• 제목/요약/키워드: DFT study

검색결과 379건 처리시간 0.029초

A Study on the Low Power Line Modulation and Power Line Channel Modeling (저압 전력선 통신 변조 기법 및 전력선 채널 특성)

  • Kand Duk-Ha;Heo Yoon-Seok;Cho Ki-Hyung;Lee Dae-Young
    • The Journal of Information Technology
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    • 제5권4호
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    • pp.1-8
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    • 2002
  • This thesis is about power line communication(PLC) over the low voltage grid. The main advantage with power line communication is the use of an existing infrastructure. The PLC channel can be modeled as having multi-path propagation with frequency-selective fading, typical power lines exhibit signal attenuation increasing with length and frequency. OFDM(Orthogonal Frequency Division Multiplexing) is a modulation technique where multiple low data rate carriers are combined by a transmitter to form a composite high data rate transmission. To implement the multiple carrier scheme using a bank of parallel modulators would not be very efficient in analog hardware. Each carrier in an OFDM is a sinusoid with a frequency that is an integer multiple of a base or fundamental sinusoid frequency. Therefore, each carrier is a like a Fourier series component of the composite signal. In fact, it will be shown later that an OFDM signal is created in the frequency domain, and then transformed into the time domain via the Discrete Fourier Transform(DFT).

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FRF based Position Controller Design through System Identification for A Hydraulic Cylinder (유압실린더의 위치제어를 위한 시스템 인식을 통한 FRF 기반의 제어기 설계 방법)

  • Seo, Hyoung Kyu;Kim, Dong Hwan;Park, Jong Won
    • Transactions of the Korean Society of Mechanical Engineers A
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    • 제39권11호
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    • pp.1113-1121
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    • 2015
  • In this study, we have focused on the design of a controller and an operating program for the operation of the hydraulic actuators used in a shaker. To control the motion of the shaker accurately, the position of each hydraulic cylinder should be controlled precisely even under an uncertain environment. For this purpose, we have suggested a control algorithm using an FRF (frequency response function) based control which senses the behavior of the actuator in advance, calculates a transfer function through the system identification method, and provides the final control input. The experimental results on the performance of this system were compared with that of a simple PID control algorithm.

Frontier Orbitals of Fifteen C20H17(OH)3 Regioisomers: Hybrid DFT B3LYP Study

  • Lee, Seol;Lee, Ji Young;Lee, Kee Hag
    • Bulletin of the Korean Chemical Society
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    • 제34권8호
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    • pp.2403-2407
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    • 2013
  • The hybrid density-functional (B3LYP/6-31G(d,p)) method was used to analyze the substitution effect on the $C_{20}H_{20}$ cage based on calculation of the frontier orbitals of fifteen $C_{20}H_{17}(OH)_3$ derivatives. All substitution products were geometrically optimized without constraints and confirmed by frequency analysis. The results suggest that the cis-1 cis-1 cis-2 regioisomer is the most stable isomer, which implies that hydrogen bonding exerts a stronger effect on the relative energies of the trihydroxide than long-range interactions. Thus, this supports the experimental result in which the bisvicinal tetrol was of particular preparative-synthetic interest. While the LUMO of each of the $C_{20}H_{17}(OH)_3$ regioisomers was equivalently delocalized over the void within the cage, the HOMO was limitedly delocalized on substituents and carbons in close proximity to the substituents. The characteristics of the HOMO of each of the regioisomers vary based on the substitution sites. This indicates that the 15 regioisomers of each $C_{20}H_{20}$ trisubstituted derivative might undergo an entirely different set of characteristic chemical reactions with electrophilic reagents. The results further suggest that the penta-substituted OH groups on the surface of the fullerene cage are more likely to be localized on a pentagon than to be homogeneously delocalized.

