• Radiation Oncology Journal
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• v.20 no.1
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• pp.24-33
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• 2002

Purpose : In order to improve dose homogeneity and to reduce acute toxicity in tangential whole breast radiotherapy, we evaluated two treatment techniques using multiple static fields or universal compensators. Materials and Methods : 1) Multistatic field technique : Using a three dimensional radiation treatment planning system, Adac Pinnacle 4.0, we accomplished a conventional wedged tangential plan. Examining the isodose distributions, a third field which blocked overdose regions was designed and an opposing field was created by using an automatic function of RTPS. Weighting of the beams was tuned until an ideal dose distribution was obtained. Another pair of beams were added when the dose homogeneity was not satisfactory. 2) Universal compensator technique : The breast shapes and sizes were obtained from the CT images of 20 patients who received whole breast radiation therapy at our institution. The data obtained were averaged and a pair of universal physical compensators were designed for the averaged data. DII (Dose Inhomogeneity Index : percentage volume of PTV outside $95\~105\%$ of the prescribed dose) $D_{max}$ (the maximum point dose in the PTV) and isodose distributions for each technique were compared. Results : The multistatic field technique was found to be superior to the conventional technique, reducing the mean value of DII by $14.6\%$ (p value<0.000) and the $D_{max}$ by $4.7\%$ (p value<0.000). The universal compensator was not significantly superior to the conventional technique since it decreased $D_{max}$ by $0.3\%$ (p value=0.867) and reduced DII by $3.7\%$ (p value=0.260). However, it decreased the value of DII by maximum $18\%$ when patients' breast shapes fitted in with the compensator geometry. Conclusion : The multistatic field technique is effective for improving dose homogeneity for whole breast radiation therapy and is applicable to all patients, whereas the use of universal compensators is effective only in patients whose breast shapes fit inwith the universal compensator geometry, and thus has limited applicability.

• The Korean Journal of Physiology and Pharmacology
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• v.4 no.3
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• pp.197-210
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• 2000

Suppressive role of $Na^+-Ca^{2+}$ exchange in myocardial tension generation was examined in the negative frequency-force relationship (FFR) of electric field stimulated left atria (LA) from postnatal developing rat heart and in the whole-cell clamped adult rat ventricular myocytes with high concentration of intracellular $Ca^{2+}$ buffer (14 mM EGTA). LA twitch amplitudes, which were suppressed by cyclopiazonic acid in a postnatal age-dependent manner, elicited frequency-dependent and postnatal age-dependent enhancements after $Na^+-reduced,\;Ca^{2+}-depleted$ (26 Na-0 Ca) buffer application. These enhancements were blocked by caffeine pretreatment with postnatal age-dependent intensities. In the isolated rat ventricular myocytes, stimulation with the voltage protocol roughly mimicked action potential generated a large inward current which was partially blocked by nifedipine or $Na^+$ current inhibition. 0 Ca application suppressed the inward current by $39{\pm}4%$ while the current was further suppressed after 0 Na-0 Ca application by $53{\pm}3%.$ Caffeine increased this inward current by $44{\pm}3%$ in spite of 14 mM EGTA. Finally, the $Na^+$ current-dependent fraction of the inward current was increased in a stimulation frequency-dependent manner. From these results, it is concluded that the $Ca^{2+}$ exit-mode (forward-mode) $Na^+-Ca^{2+}$ exchange suppresses the LA tension by extruding $Ca^{2+}$ out of the cell right after its release from sarcoplasmic reticulum (SR) in a frequency-dependent manner during contraction, resulting in the negative frequency-force relationship in the rat LA.

