• 한국축산식품학회지
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• 제36권2호
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• pp.215-222
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• 2016

The combined effects of irradiation and aging temperature on the microbial and chemical quality of beef loin were investigated. The samples were vacuum-packaged, irradiated at 0 or 2 kGy using electron-beam (EB), and stored for 10 d at different aging temperatures (2, 14, or 25℃). The microbial growth, shear values, meat color, and nucleotide-related flavor compounds of the samples were analyzed. The irradiation effect on inactivation of foodborne pathogens was also investigated. The population of Listeria monocytogenes and Escherhia coli O157:H7 inoculated in beef samples decreased in proportion to the irradiation dose. Irradiation reduced the total aerobic bacteria (TAB) over the storage, but higher aging temperature increased the TBA. Thus TAB increased sharply in non-irradiated and high temperature-aged (14, 25℃) beef samples after 5 d. With increasing aging temperature and aging time, shear force values decreased. Lipid oxidation could be reduced by short aging time at low aging temperature. The color a* values of the irradiated beef were lower than those of the non-irradiated throughout the aging period. As aging period and temperature increased, IMP decreased and hypoxanthine increased. Considering microbial and physicochemical properties, irradiation can be used for raw beef to be aged at relatively high temperature to shorten aging time and cost.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 추계학술발표대회
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• pp.30.1-30.1
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• 2011

Silicon is one of useful materials in various industry such as semiconductor, solar cell, and secondary battery. The metallic silicon produces generally melting process for ingot type or chemical vapor deposition (CVD) for thin film type. However, these methods have disadvantages of high cost, complicated process, and consumption of much energy. Electrodeposition has been known as a powerful synthesis method for obtaining metallic species by relatively simple operation with current and voltage control. Unfortunately, the electrodeposition of the silicon is impossible in aqueous electrolyte solution due to its low oxidation-reduction equilibrium potential. Ionic liquids are simply defined as ionic melts with a melting point below $100^{\circ}C$. Characteristics of the ionic liquids are high ionic conductivities, low vapour pressures, chemical stability, and wide electrochemical windows. The ionic liquids enable the electrochemically active elements, such as silicon, titanium, and aluminum, to be reduced to their metallic states without vigorous hydrogen gas evolution. In this study, the electrodeposion of silicon has been investigated in ionic liquid of 1-butyl-3-methylpyrolidinium bis (trifluoromethylsulfonyl) imide ([bmpy]$Tf_2N$) saturated with $SiCl_4$ at room temperature. Also, the effect of electrode materials on the electrodeposition and morphological characteristics of the silicon electrodeposited were analyzed The silicon electrodeposited on gold substrate was composed of the metallic Si with single crystalline size between 100~200nm. The silicon content by XPS analysis was detected in 31.3 wt% and the others were oxygen, gold, and carbon. The oxygen was detected much in edge area of th electrode due to $SiO_2$ from a partial oxidation of the metallic Si.

• Nuclear Engineering and Technology
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• 제53권4호
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• pp.1236-1249
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• 2021

Although there are still controversial opinions and uncertainty on application of SiC_f/SiC composite cladding as next-generation cladding material for its great oxidation resistance in high temperature steam environment and other outstanding advantages, it cannot deny that SiC_f/SiC cladding is a potential accident tolerant fuel (ATF) cladding with high research priority and still in the engineering design stage for now. However, considering its disadvantages, such as low irradiated thermal conductivity, ductility that barely not exist, further evaluations of its in-pile behaviors are still necessary. Based on the self-developed code we recently updated, relevant thermohydraulic and mechanical models in FROBA-ATF were applied to simulate the cladding behaviors under normal and accident conditions in this paper. Even through steady-state performance analysis revealed that this kind of cladding material could greatly reduce the oxidation thickness, the thermal performance of UO₂-SiC was poor due to its low inpile thermal conductivity and creep rate. Besides, the risk of failure exists when reactor power decreased. With geometry optimization and dopant addition in pellets, the steady-state performance of UO₂-SiC was enhanced and the failure risk was reduced. The thermal and mechanical performance of the improved UO₂-SiC was further evaluated under Loss of coolant accident (LOCA) and Reactivity Initiated Accident (RIA) conditions. Transient results showed that the optimized ATF had better thermal performance, lower cladding hoop stress, and could provide more coping time under accident conditions.

