• Research in Community and Public Health Nursing
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• v.24 no.3
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• pp.314-322
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• 2013

Purpose: The purpose of the study was to examine associations between job stress and work-related musculoskeletal symptoms (WRMS) in street sanitation workers. Methods: A cross-sectional correlational study was conducted with 87 male street sanitation workers at E Gu in Seoul. The Job stress and WRMS were measured by using the Korean Occupational Stress Scale-Short Form and the KOSHA GUIDE H-9-2012 instrument, respectively. The WRMS was evaluated according to the National Institute of Occupational Safety and Health criteria. Results: The participants reported greater levels of insufficient job control and interpersonal conflict than the general Korean population. Of the participants, 44.8% reported WRMS at any body parts. Specifically, 28.7% reported WRMS at upper parts, while 16.5% reported WRMS at lower parts. Compared to low levels of job demand, its high levels were significantly associated with WRMS at both upper and lower parts of the body (OR=3.62, 95% CI=1.15~11.38; OR=3.60, 95% CI=1.04~12.39). Compared to low levels of occupational climate, its high levels were significantly associated with WRMS at upper parts of the body (OR=3.18, 95% CI=1.22~8.26). Conclusion: Among street sanitation workers, job stress may be a correlate of WRMS. Therefore, nursing strategies for reducing job stress are needed to prevent and manage WRMS.

• Korean Journal of Occupational Health Nursing
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• v.23 no.4
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• pp.245-253
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• 2014

Purpose: School foodservice employees (SFEs) could be exposed to the risk of musculoskeletal disease and of job stress due to their job characteristics. This study was to evaluate the level of job stress and the prevalence of work-related musculoskeletal symptoms (WRMS) in Seoul city's SFEs, and to determine associations between job stress and WRMS. Methods: The study design was cross-sectional, and 975 SFEs were recruited. Self-administered questionnaire included the 'Korean occupational stress scale-short form' and the 'KOSHA GUIDE H-9-2012' instrument to evaluate the job stress and WRMS, respectively. SFEs' medians of job stress were compared to the reference values of published study in Korean workers. Results: The participants reported greater levels of job demand and physical environment than the general Korean population. WRMS were reported in 89.0% of participants at any body part, and 41.1% were presumed to need for medical intervention. High levels of job demand and of physical environment were significantly associated with WRMS. Conclusion: Subscales of job demand and physical environment were relatively high in SFEs and those were related to the occurrence of WRMS. To reduce the WRMS prevalence, a job stress management program focused on job demand and physical environment may be required.

• 대한방사선방어학회:학술대회논문집
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• 2009.11a
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• pp.212-213
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• 2009

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.1
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• pp.16-26
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• 1998

The major effective factors on the ride quality of a vehicle are the vibration and noise of the engine and drive system. Engine contributes about 80% of the vibration and noise in the vehicle, and exciting forces of the engine are transmitted onto the vehicle frame through the engine mount. This paper studies the vibration reduction of a vehicle through the improvement of the engine mount. A computer program for optimal design is developed and the engine mount conditions are optimized to reduce the WRMS of PSD of acceleration at the driver's seat, which are caused by the exciting forces at the idle speed. Design variables are selected as the stiffness, mount angle and the location of the engine mount rubber. It is shown through computer simulation that the PSD of acceleration at the driver's seat can be improved by redesigning the engine mount system.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.5
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• pp.463-471
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• 2013

This paper presents design and control of electronic control suspension(ECS) equipped with controllable magnetorheological(MR) damper for passenger vehicle. In order to achieve this goal, a cylindrical type MR fluid damper that satisfies design specification of a middle-sized commercial passenger vehicle is proposed. After manufacturing the MR damper with design parameters, their field-dependent damping forces are experimentally evaluated and compared with those of a conventional damper. A quarter-vehicle MR ECS system consisting of sprung mass, spring, tire, controller and the MR damper is established in order to investigate the ride comfort performances. On the basis of the governing equation of motion of the suspension system, five control strategies(soft, hard, comfort, sport and optimal mode) are formulated. The proposed control strategies are then experimentally realized with the quarter-vehicle MR ECS system. Control performances such as vertical acceleration of the car body and tire deflection are evaluated in frequency domains on random road condition. In addition, performance comparison of WRMS(weighted root mean square) of the quarter-vehicle MR ECS system on random road are undertaken in order to investigate ride comfort characteristics.

• International Journal of Automotive Technology
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• v.6 no.2
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• pp.141-148
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• 2005

In order to reduce the time and costs of improving the performance of vehicle suspensions, the techniques for optimizing damping and air spring characteristic were proposed. A full vehicle model for a bus is constructed with a car body, front and rear suspension linkages, air springs, dampers, tires, and a steering system. An air spring and a damper are modeled with nonlinear characteristics using experimental data and a curve fitting technique. The objective function for ride quality is WRMS (Weighted RMS) of the power spectral density of the vertical acceleration at the driver's seat, middle seat and rear seat. The objective function for handling performance is the RMS (Root Mean Squares) of the roll angle, roll rate, yaw rate, and lateral acceleration at the center of gravity of a body during a lane change. The design variables are determined by damping coefficients, damping exponents and curve fitting parameters of air spring characteristic curves. The Taguchi method is used in order to investigate sensitivity of design variables. Since ride and handling performances are mutually conflicting characteristics, the validity of the developed optimum design procedure is demonstrated by comparing the trends of ride and handling performance indices with respect to the ratio of weighting factors. The global criterion method is proposed to obtain the solution of multi-objective optimization problem.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.4
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• pp.353-360
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• 2015

Commercial drivers feel tired more than the general public, because their driving times are long and they experience more idle vibration. In this study, we developed a nonlinear model of a magnetic, linear spring seat suspension to determine the optimal design to improve ride comfort. The resonant frequency for the optimal design of the suspension was found to be 3.5 Hz, and the stiffness was analyzed through displacement-load experiments. Additionally, the vibration transmissibility was analyzed by the suspension stiffness, and the existing coil spring type vibration transmissibility was found to be 0.99. A parallelogram type magnetic spring was determined to result in a better performance than the existing spring with a vibration transmissibility of 0.823.