• Korean Journal of Veterinary Research
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• v.36 no.3
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• pp.599-605
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• 1996

This study was designed to examine the mechanism of penile erection in adult bull by analyzing the responses of bovine proximal retractor penile muscle strips(BRP) to electtical field stimulation(EFS), exogenous nitric oxide(NO), NO synthesis precursor(L-arginine), NO synthase inhibitors(L-NAME, L-NMMA), guanylate cyclase inhibitor(methylene blue) and nonspecific potassium channel blocker(tetraethylammonium, TEA) treatments. Isometric tension of BRP was measured using physiograph. Results were summarized as follows: 1. EFS of nonadrenergic noncholinrgic(NANC) nerve in BRP produced frequency-dependent inhibitory responses to the contraction induced by co-treatment of epinephrine, guanethidine and atropine. The inhibitory responses to EFS were blocked by tetrodotoxin(TTX, $1{\mu}M$). 2. Treatment of L-NAME ($10,\;20{\mu}M$) inhibited the relaxation to EFS whereas L-NMMA ($100{\mu}M$) had no effect. 3. Treatment of NO($20,\;40{\mu}M$; as an acidified solution of $NaNO_2$) induced concentration-dependent relaxation whereas preincubation of TTX($1{\mu}M$) and L-NAME($20{\mu}M$) had no effect on the relaxation response. 4. L-arginine treatment(10mM) blocked the inhibitory effect of L-NAME($20{\mu}M$). 5. Pretreatment of methylene blue($40{\mu}M$) reduced the NANC-induced relaxation of BRP. 6. Tetraethylammonium(TEA, 80mM) reduced NANC relaxation. These results suggest that NO may act as a NANC neurotransmitter in BRP and the effects might be mediated by cGMP and potassium channel.

• International Journal of Highway Engineering
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• v.18 no.1
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• pp.119-129
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• 2016

PURPOSES : The purpose of this study is to develop a methodology for estimating additional carbon emissions due to freeway incidents. METHODS : As our country grows, our highway policy has mainly neglected the environmental and social sectors. However, with the formation of a national green growth keynote and an increase in the number of people interested in environmental and social issues, problems related to social issues, such as traffic accidents and congestion, and environmental issues, such as the impact of air pollution caused by exhaust gases that are emitted from highway vehicles, are beginning to be discussed. Accordingly, studies have been conducted on a variety of environmental aspects in the field of road transport, and for the quantitative calculation of greenhouse gas emissions, using various methods. However, in order to observe the effects of carbon emissions, microscopic simulations must use many difficult variables such as cost, analysis time, and ease of analysis process. In this study, additional greenhouse gas emissions that occur because of highway traffic accidents were classified by type (incident handling time, number of lanes blocked, freeway level of service), and the annual additional emissions based on incidents were calculated. According to the results, congestion length and emissions tend to increase with an increase in incident clearance time, number of occupied lanes, and worsening level of service. Using this data, we analyzed accident data on the Gyeong-bu Expressway (Yang-Jae IC - Osan IC) for a year. RESULTS : Additional greenhouse gas emissions that occur because of highway traffic accidents were classified by type (incident handling time, number of lanes blocked, freeway level of service) and annual additional emissions caused by accidents were calculated. CONCLUSIONS : In this study, a methodology for estimating carbon emissions due to freeway incidents was developed that incorporates macroscopic flow models. The results of the study are organized in the form of a look-Up table that calculates carbon emissions rather easily.

• Korean Journal of Veterinary Research
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• v.35 no.2
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• pp.279-285
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• 1995

To characterize non-adrenergic non-cholinergic(NANC) nerve mediated contractile responses in circular smooth muscle of bovine reticular groove, we investigated NANC relaxation and contraction induced by electric field stimulation to enteric nerves. In the presence of atropine($1{\mu}M$) and guanethidine($50{\mu}M$), electric field stimulation at frequency of 1 to 16Hz(square pulses, 0.5ms duration, 70V) evoked clear-cut relaxations through stimulations. Transient 'rebound contraction' was occured when the stimulus was switched off. All of the responses (relaxation and rebound contraction) were dose-dependently blocked by Nw-nitro-$_{\small{L}}$-arginine methyl ester(L-NAME), an inhibitor of nitric oxide synthesis, and methylene blue, and inhibitor of soluble guanylate cyclase. Tetraethyl ammonium(TEA), a potassium channel blocker, did not block the NANC relaxations.

