• Wind and Structures
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• v.37 no.4
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• pp.289-302
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• 2023

Insulating glass units (IGUs) have been widely used in buildings in recent years due to their superior thermal insulation performance. However, because of the panel reciprocating motion and fatigue deterioration of sealants under long-term wind loads, many IGUs have the problem of early failure of watertight properties in real usage. This study aimed to propose a statistical method for wind-induced deflection of IGU panels during the whole life service period, for further precise analysis of the accumulated fatigue damage at the sealed part of the edge bond. By the estimation of the wind occurrence regularity based on wind pressure return period, the events of each wind speed interval during the whole life were obtained for the IGUs at 50m height in Beijing, which are in good agreement with the measured data. Also, the wind-induced deflection analysis method of IGUs based on the formula of airspace coefficient was proposed and verified as an improvement of the original stiffness distribution method with the average relative error compared to the test being about 3% or less. Combining the two methods above, the deformation of the outer and inner panes under wind loads during 30 years was precisely calculated, and the deflection and stress state at selected locations were obtained finally. The results show that the compression displacement at the secondary sealant under the maximum wind pressure is close to 0.3mm (strain 2.5%), and the IGUs are in tens of thousands of times the low amplitude tensile-compression cycle and several times to dozens of times the relatively high amplitude tensile-compression cycle environment. The approach proposed in this paper provides a basis for subsequent studies on the durability of IGUs and the wind-resistant behaviors of curtain wall structures.

• Archives of Plastic Surgery
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• v.41 no.2
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• pp.158-162
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• 2014

Background Loss of nipple projection is a common problem following nipple reconstruction. The aim of this study was to demonstrate that the use of a tightly rolled dermal graft is effective in the long-term maintenance of nipple projection. Methods Nipple reconstruction was performed using the C-V flap technique. A dermal graft was harvested from the dog-ear portion of previous scars. The graft was rolled tightly into a compact cylinder and used to augment the nipple reconstruction. Postoperatively, stacked Allevyn dressing was used for protecting the nipple from compression for a minimum of two months. Nipple projection was measured at the time of surgery and at 12 months postoperatively. Results Forty nipple reconstructions were performed using this technique. There were 19 transverse rectus abdominis musculocutaneous (TRAM) flaps, 10 latissimus dorsi (LD) flaps, and 11 tissue-expanded breast mounds. At one year, the mean projection was 0.80 cm (range, 0.62-1.22 cm). The twelve-month average maintenance of nipple projection was 70.2% for the TRAM flap group, 76.3% for the LD flap group, and 61.8% for the tissue-expanded group. In two patients with previous irradiation of the reconstructed breasts, relatively poor maintenance of nipple projection was noted (45.7%). No complications were noted, and all of the donor sites healed well primarily. Conclusions Our results demonstrated that the use of a C-V flap with a tightly rolled dermal graft for nipple reconstruction improves the long-term maintenance of nipple projection. Its advantages include reproducibility, technical simplicity, cost-effectiveness, and minimal donor site morbidity.

• Applied Chemistry for Engineering
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• v.19 no.1
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• pp.86-91
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• 2008

The rubber was compounded with carbon black and silica series-filler to examine the effects of the various rubber fillers on a gasket material's suitability and fuel cell stack conclusion. The evaluation of a long term heat resistance and oil resistance of the mixed rubber material was performed considering at the drive environment of PEMFC. Test results of compression set for the most influencing property of gasket showed that it was about less than 15% at long term of up to 1000 h. In this experiment, FEM analysis is carried out about the rubber material's properties depending on each filler and the stress which is produced when a gasket is contracted by using various filler. Sealing force was expected to maximum 2.5 MPa from minimum 0.2 MPa by using FEM (finite element method) at stacking gasket to gasket.

• Journal of Korean Neurosurgical Society
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• v.30 no.4
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• pp.493-500
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• 2001

