• Bulletin of the Korean Chemical Society
• /
• v.24 no.6
• /
• pp.739-743
• /
• 2003

New quaternary compounds $ANb_2PS_{10}$ (A = Na, Ag) and $AuNb_4P_2S_{20}$ were synthesized and characterized. The structures of three compounds consist of one-dimensional infinite chains built by [$Nb_2S_{12}$] and [$PS_4$] units. Cation atoms are occupied within the van der Waals gap of sulfur atoms between infinite chains to make -S…$M^+$…S- contacts. There is only one Au atom site and so crystallographically a unit cell contains four equivalent Au atoms in $AuNb_4P_2S_{20}$. This is only the half of the numbers of Na or Ag atoms in $NaNb_2PS_{10}$ or $AgNb_2PS_{10}$. The ratio between $Nb_2PS_{10}$ matrix vs the cation is, therefore, 1 : 1 for Ag and Na, but it is 2 : 1 for Au. Mixed valency in Au or Nb was expected to balance the charge in the latter compound. The electronic structures calculated based on the extended Huckel tight-binding method show that $ANb_2PS_{10}$ (A = Ag, Na) are semiconducting, while $AuNb_4P_2S_{20}$ is metallic, which is not consistent with the experimental results of these three compounds that all exhibit semiconducting property. The result of calculation suggests that $AuNb_4P_2S_{20}$ might be a magnetic insulator. Magnetic measurement experiment exactly proved that the compound is a Slater antiferromagnetic material with the Neels' temperature of 45 K. It is recognized, therefore, that electronic structure analysis is very useful to understand the properties of compounds.

• Journal of Environmental Science International
• /
• v.17 no.7
• /
• pp.817-826
• /
• 2008

Using high voltage electric fields induced by high voltage AC (10-12 kV/cm, 20 kHz) and pulsed (20-30 kV/cm, 40 Hz) electric field generator as a semipermanent and environment-friendly disinfecting apparatus, the disinfection effect of coliform group in the effluent of sewage plant was investigated. The effects of electric field strength, treatment time, discharge area of a discharge tube, water quality factors (electric conductivity, pH and SS) on its death rate were examined. The death rate of coliform group was increased with increasing electric field strength and treatment time. For AC and pulsed electric field generator, the critical electric field strength was 6 kV/cm and 2 kV/cm, respectively, and the critical treatment time was 5 min and 2 min, respectively, regardless of electric field strength. Comparing the death rate of coliform group by AC and pulsed electric fields used in this study, its death rate was higher for the latter than the former, but did not increase linearly with increasing electric field strength. The results obtained for the effects of discharge area, electric conductivity, pH and SS on the death rate of coliform group using AC electric field (12 kV/cm, 20 kHz) were as follows: its death rate showed the trend to increase linearly with increasing discharge area; for the effect of electric conductivity, its death rate was increased with increasing electric conductivity, regardless of ionic species, increased with increasing cationic valency, but was similar between the same cationic valency; the pH $5{\sim}9$ used in this study did not affect its death rate; its death rate was decreased with increasing SS concentration.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.14 no.2
• /
• pp.35-42
• /
• 2014

This paper suggests a method that obtains the minimum spanning tree (MST) far more easily and rapidly than the present ones. The suggested algorithm, firstly, simplifies a graph by means of reducing the number of edges of the graph. To achieve this, it applies a method of eliminating the maximum weight edge if the valency of vertices of the graph is equal to or more than 3. As a result of this step, we can obtain the reduced edge population. Next, it applies a method in which the maximum weight edge is eliminated within the cycle. On applying the suggested population minimizing and maximum weight edge deletion algorithms to 9 various graphs, as many as the number of cycles of the graph is executed and MST is easily obtained. It turns out to lessen 66% of the number of cycles and obtain the MST in at least 2 and at most 8 cycles by only deleting the maximum weight edges.

