• 한국수소및신에너지학회논문집
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• 제32권5호
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• pp.410-416
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• 2021

The initial electrochemical performance of ceramic fuel cell with thin-film electrolyte was evaluated in terms of peak power density ratio, open circuit voltage ratio, and activation/ohmic resistance ratios at 500℃. Hydrogen and air were used as anode fuel and cathode fuel, respectively. The peak power density ratio reduced as ~17% for 40 minutes, which rapidly decreased in the early stage of the performance evaluation but gradually decreased. The open circuit voltage ratio decreased with respect time; however, its time behavior was remarkably different with the reduction behavior of the peak power density ratio. The activation resistance ratio increased as ~15% for 40 minutes, which was almost similar with the time behavior of the peak power density ratio.

• 한국수소및신에너지학회논문집
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• 제32권5호
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• pp.340-346
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• 2021

The initial electrochemical performance of ceramic fuel cell with thin-film electrolyte fabricated by plasma-enhanced atomic layer deposition method was evaluated in terms of peak power density ratio, open circuit voltage ratio, and activation/ohmic resistance ratios at 500℃. Hydrogen and air were used as anode fuel and cathode fuel, respectively. The peak power density ratio reduced as ~52% for 30 min, which continually decreased as time increased but degradation rate gradually decreased. The open circuit voltage ratio decreased with respect time; however, its behavior was evidently different from the reduction behavior of the peak power density. The activation resistance ratio increased as ~127% for 30 min, which was almost similar with the reduction behavior of the peak power density ratio.

• Steel and Composite Structures
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• 제49권4호
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• pp.441-456
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• 2023

Aiming at the development trend of light weight and high strength of engineering structures, this paper experimentally investigated the seismic performance of circular-in-square high-strength concrete-filled double skin steel tubular (HCFDST) stub columns with out-of-code width-to-thickness (B/t) ratios. Typical failure mode of HCFDST stub columns appeared with the infill material crushing, steel fracture and local buckling of outer tubes as well as the inner buckling of inner tubes. Subsequently, the detailed analysis on hysteretic curves, skeleton curves and ductility, energy dissipation, stiffness degradation and lateral force reduction was conducted to reflect the influences of hollow ratios, axial compression ratios and infill types, e.g., increasing hollow ratio from 0.54 to 0.68 and 0.82 made a slight effect on bearing capacity compared to the ductility coefficients; the higher axial compression ratio (e.g., 0.3 versus 0.1) significantly reduced the average bearing capacity and ductility; the HCFDST column SCFST-6 filled with concrete obviously displayed the larger initial secant stiffness with a percentage 34.20% than the column SCFST-2 using engineered cementitious composite (ECC); increasing hollow ratios, axial compression ratios could accelerate the drop speed of stiffness degradation. The out-of-code HCFDST stub columns with reasonable design could behave favorable hysteretic performance. A theoretical model considering the tensile strength effect of ECC was thereafter established and verified to predict the moment-resisting capacity of HCFDST columns using ECC. The reported research on circular-in-square HCFDST stub columns can provide significant references to the structural application and design.

• Journal of Korean Neurosurgical Society
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• 제38권5호
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• pp.331-337
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• 2005

Objective : The purpose of this study is to identify correlations between diffusion tensor imaging[DTI] and motor improvement by quantifying and visualizing the corticospinal tract on DTI to predict motor impairment in patients with hypertensive intracerebral hemorrhage[ICH]. Methods : Fifteen normal subjects and 7 patients with hypertensive ICH were examined and the latter were treated surgically. DTI was performed with a 3.0 T MRI. The region of interest[ROI] from the posterior limbs of both internal capsules was measured on a fractional anisotropy[FA] map, and the ratios of ROIs were calculated. Tractography, 3-dimensional DTI was then constructed. Motor impairment was assessed on admission and 2weeks after stroke by the Motricity Index[MI]. The FA ratio, tractography and score on MI were analyzed for correlations. Results : The FA ratio from the initial DTI did not show a linear correlation with motor impairment. However, after 2weeks, patients with high FA ratios showed high degrees of motor recovery, regardless of the initial severity, and patients with low FA ratios showed low recovery rates. Otherwise, a relationship between the amount of hematoma and the degree of motor recovery could not be determined. On tractography, injury of the corticospinal tract could be visualized and estimated 3-dimensionally. Conclusion : FA ratio analysis and tractography constructed from DTI may be useful in understanding corticospinal tract injury and in predicting the recovery from motor impairment in patients.

