• 한국염색가공학회지
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• 제30권3호
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• pp.180-189
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• 2018

To study the effect of stereoisomeric structures of curing agents on curing behaviors, thermal and mechanical properties of epoxy resins, DGEBA(diglycidyl ether of bisphenol A) epoxy resin and 3,3'- and 4,4'-DDS(diaminodiphenyl sulfone) curing agents were selected. The curing initiation temperature and activation energy of DGEBA/3,3'-DDS was lower than DGEBA/4,4'-DDS. DGEBA/3,3'-DDS has a faster curing rate and higher degree of cure than DGEBA/4,4'-DDS, suggesting that 3,3'-DDS has higher reactivity than 4,4'-DDS. Tensile strength and fracture toughness of DGEBA/3,3'-DDS was lower than those of DGEBA/4,4'-DDS, indicating that mechanical properties of the epoxy resin can be different only by the stereoisomeric difference in chemical structure of the curing agent.

• 한국전자파학회논문지
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• 제25권12호
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• pp.1243-1250
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• 2014

본 논문에서는 0.5~1.1 GHz 주파수 범위를 갖는 광대역 DDS(Direct Digital Synthesizer) 모듈의 설계 및 제작 결과에 대해 기술하고자 한다. 600 MHz 대역폭을 갖는 광대역 DDS 구현을 위해 DDS의 클럭을 2.4 GHz로 선정하였다. 광대역 DDS의 불요신호(spurious) 특성을 개선하기 위해 출력 불요신호 대비 크기가 같고, 역위상을 갖는 여러 개의 신호들을 동시에 발생시킨 후 DDS 내부에서 출력 신호와 합성하였다. 제작된 DDS 모듈의 불요신호는 상용 DDS 대비 10 dB 정도 개선되었고, DDS 모듈의 동조 속도는 340 ns 이하임을 확인하였다.

• 한국정보통신학회논문지
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• 제20권4호
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• pp.739-746
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• 2016

철도 안전사고 예방을 목표로 하는 실시간 철도 안전관제 시스템에서는 DDS (Data Distribution Service) 표준 기술 기반의 데이터 전송 방안을 적용함으로 기존 현장의 안전검지장치로부터 발생한 데이터를 통합 및 관리하고 있다. 본 논문에서는 수많은 현장 데이터 중 일반철도 현장에서 발생한 신호설비 데이터 규격 설계를 소개하고 있다. 신호설비 데이터의 DDS 전송을 위하여 기존 표준 규격인 KRS SG 0062를 모델링하고, DDS 데이터 전송 단위인 Topic 설계 및 데이터 변환 방안을 제시하고, 데이터 성격 별로 네트워크 제어 QoS 정책 설계를 제시하고 있다. 또한 실제 현장 데이터를 분석하여 설계된 규격이 현장에 적용 가능한지를 확인해 보았다.

• 한국도시철도학회논문집
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• 제6권4호
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• pp.279-286
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• 2018

최근 열차운행의 안전을 실시간으로 감시하고 통제를 통해 사고 및 위험을 예방하는 안전관제 플랫폼의 연구가 진행 중에 있다. 초기 설계에서 기존 분산된 안전 데이터의 통합에 따른 대용량 데이터의 실시간 처리를 위하여 분산 네트워크를 지원하는 DDS통신 방식을 채택하였으나, 안전관제 플랫폼 내부의 서버와 콘솔 간 통신은 기존의 TCP소켓통신을 그대로 적용하였다. TCP소켓통신의 경우 1대1 통신으로 안전관제 테스트베드의 소규모 시스템을 위한 데이터 처리는 가능하지만, 추후 전국으로 확대되면 방대한 데이터로 인해 통신 트래픽이 발생하는 경우 대처가 어렵게 된다. 본 논문에서는 안전관제 플랫폼의 서버와 콘솔 간 인터페이스 방식을 분산네트워크를 지원하는 DDS통신으로 제안하였으며, TCP소켓방식과 DDS방식의 데모를 구현하고 처리량 및 속도 비교 분석을 수행하였다. 그 결과, DDS통신을 적용하는 경우 향후 변경될 수 있는 시스템에 대비하여 확장성과 유연성이 개선된다는 사실을 도출하였다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 1999년도 추계학술발표대회 논문집
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• pp.73-76
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• 1999

