• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2002.11a
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• pp.63-63
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• 2002

현재 기계적 합금화법에서는 주로 합금을 구성하는 성분원소 분말을 불활성분위기에서 볼밀처리 함으로써 함금화를 시키거나 모합금에 산화물을 분산시켜 복합화시키는 공정을 통하여 각종 화합물, 비정질상 및 과포화고용체등의 준안정상의 합성 뿐만이 아니라 초미세조직의 생성에 관한 폭 넓은 분야의 연구가 행하여지고 있다. 한편 MA에서는 볼멀처리중 기계적 에너지의 투여에 의하여 실제 반응온도보다 낮은 온도에서 발생하는 특이한 화학반응 즉 Mechanochemical 반응을 일으키 기도 한다. 본 연구에서는 헤마타이트($Fe_20_3$)와 금속윈소인 Ti의 MA처리에 의하여 고상환원반응 을 유기시켜 $Fe-TiO_2$계 nanocomposite 분말재료를 제조하고자 한다. 특히 MA 공정에 있어서 자기 물성의 변화와 X선 회절을 통하여 고상환원반응에 의한 복합분말의 생성과정을 조사하였다. 출발원료는 $Fe_20_3$(고순도화학제,99.9%, 평균입경 0.1$\mu\textrm{m}$)와 금속원소인 Ti(99.9%, 명균업경 150$\mu\textrm{m}$)을 몰비 2:3의 조성이 되도록 하여 MA를 실시하였다. 볼멀은 고에너지 유성형 볼밀장치(독일 제, Fritsch P-5)를 이용하였으며 진공치환형 용기에 원료분말을 장입하여 2회정도 진공배기한 후 아르곤 가스를 충전하여 볼밀을 행하였다. 얻어진 분말시료에 대하여 x-선 회절장치, 전자현미경 (SEM) 및 진동시료형자력계(VSM)를 통하여 결정구조, 미셰조직 빛 자기특성을 조사하였다. $Fe_2O_3-Ti$ 혼합분말의 MA처리 에 의하여 초기단계부터 환원반응과 함께 $Fe_3TIO_{lO}$ 중간상이 관찰 되었으나 30hrs의 MA처리 후 Fe와 산화물 $TiO_2$로 모두 환원되어 $Fe-TiO_2$계 나노복합분말이 얻어짐을 알 수 있었다. 이 때 X션 회절피크의 line broadening으로부터 복합분말의 Fe 명균 결정립 크기는 24nm로 초미세 결정럽의 분말합금이었다. 포화자화값은 볼밀처리에 따라 점점 증가하여 MA 30시간에는 20.3emu/g로 포화됨을 알 수 있었다. 또한 보자력 Hc는 MA초기단계에 350e로 매우 낮으나 30시간 후에는 Hc값이 2600e로 매우 큰 값을 나타내었다. 이것은 환원반응결과 초기에 생성된 Fe의 결정립이 비교적 크고 결정결함이 적으나 볼밀처리를 30시간까지 행하면 Fe 결정렵의 미세화 빛 strain 증가로 magnetic hardening이 일어나기 때문인 것으로 사료된다.

• Journal of Energy Engineering
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• v.24 no.4
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• pp.175-182
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• 2015

A methodology to determine the most conservative initial condition based on random sampling of operation parameters is established, in which a best-estimate computer code is adopted to minimize the conservatism in code models. To validate the applicability of the suggested method, safety evaluation for a transient of loss of condenser vacuum in a pressurized water reactor is performed. One-hundred different initial conditions are generated by MOSAIQUE program automatically and the peak pressure for the most conservative case is determined from transient analyses. The safety margin obtained with the new approach is almost equivalent to the values determined with the existing methodologies. It is found that the time and human resources required for the safety evaluation could be reduced with the suggested approach.

