• Structural Engineering and Mechanics
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• 제52권4호
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• pp.723-738
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• 2014

Prestressing is the most commonly employed technique in bridges and long span beams in commercial buildings as prestressing results in slender section with higher load carrying capacities. This work is an attempt to study the performance of a minimum weight prestressed concrete beam adopting a non-prismatic section so that there will be a reduction in the volume of concrete which in turn reduces the self-weight of the structure. The effect of adopting a non-prismatic section on parameters like prestressing force, area of prestressing steel, bending stresses, shear stresses and percentage loss of prestress are established theoretically. The analysis of non-prismatic prestressed beams is based on the assumption of pure bending theory. Equations are derived for dead load bending moment, eccentricity, and depth at any required section. Based on these equations an algorithm is developed which does the stress checks for the given section for every 500 mm interval of the span. Limit state method is used for the design of beam and finite difference method is used for finding out the deflection of a non-prismatic beam. All the parameters of nonprismatic prestressed concrete beams are compared with that of the rectangular prestressed concrete members and observed that minimum weight design and economical design are not same. Minimum weight design results in the increase in required area of prestressing steel.

• 대한전자공학회논문지
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• 제24권3호
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• pp.400-407
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• 1987

Thin film filter type 4-channel wavelength division multiplexing(WDM) device was designed and fabricated for the application in optical subscriber loop system. It has multi-mode fiber pigtails and four wavelength division consisting of 0.81, 0.89, 1.2 and 1.3 um. The evaluated performances are 1-2d B of insertion loss(connector loss excluded)and 30-35d B of crosstalk attenuation for all channels. The performance of the fabricated device was tested in the wideband optical transmission experiment, where the SNR degradation due to the crosstalk of the device was found to be within a measurement error.

• 한국항해학회지
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• 제18권3호
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• pp.51-79
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• 1994

Section 55 (1) of the Marine Insurance Act 1906 states that the insurer is liable for any loss proximately caused by a peril insured against but is not liable for any loss not proximately caused by a peril insured against. It is, therefore, essential to determine whether it is to be recoverable under the Marine Insurance Policy attaching the Institute Cargo or Hull Clauses. But a number of important losses are excluded from the policy by subsection 2 of the same section, unless the policy otherwise provides, although these losses are proximate causes of them. The purpose of this study is to investigate the meaning of proximate cause and excluded losses in the Act. The method of this study is a literature survey. In summary, (1) if the loss is considered to have been proximately caused by a certain peril, and the peril is insured against, the claim is recoverable, (2) if there are different causes resulting in separate losses, the claims recoverable will be those due to insured perils, (3) when the effective cause of the loss is established, remote causes can be ignored, (4) when causes of loss are combined, the claim is recovera-ble if the cause which is proximate in efficiency is an insured peril, (5) if there are two causes, equal in efficiency, the loss is recoverable if one of the causes is an insured peril, but always providing the other cause is merely an uninsured peril rather than a specific exclusion, (6) although certain losses are exclu-ded by section 55 (2) of the Act, with the exception of wilful misconduct of the insured, it is permitted for provision to be made in the policy to widen the terms to include such losses.

• 한국식품저장유통학회지
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• 제4권1호
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• pp.11-15
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• 1997

This experiment carried out to find the storage life according to the kinds of packaging material. Sheridan(Grape) which was fumigated SO2 were wrapped with polyethylenes(Bio-PE and PE) and stored at $0^{\circ}C$ under 90% RH modified condition. The resorts were summarized as follow. Natural weight loss was increased according to the storage time during the 135days storage that was only 1.0-1.7% in sealing section while 10% in non-sealing section. Abonrmal fruits were increased as the storage time was increased and it was 6.6-6.7% in sealing section while 100% in non-sealing during the 135days storage. Quality of appearance and taste are better in sealing section than non-sealing section and it was good in Bio-PE sealing section between packaging materials. Moistrue content was de creased as the storage range was increased and the decreasing rate of that during the storage was 4.9-5.2% in sealing section between treatments. During the storage range increased, the soluble solid degree was increased in non-sealing section but decreased in sealing section.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제41권
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• pp.36.1-36.8
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• 2019

Background: This study aims to examine the outcome of simultaneous maxillary sinus lifting, bone grafting, and vertical ridge augmentation through retrospective studies. Methods: From 2005 to 2010, patients with exhibited severe alveolar bone loss received simultaneous sinus lifting, bone grafting, and vertical ridge augmentations were selected. Fifteen patients who visited in Seoul National University Bundang Hospital were analyzed according to clinical records and radiography. Postoperative complications; success and survival rate of implants; complications of prosthesis; implant stability quotient (ISQ); vertical resorption of grafted bone after 1, 2, and 3 years after surgery; and final observation and marginal bone loss were evaluated. Results: The average age of the patients was 54.2 years. Among the 33 implants, six failed to survive and succeed, resulting in an 81.8% survival rate and an 81.8% success rate. Postoperative complications were characterized by eight cases of ecchymosis, four cases of exposure of the titanium mesh or membrane, three cases of periimplantitis, three cases of hematoma, two cases of sinusitis, two cases of fixture fracture, one case of bleeding, one case of numbness, one case of trismus, and one case of fixture loss. Prosthetic complications involved two instances of screw loosening, one case of abutment fracture, and one case of food impaction. Resorption of grafted bone material was 0.23 mm after 1 year, 0.47 mm after 2 years, 0.41 mm after 3 years, and 0.37 mm at the final observation. Loss of marginal bone was 0.12 mm after 1 year, and 0.20 mm at final observation. Conclusions: When sinus lifting, bone grafting, and vertical ridge augmentation were performed simultaneously, postoperative complications increased, and survival rates were lower. For positive long-term prognosis, it is recommended that a sufficient recovery period be needed before implant placement to ensure good bone formation, and implant placement be delayed.

