• Progress in Superconductivity
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• v.7 no.1
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• pp.46-51
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• 2005

We have developed control electronics to operate flux-locked loop (FLL), and analog signal filters to process FLL outputs for 64-channel Double Relaxation Oscillation SQUID (DROS) magnetocardiography (MCG) system. Control electronics consisting of a preamplifier, an integrator, and a feedback, is compact and low-cost due to larger swing voltage and flux-to-voltage transfer coefficients of DROS than those of dc SQUIDs. Analog signal filter (ASF) serially chained with a high-pass filter having a cut-off frequency of 0.1 Hz, an amplifier having a gain of 100, a low-pass filter of 100 Hz, and a notch filter of 60 Hz makes FLL output suitable for MCG. The noise of a preamplifier in FLL control electronics is $7\;nV/{\surd}\;Hz$ at 1 Hz, $1.5\;nV/{\surd}\;Hz$ at 100 Hz that contributes $6\;fT/{\surd}\;Hz$ at 1 Hz, $1.3\;fT/{\surd}\;Hz$ at 100 Hz in readout electronics, and the noise of ASF electronics is $150\;{\mu}V/{\surd}\;Hz$ equivalent to $0.13\;fT/{\surd}\;Hz$ within the range of $1{\sim}100\;Hz$. When DROSs are connected to readout electronics inside a magnetically shielded room, the noise of 64-channel DROS system is $10\;fT/{\surd}\;Hz$ at 1 Hz, $5\;fT/{\surd}\;Hz$ at 100 Hz on the average, low enough to measure human MCG.

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.2
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• pp.301-306
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• 2015

An ultra-compact and wideband low noise amplifier (LNA) in a quad flat non-leaded (QFN) package is presented. The LNA monolithic microwave integrated circuit (MMIC) is implemented in a $0.25{\mu}m$ GaN IC technology on a Silicon Carbide (SiC) substrate provided by Triquint. A source degeneration inductor and a gate inductor are used to obtain the noise and input matching simultaneously. The resistive feedback and inductor peaking techniques are employed to achieve a wideband characteristic. The LNA chip is mounted in the $3{\times}3-mm^2$ QFN package and measured. The supply voltages for the first and second stages are 14 V and 7 V, respectively, and the total current is 70 mA. The highest gain is 13.5 dB around the mid-band, and -3 dB frequencies are observed at 0.7 and 12 GHz. Input and output return losses ($S_{11}$ and $S_{22}$) of less than -10 dB measure from 1 to 12 GHz; there is an absolute bandwidth of 11 GHz and a fractional bandwidth of 169%. Across the bandwidth, the noise figures (NFs) are between 3 and 5 dB, while the output-referred third-order intercept points (OIP3s) are between 26 and 28 dBm. The overall chip size with all bonding pads is $1.1{\times}0.9mm^2$. To the best of our knowledge, this LNA shows the best figure-of-merit (FoM) compared with other published GaN LNAs with the same gate length.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.2
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• pp.134-142
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• 2012

A bipolar plate is a major component of a fuel cell stack, which occupies 50~60% of the total weight and over 50% of the total cost of a typical fuel cell stack. In this study, a composite bipolar plate is designed and fabricated to develop a compact and light-weight direct methanol fuel cell (DMFC) stack for a small-scale Unmanned Aerial Vehicle (UAV) application. The composite bipolar plates for DMFCs are prepared by a compression molding method using resole type phenol resin as a binder and natural graphite and carbon black as a conductor filler and tested in terms of electrical conductivity, mechanical strength and hydrogen permeability. The flexural strength of 63 MPa and the in-plane electrical conductivities of 191 S $cm^{-1}$ are achieved under the optimum bipolar plate composition of phenol : 18%; natural graphite : 82%; carbon black : 3%, indicating that the composite bipolar plates exhibit sufficient mechanical strength, electrical conductivity and hydrogen permeability to be applied in a DMFC stack. A DMFC with the composite bipolar plate is tested and shows a similar cell performance with a conventional DMFC with graphite-based bipolar plate.

