• Journal of Korean Vacuum Science & Technology
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• v.3 no.1
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• pp.49-53
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• 1999

We have studied the field emission characteristics of diamond-like-carbon (DLC) films deposited by a layer-by-layer technique using plasma enhanced chemical vapor deposition, in which the deposition of a thin layer of DLC and a CH4 plasma exposure on its surface were carried out alternatively. The hydrogen-free DLC can be deposited by CH4 plasma exposure for 140 sec on a 5 nm DLC layer. N2 gas-phase doping in the CH4 plasma was also carried out to reduce the work function of the DLC. The optimum [N2]/[CH4] flow rate ratio was found to be 9% for the efficient electron emission, at which the onset-field was 7.2 V/$\mu\textrm{m}$. It was found that the hydrogen-free DLC has a stable electron emitting property.

• Journal of the Korean Statistical Society
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• v.12 no.1
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• pp.10-17
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• 1983

Let $X^{(n)}_j, j=1,2,\cdots,n, n=1,2,\cdots$ be a triangular array of random variables which arise naturally in a study of ferromagnetism in statistical mechanics. This paper presents weak convergence of random function $W_n(t)$, an appropriately normalized partial sum process based on $S^{(n)}_n = X^{(n)}_i+\cdot+X^{(n)}_n$. The limiting process W(t) is shown to be Gaussian when weak dependence exists. At the critical point where the change form weak to strong dependence takes place, W(t) turns out to be non-Gaussian. Our results are direct extensions of work by Ellis and Newmam (1978). An example is considered and the relation of these results to critical phenomena is briefly explained.

• International Journal of Aeronautical and Space Sciences
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• v.15 no.2
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• pp.190-198
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• 2014

The pyramidal reaction wheel arrangement is one of the configurations that can be used in attitude control simulators for evaluation of attitude control performance in satellites. In this arrangement, the wheels are oriented in a pyramidal configuration with a tilt angle. In this paper, a study of pyramidal reaction wheel arrangement is carried out in order to find the optimum tilt angle that minimizes total power consumption of the system. The attitude control system is analyzed and the pyramidal configuration is implemented in numerical simulation. Optimization is carried out by using an iterative process and the optimum tilt angle that provides minimum system power consumption is obtained. Simulation results show that the system requires the least power by using optimum tilt angle in reaction wheels arrangement.

• Steel and Composite Structures
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• v.21 no.4
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• pp.775-789
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• 2016

This paper presents the flexural behavior & ultimate strength performance of innovative light weight sandwich panels of size $3{\times}1.2m$ with two different solidity ratios viz. 0.5 and 0.33 under out of plane bending load. From the experimental studies, it is observed that the flexural strength and the stiffness are increased by about 46% and five folds for lesser solidity ratio case. From the measured strains of the shear connectors, full shear transfer between the concrete wythes is observed. The yielding occurred approximately at 4% and 0.55% of the ultimate deformation for 100 mm & 150 mm thick panels, which shows the large ductility characteristics of the panels. From the study, it is inferred that the light weight sandwich panels behave structurally in a very similar manner to reinforced concrete panels. Further from the numerical study, it is observed that the numerical values obtained by FE analysis are in good agreement with the experimental observations.

• Journal of the Korean Mathematical Society
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• v.57 no.6
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• pp.1407-1433
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• 2020

Parts I-IV showed that the number of ways to place q nonattacking queens or similar chess pieces on an n × n chessboard is a quasipolynomial function of n whose coefficients are essentially polynomials in q. For partial queens, which have a subset of the queen's moves, we proved complete formulas for these counting quasipolynomials for small numbers of pieces and other formulas for high-order coefficients of the general counting quasipolynomials. We found some upper and lower bounds for the periods of those quasipolynomials by calculating explicit denominators of vertices of the inside-out polytope. Here we discover more about the counting quasipolynomials for partial queens, both familiar and strange, and the nightrider and its subpieces, and we compare our results to the empirical formulas found by Kotššovec. We prove some of Kotššovec's formulas and conjectures about the quasipolynomials and their high-order coefficients, and in some instances go beyond them.

• Journal of the Korean Chemical Society
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• v.19 no.1
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• pp.11-15
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• 1975

Kinetic study of halogen exchange for N,N-dimethylcarbamoyl chloride and N,N-diethylcarbamoyl chloride in acetone by using radioisotopic halide ions has been carried out at two temperatures as a part of studying the reactivity of carbonyl carbon atom. The order of nucleophilicity showed a similar tendency as that for alkyl chloroformate, but reaction rate is much slower than that for solvolysis and alkyl chloroformate. The activation parameters,${\Delta}H^*$and${\Delta}S^*$ were found to decrease in sequence $Cl^{\rightarrow}Br^{\rightarrow}I^-$ for N,N-dialkylcarbamoyl chlorides. The results are interpreted in terms of solvation effect, degree of bond-breaking and bond-formation and electronic requirements.

