• Journal of the Korean Society for Precision Engineering
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• v.19 no.8
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• pp.71-76
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• 2002

In this study low cycle fatigue (LCF) behavior of 12Cr steel at high temperature are described. Secondly, comparisons between predicted lives and experimental lives are made for the several sample life prediction models. Two minute hold period in either tension or compression reduce the number of cycles to failure by about a factor of two. Twenty minute hold periods in compression lead to shorter lives than 2 minute hold periods in compression. Experiments showed that life predictions from classical phenomenological models have limitations. More LCF experiments should be pursued to gain understanding of the physical damage mechanisms and to allow the development of physically-based models which can enhance the accuracy of the predictions of components. From a design point-of-view, life prediction has been judged acceptable for these particular loading conditions but extrapolations to thermo-mechanical fatigue loading, for example, require more sophisticated models including physical damage mechanisms.

• Elastomers and Composites
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• v.32 no.1
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• pp.20-28
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• 1997

This study have Investigated the effect of various factors related to the physical properties of vulcanizated rubber compounds. rubber type, carbon black type and carbon black loading were selected as main factors and evaluation were tested by tables of orthogonal arrays with 3 factors and 3 levels. rubber types have affected cure time, tensile strength, and $T_g$ as main factor and carbon black loading have affected viscosity, scorch time, maximum torque, hardness, 300% modulus, rebound, heat build-up, $0\;&\;60^{\circ}C$ tangent delta, PICO and CUT/CHIP loss as main factor but the effects of carbon black type have affected only bound rubber content.

• Elastomers and Composites
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• v.33 no.1
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• pp.17-26
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• 1998

Natural rubber was filled with 8 commercial carbon blacks covering range of rubber-grade products at different levels of filler loadings in order to investigate physical compound and vulcanizate properties. It was found that the curves of rubber property vs filler loading of both uncured compounds and vulcanizates can be superposed to one single master curve by introducing an effective volume fraction which is based on CDBP. The effective volume fraction, $V_{EFF}$ was utilized to explain the variation of the stiffness of all rubber compounds. The surface area-corrected effective volume fraction, V', was utilized to explain the formation of bound rubber, rebound and lambourn wear.

• Fibers and Polymers
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• v.6 no.2
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• pp.139-145
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• 2005

The paper reports the physical and mechanical properties of hand-woven carpets, which have been put under static force. Two groups of wool fibres, from two parts of Iran, were prepared to spin pile yams for the carpets. Each group of the fibres included both conventional and tanned wool. Then two yam counts, $N_m$ = 4/2 and 6/2, were spun for two different knot densities. After weaving the carpets, they were put under static force and their thickness variations were measured and plotted against time, in logarithm scale. The resiliency of the carpets piles after eliminating the static force, were measured and plotted against time, in logarithm scale, too. The results were compared to each other and analysed with respect to parameters such as the type and quality of the wool fibres as well as knot density of the carpets.

• Structural Engineering and Mechanics
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• v.32 no.2
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• pp.321-335
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• 2009

When a roof frame is subjected to the airblast loading, the conventional way to analyze the damage of the frame or design the frame is to use single degree of freedom (SDOF) model. Although a roof frame consists of beams and girders, a typical SDOF analysis can be conducted only separately for each component. Thus, the rigid body motion of beams by deflections of supporting girders can not be easily considered. Neglecting the beam-girder interaction in the SDOF analysis may cause serious inaccuracies in the response values in both Pressure-Impulse curve (P-I) and Charge Weight-Standoff Diagrams (CWSD). In this paper, an inelastic two degrees of freedom (TDOF) model is developed, based on force equilibrium equations, to consider beam-girder interaction, and to assess if the modified SDOF analysis can be a reasonable design approach.

• Journal of Biomedical Engineering Research
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• v.22 no.1
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• pp.109-117
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• 2001

본 연구는 요통재해를 일으킬 수 있는 위험요소를 많이 내포한 운수유통업의 인력운반방법(Manual Material Handing)에 대한 요통발병의 위험정도를 측정하였다. 운수유통업에서 이루어지고 있는 운반작업은 우리나라의 제반환경특성상 도구를 사용하지 않고 대부분 사람에 의해 이루어지고 있다. 운반방법도 짊어지는 형태인 등짐작업이 많이 이용되고 있다. 그러나 이에 대한 체계적인 연구가 수행되고 있지 않은 실정이다. 본 연구의 목적은 등짐자세로 물건을 운반할 때와 물건을 하역하여 정리하는 작업이 요추에 미치는 물리적 힘이 어느정도인지 규명하여 위험수준을 파악하는데 그 목적이 있다. 등짐운반과 정리작업(비대칭형 작업)에 대한 역학적인 연구를 수행하기 위하여 몸통근육에 미치는 internal force을 규명하여 정량화한 Han's (1991) model을 이용하여, 이들 작업에 대한 역학적인 분석을 실시하였다.

