• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.7 no.2
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• pp.196-206
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• 1995

Experimental investigations on heat and mass transfer characteristics in a vertical tube absorber have been carried out. Three different copper tubes with a length of 1.5m have been tested using LiBr solution and LiBr-$CaCl_2$ solution. The effects of solution flow rate, cooling water temperature, solution inlet temperature and evaporation temperature have been investigated in detail. It is found that heat transfer coefficient increases gradually with the increase of solution flow rate, but decreases rapidly for the flow rates less than 0.02kg/ms. The grooved tube generally shows better heat transfer performances than the smooth tube. LiBr solution shows almost no absorption capability for the cooling water temperatures over $40^{\circ}C$. LiBr-$CaCl_2$ gives less decreasing rate in absorption capability at these temperatures and the heat transfer coefficient becomes less dependent on the types of tubes in use. Considering heat and mass transfer rates, LiBr-$CaCl_2$ solution is found to be more suitable than LiBr solution for air cooled absorber, which operates at higher temperature than water cooled absorber.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.15 no.1
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• pp.13-20
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• 1985

The author obtained the oblique lateral trans cranial radiograms from 376 patients (114 of male, and 262 of female) with temporomandibular joint arthrosis. After tracing each film, the author analyzed the dimensional changes of the condylar heads with pain, clicking, mouth opening limitation, and masticatory difficulty respectively, which were the chief complaints of the TMJ arthrosis and compared these data with control group. The results were as follows; 1. There was a great predilection for occurrence of the TMJ arthrosis in female (262 cases) over male (114 cases). But there was no significant difference in ratio between the sexes on each symptom. In male, 60 patients (52.6%) had pain, 28 patients (24.6%) had clicking, 21 patients (18.4%) had mouth opening limitation, and 5 patients (4.4%) had masticatory difficulty. In female, 148 parients (56.5%) had pain, 57 patients (21.8%) had clicking, 47 patients (17.9%) had mouth opening limitation, and 10 patients (3.8%) had masticatory difficulty. 2. Examined controlled group, the author analyzed the dimension of W-W', 0-H, 0-A, 0-B on the right side first, and left side second. In male, the dimension of W-W' was 14.52㎜, 14.13㎜; 0-H was 13.92㎜, 13. 71㎜' 0-A was 8.91㎜, 9.0㎜ and 0-B was 8.67㎜, 8.78㎜. In female, W-W' was 13.77㎜, 13.51㎜; 0-H was 13.42㎜, 13.35㎜; 0-A was 8.92㎜, 9.01㎜; and 0-B was 8.59㎜, 8.80㎜. 3. W-W' and 0-H of the experimental group were distinctly lesser than the controlled group. Male with mouth opening limitation show the least (12.70㎜, 13.00㎜) on W-W', but both sexes with pain show the least on 0-H. There was no significant difference between experimental group with Clicking and controlled group on 0-H, 0-A, and 0-B. And also there was no difference on 0-B in patients with every symptom except masticatory difficulty. The dimensional changes of the condylar heads with those symptoms were as follows; a) In male patients, complaing of pain, W-W' of the right and left was 13.80㎜, 12.80㎜; 0-H was 13.10㎜, 12.90㎜; 0-A was 8.69㎜, 8.18㎜; 0-B was 8.33㎜, 8.42㎜. In female, W-W' was 13.01㎜, 12.90㎜; 0-H was 12.48㎜, 12.80㎜; 0-A was 8.60㎜, 8.49㎜; 0-B was 8.48㎜, 8.50㎜. b) In male patients with clicking, W-W' was 13.70㎜, 13.10㎜; 0-H was 13.90㎜, 13.10㎜; 0-A was 8.81㎜, 8.16㎜ 0-B was 8.34㎜, 8.25㎜. In female, W-W' was 13.10㎜, 13.50㎜; 0-H was 13.30㎜, 12.91㎜; 0-A was 8.95㎜, 8.49㎜; 0-B was 8.23㎜, 8.70㎜. c) In male patients with mouth opening limitation, W-W' was 12.70㎜, 13.00㎜; 0-H was 13.40㎜, 13.40㎜; 0-A was 8.37㎜, 8.48㎜; 0-B was 8.33㎜, 8.62㎜. In female, W-W' was 13.00㎜, 12.50㎜ 0-H was 12.90㎜, 13.10㎜; 0-A was 8.49㎜, 8.09㎜; 0-B was 8.77㎜, 8.01㎜. d) In male patients with masticatory difficulty, W-W' was 13.30㎜, 13.20㎜; 0-H was 13.40㎜, 12.60㎜; 0-A was 8.26㎜, 8.32㎜; 0-B was 7.80㎜, 8.20㎜. In female, W-W' was 12.30㎜, 12.00㎜; 0-H was 13.10㎜, 13.20㎜; 0-A was 8.68㎜, 7.95㎜; 0-B was 7.46㎜, 7.87㎜.

