• Transactions of the Korean Society of Mechanical Engineers
• /
• v.10 no.2
• /
• pp.188-197
• /
• 1986

With respect to structural carbon steel(SM 22C), it was studied how the overstress or the understress has effects on fatigue inside crack propagation curve of a two level stress. Obtained results are summarized as follows. (1) The overstress or the understress, at a slip band occurrence stage, does not change the inside crack propagation curve because the crack closure and opening phenomena do not happen. (2) The overstress, at a crack propagation stage, does not change the inside crack propagation curve because the crack closure of overstress in compressive state is nearly same that of base stress in compressive state. (3) The understress, at a crack propagation stage, give rise to an acceleration of crack growth because the crack closure of understree in compressive state is more open than that of base stress in compressive state and the phenomenon is the essential increase of the actual applied stress of the specimen.

• Proceedings of the KOSOMBE Conference
• /
• v.1996 no.11
• /
• pp.22-24
• /
• 1996

Small size DC motor control method for portable drug delivery system has been developed to be used for the actuator of insulins pump. The control method gives the controllabilities both in high speed(40-50 revolution per second(rps)) DC motor drive and also in low speed(0.5-1rps). In low speed mode DC motor is controlled to act like stepping motor and in high speed to optimize power consumption. To control both mode modified bang bang control is suggested. Using this method small size DC motor(spec.) speed is controlled from 0.2 rps to 50 rps. Experimental setup is developed using micro-processor(PIC16C73, Micro Chips co., USA), motor turns checking circuitry, small size DC motor for pager(SM1012, Samhong co., Korea) and gear box. Results from experiment meet need for vailable load condition which is require for portable drug delivery system.

• Journal of Environmental Science International
• /
• v.22 no.6
• /
• pp.705-715
• /
• 2013

The response of the freshwater microalga Chlorella vulgaris to mercuric ion ($Hg^{2+}$) stress was examined using chlorophyll a fluorescence image analysis and O-J-I-P analysis as a way to monitor the toxic effects of mercury on water ecosystems. The levels of photosynthetic pigments, such as chlorophyll a and b and carotenoids, decreased with increasing $Hg^{2+}$ concentration. The maximum photochemical efficiency of photosystem II(Fv/Fm) changed remarkably with increasing $Hg^{2+}$ concentration and treatment time. In particular, above $200{\mu}M\;Hg^{2+}$, considerable mercury toxicity was seen within 2 h. The chlorophyll a fluorescence transient O-J-I-P was also remarkably affected by $Hg^{2+}$; the fluorescence emission decreased considerably in steps J, I, and P with an increase in $Hg^{2+}$ concentration when treated for 4 h. Subsequently, the JIP-test parameters (Fm, Fv/Fo, RC/CS, TRo/CS, ETo/CS, ${\Phi}_{PO}$, ${\Psi}_O$ and ${\Phi}_{EO}$) decreased with increasing $Hg^{2+}$ concentration, while N, Sm, ABS/RC, DIo/RC and DIo/CS increased. Therefore, a useful biomarker for investigating mercury stress in water ecosystems, and the parameters Fm, ${\Phi}_{PO}$, ${\Psi}_O$, and RC/CS can be used to monitor the environmental stress in water ecosystems quantitatively.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.22 no.1
• /
• pp.145-151
• /
• 2016

Temperature variability at the upper layer related to climate regime shifts in the Korean waters was illustrated using water temperature, climate index. Three major climate regime shifts (CRS) in 1976, 1988 and 1998 in north Pacific region had an significant influence on the major marine ecosystems structure pattern. Three marginal seas around Korean peninsula; East Sea, East China Sea and Yellow Sea also got important impact from this kind of decadal shift. We used 10m sea water temperatures in four regions of Korean waters since 1950 to detect major fluctuation patterns both seasonally and also decadal shift. 1988 CRS was occurred in all of the study areas in most seasons however, 1998 CRS was only detected in the Yellow Sea and in the southern part of the East Sea. 1976 CRS was detected in all of the study area mainly in winter. After 1998 CRS, the water temperature in the southern part of the East Sea, East China Sea and Yellow Sea were going into decreased pattern; however, in the northern part of the East Sea, it was further shifted to increasing pattern which was started from 1988 CRS period.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.26 no.1
• /
• pp.22-26
• /
• 2013

