• Archives of Reconstructive Microsurgery
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• v.16 no.2
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• pp.125-132
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• 2007

Introduction: Ulna is nearly equal to radius in function and bony architecture and strength in forearm. But in lower extremity, fibula is 1/5 of tibia in anatomic and functional point so we can find fibula transposition is commonly used in defect of tibia. We cannot find other article about segmental forearm bone transposition in man. The purpose of this study was to report our clinical and functional result of undergoing segmented transposition of ipsilateral ulna with its own vascular supply in defect of radius in 6 cases. Material and method: From June 1994 to October 2007, 7 segmented bone transpositional grafts in forearm were performed in Kyung Hee Medical Center. The distribution of age was from 20 years old to 73 years old. There was male in 6 cases and female in 1 case. The causes of operation were giant cell tumor in 1 case and traumatic origin in 6 cases; it was nonunion in 2 cases and fracture with severe comminution in 4 cases. Ipsilaterally segmented ulna keeping its own vascular supply was transported to defect of radius in severe traumatic patients and one patient whose tumor in radius had been excised. Transported ulna was fixed to proximal and distal radius remnants by plate and screw. In one case with giant cell tumor, transported ulna was connected to radius across wrist joint as wrist joint fusion. Joint preserving procedures were performed in 6 cases with crushing injury of radius. Results: We could obtain solid bony union in all cases and good functional results. The disadvantage was relative shortening of forearm, but we could overcome this problem. Conclusion: We think that ipsilateral segmented ulna transposition keeping its own vascular supply to radius can be perfomed with one of procedures in cases with wide defect in radius.

• Journal of the Korean Geotechnical Society
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• v.31 no.3
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• pp.27-38
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• 2015

Triaxial tests on sand-silt mixture specimens under low and high confining pressures were performed to understand their shear behaviors. The fines content in the mixture is lower than the threshold value. A series of tests under different conditions including fines contents (0%, 9.8%, 14.7%, 19.6%), density of specimen (controlled by different compaction energies of $E_c=22kJ/m^3$, $E_c=504kJ/m^3$), confining pressure (100 kPa, 1 MPa, 3 MPa, 5 MPa) were performed to investigate influences of these factors. Based on the test results, the threshold fines content, where the dominant structure of mixture changes from sand-matrix to fines-matrix, decreases with the increase of confining pressure. Under very high confining pressures, as a result of sand particle crushing, the behavior of the dense specimen is similar to that of the loose specimen which shows hardening, compression behavior, and shear strength increases with increase of fines content. In conclusion, silt is granular material like sand, and its influence on shear behavior of sand-silt mixture is very different from that of plastic fines on sand-fines mixture.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.3
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• pp.333-348
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• 2020

The present review dealt with the state-of-art on utilization of coal bottom ash in cement-based concrete and mortar. Two types of bottom ashes generated from pulverized coal combustion and circulating fluidized-bed combustion systems have been considered. The production process, chemical and physical characteristics of both ashes, and the methodology of utilization in various cement composites are summarized. The effect of bottom ash on various properties of concrete, such as workability, strength, and durability, were reviewed from the literature. In addition, the environmental and economic aspects of utilizing bottom ash in concrete are analyzed to explore the perspectives of bottom ash utilization, and through this, the future of the utilization was considered. The effect of bottom ash on the performance of concrete and mortar was greatly depended on the condition, pretreatment, and processing of the ash. Additional processing such as crushing might contribute to stimulating the utilization in this field. In particular, if economic support is possible in terms of policy, utilization rate is expected to be improved.

• Journal of the Korea Concrete Institute
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• v.13 no.2
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• pp.114-122
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• 2001

The purpose of this study was to manufacture sintered lightweight aggregate using paper sludge ash and to evaluate the qualities of the aggregate according to various mix proportions, conditions of pelletization and sintering. The paper sludge ash alone, due to its mineral and chemical compositions could not gain suitable expansion and strength. Hence, it was essential to add mineral additives such as clay, fly ash etc. The optimum muting ratio range determined in this study is as follows , paper sludge ash 30∼50 %, clay 30∼50 %, fay ash 0∼40 %, Paper sludge 0∼10% and hematite 2∼3 %(for manufacturing lightweight aggregate both for non-structural and structural concrete). It was possible to manufacture various lightweight aggregate whose dry specific gravity ranged about from 0.6 to 1.4 by using this optimum mixing ratio. From the test results of the qualities of aggregate, it showed that the 10% granules crushing value test and water absorption percentage ranged about 5∼10 ton and 10∼20%. Thus, it was favorably comparable to those of the imported aggregate. The manufactured lightweight aggregate could be used for structural concrete and non-structural concrete.

• Advances in concrete construction
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• v.8 no.3
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• pp.173-185
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• 2019

