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This study investigates workers' favoured rotation types by their age and compares means between subjective and actual scores on productivity, quality and musculoskeletal disorders (MSDs). The subjects of research were 422 assembly line units in Hyundai Motor Company. The survey of 422 units focused on the workers' preference for 11 different rotation types and subjective scores for each type's perceived benefits, both by the workers' age. Then, actual scores on production-related indices were traced over a five-year period. The results suggest that different rotation types lead to different results in productivity, product quality and MSDs. Workers tend to perceive job rotation as a helpful method to enhance satisfaction, productivity and product quality more so than the actual production data suggests. Job rotation was especially effective in preventing MSDs for workers aged under 45, while its effects were not clear for the workers aged 45 years or older. Practitioner's Summary: This research presents appropriate rotation type for different age groups. Taking workers' age into account, administrators can use the paper's outcomes to select and implement the suitable rotation type to attain specific goals such as enhancing productivity, improving product quality or reducing MSDs.

The production of electricity from wind energy is noticed as economic power generation system in the natural resource. Lately, since lots of wind turbine have installed globally, the accidents have increased gradually. In this paper, we classified domestic information for 10 years, information of new energy and industrial technology development organization(NEDO) for 4years and caithness windfarms information forum(CWIF) for 15 years according to part and cause of wind turbine accident . We found that the main causes of accidents are storm, lightening and carelessness. The results of classifying and analyzing the informations, should be used to take measures on the accident prevention of wind turbine. Key Words ：Wind turbine, Natural resource, CWIF, Accident prevention **†정지현(교신저자) : 제주대학교 기계공학전공E-mail : badaro@jejunu.ac.kr, Tel : 064-754-3627 * 김귀식 : 제주대학교 기계공학전공 **†Ji-Hyun Jeong(corresponding author) : Major of Mechanical Engineering, Jeju National University.E-mail : badaro@jejunu.ac.kr, Tel : 064-754-3627* Gui-Shik Kim : Major of Mechanical Engineering, Jeju National University.

The food waste that occurs in one year is very high in our country and disposal is expensive. However, disposers for food waste are not used wisely at real life. This is because most of them some kind of problem, for example big volume, complicated construction, high cost, lots of troubles, low energy efficiency and so on. In this study, we propose the new dryer system to decrease drying times by injecting hot air in down the side of the drying bucket. The designed drying bucket has inclined inlet holes down both sides. The inlet holes have variable gradients, we adjust the inlet velocity of the hot air to find a suitable vortex in the drying bucket. We verify the properties of the proposed system though simulation. The results show the proposed dryer system can improve the drying time and save energy for food waste disposal.

Roll and pitching motions of a vessel can seriously degrade the performance of mechanical systems and the effectiveness of personnel. Many studies on roll stabilization and trimming control system design have focused on stabilizing the vessel through the use of fins, tanks, rudders and flaps. However the ultimate objective of such approaches must be to improve boarding sensitivity. This paper presents an anti-seasickness bed that consists of a rotator and bearing system that does not make use of electric power. The advantages of this system are its simple construction, usefulness, and safe operation. In this study, the rotation angles of the upper plate of a bed according to change weight of the rotator have been calculated to determine the stability. As a result, it can be concluded that proposed stabilizing bed can be of practical use in the field.

The purpose of this paper is to manufacture the non-sintered ceramic used lime and industrial waste. The used materials were basalt powder sludge, calcium hydroxide(Ca(OH)2) and additives such as calcium stearate and TiO  . The mixing ratios between Ca(OH)2 and sludge were 5:5, 6:4 and 8:2, respectively. The ceramic forms were pressured by 100, 200 and 300 bar and cured in 14% CO2 for 12 days. The behaviors of compressive strength, specific gravity, water absorption and pH of ceramic form were investigated. The results were compressive strength of over 36 MPa, water absorption of over 8.8%, pH value of over 12.3. And these results satisfied GR F 4006 and 4031 standard. Key Words ：Basalt Powder Sludge, Calcium Hydroxide, Carbonation, Compressure Strength *†정지현(교신저자) : 제주대학교 기계공학전공E-mail : badaro@jejunu.ac.kr, Tel : 064-754-3627 *김귀식 : 제주대학교 기계공학전공**김정윤 : 제주대학교 산업대학원 *†Ji-Hyun Jeong(corresponding author) : Major of MechanicalEngineering, Jeju National University.E-mail : badaro@jejunu.ac.kr, Tel : 064-754-3627*Gui-Shik Kim : Major of Mechanical Engineering, Jeju NationalUniversity.**Jung-Yun Kim : Industial Graduate School, Jeju National University.