A Study on the Vibration Decibel Related to the Shape of Rumble Strip Located on the Highway Tollgate (고속도로 톨게이트 근처 럼블스트립 형태에 따른 진동 데시벨 연구)

  • Kim, Do Wan;Jang, Yeong Sun;Mun, Sung Ho
    • International Journal of Highway Engineering
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    • 제15권6호
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    • pp.93-101
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    • 2013
  • PURPOSES : The rumble strip installed at the highway near the tollgate has the purpose to reduce the vehicle velocity or prevent sleepiness by awakening people to the danger. These rumble strip has different vibration decibel from the rumble strip shapes, resulting in some fatigue damage to human because a driver suffers from a lot of stress and displeasure. In this connection, the objective of this paper is to analyze the vibration decibel perceived by a driver in the vehicle under some conditions. METHODS : The vibration decibel conveyed from the tire can be analyzed. The frequency analysis methods were used according to DFT (Discrete Fourier Transform) analysis, FFT (Fast Fourier Transform) analysis, CPB (Constant Percentage Bandwidth) analysis. But the frequency analysis method in this paper is the 1/24 OCT(Octave) band analysis because of the convenience of the analysis and the overall vibration amplitude along the frequency. RESULTS : By using the results of the vibration decibel after analyzing the 1/24 OCT band analysis, these results can be compared from some conditions (e.g., rumble strip shape, uniform velocity of a vehicle, road condition, mass of a vehicle). As a result, the numerical values of decibel are not directly proportional to the vehicle velocity. CONCLUSIONS : At the condition that a vehicle is passing by the rumble strip, the value of a vibration decibel at the rumble strip of the cylinder shape is smaller than the rumble strip of rectangular shape regardless of the rumble strip depth and width. At the mass condition, the more a vehicle is massive, the more the vibration decibel increases. At the road condition, the vibration decibel at the wet road is smaller than the value at dry road condition.

Theoretical Investigation of Water Adsorption Chemistry of CeO2(111) Surfaces by Density Functional Theory (전자밀도함수이론을 이용한 세륨 산화물의 (111) 표면에서 일어나는 물 흡착 과정 분석)

  • Choi, Hyuk;Kang, Eunji;Kim, Hyun You
    • Korean Journal of Materials Research
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    • 제30권5호
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    • pp.267-271
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    • 2020
  • Cerium oxide (ceria, CeO2) is one of the most wide-spread oxide supporting materials for the precious metal nanoparticle class of heterogeneous catalysts. Because ceria can store and release oxygen ions, it is an essential catalytic component for various oxidation reactions such as CO oxidation (2CO + O2 2CO2). Moreover, reduced ceria is known to be reactive for water activation, which is a critical step for activation of water-gas shift reaction (CO + H2O → H2 + CO2). Here, we apply van der Waals-corrected density functional theory (DFT) calculations combined with U correction to study the mechanism of water chemisorption on CeO2(111) surfaces. A stoichiometric CeO2(111) and a defected CeO2(111) surface showed different water adsorption chemistry, suggesting that defected CeO2 surfaces with oxygen vacancies are responsible for water binding and activation. An appropriate level of water-ceria chemisorption energy is deduced by vdW-corrected non-local correlation coupled with the optB86b exchange functional, whereas the conventional PBE functional describes weaker water-ceria interactions, which are insufficient to stabilize (chemisorb) water on the ceria surfaces.

Interaction of $HfCl_4$ with Two Hydroxyl's on Si (001) Surface: A First Principles Study ($HfCl_4$와 Si (001) 표면에 결합된 두 개의 수산화기와의 상호작용: 제일원리 연구)

