• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.9
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• pp.1015-1021
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• 2004

Micro-resolution Particle Image Velocimetry(Micro-PIV) was used to measure the flow in a micro-branch(Micro-Bypass). In this paper, effects of particle lump at the tip of a Micro-branch and difficulties of Micro-PIV measurements for microfluidics with branch passage were described. Micro-bypass was composed of a straight channel(200(100)${\mu}$m width ${\times}$ 80${\mu}$m height) and two branches which has 100(50)${\mu}$m width ${\times}$ 80${\mu}$m height. One of branches was straight and the other was curved. Experiments were performed at three regions along streamwise direction(entrance, middle and exit of branch) and five planes along vertical direction (0, ${\pm}$10, ${\pm}$20 ${\mu}$m) for the range of Re=0.24, 1.2, 2.4. Numerical simulation was done to compare with the measurements and understand the effects of particle lump at the tip of branch. And another fluid(3% poly vinyl Alcohol aqueous solution) were adapted for this study, so there were no particle sticking. In this case, we could get velocity difference between straight and curved branches.

• Journal of Electrical Engineering and Technology
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• v.9 no.6
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• pp.1822-1831
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• 2014

Micro-grid is connected to the main power grid through a static switch. One of the critical issues in micro-grids is protection which must disconnect the micro-grid from the network in short-circuit contingencies. Protective methods of micro-grid mainly follow the model of distribution system protection. This protection scheme suffers from improper operation due to the presence of single-phase loads, imbalance of three-phase loads and occurrence of power swings in micro-grid. In this paper, a new method which prevents from improper performance of static micro-grid protection is proposed. This method works based on artificial neural network (ANN) and able to differentiate short circuit from power swings by measuring impedance and the rate of impedance variations in PCC bus. This new technique provides a protective system with higher reliability.

• Journal of the Korean Institute of Telematics and Electronics
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• v.18 no.3
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• pp.21-24
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• 1981

A simple optial fiber Y-branch is fabricated using micro - torch and fusion splicer. Tapered end of two fibers - in -contact is spliced with another fiber. Total insertion loss is 26dB and optical power branchi ng ratio is 0.98. Using fiber Y-branch, an UTDR with simple optical system is realized The resolution of the OTDR is $\pm$ 5m in length and t 0.5 dB/km in loss coefficient.

• The Journal of the Korea Contents Association
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• v.10 no.9
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• pp.259-266
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• 2010

The study focuses on the value of Micro CT, a high resolution X-ray imaging device, by using it on rats to observe the overall portal vein image of the liver and the microvasculature of each lobes, visualize the 4 segmental lobes and acquire 3D image of the microvasculature through the reconstruction of sectional image data. Less of the damage to liver of the 5 mice, the device was able to separate the liver into 4 segmental lobes and displayed the 4 portal vein microvasculature in 2D. By using the 3D MIP technique, observation of the whole portal vein system microvasculature in 3D image was made possible along with each of the portal vein segment's branches until the 6th branch. Measured the size of 6branch, the average was measured at 1branch : $0.51mm{\pm}0.08$, 2 branch : $0.32mm{\pm}0.12$, 3 branch : $0.23mm{\pm}0.11$, 4 branch : $0.19mm{\pm}0.08$, 5 branch : $0.13mm{\pm}0.06$, 6 branch : $70.5{\mu}m{\pm}14.1$. The 3D image and the images of the microvasculatures in the result of study proved that the Micro-CT can be considered many useful device in obtaining high resolution images.

• Steel and Composite Structures
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• v.18 no.6
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• pp.1541-1555
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• 2015

In this paper mechanical behavior of the functional gradient materials (FGM) micro-gripper under thermal load and DC voltage is numerically investigated taking into account the effect of intermolecular forces. In contrary to the similar previous works, which have been conducted for homogenous material, here, the FGM material has been implemented. It is assumed that the FGM micro-gripper is made of metal and ceramic and that material properties are changed continuously along the beam thickness according to a given function. The nonlinear governing equations of the static and dynamic deflection of microbeams have been derived using the coupled stress theory. The equations have been solved using the Galerkin based step-by-step linearization method (SSLM). The solution procedure has been evaluated against available data of literature showing good agreement. A parametric study has been conducted, focusing on the combined effects of important parameters included DC voltage, temperature variation, geometrical dimensions and ceramic volume concentration on the dynamic response and stability of the FGM micro-gripper.

