• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.1
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• pp.85-90
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• 2010

Friction welding is a common practice to join axially symmetrical parts for automobile industry applications. The shaft for automobile reverse idle gear is generally produced by forging steel, SF 45. This method is not so good because of high cost of material and production. In this study, in order to investigate the possibility of application of SM 45C to SF 45 dissimilar friction welding, the dissimilar friction welded joints were performed using 20 mm diameter solid bar in forging steel(SF 45) to carbon steel(SM 45C). The optimal friction welding parameters were selected to ensure reliable quality welds on the basis of visual examination, tensile test, micro-Virkers hardness surveys of the bond of area and optical microstructure investigations for welded joint parts. Finally, post weld heat treatment(PWHT) of the high-frequency induction hardening was performed for the friction welded specimens under the optimal welding conditions. And then, the mechanical properties were compared for as-welded and PWHT in SM 45C to SF 45.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.3
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• pp.319-325
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• 2015

High-strength steel has replaced mild steel as the material of choice for truck decks or frames, owing to the growing demand for lightweight vehicles. Although studies on the weld fatigue characteristics of mild steel are available, studies on high-strength steels have been seldom conducted. In this study, firstly, we surveyed a chosen number of approaches and selected the Radaj method, which uses the notch factor approach, as the one suitable for evaluating the fatigue life of commercial vehicles. Secondly, we obtained the S-N curves of HARDOX and ATOS60 steel welds, and the F-N curves of the T-weld and overlapped-weld structures. Thirdly, we acquired a general S-N curve of welded structures made of high-strength steel from the F-N curve, using the notch factor approach. Fourthly, we extracted the weld fatigue characteristics of high-strength steel and incorporated the results in the database of a commercial fatigue program. Finally, we compared the results of the fatigue test and the CAE prediction of the example case, which demonstrated sufficiently good agreement.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.25 no.1
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• pp.45-50
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• 1992

To utilize shellfish by-products effectively, chitin, chitosan, and microcrystalline chitin were prepared from 6 kinds of crustacean shells(Antarctic krill, Euphausia superba; Red snow crab, Chinonecetes japonicus: Daelongsuyum shrimp, Solenocera prominentis: Lobster, Linuparus trigonus: Gasibal shrimp, Nephrops thomsoni: Blue crab, Portunus trituberculatus) and their functional properties were studied. Apparent volume(AV), settling volume(SV), water binding capacity(WBC), and fat binding capacity(FBC) of various chitins, chitosans, and microcrystalline chitins ranged from $3.1\pm0.1ml/g\;to\;27.0\pm0.2ml/g$ from $5.1\pm0.1ml/g\;to\;45.0\pm0.2ml/g,\;from\;318\pm40g/100g\;to\;2,382\pm12g/100g,\;and\;from\;235\pm20g/100g\;to\;2,169\pm20g/100g$, respectively, and the krill chitin and chitosan had the highest AV, SV, WBC, and FBC of them. Chitins and chitosans did not produce emulsion but microcrystalline chitins showed emulsifying properties. Emulsifying capacity and stability of various microcrystalline chitins ranged from $18.2\pm4.0\%\;to\;50.1\pm2.5\%\;and\;from\;15.2\pm3.5\%\;to\;31.1\pm1.0\%$, respectively. Dye binding capacity of microcrystalline chitins was higher than that of chitins or chitosans.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.11
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• pp.446-457
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• 2019

The purpose of this study was to analyze the association between family members and adolescent boys smoking. The data were evaluated by frequency analysis, 𝑥² test and logistic regression analysis using 27,276 people who responded to the 14th(2018) Korean Youth Risk Behavior Survey. Among male students, the nonsmoking rate was 91.5% and the smoking rate was 8.5%(2.5% of occasional smoking and 6.0% of frequent smoking). The study results showed that the smoking status of male students was varied significantly according to the number of smokers among the family members(p<0.001). Meanwhile, smoking based on the characteristics of socio-demographic factors was affected by grades, school records, economic status, and parents' educational background(p<0.001). Smoking by health factors showed a significant difference in alcohol consumption, suicidal thoughts, depression experiences, stress recognition, frequency of breakfast consumption, level of fatigue after sleep, and subjective perception of health(p<0.001). Male smokers were more likely to smoke when two family members smoked than only one(p<0.001). These results confirmed that smoking in boys was affected by the smoking status of family members and suggested that the smoking cessation program of family smokers can be effective in designing smoking cessation prevention and smoking cessation projects.

• Journal of Biomedical Engineering Research
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• v.24 no.1
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• pp.1-8
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• 2003

The job of long distance driving is likely to be fatiguing and requires long period alertness and attention, which make considerable demands of the driver. Driving fatigue contributes to driver related with accidents and fatalities. In this study, we investigated the relationship between the number of hours of driving and driving fatigue using heart rate variability(HRV) signal. With a more traditional measure of overall variability (standard deviation, mean, spectral values of heart rate). Nonlinear characteristics of HRV signal were analyzed using Approximate Entropy (ApEn) and Poincare plot. Five subjects drive the four passenger vehicle twice. All experiment number was 40. The test route was about 300Km continuous long highway circuit and driving time was about 3 hours. During the driving, measures of electrocardiogram(ECG) were performed at intervals of 30min. HRV signal, derived from the ECG, was analyzed using time, frequency domain parameters and nonlinear characteristic. The significance of differences on the response to driving fatigue was determined by Student's t-test. Differences were considered significant when a p value < 0.05 was observed. In the results, mean heart rate(HRmean) decreased consistently with driving time, standard deviation of RR intervals(SDRR), standard deviation of the successive difference of the RR intervals(SDSD) increased until 90min. Hereafter, they were almost unchanging until the end of the test. Normalized low frequency component $(LF_{norm})$, ratio of low to high frequency component (LF/HF) increased. We used the Approximate Entropy(ApEn), Poincare plot method to describe the nonlinear characteristics of HRV signal. Nonlinear characteristics of HRV signals decreased with driving time. Statistical significant is appeared after 60 min in all parameters.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.2
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• pp.535-541
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• 2020

