• The Journal of Korean Society for Radiation Therapy
• /
• v.24 no.1
• /
• pp.15-21
• /
• 2012

Purpose: Image Guided Radiation Therapy (IGRT) has been carried out using On-Board Imager system (OBI) in Asan Medical Center. For this reason, This study was to analyze and evaluate the impact on Cone-Beam CT according to variation of material and respiration. Materials and Methods: This study was to acquire and analyze Cone-Beam CT three times for two material: Cylider acryl (lung equvalent material, diameter 3 cm), Fiducial Marker (using clinic) under Motion Phantom able to adjust respiration pattern randomly was varying period, amplitude and baseline vis-a-vis reference respiration pattern. Results: First, According to a kind of material, when being showed 100% in the acryl and 120% in the Fiducial Marker under the condition of same movement of the motion phantom. Second, According to the respiratory alteration, when being showed 1.13 in the baseline shift 1.8 mm and 1.27 in the baseline shift 3.3 mm for acryl. when being showed 1.01 in 1 sec of period and 1.045 in 2.5 sec of period for acryl. When being showed 0.86 in 0.7 times the standard of amplitude and 1.43 in 1.7 times the standard of amplitude for acryl. when being showed 1.18 in the baseline shift 1.8 mm and 1.34 in the baseline shift 3.3 mm for Fiducial Marker. when being showed 1.0 in 1 sec of period and 1.0 in 2.5 sec of period for Fiducial Marker. When being showed 0.99 in 0.7 times the standard of amplitude and 1.66 in 1.7 times the standard of amplitude for Fiducial Marker. Conclusion: The effect of image size of CBCT was 20% in the case of Fiducial marker. The impact of changes in breathing pattern was minimum 13% - maximum 43% for Arcyl, min. 18% - max. 66% for Fiducial marker. This difference makes serious uncertainty. So, Must be stabilized breathing of patient before acquiring CBCT. also must be monitored breathing of patient in the middle of acquire. If you observe considerable change of breathing when acquiring CBCT. After Image Guided, must be need to check treatment site using fluoroscopy. If a change is too big, re-acquiring CBCT.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.43 no.6
• /
• pp.16-24
• /
• 2015

This study quantified storage and annual uptake of carbon for riparian greenspaces established in watersheds of four major rivers in South Korea and explored desirable strategies to improve carbon reduction effects of riparian greenspaces. Greenspace structure and planting technique in the 40 study sites sampled were represented by single-layered planting of small trees in low density, with stem diameter at breast height of $6.9{\pm}0.2cm$ and planting density of $10.4{\pm}0.8trees/100m^2$ on average. Storage and annual uptake of carbon per unit area by planted trees averaged $8.2{\pm}0.5t/ha$ and $1.7{\pm}0.1t/ha/yr$, respectively, increasing as planting density got higher. Mean organic matter and carbon storage in soils were $1.4{\pm}0.1%$ and $26.4{\pm}1.5t/ha$, respectively. Planted trees and soils per ha stored the amount of carbon emitted from gasoline consumption of about 61 kL, and the trees per ha annually offset carbon emissions from gasoline use of about 3 kL. These carbon reduction effects are associated with tree growth over five years to fewer than 10 years after planting, and predicted to become much greater as the planted trees grow. This study simulated changes in annual carbon uptake by tree growth over future 30 years for typical planting models selected as different from the planting technique in the study sites. The simulation revealed that cumulative annual carbon uptake for a multilayered and grouped ecological planting model with both larger tree size and higher planting density was approximately 1.9 times greater 10 years after planting and 1.5 times greater 30 years after than that in the study sites. Strategies to improve carbon reduction effects of riparian greenspaces suggest multilayered and grouped planting mixed with relatively large trees, middle/high density planting of native species mixed with fast-growing trees, and securing the soil environment favorable for normal growth of planting tree species. The research findings are expected to be useful as practical guidelines to improve the role of a carbon uptake source, in addition to water quality conservation and wildlife inhabitation, in implementing riparian greenspace projects under the beginning stage.

• Journal of radiological science and technology
• /
• v.26 no.2
• /
• pp.57-61
• /
• 2003

