• Korean Chemical Engineering Research
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• v.56 no.4
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• pp.536-541
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• 2018

Excess molar volumes ($V_m^E$) of binary mixtures of 1-propanol or 2-propanol (1) + cyclohexane or n-hexane (2) were measured with V-shaped dilatometer at 303.15 K. The $V_m^E$ data for these mixtures varied as: 2-propanol > 1-propanol and were higher for cyclohexane than n-hexane for both propanol systems. The experimental data were correlated with Redlich-Kister polynomial. The $V_m^E$ data were interpreted qualitatively as well as quantitatively in terms of Flory-Treszczanowicz-Benson model and Prigogine-Flory-Patterson theory. Both models correctly described the sign and shape of $V_m^E$ vs $x_1$ curves. The values calculated by both the models agree well with the experimental data.

• Journal of the Korean Ceramic Society
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• v.34 no.7
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• pp.693-698
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• 1997

The refractive index and dispersion in the (100-x)(0.6CaO.0.4Al2O3).xSiO2(x=0~30) glasses were investigated. As the amount of SiO2 increased, the refractive index decreased. The change of refractive index was attributed to the change of the molar refraction rather than the molar volume. When the amount of SiO2 was smaller than 20 mol%, the average electronic transition energy gaps(E0) and the electronic oscillator strengths(Ed) were about 10.9($\pm$0.1) nd 18($\pm$0.5)eV, respectively. However E0 and Ed of the glass (CAS30) with 30 mol% SiO2 increased to 12.63 and 19.89eV, respectively. The similar results was observed in the variation of Abbe Number. Abbe number of the glass in the range of 0~20 mol% SiO2 was about 46 and that of CAS30 increased to 60. The zero-material dispersion wavelength({{{{ lambda }}0) of pure calcium aluminate glass was 1.8 ${\mu}{\textrm}{m}$. As the amount of SiO2 increased, the zero-material dispersion wavelength shifted to a shorter wavelength. {{{{ lambda }}0 of CAS30 was 1.5 ${\mu}{\textrm}{m}$, that is currently using for the optical telecommunication system.

• Bulletin of the Korean Chemical Society
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• v.33 no.6
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• pp.1962-1966
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• 2012

Boehmite sols have been prepared by crystallization of amorphous aluminum hydroxide gel obtained by hydrolysis and peptization of aluminum using acetic acid. The size of the boehmite crystallites could be controlled by Al molar concentration in amorphous gel by means of controlling grain growth at nucleation stage. The size of boehmite increases as a function of Al molar concentration. With increasing boehmite crystallite size, the $d_{(020)}$ spacing and the specific surface area decreases, whereas the pore volume increases along with pore size. Especially, the pore size of the boehmite sol particles is comparable to the crystallite size along the b axis, suggesting that the fibril thickness along the b axis among the crystallite dimensions of the boehmite contributes to the pore size. Therefore, the physical properties of boehmite sols can be determined by the crystallite size controlled as a function of initial Al concentration.

• Coupled systems mechanics
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• v.8 no.2
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• pp.129-146
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• 2019

The main goal of this work is to develop a numerical simulator to study an isothermal single-phase two-component flow in a naturally fractured oil reservoir, taking into account advection and diffusion effects. We use the Peng-Robinson equation of state with a volume translation to evaluate the properties of the components, and the discretization of the governing partial differential equations is carried out using the Finite Difference Method, along with implicit and first-order upwind schemes. This process leads to a coupled non-linear algebraic system for the unknowns pressure and molar fractions. After a linearization and the use of an operator splitting, the Conjugate Gradient and Bi-conjugated Gradient Stabilized methods are then used to solve two algebraic subsystems, one for the pressure and another for the molar fraction. We studied the effects of fractures in both the flow field and mass transport, as well as in computing time, and the results show that the fractures affect, as expected, the flow creating a thin preferential path for the mass transport.

