• Applied Chemistry for Engineering
• /
• v.24 no.3
• /
• pp.227-230
• /
• 2013

The phase change of $(U_{1-x}Nd_x)_3O_8$ powder produced by oxidation of Nd-doped $UO_2$ pellet at $500^{\circ}C$ was investigated by high temperature oxidation heat treatment at $900{\sim}1500^{\circ}C$ under an air atmosphere. The XRD analysis results showed that the formation of $(U_{1-y}Nd_y)O_{2+z}$ phase and $U_3O_8$ phase from metastable $(U,Nd)_3O_8$ phase initiated at a temperature of $1000^{\circ}C$. The relative integrated intensity of $(U_{1-y}Nd_y)O_{2+z}$ phase to $U_3O_8$ phase increased with increasing of the oxidation temperature from 1100 to $1500^{\circ}C$. And also, it was found from the SEM observation that the particle size of $(U_{1-y}Nd_y)O_{2+z}$ phase increased with increasing of the oxidation temperature. However, electrone probe X-ray microanalyzer (EPMA) analysis results showed that Nd contents in $(U_{1-y}Nd_y)O_{2+z}$ phase decreased with increasing of the oxidation temperature. This behavior on the ground of XRD, SEM, and EPMA analysis data could be interpreted in terms of the transportation of U ions from $U_3O_8$ phase into $(U_{1-y}Nd_y)O_{2+z}$ phase through the interface of two phases during high temperature oxidation.

• Journal of Biomedical Engineering Research
• /
• v.26 no.6
• /
• pp.393-398
• /
• 2005

An electromechanical type is the most useful mechanism in the various pumping mechanisms. It, however, requires a movement converting system including a ball screw, a helical cam, or a solenoid-beam spring, which makes the device complex and may lessen reliability. Thus, the authors have hypothesized that an electromagnetic actuator mechanism can eliminate the movement converting system and that thereby enhance the mechanical reliability and operative simplicity of an electro­pneumatic pump. The purpose of this study was to show a novel application of electromagnetic actuator mechanism in pulsatile pump and to provide preliminary data for further evaluations. The electromagnetic actuator consists of stators with a single winding excitation coil and movers with a high energy density neodymium-iron-boron permanent magnet. A 0.5mm diameter wire was used for the excitation coil, and 1000 turns were wound onto the stators core with parallel. A prototype of extracorporeal electro-pneumatic pump was constructed, and the pump performance tests were performed using a mock system to evaluate the efficiency of the electromagnetic actuator mechanism. When forward and backward electric currents were supplied to the excitation coil, the mover effectively moved back and forth. The nominal stroke length of the actuator was 10mm. The actuator dimension was 120mm in diameter and 65mm in height with a mass of 1.4kg. The prototype pump unit was 150mm in diameter, 150mm in thickness and 4.5kg in weight. The maximum force output was 70N at input current of 4.5A and the maximum pump rate was 150 beats per minute. The maximum output was 2.0 L/minute at a rate of 80bpm when the afterload was 100mmHg. The electromagnetic actuator mechanism was successfully applied to construct the prototype of extracorporeal electro­pneumatic pump. The authors provide the above results as a preliminary data for further studies.

• Economic and Environmental Geology
• /
• v.41 no.3
• /
• pp.315-326
• /
• 2008

Recently, the occurrence and intensity of Asian Dust have dramatically increased in Korean peninsula, resulting in severe damages to the domestic social and economic field. The most useful way to prevent the damage of Asian Dust is the restraint of the occurrence of Asian Dust itself. However, Asian dust is the one of the natural phenomena, thus there is a basic limit to manage the Asian Dust. Though it is impossible to restrain the occurrence of Asian Dust in short time at present, it is a urgent matter to minimize the damage of Asian Dust. It is necessary to construct the basic data for understanding the harmfulness of Asian Dust, and to elucidate the source area of Asian Dust in connection with the maleficence of itself. In this study, the source area of Asian Dust in spring, 2007, is investigated using the Sr-Nd isotopic ratios which is the most common method to trace the source of geological materials. The relationships of Sr-Nd isotope ratios indicate that Asian Dust was originated from Central Loess Plateau and/or Ordos desert in spring, 2007.

