• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.5
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• pp.59-66
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• 2013

Because ordinary concrete cannot be hardened well under sub-zero temperatures, anti-freeze agents are typically added to prevent the frost damage and to ensure the proper hardening of concrete. With the advantage of a rapid exothermic reaction property, jet set concrete may be used as a cold weather concrete because it can reach the required strength before being damaged by cold weather. Recent studies are reported that magnesia-phosphate composites can be hardened very quickly and hydrated even in low temperature, which can be used as an alternative of severe cold weather concrete in arctic regions. This study developed the magnesia-phosphate composites that can be used in severe cold regions and suggested an appropriate mixture design from the experimental results.

• Journal of the Semiconductor & Display Technology
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• v.22 no.3
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• pp.119-124
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• 2023

In this study, experimental approach of the measurement of condensation and evaporation heat transfer coefficients is discussed for mixed refrigerants using in the ultra low-temperature cooling system for semiconductor etching process. An experimental apparatus was described performing the condensation and evaporation heat transfer measurements for mixed refrigerants. The mixed refrigerant used in this study was composed of the optimal mixture determined in previous research, with a composition of Ar:R14:R23:R218 = 0.15:0.4:0.15:0.3. The experiments were conducted over a temperature range from -82℃ to 15℃ and at pressures ranging from 18.5 bar to 5 bar. The convection heat transfer coefficients of the mixed refrigerant were measured at flow rates corresponding to actual operating conditions. The condensation heat transfer coefficient ranged from approximately 0.7 to 0.9 kW/m2K, while the evaporation heat transfer coefficient ranged from 1.0 to 1.7 kW/m2K. The detailed discussion of the experimental methods, procedures, and results were described in this paper.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.5
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• pp.37-42
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• 2004

Shallow $p^{＋}$-n junctions were formed by preamorphization, low-energy ion implantation and dual-step annealing processes. Germanium ions were implanted into silicon substrates for preamorphization. The dopant implantation was performed into the preamorphized and non-preamorphized substrates using B $F_2$2 ions. Rapid thermal anneal (RTA) and furnace anneal (FA) were employed for dopant activation and damage removal. Samples were annealed by one of the following four methods; RTA(75$0^{\circ}C$/10s)＋Ft FA＋RTA(75$0^{\circ}C$/10s), RTA(100$0^{\circ}C$/10s)＋FA, FA＋The Ge Preamorphized sample exhibited a shallower junction depth than the non-preamorphized sample. When the employed RTA temperature was 100$0^{\circ}C$, FA＋RTA annealing sequence exhibited better junction characteristics than RTA＋FA thermal cycle from the viewpoint of junction depth, sheet resistance, $R_{s}$$.$ $x_{j}$, and leakage current.t.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.207-207
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• 2012

Si quantum dot (QD) imbedded in a $SiO_2$ matrix is a promising material for the next generation optoelectronic devices, such as solar cells and light emission diodes (LEDs). However, low conductivity of the Si quantum dot layer is a great hindrance for the performance of the Si QD-based optoelectronic devices. The effective doping of the Si QDs by semiconducting elements is one of the most important factors for the improvement of conductivity. High dielectric constant of the matrix material $SiO_2$ is an additional source of the low conductivity. Active doping of B was observed in nanometer silicon layers confined in $SiO_2$ layers by secondary ion mass spectrometry (SIMS) depth profiling analysis and confirmed by Hall effect measurements. The uniformly distributed boron atoms in the B-doped silicon layers of $[SiO_2(8nm)/B-doped\;Si(10nm)]_5$ films turned out to be segregated into the $Si/SiO_2$ interfaces and the Si bulk, forming a distinct bimodal distribution by annealing at high temperature. B atoms in the Si layers were found to preferentially substitute inactive three-fold Si atoms in the grain boundaries and then substitute the four-fold Si atoms to achieve electrically active doping. As a result, active doping of B is initiated at high doping concentrations above $1.1{\times}10^{20}atoms/cm^3$ and high active doping of $3{\times}10^{20}atoms/cm^3$ could be achieved. The active doping in ultra-thin Si layers were implemented to silicon quantum dots (QDs) to realize a Si QD solar cell. A high energy conversion efficiency of 13.4% was realized from a p-type Si QD solar cell with B concentration of $4{\times}1^{20}atoms/cm^3$. We will present the diffusion behaviors of the various dopants in silicon nanostructures and the performance of the Si quantum dot solar cell with the optimized structures.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.67-67
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• 2018

