• Asian Pacific Journal of Cancer Prevention
• /
• v.15 no.8
• /
• pp.3687-3690
• /
• 2014

MicroRNA 200c is a microRNA 200 family member that plays an important role in regulation of the epithelial-to-mesenchymal transition (EMT). The prognostic value of microRNA 200c in solid tumors remains controversial because of inconsistent data. Here, we report a meta-analysis of the association of microRNA 200c expression and survival in patients with solid tumors. Pubmed was searched up to November 2013 for studies investigating microRNA 200c expression and overall survival (OS) in solid tumors. Hazard ratios (HRs) with 95% confidence intervals (CIs) for OS were extracted from each study. Pooled HR and CIs were calculated using the Mantel-Haenszel fixed-effects models. A total of five studies evaluating colorectal cancer, gastric cancer, ovarian cancer, pancreatic cancer and endometrial cancer were included in the analysis. Data were divided into tissue microRNA 200c expression group and serum microRNA 200c expression group. The combined HRs [95%CIs] estimated for OS were 0.62 [0.42-0.91] and 2.16 [1.32-3.52] respectively. Low expression of microRNA 200c in tumor tissue and high expression of microRNA 200c in serum are associated with worse survival in solid tumors. Further study is needed to elucidate this contradiction.

• Proceedings of the KSME Conference
• /
• 2001.06c
• /
• pp.47-52
• /
• 2001

Micro-injection molding and microfluidic devices with the help of MEMS technologies including the LIGA process are expected to play important roles in. micro-system industries, in particular the bioapplication industry, in the near future. Understanding fluid flows in micro-channels is important since micro-channels are typical geometry in various microfluidic devices and mold inserts for micro-injection molding. In the present study, both experimental and numerical studies have been carried out to understand the detailed flow phenomena in micro-channel filling process. Three sets of micro-channels of different thickness were fabricated and a flow visualization system was also developed to observe the filling flow into the micro-channels. Experimental flow observations were extensively made to find the effects of channel width and thickness, and effects of surface tension and volume flow rate and so on. And a numerical analysis system has been developed to simulate the filling flow into micro-channels with the surface tension effect taken into account. Discussed are the flow visualization experimental observations along with the predictability of the numerical analysis system.

• 유체기계공업학회:학술대회논문집
• /
• 2004.12a
• /
• pp.109-115
• /
• 2004

The micro turbo generator is new portable power source based on the Brayton cycle, which consists of a compressor, a turbine, a generator, and a combustion chamber. In this paper, the thermodynamic analysis was performed to find the required condition for hundreds watts power in the micro turbo generator, and also the rotordynamic stability was predicted using the numerical analysis of air foil bearings which support the micro turbo generator. By experimental works, the rotordynamic stability of the micro turbo generator with foil bearings was verified. While various transient dynamic situation, the micro turbo generator had stable performances. From the result, it was demonstrated that air foil bearings could be adapted to the micro turbo generator as a excellent lubrication element.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.16 no.6
• /
• pp.187-192
• /
• 2007

In this paper we present a 3-DOF manipulator of which task is to unload the product from a micro factory. The micro factory developed by KITECH presses sheet metal to produce a micro valve that is used for micro pump. Our research is focused on the development of a small-sized unloading manipulator which works in the narrow workspace between the dies. We have implemented pick-and-place task with vacuum pressure and 3-DOF motion with stepping motors. We present the design procedures and analysis required in each module.

• Korean Journal of Metals and Materials
• /
• v.46 no.12
• /
• pp.809-816
• /
• 2008

The influences of various parameters such as inclusions, surface roughness, exposed areas and chloride ion concentrations on the initiation of pitting of Fe-17Cr alloy were investigated, using micro-droplet cell technique. Micro-droplet cell allows one to align the micro-electrode to the desired spot of the working electrode and measure directly local currents with the potentiodynamic polarization. Micro electrochemical tests were carried out at the inclusions after EDX analysis of inclusion. EDX analysis identified inclusions as Cr-oxides. It was found that some active inclusions among Cr-oxide inclusions acted as initiation sites for pitting corrosion. In addition, the rougher surface and the denser chloride ion concentration offered easier pit initiation sites, causing the more susceptible to pitting corrosion.

