• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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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.

• Applied Chemistry for Engineering
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• v.16 no.2
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• pp.169-179
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• 2005

Porous materials are useful in a wide range of applications including bio/electronic products. The preparation and processing of these materials are mainly progressed by using an organic solvent, which gives rise to air pollution by its emissions. Alternatively, supercritical fluids are well suited to the production of functional porous materials due to a number of specific physical, chemical, and toxicological advantages. In this review, we will introduce the preparation and processing techniques for the formation of the nano/macro pore structure and their morphology, which can be controled by using supercritical fluids.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.10
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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.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.5
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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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• v.76 no.5
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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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• v.44 no.2
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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.

• Polymer(Korea)
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• v.36 no.3
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• pp.357-363
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• 2012

Surface-modified poly(L-lactic acid) (PLLA) films and scaffolds were treated with plasma discharge in oxygen gas and subsequently subjected to $in$ $situ$ grafting of acrylic acid (AA) in order to increase the cell compatibility. The surface of AA-grafted PLLA was converted to hydroxyapatite (HA)-deposited PLLA in stimulated body fluid (SBF). After the samples were immersed in phosphate-buffered saline (PBS), fetal bovine serum (FBS), normal saline, or cell medium, the water contact angles were significantly reduced on the surface of HA-deposited PLLA. Chondrocyte and osteoblast showed a higher attachment and cell proliferation on HA-deposited surfaces and in particular, it was confirmed that chondrocyte was considerably influenced by HA. However, osteoblast showed better cell proliferation on the surfaces immersed in FBS, cell medium or HA-deposited surface. In addition, the cell proliferation in 3D scaffolds was much higher than that on film type, irrespective of chondrocyte and osteoblast. Therefore, such surface-modified PLLAs are expected to be useful as organic-inorganic hybrid scaffolds in the regeneration of cartilage and bone.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.6
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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.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.1
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• pp.77-82
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• 2010

Our study aims to understand the flow of liquid in an open-top rectangular microchannel that can be used in micro total analysis systems ($\mu$-TAS) because it has advantages in terms of light transmission and energy efficiency. We measured the liquid velocity using particle tracking technique and conducted a simulation with computational fluid dynamics by altering the area of channel cross section and channel length for the capillary-driven flow in the open-top rectangular microchannel. When liquid water drops to an entrance of the fabricated microchannel with a height of 20 μm and a width of 20 ${\mu}m$, it flows along the microchannel by only capillary force. In the wetting behavior of the liquid, important parameters of this flow are channel size, contact angle and liquid properties such as surface tension and viscosity, which are used to control the flow of liquid in the microchannel.

• Science of Emotion and Sensibility
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• v.14 no.4
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• pp.525-530
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• 2011

Emotion is composed of various feelings such as pleasure, sorrow, comfortability, and so on. The complicated process of the measurement has long been recognized as a major hindrance for the studies of emotion. Previously, individuals' emotion has mainly been measured by means of self-report, interview, EEG (electroencephalogram), ECG (electrocardiogram), EOG (electroculography), and body temperature. With thanks to nano/micro technologies, the possibility in the development of emotion-on-a-chip (EOC) has begun to be proposed. EOC will make it possible to analyze one's psychological status by taking a drop of blood. Discovery of emotional biomarkers in body fluids, understanding of the correlation between those biomarkers and the results from brain science are prerequisites to validate the EOC technology. In this paper, paper microfluidics are introduced as a good candidate for the EOC. As paper microfluidics is cost-effective and easy to use it is expected to be a useful device for the emotion measurement. We present the design and fabrication process for the simple paper-based microfluidic device and discuss the possible application in the field of measuring the human emotion.