• Resources Recycling
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• v.16 no.6
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• pp.28-33
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• 2007

Coal is the most abundant energy source and deposited in every area of world. Combustion process with lower efficiency has been mainly used. Therefore, implementation of more efficient technologies, involving gasification, combined cycles and fuel cells, would be a key issue in the plans for more efficient power generation. In these technologies, gasification has been studied for decades. However, coal gasification to high value combustible gas such as hydrogen and carbon monoxide is focused again due to high oil price. The gaseous product, called syngas, can be effectively utilized in a variety of ways ranging from electricity production to chemical industry (as feedstock). In this study, coal gasification with ultra high temperature steam has been performed. The effect of steam/carbon ratio on the produced gas concentrations, gasification rate and additional products like tar, ammonia and cyan compounds has been determined.

• Journal of Ginseng Research
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• v.32 no.2
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• pp.155-160
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• 2008

The North American ginseng (Panax quinquefolius L.) seed crop varies from year to year. The ability to hold stratified seed for a year would ensure continuity of seed supply and no interruption in production cycles. Seed drying and rehydration protocols at room temperature $(21{\pm}2^{\circ}C)$ were developed. These protocols and seed storage at 4 ${\pm}1^{\circ}C$ and 35%, or variable, relative humidity (RH) allowed the holding of stratified seed for one year and then establishment of the following five treatments in field plots: Trt.1 : dried 2005 stratified seed (seed harvested Fall 2004) held at $4^{\circ}C$ and at variable humidity; Trt.2 : 2006 stratified seed planted directly into the field; Trt.3 : 2005 stratified seed dried in October 2005 and held at $4^{\circ}C$ and 35% RH ; Trt.4 : 2005 stratified seed held in moist sand from October to December 2005 at room temperature $(21{\pm}2^{\circ}C)$ and then in December dried and held at $4^{\circ}C$ and 35 % RH; Trt.5 : 2005 stratified seed held in moist sand from October to December 2005 at room temperature and then in December dried and held at $-12^{\circ}C$ Seedling emergence was best in Trts. 2 and 4 with 67.3 and 65.1% respectively which is similar to the industry expected rate of 68% after regular stratification. Seedling growth was similar in Trts. 2 and 4 with root dry weights of 172 and 159 mg respectively in mid-August. Therefore, if holding stratified seed in August/September for one year is desired, the seed can be placed in moist sand until December and then dried and stored at $4^{\circ}C$ and 35% RH. These seed can be planted in the following August/September and will germinate and grow in the following year to give an acceptable crop.

• Clinical and Experimental Reproductive Medicine
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• v.13 no.2
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• pp.113-119
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• 1986

The present study was designed to assess the relationships between the methods to evaluate adequacy of luteal function. We measured mid-luteal serum progesterone levels by radioimmune assay, luteal phase lengths and mean post-ovulatory basal body temperature rise rates by basal body temperature charts in 40 in-phase-cycle infertile patients and 38 out-of-phase-cycle patients who underwent late-luteal endometrial biopsies at the sterility clinic of Department of Obstetrics and Gynecology, Seoul National University Hospital from Jan. 1986 to Aug. 1986. The results were summarized as follows: 1. No significant differences were found in mean age, mean duration of infertility, mean mid-luteal serum progesterone levels, and mean post-ovulatory temperature rise rate between in-phase-cycle patients and out-of-phase-cycle patients, but significant difference in mean luteal phase length between 2 groups was identified. 2. 91% of total patients sho had luteal phase lengths of less than 11 days showed out-of-phase-cycles. 3. In out-of-phase-cycle group with luteal phase lengths of less than 11 days, 50% had an endometrial lag of at least 4 days, but 10.7% had an endometrial lag of 4 or more days in group with luteal phase lengths of more than 11 days. 4. There was no significant correlation between mid-luteal serum progesterone level and endometrial lag of late luteal phase endometrial biopsy.

• Journal of the Korean Solar Energy Society
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• v.38 no.1
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• pp.45-55
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• 2018

Environmentally benign lead-free solder coated ribbon (e. g. SnCu, SnZn, SnBi${\cdots}$) has been intensively studied to interconnect cells without lead mixed ribbon (e. g. SnPb) in the crystalline silicon(c-Si) photovoltaic modules. However, high melting point (> $200^{\circ}C$) of non-lead based solder provokes increased thermo-mechanical stress during its soldering process, which causes early degradation of PV module with it. Hence, we proposed low-temperature conductive paste (CP) based tabbing method for lead-free ribbon. Modules, interconnected by the lead-free solder (SnCu) employing CP approach, exhibits similar output without increased resistivity losses at initial condition, in comparison with traditional high temperature soldering method. Moreover, 400 cycles (2,000 hour) of thermal cycle test reveals that the module integrated by CP approach withstands thermo-mechanical stress. Furthermore, this approach guarantees strong mechanical adhesion (peel strength of ~ 2 N) between cell and lead-free ribbons. Therefore, the CP based tabbing process for lead free ribbons enables to interconnect cells in c-Si PV module, without deteriorating its performance.

