• 전기화학회지
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• 제24권1호
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• pp.1-6
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• 2021

In this study, new morphology of NCA cathode material for lithium ion batteries was obtained through the electrospinning method. The prepared NCA nanofibers formed a nano-bush structure, and the primary particles were formed on the surface of the nanofibers. The embossing primary particles increased the surface area thus increasing the reactivity of lithium ions. The nano-bush structure could shorten the Li+ diffusion path and improve the Li+ diffusion coefficient. Scanning electron microscopy (SEM) revealed that the synthesized material consisted of nanofibers. The surface area of the nanofibers increased by primary particles was measured using atomic force microscopy (AFM). X-ray diffraction (XRD) analysis was carried out to determine the structure of the NCA nanofibers.

• Asian Pacific Journal of Cancer Prevention
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• 제15권19호
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• pp.8271-8277
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• 2014

Aims: Apparent diffusion coefficient (ADC) values of nodes in diffusion-weighted imaging (DWI) are widely used in differentiating metastatic from non-metastatic lymph nodes. The purpose of this meta-analysis was to demonstrate whether DWI could contribute to the precise diagnosis of breast cancer (BC) with and without lymph node metastasis (LNM). Materials and Methods: English and Chinese electronic databases were searched for relevant studies followed by a comprehensive literature search. Two reviewers independently assessed the methodological quality of the included trials based on the quality assessment of diagnostic accuracy studies (QUADAS). Summary odds ratios (ORs) and corresponding 95% confidence intervals (95% CIs) were calculated. Results: Final analysis of 624 BC subjects (patients with LNM = 254, patients without LNM = 370) were incorporated into the current meta-analysis from 9 eligible cohort studies. Combined ORs of ADCs suggested that ADC values in BC patients without LNM were higher than in patients with LNM (OR=0.56, 95%CI: 0.11-1.01, p=0.015). Subgroup analysis stratified by country indicated a low ADC value in BC patients with LNM rather than those without LNM among Chinese (OR=1.27, 95%CI: 0.89-1.66, p<0.001), Italians (OR=0.75, 95%CI: 0.13-1.38, p=0.018), and Egyptians (OR=1.27, 95%CI: 0.71-1.84, p<0.001). The findings of subgroup analysis by MRI machine type revealed that ADC values from diffusion MRI may be potential diagnostic indicators for BC using Non-Philips 1.5T (OR=1.10, 95%CI: 0.84-1.36, p<0.001). Conclusions: The main findings of our meta-analysis demonstrated that increased signal intensity on DWI and decreased signals on ADC are helpful in diagnosis of BC patients with or without LNM. DWI could therefore be an important imaging investigation in patients suspected of BC.

• 공업화학
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• 제9권5호
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• pp.774-780
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• 1998

스피넬 구조인 $LiMn_2O_4$의 안정성을 향상시키기 위해서 망간과 비슷한 이온반경을 갖는 여러 가지 금속원소, Mg, Fe, V, W, Cr, Mo들을 일부 치환하였으며 ($LiM_xMn_{2-x}O_4(0.05{\leq}x{\leq}0.02)$), 이 결과 $LiM_xMn_{2-x}O_4$ 정극은 정극물질로 사용할 경우 $LiMn_2O_4$보다 낮은 용량감소를 나타냈다. 그리고 화학확산계수의 측정 결과 $LiMg_{0.05}Mn_{1.9}O_4$와 $LiCr_{0.1}Mn_{1.9}O_4$의 화학확산계수는 $LiMn_2O_4$보다 약 10배 이상 크게 나타났다. 이러한 결과를 볼 때 $LiMn_2O_4$에 여러 가지 금속원소를 치환시킴으로 구조적인 안정화로 인한 전기화학적 성능을 향상시킬 수 있었다.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2017년도 춘계학술논문요약집
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• pp.227-228
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• 2017

In this paper, electrolytic behavior of Cerium and Ce-Bi ion system was studied. The electrochemical behavior of Ce was studied in $LiCl-KCl-CeCl_3$ molten salts using electrochemical techniques Cyclic Voltammetry on tungsten electrodes at 773K. During the process of CV electrolysis, intermetallic compound were observed of Ce, Cex-Biy. Further study, in order to determine clarity of diffusion coefficient in this experiment, we will compare result of electrochemistry method and we also need to quantitative research.