Near infrared spectroscopy techniques were used to study the cure reactions of epoxy resin system based on diglycidyl ether of bisphenol A(DGEBA) resins cured with 4, 4' diaminodiphenyl sulfone (DDS) hardner. Stoichiometric DGEBA/DDS resin formulation was involved in this study. The infrared absorption spectra of the prepared formulation were obtained on an FTIR spectrometer operating in the region of 11000 to 4000$cm^{-l}$. The chemical group peaks of interest in a DFEBA/DDS spectrum were identified by a comparative study with individual spectra of DGEBA and DDS monomers. Where necessary, special model compounds were used to identify unknown bands, such as the primary amine band at 4535$cm^{-l}$. The absorption bands of interest were integrated to quantify the areas and then converted to molar concentrations. This series of quantitative analyses of the major chemical groups led us to understand not only the reaction mechanism but also the cure kinetics. In this paper, the reaction mechanisms observed in stoichiometric DGEBA/DDS resin formulation and the various properties of the resin system as a function of cure temperature are described.

• 한국염색가공학회지
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• 제31권2호
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• pp.118-126
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• 2019

This study aims to investigate the effect of polytriazolesulfone(PTS) addition on fracture toughness of diglycidyl ether of bisphenol A(DGEBA) and 4,4'-diaminodiphenylsulfone(DDS). Various amounts of PTS were added to DGEBA/4,4'-DDS in diazide and dialkyne monomer forms and polymerized during the epoxy curing process. Fracture toughness(K1C), tensile properties and thermal stability of the PTS added epoxy resin were evaluated and compared with those of PES, the conventional high Tg toughening agent, added epoxy resin. Fracture toughness of the PTS added epoxy resin was dramatically improved up to 133%, as the amount of PTS added increased, whereas that of the PES added epoxy resin was improved by only 67%. The tensile strength of PTS added DGEBA/4,4'-DDS was similar to the epoxy resin without PTS and tensile modulus was improved by 20%. And thermal stability of the PTS added epoxy resin was improved up to 14%. Therefore, PTS addition to DGEBA/4,4'-DDS, as a toughening agent, is very effective way to improve its fracture toughness without any lowering in other properties.

• 한국치위생학회지
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• 제19권1호
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• pp.141-149
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• 2019

Objectives: To investigate the real-world re-use of disposable dental supplies (DDS) in dental offices and assess the relationship between general characteristics of dental hygienists and reuse of DDS, with respect to infection control characteristics. Methods: A questionnaire was administered to 277 dental hygienists to assess their general characteristics, awareness of infection control/DDS management, and re-use of DDS. Nine DDS were categorized into the following categories based on their purpose: Critical, Semicritical, Noncritical, and Personal protective equipment (PPE). The association between general characteristics of dental hygienists and re-use of DDS, with respect to infection control characteristics, was assessed using the chi-squared test. Results: All 9 DDS were re-used to different extents. The highest reuse rate of supplies were for masks (64.6%), prophylaxis cups (61.0%) and plastic saliva ejectors (30.0%). Overall, 89.5% of the participants re-used DDS; subgroup analysis showed the following proportions of specific DDS re-use: PPE 66.4%; Semicritical DDS 63.9%; Noncritical DDS 19.5%; and Critical DDS 1.8%. Based on the type of clinic, the rate of re-use was higher in dental clinics than dental hospitals. Thus, the re-use of DDS may be caused by inappropriate or nonexistent guidelines or habitual practice, rather than the awareness or attitude of dental hygienists. Conclusions: In order to ensure a safe environment within the dental clinic, DDS classifications must be clearly outlined in the dental infection control guidelines; moreover, additional studies are needed regarding the regulations for DDS re-use and disposal.

