• Journal of Biosystems Engineering
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• v.39 no.1
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• pp.47-56
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• 2014

Purpose: In protected crop production facilities such as greenhouse and plant factory, farmers should be present and/or visit frequently to the production site for maintaining optimum environmental conditions and better production, which is time and labor consuming. Monitoring of environmental condition is highly important for optimum control of the conditions, and the condition is not uniform within the facility. Objectives of the paper were to investigate spatial and vertical variability in ambient environmental variables and to provide useful information for sensing and control of the environments. Methods: Experiments were conducted in a strawberry-growing greenhouse (greenhouse 1) and a cherry tomato-growing greenhouse (greenhouse 2). Selected ambient environmental variables for experiment in greenhouse 1 were air temperature and humidity, and in greenhouse 2, they were air temperature, humidity, PPFD (Photosynthetic Photon Flux Density), and $CO_2$ concentration. Results: Considerable spatial, vertical, and temporal variability of the ambient environments were observed. In greenhouse 1, overall temperature increased from 12:00 to 14:00 and increased after that, while RH increased continuously during the experiments. Differences between the maximum and minimum temperature and RH values were greater when one of the side windows were open than those when both of the windows were closed. The location and height of the maximum and minimum measurements were also different. In greenhouse 2, differences between the maximum and minimum air temperatures at noon and sunset were greater when both windows were open. The maximum PPFD were observed at a 3-m height, close to the lighting source, and $CO_2$ concentration in the crop growing regions. Conclusions: In this study, spatial, vertical, and temporal variability of ambient crop growing conditions in greenhouses was evaluated. And also the variability was affected by operation conditions such as window opening and heating. Results of the study would provide information for optimum monitoring and control of ambient greenhouse environments.

• Journal of the Korean Institute of Gas
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• v.20 no.6
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• pp.43-49
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• 2016

In this paper, purpose of study is emissions characteristics according to effects of heating value variations of CNG fuel in a dual-fuel engine fueled by diesel and natural gas. For heating value variation of CNG fuel, nitrogen gas was mixed with pure CNG fuel. So the higher heating value was changed from $10,400kcal/Nm^3$ to $9,400kcal/Nm^3$. Under one condition of CNG substitution rate was fixed at 80%, diesel fuel was injected at a fixed injection timing of 16 CAD BTDC and fuel pressure was also fixed at 110 MPa. The condition of tested engine was 1800 rpm and 500Nm. Emissions were sampled in exhaust pipe was located at downstream turbocharger. As a result, emissions characteristics were checked in heating value variations of CNG fuel with mixed nitrogen gas THC, $CH_4$ and CO emissions decreased and NOx and $CO_2$ increased.

• Journal of Biosystems Engineering
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• v.33 no.5
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• pp.326-332
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• 2008

A respiration measurement system for vital signs was developed. Respiration signals were measured, processed, and analyzed. Four electrodes, attached on the surface of the skin, were used to monitor respiration signals by impedance pneumography. The measured signals were amplified, detrended, filtered, and transferred toan embedded module. The Kalman filter was used to remove motion artifact from the respiration signals. Experiments were conducted at stable condition and walking condition to evaluate the performance of the system. Respiration rates of five males and five females were measured and analyzed at each condition. The referenced respiration signal was determined by temperature of nose surroundings. The results showed that the respiration rates at the walking condition had more motion artifacts than the stable condition. The accuracies of the respiration measurement system with Kalman filter were found as 96% at the stable condition and 95% at the walking condition. The results showed that the Kalman filter was an effective tool to remove the motion artifact from the respiration signal.

• Journal of Biosystems Engineering
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• v.34 no.3
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• pp.190-196
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• 2009

The temperature of root zone is known as an important factor for the growth of crops and reduction of energy in greenhouse. The purpose of this study was to design the solar energy supply system to keep the optimum condition of root zone by soil warming. As a result of this study, soil warming compared with no warming changed on a large scale temperature rise effect by depth of soil. The greenhouse's inner temperature have an effect on the temperature of surface up to 15 cm, rised to about 1 hour after warming. In case of the temperature fluctuation, soil temperature was about $12^{\circ}C$ up to 15${\sim}$25 cm and it was $13.4^{\circ}C$ at greater depths. This results showed that the position of root zone was very different after 3 weeks of growth.

