• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.4
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• pp.371-379
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• 2015

This paper represents the structural design of the light weight axle beam for medium duty commercial vehicle using hot press. To reduce the weight of the axle, axle beam of solid type was replaced by hollow type which was made by hot press. According to the change of axle beam structure and manufacturing method, we have to investigate the structural strength and fatigue performance. To verify the axle beam performance, the structural analysis was carried out by simplified axle beam model and various design parameters that are axle beam height, thickness and width. From the analysis results, the light weight axle beam structure was founded and applied the full model analysis. This study will be used as a guidance in development of the light weight axle for medium duty commercial vehicle.

• Korean Journal of Childcare and Education
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• v.3 no.1
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• pp.1-15
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• 2007

The objective of this study was to investigate the employed mother's work-mother role conflict according to the mother's work variables and parenting time. For this purpose, 202 employed mothers in dual-income family answered the questionnaire. The data were analysed by t-test, F-test, correlations and regressions. The findings of this study were: 1. Mother's role conflict showed significant difference and relationship in mother's work variables(flexibility of duty, irregular duty). 2. Mother's role conflict showed significant difference and relationship in mother's parenting time(mother-child activities, parenting time). 3. Employed mother's flexibility of duty and parenting time were correlated positively with mother's role conflict. Mother's irregular duty and mother-child activities were negatively with mother's role conflict. 4. Employed mother's work variables and parenting time influenced the mother's rolr conflict.

• International Journal of Automotive Technology
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• v.2 no.3
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• pp.93-101
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• 2001

Distribution of fuel-air mixture has a strong influence on performance and emissions of a compressed natural gas (CNG) engine. In this paper, parametric study is performed by KIVA-3V to investigate fuel-air mixture with respect to injection timing, cycle equivalence ratio and engine speed. With open-valve injection intensive mixing during intake and compression stroke results in relatively homogeneous mixture in the cylinder. Sequential induction of fuel-air mixture and fresh air results in stratification in the cylinder among the test cases at closed-valve injection. There is close similarity in the calculated distributions of the mixture in the cylinder with different cycle equivalence ratios and engine speeds. The results are compared against pressure traces and flame images obtained in a single cylinder engine converted from a 11L six-cylinder heavy duty diesel engine.

• 한국정보통신설비학회:학술대회논문집
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• 2009.08a
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• pp.242-247
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• 2009

In this paper, we investigate interference between short-range radiocommunication devices (SRDs) with frequency hopping spread spectrum (FHSS) and direct sequence spread spectrum (DSSS) methods when they are in the same frequency bands. In order to analyze interference from unwanted emission of SRD with DSSS to that of FHSS, Monte-Carlo (MC) simulation method is employed and interference probabilities are calculated. We simulate interference scenarios in accordance with several duty cycles and bandwidths. It is also assumed that the propagation model is free space The effect of distance between interfering transmitter and victim receiver is analyzed and bit error rate (BER) is simulated. From the interference analysis results, it is shown that duty cycle affects compatibility more than bandwidth does. Also, we can make sure of the separation distance which satisfies BER criterion when there are only one interfering transmitter and multiple interfering transmitters.

• Journal of Korean Physical Therapy Science
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• v.9 no.4
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• pp.73-81
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• 2002

The purpose of this study was to investigate factors affecting physical therapist's job satisfaction at public health center. The data were collected from May 10 to 12, 2002 and 117 valid questionnaires were obtained and analyzed. They were analyzed by the percent, frequency, t-test, one-way ANOVA and Pearson correlation coefficiency. The results of the study were as follows: 1. The average marks by their job satisfaction factors indicated 3.56 for identity guarantee, 3.20 for administration, 2.78 for duty volume, 2.53 for relation with colleague. 2. There was statistically a difference of the education degree in relation with colleague. 3. There were statistically a difference of the age, total career, grade in rank, the number of colleague in identity guarantee. 4. No statistical significance were observed with the factors of incumbent satisfaction, duty volume, flexibility at work, administration.

