• Korean Journal of Materials Research
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• v.14 no.9
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• pp.607-613
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• 2004

This study was to investigate the surface properties of electrochemically oxidized Ti-6Al-7Nb alloy by anodic spark discharge technique. Anodizing was performed at current density 30 $mA/cm^2$ up to 300 V in electrolyte solutions containing $DL-{\alpha}$-glycerophosphate disodium salt hydrate($DL-{\alpha}$-GP) and calcium acetate (CA). Hydrothermal treatment was done at $300^{\circ}C$ for 2 hrs to produce a thin outermost layer of hydroxyapatite (HA). The bioactivity was evaluated from HA formation on the surfaces in a Hanks' solution with pH 7.4 at $36.5^{\circ}C$ for 30 days. The size of micropores and the thickness of oxide film increased and complicated multilayer by increasing the spark forming voltage. Needle-like HA crystals were observed on anodic oxide film after the hydrothermal treatment at $300^{\circ}C$ for 2 hrs. When increasing $DL-{\alpha}$-GP in electrolyte composition, the precipitated HA crystals showed the shape of thick and shorter rod. However, when increasing CA, the more fine needle shape HA crystals were appeared. The bioactivity in Hanks' solution was accelerated when the oxide films composed with strong anatase peak with presence of rutile peak. The increase of amount of Ca and P was observed in groups having bioactivity in Hanks' solution. The Ca/P ratio of the precipitated HA layer was equivalent to that of HA crystal and it was closer to 1.67 as increasing the immersion time in Hanks' solution.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.309.2-309.2
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• 2014

산화아연은 넓은 밴드갭과 큰 엑시톤 에너지를 갖고 있어 광전자반도체 물질로 산화인듐주석의 대체물질로 유망하다. 그러나, 산화아연 박막 및 나노막대는 대부분 c-축 방향으로의 성장이 보고되고 있다. 하지만, c-축으로 성장하는 극성 산화아연은 자발분극과 압전분극을 갖으며 이는 quantum confinement Stark effect (QCSE)를 발생시킨다. 그러므로, 반극성과 무극성 산화아연의 연구가 활발히 진행 되고 있다. 더욱이, 산화아연 나노구조체는 넓은 표면적, 높은 용해도, 광범위한 적용분야 등의 이점으로 많은 연구가 이뤄지고 있다. 본 연구에서는 m-면 사파이어 기판 위에 원자층 증착법을 이용하여 비극성 산화아연의 박막을 형성 후 전기화학증착법을 이용하여 반극성 산화아연 막대를 성장하고 이에 대한 성장 메커니즘을 분석하였다. 반극성 (10-11) 산화아연 나노구조체를 성장하기 위하여 두 단계 공정을 이용하였다. 먼저 원자층 증착법을 이용하여 m-면 사파이어 기판 위에 60 nm의 산화아연 씨앗층을 $195^{\circ}C$에서 성장 하였다. X-선 회절분석을 통하여 m-면 사파이어 위에 성장한 산화아연 씨앗층이 무극성 (10-10)으로 성장한 것을 확인하였다. 무극성 산화아연 씨앗층 위에 나노구조체를 형성하기 위하여 전기화학 증착법을 이용하여 주 공정이 진행되었다. 전구체로는 질산아연헥사수화물 ($Zn(NO3)2{\cdot}6H2O$)과 헥사메틸렌테트라민을 ((CH2)6N4)을 사용하였다. 무극성 산화아연 기판을 질산아연헥사수화물과 헥사메틸렌테트라민을 용해한 전해질에 담근 뒤 $70^{\circ}C$에서 두시간 동안 -1.0V의 정전압을 인가하였다. SEM을 이용한 표면 분석에서 원자층 증착법을 이용해 성장한 무극성 산화아연 씨앗층 위에 산화아연 나노구조체를 성장 시, 한 방향으로 기울어진 반극성 산화아연 나노구조체가 성장하는 것이 관찰되었다. 산화아연 막대의 성장 시간에 따라 XRD를 측정한 결과, 성장 초기에는 매우 약한 $31.5^{\circ}$ (100), $34.1^{\circ}$ (002), $36^{\circ}$ (101) 부근의 피크가 관찰되는 반면, 성장 시간이 증가함에 따라 강한 $36^{\circ}$ 부근의 피크가 관찰되는 X-선 회절 분석 결과를 얻을 수 있었다. 이는, 성장 초기에는 여러 방향의 나노구조체가 성장하였지만 성장시간이 점차 증가함에 따라 (101) 방향으로 우선 성장되는 것을 확인하였다.

