• Journal of Korean Neurosurgical Society
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• v.29 no.5
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• pp.640-643
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• 2000

Objective : In neurosurgical practice, it has been generally accepted that when the dura is opened, it should be watertightly closed, and traditionally non-watertight closure has not been performed. We clinically tried non-watertight closure, analyzed the frequency of CSF leakage and evaluated the possible clinical application of non-watertight closure. Methods : After classifying our cases with supratentorial and infratentorial approach, we tried non-watertight and watertight closures and compared the results. We also analyzed the cases with or without dural graft. Results : In supratentorial approach, the rate of cerebrospinal fluid leakage noted in non-watertight closure was similar to that of watertight closure. In infratentorial approach, except microvascular decompression(MVD), the rate of cerebrospinal fluid leakage in non-watertight closure was higher than that of watertight closure. Dura graft application did not seemed to influence the cerebrospinal fluid leakage. Conclusion : Since the frequency of cerebrospinal fluid leakage was not higher in non-watertight closure than that of watertight closure, non-watertight closure can be applied in supratentorial approach. In infratentorial approach, non-watertight closure may be applied in surgery with relatively short dural incision, such as MVD. However, non-watertight closure doesn't seem to be appropriate in surgery that requires wide dural incision, such as skull base surgery.

• Journal of Drive and Control
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• v.14 no.2
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• pp.45-51
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• 2017

Semi-submersible drilling rigs are offshore plants that perform functions such as ocean exploration for oil and gas acquisition, drilling and production, and storage and unloading of crude oil and gas. Semi-submersible drilling rigs use watertight dampers as emergency buoyancy holders. Since the watertight damper is an emergency shutoff device, it is mainly driven by a pneumatic driving system that can operate without a power supply. The pneumatic driving system has highly non-linear characteristics due to compressibility of air and external disturbance such as static and Coulomb friction. In this paper, a new control algorithm is proposed for a watertight damper driving system based on the sliding mode control with a disturbance observer. To evaluate control performance and robust stability of the designed controller, the control results were compared with the results obtained using the state feedback controller. As a result, it was confirmed that the pneumatic driving system for driving the watertight damper using the sliding mode controller with a disturbance observer can obtain excellent control performance against the parameter changes and the disturbance input.

• Journal of Power System Engineering
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• v.20 no.6
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• pp.80-86
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• 2016

In this study, The watertight damper was designed to improve conventional DN 350A butterfly valve. The FSI(Fluid-Structure Interaction) analysis has performed to investigate the safety factor for the watertight damper. When watertight damper of disk was closed, the disk of pressure value is constant. However depending on the opening angle of disk, the flow velocity and pressure are changed. The maximum velocity was appeared at the end of disk on the small outlet area of duct. When the opening angel of disk is $90^{\circ}$, the maximum velocity was appeared at the center of ending disk. So we were found the opening angle of disk is bigger, the flow rate is increased and velocity is also increased from the result of FSI analysis. We can find the least deformation and stress when the opening angel of damper is $90^{\circ}$. When the $45^{\circ}$ opening angle of disk, the largest deformation and stress was found and the minimum safety factor 1.3 was calculated. As a result, we found that the structure of watertight damper is safe enough irrespective of opening angel.

• Journal of the Society of Naval Architects of Korea
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• v.40 no.6
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• pp.12-19
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• 2003

Corrugated bulkheads for a bulk carrier are divided into watertight bulkheads and deep tank bulkheads. Design of the watertight bulkheads is principally determined by the permissible limit of Classification and IACS requirements. But, the verification of strength through finite element analysis is indispensable for design of the deep tank bulkheads. A stage for stress evaluation of corrugated part is required for optimum structural design of the deep tank bulkheads. Since the finite element analysis for real model requires excessive amount of calculation time, in this study one corrugated structure is replaced with beam element and is idealized as 2 dimensional frame structure connected to upper and lower stool Minimum weight design of the deep tank bulkheads is performed through generalized sloped deflection method(GSDM) as direct calculation method. The purpose of this study is the development of design system for the minimization of steel weight of deep tank bulkheads as well as watertight bulkheads. Discrete variables are used as design variables for the practical design. Evolution strategies(ES) is used as an optimization technique.

• Journal of Fisheries and Marine Sciences Education
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• v.28 no.5
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• pp.1470-1477
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• 2016

This study has designed and evaluated the safety of watertight damper for Offshore Rigs. The watertight damper is an improved design for conventional DN 350 butterfly valve. Numerical analysis has been performed to investigate the safety factor and seat leakage of the designed 3-type disk dampers. The structure analysis results present the deformations, the equivalent stresses and the safety factor. It was confirmed that the designed disk, rib-disk and streamlined disk of watertight damper are safe enough in maximum operating pressure of 0.98MPa. The results show that the disk damper had the smallest maximum deformations and stress among 3-type disk dampers and the safety factor was 4.3. Therefore it is confirmed that the disk damper has the most excellent strength. Also linear static structural analysis was individually conducted for disk and body. The results show that the maximum disk deformation was larger than the body deformation, Therefore the disk damper is causes no seat leakage.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.10
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• pp.766-770
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• 2013

