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offset approximation based on reparameterizing the path of a moving point along the base circle

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Applied Mathematics(A Journal of Chinese Universities) 2009年第4期24卷 431-442页

作者： ZHAO Hong-yan WANG Guo-jin Department of Mathematics Zhejiang University Zhejiang 310027 China State Key Laboratory of CAD & CG Zhejiang University Zhejiang 310027 China College of Fundamental Studies Shanghai University of Engineering Science Shanghai 201620 China

This paper presents a novel algorithm for planar curve offsetting. The basic idea is to regard the locus relative to initial base circle, which is formed by moving the unit normal vectors of the base curve, as a unit circular arc first, then accurately to represent it as a rational curve, and finally to reparameterize it in a particular way to approximate the offset. Examples illustrated that the algorithm yields fewer curve segments and control points as well as C^1 continuity, and so has much significance in terms of saving computing time, reducing the data storage and smoothing curves entirely.

关键词： CAD/CAM offset circle convolution Bezier/B-spline curve rational curve

An offset-insensitive switched-capacitor bandgap reference with continuous output

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Journal of Semiconductors 2009年第8期30卷 132-135页

作者：郑鹏严伟张科李文宏 State Key Laboratory of ASIC & System Fudan University

An improved switched-capacitor bandgap reference with a continuous output voltage of 1.26 V has been implemented with Chartered 0.35-μm 5-V CMOS process. The output offset voltage, induced by non-ideal characteristics of operational amplifier and bias current generator, is suppressed by the proposed sample-and-hold circuit and self-bias technique. Experimental results show that the proposed circuit operates properly under a supply voltage varying from 3 to 5 V. The measured temperature coefficient is 112 ppm/℃ and the power supply rejection ratio of output voltage without any filtering capacitor is -40 dB and -33 dB at 100 Hz and 10 MHz, respectively.

关键词： bandgap reference switched-capacitor offset self-bias continuous output

Stationary response of stochastic viscoelastic system with the right unilateral nonzero offset barrier impacts

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Chinese Physics B 2019年第1期28卷 195-204页

作者： Deli Wang Wei Xu Xudong Gu Department of Applied Mathematics Northwestern Polytechnical UniversityXi’an 710072China Department of Engineering Mechanics Northwestern Polytechnical UniversityXi’an 710072China

The stationary response of viscoelastic dynamical system with the right unilateral nonzero offset barrier impacts subjected to stochastic excitations is investigated. First, the viscoelastic force is approximately treated as equivalent terms associated with effects. Then, the free vibro-impact(VI) system is absorbed to describe the periodic motion without impacts and quasi-periodic motion with impacts based upon the level of system energy. The stochastic averaging of energy envelope(SAEE) is adopted to seek the stationary probability density functions(PDFs). The detailed theoretical results for Van der Pol viscoelastic VI system with the right unilateral nonzero offset barrier are solved to demonstrate the important effects of the viscoelastic damping and nonzero rigid barrier impacts condition. Monte Carlo(MC) simulation is also performed to verify the reliability of the suggested approach. The stochastic P-bifurcation caused by certain system parameters is further explored. The variation of elastic modulus from negative to zero and then to positive witnesses the evolution process of stochastic P-bifurcation. From the vicinity of the common value to a wider range, the relaxation time induces the stochastic P-bifurcation in the two interval schemes.

关键词： viscoelastic system right unilateral nonzero offset barrier impacts stochastic averaging of energy envelope(SAEE) stochastic P-bifurcation

Effects of offset Blade on Aerodynamic Characteristics of Small-Scale Vertical Axis Wind Turbine

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Journal of Thermal Science 2019年第2期28卷 326-339页

作者： LI Yan ZHAO Shouyang QU Chunming FENG Fang KOTARO Tagawa Heilongjiang Provincial Key Laboratory of Technology and Equipment for the Utilization of Agricultural Renewable Resources in Cold Regions Northeast Agricultural University College of Engineering Northeast Agricultural University College of Science Northeast Agricultural University Faculty of Agriculture Tottori University

A new way of connecting blade to rotor shaft named offset blade method was proposed for straightbladed vertical axis wind turbine(SB-VAWT) in this study. In order to invest the efficiency of this method and effects of main parameters including offset length and blade airfoil on improving the output power performance and static starting characteristics, numerical simulations and wind tunnel tests were carried out. Four kinds of blade airfoil including NACA0012, NACA0018, NACA0024 and S809 were selected to analyze the influence of blade thickness and symmetry on SB-VAWT with offset blade. Numerical simulations were firstly carried out on output power for the rotor with 6 kinds of offset length for each airfoil. Wind tunnel tests were also carried out to compare with the results of simulations. The flow fields of rotor with different offset lengths were simulated and the effects of offset blade were analyzed. The optimum offset length among all studied for output power performance was found. Furthermore, the static starting torque and aerodynamic force characteristics of the rotor with optimum offset length were researched. According to the results, appropriate offset length can improve the output power characteristics and smooth the fluctuations of the static torque during one rotational period. The best offset length varies with the airfoil.

关键词： vertical axis wind turbine(VAWT) offset blade airfoil numerical simulations wind tunnel tests

Self-aligned offset gate poly-Si TFTs using photoresist trimming technology

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Science China(Information Sciences) 2015年第4期58卷 128-133页

作者： WANG LongYan SUN Lei HAN DeDong WANG Yi CHAN ManSun ZHANG ShengDong Institute of Microelectronics Peking University BOE Technology Co. Ltd. Department of Electronic and Computer Engineering Hong Kong University of Science and Technology School of Electronic and Computer Engineering Peking University

This paper reports a simple method of fabricating self-aligned offset gate(SAOG) polycrystalline silicon(poly-Si) thin film transistors(TFTs). The SAOG structure was formed by two key steps, i.e. an isotropic photoresist trimming and an additional gate fringe etching. The fabricated SAOG devices with this proposed method exhibit a significantly suppressed off-current increase with gate bias compared with the non-offset ones,and have identical bi-directional transfer characteristics under reversed source/drain biases. It is also shown that the performances of poly-Si TFTs with metal-induced lateral crystallization can be improved significantly by annealing in forming gas.

