• Journal of Sensor Science and Technology
• /
• v.27 no.6
• /
• pp.421-426
• /
• 2018

To develop a piezoelectric inkjet printhead for high-resolution and high-speed printing, we studied the characteristics of an inkjet printhead by analyzing the major design parameters. An analytical model for the inkjet printhead was established, and numerical analysis of the coupled first-order differential equation for the defined state variables was performed using state equations. To design the dimension of the inkjet printhead with a driving frequency of 100 kHz, the characteristics of the flow rate and discharge pressure of the nozzle were analyzed with respect to design variables of the flow chamber, effective sound wave velocity, driving voltage, and voltage waveform. It was predicted that the change in the height of the flow chamber does not significantly affect the Helmholtz resonance frequency and discharge speed of the nozzle. From the analysis of change in flow chamber width, it is observed that as the width of the flow chamber increases, the ejection speed greatly increases and the Helmholtz resonance frequency decreases considerably, thereby substantially affecting the performance of the inkjet printhead.

• Polymer(Korea)
• /
• v.31 no.1
• /
• pp.31-36
• /
• 2007

It has been reported that the surface properties of the plasma treated material were changed while maintaining its bulk properties. In this study, surface modification of nylon fiber by plasma treatment was tried to attain high water-repellency Nylon fiber was treated with RF plasma under a vacuum system using various parameters such as gas specious, processing time and processing power. Morphological changes by low pressure plasma treatment were observed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Moreover, the mechanical and inherent properties were analyzed by tensile strength, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The high water-repellency property of nylon fiber was evaluated by a water-drop standard test under various conditions in terms of aging effect. The results showed that the water-repellency of plasma-surface-treated nylon fiber was greatly improved compared to untreated nylon fiber.

• The Journal of Engineering Geology
• /
• v.27 no.3
• /
• pp.233-244
• /
• 2017

We conducted hydraulic fracturing experiments on cement samples to investigate the dependency of fracture propagation on the viscosity of injection fluid and the in situ stress state. Ten cubic samples (20 cm side length) were produced using cement that was cured in water for more than one month. Samples were placed in a tri-axial compression apparatus with three independent principal stresses. An injection hole was drilled and the sample was hydraulically fractured under a constant injection rate. We measured injection pressures and acoustic emissions (AE) during the experiments, and investigated the fracture patterns produced by hydraulic fracturing. Breakdown pressures increased exponentially with increasing viscosity of the injection fluid. Fracture patterns were dependent on differential stress (i.e., the difference between the major and minor principal stresses). At low differential stress, multiple fractures oriented sub-parallel to the major principal stress axis propagated from the injection hole, and in some samples the fracture orientation changed during propagation. However, at high differential stress, a single fracture propagated parallel to the major principal stress axis. AE results show similar patterns. At low differential stress, AE source locations were more widespread than at high differential stress, consistent with the fracture pattern results. Our study suggests that hydraulic fracturing during shale gas extraction should be performed parallel to the orientation of minimum differential stress.

• Transactions of the Korean hydrogen and new energy society
• /
• v.34 no.6
• /
• pp.657-666
• /
• 2023

In this study, experiments and numerical analysis were conducted to investigate the exhaust gas flow in a common exhaust system of multiple solid oxide fuel cells. The system was fabricated based on KGS code and operated within a pressure range of 0.12 kPa, with flow rates ranging from 79.1 to 103.4 L/min. Numerical modeling was validated with a mean absolute error of 3.8% for pressure results. The study assessed the impact of changes in area ratio and emergency stops on pressure distribution, velocity vectors, and wall shear stress. The findings revealed no significant factors causing high differential pressure or backflow.

• Journal of Microbiology and Biotechnology
• /
• v.25 no.7
• /
• pp.1056-1069
• /
• 2015

Osmotic pressure is a critical factor for erythritol production with osmophilic yeast. Protein expression patterns of an erythritol-producing yeast, Yarrowia lipolytica, were analyzed to identify differentially-expressed proteins in response to osmotic pressure. In order to analyze intracellular protein levels quantitatively, two-dimensional gel electrophoresis was performed to separate and visualize the differential expression of the intracellular proteins extracted from Y. lipolytica cultured under low (3.17 osmol/kg) and high (4.21 osmol/kg) osmotic pressures. Proteomic analyses allowed identification of 54 differentially-expressed proteins among the proteins distributed in the range of pI 3-10 and 14.4-97.4 kDa molecular mass between the osmotic stress conditions. Remarkably, the main proteins were involved in the pathway of energy, metabolism, cell rescue, and stress response. The expression of such enzymes related to protein and nucleotide biosynthesis was inhibited drastically, reflecting the growth arrest of Y. lipolytica under hyperosmotic stress. The improvement of erythritol production under high osmotic stress was due to the significant induction of a range of crucial enzymes related to polyols biosynthesis, such as transketolase and triosephosphate isomerase, and the osmotic stress responsive proteins like pyridoxine-4-dehydrogenase and the AKRs family. The polyols biosynthesis was really related to an osmotic response and a protection mechanism against hyperosmotic stress in Y. lipolytica. Additionally, the high osmotic stress could also induce other cell stress responses as with heat shock and oxidation stress responses, and these responsive proteins, such as the HSPs family, catalase T, and superoxide dismutase, also had drastically increased expression levels under hyperosmotic pressure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1995.11a
• /
• pp.113-117
• /
• 1995

