Offset Vector Research Articles

The Movement Precision Analysis of Planar Four-Bar Mechanism with Joint Clearance

The method of planar four-bar mechanism movement precision analysis is proposed when the length errors and kinematical pair clearances are taken into account. The offset vector caused by the clearance of kinematical pair is analyzed and the position vector is used to describe the position of bodies. The structure for the two-hole swing deputy is studied. The magnitude and direction of rotary vice offset is seen as random variable. The calculating formula of two-hole effective lever length model is deduced. The output accuracy of four-bar mechanism with two-hole the clearance is analyzed.

Object Detection in Terrestrial Laser Scanning Point Clouds Based on Hough Forest

This letter presents a novel rotation-invariant method for object detection from terrestrial 3-D laser scanning point clouds acquired in complex urban environments. We utilize the Implicit Shape Model to describe object categories, and extend the Hough Forest framework for object detection in 3-D point clouds. A 3-D local patch is described by structure and reflectance features and then mapped to the probabilistic vote about the possible location of the object center. Objects are detected at the peak points in the 3-D Hough voting space. To deal with the arbitrary azimuths of objects in real world, circular voting strategy is introduced by rotating the offset vector. To deal with the interference of adjacent objects, distance weighted voting is proposed. Large-scale real-world point cloud data collected by terrestrial mobile laser scanning systems are used to evaluate the performance. Experimental results demonstrate that the proposed method outperforms the state-of-the-art 3-D object detection methods.

Structural differences among subfamilies of EF-hand proteins-A view from the pseudo two-fold symmetry axis

We have analyzed the conformations of EF-lobes, adjacent pairs of EF-hand domains, in a coordinate system based on the approximate two-fold (z) axis that relates the two EF-hands. Two parameters - dE(ø), the azimuthal angle between the y-axis and the projection of the offset vector to helix E onto the yz-plane, and δdF(ø), the difference angle between the two helices (F1 and F2) of odd and even domains--characterize the openness of a single EF-hand domain and of an EF-lobe, respectively. We describe and compare values of dE(ø) and of δdF(ø) for EF-hand proteins of five subfamilies--CTER, CPV, S100, PARV, CALP--in calci- and apo- forms, with and without bound target proteins. Each subfamily has characteristic changes associated with binding calcium and/or target proteins.

The Gemini NICI planet-finding campaign: The offset ring of HR 4796 A

We present J, H, CH_4 short (1.578 micron), CH_4 long (1.652 micron) and K_s-band images of the dust ring around the 10 Myr old star HR 4796 A obtained using the Near Infrared Coronagraphic Imager (NICI) on the Gemini-South 8.1 meter Telescope. Our images clearly show for the first time the position of the star relative to its circumstellar ring thanks to NICI's translucent focal plane occulting mask. We employ a Bayesian Markov Chain Monte Carlo method to constrain the offset vector between the two. The resulting probability distribution shows that the ring center is offset from the star by 16.7+/-1.3 milliarcseconds along a position angle of 26+/-3 degrees, along the PA of the ring, 26.47+/-0.04 degrees. We find that the size of this offset is not large enough to explain the brightness asymmetry of the ring. The ring is measured to have mostly red reflectivity across the JHK_s filters, which seems to indicate micron-sized grains. Just like Neptune's 3:2 and 2:1 mean-motion resonances delineate the inner and outer edges of the classical Kuiper Belt, we find that the radial extent of the HR 4796 A and Fomalhaut rings could correspond to the 3:2 and 2:1 mean-motion resonances of hypothetical planets at 54.7 AU and 97.7 AU in the two systems, respectively. A planet orbiting HR 4796 A at 54.7 AU would have to be less massive than 1.6 Mjup so as not to widen the ring too much by stirring.

Study of Non-Smooth Gear Based on MÜLLER Algorithm

It is found that the relationship the detection function and collision function of non smooth point by using MÜLLER algorithm, and launched the conversion between the different states of gear system of the offset vector. So the unified algorithm of maximal Lyapunov exponent of non smooth gear system is obtained. An example is given to verified this method. The validities of algorithm for largest Lyapunov exponent of gear power systems is proved by comparing the the largest Lyapunov, system phase and Poincaré section.