• Transactions of the Korean hydrogen and new energy society
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• v.13 no.3
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• pp.190-196
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• 2002

Ni/MH 박막전지의 전극으로 사용될 수 $Mg_{2}Ni$박막을 스퍼터링방법으로 제조하였다. $Mg_{2}Ni$합금박막은 Mg, Ni타?을 이용하여 동시에 스퍼터링함으로서 제조하였다. KOH 액체전해질 및 $Ni(OH)_2$전극을 이용하여 전기화학실험을 하였다. $Mg_2Ni$ 박막의 초기 싸이클 특성에 미치는 열처리 효과를 조사하기 위하여, $200-550^{\circ}C$로 변화시키면서 진공중에서 열처리를 하였다. 열처리온도가 $300^{\circ}C$ 이하에서는 초기방전용량이 증가하였으며, $400^{\circ}C$ 열처리시에는 활성화시의 방전용량이 약 160mAh/g으로 가장 크게 나타났다.

• Journal of the Korean Wood Science and Technology
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• v.37 no.3
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• pp.192-199
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• 2009

This study was carried out to investigate the performance of a radio-frequency/vacuum dryer combined with a mechanical compressive load (RF/VC) with a scale of about $3m^3$ during drying board of Azobe (Lophira alata) and Korean red pine (Pinus densiflora). The degree of vacuum of the RF/VC system was maintained at 80~105 torr, and wood temperature was increased from $40^{\circ}C$ at the beginning of drying to $60^{\circ}C$ at the end of drying and the radiofrequency generator was operated with schedule of 7 minute-ON and 3 minute-OFF. The wood temperatures near charge plate always remained higher than those of the control during all of the drying stage, whereas the wood temperature near ground plate always remained lower than those of the controlled. As drying time proceeding, the temperature of the wood near ground plate presented lower than those of the control. Whereas the temperature of the wood near charge plate presented higher than those of the controlled. The final average moisture contents of the Azobe boards stacked near the input side of the RF generator showed slightly lower than those near the opposite side. Those of the wood stacked in the layers near the charge plate were lower than those of near the ground plate. The average length of surface checks of the Azobe boards stacked near the charge plate was very slight, whereas that toward the ground plate represented high values. The efficiency of input energy was simliar with the commercial systems.

• Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
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• 2003.10a
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• pp.194.1-194
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• 2003

본 연구는 수출방법의 개선과 절임 가공식품의 개발하고 일본 수출용으로 재배하고 있는 가지 품종의 최적 염절임 방법과 더불어 절임가지의 저장중에 물성 및 일반성분의 변화를 조사하였다. 절임가지의 명도와 황색도는 저장기간이 길어질수록 모든 조건에서 증가하지만, 진공포장한 절임가지의 명도와 황색도는 침지 저장한 것에 비해 변화 정도가 작았다. 절임가지의 염도는 절임 초기에는 축양 품종과 시키부 품종에서 각각 24.67, 20.27% 이었으며, 진공포장한 것은 저장 5일 이후에는 변화가 없었으나 침지 저장한 것에는 저장 중에 계속 감소하였다. pH의 변화는 품종과 저장방법에 관계없이 저장중에 감소하였으며, 수분함량은 절임중에 급격하게 감소하여 축양 품종과 시키부 품종에서 각각 79.93, 82.56% 이었으며, 진공 포장하여 저장한 절임가지에서는 5일째에 증가하였고 이후에는 변화가 없었으나, 침지 저장 방법에서는 두 품종 모두 15일까지 증가하였다. 또한 수용성 단백질 함량의 변화도 수분함량의 변화와 비슷하였다. 비타민 C의 함량은 생가지 보다 두 품종 모두 최적조건으로 염절 임 한 가지에서 높아 축양 품종과 시키부 품종에서 각각 21.41, 24.53mg/100g 이었으며, 저장기간 동안 그 함량이 감소하였고, 진공포장 저장한 방법이 침지 저장한 방법에 비해 감소하는 경향이 적었다. 저장기간에 길어질수록 나트륨과 마그네슘의 함량은 감소하였으나 반대로 칼륨의 함량은 증가하였고 특히 침지 저장한 방법에서 이와 같은 변화가 두드러졌다. 두 품종의 절임가지의 저장방법과 저장기간에 따른 물성 및 성분의 변화를 조사한 결과, 진공포장하는 것이 절임가지의 품질 유지할 수 있는 것으로 생각된다.부로 유출되어 균체의 생육이 억제되며 성장을 저해 또는 사멸시키는 것으로 나타났다. 대장균수는 우유, 달걀 및 콩나물의 모든 처리구에서 BAAG의 첨가에 의해 성장이 억제되었으며 농도가 증가시킬수록 균증식 억제 효과가 뚜렷하였으며, 총균수도 압도적으로 낮은 간을 보여주었다. 달걀의 조단백함량의 변화는 BAAG를 처리하지 않은 무처리 대조구에 비하여 침지 처리한 경우가 조단백 변화가 크지 않았다. 즉, BAAG의 침지 처리한 경우, 저장기간 14일이 경과 한 후에 10%정도의 수준으로 감소한데 반하여, 무처리구인 대조구의 경우, 23%수준으로 감소 증도가 증가하였다. 외관상의 변화와 상품 가치를 측정한 결과는 달걀의 경우, 14일이 경과후에는 무처리 대조구에서 흰자위의 감소와 노른자위와의 경계가 뚜렷하지 못하여 상품으로서의 가치가 크게 떨어진 상태였다. 우유의 경우에는 4$^{\circ}C$와 2$0^{\circ}C$에 저장된 대조구에서는 각각 3일과 12일경과 후 강한 부패취와 아울러, 표피의 갈변정도가 심하되어 관능적으로 부패상태를 인지할 수 있었다. 콩나물의 경우도 저장3일 경과 후에 부패취와 함께 점질성 갈변물질이 생성되었다. 이와 같은 결과로 볼 때, BAAG의 처리는 BAAC의 경우보다 가격은 저렴하면서도 항균력은 우수한 천연 항균복합제재로써 농산물 식품원료에 적용하여 선도유지 기간을 연장할 수 있는 효과를 기대할 수 있었다. 과일 등의 포장제로서 이용할 가능성을 확인하였다.로 [-wh] 겹의문사는 복수 의미를 지닐 수 없 다. 그러면 단수 의미는 어떻게 생성되는가\ulcorner 본 논문에서는 표면적 형태에도 불구하고 [-wh]의미의

