• Title/Summary/Keyword: spiral

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SPIRAL WAVE GENERATION IN A DIFFUSIVE PREDATOR-PREY MODEL WITH TWO TIME DELAYS

  • GAN, WENZHEN;ZHU, PENG
    • Bulletin of the Korean Mathematical Society
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    • v.52 no.4
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    • pp.1113-1122
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    • 2015
  • This paper is concerned with the pattern formation of a diffusive predator-prey model with two time delays. Based upon an analysis of Hopf bifurcation, we demonstrate that time delays can induce spatial patterns under some conditions. Moreover, by use of a series of numerical simulations, we show that the type of spatial patterns is the spiral wave. Finally, we demonstrate that the spiral wave is asymptotically stable.

A Study on Steel Pipe Coupler for Splicing Spiral Rebars (나선철근 이음을 위한 강관압착식 커플러에 관한 연구)

  • 오민수;이규세;김수만
    • Proceedings of the Korea Concrete Institute Conference
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    • 1999.10a
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    • pp.433-436
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    • 1999
  • The spiral provides the column with the ability to absorb considerable deformation prior to failure. Although this toughness is the principal gain that is achieved by the use of spiral reinforced columns, the its serviceability is limited by the fault of lap splices. The mechanical connection for the spiral bar placement is development in the study. The study contains for the experiment of the mechanical connection.

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Enhanced Parallel-Branch Spiral Inductors (병렬분기 방법을 이용한 박막 나선 인덕터의 특성 향상)

  • 서동우;민봉기;강진영;백문철
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2002.07a
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    • pp.89-93
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    • 2002
  • In the present paper we suggested a parallel-branch structure of aluminum spiral inductor for the use of RF integrated circuit at 1∼3 GHz. The inductor was implemented on P-type silicon wafer (5∼15 Ω-cm) under the standard CMOS process and it showed a improved quality(Q) factor by more than 10% with no degradation of inductance. The effect of the structure modification on the Q factor and the inductance was scrutinized comparing with those of the conventional spiral inductors.

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Interleaved Spiral Scan Imaging (Interleaved 나선 주사 영상)

  • Ahn, C.B.;Kim, H.J.;Shin, J.K.
    • Proceedings of the KOSOMBE Conference
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    • v.1998 no.11
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    • pp.98-99
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    • 1998
  • In this paper, an interleaved spiral scan imaging is investigated for an ultra fast MR imaging. The interleaved spiral technique has relative advantage over single shot spiral imaging with improved resolution and less inhomogeneity-related artifact. An improved reconstruction algorithm is devised with DC-offset correction. Some preliminary experimental results are shown at 1.0 Tesla and 3.0 Tesla whole body MRI system.

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Construction of Logarithmic Spiral-like Curve Using G2 Quadratic Spline with Self Similarity

  • Lee, Ryeong;Ahn, Young Joon
    • Journal of Integrative Natural Science
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    • v.7 no.2
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    • pp.124-129
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    • 2014
  • In this paper, we construct an logarithmic spiral-like curve using curvature-continuous quadratic spline and quadratic rational spline. The quadratic (rational) spline has self-similarity. We present some properties of the quadratic spline. Also using this $G^2$ quadratic spline, an approximation of logarithmic spiral is proposed and error analysis is obtained.

Impedence Analysis of Planar Air Core Inductor (공심 평면인덕터의 임피던스 해석)

  • 김영학;송재성
    • Journal of the Korean Magnetics Society
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    • v.6 no.3
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    • pp.179-188
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    • 1996
  • This paper discussed on the impedance analysis of the planar air core inductors having spiral pattern and meander pattern. The width and distance of conductor, and number of turns were varied. As the width of conductor increased, both resistance and inductance decreased and there existed an maximum value in Q for spiral pattern. But Q increased with increasing width of conductor in meander pattern. In spiral pattern, there existed a distance between conductors where inductance became constant and Q became maximum, while the distance between conductors must be as large as possible to obtain large Q because the mutual inductance of meander pattern inductor has negative sign due to opposite current direction at adjacent conductor. Resistance and inductance increased with increasing the number of turns. There existed maximum Q at certain number of turns in spiral pattern. But Q became small in the meander pattern because increase of resistance was larger than increase of inductance with increasing number of turns.

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Application of Capacitive Deionization Packed Ion Exchange Resins in Two Flow Channels (두 가지 유로 형태에 따라 이온교환수지를 채운 축전식 탈염기술)

  • Lee, Dong-Ju;Park, Jin-Soo
    • Journal of the Korean Electrochemical Society
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    • v.18 no.1
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    • pp.24-30
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    • 2015
  • To desalinate the aqueous solutions with high salt concentration using the capacitive deionization technology, two resin/membrane capacitive deionization(RMCDI) cells were fabricated by filling mixed ion exchange resins in two different flow channels (spacer and spiral type). The salt removal efficiency of the spacer- and spiral-RMCDI was 77.21 and 99.94%, respectively. Many ions were significantly removed in a spiral RMCDI cell because the feed solution could be more evenly contacted with the ion exchange resins filled on the spiral type flow channel. As the result of the changes of pH and accumulative charges, it was observed that Faradaic reaction was diminished for a spiral RMCDI cell filled by the mixture of cation and anion exchange resins. Therefore, the desalination of the aqueous solutions with high salt concentration by the capacitive deionization technology was proven. In addition, further studies on the optimization of the mixing ratio with ion exchange resins and the introduction of the regeneration process generally occurred in the continuous electrodeionization (CEDI) technology are required to improve the RMCDI technology.