• Journal of Korean Society on Water Environment
• /
• v.22 no.5
• /
• pp.768-783
• /
• 2006

Biological stream environment assessment has been an essential trend of aquatic ecosystems among advanced countries, because the chemical water quality assessment has limitations that only represent temporal water environmental status. Benthic macroinvertebrates are the most popular bioindicator group useful to biological water quality assessment for a long time. In addition, a number of indices using benthic macroinvertebrates have recently been developed not only for water quality assessment but also for ecological health assessment. In this paper Korean Saprobic Index (KSI) based on Zelinka-Marvan's saprobic valency concept is developed by applying DIN 38410 in Germany. The KSI value was widely applicable to most Korean streams with the exception of sand-based large streams, for example main stream of Nakdong River. But as a result of non-linear regression analysis the correlation between KSI and $BOD_5$ concentration was high and KSI reflected water quality alteration for mid and long-term period. In spite of applicability of KSI, it should be supplemented and developed to make it strong by accumulating field data as well as to manage integrated water environment in general through continuous biomonitoring.

• Economic and Environmental Geology
• /
• v.28 no.4
• /
• pp.351-367
• /
• 1995

The elemental geochemistry and oxygen isotopes of illite/smectite (I/S) have been studied in relationship to the mineralogical trend in the Reindeer D-27 well, Beaufort-Mackenzie Basin. The increase in concentrations of $K_2O$, Rb and rare earth elements (REE), the decrease in concentrations of tetrahedral elements such as Mg, Ti, Sc, Zn and Zr, and the increase in concentrations of tetrahedral elements such as Be and V can be related to I/S compositions that vary systematically with depth. Layer formulae of S- and I-layers are estimated as $[Al_{1.57}Fe_{.19}Mg_{.31}Ti_{.07}][Si_{3.84}Al_{.16}]O_{10}(OH)_2$ and $[Al_{1.84}Mg_{.16}][Si_{3.33}Al_{.67}]O_{10}(OH)_2$, respectively. The mobilization of REE appears to occur during illitization. The increase in concentrations of REE, especially La and Ce, with depth is probably linked to incorporation of ions with high valency (e.g. $V^{5+}$) in tetrahedral sites. The excess valency due to V is partly counter-balanced by ions with low valency (e.g. $Be^{2+}$) and, in turn, the local valency deficiency caused by $Be^{2+}$ could be compensated by high-charge interlayer cations such as REE (＋3). ${\delta}^{18}O$ values of I/S range from 2.91 to 15.72‰ (SMOW), and increase with depth, contrasting to trends observed in the Gulf Coast and elsewhere. The increase in ${\delta}^{18}O$ of I/S results from the rapid increase in ${\delta}^{18}O$ of pore water that overcomes the decrease in temperature-dependent fractionation values with increasing burial depth (${\delta}^{18}O_{pore\;water}>-d{\Delta}/_{I/S-water};\;d{\delta}^{18}O_{I/S}>0$). Calculated ${\delta}^{18}O$ values of pore water in equilibrium with I/S suggest that the original water was probably meteoric water. The stratification of pore water is postulated from the presence of an isotopically light interval, about 450m thick. The depth range of the isotopically light zone overlaps, but does not coincide with the interval of lowered I-content and $K_2O$ concentrations, suggesting that oxygens may have been exchanged independently of mineralogical and geochemical reactions.

• Journal of the Korean Chemical Society
• /
• v.28 no.2
• /
• pp.135-142
• /
• 1984

New type dioxygen bridged complexes of palladium were prepared by using $KO_2$ as a source of superoxide ion $(O_2^-)$. The method is completely different from the traditional one which has adopted the oxidative addition of molecular oxygen to transition metal complexes in low valency. It was suggested that the reaction to prepare the dioxygen complexes proceeded via nucleophilic displacement followed by electron transfer reaction. Five new type dioxygen complexes having ${\pi}$-allyl ligand were prepared and characterized by the application of the reaction of $O_2^-$.

• Annual Conference on Human and Language Technology
• /
• 2001.10d
• /
• pp.431-438
• /
• 2001

