• 한국방사선학회논문지
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• 제16권7호
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• pp.857-862
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• 2022

본 연구의 목적은 토모다이렉트를 이용한 토모테라피 방사선치료에서 두상 각도(head tilting)에 따라 3차원 입체조형 전뇌 방사선치료 계획을 평가하고 자 하였다. 총 다섯 가지 두상 각도(-20°, -10°, 0°, +10°, +20°)를 비교 평가하였다. 두상 각도에 따라 표적에 대한 선량균질지수(homogeneity index, HI)와 처방선량지수(conformity index, CI)를 계산하였고, 정상 장기인 수정체, 안구, 귀밑샘에 대한 최대선량과 평균 선량을 구하였다. 선량균질지수와 처방선량지수는 두상 각도가 +10°와 +20°에서 수치 1에 가까웠다. 두상 각도 +10°에서 수정체와 안구의 선량은 기준 두상각도(0°)에 비해 각각 약 74%와 30% 감소하였다. 턱을 올린 상태의 +10°의 두상 각도는 표적에 대한 선량균일지수와 처방선량지수가 적합하며 렌즈와 안구의 선량을 줄일 수 있는 각도로써 권장한다.

• 한국정보전자통신기술학회논문지
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• 제15권1호
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• pp.8-13
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• 2022

본 논문에서는 RF (Radio Frequency) 에너지 하베스팅 센서 노드의 설계 방안과 CATV 망과 누설 동축 케이블 (leaky coaxial cable)을 활용한 센서 네트워크 구축 방안을 연구하였다. 센서 노드는 915MHz 주파수 대역에서 동작하는 WPTS (Wireless Power Transfer System) 전력 수신기로 전원공급부를 설계하였다. WOC (WiFi over Coax) 기술을 활용하여 CATV 망으로 센서의 BLE 무선통신 신호와 WPTS 전력 송신기 신호를 전송하고, 누설 동축 케이블로 RF 신호를 방사시키는 센서 네트워크 구축 방안을 제안하였다. 센서 네트워크를 구축하는 지점에 누설 동축 케이블을 활용하면 센서 노드의 수신 신호 강도 지표가 허용되는 최소값 (-78dBm)을 만족하는 지점까지 센서 네트워크의 커버리지를 확장할 수 있다.

• Journal of Preventive Medicine and Public Health
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• 제56권3호
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• pp.221-230
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• 2023

Objectives: The second wave of coronavirus disease 2019 (COVID-19) cases in Indonesia, during which the Delta variant predominated, took place after a vaccination program had been initiated in the country. This study was conducted to assess the impact of COVID-19 vaccination on unfavorable clinical outcomes including hospitalization, severe COVID-19, intensive care unit (ICU) admission, and death using a real-world model. Methods: This single-center retrospective cohort study involved patients with COVID-19 aged ≥18 years who presented to the COVID-19 emergency room at a secondary referral teaching hospital between June 1, 2021 and August 31, 2021. We used a binary logistic regression model to assess the effect of COVID-19 vaccination on unfavorable clinical outcomes, with age, sex, and comorbidities as confounding variables. Results: A total of 716 patients were included, 32.1% of whom were vaccinated. The elderly participants (≥65 years) had the lowest vaccine coverage among age groups. Vaccination had an effectiveness of 50% (95% confidence interval [CI], 25 to 66) for preventing hospitalization, 97% (95% CI, 77 to 99) for preventing severe COVID-19, 95% (95% CI, 56 to 99) for preventing ICU admission, and 90% (95% CI, 22 to 99) for preventing death. Interestingly, patients with type 2 diabetes had a 2-fold to 4-fold elevated risk of unfavorable outcomes. Conclusions: Among adults, COVID-19 vaccination has a moderate preventive impact on hospitalization but a high preventive impact on severe COVID-19, ICU admission, and death. The authors suggest that relevant parties increase COVID-19 vaccination coverage, especially in the elderly population.