• The Korean Journal of Emergency Medical Services
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• v.18 no.3
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• pp.53-62
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• 2014

Purpose: This study aimed to investigate duty-related incidental stress, coping method, and stress factors in 133 new firefighters. Methods: A self-reported questionnaire was administrated to 133 new firefighters between April and May 2010. It consisted of 33 and 62 items concerning duty-related incident stress and coping methods, respectively. Data were analyzed by using the t-test, analysis of variance, Pearson correlation coefficient analysis, and multiple regression analysis. Results: New firefighters experienced the most stress when inappropriately dispatched. Duty-related incidental stress correlated with active (r = .420, p < .001) and passive coping (r = .450, p < .001). Also active coping statistically correlated with passive coping (r = .890, p < .001). Influencing factors of duty-related incidental stress were passive coping (t = 2.12, p < .05), experience of having a co-worker in a dangerous situation (t = 3.30, p < .001), having less than 6 months of work experience (t = 2.30, p < .05), and experience of having oneself in a dangerous situation (t = 2.05, p < .05). Conclusion: New firefighters need to be provided with training on active coping to prevent posttraumatic stress disorders and, social support immediately after an inappropriate and stressful dispatch.

• International Journal of Automotive Technology
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• v.6 no.3
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• pp.221-227
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• 2005

Aim of this study is to investigate an aerodynamic effect of a drag-reducing device on a heavy-duty truck. The vehicle experiences two different kinds of aerodynamic forces such as drag and uplifting force (or downward force) as it is traveling straight forward at constant speed. The drag force on a vehicle may cause an increase of the rate of fuel consumption and driving instability. The rolling resistance of the vehicle may be increased as result of the negative uplifting or downward force on the vehicle. A device named roof-fairing system has been applied to examine the reduction of aerodynamic drag force on a heavy-duty truck. As for a engineering design information, the drag-reducing system should be studied theoretically and experimentally for the best efficiency of the device. Four different types of roof-fairing model were considered in this study to investigate the aerodynamic effect on a model truck. The drag and downward force generated by vehicle has been obtained from numerical calculation conducted in this study. The forces produced on four fairing models considered in this study has been compared each other to evaluate the best fairing model in terms of aerodynamic performance. The result shows that the roof-fairing mounted truck has bigger negative uplifting or downward force than that of non-mounted truck in all speed ranges, and drag force on roof-fairing mounted truck has smaller than that of non-mounted truck. The drag coefficient $(C_D)$ of the roof-fairing mounted truck (Model-3) is reduced up to $41.3\%$ than that of non-mounted trucks (Model-1). A downward force generated by a roof-fairing mounted on a truck is linearly proportional to the rolling resistance force. Therefore, the negative lifting force on a heavy-duty truck is another important factor in aerodynamic design parameter and should be considered in the design of a drag-reducing device of a tractor-trailer. According to the numerical result obtained from present study, the drag force produced by the model-3 has the smallest of all in all speed ranges and has reasonable downward force. The smaller drag force on model-3 with 2/3h in height may results of smallest thickness of boundary layer generated on the topside of the container and the lowest intensity of turbulent kinetic energy occurs at the rear side of the container.

• Journal of the Korean institute of surface engineering
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• v.47 no.2
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• pp.86-92
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• 2014

The purpose of this comparative study was to investigate the properties of chromium nitride coatings deposited by asymmetric bipolar pulsed DC sputtering and DC sputtering system. Oscilloscope traces of the I-V waveforms indicate high power and high current density outputs during the asymmetric bipolar pulsed mode. The grain size decreases with decreasing duty cycle. The duty cycle has a strong influence not only on the microstructural properties but also on the mechanical properties of chromium nitride coatings. Comparing with the continuous DC sputtering, the chromium nitride coatings prepared by pulsed DC asymmetric bipolar process also exhibit better surface roughness.

• Journal of Pharmaceutical Investigation
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• v.37 no.6
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• pp.365-368
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• 2007

The primary aim of this study was to investigate the enhancement effect of low-frequency ultrasound on skin permeation. In vitro permeation experiments were performed using Franz modified diffusion cells with ketoprofen as model drug. The effect of various ultrasound factors-ultrasound application mode (continuous mode and discontinuous mode), ultrasound intensity (0.26 $W/cm^2$, and 0.29 $W/cm^2$) and duty cycle (3%, 16%, 50%, and 83%) were studied. The highest permeation was observed at 0.29 $W/cm^2$ intensity, 50% duty cycle, and discontinuous mode. The result suggested the feasibility of low frequency ultrasound application for the phonophoretic transdermal drug delivery system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.5
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• pp.788-792
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• 2006

The test was conducted on an 8000cc heavy-duty turbo-charged heavy-duty diesel engine on which continuous regeneration DPF was installed in order to investigate regeneration characteristics fur DPF and engine performance under conditions of standard (430ppm) or ultra low sulfur diesel (50ppm) and the results were compared with each other. Exhaust emissions, CO, HC, NOx, PM and soot were investigated carefully and tested under D-13 and D-3 modes.