일반적으로 한국어 문장에서 명사는 용언의 항가(valency)에 의해 격이 할당된다. 그러한 이유로, 한국어는 용언이 문장 끝에 온다는 일반적인 제약 이외에는 그 어순이 비교적 자유롭다. 그러나 격 할당과 자유 어순에 대한 여러 가지 비규칙적인 현상들 때문에 문장 분석이나 생성에 문제가 일어난다. 예를 들면, "나 머리 아프다"에서처럼 명사에 격조사가 표시되지 않고 문장이 생성될 수도 있고, "은/는"이나 "도"와 같은 특수조사와 결합할 때는 그 격이 드러나지도 않는다. 어순의 경우, "물이 얼음이 되었다"=/= "얼음이 물이 되었다" 에서처럼 주격이 이중으로 나타나면 어순이 자유롭지 않는 반면, 용언의 어미가 문장 종결형일 때에는 "어서 가자 백두산으로"에서처럼 용언이 문미에 오지 않을 수도 있다. 이 논문은 한국어의 어순과 격 할당에 관한 이러한 문제를 어떻게 처리할 것인가를 보이는 것이 그 목적이다. 문제를 가급적 명시적으로 해결하기 위하여, 본 논문은 문장 분석과 생성에 대한 규칙과 제약 조건들을 형식화하고 문장 처리 과정에서 일어나는 격 할당과 어구 결합 및 배열 과정을 malaga라는 프로그래밍 언어로 구현하여 실험할 것이다.

• Bulletin of the Korean Chemical Society
• /
• v.11 no.5
• /
• pp.379-383
• /
• 1990

$YBa_2Cu_{3-x}Ni_xO_{7-{\delta}}$, with x = 0.05, 0.2, 0.4, 0.7 and 1.0 had been prepared by the thermal decomposition of corresponding nitrates. Among them, the sample with x = 0.05 shows above-liquid-$N_2$ temperature superconductivity with $T_c$ of 88.7K. According to the X-ray diffraction analysis, its crystal symmetry was estimated as orthorhombic with the lattice parameters of a = 3.866${\AA}$, b = 3.893${\AA}$, c = 11.715${\AA}$. The chemical composition of the sample was determined by electron probe microanalysis and the chemical composition around its grain boundaries was carefully studied by the X-ray line scanning technique. From the observed binding energy of Ni-$2p_{3/2}$ orbital electron (B.E. = 853 eV) measured by X-ray photoelectron spectroscopy, the valency state of nickel stabilized in $YBa_2Cu_{2.95}Ni_{0.05}O_{7-{\delta}}$ oxide lattice could be determined to be Ni(II).

• Ceramist
• /
• v.21 no.4
• /
• pp.416-426
• /
• 2018

Water splitting is regarded as one of the most environmentally benign routes for hydrogen production. Nevertheless, the low energy efficiency to produce the hydrogen has been a critical bottleneck, which is attributable to the multi-electron and multi-step reactions during water splitting reaction. In this respect, the development of efficient, durable, and inexpensive catalysts that can promote the reaction is indispensable. Extensive searching for new catalysts has been carried out for past decades, identifying several promising catalysts. Recently, researchers have found that conventional battery materials; particularly high-voltage intercalation-based cathode materials, could exhibit remarkable performance in catalyzing the water splitting process. One of the unique capabilities in this class of materials is that the valency state of metals and the atomic arrangement of the structure can be easily tailored, based on simple intercalation chemistry. Moreover, taking advantage of the rich prior knowledge on the intercalation compounds can offer the unexplored path to identify new water splitting catalysts.

• Journal of the Korean Chemical Society
• /
• v.38 no.12
• /
• pp.873-879
• /
• 1994

A series of samples of solid solutions in the $Sr_xEu_{1-x}FeO_{3-y}(0.00{\leq}x{\leq}1.00)$ system has been prepared at $1200^{\circ}C$ under an atmospheric air pressure. The structures of solid solutions are studied by X-ray diffraction, thermal, Mohr salt, and Mossbauer spectroscopic analyses. Their physical properties are also discussed with the electrical conductivities. X-ray diffraction data for the compositions of x = 0.00, 0.25, and 1.00 are assigned to the orthorhombic and the compositions of x = 0.50 and 0.75 to the cubic systems. The lattice volume reduced to cubic cell increases with the x value. The mole ratio of $Fe^{4+}$ iometric chemical formulas of the system are formulated from the x, $\tau$, and y values. The mixed valency state of Fe ions, the oxygen coordination, and covalent bond character are discussed with the Mossbauer spectroscopic data. The activation enegy of the electrical conductivities depends on the $\tau$ value in the temperature range of -$100^{\circ}C$ to $600\circC$ under the air pressure. The Mossbauer spectrum and electrical conductivity of the solid solutions are discussed with nonstoichiometric chemical compositions.