A Robust Fractal Color Image Watermarking Algorithm

One of the main objectives of watermarking is to achieve a better tradeoff between robustness and high visual quality of a host image. In recent years, there has been a significant development in gray-level image watermarking using fractal-based method. This paper presents a human visual system (HVS) based fractal watermarking method for color images. In the proposed method, a color pixel is considered as a 3-D vector inRGBspace. And a general form of 3 × 3 matrix is utilized as the scaling operator. Meanwhile, the luminance offset vector is substituted by the range block mean vector. Then an orthogonalization fractal color coding method is achieved to obtain very high image quality. We also show that the orthogonalization fractal color decoding is a mean vector-invariant iteration. So, the range block mean vector is a good place for hiding watermark. Furthermore, for consistency with the characteristics of the HVS, we carry out the embedding process in theCIE La*b*space and incorporate a just noticeable difference (JND) profile to ensure the watermark invisibility. Experimental results show that the proposed method has good robustness against various typical attacks, at the same time, with an imperceptible change in image quality.

The effects of cutter eccentricity on the cutting force in the ball-end finish milling

Ball-end mill are usually used for finish machining with multi-axis CNC milling centers. Cutter eccentricity (offset magnitude ec, angular location of the offset vector λc) is very important when predicting cutting forces accurately. In the process of cutting force modeling, not only the ec, but also the λc, affects the cutting forces by associating with the rotation angle, the chip thickness, and the entry and exit angles of the cutting forces. The ec affects the values of the cutting forces, while λc causes the delay phenomenon of the cutting forces mainly. Experiment results show that the cutting forces, considering the cutter eccentricity, more especially considering the influence of the λc, agree better with the measured cutting forces than the cutting forces without considering the cutter eccentricity.

Three-dimensional tool radius compensation for multi-axis peripheral milling

Few function about 3D tool radius compensation is applied to generating executable motion control commands in the existing computer numerical control (CNC) systems. Once the tool radius is changed, especially in the case of tool size changing with tool wear in machining, a new NC program has to be recreated. A generic 3D tool radius compensation method for multi-axis peripheral milling in CNC systems is presented. The offset path is calculated by offsetting the tool path along the direction of the offset vector with a given distance. The offset vector is perpendicular to both the tangent vector of the tool path and the orientation vector of the tool axis relative to the workpiece. The orientation vector equations of the tool axis relative to the workpiece are obtained through homogeneous coordinate transformation matrix and forward kinematics of generalized kinematics model of multi-axis machine tools. To avoid cutting into the corner formed by the two adjacent tool paths, the coordinates of offset path at the intersection point have been calculated according to the transition type that is determined by the angle between the two tool path tangent vectors at the corner. Through the verification by the solid cutting simulation software VERICUT® with different tool radiuses on a table-tilting type five-axis machine tool, and by the real machining experiment of machining a soup spoon on a five-axis machine tool with the developed CNC system, the effectiveness of the proposed 3D tool radius compensation method is confirmed. The proposed compensation method can be suitable for all kinds of three- to five-axis machine tools as a general form.

QZS-1 Yaw Attitude Estimation Based on Measurements from the CONGO Network

The first satellite of Japan’s Quasi-Zenith Satellite System (QZSS) has been launched in September 2010, and its signal transmission has been activated at the end of the same year. The satellite transmits five signals from its L-band main antenna, including C/A code and L1C on L1, and the SAIF signal from a dedicated antenna mounted with an offset to the main antenna. Using differential pseudorange and carrier-phase measurements, it is possible to compute the phase center offset vector, or baseline vector, between these two antennas, if the satellite’s attitude is known. Using this vector as a priori information, it is furthermore possible to compute the yaw attitude of the spacecraft. This is a unique feature of the QZSS satellites and particularly interesting since their attitude mode is switched between yaw-steering and orbit-normal orientation during certain periods. Precise knowledge and consistent modeling of the satellite’s attitude is essential when processing carrier-phase measurements or satellite laser ranging measurements. This paper introduces the algorithm for baseline vector and yaw attitude estimation and presents results based on real measurements collected with five QZSS-capable receivers of the CONGO network. The observability of the baseline vector and the accuracy of the yaw angle estimates are discussed. The analysis for the yaw attitude estimation includes a switch from yaw-steering to orbit-normal orientation as well as changes of the attitude mode during an orbit maintenance maneuver.

