• Korea-Australia Rheology Journal
• /
• 제17권4호
• /
• pp.207-215
• /
• 2005

We present a finite difference solution for electrokinetic flow in rectangular microchannels encompassing Navier's fluid slip phenomena. The externally applied body force originated from between the nonlinear Poisson-Boltzmann field around the channel wall and the flow-induced electric field is employed in the equation of motion. The basic principle of net current conservation is applied in the ion transport. The effects of the slip length and the long-range repulsion upon the velocity profile are examined in conjunction with the friction factor. It is evident that the fluid slip counteracts the effect by the electric double layer and induces a larger flow rate. Particle streak imaging by fluorescent microscope and the data processing method developed ourselves are applied to straight channel designed to allow for flow visualization of dilute latex colloids underlying the condition of simple fluid. The reliability of the velocity profile determined by the flow imaging is justified by comparing with the finite difference solution. We recognized the behavior of fluid slip in velocity profiles at the hydrophobic surface of polydimethylsiloxane wall, from which the slip length was evaluated for different conditions.

• Journal of Chest Surgery
• /
• 제21권2호
• /
• pp.231-239
• /
• 1988

Currently numerous methods are in use for myocardial hypothermia as a myocardial preservation modality for cardiac operation. During cardiac ischemia after crystalloid cardioplegia[4C GIK solution], topical cold saline[Group I, a=9], topical ice slush[Group II, n=9] and topical ice chip[Group III, a=10] have been compared for myocardial surface cooling in the isolated rat heart model of cardiopulmonary bypass. During postischemic period, hemodynamic functions[aortic flow, coronary flow, peak aortic pressure and heart rate], biochemical enzymatic activities and cellular injuries with electron microscope were evaluated in this isolated rat heart perfusion model. Postischemic aortic flow, cardiac output and peak aortic pressure in Group I and Group II recovered better than Group III.[p< 0.05] Postischemic creatine kinase and lactate dehydrogenase leakages in Group II and Group III increased more than Group l and postischemic mitochondrial swelling in Group III was more severe than Group I, and Group II.[p< 0.05] These results suggest that topical cold saline was the better method than topical ice slush or topical ice chip as a myocardial preservation modality in the isolated rat heart model of cardiopulmonary bypass.

• Journal of Welding and Joining
• /
• 제25권3호
• /
• pp.45-50
• /
• 2007

The present study is devoted to investigate the transient flow and to estimate the filling time fur underfill process by using the numerical model established on the fluid momentum equation. For optimization of the design and selection of process parameters, this study extensively presents an estimation of the filling time in the view points of some important factors related to underfill materials and flip-chip geometry. From the results, we conclude that the filling time changes with respect to the under fill materials because of different viscosity, surface tension coefficient and contact angle. It reveals that, as the gap height increases, the filling time decreases substantially, and goes to the saturated values.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 2001년도 ICCAS
• /
• pp.86.5-86
• /
• 2001

This work describes a design and implementation of the level & flow rate control system by using a single-chip microcontroller. The proposed model system is designed based on the use of the single-chip microcontroller 8031 with the EPROM emulator for programming the computer software. The microcontroller reaches the input level and flow signals from the level sensor and the turbine flowmeter, respectively, via the signal conditioning circuits and A/D converters in order to calculate the control signal. Moreover, the status of the process variable can easily be set up and controlled by program monitoring through the emulator, and can be graphically displayed on the computer screen. Experiment results were carried out which can be ...

