• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.4
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• pp.686-692
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• 2013

Today, environmental issues have become a matter of worldwide concern. In particular, automobile industries engage in considerable research and investment to develop high-efficiency and ecofriendly cars. Most ecofriendly cars use natural gas or hydrogen gas instead of fossil fuels. In this regard, low-weight and high-pressure vessels have gradually been developed to increase the driving distance of a car. However, most pressure vessels installed in cars develop many defects over time owing to shocks sustained when the car is being driven. Such defects can cause the explosion of the pressure vessel. Therefore it is important to prevent such explosions due to internal defects. The use of shearography for measuring the internal defects of objects afford many advantages. It is a non-contact and non-destructive method, and it is not limited by the object shape. In this study, the internal defect deformation and strain of an aluminum liner that is used in a CNG bus for the fuel storage tank is measured using shearography. It is important to measure the strain and deformation in order to detect defects and repair the pressure vessel. To verify the accuracy of the shearography measurement method, the measurement results of shearography, out-of-plane ESPI, and FEM are compared quantitatively.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.1
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• pp.112-118
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• 1990

Catastrophic fracture cannot be avoided after cracks(initiated from pre-existing defects) propagate rapidly with speeds comparable to a sound wave velocity of the materials. Preventing catastropic failure, crack arrest fracture toughness defined from dynamic(or kinetic) fracture mechanics point of view has been introduced in determining accurate and/or proper crack arrest fracture toughness of a material. For the past decades, many studies have been carried out to render proper theoretical and experimental backgrounds on the use of the static plain strain crack arrest fracture toughness, $K_{1a}$ (which seems to be a material property). $K_{1a}$ has been used to predict the performance of thick walled structures and has been considered as a measure of the ability of a material to stop a fast running crack. Determination of such a material property is of prime importance to the nuclear reactor pressure vessel and bridge materials industries. However, standards procedures for measuring toughness associated with fast running cracks are yet to exist. This study intends to give insight on the determination of the crack arrest fracture toughness of materials such as polymethylmethacrylate(PMMA), SM45C-steel, and A1 7075-T6. The effects of crack jump lengths and fast crack initiation stress intensity factor on the determination of $K_{1a}$ have been experimentally observed.erved.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.4
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• pp.402-410
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• 2002

Recently the necessity of study on optical measuring method using laser to detect the pipeline's defect in nuclear facilities, chemical industries and power plants has been increased. Because laser light can be delivered to a remote area without any difficulties, the application of laser in many industries can solve several difficulties from the limitation of access in danger area and reduce the risks of workers. Therefore, we applied a new experimental technique to the measurement of internal defects in pressure vessels with the combination of shearography and image processing technique and detected the internal cracks of pressure vessels in the former paper. In this paper, we used the same optical system as in the former study and found the optimum shearing magnitude by comparing the real length of specimen with experimental results. A variety of conditions were applied to certify the validity of this method. Actually, several specimens which have different lengths and depths were used in this experiment under the three diverse pressure. Consequently, we have carried out this experiment to determine the limit of measurement ability with analyzing errors.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.4
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• pp.393-401
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• 2002

Pipelines in power plants, nuclear facilities and chemical industries are often affected by corrosion effects. It is important to inspect the internal defects in pipelines in oder to guarantee safe operational condition. We have taken relatively much time, cost and manpower to use conventional NDT methods because these methods are contact measuring methods. In this paper, we used digital shearography, a laser-based optical method which allows full-field measurement of surface displacement derivatives. This method has many advantages in practical use, such as low sensitivity to environmental noise, simple optical configuration and real time measurement. The experiment was performed with pressure vessels which has different internal cracks and detected internal cracks in the pressure vessels at a real time using phase shifting method.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.1
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• pp.48-55
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• 2012

Pressure vessels in vehicle industries, power plants, and chemical industries are often affected by flaw and defect generated inside the pressure vessels due to production processes or being used. It is very important to detect such internal defects of pressure vessel because they sometimes bring out serious problems. In this paper, an optical defect detection method using digital shearography is used. This method has advantages that the inspection can be performed at a real time measurement and is less sensitive to environmental noise. Shearography is a laser-based technique for full-field, non-contacting measurement of surface deformation (displacement or strain). The ultimate goal of this paper is to detect flaws in pressure vessels and to measure the lengths of the flaws by using unwrapping, phase images which are only obtained by Phase map. Through this method, we could decrease post-processing (next processing). Real length of a pixel can be calculated by comparing minimum and maximum unwrapping images with shearing angle. Through measuring several specimen defects which have different lengths and depths of defect, it can be possible to interpret quantitatively by calculating gray level.