• 한국전자파학회논문지
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• 제26권3호
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• pp.333-341
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• 2015

본 논문에서는 0.5~4 GHz 주파수 범위에서 낮은 위상잡음 특성을 갖는 광대역 고속 주파수 합성기 구조를 제안하였다. 광대역에서 빠른 동조 속도를 얻기 위해 DDS(Direct Digital Synthesizer)와 아날로그 직접 주파수 합성 기술을 적용하여 주파수 합성기의 출력을 합성하였다. 특히 낮은 위상잡음 특성을 확보하기 위해 DDS 구동에 필요한 2.4 GHz 클럭신호는 SPD(Sample Phase Detector)를 통해 100 MHz 기준 발진기 신호에 위상 고정된 2.4 GHz VCO(Voltage Controlled Oscillator)를 이용하여 발생시켰다. 그리고 광대역 주파수 합성기의 위상잡음 특성을 이론적으로 예측하고, 이를 측정결과와 비교하였다. 제작된 주파수 합성기의 위상잡음은 최고 주파수에서 -121 dBc @ 100 kHz 이하를 갖는다.

• Clinical Nutrition Research
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• 제11권4호
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• pp.289-301
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• 2022

This study was conducted to evaluate the associations between dietary diversity score (DDS) and cardiovascular risk factors in this population. In this cross-sectional study, 187 patients, aged 18-65 years with pemphigus vulgaris were included. DDS was assessed by a 24-hour dietary recall method. Anthropometric measures and biochemical parameters assessed according to standard protocols. Multivariate linear regression analyses used for detecting any associations between DDS and cardiovascular risk factors. The mean ± standard deviation age and body mass index of studied participants were (46.71 ± 11.49 years) and (27.83 ± 4.39 kg/m²) respectively. Our findings showed that a higher DDS intake was related with higher consumption of vegetables (p = 0.001), dairy products (p < 0.001), cereals (p = 0.002), red and processed meat (p < 0.001), sweets and desserts (p < 0.001). After controlling for confounding variables, the results showed positive associations between DDS and high-density lipoprotein cholesterol (HDL-C, β = 1.87, 95% confidence interval [CI], 0.30-3.45, p = 0.02) and total cholesterol (TC) levels (β = 6.41, 95% CI, 1.62-11.03, p = 0.02) (β = 1.75, 95% CI, 0.20-3.30, p = 0.02). However, there were no associations between DDS and prevalence of obesity and glucose homeostasis. The results of this cross-sectional study showed that DDS might be associated with increased HDL-C and TC. However, further prospective studies are needed to prove these findings.

• Journal of Nutrition and Health
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• 제37권10호
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• pp.908-916
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• 2004

Due to the common dietary practice of preparing foods in various ways using the same food item, in addition to rather a large number of food items that average Koreans consume, it is difficult to accurately assess the nutritional adequacy. In an effort to identify a reliable means of assessing the nutritional adequacy of Korean adults, we analyzed the association between the scores of dietary diversity (DDS) and dietary variety (DVS), and the quality of nutrient intake as assessed by Nutrient Adequacy Ratio (NAR) and Mean Adequacy Ratio (MAR). A three day-dietary record was obtained from each of 324 inhabitants, aged 40 to 69 years (mean :t SD,52.4 $\pm$ 8.7), of a rural area (Ansung) and a mid-sized city (Ansan) of Korea. These individuals were randomly selected among the participants of the Korean Health and Genome Study. The number of consumed foods and food groups were assesses by DDS (scored 1 to 5) and DVS (ranked 30 $\leq$,31 - 40, 41 - 50, 51 - 60, and 60 <) over three-day period, respectively. As DDS/DVS increased, mean daily food intakes tended to increase, and NARIMAR was improved. Thus, DDS and DVS were significantly correlated with the quality of nutrient intake. Over 95% of the subjects scored less than 2 in DDS for the first one-day period, whilst over 62% recorded 4 during the full three-day period (p < .0001). The mean number of consumed food items increased from 24.9 to 44.4 as a function of days of the record period (p < .0001). We also analyzed the association of DDS and DVS with MAR, using regression analysis, controlling age and sex as covariates. For DDS, the adjusted coefficient determination (adj $R^2$) values were 8.7%,15.8%,23.3% of MAR, also increasing as a function of the record duration, whereas they were 27.3%, 33.3%, 37.6% for DVS, respectively, demonstrating that NAR/MAR has a better correlation with DVS than DDS. Our data show that DDS, and DVS in particular, are useful parameters for evaluating nutrient intake in the Korean population. Our data also support that one day-dietary records are by no means adequate for accurately describing a wide variety of food choices offered for average Koreans, and that dietary assessment at least for 3 days or longer should be obtained for a reliable evaluation of dietary quality using DDS or DVS.