• Title/Summary/Keyword: adhesion

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Experimental Study on Adfreeze Bond Strength Between Frozen Sand and Aluminium with Varying Freezing Temperature and Vertical Confining Pressure (동결온도와 수직구속응력 변화에 따른 모래와 알루미늄 재료의 접촉면에서 작용하는 동착강도 실험 연구)

  • Ko, Sung-Gyu;Choi, Chang-Ho
    • Journal of the Korean Geotechnical Society
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    • v.27 no.9
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    • pp.67-76
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    • 2011
  • Bearing capacity of pile foundations in cold region is dominated by adfreeze bond strength between surrounding soil and pile perimeter. Adfreeze bond strength is considered to be the most important design parameter for foundations in cold region. Many studies in last 50 years have been conducted to analyze characteristics of adfreeze bond strength. However, most studies have been performed under constant temperature and normal stress conditions in order to analyze affecting factors like soil type, pile material, loading speed, etc. In this study, both freezing temperature and normal stress acting on pile surface were considered to be primary factors affecting adfreeze bond strength, while other factors such as soil type, pile material and loading speed were predefined. Direct shear box was used to measure adfreeze bond strength between Joomoonjin sand and aluminium because it is easy to work for various roughness. Test was performed with temperatures of > $0^{\circ}C$, $-1^{\circ}C$, $-2^{\circ}C$, $-5^{\circ}C$, and $-10^{\circ}C$ and vertical confining pressures of 1atm, 2atm, and 3atm. Based on the test results, the effects of temperature and vertical stress on adfreeze bond strength were analyzed. The test results showed that adfreeze bond strength increases with decreased temperature and increased vertical stress. It was also noted that two types of distinct sections exist, owing to the rate of increase of adfreeze bond strength along the change of freezing temperature: 1)rapidly increasing section and 2)gradually decreasing section. In addition, the results showed that a main factor affecting adfreeze bond strength switches from friction angle to adhesion as freezing temperature decreases.

Artificial Control of ZnO Nanorods via Manipulation of ZnO Nanoparticle Seeds (산화아연 나노핵의 조작을 통한 산화아연 나노로드의 제어)

  • Shin, Kyung-Sik;Lee, Sam-Dong;Kim, Sang-Woo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2008.11a
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    • pp.399-399
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    • 2008
  • Synthesis and characterization of ZnO structure such as nanowires, nanorods, nanotube, nanowall, etc. have been studied to multifunctional application such as optical, nanoscale electronic and chemical devices because it has a room-temperature wide band gap of 3.37eV, large exiton binding energy(60meV) and various properties. Various synthesis methods including chemical vapor deposition (CVD), physical vapor deposition, electrochemical deposition, micro-emulsion, and hydrothermal approach have been reported to fabricate various kinds of ZnO nanostructures. But some of these synthesis methods are expensive and difficult of mass production. Wet chemical method has several advantage such as simple process, mass production, low temperature process, and low cost. In the present work, ZnO nanorods are deposited on ITO/glass substrate by simple wet chemical method. The process is perfomed by two steps. One-step is deposition of ZnO seeds and two-step is growth of ZnO nanorods on substrates. In order to form ZnO seeds on substrates, mixture solution of Zn acetate and Methanol was prepared.(one-step) Seed layers were deposited for control of morpholgy of ZnO seed layers by spin coating process because ZnO seeds is deposited uniformly by centrifugal force of spin coating. The seed-deposited samples were pre-annealed for 30min at $180^{\circ}C$ to enhance adhesion and crystallinnity of ZnO seed layer on substrate. Vertically well-aligned ZnO nanorods were grown by the "dipping-and-holding" process of the substrates into the mixture solution consisting of the mixture solution of DI water, Zinc nitrate and hexamethylenetetramine for 4 hours at $90^{\circ}C$.(two-step) It was found that density and morphology of ZnO nanorods were controlled by manipulation of ZnO seeds through rpm of spin coating. The morphology, crystallinity, optical properties of the grown ZnO nanostructures were carried out by field-emission scanning electron microscopy, high-resolution electron microscopy, photoluminescence, respectively. We are convinced that this method is complementing problems of main techniques of existing reports.

