• Journal of the Korean Magnetics Society
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• v.13 no.2
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• pp.53-58
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• 2003

Annealing effects of exchange bias fields ($H_{2ex}$(top), $H_{lex}$ (bottom)) on composite type NiFe/[FeMn/Mn]$_{80}$/NiFe multilayers have been studied. Three samples with ultra-thin Mn inserted layers on glass/Ta(50 $\AA$)/NiFe(150 $\AA$)/[F $e_{53}$M $n_{47}$(1.25 $\AA$)/Mn(0 $\AA$, 0.11 $\AA$, 0.3 $\AA$)]$_{80}$/NiFe(90 $\AA$)/Ta(50 $\AA$) were prepared by ion beam sputtering. The average x-ray diffraction peak ratios NiFe(111) of FeMn (111) fcc textures for the Mn inserted total thicknesses of 0 $\AA$, 9 $\AA$, and 24 $\AA$ were about 0.65, 0.90, and 1.5, respectively. For the sample without Mn inserted layer, the $H_{2ex}$ of 260 Oe up to 300 $^{\circ}C$ disappeared at 350 $^{\circ}C$. For two multilayer samples with ultra-thin Mn layers of 0.11 $\AA$ and 0.3 $\AA$, the $H_{2exs}$ of 310 Oe and 180 Oe up to 300 $^{\circ}C$ endured of 215 Oe and 180 Oe at 350 $^{\circ}C$, respectively. The $H_{ex}$ (bottom)s of three samples decreased from 100 Oe to 70 Oe up to 250 $^{\circ}C$, while these values increased beyond 300 $^{\circ}C$. This observation can be attributed to less diffusive path of Mn atoms in bottom NiFe than top NiFe layer. The top and bottom coercive fields slightly varied about 5 Oe∼10 Oe. From these results, we could obtain the enhancement of exchange coupling intensity and thermal stability by an ultra-thin Mn inserted layer on NiFe/[FeMn/Mn]$_{80}$/NiFe Multilayers.

• Tuberculosis and Respiratory Diseases
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• v.39 no.1
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• pp.28-34
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• 1992

Background: Diffuse panbronchiolitis (DPB) is a chronic obstructive pulmonary disease distinguished from bronchial asthma, chronic bronchitis, pulmonary emphysema, bronchiectasis, or alveolitis. It is prevalent in Japan, but is known to be rare outside of Japan. Only a few cases in Chinese, Italian, Noirth American and Korean have been reported. During recent two years we have found 16 cases of DPB in Seoul National University Hospital and analyzed the clinical characteristics. Method: We reviewed the patients' age, sex, duration of illness, smoking history, occupational history and past medical history. And we analyzed patients' symptoms, physical signs, laboratory findings and responses to treatment. Results: 1) Male: female ratio was 2.2:1, the ages ranged from 27 to 72 years old, and the duration of disease varied from 1 to 20 years. 2) Most of the patients were being treated as bronchiectasis, miliary tuberculosis, chronic bronchitis or bronchial asthma before they were diagnosed as DPB. 3) Only one patient was a smoker, and 25% of patients had the occupational history of exposure to particles or gas. And all patients had paranasal sinusitis. 4) High resolution computed tomography (HRCT) was very useful in diagnosing the disease in most of the patients. 5) PFT showed obstructive and restrictive abnormalities, and blood gas revealed hypoxemia in most of the patients. 6) Pseudomonas aeruginosa was isolated in the sputum of four patients (25%). 7) The titers of cold hemaglutinin, RA factor and CRP were elevated in most of the patients. 8) Most of the patients improved after treatment with erythromycin. Conclusion: DPB might not be a rare disease in Korea. So DPB should be suspected in a patient who has chronic cough, sputum, dyspnea and diffuse fine nodular chest X-ray abnormality. HRCT and open lung biopsy should be considered in a patient suspected of DPB.