Objective : Anterior cervical locking plates are the devices for achieving anterior cervical spinal fusion. This study was conducted to evaluate the locking plate system regarding its long-term advantages and disadvantages in the view of interbody fusion rate, hardware-related failures, vertebral change close to the fusion segment and postoperative complications. Method : Eight-six patients, operated from Jan., 1996 to Jun. 1998, were followed-up for more than two years. All of the cases were fused with iliac bone graft and ORION locking plate(Sofamor Danek USA, Inc., Memphis, TN) fixation. The patients were discharged or transferred to rehabilitation department 2-7 days after operation. A comprehensive evaluation of the interbody fusion state, instrument failure, vertebral change and postoperative complications were made by direct interview and cervical flexion-extension lateral plain films. Results : There were 55 male and 31 female with a mean age of 45 years(18-75 years). The mean follow-up period was 29 months(24-43 months). Various disorders that were operated were 40 cervical discs, 6 cervical stenosis including OPLL, 2 infections, and 38 traumas. Fusion level was single in 59 cases, two levels of each disc space in 15 cases, and two levels after one corpectomy in 12 cases. There was no instrument failure. Pseudoarthrosis was observed in two cases(2%) without radiological instability. The other patients(98%) showed complete cervical fusion with stable instrument. Mild settling of interbody graft with upward migration of screws was found in 12 cases(14%). Anterior bony growth at the upper segment was found in 5 cases(6%). Postoperative foreign body sensation or dysphagia was observed in 12 cases(4%), and disappeared within one month in 7 cases and within six months in 4 cases. One patient complained for more than six months and required reoperation to remove paraesophageal granulation tissue. Conclusion : The results show that Orion cervical locking plate has some disadvantages of upward migration of screws, anterior bony growth at the upper segment, or possibility of esophageal compression even though it has advantages of high interbody fusion rate or low instrument failure. Author believe that anterior cervical locking plate in the future should be thinner, and should have short end from the screw hole, and movable screw with adequate stability.

• Journal of Korean Neurosurgical Society
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• v.37 no.6
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• pp.416-421
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• 2005

Objective: Despite general agreement on the goals of surgical treatment in thoracolumbar burst fractures, considerable controversy exists regarding the choice of operative techniques. This study is to evaluate the efficacy of short-segment fixation for thoracolumbar burst fractures after long-term follow-up and to analyze the causes of treatment failures. Methods: 48 out of 60 patients who underwent short-segment fixation for thoracolumbar burst fractures between January 1999 and October 2002 were enrolled in this study. Their neurological status, radiological images, and hospital records were retrospectively reviewed. Simple radiographs were evaluated to calculate kyphotic angles and percentages of anterior body compression (%ABC). Results: The average kyphotic angles were $20.0^{\circ}$ preoperatively, $9.6^{\circ}$ postoperatively, and $13.1^{\circ}$ at the latest follow-up. The average %ABC were 47.3% preoperatively, 31.2% postoperatively, and 33.3% at the latest follow-up. The treatment failure, defined as correction loss by $10^{\circ}$ or more or implant failure, was detected in 6 patients (12.5%). 5 out of 6 patients had implant failures. 2 out of 5 patients were related with osteoporosis, and the other 2 were related with poor compliance of spinal bracing. 3 patients with poor initial postoperative alignment had implant failure. 4 patients with screws only on the adjacent vertebrae and not on the injured vertebra itself showed poor initial and overall correction. Conclusion: With proper patient selection, adequate intraoperative reduction with screw fixation involving the injured vertebra, and strict postoperative spinal bracing, the short-segment fixation is an efficient and safe method in the treatment of thoracolumbar burst fracture.

• Polymer(Korea)
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• v.37 no.3
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• pp.399-404
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• 2013

In order to develop the blends with good long-term thermal stability and tensile elongation, the blends of polyphenylene sulfide (PPS) and 7 kinds of elastomer were tested. PPS/elastomer (90/10, 80/20, 70/30) blend samples were prepared by compression molding after twin screw extrusion or punching after sheet extrusion. Rheological, mechanical property and morphology of the blends were analyzed by capillary rheometer, UTM, impact tester, and SEM. For long-term thermal stability tests, the mechanical properties were measured again after the samples were stored in a convection oven for a week. The tensile strengths were almost same regardless of kinds of elastomer and the tensile elongation was the maximum for the PPS/m-EVA blend. As the content of elastomer increased, the elongation increased but delamination occurred at 30 wt% of elastomer content. The tensile strength increased but the elongation decreased seriously after thermal aging. Many problems related with PPS processing could be solved by adding a small amount of the elastomers partially compatibile with PPS and it would be applicable to develop various PPS grades.

• Journal of the Korea Concrete Institute
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• v.26 no.6
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• pp.707-714
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• 2014

CFT (Concrete-Filled Tube) is a type of steel column comprised of steel tube and concrete. Steel tube holds concrete and the concrete inside tube takes charge of compressive load. This study presents structural performance of the CFT column which has 73~100 MPa high strength concrete inside. Fluidity, mechanical compression, pump pressure test in flexible pipe were conducted for understanding properties of the high strength concrete. Material properties were achieved by various experimental tests, such as slump, slump flow, air content, U-box, O-Lot, L-flow. In addition, mock-up tests were conducted to monitor concrete filling, hydration heat, compressive strength. From construction sites in Sang-am dong and University of Seo-kang, long-term behaviors could be effectively predicted in terms of ACI 209 material model considering elastic deformation, shrinkage and creep.

