• Bulletin of the Korean Chemical Society
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• 제31권4호
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• pp.1004-1013
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• 2010

Three-dimensional superstructures of unique self-assemblies generated by exploring the conformational flexibility of various dipyrromethenes through creation of hydrogen-bonds with metal-halide anions are reported and the conformational diversity is thoroughly described in the solid and solution states by X-ray diffraction analysis and variable temperature NMR spectroscopy. The tetrahedral or octahedral structures of their precursors, various metal-dipyrromethene complexes, are also reported, based on the crystallographic data. STM images of the self-assemblies observed on graphite surfaces present interesting arrangements and appear as tubular bunches.

• Natural Product Sciences
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• 제27권3호
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• pp.183-186
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• 2021

A new acridone alkaloid, melixyloidin (1), and two known alkaloids (2-3) were isolated from Melicope xanthoxyloides (F. Muell) T.G. Hartley leaves. The structure of melixyloidin were elucidated using NMR spectra and high-resolution ESIMS data. Acridone alkaloids 1-3 were evaluated against MCF-7 and HeLa cells. 1,3,4-Trimethoxy-10-methylacridin-9-one (2) showed potent cytotoxic activity against MCF-7 cells with an IC₅₀ value of 5.31 μM.

• Journal of Industrial and Engineering Chemistry
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• 제67권
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• pp.407-416
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• 2018

This study presents a novel complete solution starting with a synthesis of silica modified with potassium-nickel hexacyanoferrate and ethanolamine (SiEA-KNiFe) sorbent through radiocesium sorption in different process configurations and moving on to the vitrification of the spent sorbent, using the sol-gel method. The experimental data for deionized water solution, as well as seawater solution, correlates strongly with the Langmuir isotherm model. Moreover, the study also presents a method for spent sorbent solidification in the glass matrix. The cesium leaching test confirmed that spent sorbent can be stably bound in the glass matrix after radionuclide removal.

• Bulletin of the Korean Chemical Society
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• 제25권7호
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• pp.1061-1064
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• 2004

Molecular visualization software has the common objective of manipulation and interpretation of data from numerical simulations. They visualize many complicated molecular structures with personal computer and workstation, to help analyze a large quantity of data produced by various computational methods. However, users are often discouraged from using these tools for visualization and analysis due to the difficult and complicated user interface. In this regard, we have developed an easy-to-use three-dimensional molecular visualization and analysis program named POSMOL. This has been developed on the Microsoft Windows platform for the easy and convenient user environment, as a compact program which reads outputs from various computational chemistry software without editing or changing data. The program animates vibration modes which are needed for locating minima and transition states in computational chemistry, draws two and three dimensional (2D and 3D) views of molecular orbitals (including their atomic orbital components and these partial sums) together with molecular systems, measures various geometrical parameters, and edits molecules and molecular structures.

• Bulletin of the Korean Chemical Society
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• 제7권1호
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• pp.29-35
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• 1986

An empirical formula for semiconductive metal oxides is proposed relating nonstoichiometric value x to a temperature or an oxygen partial pressure such that experimental data can be represented more accurately by the formula than by the well-known Arrhenius-type equation. The proposed empirical formula is log x = A + $B{\cdot}1000/T\;+\;C{\cdot}$exp$(-D{\cdot}1000/T)$ for a temperature dependence and $log\;{\times}\;=a\;+b{\cdot}log\;Po_2\;+\;c{\cdot}$exp$(-d{\cdot}log\;Po_2)$ for an oxygen partial pressure dependence. The A, B, C, D and a, b, c, d are parameters which are evaluated by means of a best-fitting method to experimental data. Subsequently, this empirical formula has been applied to the n-type metal oxides of $Zn_{1+x}O,\; Cd_{1+x}O,\;and\;PrO_{1.8003-x}$, and the p-type metal oxides of $CoO_{1+x},\; FeO_{1+x},\;and\;Cu_2O_{1+x}$. It gives a very good agreement with the experimental data through the best-fitted parameters within 6% of relative error. It is also possible to explain approximately qualitative characters of the parameters A, B, C, D and a, b, c, d from theoretical bases.