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Adhesive Strength in Tension of SBR-Modified Cement Mortar with Self-Flowability Material for Floor-Finishing (자기 평활성 바닥 마감용 SBR 시멘트 모르타르의 인장부착강도)

  • Do, Jeong-Yun;Soh, Yang-Seob
    • Journal of the Korea Concrete Institute
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    • v.15 no.4
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    • pp.549-556
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    • 2003
  • Various researches on the application of polymer dispersions to the cement mortar and concrete have been practised in many countries like America, Japan and Germany and so on because of high performance and good modification effect of these. In this study, SBR, Polymer dispersion that widely used in situ is employed that the self-flowability may be induced in the cemen mortar. In order to comprehend and investigate the modification of cement mortar with self-flowability by SBR and properties and fracture mode of adhesive strength in tension of that, experimental parameter was set as SBR solid-Cement ratio(S/C) and Cement:Fine aggregate(C:F) and the experiments such as Unit weight, Flow, Consistency change, Crack resistance and Segregation that inform on the general properties have been done. In addition of that, Adhesion in tension is measured with a view to comprehending the properties and fracture mode in tensile load. Consistency change of cement mortar modified by SBR did grow better as the ratio of SBR solid-Cement increased and was much superior to that of resin based flooring such as polyurethane and epoxy which recorded the loss of consistency in 90min. after mixing. Adhesive strength in tension increased with continuity in the curing age and showed the maximum in case of C:F=1:1 and S/C=20%. As the increase of curing age, the fracture mainly happened in the concrete substrate and the interface between the specimen and concrete substrate.

Weatherability of Epoxy Cement Mortars without Hardener (경화제를 첨가하지 않은 에폭시 시멘트 모르타르의 내후성)

  • Jo, Young-Kug
    • Journal of the Korea Concrete Institute
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    • v.18 no.6 s.96
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    • pp.801-809
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    • 2006
  • Epoxy resin has widely been used as adhesives and corrosion-resistant paints in the construction industry for many years, since it has desirable properties such as high adhesion and chemical resistance. Until now, in the production of conventional epoxy cement mortars, the use of any hardener has been considered indispensable for the hardening of the epoxy resin. However we have noticed the fact that even without any hardener, the hardening process of the epoxy resin can proceed by the action of hydroxides in cement mortars. As a result the disadvantages of the two-component mixing of the epoxy resin and hardener have been overcome. The purpose of this study is to evaluate the mechanical properties and durability of epoxy cement mortar without a hardener exposed at indoor and outdoor for one year. The epoxy cement mortars without and with a hardener were prepared with various polymer-cement ratios, and tested for weight change, flexural and compressive strengths, water absorption, carbonation depth and pore size distribution. Especially, the basic properties of the epoxy cement mortars without hardener are discussed in comparison with ones with the hardener. From the test results, it is concluded thai the epoxy cement mortars without a hardener exposed at indoor and outdoor for one year have higher strength and better durability than ones with the hardener within the polymer-cement ratios of 10 to 20%.

Strength Properties of Polymer-Modified Repair Mortars According to Curing Conditions and Repair Methods (양생조건 및 보수방법에 따른 폴리머시멘트모르타르의 강도 성상)

  • Kim, Wan-Ki;Jo, Young-Kug
    • Journal of the Korea Concrete Institute
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    • v.19 no.4
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    • pp.457-465
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    • 2007
  • In this paper, polymer-modified repair materials using polymer dispersions with six repair methods are prepared with various polymer-cement ratios, and tested for compressive and flexural strengths through each curing condition such as dry cure, water cure, and freezing and thawing cyclic action. And, the adhesive interface between the polymer-modified mortar and mortar substrate is observed by a scanning electron microscope. From the test results, the compressive and flexural strengths of cement mortar repaired by polymer-modified mortar are improved with a rise in the polymer-cement ratio regardless of the type of polymer and curing conditions. Such an improvement in the strengths of polymer-modified repair materials to ordinary cement mortar is explained by the high adhesion of polymer-modified mortar. Strength reduction of polymer-modified repair materials after freezing and thawing cyclic actions is recognized, but it is lower than that of unmodified mortar. Especially, cement mortar repaired by polymer-modified mortar with a St/BA emulsion has good strength properties compared with those of SBR latex and PA emulsion. Accordingly, it is judged that polymer-modified mortars with a St/BA emulsion are possible to use as repair materials to ordinary cement mortar and concrete.

