• Tribology and Lubricants
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• v.23 no.5
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• pp.187-194
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• 2007

The profile of the roller in the axial direction is the main design factor in order to increase endurance life against the contact fatigue due to the stress concentration along the edge of the roller. Even under the elas-tohydrodynamic lubrication (ehl) conditions, the stress concentration along the edge of the roller greatly worsens the fatigue life both for the roller and contacting body. In this study, roller contacts of finite axial length are studied for the film thickness and pressure of ehl. For the real contact behaviors under the ehl conditions, multigrid and multi-level method is applied so that much higher loading conditions can be investigated. Several axial profiles of roller are investigated to verify how both ehl film and pressure are generated and some of them are recommended for the ehl contact condition.

• Journal of Korean society of Dental Hygiene
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• v.12 no.4
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• pp.685-693
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• 2012

Objectives : This research was conducted to find the subjective symptoms of musculoskeletal system for main jobs and job posture. Methods : A survey was conducted from September 15, 2011 to October 7, 2011 and 357 dental hygienists were responded. The survey was consisted of the working environment and medical equipments, psycho-social characteristics, health habits and education, job posture, subjective symptoms of musculoskeletal system pain, and so on. Results : In the survey on the frequency of job posture of dental hygienists by jobs, said they cast down or tilt their head by 15 degrees or more or twist or bend their back. The result of the analysis on the subjective symptoms of musculoskeletal system by main job showed that they experienced a pain in neck, shoulder, and back, although the order differed. The order of subjective symptoms of musculoskeletal system for casting down or turning head by 15 degrees or more, twisting or bending back, having shoulders not parallel to the ground, sitting at the end of a chair, and supporting the whole body with one leg or pressing on a pedal for treatment was from the shoulders to the neck to the back. The order of subjective symptoms of musculoskeletal system for having arms too far from the body or hunching for treatment and bending wrists inward or outward for treatment was from the shoulders to the back to the neck. Conclusions : Due to the characteristics of the job which requires one to have a proper view of a patient's oral cavity, most of the postures included casting down of head or bending of back. Therefore a development of new postures is needed to replace the existing job postures which pressure the musculoskeletal system. And shift rotation can be used as a preventive measure.

• International Journal of Aeronautical and Space Sciences
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• v.11 no.1
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• pp.1-9
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• 2010

Numerical simulation of unsteady flows around helicopters was conducted to investigate the aerodynamic interaction of main rotor and other components such as fuselage and tail rotor. For this purpose, a three-dimensional inviscid flow solver has been developed based on unstructured meshes. An overset mesh technique was used to describe the relative motion between the main rotor, and other components. As the application of the present method, calculations were made for the rotor-fuselage aerodynamic interaction of the ROBIN (ROtor Body INteraction) configuration and for a complete UH-60 helicopter configuration consisted of main rotor, fuselage, and tail rotor. Comparison of the computational results was made with measured time-averaged and instantaneous fuselage surface pressure distributions for the ROBIN configuration and thrust distribution and available experimental data for the UH-60 configuration. It is demonstrated that the present method is efficient and robust for the simulation of complete rotorcraft configurations.

• Health Policy and Management
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• v.30 no.4
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• pp.522-530
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• 2020

Background: In 2008, Korea implemented a new type of social insurance known as "long-term care insurance". We examined the association between ownership of long-term care facilities and the incidence of pressure ulcers after the implementation of "long-term care insurance". This study is a population-based retrospective cohort study from 2006 to 2013. Methods: We used medical claims data from the Korean National Health Insurance Corporate Elderly Cohort Database from 2006 to 2013. These data comprise a nationally representative sample. To avoid confounders, only patients admitted to one long-term care facility and who stayed for >70% of the follow-up time were included; as a result, 3,107 individuals were enrolled. The main independent variable was the operating entity of the long-term care facility (local government, corporate bodies, and private for-profit owners), and the dependent variable was the 1-year incidence of pressure-ulcers. Survival analysis (Cox proportional hazard model) was used as an analysis method. Results: Compared to patients admitted to local government long-term care facilities, patients admitted to private long-term care facilities had a significantly higher 1-year risk of pressure ulcers (hazard ratio [HR], 1.94; 95% confidence interval [CI], 1.29-2.91); the risk was especially high among patients who were cognitively dependent (HR, 2.34; 95% CI, 1.25-4.37). Conclusion: Patients admitted to private for-profit long-term care facilities were more likely to have pressure ulcers compared to those in local government and corporate body long-term care facilities. Appropriate assessment tools and publicly available information, as well as more restricted legal requirements, are needed to improve the care quality and outcomes of patients in long-term care facilities.

