• Journal of Mechanical Science and Technology
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• v.18 no.5
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• pp.770-779
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• 2004

This paper describes the micro cutting of wear resistant tungsten carbides using PCD (Poly-Crystalline Diamond) cutting tools in performance with SEM (Scanning Electron Microscope) direct observation method. Turning experiments were also carried out on this alloy (V50) using a PCD cutting tool. One of the purposes of this study is to describe clearly the cutting mechanism of tungsten carbides and the behavior of WC particles in the deformation zone in orthogonal micro cutting. Other purposes are to achieve a systematic understanding of machining characteristics and the effects of machining parameters on cutting force, machined surface and tool wear rates by the outer turning of this alloy carried out using the PCD cutting tool during these various cutting conditions. A summary of the results are as follows: (1) From the SEM direct observation in cutting the tungsten carbide, WC particles are broken and come into contact with the tool edge directly. This causes tool wear in which portions scrape the tool in a strong manner. (2) There are two chip formation types. One is where the shear angle is comparatively small and the crack of the shear plane becomes wide. The other is a type where the shear angle is above 45 degrees and the crack of the shear plane does not widen. These differences are caused by the stress condition which gives rise to the friction at the shear plane. (3) The thrust cutting forces tend to increase more rapidly than the principal forces, as the depth of cut and the cutting speed are increased preferably in the orthogonal micro cutting. (4) The tool wear on the flank face was larger than that on the rake face in the orthogonal micro cutting. (5) Three components of cutting force in the conventional turning experiments were different in balance from ordinary cutting such as the cutting of steel or cast iron. Those expressed a large value of thrust force, principal force, and feed force. (6) From the viewpoint of high efficient cutting found within this research, a proper cutting speed was 15 m/min and a proper feed rate was 0.1 mm/rev. In this case, it was found that the tool life of a PCD tool was limited to a distance of approximately 230 m. (7) When the depth of cut was 0.1 mm, there was no influence of the feed rate on the feed force. The feed force tended to decrease, as the cutting distance was long, because the tool was worn and the tool edge retreated. (8) The main tool wear of a PCD tool in this research was due to the flank wear within the maximum value of $V_{max}$ being about 260 $\mu\textrm{m}$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.6
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• pp.646-651
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• 2018

This paper reports that the electronic properties at a $P3HT/TiO_2$ interface associated with exciton dissociation and transport can be tailored by the insertion of a graphene quantum dot (GQD) layer. For donor/acceptor interface modification in an $ITO/TiO_2/P3HT/Al$ photovoltaic (PV) device, a continuous GQD film was prepared by a sonication treatment in solution that simplifies the conventional processes, including laser fragmentation and hydrothermal treatment, which limits a variety of component layers and involves low cost processing. The high conductivity and favorable energy alignment for exciton dissociation of the GQD layer increased the fill factor and short circuit current. The origin of the improved parameters is discussed in terms of the broad light absorption and enhanced interfacial carrier transport.

• Korean Journal of Materials Research
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• v.9 no.8
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• pp.837-842
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• 1999

The Ta/TaN multilayer structure with repeating layers of a poly-crystalline Ta layer of high ductility and a TaN layer of high hardness is expected to exhibit toughness. This paper reports the results on the hardness and the adhesion strength of Ta/TaN multilayers and compositional gradient Ta/TaN layers deposited on the high speed steel substrate by reactive sputtering as a function of annealing temperature. The TaN film deposited with the $N_2$/Ar ratio of 0.4 in the reactive sputtering process exhibits the highest crystallinity, and the highest hardness and the results of scratch test of the Ta/TaN multilayers. The hardness and adhesion strength of the Ta/TaN multilayers becomes deteriorated with increasing the annealing temperature in the heat treatment right after depositing the layers. Therefore, post-annealing treatments are not desirable in the case of the Ta/TaN multilayers from the standpoint of mechanical properties. Also the hardness of Ta/TaN multilayers increases with decreasing the compositional modulation wavelength, but the adhesion property of the layers is nearly independent of the wavelength. On the other hand, the compositional gradient Ta/TaN film exhibits the highest hardness and the value of scratch test for the post-annealing temperatures of 20$0^{\circ}C$ and 40$0^{\circ}C$, respectively. This tendency of the compositional gradient Ta/TaN films differs from that of the Ta/TaN multilayers.

