• Applied Microscopy
• /
• v.47 no.3
• /
• pp.105-109
• /
• 2017

The effect of temperature and vanadium metal concentration on the electronic and thermoelectric properties of Si in the diamond cubic structure has been investigated using a combination of density functional theory simulations and the semi classical Boltzmann's theory. The BotzTrap code within the constant relaxation time approximation has been used to obtain the Seebeck coefficient and other transport properties of interest for alloys of the structure $Si_{1-x}V_x$, where x is 0, 0.125, 0.25, 0.375, and 0.5. The thermoelectric properties have been extracted for a temperature range of 300 K to 1,000 K. The general trend with V atom substitution for Si causes the Seeback coefficient to increase and the thermal conductivity to decrease for the various alloys. The optimum values are for $Si_5V_3$ and $Si_4V_4$ alloys for charge carrier concentrations of $10^{21}cm^{-3}$ in the mid temperature range of 500~800 K. This is a very desirable effect for a promising thermoelectric and the figure of merit ZT approaches 0.2 at 600 K for the p-type $Si_5V_3$ alloy.

• Applied Microscopy
• /
• v.47 no.1
• /
• pp.50-54
• /
• 2017

The microstructure, the crystallization behavior, and magnetic properties of FeSi-based soft magnetic alloys (FINEMET) were investigated using transmission electron microscopy, X-ray diffraction, and coercive force measurements. The amorphous $Fe_{73.28}Si_{13.43}B_{8.72}Cu_{0.94}Nb_{3.63}$ alloys particles, prepared in $10^{-4}$ torr by gas atomization process, were heat treated at $530^{\circ}C$, $600^{\circ}C$, and $670^{\circ}C$ for 1 hour in a vacuum of $10^{-2}$ torr. Nanocrystalline Fe precipitation was first formed followed by the grain growth. Phase formation and crystallite sizes was compared linked to its magnetic behavior, which showed that excellent soft magnetic property can directly be correlated with its microstructure.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.16 no.1
• /
• pp.39-43
• /
• 2016

The structural, electrical properties of Ga doped MgZnO transparent conductive oxide (TCO) films by ratio-frequency(RF) magnetron sputtering were investigated. Ga doped MgZnO TCO films were deposited on the sapphire substrates at $200^{\circ}C$ varying growth thickness 200 to 600 nm. The optical properties of Ga doped MgZnO TCO films were showed above 85% transmittance from 300 to 1000 nm region. In addition, the current density ($J_{SC}$) of $Cu(In,Ga)Se_2$ (CIGS) solar cells was improved by using the MgZnO:Ga films of 500 nm thickness because of outstanding electrical properties. The $Cu(In,Ga)Se_2$ solar cells with MgZnO:Ga transparent conducing layer yielded an efficiency of 9.8% with current density ($31.8mA/cm^2$), open circuit voltage (540.2 V) and fill factor (62.2) under AM 1.5 illumination.

• 한국신재생에너지학회:학술대회논문집
• /
• 2011.11a
• /
• pp.57.1-57.1
• /
• 2011

We studied the performance of CdSe nanoparticle in the active layer of organic photovoltaics (OPVs) by changing concentration of the CdSe NPs in the P3HT:PCBM layer. We observed that the absorption peak value gradually increases with the increasing amount of CdSe NPs at 600nm wave length. However, the electrical properties of OPVs correspond less with the tendency of UV/visible result. The highest performance was shown with 10% of CdSe NPs. The device performance decreased after 10% of CdSe NPs, this shows the dependencies of performanc of hybrid solar cells on the CdSe NPs loading amount. The resulting OPVs with 10 % of CdSe NPs show a short circuit current density ($J_{sc}$) of $6.96mA/cm^2$, open circuit voltage ($V_{oc}$) of 0.61V, fill factor (FF) of 0.59, and power conversion efficiency (PCE) of 2.53% under AM 1.5 ($100mW/cm^2$).