• Tribology and Lubricants
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• v.15 no.3
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• pp.272-277
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• 1999

The objective of this investigation is to examine the influence of the micro catheters, which mimic the intravascular micro active endoscopes, on local pressure changes and flow rate in an arterial branch model similar to the femoral artery of human. The effects of branch to main lumen flow rate ratios and the locations of a catheter tip were found to be significant on the local pressure changes. Relatively large pressure drops and an increase in shear stress due to the obstruction effects may induce an endothelial cell damage and a change in arterial wall permeability, which have been reported to be the primary cause of the initiation of the atherosclerosis and other major vascular diseases.

• Structural Engineering and Mechanics
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• v.62 no.5
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• pp.551-565
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• 2017

Based on the strain gradient theory (SGT), vibration analysis of an embedded micro cylindrical shell reinforced with agglomerated carbon nanotubes (CNTs) is investigated. The elastic medium is simulated by the orthotropic Pasternak foundation. The structure is subjected to magnetic field in the axial direction. For obtaining the equivalent material properties of structure and considering agglomeration effects, the Mori-Tanaka model is applied. The motion equations are derived on the basis of Mindlin cylindrical shell theory, energy method and Hamilton's principal. Differential quadrature method (DQM) is proposed to evaluate the frequency of system for different boundary conditions. The effects of different parameters such as CNTs volume percent, agglomeration of CNTs, elastic medium, magnetic field, boundary conditions, length to radius ratio and small scale parameter are shown on the frequency of the structure. The results indicate that the effect of CNTs agglomeration plays an important role in the frequency of system so that considering agglomeration leads to lower frequency. Furthermore, the frequency of structure increases with enhancing the small scale parameter.

• Advances in Energy Research
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• v.5 no.2
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• pp.129-145
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• 2017

In this study, the use of a micro gas turbine system using biogas to supply heating, cooling and electricity loads of a rural building located in rural area around Tehran has been studied. Initially, the amount of energy needed by the farmhouse was calculated and then the number of needed microturbines was determined. Accordingly, the amount of substances entering biogas digester as well as tank volume were determined. The results of this study showed that village house loads including electrical, heating and cooling and hot water loads can be supplied by using a microturbine with a nominal power of 30 kW and $33.5m^3/day$ of biogas. Digester tank and reservoir tank volumes are $67m^3$ and $31.2m^3$, respectively. The cost of electricity produced by this system is 0.446 US$/kWh. For rural area in Iran, this system is not compatible with micro gas turbine and IC engine system use urban natural gas due to low price of natural gas in Iran, but it can be compatible by wind turbine, photovoltaic and hybrid system (wind turbine& photovoltaic) systems.

• Advances in nano research
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• v.16 no.6
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• pp.615-622
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• 2024

This study investigates the impact of educational management on the performance of scholars in the field of nano/micro-level composites. The objective is to understand how effective management strategies can enhance the academic achievements and research outcomes of students specializing in this advanced area of materials science. Through a combination of qualitative and quantitative methodologies, data was collected from various educational institutions renowned for their programs in nano/micro-level composites. Our results indicate that tailored educational management practices significantly improve student performance. Key strategies identified include personalized mentorship programs, interdisciplinary collaboration opportunities, and access to state-of-the-art laboratory facilities. Institutions that implemented these practices observed a marked increase in the quality and quantity of research outputs, higher student satisfaction rates, and improved post-graduation employment prospects in relevant industries. Furthermore, the study highlights the importance of continuous professional development for educators to stay abreast of the latest advancements in nano/micro-level composites. By fostering an environment of innovation and support, educational management can play a crucial role in shaping the next generation of researchers and professionals in this cutting-edge field. These findings underscore the necessity of strategic educational management in optimizing the academic and professional trajectories of scholars in nano/micro-level composites, ultimately contributing to advancements in technology and industry applications.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.44 no.2
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• pp.8-17
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• 2012

Three kinds of cationic acrylamide copolymer with different branch degree were prepared controlling the dosage of N, N'-methylenebisacrylamide. The physical characteristics of the branch-degree-modified copolymers were analyzed by intrinsic viscosity and charge density. The branch degree measurements were investigated by applying the colloidal titration phenomena using a spectrophotometer and comparison with the cationic regain measurement method. The results showed that the absorbance behaviors of spectrophotometer were distinctively different with the branch degree of copolymers. Also, the branch degree determinations and molecular structure estimations of the copolymers were numerically measured by applying the titration phenomena using a spectrophotometer. Finally, three kinds of branch-degree-modified copolymers were applied to flocculation test using arbocel micro pulp for the determination of flocculation behavior by different morphology of cationic acrylamide copolymers.