• Journal of Korea Multimedia Society
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• v.22 no.11
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• pp.1280-1287
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• 2019

For developing a wireless implantable device to monitoring the artery variation in real-time. The concept of a special vessel variation measurement capacitive sensor is presented in this paper. The sensor consists of two part; main sensor to measuring the arterial variation, and reference sensor is used to improve the accuracy of the capacitance value variation. Before sensor manufacture, a model of the sensor attached on the artery was designed in 3D to conduct in the FEA simulation to validate the validity and feasibility of the idea. The artery model was designed as layered structures and made of collagenous soft tissues with intima inside, followed by the media and the adventitia. Also, a grease layer was designed in the inner of the arterial wall to imitate the clogged arteries. The simulation was divided into two parts; sensor performance test by changing the diameter of the grease layer, and arterial wall tension test by changing the blood pressure. As the simulation results, the capacitance value measured by the proposed sensor is decreased follow the diameter of the grease increased. Also, large elastic deformation of the arterial wall since changing the blood pressure has been observed.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.43 no.1
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• pp.62-70
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• 2007

Marine casualties of vessel are serious problems on social and national aspects, because it results in sacrifice of lives, a great lose of properties and marine pollution. According to recent statistics of marine casualties of vessel, fishing boats are more likely to be ended in the casualty, and especially, small fishing boats cause much more accidents than any other big vessels. Most of marine casualties were caused by the human factors such as poor watch keeping, inadequate manoeuvering and negligent action for engine, etc. This study is intended to provide navigator of small fishing boat with a specific information of necessary to assist both the manoeuvering and the avoidance of capsizing. The manoeuvering characteristics of ship can be adequately judged by the results of typical ship trials manoeuvres. For this purpose, the author measured the roll responses of a small fishing boat in waves using the real sea experimental measuring system, and analyzed the experimental data by the statistical and spectral analyzing methods to get the characteristics of the roll motion responses of the small boat through the wave directions and the ship's speed.

• Analytical Science and Technology
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• v.34 no.5
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• pp.193-201
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• 2021

We have demonstrated a sensitive analytical method of measuring oleracone D in mouse plasma using a liquid chromatography-tandem mass spectrometry (LC-MS/MS). Oleracone D and oleracone F (internal standard) in mouse plasma samples were processed using a liquid-liquid extraction method with methyl tertbutyl ether, resulting in high and reproducible extraction recovery (80.19-82.49 %). No interfering peaks around the peak elution time of oleracone D and oleracone F were observed. The standard calibration curves for oleracone D ranged from 0.5 to 100 ng/mL and were linear with r² of 0.992. The inter- and intra-day accuracy and precision and the stability fell within the acceptance criteria. The pharmacokinetics of oleracone D following intravenous and oral administration of oleracone D at doses of 5 mg/kg and 30 mg/kg, respectively, were investigated. When oleracone D was intravenously injected, it had first-order elimination kinetics with high clearance and volume of distribution values. The absolute oral bioavailability of this compound was calculated as 0.95 %, with multi-exponential kinetics. The low aqueous solubility and a high oral dose of oleracone D may explain the different elimination kinetics of oleracone D between intravenous and oral administration. Collectively, this newly developed sensitive LC-MS/MS method of oleracone D could be successfully utilized for investigating the pharmacokinetic properties of this compound and could be used in future studies for the lead optimization and biopharmaceutic investigation of oleracone D.

• Korean Journal of Clinical Laboratory Science
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• v.50 no.4
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• pp.477-483
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• 2018

Transcranial doppler is a non-invasive method that measures the blood flow velocity and the direction of cerebral blood vessels through the doppler principle. The pulsatility index is an index for measuring the transcranial doppler that reflects the distal vascular resistance and is used as an index for the presence and diffusion of cerebral small vessel diseases. The purpose of this study was to evaluate the risk factors affecting the basilar artery pulsatility index in ischemic stroke patients. From January 2014 to May 2015, 422 patients were selected by measuring the transcranial doppler pulsatility index, considering their basilar artery pulsatility index. Univariate analysis was performed using the basilar artery pulsatility index as a dependent variable. Multiple regression analysis was performed considering the factors affecting the pulsatility index as variables. Univariate analysis revealed age, presence of hypertension, presence of diabetes mellitus, presence of hyperlipidemia, and hematocrit (P<0.1) as factors. Multiple regression analysis showed statistically significant results with age (P<0.001), presence of diabetes (P=0.004), and presence of hyperlipidemia (P=0.041). The risk factors affecting the basilar artery pulsatility index of transcranial doppler were age, diabetes, and hyperlipidemia. Further research will be needed to increase the cerebral pulsatility index as a surrogate marker of the elderly, diabetes, and hyperlipidemia.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.7
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• pp.754-759
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• 2015

Nowadays, short distance communication systems with low power energy (LPE) are developed for identification and monitoring of site identification of vessel crews and passengers (SIVCP). LPE communication modules, such as Bluetooth low energy (BLE) and Zigbee, are used for short distance communications with LPE. These modules enable 1:N communications and their popularity is growing since the modules can be mounted on movable objects, such as mobile devices and human body. When these modules are used, the important factor that affects their operation time and design are the capacity and size of battery. Therefore, they must be made as small as possible, and the battery should be selected to be slightly smaller than the module. In this study, we calculate the theoretical life of batteries used in SIVCP BLE modules using data sheet and discharge characteristic graph under the condition of a 1/250 transmission-ratio (TR). We thus calculate experimental life by measuring transmission current for the same TR, and low speed mode current for a 1/5000 TR and measure long-term experimental life using 1/25 TR for days. Through these experiments, we verify experimental methods for the prediction and extension of battery life that would enable us to select appropriate sizes of batteries based on vessel usage and passenger types. The selections of the module TR and battery size are important factors affecting the cost reduction of module design, the battery maintenance, and passenger convenience.