• Journal of the Society of Naval Architects of Korea
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• v.55 no.2
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• pp.153-160
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• 2018

In order to develop the driving pump for High-speed Cavitation Tunnel(HCT) which can experiment the super-cavitating submerged body, KRISO decided on the pump specification, designed the mixed-flow pump on the basis of the existing pump data and predicted the performance of the design pump using commercial CFD code (CFX-10). After the manufacture and installation of the driving pump, KRISO conducted the trial-test for HCT, analyzed the pump performance and compared trial-test results to those of design stage. The trial-test items for the HCT driving pump are measurements of output current/voltage at the inverter of the driving pump and the flow velocity in the HCT test section. The trial-test results showed the decrease in the flow rate of about 4.6% and the increase in pump head of about 8%, compared with those of the pump prediction. After the trial-test, the performance of the driving pump is predicted using CFX-10 with measured flowrates and pump rotational velocities. Though there is some difference between trial-test and prediction results due to inadequate motor data, it is thought that the tendency is reasonable. It is found that CFX-10 is useful to predict a mixed-flow pump.

• Restorative Dentistry and Endodontics
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• v.16 no.1
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• pp.209-215
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• 1991

The propose of this study was to evaluate the effect of the variuos antiseptic solutions and distilled water on physical properties of endodontic gutta-percha cone. The antiseptic solutions were 70% isoprophyl alcohol, 5% NaOCl and 2.5% NaOCl, as control gutta-percha cones, did not stored antiseptic solution was used. Observation periods were 1, 5, 10, 20, and 30 days. In each group,. the 15 gutta-percha cones used. A tensile strength and elongation rate measurements were performed with Instron (Instron 4501), cross - head speed was set 10 inch / min. The data were statistically analyzed and the results were as followed. 1. The tensile strength of the gutta-percha cones, stored in distilled water, were slightly decreased (p<0.05). Elongation rate was not significantly different 2. The tensile strength of the gutta-percha cones, stored in 70% isopropyl alcohol, were increased (p<0.01) except 1 day group. 3. The tensile strength of the gutta-percha cone, stored in 2.5% NaOCl, were decreased (p<.0.05). Elongation rate significantly decreased (p<0.01). 4. The tensile strength of the gutta-percha cone, stored in 5% NaOCl, were decreased (p<0.05). Elongation rate significantly decreased (p<0.01). These results showed that the changes of physical properties (tensile strength and elongation rate) in gutta-percha cone were developed after a day' when gutta-percha cone were stored at 70% isopropyl alcohol, 2.5% or 5% NaOCl. So, It was concluded that gutta-percha cone must have been used at least within one day, when they were stored at the above antiseptics. I thought that the study of substantial effects on endodontic treatment due to changes of physical properties in gutta-percha cone will be needed.

• Physical Therapy Rehabilitation Science
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• v.7 no.1
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• pp.35-40
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• 2018

Objective: The purpose of this study was to investigate the immediate effect of applying self-myofascial release (SMR) to the plantar fascia using a foam roller on hamstring and lumbar spine superficial back line (SBL). Design: Randomized controlled trial. Methods: Thirty-one healthy adults agreed to the method and purpose of the study. Selection and exclusion criteria were screened, and baseline measurements for the Toe Touch test and passive straight leg raise (PSLR) test were obtained. The participants were then randomly assigned to the SMR group or the sham group. After group assignment, the SMR group rolled the surface of the foot from the heel to the metatarsal head using a foam roller for 5 minutes. The sham group received passive mobilization of the ankle joint in the supine position. Afterwards, the Toe Touch test and the passive straight leg-raise test were re-assessed. Results: In the SMR group, the Toe Touch test results showed significant improvement (p<0.05). Left and right PSLR test results showed a significant increase (p<0.05). In the sham group, there was no significant difference between pre and post-test results. The SMR group showed a significant difference in the PSLR test and Toe Touch test compared to the sham group (p<0.05). Conclusions: The results of this study showed that SMR on the plantar fascia was immediately effective for improving the flexibility of the SBL of the lumbar spine and hamstring.