• Journal of Korean Society of Forest Science
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• v.5 no.1
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• pp.4-9
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• 1966

1. On 13 September 1964 a storm raged for 3 hours and 20 minutes with pounding heavy rainfalls, and precipitation of 287.5 mm was recorded on that day. The numerous landslides were occured in the eroded forest land neighbouring Mt. Chunbo, while no landslides recorde at all on Mt. Jookyup within the premise of Kwangnung Experiment Station, the Forest Experiment Station. 2. Small-scalled Landslides were occured in 43 different places of watershed area (21.97 ha.) in which the survey had already been done, in and around Mt. Chunbo (378 m a.s.l.). The accumulated soil amount totaled $2,146,56m^3$ due to the above mentioned landslides, while soil accumulated from riverside erosion has reached to $24,168.79m^3$, consisting of soils, stones, and pebbles. However, no landslides were reported in the Mt. Jook yup area because of dense forest covers. The ratio of the eroded soil amount accumulated from the riversides to that of watershed area was 1 to 25. On the other hand, the loss and damage in the research area of Mt. Chonbo are as follows: 28 houses completly destroyed or missing 7 houses partially destroyed 51 men were dead 5 missing, and 57 wounded. It was a terrible human disaster However, no human casualties were recorded at all, 1 house-completly destroyed and missing, 2 houses-partially destroyed. Total:3 houses were destroyed or damaged, in The area of Mt. Jookyup 3. In the calculation of the quanty of accumulated soil, the or mula of "V=1/3h ($a+{\sqrt{ab}}+b$)" was used and it showed that 24, 168.79m of soil, sands, stones and pebbles carried away. 4. Average slope of the stream stood 15 at the time of accident and well found that there was a correlation between the 87% of cross-area sufferd valley erosion and the length of eroded valley, after a study on regression and correlation of the length and cross-area. In other works, the soil erosion was and severe as we approached to the down-stream, counting at a place of average ($15^{\circ}1^{\prime}$) and below. We might draw a correlation such as "Y=ax-b" in terms of the length and cross-area of the eroded valley. 5. Sites of char-coal pits were found in the upper part of the desert-like Mt. Chunbo and a professional opinion shows that the mountain was once covered by the oak three species. Furthermore, we found that the soil of both mountains have been kept the same soil system according to a research of the soil cross-area. In other words, we can draw out the fact that, originally, the forest type and soil type of both Mt. Chunbo (378m) and Mt. Jookyup (610m) have been and are the same. However, Mt. Chunbo has been much more devastated than Mt. Jookyup, and carried away its soil nutrition to the extent that the ratios of N. $P_2O_5K_2O$ and Humus C.E.C between these two mountains are 1:10;1:5 respectively. 6. Mt. Chunbo has been mostly eroded for the past 30 years, and it consists of gravels of 2mm or larger size in the upper part of the mountain, while in the lower foot part, the sandy loam was formulated due to the fact that the gluey soil has been carried and accumulated. On the hand, Mt. Jookyup has consitantly kept the all the same forest type and sandy loam of brown colour both in the upper and lower parts. 7. As for the capability of absorbing and saturating maximum humidity by the surface soil, the ratios of wet soil to dry soil are 42.8% in the hill side and lower part of the eroded Mt. Chunbo and 28.5% in the upper part. On the contrary, Mt. Jookyup on which the forest type has not been changed, shows that the ratio in 77.4% in the hill-side and 68.2% in the upper part, approximately twice as much humidity as Mt. Chunbo. This proves the fact that the forest lands with dense forest covers are much more capable of maintaining water by wood, vegitation, and an organic material. The strength of dreventing from carring away surface soil is great due to the vigorous network of the root systems. 8. As mentioned above, the devastated forest land cause not only much greater devastation, but also human loss and property damage. We must bear in mind that the eroded forest land has taken the valuable soil, which is the very existance of origin of both human being and all creatures. As for the prescription for preventing erosion of forest land, the trees for furtilization has to be planted in the hill,side with at least reasonable amount of aertilizer, in order to restore the strength of earth soil, while in the lower part, thorough erosion control and reforestation, and establishments along the riversides have to be made, so as to restore the forest type.

