• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.28 no.2
• /
• pp.197-205
• /
• 2015

Offshore structures for the gas production are exposed to the risk of gas leaks, and gas explosions can result in fatal damages to the primary structures as well as secondary structures. To minimize the damage from the critical accidents, the study of the dynamic response of structural members subjected to blast loads must be conducted. Furthermore, structural dynamic analysis has to be performed considering relationships between the natural frequency of structural members and time duration of the explosion loading because the explosion pressure tends to increase and dissipate within an extremely short time. In this paper, the numerical model based on time history data were proposed considering the negative phase pressure in which considerable negative phase pressures were observed in CFD analyses of gas explosions. The undamped single degree of freedom(SDOF) model was used to characterize the dynamic response under the blast loading. A blast wall of FPSO topside was considered as an essential structure in which the wall prevents explosion pressures from the process area to utility and working areas. From linear/nonlinear transient analyses using LS-DYNA, it was observed that dynamic responses of structures were influenced by significantly the negative time duration.

• Journal of the Korea Institute of Building Construction
• /
• v.23 no.5
• /
• pp.571-581
• /
• 2023

The contemporary domestic construction landscape has witnessed a contraction, primarily attributed to the operational challenges faced by construction entities and a downtrend in the initiation of new projects. In light of this, domestic construction enterprises are ardently seeking avenues to economize whilst simultaneously amplifying the quality across diverse construction genres. Value engineering (VE), heralded for its prowess in not only cost mitigation but also in accelerating project timelines and bolstering construction quality, has been extensively adopted in refining finishing tasks. However, its application to framework enhancements remains conspicuously limited. Particularly in factory edification, framing emerges as a pivotal process exerting significant influence over the entire construction continuum. Thus, it becomes imperative to integrate VE techniques at the inception phase of framing. This would facilitate a meticulous examination of design schematics and on-site conditions, paving the way for alternative strategies that condense construction durations, economize on costs, and augment work efficiency, all the while upholding paramount standards of quality and safety. Such a venture stands to be foundational in expediting construction timelines, fostering economic efficiency, and buttressing construction safety protocols.

• Journal of Navigation and Port Research
• /
• v.41 no.4
• /
• pp.215-228
• /
• 2017

Taking a look at recent trends of port cities, many port cities in the world have been shedding new light on the function being kept by existing port spaces, caused by changes of industrial structure according to the stream of the times, developments of surrounding areas, and etc., and we can see that its meaning also has been changing. However, in case of domestic port spaces they are in the real situation not responding to those movements quickly. Therefore, unlike the existing zoning system dividing functionally urban spaces according to use simply, in this study FBCs getting the timelight recently as a system capable of reflecting spatial characteristics at the maximum have been utilized as a measure for solving current problems of urban spaces. The purpose of this study is to propose the direction of urban planning approach that harmonizes the whole harbor space by strengthening the interlinkage between heterogeneous spaces of port area and port area using FBCs. FBCs are institutional devices that are proposed and implemented in the United States to reflect the unique characteristics of the space, that is, the location and the uniqueness, and the pedestrian-oriented space planning.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.12 no.5
• /
• pp.169-178
• /
• 2008

Compressive flanges of steel box girder is designed based on the ultimate strength behavior of sub-panel which is enclosed with longitudinal stiffeners and transverse stiffeners on appropriate safety factor. However, it is rational that the ultimate strength is calculated considering the various factors such as number and stiffness of longitudinal stiffener, spacing of transverse stiffener, initial deformation and residual stress distribution. In this study, an analysis program based on Folded Plate theory is developed considering the geometric effects and the material nonlinearity. The analysis program is applicated to the steel box girder bridges which is really constructed in domestic.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.6B
• /
• pp.954-961
• /
• 2010

Stream cipher was worse than block cipher in terms of security, but faster in execution speed as an advantage. However, since so far there have been many algorithm researches about the execution speed of block cipher, these days, there is almost no difference between them in the execution speed of AES. Therefore an secure and fast stream cipher development is urgently needed. In this paper, we propose a 32bit output fast stream cipher, AA32, which is composed of ASR(Arithmetic Shifter Register) and simple logical operation. Proposed algorithm is a cipher algorithm which has been designed to be implemented by software easily. AA32 supports 128bit key and executes operations by word and byte unit. As Linear Feedback Sequencer, ASR 151bit is applied to AA32 and the reduction function is a very simple structure stream cipher, which consists of two major parts, using simple logical operations, instead of S-Box for a non-linear operation. The proposed stream cipher AA32 shows the result that it is faster than SSC2 and Salsa20 and satisfied with the security required for these days. Proposed cipher algorithm is a fast stream cipher algorithm which can be used in the field which requires wireless internet environment such as mobile phone system and real-time processing such as DRM(Digital Right Management) and limited computational environments such as WSN(Wireless Sensor Network).