• The Journal of Advanced Prosthodontics
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• v.5 no.2
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• pp.75-83
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• 2013

PURPOSE. Maxillofacial silicone elastomer is usually colored intrinsically with color pigments to match skin colors. The purpose of this study was to investigate the color stability of a maxillofacial silicone elastomer, colored with a thermochromic, color changing pigment. MATERIALS AND METHODS. Disc-shaped maxillofacial silicone specimens were prepared and divided into 3 groups: a conventionally colored control group, one group additionally colored with 0.2 wt% thermochromic pigment, and one group with 0.6 wt% thermochromic pigment. Half of the surface of each specimen was covered with an aluminium foil. All of the specimens were exposed to UV radiation in 6 hour cycles over 46 days. In between the UV exposures, half of the specimens were stored in darkness, at room temperature, and the other half was stored in an incubator, at a humidity of 97% and a temperature of $+37^{\circ}C$. Color measurements were made with a spectrophotometer and registered according to the CIELAB $L^*a^*b^*$ color model system. The changes in $L^*$, $a^*$ and $b^*$ values during artificial aging were statistically analyzed by using paired samples t-test and repeated measures ANOVA. P-values <.05 were considered as statistically significant. RESULTS. The UV exposure resulted in visually noticeable and statistically significant color changes in the $L^*$, $a^*$ and $b^*$ values in both of the test groups containing thermochromic pigment. Storage in the incubator lead to statistically significant color changes in the $a^*$ and $b^*$ values of the specimens containing thermochromic pigment, compared to those stored at room temperature. CONCLUSION. The specimens containing thermochromic pigment were very sensitive to UV radiation, and the thermochromic pigment is not suitable, as such, to be used in maxillofacial prostheses.

• Clinical and Experimental Reproductive Medicine
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• v.38 no.2
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• pp.82-86
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• 2011

Objective: To evaluate sperm nuclear DNA fragmentation and chromatin structure after 18 hours' incubation at room temperature. Methods: Twenty-eight male partners who participating IVF treatment were prospectively included in this study. Ejaculated sperm count and motility were assessed. The sperm was then immediately processed by the conventional swim-up method. After utilization of some of the sample for routine clinical use, the remainder of each of the samples was divided into two aliquots. One aliquot was immediately assessed for sperm nuclear DNA fragmentation (TUNEL assay) and chromatin structure (toluidine blue [TB] staining). The other aliquot was incubated at room temperature for 18 hours and then assessed by two methods. Only dark-TB sperms were considered as having abnormal chromatin structure. Data before and after extended incubation were compared using a paired Student's $t$-test. Results: Before and after extended culture, nuclear DNA fragmentation assessed by TUNEL was $4.9{\pm}4.7%$ and $7.0{\pm}6.4%$, respectively ($p$=0.008). The proportion of abnormal chromatin structure (dark-TB sperm) was $8.2{\pm}5.6%$ and $10.3{\pm}6.5%$ ($p$ <0.001), before and after incubation, respectively. Conclusion: After 18 hours' incubation at room temperature, sperm nuclear DNA and chromatin structure were significantly affected. The IVF practitioner should bear this information in mind when performing delayed insemination, especially for $in$ $vitro$ maturation cycles.

• Journal of the Korean Ceramic Society
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• v.43 no.11 s.294
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• pp.688-692
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• 2006

