• 제목/요약/키워드: Base region

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인공위성 플룸과 기저면의 상호 작용에 관한 해석 (Detailed Analysis of Thrust Plume and Satellite Base Region Interaction)

  • 김재강;권오준;이균호;김수겸;유명종
    • 한국항공우주학회지
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    • 제36권11호
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    • pp.1056-1062
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    • 2008
  • 인공위성의 추력기에서 발생되는 플룸과 기저면의 상호 작용에 관한 연구를 직접모사법을 사용하여 실시하였다. 질소와 수소 분자의 충돌에 의한 회전-병진 에너지의 교환을 정확하게 모사하기 위하여 최근에 연구 되어진 질소와 수소 분자의 회전 에너지 이완 모델을 사용하였다. 추력기 플룸과 기저면의 상호 작용 해석을 위하여 플룸 분자들의 수밀도 분포와 회전, 병진 온도 분포, 열전달량, 압력 등에 대하여 다양한 운영 조건에 맞추어 해석을 실시하였다. 그 결과 기저면에서는 질소 분자보다 수소 분자의 분포가 매우 큰 것과, 분포하는 대부분의 수소 분자가 회전 에너지에 대해 비평형 상태로 분포 하는 것을 확인 하였다. 이는 수소 분자의 정확한 회전 에너지 이완 모델의 필요성을 보여주고 있는 결과이며, 본 연구의 경우 가장 최근의 수소의 회전 에너지에 관련된 모델을 사용함으로써 플룸과 기저면의 상호 작용 해석에 대한 정확도를 증진 시켰다.

자동차 차체용 SPEC590강 레이저 용접판재의 피로특성 (Fatigue Characteristics of SPFC590 Laser Welded Sheet Metal for Automobile Body Panel)

  • 한문식;이양섭
    • 한국자동차공학회논문집
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    • 제11권1호
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    • pp.143-150
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    • 2003
  • Experimental research has been carried out to investigate the characteristics of the fatigue crack initiation and propagation behavior of Tailor Welded Blank(TB) sheet used for vehicle body. We used three types of specimens which were machined of the same base metal: one is 1.4mm thick, another is 1.6mm thick, and the third(TB specimen) is laser-welded of two specimens(1.4mm and 1.6mm thick ones). The results of tensile and hardness test indicate that the yield strength of the TB specimen is the highest, and the hardness around welding bead is higher than that of base metal. Fatigue strength and fatigue limit of the TB specimen are much superior to those of the base metal up to $10^6$ cycles. The fatigue crack propagation of the heat-affected zone of the TB specimen is slower than that of the base metal. Welding bead has the fastest crack Propagation in the low stress intensity factor range$(\DeltaK)$ region, but the slowest in the high $\DeltaK$ region. The fatigue propagation characteristic of the TB specimen is relatively stable in comparison with that of the base metal in the high ${\Delta}K$ region around over $28MPa\sqrt{m}$.

일방향응고 Ni기초내열합금 GTD-111의 천이액상확산접합(II) -접합공정에서 모재조직의 변화- (Transient Liquid Phase Bonding of Directionally Solidified Ni Base Superalloy, GTD-111(II) -Microstructural Change of Base Metal during Bonding Process -)

  • 강정윤;황형철;김인배;김대업;우인수
    • Journal of Welding and Joining
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    • 제21권2호
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    • pp.89-96
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    • 2003
  • The change of microstructures in the base metal during transient liquid phase bonding process of directionally Ni base superalloy, GTD-111 was investigated. Bonds were fabricated using a series of holding times(0-7.2ks) at three different temperatures(1403, 1418 and 1453K) under a vacuum of 13.3mPa. In raw material, ${\gamma}$- ${\gamma}$' eutectic phases, platelet η phases, MC carbide and PFZ were seen in interdendritic regions or near grain boundary and size of primary ${\gamma}$' precipitates near interdendritic regions were bigger than core region. The primary ${\gamma}$' precipitates in dendrite core were dissolved early in bonding process, but ${\gamma}$' precipitates near interdendritic regions were dissolved partially and shape changed. The dissolution rate increased with increasing temperature. Phases in interdendritic regions or near pain boundary continually changed with time at the bonding temperature. In the bonding temperature of 1403K, eutectic phases had not significantly changed, but η phases had transformed from platelet shape to needle morphology and PFZ region had widened with time. The interdendritic region and near pain boundary were liquated partially at 1423k and fully at 1453k by reaction of η phases and PFZ. In the bonding temperature of 1453K, interdendritic region and near pain boundary were liquated and then new phases which mixed with η phases, PFZ and MC carbide crystallized during cooling. Crystallized η phases transformed from rod shape to platelet shape with increasing holding time.