• Proceedings of the Korean Information Science Society Conference
• /
• 2011.06b
• /
• pp.401-404
• /
• 2011

운영체제와 같은 대규모 프로그램은 확장을 용이하게 하기 위해 장치 드라이버를 모듈 구조를 통해 동작시킨다. 그러나 이러한 드라이버 모듈은 커널과 분리되어 개발되기 때문에 상대적인 취약성을 가지고 있다. 이러한 취약성으로 인해 발생한 고장은 드라이버뿐만 아니라 커널 전체에 오류를 야기해 시스템의 안정성을 저하시키는 요인이 된다. 이러한 문제를 해결하기 위해 안전하지 않은 드라이버를 커널로부터 격리하고자 하는 논의가 진행되었고, 이후 많은 연구를 통해 여러 가지 접근 방식을 통한 해결방법이 제안되었다. 그러나 기존의 방법은 드라이버 소스코드의 수정이 필요하거나 드라이버 요청에 대한 응답속도가 매우 느린 현실적인 제약이 있었다. 본 논문에서는 기존방법의 한계를 극복하는 동적 컴파일러를 이용한 고장 분리 기법을 제안한다. 본 제안 기법은 기존 드라이버를 그대로 사용가능하며 기존 기법의 분리 정책을 모두 적용할 수 있다. 리눅스 커널에 본 제안기법을 적용하여 동적 컴파일러의 성능을 측정하고 본 제안 기법의 특성을 기존 기법과 비교함으로써 본 제안기법이 매우 적은 부하만으로 장치 드라이버의 고장 분리가 가능함을 확인하였다.

• Korean Journal of Construction Engineering and Management
• /
• v.23 no.6
• /
• pp.43-53
• /
• 2022

In many cases, the construction industry in Korea has a hierarchical structure in which a general contractor in charge of the entire project is subcontracted from the client and entrusts the construction to a specialty contractor in charge of detailed work types. In this structure, the general contractor manages and takes responsibility for the entire construction, but the person directly involved in the construction is an individual specialty contractor, so the quality and safety of the facilities will vary according to their construction and management capabilities. In order to solve quality and safety problems that may arise due to the difference between the person receiving the order for construction and the person who actually constructs it, it is necessary to let the person who receives the order perform the construction directly for projects under a certain amount. The system introduced for this purpose is the direct construction mandatory system. As described above, although this system was introduced to prevent bad construction and risk transfer, it is a system that has various problems due to the characteristics of the domestic construction industry, institutional limitations, and practical problems, so it is necessary to improve it legally and institutionally.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.20 no.3
• /
• pp.273-279
• /
• 2007

Probabilistic Risk Assessment considering statistically random variables is performed for the preliminary design of an Arch Bridge. Component reliabilities of girders have been evaluated using the response surfaces of the design variables at the selected critical sections based on the maximum shear and negative moment locations. Response Surface Method (RSM) is successfully applied for reliability analyses lot this relatively small probability of failure of the complex structure, which is hard to be calculated by Monte-Carlo Simulations or by First Order Second Moment method that can not easily calculate the derivative terms in implicit limit state functions. For the analysis of system reliability, parallel resistance system composed of girders is modeled as a parallel series connection system. The upper and lower probabilities of failure for the structural system have been evaluated and compared with the suggested prediction method for the combination of failure modes. The suggested prediction method for the combination of failure modes reveals the unexpected combinations of element failures in significantly reduced time and efforts, compared with the previous permutation method or conventional system reliability analysis method.

• Journal of Korean Society of Forest Science
• /
• v.101 no.3
• /
• pp.412-425
• /
• 2012

Concrete Soil Erosion Control Dam, which blocks flow of debris flow in torrential stream, are reported to lose expected functions due to structural failure and collapses, caused by poor construction, material deterioration and external impacts. In this paper, an integrity assessment technique for debris barriers was proposed, which allows preliminary detection of problems inherent in debris barriers. The proposed integrity assessment technique is a non-destructive method based on SASW method, one of surface-wave tests. In this paper, a practical procedure and analysis guidelines in applying the SASW technique to debris barrier was proposed and its validity was verified using five decrepit debris barriers older than 20-year old. As a result, the SASW method was validated for the reliable grade evaluation method for concrete soil erosion control dam, and the resulting grades turned out to agree with the results determined by Sabang Associations.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.26 no.6
• /
• pp.601-605
• /
• 2020

In large ships with complex structures, it is difficult to locate workers. In particular, it is not easy to detect when a worker falls down, making it difficult to respond quickly. Thus, research is being conducted to detect fallen workers using a camera or by attaching a device to the body. Existing image-based fall detection systems have been designed to detect a person's body parts; hence, it is difficult to detect them in various ships and postures. In this study, the entire fall area was extracted and deep learning was used to detect the fallen shipworker based on the image. The data necessary for learning were obtained by recording falling states at the shipyard. The amount of learning data was augmented by flipping, resizing, and rotating the image. Performance evaluation was conducted with precision, reproducibility, accuracy, and a low error rate. The larger the amount of data, the better the precision. In the future, reinforcing various data is expected to improve the effectiveness of camera-based fall detection models, and thus improve safety.