• Journal of the Korean GEO-environmental Society
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• v.11 no.12
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• pp.27-35
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• 2010

The structures built under the groundwater level are affected by the buoyancy force, which is hydrostatic pressure in the up direction. Recently, buoyancy-resistant anchor method has been applied in many cases of the construction of the important structure of large size, which is built under the groundwater level so that it takes high uplift pressure. Even if the construction cost of the method is very high, it surely increases the safety rate. However, the diagnosis of the performance of the buoyancy-resistant permanent anchor and the investigation of resistance mechanism are still insufficient. Especially, the long-term behavior of the anchor has not been studied well due to the difficulty in observation procedure. The contribution of this paper is the establishment of reasonable design methodology. We have measured anchor axial forces for 10 years after the construction, by using an automated measurement and a manual measurement by establishing a load cell in anchor head. Through the data collected from the measurements, we analyze the construction-step behavior of the anchor according to the self-weight variation of the building and the long-term behavior (i.e. movement within 10 years after the construction) of the anchor according to the passage of time.

• Restorative Dentistry and Endodontics
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• v.26 no.1
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• pp.41-50
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• 2001

The purpose of this study was to examine the influences of camphoroquinone on the properties of five experimental composites. The contents of camphoroquinone were varied as 0.2%, 0.3%, 0.4%, 0.5%, and 0.6%, with silanized filler 75% and tertiary amine 0.2%. Five kinds of experimental composites were prepared, and diametral tensile strength, shear bond strength, depth of cure and yellowish discoloration were tested as a measurement. Specimen numbers of 10 were applied to all test items and experimental groups. Specimens for testing the diametral tensile strengths with internal diameter of 6mm in diameter and 3mm in height were filled with 5 experimental composites which were crushed with 1mm/min cross-head speed on Instron universal testing machine (Model No. 4467). Shear bond strength was measured on specimens attached to bovine teeth enamel etched with 37% phosphoric acid. Depth of cure was measured by the measurement of height of specimens which were removed the un-polymerized portion with acetone. Yellowness measurements were made by chromometer(Minolta Co. Japan) using L$^*$a$^*$b$^*$ values. ANOVA and Multiple range tests were used analyzed data with confidence level at 95%. The mean value of the shear bond strengths ranged from 31.03MPa to 39.49MPa. Following results were obtained ; 1. Diametral tensile strength was highest in experimental group 3, then was not affected by the contents of camphoroquinone ($r^2$=0.0422). 2. Composite resins containing 0.4% camphoroquinone showed the highest shear bond strength, but there was no statistical significance (p=0.3718). 3. Camphoroquinone reduces the depth of cure in the composite resins (p=0.0004, $r^2$=0.9483). 4. Camphoroquinone made the composites yellowish ($r^2$=0.9815). These results mean that increased content of camphoroquinone reduces the depth of cure, and that camphoroquinone make composites yellowish.

• The Korean Journal of Physiology and Pharmacology
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• v.24 no.5
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• pp.423-431
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• 2020

This study aimed to evaluate the effect of curcumin on brain hypoxic-ischemic (HI) damage in neonatal rats and whether the phosphoinositide 3-kinase (PI3K)/Akt/vascular endothelial growth factor (VEGF) signaling pathway is involved. Brain HI damage models were established in neonatal rats, which received the following treatments: curcumin by intraperitoneal injection before injury, insulin-like growth factor 1 (IGF-1) by subcutaneous injection after injury, and VEGF by intracerebroventricular injection after injury. This was followed by neurological evaluation, hemodynamic measurements, histopathological assessment, TUNEL assay, flow cytometry, and western blotting to assess the expression of p-PI3K, PI3K, p-Akt, Akt, and VEGF. Compared with rats that underwent sham operation, rats with brain HI damage showed remarkably increased neurological deficits, reduced right blood flow volume, elevated blood viscosity and haematocrit, and aggravated cell damage and apoptosis; these injuries were significantly improved by curcumin pretreatment. Meanwhile, brain HI damage induced the overexpression of p-PI3K, p-Akt, and VEGF, while curcumin pretreatment inhibited the expression of these proteins. In addition, IGF-1 treatment rescued the curcumin-induced down-regulated expression of p-PI3K, p-Akt, and VEGF, and VEGF overexpression counteracted the inhibitory effect of curcumin on brain HI damage. Overall, pretreatment with curcumin protected against brain HI damage by targeting VEGF via the PI3K/Akt signaling pathway in neonatal rats.