The purpose of this study is to compare both 1.5T and 4.7T in Praietal White matter material Phantom using the same methodology at both field strengths. Data at both field strengths are compared in terms of $T_2$ relaxation times, line widths and SNRs MR imaging and $^1H$ MR spectroscopy were performed on GE 1.5T SIGNA system and Broker Biospec 4.7T/30 MRI/MRS system. After phantom axial scan $^1H$ MRS was obtained from T2 weighted image by 3-dimensional localization technique(PRESS : Point RE solved spectroscopy Sequence) this phantom is composed of an aqueous solution 36.7 mmol/L of NAA, 25.0 mmol/L of Cr, 6.3 mmol/L of choline chloride, 30.0 mmol/L or Glu, and 22.5 mmol/L of MI(adjusted to a pH of 7,15 in a phosphate buffet). Data processed using software developed inhouse. At 1.5T, T2 relaxation times for Cho, Cr, and NAA were $0.41{\pm}0.07,\;0.26{\pm}0.04,\;0.46{\pm}0.07$ while at 4.7T they were $0.17{\pm}0.03,\;0.14{\pm}0.05,\;0.20{\pm}0.03$ respectively. At 1.5T, line widths for water, Cho, Cr and NAA were $2.9{\pm}0.7,\;1.6{\pm}0.7,\;1.7{\pm}0.8,\;2.2{\pm}0.02Hz$ while at 4.7T they were $5.2{\pm}1.1,\;4.6{\pm}1.9,\;4.01{\pm}1.8,\;4.8{\pm}1.9Hz$ respectively. It can be seen that $T_2$ relaxation times were significantly shorter at 4.7 compared to 1.5T and that the line widths were also broader. The average SNRs for NAA for subjects at short and long TEs were $23.5{\pm}11.3$ at TE=20 msec ; $15.4{\pm}7.7$ at TE=272 msec at 1.5T and $40{\pm}8.3$ and $17{\pm}3.5$ respectively at 4.7T higher field strength is superior because of improved sensitivity and chemical shift dispersion. However these improvements are partially offset by increased line widths and decrease $T_2$ relaxation times, which act to reduce both sensitivity and resolution. In our experiments with the equipment available to us, 4.7T proton spectra at short TEs exhibit moderately improved sensitivity compared to 1.5T.

• KDI Journal of Economic Policy
• /
• v.12 no.1
• /
• pp.111-125
• /
• 1990

For the last several years, considerable criticism has been leveled against Korea's exchange rate management. While Korea was designated a currency manipulator by the U.S., domestically it is often complained that the won/dollar rate did not adequately reflect changes in Korea's export competitiveness and fluctuations in the exchange rates of major currencies. In view of this situation, Korea changed its exchange regime at the beginning of March this year from the dual currency basket system to a more flexible one, called a "market average rate regime". Under this new regime, the won rate is determined in the exchange market based upon the supply of and demand for foreign exchange and is allowed to freely fluctuate each day within a + 0.4 % range. This paper, first, seeks to evaluate Korea's exchange rate management under the dual basket regime of the 1980s, and then to construct an optimal currency basket for the won which could provide a proper indicator for exchange market intervention under the new market average rate regime. The analysis of fluctuations in the real effective exchange rate (REER) of the won indicates that the won rates in the 1980s failed not only to offset changes in relative prices between home and trading partner countries, but also to properly respond to variations in major exchange rates as further evidenced by sizable fluctuations in the nominal effective rates of the won. In other words, the currency basket regime which was adopted in 1980 for the stabilization of the REER of the won has not been operated properly, mainly because authorities often resorted to policy considerations in determining the won's rate. In the second part of the paper, an optimal currency basket for Korea is constructed, designed to minimize the fluctuations in the REER of the won without including policy considerations as a factor. It is recognized, however, that both domestic and foreign price data are not available immediately for the calculation of the REER. For this problem, the approach suggested by Lipschitz (1980) is followed, in which optimal weights for currencies in the basket are determined based upon the past correlation between price and exchange rates. When the optimal basket is applied to Korea since the mid-80s, it is found that the REER of the won could have been much more stable than it actually was. We also argue for the use of variable weights rather than fixed ones, which would be determined by the changing relationship between exchange rates and relative prices. The optimal basket, and the optimal basket exchange rate based on that basket, could provide an important medium- or long-term reference for proper exchange market intervention under the market average rate regime, together with other factors, such as developments in the current account balance and changes in productivity.

• Korean Chemical Engineering Research
• /
• v.52 no.3
• /
• pp.321-327
• /
• 2014

Polymer dispersed liquid crystal lenses of the cell gap of $11{\mu}m$ and $30{\mu}m$ were made from a uniformly dispersed mixture of 40 wt% NOA65 prepolymer - 60 wt% E7 liquid crystal with the variations of the additional photoinitiator. The photoinitiator, benzophenone of 5.0 wt% was originally in the commercial prepolymer NOA65. In this works, the influence of the benzophenone amount intentionally added in the commercial NOA65 on the electrical properties of polymer dispersed liquid crystal lens for smart electronic glasses. The additional quantities of the photoinitiator were 1, 2, 4, 8 and 16 wt% of the weight of NOA65 - E7 mixture. All the electro-optical properties of the sample with added benzophenone such as the driving voltage, the slope of the linear region, the response time and contrast ratio were more improved than that of commercial NOA65 only. These improvements were due to the increase of the average size of E7 liquid crystal droplets in the samples with the increase of the added benzophenon amount. The liquid crystal droplet size was increased from $5.3{\mu}m$ to $12.2{\mu}m$ when the photoinitiator was added from 0 wt% to 8 wt%. At the same concentration range of the photoinitiator, the driving voltage was ranged from 11.1 V to 17.3 V. The slopes of the linear region were in the range of 10.35~13.96 %T/V, which were more enhanced than that of NOA65 without the additional benzophenone. In particular, though the deteriorations by cell gap of $11{\mu}m$ were so effective to offset the influence of the added benzophenone for both rising and falling response time, it is confirmed that there were still somewhat improvement by the additional benzophenone. Response time and contrast ratios of all the samples with excess benzophenone were slightly enhanced.

