• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.429-429
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• 2008

Li$[Ni_{1/2}Co_{1/2}]O_2$ powder were synthesized from co-precipitation spherical metal oxide, $[Ni_{1/2}Co_{1/2}](OH)_2$. The preparation of metal hydroxide was significantly dependent on synthetic conditions, such as pH, amount of chelating agent, stirring speed, etc. The optimized condition resulted in $[Ni_{1/2}Co_{1/2}](OH)_2$, of which the particle size distribution was uniform and the particle shape was spherical, as observed by scanning electron microscopy. Calcination of the uniform metal hydroxide with LiOH at higher temperature led to a well-ordered layer-structured Li$[Ni_{1/2}Co_{1/2}]O_2$, as confirmed by X-ray diffraction pattern. Also these materials have ${\alpha}-NaFeO_2$ ($R\bar{3}m$) structure. Due to the homogeneity of the metal hydroxide, $[Ni_{1/2}Co_{1/2}](OH)_2$, the final product, Li$[Ni_{1/2}Co_{1/2}]O_2$, was also significantly uniform, i.e., the average particle size was of about 10 to 15 ${\mu}m$ in diameter and the distribution was relatively narrow. As a result, the corresponding tap-density was also high approximately 2.41 $gcm^{-3}$, of which the value is comparable to that of commercialized $LiCoO_2$.

• The KIPS Transactions:PartC
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• v.16C no.3
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• pp.373-382
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• 2009

we present more efficient method of a medium access for real-time ubiquitous sensor networks. Proposed MAC protocol is like the randomized CSMA/CA protocol, but unlike previous legacy protocols, it does not use a time-varying contention window from which a node randomly picks a transmission slot. To reduce the latency for the delivery of event reports from sensor nodes, we carefully decide to select a fixed-size contention window with non-uniform probability distribution of transmitting in each slot. We show that the proposed method can offer up to several times latency reduction compared to legacy of IEEE 802.11 as the size of the sensor network scales up to 256 nodes using a widely-used network simulation package, NS-2. We finally show that proposed MAC scheme comes close to meet bounds on the best latency being achieved by a decentralized CSMA-based MAC protocol for real-time ubiquitous sensor networks which is sensitive to latency.

• Korean Journal of Metals and Materials
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• v.49 no.6
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• pp.474-487
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• 2011

Bars of OFHC Cu with the diameter of 45 mm were processed by equal channel angular pressing up to 16 passes via route $B_c$, and homogeneity of their microstructures and mechanical properties was examined at every four passes which develop the equiaxed ultrafine grains. In general, overall hardness, yield strength and tensile strength increased by 3, 7, and 2 times respectively compared with those of unECAPed sample. Cross-sectional hardness exhibited a concentric distribution. Hardness was the highest at the center of bar and it decreased gradually from center to surface. After 16 passes, overall hardness decreased due to recovery and partial recrystallization. Regardless of the number of passage, yield strength and tensile strength were quite uniform at all positions, but elongation showed some degree of scattering. At 4 passes, coarse and ultrafine grains coexisted at all positions. After 4 passes, uniform equiaxed ultrafine grains were obtained at the center, while uniform elongated ultrafine grains were manifested at the upper half position. At the lower half position, grains were equiaxed but its size were inhomogeneous. It was found that inhomogeneity of grain morphology and grain size distribution at different positions are to be attributed to scattering in elongation but they did not affect strength. The present results reveal the high potential of practical application of equal channel angular pressing on fabrication of large-sized ultrafine grained bars with quite homogeneous mechanical properties.

• Geomechanics and Engineering
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• v.28 no.5
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• pp.521-529
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• 2022

This research work deals with the development of air pluviation method for preparing uniform sand specimens for conducting large scale laboratory testing. Simulating real field conditions and to get reliable results, air pluviation method is highly desirable. This paper presents a special technique called air pluviation or sand raining technique for achieving uniform relative density. The apparatus is accompanied by a hopper, shutters with different orifice sizes and numbers and set of sieves. Before using this apparatus, calibration curves are drawn for relative density against different height of fall (H) and shutter sizes. From these calibration curves, corresponding to the desired relative density of 60%, the shutter size of 13mm and height of fall of 457.2 mm, are selected and maintained throughout the pluviation process. The density obtained from the mobile pluviator is then verified using the Dynamic Cone Penetrometer (DCP) test where the soil is poured in the box using defined shutter size and fall height. The results obtained from the DCP test are averaged as 60±0.5 which was desirable. The mobile pluviator used in this research is also capable of obtaining relative densities up to 90%. The instrument is validated using experimental and numerical approach. In numerical study, Plaxis 3D software is used in which the soil mass is defined by 10-Node tetrahedral elements and 6-Node plate is used to simulate plate behavior in the validation phase. The results obtained from numerical approach were compared with that of experimental one which showed very close correlation.