The automation of container cranes is one of the significant factors of global competitiveness, by improving the celerity of distribution processing in container terminals. Most container terminals operate with Rubber-Tired Gantry Crane (RTGC) type container cranes. However, the RTGC displays various uncertainties, including slips and scarcities of air pressure of tires during tracking mode, and position error during suspension, and therefore it is difficult to secure reliability for the automation level, and systematic research developments remain in inadequate status. First, the problem of tracking control that tracks the route determined at the yard with high speed and accuracy must be solved, to achieve automation of the RTGC. Since it is virtually impossible to use the steering unit of the RTGC, there exist constraints of having to perform tracking control through the speed control of both drive units. Thus, the RTGC is a system with nonholonomic constraint, as the typical nonlinear system driven by tires. In this study, the nonholonomic system is applied to conduct the overall system modeling, through kinematic modeling and dynamic modeling of the RTGC. Furthermore, the sliding mode control technique is applied as one of the discontinuous time invariant control techniques, for the purpose of simultaneously accomplishing system stabilization, and overcoming model uncertainties. The gains of sliding planes will be analytically found by using the LMI technique, and performance of the proposed control unit will be confirmed through the experiment.

Due to recent requirements for the systematization of cultivation in agriculture, many kinds of agricultural machines have been used. Vehicles with lifting utility are used to harvest and transfer crops and fruit. These vehicles have buckets that can be moved up and down to harvest crops and fruit in high places. These vehicles often have to operate on unpaved slopes. Therefore, the stability of the vehicle should be studied in the development stage. In this study, the overturn angles of the vehicle in three conditions have been calculated to determine stability. As a result, it could be concluded that these vehicle models are stable.

A Soft bending pipe is widely used for freezing equipment and shipbuilding. This pipe has some problems such that outside wrinkle, crack, phenomenon of thinning wall. However, the bending machine that can completely solve the problems is not yet. In this study, we have manufactured the self-made mandrel to guarantee both roundness and thickness of the pipe in the bending process for a soft pipe such as a copper pipe. The mandrel consisted of a ball, stick and connection pin. Also, we have manufactured the bending machine that can decrease friction between the pipe and the bending die. The experiment was tried to verify the performance of the mandrel and the pusher to the thickness guarantee of the pipe.

In general, the process of extrusion can experience some problems, such as flow problems inside molds, and strain problems of products as a result of the cooling speed. We explore the flow problems and temperature problems inside the die of an extruding machine. An optimal model has been investigated experimentally with different types of die slots and lips. The area of stress concentration has been examined, and the life has been predicted by structural analysis and fatigue analysis. An experiment was carried out to verify the stabilization of the model by modal analysis and analyzing manufactured specimens.

Soft bending pipe is widely used for freezing equipment and shipbuilding. These pipe have some problems that they cause occasionally outside wrinkle, crack, wall thinning phenomena. However, vending machines which have been made to solve the problems completely, are not yet. In this study, to settle these problems, we proved the effectiveness of the self-made mandrel by results of simulation as the basic for the development of precision high-quality vending machine ; presents the solution method of the wall thinning phenomena by analyzing circular deformation and damage of bending pipe.

Roll forming process is one of the most widely used processes in the world for forming metals such as a furniture drawer guide or an up and down slide guide. It can manufacture goods of the uniform cross section on a large scale throughout the continuous processing. In the domestic design and manufacture, roll forming process for production is taking most of the method of 2-point under rail slide. However, this method is vulnerable to the structural strength and stiffness is not suitable for high load conditions. Therefore, through systematic study of high load, low noise 3-point ball type of under rail slide its own design and manufacturing technology is the need to build. In this paper, to make center member of 3-point ball-type under rail slide for the refrigerator doors, the roll forming modeling and simulation are performed. Tensile test is performed about SCP-1 1/2H for determine the mechanical properties of materials. Modeling and simulation of roll forming is used MSC.MARC software of a dedicated analysis program used by rigid plastic finite element method. Interference between the roll and the final shape are predicted from the results of the simulation.

