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Eliades, J.A.,Kim, J.K.,Song, J.H.,Yu, B.Y. Elsevier 2015 Nuclear instruments & methods in physics research. Vol.361 No.-
<P><B>Abstract</B></P> <P>Radio-frequency quadrupole (RFQ) technology incorporated into the low energy ion beam line of an accelerator system can greatly broaden the range of applications and facilitate unique experimental capabilities. However, ten’s of keV kinetic energy negative ion beams with large emittances and energy spreads must first be decelerated down to <100eV for ion–gas interactions, placing special demands on the deceleration optics and RFQ design. A system with large analyte transmission in the presence of gas has so far proven challenging. Presented are computer simulations using SIMION 8.1 for an ion deceleration and RFQ ion guide instrument design. Code included user-defined gas pressure gradients and threshold energies for ion–gas collisional losses. Results suggest a 3mm diameter, 35keV <SUP>36</SUP>Cl<SUP>−</SUP> ion beam with 8eV full-width half maximum Gaussian energy spread and 35mrad angular divergence can be efficiently decelerated and then cooled in He gas, with a maximum pressure of 7mTorr, to 2eV within 450mm in the RFQs. Vacuum transmissions were 100%. Ion energy distributions at initial RFQ capture are shown to be much larger than the average value expected from the deceleration potential and this appears to be a general result arising from kinetic energy gain in the RFQ field. In these simulations, a potential for deceleration to 25eV resulted in a 30eV average energy distribution with a small fraction of ions >70eV.</P>
10Be, 26Al, 36Cl, 41Ca and 1291 AMS - Internal Data Analysis Software at KIST
ELIADES, John A(일랴드스존) 한국진공학회 2021 한국진공학회 학술발표회초록집 Vol.2021 No.2
Because of their very trace natural abundances, 10Be, 26Al, 36Cl, 41Ca and 129I are measured by accelerator mass spectrometry (AMS). However, chemical pretreatment techniques produce either highly resistive materials (ex. BeO and Al<sub>2</sub>O<sub>3</sub>) or compounds that are volatile at higher temperature (CaF<sub>2</sub>, AgI, AgCI). These are therefore mixed with a second powder (ex. Ag) to aid the sputtering process, and pressed into metal cathodes. Quality varies, especially when users prepare their own cathodes. Problems can include violent ion beam instability and premature drop in current. Since cathodes are analyzed for 30 minutes in 30 s block intervals, data from poor cathodes can still be used if blocks with poor current quality are excluded. While the KIST 6MV AMS system manufacturer software produces a result file that summarizes the data for each cathode, an internal Visual Basic program run through Microsoft Excel is used to analyze the raw data from each 30 s block to determine if there was a spurious period in the data acquisition. As the radio-isotope produces only several to several thousand counts in 30 mins, the stable isotope beam currents (typically in the range 1 µA to 10 µA) are monitored for inter-block beam stability using both the high energy beam stability and the accelerator injection current to high energy current ratio stability. Isotope ratio stability and rare-isotope detector dead time are also monitored by 10 min run intervals. Finally, overall cathode current during the entire 30 min period is monitored. The program calculates averages and uncertainties both for the full data set and the data less flagged points, and provides the analyst with a quick graphical interface to plot data through a user-form. Data flagging will be discussed, along with examples of data that have been discarded based on monitoring flags.
Applications of various ion beam using a KIST 400 ㎸ accelerator
W.C. Lim,J.A. Eliades,J.P. Singh,K. H. Chae,T. Seong,J. Song 한국진공학회 2021 한국진공학회 학술발표회초록집 Vol.2021 No.2
As the industrial era moves into the information era, it’s necessary to process and store a lot of data more quickly and reliably. In order to satisfy these needs, numerous studies on the development of new semiconductors are being conducted using implantation However, due to the limited number of elements that can be produced by most systems for ion implantation researches, development of new materials has likewise been limited. In particular, we have increased the number of elements available on our 400 kV accelerator system from less than 5 to 30, including Li, Be, Na, Mg, Al, and Si.
Marietta Krüsi,Demetrios J. Halazonetis,Theodore Eliades,Vasiliki Koretsi 대한치과교정학회 2023 대한치과교정학회지 Vol.53 No.3
Objective: The growth and development of the mandible strongly depend on modeling changes occurring at its ramus. Here, we investigated covariance patterns between the morphology of the ramus and the rest of the face. Methods: Lateral cephalograms of 159 adults (55 males and 104 females) with no history of orthodontic treatment were collected. Geometric morphometrics with sliding semi-landmarks was used. The covariance between the ramus and face was investigated using a two-block partial least squares analysis (PLS). Sexual dimorphism and allometry were also assessed. Results: Differences in the divergence of the face and anteroposterior relationship of the jaws accounted for 24.1% and 21.6% of shape variation in the sample, respectively. Shape variation was greater in the sagittal plane for males than for females (30.7% vs. 17.4%), whereas variation in the vertical plane was similar for both sexes (23.7% for males and 25.4% for females). Size-related allometric differences between the sexes accounted for the shape variation to a maximum of 6% regarding the face. Regarding the covariation between the shapes of the ramus and the rest of the face, wider and shorter rami were associated with a decreased lower anterior facial height as well as a prognathic mandible and maxilla (PLS 1, 45.5% of the covariance). Additionally, a more posteriorly inclined ramus in the lower region was correlated with a Class II pattern and flat mandibular plane. Conclusions: The width, height, and inclination of the ramus were correlated with facial shape changes in the vertical and sagittal planes.
Outcomes of comprehensive fixed appliance orthodontic treatment
Spyridon N. Papageorgiou,Damian Hochli,Theodore Eliades 대한치과교정학회 2017 대한치과교정학회지 Vol.47 No.6
Objective: The aim of this systematic review was to assess the occlusal outcome and duration of fixed orthodontic therapy from clinical trials in humans with the Objective Grading System (OGS) proposed by the American Board of Orthodontics. Methods: Nine databases were searched up to October 2016 for prospective/retrospective clinical trials assessing the outcomes of orthodontic therapy with fixed appliances. After duplicate study selection, data extraction, and risk of bias assessment according to the Cochrane guidelines, random-effects meta-analyses of the mean OGS score and treatment duration were performed and 95% confidence intervals (CIs) were calculated. Results: A total of 34 relevant clinical trials including 6,207 patients (40% male, 60% female; average age, 18.4 years) were identified. The average OGS score after treatment was 27.9 points (95% CI, 25.3–30.6 points), while the average treatment duration was 24.9 months (95% CI, 24.6–25.1 months). There was no significant association between occlusal outcome and treatment duration, while considerable heterogeneity was identified. In addition, orthodontic treatment involving extraction of four premolars appeared to have an important effect on both outcomes and duration of treatment. Finally, only 10 (39%) of the identified studies matched compared groups by initial malocclusion severity, although meta-epidemiological evidence suggested that matching may have significantly influenced their results. Conclusions: The findings from this systematic review suggest that the occlusal outcomes of fixed appliance treatment vary considerably, with no significant association between treatment outcomes and duration. Prospective matched clinical studies that use the OGS tool are needed to compare the effectiveness of orthodontic appliances.