• The korean journal of orthodontics
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• v.51 no.4
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• pp.241-249
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• 2021

Objective: This study aimed to evaluate the volume, amount, and localization of root resorption in the maxillary first premolars using micro-computed tomography (micro-CT) after expansion with four different rapid maxillary expansion (RME) appliances. Methods: In total, 20 patients who required RME and extraction of the maxillary first premolars were recruited for this study. The patients were divided into four groups according to the appliance used: mini-implant-supported hybrid RME appliance, hyrax RME appliance, acrylic-bonded RME appliance, and full-coverage RME appliance. The same activation protocol (one activation daily) was implemented in all groups. For each group, the left and right maxillary first premolars were scanned using micro-CT, and each root were divided into six regions. Resorption craters in the six regions were analyzed using special CTAn software for direct volumetric measurements. Data were statistically analyzed using Kruskal-Wallis one-way analysis of variance and Mann-Whitney U test with Bonferroni adjustment. Results: The hybrid expansion appliance resulted in the lowest volume of root resorption and the smallest number of craters (p < 0.001). In terms of overall root resorption, no significant difference was found among the other groups (p > 0.05). Resorption was greater on the buccal surface than on the lingual surface in all groups except the hybrid appliance group (p < 0.05). Conclusions: The findings of this study suggest that all expansion appliances cause root resorption, with resorption craters generally concentrated on the buccal surface. However, the mini-implant-supported hybrid RME appliance causes lesser root resorption than do other conventional appliances.

• Carbon letters
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• v.22
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• pp.70-80
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• 2017

Activated carbons (ACs) have been used as electrode materials of electric double-layer capacitors (EDLC) due to their high specific surface areas (SSA), stability, and ecological advantages. In order to make high-energy-density ACs for EDLC, petroleum pitch (PP) pre-carbonized at $500-1000^{\circ}C$ in $N_2$ gas for 1 h was used as the electrode material of the EDLC after KOH activation. As the pre-carbonization temperature increased, the SSA, pore volume and gravimetric capacitance tended to decrease, but the crystallinity and electrode density tended to increase, showing a maximum volumetric capacitance at a medium carbonization temperature. Therefore, it was possible to control the crystalline structure, SSA, and pore structure of AC by changing the pre-carbonization temperature. Because the electrode density increased with increasing of the pre-carbonization temperature, the highest volumetric capacitance of 28.4 F/cc was obtained from the PP pre-carbonized at $700^{\circ}C$, exhibiting a value over 150% of that of a commercial AC (MSP-20) for EDLC. Electrochemical activation was observed from the electrodes of PP as they were pre-carbonized at high temperatures above $700^{\circ}C$ and then activated by KOH. This process was found to have a significant effect on the specific capacitance and it was demonstrated that the higher charging voltage of EDLC was, the greater the electrochemical activation effect was.

• Journal of the Korean Chemical Society
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• v.36 no.4
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• pp.517-522
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• 1992

The reaction of ${\beta}$-picoline with substituted benzoyl chlorides has been studied by means of conductometry under various pressures in acetonitrile. From the values of pseudo-first order and second order rate constants, the activation parameters (${\Delta}V{\neq}$, ${\Delta}{\beta}{\neq}$, ${\Delta}H{\neq}$, ${\Delta}S{\neq}$ and ${\Delta}G{\neq}$) and the pressure dependence of Hammett ${\rho}$ value were studied. The activation volume, the activation compressibility coefficient and the activation entropy were all negative. By increasing pressure the rate constant and Hammett ${\rho}$ value were increased, and the reaction mechanism was proceed in bond formation favored.

• Journal of the Korean Chemical Society
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• v.36 no.2
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• pp.180-184
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• 1992

Kinetic studies for the reaction of pyridine with substituted benzoyl chlorides were conducted under various pressures (1-1000 bar) in acetonitrile. From rate constants, the activation parameters (${\Delta}V^{\neq}$, ${\Delta}{\beta}^{\neq}$,${\Delta}H^{\neq}$, ${\Delta}S^{\neq}$ and ${\Delta}G^{\neq}$) were evaluated. Rates of these reaction increased with an increase in the pressure. The activation volume, the activation compressibility coefficient and the activation entropy were negative. From substituents effect and these results, it was found that these reactions proceed through $S_N2$ mechanism, but the structure of transition state was slightly changed with substituents and pressure.

• Transactions of the Korean Society of Automotive Engineers
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• v.1 no.1
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• pp.50-58
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• 1993

The ignition delay of diesel oil and fish oil blended with diesel oils was investigated at various pressure and temperature conditions in a constant volume combustion bomb. The evaporation and combustion duration of diesel oil and fish oil blended with diesel oils were respectively different in high and low temperature. The dependence of ignition delay on the temperature was different in high and low temperature ranges which were divided at the 773K. The dependence of ignition delay on the pressure was almost linear, regardless of the test fuels at the constant temperature(863K). The ignition delay became longer as the blending rate of fish oil increased at the constant temperature and pressure, but it was especially short with 20% fish oil blended with diesel oils.

