• Macromolecular Research
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• v.17 no.12
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• pp.1010-1014
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• 2009

Monodispersed microparticles with a poly(D,L-lactide-co-glycolide) (PLGA) core and a poly(ethyl 2-cyanoacrylate) (PE2CA) shell were prepared by Shirasu porous glass (SPG) membrane emulsification to reduce the initial burst release of doxorubicin (DOX). Solution mixtures with different weight ratios of PLGA polymer and E2CA monomer were permeated under pressure through an SPG membrane with $1.9\;{\mu}m$ pore size into a continuous water phase with sodium lauryl sulfate as a surfactant. Core-shell structured microparticles were formed by the mechanism of anionic interfacial polymerization of E2CA and precipitation of both polymers. The average diameter of the resulting microparticles with various PLGA:E2CA ratios ranged from 1.42 to $2.73\;{\mu}m$. The morphology and core-shell structure of the microparticles were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The DOX release profiles revealed that the microparticles with an equivalent PLGA:E2CA weight ratio of 1:1 exhibited the optimal condition to reduce the initial burst of DOX. The initial release rate of DOX was dependent on the PLGA:E2CA ratio, and was minimized at a 1:1 ratio.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.219-222
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• 2009

Pyrostarters play a role as a turbopump starter in liquid propellant propulsion systems by supplying pressurized gas to power turbines for engine start. A rupture disk in pyrostarters, which is usually installed behind a nozzle throat, not only isolates the charged solid propellants from the external environment but also improves the ignitability of the solid propellants by increasing a chamber pressure at the beginning of combustion. Experimental tests have been performed to study the effects of rupture disk thickness, depth and shape of scores, and pressure build-up rates on burst pressures and burst diameters. The experimental results show that the developed rupture disk fulfills the performance requirements expected in a real operational condition.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1491-1496
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• 2009

Fluid flow and structural analyses of an electronic expansion valve (EEV) using CO2 as a working refrigerant are carried out to estimate the mass flow rate and maximum stress. An engineering sample EEV that the orifice diameter is 1.8 mm was fabricated. The mass flow rates were measured at various EEV inlet temperatures and pressures for several EEV openings using experimental heat pump system. The sample EEV has over 35 MPa burst pressure and the maximum mass flow rate of CO2 through the EEV increased to 100 g/s at full opening condition.

• Journal of Biomedical Engineering Research
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• v.41 no.5
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• pp.210-218
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• 2020

Vessel sealing is a medical device that converts electrical or ultrasonic energy into thermal energy and leads to seal, coagulate, and cut the vessel by protein modification within the walls or surrounding connective tissues. As most of surgeries have recently been conducted with minimally invasive surgery, the demand and market for vessel sealing are expected to get bigger. However, there is a problem that electrosurgical or ultrasonic surgical is applied and we have a high risk to evaluate the strength of seal, because the collateral and particular standards currently in force follows have not been establish. Therefore, in this study, we investigated some papers studied on the efficacy and safety of the device, the guidance of FDA and test papers previously conducted from 3 individual subject device made in Korea. We found there is a relationship between burst pressure and the performance of the device, therefore, we propose the vascular bursting pressure test for evaluating the safety and performance of the vessel sealing.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.169-169
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• 2023

Most distributed water is not used effectively due to water loss occurring in pipe networks. These water losses are caused by leakage, typically due to high water pressure to ensure adequate water supply. High water pressure can cause the pipe to burst or develop leaks over time, particularly in an aging network. In order to reduce the amount of leakage and ensure proper water distribution, it is important to apply pressure management. Pressure management aims to maintain a steady and uniform pressure level throughout the network, which can be achieved through various operational schemes. The schemes include: (1) installing a variable speed pump (VSP), (2) introducing district metered area (DMA), and (3) operating pressure-reducing valves (PRV). Applying these approaches requires consideration of various hydraulic, economic, and environmental aspects. Due to the different functions of these approaches and related components, an all-together optimization of these schemes is a complicated task. In order to reduce the optimization complexity, this study recommends a sequential optimization method. With three network operation schemes considered (i.e., VSP, DMA, and PRV), the method explores all the possible combinations of pressure management paths. Through sequential optimization, the best pressure management path can be determined using a multiple-criteria decision analysis (MCDA) to weigh in factors of cost savings, investment, pressure uniformity, and CO₂ emissions. Additionally, the contribution of each scheme to pressure management was also described in the application results.

• Structural Engineering and Mechanics
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• v.27 no.3
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• pp.277-292
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• 2007

Based on the composite finite element simulation and a series of hydrostatic pressure and burst tests, autofrettage effects on strength and deformation of fiber reinforced pressure vessel with metallic liners have been studied in the paper (autofrettage: during the course of one pressure taking effect, the increasing internal stress in metallic liner can surpass the yielding point and the plastic deformation will happen, which result in that when there is no internal pressure, there are press stress in liner while tensile stress in fiber lamination). By making use of a composite finite element Ansys code and a series of experiments, the autofrettage pressure is determined in order to make the aluminium liner be totally in elastic state, under given hydrostatic test pressure. The stress intensity factors of the longitudinal crack in aluminum liner end under internal pressure and thermal loads have been computed and analyzed before and after the autofrettage processing. Through numerical calculation and experiment investigations, it is found that a correct choice for autofrettage pressure can improve the gas-tightness and fatigue strength of FRP vessel.

