• Journal of Biosystems Engineering
• /
• v.24 no.2
• /
• pp.99-106
• /
• 1999

This study was conducted to provide a direction for improving the performance of triangular-type belt clutch. The power transmission characteristics and the wear of belt were investigated for two types of pulley set theoretically and experimentally. The results of research were summarized as follows: 1) Based on the theoretical analysis for the life time of belt, the wear of belt could be reduced by increasing the sizes of driving V-pulley and tension pulley, and by decreasing the tension on V-belt. 2) The pulley set # 2 could transmit more power than the pulley set # 1 could at the same slop rate. While the slip rate was 2.36% on the pulley set # 2 at the maximum power transmission, the slip rate on the pulley set # 1 was increased up to 12.2% at the same condition. 3) From the 16 hours' fatigue test, the wear of belt used n the pulley set # 1 was observed severer than that in the pulley set#2. Also, it was found that the tensile strength of belt used in the pulley set # 2 was greater than that of belt used in the pulley set # 1.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.20 no.3
• /
• pp.775-787
• /
• 1996

An optimization procedure is proposed for the design of cylindrically laminated composite shell having midplane symmetry and subjected to axial force, torsion and internal pressure. Tsai-Wu and Tsai-Hill failure criteria are taken as objective functions. The stacking sequence represents the design variable. The optimal design formulation based on state space method is adopted and solution proccedure is described with the emphasis on the method of calculations of the design sensitivities. A gradient projection algorithm is employed for the optimization process. Numerical results are presented for the several test problems.

• Computers and Concrete
• /
• v.20 no.2
• /
• pp.197-204
• /
• 2017

Typically, high lime fly ash (Class C) has been characterized as a fly ash, which at lower replacement levels is not as effective as the low lime (Class F) fly ash, in mitigating alkali-silica reaction (ASR) in portland cement concrete. The influence of fineness of Class C, obtained by grinding virgin fly ash into finer particles, on its pozzolanic reactivity and ASR mitigation performance was investigated in this study. In order to assess the pozzolanic reactivity of mortar mixtures containing virgin or ground fly ashes, the strength activity index (SAI) test and thermo-gravimetric analysis (TGA) were conducted on the mortar cubes and paste samples, respectively, containing virgin fly ash or two ground fly ashes. In addition, to evaluate any improvement in the ASR mitigation of ground fly ashes compared to that of the virgin fly ash, the accelerated mortar bar test (AMBT) was conducted on the mortar mixtures containing different dosages of either virgin or ground fly ashes. In all tests crushed glass aggregate was used as a highly reactive aggregate. Results from this study showed that the finest fly ash (i.e., with an average particle size of 3.1 microns) could increase the flow ability along with the pozzolanic reactivity of the mortar mixture. However, results from this study suggested that the fineness of high lime fly ash does not seem to have any significant effect on ASR mitigation.

• Geomechanics and Engineering
• /
• v.8 no.4
• /
• pp.477-493
• /
• 2015

In rock drilling, the most important characteristic to clarify is the wear of the drill bits. The reason that the rock drill bits fail with time is wear. In dry sliding contact adhesive wear deteriorates the materials in contact, quickly, and is the result of shear fracture in the momentary contact joins between the surfaces. This paper aims at presenting an overview of the assessment of WC/Co cemented carbide (CC) tricone bit in rotary drilling. To study wear of these bits, two approaches have been used in this research. Firstly, the new bits were weighted before they mounted on the drill rigs and also after completion their useful life to obtain bit weight loss percentage. The characteristics of the rock types drilled by using such this bit were measured, simultaneously. Alternatively, to measure contact wear, namely, matrix wear a micrometer has been used with a resolution of 0.02 mm at different direction on the tricone bits. Equivalent quartz content (EQC), net quartz content (QC), muscovite content (Mu), coarseness index (CI) of drill cuttings and compressive strength of rocks (UCS) were obtained along with thin sections to investigate mineralogical properties in detail. The correlation between effective parameters and bit wear were obtained as result of this study. It was observed that UCS shows no significant correlation with bit wear. By increasing CI and cutting size of rocks wear of bit increases.

• Journal of The Korean Astronomical Society
• /
• v.37 no.5
• /
• pp.349-353
• /
• 2004

Magnetic fields are an important ingredient of galaxy clusters and are indirectly observed on cluster scales as radio haloes and radio relics. One promising method to shed light on the properties of cluster wide magnetic fields is the analysis of Faraday rotation maps of extended extragalactic radio sources. We developed a Fourier analysis for such Faraday rotation maps in order to determine the magnetic power spectra of cluster fields. In an advanced step, here we apply a Bayesian maximum likelihood method to the RM map of the north lobe of Hydra A on the basis of our Fourier analysis and derive the power spectrum of the cluster magnetic field. For Hydra A, we measure a spectral index of -5/3 over at least one order of magnitude implying Kolmogorov type turbulence. We find a dominant scale of about 3 kpc on which the magnetic power is concentrated, since the magnetic autocorrelation length is ${\lambda}_B = 3 {\pm} 0.5\;kpc$. Furthermore, we investigate the influences of the assumption about the sampling volume (described by a window function) on the magnetic power spectrum. The central magnetic field strength was determined to be ${\~}7{\pm}2{\mu}G$ for the most likely geometries.