Mix Design Conditions at Early Curing Age of PCS-Coating Material Effected on Improvement in Bond Strength of Coated Rebar (도장철근의 부착강도 개선에 영향을 미치는 초기재령에서의 PCS 도장재 배합조건)

  • Jo, Young-Kug;Park, Dong-Yeol;Kim, Wan-Ki
    • Journal of the Korea Concrete Institute
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    • v.25 no.1
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    • pp.73-80
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    • 2013
  • Polymer cement slurry (PCS) made from organic polymer dispersion and cement has good adhesion to steel, waterproofness and acid resistance due to being of polymer films formed in cement slurry. The purpose of this study is to evaluate the mix design conditions at early curing age of PCS-coating material effected on improvement in bond strength of coated rebar. The test pieces are prepared with two types of polymer dispersions such as St/BA and EVA, four polymer-cement ratios, two types of cement, four coating thicknesses and three curing ages, and tested for the bond strength test. From the test results, in general, bond strength of PCS-coated rebar is better than that of uncoated rebar and epoxy-coated rebar. It is also high bond strength at curing ages of 7-day or less, and coating thicknesses of $75{\mu}m$ and $100{\mu}m$. The maximum bond strength of PCS-coated rebar at curing age of 3-hour is almost same as that of curing age of 1-day and 7-day. The maximum bond strength of PCS-coated rebar with ultra high-early strength cement and St/BA at polymer-cement ratio of 80%, and coating thickness of $100{\mu}m$ is about 1.52 and 1.58 times respectively, the strength of uncoated rebar and epoxy-coated rebar. It is apparent that the curing age, coating thickness, type of polymer and cement are very important factors to improve the bond strength of PCS-coated rebar to cement concrete. We can have basic information that PCS-coated rebar with curing age at 3-hour and coating thickness of $100{\mu}m$ can replace epoxy-coated rebar.

Deposition Optimization and Bonding Strength of AuSn Solder Film (AuSn 솔더 박막의 스퍼터 증착 최적화와 접합강도에 관한 연구)

  • Kim, D.J.;Lee, T.Y.;Lee, H.K.;Kim, G.N.;Lee, J.W.
    • Journal of the Microelectronics and Packaging Society
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    • v.14 no.2 s.43
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    • pp.49-57
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    • 2007
  • Au-Sn solder alloy were deposited in multilayer and co-sputtered film by rf-magnetron sputter and the composition control and analysis were studied. For the alloy deposition condition, each components of Au or Sn were deposited separately. On the basis of pure Sn and Au deposition, the deposition condition for Au-Sn solder alloy were set up. As variables, the substrate temperature, the rf-power, and the thickness ratio were used for the optimum composition. For multilayer solder alloy, the roughness and the composition of solder alloy were controlled more accurately at the higher substrate temperature. In contrast, for co-sputtered solder, the substrate temperature influenced little to the composition, but the composition could be controlled easily by rf-power. In addition, the co-sputtered solder film mostly consisted of intermetallic compound, which formed during deposition. The compound were confirmed by XRD. Without flux during bonding of solder alloy film on leadframe, the adhesion strength were measured. The maximum shear stress was $330(N/mm^2)$ for multilayer solder with Au 10wt% and $460(N/mm^2)$ for co-sputtered solder with Au 5wt%.

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Effect of Glucose at High Concentrations on the Integrin and Cathepsin Expression of the Cultured Human Periodontal Ligament Cells (고농도 포도당이 사람 치주인대세포의 Integrin과 Cathepsin 발현에 미치는 영향에 관한 연구)

  • Kim, Bang-Soo;Shin, Je-Won;Hong, Jung-Pyo;Jue, Seong-Suk
    • Journal of Oral Medicine and Pain
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    • v.33 no.1
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    • pp.35-40
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    • 2008
  • This experiment was designed to clarify the effect of high concentrations of extracellular glucose on the periodontal ligament cells. The cells were incubated for 24 and 48 hours with ${\alpha}-MEM$ including 1,000 mg/L(control group) and 4,500 mg/L(experimental group) of glucose. Then, the expressions of ${\alpha}5$ integrin, cathepsin-B and -L were examined using RT-PCR method. The results were as follows: 1. ${\alpha}5$ integrin expression was increased after incubation in high glucose media. 2. Cathepsin-B expression was increased after the 24-H incubation with high glucose media, but was decreased after the 48-H incubation. 3. The expression of cathepsin-L was decreased by the high glucose media. Theses results suggest that extracellular glucose at high concentration may be attributed to delayed wound healing in diabetes patients through increase in ${\alpha}5$ integrin and decrease in cathepsins, which lead to accumulation of extracellular matrices and adhesion molecules.

