• Geomechanics and Engineering
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• v.10 no.1
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• pp.1-19
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• 2016

This paper presents the results of an intensive experimental investigation on cyclic behavior of various sands and structural materials interface. Comprehensive measurements of the horizontal displacement and shear stresses developed during testing were performed using an automated constant normal load (CNL) cyclic direct shear test apparatus. Two different particle sizes (0.5 mm-0.25 mm and, 2.0 mm-1.0 mm) of sands having distinct shapes (rounded and angular) were tested in a cyclic direct shear testing apparatus at two vertical stress levels (${\sigma}=50kPa$, and 100 kPa) and two rates of displacement ($R_D=2.0mm/min$, and 0.025 mm/min) against various structural materials (i.e., steel, concrete, and wood). The cyclic direct shear tests performed during this investigation indicate that (i) the shear stresses developed during shearing highly depend on both the shape and size of sand grains; (ii) characteristics of the structural materials are closely related to interface response; and (iii) the rate of displacement is slightly effective on the results.

• Journal of Applied Reliability
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• v.11 no.2
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• pp.127-140
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• 2011

This paper presents an accelerated life test of aviation taxiway lights installed in the airport to help safe navigation of airplanes at night or in bad weather. Recently halogen lamps of taxiway lights are replaced by LED ones and their reliability needs yet to be verified. Thus, effective test conditions are designed reflecting the failure modes and mechanisms from the previous studies on LED, which include the accelerated degradation process. The test is performed under the temperature $70^{\circ}C$ and $90^{\circ}C$ for two types of LED lights, taxiway center line lights(TCLL) and taxiway edge lights (TEDL). The failure time data were analyzed using lognormal distribution and Arrhenius model to find the life-stress relationship, acceleration factor and life characteristics under the normal condition temperature $30^{\circ}C$.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.73-80
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• 2001

The shear strength of jointed rock is influenced by effective normal stress, joint wall compressive strength, joint roughness and so on. Since joint roughness makes considerable influences on shear strength of jointed rock, many studies tried to get quantitative joint roughness parameter. Until now, Joint Roughness Coefficient, JRC proposed by Barton has been prevalently used as a rock joint roughness parameter In spite of its disadvantages. In this study, a quantification of rock joint roughness is performed using surface roughness parameter, Rs. Proposed method is applied to rock core specimens, field joint surfaces, and JRC profiles. The scale of fluctuation is introduced to extend the suggested method to the large scale field joint surface roughness. Based on the quantification of joint surface roughness, joint shear tests are performed with the portable shear box. The relationship between joint surface roughness and joint shear strength is investigated and finally, a rock joint shear strength equation is derived from these results. The equation has considerable credibility and originality in that it is obtained from laboratory tests and expressed with quantified parameter.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1995.10a
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• pp.60-63
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• 1995

The behavior of the work materials in the chip-tool interface in extremely high strain rates and temperatures is more that of viscous liquids than that of normal solid metals. In these circumstances the principles of fluid mechanics can be invoked to describe the metal flow in the neighborhood of the cutting edge. In the present paper an Eulerian finite element model is presented that simulates metal flow in the vicinity of the cutting edge when machining a low carbon steel with carbide cutting tool. The work material is assumed to obey visco-plastic (Bingham solid) constitutive law and Von Mises criterion. Heat generation is included in the model, assuming adiabatic conditions within each element. the mechanical and thermal properties of the work material are accepted to vary with the temperature. The model is based on the virtual work-stream function formulation, emphasis is given on analyzing the formation of the stagnant metal zone ahead of the cutting edge. The model predicts flow field characteristics such as material velocity effective stress and strain-rate distributions as well as built-up layer configuration

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.04a
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• pp.23-26
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• 2009

The purpose of this study is to investigate the fatigue safety and deformation of housing in plate rolling process. For this, we carried out 3-dimensional FEM analysis for housing considering design variations of housing structure. It showed that the housing with rounds under a column is benefits to control thickness accuracy of rolled material, due to smaller elastic deformation and maximum effective stress. Also, we calculated the fatigue safety factors, the ratios of the pulsating equivalent fatigue limit to the maximum tensile stresses analyzed using the equipment force and normal rolling force.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.1540-1549
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• 2009

Shear properties of geosynthetic/geosynthetic and geosynthetic/soil were evaluated from direct shear tests. The type of geosynthetic is Velcro which is effective for geosynthetic interface and make up for the weakness of sandbag. In this study, the cohesion and the angle of internal friction of each interface was estimated. The test results showed that the cohesion and the angle of internal friction of the geosynthetics depended on the amount of normal stress, the type of the geosynthetics used, and combinations of the geosynthetics and soils. Finally, by comparing the apparent cohesion and the friction angle of the geosynthetics, the applicability to design was identified.

