• The Korean Journal of Ecology
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• v.18 no.1
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• pp.63-87
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• 1995

The present study was undertaken to classify and describe the Quercus mongolica forest on Mt. Sobaek (36°50'∼ 37°07'N, 128°25'∼ 128°35'E), Korea by a reciprocal averaging methol (RA ordination) and the methodology of the ZM school of phytosociology. Atemporal vegetation tabel was prepared by the RA ordination. As a result it showed that the RA ordination on the first axis is very applicable for selecting the character and differential species of vegetation units of the Quercus mongolica forest. The phytosociological investigations were carried out in 34 stands on the mountain. The field data obtained were classified by the tabel comparison method. For the establishment of new vegetation units, the floristic composition of the Quercus mongolica forest was compared with those of the other vegetation units of the Mt. Sobaek, Considering the candidates of the character and differential species derived from RA ordination. As the result, the forest vegetation was classified into the following vegetation units; Fagetea crenatae Miyawaki et al. 1968 Acero-Quercetalia mongolicas Song 1988 em. Takeda et al.1994 Lindero-Quercetalia mongolicae Kim 1990 1. Lindero-Quercetum mongolicae assoc. nov. 1-1. quercetosum serratae subassoc. nov 1-2. typicum subassoc. nov. Rhododendro-Qurcion mongolicas Song 1988 em. Takeda et al. 1994. It is inferred that the Lindero-Quercion mongolicae and the Rhododendro-Quercion mongolicae corresponded to the cool-temperate forests of central and northern areas, respectively, in Korean Peninsula. Syntaxonomical synonyms were also rearranged based on the result of the present study. On the other hand, the RA ordination of stands and species on the first and second axes revealed some environmental gradients such as altitute, human impact and species richness between the vegetation units. However, the RA ordinations is considered to be less indicative for the gradients of the lower vegetation units than association. With the present study. some phytosociological problems in Korea were discussed here in detail from the floristic viewpoint.

• Nuclear Engineering and Technology
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• v.56 no.5
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• pp.1781-1795
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• 2024

This study investigated the levels of radioactivity in soil surrounding a phosphate fertilizer factory in Egypt, aiming to assess potential risks to the population exposed to radiation. Concentrations of ²³⁸U, ²²⁶Ra, ²³²Th, and ⁴⁰K were measured in soil samples collected from two subsites: one near the factory (subsite 1) and another further away (subsite 2). Two different systems were used for measuring radioactivity, a high-purity gamma ray spectroscopy system with an HPGe detector for gamma-emitting isotopes and a CR-39 solid nuclear track detector for alpha-emitting radon gas. Subsite 1, located close to the factory, displayed significantly elevated levels of ²²⁶Ra compared to global background levels (514 and 456 Bq/kg vs. 35 Bq/kg). Additionally, the concentrations of ²³⁸U (241.06 Bq/kg vs. global average 35 Bq/kg), ²³²Th (16.15 Bq/kg vs. global average 30 Bq/kg), and ⁴⁰K (146.36 Bq/kg vs. global average 400 Bq/kg) were all above global averages. Furthermore, a high concentration of radon gas (337.06 μSv/y) was measured at subsite 1. The strong positive correlation observed between ²²⁶Ra and ²³⁸U (0.96256) provides further evidence of potentially elevated radioactivity levels near the factory. In contrast, subsite 2, situated farther from the factory, exhibited natural radioactive background levels within international limits. Quantitative analysis revealed that gamma ray absorbed doses for ²²⁶Ra and ²³²Th exceeded global averages in some samples. Specifically, ²²⁶Ra doses ranged from 7.8 to 46.26 ppm (exceeding the 20 ppm global average in some cases), and ²³²Th doses ranged from 1.98 to 9.14 ppm (exceeding the 10 ppm global average in some cases). The concentration of ⁴⁰K, however, remained within the global range (0.07%-0.69 %). The observed imbalances in the ratios of Th/U (0.17-0.24 Bq/kg and 0.73-0.24 ppm) and U/Ra (0.81-0.73 Bq/kg and 0.73-0.17 ppm), both of which are significantly lower than their respective global averages of 4 and 2.4, point towards the presence of fertilizer-derived contamination. This conclusion is further supported by the high phosphate concentrations detected in the samples. Overall, this study suggests that radioactive contamination near the phosphate fertilizer factory significantly exceeds global background levels and international limits in some cases. This raises concerns about potential risks posed to surrounding agricultural land and crops.