• Journal of Environmental Policy
• /
• v.8 no.2
• /
• pp.83-118
• /
• 2009

Clean Development Mechanism(CDM) projects under the Kyoto Protocol have two objectives. One is to assist the Parties included in Annex I in achieving compliance with their quantified emission limitation and reduction commitments in cost-effective ways by allowing them to implement emission reduction projects in Non-Annex I countries and receive CERs, which will offset their reduction commitments. The other is to assist Parties not included in Annex I in achieving sustainable development and technology transfers through investments by Annex I countries. However, in reality, it is said that the former objective is achievable but the latter is not. In this light, this article suggests sustainability appraisal criteria applicable for Korea. Among various methodologies, we used the 'multi-attributes utility theory(MAUT)'; one of the 'multi-criteria analysis (MCA)' methodologies judged to be the most practical and relevant. Based on the guidelines of the MAUT methodology, we identified sustainability criteria that meet the guidelines. We took two tracks, the first to find the preferences of Korean experts, and the other to check foreign cases. In all, 37 preliminary criteria were suggested to Korean experts and each criterion was scored, from between 1 and 3, in terms of relevance, possibility of real improvement, easiness of data collection, and preferences. We combined foreign cases and the results of a survey conducted in Korea and selected 12 core criteria and 10 additional criteria. After that, all the criteria were converted into indicators. The indicators were applied to a CDM project for case study. We chose the "Sihwa Tidal Power Project", which is currently the biggest tidal power plant in the world. Twelve core indicators and 3 additional indicators were applied. In order to weight each indicator, the 'analytical hierarchy process (AHP)' was used. A total of 30 experts were asked to suggest weights and 21 answered. Among them, only 14 respondents were proven to meet the consistency ratio. We analyzed the 14 responses through Expert Choice and the CDM project was scored (+)53.082. In addition, sensitivity analysis was undertaken with the result of (+)44.667 to (+)65.522. As a result of this study, it was proven that this project would contribute to the sustainable development of Korea.

• Journal of the Korea Society of Computer and Information
• /
• v.16 no.10
• /
• pp.101-109
• /
• 2011

The Riemann's zeta function $\zeta(s)$ has been known as answer for a number of primes $\pi$(x) less than given number x. In prime number theorem, there are another approximation function $\frac{x}{lnx}$,Li(x), and R(x). The error about $\pi$(x) is R(x) < Li(x) < $\frac{x}{lnx}$. The logarithmic integral function is Li(x) = $\int_{2}^{x}\frac{1}{lnt}dt$ ~ $\frac{x}{lnx}\sum\limits_{k=0}^{\infty}\frac{k!}{(lnx)^k}=\frac{x}{lnx}(1+\frac{1!}{(lnx)^1}+\frac{2!}{(lnx)^2}+\cdots)$. This paper shows that the $\pi$(x) can be represent with finite Li(x), and presents generalized prime counting function $\sqrt{{\alpha}x}{\pm}{\beta}$. Firstly, the $\pi$(x) can be represent to $Li_3(x)=\frac{x}{lnx}(\sum\limits_{t=0}^{{\alpha}}\frac{k!}{(lnx)^k}{\pm}{\beta})$ and $Li_4(x)=\lfloor\frac{x}{lnx}(1+{\alpha}\frac{k!}{(lnx)^k}{\pm}{\beta})}k\geq2$ such that $0{\leq}t{\leq}2k$. Then, $Li_3$(x) is adjusted by $\pi(x){\simeq}Li_3(x)$ with ${\alpha}$ and error compensation value ${\beta}$. As a results, this paper get the $Li_3(x)=Li_4(x)=\pi(x)$ for $x=10^k$. Then, this paper suggests a generalized function $\pi(x)=\sqrt{{\alpha}x}{\pm}{\beta}$. The $\pi(x)=\sqrt{{\alpha}x}{\pm}{\beta}$ function superior than Riemann's zeta function in representation of prime counting.