• Nuclear Engineering and Technology
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• v.48 no.1
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• pp.189-199
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• 2016

Fast neutrons with a broad energy spectrum, with which it is possible to evaluate nuclear data for various research fields such as medical applications and the development of fusion reactors, can be generated by irradiating proton beams on target materials such as beryllium. To generate short-pulse proton beam, we adopted a deflector and slit system. In a simple deflector with slit system, most of the proton beam is blocked by the slit, especially when the beam pulse width is short. Therefore, the available beam current is very low, which results in low neutron flux. In this study, we proposed beam modulation using a buncher cavity to increase the available beam current. The ideal field pattern for the buncher cavity is sawtooth. To make the field pattern similar to a sawtooth waveform, a multiharmonic buncher was adopted. The design process for the multiharmonic buncher includes a beam dynamics calculation and three-dimensional electromagnetic simulation. In addition to the system design for pulsed proton generation, a test bench with a microwave ion source is under preparation to test the performance of the system. The design study results concerning the pulsed proton beam generation and the test bench preparation with some preliminary test results are presented in this paper.

• Nuclear Engineering and Technology
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• v.51 no.3
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• pp.665-675
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• 2019

The wire-wrapped fuel bundle is an assembly design in a sodium-cooled fast reactor. A wire spacer is used to maintain a constant gap between rods and to enhance the mixing of coolants. The wire makes the flow complicated by creating a sweeping flow and vortex flow. The vortex affects the flow field and heat transfer inside the subchannels. However, studies on vortices in this geometry are limited. The purpose of this research is to investigate the vortex flow created in the wire-wrapped fuel bundle. For analysis, a RANS-based numerical analysis was conducted for a 37-pin geometry. The sensitivity study shows that simulation with the shear stress transport model is appropriate. For the case of Re of 37,100, the mechanisms of onset, periodicity, and rotational direction were analyzed. The vortex structures were reconstructed in a three-dimensional space. Vortices were periodically created in the interior subchannel three times for one wire rotation. In the edge subchannel, the largest vortex occurred. This large vortex structure blocked the swirl flow in the peripheral region. The small vortex formed in the corner subchannel was negligible. The results can help in understanding the flow field inside subchannels with sweeping flow and vortex structures.

• KIEAE Journal
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• v.7 no.2
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• pp.9-15
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• 2007

Right of view out is one of the most important environmental factors that provide biological comfort and physical stability. Construction of high rise apartment buildings have caused to increase view obstruction cases and conflicts. Generally, when a field of a vision is completely blocked by other building, the percentage of a view is 0% and if the percentage is over 40%, it is regarded as acceptable. Autodesk VIZ program and the authors'-developed program were applied to evaluate a view right in apartment buildings and its effectiveness was verified by comparing computer simulation with actual photos.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2006.04a
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• pp.151-158
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• 2006

As GPS 'selective availability' was turned off in 2000, GPS related fields and markets are explosively extended. In mapping area, GPS/INS aided photogrammetry proved it is much cost and time effective method keeping enough accuracy as compared with traditional photogrammetry works. The advantage of GPS/INS integration is interdependence. Even if GPS signal was blocked in some time, the position accuracy is not affected. In this study, various GPS signal time gap was used in GPS/INS AT process. Field surveyed ground points were used in accuracy check with GPS/INS AT check points. And the result showed enough accuracy of photogrammetry work rule of NGII. y.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.5
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• pp.96-103
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• 2001

The quality requirements for thickness accuracy in cold rolling continue to become more stringent, particularly in response to exacting design specification from automotive customers. One of the major impacts from the tighter tolerance level is more unusable product on the head end and tail end of tandem mill coils when the mill is in transition to or from steady state rolling condition. A strip thickness control system for a tandem cold steel rolling mills is composed with blocked non-interacting controller and controllers for strip thickness and tension control of each rolling stands. An intelligent mathematical model included an elastic deformation of strip has been developed and applied to the field in order to predict the rolling force. The simulated results showed that the effect of elastic recovery should be included the model, even if the effect of elastic compression was not important.