• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.10
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• pp.834-838
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• 2011

This research shows the electrical characteristic using excellent epoxy nano-composite of MgO 5.0 wt% and $SiO_2$ 0.4 wt% in mechanical strength test depending on nano-additive. First of all, volume resistance depending on nano-additive and temperature using high resistance meter (HP. 4329A) by increasing 10, 100, 1,000 V of applying voltage was measured. Moreover, temperature range of $25{\sim}120^{\circ}C$ with virgin sample was tested using TO-9B oven by Ando Company. The result showed that virgin and the samples added with MgO and $SiO_2$ had similar value of volume resistance in low temperature and low electric field region and reduced with slow slope. The nano-composite's volume resistance of sample added with MgO and $SiO_2$ had higher value than virgin sample's volume resistance in high temperature region more than $80^{\circ}C$. Moreover, the slope has steeply reduced. The volume resistance of sample added with MgO 5.0 wt% was $8.38{\times}10^{13}\;{\Omega}{\cdot}cm$ and it was 6.8 times more than virgin sample in high temperature at $120^{\circ}C$. The insulation characteristics were constant although filler has changed in low temperature region. But, in high temperature region, the value of volume resistance of sample with MgO 5.0 wt% was 7.6 times more than the virgin sample's volume resistance.

• Journal of Welding and Joining
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• v.26 no.5
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• pp.74-78
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• 2008

The laser welding of the car body and components has been spread in the automotive industry. The Nd:YAG laser welding system could be used in 3D welding with robot. However, this system cannot efficiently reduce the welding cycle time according to various welding sequences because the robot's moving time is same that of the resistant spot welding system. But the remote welding system with high power $CO_2$ laser and scanner makes it possible welding cycle time much faster than the robot laser welding system. In the $CO_2$ laser remote welding system, laser beam can be rapidly transferred to a workpiece by moving mirrors of scanner system. So, it makes reducing the cycle time of welding process and shaping various welding patterns easily. Therefore, in this paper, the characteristic of weld strength according to patterns of weld bead on $CO_2$ laser welding was investigated. Also, the relationship between shape of weld bead and value of tensile load was studied. Finally, the optimum remote welding condition for car bumper was investigated.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.12
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• pp.1425-1433
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• 2011

We investigated an early rehabilitation training system that increase the intensity of patient rehabilitation training to shorten the time it takes for patients to progress to a secondary rehabilitation training stage by allowing patients incapable of self-ambulation. It consisted of tilting bed, unstable platform using strong springs and training program for lower limb rehabilitation. We performed experimental study on the muscular activities of tibialis anterior(TA), soleus(SO), gastrocnemius(GA) in the lower extremities during training of straight line, circle, quardrangle pattern during tilting angle of $30^{\circ}$, $60^{\circ}$. The muscle activities were higher during tilting angle of $30^{\circ}$ than $60^{\circ}$. In straight line pattern, the muscle activities were higher by SO, GA and TA during medio-lateral direction, however, by TA, SO and GA during anterio-posterior direction. In circle and quardrangle pattern, the muscle activities were higher by TA, SO and GA during clockwise and counterclockwise direction. The results indicate that the early rehabilitation training system could be applied to improve the lower extremity muscular strength for elderly and patients, especially, stroke.

• Journal of Radiation Industry
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• v.9 no.4
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• pp.199-207
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• 2015

Typical radiation cross-linked hydrogels has the characteristic that high water content, but low emission efficiency of active ingredients. Therefore, the hydrogel was prepared by the addition to collagen, which is closely related to the formation of skin wrinkles in biocompatibility and highly water-soluble carboxymethyl cellulose sodium salt (CMC) in order to preparation of hydrogels has excellent emission efficiency of active ingredients. Hydrogels were prepared by dissolving CMC and collagen each of 0.5%, 10% concentration in deionized water. Then, prepared hydrogels are performed by gamma-radiation at 1, 3, 5 kGy irradiation dose. The results showed that the gel fraction of after irradiated 3 kGy hydrogel was higher than before irradiated gelation as long as the 55.3%. The swelling rate of irradiated 3 kGy hydrogel was lower than the non-irradiated sample. The compressive strength of 3 kGy irradiated hydrogel was the highest. The visco-elastic did not show any significant differences, even after irradiation. The CMC hydrogel in this study suggested a potential use as a material for the mask pack for improved emission efficiency of the active ingredient and anti-wrinkles.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.3
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• pp.187-193
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• 2019