FCAW is used mainly in the welding of carbon steel and alloy steel because it can be welded in all positions and can obtain excellent quality at sites with variable working conditions. Recently, many studies in Korea have estimated the fatigue strength, residual stress, and deformation, and to develop a fillet welding process. On the other hand, there have been few studies of the mechanical properties based on the strength, macro and magnetic particle test results for fillet welding. This study shows the following results through fillet welding, macro testing and strength testing using SM490A (solid-structure rolled steel) for thick plates using SS400 (rolled steel) for the upper plate and FCAW. The hardness test, macro test and magnetic particle test were then conducted. The hardness tests showed that all result values were smaller than the KS B 0893 standard values of 350Hv. The macro-test showed that each type of welded part was in a normal organic state and that there were no internal errors, bubbles, or impurities on the front of the welded part. Therefore, there were no concerns about lamination. The magnetic particle examination showed no problems.

• Applied Biological Chemistry
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• v.36 no.3
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• pp.163-171
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• 1993

The collagens from filefish (Novoden modestus) and cod (Gadus macrocephalus Tilesius) skin were isolated and their physicochemical properties were investigated. Glutamic acid, hydroxyproline, valine and phenylalanine in the filefish skin collagen (FSC) were presented at higher levels than those of cod skin collagen (CSC), but the contents of glycine, proline and serine were contrary. The content of essential amino acids of FSC (265 residues/1000 residues) was higher than CSC (229 residues). The solubilities of both collagens were the lowest at pH 7.0, but precipitously increased at acid zone(below pH 5.0). FSC has lower viscosity than CSC. Furthermore, while the viscosities of both collagens were the lowest at pH 7.0, the viscosities of FSC and CSC were the highest at pH 4.0 and pH 2.0, respectively. The denaturation temperature of $FS(25^{\circ}C)$ was higher than $CSD\;(17^{\circ}C)$. The free hydrophobic residue contents of FSC and CSC tended to increase till $60^{\circ}C,\;and\;50^{\circ}C$ respectively, and to decrease thereafter. Hydration capacities of both collagens were the lowest at pH 7.0, and CSC had the superior hydration capacity to FSC. In addition, emulsifying and emulsifying stability of CSC was also superior to FSC.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.5 no.1
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• pp.125-132
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• 2011

The Comprehensive Assistive Technology services delivery was devised to describe the full social and engineering context of assistive technology devices, systems, applications, and provision. It is based on a detailed decomposition of the four attributes: Person, Context, Activities, and Assistive Technology. The paper commences will a brief discussion of the different representations of the services delivery, including rental of devices, modification of manufacture goods and customized production and the use of engineering to supplement some elements of the description. The main contribution of the paper is the presentation of two case studies of different applications of the assistive technology services. These are the identification of accessibility barriers, the analysis and synthesis of assistive technology systems and the provision of a framework for identitying end-user requirements, providing assistive technology and assessing the associated outcomes. This case study involves the presentation of the concept of a personal assistive technology profile.

• Composites Research
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• v.26 no.5
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• pp.289-294
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• 2013

A thinner is used to improve the multi-walled carbon nano-tube (CNT) and carbon black (CB) dispersion in a polymer matrix and to make a soft electrode. The electrical and mechanical properties of the soft electrodes are investigated as functions of CNT, CB and thinner content. The optimal mixing condition for the electrode is thinner 80, CNT 3.5, CB 18 (phr) on the basis of matrix (KE-12). The specific resistance of that is 73 (${\Omega}{\cdot}cm$), and tensile strength, tensile modulus, and elongation of that is 0.45 MPa, 0.21 MPa, and 184%, respectively. Also, a simple structure of the actuator with an optimized electrode and elastomer is fabricated and its characteristic is evaluated. At the operating voltage 25 kV, the displacement of an elastomer KE-12 is 2.24 mm, and that of an elastomer KE-12 with thinner 50 (phr) is 4.05 mm. It shows a higher displacement compared to that of 3M 4910 which has similar modulus. The actuator made with elastomer and electrode of the same material (KE-12) may have advantages for fatigue life and application.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.3
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• pp.1153-1163
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• 2013

Bonded concrete overlay is a favorable maintenance method since the material properties are similar to existing concrete pavements. In addition, bonded concrete overlay has advantage of structural performance based on being bonded together, both for the overlay layer and the existing pavement which perform as one monolithic layer. Therefore, it is important to have a suitable bond strength criteria for long term performance of bonded concrete overlay. This study aimed to investigate the affecting of bond strength on various bond characteristics, and to compare the bond strength between direct tensile test and indirect tensile test due to various conditions such as overlay materials, compressive and flexure strength of existing pavement, and deterioration status of existing pavement. As a result of this study, bond strength occurred by both of direct and indirect tensile test due to monotonic load is highly correlated such as coefficient of determination of 0.75 and P-value of 0.002. However, bond strength by indirect tensile test was relatively higher than bond strength by direct tensile test. It was known that correlation between direct and indirect tensile test was possible to use the characteristics analysis of bond fatigue behavior based on bond strength due to cyclic load which can simulate real field behavior of bonded concrete overlay.