• Composites Research
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• v.19 no.5
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• pp.20-27
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• 2006

Self-sensing and interfacial evaluation of Ni nanowire/polymer composites were investigated using electro-macromechanical technique, which can be used fur a feasible sensing measurement on tensile and compressive loading/consequent unloading, temperature, and humidity. Mechanical properties of Ni nanowire with different aspect ratio and adding contents in either epoxy or silicone composites were measured indirectly using electro-pullout test under uniform and non-uniform cyclic loadings. Comparing apparent modulus with the conventional mechanical tensile modulus of Ni nanowire/epoxy composites, the trends were consistent with each other. Ni nanowire/epoxy composites showed the sensing response on humidity and temperature. Self-sensing on applied tensile and compressive loading/unloading was also responded for Ni nanowire/silicone composites via electrical contact resistivity showing the opposite trend between tension and compression. It can be due to the different electrically-interconnecting mechanisms of dispersed Ni nanowires embedded in silicone matrix.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.69-69
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• 2011

태양열 발전 플랜트에 사용되는 중고온 범위의 축열조에 고체-액체간 상변화를 수행하는 용융염을 축열물질로 사용하면 액체상 또는 고체상만으로 된 열저장 매체에 비해 축열조의 규모를 축소함과 동시에 축열온도의 균일성 향상에 기여할 수 있다. 중온인 $250{\sim}400^{\circ}C$ 범위에서 이용 가능한 용융염으로는 질산칼륨($KNO_3$), 질산리튬($LiNO_3$)등이 있다. 그러나 이러한 용융염의 가장 큰 단점은 열전도율이 매우 낮다는 것이며, 이로 인해 요구되는 열전달률을 성취하기 위해서는 많은 열접촉면적이 필요하다는 것이다. 이러한 단점을 극복하는 방법을 도입하지 않고서는 축열시스템의 소규화를 성취하는데 큰 효과를 가져올 수 없다. 한편 열수송 성능이 탁월한 히트파이프를 사용하면 열원 및 열침과 축열물질 사이의 열전달 효율을 증가시켜 시스템의 성능 향상과 동시에 소규모화에 기여할 수 있다. 중온 범위 히트파이프의 작동유체로서 다우섬-A(Dowtherm-A)는 $150^{\circ}C$이상 $400^{\circ}C$까지의 범위에서 소수에 불과한 선택적 대안 중 하나이다. 따라서 본 연구에서는 용융염을 사용하는 중온 태양열축열조에 적용 가능한 다우섬-A 히트파이프의 성능을 파악하여 기술적 자료를 제시하고자 하였다. 열원으로는 고온 고압의 과열증기, 그리고 열침으로는 중온의 포화증기를 고려하였다. 용융염 축열조를 수직으로 관통하는 히트파이프는 하단부에서 열원 증기와 열교환 가능하며, 중앙부에서 축열물질과 열교환하고, 상단부에서는 중온 증기와 접촉할 수 있도록 배치하였다. 축열모드에서는 히트파이프의 하단부가 증발부로 작동하고, 중앙부가 응축부로 작동하여 용융염으로 열을 방출하면 용융염의 온도가 상승하고 용융점에 도달하면 액상으로의 상변화가 진행되면서 축열이 활성화된다. 축열모드에서 히트파이프의 상단부는 단열부로 작동한다. 방열과정에서는 히트파이프의 하단부가 단열된 상태이고, 중앙부는 용융염으로부터 열을 받아 증발부로 작동하며, 상단부는 중온 증기로 열을 방출하므로 응축부로 작동한다. 즉, 축열시스템의 작동모드에 따라 하나의 히트파이프에서 증발부, 응축부, 단열부의 위치가 변하게 된다. 특히, 히트파이프의 중앙 부분이 응축부에서 증발부로 전환될 때에도 작동이 보장되려면 내부 작동유체의 연속적인 재순환이 가능해야 하므로, 일반 히트파이프에서와는 달리 초기 작동액체의 충전량을 증발부 전체의 체적보다 더 많이 과충전해야 한다. 이러한 히트파이프의 성능 파악을 위한 실험에서 고려한 변수들은 열부하, 작동액체의 충전률, 작동온도 등이며, 열수송 성능의 지표로서는 유효열전도율과 열저항을 이용하였다. 중온범위에서 적정한 작동온도를 성취하기 위해 실험에서는 전압 조절기로 열부하를 조절하는 동시에 항온조로 응축부의 냉각수 입구 온도를 제어하였다. 하나의 히트파이프에 대해서 최대 1 kW까지의 열부하에서 냉각수 입구 온도를 $40^{\circ}C$에서 $80^{\circ}C$ 범위로 변화시키면 히트파이프 작동온도를 약 $250^{\circ}C$ 내외로 조절 가능하였다. 히트파이프 작동액체 충전률은 윅구조물의 공극 체적을 기준으로 372%에서 420%까지 변화 시켰다. 실험 결과를 토대로 열저항과 유효 열전도율을 각각 입력 열유속, 작동온도, 작동액체 충전률 등의 함수로 제시했다. 동일한 냉각수 온도에서는 충전률이 높을수록 히트파이프의 작동온도가 감소하였다. 열저항 값의 범위는 최소 $0.12^{\circ}C/W$에서 최대 $0.15^{\circ}C/W$까지로 나타났으며 유효 열전도율의 값은 최소 $7,703W/m{\cdot}K$에서 최대 $8,890W/m{\cdot}K$까지 변화했다. 최소 열저항은 충전률 420%인 경우에 나타났는데 이때의 작동온도는 약 $262^{\circ}C$이었다. 히트파이프의 작동한계로서 드라이아웃(dry-out)은 충전률 372%의 경우에 열부하 950 W에서 발생하였으나, 그 이상의 충전률에서는 열부하 1060 W까지 작동한계 발생이 관찰되지 않았다. 실험 결과 본 연구에서의 히트파이프는 중온 태양열 축열조에 적용되어 개당 약 1 kW의 열부하를 이송하면서 축열물질 및 축방열 대상 유동매체와 열교환을 하는데 사용하는데 충분할 것이라 판단된다.