This article presents a comparative study of the effect of steel layouts on the seismic behavior of transition steel-concrete composite connections, both experimental and analytical investigations of concrete filled steel tube-reinforced concrete (CFST-RC) and steel reinforecd concrete-reinforced concrete (SRC-RC) structures were conducted. The steel-concrete composite connections were subjected to combined constant axial load and lateral cyclic displacements. Tests were carried out on four full-scale connections extracted from a real project engineering with different levels of axial force. The effect of steel layouts on the mechanical behavior of the transition connections was evaluated by failure modes, hysteretic behavior, backbone curves, displacement ductility, energy dissipation capacity and stiffness degradation. Test results showed that different steel layouts led to significantly different failure modes. For CFST-RC transition specimens, the circular cracks of the concrete at the RC column base was followed by steel yielding at the bottom of the CFST column. While uncoordinated deformation could be observed between SRC and RC columns in SRC-RC transition specimens, the crushing and peeling damage of unconfined concrete at the SRC column base was more serious. The existences of I-shape steel and steel tube avoided the pinching phenomenon on the hysteresis curve, which was different from the hysteresis curve of the general reinforced concrete column. The hysteresis loops were spindle-shaped, indicating excellent seismic performance for these transition composite connections. The average values of equivalent viscous damping coefficients of the four specimens are 0.123, 0.186 and 0.304 corresponding to the yielding point, peak point and ultimate point, respectively. Those values demonstrate that the transition steel-concrete composite connections have great energy dissipating capacity. Based on the experimental research, a high-fidelity ABAQUS model was established to further study the influence of concrete strength, steel grade and longitudinal reinforcement ratio on the mechanical behavior of transition composite connections.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.33 no.12
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• pp.45-52
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• 2017

The precast concrete (PC) method has many advantages in fast construction, quality control, etc. In domestic construction market, however, its application has been quite limited because of the concerns about structural integrity and seismic performances due to the discrete connections between precast concrete members. By applying the post-tensioning method, the precast beam-column connection can be well tightened, allowing improved structural integrity, and proper seismic performances can be also achieved. In this study, reversed cyclic tests have been conducted on the beam-column connection specimens, where the test variables included the compressive strength of grouting mortar and the tensile strengths of prestressing strands, based on which their seismic performances have been examined in detail. The post-tensioned PC beam-column connections showed good seismic performances comparable to that of the monolithic reinforced concrete connection specimen. When 2400 MPa prestressing strands are applied to the beam-column connection, it is preferable to adjust the prestress level similar to that applied for the 1860 MPa prestressing strands to avoid premature local crushing failures at the beam-column connections.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.6_2
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• pp.971-977
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• 2020

In this paper, We propose a portable electrostatic meter which can measure high voltage static electricity caused by friction to prevent fire or explosion accidents in grinding, crushing, power injection, transport, filling, dust removal, painting, and foreign matter removal processes. The proposed device not only shows static electricity strength in 4 steps with respect to distance and voltage but also gives warning with a buzzer, on process facilities that are likely to generate high voltage static electricity due to friction. The device is implemented by filtering the signal detected by the wireless antenna, amplifying the signal by 6 times, and passing the signal through the integrator circuit. Tests are carried out with an electrostatic discharge simulator. And the results show that 4 LEDs are turned on at the distance of 10cm, 3 LEDs at 12cm, 2 LEDs at 13cm, and 1 LED at 15cm, when a fixed voltage of 500V is given. And also, the tests show that the static electricity can be detected at 5cm on 100V, 10cm on 200V, 15cm on 500V, 20cm on 1000V, and 25cm on 1500V. We expect to reduce accidents caused by static electricity by allowing safety managers on fields where fire or explosion accidents can happen to monitor static electricity.

• Applied Chemistry for Engineering
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• v.22 no.6
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• pp.642-647
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• 2011

The fabrication characteristics of porous uranium oxide granules from $U_3O_8$ powder was investigated in terms of initial particle bed motions such as slumping and rolling, thermal treatment conditions, and rotational velocities in slumping motion using a rotary voloxidizer. With respect to the initial particle bed motion the recovery rate of granule of above 1 mm in slumping motion was higher than that in the rolling motion. Rolling motion was changed into slumping motion with high slumping frequency by formation of granules from fine particles. Recovery rate of granule significantly increased with the increas in thermal treatment temperature and time of upto 10 h. As the rotational velocity of voloxidizer in the case of the initial particle bed showing slumping motion increased, the recovery rate of granule increased from 81.5 to 88.7%. However, the rotational velocity of 2 rpm provided an effective density, crushing strength and sphericity of granules.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.4
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• pp.420-427
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• 2022

The present study evaluated the physical, mechanical and thermal properties of the foam glass aggregate and insulation foundation with this, in order to promote the use of insulated foundations using domestically produced foamed glass aggregates. As a result of the evaluation, the compacted foam glass aggregate showed at the same level as overseas products in terms of unit volume mass, particle size and other characteristics, and a compressive strength of 40.6 N/cm², which was superior to the existing organic insulation materials such as XPS. And the thermal conductivity of the foam glass aggregate was 0.84 W/mK, and the thermal transmittance of the specimen simulating the insulation foundation was 0.37 W/mK, so the thermal conductivity of the foam glass aggregate was estimated to be 0.80 W/mK. With these results, it was found that it is possible to use the insulation foundation with re-producted foam glass aggregate by crushing the waste from the process of producing foam glass products.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1A
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• pp.229-236
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• 2006

Recently, the use of crushed sand produced by the crushing of stone is continuously increasing to reach an utilization rate of about 20% of the whole fine aggregates that is foreseen to grow larger in the future. However, the lack of recognition concerning quality during the production of crushed sand results in the use of crushed sand that do not satisfy the KS F 2527 standard during the manufacture of concrete. And, studies investigating the effects of such crushed sand on concrete are still neglected. Therefore, this study intends to provide data that can be exploited for concrete using crushed sand through the analysis of the effects of the grain shape of crushed sand on the quality of concrete. Results revealed problems in the workability, air entraining and durability for a value of 53% for the solid volume percentage for shape determination specified by the current KS F 2527. Analysis showed that the adjustment of the solid volume percentage for shape determination from the currently specified 53% to 55% will improve the quality of concrete using crushed sand in high strength concrete particularly.