• Design & Manufacturing
• /
• v.14 no.4
• /
• pp.1-10
• /
• 2020

The seal plays a role in preventing oil leakage when the lip and the rotating shaft come into contact with the fluid and air pressure. Recently, micro dimples or micro pockets are processed and used on the lubrication surfaces of thrust bearings, mechanical bearings, and piston rings. Compared to a smooth surface, micro dimples reduce friction and increase the life of parts. This paper analyzed various kinds of micro dimple shapes on the sealing surface, i.e. circle, rectangle, triangle, and trapezoid. For this purpose, Introduced the design of experiments to work out a micro dimple configuration, unlikely to be damaged from cracks and low in contact stress. As a result, the triangular dimple showed the best results. Optimal factors were dimple size 0.15 mm, dimple depth 0.0383 mm, dimple density 40%, and the maximum equivalent stress was 9.1455 MPa, and the maximum contact pressure was 9.6612 MPa. This paper analyzed the optimal shape of dimples by finite element analysis. As a research project, experiments and comparative analysis of micro dimple shapes are needed.

• 한국태양에너지학회:학술대회논문집
• /
• 2012.03a
• /
• pp.498-501
• /
• 2012

A methodology to evaluate the performance analysis for micro hydropower sites has been studied. It consists of two main parts; flow duration function which can describe micro hydropower sites and performance analysis to estimate the output characteristics of micro hydropower plants. The output performance characteristics for Magok stream was analyzed, using developed model. Also, primary design specifications such as design flowrate, installed capacity, operational rate and annual electricity production were estimated and dicussed. Additionally, it was found that the developed model in this study is useful tool to estimate feasibility assessment for micro hydropower sites.

• Transactions of Materials Processing
• /
• v.17 no.8
• /
• pp.649-656
• /
• 2008

Springback is one of factors affecting precision in metal forming. Its effect is particularly prominent in bending process. In this study, bending and forging process are used in order to manufacture a micro spring with two bending region from $60{\mu}m$ diameter wire. Springback in the process lowers the precision of the micro spring. Overbending for springback compensation has wide usage in a general way. However, this method requires repeated modifications of press dies until the tolerance is allowable, which causes that production cost and time increase. In this paper, we analyzed the mechanism of springback in the forming process of the micro spring using finite element method. In addition, a simple method to control springback without modifying dies was proposed by performing numerical analysis with various parameters.

• Journal of Power System Engineering
• /
• v.10 no.4
• /
• pp.105-110
• /
• 2006

Among many other alternative energy resources, small scale hydro power has been brought into attention as a reliable source of energy today, which had been relatively neglected since 1960s. Especially, Kaplan micro-turbine can be applied to various kind of small hydro power plants, such as reservoirs for agriculture purpose, sewage treatment plants and water purification plants. However present low head of Kaplan micro-turbines and small scale hydro turbines, have limitations in the minimum required head and flow rate for efficient operation. This research is to develop modeling analysis for the Kaplan micro-turbine, which can improve economical features of small hydro power plants. The contents and scope of this research are the efficiency improvement of Kaplan micro-turbine.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.4 no.4
• /
• pp.7-13
• /
• 2005

In the case of fabricating micro pole structures such as column, square-pole and gear shaft by the micro end-milling process, it can be useful in the fields of industry, for example, micro parts, electrode for electrical discharge machining and micro mold for injection molding. In this study, machining factors and the process were analyzed. Machining experiments of various micro pole configurations were performed. Analysis of the change and effect of the cutting force according to the machining conditions was carried out. An analytical study of the deformation of the micro pole caused cutting conditions and cutting force through the finite element method and ANSYS program was carried out. As a result, this research presented a method of fabricating the column pole of below $100{\mu}m$ diameter with high aspect ratio by using micro end-milling process, and based on that, a method of fabricating a variety of applicable structures. Also the minimum size of the pole capable of fabricating through theory and experiment were demonstrated.