• Bulletin of the Korean Chemical Society
• /
• 제12권2호
• /
• pp.163-169
• /
• 1991

The photochemical and photophysical properties of N-(2-haloarylmethyl)pyridinium, N-(arylmethyl)-2-halopyridinium, N-(2-haloarylmethyl)-2-halopyridinium salts and N-(2-halobenzyl)-isoquinolinium salt are studied. The pyridinium salts photocyclize to afford isoindolium salts, while the isoquinolium salts do not. In the photocyclization of N-(2-chlorobenzyl)-2-chloropyridinium salts, pyrido[2,1-a]-4-chloroisoindolium salt is formed by the cleavage of chlorine of pyridinium ring. This indicates that the excited moiety is not the phenyl ring, but the pyridinium ring. The triplet states of the pyridinium salts are believed to be largely involved in the photocyclization, since oxygen retards most of the reaction. Some assistance of a ${\pi}$-complex between the excited chlorine moiety of the salt and phenyl plane of the same molecule is required to explain the reactivity of the salts. N-(Benzyl)-2-chloropyridinium salt is two times more reactive than N-(2-chlorobenzyl)pyridinium salt. N-(Benzyl)-2-chloropyridinium salt can form ${\pi}-complex$ effectively because of the electron-rich phenyl group. The ${\pi}$-complex affords an intermediate, phenyl radical by cleaving the chlorine atom. The photocyclized product, isoindolium salt is obtained by losing the hydrogen atom from the phenyl radical. The reactive pyridinium salts 1a, 2a and 3a have a low fluorescence quantum yield (${\Phi}F$ < 0.01) and a higher triplet energy (ET > 68 kcal/mole) than the unreactive quinolinium salt. The unreactivity of isoquinolinium salt can be understood in relation to its high fluorescence quantum yield and its low triplet energy $(E_T = 61 kcal/mole).$.

• Bulletin of the Korean Chemical Society
• /
• 제15권5호
• /
• pp.399-404
• /
• 1994

The non-Newtonian viscosities (the specific or intrinsic viscosities) of poly(L-proline) (PLP, $M_v$=19,000 and 32,000) in various mixed-solvent systems like water-propanol and acetic acid-propanol of varying compositions were measured during the reverse mutarotation (Form II ${\rightarrow}$Form I) by the application of external pressure (up to 4.5 psi). The non-Newtonian viscosity effect was found to be larger in acetic acid-propanol system than in water-propanol system and to somewhat decrease during the reverse mutarotation at a given solvent system. The non-Newtonian viscosity behavior of PLP in aqueous salt ($CaCl_2$) solution was also studied, from which it was found that the degree of the non-Newtonian effect decreased with increasing salt concentration, and increased with increasing PLP molecular weight. These findings could be explained in terms of conformational changes of PLP in solution (like the helix-helix or helix-coil transition) involved.

• The Korean Journal of Ecology
• /
• 제6권3호
• /
• pp.167-176
• /
• 1983

Species composition, life form, biomass and soil properties of the halophyte communities were investigated from July to September, 1982. At the reclaimed land of Sanho-ri, sand dune of Jido, salt marsh of Suncheon Bay, and Somjin River estuary of Baealdo, species numbers were 26, 14, 13 and 7, dominant species were Salicornia herbaceae, Carex pumila and Suaeda japonica, respectively. Species composition of the 4 investigated areas was 13 families, 25 genera and 39 species, and of them, 10 families, 21 genera and 24 species were attributed to halophytes. Out of 22 life forms, the representative for Jido was $ G-D_4-R_1-3-e.t$and those for the other sites were Th-G4-R5-e. Above ground biomass of all species for Sanho-ri, Jido, Suncheon Bay and Baealdo were 441.3, 202.0, 150.7 and 353.3 g.dw/m2 and the ratios of above ground biomass halophytes to all species were 93.5, 92.7, 90.8 and 100%, respectively. The leading dominant species formed a continuum according to the salt gradiant. The similarity between Baealo and Suncheon Bay was relatively high, and Jido was quite different from the others in species composition. Aster tripolium was stenohaline and appeared at the low salt concentration, but Suaeda maritima and Suaeda asparagoides were duryhaline and occured at the relatively high salt concentration.

