• Journal of the Optical Society of Korea
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• 제20권6호
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• pp.733-738
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• 2016

We calculate optical properties of guided modes of a hybrid-guiding photonic crystal fiber. The design and modeling of such hybrid-guiding PCF is made by replacing air holes with inserts of high refractive index material layer by layer in order. The optical properties such as mode intensity profile, mode dispersion, optical birefringence, confinement loss, and chromatic dispersion during transition of the guiding mechanism are analyzed and discussed. The guided modes in the hybrid-guiding region are also compared with those of reference index-guiding and bandgap-guiding photonic crystal fibers.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2001년도 추계학술발표회 초록집
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• pp.10-10
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• 2001

In this paper, initial depositing process of electroless Ni-Cu-P alloy was investigated by means of SEM, TEM and AES. The results show that the initial deposition is inhomogeneous and there exist different transition layers between different coatings and substrates, which are decided by the structures and compositions of the bath. For Ni-P binary alloy, its deposition takes place superiorly at grain boundary and on some grains with beneficial texture, the thickness of transition layer composed of Ni-Fe-P reaches 2000 angstrom. But during initiation of Ni-Cu-P trinary alloy, only at grain boundary is prIor to be deposited electrolessly, transited layer contains Ni-Fe-Cu-P and is decreased to about 500 angstrom. The structures of the films of Ni-P and Ni-Cu-P are crystalline at the initial depositing stage. The mechanisms of the process are put forward in this paper.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2000년도 제18회 학술발표회 논문개요집
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• pp.155-155
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• 2000

Adsorption of alkali metals on a silicon surface has attracted much attention due to its importance in metal-semiconductor interface technology, In particular, the bonding nature of alkali metal to silicon substrate has been a focus of fundamental research efforts. We examined the adsorbed layer of Cs on a Si(111)-(7$\times$) surface by reactive ion scattering (RIS) of hyperthermal Cs+ beams. RIS from a Cs-adsorbed surface gives rise to Cs, representing pickup of surface Cs by Cs projectile. The Cs intensity is proportional to surface coverage of Cs at a high substrate temperature (473 K), while it varies anomalously with Cs coverage at low temperatures (130-170 K). This observation indicates that RIS selectively detects metallic Cs on surface, but discriminates ionic Cs. Transition from ionic to metallic Cs adlayer is driven by thermal diffusion of Cs and their clustering process.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.896-899
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• 1991

This paper presents the neural network method to predict the Korea composition stock price index. The error back-propagation method is used to train the multi-layer perceptron network. Ten of the various economic indices of the past 7 Nears are used as train data and the monthly transition of the composition stock price index is represented by five output neurons. Test results of this method using the data of the last 18 months are very encouraging.

• 한국결정성장학회지
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• 제14권2호
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• pp.63-67
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• 2004

층상 구조의 cobalt dedecanesulfate 화합물을 합성하였다. 여러 온도 영역에서 상 전이가 일어나면서 층간 거리의 큰 변화가 생겼다. 상온에서 단일 층 구조의 cobalt dodecanesulfate 화합물이 고온에서 탈수된 화합물의 이중층의 구조로 변화되었다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2003년도 The Fifth Asian Computational Fluid Dynamics Conference
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• pp.107-109
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• 2003

We propose a wall distance free one-equation turbulence model. The model is organized in an extremely simple form. Only a few model constants were introduced into the model. The model is numerically tough and easy-of-use. The model also demonstrated the ability to simulate the laminar to turbulent flow transition. The model has been applied to the channel flow, the plane jet, the backward facing step flow, the flat plate boundary layer, as well as the flow around the 2D airfoil at large angles of attack, which obtained satisfactory results.

