• Journal of Korea Society of Industrial Information Systems
• /
• v.28 no.6
• /
• pp.83-90
• /
• 2023

In a reefer container, temperature deviation occurs between the front of the loading part with the refrigerator and the rear of the loading part with the container door due to the external environment. In particular, this temperature deviation in the transport of fresh cargo has a great influence on the freshness of the cargo. In this study, we propose a method to minimize the temperature deviation by partially shielding the T-Floor to reduce the temperature deviation and evaluating the effect of the T-Floor shielding rate on the temperature change of the reefer container loading part. The subject of the experiment was a 40 feet smart reefer container, and the T-Floor shielding rates were set to 0%, 50%, 60%, 70%, and 80%. As a result of the experiment, it occurred differently in the temperature deviation of the reefer container loading part according to the shielding rate, and it was confirmed that the temperature deviation was the most uniform when the shielding rate was 60%. By minimizing the temperature deviation of the loading part, it is possible to prevent corruption and cold damage of cargo during transportation of fresh cargo by using the smart reefer container.

• Nuclear Engineering and Technology
• /
• v.38 no.3
• /
• pp.293-300
• /
• 2006

A liquid metal reactor (LMR) operated at high temperatures is subjected to both cyclic mechanical loading and thermal loading; thus, creep-fatigue is a major concern to be addressed with regard to maintaining structural integrity. The Korea Advanced Liquid Metal Reactor (KALIMER), which has a normal operating temperature of $545^{\circ}C$ and a total service life time of 60 years, is composed of various cylindrical structures, such as the reactor vessel and the reactor baffle. This study focuses on the creepfatigue crack initiation for a cylindrical Y-junction structure made of 316 stainless steel (SS), which is subjected to cyclic axial tensile loading and thermal loading at a high-temperature hold time of $545^{\circ}C$. The evaluation of the considered creep-fatigue crack initiation was carried out utilizing the ${\sigma}_d$ approach of the RCC-MR A16 guide, which is the high-temperature defect assessment procedure. This procedure is based on the total accumulated strain during the service time. To confirm the evaluated result, a high-temperature creep-fatigue structural test was performed. The test model had a circumferential through wall defect at the center of the model. The defect front of the test model was investigated after the $100^{th}$ cycle of the testing by utilizing a metallurgical inspection technique with an optical microscope, after which the test result was compared with the evaluation result. This study shows how creep-fatigue crack initiation for a high-temperature structure can be predicted with conservatism per the RCC-MR A16 guide.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.39 no.2
• /
• pp.106-113
• /
• 2011

This paper was conducted on experimental analysis in the free vibration analysis of rectangular plates under uniform thermal loading. Materials of three rectangular plates were aluminum, steel and stainless-steel respectively. The dimension of rectangular plates was 0.1 $\times$ 0.1 $\times$ 0.002 m. Infrared quartz lamps were used for thermal loading. The PCS(Power Control System) electric control system was applied for control and scanning vibrometer (Poly Tech) was used for acquisition of frequency response function. Applied temperature was increased from room temperature to $300^{\circ}C$ by $50^{\circ}C$. Boundary condition was free-free condition using bungee cord. Front face of rectangular plate was heated uniformly.

• The KSFM Journal of Fluid Machinery
• /
• v.15 no.2
• /
• pp.12-19
• /
• 2012

This study presents unsteady and unstable characteristics of three stage transonic axial compressor, developed by Korea Aerospace Research Institute. As approaching to the unstable operating region at the 103% design speed of the compressor, a modal type stall precursor appears in front of highly loaded 3rd rotor row at first, and it propagates to the upstream. On the contrary, actual stall cell initiates from the stall precursor in front of the 1st rotor row, and it propagates to the downstream of the compressor. After the stall region reached the 3rd stage and stall cell rotates circumferentially about 360 deg, it develops to one dimensional compressor surge mode. It shows a mild surge behaviour with 3~4 Hz frequency. From the test data, it can be suggested that there is a priority to give an optimum blade loading distributions to construct a multi stage transonic axial compressor stages either to secure more stable compressor operating ranges, or to maximize the compressor efficiency.

• Journal of Power Electronics
• /
• v.14 no.2
• /
• pp.402-412
• /
• 2014

This paper proposes a novel electric propulsion system for naval ships, which consists of Active Front End (AFE) converters directly connected to battery Energy Storage Modules (ESMs). Employing the proposed AFE converters with ESMs in the power systems of naval ships can enhance the reliability and quality of the electric power. Furthermore, the fuel-efficiency of the generator can be improved by a higher loading factor of the generator and its prime movers. The proposed AFE configuration does not require an additional dedicated DC/AC converter for the ESMs. Instead of that, the AFE converter itself can control the DC link voltage and the discharging and/or charging of the ESMs. A control scheme to achieve these control objectives is also presented in this paper. The overall power system, including the generators and electrical loads of a naval ship, is implemented by a small scaled Power Hardware-In-the-Loop (PHIL) simulator. Through this experimental setup, the proposed system configuration and the power control strategies are verified. It is shown that the fuel-efficiency and transient dynamics can be improved in the normal and contingency operation modes.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2014.04a
• /
• pp.121-121
• /
• 2014

