• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.1
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• pp.78-85
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• 1986

This study has been made to investigate Behavior of the fatigue crack propagation for the purpose of taking into consideration the fatigue behavior Which initiate and propagate in tip of defect of the defected specimens, Which Contain the micro-hole or micro-slit. Especially, the specimens have been conducted with high-freguency heat treatment of 850.deg. C, 1050.deg. C to consider strength elevation of defected specimens. The results of this study are as follow; (1) The case of the same in the length of crack, the fatigue crack propagation rate of the micro-slit is always faster than that of micre-hole. But, the first step of the fatigue crack propagation it is not always so. (2) Fatigue crack propagation rate of specimens with micro-slit or micro-hole which have been treated with high-frequency heat treatment satisfy the following formula between the fatigue crack propagation rate and nominal stress; dl/dN .var..sigma.$^{m}$ *l$^{n}$ .

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.6
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• pp.758-765
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• 2001

Purpose of the present is to investigate the food configuration at a tunnel entrance for reducing the micro pressure wave that is generated according to train speed. Two configurations were examined for tunnel of 0.5 km length. The experimental results show that a slit cover hood installed at the entrance of the tunnel reduces the maximum micro pressure wave by 41.2%, and a configuration with a slit cover hood installed at the entrance and a 45$^{\circ}$slanted portal at the exit of the tunnel suppresses it by 47.7%.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.619-624
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• 2000

The purpose of present study is to investigate for reducing micro pressure waves generated according to train speeds $(240km/h{\sim}380km/h)$ through tunnels with countermeasures as followings; the hood configuration in tunnel entrance. We developed hoods for tunnel of 0.5 km length in the condition of tunnel cross-section area of $107m^2$ on the slab track. According to the results the maximum micro-pressure wave is reduced by 41.2% for the slit hood installed at the entrance of the tunnel and reduced by 47.7% for the slit hood installed at the entrance of the tunnel and the $45^{\circ}$ slanted portal at the exit of the tunnel

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.335-340
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• 2001

There are many tunnels located apart short distance from each other in mountainous country like Korea. Serial tunnels are connected by snow shelter in many cases. This study presents some countermeasures against micro-pressure wave at the tunnel exit using snow shelter. Through 1/60 scale model laboratory test, we find that snow shelter with 3.6m slit and slit cover show the effect of reducing the micro pressure wave to about 50.6%.

• Journal of Korean Tunnelling and Underground Space Association
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• v.2 no.3
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• pp.3-11
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• 2000

Purpose of this paper is to investigate the hood configuration at a tunnel entrance to reduce the micro pressure wave that is generated according to train speed. Two configurations were examined for the tunnel of 0.5 km in length. The experimental results show that a slit cover hood installed at the entrance of the tunnel reduces the maximum micro pressure wave by 41.2%, and the configuration with a slit cover hood installed at the entrance and the $45^{\circ}$ slanted portal at the exit of the tunnel suppress the pressure wave by 47.7%.

• Proceedings of the KSR Conference
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• 2000.11a
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• pp.390-395
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• 2000

There are many tunnels located apart short distance from each other in mountainous country like Korea. Serial tunnels are connected by snow shelter in many cases. This study presents some countermeasures against micro pressure wave at tile tunnel exit using snow shelter. Through 1/60 scale model laboratory test. we find that snow shelter with 3.6m slit and slit cover show the effect of reducing the micro pressure wave to about 60.5%.

• Journal of the Korean Society of Clothing and Textiles
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• v.17 no.4
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• pp.539-549
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• 1993

The purpose of this study was to find out the moving fitness and slit length of tight skirt in relation to its length & silhouette. Five kinds of length, micro mini, mini, natural line, medi and maxi, and two kinds of siihuette, slim & straight-a total of ten tight skirts-were investigated. Ten college students were chosen for this experiment. The moving fitness was tested by measuring the step length, step width and step angle in the case of walking on the flat and going up the stairway & bus stair. The slit length was tested by measuring the back slit length needed in the case of going up stairway & bus stair. Data were analyzed with use of SAS pakage. The statistics were based on average, standard diviation, two-way ANOVA, Pearson's correlation and multiple regression analysis. The main results were as follows. 1. There was significant difference in the moving fitness according to length & silhouette of tight skirt. The moving fitness of slim type was lower than that of straight type and the longer the skirt length was, the lower the moving fitness was. The significance appeared particularly in the case of going up the bus stair. 2. There was significant difference in the skirt length obove slit accorting to length & silhouette of tight skirt. The skirt length obove slit of slim type was shorter than that of straight type. The longer skirt length was, the longer it was from micro mini to natural line, that of medi skirt was shorter or a little longer than that of natural line skirt and there was little change from medi skirt to maxi skirt.

• Korea-Australia Rheology Journal
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• v.19 no.2
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• pp.51-59
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• 2007

A polyelectrolyte chain confined in a slit nanochannel exhibits a structural transition from the one in free space. In this paper, the effect of the long-range electrostatic interactions between the xanthan polyelectrolyte and the slit wall on the confined xanthan conformation is investigated via the Brownian dynamics simulation. A neutral and two negatively charged surfaces of polydimethylsiloxane (PDMS) and glass are combined to make four kinds of slit channels with different charge characteristics: i) neutral-neutral, ii) glass-glass, iii) neutral-PDMS and iv) neutral-glass walls. Their walls are characterized by uniform surface charge densities determined from experimental data of zeta potential. Both the nonmonotonic chain size variation and the loss of long-range bond vector correlation, previously observed under confinement in the PDMS-PDMS slit, are also found in the neutral slit, demonstrating the nonelectrostatic origin of such crossover behaviors. As expected, the effect of wall charges is negligible at sufficiently high medium ionic strength of 100mM but it becomes significant in the opposite limit of 0.01mM. In the latter case, the high charge density of glass walls strengthens the effective confinement of a negatively charged polyelectrolyte and produces a xanthan structure comparable to that confined in a much narrower neutral slit. The obtained structural data suggest the possibility of controlling the structure of confined polyelectrolytes by the modification of surface charge characteristics of micro/nanofluidic devices in combination with the adjustment of the medium ionic strength.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.561-564
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• 2003

The machining technology for the removal of micro-burr has been demanded because electrode parts of electron gun have minute holes. In this study, Magnetic Assisted Polishing(MAP) is applied to remove the micro-burr instead of the contentional polishing process such as the etching and barrel. Optimal polishing conditions are selected from many experiments using the tool of the flat end slit type. On the basis of experimental results, the deburring machine for the Magnetic Assisted Polishing of electrode part is developed and its performance is evaluated.

• Korean Journal of Optics and Photonics
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• v.24 no.2
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• pp.53-57
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• 2013

A polarization selective blazed grating employing metal-slit arrays was proposed. Nano-scale metal-slits were applied to the micro-scale blazed grating to give the functionality of polarization selection. Case study was carried out for the proposed structure utilizing numerical FDTD (Finite Difference Time Domain method) simulation. Diffraction efficiency of 77.61% and polarization extinction ratio of 8.99 was achieved with arbitrary parameters and diffraction efficiency of 64.22% and polarization extinction ratio of 81.09 was achieved with other parameters to enhance extinction ratio.