The mechanism of the displacement current generation for stimulation transmit observed in the present displacement current measurement and theoretically analysed. The orientational change of molecules in monolayers was discussed on the basis of the Maxwell-displacement-current obtained. Maxwell displacement current was generated from monolayers on a water surface by monolayerr compression, and it measuring technique has been applied to the study of monolayers of Dipalmitoylphosphatidyl choline (L-${\alpha}$-DPPC). Finally, We measured that differential thermal analysis(DTA) of sample. Displacement current was generated when the area per molecule about 180${\AA}$$^2$in low pressure, and it was generated when the area per molecule about 110${\AA}$$^2$in high pressure. A result of DTA was showed that temperature at 124.6$^{\circ}C$.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 1995.03a
• /
• pp.34-39
• /
• 1995

To reduce the shock in shifting the clutches and the brakes in automatic transmission have to be connected smoothly and disconnected rapidly. It is PCSV(Pressure Control Solenoid Valve) that play this role of automatic transmission. In this paper there were two steps in the analysis of the PCSV. The first step was modeling the elctromagnet by the permeance method. The second step was modeling the hydraulic circuit by the pressure differential equation. In addition to this modeling a experiment was performed and the commercial package program was used in order to justify modeling. The result of modeling coincide with the result of experiment and commercial package program. As a result this modeling is usable in analysis of dynamic characteractic of the PCSV.

• Proceedings of the KSME Conference
• /
• 2008.11b
• /
• pp.2771-2776
• /
• 2008

AOV is fluid capacity and fluid pressure control in nuclear power plant with heating power plant. The control valve in order channel to control a high differential pressure developed in the form which is complicated and precise control form. Form the research which sees in order description below analyzed the performance comparison which follows in trim forms of the control valve with CFD. The Result, multi-stage trim are a fluid kinetic energy small will prevent damages of AOV.

• Journal of the Korean institute of surface engineering
• /
• v.29 no.5
• /
• pp.424-429
• /
• 1996

Thin films of Ti-Ni alloy were formed by sputtering under various Ar gas pressures and r. f. powers to investigate the optimum sputtering conditions and to demonstrate their shape memory effect. The composition and structure of the films were examined by electron micro-probe analysis and scanning electron microscope. These films were annealed in order to crystallize them. The mechanical property of the annealed films was evaluated by a conventional bending test. The transformation tmeperatures were determined by differential scanning calorimetry. The shape memory behaviour was examined quantiatatively by changing in sample temperature under various constant loads. It was found that the Ar gas pressure had a critical effect on the mechanical property of the thin film,s although the r.f. power also affected it. The films formed at a high Ar gas pressure were too brittle to be bent successfully. However, the films formed at a low Ar gas pressur could be bent and their shape memory behavior was found to be comparable with that of bulk Ti-Ni alloys.

• Journal of Magnetics
• /
• v.22 no.2
• /
• pp.299-305
• /
• 2017

Magnetic fluid, a new type of magnetic material, is a colloidal liquid constituted of nano-scale ferromagnetic particles suspended in carrier fluid. Magnetic fluid sealing is one of the most successful applications of magnetic fluid. As a new type of seal offering the advantages of no leakage, long life and high reliability, the magnetic fluid seal has been widely utilized under vacuum- and low-pressure-differential conditions. In practical applications, for improved pressure capacity, a multistage sealing structure is always used. However, in engineering applications, a uniform distribution of magnetic fluid under each tooth often cannot be achieved, which problem weakens the overall pressure capacity of the seals. In order to improve the pressure capacity of magnetic fluid seals and broaden their applications, the present study theoretically and experimentally analyzed the degree of non-uniform distribution of multistage magnetic fluid seals. A mathematical model reflecting the relationship between the pressure capacity and the distribution of magnetic fluid under a single tooth was constructed, and a formula showing the relationship between the volume of magnetic fluid and its contact width with the shaft was derived. Furthermore, the relationship of magnetic fluid volume to capacity was analyzed. Thereby, the causes of non-uniform distribution could be verified: injection of magnetic fluid; the assembly of magnetic fluid seals; the change of magnetic fluid silhouette under pressure loading; the magnetic fluid sealing mechanism of pressure transmission, and seal failure. In consideration of these causes, methods to improve the pressure capacity of magnetic fluid seals was devised (and is herein proposed).