One of the main problems concerning the shallow seismic survey is how to generate high frequency signals with large amplitudes using small seismic sources. If one could focus the seismic energy in the direction of the survey line, it will be much helpful in identifying the first break. In this research, we have used hammer as an impulsive source and compared the signal powers generated by different shapes of the hammer plates: circular, square, and rectangular. The experiment was conducted by calculating the power spectral density function to compare the frequency spectrum and signal power. In the direction perpendicular to the long side of the rectangular plate, the largest seismic energy with the highest frequency was achieved even with the same weights of hammer plates. Our conclusion is that it is more efficient to use a rectangular plate than a circular (or square) one when conducting a 2-D shallow seismic survey.

The handling ability of containers at the terminal strongly depends on the performance of the cargo handling system such as RTGC(Rubber Tired Gantry Crane). This paper introduces a new guide line position measurement method using a camera for the RTGC which plays a important role in the harbor area. Because the line tracking is the basic technique for control system design of RTGC, it is necessary to develop a useful and reliable measurement system. If the displacement and angle of the RTGC relative to a guide line as trajectory to follow is obtained, the position of RTGC is calculated. Therefore, in this paper, a camera-based measurement system is introduced. The proposed measurement system is robust against light fluctuation and cracks of the guideline. This system consists of a camera and a PC which are installed at the lower side of the RTGC. Two edges of the guide line are detected from an input image taken by the camera, and these positions are determined in a Hough parameter space by using the Hough transformation method. From the experimental results, high accurate standard deviations were found as 0.98 pixel of the displacement and 0.24 degree of the angle, including robustness against lighting fluctuation and cracks of the guide line also.

*,**,***Graduate School of Pukyong National University, Busan 608-739, Korea †Department of Mechanical System Engineering, Pukyong National University, Busan 608-739, Korea 요 약 :컨테이너의 신속한 이송 및 처리는 작업시간 단축에 의한 비용절감을 의미하므로 항만에서는 가능한 작업효율을 향상시키기 위해 다양한 노력이 추진되고 있다. 1990년대 중반부터 RMGC 및 RTGC 등의 크레인이 개발되어 컨테이너 이송 및 적재를 위한 필수장비로 널리 이용되고 있다. 특히 RTGC는 타이어 구동방식이므로 주행환경에 크게 제약을 받지 않는 장점도 있으나, 타이어 슬립, 타이어에 의한 샤시의 기울어짐 등 설정된 경로를 고정도로 주행해야 하는 목적달성에 장애가 되는 요인도 많아 레일 위를 주행하는 RMGC에 비해 자동화가 용이하지 않다. 이것은 무인 RTGC 시스템 구축을 어렵게 하는 가장 큰 요인이 되어 이와 관련한 기술개발 또한 미비한 수준에 이르고 있다. 따라서 본 논문에서 RTGC의 무인자동화에 있어서 가장 기초단계라고 볼 수 있는 수학적 모델링을 기반으로 한 고정도 주행제어기를 설계하고자 한다. 먼저 제어대상인 RTGC의 주행에 따른 운동특성을 분석하여 모델링을 수행한다. 기본적인 주행성능을 달성하기 위한 주행제어기를 설계하고 시뮬레이션을 통해 설계된 제어기의 유용성을 확인하도록 한다.핵심용어 : RTGC, RMGC, 자동화 컨테이너 터미널, 주행제어, 2자유도 서보계Abstract :To handle container effectively is one of the most important factors in a port because working time is linked soon into cost. Since the middle of 1990s, RMGC(Rail-Mounted Gantry Crane) and RTGC(Rubber-Tired Gantry Crane) have been developed and widely used to operate containers in the yard. The RTGC is more difficult than RMGC in the automatic control system design. Although, the RTGC is largely advantaged to free driving environment, it has some considerable disadvantages in the system operating. In general, the problems are due to tire slip and lack of tire pressure etc. Therefore, a desirable research result has not been shown in this time. So, in this paper, we propose a new approach to design tracking control system for the RTGC in which the mathematical modeling is included. From the simulation results, the control performance of the designed control systems is evaluated.Key words :RTGC(Rubber-Tired Gantry Crane), RMGC(Rail-Mounted Gantry Crane), ACT(Automatic Container Terminal), tracking control, Two-degree-of-freedom(2DOF) servosystem * 대표저자 : 연회원, bada@pknu.ac.kr 010)8488-4098 ** 학생회원, lds_dong@naver.com 010)5158-6227*** 학생회원, fuheaven@nate.com 017)564-0129 †교신저자 : 연회원, kpjiwoo@pknu.ac.kr 051)629-6197