• 대한기계학회논문집A
• /
• 제29권6호
• /
• pp.876-888
• /
• 2005

Tensile properties and fracture toughness of monolithic aluminum, fiber reinforced plastics and glass fiber/aluminum hybrid laminates under tensile loads have been investigated using plain coupon and single-edge-notched specimens. Elastic modulus and ultimate tensile strength of GFMLs showed different characteristic behaviors according to the Al kind, fiber orientation and composition ratio. Fracture, toughness of A-GFML-UD which was determined by the evaluation of $K_{IC}$ and $G_{IC}$ based on critical load was similar to that of GFRP-UD and was much higher than monolithic Al. Therefore, A-GFML-UD presented superior fracture toughness as well as prominent damage tolerance in comparison to its constituent Al. By separating Al sheet from GFMLs after the test, optical microscope observation of fracture zone of GFRP layer in the vicinity of crack tip revealed that crack advance of GFMLs depended on the orientation of fiber layer as well as Al/fiber composition ratio.

• 설비공학논문집
• /
• 제25권1호
• /
• pp.14-19
• /
• 2013

The present study has been conducted for evaluating and comparing the performance of the underfloor air distribution system(UFAD) and the ceiling based air distribution system(CBAD) under cooling condition. Simulations and experiments were carried out for verifying the model by TRNSYS program about UFAD and CBAD. The results of simulation for various conditions of thermal load are summarized as followings. UFAD had an advantage for making thermal comfort because of lower temperature of the floor surface. Moreover, UFAD showed lower fan power about 30~50% than CBAD under the same conditions of thermal load. The energy saving rates of UFAD were increased to 17.7% in proportion to the thermal load on unoccupied zone(lighting). Ultimately, additional investigations should be done for analyzing optimized operating conditions of UFAD with considering the thermal performance of building envelop and the thermal load.

• 대한교통학회지
• /
• 제22권7호
• /
• pp.49-59
• /
• 2004

상하이항을 비롯한 북중국 항만이 우리나라 항만을 위협하는 상황으로 전개됨에 따라, 현재 이러한 항만들 사이에서 부산항 및 광향항의 경쟁력을 도모하기 위한 많은 연구들이 수행되고 있다. 그러나, 이러한 연구들은 경쟁력을 도출하고, 그것을 평가하는 데 비중을 두고 있는 반면, 평가된 결과를 토대로 경쟁력 도모를 위한 Critical Point를 명확히 추출한 연구는 전무한 실정이다. 즉, 기존의 분석법이 단순히 평가결과를 도출하는 것에 국한된 나머지, 평가결과로부터 평가에 영향을 끼친 항목이 명확히 무엇인지, 평가우위를 차지하기 위해 어떠한 부분을 개선시켜야 하는 지에 대한 해답을 제시하지는 못했다. 결과적으로, 이와 같은 문제는 평가결과로부터 경쟁력에 영향을 미쳤던 핵심 요인을 추출하는 알고리즘이 마련되어 있지 않은 것에 기인한다. 본 연구는 이러한 점에 주목하고, 우리나라 및 상하이 북중국 주요 항만을 대상으로 기존연구의 항만경쟁력 평가결과로부터 퍼지 역관계법을 이용하여 주요 항만의 경쟁력 상승에 영향을 미치는 핵심요인을 추출하고, 간단한 시나리오 분석을 통해 몇 가지 중요한 시사점을 제안하는 것을 연구의 목적으로 한다. 연구결과 부산항은 현 시점에서 무엇보다 역량을 집중해야 할 항목으로 배후지 여건 즉 항만배후지역의 자유무역지대의 활성화가 가장 큰 관건으로 나타났다. 광양항은 주요화물발생지까지의 거리, 효율적인 배후연계 네트워크 등에 역점을 두어야 하는 것으로 나타났다.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
• /
• pp.531-536
• /
• 2002

Silica fume influences concrete diffusivity and permeability as well as strength by densifying the microstructure of the interfacial transition zone (ITZ) of high strength concrete, by reducing the capillary porosity of cement paste and by producing less diffusible and permeable pozzolanic CSH gel than CSH gel of conventional cement hydration. This paper presents a procedure to predict the chloride ion diffusivity and water permeability of the high strength concrete containing silica fume. Water binder ratio, silica fume addition, degree of hydration and volume fraction of aggregates are considered as the major factors influencing concrete diffusivity and permeability in the procedure. Analytical results using the procedure are shown and verified with other data.

