• Journal of Korean Society of Transportation
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• v.27 no.4
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• pp.55-61
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• 2009

In order to observe the impact of a type of vehicles for traffic flows and pavement, vehicle classifications is conducted. Korean Ministry of Land, Transport and Maritime Affairs provides 12-type vehicle classifications on National expressways, National highways, and Provincial roads. Current AVC (Automatic Vehicle Classification) devices decide vehicle types comparing measurements of vehicle lengths, wheelbases, overhangs etc. to a reference table including those of all types of models. This study developed an algorithm for macroscopic vehicle classification which is less sensitive to tuning sensors and updating the reference table. For those characteristics, trend lines in vehicle lengths and wheelbases are employed. To assess the algorithm developed, vehicle lengths and wheelbases were collected from an AVC device. In this experiment, this algorithm showed the accuracy of 88.2 % compared to true values obtained from video replaying. Our efforts in this study are expected to contribute to developing devices for macroscopic vehicle classification.

• Journal of the Korean Society for Heat Treatment
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• v.16 no.5
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• pp.260-266
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• 2003

In order to study the interfacial reaction between Nb thin sheet and Fe-C-(Si) alloy with different Chemical compositions, they were cast-bonded. The growth of carbide layer formed at the interface after isothermal heat treatment at 1173K, 1223K, 1273K and 1323K for various times was investigated. The carbide formed at the interface was NbC and the thickness of NbC layer was increased linearly in proportional to the heat treating time. Therefore, It was found that the growth of NbC layer was controlled by the interfacial reaction. The growth rate constant of NbC layer was slightly increased with increase of carbon content when the silicon content is similar in the cast irons. However, as silicon content increases with no great difference in carbon content, the growth of NbC layer was greatly retarded. The calculated activation energy for the growth of NbC layer was varied in the range of 447.4~549.3 kJ/moI with the compositions of cast irons.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.49 no.1
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• pp.29-39
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• 2013

Fishing vessels have been causing more than 70% of marine casualty in Korea. As a view of the occurring number of marine casualty, it is obvious for fishing vessel to account for the absolute high portion of that in comparison with the non-fishing vessels. That is a natural outcome because fishing vessels have occupied more than 90% of all registered Korean vessels. If we consider it not occurring number, but occurring ratio, we could find out that fishing vessels accounted for 5 times lower than non-fishing vessels in marine casualties. Nevertheless, fishing vessels have not immunity from responsibility for marine casualties at all, because the tendency of it in fishing vessel has been dominating the whole marine casualties in Korea. So for reduction of them, it is indispensable to decrease the casualties of fishing vessel. In this study, the authors tried to carry out many items of them to compare the occurring number with the occurring ratio, and dealt with the casualties of collision and machine damage in detail, because those have not only been occurring most frequently in casualties in Korea, but also led to the death and injury of lives. To reduce the collision and the machine damage, the operator have to keep the watch more strictly and check and keep the machine in good order. And it is necessary for the operator to take more education and training intended to decrease those systematically and continuously, especially for the crews of fishing vessels.

• Steel and Composite Structures
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• v.34 no.4
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• pp.499-509
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• 2020

The purpose of this paper is to investigate the degradation law of stiffness of steel-concrete composite beams after certain fatigue loads. First, six test beams with stud connectors were designed and fabricated for static and fatigue tests. The resultant failure modes under different fatigue loading cycles were compared. And an analysis was performed for the variations in the load-deflection curves, residual deflections and relative slips of the composite beams during fatigue loading. Then, the correlations among the stiffness degradation of each test beam, the residual deflection and relative slip growth during the fatigue test were investigated, in order to clarify the primary reasons for the stiffness degradation of the composite beams. Finally, based on the stiffness degradation function under fatigue loading, a calculation model for the residual stiffness of composite beams in response to fatigue loading cycles was established by parameter fitting. The results show that the stiffness of composite beams undergoes irreversible degradation under fatigue loading. And stiffness degradation is associated with the macrobehavior of material fatigue damage and shear connection degradation. In addition, the stiffness degradation of the composite beams exhibit S-shaped monotonic decreasing trends with fatigue cycles. The general agreement between the calculation model and experiment shows good applicability of the proposed model for specific beam size and fatigue load parameters. Moreover, the research results provide a method for establishing a stiffness degradation model for composite beams after fatigue loading.

• Journal of the Korean Society for Marine Environment & Energy
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• v.12 no.3
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• pp.209-216
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• 2009

IMO has established International Convention for the Control and Management of Ships' Ballast Water and Sediment 2004 in February 2004 in order to prevent transfer of aquatic organisms through ballast water. According to the Convention, Each countries are preparing ratification and legislation process and encouraging the development of treatment system to satisfy the performance standard in the Convention. This Electro-$Cleen^{TM}$ treatment system was granted IMO basic approval in March 2006, and final approval in October 2008. The Type Approval Certificate was issued in December 2008 by the Government of Republic of Korea. This paper considers the matter of principle mechanism, overview of the system, installation on shipboard and shipboard test results for the Electro-$Cleen^{TM}$. Shipboard tests with the 8300 GT M/V Yokohama and 27,000 DWT M/V Greenwing have already been conducted. These tests confirmed that the Electro-$Cleen^{TM}$ system satisfies all of the IMO standards and is suitable for installation in new and existing ships.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.43 no.5
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• pp.551-556
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• 2010