• Journal of the Korean Applied Science and Technology
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• v.27 no.2
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• pp.137-143
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• 2010

Oxide semiconductors Thin-film transistors are an exemplified one owing to its excellent ambient stability and optical transparency. In particular zinc oxide (ZnO) has been reported because It has stability in air, a high electron mobility, transparency and low light sensitivity, compared to any other materials. For this reasons, ZnO TFTs have been studied actively. Furthermore, we expected that would be satisfy the demands of flexible display in new generation. In order to do that, ZnO TFTs must be fabricated that flexible substrate can sustain operating temperature. So, In this paper we have studied low-temperature process of zinc oxide(ZnO) thin-film transistors (TFTs) based on silicon nitride ($SiN_x$)/cross-linked poly-vinylphenol (C-PVP) as gate dielectric. TFTs based on oxide fabricated by Low-temperature process were similar to electrical characteristics in comparison to conventional TFTs. These results were in comparison to device with $SiN_x$/low-temperature C-PVP or $SiN_x$/conventional C-PVP. The ZnO TFTs fabricated by low-temperature process exhibited a field-effect mobility of $0.205\;cm^2/Vs$, a thresholdvoltage of 13.56 V and an on/off ratio of $5.73{\times}10^6$. As a result, We applied experimental for flexible PET substrate and showed that can be used to ZnO TFTs for flexible application.

• Applied Biological Chemistry
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• v.13 no.1
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• pp.59-64
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• 1970

Human Bence Jones Protein could be purified by DEAF-Sephadex A-50 column $(2{\times}37cm)$ with 0.02M phosphate Buffer (pH 8.0) and gradient increasing with NaCl concentration as in Fig. 2-4. Sample As (K-type Bence Jones Protein) had two component, F-I was major component and its dried weight was 350mg. of starting material of 500mg. Other Sample Im and Ik (${\lambda}$-type Bence Jones Protein) was purified by DEAE-Sephadex A-50 with 0.02M phosphate Buffer(pH 8.0)too. F-I (major component) of Im and F-I of Ik were 242mg and 146mg. its dried weight respectively. K-type of Bence Jones Protein's(As, Ko, Ta.) N-terminal amino acid residue was determined by method of DNP,. K-type of Bence Jones Protein's amino acid residue were either glutamic acid or aspartic acid. Sample Ta was confirmed as glutamic acid its N-Terminal. As and Ko were aspartic acid. Each yellowish spot (DNP-amino acids) were extracted with 4ml. of pH 8.05% $NaHCO_3$ solution and calculated its recovery by O.D. $(360m{\mu}$ using the ${\varepsilon}=18.1{\times}10^3DNP$ $Asp\;{\varepsilon}=17.41{\times}10^(3)\;DNP\;Glu$ considering 50% lose during; the acid (6N-HCI) hydrolysis. Recovery of ko and As were 54.3% and 65% of its starting materials (DNP-Protein). Sample Ta's recovery was 85% of its DNP-protein. ${\lambda}$-type of Bence Jones Protein was rot investigated its N-terminal amino acid residue by DNP-method, probably it was blocked its N-terminal residue with glutamic acid.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.32 no.3
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• pp.233-244
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• 2014

Precise Point Positioning (PPP) is an increasingly recognized precisely the GPS/GNSS positioning technique. In order to improve the accuracy of PPP, the error sources in PPP measurements should be reduced as much as possible and the ambiguities should be correctly resolved. The correct ambiguity resolution requires a careful control of residual errors that are normally categorized into random and systematic errors. To understand effects from two categorized errors on the PPP ambiguity resolution, those two GPS datasets are simulated by generating in locations in South Korea (denoted as SUWN) and Hong Kong (PolyU). Both simulation cases are studied for each dataset; the first case is that all the satellites are affected by systematic and random errors, and the second case is that only a few satellites are affected. In the first case with random errors only, when the magnitude of random errors is increased, L1 ambiguities have a much higher chance to be incorrectly fixed. However, the size of ambiguity error is not exactly proportional to the magnitude of random error. Satellite geometry has more impacts on the L1 ambiguity resolution than the magnitude of random errors. In the first case when all the satellites have both random and systematic errors, the accuracy of fixed ambiguities is considerably affected by the systematic error. A pseudorange systematic error of 5 cm is the much more detrimental to ambiguity resolutions than carrier phase systematic error of 2 mm. In the $2^{nd}$ case when only a portion of satellites have systematic and random errors, the L1 ambiguity resolution in PPP can be still corrected. The number of allowable satellites varies from stations to stations, depending on the geometry of satellites. Through extensive simulation tests under different schemes, this paper sheds light on how the PPP ambiguity resolution (more precisely L1 ambiguity resolution) is affected by the characteristics of the residual errors in PPP observations. The numerical examples recall the PPP data analysts that how accurate the error correction models must achieve in order to get all the ambiguities resolved correctly.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.11
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• pp.83-94
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• 2003

