• Journal of the Korean Chemical Society
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• v.40 no.10
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• pp.649-655
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• 1996

The chemical behaviour of Pt(Ⅱ) and Pd(Ⅱ) complexes with the organic ligand tetramethylenesulfoxide(TMSO) has been investigated by UV/vis-spectrophotometric, magnetic, and electrochemical methods. Two energy absorption bands are observed in the spectra of these complexes. The crystal field splitting energy, spin pairing energy, and bond strength were obtained from the spectra of the complexes. The electronic properties of the complexes are found to be delocalized, and low-spin state. The correlation between ligand and metals were strong bonding strength. These complexes are diamagnetics. The redox reaction processes of the complexes were investigated by cyclic voltammetry in an aprotic solvent. The redox processes of complexes turned out to be respect to one-electrton one step. These complexes were considerably diffusion and reaction controlled.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.1
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• pp.15-21
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• 2008

SiC has an excellent resistance to oxidation and corrosion, high temperature strength and good thermal conductivity. However, it is difficult to density because of its highly covalent bonding characteristics. Hot-press sintering process was applied to fabricate fully densified SiC ceramics with carbon and boron addition as a sintering additive. The addition of carbon improved the mechanical properties of SiC because it could induce a fine and homogeneous microstructure by the suppression of abnormal growth of SiC grain. Also, the addition of carbon could control the phase transformation of SiC. The phase transformation of 6H to 4H increased with sintering temperature but the addition of carbon decreased that kind of phase transformation.

• Magazine of the Korea Concrete Institute
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• v.9 no.2
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• pp.167-177
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• 1997

In thtx design of ductile moment -1csist1ng frnmcls (DMRFs) f'ollow~ng the. stlong columnweakbeam design philosophy, it is desirable that the joint and column remain essentiallyelastic in order to insure proper energy dissipation and lateral stability of the structure.Thv joint has been identifid as the "weak link: in DMRFs because any stiffness orstrength deterioration in this region can lead to substantial drifts and the possibility ofcollapse due to t'-delta effects. h3oreove1.. the tngintw is faced with the difficult task ofdetailing an element whose size is determined by theframing members, but \vhich mustresist a set of loads very different from those used in the design of the beams and columns.Four 3 -scale beam-column-slab joint assemblies were designed according to existing cod\ulcornerrequirements of' ACI 318-89. representing perimeter joints of DMRFs with reinforced highstrength concrete. The influence on aseismic behavior of beam-column joints due tomonolithic slab, has been investigated.lab, has been investigated.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.16 no.6
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• pp.267-272
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• 2006

A series of $Sr_{1-x}Ca_xGa_2S_4:Ce,Na$ phosphors have been synthesized by solid-state reaction. The photoluminescence and structural properties of $Sr_{1-x}Ca_xGa_2S_4:Ce,Na$ have been examined. The $Sr_{1-x}Ca_xGa_2S_4:Ce,Na$ phosphors have a strong absorption at 400 nm, which is the emission wavelength of a violet light emitting diode (LED). The emission peaks of $SrGa_2S_4:Ce,Na$are located at 448 nm and 485 nm. The partial replacement of Sr by Ca in $Sr_{1-x}Ca_xGa_2S_4:Ce,Na$ causes a red shift of emission wavelengths. The $Sr_{1-x}Ca_xGa_2S_4:Ce,Na$ can be used as blue emitting phosphors pumped by the violet LED for fabricating the multi-band white LED.

• Membrane Journal
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• v.5 no.2
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• pp.89-96
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• 1995

The monolayer characteristics of phosphate amphiphiles with azobenzene at air/water interface were studied by the measurment of $\pi-A$ curves and absorption spectra. Immediately after being spread on the water surface, these amphiphiles having strong intermolecular hydrogen bonding interactions showed the typical absorption spectra which resulted from domain formation. But the aggregated domains could be controlled by changing the subphase conditions (adding bulky salt and rasing pH). Addition of metal ions in subphase changes the molecular orientation of monolayer. As the metal ion charge increases ($1\leq2$ < 3 < 4 valence), the absorption maximum (310nm) of the amphiphile with azobenzene shifts to a longer wavelength (350nm) which means that the orientation of the amphiphile is tilted. These results suggest that the molecular orientation, and furthermore the aggregation state of monolayer can be possibly controlled by the interaction of metal ions with different charge types.

• Journal of Radiation Protection and Research
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• v.30 no.2
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• pp.69-75
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• 2005

Gas avalanche microdetectors, such as micro-strip gas chamber (MSGC), micro-gap chamber (MGC), micro-dot chamber (MDOT), etc., are operated under high voltage to induce large electron avalanche signal around micro-size anodes. Therefore, the anodes are highly exposed to electrical damage, for example, sparking because of the interaction between high electric field strength and charge multiplication around the anodes. Gas electron multiplier (GEM) is a charge preamplifying device in which charge multiplication can be confined, so that it makes that the charge multiplication region can be separate from the readout micro-anodes in 9as avalanche microdetectors possible. Primary electron collection efficiency is an important measure for the GEM performance. We have defined that the primary electron collection efficiency is the fractional number of electron trajectories reaching to the collection plane from the drift plane through the GEM holes. The electron trajectories were estimated based on 3-dimensional (3D) finite element method (FEM). In this paper, we present the primary electron collection efficiency with respect to various GEM operation parameters. This simulation work will be very useful for the better design of the GEM.