• Korean Chemical Engineering Research
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• v.44 no.6
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• pp.588-596
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• 2006

The surface of polystyrene membrane treated by Ar, $O_2$ plasma, and the effects were observed before and after the treatment and permeability of $CO_2$, $N_2$ and selectivity of $CO_2$ relative to $N_2$ was measured using continuous flow gas permeation analyzer (GPA). The mole ratio of O over C in the surface was increased from 0 to 0.179 with Ar plasma treatment and route mean square of surface was increased from $15.86{\AA}$ to $71.64{\AA}$. Therefore the contact angle was decreased from $89.16^{\circ}$ to $18.1^{\circ}$. Thus Plasma treatments made surface of membrane tend to be highly hydrophilic. The optimum condition for the $CO_2$ permeability and ideal selectivity of the plasma treated membrane was as follows: the measurement of Ar (60 W, 2 min, $70^{\circ}C$) plasma treatment was $1.14{\times}10^{-12}[m^3(STP){\cdot}m/m^2{\cdot}sec{\cdot}atm]$ and 4.22. In the case of $O_2$ plasma treatment, the contact angle was decreased at $13.56^{\circ}$ with increase of O/C ratio ($0.189{\AA}$) and route mean square of surface ($57.10{\AA}$). The optimum condition for the $CO_2$ permeability and ideal selectivity of the plasma treated membrane was as follows: the measurement of $O_2$ (90 W, 2 min, $70^{\circ}C$) plasma treatment was $7.1{\times}10^{-12}[m^3(STP){\cdot}m/m^2{\cdot}sec{\cdot}atm]$ and 11.5. After plasma treatment, the changes of membrane surface were all subtly linked with both cross-linking and etching effects. Finally, it was confirmed that the gas permeation capacity and selectivity of the modified membrane with plasma could be improved by an appropriate control of the plasma conditions such as treatment time, the power input and sort of plasma gas.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.4 no.4
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• pp.79-93
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• 1984