• Journal of Energy Engineering
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• v.23 no.4
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• pp.160-168
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• 2014

In the present study, water vapor adsorption was evaluated at 298.15K for 9 different zeolites having LTA, FAU, CHA, and RHO frameworks, and then effect of framework type, Si/Al molar ratio, and alkali ion type on water up-take was investigated. Zeolites showed water up-takes which were increased in an order of $RHO<CHA{\approx}LTA<FAU$ frameworks. NaY zeolite having FAU framework showed a water up-take of 406 mg/g at p/po=0.5. The up-take was a little larger than that of 13X zeolite with the same framework. Among LTA zeolites, Ca-type 5A zeolite showed the highest water adsorption (282 mg/g at p/po=0.5) which could be explained by the large pore volume. Both CHA zeolite with a Si/Al molar ratio of 2.35 and RHO zeolite with a Si/Al molar ratio of 3.56 showed considerable water up-takes, even though the Si/Al molar ratio was much larger than that of LTA zeolite. In the present study, it is announced that in addition to FAU and LTA zeolites, CHA and RHO zeolites can be a promising dehumidification adsorbent.

• Korean Chemical Engineering Research
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• v.57 no.1
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• pp.78-84
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• 2019

Recently, bio-butanol is being promoted as environmentally friendly sustainable energy. However, some problems are still obstacle for commercialization of bio-butanol: the development of cheap biomass and enhancement of fermentation ratio and preparation of economical separation process for fermented products. In the conventional ABE biobutanol fermentation process, organic acids with acetone, butanol, and ethanol are produced. Therefore, it is necessary to study phase equilibrium data and mixture properties for the design and operation of separation process. However, there is lack of design data for organic acids except acetic acid contained system. In this study, therefore, binary solid-liquid equilibria (SLE) and mixture properties: the excess molar volumes ($V^E$), molar refraction deviation (${\Delta}R$) and deviation of viscosity (${\Delta}v$) at 298.15 for $C_3-C_6$ organic acid were reported. The experimental SLE data were correlated with the NRTL and UNIQUAC activity coefficient model with less than 0.5 K of root mean square deviation (RMSD). In addition, $V^E$, ${\Delta}R$ and ${\Delta}v$ for the same binary systems were satisfactorily fitted using the Redlich-Kister polynomial with less than ca. 0.004 standard deviation.

• Imaging Science in Dentistry
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• v.45 no.3
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• pp.147-151
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• 2015

Purpose: The aim of this study was to investigate the effects of metal artifacts on the accurate diagnosis of root fractures using cone-beam computed tomography (CBCT) images with large and small/limited fields of view (FOVs). Materials and Methods: Forty extracted molar and premolar teeth were collected. Access canals were made in all teeth using a rotary system. In half of the teeth, fractures were created by the application of mild pressure with a hammer. The teeth were then randomly put into a wax rim on an acryl base designed in the shape of a mandible. CBCT scans were obtained using a Newtom 5G system with FOVs of $18cm{\times}16cm$ and $6cm{\times}6cm$. A metal pin was then placed into each tooth, and CBCT imaging was again performed using the same fields of view. All scans were evaluated by two oral and maxillofacial radiologists. The specificity, sensitivity, positive predictive value, negative predictive value, and likelihood ratios (positive and negative) were calculated. Result: The maximum levels of sensitivity and specificity (100% and 100%, respectively) were observed in small-volume CBCT scans of teeth without pins. The highest negative predictive value was found in the small-volume group without pins, whereas the positive predictive value was 100% in all groups except the large-volume group with pins. Conclusion: The specificity of CBCT decreased with the presence of a pin in the large-volume group, but not in the small-volume group.