  • Kim, Dae-Hyun;Kim, Dae-Hee;Seo, Hwa-Il;Kim, Yeong-Cheol
    • Journal of the Semiconductor & Display Technology
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    • 제8권2호
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    • pp.55-58
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    • 2009
  • Density functional theory was used to investigate the adsorption and reaction of $HfCl_4$ with two hydroxyls on Si (001)-$2{\times}1$ surface in atomic layer deposition (ALD) process. We prepared a reasonable Si substrate which consisted of six inter-dimer dissociated $H_2O$ molecules and two intra-dimer dissociated $H_2O$ molecules. The $HfCl_4$must react with two hydroxyls to be a bulk-like structure. When $HfCl_4$ was adsorbed on a hydroxyl, there was energy benefit of -0.55 eV. Though there was energy loss for $HfCl_4$ to react with H of hydroxyl, thermal energy of ALD chamber would be enough to pass the energy barriers. There were five reaction pathways for $HfCl_4$ to react with two hydroxyls; inter-dimer, intra-dimer, cross-dimer, inter-row, and cross-row. Inter-row, inter-dimer and intra-dimer were relatively favorable among the five reaction pathways based on the energy difference. The electron densities between O and Hf in these three reactions were higher than the others and they had shorter Hf-O and O-O bond lengths than the other two reaction pathways.

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Selection of appropriate nutrient solution for simultaneous hydroponics of three leafy vegetables (Brassicaceae)

  • Young Hwi, Ahn;Seung Won, Noh;Sung Jin, Kim;Jong Seok, Park
    • Korean Journal of Agricultural Science
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    • 제49권3호
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    • pp.643-653
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    • 2022
  • This study investigated which nutrient solution is suitable for growth and secondary metabolite contents when three different vegetable plants are grown simultaneously in one hydroponic cultivation bed. Seeds of pak choi (Brassica compestris L. ssp chinsensis), red mustard (Brassica juncea L.), and arugula (Eruca sativa Mill.) were sown in the shape of a triangle in three places on rockwool cubes. The rockwool cubes were placed in semi deepflow technique (semi-DFT) hydroponic systems in a rooftop greenhouse after three weeks of growth as seedlings then cultivated with four different nutrient solutions, Korea Horticultural Experiment Station (KHE), Hoagland, Otsuka-A, and Yamazaki, at the rooftop greenhouse for two weeks. The leaf area of pak choi cultivated in Otsuka-A was the largest but SPAD values, leaf area, and fresh weight of arugula were highest with KHE treatment. The total glucosinolate (GSL) content of pak choi was 151.7% higher in KHE than in Hoagland, and there was no significant difference in Yamazaki and Otsuka-A treatments. The total GSL content of red mustard was 34.6 μmol·g-1 in Hoagland, and it was 32.6% higher in Hoagland than in Yamazaki. Total GSL content of arugula was 57.5% higher in Yamazaki and Hoagland nutrients than in KHE and Otsuka-A nutrients solutions. The total GSL content of three plants grown with KHE was 40.7% higher than with Yamazaki, and the other nutrient solutions did not show significant differences. Therefore, KHE nutrient solution is considered suitable for nutrient solution composition for the cultivation of three different Brassicaceae crops in a single hydroponic cultivation system.

Identification of Selective STAT1 Inhibitors by Computational Approach

  • Veena Jaganivasan;Dona Samuel Karen;Bavya Chandrasekhar
    • Journal of Integrative Natural Science
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    • 제16권3호
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    • pp.81-95
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    • 2023
  • Colorectal cancer is one of the most common types of cancer worldwide, ranking third after lung and breast cancer in terms of global prevalence. With an expected 1.93 million new cases and 935,000 deaths in 2020, it is more prevalent in males than in women. Evidence has shown that during the later stages of colon cancer, STAT1 promotes tumor progression by promoting cell survival and resistance to chemotherapy. Recent studies have shown that inhibiting STAT1 pathway leads to a reduction in tumor cell proliferation and growth, and can also promote apoptosis in colon cancer cells. One of the recent approaches in the field of drug discovery is drug repurposing. In drug repurposing approach we have virtually screened FDA database against STAT1 protein and their interactions have been studied through Molecular docking. Cross docking was performed with the top 10 compounds to be more specific with STAT1 comparing the affinity with STAT2, STAT3, STAT4, STAT5a, STAT5b and STAT6. The drugs that showed higher affinity were subjected to Conceptual - Density functional theory. Besides, the Molecular dynamic simulation was also carried out for the selected leads. We also validated in-vitro against colon cancer cell lines. The results showed mainly Acetyldigitoxin has shown better binding to the target. From this study, we can predict that the drug Acetyldigitoxin has shown noticeable inhibitory efficiency against STAT1, which in turn can also lead to the reduction of tumor cell growth in colon cancer.