The large jellyfish Nemopilema nomurai causes serious damage to fisheries, particularly around the seas of Korea and Japan. Decreasing this damage requires knowledge of the distribution and abundance of jellyfish. Acoustic technology using quantitative echosounders is one method of studying the distribution and abundance of jellyfish. Such methods are commonly used worldwide because they have the advantage of providing substantial information about all water layers in a wide area in a short time. However, in order to conduct an acoustic survey, the acoustic characteristics of the target organism must be known. These can be altered by a number of factors, including pulsation, swimming angle, frequency and size. Accordingly, this study determined the variation in target strength according to pulsation of N. nomurai. Data were analyzed for two jellyfish with bell diameters in air of (a) was 32.0 and (b) 25.0 cm. The pulsation cycle of jellyfish (a) was 1.5~2.0 sec and the target strength (TS) cycle was 1.0~2.5 sec, while jellyfish (b) had a pulsation cycle of 1.0~1.5 sec and TS cycle of 1.0~3.0 sec. The variation width of the TS with the change in pulsation was 7.8 dB (-72.4~-64.6 dB) for jellyfish (a) and 10.3 dB (-71.6~-61.3 dB) for jellyfish (b). The variation in bell diameter was about 0.28 and 0.35, respectively. These results confirmed that the variation in bell diameter caused by pulsation is closely related to the variation in TS.

• Journal of the Korean Geosynthetics Society
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• v.9 no.3
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• pp.57-65
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• 2010

The main objective of this study is to investigate the time-dependent deformation of EPS blocks under repeated loading conditions which is the one of the flexible pavement structure. The study comprised of both the experimental work and analytical modeling in order to understand the behavior of EPS blocks under repeated loading. The analytical modeling included the selection of a suitable model for describing the deformation behavior observed under repeated loading conditions, investigating the relationship among the unit weight, deformation and applied stress, analyzing the effect of repeated load on deformation. The test results were compared with the Findley's theory and model analysis with the results of this research under repeated loading conditions. Both Modified Findley's model and the proposed model can be adopted to illustrate the deformation behavior of EPS blocks under repeated loads.

• Journal of the Korean Geographical Society
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• v.45 no.5
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• pp.628-646
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• 2010

The subject of this research is the small-scale trade between South Korea and China (this trade is a so-called shuttle trade.) This research attempts to find the background to the emergence of the Sino-South Korean (cross-border) small-scale trade and the role of travel routes between the two countries. This research also aims to identify the development process of the bilateral small-scale trade by studying the scale of the small-scale trade and the organization of small-scale traders. Moreover, this research tries to discover the spatial characteristics of the interregional small-scale trade by reviewing the characteristics of traded goods; process of export and import and nodes of small-scale trade. To accomplish aforementioned purposes, the author discussed the relations between small-scale traders and maritime companies. The author also studied the internal change in the small-scale trade by focusing on the reinforcement of the regulation against the small-scale trade. Lastly, the author cited the case of the Soviet Union and middle-eastern Europe, which tremendously expanded the small-scale trades in the 1980s, in order to explain the growth of the Sino-South Korean small-scale trade.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.56 no.2
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• pp.163-171
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• 2020

Engaged in trawling in limited fishing grounds with a number of fish schools could cause collisions between fishing vessels. Therefore, providing accurate maneuver information according to the situation could be regarded as essential for improving seafarers safety and fishing efficiency as well as safety of navigation. It is difficult to obtain all maneuver information through sea trial tests only, so a method through empirical formula is necessary. Since most empirical formulas are developed for merchant ship types, especially the characteristics of hull shape parameter like C_bB/L and dC_b/B etc. are clearly different between fishing vessels and merchant ships, this could occur estimation errors. Therefore, in this study, the authors have selected target fishing vessels and merchant ships and analyzed the characteristics of hull shape parameter according to the ship types. Based on this analysis, the empirical formula developed for the merchant ship type has applied to the target fishing vessels; it has verified through the turning motion simulation that the estimation error could be generated. In conclusion, it is necessary to include the characteristics of the hull shape parameter of fishing vessels in the empirical formula in order to apply the empirical formula has developed for merchant ship types to fishing vessel types.

• Smart Structures and Systems
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• v.6 no.3
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• pp.183-196
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• 2010

Monitoring and economical design of alternative energy generators such as wind turbines is becoming increasingly critical; however acquisition of the dynamic output data can be a time-consuming and costly process. In recent years, low-cost wireless sensors have emerged as an enabling technology for structural monitoring applications. In this study, wireless sensor networks are installed in three operational turbines in order to demonstrate their efficacy in this unique operational environment. The objectives of the first installation are to verify that vibrational (acceleration) data can be collected and transmitted within a turbine tower and that it is comparable to data collected using a traditional tethered system. In the second instrumentation, the wireless network includes strain gauges at the base of the structure. Also, data is collected regarding the performance of the wireless communication channels within the tower. In both turbines, collected wireless sensor data is used for off-line, output-only modal analysis of the ambiently (wind) excited turbine towers. The final installation is on a turbine with embedded braking capabilities within the nacelle to generate an "impulse-like" load at the top of the tower. This ability to apply such a load improves the modal analysis results obtained in cases where ambient excitation fails to be sufficiently broad-band or white. The improved loading allows for computation of true mode shapes, a necessary precursor to many conditional monitoring techniques.