• Biotechnology and Bioprocess Engineering:BBE
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• v.10 no.1
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• pp.29-33
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• 2005

A DNA vaccine methodology using eukaryote expression vectors to produce immunizing proteins in the vaccinated hosts is a novel approach to the development of vaccine and immuno-therapeutics, and it has achieved considerable success over several infectious diseases and various cancers. To further enhance its efficiency, attempts were made to develop novel plasmid vectors containing multiple immunostimulatory CpG motifs, for rapid and strong immune response. First, a 2.9 kb compact plasmid vector (pVAC), containing CMV promoter, polycloning site, BGH poly(A) terminator, ampicillin resistance gene and pBR322 origin was constructed. A pVAC-hEPO was also constructed, which contained a human erythropoietin gene, for evaluating the transfection efficiency of naked plasmid DNA both in vitro and in vivo. To examine the adjuvant effect of multi-CpG motifs on naked plasmid DNA, 22 and 44 enriched and unmethylated CpG motifs were introduced into pVAC to generate pVAC-ISS1 and pVAC-ISS2, respectively. $100{\mu}g$ of pSecTagB, pVAC, pVAC-ISS1 or pVAC-ISS2 were each injected intramuscularly into the tibilias anterior muscle of Balb/c mice. The level of interleukin-6 induced in the mice injected with pVAC-ISS1 and pVAC-ISS2 were significantly elevated after 12 hours, which were almost 2 and 2.5 times higher than that in the mice injected with pSecTagB, respectively. These results suggest that DNA vaccine plasmids with enriched CpG motifs can induce rapid secretion of interleukin-6 by lymphocytes. In conclusion, these vectors can contribute to the development of adjuvant-free DNA vaccinations against infectious diseases and various cancers.

• Industrial Engineering and Management Systems
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• v.10 no.3
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• pp.185-190
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• 2011

A driver interacts directly with the car seat at all times. There are ergonomic characteristics that have to be followed to produce comfortable seats. However, most of previous researches focused on either static or dynamic condition only. In addition, research on car seat development is critically lacking although Malaysia herself manufactures its own car. Hence, this paper integrates objective measurements and subjective evaluation to predict seat discomfort. The objective measurements consider both static and dynamic conditions. Steven's psychophysics power law has been used in which after expansion; ${\psi}\;=\;a+b{\varphi}_s^{\alpha}+c{\varphi}_v^{\beta}$ where ${\psi}$ is discomfort sensation, ${\varphi}_s^{\alpha}$ is static modality with exponent ${\alpha}$ and ${\varphi}_v^{\beta}$ is dynamic modality with exponent ${\beta}$. The subjects in this study were local and the cars used were Malaysian made compact car. Static objective measurement was the seat pressure distribution measurement. The experiment was carried out on the driver's seat in a real car with the engine turned off. Meanwhile, the dynamic objective measurement was carried out in a moving car on real roads. During pressure distribution and vibration transmissibility experiments, subjects were requested to evaluate their discomfort levels using vehicle seat discomfort survey questionnaire together with body map diagram. From subjective evaluations, seat pressure and vibration dose values exponent for static modality ${\alpha}$ = 1.51 and exponent for dynamic modality ${\beta}$ = 1.24 were produced. The curves produced from the $E_{q.s}$ showed better $R_{-sq}$ values (99%) when both static and dynamic modalities were considered together as compared to Eq. with single modality only (static or dynamic only R-Sq = 95%). In conclusion, car seat discomfort prediction gives better result when seat development considered both static and dynamic modalities; and using ergonomic approach.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.289-290
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• 2006

In general, atomic force microscope (AFM) used for metrological purpose has measuring range less than a few hundred micrometers. We design and fabricate an AFM with long measuring range of $200mm{\times}200mm$ in X and Y axes. The whole stage system is composed of surface plate, global stage, microstage. By combining global stage and microstage, the fine and long movement can be provided. We measure the position of the stage and angular motions of the stage by laser interferometer. A piezoresistive type cantilever is used for compact and long term stability and a flexure structure with PZT and capacitive sensor is used for Z axis feedback control. Since the system is composed of various actuators and sensors, a real time control program is required for the implementation of AFM. Therefore, in this work, we designed a multi-axis control program using a FPGA module, which has various functions such as interferometer signal converting, PID control and data acquisition with triggering. The control program achieves a loop rate more than 500 kHz and will be applied for the measurement of grating pitch and step height.