The dissolved air flotation(DAF) has been shown to be efficient process for the removal of algae ftom water. The efficiency of DAF can be affected by the volume ratio of pressurized liquid to sample, the pressure pressurized liquid, the contact time, the appropriate coagulant and its amount, the water temperature, the turbulence of reactor, the bubble size and rising velocity etc. The purpose of this paper is to compare the practical bubble rising velocity with the theoretical one, to investigate the adhesion phenomenon of bubbles and floc, and the influence of bubble size and velocity upon the process. The results through theoretical review and experimental investigation are as follows: Ives' equation is more suitable than Stokes' equation in computation of the bubble rising velocity. The collection of bubble and algae floc is convective collection type and resulted from absorption than adhesion or collision. The treatment efficiency is excellent when the bubble sizes are smaller than $l00{\mu}m$, and the turbulence of reactor is small. In the optimum condition of continuous type DAF the volume ratio of pressurized liquid to sample is 15%, the contact time in reactor is 15 minutes, the pressure of pressurized liquid is $4kg/cm^2$ and the distance from jet needle to inlet is 30cm.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1860-1864
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• 2006

본 연구는 강우시 발생되는 강우유출수와 합류식하수관거월류수에 의해 하천으로 유입되는 오염부하를 저감시키기 위한 공법으로, 고수부지 및 제방사면부와 둔치부를 형상화하여 pilot를 제작하였고, 연속적으로 시운전을 한 SRTS(Stormwater Runoff Treatment System)에 관한 것이다. SRT system 내부의 사면수처리부와 평면수처리부에는 다공성 콘크리트를 충진하였다. system 상부에는 식생을 조성하여 뿌리가 수면에 닿아 영양물질을 흡수하는 목적으로 사면수처리부와 평면수처리부에 각각 정육각형과 직사각형인 식생포트를 탈.부착이 가능하도록 고안하였다. 내부에서는 토양과 수처리조 사이에 연결관을 부착하였고, 모세관현상에 의해 토양이 수분을 흡수하도록 구성하였다. pilot plant는 유입부, 사면 수처리부, 평면 수처리부, 유출부로 나누었다. 유입부는 유입펌프와 V-notch로 구성하였고, 유입펌프는 2대를 설치하여 1시간 간격으로 연속적 유입으로 유량조절이 가능하도록 상호교대 운전을 하였다. 평면 수처리부$(W(1.0m){\times}(L(2.4m){\times}H(0.6m))$는 장방형의 접촉산화조로서 하부에 슬러지 침전 및 저류를 위한 hopper를 설치하여 슬러지의 원활한 수집 및 인발이 가능하도록 하였다. 유출부는 사각weir를 설치하였다. 강우유출수의 pH는 $7.27{\sim}7.92$이고, DO농도는 $7.12{\sim}7.88mg/l$로 관측되었다. 2차처리수의 pH는 평균7.4이고 DO농도는 최저 4.5 mg/l에서 최고 8.9 mg/l로 평균 6.8 mg/l로 관측되었다. 또한 강우유출수의 유입수의 T-N, T-P 농도는 각각 $17.5{\sim}22.5mg/l,\;8.9{\sim}11.4mg/l$의 범위이고, 2차 처리수의 유입수의 T-N, T-P 농도와 유사하였다.적인 방법론을 제시할 수 있을 것으로 사료된다.첨두홍수량을 저류하기 위해서 상대적으로 넓은 저류면적이 필요한 것으로 나타난다. 대등한 수위감소값의 홍수저감효과를 발휘하기 위해서 본 연구에서는 On-Line 저류지 면적은 Off-Line 저류지에 비 두배 이상이 필요한 것으로 보여졌다.들에 관한 정보는 종종 현장관측에서 조차 무시되는 경우가 많다. 이에 본 연구에서는 수질모형의 매개변수 중 특히 수리특성에 관련된 매개변수들이 수질에 미치는 영향을 파악하는 것을 목적으로 하고 있다. 이를 위해 적용된 수질모형은 QualKo를 사용하였으며, 대상 하천은 낙동강 본류 경남구간 시점 부근인 회천 합류 전부터 낙동강 본류 경남구간 종점 부근인 밀양강 합류 전까지의 경남 오염총량관리 기본계획 시 구축된 모형 매개변수를 바탕으로 분석을 수행하였다. 일차오차분석을 이용하여 수리매개변수와 수질매개변수의 수질항목별 상대적 기여도를 파악해 본 결과, 수리매개변수는 DO, BOD, 유기질소, 유기인 모든 항목에 일정 정도의 상대적 기여도를 가지고 있는 것을 알 수 있었다. 이로부터 수질 모형의 적용 시 수리 매개변수 또한 수질 매개변수의 추정 시와 같이 보다 세심한 주의를 기울여 추정할 필요가 있을 것으로 판단된다.변화와 기흉 발생과의 인과관계를 확인하고 좀 더 구체화하기 위한 연구가 필요할 것이다.게 이루어질 수 있을 것으로 기대된다.는 초과수익률이 상승하지만, 이후로는 감소하므로, 반전거래전략을 활용하는 경우 주식투자기간은 24개월이하의 중단기가 적합함을 발견하였다. 이상의 행태적 측면과 투자성과측면의 실증결과를 통하여 한국주식시장에 있어서 시장수익률을 평균적으로 초과할 수 있는 거래전략은 존재하므로 이러한 전략을 개발 및 활용할 수 있으며, 특히, 한국주식시장에 적합한 거래전략은 반전거래전략이고, 이 전략의 유용성은 투자자가 설정한 투자기간보다 더욱 긴 분석기간의 주식가격정보에 의하여 최대한 발휘될 수 있음을 확인하