• Proceedings of the Korean Radioactive Waste Society Conference
• /
• 2005.06a
• /
• pp.335-343
• /
• 2005

The Methodology of burnup calculation with EPMA test set up in this study. The spent fuel from PWR nuclear power plant was used as specimen. This $UO_2$ fuel with $3.2\%$ of enrichment had been irradiated up to 35,000 MWd/MTU(reference data). The burnup is very important factor for nuclear fuel to estimate all fuel behaviors in reactor. To measure amounts of fission products and actinides for the burnup calcualation, chemical analysis (destructive method) has been used but it mattes long experimental time and second radio-wastes. In this study, EPMA test was available to measure amount of fission products. Neodymium is able to be detected and quantified. It can be compared with the results from chemical analysis and ORIGEN-2 code calculation. Concentration of Nd from EPMA test showed good agreement with result of ORIGEN-2 code in the same burnup.

• The Journal of Korean Academy of Prosthodontics
• /
• v.37 no.1
• /
• pp.1-22
• /
• 1999

In order to investigate various physical and biological properties of dental magnetic attachments studies on retentive characteristics, corrosion properties, cytotoxicity of different magnetic systems for dental applications were done. For the study of retentive characteristics changes of retentive force by increasing air gap, wear properties of various attachment systems and loss of magnetic force by heat treatment were measured. Forte study of corrosion property of magnet covering metal electrochemical corrosion was done in artificial saliva and 0.9% NaCl solution between $-1,000mV_{SCE}\;and\;+1,000mV_{SCE}$. Anodic polarization curves are obtained about 6 types of samples and 2 types of solution. Corroded surfaces were examined with metallurgical microscope, scanning electron microscope and surface profilometer. For the study of cytotoxicity of magnetic attachment and its field cell growth and agar overlay test were done. The results of this study were as follows. 1. In Magnetic attachments using closed circuit retentive force at zero air gap was greater than magnets using open circuit, but decrease of retentive force by increasing air gap was also greater than open systems. 2. After 40,000 cycles of wear test all mechanical attachment resulted in varing degree of retention loss but in magnetic attachments no loss of retentive force was observed. 3. The magnetic attachment using Neodymium magnet showed early loss of retentive force about $200^{\circ}C$ but attachment using Samarium magnet showed some resistance to heat treatment and complete retention loss was observed about $500^{\circ}C$. The keeper was not influenced by heat treatment in retention. 4. In electrochemical corrosion test Dyna magnetic attachment covering metal showed the highiest corrosion resistance and Shiner magnet covering metal showed the least corrosion resistance and examination of corroded surface with metallurgical microscope, scanning electron micro-scope and surface profilometer also showed same results with anodic polarization corves. 5. The result of cell culture tests on the magnet covered with metal showed least recognizable cytotoxicity.

• Tuberculosis and Respiratory Diseases
• /
• v.76 no.3
• /
• pp.141-145
• /
• 2014

Although endobronchial hamartoma is a rare benign tumor, most patients with endobronchial hamartoma have respiratory symptoms such as obstructive pneumonia, hemoptysis, cough, or dyspnea due to bronchial obstruction. It can cause irreversible post-obstructive pulmonary destruction, thus early diagnosis and treatment is very important. Recently, there have been cases of neodymium-doped yttrium aluminum garnet (Nd:YAG) laser and electrocautery procedures for bronchoscopic treatment of malignant or benign central airway obstruction with comparable therapeutic efficacy and few complications. Bronchoscopic cryotherapy is a newly developed technique for management of central airway obstruction. Moreover, it provides diagnostic methods with improving diagnostic yield and safety. We report two cases of endobronchial hamartoma, each diagnosed and definitively treated with bronchoscopic techniques. Endobronchial biopsy and removal was successfully performed by cryotherapy via flexible bronchoscopy without notable complications. Follow-up bronchoscopic examinations excluded residual or recurrent disease.