• Journal of Power System Engineering
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• v.9 no.3
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• pp.71-78
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• 2005

A high-pressure hose includes rebar layers of the synthetic fiber such as nylon or a steel wire to control internal pressure. The hose assembly is manufactured through the swaging process to clamp the hose into the metal fittings. Usually, the hose behavior is affected by the resultant of the longitudinal and circumferential forces produced by the internal pressure. The rebar layers can appear the most ideal rebar effect when they are arranged to the same direction as the resultant force. The braid angle applied in the rebar layers is an important factor in determining ultimate burst pressure and overall hose life. Failure can occur on the contacted parts of a hose with the metal fittings under severe operating conditions such as high pressure and temperature of the inner fluid. In this paper, the mechanical behavior between the hose and the metal fittings during the swaging process and the stress variation characteristics of a high-pressure hose under a constant applied pressure are analyzed with respect to the braid angle of steel wire using the finite element method.

• Journal of the Korean Institute of Gas
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• v.16 no.2
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• pp.18-24
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• 2012

This research seeks to evaluate damage on type II gas cylinder by an acoustic emission test when executing 20000 cycles fatigue test and thereafter burst test. Used gas cylinders in the experimental are three types as follows; one is sound cylinder, others are cylinders which contain longitudinal and transverse artificial defect. The size of artificial defect is a depth of 3 mm, width of 3 mm and length of 50 mm. In the case of the cylinder which artificial defect, unlike the expectation that it will burst in low pressure, the burst pressure of the cylinder did not differ much according to whether or not there were defects. However, when there was longitudinal defect, the location of burst was near the location of defect. This leads to the effect in which the thickness of the composite material becomes thinner according to the length of the longitudinal defect and this is judged to have an effect on the location of initiation and growth of crack in the liner. Also, for the acoustic emission signal, when there is longitudinal defect, the ratio of an event occurring at defect position among overall hits is more than 50 %, and the source location also accords very precisely with defect position.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.269-274
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• 2008

For fitness-for-service analyses of underground natural gas pipelines, engineering assessment methods against possible defects need to be developed. The assessment methods for high pressure pipeline of KOGAS, was developed using the full size pipe burst tests and the finite element analysis. It included the defect assessment methods for a single and multi-corrosion, corrosion in girth welding part, corrosion in seam welding part, the mechanical damage defects as dent and gouge, crack and large plastic deformation of API 5L X65 pipe. In addition, we developed method to assess pipeline integrity by internal and external load to buried pipeline. Evaluation results were compared with other methods currently being applied to the gas pipeline. The program of Windows environment is made for easily using assessment methods. It provides a consistent user interface, so non-professional technician can easily and friendly use the FFS program from company intranet. Several evaluation programs is easily installed using one installer. Each program constitutes a common input interface and the output configuration program, and evaluation result store and can be recalled at any time. The FFS program based on independent evaluation method is used to evaluate the integrity and safety of KOGAS pipeline, and greatly contribute to safe and efficient operation of pipeline. This paper presents experimental, analytical and numerical investigations to develop the FFS methods for KOGAS pipeline, used as high pressure natural gas transmission pipeline within KOREA. Also, it includes the description of the integrated program for FFS methods.

• Journal of the Korean Institute of Gas
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• v.13 no.4
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• pp.33-39
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• 2009

This study is intended to experiment performance of pressure relief device and to extend the effective ways to prevent cylinders of NGV from bursting when they are exposed to local fire intensively or when they are overcharged under ambient temperature at fueling stations in summer. In the results of thermal cycling experiments, all products of three companies met the requirements for gas leakage in the qualification criteria between $82^{\circ}C$ and $-40^{\circ}C$. But the o-rings of two companies' specimens among the three companies' specimens got damaged under the accelerated conditions between $135^{\circ}C$ and $-45^{\circ}C$. It took one minute and thirty nine seconds for a glass bulb type of a thermal sensitive type PRD to activate and it took two minutes and thirty one seconds for a fusible plug type of a thermal sensitive type PRD to activate. These results indicated that a glass bulb type of a thermal sensitive type PRD was one minute faster than a fusible plug type of a thermal sensitive type PRD. Under the accelerated condition $135^{\circ}C$, the activation pressure of a pressure sensitive type PRD burst at 32.1 MPa and, under the condition of qualification criteria, it burst from 30.7 MPa to 32.1 MPa.. As a result of the experiment for performance of pressure relief device, in the case of the thermal sensitive type PRD, a glass bulb type is more effective to flame than a fusible plug type. we confirmed that the rupture pressure of a pressure sensitive type PRD could not be affected by temperature and pressure cycling.