• Journal of Environmental Science International
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• v.18 no.5
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• pp.569-578
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• 2009

Aircraft Measurements of gaseous pollutants($SO_2$, NOx and $O_3$) in the Yellow Sea area, were carried out on 1997-2007. Main measurement site in 124$^{\circ}$-127$^{\circ}$E, 35$^{\circ}$-37$^{\circ}$N (in the Yellow Sea), have been done along the paths classified vertically and zonally. To understand how the air stream affects Long-range transboundary pollutants in Northease Asia (LTP), the tracks of pollutants in northeast Asia have been analyzed by dividing into 6 different regions(regions I-V and L). Compared with Korea's local sources and western north Pacific influenced by the Yellow Sea, when the air stream from region II is dominant, the $SO_2$ concentrations are 3-6times higher. In region II and III, $SO_2$ concentrations are represented highest at 25.0 and 14.7 ppb, respectively. However, in other regions, $SO_2$ concentration was recorderd the highest at 1.1-3.8 ppb, which is 7-15% higher then the highest one over the region II and III. During 1997-2007, the mean amount of incoming pollutants is 0.162 $ton/km{\cdot}hr$ exceeding about 5-times mean amount of outgoing pollutants over the West Sea. During the observed period, the amount of incoming and outgoing $SO_2$ over the Yellow Sea is the highest in winter, at 0.224 $ton/(km{\cdot}hr)$ and 0.120 $ton/(km{\cdot}hr)$, respectively.

• Journal of Environmental Impact Assessment
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• v.21 no.3
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• pp.483-501
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• 2012

The purpose of this study was to apply a multi-metric model of Lentic Ecosystem Health Assessments(LEHA) for environmental impact assessments of Cheongpyung Reservoir during 2005 - 2006 and assessed the ecological model values. The ecosystem model of LEHA was composed of eleven metrics such as biological parameters($B_p$), physical parameters($P_p$), and chemical parameters($C_p$), and determined the rank of ecological health by the criteria. The variables of $B_p$ were metrics of % sensitive species($M_2$, NMS) and insectivore species($M_5$, % $I_n$), which decrease as the water quality degradates, and these metric values were low as 1.5% and 32.4%, respectively. In contrast, the proportions of tolerant species and omnivore species as the other $B_p$ parameters were 43% and 62%, respectively, which indicate a degradation and disturbance of the ecosystem. Riparian vegetation coverage($M_9$, % $V_c$) as a variable of $P_p$, were higher in the 2nd than 1st survey, and decreased toward the dam site from the headwaters. This was due to a habitat simplification(modifications) by frequent bottom dredging of sand and rocks. The variables of $C_p$ were two metrics of specific conductivity($M_{10}$, $C_I$) as an indicator of ionic contents(cations and anions) and the Trophic State Index(TSI) based on chlorophyll-a($M_{11}$, $TSI_{CHL}$) as an indicator of trophic state. These metric values of $C_p$ had high temporal variations, but low spatial variations on the main axis of the reservoir along with the ecological health of a good condition. The environmental impact assessments using the LEHA multi-metric model indicated that the model values of LEHA averaged 30.7 in 1st survey(fair - poor condition) vs. 28 in 2nd survey(poor condition), indicating a temporal variation of the ecological health. The model values of LEHA showed a minimum(28) in the lacustrine zone(S5) and ranged from 29 to 30 in the other locations sampled, indicating a low longitudinal variation. Overall, environmental impact assessments, based on LEHA model, suggest that chemical water quality conditions were in good, but biological conditions were disturbed due to habitat modifications by frequent dredgings in the system.