• Journal of the Korean Society of Clothing and Textiles
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• v.34 no.8
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• pp.1378-1391
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• 2010

This study examines the wearing conditions of working clothes according to the working environment and working processes at machinery, automobile, shipbuilding industry sites. It also investigates the relationship between the wearing sense of working clothes and the overall comfort according to work processes. The hazardous working environment was high in the order of the shipbuilding industry, machinery, and automobiles. The findings on the harmful overall work environmental factors were the noise, heavy dust, and noxious fumes, respectively. In general, the satisfaction with the wearing performance of working clothes was low especially with regard to sweat absorbency, sweat permeability, body protection and covering, and the work motion suitability. In respect of the correlation between the overall comfort and the wearing sense of working clothes, the satisfaction was decreased in the order of movement comfort, sensual comfort, and physiological comfort.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.7
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• pp.583-589
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• 2008

For the purpose of monitoring by ultrasonic test of the ball bearing conditions in rotating machinery, a system for their diagnosis was developed. ultrasonic technique is used to detect abnormal conditions in the bearing system. And various data such as frequency spectrum, energy and amplitude of ultrasonic signals, and ultrasonic parameters were acquired during experiments with the simulated ball bearing system. Based on the above results and practical application for power plant, algorithms and judgement criteria for diagnosis system was established. Bearing diagnosis system is composed of four parts as follows : sensing part for ultrasonic sensor and preamplifier, signal processing part for measuring frequency spectrum, energy and amplitude, interface part for connecting ultrasonic signal to PC using A/D converter, graphic display and software part for display of bearing condition and for managing of diagnosis program.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.11
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• pp.1297-1308
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• 2011

The light-weight design of UTM (Urban Transit Maglev)-02 car-body frames are performed, based on initial configuration. The thicknesses of fourteen sub-structures are defined as design variables and the loading condition is considered according to weight of sub-structures, electronic and pneumatic modules and passengers. For efficient and robust process of design optimization, objective function and constraints are approximated by response surface approximation. Structural analysis is performed at some sampling points to construct the approximated objective function and constraints composed of design variables. Design space is changed to find many optimal candidates and best optimal design can be found eventually. The Matlab Optimization Toolbox is used to find optimal value and sensitivity analysis about each design variable is also performed.

• Journal of Biosystems Engineering
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• v.33 no.5
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• pp.289-295
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• 2008

The task of chemical spraying has been seriously considered as an irritating and annoying job for Korean rice farmers. An agricultural unmanned helicopter was suggested to solve this problem so as the farmers to have more decent farming condition. The objectives of this study were to analyze the adoptability of an experimental rotor blade (SW05) using the CFD simulation and also to compare the simulation results with experimental results. The simulation results showed that the induced power of this rotor reached to $57{\sim}63%$ of total power and the profile power was about $37{\sim}43%$ of total power. Therefore it can be concluded that this rotor's performance characteristics were not so efficient for the size of unmanned helicopter due to the low induced power and high profile power relatively compared with ones of conventional rotors. The comparison with experimental results showed that the tested lifts were less than 70% of simulated ones at the grip pitch of $12^{\circ}$ and decreased to 40% at the $18^{\circ}$ grip pitch. Therefore, it can be concluded that the rotor was too oversized to be used for a 15.4 kW (21 PS) engine.

• Structural Engineering and Mechanics
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• v.43 no.3
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• pp.311-320
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• 2012

The higher-order asymptotic C(t) - $A_2(t)$ approach was employed to investigate the crack-tip stress of two collinear cracks in a power-law creeping material under the plane strain conditions. A comprehensive calculation was made of the single crack, collinear crack model with S/a = 0.4 and 0.8, by using the C(t) - $A_2(t)$ approach, HRR-type field and the finite element analysis; the latter two methods were used to check the constraint significance and the calculation accuracy of the C(t) - $A_2(t)$ approach, respectively. With increasing the creep time, the constraint $A_2$ was exponentially increased in the small-scale creep stage, while no discernible dependency of the constraint $A_2$ on the creep time was found at the extensive creep state. In addition, the creep time and the mechanical loads have no distinct influence on accuracy of the results obtained from the higher-order asymptotic C(t) - $A_2(t)$ approach. In comparison with the HRR-type field, the higher-order asymptotic C(t) - $A_2(t)$ solution matches well with the finite element results for the collinear crack model.

• International Journal of Railway
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• v.9 no.2
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• pp.41-45
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• 2016

In this paper, a study on the efficiency improvement of the magnetic levitation train using the LIM (Linear Induction Motor) was presented. The maglev train has the advantage of being environmentally friendly since much less noise and dust is produced. However, due to structural limitation, compared to a rotating induction motor, linear induction motor, the main propulsion engine of the maglev train has a relatively greater air gap and hence has the lower operation efficiency. In this paper, the relationship between the operating condition of the train and the slip frequency has been investigated to find out the optimum slip frequency that might improve the efficiency of the magnetic levitation train with linear induction motor. The slip frequency is variable during the operation by this relationship only within a range that does not affect the levitation system of the train. After that, the comparison of the efficiency between the conventional control method with the slip frequency fixed at 13.5[Hz] and the proposed method with the slip frequency variable from 9.5[Hz] to 6.5[Hz] has been conducted by simulation using Simplorer. Experiments of 19.5[ton] magnetic levitation trains owned by Korea Institute of Machinery and Materials were carried out to verify the simulation results.