• 폴리머
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• 제24권6호
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• pp.802-809
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• 2000

Poly(L-glutamic acid) (PLGA)와 PVA 블렌드막을 제조한 후, ethanol 수용액중에서 막증의 polypeptide 사슬의 2차구조 전이거동에 미치는 용매조성 및 대이온종의 영향과 알칼리 금속 이온 (Li, na, K, Cs)에 대한 투과특성을 조사하였다. 막중 PLG 알칼리 금속염의 helix 형성거동에 있어 대이온 선택성은 Li>Na>K>Cs의 순으로 관찰되었고, 이와 같은 특이성은 탈용매화 에너지와 정전에너지의 감소에 따른 고분자 하전기와 대이온과의 contact ion-pair 형성에 의한 것으로 설명하였다. 또한 PLGA/PVA 블렌드막의 ethanol 수용액 중에서의 알칼리 금속이온의 투과거동을 살펴보면, ethanol 농도가 점차 증가함에 따라 K, Cs의 경우는 투고도가 증가한, Li, Na의 경우에는 감소하였다. K, Cs 이온의 경우 대이온과 염소이온간의 ion-pair (M$^{+}{\cdot}$Cl$^{-}$)형성에 의한 Donnan배제효과의 감소와 중성염 형태로의 분배량 증가때문인 것으로, Li, Na 이온의 경우 막중의 coil-helix 구조전이에 따른 자유체적의 감소와 고분자 하전기와의 상호작용이 증가하여 확산성이 크게 감소하였기 때문인 것으로 생각된다.

• 방사성폐기물학회지
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• 제18권1호
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• pp.1-18
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• 2020

Molten salt solutions consisting of eutectic LiCl-KCl and concentrations of samarium chloride (0.5 to 3.0 wt%) at 500℃ were analyzed using both cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The CV technique gave the average diffusion coefficient for Sm³⁺ over the concentration range. Equipped with Sm³⁺ diffusion coefficient, the Randles-Sevcik equation predicted Sm³⁺ concentration values that agree with the given experimental values. From CV measurements; the anodic, cathodic, and half-peak potentials were identified and subsequently used as a parameter to acquire EIS spectra. A six-element Voigt model was used to model the EIS data in terms of resistance-time constant pairs. The lowest resistances were observed at the half-peak potential with the associated resistance-time constant pairs characterizing the reversible reaction between Sm³⁺ and Sm²⁺. By extrapolation, the Voigt model estimated the polarization resistance and established a polarization resistance-concentration relationship.

• Computers and Concrete
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• 제10권1호
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• pp.79-93
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• 2012

This paper estimates theoretically the diffusion-reaction behaviour of sulfate ion in concrete caused by environmental sulfate attack. Based on Fick's second law and chemical reaction kinetics, a nonlinear and nonsteady diffusion-reaction equation of sulfate ion in concrete, in which the variable diffusion coefficient and the chemical reactions depleting sulfate ion concentration in concrete are considered, is proposed. The finite difference method is utilized to solve the diffusion-reaction equation of sulfate ion in concrete, and then it is used to simulate the diffusion-reaction process and the concentration distribution of sulfate ion in concrete. Afterwards, the experiments for measuring the sulfate ion concentration in concrete are carried out by using EDTA method to verify the proposal model, and results show that the proposed model is basically in agreement with the experimental results. Finally, Numerical example has been completed to investigate the diffusion-reaction behavior of sulfate ion in the concrete plate specimen immersed into sulfate solution.

