• The Plant Pathology Journal
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• v.37 no.3
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• pp.291-298
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• 2021

False smut caused by Ustilaginoidea virens is an important rice fungal disease that significantly decreases its production. In the recent past, conventional methods have been developed for its detection that is time-consuming and need high-cost equipments. The research and development in nanotechnology have made it possible to assemble efficient recognition interfaces in biosensors. In this study, we present a simple, sensitive, and selective oxidized graphene-based geno-biosensor for the detection of rice false smut. The biosensor has been developed using a probe DNA as a biological recognition element on paper electrodes, and oxidized graphene to enhance the limit of detection and sensitivity of the sensor. Probe single-stranded DNA (ssDNA) and target ssDNA hybridization on the interface surface has been quantitatively measured with the electrochemical analysis tools namely, cyclic voltammetry, and linear sweep voltammetry. To confirm the selectivity of the device, probe hybridization with non-complementary ssDNA target has been studied. In our study, the developed sensor was able to detect up to 10 fM of target ssDNA. The paper electrodes were employed to produce an effective and cost-effective platform for the immobilization of the DNA and can be extended to design low-cost biosensors for the detection of the other plant pathogens.

• Journal of KIISE:Software and Applications
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• v.35 no.8
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• pp.501-511
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• 2008

Probe design is one of the essential tasks in successful DNA microarray experiments. The requirements for probes vary as the purpose or type of microarray experiments. In general, most previous works use the simple filtering approach with the fixed threshold value for each requirement. Here, we formulate the probe design as a multiobjective optimization problem with the two objectives and solve it using ${\epsilon}$-multiobjective evolutionary algorithm. The suggested approach was applied in designing probes for 19 types of Human Papillomavirus and 52 genes in Arabidopsis Calmodulin multigene family and successfully produced more target specific probes compared to well known probe design tools such as OligoArray and OligoWiz.

• Journal of the Microelectronics and Packaging Society
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• v.25 no.3
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• pp.37-41
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• 2018

This paper presents the integrated fluorescent oxygen sensor probe module based on planner lightwave circuits using UV imprint lithography. The oxygen sensor system is consisted of the optical source part, optical detector part and optical sensing probe part to be composed of the planner lightwave circuit and oxygen sensitive thin film layer. Firstly, we optimally designed the planner lightwave circuit with asymmetric $1{\times}2$ beam splitter using beam propagation method. Then, we fabricated the planner lightwave circuits using UV imprint lithography process. This planner lightwave circuits transmitted the optical power with 76% efficiency and the fluorescence signal with 70% efficiency. The oxygen sensitive thin film layer is coated on the end face of planner lightwave circuit. The oxygen sensor system using this sensor probe module with planner lightwave circuit could measure the concentration with 0.3% resolution from 0% to 20% gas range. This optical oxygen sensor probe module make it possible to compact, simple and cheap measurement system.

• Gut and Liver
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• v.12 no.6
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• pp.641-647
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• 2018

Background/Aims: Helicobacter pylori eradication rates are decreasing because of increases in clarithromycin resistance. Thus, finding an easy and accurate method of detecting clarithromycin resistance is important. Methods: We evaluated 70 H. pylori isolates from Korean patients. Dual-labeled peptide nucleic acid (PNA) probes were designed to detect resistance associated with point mutations in 23S ribosomal ribonucleic acid gene domain V (A2142G, A2143G, and T2182C). Data were analyzed by probe-based fluorescence melting curve analysis based on probe-target dissociation temperatures and compared with Sanger sequencing. Results: Among 70 H. pylori isolates, 0, 16, and 58 isolates contained A2142G, A2143G, and T2182C mutations, respectively. PNA probe-based analysis exhibited 100.0% positive predictive values for A2142G and A2143G and a 98.3% positive predictive value for T2182C. PNA probe-based analysis results correlated with 98.6% of Sanger sequencing results (${\kappa}$-value=0.990; standard error, 0.010). Conclusions: H. pylori clarithromycin resistance can be easily and accurately assessed by dual-labeled PNA probe-based melting curve analysis if probes are used based on the appropriate resistance-related mutations. This method is fast, simple, accurate, and adaptable for clinical samples. It may help clinicians choose a precise eradication regimen.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.05a
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• pp.303-306
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• 2001

Using THz time-domain spectroscopy (THz-TDS), the power absorption and the real conductivity of silica sand are measured terahertz frequency range. It is impossible to measure the characterization of the silica sand by simple electrical measurements using mechanical contacts, e.g., Hail effect or four-point probe measurements. However, the THz-TDS technique can measure not only electrical but also optical characterization of the sample. Also this technique can measure frequency dependent results. Especially, the real conductivity was increased according to THz frequency this is unusual material compare with metal and semiconductor materials; the measured real conductivity are not followed by the simple Drude theory.