• Geomechanics and Engineering
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• v.12 no.2
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• pp.211-221
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• 2017

A laboratory investigation into crude oil contaminated sand-concrete interface behavior is performed. The interface tests were carried out through a direct shear apparatus. Pure sand and sand-bentonite mixture with different crude oil contents and three concrete surfaces of different textures (smooth, semi-rough, and rough) were examined. The experimental results showed that the concrete surface texture is an effective factor in soil-concrete interface shear strength. The interface shear strength of the rough concrete surface was found higher than smooth and semi-rough concrete surfaces. In addition to the texture, the normal stress and the crude oil content also play important roles in interface shear strength. Moreover, the friction angle decreases with increasing crude oil content due to increase of oil concentration in soil and it increases with increasing interface roughness.

• Journal of People, Plants, and Environment
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• v.22 no.4
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• pp.355-364
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• 2019

This study was conducted to find out the effects of agro-healing activities and strolling on the physiological conditions of patients with chronic metabolic diseases. A total of 11 subjects participated in agro-healing activities, and their average age was 49.6±11.3. Changes in their salivary cortisol were compared and analyzed before and after participating in the agro-healing activity program, and it was found that the stress hormone decreased after participating in the program. Differences in brain wave between before and after participating in agro-healing activities and strolling were measured, and the ratio of alpha to high beta (RAHB) of subjects increased in most of the measured points after participating in agro-healing activities. In addition, the increase in the value in the temporal lobe (T3) that controls mortor skills and occipital lobe (O2) that controls visual functions indicates that the activities were effective in improving relaxation and stability. The relative low beta (RLB) power spectrum of subjects also statistically significantly decreased in the right occipital lobe (O2) that controls visual functions, the relative mid beta (RMB) and relative high beta (RHB) power spectrum decreased in the left temporal lobe (T3) and the right occipital lobe (O2). These results indicate that the activities were effective in improving relaxation under no stress and tension. The systolic and diastolic blood pressure of subjects after participating in agro-healing activities decreased from the prehypertension level to the normal level. These results indicate that horticultural activities and visual elements in healing farms, such as agro-healing activities and strolling, have positive impacts on patients with chronic metabolic diseases accompanied with diabetes or high blood pressure by increasing the brain activity and psycho-physiological conditions of participants.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.11
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• pp.1896-1911
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• 1997

Effects of fiber-matrix interphases on the micro-and macro-mechanical behaviors of unidirectionally fiber-reinforced composites subjected to transverse shear loading at remote distance have been studied. The interphases between fibers and matrix have been modeled by the spring-layer which accounts for continuity of tractions, but allows radial and circumferential displacement jumps across the interphase that are linearly related to the normal and tangential tractions. Numerical calculations for basic cells of the composites have been carried out using the boundary element method. For an undamaged composite the micro-level stresses at the matrix side of the interphase and effective shear stiffness have been computed as functions of fiber volume ratio $V_f$ and interphase stiffness k. Results are presented for various interphase stiffnesses from the perfect bonding to the case of total debonding. For a square array composite the results show that for a high interphase stiffness k>10, an increase of $V_f$ increases the effective transverse shear modulus G over bar of the composite. For a relatively low interphase stiffness k<1, it is shwon that an increase of $V_f$ slightly decreases the effective transverse shear modulus. For the perfect bonding case, G over bar for a hexagonal array composite is slightly larger than that for a square array composite. Also for a damaged composite partially debonded at the interphase, local stress fields and effective shear modulus are calculated and a decrease in G over bar has been observed.

• Women's Health Nursing
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• v.7 no.4
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• pp.536-546
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• 2001

The purposes of this descriptive study were to identify the prevalence rate of urinary incontinence(UI) and the differences in frequency of incontinent and normal women by general characteristics, obstetrical history, and the conditional events for urinary incontinence of the elderly women in a community. By the results of this study, it is intended to provide nursing practice guidelines for incontinent women. The research design of this study was a preliminary descriptive study. The 173 subjects were 55 years old and over, and resided in a small city area. Data were collected from June 20 to July 20, 2001, by an interview or a self-report with questionaire. The questionaire was composed of items of general characteristics, obstetrical characteristics, and conditions of UI by the modified Henderickon's Stress Incontinence Scale(1981). The results were summariezed as follows: 1. The UI prevalence rate of the sample was 64.2%. Of the incontinent women, 31.5% had experienced UI for a period of three to five years, and 84.7% had never treated or managed their UI. Frequency of UI was once or twice times per month(46.8%). 2. The total mean of UI on the scale in the incontinent women was 25.50 of 85, ranging from 18 to 41. 3. The most frequent condition of UI was coughing, followed by laughing, sneezing, heavy exercise, and preparation of urination in descending order. 4. There were significant differences in age, education, social activity, and urinary difficulty between the incontinent women and the normal women. 5. There were significant differences in frequency of spontaneous abortion, age of menopause between the incontinent women and the normal women. 6. There were no significant differences in number of delivery, frequency of artificial abortion, age of the last delivery, and postal health management between the incontinent women and the normal women. In conclusion, the incidence of UI in this study was high, but there were no effective treatments or management. It is suggested to provide the adult women with knowledge about UI, and to educate preventive behavior and control skill of urinary incontinence. Also episodes of urinary incontinence were high in the situation of sudden increase of abdominal pressure. This data can be used for the prevention strategy of urinary incontinence, In future research it is recommended to identify comprehensive factors related to urinary incontinence including psychosocial factors, and effective strategies of urinary incontinence.