• Composites Research
• /
• v.16 no.6
• /
• pp.1-9
• /
• 2003

In this paper, probabilistic failure analysis based on Weibull distribution function is proposed to predict the fiber strength of composite pressure vessel. And, experimental tests were performed using fiber strand specimens, unidirectional laminate specimens and composite pressure vessels to confirm the volumetric size effect on the fiber strength. As an analytical method, the Weibull weakest link model and the sequential multi-step failure model are considered and mutually compared. The volumetric size effect shows the clearly observed tendency towards fiber strength degradation with increasing stressed volume. Good agreement of fiber strength distribution was shown between test data and predicted results for unidirectional laminate and hoop ply in pressure vessel. The site effect on fiber strength depends on material and processing factors, the reduction of fiber strength due to the stressed volume shows different values according to the variation of material and processing conditions.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.21 no.11
• /
• pp.987-994
• /
• 2008

The optimal structure of the Tonpilz transducer was designed. First, the FE model of the transducer was constructed, that included all the details of the transducer which used practical environment. The validity of the FE model was verified through the impedance analysis of the transducer. Second, the resonance frequency, the sound pressure, the bandwidth, and the impulsive shock pressure of the transducer in relation to its structural variables were analyzed. Third, the design method of $2^n$ experiments was employed to reduce the number of analysis cases, and through statistical multiple regression analysis of the results, the functional forms of the transducer performances that could consider the cross-coupled effects of the structural variables were derived. Based on the all results, the optimal geometry of the Tonpilz transducer that had the highest sound pressure level at the desired working environment was determined through the optimization with the SQP-PD method of a target function composed of the transducer performance. Furthermore, for the convenience of a user, the automatic process program making the optimal structure of the acoustic transducer automatically at a given target and a desired working environment was made. The developed method can reflect all the cross-coupled effects of multiple structural variables, and can be extended to the design of general acoustic transducers.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.07a
• /
• pp.220-223
• /
• 2004

Inductively coupled plasma is commonly used for electrodeless lamp due to its ease of plasma generation. Optical characteristics significantly depend on the RF power and gas pressure of the plasma. This paper describes the measurement of luminance as a function of RF power and gas pressure with a goal of finding optimal operating conditions of the electrodeless lamp. The gas pressure was varied from 10[mTorr] to 300[mTorr] or 500[mTorr] and the RF power was varied from 10[W] to 200[W]. It was found that the luminance tends to be decreased when argon and neon pressure is increased, and the luminance is increased as RF power is increased. It was also found that the luminance per unit RF power is high when the argon and neon pressure is low and when the RF power is in the range of $30[W]{\sim}40[W]$ or 10[W].

• Textile Coloration and Finishing
• /
• v.35 no.3
• /
• pp.179-187
• /
• 2023

In this study, we developed a microfiber-based flexible pressure sensor with high sensitivity and excellent skin breathability. A nonwoven fabric composed of microfibers was prepared by electrospinning, which resulted in excellent moisture permeability of the sensor (143 g∙m^-2∙h^-1). In particular, high-pressure sensitivity (0.36 kPa^-1) was achieved by introducing submicron structures on the microfiber surface by controlling the ambient humidity during electrospinning. The fabrication technology of the microfiber-based flexible pressure sensors reported in this study is expected to contribute to the commercialization of flexible pressure sensors applicable to long-term wearable health monitoring as well as virtual/augmented reality and electronic skin applications.

• Korean Journal of Medicinal Crop Science
• /
• v.19 no.2
• /
• pp.103-110
• /
• 2011

