• Bulletin of the Korean Chemical Society
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• v.4 no.1
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• pp.10-14
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• 1983

Anisotropic rotation of C$_{6}$F$_{6}$ in neat liquid is investigated by the analysis of the ν$_{1}$ and ν$_{15}$ (both C-F stretching) bands of Raman spectrum and diffusion constants for the spinning (D$_{II}$) and tumbling (D$_{⊥}$) motions are obtained by the rotational dffusion theory. The same analysis is also carried out for the ν$_{2}$ and ν$_{16}$ (both C-C stretching) bands and both results are compared with the results obtained for benzene in neat liquid. The results show that the reorientation of C$_{6}$F$_{6}$ is highly anisotropic and the anisotropy is greater for C$_{6}$F$_{6}$ than benzene. This is due to the fact that the spinning rate is about the same but the tumbling rate is sharply reduced for C$_{6}$F$_{6}$.

• Bulletin of the Korean Chemical Society
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• v.17 no.11
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• pp.1004-1009
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• 1996

The interactions between a rod-coil liquid crystalline oligomer, ethyl 4-[4'-oxy-4-biphenylcarbonyloxy]-4'-biphenylcarboxylate with poly(ethylene oxide) (DP=12) (12-4) and LiCF3SO3 have been characterized by using Raman spectroscopy. Band assignments were made comparing the spectrum of 12-4 with those of the poly(ethylene glycol) monomethyl ether(PEGME) (Mw=550) and the ethyl-4'-hydroxybiphenyl-4-carboxylate (EHBPC), which are the coil and mesogen analogues, respectively. Analyzing characteristic bands of the 12-4-salt complex, we have found that the bands belonging to the coil and mesogenic units are changed in both intensities and frequencies. The spectral changes were interpreted from the viewpoint of the complexation between 12-4 and the Li+ ion. However, the possibility that the spectral changes in the mesogenic unit are not due to the complexation with the Li+ ion, but due to the conformational changes by the intercalation of nondissociated LiCF3SO3, is not ruled out.

• Bulletin of the Korean Chemical Society
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• v.21 no.10
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• pp.1035-1038
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• 2000

Vibrational properties of dopamine neutral species in powder state have been studied by means of the normal mode analysis based on the force constants obtained from the density functional calculation at B3LYP level and the results of Fourier trans form Raman and infrared spectroscopic measurements. Ab initio calculation at MP2 level shows that the trans conformer of dopamine has higher electronic energy about 1.4 kcal/mol than those of the gauche+ and the gauche-conformers, and two gauche conformers have almost the same energies. Free energies calculated at HF and B3LYP levels show very similar values for three conformers within 0.3 kcal/mol. Empirical force field has been constructed from force constants of three conformers, and refined upon ex-perimental Raman spectrum of dopamine to rigorous values. The major species of dopamine neutral base in the powder state is considered a trans conformer as shown in the crystallographic study of dopamine cationic salt.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.562-569
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• 2019

Raman spectroscopy has been receiving increased attention as a standoff explosive detection technique. In addition, there is a growing need for a fast search method that can identify raman spectrum for measured chemical substances compared to known raman spectra in large database. By far the most simple and widely used method is to calculate and compare the Euclidean distance between the given spectrum and the spectra in a database. But it is non-trivial problem because of the inherent high dimensionality of the data. One of the most serious problems is the high computational complexity of searching for the closet spectra. To overcome this problem, we presented the MPS Sort with Sorted Variance+PDS method for the fast algorithm to search for the closet spectra in the last paper. the proposed algorithm uses two significant features of a vector, mean values and variance, to reject many unlikely spectra and save a great deal of computation time. In this paper, we present two new methods for the fast algorithm to search for the closet spectra. the PCA+PDS algorithm reduces the amount of computation by reducing the dimension of the data through PCA transformation with the same result as the distance calculation using the whole data. the Hierarchical Cluster Tree algorithm makes a binary hierarchical tree using PCA transformed spectra data. then it start searching from the clusters closest to the input spectrum and do not calculate many spectra that can not be candidates, which save a great deal of computation time. As the Experiment results, PCA+PDS shows about 60.06% performance improvement for the MPS Sort with Sorted Variance+PDS. also, Hierarchical Tree shows about 17.74% performance improvement for the PCA+PDS. The results obtained confirm the effectiveness of the proposed algorithm.

