• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.49-49
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• 2010

Nanopiezotronics is an emerging area of nanotechnology with a variety of applications that include piezoelectric field-effect transistors and diodes, self-powered nanogenerators and biosystems, and wireless nano/biosensors. By exploiting coupled piezoelectric and semiconducting characteristics, it is possible for nanowires, nanobelts, or nanorods to generate rectifying current and potential under external mechanical energies such as body movement (handling, winding, pushing, and bending) and muscle stretching, vibrations (acoustic and ultrasonic waves), and hydraulic forces (body fluid and blood flow). Fully transparent, flexible (TF) nanogenerators that are operated by external mechanical forces will be presented. By controlling the density of the seed layer for ZnO nanorod growth, transparent ZnO nanorod arrays were grown on ITO/PES films, and a TF conductive electrode was stacked on the ZnO nanorods. The resulting integrated TF nanodevice (having transparency exceeding 70 %) generated a noticeable current when it was pushed by application of an external load. The output current density was clearly dependent on the force applied. Furthermore, the output current density depended strongly on the morphology and the work function of the top electrode. ZnO nanorod-based nanogenerators with a PdAu, ITO, CNT, and graphene top electrodes gave output current densities of approximately $1-10\;uA/cm^2$ at a load of 0.9 kgf. Our results suggest that our TF nanogenerators are suitable for self-powered TF device applications such as flexible self-powered touch sensors, wearable artificial skins, fully rollable display mobile devices, and battery supplements for wearable cellular phones.

• 공업화학
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• 제16권2호
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• pp.169-179
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• 2005

다공성 소재는 바이오 및 전기전자소재 등 다양한 분야에 폭넓게 응용될 수 있다. 이러한 가공소재의 제조 및 공정은 주로 유기용매의 사용에 의해 이루어지고 있으나 유기용매는 대기 방출과 같은 많은 환경성 문제를 야기시키고 있다. 이에 반하여 초임계 유체는 기능성 기공 소재의 제조를 위한 대안 용매로서 수많은 물리적, 화학적 그리고 유독성 측면에서 유용한 장점을 보여주고 있다. 본 총설에서는 초임계 유체를 이용하여 나노/마크로 크기의 미세 기공구조 설계 및 형상 제어를 위한 공정 기술과 초임계 유체 내에서의 화학적 합성 반응을 통한 다공성 소재의 제조 기술을 소개하고자 한다.

• 설비공학논문집
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• 제18권10호
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• pp.826-834
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• 2006

A heat sink system using nanofluidic thermosyphon for electronics systems was studied. The experimental results indicate that a cooling capacity of up to 150 W at an overall temperature difference of $50^{\circ}C$ can be attainable. The heat sink design program also showed that a computer simulation can predict the most of the parameters involved. In the experimental study, the volume concentration of nano particles affect the system performance. Nanofluidic thermosyphon with 0.5% volume concentration showed the best performance. Nanofluid can increase CHF of the system compared with water as a working fluid. The current simulation results were close to the experimental results in acceptable range. The simulation study showed that the design program can be a good tool to predict the effects of various parameters involved in the optimum design of the heat sink.

• 한국기계가공학회지
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• 제18권5호
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• pp.60-65
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• 2019

Since nanofluids (NFs), which are a mixture of a small amount of nanoparticles and a bulk liquid solvent, were first proposed by Stephen Choi at the Argonne National Lab in 1995, they have been considered for use in many technical studies of power cooling systems and their practical application due to their high thermal conductivity and heat transfer coefficients compared to conventional coolants. Although nanofluids are a well-known form of engineering fluid that show great promise for use in future cooling systems, their underlying physics as demonstrated in experiments remain unclear. One proven method of determining the heat transfer performance of nanofluids is measuring the concentration of nanoparticles in a mixture. However, it is experimentally inefficient to build testbeds to systematically observe particle distributions on a nanoscale. In this paper, we demonstrate the distribution of nanoparticles under a temperature gradient in a solution using molecular dynamics simulations. First, temperature profiles based on substrate temperature are introduced. Following this, the radial pair distribution functions of pairs of nanoparticles, solvents, and substrates are calculated. Finally, the distribution of nanoparticles in different heating regions is determined.