This study was performed to enhance anticancer activities of Lithospermum erythrorhizon by eluting high amount of shikonin through ultra high pressure process. Extraction yield was increased up to 5~10% by ultra high pressure process, compare to the normal extraction processes such as water solvent extraction, 70% ethyl alcohol solvent extraction. The cytotoxicity of the extracts ($1.0{\mu}g/m{\ell}$) from ultra high pressure process was showed the lowest cytotoxicity 13.4% for human lung cell (HEL299). The anticancer activities showed 80~85% by adding $1.0{\mu}g/m{\ell}$ of the extracts from ultra high pressure process in several cancer cell lines such as AGS, Hep3B, MCF-7 and HeLa cells. Among them, MCF-7 cell of the endocrine system was highest inhibited than other cells. The anticancer activities of the extracts from ultra high pressure extraction process showed 10~15%, which was higher than the extracts from normal extraction processes. From HPLC analysis of the extracts, the contents of shikonin in the extracts from ultra high pressure process was 11.42% (w/w), which was 20% higher than others. This results indicate that ultra high pressure process could increase the extraction yield of shikonin and other contents, which resulted in higher anticancer activities.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2009.08a
• /
• pp.122-122
• /
• 2009

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.20 no.9
• /
• pp.2909-2915
• /
• 1996

Precise and accurate pressure measurements are obtained using deadweight piston gauges. Pressure distribution and elastic distortion in the piston-cylinder unit are the leading factors in determination of effective area. The distortion depends upon the pressure distribution in the clearance between piston and cylinder and those are coupled each other. Considering the viscosity pressure relation of oil and governing flow equation in the clearance, a new numerical iterative algorithm is developed. The disagreement between the monotonous and sharp pressure profiles is an indication that the pressure profile will be different for each piston and cylinder unit due to material variances.

• Electrical & Electronic Materials
• /
• v.10 no.10
• /
• pp.1022-1028
• /
• 1997

In this paper we present the construction details and output characteristics of a diaphragm-type pressure sensor with Cu-Ni(53:47) thin-film strain gauges. In order to improve the sensitivity and the temperature compensation two circumferential gauges are placed near the center of the diaphragm and two radial gauges are located near the edge. For all the gauges the relative change in resistance ΔR/R with pressure is of the order 10$^{-3}$ for the maximum pressure. The output is found to be linear over the entire pressure range(0-30kfg/cm$^2$)and the output sensitivity obtained is 1.6mV/V. The maximum nonlinearity observed in output characteristics is 0.35%FS for 5V excitation and the hysteresis is less than 0.1%FS.

• Journal of the Korean Society for Precision Engineering
• /
• v.12 no.3
• /
• pp.15-22
• /
• 1995

This paper presents the effects of assistant gas pressure on laser cutting. To investigate the effects of assistant gas pressure, pressure measuring system was constructed with good handling and precision at low price. The measured results discussed compare with that of laser cutting of STS304. The assistant gas pressure varied with the variation of distance between nozzle and workpiece. The peak pressure existed at some distance and could be known by using the deviced pressure measuring system. The higher assistant gas pressure helps to remove the dross and the exothermic energy out of the material. The quantity of dross beneath the workpiece decreases and the kerf width narrows at measured peak pressure.

• Transactions of the Korean Society of Pressure Vessels and Piping
• /
• v.4 no.2
• /
• pp.13-19
• /
• 2008

In order to predict a remaining life of a plant, it is necessary to select the components that are critical to the plant life. The remaining life of those components shall be evaluated by considering the aging effect of materials used as well as numerous factors. However, when evaluating reliability of nuclear structural components, some problems are quite formidable because of lack of information such as operating history, material property change and uncertainty in damage models. Accordingly, if structural integrity and safety are evaluated by the deterministic fracture mechanics approach, it is expected that the results obtained are too conservative to perform a rational evaluation of plant life. The probabilistic fracture mechanics approaches are regarded as appropriate methods to rationally evaluate the plant life since they can consider various uncertainties such as sizes and shapes of cracks and degradation of material strength due to the aging effects. The objective of this study is to evaluate the structural integrity for a reactor pressure vessel under the small break loss of coolant accident by applying the deterministic and probabilistic fracture mechanics. The deterministic fracture mechanics analysis was performed using the three dimensional finite element model. The probabilistic integrity analysis was based on the Monte Carlo simulation. The selected random variables are the neutron fluence on the vessel inside surface, the content of copper, nickel, and phosphorus in the reactor pressure vessel material, and initial RTNDT.