• Journal of the Korean earth science society
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• v.42 no.2
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• pp.164-174
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• 2021

The study examines the shearing and crushing characteristics of land-derived subaqueous granular materials in a gravel-bed river. A series of large-sized ring shear tests were performed to examine the effect of shear time and shear velocity on the shear stress characteristics of aquarium gravels with a 6-mm mean grain size. Three different shear velocities (i.e., 0.01, 0.1, and 1 mm/sec) were applied to measure the shear stress under the drained (long-term shearing) and undrained (short-term shearing) conditions. Different initial shear velocities, i.e., 0.01→0.1→1 mm/sec and 0.1→0.01→1 mm/sec, were considered in this study. The test results show that the grain crushing effect is significant regardless of drainage conditions. The shear stress of coarse-grained materials is influenced by initial shear velocities, regardless of the drainage conditions. In particular, particle breakage increases as grain size increases. The shearing time and initial shear velocity are the primary influencing factors determining the shear stress of gravels. The granular materials may be broken easily into particles through frictional resistance, such as abrasion, interlocking and fracture due to the particle-particle interaction, resulting in the high mobility of granular materials in a subaqueous environment.

• Journal of the Microelectronics and Packaging Society
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• v.30 no.4
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• pp.86-90
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• 2023

The packaging of electronic devices performs a protective function to ensure that their durability and reliability are not affected by changes in the operating environment caused by external factors. Recent advances in materials have led to ongoing research into bonded packaging of heterogeneous materials such as polymers and inorganic materials in electronic devices. In this packaging process, it is important to have a binding that joins the materials and ensures the operating environment, which includes adhesion to the substrate, corrosion and oxidation resistance through moisture removal, and durability. In this study, the hygroscopicity of the coating layer by modifying the polymer surface based on PVA was evaluated by controlling and measuring the contact angle, and the adhesion was confirmed by applying water-based ink and testing according to ASTM_D3363. For the durability of the polymer surface, the IPL post-treatment process was used to improve the hardness and toughness against applied voltage, and the pencil hardness test and nanoindentation test were conducted. Through this, we analyzed and proposed solutions to ensure the reliability and durability of polymer devices in polymer microfabrication against environmental factors such as moisture, temperature fluctuations and adhesion, and surface abrasion.

• The Journal of Korean Academy of Prosthodontics
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• v.60 no.3
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• pp.231-238
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• 2022

Purpose. This study aimed to investigate the effect of different veneering methods on the tensile bond strength between polyetherketoneketone (PEKK) and denture base resins. Materials and methods. A total of 80 PEKK T-shaped specimens were fabricated and the primer (Visio.link) was applied after airborne-particle abrasion with 110 ㎛ alumina oxide powder. According to the veneering method, the specimens were divided into four groups (n = 20) to be veneered with the gingival colored packable photopolymerized composite resin (SR Adoro); flowable photopolymerized composite resin, (Crea.lign); heat-polymerized resin (Vertex); and self-polymerized resin (ProBase Cold). Each group was divided into two subgroups (n = 10) according to the artificial thermal aging. After the tensile bond strength measurement via universal testing machine, the fracture sections of all specimens were observed. Two-way ANOVA and Tukey's HSD post hoc test were used for the statistical analysis (α = .05). Results. The results of the two-way ANOVA showed statistically significant differences in the tensile bond strength according to the veneering method and artificial thermal aging of denture base resins (P<.001). The highest tensile bond strength showed in the packable photopolymerized resin group before and after the artificial thermal aging. The lowest tensile bond strength showed in the heat-polymerized resin group. The mixed and adhesive fracture showed in all groups. Conclusion. The veneering method and artificial thermal aging can influence in the tensile bond strength between the resin and PEKK. The artificial thermal aging can reduce the tensile bond strength.

• Economic and Environmental Geology
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• v.57 no.2
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• pp.205-217
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• 2024