Ferroelectric lanthanides-substituted $Bi_4Ti_3O_{12}$ $(Bi_{4-x}Ln_xTi_3O_{12}, BLnT)$ thin films approximately 200 nm in thickness were deposited by metal organic chemical vapor deposition onto Pt(111)/Ti/SiO$_2$/Si(100) substrates. Many researchers reported that the lanthanides substitution for Bi in the pseudo-perovskite layer caused the distortion of TiO$_6$ octahedron in the a-b plane accompanied with a shift of the octahedron along the a-axis. In this study, the effect of lanthanides (Ln=Pr, Eu, Gd, Dy)-substitution and crystallization temperature on their ferroelectric properties of bismuth titanate $(Bi_4Ti_3O_{12}, BIT)$ thin films were investigated. As BLnT thin films were substituted to lanthanide elements (Pr, Eu, Gd, Dy) with a smaller ionic radius, the remnant polarization (2P$_r$) values had a tendency to increase and made an exception of the Eu-substituted case because $Bi_{4-x}Eu_xTi_3O_{12}$ (BET) thin films had the smaller grain sizes than the others. In this study, we confirmed that better ferroelectric properties can be expected for films composed of larger grains in bismuth layered peroskite materials. The crystallinity of the thin films was improved and the average grain size increased as the crystallization temperature,increased from 600 to 720$^{\circ}C$. Moreover, the BLnT thin film capacitor is characterized by well-saturated polarization-electric field (P-E) curves with an increase in annealing temperature. The BLnT thin films exhibited no significant degradation of switching charge for at least up to $1.0\times10^{11}$ switching cycles at a frequency of 1 MHz. From these results, we can suggest that the BLnT thin films are the suitable dielectric materials for ferroelectric random access memory applications.

• Korean Journal of Materials Research
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• v.15 no.9
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• pp.589-593
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• 2005

Nanoimprinting lithography (NIL) is known as a suitable technique for fabricating nano and micro structures of high definition. Hot embossing is one of NIL techniques and can imprint on thin films and bulk polymers. Key issues of hot embossing are time and expense needed to produce a stamp withstanding a high temperature and pressure. Fabrication of a metal stamp such as an electroplated nickel is cost intensive and time consuming. A ceramic stamp made by silicon is easy to break when the pressure is applied. In this paper, a plastic stamp using a high temperature epoxy was fabricated and tested. The plastic stamp was relatively inexpensive, rapid to produce and durable enough to withstanding multiple hot embossing cycles. The merits of low viscosity epoxy solutions were a fast degassing and a rapid filling the microstructures. The hot embossing process with plastic stamp was performed on PMMA substrates. The hot embossing was conducted at 12.6 bar, $120^{\circ}C$ and 10 minutes. An imprinted PMMA wafer was almost same value of the plastic stamp after 10 times embossing. Entire fabrication process from silicon master to plastic stamp was completed within 12 hours.

• Korean Journal of Ecology and Environment
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• v.37 no.3 s.108
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• pp.304-312
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• 2004

The transient dynamics of three-trophic populations (prey, predator, and super predator) using ratio-dependent models responding to environmental impacts is analyzed. Environmental factors were divided into two parts: periodic factor (e.g., temperature) and general noise. Periodic factor was addressed as a frequency and bias, while general noise was expressed as a Gaussian distribution. Temperature bias ${\varepsilon}$, temperature frequency ${\Omega}$, and Gaussian noise amplitude ${\`{O}}$ accordingly revealed diverse status of population dynamics in three-trophic food chain, including extinction of species. The model showed stable limit cycles and strange attractors in the long-time behavior depending upon various values of the parameters. The dynamic behavior of the system appeared to be sensitive to changes in environmental input. The parameters of environmental input play an important role in determining extinction time of super predator and predator populations.

• Structural Engineering and Mechanics
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• v.72 no.2
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• pp.245-256
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• 2019

The experimentally determined mechanical behavior of the material under the prescribed service conditions is the basis of advanced engineering optimum design. To allow experimental data on the behavior of the material considered, uniaxial stress tests were made. The aforementioned tests have enabled the determination of mechanical properties of material at different temperatures, then, the material's resistance to creep at various temperatures and stress levels, and finally, insight into the uniaxial high cyclic fatigue of the material under different applied stresses for prescribed stress ratio. Based on fatigue tests, using modified staircase method, fatigue limit was determined. All these data contributes the reliability of the use of material in mechanical structures. Data representing mechanical properties are shown in the form of engineering stress-strain diagrams; creep behavior is displayed in the form of creep curves while fatigue of the material is presented in the form of S-N (maximum applied stress versus number of the cycles to failure) curve. Material under consideration was 18CrNi8 (1.5920) steel. Ultimate tensile strength and yield strength at room temperature and at temperature of $600^{\circ}C$: [${\sigma}_{m,20/600}=(613/156)MPa$; ${\sigma}_{0.2,20/600}=(458/141)MPa$], as well as endurance (fatigue) limit at room temperature and stress ratio of R = -1 : (${\sigma}_{f,20,R=-1}=285.1MPa$).