• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.38 no.2
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• pp.156-163
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• 2002

In order to development the construction and dimension of fishing gear for gizzard shad coastal purse seine, first of all investigated to the sinking speed and underwater geometry of net, behaviour of fish school to the net during the fishing operation In the field. The results obtained are summarized as follows; 1. Average sinking speed of net was 13cm/sec in bunt, 9.0cm/sec and 9.5cm/sec in 170m and 280m of center, 4.9cm/sec in end wing side, therefore was fastest in start of shooting and decreased gradually during the shooting process. 2. The most of leadline was reached in bottom from the shooting immediately to hauling time and the mean depth of timber bar used equipment for the escaping prevention of fish school was within the 2.7m. 3. The fish school of gizzard shad was appearanced higher density and remained to the most time in bottom than the surface and repeated to vortical movement, and its tendency to distinct in rapid time of tide current. 4. Behaviour of fish school in the net was showed to the vortical movement by sinking and rising immediately with the shooting of net and then divide with the two shape to follow round the wall of net and no patterns straightly movement in the net, and tendency easily catched in fish school of the wall of net. 5. Escaping of fish school in the gap of wing side was to busy after that seting the timber bar, therefore its function for escaping prevention of fish school was very lowed. 6. Escaping behaviour of fish school was differenced with the depth of fishing ground, the above 20m escaped to busy through the below in ledline because the sinking speed of fish school is fast than the net.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.40 no.1
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• pp.29-36
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• 2004

This study deals with an analysis on the sinking resistance for the model purse seine, in the case of different netting material and sinkers. The experiment was carried out using rune simplified model seines of knotless nettings. Dimension of model seines 420cm for corkline and 85cm for seine depth, three groups of models rigged 25, 45 and 60g with the same weighted sinkers in water were used. These were named PP-25, PA-25, PES-25, PP-45, PA-45, PES-45, PP-60, PA-60 and PES-60 seine. The densitie($\rho$) of netting materials were 0.91g/cm$cm^3$, 1.14g/cm$cm^3$ and 1.38g/cm$m^3$. Experiments carried out in the observation channel in a flume tank under still water conditions. Sinking motion was recorded by the one set of TV-camera for VTR, and reading coordinate carried out by the video digitization system. Differential equations were derived from the conservation of momenta of the model purse seines and used to determine the sinking speeds of the depths of leadline and the other portions of the seines. An analysis carried out by simultaneous differential equations for numerical method by sub-routine Runge-Kutta-Gill The results obtained were as follows : 1. Average sinking speed of leadline for the model seines rigged 60g with the same weighted sinkers in water was fastest for 12.2cm/sec of PES seine, followed by 11.4cm/sec of PA and 10.7cm/sec of PP seines. 2. The coefficient of resistance for netting of seine was estimated to be $K_D=0.09(\frac{\rho}{\rho_w})^4$ 3. The coefficient of resistance for netting bundle of seine was estimated to be $C_R=0.91(\frac{\rho}{\rho_w})$ 4. In all seines, the calculated depths of leadline closely agreed with the measured ones, each 25g, 45g, 60g of weighted sinkers were put into formulas meas.=1.04cal., meas.=0.99cal. and meas.=0.98 cal.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.34 no.3
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• pp.294-301
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• 1998

Towing performance of a midwater trawl system was examined aboard the training ship KAYA(2900ps) at the East Sea using the midwater trawl gear that had been designed and manufactured in accordance with the vessel. In this experiment, the trawl system data, the towing speed, the length and tension of the warp, net mouth height, and the depth of otter boards and net were measured and analyzed. The results are as follows: 1. In case of heaving in the warp with constant towing speed, the tension was suddenly increased and then again was reduced and after returned to the original steady state tension. At this time, net height was reduced a bit by ascension of ground rope, but returned to it’s original value. In the case where the warp was paid out, the tension was suddenly decreased and after increased and then returned to the tension of the original state, and the net height was greatly increased instantly by the sinking of the ground rope and then returned to the steady state 2. In the case of increased towing speed mm constant warp length, the tension was increased, and reducing the net height, the gear depth was decreased. On the other hand, in the case where towing speed was reduced, the tension was reduced and the gear depth and net height was increased. 3. Otter boards show a swing motion in the scope of 5~ 10m continuously. Otter boards responded to the state change of the trawl system at first, and then the motion of the net appeared. 4. The depth of net center was about 20m deeper than that of the otter boards, it shows about 0.4 times the warp length at the 4knots towing speed.

• Journal of the Society of Naval Architects of Korea
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• v.53 no.3
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• pp.217-227
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• 2016

Recent accidents of crude oil tankers have resulted in sinking, grounding of vessels and significant levels of marine pollution. Therefore, International Maritime Organization (IMO) has been strengthening the regulations of ship maneuvering performance in MSC 137. The evaluation of maneuvering performance can be made at the early design stage; it can be investigated numerically or experimentally. The main objective of this paper was to investigate the maneuvering performance of a VLCC due to the increase of rudder force at an early design stage for low speed in shallow water conditions. It was simulated in various operating condition such as deep sea, shallow water, design speed and low speed by using the numerical maneuvering simulation model, developed using MMG maneuvering motion equation and KVLCC 2 (SIMMAN 2008 workshop). The effect of increasing the rudder force can be evaluated by using numerical simulation of turning test and ZIG-ZAG test. The research showed that, increasing the rudder force of a VLCC was more effective on improving the turning ability than improving the course changing ability especially. The improvement of turning ability by the rudder force increasing is most effective when the ship is sailing in shallow water at low forward speed.