• Journal of Korea Foundry Society
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• v.22 no.3
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• pp.109-113
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• 2002

A good fluidity of high strength Al-alloys is required to cast thin wall castings needed to reduce the weight of cast parts. The fluidity, measured as the length to which the metal flows in a standard channel, is affected by many factors, such as the pouring temperature, solidification type of the alloy, the channel thickness, melt head, mold materials and temperature, coating etc. Therefore the experimentally measured fluidity scatters very much and makes it difficult to estimate the fluidity of a melt with a few measurements. The effect of Ti content and grain refinement on the fluidity of high strength aluminum alloy was investigated with a test casting with 8 thin flow channels to reduce the scattering of the fluidity results. The fluidity of Al-4.8%Cu-0.6%Mn Al-6.2%Zn-1.6%Mg-1.0%Cu and well-known commercial aluminum alloy, A356 was tested. Initial content of Ti was varied from 0 to 0.2wt% and Al-5Ti-B master alloy was added for grain refinement. The flow length varied linearly with superheat. By adding Ti and Al-5Ti-B, the fluidity increased. The grain size decreased by adding grain refiner at the same time. The fluidity depended on the degree of grain refinement. The fluidity of the alloy solidifying in mushy type is improved by grain refinement, because grain refinement increases the solid fraction at the time of flow stoppage.

• Safety and Health at Work
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• v.9 no.3
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• pp.326-333
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• 2018

Background: Echocardiography involves strenuous postures of the upper limbs. This study explored the physical workload in the neck and upper limbs in sonographers performing echocardiography, and the extent to which the workload differs from than in other work tasks (other sonographic examinations, and nonsonographic tasks). Methods: The physical load was assessed by inclinometry, goniometry, and electromyography methods in 33 female sonographers during authentic work using three different echocardiography techniques and other work tasks. Results: Echocardiography was characterized by low velocities of the head, arms, and wrists, and a low proportion of muscular resting time in the forearms, in the transducer limb, and the computer limb. The transducer limb was more elevated in one of the techniques, but this technique also involved a higher proportion of muscular resting time of the trapezius muscle. We also found a high proportion of awkward wrist postures in the transducer wrist in all three techniques; in one due to prolonged flexion, and in the others due to prolonged extension. Other work tasks were less static, and were performed with higher upper arm and wrist velocities. Conclusion: None of the three echocardiography techniques was optimal concerning physical workload. Thus, to achieve more variation in physical load we recommend that the equipment be arranged so that the sonographer can alternate between two different techniques during the workday. We also propose alternation between echocardiography and nonsonographic tasks, in order to introduce variation in the physical workload. Clinical expertise should be used to achieve further improvements.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.32 no.5
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• pp.72-79
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• 2000

On the other hand, the fiber orientation at the surface and middle layer of the sheet controls the bending stiffness of paperboard. Therefore, a reliable measurement of paper surface fiber orientation gives us a magnificent tool to investigate and predict paper curling and cockling tendency, and provides the necessary information to fine-tune the manufacturing process for optimum quality. Many papers, especially heavily calendered and coated grades, do resist liquid and gas penetration very much, being beyond the measurement range of the traditional instruments or resulting inconveniently long measuring time per sample. The increased surface hardness and use of filler minerals and mechanical pulp make a reliable, non-leaking sample contact to the measurement head a challenge of its own. Paper surface coating causes, as expected, a layer which has completely different permeability characteristics compared to the other layers of the sheet. The latest developments in sensor technologies have made it possible to reliably measure gas flow n well controlled conditions, allowing us to investigate the gas penetration of open structures, such as cigarette paper, tissue or sack paper, and in the low permeability range analyze even fully greaseproof papers, silicon papers, heavily coated papers and boards or even detect defects in barrier coatings! Even nitrogen or helium may be used as the gas, giving us completely new possibilities to rank the products or to find correlation to critical process or converting parameters. All the modern paper machines include many on-line measuring instruments which are used to give the necessary information for automatic process control systems. Hence, the reliability of this information obtained from different sensors is vital for good optimizing and process stability. If any of these on-line sensors do not operate perfectly as planned (having even small measurement error or malfunction), the process control will set the machine to operate away from the optimum, resulting loss of profit or eventual problems in quality or runnability. To assure optimum operation of the paper machines, a novel quality assurance policy for the on-line measurements has been developed, including control procedures utilizing traceable, accredited standards for the best reliability and performance.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.1
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• pp.58-65
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• 2018

To improve the performance of high-speed vehicles, various studies have been carried out on the head of vehicles. In this study, tests are conducted on flow characteristics and drag reduction using counterflow air jets in supersonic flow. The flow is visualized by the Schlieren method using a high-speed camera, and the drag is measured using a torque sensor according to the injection pressure conditions. The results of the measurements indicate that the flow changes from unsteady state to steady state for injection pressure ratios between 1.58 and 1.70, and drag reduction is observed as the pressure of the counterflow air jets increases.