• Title, Summary, Keyword: Gradient Correction

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A Feature Vector Generation Technique through Gradient Correction of an Outline in the Mouth Region (입 영역에서 외곽선의 기울기 보정을 통한 특징벡터 생성 기법)

  • Park, Jung Hwan;Jung, Jong Jin;Kim, Guk Boh
    • Journal of Korea Multimedia Society
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    • v.17 no.10
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    • pp.1141-1149
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    • 2014
  • Recently, various methods to effectively eliminate the noise are researched in image processing techniques. However, the conventional noise filtering techniques, which remove most of the noise, are less efficient for remained noise detection after filtering due to exploiting no face feature information. In this paper, we proposed a feature vector generation technique in the mouth region by distinguishing and revising the remained noise through gradient correction, when the outline is extracted after performing noise filtering.

Lens Distortion Correction of images with Gradient Components

  • Park, Junhee;Lee, Byung-Uk
    • Journal of the Institute of Electronics and Information Engineers
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    • v.50 no.7
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    • pp.231-235
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    • 2013
  • Lens distortions have a significant impact on captured or projected image geometry. This paper proposes a lens distortion correction with gradient components for wide-angle lenses. In most cases, distortion coefficients are estimated using a distortion model by point correspondences. Corrected images using only point correspondences can be compensated excessively, therefore, producing bended lines into the opposite direction near the corners. To curtail these phenomena, we propose to adopt the gradient components in addition to positions to obtain the distortion coefficients. We verified the improved accuracy and the straightness of the proposed method through experimentation.

The Effect Analysis and Correction of Phase errors by Satellite Attitude Errors using the FSA for the Spotlight SAR Processing (Spotlight SAR 신호처리기법 FSA를 이용한 위성 자세오차로 인한 위상오차 영향분석 및 보정)

  • Shim, Sang-Heun
    • Journal of the Korea Institute of Military Science and Technology
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    • v.10 no.2
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    • pp.160-169
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    • 2007
  • In this paper, we have described and simulated the effect analysis and correction of phase errors in the SAR rawdata induced by satellite attitude errors such as drift, jitter. This simulation is based on the FSA(Frequency Scaling Algorithm) for high resolution image formation of the Spotlight SAR. Phase errors produce the degradation of SAR image quality such as loss of resolution, geometric distortion, loss of contrast, spurious targets, and decrease in SNR. To resolve this problem, this paper presents method for correction of phase errors using the PGA(Phase Gradient Algorithm) in connection with the FSA. Several results of the phase errors correction are presented for Spotlight SAR rawdata.

터널 전계 효과 트랜지스터의 양자모델에 따른 특성 변화

  • Lee, Ju Chan;Ahn, Tae Jun;Yu, Yun Seop
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • pp.454-456
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    • 2017
  • Current and capacitance-voltage characteristics of tunnel field effect transistor (TFET) with various quantum models were investigated. Density gradient, Bohm quantum potential (BQP), and Vandort quantum correction are used with calibrating against Schrodinger-Poisson model. Drive-currents in all models. are decreased. When only BQP is used, SS and $V_{onset}$ are fixed but drive-current is decreased 3 times more than those of no quantum model. And When BQP with Vandort and density gradient are used, SS increased more than 40 mV./dec and $V_{onset}$ shifted as 0.07 eV.

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Background Gradient Correction using Excitation Pulse Profile for Fat and $T_2{^*}$ Quantification in 2D Multi-Slice Liver Imaging (불균일 자장 보정 후처리 기법을 이용한 간 영상에서의 지방 및 $T_2{^*}$ 측정)

