• The Journal of Advanced Prosthodontics
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• v.13 no.6
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• pp.385-395
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• 2021

PURPOSE. To characterize the microstructure of three yttria partially stabilized zirconia ceramics and to compare their hardness, indentation fracture resistance (IFR), biaxial flexural strength (BFS), and fatigue flexural strength. MATERIALS AND METHODS. Disc-shaped specimens were obtained from 3Y-TZP (Vita YZ HT), 4Y-PSZ (Vita YZ ST) and 5Y-PSZ (Vita YZ XT), following the ISO 6872/2015 guidelines for BFS testing (final dimensions of 12 mm in diameter, 0.7 and 1.2 ± 0.1 mm in thicknesses). Energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were performed, and mechanical properties were assessed by Vickers hardness, IFR, quasi-static BFS and fatigue tests. RESULTS. All ceramics showed similar chemical compositions, but mainly differed in the amount of yttria, which was higher as the amount of cubic phase in the diffractogram (5Y-PSZ > 4Y-PSZ > 3Y-TZP). The 4Y- and 5Y-PSZ specimens showed surface defects under SEM, while 3Y-TZP exhibited greater grain uniformity on the surface. 5Y-PSZ and 3Y-TZP presented the highest hardness values, while 3Y-TZP was higher than 4Y- and 5Y-PSZ with regard to the IFR. The 5Y-PSZ specimen (0.7 and 1.2 mm) showed the worst mechanical performance (fatigue BFS and cycles until failure), while 3Y-TZP and 4Y-PSZ presented statistically similar values, higher than 5Y-PSZ for both thicknesses (0.7 and 1.2 mm). Moreover, 3Y-TZP showed the highest (1.2 mm group) and the lowest (0.7 mm group) degradation percentage, and 5Y-PSZ had higher strength degradation than 4Y-PSZ group. CONCLUSION. Despite the microstructural differences, 4Y-PSZ and 3Y-TZP had similar fatigue behavior regardless of thickness. 5Y-PSZ had the lowest mechanical performance.

• Journal of Aerospace System Engineering
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• v.16 no.4
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• pp.60-67
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• 2022

An Electro-Optical Tracking System (EOTS) is an electric optical system with EO/IR cameras, laser sensors, and an IMU. The EOTS calculates coordinates of targets, using attitude and acceleration measured by the IMU. In particular for an armed aircraft, the performance of the weapon system depends on how quickly and accurately it acquires the target coordinates. The IMU should be operated after alignment is complete, to meet the coordinate accuracy required by the weapon system so the initial stabilization time of the IMU should be reduced, by quickly measuring the attitude and acceleration. Alignment is the process of determining the initial attitude by resolving the attitude error of the IMU, and the IMU of mission equipment such as an airborne EOTS, uses velocity matching based on the velocity from GPS/INS for aircraft navigation. In this paper, a method is presented to improve the transfer alignment performance of the airborne EOTS, by maneuvering aircraft and the mission equipment. First, the performance factor of the alignment was identified, as a heading error through the velocity matching model and simulation results. Then acceleration maneuvers and attitude changes were necessary, to correct the error. As a result of flight tests applied to an EOTS on a OOO aircraft system, the transfer alignment performance was improved as the duration time was decreased, by more than five times when the aircraft accelerated by more than 0.2g and the EOTS was moving until 6.7deg/s.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.1
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• pp.12-23
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• 2024

In this study, a structural concrete square beam was developed using the centrifugal molding technique. In order to secure the bending stiffness of the cross section, the hollow rate of the cross section was set to 10% or less. Instead of using the current poor mixture of concrete and a concrete mixing ratio with a high slump (150-200) and a design strength of 100 MPa or more was developed and applied. In order to investigate the durability of centrifugally formed PSC square beams to be used as the superstructure of the avalanch tunnel or ramen bridge, the durability performance of ultra-high-strength centrifugally formed concrete with a compressive strength of 100 MPa was evaluated in terms of deterioration and chemical resistance properties.Concrete durability tests, including chloride penetration resistance, accelerated carbonation, sulfate erosion resistance, freeze-thaw resistance, and scaling resistance, were performed on centrifugally formed square beam test specimens produced in 2022 and 2023. Considering the information verified in this study, the durability of centrifugally molded concrete, which has increased watertightness in the later manufacturing stage, was found to be superior to that of general concrete.

