• 대한금속재료학회지
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• 제46권4호
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• pp.257-266
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• 2008

AHydrogen induced cracking (HIC) was phenomenologically studied in terms of the effect of nonmetallic inclusions and hot rolling process parameters. By comparing the level of non-metallic inclusions in two different kinds of commercial grade steels having different HIC resistance, the role of non-metallic inclusions in HIC occurrence was investigated. Change in inclusion morphology and distribution during hot rolling was also studied throughout slab, rolling at austenite recrystallization region (roughing mill; RM) and rolling at austenite non-recrystallization region (finish mill; FM). In addition, the contribution of RM and FM parameters to HIC was investigated from the standpoint of change in inclusion morphology during hot rolling processes. As a result, HIC was closely related to the separation of large complex inclusion during hot rolling process. Large complex inclusions originated from the improper Ca treatment, after which equilibrium composition of slag should have resulted in eutectoid composition. By controlling the equilibrium slag composition equivalent to eutectoid one, HIC resistance could be improved due to the reduced size of inclusions. In addition, change in reduction/pass in RM had an effect on HIC resistance of steels while that in FM did not. Increase in the reduction/pass in the latter stage of RM improved HIC resistance of steels by enhancing the void enclosure around inclusions.

• 공업화학
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• 제10권5호
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• pp.677-681
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• 1999

휘발성 액체 혼합물의 분리공정에 필요한 증류탑 설계의 필수 요건인 기-액평형에 관한 연구로서 cyclohexanol-cyclohexanone 2성분계에 대한 감압하 즉 150, 300 및 500 mmHg에서의 기-액평형치를 측정하고, 이 측정치와 30, 100, 200, 395 및 750 mmHg에서의 이미 발표된 기-액평형치를 이용하여 비휘발도와 익조성의 관계로부터 cyclohexanol-cyclohexanone 2성분계의 기-액평형치를 추산하는 추산식을 구하고, 여기서 구한 추산치를 실측치 및 문헌치와 비교 검토하였다. 그 결과 적은 오차 범위에서 잘 일치함을 확인하였다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 추계학술대회 논문집
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• pp.254-257
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• 2008

For crystalline slags, of which the viscosity rapidly increases at $T_{cv}$ due to the formation of crystalline phases, the Tcv is affected by measurement conditions. In this study, we investigated the effect of cooling rate, and alumina dissolution on the determination of $T_{cv}$. Using synthetic slag samples based on the composition of Alaska Usibelli slag, $T_{cv}$ were determined under a constant cooling rate of $2^{\circ}C$/min, and under rapid cooling with holding time to allow the slag to reach thermal and rheological equilibrium. The effect of alumina dissolution was investigated using platinum lined crucibles. The constant cooling resulted in lower $T_{cv}$ by $33^{\circ}C$ as compared to the equilibrium measurements. Under $2^{\circ}C$/min cooling, the blocking alumina dissolution resulted in lower $T_{cv}$ by $23^{\circ}C$. When the $T_{cv}$ was measured under $2^{\circ}C$/min cooling using an alumina crucible, therefore, the effects of a constant cooling is somewhat offset by the alumina dissolution effect, and bring the measured value closer to the true value.

• The Korean Journal of Ceramics
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• 제4권2호
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• pp.68-71
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• 1998

The effect of Mn and Nb additions on the electrical properties of BaTiO$_3$ has been studied by means of equilibrium electrical conductivity as a function of temperature, oxygen partial pressure(Po$_2$) and composition. If the manganese ion is added to the normal Ti site, i.e. BaTi$_{1-x}Mn_xO_{\delta-6}$, the equilibrium conductivity shows strong evidence of acceptor-doped behavior. The conductivity minimum, corresponding to the transition from oxygen excess, p-type behavior to oxygen deficient, n-type behavior with decreasing Po$_2$, is displaced to lower Po$_2$ and is broadened and flattened. The partial replacement of Mn ion with Nb decreases the acceptor-doped effect and the total replacement exhibits a typical donor-doped behavior. It was confirmed that unlike undoped or other acceptor-doped behavior. It was confirmed that unlike undoped or other acceptor-doped samples, for the p-type region, the electrical conductivity follows the 1/6th power dependence of oxygen partial pressure.