A Study on the Oral Health State in Children at Age 5 and the Oral Health Behavior in Mothers for Some Parts of Gyeonggi Region (일부 경기지역 5세 아동의 구강건강실태와 어머니의 구강건강행위에 관한 연구)

  • Han, Ji-Hyoung;Lim, Do-Seon;Ahn, Yong-Soon
    • Journal of dental hygiene science
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    • 제9권1호
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    • pp.115-120
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    • 2009
  • The purpose of this study was to utilize it as a basic data for local self-government in each region to plan and perform the oral health program targeting children and mothers as guardian. Data had been obtained by using children's oral examination and mothers' self-reported questionnaire method from June 1 to June 30 in 2007 targeting kindergartens where are located in the region of Hwaseong city. The survey was conducted targeting totally 239 people. Its results are as follows. 1. The healthy-tooth rate in the whole children accounted for 79.12%, thus girls were indicated to be a little higher with 80.36% than boys with 78.13%. Carious-tooth rate showed 8.74% for boys and 6.07% for girls. The dental-caries experience treatment rate showed 11.37% for boys and 12.59% for girls. 2. The index of children at age 5, df rate was 39.3% in the whole, thereby having been indicated that boys with 41.3% are higher than girls with 37.2%. Even dft index is showing the higher index in boys with 3.9 than girls with 3.2. 3. As a result of examining mothers' oral-health behavior, mothers with out employment thought the self oral-health state to be good(p = 0.002). In appearance of scaling experience or of periodic dental checkup, a slight difference is being shown according to general characteristics, but wasn't significant. 4. As a result of examining children's oral management, it was indicated that the higher economic level(p = 0.011) and the more in mothers without employment lead to giving a light meal less(p = 0.41). In appearance of children's periodic dental checkup, the higher academic background level(p = 0.047) and the more employment(p = 0.044) led to receiving dental examination.

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ORAL HEALTH BEHAVIORS OF MOTHERS AND DENTAL CARIES IN CHILDREN FROM MULTICULTURAL FAMILIES (다문화가족 어머니의 구강건강행동과 자녀의 치아우식경험에 관한 연구)

  • Lee, Hye-Lim;Lee, Kwang-Hee;La, Ji-Young;An, So-Youn;Kim, Yun-Hee
    • Journal of the korean academy of Pediatric Dentistry
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    • 제39권2호
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    • pp.111-119
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    • 2012
  • The objectives of this study were to evaluate oral health status of children in multicultural families and compare oral health behaviors of multicultural mothers with those of ordinary Korean families. The mothers' social characters, oral health behaviors and oral health status of children were investigated so that the data from this study can be utilized in developing programs for oral health care promotion especially designed for multicultural families. The subjects were 135 pairs of multicultural mothers and their children who participated in the community programs in suburban areas of Ik-san city and 168 pairs of ordinary Korean mothers and their children residing in Ik-san city. The results were as follows : 1. The dft index and dfs index of multicultural subjects were 4.17 and 6.67, respectively, while ordinary Korean subjects were found to have 2.69 and 4.63($p$ <0.05). 2. The frequency of tooth brushing per day of children from multicultural families was lower than that of children from ordinary Korean families($p$ <0.01). 3. The ratio of practice of oral health behaviors of mothers from multicultural families was lower than that of mothers from ordinary Korean families($p$ <0.01). Tooth brushing instructions were the most frequently carried out by multicultural mothers, which was followed by teaching the importance of oral health, restriction of carbohydrates, and dental check-ups. Significant correlations were not detected between mothers'oral health behaviors and children's dental caries experiences($p$ >0.05).