• Journal of Korean Academy of Nursing
• /
• v.37 no.4
• /
• pp.568-575
• /
• 2007

Purpoes: The study was done to investigate the effects of an exercise program on body composition, cardiopulmonary function and physical fitness in obese children. Methods: Thirty nine children in grades 4, 5, and 6 in elementary school were employed: experimental group(20) and control group(19). The subjects in the experimental group participated in an exercise program for 8weeks, thirty five minutes per session, four times per week. This data was analyzed by ANCOVA and paired t-test. Result: The Height(F=2.615, p=0.027) of the experimental group was significantly different from the control group. Also, in the experimental group, there were significant differences of height(t=4 79, p=0.000), cardiac rate(t=-6.461, p=0.000), body mass index(t=-2.13 p=0.046), muscle strength(t=3.48, p=0.003), and muscle endurance(t=3.20, p=0.005). Otherwise, in the control group, there were significant differences of weight(t=2.27, p=0.036), waist-hip ratio(t=3.16, p=0.005), and muscle endurance(t=-2.38, p=0.030). Conclusion: Jumping rope improved the body composition, cardiopulmonary function, and physical fitness for obese children.

• Archives of Reconstructive Microsurgery
• /
• v.10 no.1
• /
• pp.7-11
• /
• 2001

Purpose : To evaluate the neurologic abnormalities in the donor limb after contralateral C7 transfer in brachial plexus injury. Materials and Methods : From August 1996 to December 1999, five patients with brachial plexus injury were treated with contralateral C7 nerve root transfer. The average follow up was 16 months(range, 5 to 36 months). The clinical findings were assessed using the British Medical Research Council Grading System, and also measured grip power, pinch power of hand and two point discrimination of the fingers. Results : We had no difference in shoulder abduction and elbow flexion after contralateral C7 transfer. The grip and pinch strength were recovered within 4weeks. Sensory loss occurred in all patients and was noted to be more severe on index and middle finger. Four patients recovered within 2 weeks, one continued till one year. Subjective numbness and pain on percussion minimally persisted until last follow-up. Conclusion : The division of the C7 nerve root resulted in minimal and temporary functional deficit in the donor upper limb.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.29 no.10 s.241
• /
• pp.1148-1155
• /
• 2005

In this study, the influence of changing combustor pressure on nitric oxide emission was investigated. Expansion of reaction region was more clear in the P$^{*}$ <1 conditions compared to the P$^{*}\geq1$ conditions, and it could be observed that flames are distinct in the P$^{*}\geq1$ conditions and that brightness is relative low and wide distribution is shown in the P$^{*}$ <1 conditions. In the respect of temperature distribution, narrow and high-temperature region was shown in the P$^{*}\geq1$ conditions. On the other hands, overall uniform temperature distributions were shown in the P$^{*}$ <1 conditions. Nitric oxide emission decreased with decreasing combustor pressure. This tendency was explained by the mean flame temperature distribution. Low NOx combustion is ascribed to wide-spread reaction region in the low combustor Pressure and oscillation were shown P$^{*}\leq0.97$, and strength and sizes of oscillation were more increased with lower pressure index. These results demonstrate that flame shape and nitric oxide emission can be controlled with changing combustor pressure.

• Journal of the Korean Society of Physical Medicine
• /
• v.11 no.2
• /
• pp.103-114
• /
• 2016

PURPOSE: The purpose of this study was first to develop a Korean version of pediatric functional muscle testing for children with a motor developmental disorder who have a communication problem and who are aged below five years, and also to verify the content validity. METHODS: First, the preliminary study was conducted to verify the reliability of pediatric functional muscle testing, developed by Venita in Korea. Based on the results of the study, the primary evaluation items were selected and modified. Second, the first test of content validity was conducted through a panel discussion, and a second investigation of content validity was carried out by utilizing the Item Content Validity Index (I-CVI). In this study, we selected only 0.78 or more items from I-CVI. RESULTS: Based on the results of the preliminary study, 19 primary evaluation items were selected. Based on the results of the first and second content validity tests, 15 tertiary evaluation items for the Korean version of pediatric functional muscle testing were determined. CONCLUSION: This study developed a new Korean version of pediatric functional muscle testing and suggested that it will be a useful tool to measure muscle strength for Korean children with a motor developmental disorder and a communication problem, aged below five years.

• Communications for Statistical Applications and Methods
• /
• v.18 no.3
• /
• pp.343-355
• /
• 2011

For a data with the assumption of the mixture distribution, it is important to find an appropriate threshold and evaluate its performance. The relationship is found of well-known nine classification accuracy measures such as MVD, Youden's index, the closest-to-(0, 1) criterion, the amended closest-to-(0, 1) criterion, SSS, symmetry point, accuracy area, TA, TR. Then some conditions of these measures are categorized into seven groups. Under the normal mixture assumption, we calculate thresholds based on these measures and obtain the corresponding type I and II errors. We could explore that which classification measure has minimum type I and II errors for estimated mixture distribution to understand the strength and weakness of these classification measures.