The 5xxx series aluminum alloys are recently used in not only marine system but also automotive area because of a low density material, good mechanical properties and better resistance to corrosion. However, Aluminum alloys are less resistant than the purest aluminum such as 1xxx aluminum alloy. Electrochemical anodization technique has attracted in the area of surface treatment because of a simple procedure, a low-cost efficiency than other techniques such as lithography and a large volume of productivity, and so on. Here, The relationship between the corrosion behavior and the thickness of aluminum anodic oxide have been studied. Prior to anodization, The 5052 aluminum sheets ($30{\times}20{\times}1mm$) were degreased by ultra-sonication in acetone and ethanol for 10 minutes and eletropolished in a mixture of perchloric acid and ethanol (1:4, volume ratio) under an applied potential of 20V for 60 seconds to obtain a regular surface. During anodization process, Aluminum alloy was used as a working electrode and a platinum was used as a counter electrode. The two electrodes were separated at a distance of 5cm. The applied voltage of anodization is conducted at 40V in a 0.3M oxalic acid solution at $0^{\circ}C$ with appropriate magnetic stirring. The surface morphology and the thickness of AAO films was observed with a Scanning Electron Microscopy (SEM). The corrosion behavior of all samples was evaluated by an open-circuit potential and potentio-dynamic polarization test in 3.5wt% NaCl solution. Thus, The corrosion resistance of 5052 aluminum alloy is improved by the formation of an anodized oxide film as function of increase anodization time which artificially develops on the metal surface. The detailed electrochemical behavior of aluminum 5052 alloy will be discussed in view of the surface structures modified by anodization conditions such as applied voltages, concentration of electrolyte, and temperature of electrolyte.

• Journal of the Microelectronics and Packaging Society
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• v.24 no.2
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• pp.37-41
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• 2017

Cuprous oxide ($Cu_2O$) is one of the potential candidates as an absorber layer in ultra-low-cost solar cells. $Cu_2O$ is highly desirable semiconducting oxide material for use in solar energy conversion due to its direct band gap ($E_g={\sim}2.1eV$) and high absorption coefficient that absorbs visible light of wavelength up to 650 nm. In addition, $Cu_2O$ has other several advantages such as non-toxicity, low cost and also can be prepared with simple and cheap methods on large scale. In this work, we deposited the $Cu_2O$ thin films by electrodeposition on gold coated $SiO_2/Si$ wafers. We changed the process conditions such as pH of the solution, applied potential on working electrode, and solution temperature. Finally, we confirmed the structural properties of the thin films by XRD and SEM.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2019.04a
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• pp.81-81
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• 2019

Ginseng seeds are one of short-lived seeds species which loose their viability easily in the condition of conventional storage. Cryopreservation using liquid nitrogen (LN) has been recommended as a alternative storage for this kind of germplasm short lived or dessiccation-sensitive. This study was performed to find out whether cryopreservation could affect physiological change such as enzyme activity induced by reactive oxygen species. In this work, the redox ratio of ascorbate and glutathione were examined onto ginseng seedlings before and after LN storage of seeds for 1 day using spectrophotometer method. Reduced ascorbate (ASA) was increased while oxidized ascorbate (DHA) was decreased slightly for both after 1d-LN storage. And for glutathione also, reduced form (GSH) was increased while oxidized form (GSSG) was decreased slightly for both after 1d-LN storage. Consequently total phenol compound and ion leakage after LN storage showed no significant differences. Additionally root growth from the seeds after LN storage was not affected by ultra low temperature. From the above results, we may suggest that cryopreservation could be recommended for storage tool of ginseng seeds even with low viability also and expected to make slower seed aging process during preservation period through further study.

