• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.334-339
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• 2020

In this study, the adhesion properties between aluminum and composite materials, composite materials, and composite materials were compared according to the physical surface treatment to improve mechanical bonding at the bonding surface when considering carbon fiber and glass fiber-reinforced composite materials. Bonded specimens were classified into the type of base material and the surface treatment method of the bonding surface. Sandpaper, sandblasting, and plasma were applied as physical surface treatment methods. The bonded specimen was prepared as a single lap joint test specimen. An experiment to measure the lap shear strength was conducted, and the results were compared. The experimental results confirmed that the mechanical abrasion and sandblasting treatment improved the lap shear strength approximately 4 to 5 fold compared to the general specimen without physical surface treatment. In plasma treatment, the experiment was conducted by defining the respective plasma output and treatment time as follows: 150 W and 5 minutes, 150 W and 10 minutes, and 300 W and 3 minutes. Moreover, the lap shear strength results were similar to the previous mechanical surface treatments. On the other hand, the effect on the adhesion properties was small, depending on the plasma treatment conditions.

• International Journal of Highway Engineering
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• v.6 no.2 s.20
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• pp.47-59
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• 2004

The temperature variation of concrete pavement at early-age significantly affects the initiation and propagation of its early-age cracks. This implies that the measurement and analysis of early age temperature trend are necessary to examine the causes of early age cracks in the concrete pavement. In this study, it is investigated how the early age temperature trend in concrete pavement affects the random crack initiation and behaviors of saw-cut joints using the actual construction site which is located at the KHC test road. During 72 hours after placing the concrete pavement, the ambient air temperature and temperatures at the top, middle, and bottom in concrete pavement were measured and the random crack initiation in concrete slabs and early age behaviors in the joints were surveyed. The investigation results indicate that the first random crack was initiated at one of the slabs placed in the early morning which have higher temperature changes during early 72 hours. The movement of slab was influenced by the early-age crack in the joint. It suggested that the different occurrence time of the cracks in the joint had an influence on the behavior of the cracks. Besides, the slab constructed In the morning had higher possibility of crack initiation than that in the afternoon. The rarely occurred cracks had bigger gap than other cracks.

• Journal of radiological science and technology
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• v.29 no.3
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• pp.157-165
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• 2006

In order to analyze clinical characteristics like sex- and age-based onset frequency and onset region from vertebral disease cases, this study investigated total 1,291 cases of vertebral disease that were diagnosed via magnetic resonance imaging(MRI) from January to December 2004 at B University Hospital in metropolitan area. For higher diagnostic accuracy in cases of spinal disorder diagnosed, this study analyzed findings from data reading conducted by veteran specialists in diagnostic radiology. But this study excluded uncertain lesion cases, the cases requiring differential diagnosis from other disorders and so on from subjects under analysis. This study employed superconductive 1.5 Tesla SIGNA MR/i for MRI test and basically received resulting images via FSE(fast spin echo). In particular, this study obtained T1 and T2 myelogram with regard to regional characteristics(such as cervical vertebrae, thoracic vertebrae and lumbar vertebra) and imaging characteristics for sagittal and transverse section. As a result, this study came to the following conclusions : 1. In terms of general characteristics of subjects under analysis, male group comprised 53.5% and female 46.5% out of total 1,291 subjects. 2. The regional onset frequency of spinal disorders was converged primarily on lumbar vertebra(65.5%), which was followed by cervical vertebrae(27.3%) and thoracic vertebrae(7.0%) respectively. 3. Top 10 cases with high onset frequency of spinal disorders can be listed as follows : 1) posterior bulging disc 65.8% 2) narrowing of neural foramen 23.8% 3) herniated intervertebral disc (HIVD) 22.4% 4) spinal stenosis 16.7% 5) osteochondrosis 6.4% 6) compression fracture 6.4% 7) facet joint arthropathy 6.2% 8) spondylolisthesis 6.0% 9) spinal cord tumor 3.5% 10) inter body fusion 2.6%

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.7
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• pp.765-770
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• 2014

This paper describes the study on a method for improving the structural durability of bolted joints applied to a composite bogie frame. In this study, three bolted joints with and without inserts and screw threads were selected for determining the effect of the inserts, using experiment and analysis. The structural performances of the proposed bolted joints were compared and evaluated using the test method prescribed by the ASTM D5961 standard. The results revealed that the bolted joint having an insert shape without the screw thread offered improved durability for application to a composite bogie frame. Furthermore, the structural integrity of the frame comprising the bolted joints was evaluated using finite element analysis according to the JIS E 4207 standard. The Tasi-Wu and Von-Mises failure criteria were used for determining the failure of the composite structure and bolted joints, respectively. A sub-modeling technique was introduced for investigating the performance of the bolted joints in greater detail. The analysis results demonstrated that the Tasi-Wu failure index of the composite structure near the bolted joints was reduced by approximately one-half after applying an insert without the screw thread. This implies that the structural durability of the bolted joints of a composite bogie frame could be improved by using a metal insert without the screw thread.

