• The korean journal of orthodontics
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• v.36 no.5
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• pp.331-338
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• 2006

Objective: The purpose of this study was to evaluate whether the bond strength of polycarbonate brackets can be increased through surface treatment. Methods: One hundred polycarbonate brackets (Alice) were bonded to bovine incisors with light-cured adhesive. The bracket bases were treated with one of three methods; sandblasting, plastic conditioner application, and combined treatment with sandblasting and plastic conditioner. The brackets without any suraace treatment served as the control. The shear bond strength was tested with a universal testing machine, and failure pattern was assessed with the adhesive remnant index. Results: The shear bond strength in all experimental groups was higher than that of the control group (p < 0.001). The group treated with plastic conditioner after sandblasting showed statistically higher shear bond strength than the sandblasting only group to (p < 0.05). The group treated with plastic conditioner after sandblasting showed higher shear bond strength than plastic conditioner only group, but the difference was not statistically significant. Conclusion: The above results suggest that the surface treatments of polycarbonate bracket is mandatory to improve bond strength, and the most effective method is an application of plastic conditioner after sandblasting.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.339-345
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• 2018

We investigated the curing properties of cured coatings for a multi-focal UV-LED. The coatings are for LEDs that operate at multiple UV wavelengths, unlike conventional single-wavelength UV-LEDs. Using UV-LED light sources with wavelengths of 365, 395, 420, and 450 nm, we analyzed the optical characteristics such as the direction of light flux and light source. We also analyzed the curing characteristics at each UV-LED wavelength to optimize the LED for composite wavelengths. The curing performance state was predicted through computer simulation for when the multiple wavelengths of UV light sources are superimposed, and then actual LEDs were designed and fabricated. To improve the internal high-speed curing, a multi-spot module was fabricated, in which each LED is condensed, and multiple wavelengths are synthesized and condensed at the same position. The adhesive strength, surface hardness, and internal hardness of the curing agent were tested by varying the wavelength combination conditions. The surface hardening and internal hardening were compared and analyzed using a hardness tester and FT-IR analyzer. As a result, the characteristics of the surface and internal hardness were improved by a multi-spot method in which four wavelengths were overlapped in a UV-LED rather than a single wavelength.

• Journal of Conservation Science
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• v.35 no.6
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• pp.701-708
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• 2019

Animal glue is a natural adhesive made from processed skins or bones of animals. It is widely used in wooden crafts, papercrafts, dancheong painting, and pictures. Accurate evaluation of the quality of animal glues during production and use is difficult because there is no formal method for testing the glue's properties during pretreatment and measurement conditions. Thus, in this study, a series of tests were carried out by changing the conditions of swelling, temperature, and concentration of animal glue and gelatin sold on the market. Twelve types of animal glues were evaluated, having a viscosity range of 12.67 cP to 29.43 cP. The results showed that the physical characteristics of the glues were stable when allowed to swell for six h in distilled water(23℃). When 10%(by weight in distilled water) of the animal glue was measured in the reflective mode of a spectrophotometer, the optical characteristics of the glues were stable. Powdered animal glues have a medium brightness and middle-high chroma. Relative to powdered glues, stick animal glues have a low brightness and a medium chroma. Based on the results of this study, it is expected that the data can be assembled into a form so that animal glue workers can use it as a reference for the preparation of evaluation standards for testing the characteristics of animal glues.

• Analytical Science and Technology
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• v.29 no.3
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• pp.136-141
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• 2016

In the present study, the distribution of glass particles inside 10 patrol cars of Chungnam Province has been studied. The target seats were front seats (driver’s seat, passenger’s seat) and the back seat. The target areas were the bottom of the seat (seat contacting buttocks, back of the seat, and the corner of the seat (the bottom and back attached part)). The target areas were tape lifted with an adhesive tape. The glass particles adhering to the adhesive tape were examined and counted under a stereomicroscope. The total number of glass particles found was 679. Among them, 471 (driver’s seat 293, passenger seat 178) were collected from front seats, which are usually occupied by police officers. The majority of glass particles were under 0.49 mm size. The results show that the majority of glass particles can be found on the front seats, rather than on the back seat. There is a high probability that glass particles found on the front seat adhere to police officers, so that to get further transferred to the convict upon physical contact (secondary transfer). Thus, there is a risk of misinterpretation of the value of glass evidence in the course of forensic examinations. Hence, a separate method to prevent cross contamination has to be prepared by police authorities as soon as possible.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.146-157
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• 2018

