• Title, Summary, Keyword: conformal density

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CONFORMAL DENSITY OF VISIBILITY MANIFOLD

  • Kim, Hyun-Jung
    • Bulletin of the Korean Mathematical Society
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    • v.38 no.1
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    • pp.211-222
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    • 2001
  • In this paper, we prove the existence and uniqueness of a $\delta(\Gamma)$-conformal density on the limit set of $\Gamma$ acting on visibility manifold H for a Fuchsian group $\Gamma$.

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Conformal Symmetry Wormholes and the Null Energy Condition

  • Kuhfittig, Peter K.F.
    • Journal of the Korean Physical Society
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    • v.70 no.11
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    • pp.962-966
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    • 2017
  • In this paper, we seek a relationship between the assumption of conformal symmetry and the exotic matter needed to hold a wormhole open. By starting with a Morris-Thorne wormhole having a constant energy density, we show that the conformal factor provides an extra degree of freedom sufficient to account for the exotic matter. The same holds for Morris-Thorne wormholes in a noncommutative-geometry setting. Applied to thin shells, a radius that results in a wormhole with positive surface density and negative surface pressure and that violates the null energy condition on a thin shell would exist.

Low Noise Characteristics of the Comformal Sensor Array's Support Structure (곡면배열 센서의 저소음화를 위한 지지구조 설계 구조)

  • Lee, Jong-Kil;Lee, Sang-Won;Seo, Hee-Sun
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.340-341
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    • 2010
  • Noise reduction is an important factor to design low noise sensor array. In this paper three layers of the de-coupler in the conformal sensor array were used to investigate noise reduction. Conformal sensor array is positioned in the layers and the distance from the layer is 0.25cm~1.5cm. Transfer function in the frequency density function is investigated according to the three different positions. When increasing the embedded distance the flow noise decreased in the region of the kx>10.

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MYRBERG-AGARD DENSITY POINTS AND SCHOTTKY GROUPS

  • Do, Il-Yong;Hong, Sung-Bok
    • Journal of the Korean Mathematical Society
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    • v.34 no.1
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    • pp.77-86
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    • 1997
  • Let $\Gamma$ be a discrete subgroup of hyperbolic isometries acting on the Poincare disc $B^m, m \geq 2$. The discrete group $\Gamma$ acts properly discontinously in $B^m$, and acts on $\partial B^m$ as a group of conformal homemorphisms, but need not act properly discontinously on $\partial B^m$.

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Investigation of Outer Flow Noise Reduction of the Hydrophones Embedded in the Elastomer (탄성층에 삽입된 음향 하이드로폰의 외부 유입소음 영향 연구)

  • Park, Ji-hye;Lee, Jong-kil;Shin, Ku-kyun;Cho, Chi-yong
    • 대한공업교육학회지
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    • v.33 no.2
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    • pp.273-286
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    • 2008
  • Underwater acoustic sensor array can detect acoustic signal in underwater and the sensor array can be mounted in each left, right or front side of the UUV(Unmanned Underwater Vehicle). The sensor array could be conformal array and effected turbulent boundary layer flow noise. Therefore, in this paper numerical simulations were performed to know the how the outer flow noise affect the hydrophone which embedded in the elastomer. Corcos wall pressure model was used as turbulent boundary layer flow noise and this model was applied to the frequency density function. Characteristics of transfer function according the kx wave number were simulated and design parameters were thickness of elastomer, density, and modulus of elasticity. Based on the simulation results when increasing the thickness of elastomer noise reduction was increased. This results can be applied to the design of conformal array of UUV.

Inflow Noise Characteristics of the Sensor in Low Wave Number Region Using Transfer Function (전달함수를 이용한 저파수 영역에서의 센서 유입 소음 특성 연구)

  • Park, Ji-hye;Lee, Jongkil;Shin, Ku-kyun;Cho, Chi-yong
    • 대한공업교육학회지
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    • v.34 no.1
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    • pp.238-251
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    • 2009
  • The noise itself that affects the sensor array is defined as the noise which happens in the place where the system is installed and the circumference noise which comes from the ocean. The array structure for detecting acoustic signal in the underwater effected turbulent layer flow noise. In this paper to design the conformal array spectral density function was introduced and several cases of flow induced noise which affect transfer function were simulated. Modified Corcos wall pressure model was used as turbulent boundary layer flow noise. The effect of noise has been reduced as integrated sum of transfer function has been reduced by decreasing elastomer thickness and density when kx is in low wave number area. Also the characteristics of transfer function by Corcos wall pressure displayed the product of frequency density function. This simulation results can be applied to the conformal array design in unmmaned underwater vehicle in the near future.