• 대한의용생체공학회:의공학회지
• /
• 제37권5호
• /
• pp.186-194
• /
• 2016

In this study, a co-axial flow induced microfluidic chip to fabricate pure collagen type I microfiber via the control of collagen type I and Na-alginate gelation process. The pure collagen type I microfiber was generated by selective degradation of Ca-alginate from 'Core-Shell' structured hydrogel microfiber. To make 'Core-Shell' structure, collagen type I solution was introduced into core channel and 1.5% Na-alginate solution was injected into side channel in microfluidic chip. To evaluatethe 'Core-Shell' structure, the red and green fluorescence substances were mixed into collagen type I and Na-alginate solution, respectively. The fluorescence substances were uniformly loaded into each fiber, and the different fluorescence images were dependent on their location. By immoblizing EpH4-Ras and C6 cells within collagen type I and Na-alginate solution, we sucessfully demonstrated the co-culture of EpH4-Ras and C6 cells with 'Core-Shell' like hydrogel microfiber for 5 days. Only to produce pure collagen type I hydrogel fiber, tri-sodium citrate solution was used to dissolve the shell-like Ca-alginate hydrogel fiber from 'Core-Shell' structured hydrogel microfiber, which is an excellent advantage when the fiber is employed in three-dimensional scaffold. This novel method could apply various application in tissue engineering and biomedical engineering.

• 대한기계학회논문집A
• /
• 제28권6호
• /
• pp.774-782
• /
• 2004

This article presents a numerical and experimental investigation for the single-phase forced laminar convective heat transfer through arrays of micro-channels in micro heat exchangers to be used for cooling power-intensive semiconductor packages, especially the stacked multi-chip modules. In the numerical analysis, a parametric study was carried out for the parameters affecting the efficiency of heat transfer in the flow of coolants through parallel rectangular micro-channels. In the experimental study, the cooling performance of the micro heat exchanger was tested on prototypes of stacked multi-chip modules with difference channel dimensions. The simulation results and the experiment data were acceptably accordant within a wide range of design variations, suggesting the numerical procedure as a useful method for designing the cooling mechanism in stacked multi-chip packages and similar electronic applications.

• 한국정밀공학회지
• /
• 제16권6호
• /
• pp.190-196
• /
• 1999

In this study, a procedure for analyzing chip-tool friction and shear processes in 3-D cutting with a single point tool has been established. The edge of a single point tool including circular nose is modified to the equivalent straight edge, then 3-D cutting with a single point tool is reduced to equivalent oblique cutting. Transforming the conventional coordinate systems and using the measured three component of cutting forces, force components on the rake face and the shear plane of the equivalent oblique cutting system can be obtained. And it can be possible to assess the chip-tool friction and shear characteristics in 3-D cutting with a single point tool.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2006년도 하계종합학술대회
• /
• pp.723-724
• /
• 2006

Exploiting the instruction level parallelism encountered with the limit. Single chip multiprocessor was introduced to overcome the limit of traditional processor using the instruction level parallelism. Also, a branch miss prediction is one of the causes that reduce the processor performance. In order to overcome the problems, in this paper, we make single chip multiprocessor having the idle core execute the two control flow of conditional branch. This scheme is a kind of multi-path execution technique based on single chip multiprocessor architecture.

• 한국기계가공학회지
• /
• 제11권6호
• /
• pp.55-61
• /
• 2012

In this study, it was grasped to the flow characteristics of injection nozzle installed in high pressure holder for improving productivity. Chip curling occurred during cutting process for difficult-to-cut material detracts product qualities and productivity. Among of method preventing the phenomenon, high pressure injecting cutting oil is an alterative. In this study, the optimal nozzle was designed by CFD method and it was conducted to analyse on the effect of high pressure injection on chip shape generated during cutting process and wear of insert by experimental method. As the result, it could be confirmed that high pressure injection is favorable for preventing chip curling and insert from wearing.

• 한국정밀공학회지
• /
• 제13권12호
• /
• pp.13-21
• /
• 1996

In this paper, methods to reduce wire sweep during the chip-encapsulation process have been studide. Two methods have been tried for this purpose, namely runner balancing and ram velocity control. Runner balancing has been achieved automatically by using a computer program. Ram-velocity control has been achieved using empirical rules and results from a flow simulation of the encapsulation process. A mold which has 12 cavities for chip has been used as a case study. The simulation results show that the wire sweep obtained from the optimal process condition is about 1/5 of that from initial, unoptimized condition.