• Food Science and Preservation
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• v.5 no.4
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• pp.326-330
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• 1998

Freeze storage technique is widely used for food processing to keep freshness and quality of the product. This technique was applied to fresh, unshelled groundnut to develop a new type of product which could maintain fresh taste and nutritive values even after several months of storage. The groundnut varieties, Daepungtangkong, Daekwangtangkong and Sindaekwangtangkong were grown at the experimental field of NCES in 1996. Immatured pods or groundnut were harvested around 20 to 3o days before full maturity, washed, and steamed at 100$^{\circ}C$ for 5 min. to stop enzyme activity. After vacuum packing (at -760mmHg for 10 min.) with 0.08mm polyvinyldichloride film, the pods were immediately frozen at -70$^{\circ}C$ for 24h and transfered at -20$^{\circ}C$ for long-term storage. Physico-chemical properties of frozen vegetable groundnut were investigated at 2 months after storage and compared to those of conventionally dried groundnut. After 2 months storage, the thawed kernels were very palatable with softness and fresh taste. Acid value and hardness (measured as the compression force on the probe of a texture analyzer) were much lower in frozen vegetable groundnut than those in the air-dried ones. Presence of free sugars is one of the important factors affecting groundnut taste, and the free sugar contents were considerably decreased in the frozen vegetable groundnut compared to freshly harvested groundnut. But in dried groundnut no free sugar was detected.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.2
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• pp.37-55
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• 1997

최근 선진국가들에서는 전자파 장애 증후군에 관심이 집중되고 있는데, 전자파에 장기 노출 되는 인구에서 뇌암이나 유방암, 백혈병 등의 발생률이 높다는 보고(Kolmodin-Hedman 등, 1988 ; Demers등, 1991)가 있어서 전자제품의 생산업체는 물론이고 사용자에 대해서도 불안한 관심사가 되 어 있다. 전자파가 생체에 미치는 영향은 열적 효과와 비열적 효과에 의한 것으로 구분된다. Microwave는 약 300MHz에서 300GHz 사이(파장 1m에서 1mm사이)의 주파수를 가지는 전자파로서 이온의 운동이나 쌍극자분자(dipole molecule)들을 진동시키므로서 조직에 열이 발생한다. 열이 과도하게 발생하면 세포 단백질이 응고하게 되는 등 일반적으로 생각할 수 있는 고열로 인한 여러 가지 유해환경이 조직 에 조성될 수 있다. 실제로 고전압의 전자파에 노출된 안구의 수정체에 백내장 등의 병변이 발생한 것 으로 보고된 바 있다(Adey,1981). 일반적으로 전자파의 생체에 대한 작용으로는 이렇듯 조직에 흡수 되는 전자파의 에너지에 의한 열작용이 지배적인 것으로 생각되어 왔다. 그러나 초저주파역대(Extre- mely low frequency, EMF)의 변조 및 펄스파 등의 영향에 관해서도 조직의 온도상승으로는 설명할 수 없는 현상이 보고된 바 있다. 이러한 비열적 효과가 신경계에 끼치는 영향에 대해서는 혈액뇌관문 의 투과성 변화(Oscar와 Hawkins, 1977), 뇌종양 발생, 칼슘대사 이상 및 신경전달물질에 대한 영향 등이 주장(Anderson, 1993)되고 있으나 아직 그 분명한 기전이 밝혀져 있지 않은 상태이다. 또한 그 영향의 평가에 서도 일정한 기준이나 지표가 정해지지 않은 실정이다. 그러므로 신경계에 대한 대체적인 소개와 더불어 전자기파의 영향에 대한 이제까지의 보고를 종합 하고 향후 연구의 방향을 소개하고자 한다.> 이온이 공동 첨가제로 더 적합하다.u(30 .angs. )/CoFe(35 .angs. )/NiO(800 .angs. ) 구조를 갖는 spin-valve 박막은 극대 MR비 6.3%, 유효자기장감응도 약 0.5(%/Oe)를 보여 spin-valve head 재료로 적합함을 알 수 있었다.다.다.다.는 각각 148 meV .angs. $^{2}$, 103.8 meV .angs. $^{2}$와 1.77 * $10^{-6}$ erg/cm, 0.67 * $10^{-6}$ erg/cm 였다.다.자 노인들을 영주권자와 귀화 시민권자의 구분없이 하나의 집단으로 간주하고 분석해 왔던 것을 볼 때, 앞으로의 연구는 이론적으로나 방법론적으로 시민권의 유무가 주거형태에 끼치는 영향도 함께 고려해야 할 것이다.에 나타난 인도의 영향은 여성복식과 남성복식에 있어서 서로 유사점과 차이점이 보이는데, 인도의 영향이 여성복식에 있어서 그 빈도가 더 높고, 종류가 더 다양함을 볼 수 있다. 여성복식에 있어서는 12가지의 다양한 인도복식스타일이 나타났으며, 그중 가장 많이 보이는 스타일은 Indian Shirt/Blouse/Smock/ Dress이며, 그 뒤를 이어 Madras, Indian lowery등을 볼 수 있다. 남성복식애 나타난 7가지의 스타일 중에는 Madras가 가장 빈도가 높으며 그외의 스타일들은 그 빈도가 매우 낮음을 볼 수 있다. 인도의 영향의 정도 (Attribution Categories) 있어서는 여성과 남성복식 모두에 있어서 인도에서 직접 수입된(originated) item이 각각 전체의 90%와 81%를 차지하여, 인도복식의 영향은 받았으나 미국내에서 제작된(attributed and connotated) item 보다 휠씬 더 많은 수를 보였다. 인도복식스타일이 가장