• 한국광물학회지
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• 제9권2호
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• pp.93-101
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• 1996

Behavior of platinum group elements during crystallization within ore magma is of interest. In this study platinum is selected and its mineralogical and geochemical behavior in the presence of antimony and tellurium is investigated at 600$^{\circ}C$. High purity Pt, Sb, and Te are used as starting material and silica quartz tubings are as container. Rection products have been examined by use of ore microscope, X-ray diffractometer, electron microprobe analyser and micro-indentation hardness tester. stable phases at 600$^{\circ}C$ are platinum (Pt), Pt5Sb, Pt3Sb, PtSb, stumpflite (PtSb), geversite (PtSb), PtTe, Pt3Te4, Pt2Te3, moncheite (PtTe2), tellurantimony (Sb2Te3), and antimony (Sb). Geversite is the mineral showing the most significant extent of solid solution by up to 27 at% between Sb and Te elements. Isothermal section of 600$^{\circ}C$ is established in this study. It is noted that platinum cannot coexists with stumpflite or geversite under equilibrium condition, and stumpflite composition in equilibrium with geversite may be used as geothermometer.

• Journal of Dairy Science and Biotechnology
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• 제26권2호
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• pp.57-60
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• 2008

During cheese ripening, the textural properties of cheese undergo significant changes from short, grainy, irregular to smooth, homogeneous and connected (well-net) structure. To make this change, many biochemical reactions occur during ripening and there have been tremendous researches in this topic for decades. In this review, several key parameters, such as cheese composition (especially cheese moisture and cheese pH), proteolytic activity and changes in Ca equilibrium will be discussed to understand the development of cheese texture during ripening.

• 한국세라믹학회지
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• 제48권3호
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• pp.205-210
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• 2011

The dependence of sulfur redox behavior and its diffusivity on temperature and composition was studied in mixed alkali silicate melts by means of square wave voltammetry (SWV) at different frequencies in a temperature range of $1000^{\circ}C$ to $1400^{\circ}C$. The voltammograms showed two reduction peaks at high frequency but only one peak at low frequency. Irrespective of $K_2O/(Na_2O+K_2O)$, each peak potential due to reduction of $S^{6+}$ to $S^{4+}$ and $S^{4+}$ to $S^0$ moved toward a negative direction with temperature decrease, and the peak current showed a strong dependence on frequency at a constant temperature. However, the compositional dependence of the peak potential showed an inconsistent behavior with an increase of $K_2O$. The mixed alkali effect was not observed in sulfur diffusion. This inconsistency of both peak potential and diffusion for compositional dependence may be derived from the strong volatilization of sulfur in melts.

• Macromolecular Research
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• 제11권1호
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• pp.53-61
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• 2003

A molecular-thermodynamic model is developed for the salt-induced protein precipitation. The protein molecules interact through four intermolecular potentials. An equation of state is derived based on the statistical mechanical perturbation theory with the modified Chiew's equation for the fluid phase, Young's equation for the solid phase as the reference system and a perturbation based on the protein-protein effective two body potential. The equation of state provides an expression for the chemical potential of the protein. In a single protein system, the phase separation is represented by fluid-fluid equilibria. The precipitation behaviors are simulated with the partition coefficient at various salt concentrations and degree of pre-aggregation effect for the protein particles. In a binary protein system, we regard the system as a fluid-solid phase equilibrium. At equilibrium, we compute the reduced osmotic pressure-composition diagram in the diverse protein size difference and salt concentrations.

• 대한치과교정학회지
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• 제53권6호
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• pp.345-357
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• 2023

Enamel demineralization represents the most prevalent complication arising from fixed orthodontic treatment. Its main etiology is the development of cariogenic biofilms formed around orthodontic appliances. Ordinarily, oral biofilms exist in a dynamic equilibrium with the host's defense mechanisms. However, the equilibrium can be disrupted by environmental changes, such as the introduction of a fixed orthodontic appliance, resulting in a shift in the biofilm's microbial composition from non-pathogenic to pathogenic. This alteration leads to an increased prevalence of cariogenic bacteria, notably mutans streptococci, within the biofilm. This article examines the relationships between oral biofilms and orthodontic appliances, with a particular focus on strategies for effectively managing oral biofilms to mitigate enamel demineralization around orthodontic appliances.