• Animal Bioscience
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• 제34권12호
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• pp.1987-1994
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• 2021

Objective: The present study aimed to evaluate the effects of varying standardized ileal digestible lysine:threonine (SID Lys:Thr) ratio in the diet on the performance and meat quality of finishing pigs. Methods: In total 192 crossbred pigs ([Landrace×Yorkshire]×Duroc, 17 weeks old), with an initial body weight (BW) of 70.6±3.9 kg were used in an 8-wk trial. Pigs were randomly allotted to one of six dietary treatments based on their initial BW and sex (8 replications; 4 pigs per pen, 2 barrows and 2 gilts). The pigs in the 6 treatments were fed diets having different SID Lys:Thr ratios such as 1:0.65, 1:0.66, 1:0.67, 1:0.68, 1:0.69, and 1:0.70. Results: A linear increment (p<0.05) in average daily gain (ADG) and trends in reduction in feed conversion ratio (FCR) were observed during day 29 to 56 of the experiment and the apparent total tract digestibility (ATTD) of dry matter tended to increase linearly (p = 0.094) at the end of the experiment (day 56) with the increase in the dietary SID Lys:Thr ratios. The backfat thickness and lean percentage increased (linear effect, p<0.05) on day 28. In addition, at day 56, a linear (p<0.05) increment in lean percentage was observed. Significant quadratic responses (p = 0.02) for pH and drip loss at day 7 (p = 0.02), a linear increase (p<0.05) in cooking loss and drip loss at day 7, and a trend in quadratic response (p = 0.07) in the lightness of meat color (L^*) were observed, whereas other meat quality indices were unaffected by varying the SID Lys:Thr ratios. Conclusion: The SID Lys:Thr ratio for maximum ADG, minimum FCR and enhanced digestibility was found to be 0.70. However, for carcass trait and meat quality, the SID Lys:Thr ratio of 0.65 was enough.

• Structural Engineering and Mechanics
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• 제68권2호
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• pp.247-259
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• 2018

In this study (Part I), an advanced empirical formulation was proposed to predict the ultimate strength of initially deflected steel plate subjected to longitudinal compression. An advanced empirical formulation was proposed by adopting Initial Deflection Index (IDI) concept for plate element which is a function of plate slenderness ratio (${\beta}$) and coefficient of initial deflection. In case of initial deflection, buckling mode shape, which is mostly assumed type in the ships and offshore industry, was adopted. For the numerical simulation by ANSYS nonlinear finite element method (NLFEM), with a total of seven hundred 700 plate scenarios, including the combination of one hundred (100) cases of plate slenderness ratios with seven (7) representative initial deflection coefficients, were selected based on obtained probability density distributions of plate element from collected commercial ships. The obtained empirical formulation showed good agreement ($R^2=0.99$) with numerical simulation results. The obtained outcome with proposed procedure will be very useful in predicting the ultimate strength performance of plate element subjected to longitudinal compression.

• 자원환경지질
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• 제29권2호
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• pp.151-158
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• 1996

Rb-Sr isochron ages, Sr and Nd isotopic compositions were determined for late Cretaceous granophyre on the Haenam-Wando areas, the southwestern part of the Yeongdong-Kwangju depression in Korea. The granophyre in the Haenam-Wando areas are distributed in the shape of a resurgent cauldron. Five samples of Haenam granophyre give a defined Rb-Sr whole rock isochron age of $75.7{\pm}7.2Ma$ and Sr initial ratio of $0.70826{\pm}0.00020(2{\sigma})$. Plagioclase, orthoclase and whole rock of Haenam granophyre give a defined Rb-Sr whole rock-mineral isochron age of $67.0{\pm}5.8Ma$ and Sr initial ratio of $0.708880{\pm}0.00028(2{\sigma})$. Five samples of Wando granophyre give a defined Rb-Sr whole rock isochron age of $70.6{\pm}3.3Ma$ and Sr initial ratio of $0.70850{\pm}0.00088(2{\sigma})$. Eight samples of Haenam granophyre give a defined Nd isotope ratios of 0.512180~0.512259 and ${\varepsilon}Nd$ (T) values of -6.53~-8.15, ${\varepsilon}Sr$ (T) values of +51.49~+66.48 and model age of 1.28~1.60 Ga. Four samples of Wando granophyre give a defined Nd isotope ratios of 0.512228~0.512289 and ${\varepsilon}Nd$ (T) values of -6.74~-8.00, ${\varepsilon}Sr$ (T) values of +54.88~+78.98 and model age of 1.14~1.42 Ga.