• Journal of Technologic Dentistry
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• v.37 no.4
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• pp.205-212
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• 2015

Purpose: The objective of this study was to compare the surface roughness according to polishing process in conventional laboratory techniques used for polishing three different acrylic denture base resins. Materials and methods: Specimen preparation and surface polishing procedures were conducted to manufacturer's recommendation with three heat-polymerized denture base resins. Surface roughness and gloss were measured by a contact type tester and a LED gloss checker using thickness 2 mm and diameter 10 mm. There were five specimens for each acrylic resin material and polishing procedures. Mean average surface roughness (Ra) values of each specimen group were analyzed using a one-way ANOVA analysis of variance and Scheffe's post hoc test. Surfaces after surface roughness and gloss testing according to each polishing process were evaluated under a stereoscopic microscope. Results: The highest mean average surface roughness was measured($Ra=2.43{\pm}0.47$) for surfaces finished with a denture tungsten carbide bur in Triplex. The lowest surface roughness values ($Ra=0.11{\pm}0.07$) were determined in Vertex polished with a lathe. In addition, all materials revealed that surface roughness determined highly in HP1 and HP2 than other procedures. All correlation between surface roughness and gloss showed highly with three heat-polymerized resins. Specially, topmost correlation revealed than other material in Triplex. Significant differences in mean average surface roughness were found between polishing process used high speed lathe and low speed hand-piece. Conclusion: Laboratory polishing used to high speed was found to produce the smoothest surface of heat-polymerized denture base acrylic resin. Therefore, we recommended that high polishing process need to get smooth surface.

• Journal of Preventive Medicine and Public Health
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• v.35 no.3
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• pp.245-254
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• 2002

Objective : To test if the intake of $H_2$ receptor antagonists ($H_2$-RAs) increases the risk of gastric cancer in the elderly. Methods : The source population for this study was drawn from the responders to a questionnaire survey administered to the Korea Elderly Pharmacoepidemiological Cohort (KEPEC), who were beneficiaries of the Korean Medical Insurance Corporation, were at least 65 years old, and residing in Busan in 1999. The information on $H_2$-RAs exposure was obtained from a drug prescription database compiled between inn. 1993 and Dec. 1994. The cases consisted of 76 gastric cancer patients, as confirmed from the KMIC claims data, the National Cancer Registry and the Busan Cancer Registry. The follow-up period was from Jan. 1993 to Dec. 1998. Cancer free controls were randomly selected by 1:4 individual matching, which took in to consideration the year of birth and gender. Information on confounders was collected by a mail questionnaire survey. The odds ratios, and their 95% confidence intervals, were calculated using a conditional logistic regression model. Results : After adjusting for a history of gastric ulcer symptoms, medication history, and body mass index, the adjusted OR (aOR) was 4.6 (95% CI=1.72-12.49). The odds ratio of long term use (more than 7 days) was 2.3 (95% CI=1.07-4.82). The odds ratio of short term use was 4.6 (95% CI=1.26-16.50). The odds ratio of parenteral use was 4.4 195% CI=1.16-17.05) and combination use between the oral and parenteral routes (aOR, 16.8; 95% CI=1.21-233.24) had the high risk of gastric cancer. The aOR of cimetidine was 1.7 (95% CI=1.04-2.95). The aOR of ranitidine was 2.0 (95% CI=1.21-3.40). The aOR of famotidine was 1.7 (95% CI=0.98-2.80). Conclusion : The intake of $H_2$-RAs might increase the risk of gastric cancer through achlorhydria in the elderly.

• Information and Communications Magazine
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• v.25 no.1
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• pp.59-63
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• 2008

2007년 10월 18일, 우리의 와이브로 기술이 ITU-R-RA-07 회의에서 OFDMA TDD WMAN이란 이름으로 IMT-2000 국제표준 중 여섯 번째 표준으로 채택되었다. 아울러 해당 주파수($2.3{\sim}2.4GHz$)가 4G 이동통신 공통대역으로 선정됨으로써 우리나라 기술이 세계로 진출할 수 있는 교두보를 마련하였다. 그에 앞서 TTA는 2006년 7월에 세계에서 두 번째로 WiMAX포럼 국제공인 인증시험소로 지정되어 내년 초부터 공식 시험인증 서비스를 시작할 예정이다. 이는 제품이 시장에 출시되기 전에 공인인증시험소를 통한 적합성 시험과 상호운용성 시험을 권고하고 있기에 국내 WiMAX 산업의 국제 경쟁력 강화를 위해 TTA와 정부, 사업자 및 장비업체들과의 공동 노력으로 이뤄낸 결과이다. 이렇듯 표준화의 중요성과 시험인증의 필요성이 날로 커져가고 있음에 본 고에서는 TTA의 표준/시험인증 현황 및 향후 추진전략에 대해 살펴보고자 한다.