• Tuberculosis and Respiratory Diseases
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• v.52 no.3
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• pp.241-250
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• 2002

Background : Coal-worker's pneumoconiosis(CWP) is characterized by a chronic inflammatory lung reaction associated with macrophage accumulation in the alveolar spaces. CWP is usually divided into two stage : simple pneumoconiosis(SP) where there are a limited number of fibrotic lesions remain limited, with radiological opacities smaller than 1cm and progressive massive fibrosis(PMF), which is characterized by the development of a perifocal extensive fibrotic response of the lung and severe alterations in pulmonary function. In this study, the lymphocyte compartment and cytokine were evaluated by measuring the serum levels in the control, SP and PMF groups. Materials and Methods : The coal workers selected for this study were employees(patients?) of the Tae-Baek and Dong-Hae hospital. All were men, 45-76 years old and the mean duration of their exposure to coal dust was 23.2 years in the lymphocyte compartment and 24.3 years in the cytokine checked group. According to X-ray examination results, the patients were classified into either one of the SP, PMF categories. The normal controls examined were 26-70 years old men. The serum cytokine levels were estimated by using an end point enzyme immunoassay technique. Results : T lymphocyte, helper and suppressor T cells were highly related to pneumoconiosis in this study. A statistically significant decrease in the number of suppressor T lymphocytes was observed in the simple pneumoconiosis patients and at the same time, there was an increase in the lymphocyte index. Howevere, there was no statistically difference in the serum cytokines levels among the SP, PMF and control groups. Conclusion : T lymphocyte, helper T, and suppressor T cells may be highly related to the development of CWP compared to the control group particularly in the early stage of pneumoconiosis. The changes observed in the immunological system in patients with pneumoconiosis may lie at the bottom of the pathogenesis of fibrosis. Further study is needed to evaluate the lymphocyte compartment as a marker for pneumoconiosis development in the early stage.

• Journal of Technologic Dentistry
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• v.20 no.1
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• pp.37-49
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• 1998

The specimens used were Ag-25 Pd-15 Cu ternary alloy and Au addition alloy. These alloys were melted and casted by induction electric furnace and centrifugal casting machine in Ar atmosphere. These specimens were solution treated for 2hr at $800^{\circ}C$ and were then quenched into iced water, and aged at $350{\sim}550^{\circ}C$ Age- hardening characteristics of the small Au-containing Ag-Pd-Cu dental alloys were investigated by means of hardness testing. X-ray diffraction and electron microscope observations, electrical resistance, ergy dispersed spectra and electron probe microanalysis. Principal results are as follows : Hardening occured in two stages, i.e., stage I in low temperature and stage II in high temperature regions, during continuous aging. The case of hardening in stage I was due to the formation of the $L1_0$ type face-centered tetragonal PdCu-ordered phase in the grain interior and hardening in stage I was affected by the Cu concentration. In stage II, decomposition of the ${\alpha}$ solid solution to a PdCu ordered phase($L1_0$ type) and an Ag-rich ${\alpha}2$ phase occurred and a discontinuous precipitation occurred at the grain boundary. From the electron microscope study, it was conclued that the cause of age-hardening in this alloy is the precipitation of the PdCu ordered phase, which has AuCu I type face-centered tetragonal structure. Precipetation procedure was ${\alpha}{\to}{\alpha}+{\alpha}_2+PdCu {\to}{\alpha}_1+{\alpha}_2+PdCu$ at Pd/Cu = 1.7 Ag-Pd-Cu alloy is more effective dental alloy as ageing treatment and is suitable to isothermal ageing at $450^{\circ}C$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.13 no.3
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• pp.122-126
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• 2003

In this study, $Zn_{0.86}Mn_{0.14}$Te epilayer of 0.7 $\mu\textrm{m}$-thickness was grown on GaAs(100) substrate by using hot wallepitaxy. GaAs(100) substrate was removed from $Zn_{0.86}Mn_{0.14}$Teepilayer by the selective etching solution. The crystal structure and the lattice constant of only Z $n_{0.86}$ M $n_{0.14}$Te epilayer were investigated to be zincblende and 6.140 $\AA$ from X-ray diffraction pattern, respectively. Mn composition x of $Zn_{1-x}Mn_x$Te epilayer was found to be 0.14 using this lattice constant and Vegard's law. The crystal quality of the epilayer was confirmed to be very good due to 256 arcsec-full-width at half-maximum of the double crystal rocking curve. The absorption spectra from the transmission ones were obtained to measure the band gap energy of $Zn_{0.86}Mn_{0.14}$Te epilayer from 300 K to 10 K. With the decreasing temperature,. strong absorption regions in the absorption spectra were shifted to higher energy side and the absorption peak meaning the free exciton formation appeared near the absorption edge. The band gap energy values of $Zn_{0.86}Mn_{0.14}$Te epilayer at 0 K and 300 K were found to be almost 2.4947 eV and 2.330 eV from the temperature dependence of the free exciton peak position energy of $Zn_{0.86}Mn_{0.14}$Te epilayer, respectively. The free exciton peak position energy of $Zn_{0.86}Mn_{0.14}$Te epilayer without GaAs substrate was larger 15.4 meV than photoluminescence peak position energy at 10 K. This energy difference between two peaks was analysed to be Stokes shift.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.2
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• pp.96-113
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• 1996