SIMPLE DOUBLE EYELID OPERATION (ORIENTAL BLEPHAROPLASTY) USING Y NEEDLE (Y needle을 이용한 간단한 이중검 수술)

  • Yang, Byoung-Eun;Kim, Seong-Gon;Kim, Yong-Kwan
    • Journal of the Korean Association of Oral and Maxillofacial Surgeons
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    • v.30 no.2
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    • pp.157-161
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    • 2004
  • The eyes, the saying goes, are the windows of the soul. It's the first thing you notice about a person. Therefore, many people want to possess beautiful eyelids. Surgical formation of a palpebral fold and sulcus divides the lid into two well-defined segments (palpebral and pretarsal), producing the double eyelid desired by many Oriental women as well as an increasing number of man recently. Upper lid blepharoplasty is the Oriental eye is one of the variations of standard upper lid blepharoplasty. In Oriental double eyelid surgery, there have been two approaches to form a superior palpebral fold: the buried suture(nonincision) method and the full external incision method. Conventionally, the nonincision technique has been shown to produce little postoperative edema. However, the probability of the fold disappearing is high, and this technique cannot be performed in patients with fatty eyelids. Conversely, the incision technique has contrary characteristics. Recently, partial incision(or semi-open) technique which is combination of mentioned methods is used, this technique is removal of pretarsal tissue, muscle, and/or orbital fat around 2 or 3 incision site to facilitate tarsus-dermal adhesion. Our method is on the basis of this technique, furthermore, compared with conventional semi-open method, Y(Yang's) needle assisted double eyelid operation is more easy, convenient, saving-time method and provide satisfactory results.

Clinical experience in managing temporomandibular joint ankylosis: five-year appraisal in a Nigerian subpopulation

  • Braimah, Ramat;Taiwo, Abdurrazaq;Ibikunle, Adebayo;Oladejo, Taoreed;Adeyemi, Mike;Adejobi, Francis;Abubakar, Siddiq
    • Journal of the Korean Association of Oral and Maxillofacial Surgeons
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    • v.44 no.3
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    • pp.112-119
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    • 2018
  • Objectives: Temporomandibular joint ankylosis (TMJA) is a joint pathology caused by bony and/or fibrous adhesion of the joint apparatus, resulting in partial or total loss of function. Materials and Methods: This is a retrospective study conducted between 2012 and 2016 in the northwest region of Nigeria. The data retrieved includes gender, age, etiology of ankylosis, duration of ankylosis, laterality of ankylosis, type of imaging technique, type of airway management, types of incision, surgical procedure, mouth opening, interpositional materials used, and complications. Results were presented as simple frequencies and descriptive statistics. Results: Thirty-six patients with TMJA were evaluated during the study period. There were 21 males (58.3%) and 15 females (41.7%), yielding a male:female ratio of 1.4:1. The patients' age ranged from 5 to 33 years with $mean{\pm}standard$ deviation ($13.8{\pm}6.6years$). Thirty-five cases (97.2%) were determined to be true/bony ankylosis, while only 1 case (2.8%) was false/fibrous ankylosis. Most of the TMJA cases (16 cases, 44.4%) were secondary to a fall. In our series, the most commonly utilized incision was the Bramley-Al-Kayat (15 cases, 41.7%). The mostly commonly performed procedures were condylectomies and upper ramus ostectomies (12 cases each, 33.3%), while the most commonly used interpositional material was temporalis fascia (14 cases, 38.9%). The complications that developed included 4 cases (11.1%) of severe hemorrhage, 1 case (2.8%) of facial nerve palsy, and 1 case (2.8%) of re-ankylosis. Conclusion: Plain radiographs, with their shortcomings, still have significant roles in investigating TMJA. Aggressive postoperative physiotherapy for a minimum of 6 months is paramount for successful treatment.