• 대한치과보철학회지
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• 제43권5호
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• pp.662-670
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• 2005

Statement of problem: Little is known about the effect of abutment preparation procedure on do-torque values in different implant platform and the relationship of final do-torque values with different implant platform size. Purpose: This study evaluated the effect of abutment preparation procedure on do-torque values in different implant platform and the relationship of final do-torque values with different implant platform size. Material and method: Six ITI implants (2 narrow-neck implants, 2 regular-neck implants, 2 wide-neck implants) and six Branemark implants (2 narrow platforms, 2 regular platforms, 2 wide platforms) were embedded in each acrylic resin block with epoxy resin. Eighteen $synOcta^(R)$ abutments (6 narrow-neck implant-abutments, 6 regular-neck implant-abutments, 6 wide-neck implant-abutments) and eighteen esthetic abutments (6 narrow platform-abutments, 6 regular platform-abutments, 6 wide platform-abutments) were tightened to each implant with digital torque gauge. Initial do-torque values were measured using digital torque gauge. After preparation of abutments, Final do-torque values were measured with digital torque gauge. Results and conclusion: 1. Screws loosening or abutments motion were not detected in all experimental group, but some scratches of implant-abutment joints were detected in all group 2. Reduction ratios of final do-torque values were greater than initial do-torque values in all measured group, except in narrow-neck implant-abutment group (p<0.05). 3. Reduction ratios of final do-torque values in wide-neck implant-abutment group were greater than regular-neck implant-abutment group (p<0.01). 4. The greatest standard deviation value was detected in wide platform group in both implant systems.

• Archives of Pharmacal Research
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• 제15권2호
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• pp.162-168
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• 1992

Release characteristics of five different types of hydrophilic albumin microspheres (HAM) containing different ratios of methotrexate-albumin (MTX-HSA) conjugates to free MTX: 1 : 0 (HAMC), 3 :1 (HAMC 3F), 1 :1 (HAMCF), 1:3 (HAMCF3) and 0 : 1 (HAMF) were investigated in the absence or presence of protease using dissolution tester. In all the HAMs studied except HAMC, the MTX was released bi-exponentially in the absence of protease; an initial fast release period up to approximately 6h, and thereafter the release rate was very much slower. The fast release of MTX from the HAMs (such as HAMC3F, HAMCF, HAMCF3 and HAMF) at the initial phase in probably due to the release of "physically associated" MTX from the core of the HAMs. The initial rate constants were 7.2, 8.7, 8.5 and 5.9 times greater than the second rate constants for HAMF, HAMCF3, HAMCF and HAMC3F, respectively. MTX release from HAMC was very slow and mono-phasic. It was at most 2.2% of the total entrapped amount by 24 h. The protease accelerated the release of MTX from the HAMs. The percentages of MTX released from HAMs up to 24 h were 100, 89.0, 75.0, 66.0 and 61.0% for HAMF, HAMCF3, HAMCF, HAMC3F and HAMC, respectively in the presence of protease and the corresponding values in the absence of protease were 30.2 19.0, 10.0, 6.5 and 2.2%, respectively. In vitro release of MTX in the presence of protease varied according to the ratios of MTX-HSA conjugates to MTX; the data set from HAMF, HAMCF3 and HAMCF fits better to monophasic first-order profile more adequately than to zero-order profile, that of HAMC3 monophasic first-order, and that of HAMC to bi-phasic zero-order. Above results suggested that zero-order release rate can be achieved by adjusting the ratio of MTX-HSA conjugates to MTX in the preparation of HAMs such as HAMC3F.as HAMC3F.

• 천문학회지
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• 제56권1호
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• pp.11-22
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• 2023

We report the result of a high-resolution spectroscopic study on seven magnesium (Mg) enhanced stars. The high Mg abundances in these stars imply that they were born in an environment heavily affected by the nucleosynthesis products of massive stars. We measure abundances of 16 elements including Mg and they show various abundance patterns implying their diverse origin. Three of our program stars show a very high Mg to Si ratio ([Mg/Si] ≈ 0.18-0.25), which might be well explained by fall-back supernovae or by supernovae with rapid rotating progenitors having an initial mass higher than about 20 M_⊙. Another three of our program stars have high light to heavy s-process element ratios ([Y/Ba] ≈ 0.30-0.44), which are consistent with the theoretical prediction of the nucleosynthesis in rapidly rotating massive stars with an initial mass of about M = 40 M_⊙. We also report a star having both high Y ([Y/Fe] = 0.2) and Ba ([Ba/Fe] = 0.28) abundance ratios, and it also shows the highest Zn abundance ratio ([Zn/Fe] = 0.27) among our sample, implying the nucleosynthesis by asymmetric supernova explosion induced by very rapid rotation of a massive progenitor having an initial mass between 20 M_⊙ ≲ M ≲ 40 M_⊙. A relative deficiency of odd-number elements, which would be a signature of the pair-instability nucleosynthesis, is not found in our sample.