• Textile Coloration and Finishing
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• v.30 no.3
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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.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.12
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• pp.1243-1250
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• 2014

In this paper, a wideband DDS module covering the frequency range from 0.5 to 1.1 GHz was designed and fabricated. The clock frequency of the DDS was selected 2.4 GHz in order for 600 MHz output bandwidth. Multiple spurious cancelling signals having same amplitude and $180^{\circ}$ phase difference compared to the spurious were created at the additional path and added to the output signal within DDS for the spurious performance improvement. The fabricated DDS module showed better spurious performance than the commercial DDS one more than 10 dB and frequency tuning time was 340 ns below.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.4
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• pp.739-746
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• 2016

The real-time railway safety monitoring and control system is for prevention of safety accidents, and this system adopts DDS (Data Distribution Service) standard based data transmission method to support integrated management of data from existing on-site safety detection devices. In this paper, we introduce the design of DDS-based data specification from on-site signal equipment on the conventional railway. For this, we (1) design UML data model of KRS SG 0062 standard which defines existing data specification, (2) define DDS Topics for DDS transmission and map KRS model to DDS Topic model, (3) suggest data transformation rules and (4) design network control QoS polices. In addition, we analysis actual on-site log data and validate our data specification design. DDS-based data transmission enables data compatibility among on-site devices and the real-time railway safety monitoring and control system, and allows efficient network management for a large amount of data transfer.

• Journal of The Korean Society For Urban Railway
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• v.6 no.4
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• pp.279-286
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• 2018

Recently, a safety control platform to monitor the safety of train operation in real time and prevent accidents and risks through control is under study. In the initial design, DDS communication method supporting distributed network is adopted for real-time processing of large amount of data according to the integration of existing distributed safety data. However, communication between server and console inside the safety control platform is applied to existing TCP socket communication. In the case of TCP socket communication, it is possible to process data for a small system of a safety control test bed by one-to-one communication. However, if the data is expanded all over the country in the future, it becomes difficult to cope with a case where communication traffic occurs due to vast amount of data. In this paper, we propose DDS communication method to support distributed network between server and console of security control platform, and demonstrate TCP socket and DDS method, and compare throughput and speed. As a result, we have found that the scalability and flexibility are improved in case of applying DDS communication to future systems.

• Proceedings of the Korean Society For Composite Materials Conference
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• 1999.11a
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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.

• Textile Coloration and Finishing
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• v.31 no.2
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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.

• Journal of Korean society of Dental Hygiene
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• v.19 no.1
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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.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.3
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• pp.333-341
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• 2015

In this paper, a 0.5~4 GHz frequency synthesizer having good phase noise performance is proposed. Wideband output frequencies of the synthesizer were synthesized using DDS(Direct Digital Synthesizer) and analog direct frequency synthesis technology in order to obtain fast settling time. Also in order to get good phase noise performance, 2.4 GHz DDS clock was generated by VCO(Voltage Controlled Oscillator) which was locked by the 100 MHz reference oscillator using SPD(Sample Phase Detector). The phase noise performance of wideband frequency synthesizer was estimated and the results were compared with the measured ones. The measured phase noise of the frequency synthesizer was less then -121 dBc @ 100 kHz at 4 GHz.

• Journal of Nutrition and Health
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• v.37 no.10
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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.

• Journal of Nutrition and Health
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• v.39 no.3
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• pp.274-285
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• 2006

The differences in food consumption between highly educated, married, unemployed and employed women were analyzed by food group and common food item intake, DDS (dietary diversity score), and DVS (dietary variety score) & DVSS (dietary variety score including condiment). In food group intake, the total amount of food intake of the unemployed women (1,554.0 g) were significantly higher than those of the employed (1,477.9 g), while the amount of food from fungi and mushrooms (4.2 g), seaweeds (2.4 g), and fish and shellfish (60.5 g) of the unemployed women was significantly lower than those of the employed. And the amount of meat, poultry and their products (102.8 g), eggs (29.9 g), and animal oil and fats (4.0 g) was significantly higher than those of the employed. Moreover, the common food items of the unemployed women were ranked as eggs (29.7 g), pork (28.9 g), chicken (27.2 g), and beef (26.7 g) at 7, 8, 9, and 10, respectively. When counting the major food groups consumed, DDS=4 has the highest proportion in both groups (unemployed 47.4%, employed 49.1 %). In case of the subjects who had not consumed one particular food group in DDS=4, dairy group was the first (83%), followed by fruit, meat, and vegetables. This order is same in other DDS levels. In dietary variety score (DVS & DVSS), the average number of foods consumed per day of employed women was higher than those of the unemployed. The level of DVSS in the employed women (31.9), especially, is significantly higher than in the unemployed women (30.6). Consequently, highly educated women should pay more attention to increasing dairy intake, and they have need of various foods, over thirty foods without condiments in their diet every day. In addition, encouraging unemployed women to have a nutritionally balanced diet, and offering nutrition education and guidance, such as appropriate choices about animal foods, are needed.