• 한국응용약물학회:학술대회논문집
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• 한국응용약물학회 1996년도 춘계학술대회
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• pp.286-286
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• 1996

In order to elucidate the mechanism of action of transdermal absorption-enhancing compounds, i.e., pyrrolidone derivatives (2-pyrrolidone, 1-methyl-2-pyrrolidone, 1-ethyl-2-pyrrolidone, 1,5-dimethyl-pyrrolidone and 5-methyl-2-pyrrolidone), multilamellar liposome was prepared from the simulated stratum corneum lipid and employed as a model system for the barrier function of the stratum corneum. The liposomal membrane of the stratum corneum lipid liposome (SCLL) behaves as an osmometer and has an excellent barrier function. In addition, its phase transition temperatures are similar to those of human stratum corneum intercellular lipid region. Therefore, SCLL seems to be a useful skin model. To estimate the barrier function of SCLL, the osmotic behavior of SCLL was measured in the presence of pyrrolidone derivatives and the effect on the phase transition temperature of SCLL was also investigated using differential calorimetry. Above a certain concentration (MLAC), enhances perturb the barrier function of the liposome. The relationship between MLACs and the partition coefficient of the pyrrolidone derivatives was observed; the greater the partition coefficients, the smaller the MLAC. This suggests that the more hydrophobic enhancers penetrate into the lipid layer more easily and reduce the barrier function of membrane more effectively. The results of differential scanning thermograms of the SCLL suggest that the pyrrolidone derivatives had incorporated into the lipid layer in the liposome and increased the fluidity of the lipid layer in the liposome. Such activity might have some correlation with the transdermal absorption-enhancing activity these compounds.

• International Journal of Air-Conditioning and Refrigeration
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• 제10권1호
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• pp.50-63
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• 2002

The Karman boundary-layer has been numerically investigated for the disturbance wave number, wave velocity, azimuth angle and radius (Reynolds number, Re). The disturbed flow over rotating disk can lead to transition at a much lower Re than that of the well-known Type I instability. This early transition is due to the excitation of the Type II. Presented are the neutral stability results concerning these instabilities by solving newly formulated stability equations with consideration of whole convective terms. When the present numerical results are compared with the previously known results, the value of critical Re corresponding to Type I is moved from ${Re}_{c.1}$=285.3 to 270.2 and the value corresponding to Type II from ${Re}_{c.2}$=69.4 to 36.9, respectively. Also, the corresponding wave number is moved fro)m $k_1$=0.378 to 0.386 for Type I; from $k_2$=0.279 to 0.385 for Type II. For Type II, the upped limit of wave number and azimuth angle is $k_u$=0.5872, $\varepsilon_u$=$-17.5^{\circ}$, while its lower limit is near $k_u$=0, $\varepsilon_u$=$-28.4^{\circ}$. This implies that the disturbances will be relatively fast amplified at small Re and within narrow bands of wave number compared with the previous results.

• 대한기계학회논문집B
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• 제21권4호
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• pp.509-517
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• 1997

Results of flat plate compressible boundary layer calculation, based on discrete formulation of DSMC method, are presented in low Mach number and low Knudsen number range. The free stream is a uniform flow of pure nitrogen at various Mach numbers in low pressures (i.e. rarefied gas). Complete thermal accommodation and diffuse molecular reflections are used as the wall boundary condition, replacing unreal no-slip condition used in continuum calculations. In the discrete formulation of DSMC method, there is no need to use ad hoc assumptions on transport properties like viscosity and thermal conductivity, instead viscosity is calculated from values of other field variables (velocity and shear stress). Also the results are compared with existing self-similar continuum solutions. In all Mach number cases computed, velocity slip is most pronounced in regions near the leading edge where continuum formulation renders the solution singular. As the boundary layer develops further downstream, velocity slips asymptote to values that are between 10 to 20% of the magnitude of free stream velocity. When the free stream number density is reduced, so the gas more rarefied, the velocity slip increases as expected.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.191-192
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• 2008

For phase transition method, good record sensitivity, low heat radiation, fast crystallization and hi-resolution are essential. Also, a retention time is very important part for phase-transition. In our past papers, we chose composition of $Ge_1Se_1Te_2$ material to use a Se factor which has good optical sensitivity than conventional Sb. Ge-Se-Te and Ag/$Ge_1Se_1Te_2$ samples are fabricated and irradiated with He-Ne laser and DPSS laser to investigate a reversible phase change by light. Because of Ag ions, the Ag layer inserted sample showed better performance than conventional one. We should note that this novel one showed another possibility for phase-change random access memory.