• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.4
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• pp.322-327
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• 2003

Giant magnetoresistance(GMR) NiO multilayer, which has been used to reading head of highly dense magnetic recording, was fabricated, and oxidized in an air during 80 days to study the dependence of magnetoresistance properties on residual stress in the interfaces. The magnetoresistance ratio and the exchange biasing $field(H_{ex})$ of $NiO(60nm)/Ni_{81}Fe_{19}(5nm)/Co(0.7nm)/Cu(2nm)/Co(0.7nm)/Ni_{81}Fe_{19}(7nm)$ spin valves were increased from 4.9% to 7.3%, and 110 Oe to 170 Oe after natural oxidation in the atmosphere for 80 days, respectively. The sheet resistivity ${\rho}$ decreased from $28{\mu}{\Omega}m$ to $17{\mu}{\Omega}m$, but ${\Delta}p$ did not almost change after the oxidation. Therefore, the increase of MR ratio is due to the decrease in the sheet resistivity. the reduced resistance may result from the increase in the reflection of conduction electrons at the oxidized top surface. Also, the increase in the exchange biasing field is originated from the reduction of residual stress at the interface of $NiO/Ni_{81}Fe_{19}$ according as the aging time increases.

• Journal of Biomedical Engineering Research
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• v.22 no.5
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• pp.449-458
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• 2001

This is a test report of system efficiency for the moving-actuator type Bi-ventricular assist device (AnyHear $t^{MT}$ ) Seoul National University). $AnyHeart^{TM}$), as an energy converter. utilities a brushless DC motor(S/M 566-26A. Sierracin/ Magnedyne, Carlsbad, CA. U.S.A.) generating their pendulous motion in the epicyclic gear train. It is necessary to know about the overall efficiency of the system. The system is subdivided into three parts: motor part, actuator part and blood sac part (including valves, etc.) according to system mechanism. The motor was operated with a variable range of torque. angular speed and width of voltage Pulse In this report. $AnyHeart^{TM}$ is focused on the efficiency of the motor and actuator parts. 4 $\ell/min$ pump output. which is normal condition of $AnyHeart^{TM}$ system, the total system efficiency is 8%, which is composed of 50%, 85% and 17% efficiency (motor Part, actuator Part and blood sac Part) respectively. In the analyzed result. applied input voltage on normal condition of $AnyHeart^{TM}$ is determined. Also speed Profile with considering filling state of blood sac is Provided. In the test of the in vitro mock circulation. some experimental results are Provided to demonstrate the effectiveness of the Presented approach.

• Journal of Biomedical Engineering Research
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• v.22 no.5
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• pp.439-448
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• 2001

This paper considers the acoustical characteristics of the closing click sounds of the mechanical valves employed in an implantable biventricular assist device (BYAD) and their re1evance to the Physical states of the valved. Bj rk Shiley Convexo Concave tilting disk valve was chosen for the study and acoustic measurement was made for the BYAD operated in a mock circulatory system as well as implanted in an animal (sheep). In the BYAD operated in the mock circulatory system. three different states of the valve were examined, ie. normal. mechanically damaged. pseudo-thrombus attached. Microphone measurement for the BVAD implanted in the animal was carried out for five days at a regular time interval from one day after implantation. Characteristic spectrum of the sound from the valve was estimated using Multiple Signal Classification (MUSIC) in which the optimal order was determined according to Bayesian Information Criterion (BIC) . It was observed that the mechanical damage of the valve resulted in changes of the structure of the acoustic spectrum. In contrast. the thrombus formed on the valve did not change much the basic structure of the spectrum but brought about altering the spectral Peak frequencies and energies. Maximum spectral Peak (MSP) with the greatest energy was seen at 2 kHz for the normal valve and it was shifted to 3 kHz for the calve attaching the Pseudo-thrombus. Unlike the normal valve, strong spectral Peak appeared around 7 kHz in the sound from the valve mechanically damaged. In the case of the BYAD implanted in the animal. as the thrombus grew, acoustic energy was reduced relatively more in the low frequency components (〈 2 kHz) and the frequencies of the 1st, 2nd and 3rd MSP were increased little. The thrombus formation would result in reduction in both the variability of the 1st, 2nd and 3rd MSP and the value of the BIC optimal order.

