• Bulletin of the Korean Chemical Society
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• v.28 no.1
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• pp.68-72
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• 2007

A new PVC membrane potentiometric sensor that is highly selective to Hg2+ ions was prepared, using bis(2-hydroxybenzophenone) butane-2,3-dihydrazone (HBBD) as an excellent hexadendates neutral carrier. The sensor works satisfactorily in the concentration range of 1.0 × 10-6 to 1.0 × 10-1 mol L-1 (detection limit 4 × 10-7 mol L-1) with a Nernstian slope of 29.7 mV per decade. This electrode showed a fast response time (~8 s) and was used for at least 12 weeks without any divergence. The sensor exhibits good Hg2+ selectivity for a broad range of common alkali, alkaline earth, transition and heavy metal ions (lithium, sodium, potassium, magnesium, calcium, copper, nickel, cobalt, zinc, cadmium, lead and lanthanum). The electrode response is pH independent in the range of 1.5-4.0. Furthermore, the developed sensor was successfully used as an indicator electrode in the potentiometric titration of mercury ions with potassium iodide and the direct determination of mercury in some binary and ternary mixtures.

• Bulletin of the Korean Chemical Society
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• v.10 no.6
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• pp.485-488
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• 1989

A carbon paste coated-wire ion-selective electrode for chloride (carbon chloride-CWE) was constructed using epoxy resin, ion-exchanger and carbon powder as a polymer membrane. Its utility, the composition of a polymer membrane, the response characteristics, and the selectivity were examined and applied to the environmental water analysis. The carbon chloride-CWE was prepared using a silver wire, which was covered with silver chloride and then coated with epoxy resin into which chloride ion-exchanger and carbon powder were previously incorporated in advance. The response of the carbon chloride-CWE was Nernstian for $1.0{\times}10^{-2}-2{\times}10^{-5}$ M chloride and the useful pH range from $10^{-2} M Cl- to 10^{-4} M Cl^-$ was 3.0-9.0. Furthermore, the selectivity of chloride over iodide, bromide, and cyanide was much improved compared with those for a solid state epoxy body chloride electrode and a liquid membrane chloride electrode. The carbon chloride-CWE was applied to determine Cl^-$ in tap and ground water. The obtained results were in good agreement with those by the established methods such as spectrophotometric or other chloride-selective electrode methods.

• Journal of Korea Society of Digital Industry and Information Management
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• v.15 no.1
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• pp.67-76
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• 2019

Despite attractive advantages such as good time-frequency localization and improved spectral efficiency, filter bank multicarrier with offset quadrature amplitude modulation (FBMC/OQAM) suffers from multipath fading. In highly frequency-selective channels, the effect of multipath interference can significantly distort the FBMC/OQAM signal due to the absence of cyclic prefix. To resolve the problem of the multipath interference in FBMC/OQAM, this paper proposes applying an antenna array that provides well shaped beam pattern for each multipath. To evaluate the performance of the proposed array system, various computer simulations have been conducted. The accuracy of direction of arrival estimation is demonstrated through spatial spectrum for a different number of antennas in a sub-array. The performance improvement is presented in terms of bit error rate. We found that the proposed array system mitigate the multipath interferences in Extended Typical Urban model with 12 antennas in a sub-array. Moreover, as the number of antennas in a sub-array increases, the system provides a signal-to-noise ratio gain.

• Composites Research
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• v.36 no.3
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• pp.173-179
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• 2023

The sandwich structure, consisting of a core and a face sheet, is used for lightweight structural application. Generally, cellular structures like honeycomb, foam, and lattice structures are utilized for the core. Among these, lattice structures have several advantages over other types of structures. In other studies, curved lattice structures were reported to have higher mechanical properties than straight structures by converting shear stresses acting on the structure into compressive stresses. Moreover, the addition of vertical struts can have a positive effect on the mechanical properties of the lattice structure. For the purpose, two lattice structures with Circle Arch (CC) and Circular Arch with a vertical column (CC_C) were studied, which were fabricated by using selective laser sintering was conducted. The result showed that CC_C has dramatic performance improvements in specific strength, modulus, and strain energy density compared to CC, confirming that vertical struts played a significant role in the lattice core. Finite element analysis was employed to determine the cause of the stress behavior of CC and CC_C. This study is expected to help design structurally superior lattice cores and sandwich structures.