단순화된 2차원 자동차형 물체주위의 유동에 관한 실험적 연구 (An Experimental Study on the Flow Around a Simplified 2-Dimensional Vehicle-Like body)

  • 유정열;김사량;강신형;백세진;이택시;김응서
    • 대한기계학회논문집
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    • 제13권1호
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    • pp.178-189
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    • 1989
  • 본 연구에서는 우선 승용차의 1/10 모형의 형상을 더욱 단순화시킨 2차원 자동차형 물체를 대상으로 하여 그 주위의 압력, 속도 및 난류량의 분포를 측정하고, 또한 울터프트(wool tuft)를 이용한 유동가시화법으로 후류구조를 파악함으로써 향후 계속될 실험적 및 수치해석적 연구의 기초를 마련하고자 한다.

무선 센서 네트워크에서 스마트기지국을 이용한 균형된 에너지소비 방안 (A Balanced Energy Consumption Strategy using a Smart Base Station in Wireless Sensor Networks)

  • 박선영
    • 한국멀티미디어학회논문지
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    • 제17권4호
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    • pp.458-465
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    • 2014
  • In this paper, we propose a strategy to distribute the energy consumption over the network. The proposed strategy is based on geographic routing. We use a smart base station that maintains the residual energy and location information of sensor nodes and selects a head node and an anchor node using this information. A head node gathers and aggregates data from the sensor nodes in a target region that interests the user. An anchor node then transmits the data that was forwarded from the head node back to the smart base station. The smart base station extends network lifetime by selecting an optimal head node and an optimal anchor node. We simulate the proposed protocol and compare it with the LEACH protocol in terms of energy consumption, the number of dead nodes, and a distribution map of dead node locations.

NMR Study on the Preferential Binding of the Zα Domain of Human ADAR1 to CG-repeat DNA Duplex

  • Lee, Ae-Ree;Choi, Seo-Ree;Seo, Yeo-Jin;Lee, Joon-Hwa
    • 한국자기공명학회논문지
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    • 제21권3호
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    • pp.90-95
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    • 2017
  • The Z-DNA domain of human ADAR1 ($Z{\alpha}_{ADAR1}$) produces B-Z junction DNA through preferential binding to the CG-repeat segment and destabilizing the neighboring AT-rich region. However, this study could not answer the question of how many base-pairs in AT-rich region are destabilized by binding of $Z{\alpha}_{ADAR1}$. Thus, we have performed NMR experiments of $Z{\alpha}_{ADAR1}$ to the longer DNA duplex containing an 8-base-paired (8-bp) CG-repeat segment and a 12-bp AT-rich region. This study revealed that $Z{\alpha}_{ADAR1}$ preferentially binds to the CG-repeat segment rather than AT-rich region in a long DNA and then destabilizes at least 6 base-pairs in the neighboring AT-rich region for efficient B-Z transition of the CG-repeat segment.

기계적 합금법으로 제조된 MA754 산화물 분산강화 합금의 마찰압접에 관한 연구 (Friction Welding of MA754 ODS Alloy Produced by Mechanical Alloying)

  • 강지훈
    • 한국분말재료학회지
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    • 제1권2호
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    • pp.198-207
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    • 1994
  • In order to find an optimal friction-welding condition for Ni-base ODS alloy (MA 754) produced by mechanical alloying, joint experiments were performed with various conditions of friction pressures (50~500 MPa), friction times (1~5 sec) and upset pressures (50~600 MPa). The optimal friction pressure and upset pressure must be above 400 MPa and 500 MPa, respectively, which are determined by tensile strengths and fracture features of as-welded joints. A maximum stress설h of 975 MPa could be obtained under these pressure conditions at friction time of 2 sec. Microstructural features of bonded interface by optical microscope and SEM revealed that the interface regions of all specimens are consisted with three distinct regions and defects such as voids, cracks and wavy interfaces exist in the joints produced under not-optimized conditions. EDS results showed that these defects include oxides composed with elements of Al, Y and Ti. The hardness on the bonded interface was higher than in the base metal region. Specimens fractured in bonded interface region had lower strength values compared to those fractured in base metal region. Surfaces of the former showed a typical intergranular fracture.