• 한국축산식품학회지
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• 제38권5호
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• pp.959-969
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• 2018

This study investigated the effects of deep freezing and storage temperature ($-50^{\circ}C$, $-60^{\circ}C$, and $-80^{\circ}C$) on the quality and freshness of lamb. To compare the qualities of deep frozen and stored lamb, fresh control and normal freezing conditions ($-18^{\circ}C$) were adopted. As quality and freshness parameters, drip loss (thawing loss and cooking loss), water-holding capacity (WHC), texture profile analysis (TPA), thiobarbituric acid reactive substances (TBARS), and total volatile basic nitrogen (TVBN) were evaluated during 5 months of storage. Temperature influenced the drip loss and WHC, and deep freezing minimized the moisture loss during frozen storage compared to the normal freezing condition. Lamb frozen and stored at deep freezing temperature showed better tenderness than that stored in normal freezing conditions. In particular, lamb frozen at lower than $-60^{\circ}C$ exhibited fresh lamb-like tenderness. Regardless of temperature, evidence of lipid oxidation was not found in any frozen lamb after 5 months, while TVBN was dependent on the applied temperature. Therefore, this study demonstrated that deep freezing could potentially be used to maintain freshness of lamb for 5 months. From the quality and economic aspects, the freezing and storage condition of $-60^{\circ}C$ is estimated as the optimum condition for frozen lamb.

• Journal of Nutrition and Health
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• 제11권3호
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• pp.25-30
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• 1978

A study was planned to evaluate the influence of continual heating at $150{\pm}5^{\circ}C$ and $170{\pm}5^{\circ}C$ respectively upon edible oils for frying the several food. Two kinds of domestic edible oils (Sample A and B) were collected by random sampling from market and in order to estimate deterioration degrees at both temperatures previously mentioned, thiobarbituric acid (TBA) value, acid value (AV), peroxide value (POV) and carbonyl value (CV) were measured at intervals due to its optical density. Those values were examined and compared according to the temperatures and times, and it was concluded as follows: 1) TBA value was rapidly increased until 24 hours in both temperatures and after 1 day its value have shown a slower increase as compared with initial rapid reaction. 2) Acid value and peroxide value of both oils (A & B) used for frying were increased continuously during heating and the changes in these values were dependent on the thermal oxidation, and moreover at low temperature $(150{\pm}5^{\circ}C)$ these values were found to be increased more readily than at high temperature $(170{\pm}5^{\circ}C)$. 3) Carbonyl value of both sample A and B show almost the same increasing rate at either $150{\pm}5^{\circ}C$ or $170{\pm}5^{\circ}C$ in proportion to the heating time. 4) It was found that there were differences between the chemical changes caused by heating sample A and B at high and low temperature.

• 마이크로전자및패키징학회지
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• 제27권3호
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• pp.55-60
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• 2020

최근 참단 반도체 패키징 기술은 고성능 SIP(system in packaging) 구조로 발전해 가고 있고, 이를 실현시키기 위해서 구리 대 구리 접합은 가장 핵심적인 기술로 대두되고 있다. 구리 대 구리 접합 기술은 아직 구리의 산화 특성과 고온 및 고압력 공정 조건, 등 해결해야 할 문제점들이 남아 있다. 본 연구에서는 아르곤과 질소를 이용한 2단계 플라즈마 공정을 이용한 저온 구리 접합 공정의 접합 계면 품질을 정량적 접합 강도 측정을 통하여 확인하였다. 2단계 플라즈마 공정은 구리 표면에 구리 질화막을 형성하여 저온 구리 접합을 가능하게 한다. 구리 접합 후 접합 강도 측정은 4점 굽힘 시험법과 전단 시험법으로 수행하였으며, 평균 접합 전단 강도는 30.40 MPa로 우수한 접합 강도를 보였다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2010년도 춘계학술발표대회
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• pp.18.2-18.2
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• 2010

For the past a few years, we have intensively researched the printable inorganic conductors and ZnO-based amorphous oxide semiconductors (AOSs) for thin-film transistors. For printable conductor materials, we have focused on the aqueous Ag and Cu ink which possess a variety of advantages, comparing with the conventional metal inks based on organic solvent system. The aqueous Ag ink was designed to achieve the long-term dispersion stability using a specific polymer which can act as a dispersant and capping agent, and the aqueous Cu ink was carefully formulated to endow the oxidation stability in air and even aqueous solvent system. The both inks were successfully printed onto either polymer or glass substrate, exhibiting the superior conductivity comparable to that of bulk one. For printable ZnO-based AOSs, we have researched the noble way to resolve the critical problem, a high processing-temperature above $400^{\circ}C$, and recently discovered that Ga doping in ZnO-based AOSs promotes the formation of oxide lattice structures with oxygen vacancies at low annealing-temperatures, which is essential for acceptable thin-film transistor performance. The mobility dependence on annealing temperature and AOS composition was analyzed, and the chemical role of Ga are clarified, as are requirements for solution-processed, low-temperature annealed AOSs.

• 한국재료학회지
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• 제19권8호
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• pp.427-431
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• 2009

ZnO wire-like thin films were synthesized through thermal oxidation of sputtered Zn metal films in dry air. Their nanostructure was confirmed by SEM, revealing a wire-like structure with a width of less than 100 nm and a length of several microns. The gas sensors using ZnO wire-like films were found to exhibit excellent $H_2$ gas sensing properties. In particular, the observed high sensitivity and fast response to $H_2$ gas at a comparatively low temperature of $200^{\circ}C$ would lead to a reduction in the optimal operating temperature of ZnO-based $H_2$ gas sensors. These features, together with the simple synthesis process, demonstrate that ZnO wire-like films are promising for fabrication of low-cost and high-performance $H_2$ gas sensors operable at low temperatures. The relationship between the sensor sensitivity and $H_2$ gas concentration suggests that the adsorbed oxygen species at the surface is $O^-$.

