• Journal of the Korea Institute of Building Construction
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• v.10 no.5
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• pp.37-44
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• 2010

This study examined the practical application of ground granulated blast-furnace slag (GGBS) based alkali-activated (AA) binders for the development of cementless environmental-friendly secondary products of concrete, such as brick, shore protection blocks and interlocking blocks. The addition amount and type of alkaline ion to activate GGBS varied according to the diverse qualities of the secondary products of concrete required in Korean industrial standards (KS) and other specifications. Test results showed that the secondary products of concrete using GGBS-based AA binders surpassed the demanded capacities of KS and other specifications. In addition, shore protection block had a pH value close to neutral, enabling an advantageous environment for marine life. Therefore, the GGBS-based AA binders can be effectively applied to develop eco-friendly secondary products of concrete with reduced $CO_2$.

• Journal of the Korean Recycled Construction Resources Institute
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• v.1 no.1
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• pp.35-41
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• 2013

In this study, we investigated the strength development and durability of geopolymer mortar using blast furnace slag only, and admixed with blast-furnace slag and fly ash as cementious materials in oder to develop cementless geopolymer concrete. In order to compare with the geopolymer mortar, the normal mortar using ordinary portland cement was also test. In view of the results, we found out that strength development, the resistance to freezing-thawing of the geopolymer mortar have better than the mortar using ordinary portland cement. Especially, using the combined with blast furnace slag and fly ash develop high strength of above 60 MPa, and improve the resistance of freezing-thawing of approximately 20%, but promote the velocity of carbonation of 2.2~3.5 times.

• Journal of Biomedical Engineering Research
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• v.17 no.1
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• pp.61-70
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• 1996

In cementless total hip arthroplasty(THA), an initial stability of the femoral component is mandatory to achieve bony inyowth and secondary long term fixation. Primary stability of the femoral component can be obtained by minimizing the magnitude of relative micromotions at bone stem interface. An accurate evaluation of interf'ace micromotion and stress/strain fields in the bone-implant system may be relevant for better understanding of clinical situations and improving THA design. Recently finite element method(FEM) was introduced in'orthopaedic research field due to its unique capacity to evaluate stress in structure of complex shape, loading and material behavior. The authors developed the 3-dimensional finite element model of proximal femur with $Multilock^{TM}$ stem of 1179 blick elements to analyse the micromotions and mechanical behaviors at the bone-stem inteface in early post-operative period for the load simulating single leg stance. The results indicates that the values of relative motion for this well fit stem were $150{\mu}m$ in maximum $82{\mu}m$ in minimum and the largest relative motion was developed in medial region of Proximal femur and in anterior-posterior direction. The motion in the proximal bone was much greater than in the distal bone and the stress pattern showed high stress concentration on the cortex near the tip of the stem. These findings indicate that the loading on the hip joint in the early postoperative situation before achieving bony ingrowth could produce large micromotion of $150{\mu}m$ and clinicaly non-cemented THA patient should not be allowed weight bearing strictly early in the postoperative period.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.3
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• pp.255-261
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• 2019

The purpose of this study is to investigate effects of types of synthetic fibers on mechanical properties of alkali-activated slag composite. Materials and mixture proportion for matrix are determined, and the compressive strength, tensile performance, and cracking patterns of three composites reinforced by polypropylene, polyvinyl-alcohol, and polyethylene fibers. From the test results, it was observed that polyvinyl-alcohol fiber-reinforced composite and polyethylene fiber-reinforced composite had similar tensile performance. On the other hand, polypropylene fiber-reinforced composite showed low tensile performance. And it was exhibited that other factors except tensile strength and aspect ratio of fiber influence significantly tensile behavior of composite.

• Biomaterials and Biomechanics in Bioengineering
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• v.2 no.3
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• pp.143-157
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• 2015

Successful integration of cementless femoral stems using porous surfaces relies on effective periimplant bone healing to secure the bone-implant interface. The initial stages of the healing process involve protein adsorption, fibrin clot formation and cell osteoconduction onto the implant surface. Modelling this process in vitro, the current work considered the effect of fibrin deposition on the responses of human mesenchymal stromal cells cultured on ferritic fibre networks intended for magneto-mechanical actuation of in-growing bone tissue. The underlying hypothesis for the study was that fibrin deposition would support early stromal cell attachment and physiological functions within the optimal regions for strain transmission to the cells in the fibre networks. Highly porous fibre networks composed of 444 ferritic stainless steel were selected due to their ability to support human osteoblasts and mesenchymal stromal cells without inducing untoward inflammatory responses in vitro. Cell attachment, proliferation, metabolic activity, differentiation and penetration into the ferritic fibre networks were examined for one week. For all fibrin-containing samples, cells were observed on and between the metal fibres, supported by the deposited fibrin, while cells on fibrin-free fibre networks (control surface) attached only onto fibre surfaces and junctions. Initial cell attachment, measured by analysis of deoxyribonucleic acid, increased significantly with increasing fibrinogen concentration within the physiological range. Despite higher cell numbers on fibrin-containing samples, similar metabolic activities to control surfaces were observed, which significantly increased for all samples over the duration of the study. It is concluded that fibrin deposition can support the early attachment of viable mesenchymal stromal cells within the inter-fibre spaces of fibre networks intended for magneto-mechanical strain transduction to in-growing cells.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.1
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• pp.50-56
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• 2019

This study aims to make artificial stone by recycling blast furnace slag powder, red mud and recycled aggregate, which are known as industrial waste. Recycled aggregate is a typical construction waste, and various recycled products such as concrete block are being sold. In this study, we tried to make artificial stone mixed with waste such as recycled aggregate, and experimented with the use of artificial stone and further study. As the red mud replacement ratio increased, the absorption ratio, fluidity and air content of the matrix were measured to be decreased, and the strength and density were found to increase. The fluidity and absorption ratio decreased with increasing the replacement ratio of recycled aggregate, and the air quantity, rate of aggregate on the surface, density and intensity increased to a certain level. Therefore, this study intends to make artificial stone using recycled resources and conducted basic experiments for further study.