• Journal of the Korean Society for Heat Treatment
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• v.1 no.1
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• pp.8-12
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• 1988

This study has been carried out to evaluate gaseous nitrocarburizing treatment undertaken for pure iron at $570^{\circ}C$ in an atmosphere containing 50% endothermic gas, generated from natural gas, and 50% ammonia. The results obtained from the experiment are as follows ; 1) The microstructure of gaseous nitrocarburized pure iron consists of the compound layer on the surface and the diffusion zone beneath it. The compound layer progresses uniformly into ferrite with a thickness of $20{\mu}$ obtained after treating for 3 hours. 2) Chemical analysis has shown that the compound layer has a C/N ratio of 0.19 and that the average combined interstitial content of the compound layer is about 30 atomic percent, which is close to the lower limit of the ${\varepsilon}$-carbonitride phase field in Fe-C-N phase diagram. 3) X-ray diffraction analysis has revealed that the compound layer consists mainly of the c.p.h. phase, ${\varepsilon}-Fe_3$(C.N) and a small amount of $Fe_4N$ and traces of ferrite are also present in the compound layer. 4) The microhardness of the compound layer is about 600 V.H.N and shows a relatively sharp fall-off at the compound layer/diffusion zome interface. 5) The average actual degree of ammonia dissociation is calculated to be 27% for a gaseous nitrocarburizing treatment carried out at $570^{\circ}C$.

• Journal of the Korean Society of Physical Medicine
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• v.11 no.4
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• pp.79-84
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• 2016

PURPOSE: The purpose of this study was to investigate effects of Horse riding simulator exercise on pain, dysfunction and dynamic balance in adults with nonspecific chronic low back pain. METHODS: In this study, total 19 college students usually complain of low back pain who were randomly divided into the horse riding simulator exercise group (n=10), lumbar strengthening exercise group (n=9) were recruited. Each group carried out for 30 minutes exercise three times a week for 4 weeks. Horse riding simulator exercise group carried out 15 minutes horse riding simulator exercise and 15 minutes lumbar strengthening exercise. Lumbar strengthening exercise group carried out 30 minutes lumbar strengthening exercise. Visual analogue scale (VAS) were measured for evaluation back pain. Korean oswestry disability index (KODI) were measured for dysfunction. Limits of stability (LOS) were measured for dynamic balance. RESULTS: VAS, KODI, LOS results showed a significant change within both horse riding simulator exercise group, lumbar strengthening exercise group. CONCLUSION: Present study suggested that the horse riding simulator exercise can improve back pain, dysfunction, dynamic balance. Horse riding simulator exercise provides more convenience, interest and motivation than conversional therapy and it could be a possible approach to adults with nonspecific chronic low back pain.

• Journal of the Korean Applied Science and Technology
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• v.11 no.2
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• pp.113-120
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• 1994

Amphoteric surfactants were synthesized by the cyclization of 1-(2-hydroxyethyl)-2-undecyl-2-imidazoline [I] with acrylic acid ethyl ester. Compound [I] was easily hydrolyzed with water, especially in the presence of a alkali, to afford amidoamines. After [I] was hydrolyzed, the reaction mixture was allowed to react with acrylic acid ethyl ester and then soapoinfied. Only sodium salts of N- -(2-carboxyethyl)-N'-(2-hydroxyethyl)aminoethyl]dodecanoyl amide[III] was obtained. However, when the reacton of [I] with acrylic acid ethyl ester was carried out in the presence of water, followed by soapnification, ring cleavage of [I] occurred at 2, 3 position, different from hydrolysis of [I] where the cleavage occurred at 1, 2 position, to give sodium salts of N-[N'-(2-carboxyethyl)aminoethyl]-N-(2-hydroxyethyl)dodecanoyl amide [IV] and N-[N', N'-bis(2-carboxyethyl)aminoethyl]-N(2-hydroxyethyl)dodecanoyl amide [V] as main products.

• Proceedings of the Membrane Society of Korea Conference
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• 2004.05a
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• pp.69-69
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• 2004

Cellulose hollow fiber membranes (CHFM) were prepared from the cellulose/N-methylmorpholine-N-oxide/$H_2O$ system by immersion-precipitation and wet spinning. Different drying methods were carried out to investigate their influences on the properties of CHFM.(omitted)