• Current Applied Physics
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• v.18 no.11
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• pp.1255-1260
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• 2018

In this work, a green and simple one-pot route was developed for the synthesis of highly fluorescent aminofunctionalized graphene quantum dots (a-GQDs) via hydrothermal process without any further modification or surface passivation. We synthesized the a-GQDs using glucose as the carbon source and ammonium as a functionalizing agent without the use of a strong acid, oxidant, or other toxic chemical reagent. The as-obtained aGQDs have a uniform size of 3-4 nm, high contents of amino groups, and show a bright green emission with high quantum yield of 32.8%. Furthermore, the a-GQDs show effective fluorescence quenching for $Cu^{2+}$ ions which can serve as effective fluorescent probe for the detection of $Cu^{2+}$. The fluorescent probe using the obtained aGQDs exhibits high sensitivity and selectivity toward $Cu^{2+}$ with the limit of detection as low as 5.6 nM. The mechanism of the $Cu^{2+}$ induced fluorescence quenching of a-GQDs can be attributed to the electron transfer by the formation of metal complex between $Cu^{2+}$ and the amino groups on the surface of a-GQDs. These results suggest great potential for the simple and green synthesis of functionalized GQDs and a practical sensing platform for $Cu^{2+}$ detection in environmental and biological applications.

• Journal of the Microelectronics and Packaging Society
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• v.16 no.2
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• pp.33-42
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• 2009

A polymer-based flexible neural probe was fabricated for monitoring of neural activities from a brain. To improve the insertion stiffness, a 5 ${\mu}m$ thick biocompatible Au layer was electroplated between the top and bottom polymer layers. The developed neural probe penetrated a gel whose elastic modulus is similar to that of a live brain tissue without any fracture, To minimize mechanical residual stress and bending from the probe, two new methods were employed: (1) use of a thermal annealing process after completing the device and (2) incorporation of multiple different layers to compensate the residual stress between top and bottom layers. Mechanical bending around the probe tip was clearly removed after employing the two processes. In electrical test, the developed probe showed a proper impedance value to record neural signals from a brain and the result remained the same for 72 hours. In simple in-vitro probe characterization, the probe showed a great removal of residual stress and an excellent recording performance. The in-vitro recording results did not change even after 1 week, suggesting that this electrode has the potential for great recording from neuron firing and long-term implant performance.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.4
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• pp.285-289
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• 2000

This study suggests a rebar detection technique for simultaneous detection of size and cover of embedded reinforcement in concrete. The structure of the probe made in this study is somewhat different from commercial ones. This probe has three sensing coils. Rebar size and cover depth can be evaluated by detecting and analyzing the signal from them. Amplitude and phase variation of each coil in the probe was investigated using an impedance analyzer and the loci of transfer functions of the coils were analyzed. The locus of transfer function from the sensing coil positioned inside excitation coil was simple as well known, but the others from the coils outside excitation coil were not so. Actual experiment on rebar detection was performed with our probe and an eddy current test system for various rebar sizes and depths. The signal shape according to variation of cover depths showed the same tendency with the transfer function loci acquired by impedance analyzer. The different variation pattern of signal enabled to evaluate rebar size and cover depth simultaneously.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.8
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• pp.483-488
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• 2016

Ultrasound imaging by using piezoelectric materials, such as lead zirconium titanate (PZT) has been one of the most preferred modes of imaging in the medical field due to its simple, low cost and non-ionizing radiation in comparison to other imaging techniques. Recently, the market demand for portable ultrasound is becoming larger with applications in developing countries, disaster area, military, and emergency purposes. However, most of ultrasound probes used is bulky and high power consumable, so unsuitable for such applications. In this study, the 3 layered ceramic specimen consisted of 128 pitches of $420{\mu}m$ in width and $450{\mu}m$ in thickness were prepared by using the Ti-rich PZT compositions co-fired at $1,050^{\circ}C$. Their electrical and ultrasound pulse-echo properties were investigated and compared to the single layer specimen. The 3 layered ultrasound probe showed 1.584 V of Vp-p, which is 3.2 times higher than single layered one, implying that it would allow effectively such a portable ultrasound probe system. The result were discussed in terms of higher capacitance, lower impedance and higher dielectric coefficient of the 3 layered ultrasound probe.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.7
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• pp.1234-1242
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• 2003

In this paper we present a simple and efficient robust optimal design formulation for MEMS structures and its application to a resonant-type micro probe. The basic idea is to use the gradient index (GI) to improve robustness of the objective and constraint functions. In the robust optimal design procedure, a deterministic optimization for performance of MEMS structures is followed by design sensitivity analysis with respect to uncertainties such as fabrication errors and change of operating conditions. During the process of deterministic optimization and sensitivity analysis, dominant performance and uncertain variables are identified to define GI. The GI is incorporated as a term of objective and constraint functions in the robust optimal design formulation to make both performance and robustness improved. While most previous approaches for robust optimal design require statistical information on design variations, the proposed GI based method needs no such information and therefore is cost-effective and easily applicable to early design stages. For the micro probe example, robust optimums are obtained to satisfy the targets for the measurement sensitivity and they are compared in terms of robustness and production yield with the deterministic optimums through the Monte Carlo simulation. This method, although shown for MEMS structures, may as well be easily applied to conventional mechanical structures where information on uncertainties is lacking but robustness is highly important.