• Korean Chemical Engineering Research
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• v.46 no.3
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• pp.451-464
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• 2008

Three-phase inverse fluidized bed has been widely adopted with its increasing demand in the fields of bioreactor, fermentation process, wastewater treatment process, absorption and adsorption processes, where the fluidized or suspended particles are small or lower density comparing with that of continuous liquid phase, since the particles are frequently substrate, contacting medium or catalyst carrier. However, there has been little attention on the three-phase inverse fluidized beds even on the hydrodynamics. Needless to say, the information on the hydrodynamics and transport phenomena such as heat and mass transfer in the inverse fluidized beds has been essential for the operation, design and scale-up of various reactors and processes which are employing the three-phase inverse beds. In the present article, thus, the information on the three-phase inverse fluidized beds has been summarized and reorganized to suggest a pre-requisite knowledge for the field work in a sense of engineering point of view. The article is composed of three parts; hydrodynamics, heat and mass transfer characteristics of three-phase inverse fluidized beds. Effects of operating variables on the phase holdup, bubble properties and particle fluctuating frequency and dispersion were discussed in the section of hydrodynamics; effects of operating variables on the heat transfer coefficient and on the heat transfer model were discussed in the section of heat transfer characteristics ; and in the section of mass transfer characteristics, effects of operating variables on the liquid axial dispersion and volumetric liquid phase mass transfer coefficient were examined. In each section, correlations to predict the hydrodynamic characteristics such as minimum fluidization velocity, phase holdup, bubble properties and particle fluctuating frequency and dispersion and heat and mass transfer coefficients were suggested. And finally suggestions have been made for the future study for the application of three-phase inverse fluidized bed in several available fields to meet the increasing demands of this system.