It has been found that the misfit dislocations in heavily boron-doped layers originate from wafer edges. Moreover, the propagation of the misfit dislocation into a heavily boron-doped region can be suppressed by placing a surrounding undoped region. Using a surrounding undoped region the disloction-free heavily boron-deoped silicon membranes have been fabricated. The measured surface roughness, fracture strength, and residual tensile stress of the membrane are 20.angs. peak-to-peak, 1.39${\times}$10$^{10}$ and 2.7${\times}$10$^{9}$dyn/cm$^{2}$, while those of the conventional heavily boron-doped silicon membrane with high density of misfit dislocations are 500 peak-to-peak, 8.27${\times}$10$^{9}$ and 9.3${\times}$10$^{8}$dyn/cm$^{2}$ respectively. The differences between these two membranes are due to the misfit dislocations. Young's modulus has been extracted as 1.45${\times}$10$^{12}$dyn/cm$^{2}$ for both membranes. Also, the effective lattice constant of heavily boron-doped silicon, the in-plane lattice constant of the conventional membrane, and the density of misfit dislocation contained in the conventional membrane have been extracted as density of misfit dislocation contained in the conventional membrane have been extracted as density of misfit dislocation contained in the conventional membrane have been extracted as 5.424.angs. 5.426.angs. and 2.3${\times}$10$^{4}$/cm for the average boron concentration of 1.3${\times}$10$^{20}$/cm$^{-23}$ cm$^{3}$/atom. Without any buffer layers, a disloction-free lightly boron-doped epitaxial layer with good crsytalline quality has been directly grown on the dislocation-free heavily boron-doped silicon layer. X-ray diffraction analysis revealed that the epitaxial silicon has good crystallinity, similar to that grown on lightly doped silicon substrate. The leakage current of the n+/p gated diode fabricated in the epitaxial silicon has been measured to be 0.6nA/cm$^{2}$ at the reverse bias of 5V.

• Tuberculosis and Respiratory Diseases
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• v.46 no.2
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• pp.165-174
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• 1999

Background: Coal-worker's pneumoconiosis(CWP) is radiologically divided into two major groups: simple pneumoconiosis (SP), in which small, rounded or irregular opacities smaller than 1cm are observed, and progressive massive fibrosis(PMF), which is characterized by opacities larger than 1cm. SP has a life expectancy equivalent to miners with no radiographic evidence of CWP, but PMF is associated with more obvious impairments of ventilatory capacity and premature death. But only minority of workers develop PMF when exposed to dust concentrations similar to those experienced by workers who develop only SP. In this study, immune status in patients with CWP were evaluated by measurement of the serum immunoglobulin levels between control, SP and PMF groups. Method: Coal workers selected for this study were emplyees of the Tae-Baek and Dong-Hae Hospital. All the patients were men of 45-76 years old and the mean duration of exposure to coal dust were 23.2 years. By X-ray examination, 51 patients were classified in SP, 59 in PMF category. The normal controls examined were 58 men of 26-70 years old. Serum Ig levels were estimated by using Nephelometer(Behring Nephelometer : Germany) and serum were collected 51 in SP, 49 in PMF and 57 cases in control group. Results: The levels of IgG were increased but the levels of IgM were decreased with increasing age in control groups. There were no statistical difference of immunoglobulin levels between smokers and nonsmokers in control groups. There were no statistical difference of immunoglobulin levels between Control, SP and PMF groups. Multiple regression analysis were undertaken to determine the statistical significance of the apparent trends and estimate the effects associated with age, smoking habit and radiological category of CWP. According to this analysis, the levels of IgG were decreased significantly in SP group and had decreasing tendancy, but not statistically significant in PMF group. Conclusion : From the observations described, CWP patients had decreased IgG concentration compared to control gorup. Therefore, there was some relation between CWP and immunoglobulin concentration.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.2
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• pp.95-109
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• 1993