This study evaluated the physical characteristics and quality of volcanic rocks distributed in the Jeju Island-Ulleung Island area as aggregate resources. The main rocks in the Jeju Island area include conglomerate, volcanic rock, and volcanic rock. Conglomerate is composed of yellow-red or gray heterogeneous sedimentary rock, conglomerate, and encapsulated conglomerate in a state between lavas. Volcanic rocks are classified according to their chemical composition into basalt, trachybasalt, basaltic trachytic andesite, trachytic andesite, and trachyte. By stratigraphy, from bottom to top, Seogwipo Formation, trachyte andesite, trachybasalt (I), basalt (I), trachybasalt (II), basalt (II), trachybasalt (III, IV), trachyte, trachybasalt (V, VI), basalt (III), and trachybasalt (VII, VIII). The bedrock of the Ulleung Island is composed of basalt, trachyte, trachytic basalt, and trachytic andesite, and some phonolite and tuffaceous clastic volcanic sedimentary rock. Aggregate quality evaluation factors of these rocks included soundness, resistance to abrasion, absorption rate, absolute dry density and alkali aggregate reactivity. Most volcanic rock quality results in the study area were found to satisfy aggregate quality standards, and differences in physical properties and quality were observed depending on the area. Resistance to abrasion and absolute dry density have similar distribution ranges, but Ulleung Island showed better soundness and Jeju Island showed better absorption rate. Overall, Jeju Island showed better quality as aggregate. In addition, the alkaline aggregate reactivity test results showed that harmless aggregates existed in both area, but Ulleungdo volcanic rock was found to be more advantageous than Jeju Island volcanic rock. Aggregate quality testing is typically performed simply for each gravel, but even similar rocks can vary depending on their geological origin and mineral composition. Therefore, when evaluating and analyzing aggregate resources, it will be possible to use them more efficiently if the petrological-mineralological research is performed together.

• Journal of the Korean Society of Clothing and Textiles
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• v.18 no.1
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• pp.23-30
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• 1994

The objective of this study was to analyze the effect of the dissolution of detergent on washing and rinsing efficiency, and the possibility of saving detergent in washing. Washing and rinsing efficiency were reviewed in three different ways : A method was to input dissolved detergent by the use of rapid detergent dissolution instrument, B method was to input dissolved detergent beforehand, and C method was to input undissolved detergent. The results were as follows 1. A method > B method > C method was shown in detergency with washing time and three method's gaps were reduced because detergent dissolution effect was reduced by mechanical action in proportion of washing time. Especially, according to detergency of A method of 0.07% and C method of 0.1% was appeared approximately, saving detergent was expected by rapid dissolution of detergent. 2. A method > B method > C method was shown in detergency with washing temperature. As the washing temperature rose, the detergent reached chemically more activated state and become easily soluble. It resulted for the detergent to penetrate and adhere to laundry easily. 3. A method > B method > C method was shown in detergency with detergent concentration and C method was more sensitive than A, B method against change of detergent cocentration. Rapid detergent dissolution made it possible not only to enhance the washing efficiency but also to save the detergent because detergency of A method in low concentration is higher than that of C method. 4. A method $\geq$ B method > C method was shown in rinsing ratio with detergent input method. It indicated input dissolved detergent was advantageous in rinsing. 5. The result of anion surfactant concentration test of each process with detergent input method was shown like that A method In B method > C method in washing and reverse result was shown in rinsing. The anion surfactant concentration of C method was low during washing but high during rinsing. This was identical with previous results which shown the washing and rinsing efficiency improved with dissolved detergent usasge. 6. C method > B method > A method was shown in the degree of remaining detergent after rinsing. There was no remaining detergent after second rinsing in A and B method, but in C method four rinsings were required for the same result. Consequently, in A and B methods, less water and electricity were used, and less abrasion of cloth.

• The Journal of Korean Academy of Prosthodontics
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• v.38 no.5
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• pp.595-605
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• 2000

Dental ceramics have good aesthetics, biocompatibility, low thermal conductivity, abrasion resistance, and color stability. However poor resistance to fracture and shrinkage during firing process have been limiting factors in their use, particularly in multiunit ceramic restorations. A new method for making all-ceramic crowns that have high strength and low processing shrinkage has been developed and is referred to as the Vita In-Ceram method. This study was performed to investigate the effect of $CeO_2$ addition in borosilicate glasses on the strength of alumina-glass composites. Porous alumina compacts were prepared by slip casting and sintered at $1,100^{\circ}C$ for 2 hours. Dense composites were made by infiltration of molten glass into partially sintered alumina at $1,140^{\circ}C$ for 4 hours. Specimens were polished sequentially from #800 to #2000 diamond disk. and the final surface finishing on the tensile side was received an additional polishing sequence through $1{\mu}m$ diamond paste. Biaxial flexure test was conducted by using ball-on-three-ball method at a crosshead speed of 0.5mm/min. To examine the microstructural aspect of crack propagation in the alumina-glass composites, Vickers-produced indentation crack was made on the tensile surface at a load of 98.0 N and dwell time of 15 sec, and the radial crack patterns were examined by an optical microscope and a scanning electron microscope. The results obtained were summarized as follows; 1. The porosity rates of partially sintered alumina decreased with the rising of firing temperature. 2. The maximum biaxial flexure strength of 423.5MPa in alumina-glass composites was obtained with an addition of 3 mol% $CeO_2$ in glass composition and strength values showed the aspect of decrease with the increase of $CeO_2$ content. 3 The biaxial flexure strength values of alumina-glass composites were decreased with rising the firing temperature. 4. Observation of the fracture surfaces of alumina-glass composites indicated that the enhancement of strength in alumina-glass composites was due to the frictional or geometrical inter-locking of rough fracture surfaces and ligamentary bridging by intact islands of materials left behind the fracture front.