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병합트랜지스터를 이용한 고속, 고집적 ISL의 설계 (Design of a high speed and high intergrated ISL(Intergrated Schottky Logic) using a merged transistor)

  • 장창덕;이용재
    • 한국정보통신학회:학술대회논문집
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    • 한국해양정보통신학회 1999년도 춘계종합학술대회
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    • pp.415-419
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    • 1999
  • Many bipolar logic circuit of conventional occurred problem of speed delay according to deep saturation state of vertical NPN Transistor. In order to remove minority carries of the base region at changing signal in conventional bipolar logic circuit, we made transistor which is composed of NPN transistor shortened buried layer under the Base region, PNP transistor which is merged in base, epi layer and substrate. Also the Ring-Oscillator for measuring transmission time-delay per gate was designed as well. The structure of Gate consists of the vertical NPN Transistor, substrate and Merged PNP Transistor. In the result, we fount that tarriers which are coming into intrinsic Base from Emitter and the portion of edge are relatively a lot, so those make Base currents a lot and Gain is low with a few of collector currents because of cutting the buried layer of collector of conventional junction area. Merged PNP Transistor's currents are low because Base width is wide and the difference of Emitter's density and Base's density is small. we get amplitude of logic voltage of 200mv, the minimum of transmission delay-time of 211nS, and the minimum of transmission delay-time per gate of 7.26nS in AC characteristic output of Ring-Oscillator connected Gate.

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두개저부 종양 절제 및 재건 후 장기 추적관찰 (Long Term Follow-Up after Skull Base Reconstrucion)

  • 진웅식;민경원;허찬영
    • Archives of Plastic Surgery
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    • 제32권2호
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    • pp.175-182
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    • 2005
  • Skull base tumors have been determined inoperable because it is difficult to accurately diagnose the extent of the involvement and to approach and excise the tumor safely. However, recently, the advent of sophisticated diagnostic tools such as computed tomography and magnetic resonance imaging as well as the craniofacial and neurosurgical advanced techniques enabled an accurate determination of operative plans and safe approach for tumor excision. Resection of these tumors may sometimes result in massive and complex extirpation defects that are not amenable to local tissue closure. The purpose of this study is to analyze experiences of skull base reconstruction and to evaluate long term survival rate and complications. All cranial base reconstructions performed from July 1993 to September 2000 at Department of Plastic and Reconstructive Surgery of the Seoul National University Hospital were observed. The medical records were reviewed and analysed to assess the location of defects, reconstruction method, existence of the dural repair, history of preoperative radiotherapy and chemotherapy, complications and causes of death of the expired patients. There were 12 cases in region II, 8 cases in region I and 1 case in region III according to the Irish classification of skull base. Cranioplasty was performed in 4 patients with a bone graft and microvascular free tissue transfer was selected in 17 patients to reconstruct the cranial base and/or mid-facial defects. Among them, 11 cases were reconstructed with a rectus abdominis musculocutaneous free flap, 2 with a latissimus dorsi muscluocutaneous free flap, 1 with a fibular osteocutaneous free flap, 2 with a scapular osteocutaneous free flap, and 1 with a forearm fasciocutaneous free flap, respectively. During over 3 years follow-up, 5 patients were expired and 8 lesions were relapsed. Infection(3 cases) and partial flap loss(2 cases) were the main complications and multiorgan failure(3 cases) by cancer metastasis and sepsis(2 cases) were causes of death. Statistically 4-years survival rate was 68%. A large complex defects were successfully reconstructed by one-stage operation and, the functional results were also satisfactory with acceptable survival rates.

괴산군 일대의 식생 및 식생기반에 관한 연구 (A Study of the Vegetation and Vegetation Base around the Goesan Gun)

  • 윤재로;민현기;주진희;윤용한
    • 한국환경과학회지
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    • 제19권5호
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    • pp.533-541
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    • 2010
  • The purpose of this study is to grasp what characterizes the vegetation base of the natural forest as a latent vegetation in the middle region of Korea and thus to offer basic data when improving the vegetation base in the middle region being built or to be built in the future. The findings of this soil section survey show the following: The soil is brown to red color soil group on the whole. In addition, the soil's physical features like soil hardness are rated as high level, which results from the fact that the forest soil exits in its natural form under less influence of stamping. The pH of soil shows a weak acidity, like Korean normal soil. Specific electrical conductance is also rated as middle to high level in accordance with the standards of landscape architecture. The Salix koreensis community and the Pinus rigida community are different from other communities in terms of total nitrogen, available phosphate and exchangeable $K^+$ content. Specifically, the two communities are opposed to each other in terms of total nitrogen and available phosphate, while being similar to each other in terms of available phosphate and exchangeable $K^+$ content. This seems to result from the fact that they are located near each other. In addition, the two communities are characterized by the fact that they are distributed at the altitude mean relatively lowest and in the valley. To sum up, the forest soil around Goesan Gun is of middle level on the whole according to the landscape standards, when judging it in terms of vegetation base. Accordingly, it seems that the construction of the vegetation base around Goesan Gun will not require large investment expenses for soil improvement. Also, it seems that the spatial scope of research is needed to expand the basic data on the construction of the vegetation base for the whole middle region of Korea.