Over the last 10 years, the number of disasters has been increasing in Korea. As a result, the need for temporary residences or shelters for disaster conditions is increasing. In this study, post-disaster refugees housing was developed using lightweight composite panels that are lighter than the materials that make up the existing shelter. To accomplish this, the structural performance of the lightweight composite panel was validated. Among the performance tests on the panels, the transverse load test was conducted according to the ASTM E 72 criteria. As a result of the experiment, when each specimen was subjected to a uniformly distributed load, the allowable load was determined according to the span. All the experiments were ended due to a loss of adhesive at the junction of the skin and core. Further analysis was conducted to calculate the shear stress when the junction was dropped. The mean shear stress at the adhesive surface of a specimen, 150 mm and 200 mm in thickness, was 0.0170MPa and 0.0156MPa, respectively. This suggests that similar values were obtained from panels of equal thickness. In addition, this stress provides a criterion of judgment that could be used to inspect the structural performance of the panels. The performance of the panel was evaluated based on the allowable load, but it may be possible to increase the strength of the lightweight composite panel by improving the joining method to avoid separation from the junction.

• Journal of the Microelectronics and Packaging Society
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• v.20 no.4
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• pp.13-16
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• 2013

A lot of various researches have been going on to use heat spreader for LED module. Nano porous aluminum anodic oxide (AAO) applied LED, which is produced from anodization, is easy and economically advantageous. Convensional LED module is consist of aluminum/adhesive/copper circuit. The polymer adhesive in this module is used as heat spreader. However the thermal emission of LED component is degraded because of low heat conductivity of polymer and also reliability of LED component is reduced. Therefore, AAO in this work was applied to heat spreader of LED module which has higher heat conductivity compare to polymer. Bonding strength between AAO and copper circuit was improved with Ti/Cu seed layer by copper sputtering process (DBC) before the bonding. And this copper circuit has been fabricated by electro plating method. Peel strength of AAO and copper circuit in this work showed range between 1.18~1.45 kgf/cm with anodizing process which is very suitable for high power LED application.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.5
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• pp.1741-1746
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• 2010

This study is on development of UV-cured anti-stain coating compounds which have more improved anti-stain function to prevent a surface of PVC tile from stain. To make an anti-stain coating composition, water soluble antistatic agent made from ammonium(IV) salt, antistatic agents for acrylic and polyurethane were used. Their contents varied from 5 to 20wt% against quantities of resin in coating composition. After coating PVC tiles using bar-coating method that can adjust a thickness, we estimated surface properties of coated layer such as anti-stain, electric resistance, adhesive power, thickness of coating, and so on. Results showed that a coating composition added 15wt% of water soluble antistatic agent and coated with No.12 bar-coater had the optimum surface property in electric resistance($3.24{\times}10^9{\Omega}/cm^2$), anti-stain(ink Test, Dust Test) and adhesive power. We could also find electric resistance and anti-stain effect were improved as antistatic agent content increased. However, excessive addition of antistatic agents(over 20wt%) caused the migration.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.2
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• pp.267-272
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• 2004

This case report describes an uncommon treatment method for crown-root fractured incisor with immature root. A 7-year-old girl was referred for treatment of crown-root fractured maxillary central incisor. The fracture line extended to 1/2 of the total tooth length with incomplete root formation. The prognosis of crown-root fracture is usually poor and extraction is usually undertaken. But, in the mixed dentition, extraction of maxillary permanent incisor results in many complications, such as resorption of alveolar bone, poor esthetics, pronunciation and mastication. Conservative therapy in the permanent dentition comprises of few treatment modalities; supragingival restoration, gingivectomy, orthodontic extraction of apical fragment, surgical extrusion of apical fragment with or without rotational replantation. However, in this case, these indications are not applicable, so intentional replantation with adhesive resin system is the treatment of choice. The tooth was followed-up for 12 months. Currently, there are no symptoms. Since this modality adopts the respective advantages of both intentional replantation and adhesive treatment, it might be the treatment of choice in cases of vertical crown-root fracture.