• Asian-Australasian Journal of Animal Sciences
• /
• 제7권2호
• /
• pp.159-164
• /
• 1994

Two studies were conducted using 40 cross-bred bulls to study the effect of chopping, moistening with water or common salt solution on the nutritive value of rice straw (variety BG-400). Moistening with water did not significantly effect digestibility or intake of rice straw. As compared to straw fed in the long form, chopping did not significantly influence intake (2.33 vs 1.97kg $100kgBW^{-1}day^{-1}$, respectively), but significantly (p<0.05) decreased the digestibility (41.6 vs 37.4%) and intake of digestible dry matter (0.99 vs 0.74kg $100kgBW^{-1}day^{-1}$). Rice straw moistened with 2 or 4% common sea salt solution and directly fed to animals (Exp. 1) did not significantly effect its digestibility (43.9 and 43.1%, respectively) or intake (2.66 or 2.59kg $100kgBW^{-1}day^{-1}$, respectively), but over night storing of 2% salt solution sprayed straw (Exp. 2) significantly reduced its digestibility (33.6%). The latter is difficult to explain because the sodium concentration (mg/g straw dry matter) was lower than 4% salt solution treatment used in experiment 1 (3.30 vs 5.22). It is concluded that chopping, moistening with water or NaCl salt solution did not significantly improve the nutritive value of rice straw.

• Carbon letters
• /
• 제28권
• /
• pp.47-54
• /
• 2018

High surface carbon aerogels with hierarchical and tunable pore structure were prepared using ionic liquid as carbon precursor via a simple salt templating method. The as-prepared carbon aerogels were characterized by nitrogen sorption measurement and scanning electron microscopy. Through instant visual observation experiments, it was found that salt eutectics not only serve as solvents, porogens, and templates, but also play an important role of foaming agents in the preparation of carbon aerogels. When the pyrolyzing temperature rises from 800 to $1000^{\circ}C$, the higher temperature deepens the carbonization reaction further to form a nanoporous interconnected fractal structure and increase the contribution of super-micropores and small mesopores and improve the specific surface area and pore volume, while having few effects on the macropores. As the mass ratio of ionic liquid to salt eutectics drops from 55% to 15%, that is, the content of salt eutectics increases, the salt eutectics gradually aggregate from ion pairs, to clusters with minimal free energy, and finally to a continuous salt phase, leading to the formation of micropores, uniform mesopores, and macropores, respectively; these processes cause BET specific surface area initially to increase but subsequently to decrease. With the mass ratio of ionic liquids to salts at 35% and carbonization temperature at $900^{\circ}C$, the specific surface area of the resultant carbon aerogels reached $2309m^2g^{-1}$. By controlling the carbonization temperature and mass ratio of the raw materials, the hierarchically porous architecture of carbon aerogels can be tuned; this advantage will promote their use in the fields of electrodes and adsorption.

• 멤브레인
• /
• 제24권6호
• /
• pp.431-437
• /
• 2014

소수성의 폴리에틸렌 다공성막 표면에 오염물질이 흡착됨으로써 발생되는 파울링 현상으로 인한 투과도 감소 문제를 해결하고자 함산소불소화법을 이용하여 막 표면을 친수화 하였다. 함산소불소화 처리 후 접촉각은 $93^{\circ}$에서 $50^{\circ}$까지 감소하였고, 수투과량은 60% 이상 증가하였다. 또한, 모델오염물질 Albumin (form bovine serum, BSA), Humic acid sodium salt (HA), Alginic acid sodium salt (SA) 100 ppm의 수용액을 이용하여 투과도 평가 실험을 수행한 결과 막이 친수화 됨에 따라 오염물질이 흡착되는 정도가 감소하여 투과도가 향상된 것을 확인할 수 있었으며, 특히 SA에 대해서는 파울링 개선효과가 크게 나타나 처리하지 않은 PE막에 비해 투과도가 두 배 이상 향상된 값을 나타내었다.