Improving In-Building Asset Localization by Offset Vector and Convergence Calibration Methods

AbstractAccessibility of assets impacts the efficiency of various work processes during building operations. An effective in-building asset localization solution that can locate assets accurately is needed to improve the efficiency of building asset management. Multipath and fading effects caused by the complexity of buildings make it challenging to locate building assets (e.g., equipment, components, tools) by radio frequency identification (RFID)-based indoor location solutions. This study tests two calibration methods, namely, the offset vector method (OVM) and convergence method (CM), to mitigate multipath and fading effects in indoor environments to support in-building asset management. A RFID-based indoor asset localization solution is tested in two building-scale test beds with different complexities and functions. The proposed solution locates assets by utilizing a virtual-tag-enabled (VTE) algorithm, and two calibration methods are integrated into the VTE algorithm to improve the location accurac...

Estimation of Motion in Angiographic Images

The effect of organ and tissue motion on Xray image quality in angiography is discussed. It is shown that esti� mation of such motion may benefit the diagnostic value of images in several ways. The blockmatching method is described. This method provides information on motion in the form of an offset vector field. The modifications of the blockmatching algorithm described in this work include static region segmentation based on noise esti� mation and application of an additional flicker coefficient that improves the confidence of the method in case of changes in illumination.

Computing medial axes of generic 3D regions bounded by B-spline surfaces

A new approach is presented for computing the interior medial axes of generic regions in R3 bounded by C(4)-smooth parametric B-spline surfaces. The generic structure of the 3D medial axis is a set of smooth surfaces along with a singular set consisting of edge curves, branch curves, fin points and six junction points. In this work, the medial axis singular set is first computed directly from the B-spline representation using a collection of robust higher order techniques. Medial axis surfaces are computed as a time trace of the evolving self-intersection set of the boundary under the the eikonal (grassfire) flow, where the bounding surfaces are dynamically offset along the inward normal direction. The eikonal flow results in special transition points that create, modify or annihilate evolving curve fronts of the (self-) intersection set. The transition points are explicitly identified using the B-spline representation. Evolution of the (self-) intersection set is computed by adapting a method for tracking intersection curves of two different surfaces deforming over generalized offset vector fields. The proposed algorithm accurately computes connected surfaces of the medial axis as well its singular set. This presents a complete solution along with accurate topological structure.

Using reference RFID tags for calibrating the estimated locations of construction materials

Effective automated tracking and locating of the thousands of materials on construction sites improve materials management and project performance. Utilizing location sensing technologies such as RFID, GPS, Ultra-wideband, infrared, and others help to achieve this objective; however, they generally provide imperfect data which results in lack of accuracy, precision and robustness. One possibility of improving the precision, accuracy, and robustness of such systems is the use of reference tags. In this paper active RFID tags are employed as reference points at known and fixed locations on a construction site and are used to calibrate the location estimation of other materials on the site. Materials on the site are uniquely attached with RFID tags and are subject to tracking. The basic principle of the calibration technique using reference points is to adjust the estimated location of neighboring tags by adding a unique offset vector to each individual tag location-estimation. In a two level approach, first the locations of all tags are estimated using a proximity method. Then a unique offset vector is calculated and added to each individual tag location to calibrate the estimated location in level 1. The offset vector is a weighted average of the shift-vectors between the observed and the true location of the reference tags. The weights are based on the relative distance between the observed location of the target tag and the reference tags. The experimental results show that calibrating the location estimates using reference tags can successfully deal with the challenges of a very noisy and dynamic environment and imperfect construction data and improve the precision of the estimated locations.

Wide-azimuth land processing: Fracture detection using offset vector tile technology

Using a modern wide-azimuth land survey, we demonstrate the power of offset vector tile (OVT) processing and subsequent analysis of offset vector gathers (OVG) to identify potential anisotropy and fracture characteristics of certain reservoirs of interest. Migration of the inherently azimuth-limited OVT gathers and the accompanying velocity updating scheme, based on surface fitting in offset and azimuth, yields robust measurements critical to this analysis. Both the kinematic and dynamic aspects of the processing are considered and contrasted. The results of the processing and analysis are then confirmed by comparison to the values predicted from two wells in the area.

