• Journal of the Korean Chemical Society
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• v.45 no.1
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• pp.31-39
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• 2001

Newly synthesized 15-Crown-5 derivatives including anthracene were used as neutral carriers for ion selective electrodes to determine potassium ion by potentiometry. Among the five neutral carriers studied in this work, N-(4'-benzo-15-crown-5-ether)-anthracene-9-imine was found to be the best in terms of selectivity and stability. The optimal composition of ion selective membrane was 1.0, 33.0 and 66.0 wt% for neutral carrier, PVC and plasticizer, resperctively. Addition of KTpCIPB used as a lipophilic additive improved the Nernst slope and the selectivity of potassium ion over alkali and alkaline earth metals. Especially, the selectivity of potassium ion over ammonium ion was remarkably good ($logK^{pot}_(K^+,NH_4^+}$=-2.59). The response time was also excellent ($t_{100}$=5sec) and continuous use of this electrode for three weeks has not changed the selectivity and analytical characteristics.

• Membrane Journal
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• v.17 no.2
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• pp.134-139
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• 2007

Experimental and numerical analysis were performed for separation of carbon dioxide from carbon dioxide and nitrogen gas mixture using a polyethersulfone hollow fiber membrane. The experimental results were compared with those obtained at the same operating condition by the numerical analysis. It was observed that there was a big difference between the experimental results and those by a numerical analysis where the permeance of carbon dioxide and its ideal selectivity over nitrogen were obtained from the pure gas permeation. Therefore, the permeance of carbon dioxide and its selectivity were obtained from the separation experimental results using the numerical analysis as a function of the mole fraction of carbon dioxide, the feed pressure and the permeate pressure in the gas mixture. The results of the numerical analysis using the selectivity obtained from the gas mixture were in good agreement with those of the experimental.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.2
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• pp.89-95
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• 2000

Test fishing was carried out to examine the selectivity of the mesh size in trammel net for tonguefish (Cynoglossidae spp.) from May to August, 1999 and a total of 30 times of test fishing have been done in the coastal waters around Dolsando, Yosu, South Chunra province, Korea. A gill net and a trammel net which were composed of three different mesh sizes (70.5mm, 86.6mm and 101mm) were used for the experiment. The selectivity curve of mesh size was estimated by Kitahara's method for Robust tonguefish (Cynoglossus robustus). The results obtained are summarized as follows ; 1. Catching efficiency of the trammel net (70.5mm-sized-lint main net) was 39.0% and it was 2.5 times higher than 15.8% for the gill net. 2. The optimum l/m value of the trammel net was 3.51 and it was 0.13 higher than 3.38 for the gill net. 3. The selectivity of trammel net was similar to that of the gill net for low length-class. However, the selectivity of trammel net was not good compared with that of the gill net for high length-class. The 50% selectivity was 1.33 for the trammel net and 0.83 for the gill net. According to the experimental results, fishing efficiency of the trammel net was better than that of the gill net for tonguefish (Cynoglossidae spp.) and it was known that catch length for targeted species could be selected by controlling the mesh size.

• Proceedings of the IEEK Conference
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• 2004.06b
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• pp.387-390
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• 2004

Thick film alcohol gas sensors were fabricated. Their electrical properties and gas sensing characteristics were investigated. The sensitivity of $1wt.\%$ Pd-doped ${\gamma}-Fe_2O_3$ thick film heat treated at $400^{\circ}C$, 2hrs was $74\%$ to 500ppm alcohol gas at the operating temperature of $250^{\circ}C$. The selectivity of the film to alcohol was good. It showed fast response time to low concentrations of alcohol in air, hence this sensor can be used as a breath sensor.