• 방사성폐기물학회지
• /
• 제8권1호
• /
• pp.41-48
• /
• 2010

전해정련공정을 통해 생산된 우라늄 전착물은 약 30%의 용융염을 포함하고 있으므로, 순수한 우라늄을 회수하여 금속 잉곳으로 용이하게 제조하기 위해서는 용융염을 먼저 제거하는 공정이 필요하다. 우라늄 전착물의 염증류 거동을 고찰하기 위해서는 염증류의 주요 공정변수인 유지온도와 진공압의 염제거율에 대한 영향를 고찰해야 한다. 이전 연구에서 우라늄전착물에 대한 염증류 거동에 대해 Hertz-Langmuir 관계식을 적용하여 각 용융염의 휘발 조건에 대해 염휘발계수를 얻을 수 있었으며 이로부터 우라늄 전착물에 대해 99% 이상의 염제거율을 나타내는 염증류공정의 조업조건을 도출하였다[1]. 한편, 염증류 장치에서 사용되는 재질인 스테인리스강에 대해 우라늄 전착물에서 염휘발된 우라늄 금속이 스테인리스강의 주성분인 철, 니켈, 크롬 등과 공정(eutectic melt)을 형성하지 않는 온도에서 염증류공정을 수행해야 하는 제한 조건이 따른다. 이번 연구에서는 우라늄 금속과 스테인리스강과의 반응성을 검토함으로써 우라늄 전착물의 염을 99% 이상 제거할 수 있는 조건을 확인하였다. 그리고 염증류 속도를 증진시키며 휘발된 염을 더 효율적으로 회수하기 위해 공급되는 알곤 흐름에 의한 염증류 장치의 열해석을 수행함으로써 알곤 흐름에 의한 우라늄 전착물에 대한 염증류 거동을 고찰하였다.

• 한국수자원학회논문집
• /
• 제33권1호
• /
• pp.31-38
• /
• 2000

수문변량 사이의 관계는 대부분 비선형 관계를 보이고 있다. 일반적으로 이런 비선형 관계는 어떤 선행하는 명백한 하나의 함수적인 형태로 표현할 수 없는 것이 일반적이다. 본 논문에서는, 비매개변수적 다변량 회귀분석 방법을 지역적으로 가중된 다항식을 이용하여 비선형 예상 함수를 추정하였다. 지역적으로 가중된 다항식은 추정치 각 점에서의 인접한 이웃자료를 가지고 목적 함수를 테일러 급수 확장을 통하여 고려하였다. 이런 비매개변수적 회귀분석을 실용성을 Great Salt Lake의 격주 체적자료에 대한 단기간 예측을 통하여 보여주었다.

• 한국방사성폐기물학회:학술대회논문집
• /
• 한국방사성폐기물학회 2003년도 가을 학술논문집
• /
• pp.215-219
• /
• 2003

현재 국내에서 개발 중인 사용후 핵연료의 금속전환공정에서 발생이 예상되는 LiCl 염폐기물을 제올라이트로 고정화한 후 최종 고화체를 만드는 기술을 개발 중에 있다. 여러 혼합조건에 대해 고정화 생성물의 결정을 분석한 결과 모든 혼합조건에서 제올라이트 A형이 제올라이트 Li-A으로 전이되었으며, 일부 혼합조건에서는 Minor phase로 소달라이트 형도 발견되었다. 자유염 발생이 최소가 되는 혼합조건은 Cs, Sr 핵종이 포함된 LiCl 제올라이트 비가 1.0인 조건이었다.

• E2M - 전기 전자와 첨단 소재
• /
• 제9권4호
• /
• pp.351-356
• /
• 1996

The quartemary system ceramics 0.5[xPb(Zn$_{1}$3/Nb$_{2}$3/)O$_{3}$-(1-x)Pb(Ni$_{1}$3/Nb$_{2}$3/)O$_{3}$]-0.5[yPbTiO$_{3}$-(1-y) PbZrO$_{3}$ for piezoelectric actuators were prepared bv the were added to the raw materials up to 5 mole. Sintering temperature was varied form 1000.deg. C to 1200.deg. C. Sintering characteristrics, dielectric and piezoelectric properties were then investigated. Piezoelectric properties of sample prepared by the molten salt method were improved compared to those prepared by the conventional method. Addition of PZN shifted morphotropic phase boundary to more Zr-rich composition and decreased the piezoelectric properties.