• The Journal of Korean Physical Therapy
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• v.25 no.5
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• pp.260-265
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• 2013

Purpose: This study was conducted in order to evaluate the quantitative effectiveness of region of interest (ROI) setting in MR-DTI analysis with and without fMRI activation results. Methods: Ten right-handed normal volunteers participated in this study. DTI and fMRI datasets for each subject were obtained using a 1.5T MRI system. For neural fiber tracking, ROIs were drawn using two methods: The drawing points were located in the fMRI activation areas or areas randomly selected by users. In this study, the neural fiber tract targeted the corticospinal tract (CST) Quantitative analyses were performed and compared. The pixel numbers passing through the fiber tract in the individual brain volume were counted. The ratios between the ROI pixel numbers and the extracted fiber pixel numbers, and the ratios between the fiber pixel numbers and the whole-brain pixel numbers were also calculated. Results: According to our results, extracted CST fiber tract in which the ROI was drawn with fMRI activation areas showed higher distribution than drawing the ROI by users' hands. In addition, the quantitatively measured values represented higher pixel distribution: The counted average pixel numbers were 4553.8 and 1943.3. The average ratios of the ROI areas were 33.87 and 22.52. The average percentages of the individual whole-brain volume numbers were 2.06 and 0.87. Conclusion: Results of this study appear to indicate that use of this method can allow for more objectives and significant for study of the recovery of neural fiber mechanisms and brain rehabilitation.

• Clean Technology
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• v.19 no.3
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• pp.279-286
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• 2013

Using a cation exchange resin of polystyrene-DVB copolymer as a carbon source for the production of activated carbon, the effects of operating parameters on the physical properties of activated carbon such as specific surface area and specific pore volume were experimentally studied. In carbonization process specific surface area and specific pore volume of carbonized product decreased with the increase of carbonization temperature and time. They were proportional to activation temperature and time up to the specific temperature and time in activation process. In carbonization process the increase of heating rate gave negative effect to the properties. The properties of activated product, on the contrary, increased with the heating rate in carbonization process. The properties of activated carbon manufactured with the resin exchanged with divalent cations were lower than those with raw resin.

• Journal of Radiation Protection and Research
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• v.29 no.1
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• pp.17-23
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• 2004

In order to save time and money needed in the purchase commonly used gamma-ray standard sources, a new radioactive standard source was manufactured by the neutron activation of some regent in the research reactor HANARO. The source was manufactured with an aqueous solution by mixing and dissolving the irradiated reagents. The manufactured source was compared with a commercial standard source. It was confirmed that it could be used as an efficiency calibration source. Also, in order to compare the variation of efficiency due to the volume difference for various containers used in radioactivity assay, the efficiency variation as a function of sample volume was investigated.

• Journal of the Korean Chemical Society
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• v.40 no.5
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• pp.327-332
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• 1996

The rates of solvolylsis of methyl chloroformate, phenyl chloroformate and 1-adamantyl derivatives in binary solvent mixtures have been measured by conductometric method at various temperatures and pressures. The activation parameters were estimated from the rate constants. The activation volume (${\Delta}V_o^{\neq}$) and the activation entropy (${\Delta}S^{\neq}$) are both negative, but the activation enthalpy (${\Delta}H^{\neq}$) is positive. This behavior is discussed in terms of electrostriction of solvation. The reactivities of these reactions were also estimated from the correlation of the activation volumes with the activation entropies. From these results, it could be estimated that the solvolyses of 1-adamantyl fluoroformate (in aqueous TFE) and 1-adamantyl tosylate have pathway involving unimolecular reaction, while the reaction of methyl chloroformate, phenyl chloroformate and 1-adamantyl fluoroformate (in aqueous alcohol) proceed through a bimolecular reaction.

• Journal of the Korean Society of Physical Medicine
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• v.16 no.1
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• pp.111-121
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• 2021

PURPOSE: This study examined the effects of core stability exercise on the strength, activation of the trunk muscle, and pulmonary function in a Guillain-Barre syndrome (GBS) patient. METHODS: A 38-year-old male with GBS was enrolled in the study. A core stability exercise program was implemented for four weeks with a duration of 30 min/day and a frequency of three days/week. The program consisted of abdominal crunch, Swiss ball crunch, bicycle crunch, medicine ball sit-up with a toss, medicine ball rotational chest pass, raised upper body and lower body, and dead bug. Measurements of the strength of the trunk muscle (trunk flexion and hip flexion), activation of trunk muscles (rectus femoris; RA, external oblique abdominal; EOA, internal oblique abdominal; IOA, erector spinae; ES), and pulmonary function (forced expiratory capacity; FVC, forced expiratory volume at one second; FEV1) were taken before and after four weeks of core stability exercise. RESULTS: The strength of trunk muscles increased in the trunk and hip flexion after four weeks of core stability exercise, respectively, compared to the baseline levels. Activation of the trunk muscles increased in RA, EOA, and IOA after four weeks of core stability exercise compared to baseline levels, but decreased in ES after four weeks of core stability exercise compared to the baseline levels. The pulmonary function increased in FVC and FEV1 after four weeks of core stability exercise compared to the baseline levels. CONCLUSION: These results suggest that core stability exercise improves strength, Activation of the trunk muscle, And pulmonary function in patients with GBS.