This paper tried to develop a BLDC electric motor securing the 800 W-level watertight structure for driving the outboard motor. For this purpose, this paper developed a high-efficient controller-integrating BLDC electric motor system for underwater propulsion and designed and developed a triple watertight structure. Besides, this study developed a outboard motor integrating motor, propeller and controller based on the production of a controller for BLDC motor which can the speed control by selecting low-voltage, high-current power element. The characteristics of developed outboard motor were 24 V input voltage, over 800 W motor output, and max. 3,000 rpm motor, and 84.9% motor efficiency, and the developed outboard motor could secure the watertight structure in 5 m in water depth.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.05b
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• pp.247-252
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• 2009

The LMC method of construction which have application to the road bridge is being considered the least relative importance about the watertight performance, because it focused on the durability of concrete. However, The LMC which is being expanded scope of application to the method of construction has grown importance about the watertight performance on the usability and maintenance side as well as durability. In this study, The latex concrete of two types which are different from mingled-ratio of the latex made a comparison to the compressive strength, watertight performance, dynamic wheel load resistance performance and confirmed what it has resistibility about chemical action through the chemical resistance test. The initial strength and watertight performance showed that were tendency the downward at 14 days. However, The long-term strength after 28 days showed that it has firm performance. In consequence, The initial curing of latex concrete is required to scrupulous care and attention at the site application. As a chemical resistance test result, The specimen that is steeped in sulphuric acid solution of 2% discovered the delamination phenomenon. However, it was confirmed that delamination phenomenon don't have an effect on the compressive strength. Moreover, As a dynamic wheel load resistance test result, The latex concrete was concluded to confirming the durability and running stability, because it had hardly any thickness reduction of latex concrete surface about dynamic wheel load and rarely found crack and delamination.

• Korean Institute of Interior Design Journal
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• v.16 no.6
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• pp.224-231
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• 2007

Superyachts are passenger vessels whose hull exceeds 24m. They are a kind of luxurious leisure ships. Interior designers can contribute in the field of space design of superyachts. This study is intended to investigate the space elements and their organization of superyachts for putting the base of superyachts interior design. Especially it is focused on the interior space division by structural elements such as the watertight bulkheads and decks. In this study we analyze general arrangements, floor plans of decks, of 31 superyachts and extract space elements and their disposition in three dimension. On the basis of the space arrangement we classify the types of space organization of superyachts. And then we inquire the interior space division of superyachts, which is characterized by the structural elements of the ship. The watertight compartments made by the bulkheads and decks have a great effect on interior space design in super yachts. The results of this study are summed up as follows: At first, the small-size superyacht has 3 decks and the midium or large-size superyachts has 4decks. Secondly, depending on the number of decks the superyachts has several typical patterns of space organization. Thirdly, in general there are 5-6 watertight compartments on a deck depending on the superyachts scale. Finally, there are distinct separation between the passenger's movement and the crew's movement on the ship.

• Journal of Korean Neurosurgical Society
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• v.59 no.1
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• pp.52-57
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• 2016

Objective : Many surgeons advocate for watertight dural reconstruction after posterior fossa surgery given the significant risk of cerebrospinal fluid (CSF) leak. Little evidence exists for posterior fossa dural reconstruction utilizing monolayer collagen matrix onlay graft in a non-watertight fashion. Our objective was to report the results of using collagen matrix in a non-watertight fashion for posterior fossa dural reconstruction. Methods : We conducted a retrospective review of operations performed by the senior author from 2004-2011 identified collagen matrix (DuraGen) use in 84 posterior fossa operations. Wound complications such as CSF leak, infection, pseudomeningocele, and aseptic meningitis were noted. Fisher's exact test was performed to assess risk factor association with specific complications. Results : Incisional CSF leak rate was 8.3% and non-incisional CSF leak rate was 3.6%. Incidence of aseptic meningitis was 7.1% and all cases resolved with steroids alone. Incidence of palpable and symptomatic pseudomeningocele in follow-up was 10.7% and 3.6% respectively. Postoperative infection rate was 4.8%. Previous surgery was associated with pseudomeningocele development (p<0.05). Conclusion : When primary dural closure after posterior fossa surgery is undesirable or not feasible, non-watertight dural reconstruction with collagen matrix resulted in incisional CSF leak in 8.3%. Incidence of pseudomeningocele, aseptic meningitis, and wound infection were within acceptable range. Data from this study may be used to compare alternative methods of dural reconstruction in posterior fossa surgery.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2006.05a
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• pp.57-61
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• 2006

Waste foundry sand of industrial waste which is happening by vast quantity according to fast development of industry has much the occurrence amount and processing method is depended on reclamation, and is using by fine aggregate for construction by recycling method among others. In this research Waste foundry sand powder into cement replace fare use possibility availability judge wish to Slump and air content decreased the replacement ratio increases by concrete special quality that do not harden according to experiment result, and unit capacity mass and bleeding increased the replacement ratio increases. Hardening concrete intensity special quality displayed strength improvement to replacement ratio 20%, and tendency that watertightness increases most in replacement ratio loft in watertight property appear. Considering the strength and watertight properties, the adequate usage of waste foundry sand powder is the 10% of replacement ratio.