• Journal of Welding and Joining
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• v.32 no.6
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• pp.22-28
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• 2014

Most publications on friction stir welding describe phenomena or results with given process parameters like feed rate, rotation speed, angle and depth of penetration. But without a complete documentation of tool design, the results under the same process parameters are completely different. For this purpose, the Institute of Cutting and Joining Manufacturing Processes (tff), University of Kassel investigated the influence of tool roughness on the friction stir welding process. Therefore a defined surface finish was produced by turning and die sinking. As basis of comparison the constant parameters were rotation speed, feed rate, tilt angle and a heel plunge depth. Sound butt-welds were produced in aluminium alloy 6082 (AlMgSi1) with 1.5 mm sheet thickness with a turned reference tool with a surface of $Ra=0.575{\mu}m$ in position controlled mode. The surfaces are manufactured from a very fine to a very rough structure, classified by the VDI-classes with differences in the arithmetical mean roughness. It can be demonstrated with the help of temperature measures, that less heat is generated at the surfaces of the shoulder and the pin by the higher roughness due to lower active friction contact surface. This can also be seen in the resulting wormhole defects.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.794-797
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• 2001

The basic design of today s rolling linear guides with rails is outlined in a French patent from 1932, it was not until the early 1970s that linear guides were commercialized. Progress with the numerical control of machine tools led to higher speed and accuracy of machines that exposed limitations of conventional sliding guides in terms of durability and response capability. As a result, rolling guides, having better high-speed performance and greater compatibility with electronics, began to be used widely. This paper examined theoretically and experimentally the influence of rail bolt tightening on the motion accuracy of linear guides. The rail of a linear guide is tightened and fixed to the base component by bolts. Naturally, the rail is an elastic body and the compression force generated by tightening the volts causes its deflection. Compromising motion accuracy, the rail deforms wavily in a longitudinal direction corresponding to the bolt pitch. The relation between rail position and deflection(sinking) amount caused by bolt tightening was analyzed through FEM analysis in this paper.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.11a
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• pp.69-72
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• 2003

This study is intended to investigate the fundamental properties of concrete which AE water reducing agent for reduction of bleeding is used, and the properties of bleeding reduction. According to the results, when the adding ratio of AE water reducing agent for reduction of bleeding increases, a range of normal fluidity and aimed air content arc satisfied, setting time is faster than that of normal AE water reducing agent. And bleeding amount decreases, bleeding speed is highest between 60 and 90 min, and sinking depth increases drastically in 60 min. When, AE water reducing agent for reduction of bleeding is added, compressive strength shows a slight variation by air content, but there is not a large influence by addition of AE water reducing agent for reduction of bleeding. Synthetically, it proves that AE water reducing agent for reduction of bleeding satisfies aimed air content in the range of normal slump and can reduce only bleeding without quality variation of compressive strength.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.05a
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• pp.69-72
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• 2003

This study is intended to investigate the fundamental properties of concrete which AE water reducing agent for reduction of bleeding is used, and the properties of bleeding reduction. According to the results, when the adding ratio of AE water reducing agent for reduction of bleeding increases, a range of normal fluidity and aimed air content are satisfied, setting time is faster than that of normal AE water reducing agent. And bleeding amount decreases, bleeding speed is highest between 60 and 90 min, and sinking depth increases drastically in 60 min. When. AE water reducing agent for reduction of bleeding is added, compressive strength shows a slight variation by air content, but there is not a large influence by addition of AE water reducing agent for reduction of bleeding. Synthetically, it proves that AE water reducing agent for reduction of bleeding satisfies aimed air content in the range of normal slump and can reduce only bleeding without quality variation of compressive strength.

• Journal of the Korean Institute of Navigation
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• v.11 no.2
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• pp.33-52
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• 1987

The disasters of wet bound vessels have been more frequent than those of east bound ones on the sea routes of the North Pacific Ocean in winter season. M/V Hanjin-Inchon was also west bound in her missing voyage. The container vessel of 17, 676 gross tons, M/V Hanjin-Inchon owned by Hanjin Shipping Co.Ltd in Seoul Korea left seattle in west coast of U.S.A for Pusan , Korea on the 5th Feb., 1987 and sailed along the exact courses recommended by Ocean Routes until she reported her position and speed as 49-30N, 158-00E and 8 knots to her head office in Seoul by this ship's time 2200 hours on the 13th Feb., 1987. The above message turned out to be last message from her because she had been missing since then leaving no message but only two life boats of her name, three containers cases, large scale of oil slicks and the corpse of her 3rd mate drifting on the sea near the position reported by her last message.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.10a
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• pp.334-343
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• 2003

The discharge gap clearly is to order and to promote the improvement of processing feature of die-sinking electro discharge machining(EDM). If creation carbon, which generated by Pyrolysis of EDM oil and processing pace power which is generated in between an electrode and a workpiece, are overproduced, they will lower the processing speed and roughness of the surface. Therefore, it is gone through an experiment and the flow analysis of EDM oil in order to improve the treatment of processing chips, which is an important problem by contriving a new flushing method. The condition of an electric discharge is not considered to be a progressing of processing. It is assumed that the flow of processing fluid is equal to the flow of processing chip, which is remaining in the discharge gap, and thus, analyzing then comparing with the data of the experiment and investigate its correlation.