Jaebong Choi

Anemia is a common cause of morbidity and disease and reduces the quality of life. This study examined the effect of a combination treatment (AAC) using Astragali radix (AMW) and Angelicae radix (AGW) in cyclophosphamide (CYP)-induced anemic rats on erythropoietin (EPO) expression and hematological parameters. Male 4-week-old Sprague-Dawley rats were divided into five groups with or without CYP-induced anemia and individual or the combined herbal treatments according to the experimental protocol

The effects of sandwich-like catalysts on the vertical growth of multiwalled carbon nanotubes (MWCNTs) are investigated. We achieved the synthesis of 2.2-mm-long MWCNT forests with carefully designed catalyst films by thermal chemical vapor deposition. Two types of sandwich-like catalysts were prepared by electron beam evaporation. Fe and Al2O3 layers were deposited on a SiO2 surface of 300 nm in thickness. Here, Fe and Al2O3 were used for the catalyst and the supporting buffer layer, respective

Over the last decade, primary water stress corrosion cracking (PWSCC) has been frequently found in pressurized water reactor (PWR)applications. Especially, PWSCC has occurred in long-term operated PWRs. As this phenomenon leads to serious accidents, we must bebeforehand with the anticipated problems. A typical PWR consists of J-groove welded components such as reactor pressure vessel closurehead and nozzles. Reactor pressure vessel closure head is made of SA508 and it is covered by cladding. All

Graphene has recently received high attention as a promising material for various applications,and many related studies have been undertaken to reveal its basic mechanical properties. However, the tribological properties of graphene film fabricated by the chemical vapor deposition (CVD) method are barely known. In this study, the contact angle and frictional wear characteristics of graphene coated copper film were investigated under room temperature, normal air pressure, and no lubrication condi

To clarify the characteristics of surface damage due to fretting in press-fitted shaft, experimental methods were applied to small scale specimen with different bending load condition. Fatigue tests and interrupted fatigue tests of press-fitted specimen were carried out by rotate bending fatigue test. Macroscopic and microscopic characteristics were examined using scanning electron microscope (SEM), optical microscope or profilometer. It is found that small fatigue cracks are nucleated early in

Thermal stratification has continuously caused several piping failures in nuclear power plants since the early 1980s. However, this critical thermal effect was not considered when the old nuclear power plants were designed. Therefore, it is urgent to evaluate this unexpected thermal effect on the structural integrity of piping systems. In this paper, the thermal effects of stratified flow in two different safety injection piping systems were investigated by using a coupled CFD-FE method. Since s

This paper is to report enhancement of engineering J estimation for semi-elliptical surface cracks under tensile load. Firstly, limitation of the sole solution suggested by Zahoor is shown for reliable structural integrity assessment of thin-walled nuclear pipes. An improved solution is then developed based on extensive 3D FE analyses employing deformation plasticity theory for typical nuclear piping materials. It takes over the structure of the existing solution but provides new tabulated plast

Although it is widely known that both size and chirality play significant roles in vibration behaviors of single-walled carbon nanotubes (SWCNTs), there haven’t been yet enough studies specifying the relationship between structure and vibration mode shape of SWCNTs. We have analyzed the chirality and length dependence of SWCNT by using normal mode analysis based elastic network model in which all interatomic interactions of the given SWCNTs structure are represented by a network of linear spring

Although the well-known master curve method has been widely used to estimate the ductile to brittle transition temperature and to prevent subsequent brittle fracture of reactor pressure vessels, it has a limitation to determine reference temperatures on heat affected zone and weld metals. The present paper is to propose an enhanced master curve method. Prior to this, several schemes to provide the master curve of inhomogeneous materials such as bimodal master curve estimation, randomly inhomogen

To ensure the safety margin of a reactor pressure vessel (RPV) under normal operating conditions, it isregulated through the pressure-temperature (P-T) limit curve. The stress intensity factor (SIF) obtainedby the internal pressure and thermal load should be obtained through crack analysis of the nozzle cornercrack in advance to generate the P-T limit curve for the nozzle. In the ASME code Section XI, Appendix G,the SIF via the internal pressure for the nozzle corner crack is expressed as a func

The objective of the present paper is to evaluate the effect of the evolution of contact surface profile caused by fretting wear on fatigue life of press-fitted shaft by means of an analytical method based on experimental data. A finite element analysis was performed to analyze the stress states of press-fitted shaft, considering the worn contact profiles of shaft. The fatigue lives of the press-fitted shaft reflecting the evolution of contact stress induced by fretting wear were evaluated by st

Many surface finish methods are used to connect a substrate with the electric components of IT products in the micro-packaging process, and various types of lead-free solder have been developed as alternative materials to lead-based solder to reduce environmental contamination. However, there has been little research on the mechanical properties of the inter-metallic surface which is generated in the bumping process between the lead-free solder and surface films such as Ni/Au. The present work i

A district heating(DH) system supplies environmentally-friend heat and is appropriate for reduction of energy consumption and/or air pollutions. The DH transmission pipe, composed of supply and return pipes, has been used to transmit the heat and prevent heat loss during transportation. The two types of pipes are operated at a temperature of 75~115C and 40~65C, respectively, with an operating pressure of less than 1.568MPa. The objectives of this paper are to systematize data processing of trans