• Food Science and Preservation
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• v.15 no.6
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• pp.810-815
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• 2008

Improving quality is a very important component of maintaining competitiveness of agricultural products. However, evaluation of 'high quality' indicates it is a very abstract concept and independent of some quality attributes, leading to differences in the perception of quality. Thus, there is a pressing need to objectively define 'high quality' and to develop basic technologies for its measurement, for application in the production, storage and distribution of competitive agricultural products. To objectively quantify apple quality, a survey was conducted on consumer preferences and awareness of quality attributes including color, taste, flavor and shape. The survey questionnaire targeted male and female adults (463 persons) ranging in age from 20 to 59 years. The questionnaire was based on purchases made at a wholesale market (50.1%) or a traditional market (18.8%). The majority of purchases were as small packets (62.0%) or as individual pieces (20.5%). Apples of moderate size (fist size, 60.5%) were preferred over small (4.3%) or large (32.6%) apples. The questionnaire provided consumer data on external quality attributes including color, shape and variety. Taste attributes were evaluated in relation to the balance between sour and sweet taste, and flavors peculiar to apples.

• The Journal of the Acoustical Society of Korea
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• v.39 no.6
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• pp.524-532
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• 2020

In this study, noise radiated from a high-speed fan-motor unit for a cordless vacuum cleaner is reduced by designing splitter blades on the existing impeller. First of all, in order to investigate the flow field through a fan-motor unit, especially impeller, the unsteady incompressible Reynolds-Averaged Navier-Stokes (RANS) equations are numerically solved by using computational fluid dynamic technique. With predicted flow field results as input, the Ffowcs Williams-Hawkings (FW-H) integral equation is solved to predict aerodynamic noise radiated from the impeller. The validity of the numerical methods is confirmed by comparing the predicted sound pressure spectrum with the measured one. Further analysis of the predicted flow field shows that the strong vortex is formed between the impeller blades. As the vortex induces the loss of the flow field and acts as an aerodynamic noise source, supplementary splitter blades are designed to the existing impeller to suppress the identified vortex. The length and position of splitter are selected as design factors and the effect of each design factor on aerodynamic noise is numerically analyzed by using the Taguchi method. From this results, the optimum location and length of splitter for minimum radiated noise is determined. The finally selected design shows lower noise than the existing one.

• Journal of The Korean Association For Science Education
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• v.36 no.2
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• pp.253-267
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• 2016

Everybody dreams of a bright future. A future career determines the direction and quality of an individual's life. Achieving positive career development is one of the most crucial tasks during adolescence. In both national and personal perspectives, the vocational identity of science-gifted students provides some important points to discuss. The purpose of this study is to examine the vocational identity of science-gifted students. Participants included 103 science-gifted students who have received an acceptance letter from a science-gifted school. The modified VISA (Vocational Identity Status Assessment) model was used to analyze the vocational identities of gifted students with 'a letter to myself in the future'. The study found that vocational identity status of the science-gifted students was determined as Foreclosed and Searching Moratorium. The science-gifted students demonstrated more Commitment than Exploration and Reconsideration. They also showed higher levels in Career Identification, In-Narrow Exploration, and Career Flexibility. In addition, they shared common orientations in vocational identity such as strong enthusiasm, challenging limits, and responsibility towards humanity. We expect that this study will contribute to the social interest of science-gifted students in the area of career education. In order for science-gifted students to nurture their full potential with a deeper awareness of education, follow-up studies have to be conducted to provide greater and ideal career education.

• The Korean Journal of Financial Management
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• v.21 no.1
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• pp.149-181
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• 2004

In this study we perform empirical tests using KOSPI return to investigate the existence of nonlinear characteristics in the generating process of stock returns. There are three categories in empirical tests; the test of nonlinear dependence, nonlinear stochastic process and nonlinear deterministic chaos. According to the analysis of nonlinearity, stock returns are not normally distributed but leptokurtic, and appear to have nonlinear dependence. And it's decided that the nonlinear structure of stock returns can not be completely explained using nonlinear stochastic models of ARCH-type. Nonlinear deterministic chaos system is the feedback system, which the past incidents influence the present, and it is the fractal structure with self-similarity and has the sensitive dependence on initial conditions. To summarize the results of chaos analysis for KOSPI return, it is the persistent time series, which is not IID and has long memory, takes biased random walk, and is estimated to be fractal distribution. Also correlation dimension, as the approximation of fractal dimension, converged stably within 3 and 4, and maximum Lyapunov exponent has positive value. This suggests that chaotic attractor and the sensitive dependence on initial conditions exist in stock returns. These results fit into the characteristics of chaos system. Therefore it's decided that the generating process of stock returns has nonlinear deterministic structure and follow chaotic process.