关键词： photoresist trimming offset polycrystalline silicon(poly-Si) thin film transistors(TFTs)

Intersections of two offset parametric surfaces based on topology analysis

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2004年第3期5卷 10-19页

作者：欧阳应秀唐敏林军呈董金祥 State Key Laboratory of CAD & CG AI Institute Zhejiang University

Conventional methods for solving intersections between two offset parametric surfaces often include iteratively using computationally expensive SSI (surface/surface intersections) algorithm. In addition, these methods ignore the relations between the intersection curves of parametric surfaces with different offset distances. The algorithm presented in this paper, makes full use of the topological relations between different intersection loops and calculates intersection loops with the help of previously calculated intersection loops. It first pre-processes two parametric surfaces to obtain the characteristic points, called topology transition points (TTPs), which can help in the subsequent finding of the topologies of the intersection curves. Then these points are categorized into several distinct groups, and we can determine the calculation strategy for searching initial points by analyzing the properties of these TTPs on the surfaces. Hence, all intersection curves can be marched from initial points by the tracing algorithm. The proposed algorithm could calculate intersection curves robustly and effectively, and has been tested to be capable of overcoming the degenerate conditions such as loop and singularities leaking that occur frequently in conventional algorithms.

关键词： offset parametric surface Topology transition point Surface intersection

MECHANISM RESEARCH FOR 3D NON-AXISYMMETRIC THIN-WALL TUBE offset SPINNING

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Chinese Journal of Mechanical Engineering 2006年第2期19卷 217-222页

作者： KUANG Weihua XIA Qinxiang RUAN Feng　 Faculty of Material and Energy Guangdong University of TechnologyGuangzhou 510006 China College of Mechanical Engineering South China University of TechnologyGuangzhou 510640 China

Difference of offset spinning with conventional symmetric spinning is analyzed. A 3D FEM model for offset tube neck-spinning is established and the spinning process is simulated by means of ANSYS software. Dynamic boundary and contact problems in simulation are solved. Transient stress distribution of contact area, transient strain distribution of nodes in typical section and strain distribution of the workpiece at last are attained, the place and the cause of crack are analyzed. Strain variation curves with time of offset spinning and conventional spinning are compared. It shows the mechanism difference between offset spinning and conventional spinning. In addition, simulation results show how strain distribution of typical section, thickness of some typical nodes, axial extension in left section and force of three rollers change with time. According to the study of the variation curve, material flow law along radial, tangential and axial direction is attained and the whole spinning process is studied. The simulation results discover that offset distance is the key to manufacture offset non-symmetric tube, and process parameters change with spinning angle. Experiment data really reflect different process parameters＇ influence on conventional symmetric and offset spinning force. Experiments accord well with simulation.

关键词： offset Symmetric Neck-spinning Simulation Mechanism

Review of United States research and guidelines on left turn lane offset:Unsignalized intersections and signalized intersections with permitted left turns

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Journal of Traffic and Transportation Engineering(English Edition) 2022年第4期9卷 556-570页

作者： Yu Song Madhav V.Chitturi William F.Bremer Andrea R.Bill David A.Noyce Connecticut Transportation Institute University of ConnecticutStorrsCT 06269USA Traffic Operations and Safety Laboratory Department of Civil and Environmental EngineeringUniversity of Wisconsin-MadisonMadisonWI 53706USA

The purposes of this paper are to better understand the design and impact of left turn lane offset and provide state transportation agencies recommendations on best practices and alternative design options to address left turn sight line obstruction *** studies and existing guidelines on left turn lane offset were reviewed and summarized to offer insights in driver sight distance and behavior,intersection safety and operations,as well as design elements related to left turn lane *** showed that at both unsignalized intersections and signalized intersections with permitted left turns,obstructed sight line could cause higher possibilities of collisions between left turning vehicles and oncoming vehicles from the opposing *** evaluations of left turn lane offset,with data from multiple states in the United States,reported that positive left turn lane offsets were beneficial in terms of safety and *** agency guidelines provided very limited discussions about left turn lane *** review demonstrated that positive left turn lane offsets are beneficial to intersection safety and *** on the review of research and guidelines,recommendations were provided for transportation agencies for left turn lane offset implementation.A discussion on new left turn design concepts was also included to point out directions for future research and practice.

关键词： Traffic engineering Intersection Left turn lane offset Safety Operation

Rational offset approximation of rational Bézier curves

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2006年第9期7卷 1561-1565页

作者： CHENG Min WANG Guo-jin Department of Mathematics Zhejiang University Hangzhou 310027 China Department of Mathematics Zhejiang University of Technology Hangzhou 310032 China

The problem of parametric speed approximation of a rational curve is raised in this paper. offset curves are widely used in various applications. As for the reason that in most cases the offset curves do not preserve the same polynomial or rational polynomial representations, it arouses difficulty in applications. Thus approximation methods have been introduced to solve this problem. In this paper, it has been pointed out that the crux of offset curve approximation lies in the approximation of parametric speed. Based on the Jacobi polynomial approximation theory with endpoints interpolation, an algebraic rational approximation algorithm of offset curve, which preserves the direction of normal, is presented.

关键词： Rational Bézier curve Parametric speed offset Rational approximation