  • Nam, Yoon-Ho;Kim, Hahn-Sung;Zho, Sang-Young;Kim, Dong-Hyun
    • Investigative Magnetic Resonance Imaging
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    • v.16 no.1
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    • pp.6-15
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    • 2012
  • Purpose : The objective of this study was to develop background gradient correction method using excitation pulse profile compensation for accurate fat and $T_2{^*}$ quantification in the liver. Materials and Methods: In liver imaging using gradient echo, signal decay induced by linear background gradient is weighted by an excitation pulse profile and therefore hinders accurate quantification of $T_2{^*}$and fat. To correct this, a linear background gradient in the slice-selection direction was estimated from a $B_0$ field map and signal decays were corrected using the excitation pulse profile. Improved estimation of fat fraction and $T_2{^*}$ from the corrected data were demonstrated by phantom and in vivo experiments at 3 Tesla magnetic field. Results: After correction, in the phantom experiments, the estimated $T_2{^*}$ and fat fractions were changed close to that of a well-shimmed condition while, for in vivo experiments, the background gradients were estimated to be up to approximately 120 ${\mu}T/m$ with increased homogeneity in $T_2{^*}$ and fat fractions obtained. Conclusion: The background gradient correction method using excitation pulse profile can reduce the effect of macroscopic field inhomogeneity in signal decay and can be applied for simultaneous fat and iron quantification in 2D gradient echo liver imaging.

A Study on the Evaluation of elastic buckling strength of Singly Symmetric I-Beams (일축대칭 I형보의 탄성좌굴강도 산정에 관한 연구)

  • Ku, So-Yeun;Ryu, Hyo-Jin;Lim, Nam-Hyoung;Lee, Jin-Ok
    • 한국방재학회:학술대회논문집
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    • pp.79-82
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    • 2008
  • The elastic critical moment of I-beams subjected to moment is directly affected by the following factors; loading type; loading position with respect to the mid-height of the cross section; end restraint conditions. Most design specifications usually provide buckling solutions derived for uniform moment loading condition and account for variable moment along the unbraced length with a moment gradient correction factor applied to these solutions. In order for the method in the SSRC Guide to be applicable for singly symmetric I-beams, improved moment gradient correction factors were proposed in this study. Finite element buckling analyses of singly symmetric I-beams subjected to transverse loading applied at different heights with respect to the mid-height of the cross section were conducted. Transverse loads consisting of a mid-span point load and a uniformly distributed load were considered in the investigation.

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COLOR CORRECTION METHOD USING GRAY GRADIENT BAR FOR MULTI-VIEW CAMERA SYSTEM

  • Jung, Jae-Il;Ho, Yo-Sung
    • Proceedings of the Korean Society of Broadcast Engineers Conference
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    • pp.1-6
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    • 2009
  • Due to the different camera properties of the multi-view camera system, the color properties of captured images can be inconsistent. This inconsistency makes post-processing such as depth estimation, view synthesis and compression difficult. In this paper, the method to correct the different color properties of multi-view images is proposed. We utilize a gray gradient bar on a display device to extract the color sensitivity property of the camera and calculate a look-up table based on the sensitivity property. The colors in the target image are converted by mapping technique referring to the look-up table. Proposed algorithm shows the good subjective results and reduces the mean absolute error among the color values of multi-view images by 72% on average in experimental results.

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Alterations in Left ventricular End-systolic Wall Stress During Short-term Follow-up After Correction of Isolated Congenital Aortic Stenosis (선천성 대동맥 협착증의 술전 및 술후 단기간의 수축말기 좌심실 내벽 스트레스의 변화)

