• Journal of Advanced Marine Engineering and Technology
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• v.37 no.8
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• pp.849-854
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• 2013

Many researches on green ship with increasing on economics, efficiency and convenience have been carried out consistently. One of them is development of diesel engines with electronic control. While small duty one for automobiles had been adopted mainly already, disseminating heavy duty one for ships has trouble due to safety and reliability. In order to solve these problem in this study, performance of electronic control and cam type engine installed in parallel on training ship HANBADA of korea maritime university was analyzed and compared. It is certain that specific fuel oil consumption of the electronic control type is lower than cam type and excellent at lower engine load, especially. And the electronic control type shows more effective characteristic at sea trial on specific fuel oil consumption.

• The Transactions of the Korea Information Processing Society
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• v.6 no.8
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• pp.2271-2280
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• 1999

In this paper, a variable motion estimation scheme based on HBMA(Hierarchical Block Matching Algorithm) to improve the performance and to reduce heavy computational and transmission load, is presented. The proposed algorithm is composed of four steps. First, block activity for each block is defined using the edge information of differential image between two sequential images, and then average block activity of the present image is found by taking the mean of block activity. Secondly, camera pan compensation is carried out, according to the average activity of the image, in the hierarchical pyramid structure constructed by wavelet transform. Next, the LUT classifying each block into one among Moving, No Moving, Semi-Moving Block according to the block activity compensated camera pan is obtained. Finally, as varying the block size and adaptively selecting the initial search layer and the search range referring to LUT, the proposed variable HBMA can effectively carries out fast motion estimation in the hierarchical pyramid structure. The cost function needed above-mentioned each step is only the block activity defined by the edge information of the differential image in the sequential images.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.359-371
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• 2017

This study qualitatively examined the lives of non-tenured, secondary school teachers who are preparing for the teachers' exam. Semi-structured, face-to-face interviews were conducted with ten teachers and the data were analyzed using the consensual qualitative research method. Most of the participants had chosen a contract-based teaching position, believing that it would meet their financial needs, provide them with the satisfaction of being a teacher and, more importantly, afford practical help with their exam preparation. In practice, however, they suffered from low self-esteem and identity confusion due to discrimination by the school administrators. Ironically, this unfair treatment strengthened the participants' commitment to studying for the exam, in order to acquire a stable and secure position in school. However, they experienced a lot of study-related stress, including a lack of study hours, heavy study load, multiple life roles, physical exhaustion, the difficulties caused by the vague exam guide, and anxiety due to previous failure in the exam. Based on the findings of this study, directions for future research are suggested.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.2 s.25
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• pp.53-63
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• 2007

This study is to evaluate the probable snowfall depth by the point frequency analysis and to draw the map of probable snowfall depth in Korea. The 14 probability distributions which has been widely used in hydrologic frequency analysis are applied to the annual maximum depth of snowfall data. The parameters of each probability distribution are estimated by method of moments, maximum likelihood method and method of probability weighted moments. The estimated parameters were checked by parameter validity conditions of each assumed probability distribution. Four tests that are $X^2-test$, Kolmogorov-Smirnov test, Cramer von Mises test and probability plot correlation coefficient test are used in this study to determine the goodness of fit of the distributions. Mostly the 2-parameter gamma distribution was determined as appropriate distribution for the annual maximum new snowfall depth. The probable snowfall depth were obtained from appropriate distribution for the selected return periods and the maps of probable snowfall depth were presented. It will be useful to specify the snowfall load for the design of agricultural facilities such as vinyl house and cattle shed.

• Journal of Korean Society of Steel Construction
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• v.12 no.2 s.45
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• pp.151-165
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• 2000

Since vehicles become large and heavy and traffic volume is increased rapidly, many fatigue damages have been reported in bridge members. In order to prevent fatigue damages of bridge members and maintain safety it is essential to perform rational fatigue check. Only one vehicle is loaded on a bridge deck for the fatigue design. But in reality it is seldom that only one vehicle passes on a bridge deck. Usually more than two vehicles are passing on a bridge deck simultaneously. Therefore, it is necessary to consider the influence of simultaneous loading for a rational fatigue design. In this study, the influence of simultaneous loading is investigated by performing stress variation analysis due to vehicle load on the basis of linear superposition method and Monte-Carlo simulation of traffic flow, and then calculating the measure of fatigue damages.

• Tribology and Lubricants
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• v.28 no.6
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• pp.315-320
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• 2012

For proper functioning, general machines usually need lubricant oil as a cooling, cleaning, and sealing agent at points of mechanical contact. The quality of lubricant oil can deteriorate during operation owing to various causes such as high temperature, combustion products and extraneous impurities. In this study, a heavy load stopped during operation, and the oil was analyzed to check whether any impurities were added. Extraction using acetonitrile followed by reaction with BSTFA(bistrimethylsilyl trifluoroacetamide) showed that, trimethylsilylated ethylene glycol was present in the lubricant oil. To quantify the ethylene glycol in the oil, deuterium-substituted ethylene glycol, which acted as an internal standard, was added to the sample and then extracted with the solvent. Next, the extract was reacted with the derivatizing agent(BSTFA) and then analyzed with GC/MS. The detection limit of this method was found to be $0.5{\mu}g/g$ and the recovery of oil containing $20,000{\mu}g/g$ of ethylene glycol was measured to be 94.8%. A damaged O-ring and eroded cylinder liner were found during the overhaul, which implied the leakage of coolant containing ethylene glycol into the lubricating system. The erosion of the cylinder liner was assumed to be due to cavitation of the coolant in the cooling system.