• Polymer(Korea)
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• v.28 no.4
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• pp.335-343
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• 2004

Carmustine (l,3-bis(2-chloroethyI)-1-nitrosourea, BICNU) used as antineoplastic drug for the treatment of brain tumor is not appropriate for the long term delivery, because it has short biological half life. Therefore, poly(D,L-lactide-co-glycolide) (PLGA) is useful as drug carrier for the long term delivery due to bulk erosion property. Glycolide monomer is applied to release of BICNU owing to non-toxic and monomeric components after biodegradation of PLGA. In this study, BICNU-loaded PLGA wafers with or without glycolide monomer were fabricated by conventional direct compression method for the sustained release of BICNU. These wafers were observed for their release profiles of BICNU and degradation rates by SEM, NMR, and GPC. Furthermore, we make multi-layer wafers and compare them with release profiles of conventional wafer. From these results, drug release of BICNU-loaded PLGA wafers was increased with increasing the glycolid monomer contents. We confirmed that glycolide monomer and BICNU contents in barrier-layer influenced the drug release profiles and degradation rate.

• Geomechanics and Engineering
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• v.18 no.5
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• pp.535-543
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• 2019

Building on/with expansive soils with no treatment brings complications. Compacted expansive soils specifically fall short in satisfying the minimum requirements for transport embankment infrastructures, requiring the adoption of hauled virgin mineral aggregates or a sustainable alternative. Use of hauled aggregates comes at a high carbon and economical cost. On average, every 9m high embankment built with quarried/hauled soils cost $12600MJ.m^{-2}$ Embodied Energy (EE). A prospect of using mixed cutting-arising expansive soils with industrial/domestic wastes can reduce the carbon cost and ease the pressure on landfills. The widespread use of recycled materials has been extensively limited due to concerns over their long-term performance, generally low shear strength and stiffness. In this contribution, hydromechanical properties of a waste tyre sand-sized rubber (a mixture of polybutadiene, polyisoprene, elastomers, and styrene-butadiene) and expansive silt is studied, allowing the short- and long-term behaviour of optimum compacted composites to be better established. The inclusion of tyre shred substantially decreased the swelling potential/pressure and modestly lowered the compression index. Silt-Tyre powder replacement lowered the bulk density, allowing construction of lighter reinforced earth structures. The shear strength and stiffness decreased on addition of tyre powder, yet the contribution of matric suction to the shear strength remained constant for tyre shred contents up to 20%. Reinforced soils adopted a ductile post-peak plastic behaviour with enhanced failure strain, offering the opportunity to build more flexible subgrades as recommended for expansive soils. Residual water content and tyre shred content are directly correlated; tyre-reinforced silt showed a greater capacity of water storage (than natural silts) and hence a sustainable solution to waterlogging and surficial flooding particularly in urban settings. Crushed fine tyre shred mixed with expansive silts/sands at 15 to 20 wt% appear to offer the maximum reduction in swelling-shrinking properties at minimum cracking, strength loss and enhanced compressibility expenses.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.2
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• pp.625-631
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• 2014

In order to obtain a low evaporation temperature ranging from $-30^{\circ}C{\sim}-50^{\circ}C$, a cascade refrigeration system and two-stage compression one-stage expansion refrigeration system is required. However, the research results of performance comparison of these refrigeration system are very scarce. This paper were compared the performance characteristics of R744-R404A cascade refrigeration system and R404A two-stage compression refrigeration system. The COP of R404A two-stage compression refrigeration system is about 36~57% greater than that of R744-R404A cascade refrigeration system in the range of evaporation temperature of $-30^{\circ}C{\sim}-50^{\circ}C$. But R404A two-stage compression refrigeration system is unstable because COP is significantly changed when evaporating temperature and compressor efficiency decreased. In particular, when compressor efficiency decreased, COP is significantly decreased. In this case, not efficient for long-term use. Whereas R744-R404A cascade refrigeration system using natural refrigerants. Therefore, it is environmentally friendly. And this system is high-efficiency refrigeration system. The reason it can be configured by selecting the suitable refrigerant at high-temperature side and low-temperature side. From the above results, select the appropriate low temperature refrigeration system by considering the environmental and performance aspects.