• Journal of Korea Association of Health Promotion
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• v.2 no.1
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• pp.1-8
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• 2004

Background : Since 2001 the Korean Association of Health Promotion has attempted to establish her own reference valves that can be used in her all fifteen branch laboratories instead of using those adapted from the published data or there commended data by the reagent companies supplied as inserts. However, the previous two reference values derived from the statistics(year 2001 and 2002) were need to adjust to apply to actual practice. Besides there was an unavoidable situation that the reagent has to be changed to other companies in 2002 that creates another statistical problem. Subsequently, the third attempt to derive the reference ranges of tests in KAHP to solve those problems and define common)v acceptable reference ranges was done and and reported here. Methods : Al1 the results performed during January 2, 2003 through September 30, 2003 were collected in Excel tile format. All the data include dthe necessary information such as age and sex. The age was grouped in six; baby(0-3y), children(4-l2y), adolescent(13-l8y), adult(19-S4y), younger elderly (65-79y),old elderly(oyer 80y), with references of statistics in medical informatics and WHO classification. The data were statistically analyzed with SAS 6.04 for-Gaussian distribution as the previous two occasions. None of the tests showed Gaussian distribution. These procedures had been repeated twice or three times after trimming out the results lying outside three standard deviations. Though, all the tests showed non-Gaussian distribution. Subsequently, the reference ranges were defined in the range from the point of lower 2.5% to the point of higher 97.5 %. And in case the lower range could be "0", the reference ranges were defined in the range of 0 to 95%.Results : The reference ranges of most of 56 test items were newly assigned. Also with adaptation of the recommendation of WHO etc. on fasting blood sugar, hemoglobin, cholesterol. Among these there were eight tests that needed reference ranges by the age groups and nine tests by the sex. Conclusions : The third attempt will credit more the reference range of all15 laboratories of Korean Association of Health Promotion, which will be essential part of the better service to the patient and clients to visit KAHP.

• Analytical Science and Technology
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• v.7 no.1
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• pp.33-39
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• 1994

The purpose on this study was to develop a new improved chromatographic method for determination of trace phenols from environmental waste water. The research was carried out with selected 8 phenols, and solid-phase extraction was employed as sample pretreatment method. The coupling of XAD-4 and Dowex $1{\times}8$ resin as preconcentration column increased the selectivities toward interferences coexisted in matrix. Automation was accomplished with on-line process of pretreatment and HPLC system. After elution of sample through XAD-4 column, phenols were adsorbed by dispersion force, then displaced from it by ACN basified, simultaneously and selectively readsorbed via anion exchange on Dowex $1{\times}8$. Dowex $1{\times}8$ column was washed by water. Phenols readsorbed were removed from Dowex $1{\times}8$ column by a minimum volumn of methanol containing HCl. Each pretreatment step was connected by switching valves and the eluate was directly on-line injected to obtain fast and reliable results into the HPLC. Recovery of phenols was greater than 90%. To examine utility of this method, analysis of phenols from laboratory waste water sample which was added some organic pollutants to find with phenols on environmental waste water were also accomplished without their interference effects.

• Korean Journal of Food Science and Technology
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• v.37 no.3
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• pp.397-404
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• 2005

Effects of ${\gamma}$-oryzanol (0.0, 0.1, 0.5, 1.0, 2.0%) addition on physical and chemical properties of yackwa were determined during storage for 6 weeks at $30^{\circ}C$. Acid, peroxide, and thiobarbituric acid (TBA) valves, color, texture, fatty acid compositions, hexanal content, and rancid flavor of yackwa were measured. Acid, peroxide, and TBA values. and hexanal contents of ${\gamma}$-oryzanol-treated groups were significantly lower than those of groups without ${\gamma}$-oryzanol treatment after 6 week (p < 0,05) and showed concentration-dependency, while no significant differences were observed in colors (p > 0.05). Effects of ${\gamma}$-oryzanol on textural characteristics were not consistent. As storage time increased, ratio of unsaturated fatty acids to saturated fatty acids or ${\gamma}$-oryzanol-added groups was higher than that of groups without ${\gamma}$-oryzanol addition. Addition of ${\gamma}$-oryzanol was effective in decreasing hexanal formation. Sensory evaluation showed rancid odor decreased with increasing concentration of ${\gamma}$-oryzanol. These results suggested ${\gamma}$y-oryzanol, as a natural antioxidant, delayed quality decrease of yackwa during storage.

• Journal of Korean Society for Quality Management
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• v.46 no.2
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• pp.301-310
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• 2018

Purpose: The purpose of this study is to investigate the effect of work intensity on fit factor and affective quality of the dustproof Background: Among the victims who suffer pneumoconiosis due to the inhalation of toxic substances or the lack of oxygen during the work, the proportion of the victims is larger than the other causes. Wearing a respirator may prevent pneumoconiosis, but it can be hazardous to workers because of the leakage through filters, cartridges, exhaust valves, broken parts, and face-to-face contact. Despite leakage through the contact area between the mask and the face has various causes such as the wearer's activity, sweat accumulation, facial shape, etc., There is a lack of relevant research and regulation compared to developed countries that have already institutionalized the law 30 years ago and give the right to sell through a test Method: The work intensity was adjusted by walking or running at 6km/h and 11km/h on the treadmill, and tasks were defined with reference to the test procedure and the exercise sequence applied in the face leakage test of the dustproof mask. And fit factor was measured objectively using 'Respirator Fit Tester 8038' which measures fit factor calculated by dividing the number of dust present outside the mask by inside the mask. In addition, affective quality was classified by the ease of use, ease of breathing, and ease of wearing, and was measured using the 5-point likert scale questionnaire. Results: There was a significant difference in fit factor, ease of breathing, and wearing convenience according to work intensity and no significant difference in ease of use(${\alpha}=0.01$). And when the work intensity was high, fit factor, ease of breathing, and wearing convenience were all lower than when the work intensity was low. Conclusion: In Korea, it is necessary to consider consideration of the work intensity when testing the leakage rate of the face part for safety certification of the respiratory protective equipment, When developing a mask, it should be possible to maintain high adhesion even under intense, active situation and high temperature conditions by selecting materials, improving the wearing style, and expanding the adjustable range.