• Resources Recycling
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• v.27 no.1
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• pp.84-91
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• 2018

In this study, a novel soft information based most probable classification scheme is proposed for sorting recyclable metal alloys with laser induced breakdown spectroscopy (LIBS). Regression analysis with LIBS captured spectrums for estimating concentrations of common elements can be efficient for classifying unknown arbitrary metal alloys, even when that particular alloy is not included for training. Therefore, partial least square regression (PLSR) is employed in the proposed scheme, where spectrums of the certified reference materials (CRMs) are used for training. With the PLSR model, the concentrations of the test spectrum are estimated independently and are compared to those of CRMs for finding out the most probable class. Then, joint soft information can be obtained by assuming multi-variate normal (MVN) distribution, which enables to account the probability measure or a prior information and improves classification performance. For evaluating the proposed schemes, MVN soft information is evaluated based on PLSR of LIBS captured spectrums of 9 metal CRMs, and tested for classifying unknown metal alloys. Furthermore, the likelihood is evaluated with the radar chart to effectively visualize and search the most probable class among the candidates. By the leave-one-out cross validation tests, the proposed scheme is not only showing improved classification accuracies but also helpful for adaptive post-processing to correct the mis-classifications.

• Journal of the Korean Wood Science and Technology
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• v.44 no.3
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• pp.415-423
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• 2016

Cylindrical laminated veneer lumber (LVL) is produced by winding the veneer tape on a circular cylinder. The veneer tape was produced by cutting the veneer into a rectangular shape and sewing it in a vertical direction to the fiber. The tensile strength test was carried out by producing the veneer tape specimen with different species of veneer, types and combinations of sewing yarn. The Radiata pine veneer tape produced with three sewing lines using the reinforced sewing thread had the best tensile strength. Also, the separation and snapping problems of the veneer tape were improved, resulting in the improvement in the workability of cylindrical LVL. The bending strength of various cylindrical LVL produced with different types of veneer tape and a different number of lamination layers and the application of reinforcement with glass fiber cloth was compared with that of Larix log. Bending MOR of cylindrical LVL reinforced with glass fiber cloth at the volume ratio of 11% was improved by 65% in comparison to the non-reinforced cylindrical LVL. In the case of the cylindrical LVL produced with 2 sewing lines of veneer tape, a fracture occurred at the butt joint between the veneer tapes. However, in the case of the cylindrical LVL produced with 3 sewing lines of veneer tape a fracture occurred in the fiber direction.

• Journal of Dental Rehabilitation and Applied Science
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• v.19 no.1
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• pp.17-25
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• 2003

Treatment with implants of single tooth missing cases is both functional and esthetic. Although the success rate of single-tooth implant treatments is increasing, sometimes it makes some problems. Problems with single-tooth implant treatments include soft tissue complications, abutment screw fracture, and most commonly, abutment screw loosening, and these involve the instability of the dental implant-superstructure interface. This study investigated and compared dental implant screw joint micromotion of various implant system with external connection or internal connection when tested under simulated clinical loading, Six groups (N=5) were assessed: (1) Branemark AurAdapt (Nobel Biocare, Goteborg, Sweden), (2) Branemark EsthetiCone (Nobel Biocare, Goteborg, Sweden), (3) Neoplant Conical (Neobiotec, Korea), (4) Neoplant UCLA (Neobiotec, Korea), (5) Neoplant 5.5mm Solid (Neobiotec, Korea), and (6) ITI SynOcta (Institute Straumann, Waldenburg, Switzerland). Six identical frameworks were fabricated. Abutment screws were tightened to 32-35 Ncm and occlusal screw were tightened to 15-20 Ncm with an electronic torque controller. A mechanical testing machine applied a compressive cyclic load of 20kg at 10Hz to a contact point on each implant crown. Strain gauge recorded the micromotion of the screw joint interface once a second. Data were selected at 1, 500, 5,000, 10,000, 20,000, 30,000, 40,000 and 50,000 cycle and 2-way ANOVA test was performed to assess the statistical significance. The results of this study were as follows; The micromotion of the implant-superstructure in the interface increased gradually through 50,000 cycles for all implant systems. In the case of the micromotion according to cycle increase, Neoplant Conical and Neoplant UCLA system exhibited significantly increasing micromotion at the implant-superstructure interface (p<0.05), but others not significant. In the case of the micromotion of the implant-superstructure interface at 50,000 cycle, the largest micromotion were recorded in the Branemark EsthetiCone, sequently followed by Neoplant Conical, Neoplant UCLA, Branemark AurAdapt, ITI SynOcta and Neplant Solid. Internal connection system showed smaller micromotion than external connection system. Specially, Neoplant Solid with internal connection system exhibited significantly smaller micromotion than other implant systems except ITI SynOcta with same internal connection system (p<0.05). In the case of external connection, Branemark EsthetiCone and Neoplant Conical system with abutment showed significantly larger micromotion than Branemark AurAdapt without abutment (p<0.05).