PTCR ceramics of $(Ba_{0.998}Sm_{0.002})TiO_3+0.001MnCO_3+xSiO_2$ (x=1, 2, 3, 4, 5, 6 mol%) were fabricated by solid state method. Disk samples of diameter 5 mm and thickness about 1mm were sintered at $1,290^{\circ}C$ for 2 h in reduced atmosphere of $5%H_2-95%N_2$ followed by re-oxidation at $600^{\circ}C$ for 30 min. in $20%O_2-80%N_2$.and their microstructures and electrical properties were investigated with SEM and Multimeter. The color of sintered samples was strongly dependent on $SiO_2$ content showing that the color of samples with $SiO_2$ of 1~2 mol% was gray but that of samples with $SiO_2$ of 4~6 mol% was changed from gray to blue, which seems to be related with the reduction of samples due to the oxygen vacancies created during the sintering in reduced atmosphere. $SiO_2$ content had a great influence on the microstructure and the electrical properties. With increasing $SiO_2$ content, the grain size of samples increased and the resistivity as well as the resistivity jump ($R_{285}/R_{min}$) decreased, which is considered to be attributed to the resistivity change at grain interior and grain boundary due to the fast mass transfer through $SiO_2$ liquide phase during the sintering. Samples with 2 mol% $SiO_2$ has the resistivity of $202{\Omega}cm$ and the resistivity jump of 3.28. It is expected that $SiO_2$ doped $BaTiO_3$ based PTC ceramics can be used for multilayered PTC thermistor due to the resistance to the sintering in reduced atmosphere.

• Journal of Animal Reproduction and Biotechnology
• /
• v.35 no.4
• /
• pp.338-346
• /
• 2020

The present study was conducted in a goat farm for pregnancy diagnosis by using vaginal cytology and B-mode real time ultrasound using 5 MHz probe by transabdominal method. Seventeen pregnant does were used for this study. The objective of the study was to determine the earliest day of pregnancy and describe the chronological characteristics of pregnancy from day 22 to day 40 for vaginal cytology and day 25 to day 60 for ultrasonography of gestation. The differences among the average percentage of cell value in different age of pregnancy were significant (p < 0.05). The average percentage of intermediate cells (81.12%) was also significantly (p < 0.05) higher than superficial (9.41%), keratinized (7.10%) and neutrophil (2.61%) on 22-40th days of pregnancy. In case of real time B-mode ultrasonography, the gestational sac was observed only in three does out of seventeen (17.6 %) at 25-30 days whereas the placentomes and heart beat of the foetus were first detected at 31-35 days in six does (35.3%). The foetal leg buds were first visualized at 36-40 days in four does (23.5%) whereas the foetal vertebral column was first observed at 36-40 days of gestation in only three does (17.6%). In conclusion, vaginal cytology and trans-abdominal ultrasonography can be used for detection of early pregnancy in does.

• The Journal of the Korea Contents Association
• /
• v.22 no.8
• /
• pp.287-296
• /
• 2022

The purpose of this study is to verify the effect of government subsidies and R&D investment on the increase in profits of Chinese environmental protection companies. The research method for this was empirically analyzed using the Chinese CSMAR database for 161 Chinese environmental protection companies and using statistical data obtained from 805 samples. The analysis results are as follows. First, government subsidies had a positive effect on the increase in profits of Chinese environmental protection companies. Second, government subsidies had a positive effect on R&D investment by Chinese environmental protection companies. Third, R&D investment had a positive effect on the increase in profits of Chinese environmental protection companies. Fourth, R&D investment through government subsidies has a partial mediating effect on the effect on the increase in profits of Chinese environmental protection companies. In this study, based on the results of the study, a plan was proposed to promote the increase in profits of Chinese environmental protection companies by expanding government subsidies to Chinese environmental protection companies and focusing on R&D investment.

