a good agreement with the experimental results in downcomer temperature, heat flux and pressure. Finally, both experiment and calculation showed that the downcomer water head with the superheated downcomer wall is lower than that of the saturated wall temperature.

• Nuclear Engineering and Technology
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• 제41권7호
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• pp.969-978
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• 2009

The ASSERT-PV subchannel code developed by AECL has been applied as a design-assist tool to the advanced $CANDU^{(R)1}$ reactor fuel bundle. Based primarily on the $CANFLEX^{(R)2}$ fuel bundle, several geometry changes (such as element sizes and pitch-circle diameters of various element rings) were examined to optimize the dryout power and pressure-drop performances of the new fuel bundle. An experiment was performed to obtain dryout power measurements for verification of the ASSERT-PV code predictions. It was carried out using an electrically heated, Refrigerant-134a cooled, fuel bundle string simulator. The axial power profile of the simulator was uniform, while the radial power profile of the element rings was varied simulating profiles in bundles with various fuel compositions and burn-ups. Dryout power measurements are predicted closely using the ASSERT-PV code, particularly at low flows and low pressures, but are overpredicted at high flows and high pressures. The majority of data shows that dryout powers are underpredicted at low inlet-fluid temperatures but overpredicted at high inlet-fluid temperatures.

• Nuclear Engineering and Technology
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• 제30권1호
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• pp.58-74
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• 1998

A PC window-based computer code, CONPAS (CONtainment Performance Analysis System), has been developed to integrate the numerical, graphical, and results-operation aspects of Level 2 probabilistic safety assessments (PSA) for nuclear power plants automatically. As a main logic for accident progression analysis, it employs a concept of the small containment phenomenological event tree (CPET) helpful to trace out visually individual accident progressions and of the detailed supporting event tree (DSET) for its detailed quantification. For the integrated analysis of Level 2 PSA, the code utilizes five distinct, but closely related modules. Its computational feasibility to real PSAs has been assessed through an application to the UCN 3&4 full scope Level 2 PSA. Compared with other existing computer codes for Level 2 PSA, the CONPAS code provides several advanced features: (1) systematic uncertainty analysis / importance analysis / sensitivity analysis, (2) table / graphical display & print, (3) employment of the recent Level 2 PSA technologies, and (4) highly effective user interface. The main purpose of this paper is to introduce the key features of CONPAS code and results of its feasibility study.

• 대한전자공학회논문지TC
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• 제49권7호
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• pp.12-22
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• 2012

직교코드를 다중화하여 데이터 비트열을 확산시켜 전송하는 멀티코드 대역확산 통신시스템의 큰 단점은 여러 코드의 합이 멀티레벨이 되어 선형성이 좋은 증폭기를 요구한다는 것이다. Walsh 코드 및 확장 $m$-시퀀스를 직교 확산코드로 사용하는 멀티코드 대역확산 시스템에서 입력 데이터를 부호화함으로써 다중 코드의 합을 일정 진폭으로 만드는 방식이 제안되어 있다. 본 논문에서는 정진폭 확장 $m$-시퀀스 기반 시스템에서 송신 신호의 정진폭화를 위해 부가로 전송되는 동반코드를 수신기에서도 이용함으로써 비트오율 성능을 개선하는 알고리즘을 제안하였다. 제안된 수신기에서는 코드검출 과정에서 1 개의 검출 오류가 있는 경우 오류를 정정하는 능력을 가져서 비트오율 성능이 개선된다. 제안된 방식의 타당성을 검증하기 위하여 시뮬레이션을 수행하였으며, 기본 수신기를 사용한 경우에 비해 성능이 개선되는 것을 확인하였다.