• Transactions on Electrical and Electronic Materials
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• 제18권2호
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• pp.62-65
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• 2017

In this paper, three DC Block designs are presented which efficiently meet the need of modern-day compactsize wireless communication systems. As one of the important parts of a complete system design, the proposed microstrip-based DC block with coupled transmission lines efficiently attenuates unwanted frequencies that cause damage to the system. The compact-sized DC block structures are created by incorporating an extended coupled-line section with a radial stub, an enveloped coupled-line section, and using alternate up-down meandering techniques. The structures are analyzed for the L-Band using a high-resistive silicon substrate. At a resonating frequency of 1.575 GHz, the designed DC Block structures have a return loss better than -10 dB, an insertion loss of around -1 dB, and also possess wide pass-band characteristics.

• 대한기계학회논문집B
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• 제23권1호
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• pp.149-157
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• 1999

Heat transfer in a duct is augmented remarkably by rib turbulators. However, increasing friction loss is accompanied due to ribs disturbing flows. Hence, pressure drops and heat transfer are considered simultaneously to decide heat/mass transfer performance in a rib-roughened duct. In the present study, the effects of rib cross section shape on pressure drop through a duct are investigated as well as those on heat transfer characteristics. The results show that the characteristics of heat/mass transfer and friction loss in the duct roughened with triangular ribs are similar to those with square ribs, while significantly different from those with semicircular ribs. The best performance in the duct is obtained by using semicircular shaped ribs among three types of ribs for the large rib angles of ${\alpha}{\geq}63^{\circ}$.

• 한국전산유체공학회지
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• 제18권1호
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• pp.91-97
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• 2013

In the present study, the effects of contaminant accumulation and surface roughness on the aerodynamic performance of wind turbine blade sections were numerically investigated by using a flow solver based on unstructured meshes. The turbulent flow over the rough surface was modeled by a modified ${\kappa}-{\omega}$ SST turbulence model. The calculations were made for the NREL S809 airfoil with varying contaminant sizes and positions at several angles of attack. It was found that as the contaminant size increases, the degradation of the airfoil performance becomes more significant, and this trend is further amplified near the stall condition. When the contaminant is located at the upper surface near the leading edge, the loss in the aerodynamic performance of the blade section becomes more critical. It was also found that the surface roughness leads to a significant reduction of lift, in addition to increased drag.

• Journal of Korean Dental Science
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• 제12권1호
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• pp.29-37
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• 2019

Purpose: This study was aimed to compare the survival and success rates, and long-term crestal bone loss according to the use of 2 connection types of dental implants (submerged-USII and non-submerged-SSII; Osstem $Implant^{(R)}$) by analyzing the change in alveolar bone height after 1 year under load and during final follow-up period. Materials and Methods: Between December 2004 and August 2008, patients with two types of Osstem implants (USII and SSII) were retrieved retrospectively. A total of 92 patients with 284 implants (USII=60, SSII=224) was finally selected. Their mean follow-up period was 7.5 years. The mesial and distal alveolar crestal bone changes were measured using radiographic images and the average was calculated at 1 year after loading and during final follow-up period. Result: Among the 284 implants, 4 USII and 7 SSII implants were removed, indicating 93.3% and 96.9% survival rates. Of the survived implants, mean crestal bone loss 1 year after loading was 0.39 mm for USII and 0.19 mm for SSII (P=0.018). During the final follow-up, mean crestal bone loss was 0.63 mm and 0.35 mm for USII and SSII, respectively, without statistical significance (P=0.092). According to the criteria for the success and failure of the implant by Albreksson and colleagues, final success rate was estimated as 86.7% for USII and 91.5% for SSII, respectively. Conclusion At 1 year after loading, the average crestal bone loss was significantly different between USII and SSII; however, both types met the criteria for implant success. During the final follow-up, both groups showed insignificant bone resorption patterns and did not show any pathological clinical symptoms. Therefore, both implants exhibited high long-term stability.

• 대한의생명과학회지
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• 제13권4호
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• pp.361-368
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• 2007

Biological samples can be fixed either by chemical method by using chemical solution or physical methods by using heat treatment. The problem in traditional heat fixation is unsatisfactory quality due to uneven heat conduction in specimen and loss of inner cell contents. Chemical fixation method also bears several intrinsic problems like the limit in specimen size, time consumption in fixative impregnation, and loss of low molecular weight cell components. These factors deteriorate the quality of fixed specimen, thus limit the magnification and contrast of tissue pictures. Microwave heat has been reported to be a good alternative to current chemical methods to overcome these problem. In this study, we tried to introduce the microwave energy method to routine fixation work in hospital. We replaced chemical fixative with saline to provide moderate reaction condition, and used frozen section to reduce time for sample preparation. Temperature was measured at each experiment. The fixation of rat kidney tissue with 2.45 GHz electromagnetic wave and saline showed similar result to the control group fixed with traditional chemical method. Human tumor tissue fixed with 2.45 GHz electromagnetic in frozen section was improved in terms of histochemistry of PAS and immunohistochemistry of tumor marker like cytokeratin. Total turnaround time was reduced from $24\sim38$ h to to $2\sim4$ h. In conclusion, the quality of samples prepared by microwave heating method was at least as good as that of traditional method. If the condition for the fixation of different specimens is standardized, this new method could be applied to routine work in hospital, and could save working time as well.