본 연구에서는 반도체 제조의 Diffusion 공정설비의 FFU (Fan Filter Unit) 진동에 의해 발생한 wafer 불량 현상을 규명 및 개선하였다. EFEM(Equipment Front End Module)의 Loading 부에 장착된 FOUP(Front Opening Unified Pod)에 들어 있는 Wafer 들이 설비 EFEM 하부로 떨어져 깨지거나 FOUP 내에서 겹침 현상이 발생하는 것을 확인하였다. 이에 생산현장의 모든 Diffusion 공정 설비를 조사하였으며, 그 결과 A 사(社)의 특정 설비에서만 발생되는 현상임을 확인하였다. 해당 A사(社)설비군에서만 월 평균 10 건의 Slot Mapping Error 가 발생하였으며, 이로 인해 Wafer가 재 제조된 매수가 월 평균 53 매로 확인되었다. 따라서 본 연구는 A 사(社)설비에서 발생하는 Mapping Error 의 원인 규명 및 개선을 위해 추진되었다. 총 12 개의 항목을 불량 발생 원인 후보 군으로 선정 후 예비 진단한 결과 FFU(Fan Filter Unit)에 의한 문제 발생 가능성이 가장 높을 것으로 추정되었다. 이에 따라 4 개의 서로 다른 물리적 환경/조건에서 진동을 측정하였으며, 최종 평가 결과 Motor 와 Blade 의 불균형에서 기인한 진동이 설비의 loader 부에 직접적으로 영향을 주는 것을 확인하였다. 진동 문제를 해결하기 위해 고 RPM blade 에서 저 RPM 및 유량 감소를 보완할 수 있는 신규모델로 교체하였다. 신규 Module(blade/motor) 장착 후 Load port 에서의 진동 측정 결과 개선 전 대비 91% 감소하였으며, 결과적으로 Slot mapping error 발생 건수가 50% 이상 감소되는 효과와 Wafer 재 제조 매수도 월 평균 약 43% 감소하는 효과를 얻을 수 있었다.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.31 no.6 s.261
• /
• pp.671-678
• /
• 2007

Front-side members of automobile, such as the hat shaped section members, are structures with the greatest energy absorbing capability in a front-end collision of vehicle. This paper was performed to analyze energy absorption characteristics of the hat shaped section members, which are basic shape of side member. The hat shaped section members consisted of the spot welded side member which was utilized to an actual vehicle and CFRP side member for lightweight of vehicle structural member. The members were tested under static axial loading by universal testing machine. Currently, stacking condition related to the collapse characteristics of composite materials is being considered as an issue fer the structural efficiency and safety of automobiles, aerospace vehicles, trains, ships even elevators during collision. So, energy absorption characteristics were analyzed according to stacking condition and shape of section and compared the results of spot welded side member with those of CFRP side member.

• Steel and Composite Structures
• /
• v.17 no.6
• /
• pp.891-906
• /
• 2014

This study aims to present a three dimensional finite element model to investigate the wave propagation in a concrete filled steel tubular column (CFSC) due to transient impact load. Both the concrete and steel are regarded as linear elastic material. The impact load is simulated by a semi sinusoidal impulse. Besides the CFSC models, a concrete column (CC) model is established for comparing under the same loading condition. The propagation characteristics of the transient waves in CFSC are analyzed in detail. The results show that at the intial stage of the wave propagation, the velocity waves in CFSC are almost the same as those in CC before they arrive at the steel tube. When the waves reach the column side, the velocity responses of CFSC are different from those of CC and the difference is more and more obvious as the waves travel down along the column shaft. The travel distance of the wave front in CFSC is farther than that in CC at the same time. For different wave speeds in steel and concrete material, the wave front in CFSC presents an arch shape, the apex of which locates at the center of the column. Differently, the wave front in CC presents a plane surface. Three dimensional effects on top of CFSC are obvious, therefore, the peak value and arrival time of incident wave crests have great difference at different locations in the radial direction. High-frequency waves on the waveforms are observed. The time difference between incident and reflected wave peaks decreases significantly with r/R when r/R < 0.6, however, it almost keeps constant when $r/R{\geq}0.6$. The time duration between incident and reflected waves calculated by 3D FEM is approximately equal to that calculated by 1D wave theory when r/R is about 2/3.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.11 no.6
• /
• pp.201-212
• /
• 2007

This study presents experimental results of Steel-PSC mixed structural system having front-rear plate connection between Steel and Prestressed Concrete. Two kinds of Steel-PSC mixed structural system of 5.4m length were tested to evaluate flexural behaviors under four point loading, and 4 kinds of specimens with and without prestressing force at R & L type connection were tested to observe the shear behavior. Based on the test results of load-deflection curves and failure modes of specimens, it is found that the proposed L shape connection with front-rear plate connection between Steel and Prestressed Concrete has higher strength and stiffness. From the study, Steel-PSC mixed structural system with L shaped connection has a better structural performance in connection part.

• Journal of Ocean Engineering and Technology
• /
• v.28 no.4
• /
• pp.331-337
• /
• 2014

We analyzed the 3-D characteristics of the dynamic response of seabed around a submerged breakwater due to wave loading using a 3-D numerical scheme (LES-WASS-3D). Using our model, which considers the wave-structure-sandy seabed interactions in a 3-D wave field, we were able to investigate the 3-D characteristics of the pore-water pressure in the seabed around the submerged breakwater under various incident wave conditions. To verify the 3-D numerical analysis method suggested in this study, we compared the numerical results with the existing experimental results and found good agreement between them. The numerical analysis reveals that high pore-water pressure in the seabed is generated below a large wave height at the front slope of the submerged breakwater. It was also shown that the non-dimensional pore-water pressure in the seabed increases as the wave period increases because the wave energy dissipation decreases on the submerged breakwater and seabed as the wave period increases.