• Journal of Korean Society of Steel Construction
• /
• v.22 no.4
• /
• pp.389-398
• /
• 2010

The flexural strength of composite HSB I-girders under a positive moment was investigated using the moment-curvature analysis method to evaluate the applicability of the current AASHTO LRFD design specifications to such girders. A total of 2,391 composite I-girder sections that satisfied the section proportion limits of the AASHTO LRFD specifications was generated by the random sampling technique to consider a wide range of section properties. The flexural capacities of the sections were calculated inthe nonlinear moment-curvature analysis in which the HSB600 and HSB800 steels were modeled as an elasto-plastic strain-hardening material, and the concrete, as a CEB-FIP model. The effects of the ductility ratio and the compressive strength of the concrete slab on the flexural strength of the composite girders made of HSB and SM520-TMC steels were analyzed. The numerical results indicated that the current AASHTO LRFD equation can be used to calculate the flexural strength of composite girders made of HSB600 steel. In contrast, the current AASHTO LRFD equation was found to be non-conservative in its prediction of the flexural strength of composite HSB800 girders. Based on the numerical results of this study for 2,391 girders, a new design equation for the flexural strength of composite HSB800 girders in a positive moment was proposed.

• Journal of Food Hygiene and Safety
• /
• v.22 no.2
• /
• pp.105-109
• /
• 2007

This study monitored and compared the contamination levels of total aerobic bacteria, coliform groups and S. aureus of 16 Shrimp Jeotgal (Salt Fermented Shrimp) products from 3 traditional markets (TM), 3 department stores (DS) and 3 super markets (SM) located on seoul, Korea. Moreover this study was carried out to survey the concentrations of NaCl and heavy metal (lead; Pb) of the Shrimp Jeotgal. The contamination levels of total aerobic bacteria in the Shrimp Jeotgai were $3.35log_{10}CFU/g$ as a mean and $3.71log_{10}CFU/g$ for TM, $3.16log_{10}CFU/g\;for\;DS,\;2.84log_{10}CFU/g$ for SM. The coliform groups were contaminated in 50% of Shrimp Jeotgal and it means that the hygienic control is needed urgently. S. aureus were not detected in every sample. The levels of NaCl were between 17.9 and 28.5%. Heavy metal (lead; Pb) was detected in only 1 product at the level of 0.02 ppm out of 16 products. Although microbiological contamination levels of Shrimp Jeotgal were not much high, hygienic management like HACCP is thought to be needed for the production of Shrimp Jeotgal in traditional market.

• The korean journal of orthodontics
• /
• v.30 no.2 s.79
• /
• pp.215-222
• /
• 2000

The purpose of this study was to determine whether the application of chlorhexidine varnish affects the shear bond strength and failure pattern of orthodontic brackets or not. The experimental group consisted of 22 human premolars which extracted after chlorhexidine varnish application (4 times for 1 week interval) in vivo, and the control group consisted of 22 human premolars which extracted without any pre-treatment. After all teeth were etched with $37\%$ phosphoric acid gel, metal orthodontic brackets (Q-3002, RMO, USA) were bonded to each tooth using auto-polymerizing orthodontic resin (Ortho-One, Bisco, USA) with the same bonding procedure. The shear bond strength was measured with Instron universal testing machine (model 4466, Instron Ltd., England), and the failure pattern of each bracket was examined with Scanning Electron Microscope (SM 840A, JEOL, Japan). The data were analysed statistically with t-test. The results were as follows : 1. Application of chlorhexidine varnish had no significant effect on the shear bond strength of the orthodontic bracket. 2. There was no significant difference in the failure pattern of orthodontic bracket between the experimental group and the control group.