• Geomechanics and Engineering
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• v.22 no.3
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• pp.255-264
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• 2020

With the ongoing development of deep mining of coal resources, some coal mine dynamic disasters have exhibited characteristics of both coal-gas outbursts and rockbursts. Therefore, research is required on the mechanism of rockburst-outburst coupling disaster. In this study, the failure characteristics of coal-rock combination structures were investigated using lab-scale physical simulation experiments. The energy criterion of the rockburst-outburst coupling disaster was obtained, and the mechanism of the disaster induced by the gas-solid coupling instability of the coal-rock combination structure was determined. The experimental results indicate that the damage of the coal-rock structure is significantly different from that of a coal body. The influence of the coal-rock structure should be considered in the study of rockburst-outburst coupling disaster. The deformation degree of the roof is controlled by the more significant main role of the gas pressure and the difference in the strength between the rock body and the coal body. The outburst holes and spall characteristics of the coal body after the failure of the coal-rock structure are strongly affected by the difference in strength between the roof and the coal body. The research results provide an in-depth understanding of the mechanism of rockburst-outburst coupling disasters in deep mining.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.2
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• pp.43-53
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• 1993

There exist two difficulties in the nonlinear wave-body problems. First is the abrupt behavior near the intersection point between the body and the free surface, and second is the far field treatment. In this paper, the far field treatment is considered. The main idea is the Taylor series expansion of free-surface geometry and the application of F.F.T. algorithm. The numerical step is as follows. The velocity potential is expressed by the Green's theorem. and the solution is obtained by iteration method. In the iteration stage, the expressions by the Green's theorem are transformed to the convolution forts with the expansion of free surface by the wave slope. Here F.F.T. is applied, so the computing time can be of O(Nlog N) where N is the number of unknowns. The numerical analysis is carried out and the results are compared with other results in linear floating body problem and nonlinear moving pressure patch problem, and good agreements are obtained. Finally nonlinear floating body radiation problem is carried out with computing time of O(Nlog N).

• Journal of Physiology & Pathology in Korean Medicine
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• v.23 no.1
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• pp.237-244
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• 2009

We investigated the effects of acupuncture stimulation on pulse wave variables and heart rate variability (HRV) in healthy adults. To evaluate twenty healthy volunteers (10 men, 10 women) had acupuncture into both Hapkok (Ll4) and Taechung (Liv3) for 15 minutes. Radial pulse, Heart Rate Variability, body temperature and blood pressure were checked before and after acupuncture to evaluate Pulse Wave Variability and Autonomous Function. The results were as follows; Heart rate was significantly increased while systolic blood pressure (mmHg) and diastolic blood pressure (mmHg) were significantly increased after acupuncture treatment. Sixteen subjects didn't change representative pulse wave variables after acupuncture treatment. Energy, height of main peak (H1), height of pre-dicrotic valley (H2) and height of descending valley (H4) were decreased while height of dicrotic peak (H5) was significantly decreased after acupuncture treatment. Time to main peak (T1), time to pre-dicrotic valley (T2), time to dicrotic peak (T5), total time (T) and T-T4 were decreased while time to descending valley (T4) was increased after acupuncture treatment. Total area (At), area of main peak (Aw) and ratio of diastolic period area (Ad) were decreased while ratio of systolic period area (As) and angle of main peak (MPA) were increased after acupuncture treatment. The standard deviation of all normal RR intervals (SDNN) was increased while the root mean square of successive differences between the normal heart beats (RMSSD) was significantly increased after acupuncture treatment by time domain analysis. Low frequency power (LF) and LF/HF ratio were decreased while high frequency power (HF) was significantly increased after acupuncture treatment by frequency domain analysis. This study suggests that acupuncture treatment changes pulse wave variability and heart rate variability. Further study on various acupuncture treatment for pulse wave variability and heart rate variability is required.

