• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.2
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• pp.291-299
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• 2002

This paper characterizes hi-directionally oscillating flow in planar microdiffusers in order to evaluate the frequency-dependent flow rectification performance of the microdiffusers. In the theoretical study, we analyze a hi-directionally oscillating flow in the planar microdiffuser. In the experimental study, we fabricate two different microdiffuser prototypes, having different neck widths of 100 ㎛ (D100) and 300 ㎛(D300), respectively. The experimental net flow rates are measured as 116.6 $\mu$ι/min. and 344.4 $\mu$ι/min. for D100 and D300, respectively. The experimental flow rate of D300 decreases at the oscillating flow frequencies higher than 90Hz, at which the net boundary layer thickness is reduced to the microdiffuser neck width. It is experimentally verified that the flow rectification performance and the net flow rate of the microdiffusers tend to decrease when the boundary layer thickness is smaller than the diffuser neck width.

• Journal of Physiology & Pathology in Korean Medicine
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• v.30 no.5
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• pp.347-354
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• 2016

This study evaluated the effects of Fructus Corni Officinalis water extract (FCE) on congnitive impairment and Aβ clearance induced by beta amyloid Aβ (1-42) injection in the hippocampus of rat. Aβ (1-42) was injected into the hippocampus using a Hamilton syringe and micropump (5 ㎍/5 ㎕, 1 ㎕/min, each hippocampus bilaterally). FCE was administered orally once a day (100, 250, 500 mg/kg) for 4 weeks after the Aβ (1-42) injection. The acquisition of learning and retention of memory were tested using the Morris water maze. Aβ accumulation and Aβ clearance in the hippocampus were observed using immunostaining. Aβ (1-42) level in plasma was confirmed using enzyme-linked immunosorbent assay (ELISA). FCE significantly shortened the escape latencies during acquisition training trials. FCE significantly increased the number of target heading to the platform site and significantly shortened the time for the 1^sttargetheadingduringtheretentiontesttrial.FCEsignificantlyattenuatedtheAβ accumulation in the hippocampus produced by Aβ (1-42) injection. FCE significantly increased LRP-1 expression around vessels in the hippocampus and Aβ (1-42) levels in plasma. The results suggest that FCE improved cognitive impairment by ameliorate Aβ clearance and Aβ accumulation in the hippocampus. FCE may be a beneficial herbal formulation in treating cognitive impairment including Alzheimer's disease.

• Journal of Sensor Science and Technology
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• v.13 no.6
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• pp.473-478
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• 2004

This study focused on the charateristic of magnetic fluids, the viscosity deviation of magnetic fluids due to temperature changes, and fabrication of a 'purely' liquid type microvalve. The viscosity of magnetic fluids decreases sharply during increasing of temperature. The viscosity of magnetic fluids is rated 1,000 cP at the room temperature and 25 cP when the temperature reaches $100^{\circ}C$. Briefly, it is remarkable that the fluid flow can be controlled by the temperature and this characteristic can be adopted to the microfluidics as a microvalve. The fabrication of a liquid type microvalve is more easy than solid state microvalves and which can increase an efficiency of the controlability with respect to the thermo-pneumatic micropump which is studied broadly for many years. When the magnetic fluid used as a sealant for high level sealing, the pressure leakage is less than solid state microvalve. The experimental results show that the pressure drop in microchannel, filled with the magnetic fluid, is significant in the temperature range of $20^{\circ}C{\sim}50^{\circ}C$ and this result explains why the use of magnetic fluids is possible as a microvalve searcher uses this characteristics. Well known thermo-pnumatic.

• Journal of the Microelectronics and Packaging Society
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• v.20 no.3
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• pp.1-6
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• 2013

3D integrated circuit(IC) technology with TSV(through Si via) liquid cooling system is discussed. As a device scales down, both interconnect and packaging technologies are not fast enough to follow transistor's technology. 3D IC technology is considered as one of key technologies to resolve a device scaling issue between transistor and packaging. However, despite of many advantages, 3D IC technology suffers from power delivery, thermal management, manufacturing yield, and device test. Especially for high density and high performance devices, power density increases significantly and it results in a major thermal problem in stacked ICs. In this paper, the recent studies of TSV liquid cooling system has been reviewed as one of device cooling methods for the next generation thermal management.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.5
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• pp.567-573
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• 2014

Since the development of microelectromechanical systems (MEMS) technology for the medical field, various micro-fluid transfer systems have been studied. This paper proposes a micro-piezoelectric pump that imitates a stomach's peristalsis by using two separate piezoelectric elements, in contrast to existing micro-pumps. This piezoelectric pump is operated by using the valve-less traveling wave of peristalsis movement. If the piezoelectric plates at the two separated plates are actuated at the input voltage, a traveling wave occurs between the two plates. Then, the fluid migrates by the pressure difference generated by the traveling wave. Finite element analysis was performed to understand the mechanics of the combined system with piezoelectric elements, elastic structures, and fluids. The effects of design variables such as the chamber height and number of ceramics on the flow rate of the fluid were examined.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1645-1646
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• 2006