• Journal of dental hygiene science
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• v.9 no.5
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• pp.557-561
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• 2009

The purpose of this study was to observe the demineralization effects of commercial drinks on bovine enamel. 12 bovine teeth without dental caries were divided into 3 experimental groups (n = 9) and control groups (n = 3). All the samples immersed in beverages maintained by $37^{\circ}C$ in incubator respectively. The differences of surface microhardness values(${\Delta}VHN$) between before and after 45 hours treatment were $166.97{\pm}51.69$(in Coca-cola), $116.26{\pm}20.81$(in Gatorade), $77.89{\pm}55.88$(in Hite), and $23.44{\pm}29.97$(in Jeju SamDaSoo). Morphological changes by scanning electron microscope were indicated that a sports drink cause significant enamel demineralization effects on the bovine enamel surface among four beverages.

• Journal of Broadcast Engineering
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• v.21 no.6
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• pp.929-943
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• 2016

This paper proposes the rate control algorithm based on the S-JND (Saliency-Just Noticeable Difference) model for considering perceptual visual quality. The proposed rate control algorithm employs the S-JND model to simultaneously reflect human visual sensitivity and human visual attention for considering characteristics of human visual system. During allocating bits for CTU (Coding Tree Unit) level in a rate control, the bit allocation model calculates the S-JND threshold of each CTU in a picture. The threshold of each CTU is used for adaptively allocating a proper number of bits; thus, the proposed bit allocation model can improve perceptual visual quality. For performance evaluation of the proposed algorithm, the proposed algorithm was implemented on HM 16.9 and tested for sequences in Class B and Class C under the CTC (Common Test Condition) RA (Random Access), Low-delay B and Low-delay P case. Experimental results show that the proposed method reduces the bit-rate of 2.3%, and improves BD-PSNR of 0.07dB and bit-rate accuracy of 0.06% on average. We achieved MOS improvement of 0.03 with the proposed method, compared with the conventional method based on DSCQS (Double Stimulus Continuous Quality Scale).

• The Korean Journal of Food And Nutrition
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• v.28 no.6
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• pp.941-946
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• 2015

Photoaging is the main extrinsic aging factor that is induced due to UVB. Many studies have revealed that application of hyaluronic acid to the skin is effective in healing photoaging. However, the effect of hyaluronic acid through oral administration is unclear. The aim of this research was to investigate the effect on skin photoaging after oral administration of hyaluronic acid. During a ten week study, hyaluronic acid was fed to hairless mice, which were illuminated by UV radiation. After ten weeks, wrinkle indicator and histological changes were determined. Compared with the control group, the sample group had a decrease in wrinkle depth, thickness, and number. Especially, the HA 160 mg/kg group had a similar value of wrinkle depth ($19.44{\pm}0.75{\mu}m$), number ($654.00{\pm}98.34$), and thickness ($1.35{\pm}0.08mm$), when compared with the RA (retinoic acid) group ($19.28{\pm}0.95{\mu}m$, $653.57{\pm}83.54$, and $1.34{\pm}0.07mm$ respectively). Also, the treated group showed improved elastosis and decreased collagen degradation resulting from UV irradiation. Thus, we can conclude that hyaluronic acid has a positive effect in improving skin photoaging induced by UV radiation. Hyaluronic acid therefore has the potential to be an ingredient in skin health function foods.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.7
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• pp.2919-2924
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• 2011

The automatic drawer is used to absorb the movement shock and adjust its velocity when it opens and closes. The tube in shock-absorber is the cylindrical case which surrounds its parts and is made of acetal. The purpose of this study is to determine the quality stability of the tube in the shock-absorber in injection molding process. The tube which had been manufactured in the process with 4 cavity cooling unit was used. In this study, the analysis and test are carried out to determine its quality stability. Which are the quality analysis with numerical simulation and performance tests of the tube compared with one of foreign make. It is calculated that the injection press is 87.6 MPa and the deflections in X, Y, Z directions are ranged in 0.07~1.00 mm. When the researched tube is compared with the foreign made tube, the maximum bending compressive load is 231 kgf higher, average axial compressive load is 0.05 kgf higher, and the roughness(Ra) on the inner surface is $0.02\;{\mu}m$. lower. In the result, it is known that the quality of researched tube in injection mold process is stable and its performance is superior.

• Journal of Broadcast Engineering
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• v.22 no.3
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• pp.381-396
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• 2017

In this paper, the perceptual rate control algorithm is studied for HEVC (High Efficiency Video Coding) encoder with bit allocation based on perceived visual quality. This paper proposes perceptual rate control algorithm which could consider perceived quality for HEVC encoding method. The proposed rate control algorithm employs adaptive bit allocation for frame and CTU level using the perceived visual importance of each CTU. For performance evaluation of the proposed algorithm, the proposed algorithm was implemented on HM 16.9 and tested for sequences in Class B under the CTC (Common Test Condition) RA (Random Access) case. Experimental results show that the proposed method reduces the bitrate of 3.12%, and improves BD-PSNR of 0.08dB and bitrate accuracy of 0.07% on average. And also, we achieved MOS improvement of 0.16 with the proposed method, compared with the conventional method based on DSCQS (Double Stimulus Continuous Quality Scale).