3D OBC seismic survey parameters optimization offshore Abu Dhabi

The flexibility of 3D ocean bottom cable (OBC) seismic survey design allows a variety of survey parameters and geometries to be chosen. From the infinite number of possible variations, we seek to optimize the trade-off between higher data quality and lower survey effort. To understand the relationship between data quality and survey effort, we acquired a pilot 3D OBC seismic survey with very high specifications, simulated several datasets by decimating the full data or reducing the survey effort, and then evaluated the quality of each dataset against the survey effort. We show that: (a) data quality is related to trace and offset vector tile (OVT) densities; (b) data quality is an asymptotic function of survey effort in general, eventually reaching a plateau with increasing survey effort; (c) a gradient of the fit curve at a certain survey effort can represent the quality efficiency, dQ/dE, where Q is data quality, and E is survey effort; and (d) the quality curve for a survey can be estimated using existing datasets in a field with the proposed equation for Q and dQ/dE.

Technology Focus: Seismic Applications (March 2010)

Technology Focus Finding and producing hydrocarbons from increasingly complex reservoirs and the push to maximize recovery stimulated a decade of steady growth in high-end seismic solutions covering the full E&P life cycle. In challenging imaging environments, the improvements achieved with the latest acquisition and processing technology are significant. Not surprisingly, associated cost pressures and budget constraints increasingly force geophysicists to strive for adequate and cost-effective solutions. Simultaneously, we experience a renewed focus on adding value by pushing the integration with other disciplines to new levels. Papers reviewed for the new Seismic Applications feature highlight how seismic technologies pay dividends on the basis of an improved understanding of the subsurface. Several contributions discuss wide-azimuth seismic, which has become the norm in complex-imaging environments such as the Gulf of Mexico. Advances are not confined to marine surveys, and densely sampled wide-cross-spread surveys are being acquired onshore also. The logistical efforts for these modern surveys are large. Accurate planning and detailed survey design are essential for efficient and successful delivery. Beyond improved imaging, rich-azimuth seismic, probably in combination with multicomponent acquisition, has a realistic potential to enable fracture detection on the basis of azimuthal-anisotropy analysis. This technology can provide considerable value in carbonates and tight reservoirs in which fractures have a strong effect on connectivity and production rates. Robust and accurately calibrated rock-physics models are a prerequisite to bridge the gap between seismic and reservoir modeling. For carbonates, this is notoriously difficult, and enhanced physical models are being developed that result in more-reliable reservoir-property predictions. Reservoir models only approximate the actual subsurface, and seismic constraints are used more routinely to reduce remaining uncertainties. Next to static-model updates, repeated 4D-seismic surveys provide information about the dynamic-reservoir behavior. Permeability maps derived from 4D seismic can be incorporated during the history-matching process, providing a promising leap toward real integration of subsurface disciplines and improved recovery. Seismic Applications additional reading available at OnePetro: www.onepetro.org IPTC 13692 • “Multicomponent-Seismic Applications for Maximizing Efficiency and Production from Fractured-Carbonate Reservoirs in Idd El Shargi Field” by E. Maili, Occidental Petroleum of Qatar, et al. IPTC 13882 • “Microseismic Reservoir Monitoring in a Deep-Wellbore Carbonate Environment in Kazakhstan” by K.G. Maver, SPE, Schlumberger, et al. IPTC 13870 • “Wide-Azimuth Seismic Azimuthal Analysis in Offset Vector Domain for Velocity and Amplitude” by Jean-Luc Boelle, Total, et al.