• Journal of the Korean Ceramic Society
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• v.40 no.8
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• pp.770-776
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• 2003

#140 mesh and #600 mesh wheels were adopted to grind (111) and (100) oriented single crystalline silicon wafer and the grinding induced change of the surface integrity was investigated. For this purpose, microroughness, residual stress and phase transformation were analyzed for the ground surface. Microroughness was analyzed using AFM (Atomic Force Microscope) and crystal structure was analyzed using micro-Raman spectroscopy. The residual stress and phase transformation were also analyzed after thermal annealing in the air. As a result, microroughness of (111) wafer was larger than that of (100) wafer after grinding. It was observed using Raman spectrum that the silicon was transformed from diamond cubic Si-I to Si-III(body centered tetragonal) or Si-XII(rhombohedral). Residual stress relaxation was also shown in cavities which were produced after grinding. The thermal annealing was effective for the recovery of the silicon phase to the original phase and the residual stress relaxation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.8
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• pp.5280-5287
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• 2014

This paper proposes a method in which classes are grouped as a hierarchical tree structure for the effective classification of the Raman spectra. As experimental data, the Raman spectra of 28 chemical compounds were obtained, and pre-treated with noise removal and normalization. The spectra that induced a classification error were grouped into the same class and the hierarchical structure class was composed. Each high and low class was classified using a PCA-MAP method. According to the experimental results, the classification of 100% was achieved with 2.7 features on average when the proposed method was applied. Considering that the same classification rates were achieved with 6 features using the conventional method, the proposed method was found to be much better than the conventional one in terms of the total computational complexity and practical application.

• Analytical Science and Technology
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• v.11 no.1
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• pp.8-12
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• 1998

The 2,2'-Biimidazole was synthesized by the reaction between glycol and ammonium solution. The correct solid structure of 2,2'-biimidazole in this method reported either trans ($C_{2h}$) or cis ($C_{2v}$) form. In this study, the correct structure of 2,2'-biimidazole was analysed by both FTIR and Raman spectroscopy using mutual exclusion properties of them. Also, it was analysed by $^1H$ and $^{13}C$ NMR and computer molecular modeling. The structure of 2,2'-biimidazole found to be trans ($C_{2h}$) than cis ($C_{2v}$) by comparison between FTIR and Raman Spectra. This results agree with computer molecular modeling and x-ray crystallography. This study provide good evidence for identifying structural orientation of the 2,2'-biimidazole containing pyridyl nitrogen.

• Journal of the Korea Institute of Military Science and Technology
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• v.24 no.3
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• pp.264-271
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• 2021

Raman spectroscopy is an equipment that is widely used for classifying chemicals in chemical defense operations. However, the classification performance of Raman spectrum may deteriorate due to dark current noise, background noise, spectral shift by vibration of equipment, spectral shift by pressure change, etc. In this paper, we compare the classification accuracy of various machine learning algorithms including k-nearest neighbor, decision tree, linear discriminant analysis, linear support vector machine, nonlinear support vector machine, and convolutional neural network under noisy and spectral shifted conditions. Experimental results show that convolutional neural network maintains a high classification accuracy of over 95 % despite noise and spectral shift. This implies that convolutional neural network can be an ideal classification algorithm in a real combat situation where there is a lot of noise and spectral shift.

• Journal of Electrical Engineering and Technology
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• v.11 no.6
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• pp.1872-1879
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• 2016

The techniques to recycle and reuse plastics attract public attention. These public attraction and needs result in improving the recycling technique. However, the identification technique for black plastic wastes still have big problem that the spectrum extracted from near infrared radiation spectroscopy is not clear and is contaminated by noise. To overcome this problem, we apply Raman spectroscopy to extract a clear spectrum of plastic material. In addition, to improve the classification ability of fuzzy Radial Basis Function Neural Networks, we apply supervised learning based clustering method instead of unsupervised clustering method. The conditional fuzzy C-Means clustering method, which is a kind of supervised learning based clustering algorithms, is used to determine the location of radial basis functions. The conditional fuzzy C-Means clustering analyzes the data distribution over input space under the supervision of auxiliary information. The auxiliary information is defined by using k Nearest Neighbor approach.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.2
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• pp.133-138
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• 2001

We studied the optical properties of poly(3-hexylthiophene) for applying to the emitting material of organic electro luminescent device. The infrared spectrum and NMR of synthesized polymer gave good evidence for the conjugation of 3-hexylthiophene monomer unit. We confirmed that poly(3-hexylthiophene) contains the HT(head-to-tail)-HT(head-to-Tail) linkage larger than 65% based on NMR analysis. FTIR and raman spectroscopy show that poly(3-hexylthiophene) has two main vibration levels which have an energy about 0.18eV and 0.36eV. Electronic absorption spectra shifted to the shorter wavelength with increasing temperature, which is related to a conformational transition of the polymer. Photoluminescence spectrum generated at low temperature(10K) is separated at 669nm, 733nm and 812nm that it's because of phonon energy generated from the lattice vibration.