• Tuberculosis and Respiratory Diseases
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• v.67 no.6
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• pp.506-511
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• 2009

Background: The smoking prevalence in asthma patients are similar to those in the general population. Asthma and active cigarette smoking can interact to create more severe symptoms, an accelerated decline in lung function and impaired therapeutic responses. Accordingly, asthmatics with a history of smoking were examined to define the clinical characteristics and lung function of smoking asthmatics. Methods: The medical records of 142 asthmatics with a known smoking history were reviewed. The patients were divided into three groups according to their smoking history - current smokers, former smokers and non-smokers. The clinical characteristics, lung function, and annual declines of the forced expiratory volume in one second ($FEV_1$) were compared. Results: Fifty-three of the 142 patients (37%) were current smokers, 24 were former smokers (17%) and 65 were non-smokers (45%). The patients with a hospital admission history during the previous year included 16 current smokers (30%), 4 former smokers (17%) and 7 non-smokers (11%) (p=0.02). The mean $FEV_1$ (% predicted) was 76.8${\pm}$19.8%, 71.6${\pm}$21.1% and 87.9${\pm}$18.7% for current smokers, former smokers and non-smokers, respectively (p< 0.001). The $FEV_1$/forced vital capacity (FVC) (ratio, %) values were 63.6${\pm}$12.6%, 59.3${\pm}$14.9% and 72.1${\pm}$11.8% in current smokers, former smokers and non-smokers, respectively (p<0.001). The corresponding mean values for the individual $FEV_1$ slopes were not significant (p=0.33). Conclusion: Asthmatic smokers demonstrated higher hospital admission rates and lower lung function. These findings suggest that the smoking history is an important predictor of a poor clinical outcome in asthma patients.

• Korean Journal of Weed Science
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• v.4 no.1
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• pp.52-61
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• 1984

Pot and laboratory tests were undertaken to investigate the influence of silicate fertilization on butachlor phytotoxicity to rice. Growth of rice seedlings at 150 ppm of $SiO_2$ was stimulated, while adverse effect was observed over 300 ppm of $SiO_2$ and growth reduction was enhanced with combination of butachlor and $SiO_2$ Rice growth in pot trial at 150kg/10a of silicate fertilization was not influenced by recommended amounts of butachlor and nitrofen, however, the growth of Seokwang byeo at 300kg/10a of silicate was markedly retarded by butachlor in the initial stage of growth. Growth reduction of Seokwang byeo caused by combined application of silicate and butachlor was recovered 50 days after herbicide application. Growth reduction from butachlor was not influenced by pH level and also degradation behaviors of butachlor in submerged soil was not altered by silicate fertilization. Adsorbed amount of butachlor on rice root was increased with addition of $SiO_2$ and its amount in Seokwang byeo was higher than that of Jinju byeo. Butachlor absorption by Seokwang byeo was accelerated by 150 ppm of $SiO_2$ applied simultaneously, but those effect was not encountered in Jinju byeo. Butachlor absorption of rice seedlings was also increased by 150 ppm of $K_2O$, while CaO hindered the absorption and $Na_2O$ had no effect on the absorption. Residual level of butachlor in Seokwang byeo treated with combined solution of butachlor and $SiO_2$ was continued higher than that with butachlor alone during 10 days after transplantation to culture solution.

• Korean journal of applied entomology
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• v.23 no.4 s.61
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• pp.221-232
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• 1984

A series of experiments were carried out in the laboratory and fields to reevaluate the effects of Padan (cartap) to the brown planthopper (BPH). Nilapanata lugens. The $LD_{50}\;land\;LC_{50}$ values for the female and male BPH were determined by the topical application and seedling- dipping/root -soaking methods. The values were differed with the sex and test methods, and the BPH mortality was greatly increased with a rise in temperatures $(25-35^{\circ}C)$. In a viewpoint of honeydew excretion and offsprings produced, there was no any possibility in BPH resurgence at the sublethal exposures of Padan. The BPH mortality to Padan 4 G was greatly low in the pot tests compared with those to diazinon and carbofuran, but in the paddy fields the efficacy of Padan 4G was nearly reversed. A single application of Padan 4G at the rate of 4kg/10a dramatically suppressed the BPH populations in the paddy fields, and the control effect was much more accelerated in the drained paddy field than in the submerged paddy field.