DOSIMETRIC IMPACT OF DAILY SETUP VARIATIONS DURING TREATMENT OF CANINE NASAL TUMORS USING INTENSITY‐MODULATED RADIATION THERAPY

Intensity-modulated radiation therapy (IMRT) can be employed to yield precise dose distributions that tightly conform to targets and reduce high doses to normal structures by generating steep dose gradients. Because of these sharp gradients, daily setup variations may have an adverse effect on clinical outcome such that an adjacent normal structure may be overdosed and/or the target may be underdosed. This study provides a detailed analysis of the impact of daily setup variations on optimized IMRT canine nasal tumor treatment plans when variations are not accounted for due to the lack of image guidance. Setup histories of ten patients with nasal tumors previously treated using helical tomotherapy were replanned retrospectively to study the impact of daily setup variations on IMRT dose distributions. Daily setup shifts were applied to IMRT plans on a fraction-by-fraction basis. Using mattress immobilization and laser alignment, mean setup error magnitude in any single dimension was at least 2.5 mm (0-10.0 mm). With inclusions of all three translational coordinates, mean composite offset vector was 5.9 +/- 3.3 mm. Due to variations, a loss of equivalent uniform dose for target volumes of up to 5.6% was noted which corresponded to a potential loss in tumor control probability of 39.5%. Overdosing of eyes and brain was noted by increases in mean normalized total dose and highest normalized dose given to 2% of the volume. Findings suggest that successful implementation of canine nasal IMRT requires daily image guidance to ensure accurate delivery of precise IMRT distributions when non-rigid immobilization techniques are utilized. Unrecognized geographical misses may result in tumor recurrence and/or radiation toxicities to the eyes and brain.

Anisotropic velocities and offset vector tile prestack-migration processing of the Durham Ranch 3D, Northwest Colorado

This article describes the anisotropic P-wave processing and resulting velocity attributes of the Durham Ranch 3D Firefly survey in the southern Sand Wash Basin of northwest Colorado (Figure 1). The goal of the seismic effort at Durham Ranch is to provide a clearer 3D image of the structures that may influence reservoir fracturing and capture anisotropy attributes that can be related to the local distribution of these fractures. With structural dip greater than 10° in portions of the reservoir, accurate imaging and properly positioned anisotropy information requires prestack migration. The high-density spatial coverage achieved in the Durham Ranch shoot afforded an opportunity to migrate in a domain that preserves a wide-azimuthal distribution of prestack data for anisotropy analysis. Improved imaging and positioning of the anisotropy attributes provides a clearer (perhaps causal) relationship between local deformation and fracturing, thus aiding in the selection of productive well locations and/or stimulation methods.

Automated retinal shadow compensation of optical coherence tomography images

We present an automated numerical method of compensating for retinal shadows in the choroid. In this method, signal extinction caused by retinal vessels is estimated by subtracting median A-scans obtained from beneath the retinal vessels and A-scans from the surrounding area. Adding the obtained offset vector to A-scans from beneath the retinal vessels allows compensating for shadows in the choroid. In vivo imaging of the human eye was performed by 840-nm-band standard resolution spectral domain optical coherence tomography (SD-OCT), and choroidal vasculature projection images were calculated. Removal of retinal shadows distinctly improved the readability of choroidal images.

Using modern processing technology to improve signal to noise ratio, a Perth basin 3D land case study

The processing of two 3D land Perth basin seismic survey gave us the opportunity to apply and test some of the modern processing technologies available. The technologies we explore through those examples take place in the early steps of processing, later in the sequence before imaging and at the imaging level itself. For each of the steps we performed comparisons with more conventional technologies. Especially with land data, often acquired with poor signal to noise ratio, it is important to remove noise in the early phases of the processing sequence. Groundroll in particular needs special attention as the characteristic features of Groundroll (low frequency, highly energy) noise in the data can hide near offset reflection data that contains important signal. In this article we review a new adaptive method for Groundroll attenuation that could potentially better attenuate noise and at the same time better preserve signal. 3D land datasets are also often characterized by a wide range of azimuths being present in the data. This differs from most 3D marine acquisitions that are (with the exception if multi and wide azimuth surveys) mostly acquired in a narrow azimuth fashion behind the boat even with the presence of a wide array of streamers. Those wide azimuths represent a challenge for conventionally sorted data regularization prior to imaging. In this article, we analyze the results of using offset vector tile (OVT) gathers regularization and OVT gathers in the imaging process against the more conventional offset volume method. Finally, the use of Controlled Beam Migration (CBM) is compared to a more conventional Kirchhoff imaging process. Controlled Beam migration has often been used to image steep dips and provide multi arrivals in extremely complex environments. However in relatively low signal to noise ratio environment like the Perth basin we have seen in the second case study that this imaging technique could potentially bring better results than the conventional Kirchhoff.