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.345-345
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• 2014

최근 디스플레이 기술은 급속도로 발전해 가고 있다. 정보화 기술의 발전으로 언제 어디서나 쉽게 정보를 얻을 수 있는 유비쿼터스 시대로 접근하고 있으며, 휴대가 간편하고 이동성을 가진 휴대용 기기가 인기를 끌고 있다. 이에 따라 더 얇고 더 가벼우며 휴대하기 쉬운 디스플레이가 요구 되고 있고, 더 나아가 떨어뜨려도 깨지지 않고 유연하며, 디자인 변형이 자유로우며, 때론 종이처럼 접거나 휘어지거나 두루마리처럼 말을 수 있는 이른바 "플렉서블 디스플레이"에 대한 필요성이 점점 대두되고 있다. 이러한 첨단 디스플레이의 핵심 소자 중 하나는 산화물 박막 트랜지스터 이다. 산화물 반도체는 넓은 밴드갭을 가지고 가시광선 영역에서 투명하며, 높은 이동도를 가지고 있어 차세대 평판디스플레이, 투명디스플레이 및 플렉서블 디스플레이용 박막트랜지스터(TFT)를 위한 채널층으로써 광범위하게 연구되고 있다. 하지만 현재 대부분의 산화물 박막 트랜지스터 제조 공정은 고온에서의 열처리를 필요로 한다. 고온에서의 열처리 공정은 산화물 박막의 제조 공정 단가를 증가시키는 문제점이 있으며, 산화물 박막이 형성되는 기판의 녹는점이 낮은 경우에는 상기 기판의 변형을 가져오므로(예를 들면, 플라스틱 기판, 섬유 기재 등), 상기 산화물 박막이 적용되는 기판의 종류에 제한이 생기는 문제점이 있었다. 이에 플렉시블 디스플레이 등을 위해서는 저온공정이 필수로 선행 되어야 한다. 산화물 TFT는 당초, ZnO계의 재료가 연구되었지만 2004년 말에 Hosono 그룹이 Nature지에 "IGZO (In, Ga, Zn, O)"을 사용한 TFT를 보고한 이후 IGZO, IZO, ISZO, IYZO, HIZO와 같은 투명 산화물반도체가 TFT의 채널물질로써 많이 거론되고 있다. 그 중에서 인듐갈륨 산화물(IGO)는 삼성분계 n-형 산화물 반도체이고, 채널 이동성이 좋고 광투과도가 우수해 투명 TFT에 매우 유용하게 사용할 수 있다. 이 실험에서 우리는 인듐갈륨 산화물 박막 및 트랜지스터 특성 연구를 진행하였다. 인듐갈륨 산화물 박막은 상온에서 rf-magnetron sputtering법을 사용하여 산소분압 1~10%에서 증착 되었다. 증착된 인듐갈륨 산화물 박막은 cubic $In_2O_3$ 다결정으로 나타났으며, 2차상은 관찰 되지 않았다. 산소분압이 10%에서 1%로 변함에 따라 박막의 전도도는 $2.65{\times}10^{-6}S/cm$에서 5.38S/cm 범위에서 조절되었으며, 이를 바탕으로 인듐갈륨 박막을 active층으로 사용하는 bottom gate 구조의 박막트랜지스터를 제작 하였다. 인듐갈륨산화물 박막트랜지스터는 산소분압 10%에서 on/off 비 ${\sim}10^8$, field-effect mobility $24cm^2/V{\cdot}S$를 나타내며 상온에서 플렉서블용 고 이동도 소자 제작의 가능성을 보여준다.