• International Journal of Fuzzy Logic and Intelligent Systems
• /
• 제16권4호
• /
• pp.299-307
• /
• 2016

While segmenting "complex" images (with multiple objects, many details, etc.) we experienced a need to explore new ways for time-efficient and meaningful image segmentation. In this paper we propose a new technique for image segmentation which has only one variable for controlling the expected number of segments. The algorithm focuses on the treatment of pixels in transition zones between various label distributions. Results of the proposed algorithm (e.g. on the Berkeley image segmentation dataset) are comparable to those of GMM or HMM-EM segmentation, but are achieved with significantly reduced computation time.

• Ocean Systems Engineering
• /
• 제10권2호
• /
• pp.163-179
• /
• 2020

Considering the huge demand of several types of subsea equipment, as Christmas Trees, PLEMs (Pipeline End Manifolds), PLETs (Pipeline End Terminations) and manifolds for instance, a critical phase is its installation, especially when the equipment goes down through the water, crossing the splash zone. In this phase, the equipment is subject to slamming loads, which can induce impulsive loads in the installation wires and lead to their rupture. Slamming loads assessment formulation can be found in many references, like the Recommended Practice RP-N103 from DNV-GL (2011), a useful guide to evaluate installation loads. Regarding to the slamming loads, RP-N103 adopt some simplifying assumptions, as considering small dimensions for the equipment in relation to wave length, in order to estimate the slamming coefficient C_S used in load estimation. In this article, an experimental investigation based on typical subsea structure dimensions was performed to assess the slamming coefficient evaluation, considering a more specific scenario in terms of application, and some reduction of the slamming coefficient is achieved for higher velocities, with positive impact on operability.

• 한국공작기계학회논문집
• /
• 제14권2호
• /
• pp.104-109
• /
• 2005

This article has been investigated the use of FFT for adhesive joints analysis between metal sheets. The method is based on the measurement of the reflection wave at the metal/adhesive interface. After describing briefly the physical aspects of the phenomenon, an index is defined to detect defective zone of the joint(both for the lack of adhesive and for insufficient adhesion): the influence of the experimental variables(variable stress...) on the measurement is discussed. By means of a control experiment it is shown that stress variation in adhesive joints are separate to be distinguished. In this paper, Nondestructive evaluation in adhesive joints are evaluated together with ultrasonic testing and finite element analysis.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
• /
• pp.879-884
• /
• 2002

The objective of this study is to investigate the seismic capacity of the non-seismically detailed RC bridge piers before and after applying a seismic retrofitting method using stainless steel wire mesh. Total nine circular section RC piers were constructed. Different lap splice longitudinal reinforcement details were adapted for four specimens and various types of stainless steel wire mesh were applied for the remaining five specimens. Harmonic cyclic lateral load was applied on each specimen under a constant axial load. The test results indicated that the existing circular piers have low seismic capacity while the stainless steel wire mesh retrofitting method improves the seismic capacity considerably. In addition, test results revealed that the circular section piers could have a considerable amount of ductility if longitudinal bars are not lap-spliced in potential plastic hinge zone. Based on this experimental study it could be concluded that the seismic performance, that is ductility and energy absorption capacity, of the non-seismically detailed RC bridge piers would be increased by applying the stainless steel wire mesh seismic retrofitting method.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2007년도 춘계학술대회A
• /
• pp.7-10
• /
• 2007

In case of large steel water pipe, it have been observed that its fracture mostly occurs due to the complicated outside fatigue load on the pipe in the underground. It is also well known that its damage and leakage happen mainly in a weld zone. In this study we evaluated the fatigue characteristics based on size effect and residual stress by comparing the test results on the standard specimen collected from real pipe with those on full scale pipe.

• Nuclear Engineering and Technology
• /
• 제35권6호
• /
• pp.547-555
• /
• 2003

Fire hazard and risk analysis at Nuclear Power Plants is implemented on the basis of the normal operational configuration. This steady configuration, however, can be changed due to the temporary displacement of equipment, electric cable and irregular movement of workers through the fire compartments when the on-line maintenance is processed during the power operation mode or the scheduled outage mode for the refueling. With the consequence of this configuration change, the fire analysis condition and the evaluation result will be different from those that were analyzed based on the steady configuration. In this context, at this paper, the general items for the reassessment are categorized when the configuration has changed. The contemporary zone models for the detail fire analysis are also illustrated for their application for each classified condition.