Micro ElectroMechanical Systems (MEMS) 기술을 이용한 초미세 유체 제어 시스템 (마이크로 펌프, 마이크로 밸브, 마이크로 채널, 마이크로 믹서 등)은 화학, 생명분야의 DNA 분석, 항원-항체 분석, 질병의 진단 등에 사용되는 lab-on-a-chip, micro total analysis system ($\mu$-TAS) 등에서 화학 및 바이오 유체를 제어하는 분석 시스템의 일부분으로서 사용되며 필수적으로 요구된다. 본 논문에서는 이러한 microchip을 구현하기 위해 초미세 유체 제어 소자인 마이크로 펌프와 밸브를 같은 기관 위에 polydimethylsiloxane (PDMS)와 indium tin oxide (ITO)-Glass를 사용하여 동일한 구조로 집적 하였다. 마이크로 펌프의 pumping rate은 인가 직류 펄스 전력의 주파수와 duty 비를 변화시켜 최적화하였다. 직류 펄스 전력 500 mW를 인가하였을 때 주파수 2 Hz, duty 비 7 %에서 약 $1.05{\mu}l/min$의 최대 유량이 측정되었다. 마이크로 밸브는 ITO 히터에 전력을 인가함으로서 유량의 on/off 제어가 잘 됨을 확인할 수 있었고 유체를 closing하기 위해 필요한 전력은 약 300 mW이다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.6
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• pp.544-551
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• 2005

The flow characteristics have been numerically investigated for various shapes of the diffuser/nozzles which are used for a valveless micro-pump. The important parameters considered in this study are the throat width ($15\~120\mu$m), the taper angle ($3.15\~25.2^{\circ}$), and the diffuser length ( $600\~4,800\mu$m), and the size of the middle chamber ($1\~16mm^2$). To find the optimal values for these parameters, steady state calculations have been performed assuming the constant pressure difference between the inlet and exit of the flow For the taper angle and the throat width, it is found that there exists an optimum at which the net flow rate is the greatest. The optimal taper angle is in the range of $10\~20^{\circ}$ for all the pressure differences; and the throat width indicates an optimal value near $75\mu$m for the case of 35 kPa pressure difference. The net flow rate is also influenced by the size of the middle chamber. With decreasing chamber size, the net flow rate is reduced because of the interference between two streams flowing into the middle chamber. The unsteady pulsating flow characteristics for a micro-pump with a given diffuser/nozzle shape have been also investigated to show the validity of the steady state parametric study.

• The Journal of Korean Medicine
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• v.35 no.4
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• pp.10-23
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• 2014

Objectives: This study evaluated the effects of Guibi-tang (GBT) on neuronal apoptosis and cognitive impairment induced by beta amyloid ($A{\beta}$), (1-42) injection in the hippocampus of ICR mice. Methods: $A{\beta}$ (1-42) was injected unilaterally into the lateral ventricle using a Hamilton syringe and micropump ($2{\mu}g/3{\mu}{\ell}$, $0.6{\mu}{\ell}/min$). Water extract of GBT was administered orally once a day (500 mg/kg) for 3 weeks after the $A{\beta}$ (1-42) injection. Acquisition of learning and retention of memory were tested using the Morris water maze. Neuronal damage and $A{\beta}$ accumulation in the hippocampus was observed using cresyl violet and Congo red staining. The anti-apoptotic effect of GBT was evaluated using TUNEL labeling in the hippocampus. Results: GBT significantly shortened the escape latencies during acquisition training trials. GBT significantly increased the number of target headings to the platform site, the swimming time spent in the target quadrant, and significantly shortened the time for the 1st target heading during the retention test trial. GBT significantly attenuated the reduction in thickness and number of CA1 neurons, and $A{\beta}$ accumulation in the hippocampus produced by $A{\beta}$ (1-42) injection. GBT significantly reduced the number of TUNEL-labeled neurons in the hippocampus. Conclusion: These results suggest that GBT improved cognitive impairment by reducing neuronal apoptosis and $A{\beta}$ accumulation in the hippocampus. GBT may be a beneficial herbal formulation in treating cognitive impairment including Alzheimer's disease.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.12
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• pp.844-861
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• 2008

The papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during the year of 2007 have been reviewed. 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 nano fluid, micropump and fuel cell. Traditional CFD was still popular and widely used in research and development. Studies about fans and pumps were performed in the field of fluid machinery. Characteristics of flow and fin shape optimization are studied in the field of piping system. (2) The research works on heat transfer have been reviewed in the field of heat transfer characteristics, heat exchangers, and desiccant cooling systems. The research on heat transfer characteristics includes thermal transport in pulse tubes, high temperature superconductors, ground heat exchangers, fuel cell stacks and ice slurry systems. For the heat 'exchangers, the research on pin-tube heat exchanger, plate heat exchanger, condensers and gas coolers has been cordially implemented. The research works on heat transfer augmenting tubes have been also reported. For the desiccant cooling systems, the studies on the design and operating conditions for desiccant rotors as well as performance index are noticeable. (3) In the field of refrigeration, many papers were presented on the air conditioning system using CO2 as a refrigerant. The issues on the two-stage compression, the oil selection, and the appropriate oil charge were treated. The subjects of alternative refrigerants were also studied steadily. Hydrocarbons, DME and their mixtures were considered and various heat transfer correlations were proposed. (4) Research papers have been reviewed in the field of building facilities by grouping into the researches on heat and cold sources, air conditioning and air cleaning, ventilation and fire research including tunnel ventilation, flow control of piping system, and sound research with drain system. Main focuses have been addressed to 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 were mostly focused on analyzing the indoor environment in various spaces like cars, old tombs, machine rooms, and etc. in an architectural environmental field. Moreover, subjects of various fields such as the evaluation of noise, thermal environment, indoor air quality and development of energy analysis program were researched by various methods of survey, simulation, and field experiment.