• Journal of Dental Anesthesia and Pain Medicine
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• v.15 no.3
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• pp.121-128
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• 2015

Background: The authors studied the hemodynamic effect influent by using the novel high concentration of lidocaine HCl for surgical removal impacted lower third molar. The objective of this study was to evaluate the hemodynamic change when using different concentrations of lidocaine in impacted lower third molar surgery. Methods: Split mouth single blind study comprising 31 healthy patients with a mean age of 23 years (range 19-33 years). Subjects had symmetrically impacted lower third molars as observed on panoramic radiograph. Each participant required 2 surgical interventions by the same surgeon with a 3-week washout period washout period. The participants were alternately assigned one of two types of local anesthetic (left or right) for the first surgery, then the other type of anesthetic for the second surgery. One solution was 4% lidocaine with 1:100,000 epinephrine and the other was 2% lidocaine with 1:100,000 epinephrine. A standard IANB with 1.8 ml volume was used. Any requirement for additional anesthetic and patient pain intra-operation was recorded. Post-operatively, patient was instructed to fill in the patient report form for any adverse effect and local anesthetic preference in terms of intra-operative pain. This form was collected at the seven day follow up appointment. Results: In the 4% lidocaine group, the heart rate increased during the first minute post-injection (P < 0.05). However, there was no significant change in arterial blood pressure during the operation. In the 2% lidocaine group, there was a significant increase in arterial blood pressure and heart rate in the first minute following injection for every procedure. When the hemodynamic changes in each group were compared, the 4% lidocaine group had significantly lower arterial blood pressure compared to the 2% lidocaine group following injection. Post-operatively, no adverse effects were observed by the operator and patient in either local anesthetic group. Patients reported less pain intra-operation in the 4% lidocaine group compared with the 2% lidocaine group (P < .05). Conclusions: Our results suggest that a 4% concentration of lidocaine HCl with 1:100,000 epinephrine has better clinical efficacy than 2% lidocaine HCl with 1:100,000 epinephrine when used for surgical extraction of lower third molars. Neither drug had any clinical adverse effects.

• Bulletin of the Korean Chemical Society
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• v.31 no.1
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• pp.146-150
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• 2010

A distinguished class of hydrophobic ionic liquids bearing a Br${\o}$nsted acidic character derived from amide-like compounds were prepared by a neutralization reaction of N,N-diethylformamide, N,N-dibutylformamide, 1-formylpiperidine, and $\varepsilon$-caprolactam with trifluoroacetic acid and physical absorptions of $CO_2$ in these ionic liquids were demonstrated and evaluated. $CO_2$ solubilities in these ionic liquids were influenced by the molecular structure of the cation and were apparently increased with the molar volume. Comparison based on a volume unit reveals that $CO_2$ solubilities in these liquids are relatively higher than those in imidazolium-based ionic liquids. Henry's coefficients calculated from low-pressure solubility tests at 313 to 333 K were used to derive the thermodynamics quantities. Enthalpy and entropy of solvation may share equal contributions in solubility.

• Bulletin of the Korean Chemical Society
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• v.4 no.3
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• pp.115-119
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• 1983

The ionic association constants (K) of 2, N-dimethyl pyridinium iodide (2NDMPI) in 95 volume percentage ethanol-water mixture were determined by a modified UV and conductance method at $20^{\circ}C{\sim}50^{\circ}C$ under 1 to 2000 bars. The K values increase with increasing pressure and decrease with temperature. The total partial molar volume change (${\Delta}V$) has relatively small negative value and the absolute ${\Delta}V$ value decrease with increasing pressure and temperature. The ion size (a) and solvation number (n) of 2NDMPI were about 5 $\AA$ and changed from 1 to 3 with decreasing temperature. Other thermodynamic parameters such as enthalpy (${\Delta}H^{\circ}$) and entropy (${\Delta}S^{\circ}$) for the equilibrium of the 2NDMPI were evaluated. From all the parameters mentioned above, we came to conclusion that the electrostriction effect of 2NDMPI in the ethanol-water mixture is enhanced with increasing pressure and decreasing temperature.