• Nuclear Engineering and Technology
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• 제53권4호
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• pp.1088-1099
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• 2021

Time-frequency analysis technique is an effective analysis tool for non-stationary processes. In the field of reactor neutron noise, the time-frequency analysis method has not been thoroughly researched and widely used. This work has studied the time-frequency analysis of the reactor neutron noise experimental signals under bubble disturbance and control rod vibration. First, an experimental platform was established, and it could be employed to reactor neutron noise experiment and data acquisition. Secondly, two types of reactor neutron noise experiments were performed, and valid experimental data was obtained. Finally, time-frequency analysis was conducted on the experimental data, and effective analysis results were obtained in the low-frequency part. Through this work, it can be concluded that the time-frequency analysis technique can effectively investigate the core dynamics behavior and deepen the identification of the unstable core process.

• 대한화학회지
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• 제47권5호
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• pp.487-494
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• 2003

이 연구에서는 탐구화학실험을 통해 고등학교 학생들의 과학 성취도 향상정도를 논리적 사고력, 과학탐구기능, 실험 태도, 수공적 기능, 탐구과정 기능 등의 측면에서 조사하였다. 이를 위해 수도권 소재의 남녀 고등학교 2개교의 5개조 150명을 대상으로 하여 논리적 사고력, 과학탐구기능의 지필평가와 탐구과정 기능의 보고서평가, 실험태도, 수공적 기능의 실험관찰 평가를 통하여 자료를 수집하였다. 연구 결과에 의하면 학생들의 탐구과정기능과 실험 태도, 수공적 기능은 전반적으로 매우 낮은 수준으로 조사되었으나 탐구과정 기능을 제외 한 나머지의 측면에서는 유의미한 향상을 보였다. 또한 탐구화학실험이 지속적으로 수행될 때 학습자의 과학 성취도가 향상됨을 알 수 있었다.

• 보존과학회지
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• 제5권1호
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• pp.69-86
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• 1996

More than eighty thousands of wooden printing blocks of the Tripitaka Koreans are accommodated in the Changkyeonggak which consists of two open structured wooden buildings, Peoppojeon and Sudarajang. These blocks are virtually in pristine state even after three quarters of a millennium. The excellent preservation could be attributed to the careful preparation and meticulous finish of the blocks. But the meteorological environment or microclimate should be one of the key factors for the preservation. To keep the blocks intact as it is or at least do not accelerate the deterioration, we should study the blocks and its microclimatic environment supplied by the Changgyeonggak and the topology of the site. As a Part of this effort we designed a computerized meteorological data acquisition system, which can handle up to 4,096 sensors. A partial but operative installation of 16 temperature/humidity sensors was set up in the Peoppojeon. We hope to have a chance to install a full fledged system in the near future for the compilation of the fuller environmental data base.

• Bulletin of the Korean Chemical Society
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• 제32권4호
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• pp.1187-1194
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• 2011

The hydrogen abstraction reaction of $CF_3CH_2CHO$ + OH has been studied theoretically by dual-level direct dynamics method. Two stable conformers, trans- and cis-$CF_3CH_2CHO$, have been located, and there are four distinct OH hydrogen-abstraction channels from t-$CF_3CH_2CHO$ and two channels from c-$CF_3CH_2CHO$. The required potential energy surface information for the kinetic calculation was obtained at the MCG3-MPWB//M06-2X/aug-cc-pVDZ level. The rate constants, which were calculated using improved canonical transitionstate theory with small-curvature tunneling correction (ICVT/SCT) were fitted by a four-parameter Arrhenius equation. It is shown that the reaction proceeds predominantly via the H-abstraction from the -CHO group over the temperature range 200-2000 K. The calculated rate constants were in good agreement with the experimental data between 263 and 358 K.

• Bulletin of the Korean Chemical Society
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• 제30권11호
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• pp.2701-2706
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• 2009

The polymer blends containing polypyrrole (PPy) and the sulphonic acids such as β-naphthalene sulfonic acid (NSA), camphor sulfonic acid (CSA), and dodecylbenzenesulfonic acid (DBSA) were synthesized by in situ deposition technique in an aqueous media using ammonium per sulfate (APS) as an initiator. The obtained films were characterized by scanning electron microscopy (SEM), and the thermal behavior of these polymer blends was analyzed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The temperature-dependent (DC) conductivity of the obtained films shows a semiconducting behavior with a negative temperature coefficient of resistivity (TCR). The conductivity data were also analyzed through Mott’s equation, which provides the variable range hopping model in three dimensions. The parameters such as density of states at the Fermi energy, hopping energy, and hopping distance were calculated for PPy, PPy-NSA, PPy-CSA, and PPy-DBSA films, and the data were compared.