• Bulletin of the Korean Chemical Society
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• v.27 no.8
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• pp.1194-1198
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• 2006

For the purpose of developing more effective chelating agents, we have synthesized a diethylene triamine pentaacetic acid(DTPA) analogue by using an amino acid. S-(N-Boc-aminophenyl)-Cys(t-Bu4-DTPA) methylester was prepared in 6 steps with total yield of 47.9%. For the sake of introducing a biomolecule to the DTPA derivative, a selective hydrolysis was performed with 3 M HCl/Ethylacetate = 1 : 3 ($25{^{\circ}C}$, 30 min, vigorous stirring). $^{166}Ho$-Cys-DTPA and $^{166}Ho$-Biotin-Cys-DTPA were prepared by mixing $^{166}Ho$ with DTPA derivatives at room temp in a HCl solution (pH = 5) and the radiochemical stabilities (> 99%) were maintained for over 6 hrs in vitro.

• Proceedings of the KIEE Conference
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• 1997.07f
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• pp.1999-2001
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• 1997

The main two drawbacks of the Sin91e Stage PFC (SS-PFC) converters employing a DCM Boost PFC cell are relatively high voltage stress on the bulk capacitor and the input current harmonic distortion. The high voltage stress on bulk capacitor makes the SS-PFC converter impractical in a universal input application and the input current harmonic distortion lowers power factor. In this paper a selective variable frequency control that reduces the voltage stress on the bulk capacitor and the input current harmonic distortion is proposed. Computer simulation results of the proposed control method are presented.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.531-536
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• 2001

The structural shape optimization is a useful tool for engineers to determine the shape of a structure. During the optimization process, relocations of nodes happen successively. However, excessive movement of nodes often results in the mesh distortion and eventually deteriorates the accuracy of the optimum solution. To overcome this problem, an efficient method for the shape optimization has been developed. The method starts from the design domain which is large enough to hold the possible shape of the structure. The design domain has pre-defined uniform fine meshes. At every cycle, the method judges whether all the elements are inside of the structure or not. Elements inside of the structure are assigned with real material properties, however elements outside of the structure are assigned with nearly zero values. The performance of the method is evaluated through various examples.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1389-1393
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• 2007

Selective Laser Sintering (SLS) is currently recognized as a leading process in the new field of solid freeform fabrication (SFF). It is used to fabricate in a short time any 3 dimensional shapes by layer-by-layer sintering of polymer, ceramic or metal powder. To develop this SFF system, it needs effective laser scanning path, temperature and z-axis control for lamination. Therefore, in this study, through the application of control algorithm for sintering process have performed, temperature evaluation for sintering process has performed and the manufacturing sample using SLS process.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.2 s.95
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• pp.60-67
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• 1999

Micro-fabrication techniques such as lithography and LIGA processes usually require large investment and are suitable for mass production. Therefore, there is a need for a new micro-fabrication technique that is flexible and more cost effective. In this paper a novel, economical and flexible method of producing micro-pattern on silicon wafer is presented. This method relies on selective removal of mask by mechanical cutting. Then micro-pattern is produced by chemical etching. V-shaped grooved of about 3 ${\mu}m$ wide and 2 ${\mu}m$ deep has been made on ${SiO_2}m$ coated silicon wafer with this method. This method may be utilized for making microstructures in MEMS application at low cost.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.07a
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• pp.560-562
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• 2011

본 논문에서는 송신단에서의 shifted TR 기법과, 이 것에 수신단에서의 선택적 MMSE 등화기를 추가한 통신시스템을 주파수 선택적 채널에서 실험해보고 이것이 shifted TR 기법만 사용했을 때와 비교하여 수신단의 선택적 MMSE 등화기가 성능에 어떤 영향을 끼치는지 관찰하였다. 이를 보호 구간 별로 실험 결과를 비교하였으며 수신단에 선택적 MMSE 등화기를 추가시켰을 경우, shifted TR 기법만을 사용했을 경우보다 비트 오차율 측면에서 성능의 이득이 있음을 확인하였다.