• Asian Pacific Journal of Cancer Prevention
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• 제16권14호
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• pp.6135-6140
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• 2015

Background: The aim of this meta-analysis was to assess the efficacy of the apparent diffusion coefficient (ADC) value of diffusion-weighted MRI (DWI) for differentiating biliary tract cancer (BTC) from benign biliary tract diseases in Asians. Materials and Methods: We systematically searched Embase and PubMed prior to December 2014. Eight studies conducted in Asians met our predetermined inclusion criteria. Results: Our meta-analysis results showed that ADC values in BTC tissues were significantly lower than in benign biliary tract tissues (SMD = -1.54, 95%CI: -1.75~-1.33, P<0.001). Subgroup analysis based on the MRI machine type showed that the ADC values were consistent, accurate and reliable in the diagnosis of BTC when comparing cancer tissue vs. benign tissue under the Siemens 1.5 T/3.0 T, Philips 1.5 T/3.0 T, GE 1.5 T, and Toshiba 1.5 T types, respectively (all P<0.05). Further, ADC values were still consistent and accurate in the differential diagnosis of BTC under the b value of 800 and $1000s/mm^2$ (all P<0.05). Conclusions: Our findings supported potential clinical applications of DWI ADC values in differentiating BTC from benign biliary tract diseases in Asians.

• Journal of Electrochemical Science and Technology
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• 제13권4호
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• pp.438-452
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• 2022

For cuboid and ellipsoid crystallites of LiFePO₄ powders, by X-ray diffraction (XRD) and microscopic (TEM) studies, it is possible to determine the anisotropic parameters of the crystallite size distribution functions. These parameters were used to describe the cathode rate capability within the model of averaging the diffusion coefficient D over the length of the crystallite columns along the [010] direction. A LiFePO₄ powder was chosen for testing the developed model, consisting of big cuboid and small ellipsoid crystallites (close to them). When analyzing the parts of big and small rate capabilities, the fitting values D = 2.1 and 0.3 nm²/s were obtained for cuboids and ellipsoids, respectively. When analyzing the results of cyclic voltammetry using the Randles-Sevcik equation and the total area of projections of electrode crystallites on their (010) plane, slightly different values were obtained, D = 0.9 ± 0.15 and 0.5 ± 0.15 nm²/s, respectively. We believe that these inconsistencies can be considered quite acceptable, since both methods of determining D have obvious sources of error. However, the developed method has a clearly lower systematic error due to the ability to actually take into account the shape and statistics of crystallites, and it is also useful for improving the accuracy of the Randles-Sevcik equation. It has also been demonstrated that the shape engineering of crystallites, among other tasks, can increase the cathode capacity by 15% by increasing their size correlation coefficients.

• 전기화학회지
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• 제3권3호
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• pp.131-135
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• 2000

[ $LiMn_2O_4$ ]박막전지의 충방전 사이클에 따른 용량 감소의 원인을 파악하기 위하여, $LiMn_2O_4/1M\;LiClO_4-PC/Li$전지를 구성하여 충방전 사이클에 따른 AC impedance분석을 수행하였다. 적절한 등가회로를 이용하여 비선형 최소자승 맞춤에서 얻은 값이 Impedance측정 결과와 잘 일치하였다. 충방전에 따른 정전용량은 초기의 급격한 감소를 보인 이후 완만한 감소를 보였다. 충방전 사이클이 초기 70-100사이클까지는 저항 성분 중 양극전해질 계면의 전하 전달저항 성분이 급격히 증가하다가 이후 안정된 값을 보임으로 초기 급격한 용량변화의 원인으로 파악되었다. 전하전달 저항이 안정된 이후에는 Warburg저항이 충방전에 따라 조금씩 증가하였으며, LiMn2O4박막의 화학확산 계수가 사이클에 따라 초기 $5.15\times10^{-11}cm^2/sec$에서 800사이클이 지난 후 $6.3\times10^{-12}cm^2/sec$로 점차 감소하는 것이 관찰되어 100사이클이 후의 용량감소의 지배적 원인으로 파악하였다. Warburg저항의 증가는 Jahn-Teller변형 또는 Mn용해에 의한 것으로 추정하였다.