• Structural Engineering and Mechanics
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• 제76권5호
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• pp.561-578
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• 2020

The present work addresses the surface integrity and chip morphology in finish hard turning of AISI D3 steel under nanofluid assisted minimum quantity lubrication (NFMQL) condition. The surface integrity aspects include microhardness, residual stress, white layer formation, machined surface morphology, and surface roughness. This experimental investigation aims to explore the feasibility of low-cost multilayer (TiCN/Al2O3/TiN) coated carbide tool in hard machining applications and to assess the propitious role of minimum quantity lubrication using graphene nanoparticles enriched eco-friendly radiator coolant based nano-cutting fluid for machinability improvement of hardened steel. Combined approach of central composite design (CCD) - analysis of variance (ANOVA), desirability function analysis, and response surface methodology (RSM) have been subsequently employed for experimental investigation, predictive modelling and optimization of surface roughness. With a motivational philosophy of "Go Green-Think Green-Act Green", the work also deals with economic analysis, and sustainability assessment under environmental-friendly NFMQL condition. Results showed that machining with nanofluid-MQL provided an effective cooling-lubrication strategy, safer and cleaner production, environmental friendliness and assisted to improve sustainability.

• Clinical and Experimental Reproductive Medicine
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• 제44권2호
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• pp.63-72
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• 2017

Objective: Hyperstimulation methods are broadly used for in vitro fertilization (IVF) in patients with infertility; however, the side effects associated with these therapies, such as ovarian hyperstimulation syndrome (OHSS), have not been well studied. N-glycoproteomes are subproteomes used for the remote sensing of ovarian stimulation in follicular growth. Glycoproteomic variation in human follicular fluid (hFF) has not been evaluated. In this study, we aimed to identify and quantify the glycoproteomes and N-glycoproteins (N-GPs) in natural and stimulated hFF using label-free nano-liquid chromatography/electrospray ionization-quad time-of-flight mass spectrometry. Methods: For profiling of the total proteome and glycoproteome, pooled protein samples from natural and stimulated hFF samples were selectively isolated using hydrazide chemistry to obtain the total proteomes and glycoproteomes. N-GPs were validated by the consensus sequence N-X-S/T (92.2% specificity for the N-glycomotif at p<0.05). All data were compared between natural versus hyperstimulated hFF samples. Results: We detected 41 and 44 N-GPs in the natural and stimulated hFF samples, respectively. Importantly, we identified 11 N-GPs with greater than two-fold upregulation in stimulated hFF samples compared to natural hFF samples. We also validated the novel N-GPs thyroxine-binding globulin, vitamin D-binding protein, and complement proteins C3 and C9. Conclusion: We identified and classified N-GPs in hFF to improve our understanding of follicular physiology in patients requiring assisted reproduction. Our results provided important insights into the prevention of hyperstimulation side effects, such as OHSS.

• 폴리머
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• 제36권3호
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• pp.357-363
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• 2012

Poly(L-lactic acid)(PLLA) 고분자 필름 및 지지체의 세포 친화성을 향상시키기 위하여 산소 플라즈마 처리후 카복실기를 함유한 아크릴산(AA)을 $in$ $situ$ 그래프트시켰다. Stimulated body fluid(SBF) 용액에 15일간 담지시킨 후 hydroxyapatite(HA)를 형성시킨 시료와 phosphate-buffered saline(PBS), fetal bovine serum(FBS), 식염수 및 세포 배양용 배지에 담지시킨 다음 PLLA 시료 표면의 접촉각을 비교해 본 결과, HA 표면이 가장 낮은 접촉각을 나타내었다. 또한 연골세포와 조골세포는 HA 표면 위에서 높은 점착과 성장을 보였으며 연골세포가 HA에 많은 영향을 받는 것으로 확인되었다. 조골세포의 경우 HA 표면 이외에도 FBS나 세포 배양배지에 담지된 표면에서도 높은 세포 증식을 보였다. 더욱이 필름형태보다는 3차원 입체 구조의 다공성 지지체에서 연골세포와 조골세포의 점착과 세포 증식이 향상됨도 확인할 수 있었다. 이러한 표면개질된 PLLA는 조직공학적으로 연골이나 뼈 재생을 위한 유-무기 하이브리드 지지체로 응용될 수 있을 것으로 기대된다.