• Journal of the Korean GEO-environmental Society
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• v.23 no.4
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• pp.21-27
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• 2022

Recently, numerous studies are being performed to examine alkali-activated cement which uses industrial by-products, such as GGBS and fly ash, as well as alkali activators. Alkali-activated cement is a type of binder that exerts the same strength as cement without using cement by mixing industrial by-products with alkali activators. Alkali activators, which are used mainly for carbon-reducing technologies and alkali activation, are expensive and difficult to apply in the field due to risks related to strong alkalinity. Therefore, this study intends to explore methods to use red mud as a substitute for an alkali activator. To that end, this study has evaluated engineering properties, such as flow and strength, of CLSM that uses red mud and paper sludge ash as binders and its possibility to cause soil pollution. This study also aims to present the appropriate mixing ratios of red mud and paper sludge ash to produce CLSM.

• Hip & pelvis
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• v.36 no.2
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• pp.120-128
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• 2024

Purpose: The purpose of this study was to compare the clinical and radiographic outcomes with use of short-curved stems versus standard-length single wedged stems over a minimum follow-up period of five years. Materials and Methods: A retrospective study of primary total hip arthroplasties performed using the Fitmore^® stem (127 hips, 122 patients) and the M/L taper^® stem (195 hips, 187 patients) between October 2012 and June 2014 was conducted. The clinical and radiographic outcomes were obtained for evaluation over a minimum follow-up period of five years. Results: In both the Fitmore^® and M/L taper^® groups, the mean Harris hip score improved from 52.4 and 48.9 preoperatively to 93.3 and 94.5 at the final follow-up, respectively (P=0.980). The mean Western Ontario and McMaster Universities Osteoarthritis Index scores also improved from 73.3 and 76.8 preoperatively to 22.9 and 25.6 at the final follow-up, respectively (P=0.465). Fifteen hips (Fitmore^®: 14 hips; M/L taper^®: one hip, P<0.001) developed intraoperative cracks and were treated simultaneously with cerclage wiring. Radiography showed a radiolucent line in 24 hips in the Fitmore^® group and 12 hips in the M/L taper^® group (P=0.125). Cortical hypertrophy was detected in 29 hips (Fitmore^® group: 28 hips; M/L taper^® group: one hip, P<0.001). Conclusion: Similarly favorable clinical and radiographic outcomes were achieved with use of both short-curved stems and standard-length single wedged stems. However, higher cortical hypertrophy and a higher rate of femoral crack were observed with use of Fitmore^® stems.

• Journal of the Korean Orthopaedic Association
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• v.55 no.6
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• pp.503-510
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• 2020

Purpose: Bipolar hemiarthroplasty is used as an alternative to open reduction and internal fixation for unstable intertrochanteric fractures in elderly patients. Recent advances in medical systems and technologies have resulted in increased survival rates after intertrochanteric fractures of the femur, requiring selection of the appropriate femoral stems considering the mid- to long-term duration of survival. Hemiarthroplasty was performed for unstable intertrochanteric fractures using a double tapered quadrilateral femoral stem (C2 stem), and the clinical and radiological results were evaluated as a five-year follow-up post-surgery. Materials and Methods: From January 2004 to December 2013, 43 patients (43 hips) who underwent hemiarthroplasty with a C2 stem were enrolled in this study. Their mean age was 78.6 years (range, 70-84 years), and the mean follow-up period was 85.4 months (range, 60-96 months). During the follow-up period, clinical parameters, such as the changes in pain, walking ability, and functional status, were examined. Radiologically, changes in the proximal femur, such as osteoporosis and bone resorption of cortical bone, were noted. Complications that occurred during the follow-up period, such as dislocation and prosthetic features, were also reviewed. Results: Initially, the pain was relieved postoperatively, but it increased four years after surgery. The walking ability was reduced by two steps in nine patients after 60 months, and the Harris hip score was reduced significantly postoperatively after two to three years. Radiologically, cortical osteoporosis occurred in 14 patients. Five patients developed cortical bone resorption. Four of them showed nonunion of the trochanteric fracture fragments, and three of them suffered reverse oblique fractures. Conclusion: Careful selection considering the general health condition and remaining lifespan of the patient would be necessary for primary hip hemiarthroplasty using a 3C type cementless femoral stem for unstable intertrochanteric fractures in elderly patients with osteoporosis.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.4
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• pp.119-126
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• 2012

Portland cement production-1.5billion tonnes yearly worldwide-contributes substantially to global atmospheric pollution(7% of total of $CO_2$ emissions). Attempts to increase the utilization of fly ash, by-products from thermal power plant to partially replace the cement in concrete are gathering momentum. But most of fly ash is currently dumped in landfills, thus creating a threat to the environment. Many researches on alkali-activated concrete that does not need the presence of cement as a binder have been carried out recently. Instead, the sources of material such as fly ash, that are rich in Silicon(Si) and Aluminium(Al), are activated by alkaline liquids to produce the binder. Hence concrete with no cement is effect reduction of $CO_2$ gas. In this study, we investigated the influence of the compressive strength of mortar on alkaline activator and curing condition in oder to develop cementless fly ash based alkali-activated concrete. In view of the results, we found out that it was possible for us to make alkali-activated mortar with 70MPa at the age of 28days by using alkaline activator manufactured as 1:1 the mass ratio of 9M NaOH and sodium silicate and applying the atmospheric curing after high temperature at $60^{\circ}C$ for 48hours.