  • 김시호
    • The Korean Journal of Thoracic and Cardiovascular Surgery
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    • v.33 no.10
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    • pp.777-784
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    • 2000
  • Congenital aortic stenosis in children is characterized by "excessive" left ventricular hypertrophy with reduced left ventricular systolic wall stress that allows for supernormal ejection performance. We hypothesized that left ventricular wall stress was decreased immediately after surgical correction of pure congenital aortic stenosis. Also measuring postoperative left ventricular wall stress was a useful noninvasive measurement that allowed direct assessment for oxygen consumption of myocardium than measuring the peak systolic pressure gradient between ascending aorta and left ventricle for the assessment of surgical results. Material and Method: Between September 1993 and August 1999, 8 patients with isolated congenital aortic stenosis who underwent surgical correction at Yonsei cardiovascular center were evaluated. There were 6 male and 2 female patients ranging in age from 2 to 11 years(mean age, 10 years). Combined Hemodynamic-Ultrasonic method was used for studying left ventricular wall stress. We compared the wall stress peak systolic pressure gradient and ejection fraction preoperatively and postoperatively. Result: After surgical correction peak aortic gradient fell from 58.4${\pm}$17.6, to 23.7${\pm}$17.7 mmHg(p=0.018) and left ventricular ejection fraction decreased but it is not statistically significant. In the consideration of some factors that influence left ventricular end-systolic wall stress excluding one patient who underwent reoperation for restenosis of left ventricular outflow tract left ventricular end-systolic pressure and left ventricular end-systolic dimension were fell from 170.6${\pm}$24.3 to 143.7${\pm}$27.1 mmHg and from 1.78${\pm}$0.4 to 1.76${\pm}$0.4 cm respectively and left ventricular posterior wall thickness was increased from 1.10${\pm}$0.2, to 1.27${\pm}$0.3cm but it was not statistically singificant whereas left ventricular end-systolic wall stress fell from 79.2${\pm}$24.9 to 57.1${\pm}$27.6 kdynes/cm2(p=0.018) in 7 patients. For one patient who underwent reoperation peak aortic gradient fell from 83.0 to 59.7 mmHg whereas left ventricular end-systolic wall stress increased from 67.2 to 97.0 kdynes/cm2 The intervals did not change significnatly. Conclusion ; We believe that probably some factors that are related to left ventricular geometry influenced the decreased left ventricular wall stress immediately after surgical correction of isolated congenital aortic stenosis. Left ventricular wall stress is a noninvasive measurement and can allow for more direct assesment than measuring peak aortic gradient particularly in consideration of the stress and oxygen consumption of the myocardium therefore we can conclude it is a useful measurement for postoperative assessment of congenital aortic stenosis.

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Gradient Optimized Gradient-Echo Gradient Moment Nulling Sequences for Flow Compensation of Brain Images

  • Jahng, Geon-Ho;Stephen Pickup
    • Investigative Magnetic Resonance Imaging
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    • v.4 no.1
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    • pp.20-26
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    • 2000
  • Gradient moment nulling techniques require the introduction of an additional gradient on each axis for each order of motion correction to be applied. The additional gradients introduce new constraints on the sequence design and increase the demands on the gradient system. The purpose of this paper is to demonstrate techniques for optimization of gradient echo gradient moment nulling sequences within the constraints of the gradient hardware. Flow compensated pulse sequences were designed and implemented on a clinical magnetic resonance imaging system. The design of the gradient moment nulling sequences requires the solution of a linear system of equations. A Mathematica package was developed that interactively solves the gradient moment nulling problem. The package allows the physicist to specify the desired order of motion compensation and the duration of the gradients in the sequence with different gradient envelopes. The gradient echo sequences with first, second, and third order motion compensation were implemented with minimum echo time. The sequences were optimized to take full advantage of the capabilities of the gradient hardware. The sequences were used to generate images of phantoms and human brains. The optimized sequences were found to have better motion compensation than comparable standard sequences.

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Modified Moment Gradient Correction Factor of Nonprismatic Beams (변단면보의 개선된 모멘트 구배 수정계수)

  • Park, Jong Sup
    • Journal of Korean Society of Steel Construction
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    • v.18 no.2
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    • pp.191-201
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    • 2006
  • New design equations for calculating the lateral-torsional buck ling moment resistances of stepped I-section beams with/without continuous lateral top-flange bracing subjected to a point load, a series of point loads, and a uniformly distributed load, are suggested based on the results of elastic finite-element analyses. The new equations presented in this study are compared with the current moment gradient modifiers presented by other researchers and specifications. Although the study paper presents mainly stepped-beam cases subjected to a point load and a uniformly distributed load. The proposed equations include the length-to-height ratio effects for stepped beams with continuous lateral top-flange bracing. The new moment gradient correction factors could be easily used to calculate the lateral-torsional buckling moment resistance of stepped I-beams.