• 한국지구물리탐사학회:학술대회논문집
• /
• 2004.08a
• /
• pp.70-83
• /
• 2004

The safety diagnosis of cultural assets is Primarily focused on its non-destructiveness. Research on the nondestructive diagnosis and conservation of masonry cultural heritage is the key which is considered by technologic kernel. Geophyscial Prospecting as nondestructive diagnostic technology plays an important role in the characterization of the foundation of stone pagodas. It is natural that understanding of shallow subsurface condition beneath them is essential for their structural safety diagnosis. As an example, the nondestructive geophysical methods were applied to two three-story stone pagodas, Seokgatap (height 10.8 m, width 4.4 m, weight 82.3 ton) and Dabotap (height 10.4 m, width 7.4 m, weight 123.2 ton) which were built in 791 at Bulkuksa temple. An earlier archaeological investigation shows that stone pagodas have experienced severe weathering process and are slightly leaning, which will threaten their stability At the base part of Dabotap, an offset of the stone alignment is also observed. Direct measurements of ultrasonic velocities was introduced for the mechanical properties of the stone The velocity ranges of ultrasonic waves for Dabotap and Seokgatap are 1217${\~}$4403 m/s and 584${\~}$5845 m/s, respectively, and the estimated averages of the uniaxial compressive strength are 463 kg/$cm^2$ and 409 kg/$cm^2$, respectively. Site characteristics, around the pagodas are determined by the measurement of multiple properties such as seismic velocity, resistivity, image of ground-penetrating radar, On the basis of the higher velocity structure, the site of Seokgatap appears to have solider stability than the Seokgatap site. Near the pagodas, higher(up to 2200 $\Omega$m) resistivity is present whereas their outskirts have as low as 200 $\Omega$m. By the combined results of each geophyscial methods, the subsurface boundaries of two stone pagodas are revealed. The Dabotap site is in the form of an octagon having 6-m-long side with the depth of ${\~}$4 m, whereas the Seokgatap site is the 8 ${\times}$ 10 m rectangle with the depth of 3 m. These subsurface structures appear to reflect the original foundations constructed against the stone load of ${\~}8 ton/m^2$. At the subsurface beneath the northeast of each pagoda, low seismic velocity as well as low resistivity is prominent. It is interpreted to represent the weak underground condition which Is the possible cause of the slightly leaning pagodas toward the NNW.

• Geophysics and Geophysical Exploration
• /
• v.11 no.1
• /
• pp.1-14
• /
• 2008

We present a method for interpreting seismic records with arrivals and waveforms having characteristics which could be generated by extremely inhomogeneous velocity structures, such as non-typical oceanic crust, decollement at subduction zones, and seamounts in oceanic regions, by comparing them with synthetic waveforms. Recent extensive refraction and wide-angle reflection surveys in oceanic regions have provided us with a huge number of high-resolution and high-quality seismic records containing characteristic arrivals and waveforms, besides first arrivals and major reflected phases such as PmP. Some characteristic waveforms, with significant later reflected phases or anomalous amplitude decay with offset distance, are difficult to interpret using only a conventional interpretation method such as the traveltime tomographic inversion method. We find the best process for investigating such characteristic phases is to use an interactive interpretation method to compare observed data with synthetic waveforms, and calculate raypaths and traveltimes. This approach enables us to construct a reasonable structural model that includes all of the major characteristics of the observed waveforms. We present results here with some actual observed examples that might be of great help in the interpretation of such problematic phases. Our approach to the analysis of waveform characteristics is endorsed as an innovative method for constructing high-resolution and high-quality crustal structure models, not only in oceanic regions, but also in the continental regions.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.53 no.5
• /
• pp.87-97
• /
• 2016

This work proposes a time-shared 10b DAC based on a two-step resistor string to minimize the effective area of a DAC channel for driving each AMOLED display column. The proposed DAC shows a lower effective DAC area per unit column driver and a faster conversion speed than the conventional DACs by employing a time-shared DEMUX and a ROM-based two-step decoder of 6b and 4b in the first and second resistor string. In the second-stage 4b floating resistor string, a simple current source rather than a unity-gain buffer decreases the loading effect and chip area of a DAC channel and eliminates offset mismatch between channels caused by buffer amplifiers. The proposed 1-to-24 DEMUX enables a single DAC channel to drive 24 columns sequentially with a single-phase clock and a 5b binary counter. A 0.9pF sampling capacitor and a small-sized source follower in the input stage of each column-driving buffer amplifier decrease the effect due to channel charge injection and improve the output settling accuracy of the buffer amplifier while using the top-plate sampling scheme in the proposed DAC. The proposed DAC in a $0.18{\mu}m$ CMOS shows a signal settling time of 62.5ns during code transitions from '$000_{16}$' to '$3FF_{16}$'. The prototype DAC occupies a unit channel area of $0.058mm^2$ and an effective unit channel area of $0.002mm^2$ while consuming 6.08mW with analog and digital power supplies of 3.3V and 1.8V, respectively.