• Journal of Veterinary Clinics
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• v.30 no.5
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• pp.346-352
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• 2013

The study was aimed to investigate the influence of diode laser on osteoarthritis (OA) of stifle joint induced by anterior cruciate ligament transection (ACLT). Sixty 10-week-old male Sprague-Dawley rats were used in this study. Right stifle joint was operated to create ACLT or sham. There were five study groups: control, Sham, ACLT, ACLT + Laser irradiation (ACLT+L) and ACLT + meloxicam administration (ACLT+M). Low-level laser therapy (LLLT) was applied at the operated stifle joint twice a week using an 808-nm indium-gallium-arsenide (InGaAs) diode laser during 8-week experimental period. Radiographical, gross morphological and histopathological findings were examined at 2, 4 and 8 weeks post-surgery. Radiography, CBC and chemistry tests showed no significant difference between groups. ACLT+L group showed remarkable cartilage damages compared with sham group morphologically and histopathologically at 2, 4 and 8 weeks after surgery. ACLT+M group also had more cartilage damages compared with sham group. Low-level laser therapy (LLLT) showed limitation to prevent progression of OA in the rat anterior cruciate ligament transection models; on the contrary it accelerated cartilage damage. It is assumed that the aggravating results of LLLT in this study might be due to excessive unstable movement of stifle joint from the pain-relieving effect of LLLT, rather than direct damaging effect of irradiation since LLLT did not affect cell viability.

• The Journal of the Korean Society for Microbiology
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• v.21 no.1
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• pp.133-144
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• 1986

This study was undertaken to assess the effect of ginseng administration on T lymphocyte induced local xenogenic graft-versus-host(GVM) reactions which were induced with thymocyte, spleen cell and lymph node cell of ICR mice. Mice received daily 10mg of 70% alcohol ginseng extract oral1y for 100days and control mice remained untreated for the same period of time. The cells from donor mice were injected intradermally into the closely shaven abdominal skin of Sprague-Dawley rats for GVH tests. The thymocyte from control(ginseng-untreated) mice showed a negative local GVH reaction, whereas thymocyte from experimental(ginseng-treated) mice showed a positive reaction with the rate of 17.4%. When spleen cells were injected, the incidence of positive local GVH reaction was 66.7% among ginseng-treated mice, as opposed to incidence of 45.5% of positive local GVH reaction among control mice. The incidence of positive local GVH reaction of the lymph node cells when injected into a recipient was 71.4% among ginseng-treated mice as compared with that of 18.9% among control mice. The relationship between spleen cell inoculum and intensity of the local GVH reaction was assessed in ginseng-untreated mice. The intensity of GVH reaction clearly appears to be dose related. In ginseng-treated mice, a minimum of $1{\times}10^7$ spleen cell was required for production of positive local GVH reaction with almost linear relationship up to an inoculum of $5{\times}10^8$ cells. In control mice, however, a minimum of $1{\times}10^8$ spleen cells was required for positive GVH reaction. These results strongly suggest that the ginseng administration augments significantly the local xenogenic GVH reaction which was used to assess T lymphocyte function and immunocompetence of mice and in addition to this, these results appear to support previous suggestions that the local GVH reaction consitutes a qualitative test of the functional activity of T lymphocytes. These results may be the first to induce local GVH reaction, employing rats as recipient and mice as donor. This study was also desingned to investigate some of the effects of ginseng extract on lymphocyte-macrophage interactions. This was accomplished by in vitro quantification of 1) migratory inhibitory factor(MIF) synthetic capacity of splenic lymphocytes in mice previously primed with ginseng 2) MIF responsiveness of mouse peritoneal macrophages or chicken peripheral leucocytes under the presence of ginseng extract 3) migration ability of chicken peripheral leucocytes by direct stimulation of ginseng extract or ginseng saponin and 4) immunosuppressive effects of immunosuppressants such as cyclophosphamide, cyclosporin A or dexamethasone. Mice divided equally into the ginseng and the saline groups, which received intraperitoneally daily 0.2ml of ginseng absolute alcohol-extract(5mg/ml) and same amount of saline for 15 days, respectively. The cellular immune responsiveness of these mice was assayed 15 days after ginseng pretreatment. Splenic lymphocytes of mice treated with ginseng, when stimulated with sensitized specific-antigen such as sheep red blood cells or toxoplasmin, or with polyclonal activator concanavalin A, produced significantly more MIF than those of control saline group. MIF responsiveness of normal mouse macrophages was significantly augmented when assayed under the presence of ginseng extract (1mg/ml). The migratory ability of normal chicken leucocytes in the absence of MIF was significantly decreased by the stimulation of ginseng extract alone. MIF response was significantly decreased by immunosuppressants and this impaired response was not restored by ginseng pretreatment. This study was additionally performed to evaluate the effect of ginseng on the expulsion of adult Trichinella spiralis in mice. ICR mice were infected experimentally by esophageal incubation of 300 T. spiralis infective muscle larvae prepared by acid-pepsin digestion of infected mice. and received oral administration of 70% alcohol ginseng extract(10mg/mouse/day) for the indicated days plus 4 days before infection. At various times after infection, the number of adult T. spiralis worms in small intestines was determined. Interestingly, ginseng-treatment was accompanied by accelerated expulson of T. spiralis. These results led to the conclusion that Panax ginseng caused some enhancing effect on GVH reaction, macrophage migration inhibition reaction and expulsion of T. spiralis. In addition these results suggested that the mechanisms responsible for this enhancement of ginseng may be chiefly or partially due to nonspecific stimulation of cell-mediated immune response.