• International Journal of Highway Engineering
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• v.13 no.2
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• pp.85-93
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• 2011

This study experimented to evaluate the environment friendly high performance ternary cement concrete deck overlay pavement using mineral admixture such as fly ash and ground granulated blast-furnace slag. It was measured to find best binder mixing according to replacement rate of mineral admixture with compressive strength and flexural strength. After finding best binder, it is also experimented to evaluate durability on chloride penetration resistance, freezing- thawing resistance, scaling resistance of deicing chemicals, abrasion resistance, alkali-silica reactivity test and bonded environment friendly high performance ternary cement concrete deck overlay pavement experimented to evaluate bonded old deck and new concrete overlay pavement using special polymer cement mortar. In additions, bonded environment friendly high performance ternary cement concrete deck overlay pavement by experimental construction was evaluated at interchange bridge of North Yeoju. Result, examination was indicated better binding with binder replacement of cement 70%, ground granulated blast-furnace slag 15% and fly ash 15%. And special polymer cement mortar used in old deck and new overlay concrete was indicated better bonding both laboratory and construction.

• The Journal of Korean Academy of Prosthodontics
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• v.48 no.4
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• pp.251-258
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• 2010

Purpose: To evaluate the effect of surface conditioning on the shear bond strength of zirconium-oxide ceramic to 4 luting agents. Materials and methods: A total of 120 diskshaped zirconium-oxide ceramic blocks (3Y-TZP, Kyoritsu, Japan) were treated as follows: (1) Sandblasting with $110\;{\mu}m$ aluminum-oxide ($Al_2O_3$) particles; (2) tribochemical silica coating (Rocatec) using $110\;{\mu}m$ $Al_2O_3$ particles modified by silica; (3) no treatment. Then zirconium-oxide ceramic blocks bonded with 4 luting cements (RelyX luting (3M ESPE), Maxcem (Kerr), Nexus3 (Kerr), Rely X Unicem (3M ESPE)). Each group was tested in shear bond strengths by UTM. A 1-way analysis of variance and 2-way analysis of variance was used to analyze the data ($\alpha$ = .05). Results: RelyX unicem in combination tribochemical silica-coating produced a highest bond strength (P < .05). Air abrasion group and Rocatec treatment groups resulted in significantly higher than no conditioning group (P < .05). RelyX Luting groups showed lower bond strength than other groups. There were significant differences among groups (P < .05). Conclusion: Within the limitation of this study, RelyX Unicem cement provided the highest bond strength and Rocatec treatment enhanced the bond strength.

• 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.

• Restorative Dentistry and Endodontics
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• v.33 no.2
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• pp.125-132
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• 2008

The purpose of this study is to compare the shear bond strength of repaired composite resin with different bonding agents and evaluate the effect of bonding agents on composite repair strength. Forty composite specimens (Z-250) were prepared and aged for 1 week by thermo cycling between 5 and $55^{\circ}C$ with a dwell time of 30s. After air abrasion with $50\;{\mu}m$ aluminum oxide, following different bonding agents were applied (n = 10); SB group: Scotchbond multipurpose adhesive (3 step Total-Etch system); XE group: Clearfil SE bond (2 step Self-Etch system); XP group: XP bond (2 step Total-Etch system); XE group: Xeno III (1 step Self-Etch system). After bonding procedure was completed, new composite resin (Z-250) was applied to the mold and cured. For control group. 10 specimens were prepared. Seven days after repair, shear bond strength was measured. Data was statistically analyzed using one-way ANOVA and Tukey's test (p<0.05). The means and standard deviations of shear bond strength (MPa ${\pm}$ S.D.) per group were as follows: SB group: 17.06; SE group: 19.10; XP group: 14.44; XE group: 13.57; Control Group: 19.40. No significant difference found in each group. Within the limit of this study, it was concluded that the different type of bonding system was not affect on the shear bond strength of repaired composite resin.