• Journal of Sensor Science and Technology
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• v.18 no.4
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• pp.263-268
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• 2009

With the increasing number of automobiles, the problem of air pollution from the exhaust gases of automobiles has become a critical issue. The principal gases that cause air pollution are nitrogen oxide or NO$_x$(NO and NO$_2$), and CO. Because NO$_x$ gases cause acid rain and global warming and produce ozone(O$_3$) that leads to serious metropolitan smog from photochemical reaction, they must be detected and reduced. Mixtures of WO$_3$ and $In_2O_3$(WO$_3$:$In_2O_3$=10:0, 7:3, 5:5, 3:7, and 0:10 in wt.%), which are NO$_x$ gas-sensing materials, were prepared, and thick-film gas sensors that included a heater and a temperature sensor were fabricated. Their sensitivity to NO$_x$ was measured at 250$\sim$400$^{\circ}C$ for NO$_x$ concentrations of 1$\sim$5 ppm. The $In_2O_3$ thick-film sensor showed excellent sensitivity($R_{gas}/R_{air}$=10.22) at 300$^{\circ}C$ to 5-ppm NO. The response time for 70 % saturated sensitivity was about 3 seconds, and the sensors exhibited very fast reactivity to NO$_x$.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.371-372
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• 2012

We have studied lead-based gapless semiconductors, $PbPdO_2$, which is very sensitive to external parameters such as temperature, pressure, electric field, etc[1]. We have fabricated pure $PbPdO_2$, Co- and Mn-doped $PbPdO_2$ thin films using the pulsed laser deposition. Because of the volatile element of Pb, it is very difficult to grow the films. Note that in case of $MgB_2$, Mg is also volatile element. So in order to enhance the quality of $MgB_2$, some experiments are carried out in annealing with Mg-rich atmosphere [2]. This annealing process with volatile element plays an important role in making smooth surface. Thus, we applied such process to our studies of $PbPdO_2$ thin films. As a result, we found the optimal condition of ex-situ annealing temperature ${\sim}650^{\circ}C$ and time ~12 hrs. The ex-situ annealing brought the extreme change of surface morphology of thin films. After ex-situ annealing with PbO-rich atmosphere, the grain size of thin film was almost 100 times enlarged for all the thin films and also the PbO impurity phase was smeared out. And from X-ray diffraction measurements, we determined highly crystallized phases after annealing. So, we measured electrical and magnetic properties. Because of reduced grain boundary, the resistivity of ex-situ annealed samples changed smaller than no ex-situ sample. And the carrier densities of thin films were decreased with ex-situ annealing time. In this case, oxygen vacancies were removed by ex-situ annealing. Furthermore, we will discuss the transport and magnetic properties in pure $PbPdO_2$, Co- and Mn-doped $PbPdO_2$ thin films in detail.

• Transactions of the Society of Information Storage Systems
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• v.2 no.3
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• pp.178-183
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• 2006

A Blu-ray disc, which has a more than 25GB optical capacity, has been known as a promising next-generation optical disc format. It commonly has a 1.1 mm thick substrate and a 0.1 mm thick cover layer for beam transmitting and the protection of the reflecting surface. The cover layer is generally formed by the spin coating process. However, in conventional spin coating, small bumps are formed along the rim of the disc, which results in the fatal reading error. Numerical simulation of the thin film flow behaviors during spin coating with the commercial solver and optimal spinning conditions was obtained. Thickness distribution of the cover layer according to the variation of substrate's edge shape could be calculated as well. By modifying the shape of the substrate edge shape, the bumps along the disc rim could be minimized, and it was proved that the chamfered edge, around $5{\sim}10$ degree, is the simplest and most effective way to minimize the bumps.