• Journal of Wetlands Research
• /
• v.4 no.2
• /
• pp.57-66
• /
• 2002

The local storm occurred Nakdong river basin from August 4 to 11 of the year 2002, resulting in a record 500-600mm rainfall. The heavy rain continued for more than 10 days and especially between 3 to 4 am of August 9, 50mm per hour local storm occurred in Hanrim-myun area, Kimhae. 8 days after the storm, the water level of Nakdong river rose rapidly and the river flowed backward the branches. T he draining of the protected low wetland was unable and the water level of the inner bank area rose suddenly, causing the inundation in several areas. Baeksan bank of Nam river, Gahyun(Samhak) bank of Hwang river, and Kwangam bank of Shinban river, where the draining facilities were under construction or constructed recently, were failed by the piping around the draining culvert. This study analyze the cause of the damage in Nakdong river banks and suggests the countermeasures for future improvement. The damaged spot of the river bank was surveyed, and the rainfall and the fluctuation in the water levels were reviewed. Finally for the flood inundation prevention at the inner bank area, new floodplain management plan as the protect of low wetland established.

• Journal of the Korea Safety Management & Science
• /
• v.25 no.1
• /
• pp.23-29
• /
• 2023

Among the Additive Manufacturing (AM) technologies, the Binder-Jetting printing technology is a method of spraying an adhesive on the surface of powder and laminate layer by layer. Recently, this technique has become a major issue in the production of large casting products such as ship-building, custom vehicles and so on. In this study, we performed research to make actual mold castings and increase mechanical property by using special sand and water-based binders. For use as a mold, it has a strength of more than 3MPa and permeability. Various experiments were carried out to obtain suitable them. The major process parameters were binder jetting volume, binder types, layer thickness and heat treatment condition. As a result of this study, the binder drop quantity was measured to be about 60 pico-liter, layer thickness was 100㎛ and the heat treatment condition was measured about 1,000℃ and compressive strength were measured to be more than 5MPa. The optimum condition of this experiment was established through actual casting of aluminum. The equipment used in this study was a Freeforms T400 model (SFS Co., Ltd.), and the printing area of 420 * 300 * 250mm and resolution of 600dpi can be realized.

• Journal of Powder Materials
• /
• v.30 no.3
• /
• pp.262-267
• /
• 2023

Boron carbide (B₄C) is highly significant in the production of lightweight protective materials when added to aluminum owing to its exceptional mechanical properties. In this study, a method for fabricating Al-B₄C composites using high-energy ball milling and directed energy deposition (DED) is presented. Al-4 wt.% B4C composites were fabricated under 21 different laser conditions to analyze the microstructure and mechanical properties at different values of laser power and scan speeds. The composites fabricated at a laser power of 600 W and the same scan speed exhibited the highest hardness and generated the fewest pores. In contrast, the composites fabricated at a laser power of 1000 W exhibited the lowest hardness and generated a significant number of large pores. This can be explained by the influence of the microstructure on the energy density at different values of laser power.

• Journal of the Korean Society of Safety
• /
• v.39 no.3
• /
• pp.20-26
• /
• 2024

The Chemical Substances Control Act of South Korea mandates submission of transportation plans containing information on the transportation of hazardous chemicals, with over 600,000 submissions recorded annually. In this study, big data analysis was performed on 2,506,985 transportation plans to identify trends and assess their correlation with chemical transportation accidents. The analysis confirmed that despite NaOH accounting for 20.7% of transportation plans, HCl constitutes 40% of chemical transportation accidents, which indicates a correlation of these accidents with the chemical properties of hazardous substances rather than with the number of submitted transportation plans. Furthermore, chemical transportation accidents show a higher probability of occurrence in the 6-8 am and 6-8 pm windows, which is in agreement with higher incidence and fatality rates. The departure points of transportation plans are closely related to the characteristics of local chemical industrial complexes such as Ulsan, Yeosu, and Gunsan, whereas the arrival points are closely related to Pyeongtaek, Hwaseong, and Icheon, which are the locations of semiconductor industries. Ultimately, achievement of safety by consideration of characteristics of transported chemicals, enhancement of driver concentration during specific times, and implementation of preventive measures tailored to local government characteristics are strategies anticipated to contribute to a reduction in chemical transportation accidents.

