Browsing by Author "Wu, Chih-Jen"

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A Novel Method for Lateral Vehicle Localization by Omni-Cameras for Car Driving Assistance
(2009)
Wu, Chih-Jen
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Tsai, Wen-Hsiang
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資訊工程學系
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Department of Computer Science
A lateral vehicle localization method by omni-image analysis is proposed for car driving assistance. The method estimates analytically the position and orientation of a lateral vehicle by utilizing the geometric properties of a circular-shaped wheel image of the lateral car taken by a single onmi-camera with a hyperboloidal-shaped mirror. Analytical solutions are made possible for fast computation by a special arrangement of affixing the omni-camera on the frontal car bumper at the height of the wheel. Experimental results showing good data estimation precision are included to prove the feasibility of the proposed method.
A Space-Mapping Method for Object Location Estimation Adaptive to Camera Setup Changes for Vision-Based Automation Applications
(2012-01-01)
Wu, Chih-Jen
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Tsai, Wen-Hsiang
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資訊工程學系
;
Department of Computer Science
A new space-mapping method for object location estimation, which is adaptive to camera setup changes, for use in various automation applications is proposed. The location of an object appearing in an image is estimated by mapping image coordinates of object points to corresponding real-world coordinates using a mapping table, which is constructed in two stages, with the first stage for establishing a basic table using bilinear interpolation in the camera manufacturing environment and the second for adapting the table to changes of camera heights and orientations in the application field. Analytic equations for table adaptation are derived by skillful utilization of both image formation and camera geometry properties. Good experimental results are shown to prove the feasibility of the proposed method.
Adaptation of Space-Mapping Methods for Object Location Estimation to Camera Setup Changes - A New Study
(2009)
Wu, Chih-Jen
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Tsai, Wen-Hsiang
;
資訊工程學系
;
Department of Computer Science
A new space-mapping method for object location estimation which is adaptive to camera Setup changes in various applications is proposed. The location of in object appearing in an image is estimated by mapping image coordinates of object points to corresponding real-world coordinates using a mapping table, which is constructed in two stages, with the first for establishing a basic table using bilinear interpolation and the second for adapting it to changes of camera heights and orientations. Analytic equations for Such adaptation are derived based oil image formation and camera geometry properties. Good experimental results are shown to prove the feasibility of the proposed method.
An Omni-vision Based Localization Method for Automatic Helicopter Landing Assistance on Standard Helipads
(2010-01-01)
Wu, Chih-Jen
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Tsai, Wen-Hsiang
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資訊工程學系
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多媒體工程研究所
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Department of Computer Science
An omni-vision-based localization method for automatic helicopter landing assistance on a helipad with a circled H-shape is proposed. The landing process includes two stages: approaching and alignment. Three types of image features, circle, line, and point, are used to derive skillfully analytic equations for computing the helicopter height, distance, and orientation with respect to the landing site. Experimental results with good location estimation accuracy are also shown.
Improvement in Mortality and End-Stage Renal Disease in Patients With Type 2 Diabetes After Acute Kidney Injury Who Are Prescribed Dipeptidyl Peptidase-4 Inhibitors
(2018-12-01)
Chen, Cheng-Yi
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Wu, Vin-Cent
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Lin, Cheng-Jui
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Lin, Chih-Sheng
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Pan, Chi-Feng
Objective: To focus on the potential beneficial effects of the pleiotropic effects of dipeptidyl peptidase-4 inhibitors (DPP4is) on attenuating progression of diabetic kidney disease in reducing the long-term effect of the acute kidney injury (AKI) to chronic kidney disease (CKD) transition. Patients and Methods: Data from the National Health Insurance Research Database from January 1, 1999, to July 31, 2011, were analyzed, and patients with diabetes weaning from dialysis-requiring AKI were identified. Cox proportional hazards models and inverse-weighted estimates of the probability of treatment were used to adjust for treatment selection bias. The outcomes were incident end-stage renal disease (ESRD) and mortality, major adverse cardiovascular events, and hospitalized heart failure. Results: Of a total of 6165 patients with diabetes weaning from dialysis-requiring AKI identified, 5635 (91.4%) patients were DPP4i nonusers and 530 (8.6%) patients were DPP4i users. Compared with DPP4i nonusers, DPP4i users had a lower risk of ESRD (hazard ratio, 0.81; 95% CI, 0.70-0.94; P=.04) and all-cause mortality (hazard ratio, 0.28; 95% CI, 0.23-0.34; P<.001) after adjustments for CKD, advanced CKD, and angiotensin-converting enzyme inhibitor or angiotensin II receptor blocker use. In contrast, the risk of major adverse cardiovascular events and hospitalized heart failure did not differ significantly between groups. Conclusion: Dipeptidyl peptidase-4 inhibitor users had a lower risk of ESRD and mortality than did nonusers among patients with diabetes after weaning from dialysis-requiring AKI. Therefore, a prospective study of AKI to CKD transitions after episodes of AKI is needed to optimally target DPP4i interventions. (C) 2018 Mayo Foundation for Medical Education and Research
Location estimation for indoor autonomous vehicle navigation by omni-directional vision using circular landmarks on ceilings
(2009-05-31)
Wu, Chih-Jen
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Tsai, Wen-Hsiang
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資訊工程學系
;
Department of Computer Science
A novel approach to location estimation by omni-directional vision for autonomous vehicle navigation in indoor environments using circular landmark information is proposed. A circular-shaped landmark is attached on a ceiling and an omni-directional camera is equipped on a vehicle to take upward-looking omni-directional images of the landmark. This way of image taking reduces possible landmark shape occlusion and image noise creation, which come from the existence of nearby objects or humans surrounding the vehicle. It is shown that the perspective shape of the circular landmark in the omnidirectional image may be approximated by an ellipse by analytic formulas with good shape-fitting effect and fast computation speed. The parameters of the ellipse are then used for estimating the location of the vehicle with good precision for navigation guidance. Both simulated and real images were tested and good experimental results confirm the feasibility of the proposed approach. (c) 2008 Elsevier B.V. All rights reserved.