• Journal of the Korean Arthroscopy Society
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• v.12 no.3
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• pp.172-179
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• 2008

Purpose: To evaluate the functional and structural results of arthroscopic double-row repair using combined knot-tying and knotless suture anchors in rotator cuff tears. Materials and Methods: From March 2006 to June 2007, twenty-one patients (15 males, 6 females; mean age 55.6 years; range 48 to 67) were included who underwent arthroscopic double-row repair for full-thickness tears of the rotator cuff following conservative treatment for a mean of 6.5 months (range 3 to 11). The tear size was carefully inspected arthroscopically and we found 2 small, 13 medium and 6 large-sized rotator cuff tears, with a mean tear size of 2.5cm(range 1.8 to 3.2). The repair constructs were consisted of horizontal mattress sutures using conventional knot-tying suture anchors medially and simple suture at the same level of medial row stitch with Bioknotless RC anchors (DePuy Mitek, Norwood, MA) as lateral row. Clinical and functional evaluations were made according to the range of motion, the ASES, UCLA scale and the isokinetic strength testing. Postoperative cuff integrity was determined through magnetic resonance imaging. The mean follow-up was 15 months (range 13 to 24). Results: The average clinical outcome scores and strength were all improved significantly at the time of the final follow-up (p < 0.01). Nineteen patients (90%) were satisfied with the result of the treatment. In 17 of 21 patients (81%) were judged to reveal healed tendon on magnetic resonance imaging at a mean of 7 months postoperatively. There were no significant functional differences according to the preoperative tear size (p<0.01), but large-sized tear shows less favorable structural results in 3 out of 6 cases(50%). Conclusion: Our results document the usefulness and variability of arthroscopic double-row rotator cuff repairs comparable to the results of the other types of double-row repairs.

• Economic and Environmental Geology
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• v.11 no.4
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• pp.127-141
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• 1978

The major structures characteristic of the Taebaegsan sedimentary basin were regionally analyzed with special reference to its southeastern extension to the Yeonhwa-Ulchin district of economic interest in zinc-lead mineralization. The basin geometry, basement setting, sedimentary components, and the characteristics of deformation and igneous activity of the Taebaegsan basin differ basically from those of the adjacent mobile belt of the Ogcheon geosyncline, although the latter affected the basin's western side considerably. The subrectangular shape of the Taebaegsan basin reflects the checkered pattern of basement-block arrangement, and the carbonate-dominated lithologic components of the basin-fill indicate a cratonic depositional setting, which is comparable to some of the North American mid-continental craton. The Taebaegsan basin, however, has somewhat been less stable than the North American megacraton that is reflected in the former's thicker sedimentary fill and steeper faults of later deformation, showing a tendency to increase in thickness close to the basement-block boundaries, which may indicate contacts of possibly detached cratonic blocks of Precambrian age; these weak zones of block boundaries have been the loci of repeated sedimentation, deformation and related igneous intrusions. A series of downthrown or uplifted tilted blocks, in which the Cambro-Ordovician sedimentary wedges and the late Cretaceous to early Tertiary igneous intrusives are involved, occurs intermittently across the Yeonhwa-Ulchin district in a noticeable pattern of en echelon type. These sedimentary wedges are correlated to the Cambro-Ordovician section of the Hambaeg syncline to the west in stratigraphy and lithology, and are considered to have resulted from the northeastern and/or northwestern cross-faulting of the pre-existing syncline belt of easterly trend, extended from the main portion of the Hambaeg syncline. These structural junctions (or intersections) of the earlier syncline belt and the later cross-faults have been acted as a guide to ascending igneous materials and hydrothermal ore-forming fluids to form a zone of zinc-lead skarn deposits across the Yeonhwa-Ulchin district showing a stepwise recurrence of these deposits toward the east.