• Current Research on Agriculture and Life Sciences
• /
• v.4
• /
• pp.132-140
• /
• 1986

Eighty one products from 36 kinds of vitamin and mineral feed supplement collected during August, 1984 to February, 1985 were examined for microbiological contamination. In addition, 83 strains of coliform isolated from the samples were tested for the resistance to 8 kinds of antimicrobial drugs and distribution of R plasmid. General bacteria were detected in all of samples tested. Bacterial population was varied from less than 10 per gram of the sample to 1,400,000 per gram and 34 (42%) of 81 samples were contaminated with 100 to 1,000 cells per gram. Coliform isolation, which was more frequent in samples with larger number of general bacteria, was possible in 14 (17.3%) out of 81 samples tested and 6 (33.3%) out of 18 companies were coliform positive in their products. Forty one (49.4%) out of 83 coliform isolates were fecal coliform. The frequency of resistant strains was the highest to sulfadimethoxine (Sa) with 92.8% and followed by streptomycin (Sm, 67.5%), tetracycline (Tc, 50.6%), kanamycin (Km, 26.5%), chloramphenicol (Cm, 18.1%) and ampicillin (Am, 15.7%). No strain was resistant to nalidixic acid (Na) and gentamicin (Gm). The resistance frequency of fecal coliform strains were higher compare to non-fecal coliform strains. There were minimum inhibitory concentration (MIC) of $3,200{\mu}g/m{\ell}$ or higher in 7 strains to Am, 3 to Sm and 3 to Km, and 70 strains had MIC of $1,600{\mu}g/m{\ell}$ of higher to Sa while Tc had MICs from $1.6{\mu}g/m{\ell}$ to $400{\mu}g/m{\ell}$. All strains had MICs of $6.3{\mu}g/m{\ell}$ of lower to Na and $3.1{\mu}g/m{\ell}$ of lower to Gm. Seventy nine (95.2%) of 83 strains were resistant to one or more drugs tested. The most frequent resistance patterns were SaSm (14.5%) and followed by SaSmTc(12%), SaSmTcKm(8.4%) SaTc (8.4%) and SaSmKm (7.2%) ; total 19 different patterns were noted. Thirty two (40.5%) of 79 resistant strains were transferred all of a part of their resistance to Escherichia coli ML 1410. The frequency of transferable resistance was high in Am (100%) and Cm (80%) while low in Tc (38.1%), Sa (18.2%), Sm (17.9%) and Km (4.5%).

• Journal of Bio-Environment Control
• /
• v.27 no.2
• /
• pp.111-116
• /
• 2018

This study were carried out to evaluate the efficiency of using burn-type $CO_2$ generators in greenhouse for cultivation 'Seolhyang' strawberry ($Fragaria{\times}ananassa\;Duch.$) during winter season. The concentration of $CO_2$ was 200 to $600{\mu}mol{\cdot}mol^{-1}$ in the control, and 800 to $1,100{\mu}mol{\cdot}mol^{-1}$ in using burn-type $CO_2$ generator between 6 and 11 hours. At other times, it was observed that at similar concentration in the control and using burn-type $CO_2$ generator. Measured greenhouse air temperature inside the of using burn-type $CO_2$ generator was $2{\sim}3^{\circ}C$ higher than the control at 6 ~ 10 am. There was no temperature difference between treatments after 11 o'clock. Plant height, leaf length, leaf width, root diameter, fresh weight, and dry weight were not different between treatments. The marketable yield (kg/10a) of using burn-type generator were 4,131 kg, which was 519 kg higher than the control. Therefore, the total fruit yields increased 17% compared to the control.