In this study, the optimal configuration of arch structure has been tested by a decomposition technique. The object of this study is to provide the method of optimizing the shapes of both two hinged and fixed arches. The problem of optimal configuration of arch structures includes the interaction formulas, the working stress, and the buckling stress constraints on the assumption that arch ribs can be approximated by a finite number of straight members. On the first level, buckling loads are calculated from the relation of the stiffness matrix and the geometric stiffness matrix by using Rayleigh-Ritz method, and the number of the structural analyses can be decreased by approximating member forces through sensitivity analysis using the design space approach. The objective function is formulated as the total weight of the structures, and the constraints are derived by including the working stress, the buckling stress, and the side limit. On the second level, the nodal point coordinates of the arch structures are used as design variables and the objective function has been taken as the weight function. By treating the nodal point coordinates as design variable, the problem of optimization can be reduced to unconstrained optimal design problem which is easy to solve. Numerical comparisons with results which are obtained from numerical tests for several arch structures with various shapes and constraints show that convergence rate is very fast regardless of constraint types and configuration of arch structures. And the optimal configuration or the arch structures obtained in this study is almost the identical one from other results. The total weight could be decreased by 17.7%-91.7% when an optimal configuration is accomplished.

• Progress in Medical Physics
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• v.9 no.1
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• pp.11-21
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• 1998

Circular metal electrodes were vacuum-deposited with chromium on the both sides of Teflon-FEP and PET film characteristic of electret and the physical properties of the two polymers were observed during an irradiation by gamma-ray from $\^$60/Co. With the onset of irradiation of output 25.0 cGy/min the induced current increased rapidly for 2 sec, reached a maximum, and subsequently decreased. A steady-state induced current was reached about in 60 second. The dielectric constant and conductivity of Teflon-FEP were changed from 2.15 to 18.0 and from l${\times}$l0$\^$-17/ to 1.57${\times}$10$\^$-13/ $\Omega$-$\^$-1/cm$\^$-1/, respectively. For PET the dielectric constant was changed from 3 to 18.3 and the conductivity from 10$\^$-17/ to 1.65${\times}$10$\^$-13/ $\Omega$-$\^$-1/cm$\^$-1/. The increase of the radiation-induced steady state current I$\^$c/, permittivity $\varepsilon$ and conductivity $\sigma$ with output(4.0 cGy/min, 8.5 cGy/min, 15.6 cGy/min, 19.3 cGy/min) was observed. A series of independent measurements were also performed to evaluate reproducibility and revealed less than 1% deviation in a day and 3% deviation in a long term. Charge and current showed the dependence on the interval between measurements, the smaller the interval was, the bigger the difference between initial reading and next reading was. At least in 20 minutes of next reading reached an initial value. It may indicate that the polymers were exhibiting an electret state for a while. These results can be explained by the internal polarization associated with the production of electron-hole pairs by secondary electrons, the change of conductivity and the equilibrium due to recombination etc. Heating to the sample made the reading value increase in a short time, it may be interpreted that the internal polarization was released due to heating and it contributed the number of charge carriers to increase when the samples was again irradiated. The linearity and reproducibility of the samples with the applied voltage and absorbed dose and a large amount of charge measured per unit volume compared with the other chambers give the feasibility of a radiation detector and make it possible to reduce the volume of a detector.

• Journal of radiological science and technology
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• v.31 no.3
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• pp.223-228
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• 2008

The most critical point in the medical use of radiation is to minimize the patient's entrance dose while maintaining the diagnostic function. Low-energy photons (long wave X-ray) among diagnostic X-rays are unnecessary because they are mostly absorbed and contribute the increase of patient's entrance dose. The most effective method to eliminate the low-energy photons is to use the filtering plate. The experiments were performed by observing the image quality. The skin entrance dose was 0.3 mmCu (copper) filter. A total of 80 images were prepared as two sets of 40 cuts. In the first set (of 40 cuts), 20 cuts were prepared for the non-filter set and another 20 cuts for the Cu filter of signal + noise image set. In the second set of 40 cuts, 20 cuts were prepared for the non-filter set and another 20 cuts for the Cu filter of non-signal image (noisy image) with random location of diameter 4 mm and 3 mm thickness of acryl disc for ROC signal at the chest phantom. P(S/s) and P(S/n) were calculated and the ROC curve was described in terms of sensitivity and specificity. Accuracy were evaluated after reading by five radiologists. The number of optically observable lesions was counted through ANSI chest phantom and contrast-detail phantom by recommendation of AAPM when non-filter or Cu filter was used, and the skin entrance dose was also measured for both conditions. As the result of the study, when the Cu filter was applied, favorable outcomes were observed on, the ROC Curve was located on the upper left area, sensitivity, accuracy and the number of CD phantom lesions were reasonable. Furthermore, if skin entrance dose was reduced, the use of additional filtration may be required to be considered in many other cases.