• Journal of the Korean Chemical Society
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• v.10 no.3
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• pp.114-118
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• 1966

The glass electrode was empirically calibrated in dioxane-and ethanol-water mixed solvents, by means of which the pH-meter reading could be converted to stoichiometric hydrogen ion concentration. By the potentiometric titration method, the thermodynamic dissociation constants of hydrogen cupferrate (HCup) with variations of ionic concentration in aqueous solution were determined, and by the extrapolation of the constants the new thermodynamic $pK_a$ value, 3.980${\pm}$0.006, at zero ional concentration was obtained. The thermodynamic dissociation constants of HCup in dioxane-and ethanol-water solution were also potentiometrically determined with the changes in composition of organic solvents at 0.01 and 0.05 of the ionic strength(${mu}$) and 25 $^{\circ}C$. The empirical formula of the constants with mole fraction(n) of the organic solvent are as follow: Dioxane-water solution. $pK_a$= 12.96n + 4.10 at ${\mu}$ = 0.01, n = 0.0228∼0.171 $pK_a$= 12.05n + 4.23 at ${\mu}$ = 0.05, n= 0.0228∼0.171 Ethanol-water solution, $pK_a$= 4.0ln + 4.26 at ${\mu}$= 0.01, n= 0.0395∼0.262 $pK_a$= 3.83n + 4.34 at ${\mu}$= 0.05, n= 0.0395∼0.262

• Macromolecular Research
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• v.14 no.3
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• pp.331-337
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• 2006

In the present study we investigated the relationship between the morphology and mechanical properties of electrospun polysulfone (PSF)/polyurethane (PU) blend nonwovens, by using the electrospinning process to prepare three types of electrospun nonwovens: PSF, PU and PSF/PU blends. The viscosity, conductivity and surface tension of the polymer solutions, were measured by rheometer, electrical conductivity meter and tensiometer, respectively. The electrospun PSF/PU blend nonwovens were characterized by scanning electron microscopy (SEM) and with a universal testing machine. The SEM results revealed that the electrospun PSF nonwoven had a structure consisting of cross-bonding between fibers, whereas the electrospun PU nonwoven showed a typical, point-bonding structure. In the electrospun PSF/PU blend nonwovens, the exact nature of the point-bonding structure depended on the PU contents. The mechanical properties of the electrospun PSF/PU blend nonwoven were affected by the structure or the morphology. With increasing PU content, the mechanical behaviors, such as Young's modulus, yield stress, tensile strength and strain, of the electrospun PSF/PU blend nonwovens were by up to 80%.

• Journal of the Korean Geotechnical Society
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• v.31 no.4
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• pp.13-18
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• 2015

Considering dredged ground is consolidated more than one meter, Compression index prediction is very important. But, UD-sampling and consolidation test are impossible because of high moisture content and weak shear strength. This paper demonstrates the compression index relation, $C_{c(d)}=F(e_d,C_c)$, between in-situ and dredged clay using N. Keith Tovey's Omega point and soil physical properties. Good relationship is confirmed between proposed formula and measured primary consolidation result on dredged ground in The Republic of Korea.

• Journal of the Korean Society of Safety
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• v.11 no.3
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• pp.81-88
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• 1996

In order to investigate the electrical properties of transformer oils for large power, the characteristics of AC and Impulse breakdown in gap length of 1.0~2.5mm and that of volume resistivity were researched in temperature range of 20~$100^{\circ}C$. An geometrical capacitance of electrode with coaxial cylindrical shape for measuring the volume resistivity was 16pF, and highmegohm meter with model no. VMG-1000 was used, and also the applied voltage were DC 100, 250 and 500V. In the dependance of breakdown characteristics due to electrode gap length, it was confirmed that breakdown voltage was nearly uniform by volume effect according to the increase of gap. In the characteristics for AC breakdown, the dielectric strength was increased to $90^{\circ}C$ but decreased over $90^{\circ}C$, and also in case of impulse breakdown, it was increased to 7$0^{\circ}C$ and at dated $70^{\circ}C$ over in temperature range. The calculated mobility of oils in the characteristics for impulse breakdown were about $10^{-5}$~$10^{-4}cm^2/V{\cdot}S$, and the value of volume resistivity was almost invariable in low temperature range, regardless of voltage by the stable thermal properties, and it indicated a peak at $50^{\circ}C$ and had a sudden change to decrease over that temperature, and also the value of volume resistivity in 250V/mm at $80^{\circ}C$ is suitable for the International electrical standards, it was confirmed.