• Journal of Ocean Engineering and Technology
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• v.19 no.5 s.66
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• pp.43-49
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• 2005

This paper is to investigate the effect of corrosion by acoustic emission method in tensile loading and the adhesiveness between substrate and coating layer. The powders used are Zn and Amdry625, respectively. They are coated on brass alloy substrate. AE signals of Zn and Amdry625 coating layer increase drastically in strain $2\%$. However, those of Zn specimen have more than those of Amdry625 specimen. When the specimens executed the corrosion test under $3.5\%$ NaCl solution for 500, 1000 hours, the salt solution penetrated into the surface of the substrate through the pores of the coating layer. As a result, corrosion production formed on the surface of the substrate. The adhesiveness between coating layers is weakened by the polarization and corrosion itself. The AE event, count, and energy of corroded coating specimens decrease, compared to specimens without corrosion. The results are summarized as follows : 1. In the tensile tests, the time that it took to start and develop the cracks and exfoliations between the surface of the substrates and the plasma spray coatings were different according to the type of plasma sprayed material, which are Zn and Amdry625. These phenomena were obvious at the strain rate 1 to $5\%$, and few available data were found after that stage. 2. The specimens with Zn coating showed the characteristics of crack, according to the changes of the tensile strength applied on the substrates while those with Amdry625 showed exfoliation as a result of low adaptation to the tensile strength. 3. The anti-corrosion specimens showed that the adhesive properties between the substrate and the plasma spray coating were strong in the order of Zn, Amdry. It showed that Corroded specimens cracked or exfoliated easily, even with the small energy, because those had a comparatively weakened adhesive property, due to corrosion. 4. Zn specimen showed no corrosion phenomena on the surface of the substrates, because they had the function of sacrifice anode however, Amdry625 specimen showed the corrosion, because it did not have that function.

• Restorative Dentistry and Endodontics
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• v.24 no.2
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• pp.416-425
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• 1999

The purpose of this study was to evaluate shear bond strength of glass ionomer cements and compomer according to dentin surface treatment method. The materials used in this study were dentin conditioner and cavity conditioner for dentin treatment: Ketacfil, Fuji II LC, and Dyract for restoration. In this study, 90 sound bovine teeth were selected and then the teeth were embeded in improved stone and were grounded with 400 to 600 grit silicon carbide paper to create a flat dentin surfaces. The teeth were divided into nine groups as follows ; Group 1A : Samples bonded to dentin surface with Ketacfil after no treatment Group 1B : Samples bonded to dentin surface with Ketacfil after applicating dentin conditioner Group 1C : Samples bonded to dentin surface with Ketacfil after applicating cavity conditioner Group 2A : Samples bonded to dentin surface with Fuji II LC after no treatment Group 2B : Samples bonded to dentin surface with Fuji II LC after applicating dentin conditioner Group 2C : Samples bonded to dentin surface with Fuji II LC after applicating cavity conditioner Group 3A : Samples bonded to dentin surface with Dyract after no treatment Group 3B : Samples bonded to dentin surface with Dyract after applicating dentin conditioner Group 3C : Samples bonded to dentin surface with Dyract after applicating cavity conditioner Treated dentin surfaces were observed under SEM. After filling of each materials, shear bond strenth was evaluated and then debonded surfaces were observed under SEM. The following results were obtained; 1. The shear bond strengths obtained were decreased as Fuji II LC, Dyract, Ketacfil in that order and there was statistically significant difference(p<0.05). 2. About Group 1. the shear bond strengths were decreased as 1C, 1B and 1A in that order. But there was no significant difference between group 1B and 1C (p<0.05). 3. About Group 2, the shear bond strengths were decreased as group 2B, 2A and 2C in that order. And there was significant difference between group 2B and 2C (p<0.05). 4. About Group 3, the shear bond strengths were decreased as group 3A, 3C and 3B in that order. And there was signicant difference between group 3A and 3B (p<0.05). 5. As a result of observation under SEM, the fracture patterns of Fuji II LC and Dyract were adhesive failures, but those of Ketacfil were cohesive failure of material and mixture of cohesive and adhesive failure.