• Management & Information Systems Review
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• v.17
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• pp.67-81
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• 2005

Harbor function has been changed into physical distribution position harbor system for providing most suitable physical distribution service with comprehensive rationalization of international physical distribution over simple loading unloading, and change function by far. Thus, to change our country into advanced economy, the factor of growth obstacles was to be eliminated, or it is so important that the physical distribution base establishment enlarges to improve potential productivity. That is, self effort is needed for physical distribution competition system, adjustable arrangement of physical distribution area, the establishment of comprehensive informations system, physical distribution rationalization. Also, to enforce harbor productivity, harbor should be developed systemically to able to function of comprehensive harbor for enlargement of harbor establishment, the device of advanced harbor function height, the linkage between and city program, harbor operation or investment system provement, harbor technique or international cooperation advancement.

• Physical Therapy Korea
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• v.5 no.3
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• pp.1-10
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• 1998

In motor learning, the relative frequency of external feedback is the proportion of external feedback presentations divided by the total number of practice trials. In earlier studies, increasing the percentage of body weight loading on the affected leg of hemiplegic patients, external feedback was continuously produced as the patient attempted to perform a movement. This feedback was produced to enhance the learning effect. However, recent studies in nondisabled populations have suggested that compared with 100% relative frequency conditions, practice with lower relative frequencies is more effective. My study compared the effect of 100% relative frequency conditions with 67% relative frequency conditions to determine what effect they exerted on motor learning for increasing the percentage of body weight loading on the affected lower limbs of patients with hemiplegia. Twenty-four hemiplegic patients were randomly assigned to one of two experimental groups. Each group practiced weight transfer motor learning on a machine. During practice, visual feedback was offered to all subjects. The experiment was carried out with full visual feedback for patients in group one but only 67% visual feedback for patients in group two. The percentage of loading on the affected leg was recorded four times: before learning (baseline value), immediately after learning, 30 minutes after learning, 24 hours after learning. The results were as follows: 1. In the 100% visual feedback group, the percentage of loading on the affected leg increased significantly in all three testing modes over the baseline value. 2. In the 67% visual feedback group, the percentage of loading on the affected leg increased significantly in all three measurements. 3. Immediately after learning, the learning effect was not significantly different between the two groups, but was significantly greater after both the 30 minutes delay and the 24 hours period. These results suggest that the 33% reduction in the provision of visual feedback may enhance the learning effect of increasing the percentage of body weight loading on the affected leg in patients with hemiplegia.

• Journal of the Korean Society of Physical Medicine
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• v.15 no.4
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• pp.67-74
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• 2020

PURPOSE: The progression of the center of pressure (COP) velocity of the stance phase may have important roles for predicting gait speed in older adults with cognitive decline. This study was conducted to identify the correlation between gait speed and the velocity of COP progression during the stance phase in older adults with cognitive decline. METHODS: Forty adults aged 65 years or older (twenty participants without cognitive decline, 20 participants with cognitive decline) were recruited. The COP progression velocity was measured using an F-scan pressure-sensitive insole system. The stance phase was divided into four sub-stages. (loading response, mid-stance, terminal stance, and pre-swing). Gait speed, double support phase, and cadence were also measured. Correlations and multiple regression analyses were performed. RESULTS: Gait speed was associated with the COP progression velocity in midstance (r = .719, p < .05), cadence (r = .719, p < .05) and the COP progression velocity in loading response velocity (r = .515, p < .05) in older adults with cognitive decline. However, no correlation was found in older adults without cognitive decline. In multiple regression analysis using gait speed as a dependent variable, the COP progression velocity in midstance and cadence were significant predictors of gait speed, with the COP progression velocity being the most significant predictor. CONCLUSION: The COP progression velocity is an important factor for predicting gait speed in older adults with cognitive decline, suggesting that the cognitive function influences gait speed and the velocity of COP progression.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.11 no.1
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• pp.65-73
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• 2005

Osteoarthritis has been considered a disease of the elderly because it is uncommon before the age of 40 years and is seen in approximately 80% of United States citizens older than 65 years. general population on kuri city in korea revealed that prevalence of knee osteoarthritis is 10.2%, increasing with age. High level of physical activity in men and age, post-menopause and obesity in women can be risk factor. Osteoarthritis is no evidence that a acquired process initiated much earlier in life through mechanical, metabolic, genetic, or other origins. A high tibial osteotomy alters static lower extremity alignment thereby decreasing medial compartment loading. As well, conservative treatment strategies, such as knee braces and valgus heel wedges, affect lover limb mechanics and attempt to reduce medial compartment loading. It was hypothesized that valgus heel wedges and modified orthoses would shift the center of pressure laterally on the foot during level walking, reducing the moment arm of the adduction moment in the frontal plane, thereby resulting in a decrease in the knee adduction moment. In the 1980s, the effect of wearing a laterally wedged insole on osteoarthritic patients with a varus deformity of the knee was firsted, and since then, kinematic and kinetic analyses concerning this condition have mainly focused on a static standing position. Since the early 1990s, the beneficial effect of wearing a laterally wedged insole to treat osteoarthritis of the knee has also been reported in dynamic conditions, but these studies did not answer the question of the kinematic and kinetic mechanisms that resulted in the reduced symptoms in patents with knee osteoarthritis. therefore, the effect of wearing laterally wedged insole has not been sufficiently studied.