• Journal of Chest Surgery
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• v.31 no.6
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• pp.586-590
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• 1998

Background: The regression of the left ventricular hypertrophy after prosthetic valve replacement in patients with aortic valvular stenosis is an important factor to determine the appropriateness of the replaced prosthetic valvular size. Methods: To assess the regression of myocardial hypertrophy, a retrospective analysis of Doppler echocardiographic and electrocardiographic data was undertaken before, soon after(7.5$\pm$2.1 day), and late after(10.7$\pm$1.8 months) surgery in 36 patients(22 males, 14 female, mean age 54$\pm$12.1 years, mean BSA 1.61$\pm$0.15m2) with predominant aortic valvular stenosis. The patients underwent St. Jude Medical aortic valve replacement. By the size of the valves used, the patients were divided into three groups(19, 21 and 23+). Results: The mean body surface area(1.48$\pm$0.13) in the patients with the 19 mm valve was smaller than that in the other groups(1.63$\pm$0.12)(p<0.05). No significant changes of ejection fraction were detected in all groups over time. Left ventricular muscle mass index(gm/m2) was reduced significantly in the 21 and 23+ groups over time(p<0.05), but there were no significant changes in the 19 mm valve group. The electric voltage height on EKG at the period of late after surgery was reduced significantly in all groups(p<0.05). Conclusion: Despite clinical improvement, the LVH was not reduced significantly in 19 mm valve group. Thus we suggest that more attention and additional procedures such as annular enlargement should be taken in patients who will undergo the replacement of 19 mm prosthetic valve.

• Journal of Chest Surgery
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• v.31 no.6
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• pp.591-597
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• 1998

Background: The aim of the current study was to analyze the early and intermediate-term performance of aortic valve replacement. Material and Method: Between January 1986 and January 1996, records of 61 consecutive patients who had received aortic valve replacement were reviewed. 38 were male and 23 were female patients, ranging from 10 to 71 years of age(mean: 40.5${\pm}$11.2). Results: The early death rate was 4.9%(3/61). A thorough follow-up rate of 93.1% was accomplished in these 58 patients who left the hospital(mean: 51.5${\pm}$32.0 patient-months) under the assistance of the same operator. Three of these patients who left the hospital died. The late death rate was 5.2%(3/58). Five patients experienced anticoagulant-related hemorrhage(all were minor). Three patients had thromboembolic episodes. There was no clinical evidence of hemolysis and structural failure of valves used. Of those patients who survived, the NYHA functional class improved significantly. Linearized rate were 1.58%/patient-year and 2.0%/patient-year respectively for thromboembolism and anticoagulant-related hemorrhage. The 10 year actuarial survival rate was 83.6%. Conclusion: This early and intermediate-term follow-up suggests that the mechanical valve is a reliable and durable prosthesis with good hemodynamic function and low rate of prosthesis-related complication.

• Journal of the Korean Vacuum Society
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• v.5 no.4
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• pp.269-277
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• 1996

The vacuum systems of PLS linac provides average pressure of $2.6\times 10^{-6}$Pa under high power microwave of 54 MW peak with 4.1 $\mu \textrm s$ pulse width and 10 Hz repetition rates. The base pressure of system is$2.4\times 10^{-6}$Pa with 45$^{\circ}C$ cooling water. The outgassing rate of the system is decreased from $3.0\times 10^{-11}Torr-l/sec-\textrm{cm}^2$ at the initial stage after installation to $1\times 10^{-12}Torr-l/sec-\textrm{cm}^2$ at present. Total accumulated microwave energy dose is about 140 GJ per module. All ion pumps are working under saturated regime and effective pumping speeds of 60 I/s, 230 I/s ion pumps are 45 I/s, 65 I/s, 140 I/s under the operating range. Main problems occurred in recent year are troubles of ion pump controller and vacuum gauge controller, vacuum leak of energy doubler window and electron gun ceramic, and water leak in the dummy load of acceleraing columns. Total of 41 troubles with 140. 8 hours down time give good system availability of 98%. Down time can be reduced by high power waveguide valves and water dummy loads under development, and then availability is expected to be increased up to 99.5%.