• Nuclear Engineering and Technology
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• v.22 no.4
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• pp.337-350
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• 1990

A post-irradiation annealing study was conducted with use of reactor pressure vessel(RPV) steel A533B Cl.1 base metal irradiated to a dose of 4.84$\times$10$^{18}$ n/$\textrm{cm}^2$ at about 38$0^{\circ}C$. Microhardness and positron annihilation (PA) methods were used to obtain better understanding of the recovery of radiation hardening. Isochronal anneal experiments indicated that two recovery processes occur during annealing of irradiated specimens. The first recovery process occurs in the temperature range of 280-3O5$^{\circ}C$, Michrohardness and positron annihilation (PA) methods were used to obtain better understanding of the recovery of radiation hardening. Isochronal anneal experiments indicated that two recovery processes occur during annealing of irradiated specimens. The first recovery process occurrs in the temperature range of 280-305$^{\circ}C$. The variations of Ip, Iw and R parameters indicated that the formation of vacancy clusters by vacancy agglomeration and the annihilation of monovacancies are the first recovery process. The second recovery process occurs in the range of 405-49$0^{\circ}C$ and positron annihilation parameters measured indicated that the dissolution of carbon atoms decorated around vacancy-type defects and possible precipitates, and the annihilation of monovacancies give rise to the second recovery process. It was further indicated that radiation anneal hardening (RAH) in the range of 305-405$^{\circ}C$ between the temperature ranges for the two processes occurs due to the formation of carbon-decorated vacancy clusters and precipitates. The activation energies, orders of reaction and other characteristics of recovery processes were determined by the Meechan-Brinkman method. The activation energy for the first recovery process was determined as 1.76 eV and that for the second recovery process as 2.00eV. These values are lower than those obtained by other workers. This difference may be attributed to the lower copper content of the RPV steel used in the present study. The order of reaction for the first recovery process was determined as 1.78, while that for the second recovery process as 1.67 Non-integer orders of reaction for recovery processes seem to be attributed to the fact that several mechanisms for the first order and the second order of reaction are compounded in one process. This result also supports for the above conclusions from measurements of PA parameters.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.1
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• pp.97-102
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• 2015

The long line fishing machine is combined with motor and two disc rollers has used on the small size fishing-boat under 1 ton located in near Jeollanam-do seaside. The long line fishing motor is controlled only one direction because the fishing line is loaded heavily at pulling up. On this paper we made the long line fishing 400W power motor controller which it was usually applied under 1 ton fishing boat, and designed the controller using PWM chip, Half bridge driver and MOSFET for one direction motor control. Furthermore some user convenience devices were added like battery indicator and safety protection circuit for battery overdischarge and battery source wire mismatch connection. So we protected the battery from overdicharging when the battery voltage was below 11.5V and fishermen didn't need to worry about source lines misconnection anymore. We confirmed the test version of controller was the good working condition at land and sea.