• Korean Journal of Exercise Nutrition
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• v.25 no.3
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• pp.16-22
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• 2021

[Purpose] Exercise-associated hyponatremia (EAH) is a well-known condition among endurance athletes at low altitudes. The incidence of EAH during ultramarathons at high altitudes warrants further investigation. This prospective observational study was conducted on the participants of the Leadville Trail 100 run, a 161-km race held at a high altitude (2,800 m-3,840 m). [Methods] Venous blood samples were collected before and immediately after the race. The participants completed an electronic survey after the race. Our main outcome measure was the post-race serum sodium ([Na⁺]) level. [Results] Of the 672 athletes who started the race, 351 (52%) successfully completed the event within the 30-hour cut-off. Post-race blood samples were collected from 84 runners (66 finishers). Both pre- and post-race blood samples were collected from 37 participants. Twenty percent of the post-race participants had EAH. Only one post-race participant had a [Na⁺] level of <130 mmol/L. All participants with EAH were asymptomatic. One participant had an abnormal pre-race [Na⁺] level (134 mmol/L). Female participants had a significantly higher rate of EAH than male participants (40% vs. 16%; p=0.039). Age, body mass index, weight changes, race completion status, nonsteroidal anti-inflammatory drug use, and urine specific gravity were not associated with the development of EAH. Lower postrace [Na⁺] levels were associated with higher serum creatine kinase values (R²=0.1, p<0.005). [Conclusion] High altitude (3,840 m peak) does not appear to enhance the incidence of EAH after an ultramarathon footrace. This suggests that ambient temperature (low temperatures reduce risk), sex (female predilection), endurance running, and overhydration are more prominent risk factors for EAH than high altitude.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.3
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• pp.663-669
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• 2014

The electrical characteristics of RRAM with different annealing temperature and thickness have been measured and discussed. The devices with Pt/Ti top electrode of 150nm, Pt bottom electrode of 150nm, $HfO_2$ oxide thickness of 45nm and 70nm have been fabricated. The fabricated device were classified by 3 different kinds according to the annealing temperature, such as non-annealed, annealed at $500^{\circ}C$ and annealed at $850^{\circ}C$. The set and reset voltages and the variation of resistance with temperatures have been measured as electrical properties. From the measurement, it was found that the set voltages were decreased and the reset voltage were increased slightly, and thus the sensing window was decreased with increasing of measurement temperatures. It was remarkable that the device annealed at $850^{\circ}C$ showed the best performances. Although the device with thickness of 45nm showed better performances in the point of the sensing window, the resistance of 45nm devices was large relatively in the low resistive state. It can be expected to enhance the device performances with ultra thin RRAM if the defect generation could be reduced at the $HfO_2$ deposition process.

• Journal of Dairy Science and Biotechnology
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• v.23 no.2
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• pp.93-98
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• 2005

Effects of heat and gamma irradiation on chemical, microbiological, and immunological changes of raw milk were compared. Free fatty acid content of milk showed increasing tendency according to the increase of heating temperature and irradiation dose, and showed similarity in UHT (ultra high temperature) and 5 kGy irradiation. Total bacterial counts and coliforms were not detected after treatment of LTLT (low temperature long time), HTST (high temperature short time), UHT, and irradiation from 1 to 10 kGy in the milk with initial microbial load at $10^3$ CFU/mL initially, but after 7 day storage, were not detected in UHT milk and that irradiated at 3 kGy or above. Heat treatment decreased (p<0.05) arginine, asparate, iso-leucine, lysine, and methionine content compared to raw milk while irradiation decreased (p<0.05) asparate, histidine, iso-luecine, leucine, and lysine content, which means irradiation could change primary structure of milk proteins. It was concluded that f kGy gamma irradiation treatment of raw milk could give a similar effect to UHT treatment in chemical and microbiological viewpoint, and may reduce allergenicity of raw milk.