The prevalence and association of chronic kidney disease and diabetes in liver cirrhosis using different estimated glomerular filtration rate equation
(2018-01-05)
Chen, Cheng-Yi
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Lin, Cheng-Jui
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Lin, Chih-Sheng
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Sun, Fang-Ju
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Pan, Chi-Feng
Background: Chronic kidney disease (CKD) in cirrhosis is one of the dreaded complications associated with a steep rise in mortality and morbidity, including diabetes. There are limited data on the prevalence of CKD and the association with diabetes in outpatients with cirrhosis. Methodology: This is a cross-sectional study of 7,440 adult liver cirrhosis patients enrolled from August 2001 to April 2010 in a medical center. Case control matching by age and sex with 1,967 pairs, and conditional logistic regression for odds of diabetes was analyzed using adjusted model. Results: CKD was present in 46.0%, 45.7% and 45.6% of the study population using the MDRD-6, CKD-EPI and MDRD-4 estimated glomerular filtration rate (eGFR) equations, respectively. Using a conditional logistic regression model after adjusting for other risk factors, odds for diabetes increased significantly compared with non-CKD in CKD stage 3 to 5 (stage 3 similar to 5) based on MDRD-6-adjusted model, ORs were: stage 3 similar to 5, 2.34 (95% CI, 1.78-3.01); MDRD-4-adjusted model, ORs were: stage 3 similar to 5, 8.51 (95% CI, 5.63-11.4); CKD-EPI-adjusted model, ORs were: stage 3 similar to 5, 8.61 (95% CI, 5.13-13.9). Conclusion: In cirrhosis patients, prevalence of diabetes was higher in patients with advanced stage of CKD. For patients with cirrhosis, patients with CKD stages 3 similar to 5 defined by MDRD-4, MDRD-6, and CKD-EPI eGFR equations had increased risk for diabetes. More severe cirrhosis, indicated by the Child-Turcott-Pugh classification was also accompanied by an increased risk for diabetes.
The role of indoxyl sulfate in renal anemia in patients with chronic kidney disease
(2017-10-10)
Wu, Chih-Jen
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Chen, Cheng-Yi
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Lai, Thung-S.
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Wu, Pei-Chen
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Chuang, Chih-Kuang
Renal anemia is a common complication in patients with advanced chronic kidney disease. In vitro studies have shown that indoxyl sulfate decreases erythropoietin production. Whether this effect is seen in vivo remains unclear. Our goal was to explore the role of indoxyl sulfate in renal anemia. We found serum indoxyl sulfate levels are significantly and negatively associated with erythropoietin levels in human. A multiple stepwise linear regression analyses after adjustment for other independent parameters revealed that free indoxyl sulfate, and total indoxyl sulfate were significantly associated with erythropoietin levels. In animal studies, erythropoietin gene and protein expression were markedly inhibited in rats with chronic kidney disease; however, this effect was significantly reversed by lowering serum indoxyl sulfate with AST-120. Indoxyl sulfate may also inhibit erythropoietin expression in animal models with chronic kidney disease. These findings further support the role of indoxyl sulfate in the development of renal anemia.
Unwarping of images taken by misaligned omnicameras without camera calibration by curved quadrilateral morphing using quadratic pattern classifiers
(2009-08-01)
Wu, Chih-Jen
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Tsai, Wen-Hsiang
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資訊工程學系
;
Department of Computer Science
A method for solving the problem of unwarping a distorted omni-image taken by a lateral-direction misaligned omni-camera with its optical axis incoincident with its mirror axis is proposed. The method does not conduct camera calibration and is based on a new concept of two-stage image mapping from the real-world space to the distorted image space. The first stage is conducted in the camera manufacturing process and includes the generation of a pano-mapping function for mapping the real-world space to an undistorted image taken by an omni-camera with its optical and mirror axes being coincident. The second stage is conducted in an in-field environment when the omni-camera becomes lateral-direction misaligned and includes the generation of a distortion-mapping function that maps undistorted image pixels to distorted ones and the generation of a misalignment adjustment table that combines the pano-mapping and distortion-mapping functions to map the real-world space to the distorted image space. The distortion mapping function is generated by a new technique of curved quadrilateral morphing using quadratic pattern classifiers. The misalignment adjustment table is last used to unwarp distorted images conveniently by table lookup. Experimental results using simulated and real-image data show the feasibility of the proposed method. (C) 2009 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.3204238]