• The Korean Journal of Nuclear Medicine Technology
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• v.13 no.1
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• pp.93-97
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• 2009

Purpose: Recognize circulation work system and fixing work system's merits and demerits that is enforced in operation of PET/CT center in sudden increase recently. Wish to estimate connectivity degree of individual exposure dose and PET/CT working that is managed periodically through this and look for operation efficiency of PET/CT center. Materials and Methods: (1) Find interrelationship of length of service to be individual exposure dose and PET/CT through TLD interpretation. Specially, evaluate on the basis of data of 2.5 years until 2 quarters 2006~2008 year that show patient increase rapidly the latest. (2) Recognize what countermeasure is evaluating problems happened at circulation work system and fixing work system. Results: Patient examination's number was 14,674 items until 2 quarters 2006~2008 year, and the $^{18}F$-FDG average injection amount was 461.5 MBq. 2 people of 10 radiotechnologist did fixing work PET area and GAMMA area each, and 8 people did circulation work of 3 times for 2.5 years. Average exposure dose that PET area and Gamma area's circulation men in service receive was 1.32 mSv, and PET area men in services came out average 0.825 mSv high than Gamma area men in services. Nurse's exposure dose is 0.28 mSv, and next 2 reason is conjectured. One is contact with patient that medicate $^{18}F$-FDG injection, and another is consultation about patient's next time schedule after examination end. Although exposure dose's amount is not much, is expected to consider continuation work possibility by exposure dose in case is a nurse with pregnancy possibility. Also, $^{131}I$-isotope therapy area's radiotechnologist that use capsule appeared by 0.12 mSv and a nuclear medicine doctor appeared by exposure dose that is less of 0.11 mSv. Conclusions: In case do PET/CT center circulation work after a long time, connoted danger that most men in service is consecutiveness deficiency of business and individual exposure dose increase at early 1 month. Specially, way for individual exposure dose's decrease should be considered. Also, need to evaluate abhorrent work form for efficient work system introduction, and enforce circulation and fixing work suggestion suitable shift working. Finally, must make normalized business guide and so on to prevent circulation work people's business efficiency decline.

• Journal of Bio-Environment Control
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• v.20 no.2
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• pp.93-100
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• 2011

Maintenance of adequate soil water potential during the period of crop growth is necessary to support optimum plant growth and yields. A better understanding of soil water movement within and below the rooting zone can facilitate optimal irrigation scheduling aimed at minimizing the adverse effects of water stress on crop growth and development and the leaching of water below the root zone which can have adverse environmental effects. The objective of this study was to evaluate the feasibility of using a portable irrigation controller with an Watermark sensor for the cultivation of drip-irrigated vegetable crops in a greenhouse. The control capability of the irrigation controller for a soil water potential of -20 kPa was evaluated under summer conditions by cultivating 45-day-old tomato plants grown in three differently textured soils (sandy loam, loam, and loamy sands). Water contents through each soil profile were continuously monitored using three Sentek probes, each consisting of three capacitance sensors at 10, 20, and 30 cm depths. Even though a repeatable cycling of soil water potential occurred for the potential treatment, the lower limit of the Watermark (about 0 kPa) obtained in this study presented a limitation of using the Watermark sensor for optimal irrigation of tomato plants where -20 kPa was used as a point for triggering irrigations. This problem might be related to the slow response time and inadequate soil-sensor interface of the Watermark sensor as compared to a porous and ceramic cup-based tensiometer with a sensitive pressure transducer. In addition, the irrigation time of 50 to 60 min at each of the irrigation operation gave a rapid drop of the potential to zero, resulting in over irrigation of tomatoes. There were differences in water content among the three different soil types under the variable rate irrigation, showing a range of water contents of 16 to 24%, 17 to 28%, and 24 to 32% for loamy sand, sandy loam, and loam soils, respectively. The greatest rate increase in water content was observed in the top of 10 cm depth of sandy loam soil within almost 60 min from the start of irrigation.