• Korean Journal of Food Science and Technology
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• v.12 no.3
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• pp.193-199
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• 1980

A series of tests were conducted on the reesterification of rice bran oil containing high free fatty acids (acid value=119.7) with theoretical equivalent of glycerol. Test results showed that reaction rate (in terms of decrease in acid value) was increased as the reaction temperature was increased regardless of the presence of the catalyst and reaction time (42.7, 21.5 and 10.0 at $170^{\circ}C,\;210^{\circ}C\;and\;250^{\circ}C$, respectively) and as the reaction time was increased regardless of the temperature and the presence of the catalyst (31.1 vs 18.3 for 3 hrs vs 6 hrs). The presence of the catalyst (0.2% tin chloride) also accelerated the rate regardless of the reaction temperature and time (36.9 vs 12.5). Analysis by column chromatography showed that content of triglyceride in the oil was increased to 72.9% and 61.1% from 10.4% and content of free fatty acids in the oil was decreased to 1.4% and 6.1% from 60.2%, when the degummed oil was esterified at $250^{\circ}C$ for 6 hrs in the presence of and in the absence of the catalyst, respectively. The results estimated from the iodine values indicate that polymer formation was not significant, when the oil was esterified for 6 hrs at temperatures up to $210^{\circ}C$. However, it was somewhat significant for the oil esterified at $250^{\circ}C$ for 6 hrs. The catalyst did not affect the polymer formation. Analysis by high performance liquid chromatography showed that oleic acid (42.5%), linoleic acid (29.0%) and palmitic acid (20.3%) were the major fatty acid components of the rice bran oil.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.1
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• pp.109-116
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• 2017

This paper describes the investigation into the durability alkali-activated materials(AAM) mortar and paste samples manufactured using fly-ash(FA) and ground granulated blast furnace slag(GGBFS) exposed to a sulfate environment with different GGBFS replace ratios(30, 50 and 100%), sodium silicate modules($Ms[SiO_2/Na_2O]$ 1.0, 1.5 and 2.0). The tests involved immersions into 10% sodium sulfate solution($Na_2SO_4$), 10% magnesium sulfate solution($MgSO_4$), 10% magnesium nitrate solution($Mg(NO_3)_2$) and 5% magnesium nitrate($Mg(NO_3)_2$+5% sodium sulfate solution+$Na_2SO_4$). The evolution of compressive strength, weight, length expansion and microstructural observation such as x-ray diffraction were studied. As a results, in case of immersed in $Na_2SO_4$, $Mg(NO_3)_2$ and $Mg(NO_3)_2+Na_2SO_4$ shows increase in long-term strength. However, for samples immersed in $MgSO_4$, the general observation was that the compressive strength decreased after immersion. The most drastic reduction of compressive strength and expansion of weight and length occurred when GGBFS or Ms ratios were higher. Also, the XRD analysis of samples immersed in magnesium sulfate indicated that expansion of AAM caused by gypsum($CaSO_4{\cdot}2H_2O$) and brucite(MgOH). The results showed that, an additional condition $Mg^{2+}$ in which ${SO_4}^{2-}$ is the presence of a certain concentration, sulfate erosion has to be accelerated.