• The Korean Journal of Food & Health Convergence
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• v.7 no.4
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• pp.23-29
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• 2021

This study analyzes the physiological changes that occur after free diving and studies peroxidants and antioxidants according to the recovery method. Accordingly, the purpose of this study is to provide proper rest methods after free diving and provide basic data for free diving research. Eight male college students recovered for 30 minutes after 20 free injections at a 5-meter diving site, 20 free injections after a week's car wash, and recovered for 30 minutes after collecting blood during recovery to analyze the effects of peroxidants and antioxidants. Comparison of changes in peroxidants and antioxidants in recovery methods after free-diving iterations showed that SOD tended to decrease immediately after free-diving, increasing MDA to 10 minutes after recovery, but no significant difference was found. The purpose of this study is to observe physiological changes according to the recovery method after free diving and to propose an appropriate recovery method after free diving. However, there was no significant difference in all the restoration methods, and 20 freediving was not high kinetic intensity for the subjects, which is believed to have resulted in the following results. Therefore, it was discussed that the repetitive diving strength should be higher to confirm a significant difference in the recovery method after free diving.

• Journal of International Academy of Physical Therapy Research
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• v.10 no.2
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• pp.1756-1762
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• 2019

Background: Functional ankle instability (FAI) indicating a decrease in muscle strength, proprioception, neuromuscular control, balance and postural control function. Objective: To investigate the effect of jumping exercise on the supporting surface on the ankle muscle thickness, proprioceptive sensation, and balance in adults with FAI. Design: Randomized Controlled Trial. Methods: Twenty young people with FAI were randomly assigned to the unstable supporting surface jump group (N=10) and the stable supporting surface jump group (N=10). The intervention was conducted three times a week for eight weeks, and for 30 minutes per session. Trampoline was used as an unstable support surface and the stable support surface was carried out on a regular floor. The thickness of the tibialis anterior muscle and medial gastrocnemius muscle was measured by ultrasonography, and the proprioception of dorsiflexion and plantarflexion was measured using an electrogoniometer. The dynamic balance was also measured with a balance meter. Results: The the muscle thickness of the medial gastrocnemius muscle was significantly higher in the stable supporting surface jump group than in the unstable supporting surface jump group (p<.05). Furthermore, the plantar flexion proprioception and dynamic balance were significantly improved in the unstable supporting surface jump group than in the stable supporting surface jump group in the intergroup comparison (p<.05). Conclusions: The conclusion has been reached in this study that the jumping exercise on the unstable supporting surface could be a more effective in improving FAI than the regular surface.

• Physical Therapy Rehabilitation Science
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• v.11 no.4
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• pp.446-453
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• 2022

Objective: The popularization of smartphones can lead to abnormal cervical alignment in university students. The aim of this study was to investigate the relationship among smartphone screen time, cervical alignment, and muscle function in university students. Design: Cross-sectional study. Methods: Seventy-five university students participated in the study. They completed the evaluation of cervical alignment and muscle function, such as handgrip strength, proprioception, and muscle quality (tone, stiffness, and relaxation time). All participants recorded their general characteristics and individual smartphone screen time before the evaluation. They were evaluated craniovertebral angle (CVA) using smartphone application (angle meter 360) for measuring cervical alignment. The muscle function was assessed using a digital hand-held dynamometer, dual inclinometer, and MyotonPRO device. Results: Of all participants, twenty-five university students had forward head posture (CVA<49°, 33.33%). Independent t-test revealed that there were significant differences on smartphone screen time, muscle stiffness, and muscle relaxation between the participants with and without forward head posture (p<0.05). There were significant correlations between the smartphone screen time and the CVA, muscle tone, and muscle relaxation (r=-0.493, 0.250, and -0.500, respectively). Conclusions: The results indicate that the university students with forward head posture had high smartphone screen time and muscle stiffness compared to the students without forward head posture, and smartphone screen time might be associated with cervical alignment and muscle quality.