• Food Science and Preservation
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• v.19 no.6
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• pp.807-812
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• 2012

This study was investigated the changes in quality of heat treated fresh-cut lotus roots using various packaging materials. Lotus roots were purchased from Daegu, Korea. Lotus roots were washed, peeled and sliced with a sharp ceramic knife. The prepared peeled and sliced lotus roots were dipped for 45 sec in water at $55^{\circ}C$. After air-dried at room temperature, the slices were packaged with polyethylene films, polyethylene terephthalate tray+wrapping, vacuum packaging and then stored at $4^{\circ}C$. Changes in weight loss, color, firmness, microorganisms and sensory characteristics were measured. In general, the weight loss rate was increased slightly in vacuum packaged lotus roots. Application of heat treatment delayed browning of lotus roots, and especially vacuum packaged lotus roots were the most lowest ${\Delta}E$ value. However, L and ${\Delta}E$ value of PE film packaged lotus roots were increased highly during storage. The heat treated and vacuum packaging inhibited the growth of microorganisms effectively. The organoleptic quality of vacuum packaged lotus roots showed the best by sensory evaluation.

• Food Science of Animal Resources
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• v.22 no.2
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• pp.137-144
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• 2002

Pork loins that retailed in market were used as experimental samples. Some pork samples in raw state were packaged with PVDC in either aerobic or vacuum condition. The other pork samples were cooked until core temperature reached at 70$\^{C}$ and then packaged immediately in the same way with the raw samples. After these samples were irradiated by electron beam 6 kGy, the samples were stored in a refrigerator (2∼4$\^{C}$). Identification and quantification of cholesterol oxides were performed at 0 and 7 days. The results were following. During the early stage of storage, cholesterol oxides were not produced from the raw meat samples, but with the passage of storage time,7 $\alpha$-hydroxycholesterol, 7$\beta$-hydroxycholesterol, 7-ketocholesterol, 20 $\alpha$-hydroxycholesterol, $\beta$-epoxide and $\alpha$-epoxide, which were not produced during the early stage of storage, were produced. The production of cholesterol and lipid oxidation products were significantly higher (P<0.05) in the meats with aerobic packaging than those with vacuum packaging, Cooked meat after irradiation showed 7 $\alpha$-hydroxycholesterol, 7 $\beta$-hydroxycholesterol, $\alpha$-epoxide and cholestanetriol on the 7th day of storage, although those chemicals were not produced during the early stage of storage. Production of cholesterol oxides was significantly increased (P<0.05) with the passage of storage time for all treatments, and showed significantly lower value (P<0.05) with the vacuum packaging than these for aerobic packaging. Species of cholesterol oxides from irradiated meat after cooking were similar to those from cooked meat after irradiation. Collectively, it was found that the production of cholesterol oxides was more easily affected by packaging condition than irradiation.

