• Bulletin of the Korean Chemical Society
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• 제33권9호
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• pp.3043-3047
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• 2012

To investigate the scattering layer effect of a $TiO_2$ multilayer in dye-sensitized solar cells (DSSCs), we designed a new DSSC system, assembled with a CdS-$TiO_2$ scattering layer electrode. A high-magnification SEM image exhibited hollyhock-like particles with a width of 1.5-2.0 ${\mu}m$ that were aggregated into 10-nm clumps in a hexagonal petal shape. The efficiency was higher in the DSSC assembled with a CdS-$TiO_2$ scattering layer than in the DSSC assembled with $TiO_2$-only layers, due to the decreased resistance in electrochemical impedance spectroscopy (EIS). The short-circuit current density ($J_{sc}$) was increased by approximately 7.26% and the open-circuit voltage ($V_{oc}$) by 2.44% over the 1.0 wt % CdS-$TiO_2$ composite scattering layer and the incident photon-to-current conversion efficiency (IPCE) in the maximum peak was also enhanced by about 5.0%, compared to the DSSC assembled without the CdS-$TiO_2$scattering layer.

• 대한기계학회논문집A
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• 제30권4호
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• pp.364-372
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• 2006

In this paper, we present a finger tip tactile sensor which can detect contact normal force as well as slip. The sensor is made up of two different materials, such as polyvinylidene fluoride (PVDF) known as piezoelectric polymer, and pressure variable resistor ink. In order to detect slip on the surface of the object, two PVDF strips are arranged along the normal direction in the robot finger tip and the thumb tip. The surface electrode of the PVDF strip is fabricated using silk-screening technique with silver paste. Also a thin flexible force sensor is fabricated in the form of a matrix using pressure variable resistor ink in order to sense the static force. The developed tactile sensor is physically flexible and it can be deformed three-dimensionally to any shape so that it can be placed on anywhere on the curved surface. In addition, a tactile sensing system is developed, which includes miniaturized charge amplifier to amplify the small signal from the sensor, and the fast signal processing unit. The sensor system is evaluated experimentally and its effectiveness is validated.

• 한국생산제조학회지
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• 제21권4호
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• pp.658-665
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• 2012

Micro-EDM is widely used in metallic pattern, electronics, nuclear power and industry in the form of precision process. The improvement of Electro Discharge Machining has been on a steady progress since $19^{th}$ century. The technology has overcome the limits of the traditional precision process, enabling micro-EDM, micro electrolytic machining, micro drilling, micro punching and laser beam machining, which create versatile products with smaller sizes. What have been known about the major feature of Micro-EDM is high thermal energy so that their products are free from the hardness of their products as long as they are electrical conductor. However, each metal is suspected to have different features and natures even if they are created through the same procedure. In this thesis, the methodology of Micro-EDM and how to categorize them are explained. Also, the nature of the examined materials with surface shape and surface roughnes are analyzed. The results of the experiments are expected to understand surface roughness and workability of other materials for Micro-EDM.

• 한국화재소방학회논문지
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• 제17권2호
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• pp.25-34
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• 2003

본 연구에서는 파라핀 연소화염을 사용하여 침대침 및 구대구 전극배치에서 직류전압을 인가하였을 때, 대기압 공기의 플래시오버특성, 인가전압의 크기 및 극성에 따른 화염의 형상변화, 고온 연소화염의 열전리현상 및 플래시오버 특성에 미치는 상대공기밀도의 영향 등에 대해 조사하였다. 실험결과, 연소화염이 존재하면, 대기압 공기의 플래시오버특성은 매우 큰 영향을 받고 있다. 이는 전극의 형태에 따라 코로나풍과 쿨롱력이 작용함으로써 화염의 형상변화와 요동이 일어나기 때문이다. 또한 고온화염으로 인한 주변 공기의 상대공기밀도의 저하로 인해 플래시오버 특성은 더욱 낮아지고 있으며, 연소화염에 대한 열전리의 영향은 크지 않는 것으로 나타났다.

• Journal of Welding and Joining
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• 제23권1호
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• pp.41-47
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• 2005

Arc pressure is one of important factors in understanding physical arc phenomena. Especially it affects on the penetration, size and shape of TIG welding. Some researches were reported on the effect of arc pressure in low and middle current region. But there are not any research in high current region. The purpose of this study is to investigate the arc pressure distribution with mixing ratio of shield gas such as Ar and He gases. A Cu block with water cooling was specifically designed and used as an anode electrode in order to measure the arc pressure in high current region. Then, the arc pressure distribution was measured with change in welding current and mixing ratio of shield gases. The arc force was obtained by numerically integrating the measured results. As the results, it was shown that the arc pressure was concentrated at the central part of the arc in middle and high current regions when a pure Ar gas was used. In case of Ar + He mixing gas, the arc pressure was much lower than that of pure Ar gas. In addition, it was widely distributed to radial direction.