Novel 3D nanofabrication technique and its applications

  • Jeon, Seok-U
    • Proceedings of the Materials Research Society of Korea Conference
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    • pp.15.1-15.1
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    • 2009
  • Nano transfer printing and micro contact printing is well known printing method based on soft lithography which uses conformal soft elastomer with designed surface relief structures. Here I introduce another class of novel 3D nanofabrication technique by using the same elastomer but in a different manner. The approach, which we refer to as proximity field nanopatterning, uses the surface-reliefed elastomers as phase masks to pattern thick layers of transparent, photosensitive materials. Aspects of the optics, the materials, and the physical chemistry associated with this method are outlined. A range of 3D structures illustrate its capabilities, and several application examples demonstrate possible areas of use in technologies ranging from microfluidics to photonic materials to density gradient structures for chemical release and high-energy density science.

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Design for Radiotherapy Room with High Density Shielding Block (고 강도 차폐벽돌을 이용한 방사선치료실의 차폐설계)

  • Suh Chang Ok;Kim Gwi Eon;Chu Sung Sil
    • Progress in Medical Physics
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    • v.15 no.4
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    • pp.247-254
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    • 2004
  • According to developing high energy linear accelerators and treatment methods, like (3 dimensional conformal radiotherapy (3D-CRT), intensity modulated radiotherapy (IMRT), many radiotherapy centers are replacing older linear accelerators with new higher technical machines. This often presents a shielding problem as the designed shield for the existing rooms is not adequate for the higher technical machines. Additional shielding in limited existing space becomes necessary. We are replacing older brachytherapy room with new higher technical linear accelerator for IMRT. This room is not adequate for the IMRT machine without additional shielding design. The logical development of optimum structural shielding designs with concrete and high density shielding blocks are presented. We obtained following results by comparison between the pre-calculating values and actual survey of completed LINAC installation. High density shielding blocks have more powerful radiation protection about 2 times.

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Dosimetric Characteristics on Penumbra Regions of the Multileaf Collimator as Compared with the Lead Alloy Block (다엽 콜리메이터(Multileaf Collimator)와 합금납 차폐물(Lead Alloy Block)의 반 그림자영역의 선량 분포상의 특성 비교)

  • Lee Sang Wook;Oh Young Tack;Kim Woo Cheol;Keum Ki Chang;Yoon Seong Ick;Kim Hyun Soo;Park Won;Chu Seong Sil;Kim Gwi Eon
    • Radiation Oncology Journal
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    • v.13 no.4
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    • pp.391-396
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    • 1995
  • Purpose : The Conformal Radiation Therapy has bee widely used under favour of development of computer technologies. The delivery of a large number of static radiation fields are being necessary for the conformal irradiation. In this paper we investigate dosimetric characteristics on penumbra regions of a multileaf collimator(MLC), and compare to those of lead alloy block for the optimal use of the system in 3-D conformal radiotherapy. Materials and Methods : The measurement of penumbra by MLC or lead alloy block was performed with 6 or 10 MV X-rays. The film was positioned at a dmax depth and 10 cm depth, and its optical density was determined using a scanning videodensitometer. The effective penumbra, the distance from $80{\%}$ to $20{\%}$ isodose lines and $90{\%}$ to $10{\%}$ were analyzed as a function of the angle between the direction of leaf motion and the edge defined by leaves. Results : Increasing MLC angle ($0-75^{\circ}$) was observed with increasing the penumbra widths and the scalloping effect. There was no definite differences of penumbra width from $80{\%}$ to $20{\%}$ isodose lines, while being the small increase of penumbra width from $90{\%}$ to $10{\%}$ isodose line varing the depth and energy. The effective penumbra width of lead alloy block are agree resonably with those of MLC within 4.8mm. Conclusion : The comparative qualitative study of the penumbra between MLC and lead alloy block demonstrate the clinical acceptability and suitability of the multileaf collimator for 3-D conformal radiotherapy.

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