• International Journal of Computer Science & Network Security
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• 제23권4호
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• pp.172-178
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• 2023

When the mobile device moves from the coverage of one access point to the radio coverage of another access point it needs to maintain its connection with the current access point before it successfully discovers the new access point, this process is known as handoff. During handoff the acceptable delay a voice over IP application can bear is of 50ms whereas the delay on medium access control layer is high enough that goes up to 350-500ms. This research provides a suitable methodology on medium access control layer of the IEEE 802.11 network. The medium access control layer comprises of three phases, namely discovery, reauthentication and re-association. The discovery phase on medium access control layer takes up to 90% of the total handoff latency. The objective is to effectively reduce the delay for discovery phase to ensure a seamless handoff. The research proposes a scheme that reduces the handoff latency effectively by scanning channels prior to the actual handoff process starts and scans only the neighboring access points. Further, the proposed scheme enables the mobile device to scan first the channel on which it is currently operating so that the mobile device has to perform minimum number of channel switches. The results show that the mobile device finds out the new potential access point prior to the handoff execution hence the delay during discovery of a new access point is minimized effectively.

• 천문학회보
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• 제46권2호
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• pp.62.1-62.1
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• 2021

Interstellar objects originate from other stellar systems. Thus, they contain information about the stellar systems that cannot be directly explored; the information includes the formation and evolution of the stellar systems and the possibility of life. The examples observed so far are 1l/Oumuamua in 2017 and 2l/Borisov in 2019. In this talk, we present the possibility of detecting interstellar objects using the Heliospheric Imagers designed for space weather research and forecasting by observing solar wind in interplanetary space between the Sun and Earth. Because interstellar objects are unpredictable events, the detection requires observations with wide coverage in spatial and long duration in temporal. The near-real time data availability is essential for follow-up observations to study their detailed properties and future rendezvous missions. Heliospheric Imagers provide day-side observations, inaccessible by traditional astronomical observations. This will dramatically increase the temporal and spatial coverage of observations and also the probability of detecting interstellar objects visiting our solar system, together with traditional astronomical observations. We demonstrate that this is the case. We have used data taken from Solar TErrestrial RElation Observatory (STEREO)/Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) HI-1. HI-1 is off-pointed from the Sun direction by 14 degrees with 20 degrees of the field of view. Using images observed from 2007 to 2019, we have found a total of 223 small objects other than stars, galaxies, or planets, indicative of the potential capability to detect interstellar objects. The same method can be applied to the currently operating missions such as the Parker Solar Probe and Solar Orbiter and also future L5 and L4 missions. Since the data can be analyzed in near-real time due to the space weather purposes, more detailed properties can be analyzed by follow-up observations in ground and space, and also future rendezvous missions. We discuss future possible rendezvous missions at the end of this talk.

• Journal of Plant Biology
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• 제18권3호
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• pp.109-121
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• 1975

The seasonal variations of the marine algal community were detected with quadrat method during May, 1974-May, 1975 at several stations in the Kwang Yang Bay. Considering the environmental factors such as salinity and water current, etc., and algal vegetation, the Bay was divided into 3 sections; Section I-Myodo and the adjacent area; Section II-Eomnamuseom and the adjacent area; Section III-inlet of the Bay from Odongdo, Yeosu. The dominant species, shown by 5-grades coverage and bimonthly investigations, appear in the order of Sargassum thunbergii(Jan.)>Chondria crassicaulis (Mar.)>Ulva pertusa(May)>U. pertusa (July)>U. pertusa and Gigartina intermedia(Sept.)> Sarg. thunbergii and Gelidium pusillum (Nov.) in Section I, and Sargassum thunbergii(Jan.)>Ulva pertusa and Hizikia fusiforme (Mar.)>U. pertusa and Sarg. thunbergii(May)>Chondria crassicaulis (Sept.)>Ch. crassicaulis (Nov.) in Section II. The members such as Srgassum thunbergii, Gelidium pusillum, G. divaricatum, Hizikia fusiforme, Carpopeltis affinis, and Chondria crassicaulis show the most luxuriant period of growth in winter (Nov.-Mar.), while Ulva pertusa shows the period in May. However, considering the dry weight of total vegetation, the most luxuriant period apperas in May and the poorest one in July. The total dry weight of the vegetation in Section II is about 3.2 times more than the one in Section I.