• Journal of the Korean Society of Costume
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• v.66 no.6
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• pp.32-45
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• 2016

The purpose of this study is to propose changes that can be made to improve nurse uniforms in terms of outfit and functionality based on actual wearing conditions and nurse's preference. The proposed nurse uniform was composed of a blouse and pants. The design was as follows: the blouse had short set-in sleeve with China collar, a princess line, and it came down to middle hip. Armhole action pleats and back inverted pleats were embedded for convenient arm movements. The pants waist had a rubber band at the back waist, and the crotch length and the knee width were increased for activity. To make the pocket more accommodative, separate pocket slots treated with silicone were added to prevent belongings from coming out of the pocket. The pink tone of the uniforms, as well as the stripes on the blouses and spandex incorporated pants were based on nurses' preference. the nurse uniforms were produced after measuring the size of women in the age of 25 to 29, and the uniform patterns were corrected after two wearing experiments. Wearing test was examined in terms of appearance and functionality. For appearance, experts gave the uniforms a mean rating of 4.30, and nurses gave a mean rating of 4.00. Functionality was evaluated in terms of ease of activity and storage aspects. The total mean of ease of activity in nursing service was 4.30, whereas the evaluation of storage in terms of pocket position and convenience was 3.80.

• Journal of the Korean Society of Costume
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• v.66 no.1
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• pp.1-12
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• 2016

Najang was the central Seori, affiliated to the Ministry of War during the Joseon dynasty. The objective of this study is to research the existing authentic Najang costumes from the late-Joseon dynasty by examining factors, such as the composition of the costume, size, and method of creation, and attempt to replicate it. The Leipzig Grassi Museum in Germany possesses an official uniform of Najang from the late-Joseon dynasty, and we visited the museum in May of 2013 to examine it for the study. Written records, or Uigwe, and other pictorial data from the Joseon Dynastry describe the Najang wearing black or navy clothing with white decoration and pointy hats. The most notable characteristic of the Najang uniform is that it has the cotton cords pattern. The hat has a brass ball attached, which was worn with the ball facing the front in the early Joseon Dynasty, and was worn facing the back in the later years. They usually wore black head cloths (Heuk-geon), but would attach feathers on the black hats (Heuk-rip) for special occasions. The Najang uniform preserved in the Leipsiz Grassi Muesim does not exist in Korea. It is made of cotton. The cotton cord pattern of the uniform of Najang was made using single-ply cords and double-ply cords. The hat worn by Najang is in a form of a cone that becomes narrower towards the top or is in a form with wide and open end. It was made of oiled paper covered with hemp, and two circular metal disks were attatched at the rear.

• Journal of the Korean Society of Clothing and Textiles
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• v.32 no.8
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• pp.1190-1201
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• 2008

The objective of this study is to compare and analyze middle and high school boys' and girls' uniform wearing conditions. The survey was conducted online and data were obtained from 907 middle and high school boys and girls. The results of this study are as follows. First, most boys and girls did not know their body sizes other than their height and weight. Second, when purchasing the school uniforms, over 70% of the boys and girls chose to try on the uniforms before their purchase and over 60% of the boys and girls had trouble selecting their sizes just by reading the labels. Third, both boys and girls considered the fit as the most important factor. When purchasing jackets, both middle and high school boys considered the shoulder width as most important. Middle school girls considered the jacket and sleeve length as most important, whereas high school girls considered the shoulder width, waist, and bust as most important. When purchasing skirts or slacks, waist girth was considered as most important. Fourth, boys repurchased more school uniforms than girls. Boys have outgrown their uniforms usually in the length categories, whereas girls have outgrown in the girth categories. Fifth, more girls(72.7%) modified their uniforms than the boys(56.8%). Boys usually bought bigger uniforms, modified them to fit and when they grow out of their uniforms they planned to modify their uniforms again whereas girls modified their uniforms to follow the trend. Sixth, the online shopping mall survey has revealed that both boys and girls liked the idea of 3D model that reflect their own body shapes, but they had low preference to purchase school uniforms online. Online purchase has been more attractive to the boys than to the girls, while the way of fashioning uniforms has been more attractive to the girls than to the boys.