• Tribology and Lubricants
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• v.30 no.2
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• pp.124-129
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• 2014

The piping system accounts for a large portion of the machinery structure of a plant, and is considered as a very important mechanical structure for plant safety. Accordingly, it is used in most energy plants in the nuclear, gas, and heavy chemical industries. In particular, the piping system for a nuclear plant is generally complicated and uses the reactor and its cooling system. The piping equipment is exposed to diverse loads such as weight, temperature, pressure, and seismic load from pipes and fluids, and is used to transfer steam, oil, and gas. In ultrasound infrared thermography, which is an active thermography technology, a 15-100 kHz ultrasound wave is applied to the subject, and the resulting heat from the defective parts is measured using a thermography camera. Because this technique can inspect a large area simultaneously and detect defects such as cracks and delamination in real time, it is used to detect defects in the new and renewable energy, car, and aerospace industries, and recently, in piping defect detection. In this study, ultrasound infrared thermography is used to detect information for the diagnosis of nuclear equipment and structures. Test specimens are prepared with piping materials for nuclear plants, and the optimally designed ultrasound horn and ultrasound vibration system is used to determine damages on nuclear plant piping and detect defects. Additionally, the detected images are used to improve the reliability of the surface and internal defect detection for nuclear piping materials, and their field applicability and reliability is verified.

• Journal of Welding and Joining
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• v.31 no.1
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• pp.58-64
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• 2013

The following results were obtained, microstructures and tensile properties in arc brazed joints of DP(dual phase) steel using Cu-5.3wt%Sn insert metal was investigated as function of brazing current. 1) The Fusion Zone was composed of ${\alpha}Fe+{\gamma}Cu$ and Cu23Sn2. The reason for the formation of these solid solutions. Despite, Fe & Cu were impossible to solid solution at room temperature. It's melting & reaction to something of insert metal & Base Metal (DP Steel) by Arc. Brazing Process has faster cooling rate then Cast Process, Supersaturated solid solution at room temperature. 2) The increase Hardness of Fusion Zone was directly proportional to the rise of welding current. Because, ${\alpha}Fe+{\gamma}Cu$ phase (higher hardness than the Cu23Sn2.(104.1Hv < 271.9Hv)) Volume fraction was Growth, due to increasing the amount of base metal melting by High current. 3) The results of tensile shear test by Brazing, All specimens happen to fracture in Fusion Zone. On the other hand, when Brazing Current increasing tend to rise tensile load. but it was very small, about 26-30% of the base metal. 4) The result of fracture analysis, The crack initiate at Triple Point for meet to Upper B.M/Under B.M/Fusion Zone. This Crack propagated to Fusion zone. So ruptured by tensile strength. The Reason to in the fusion zone fracture, Fusion zone by Brazing of hardness (strength) was very lower then the base metal (DP steel). In addition the Fusion Zone's thickness in triple point was thin than the base metal's thickness in triple point.

• Journal of The Korean Society of Agricultural Engineers
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• v.57 no.5
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• pp.129-137
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• 2015

The objective of this study was to test the non-point source pollution (NPS) control by the vegetated ridge and silt fence through field monitoring. The experiment plots were established with three sizes which are 5 m width by 22 m length with 8 %, 3 % slope and 15m width by 15 m length with 6 % slope. Flumes with the floating type stage gages were installed at the outlet of each plot to monitor the runoff. For a rainfall monitoring, tipping bucket rain gage was installed within the experiment site. Water quality samples were monitored during the heavy rainfall occurred. The amount of rainfall from 4 monitored events ranged from 27.6 mm to 130 mm. The runoff reduction rate could vary depending on slope, soil, crop growth condition, rainfall amount, rainfall intensity, antecedent moisture condition, and many other factors. The runoff from vegetated ridge and silt fence treatment plots was 24.05 % and -8.28 % lower than that from control plot, respectively. The monitoring results showed that the average pollution loads reduced by vegetated ridge compared to control were BOD 36.62~53.60 %, SS 40.41~73.71 %, COD 39.34~56.41 %, DOC 49.08~53.67 %, TN 26.74~67.23 %, and TP 52.72~91.80 %; by silt fence compared to control were SS 41.73 %, COD 1.93 %, and TN 2.38 %. The paired t-test result indicated that the vegetated ridge and silt fence were statistically significant effect in SS load reduction, with a 5 % significant level. Monitored results indicated that vegetated ridge and silt fence were both effective to reduce the pollutant from the field surface runoff.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.8
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• pp.5060-5066
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• 2015

The number of shop needed for the fabrication of sphere type LNG tank is proportional to that of the tank radius to be constructed. Due to limitation of facility investment including building sites, it is practically difficult to fabricate various size tanks of perfectly spherical shape in the yards. The efficient method to increase cargo tank capacity is to extend vertically the conventional sphere type LNG tank by inserting a cylindrical shell structure. In this study, equations for static design loads are developed for sphere type LNG tank with central extension. The results of this study will be combined with dynamic design loads to build the simplified analysis method which enable the precise initial estimate instead of time consuming finite element analysis.