• 설비공학논문집
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• 제20권6호
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• pp.427-446
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• 2008

A review on the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2006 has been accomplished. Focus has been put on current status of research in the aspect of heating, cooling, ventilation, sanitation and building environments. The conclusions are as follows. (1) The research trends of fluid engineering have been surveyed as groups of general fluid flow, fluid machinery and piping, etc. New research topics include micro heat exchanger and siphon cooling device using nano-fluid. Traditional CFD and flow visualization methods were still popular and widely used in research and development. Studies about diffusers and compressors were performed in fluid machinery. Characteristics of flow and heat transfer and piping optimization were studied in piping systems. (2) The papers on heat transfer have been categorized into heat transfer characteristics, heat exchangers, heat pipes, and two-phase heat transfer. The topics on heat transfer characteristics in general include thermal transport in a cryo-chamber, a LCD panel, a dryer, and heat generating electronics. Heat exchangers investigated include pin-tube type, plate type, ventilation air-to-air type, and heat transfer enhancing tubes. The research on a reversible loop heat pipe, the influence of NCG charging mass on heat transport capacity, and the chilling start-up characteristics in a heat pipe were reported. In two-phase heat transfer area, the studies on frost growth, ice slurry formation and liquid spray cooling were presented. The studies on the boiling of R-290 and the application of carbon nanotubes to enhance boiling were noticeable in this research area. (3) Many studies on refrigeration and air conditioning systems were presented on the practical issues of the performance and reliability enhancement. The air conditioning system with multi indoor units caught attention in several research works. The issues on the refrigerant charge and the control algorithm were treated. The systems with alternative refrigerants were also studied. Carbon dioxide, hydrocarbons and their mixtures were considered and the heat transfer correlations were proposed. (4) Due to high oil prices, energy consumption have been attentioned in mechanical building systems. Research works have been reviewed in this field by grouping into the research on heat and cold sources, air conditioning and cleaning research, ventilation and fire research including tunnel ventilation, and piping system research. The papers involve the promotion of efficient or effective use of energy, which helps to save energy and results in reduced environmental pollution and operating cost. (5) Studies on indoor air quality took a great portion in the field of building environments. Various other subjects such as indoor thermal comfort were also investigated through computer simulation, case study, and field experiment. Studies on energy include not only optimization study and economic analysis of building equipments but also usability of renewable energy in geothermal and solar systems.

• 대한기계학회논문집B
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• 제34권1호
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• pp.77-82
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• 2010

소형분석시스템에서 미세채널의 상판이 제거되면 상판에 의한 빛 에너지 손실이 대폭 감소되어 광학측정법으로 대상을 분석할 때 장점을 갖는다. 본 연구에서는 상판이 없는 사각단면 미세채널 내 액체유동을 이해하려는 목적으로 실험과 전산유체역학 해석을 수행하였다. 개방형 사각단면 미세채널에서 입자추적기법으로 유속을 측정하였고, 채널의 단면적 변화에 따른 모세관 유동현상을 이론적으로 해석하였다. 단면의 너비와 높이가 각각 20 ${\mu}m$로 제작된 미세채널의 주입부에 물을 떨어뜨렸을 때 물은 오직 모세관 힘에 의해 미세채널을 따라 이동하였다. 액체의 젖음현상에 영향을 미치는 중요한 유동 파라미터는 채널의 크기와 표면장력, 점성 등으로 볼 수 있으며, 미세채널에서 액체 유동을 조절하는데 이용될 수 있다.

• 감성과학
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• 제14권4호
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• pp.525-530
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• 2011

감성은 외부의 물리/화학적인 자극에 대한 인간 내부의 고차원적인 심리적 체험으로 기쁨, 슬픔, 쾌적, 불쾌 등에 대한 복합적인 감정이라 할 수 있다. 감성연구의 가장 큰 어려움은 측정의 문제이다. 기존 감성측정은 자기보고, 인터뷰, 뇌파 및 자율 신경계 반응, 심장혈관 활동도 등에 국한되어 있다. 최근 나노마이크로 기술의 발달과 함께 미래에는 체액 내 감성 바이오마커를 찾아내고 그것의 유무와 뇌 과학 연구결과와의 상관관계를 규명하고 피 한 방울로 인간의 심리상태를 정확히 파악할 수 있는 초소형 감성진단칩(emotion-on-a-chip)을 개발하게 할 수 있을 것으로 기대된다. 또한 종이를 이용한 종이 미세유체(paper microfluidic) 기술이 발달하고 이를 이용한 질병진단을 할 수 있음이 보고된 바 있다. 종이기반 미세유체채널은 그 제작비용이 저렴하며, 누구나 손쉽게 사용할 수 있어서 미래에 감성진단을 위한 도구로 활용할 수 있다. 본지에서는 아직까지 감성측정분야에 도입되지 않은 종이 미세유체 기술을 소개하고 향후 다양한 감성지표를 측정할 수 있는 아주 간단한 구조의 종이 기반 미세유체 디바이스의 설계 및 제작에 대해 기술한다.