• Proceedings of the Membrane Society of Korea Conference
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• 1996.10a
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• pp.92-93
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• 1996

PVA membrane was widely used in the dehydration pervaporation process. PVA membrane showed remakable selectivity towed water and an excellent film-forming polymer, with a good resistance to orgamic solvents but it has poor stability in aqueous mixtures. Generally the PVA is manufactured by the hydrolysis reaction from poly vinyl acetate(PVAc) and so the degree of PVA hydrolysis is a major parameter for properties of PVA membrane such as the crystallinity and polarity.

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.4
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• pp.407-416
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• 1988

Thick film city gas sensors were fabricated using \ulcornerFe2O3 and \ulcorner-Fe2O3 as raw materials. Their electrical properties and sensitivity characteristics were investigated and the surface conditions for various firing temperatures were analyzed. The fabricated devices exhibited high sensitivity to butane gas(75~80% n 1, 000ppm butane ambient). Also they showed good selectivity and long-term stability. A city gas alarm system using fabricated sensors was made for the practical application.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2000.11a
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• pp.154-157
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• 2000

One of the problems using DCR(Direct Conversion Receiver) type architecture are DC offset, Poor channel selectivity. APDP(Anti Parallel Diode Pair) can be mood candidate for the DCR frequency mixer due to its inherent 2nd harmonic suppression. APDP shows good IP2 and DC suppression. This paper describes single APDP LO power characteristics, IP2, and receiver structure utilizing APDP frequency mixer.

• Bulletin of the Korean Chemical Society
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• v.23 no.6
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• pp.879-884
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• 2002

A series of novel 1,3-alternate calix[4]-mono-thiacrown and -bis-thiacrowns were synhesized within good yields. The three dimensional 1,3-alternate conformation was confimed by X-ray crystal structure. From the results of two phase extraction and NMR studies on the ligand-metal complex, one can conclude that the calix[4]thiacrown ethers showed the very high selectivity for silver ion over other metal ions by an electrostatic interaction between sulfur atom and silver ion and by a $\pi-metal$ complexation.

• Proceedings of the PSK Conference
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• 2003.10b
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• pp.173.3-173.3
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• 2003

In recent years, olefin cross-metathesis (CM) has emerged as a powerful and convenient synthetic technique in organic chemistry; however, as a general synthetic method, CM has been limited by the lack of predictability in product selectivity and stereoselectivity. A number of excellent studies have recently appeared in the literature which have shown that with the correct catalyst and reaction conditions CM can be used to access a variety of di-and trisubstituted olefinic products in moderate to high yield with good E/Z ratios. (omitted)

• Applied Chemistry for Engineering
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• v.10 no.6
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• pp.895-901
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• 1999

The acid characteristics of ${\beta}$-zeolites was modified by the different calcination conditions in order to remove template and the post-treatments such as ammonium ion exchange and HCl treatment. Alkylation of benzene with propene and isopropanol was carried out over the catalysts to investigate the effect of acid characteristics on the selectivity to cumene in this reaction. The $Br{\ddot{o}}nsted$ acidity(IR $3610cm^{-1}$ band) of ${\beta}$-zeolite was significantly reduced by a deep bed calcination compared to that of ${\beta}$-zeolite calcined in a shallow bed. Moreover, extraframework aluminum species which did not show acidity were produced by the framework dealumination on the deep bed calcined ${\beta}$-zeolite. $Br{\ddot{o}}nsted$ acidity of deep bed calcined ${\beta}$-zeolite was significantly recovered by ammonium ion exchange, however, it was partially recovered by a weak HCl treatment. It was found that the framework aluminum as well as the extraframework aluminum were extracted by a strong HCl treatment. The selectivity to cumene was shown to be about 95% on the shallow bed calcined ${\beta}$-zeolite, however, it decreased to 90% on the deep bed calcined one. The post-treatment such as ammonium exchange and weak HCl treatment enhanced the selectivity to cumene up to 93% by the partial recovery of $Br{\ddot{o}}nsted$ acidity. Propene was proved to be a good alkylating agent for the selectivity to cumene compared to isopropanol.