• Journal of Powder Materials
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• v.21 no.3
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• pp.215-221
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• 2014

Translucent alumina is a potential candidate for high temperature application as a replacement of the glass or polymer. Recently, due to the increasing demand of high power light emitting diode (LED), there is a growing interest in the translucent alumina. Since the translucent property is very sensitive to the internal defect, such as voids inside or abnormal grain growth of sintered alumina, it is important to fabricate the defect-free product through the fabrication process. Powder injection molding (PIM) has been commonly applied for the fabrication of complex shaped products. Among the many parameters of PIM, the flowability of powder/binder mixture becomes more significant especially for the shape of the cavity with thin thickness. Two different positions of the gate were applied during PIM using the disc type of die. The binder was removed by solvent extraction method and the brown compact was sintered at $1750^{\circ}C$ for 3 hours in a vacuum. The flowability was also simulated using moldflow (MPI 6.0) with two different types of gate. The effect of the flowability of powder/binder mixture on the microstructure of the sintered specimen was studied with the analysis of the simulation result.

• Journal of Powder Materials
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• v.21 no.3
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• pp.185-190
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• 2014

$FeS_2$ has been widely used for cathode materials in thermal battery because of its high stability and current capability at high operation temperature. Salts such as a LiCl-KCl were added as a binder for improving electrical performance and formability of $FeS_2$ cathode powder. In this study, the effects of the addition of $Li_2O$ in LiCl-KCl binder on the formability of $FeS_2$ powder compact were investigated. With the increasing amount of $Li_2O$ addition to LiCl-KCl binder salts, the strength of the pressed compacts increased considerably when the powder mixture were pre-heat-treated above $350^{\circ}C$. The heat-treatment resulted in promoting the coating coverage of $FeS_2$ particles by the salts as $Li_2O$ was added. The observed coating as $Li_2O$ addition might be attributed to the enhanced wettability of the salt rather than its reduced melting temperature. The high strength of compacts by the $Li_2O$ addition and pre-heat-treatment could improve the formability of $FeS_2$ raw materials.

• Journal of Powder Materials
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• v.24 no.4
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• pp.292-297
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• 2017

A metallic oxide layer of a heat-resistant element contributes to the high-temperature oxidation resistance by delaying the oxidation and has a positive effect on the increase in electrical resistivity. In this study, green compacts of Fecralloy powder mixed with amorphous and crystalline silica are oxidized at $950^{\circ}C$ for up to 210 h in order to evaluate the effect of metal oxide on the oxidation and electrical resistivity. The weight change ratio increases as per a parabolic law, and the increase is larger than that observed for Fecralloy owing to the formation of Fe-Si, Fe-Cr composite oxide, and $Al_2O_3$ upon the addition of Si oxide. Si oxides promote the formation of $Al_2O_3$ and Cr oxide at the grain boundary, and obstruct neck formation and the growth of Fecralloy particles to ensure stable electrical resistivity.

• Korean Journal of Plant Resources
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• v.3 no.1
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• pp.31-40
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• 1990

Pericarp and seedcoat removal treatments were tested to determine their effectiveness in the hard-to-germinate botanical seeds of jerusalem artichoke. Fresh seed of five Helianthus tuberosus L.varieties were (A)untreated (B)water soaked overnight (C) soaked overnight followed by renoval of pericarp or (D) soaked overnight followed by renoval of pericarp and seedcoat. The results indicate that treatments which removed the pericarp and seedcoat were the very effective, giving germination of over 90%. A considerable increase in germination did not follow only the peri-carp removal treatments. The factors inhibitory to germination of fresh jerusalem artichoke seed is associated withthe seedcoat. The removal treatment of pericarp and seed-cost is recommended despite its complexity because it givesa high germination percentage and varies least from varietyto variety. Heliarthus tuberosus L., a biomass potential crop, is a member of the family compositae. The genus Helianthushas provided man with two food plants, the sunflower (H.annus) and the jerusalem artichoke or topinambour (H. tube-rosus) . (3) The jerusalem artichoke grown for its tubers, has always been an extremely minor crop, but it is stillgrown in many places as a food for man or livestock and forthe production of alcohoL. Though tubers are used for pro-pagation jerusalem artichoke also flower and produce seedin head-like in florescences. Flowers are developed acro-petaLly on flattened receptacles such that outermost flowers are oldest. Each of these epigynous flowers may develop an achene-type fruit in which outer layers of the overy wallpersist, while inner layers become disorganized. Insidethe ovary wall of mature fruit, there is a papery seedcoat, probably composed of compact cells from endosperm, integu-ments, and nucellus.In general, the efforts to improving this crop havebeen hampered by the hard-to-germinate botanical seed.Seeds did not germinate for at least IL months after harvest.Fresh seeds of some varieties require one year more to gar-minate. (5) Since the time factor between generations isof concern in a prospective breeding program of jerusalemartichoke , these observations led to investigation of thenature of delayed seed germination in jerusalem artichokeas a biomass potential crop.