• 한국약용작물학회지
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• 제11권3호
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• pp.236-245
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• 2003

한국산 백삼으로부터 온도 및 에탄올 함유 비율을 달리하여 조제된 추출물들에 대한 angiotensin converting enzyme (ACE) 저해활성을 검정하고 항산화 활성을 비교하기 위해 본 연구를 수행하였으며 그 결과는 다음과 같다. 1. 10가지 조건에서 얻어진 추출물의 인삼분말에 대한 수율과 총 페놀함량은 $85^{\circ}C$에서 50% 에탄올로 추출했을 때 42.25% 및 0.82%로 가장 높았으며 대체적으로 가온조건이 상온조건보다 높았다. 상온 50% 에탄을 추출물로부터 조제된 분획물의 수율은 물 분획이 72.08%로 가장 높았고, 총 페놀함량은 에틸아세테이트 분획이 6.59%로 가장 높았다. 2. 10가지 추출물의 ACE 저해활성을 실험한 결과 $4000{\mu}g/ml$의 농도에서 상온 50% 에탄올 추출물이 93.8%로 가장 우수한 효과를 보였으며 이 값은 시판 ACE inhibitor의 85.2%보다도 월등하게 높은 수치였으며 분획물은 핵산(201%) > 에텔 (105%) > 에틸아세테이트 (67%) > 부탄올 (46%) < 물 분획 (19%)의 순으로 효과가 높았다. 3. 사람 LDL에 대한 산화저해효과 실험에서는 $85^{\circ}C$에서 얻어진 50% 에탄올 추출물이 $200{\mu}g/ml$의 농도에서 78.2%로 가장 효과적으로 항산화력을 보였으며 모든 추출물들이 60%이상의 높은 산화저해효과를 나타내었다. 분획물에 대한 LDL산화저해효과 검정 실험에서는 에텔 분획물 및 에틸아세테이트 분획물이 $10{\sim}200\;{\mu}g/ml$의 농도에서 $34.38%{\sim}78.13%$로 높은 활성을 보였다. 4. 각 에탄올 추출물의 linoleic acid 과산화저해 및 DPPH라디칼 소거효과는 그다지 높지 않았으며 비교 실험된 시판 천연 항산화제인 ${\alpha}-tocopherol$보다 매우 낮았다. 5 상관분석의 결과 총 페놀함량과 ACE 저해활성은 P<0.05의 수준에서 0.6353의 유의적인 상관성을 나타내었다. 이상의 실험결과로부터 인삼이 ACE 저해 및 LDL산화 저해작용을 효과적으로 나타내고 총 페놀함량이 많이 추출될 수 있으며 수율을 높일 수 있는 가장 적합한 조건은 상온 혹은 가온의 50% 에탄올 추출조건이었으며 인삼은 이러한 활성에 의해 항고혈압 및 동맥경화예방의 효과를 발휘 할 수 있을 것으로 기대되었다.

• 분석과학
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• 제18권2호
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• pp.120-129
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• 2005

VOC는 대기오염의 주원인으로서 인식되어왔다. 촉매산화는 저온에서 높은 효율을 나타내기 때문에 VOCs 제거를 위한 가장 중요한 처리기술중 하나이다. 이 연구에서는 $TiO_2$ 담체에 Pt, Ir 그리고 Pt-Ir을 담시지켜 촉매를 제조하였다. 금속 분산에 따르면 $H_2O-H_2$ 처리방법이 사용되었고, 반응물로서 Xylene,Toluene 그리고 MEK을 사용하였다. 단일 또는 두 가지 이상의 촉매들은 함침법에 의해 준비하였고, XRD, XPS, TEM 분석을 통하여 특성화하였다. 그 결과 Pt 촉매는 Ir 촉매에 비해 더 높은 전환율을 나타내었고, Pt-Ir 촉매는 가장 높은 전환율을 나타내었다. $H_2O-H_2$ 처리한 촉매들은 처리하지 않은 것보다 VOCs 전환율이 높았다. VOCs 산화에서, Pt-Ir 촉매는 다양한 활성점을 나타내었고 그것은 Pt의 metal 영역을 강화시켰다. 따라서 두 가지 금속으로 이루어진 촉매가 단일 금속으로 이루어진 촉매에 비해 VOCs 전환율이 더 높았다. $H_2O-H_2$ 처리가 Pt 입자의 분산에서 형태에 영향을 미쳤다. 동역학적으로 VOCs 산화는 1차 반응이다. $H_2O-H_2$ 처리한 촉매들의 활성화에너지가 처리하지 않은 것들보다 낮았다. 이 연구에서 Pt에 Ir을 소량첨가함으로써 VOCs 산화반응에 효과적이었다.