Regarding physical absorption mechanism for fine particles(Dust), internal pore-bridging is a major parameter in porous media. In this paper, internal bridging pore system is invented through FA-based geopolymer and incorporated PLA (Polylactic Acid) fiber with biodegradability. With various mix proportions, compressive strength over 20MPa is obtained but PLA is little dissolved in the condition of NaOH 5mole and $30^{\circ}C$ of temperature, which was found that temperature rising accelerates PLA solubility. Within 24hours, beads type PLA is completely dissolved under $90{\sim}130^{\circ}C$ and NaOH 5~12mole of alkali. In room condition, geo-polymerization is limitedly occurs so that the internal pore after PLA dissolution is thought to be effective to absorption and storage of fine particles.

• Korean Journal of Soil Science and Fertilizer
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• v.48 no.5
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• pp.413-420
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• 2015

Objective of this study was to investigate adsorption characteristics and kinetic models of $NH_4-N$ to biochar produced from rice hull in respective to mitigation of greenhouse gases. $NH_4-N$ concentration was analyzed by UV Spectrophotometer. For the experiment, the soil texture used in this study was sandy loam soil, and application rates of chemical fertilizer and pig compost were $420-200-370kgha^{-1}$ (N-P-K) and $5,500kgha^{-1}$ as recommended amount after soil test for corn cultivation. Biochar treatments were 0.2-5% to soil weight. Its adsorption characteristic was investigated with application of Langmuir isotherm, and pseudo-first order kinetic model and pseudo-second order kinetic model were used as kinetic models. Adsorption amount and removal rates of $NH_4-N$ were $39.3mg^{-1}$ and 28.0% in 0.2% biochar treatment, respectively. The sorption of $NH_4-N$ to biochar was fitted well by Langmiur model because it was observed that dimensionless constant ($R_L$) was 0.48. The maximum adsorption amount ($q_m$) and binding strength constant (b) were calculated as $4.1mgg^{-1}$ and $0.01Lmg^{-1}$ in Langmuir isotherm, respectively. The pseudo-second order kinetic model was more appropriate than pseudo-first order kinetic model for high correlation coefficient ($r^2$) of pseudo-second order kinetic model. Therefore, biochar produced from rice hull could reduce $N_2O$ by adsorbing $NH_4-N$ to biochar cooperated in sandy loam soil.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.4
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• pp.521-528
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• 2021

The high-density fiber composite manufacturing method by the extrusion molding method has the characteristic that continuous production is possible, and the product is molded through a mold forming a specific cross-section. OPC is used as a defect material, an appropriate amount of SiO₂ is supplied for CaO reaction activity, and high density and high strength are expressed through steam and autoclave curing. However, due to the use of organic reinforcing fibers, the flame duration exceeds the regulations during the non-combustible performance test, making it difficult to secure performance. In this study, the product was produced by mixing alkali-resistant organic fiber and fly ash having voids as a binder by replacing the existing polypropylene fiber. appeared to be possible.