• Journal of the Korean Magnetics Society
• /
• v.22 no.3
• /
• pp.79-84
• /
• 2012

Nano-magnetic materials such as iron-nitrides have been actively studied as an alternative to the application of high density, high performance needs for next generation information storage and also alternative to the rare earth and neodymium magnet. $Fe_4N$ is the basic materials for magnetic storage media and is one of the important magnetic materials in focus because of its higher magnetic recording density and chemical stability. Single phase ${\gamma}^{\prime}-Fe_4N$ nanoparticles have been prepared by a PAD (Plasma Arc Discharge) method and nitriding in a $NH_3-H_2$ mixed gases at temperature, $400^{\circ}C$ for 4 hrs. Also $Fe_{17}Sm_2N_x$ powders were synthesized by nitriding after reduction/diffusion of $Fe_{17}Sm_2$ to compare the magnetic properties with nano-sized $Fe_4N$ particles. The saturation magnetization of $Fe_4N$ and $Fe_{17}Sm_2N_x$ were 149 and 117 emu/g, respectively, but the coercive force was considerably smaller than that of bulk or acicular $Fe_4N$.

• Journal of the Korean Magnetics Society
• /
• v.22 no.2
• /
• pp.58-65
• /
• 2012

Since Nd-Fe-B magnet was first synthesized in 1983, many new applications have emerged in the past two decades. With regard to motor market, it will expand because of strong energy saving requirements from the automobile and electric application markets. Especially, permanent magnet motors for hybrid and electric vehicles are drawing great attention and the usage of Nd-Fe-B magnets will increase all the more hereafter. There is, however, a serious problem as motors in such eco-friendly cars are said to operate in high temperatures of about $200^{\circ}C$. Nd-Fe-B magnet has a drawback of dramatically decreasing coercive force with the rise of temperature. In order to improve this aspect. the best way is to add dysprosium (Dy) into the magnet. So, Dy has become an essential element for Nd-Fe-B high-performance magnet as it helps to maintain coercive force even at high temperatures. On the other hand, the rare earth resources in the earth crust are eccentrically-located and its majority is produced in China. There is a need to reduce its usage as, especially compared to light rare earth elements as neodymium (Nd) and samarium (Sm), heavy rare earth elements including Dy are unevenly distributed to a dramatic degree, their output low, and their prices are about 10 times that of Nd. The present article includes a summary of the trend in research and development of motors and permanent magnets to solve rare-earth resources problem.

• Journal of the Korean Magnetics Society
• /
• v.27 no.1
• /
• pp.18-22
• /
• 2017

The purpose of this study was to present an improved method of dose modulation over the increase of build-up for existing 6 MV photon beam. Two neodymium permanent magnets with a strength of 0.5 T (Tesla) were applied with a magnetic field perpendicular to the photon beam. The effects of dose on build-up region with or without the magnetic field were measured according to the magnet-to-magnet distance (MMS) and the magnet-to-surface distance (MSD). For MMS = 6 cm and MSD = 2.5 cm, $D_{0mm}$, $D_{2mm}$, $D_{5mm}$, and $D_{10mm}$ showed improved doses of 6.8 %, 14.6 %, 6.9 %, and 2.1 %, respectively, as compared with 6 MV open beam. In this study, the device with low strength magnetic field can be applied directly to the outside of the human body when the target volume located close to the skin is delivered with radiation. It is expected that the method of build-up modulation using a low strength magnetic field will be feasible in the clinical applications.

• Resources Recycling
• /
• v.14 no.6 s.68
• /
• pp.10-15
• /
• 2005

In this study, the separation of samarium to neodymium with Karr column was investigated. Separation properties of Sm/Nd binary system was estimated with experimental parameters such as flow rate, initial pH of aqueous phase, saponification of PC88A in organic phase and agitation speed. The extraction rate and distribution coefficient increased with increasing initial pH of aqueous phase at 16.5 ml/min(retention time 10 minute) of flow rate of organic and aqueous phase, and equilibrium pH of aqueous phase after extraction was maintained at 1.5 by saponified PC88A. Also, the extraction rate and distribution coefficient were drastically increased with increasing saponification degree of PC88A and agitation speed, and optimal saponification degree was $40\%$. Extraction rate of Nd and Sm was $19.6\%$ and $72.5\%$ respectively at retention time 10 minute, initial pH 1, saponification degree $40\%$ and agitation speed 120 rpm.