Spiral scanning imaging and quantitative calculation of the 3-dimensional screw-shaped bone-implant interface on micro-computed tomography

  • Choi, Jung-Yoo Chesaria;Choi, Cham Albert;Yeo, In-Sung Luke
    • Journal of Periodontal and Implant Science
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    • v.48 no.4
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    • pp.202-212
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    • 2018
  • Purpose: Bone-to-implant contact (BIC) is difficult to measure on micro-computed tomography (CT) because of artifacts that hinder accurate differentiation of the bone and implant. This study presents an advanced algorithm for measuring BIC in micro-CT acquisitions using a spiral scanning technique, with improved differentiation of bone and implant materials. Methods: Five sandblasted, large-grit, acid-etched implants were used. Three implants were subjected to surface analysis, and 2 were inserted into a New Zealand white rabbit, with each tibia receiving 1 implant. The rabbit was sacrificed after 28 days. The en bloc specimens were subjected to spiral (SkyScan 1275, Bruker) and round (SkyScan 1172, SkyScan 1275) micro-CT scanning to evaluate differences in the images resulting from the different scanning techniques. The partial volume effect (PVE) was optimized as much as possible. BIC was measured with both round and spiral scanning on the SkyScan 1275, and the results were compared. Results: Compared with the round micro-CT scanning, the spiral scanning showed much clearer images. In addition, the PVE was optimized, which allowed accurate BIC measurements to be made. Round scanning on the SkyScan 1275 resulted in higher BIC measurements than spiral scanning on the same machine; however, the higher measurements on round scanning were confirmed to be false, and were found to be the result of artifacts in the void, rather than bone. Conclusions: The results of this study indicate that spiral scanning can reduce metal artifacts, thereby allowing clear differentiation of bone and implant. Moreover, the PVE, which is a factor that inevitably hinders accurate BIC measurements, was optimized through an advanced algorithm.

Absorbed and effective dose from spiral and computed tomography for the dental implant planning (치과 임프란트 치료 계획을 위한 나선형 일반 단층촬영과 전산화 단층촬영시 흡수선량 및 유효선량 평가)

  • Hong Beong-Hee;Han Won-Jeong;Kim Eun-Kyung
    • Imaging Science in Dentistry
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    • v.31 no.3
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    • pp.165-173
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    • 2001
  • Objectives : To evaluate the absorbed and effective doses of spiral and computed tomography for the dental implant planning. Materials and Methods: For radiographic projection, TLD chips were placed in 22 sites of humanoid phantom to record the exposure to skin and the mean absorbed dose to bone marrow, thyroid, pituitary, parotid and submandibular glands and nesophagus. Effective dose was calculated, using the method suggested by Frederiksen et al.. Patient situations of a single tooth gap in upper and lower midline region, edentulous maxilla and mandible were simulated for spiral tomography. 35 axial slices (maxilla) and 40 axial slices (mandible) with low and standard dose setting were used for computed tomography. All the radiographic procedures were repeated three times. Results: The mean effective dose in case of maxilla was 0.865 mSv, 0.452 mSv, 0.136 mSv and 0.025 mSv, in spiral tomography of complete edentulous maxilla, computed tomography with standard mAs, computed tomography with low mAs and spiral tomography of a single tooth gap (p<0.05). That in case of mandible was 0.614 mSv, 0.448 mSv, 0.137 mSv and 0.036 mSv, in spiral tomography of complete edentulous mandible, computed tomography with standard mAs, computed tomography with low mAs and spiral tomography of a single tooth gap (p<0.05). Conclusions: Based on these results, it can be concluded that low mAs computed tomography is recommended instead of spiral tomography for the complete edentulous maxilla and mandible dental implant treatment planning.

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Self-Complementary Spiral Antenna Design Using a Ultra-Wideband Microstrip-to-CPS Balun (초광대역 마이크로스트립-CPS 발룬을 이용한 Self-Complementary 스파이럴 안테나 설계)

  • Woo, Dong-Sik;Kim, Young-Gon;Cho, Young-Ki;Kim, Kang-Wook
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.20 no.2
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    • pp.208-214
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    • 2009
  • A design and its experimental result of a wideband self-complementary spiral antenna for UWB USPR(Ultrashort-Pulse Radar) system applications is presented. By utilizing the planar-type ultra-wideband microstrip-to-CPS balun, ultra-wideband characteristics of the inherent spiral antenna are retrieved. Also, the design procedure of the spiral antenna is simplified by performing simple impedance matching between separately designed balun and antenna. The proposed spiral antenna is equiangular self-complementary spiral antenna. The implemented antenna demonstrates widebaad performance for frequency ranges from 2.9 to 12 GHz with the relatively flat antenna gain of 2.7 to 5.3 dB and broad beamwidth of more than $70^{\circ}$. From these result, the possibility of a spiral antenna using a ultra-wideband microstrip-CPS balun is verified.