• KDI Journal of Economic Policy
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• v.42 no.1
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• pp.57-95
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• 2020

As a case study of an ex-post evaluation of regulations, in this paper I evaluate the 'uniform settlement rate requirement', a regulation that was introduced in 1986 and that was applied to the international telephone market in the U.S. for more than 20 years. In a bilateral market between the U.S. and a foreign country, each U.S. firm and its foreign partner jointly provide international telephone service in both directions, compensating each other for terminating incoming calls to their respective countries. The per-minute compensation amount for providing the termination service, referred to as the settlement rate, is determined by a bargaining process involving the two firms. In principle, each U.S. firm could have a different settlement rate for the same foreign country. In 1986, however, the Federal Communications Commission introduced the Uniform Settlement Rate Requirement (USRR), which required all U.S. firms to pay the same settlement rate to a given foreign country. The USRR significantly affected the relative bargaining positions of the U.S. and foreign firms, thereby changing negotiated settlement rates. This paper identifies two main routes through which the settlement rates are changed by the implementation of the USRR: the Competition-Induced-Incentive Effect and the Most-Favored-Nation Effect. I then empirically evaluate the USRR by estimating a bargaining model and conducting counterfactual experiments aimed at measuring the size of the two effects of the USRR. The experiments show remarkably large impacts due to the USRR. Requiring a uniform settlement rate, for instance, results in an average 32.2 percent increase in the negotiated settlement rates and an overall 13.7 percent ($3.43 billion) decrease in the total surplus in the U.S. These results provide very strong evidence against the implementation of the USRR in the 1990s and early 2000s.

• Journal of electromagnetic engineering and science
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• v.19 no.1
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• pp.64-70
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• 2019

In this study, a compact series-fed center-fed open-stub (SFCFOS) linear array antenna for K-band applications is presented. The antenna is composed of a single-line 10-element linear array. A symmetrical Chebyshev amplitude distribution (CAD) is used to obtain a low sidelobe characteristic against a uniform amplitude distribution (UAD). The amplitude is controlled by varying the width of the microstrip patch elements, and open-ended stubs are arranged next to the last antenna element to use the energy of the radiating signal more effectively. We insert a series-fed stub between two patches and obtain a low mutual coupling for a 4.28-mm center-to-center spacing ($0.7{\lambda}$ at 21 GHz). A prototype of the antenna is fabricated and tested. The overall size of the uniform linear array is $7.04{\times}1.05{\times}0.0563{\lambda}_g^3$ and that of the Chebyshev linear array is $9.92{\times}1.48{\times}0.0793{\lambda}_g^3$. The UAD array yields a ${\mid}S_{11}{\mid}$ < -10 dB bandwidth of 1.33% (20.912-21.192 GHz) and 1.45% (20.89-21.196 GHz) for the CAD. The uniform array design gives a -23 dB return loss, and the Chebyshev array achieves a -30.68 dB return loss at the center frequency with gains of 15.3 dBi and 17 dBi, respectively. The simulated and measured results are in good agreement.

• Membrane Journal
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• v.6 no.3
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• pp.166-172
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• 1996

For the preparation of polybutadiene latexes with suitable particle size, membrane e$$\mu$sification, which is capable of easy and uniform control of particle size, was used in this study. The parameters were the type and amount of surfactants, amount of additive and pressure. Particle size and distribution of prepared latexes were measured and compared with those of e$$\mu$sion prepared by homogenizer. To investigate the membrane e$$\mu$sification mechanism, theoretical drop size was calculated by Harkins-Brown equation. When the amount of surfactant with more than 0.2 wt%(based on DDI water) was added in the continuous phase, the stable e$$\mu$sion was prepared. Other parameters showed little relationship with particle size and distribution. In this membrane e$$\mu$sification, the essential factor for determining the particle size was the pore size of the membrane.