• Computers and Concrete
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• v.33 no.5
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• pp.545-557
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• 2024

A real-case incident occurred where a 9-meter-high segment of a pre-fabricated concrete separation wall unexpectedly collapsed. This collapse was triggered by improperly depositing excavated soil against the wall's back, a condition for which the wall segments were not designed to withstand lateral earth pressure, leading to a flexural failure. The event's analysis, integrating technical data and observational insights, revealed that internal forces at the time of failure significantly exceeded the wall's capacity per standard design. The Lattice Discrete Particle Model (LDPM) further replicates the collapse mechanism. Our approach involved defining various parameter sets to replicate the concrete's mechanical response, consistent with the tested compressive strength. Subsequent stages included calibrating these parameters across different scales and conducting full-scale simulations. These simulations carried out with various parameter sets, were thoroughly analyzed to identify the most representative failure mechanism. We developed an equation from this analysis that quickly correlates the parameters to the wall's load-carry capacity, aligned with the simulation. Additionally, our study examined the wall's post-peak behavior, extending up to the point of collapse. This aspect of the analysis was essential for preventing failure, providing crucial time for intervention, and potentially averting a disaster. However, the reinforced concrete residual state is far from being fully understood. While it's impractical for engineers to depend on the residual state of structural elements during the design phase, comprehending this state is essential for effective response and mitigation strategies after initial failure occurs.

• Journal of the Korean Magnetics Society
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• v.23 no.2
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• pp.77-81
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• 2013

The objective of this study is experimentally to investigate natural convective heat transfer characteristics of the ferrofluid for a concentric annuli under rotating magnetic field with variations of the revolution and the magnetic field strength. The rotating magnetic field was provided by induction motor with 6 poles and 3 phases and the revolution and the magnetic field strength were controlled by an inverter driver and a voltage meter, respectively. Temperatures of the inner pipe and the outer pipe in the tested concentric annuli were maintained at $30^{\circ}C$ and $25^{\circ}C$, respectively, during the test and the direction of the rotating magnetic field was a counterclockwise. As a result, the natural convective heat transfer characteristics of the ferrofluid for a concentric annuli were increased with the rise of the revolution and magnetic field strength due to the increased heat dissipation between hot side and cold side of the concentric annuli.

• Journal of Sasang Constitutional Medicine
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• v.7 no.1
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• pp.69-101
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• 1995

Using Bi-Digital O-Ring Test which was developed by Ohmura Toshiaki, constitution classification by the vegetables' was measured by various muscle power measurement meters and the results are as follow : 1. Pinch guage (Model : pc5030HPG, Japan) is the guage to measure finger power between the thumb and second finger, Grip Strength Dynamometer (Model : T.K.K. 5101, Japan) is to measure the hand power (hand dynamometer), Back Strength dynamometer (Model : T.K.K. 5102, Japan)is to measue back muscle strength, Vertical Jump Meter (Model : T.K.K. 5106, Japan) is to measure the height of jump. The above guages were used and its result found that the radish, potato, carrot and cucumber can influence to the muscle strength was not true. 2. When the physical constitution is distinguished vy the O-Ring Test method, Taeyangin's rate appeared as average 21% although it was insistedthat there will be only 0.03-0.1%. This means that the influence power of vegetable doest not appear according to the physical constitution but it appears accidently according to the examinee's emotion about the material such as vegetable etc. as favor or unfavor. 3. It was found that the result of O-Ring Test is the same at any time and at any place was not true. there is no reemergence character. 4. The import of O-Ring Test method to the physical discriminatio disregarded that the mental facor influences absolutely to the physical heath in the ideological physical constitution medicla science. 5. 'O-Ring Test method is a objective judgement method'. is wrong judgement. As you see on the above result, Bi-Digital O-Ring Test set the changeable voluntary muscle as the standard of the judgement, that was first mistake logically, second in spite of leass influence of mental influence by the examiner and examinee than the vegetable discrimination influence, the test disregarded the influence. Thire, only grasp of some material on hand can influence to the voluntary was a wrong theory disregarding the physiology. Finally the misunderstaning his subjective view as an objective view in spite of examiner and examinee's strong influence. Therefore such kind of physical descrimination method must be sublated.