• The Journal of Engineering Geology
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• v.33 no.3
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• pp.371-388
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• 2023

A stratum with a complex composition and a distributed low-permeability soil layer is difficult to remediate quickly because the soil remediation does not proceed easily. For efficient purification, the permeability should be improved and the soil remediation agent (H₂O₂) should be injected into the contaminated section to make sufficient contact with the TPH (Total petroleum hydrocarbons). This study analyzed a method for crack formation and effective delivery of the soil remediation agent based on pneumatic fracturing, plasma blasting, and vacuum suction (the PPV method) and compared its improvement effect relative to chemical oxidation. A demonstration test confirmed the effective delivery of the soil remediation agent to a site contaminated with TPH. The injection amount and injection time were monitored to calculate the delivery characteristics and the range of influence, and electrical resistivity surveying qualitatively confirmed changes in the underground environment. Permeability tests also evaluated and compared the permeability changes for each method. The amount of soil remediation agent injected was increased by about 4.74 to 7.48 times in the experimental group (PPV method) compared with the control group (chemical oxidation); the PPV method allowed injection rates per unit time (L/min) about 5.00 to 7.54 times quicker than the control method. Electrical resistivity measurements assessed that in the PPV method, the diffusion of H₂O₂2 and other fluids to the surface soil layer reduced the low resistivity change ratio: the horizontal change ratio between the injection well and the extraction well decreased the resistivity by about 1.12 to 2.38 times. Quantitative evaluation of hydraulic conductivity at the end of the test found that the control group had 21.1% of the original hydraulic conductivity and the experimental group retained 81.3% of the initial value, close to the initial permeability coefficient. Calculated radii of influence based on the survey results showed that the results of the PPV method were improved by 220% on average compared with those of the control group.

• Analytical Science and Technology
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• v.5 no.3
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• pp.303-308
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• 1992

Initial reactions of Ti and Si have been studied to examine the surface roughness of titanium silicide. Formation mechanism has been explored with in-situ measurement tools such as AES(Auger electron spectroscopy) and LEED (low energy electron diffraction). One or two monolayers of Ti films have been deposited in ultrahigh vacuum on atomically clean Si(111) substrates. Atomically clean Si substrates which are reconstructed $7{\times}7$ Si(111) have been obtained after in-situ heat cleaning in ultrahigh vacuum. Deposition of the films were monitored by a quartz cuystal oscillator and the Ti films were analyzed with in-situ AES and LEED. The in-situ measurements show that the initial reactions of Ti and Si occur at room temperature and form a disordered layer. At low temperatures($200^{\circ}C{\sim}300^{\circ}C$) intermixing of Ti and Si is detected by AES. Substrate $1{\times}1$ LEED patterns are displayed after $400^{\circ}C$ anneal. This indicates that the disordered layer has transformed to form an ordered surface. The reappearance of the $7{\times}7$ LEED pattern in observed with further high temperature anneals and indicates three dimensional titanium silicide island formation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.3
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• pp.258-263
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• 2012

In this paper the Chemical Propulsion Subsystem of COMS is briefly explained and some telemetries acquired by a series operations of CPS during the Launch and Early Operation Phase of COMS are presented. The pressure and temperature of pressurant tank telemetries are compared with the results of the developed computer program. The changes in pressure are due to the two major phases. The first one is the initialization phases of CPS composed of the venting phase to vent the helium gas in the pipe network from the downstream of the propellant tanks to the thrusters for safety, the priming phase to fill the vented pipe network with oxidizer and fuel respectively and then the pressurization phase to pressurize the ullage of propellant tank to regulated pressure. And the other is the apogee engine firings in which COMS CPS is in the orbit raising phase to use helium as a pressurant to keep the pressure of propellant tank as the liquid apogee engine get fired until COMS reached to the target orbit. This program can be applicable to prepare basis design data of the next Geostationary Satellite CPS.