In this paper. a highly linear and low glitch CMOS current mode digital-to-analog converter (DAC) by self calibration bias circuit is proposed. The architecture of the DAC is based on a current steering 6＋4 segmented type and new switching scheme for the current cell matrix, which reduced non-linearity error and graded error. In order to achieve a high performance DAC . novel current cell with a low spurious deglitching circuit and a new inverse thermometer decoder are proposed. The prototype DAC was implemented in a 0.35${\mu}{\textrm}{m}$ n-well CMOS technology. Experimental result show that SFDR is 60 ㏈ when sampling frequency is 32MHz and DAC output frequency is 7.92MHz. The DAC dissipates 46 mW at a 3.3 Volt single power supply and occupies a chip area of 1350${\mu}{\textrm}{m}$ ${\times}$750${\mu}{\textrm}{m}$.

• KSBB Journal
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• v.22 no.6
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• pp.371-377
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• 2007

Polyhydroxyalkanoates (PHAs) are a family of microbial polyesters that can be produced by fermentation from renewable resources. PHAs can be used as completely biodegradable plastics or elastomers. In this paper, novel applications of PHAs in biosensor are described. A general platform technology was developed by using the substrate binding domain (SBD) of PHA depolymerase as a fusion partner to immobilize proteins of interest on PHA surface. It could be shown that the proteins fused to the SBD of PHA depolymerase could be specifically immobilized onto PHA film, PHA microbead, and microcontact printed PHA surface. We review the results obtained for monitoring the specific interaction between the SBO and PHA by using enhanced green fluorescent protein, red fluorescent protein, single chain antibody against hepatitis B virus preS2 surface protein and severe acute respiratory syndrome coronavirus surface antigen as model proteins. Thus, this system can be efficiently used for studying protein-protein and possibly protein-biomolecule interactions for various biotechnological applications.

• Journal of Sensor Science and Technology
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• v.8 no.3
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• pp.265-273
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• 1999

Various oxide films are commonly used as a sacrificial layer or etch mask in the fabrication of microelectromechanical systems (MEMS). Large residual strain of these oxide films causes the wafer to bow, which can have detrimental effects on photolithography and other ensuing processes. This paper investigates the residual strain of tetraethoxysilane (TEOS), low temperature oxide (LTO), 7 wt% and 10 wt% phosphosilicate glass (PSG). Euler beams and a bent-beam strain sensor are used to measure the residual strain. A poly silicon layer is used as the sacrificial layer, which is selectively etched away by $XeF_2$. First, the residual strain of as-deposited films is measured, which is quite large. The residual strain of the films is also measured after annealing them not only at $500^{\circ}C$, $600^{\circ}C$, $700^{\circ}$ and $800^{\circ}C$ in $N_2$ environment for 1 hour but also at the conditions for depositing a $2\;{\mu}m$ thick polysilicon at $585^{\circ}C$ and $625^{\circ}C$. Our results show that the 7 wt% PSG is best suited as the sacrificial layer for $2\;{\mu}$ thick polysilicon processes.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.5
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• pp.538-542
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• 2018

Echo generated in digital hearing aid vent give rise to user's discomfort. For cancelling feedback echo in vent, it is required to estimate vent impulse response exactly. The vent impulse response has time varying and sparse characteristics. The IPNLMS has been known a useful adaptive algorithm to estimate vent impulse response with these characteristics. In this paper, subband sparse adaptive filter which applying IPNLMS to subband hearing aid structure is proposed to cancel echo of vent by estimating sparse vent impulse response. In the propose method, the decomposition of input signal to subband can pre-whiten each subband signal, so adaptive filter convergence speed can be improved. And the poly phase component decomposition of adaptive filter increases sparsity of each components, and the better echo cancellation can be possible without additional computation. To derive coefficients update equation of the adaptive filter, by defining the cost function based weight NLMS is defined, and the coefficient update equation of each subband is derived. For verifying performances of the adaptive filter, convergence speed, and steady state error by white signal input, and echo cancelling results by real speech input are evaluated by comparing conventional adaptive filters.