• Journal of Drive and Control
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• v.16 no.3
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• pp.51-58
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• 2019

The objective of this study was to investigate a simulation technology for the AM field based on ANSYS Inc.. The introduction of metal 3D printing AM process, and the examining of the present status of AM process simulation software, and the AM process simulation processor were done in the previous study (part 1). This present study (part 2) examined the use of the AM process simulation processor, presented in Part 1, through direct execution of Topology Optimization, Ansys Workbench, Additive Print and Additive Science. Topology Optimization can optimize additive geometry to reduce mass while maintaining strength for AM products. This can reduce the amount of material required for additive and significantly reduce additive build time. Ansys Workbench and Additive Print simulate the build process in the AM process and optimize various process variables (printing parameters and supporter composition), which will enable the AM to predict the problems that may occur during the build process, and can also be used to predict and correct deformations in geometry. Additive Science can simulate the material to find the material characteristic before the AM process simulation or build-up. This can be done by combining specimen preparation, measurement, and simulation for material measurements to find the exact material characteristics. This study will enable the understanding of the general process of AM simulation more easily. Furthermore, it will be of great help to a reader who wants to experience and appreciate AM simulation for the first time.

• Annals of Clinical Neurophysiology
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• v.21 no.2
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• pp.79-86
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• 2019

Background: Magnetic resonance (MR) images are useful for diagnosing myopathy. The purpose of this study was to determine the usefulness of lower-limb MR images in Korean patients with distal myopathy. Methods: We reviewed medical records in the myopathy database from January 2002 to October 2016. We selected 21 patients from 91 unrelated families with distal myopathy: four with GNE myopathy, 11 with dysferlinopathy, and six with ADSSL1 myopathy. Results: Ten (48%) of the 21 patients were men. The ages of the participants at symptom onset and imaging were $19.2{\pm}9.5$ and $30.4{\pm}9.0$ years (mean${\pm}$standard deviation), respectively. Their grade on the modified Gardner-Medwin and Walton grade was $3.3{\pm}1.7$. The strength grade of the knee extensors was not correlated with the Mercuri scale for the quadriceps (r = -0.247, p = 0.115). However, the Medical Research Council grades of the knee flexors, ankle dorsiflexors, and ankle plantar flexors were significantly correlated with the Mercuri scale ratings of the knee flexors (r = -0.497, p = 0.001), tibialis anterior (r = -0.727, p < 0.001), and ankle plantar flexors (r = -0.620, p < 0.001), respectively. T1-weighted MR images showed characteristic fatty replacement patterns that were consistent with the causative genes. Unsupervised hierarchical clustering of the Mercuri scale showed that the main factors contributing to the dichotomy were the causative gene and the clinical severity. Conclusions: This study is the first to reveal the usefulness of lower-limb MR images in the differential diagnosis of distal myopathy in Korea.

• International Journal of Advanced Culture Technology
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• v.7 no.1
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• pp.231-236
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• 2019

Background/Objectives: This paper proposes a dual mode feedback-controlled cycling system for children with spastic cerebral palsy to rehabilitate upper extremities. Repetitive upper limb exercise in this therapy aims to both reduce and analyze the abnormal torque patterns of arm movements in three- dimensional space. Methods/Statistical analysis: We designed an exercycle robot which consists of a BLDC motor, a torque sensor, a bevel gear and bearings. Mechanical structures are customized for children of age between 7~13 years old and induces reaching and pulling task in a symmetric circulation. The shafts and external frames were designed and printed using 3D printer. While the child performs active/passive exercise, angular position, angular velocity, and relative torque of the pedal shaft are measured and displayed in real time. Findings: Experiment was designed to observe the features of a cerebral palsy child's exercise. Two children with bilateral spastic cerebral palsy participated in the experiment and conducted an active exercise at normal speed for 3 sets, 15 seconds for each. As the pedal reached 90 degrees and 270 degrees, the subject showed minimum torque, in which the child showed difficulty in the pulling task of the cycle. The passive exercise assisted the child to maintain a relatively constant torque while visually observing the movement patterns. Using two types of exercise enabled the child to overcome the abnormal torque measured in the active data by performing the passive exercise. Thus, this system has advantage not only in allowing the child to perform the difficult task, which may contribute in improving the muscle strength and endurance and reducing the spasticity but also provide customizable system according to the child's motion characteristic. Improvements/Applications: Further study is needed to observe how passive exercise influences the movement characteristics of an active motion and how customized experiment settings can optimize the effect of pediatric rehabilitation for spastic cerebral palsy.