• Korean Journal of Construction Engineering and Management
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• v.11 no.6
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• pp.111-121
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• 2010

As the customer's interest for sidewalk block in the street or apartment complex is increasing, the materials of block which had been a concrete block exclusively are varied to clay paver, native rock and wood etc. Especially, the sales volume of clay paver which is environment-friendly and ergonomic is dramatically increasing every year with two digits growth rate, however, many problems like "Edge Cracking" "Freezing Breakage" "Bending Breakage" "Joint Gap" are happening frequently within a couple of hours after installation due to the durabilities. Because of the characteristics of Ceramic products, clay pavers are very easy to be broken when they are bumped against each other. In addition, they are relatively fragile by a freezing expansion breakage when exposed to water due to hydrophilic property as well as the intensity and absorptance of the products are varied with small difference from the production process such as production equipment and process control. Therefore, it costs a lot of money to repair the breakdown unless production and installation is carried out according to the strict criteria of the quality control. In this study, the symptoms of breakdown frequently happened in clay paver are classified by each type and finally the solution for this problem in the production of brick, installation and criteria of quality control through compressive strength and absorptance test is suggested.

• Journal of the Microelectronics and Packaging Society
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• v.21 no.1
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• pp.1-6
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• 2014

Flip chip bonded LED packages possess lower thermal resistance than wire bonded LED packages because of short thermal path. In this study, thermal and bonding properties of flip chip bonded high brightness LED were evaluated for Au-Sn thermo-compression bonded LEDs and Sn-Ag-Cu reflow bonded LEDs. For the Au-Sn thermo-compression bonding, bonding pressure and bonding temperature were 50 N and 300oC, respectively. For the SAC solder reflow bonding, peak temperature was $255^{\circ}C$ for 30 sec. The shear strength of the Au-Sn thermo-compression joint was $3508.5gf/mm^2$ and that of the SAC reflow joint was 5798.5 gf/mm. After the shear test, the fracture occurred at the isolation layer in the LED chip for both Au-Sn and SAC joints. Thermal resistance of Au-Sn sample was lower than that of SAC bonded sample due to the void formation in the SAC solder.

• Journal of muscle and joint health
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• v.6 no.2
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• pp.253-277
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• 1999

Patients with chronic disease have various treatment patterns because it shows a progressive degenerative feature. Especially various physical and emotional problems of the rheumatoid arthritis patients leave them shopping around various types of treatment. According to previous studies, over 70% of patients with arthritis experienced the traditional oriental medicine or folk remedies simultaneously with medical treatment within one year after the onset of disease. The purposes of this study are 1) to compare the patterns of treatment-seeking behaviors between Korean arthritis patients and Americans ; and 2) test two models of treatment-seeking behaviors by path analysis, one for early treatment-seeking behavior model(ETBM) and the other is chronic treatment-seeking behavior model (CTBM) in Korean sample. The interview survey was performed to 133 RA patients with structured questionnaire at out-patient clinic or public health center. Patients characteristics such as age, duration of disease were similar in two countries except higher educational background in Americans. There were no patients using only alternative therapies or no medical treatment in the US. Most of the American patients have chosen both medical treatment and alternative therapy, while the Koreans less than American. In Korea, combined treatment group usually consists of the people who are younger, more educated and higher economic status than the characters of other groups in early or chronic stages. In early stage, they tend to have strong belief of curing from the disease, satisfy the relationship with their physicians and comply with direction of the medical professional. The paths of two models were explained by 70% in ETBM and 33% in CTBM. When the models were modified, almost all paths of the CTBM were the same as the previous one, but direct determinant factor was changed from the relationship with physicians to the lay referral system in chronic model. These two models' explanation powers became 94% and 88%, respectively. The attitude or perception of disease, lay referral system and the relationship with medical personnel are the main determinants of treatment-seeking behaviors.