• 한국조경학회지
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• 제23권3호
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• pp.80-93
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• 1995

The purpose of this study was to assess functioni fo urban greenspace to reduce atmospheric CO\sub 2\ concentration. The study quantified carbon storage in urban greenspace and carbon emission by fossil fuel consumptio in Chuncheon. The amount of carbon storage in vegetation by land use type was 0.02kg/$m^2$ for commercial land, 4.36kg/$m^2$ for natural land, and 0.54kg/$m^2$ for the other urban lands. In 1994, total amount of carbon emission by fossil fuel consumption was about 257,358 metric tons, and the per capita carbon emission was 1.4 metric ton. Total amount of carbon storage in vegetation was 42,942 metric tons, approximately 17% of the carbon emission. This study excluded quantification of carbon storage in soils. The role of urban greenspace to sequester atomspheric carbon might be much greater, if a soil greenspace to sequester atmospheric carbon might be much greater, if a soil greenspace to sequester atmospheric carbon might be much greater, if a soil carbon storage is included quantification of carbon storage is included. However, increasing coverage of trees and managing them for healthy growth would not be sufficient for avoiding adverse impacts by future climate change. Additional measures should be followed such as an increase of energy use efficiency and development of substitute energy.

• 한국표면공학회지
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• 제26권1호
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• pp.3-9
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• 1993

Chemical vapor deposited tungsten films were formed in a cold wall reactor at pressures higher (10~120torr) than those conventionally employed (<1torr). SiH4, in addition to H2, was used as the reduction gas. The effects of pressure and reaction temperature on the deposition rate and morphology of the films were ex-amined under the above conditions. No encroachment or silicon consumption was observed in the tungsten de-posited specimens. A high deposition rate of tungsten and a good step coverage of the deposited films were ob-tained at 40~80 torr and at a temperature range of $360~380^{\circ}C$. The surface roughness and the resistivity of the deposited film increased with pressure. The deposition rate of tungsten increased with the total pressure in the reaction chamber when the pressure was below 40 torr, whereas it decreased when the total pressure ex-ceedeed 40 torr. The deposition rate also showed a maximum value at $360^{\circ}C$ regardless of the gas pressure in the chamber. The results suggest that the deposition mechanism varies with pressure and temperature, the surface reac-tion determines the overall reaction rate and (2) at higher pressures(>40 torr) or temperatures(>36$0^{\circ}C$), the rate is controlled by the dtransportation rate of reactive gas molecules. It was shown from XRD analysis that WSi2 and metastable $\beta$-W were also formed in addition to W by reactions between WF6 and SiH4.

• The Journal of Asian Finance, Economics and Business
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• 제6권1호
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• pp.241-248
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• 2019

The purpose of this study is to investigate empirical evidences of productivity of life insurance institutions in Malaysia. Therefore, this study attempts to explore the productivity of the life insurance institutions in Malaysia. The overall findings show that the total factor productivity (TFP) has progressed by 2.5% per year during the study period from 2012 to 2016 in the Malaysian insurance industry. However, TFP change has declined from 2012 to 2015 and observed a negative growth in 2015-16 (3.3%). The highest productivity progress was documented during 2012-13 at a rate of 11.7% while the minimum productivity progress was during 2014-15 (only 0.2%). The results also indicate that the decomposition of TFP found that overall progress could mainly be attributed to technological change (TC). However, technical efficiency change (TEC) and pure technical efficiency change (PTE) have negative impact on TFP. The findings also show that most of the insurance companies have a steady growth. Therefore, this study will contribute new insights for the policy makers and insurance institutions to take appropriate steps in developing relevant policies for increasing productivity of insurance institutions in Malaysia.

• 한국의류산업학회지
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• 제25권5호
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• pp.615-625
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• 2023

This study aimed to analyze the characteristics of the lower-body shape of middle-aged males with abdominal obesity by type and consider dimensional distribution to present a suit-pants size. The criteria were having a waist circumference greater than 90 cm and a waist-to-hip ratio(WHR) greater than 0.90; a total of 566 middle-aged males were surveyed. The findings revealed that, first, compared to standard lower-body types, the average body size of abdomenobese middle-aged males was significantly larger, especially in the horizontal area than in the vertical ares. Second, through a cluster analysis, a total of three categories of abdominal obesity were defined: small oval, large cylinder, and trapezoid type. The coverage rates of each type were 93.8%, 75.9%, and 93.0%, respectively. Finally, the suit-pants size system established according to lower-body types indicated the basic body size and reference body size were different for each type and also for the KS K 0050 male adult's garments size system. According to the definition of abdominal obesity, the types of abdominal obesity and the dimensions of each area are different, even if they belong to the same obesity group, suggesting that it is necessary to develop a pattern based on the analysis of obesity types.