• Journal of the Korean Magnetics Society
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• v.17 no.2
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• pp.81-85
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• 2007

MnTe layers of high crystalline quality were successfully grown on Si(100) : B and Si(111) substrates by molecular beam epitaxy (MBE). Under tellurium-rich condition and the substrate temperature around $400^{\circ}C$, a layer thickness of $700{\AA}$ could be easily obtained with the growth rate of $1.1 {\AA}/s$. We investigated the structural, magnetic and transport properties of MnTe layers by using x-ray diffraction (XRD), superconducting quantum interference device (SQUID) magnetometry, and physical properties measurement system (PPMS). Characterization of MnTe layers on Si(100) : B and Si(111) substrates by XRD revealed a hexagonal structure of polycrystals with lattice parameters, ${\alpha}=4.143{\pm}0.001{\AA}\;and\;c=6.707{\pm}0.001{\AA}$. Investigation of magnetic and transport properties of MnTe films showed anomalies unlike antiferromagnetic powder MnTe. The temperature dependence of the magnetization data taken in zero-field-tooling (ZFC) and field-cooling (FC) conditions indicates three magnetic transitions at around 21, 49, and 210 K as well as the great irreversibility between ZFC and FC magnetization in the films. These anomalies are attributable to a magnetic-elastic coupling in the films. Magnetization measurements indicate ferromagnetic behaviour with hysteresis loops at 5 and 300 K for MnTe polycrystalline film. The coercivity ($H_c$) values at 5 and 300 K are 55 and 44 Oe, respectively. In electro-transport measurements, the temperature dependence of resistivity revealed a noticeable semiconducting behaviours and showed conduction via Mott variable range hopping at low temperatures.

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1540-1542
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• 1997

Plasma polymerized thin films were fabricated by interelectrode capacitively coupled type apparatus. FT-IR analyses indicated that the thin film spectra are composed not only of the corresponding monomer bands but also of several new bands. Relative dielectric constant and dielectric loss tangent of thin films fabricated in the discharge power of 90[W] showed $3.212{\sim}3.805$ and $0.0026{\sim}0.0451$ in alternating frequency of $10^3{\sim}10^6$[Hz]. Contact angle measurement indicated that cross-link of the films is increased with the discharge power.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.193-193
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• 2012

In thin film silicon solar cells, p-i-n structure is adopted instead of p/n junction structure as in wafer-based Si solar cells. PECVD is the most widely used thin film deposition process for a-Si:H or ${\mu}c$-Si:H solar cells. Single-chamber PECVD system for a-Si:H solar cell manufacturing has the advantage of lower initial investment and maintenance cost for the equipment. However, in single-chamber PECVD system, doped and intrinsic layers are deposited in one plasma chamber, which inevitably impedes sharp dopant profiles at the interfaces due to the contamination from previous deposition process. The cross-contamination between layers is a serious drawback of single-chamber PECVD system. In this study, a new plasma process to solve the cross-contamination problem in a single-chamber PECVD system was suggested. In order to remove the deposited B inside of the plasma chamber during p-layer deposition, a high RF power was applied right after p-layer deposition with SiH4 gas off, which is then followed by i-layer, n-layer, and Ag top-electrode deposition without vacuum break. In addition to the p-i interface control, various interface control techniques such as FTO-glass pre-annealing in O2 environment to further reduce sheet resistance of FTO-glass, thin layer of TiO2 deposition to prevent H2 plasma reduction of FTO layer, and hydrogen plasma treatment prior to n-layer deposition, etc. were developed. The best initial solar cell efficiency using single-chamber PECVD system of 10.5% for test cell area of 0.2 $cm^2$ could be achieved by adopting various interface control methods.

• Journal of the Korean Society for Heat Treatment
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• v.22 no.5
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• pp.290-297
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• 2009

In case of using Asymmetric Bipolar Pulsed DC (ABPD) power generator, thin film is efficiently deposited as ions are getting higher energy by suppressing target poisoning and electric arc. In this article, the mechanical properties of CNx thin films deposited on the STS 316L were compared with DC and ABPD power generators. The CNx thin films deposited with ABPD clearly improved wear resistance by higher ratio of sp3CN as compared with DC. Nb interlayer affected to increase the value of 10N of adhesion between CNx thin films and substrate. But, CNx thin films deposited with ABPD couldn't endure to wear load and decreased wear resistance as the films were too thinner than substrate. Nevertheless the higher substrate bias energy applied to perform the dense films, it wasn't shown benefits about the wear properties from DC sputtering. But, in case of using ABPD sputtering, the wear resistance was largely improved without changing morphology despite of thin films.

• Journal of Information Display
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• v.6 no.3
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• pp.12-17
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• 2005

The need for low cost, flexible, thin film transistor (TFT) display backplanes has focused attention on new processing techniques and materials. We report the development of TFT backplane technology based entirely on jet-printing, using a combination of additive and subtractive processing, to print active materials or etch masks. The technique eliminates the use of photolithography and has the potential to reduce the array manufacturing cost. The printing technique is demonstrated with both amorphous silicon and polymer semiconductor TFT arrays, and we show results of small prototype displays.