• 한국재료학회지
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• 제24권6호
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• pp.319-325
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• 2014

Cobalt nano-rods were fabricated using a template-free electrochemical-deposition process. The structure of cobalt electro-deposits strongly depends on the electrolyte composition and on the density of the applied current. In particular, as the content of boric acid increased in the electrolyte, deposits of semi-spherical nuclei formed, and then grew into one-dimensional nano-rods. From analysis of the electro-deposits created under the conditions of continuous and pulsed current, it is suggested that the distribution of the active species around the electrode/electrolyte interface, and their transport, might be an important factor affecting the shape of the deposits. When transport of the active species was suppressed by lowering the deposition temperature, more of the well-defined nano-rod structures were obtained. The optimal conditions for the preparation of well-defined nano-rods were determined by observing the morphologies resulting from different deposition conditions. The maximum height of the cobalt nano-rods created in this work was $1{\mu}m$ and it had a diameter of 200 nm. Structural analysis proved that the nano-rods have preferred orientations of (111).

• 전기학회논문지
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• 제65권9호
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• pp.1511-1517
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• 2016

The aim of this study is to improve of properties for electrical AC insulation breakdown strength using epoxy/micro-nano alumina composites with adding glycerol diglycidyl ether (GDE:1,3,5g). This paper deals with the effects of GDE addition for epoxy/micro alumina contents (40,50,60wt%)+surface modified nano alumina(1_phr) composites. 14 kinds specimen were prepared with containing epoxy resins, epoxy micro composites and epoxy nano-micro alumina mixture composites. Average particle size of nano and micro alumina used were 30nm and $1{\sim}2{\mu}m$, respectively. The micro alumina used were alpha phase with Heterogeneous and nano alumina were gamma phase particles of spherical shape. The electrical AC insulation breakdown strength was evaluated by sphere to sphere electrode system and raising velocity 1kV/s. The AC breakdown strength decreased insulation properties of multi-composites according to increasing micro alumina and GDE addition contents.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.693-698
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• 2002

For the evaluation of the plasma display panel (PDP)'s noise, vibration and sound characteristics of fanless PDP are measured and investigated. PDP is a type of two-electrode vacuum tube which operates on the same principle as a household fluorescent light. An inert gas such as argon or neon is injected between two glass plates on which transparent electrodes have been formed, and the glass is illuminated by generating discharge. For this discharge, both high voltage and currents are needed and cause an acoustic noise. We investigated the noise characteristics connected with both a electromagnetic elements from SMPS to panel through X, Y and logic board, and a mechanical elements form panel to case through transfer path which related with vibration and heat. To reduce the noise of PDP, a discharge pulse memory design related with both higher brightness and lower power consumption is important and mechanical characteristics connected with dissipation process of both heat and vibration generated by panel discharge must be investigated.

• 한국자동차공학회논문집
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• 제15권2호
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• pp.101-108
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• 2007

This paper presents an efficient meshless method for analyzing cracked piezoelectric structures subjected to mechanical and electrical loading. The method employs an element free Galerkin (EFG) formulation and an enriched basic function as well as special shape functions that contain discontinuous derivatives. Based on the moving least squares (MLS) interpolation approach, The EFG method is one of the promising methods for dealing with problems involving progressive crack growth. Since the method is meshless and no element connectivity data are needed, the burdensome remeshing procedure required in the conventional finite element method (FEM) is avoided. The numerical results show that the proposed method yields an accurate near-tip stress field in an infinite piezoelectric plate containing an interior hole. Another example is to study a ceramic multilayer actuator. The proposed model was found to be accurate in the simulation of stress and electric field concentrations due to the abrupt end of an internal electrode.

• 한국분말재료학회지
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• 제20권4호
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• pp.285-290
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• 2013

$Ti_2AlN$ composites are a laminated compounds that posses unique combination of typical ceramic properties and typical metallic(Ti alloy) properties. In this paper, the powder synthesis, SPS sintering, composite characteristics and machinability evaluation were systematically conducted. The random orientation characteristics and good crystallization of the $Ti_2AlN$ phase are observed. The electrical and thermal conductivity of $Ti_2AlN$ is higher than that of Ti6242 alloy. A machining test was carried out to compare the effect of material properties on micro electrical discharge drilling for $Ti_2AlN$ composite and Ti6242 alloy. Also, mixture table as a kind of tables of orthogonal arrays was used to know how parameter is main effective at experimental design. Consequently, hybrid $Ti_2AlN$ ceramic composites showed good machining time and electrode wear shape under micro ED-drilling process. This conclusion proves the feasibility in the industrial applications.