• Economic and Environmental Geology
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• v.12 no.4
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• pp.197-206
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• 1979

Sangdong scheelite deposit is confirmed to have been formed by replacement of limestone beds by metasomatic mineralization. Mineralogical zonal distribution and filling temperatures are related with order of its formation and tungsten mineralization. The first formed garnet-pyroxene zone, left in the margins of the ore body, shows the highest filling temperature of fluid inclusions in pyroxene, averaging $420^{\circ}C$. The central part of the ore body, mainly composed of quartz-mica-scheelite, shows higher fi11ing temperatures of fluid inclusions in quartz, than hornblende-quartz-scheelite zone surrounding the quartz-mica-scheelite zone, averaging $240^{\circ}C$. The distribution of highter filling temperatures above average temperature is applicable to the richest part of scheelite distribution. Generally scheelite shows higher filling temperature by about 20 to $100^{\circ}C$ than quartz in a given sample. The crystallization temperature of the main phase of scheelite deposition is $311^{\circ}C$ at the pressure of 230 to 500 bars at Sangdong area. Gas-rich inclusions in the pyroxene are homogenized into either gas or liquid phase or into both phases in a given crystal of the pyroxene, which suggests boiling at the formation of skarn.

• Journal of Nutrition and Health
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• v.22 no.3
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• pp.175-184
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• 1989

This survey was carried out to obtain the information concerning nutritional status, including factors of food intake and health condition of elderly women living in Ulsan city. Main results were as follows. 1) Dietary intake data showed the average daily intake of energy, protein, vitamin A, riboflavin and ascorbic acid were lower than Korean recommended dietary allowances (RDA). According to the percentage of RDA, Vitamin A was the nutrient found to be least sufficient. 2) Among the various influencial factors, pocket money, meal-mate, skip meal and health concern influenced on nutrient intake considerably. A meal condition score based on influencial factors, showed significant correlations with all nutrient intake(P<0.001). A health score based n the subjects complains about health condition, showed significant correlations with intake of energy, carbohydrate, thiamin, and niacin(P<0.05). 3) Average hight was below Korea reference, while average body weight of subjects was close to Korean reference. Average body mass index was 23.0. 4) The average systolic and diastolic blood pressure was 140mmHg/88mmHg, the proportion of hypertension was 32.4 percent. The average hemglobin concentration was 12.7g/dl, only 6.7 percent of subjects were anemic. Serum cholesterol concentration was normal range(140~220mg/dl) in all subjects.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.191-194
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• 2006

In this paper, we present a detailed mechanism of drag reduction by dimples and roughness on a sphere by measuring the streamwise velocity above the dimpled and roughened surfaces, respectively. Dimples cause local flow separation and trigger the shear layer instability along the separating shear layer, resulting in generation of large turbulence intensity. With this increased turbulence, the flow reattaches to the sphere surface with high momentum near the wall and overcomes strong adverse pressure gradient formed in the rear sphere surface. As a result, dimples delay main separation and reduce drag significantly. The present study suggests that generation of a separation bubble, i.e. a closed-loop streamline consisting of separation and reattachment, on a body surface is an important flow-control strategy for drag reduction on a bluff body such as the sphere and cylinder. In the case of roughened sphere, the boundary layer flow is directly triggered by roughness and changes to a turbulent flow. Due to this change, the drag significantly decreases. As the Reynolds number further increases, transition to turbulence occurs earlier on the sphere surface. Because of faster growth of turbulent boundary layer by roughness, earlier transition thickens the boundary layer, resulting in earlier separation and drag increase with increasing Reynolds number