Offset Method Research Articles

A Voxel Model-Based Process-Planning Method for Five-Axis Machining of Complicated Parts

Abstract This paper presents a new process planning method for five-axis machining, which is particularly suitable for parts with complex features or weak structures. First, we represent the in-process workpiece as a voxel model. Facilitated by the voxel representation, a scalar field called subtraction field is then established between the blank surface and the part surface, whose value at any voxel identifies its removal sequence. This subtraction field helps identify a sequence of intermediate machining layers, which are always accessible to the tool and are free of self-intersection and the layer redundancy problem as suffered, respectively, by the traditional offset layering method and the morphing method. Iso-planar collision-free five-axis tool paths are then determined on the interface surfaces of these machining layers. In addition, to mitigate the deformation of the in-process workpiece and avoid potential dynamic problems such as chattering, we also propose a new machining strategy of alternating between the roughing and finishing operations, which is able to achieve a much higher stiffness of the in-process workpiece. Ample experiments in both computer simulation and physical cutting are performed, and the experimental results convincingly confirm the advantages of our method.

Combination use of gravimetry, CSAMT and SOTEM methods in geophysical prospection of a polymetallic silver-copper deposit: Case studies in the Inner Mongolia, China

Geophysical methods, which use physical properties to reveal the structure of the underground spaces, have been widely applied in geological exploration. However, a single geophysical approach only reflects the distribution of a kind of physical property and therefore has its limitations. To improve the reliability of geophysical methods in actual geological exploration, in this paper, we are trying to combine the use of a variety of geophysical exploration methods, such as gravity, control source audio magnetotelluric method (CSATMT) and electrical source short offset transient electromagnetic method (SOTEM), to a specific metal in Inner Mongolia. Firstly, the gravimetry method is applied to figure out the anomalous area, and then the CSAMT method is adopted to probe the deep electrical distribution. Finally, the SOTEM method is applied for further auxiliary verification. Results show that the underground structure is well revealed by combing the use of these methods. This paper can be used as a reference for the exploration of concealed ore bodies in polymetallic ore deposits. To use a combination of methods to measure. In the geological exploration of a polymetallic silver-copper mine in Inner Mongolia, a variety of geophysical exploration methods such as gravity measurement, controllable source audio magnetotelluric measurement and electrical source short offset transient electromagnetic method were combined, and geological data were combined. The better exploration results provide reference for the layout of the drilling location of the drilling project, and provide assistance for the prospecting breakthrough of the concealed ore body in the polymetallic mining area.

Rectified Gaussian noise estimation and its use in position sensitive detection systems

Noise estimation of an amplified sensor output is essential for not only operating the position sensitive detection (PSD) system efficiently but also for improving accuracy. The noise can vary from device to device and depends on the operating environment; thus, its estimation should be conducted in real time. However, the rectified noise owing to the limited dynamic range of the analogue-to-digital converter makes this estimation challenging. This Letter presents the use of noise parameter estimation, such as non-uniform offset compensation, detection threshold calculation, and variance estimation of a beam's estimated angular position in PSD systems. Moreover, the estimation of rectified Gaussian noise parameters is proposed. Experiments with the implemented PSD system verify the performance of the proposed estimation method for the rectified Gaussian noise characteristics and the offset compensation method for the estimated beam position.

Optimisation and Reliability for Geometrical Tolerance Value against Positional Characteristic in Rotational Shaft System

In the process of manufacture and installation, geometrical dimensions and tolerances (GD&T) should be taken into consideration to improve reliability and reduce the adverse impact on critical parts of the rotating system. GD&T must be considered by manufacturers and assembly worker. This paper presents an analysis of geometrical tolerance (GT) values in rotational shaft using the genetic algorithm (GA) method. GA optimization uses a geometric mathematical model. Mathematical models were developed using the offset and algebraic methods to calculate the ideal geometric features that best fit a set of positioning points based on the standard equations criteria. The calculation using the Matlab software application will use the optimal GA parameter. There is a combination of four genetic parameters associated with size population, crossover, mutation and stop state will develop algorithm performance which will produce optimum GT value. The geometric tolerance value for the position characteristic was analyzed to determine and predict the probability and reliability shaft in rotational system. Comparative values of each GT value are compared to find out the reliability values obtained can be used and verify the GT value requirements require mathematical representation. Tolerance analysis at the design stage to evaluate and predict quality by considering the probability of failure rates. The Actual value of the radius must be small from the allowable radius (Ract <Rallow) to cope with the high failure rate throughout the operating period. Due to dynamic nature of the shaft round and the possibility of a variable size of shafts, the GT value should be analyzed to ensure that the value obtained is correct and can be optimum solution to this problem. The GT value to be considered is at the center of the shaft involved which will affect the relevant components. Impact of GT value on the destruction of system critical component such as bearings, gear and couplers as benchmark for review for the optimization of shaft geometric tolerances in rotating machines to overcome the problem and improve concentricity shaft. The contribution of this study is to examine the effect of shaft size and the value of geometric tolerance on system reliability. Estimating and predicting levels of reliability more accurately improves system life, knows the system's impact accurately, knows the security level of a rotating system and also knows the quality of the mechanism at the design level.

Enhanced sampling frequency offset resistance method based on precoding technique in W-band OFDM RoF systems

Precoding technique is proposed and experimental demonstrated to resist sampling frequency offset (SFO) in W-band OFDM RoF systems. Walsh–Hadamard transform (WHT)-precoding, discrete Hartley transform (DHT)-precoding, Zadoff–Chu transform (ZCT)-precoding, and orthogonal circulant matrix transform (OCT)-precoding are investigated and compared. SFO-induced inter-carrier interference (ICI) on each subcarrier of conventional OFDM and OFDM with precoding (precoded-OFDM) are theoretical analyzed. Experimental results indicate OFDM with OCT-precoding (OCT-OFDM) can obtain a remarkable resistance to the SFO-induced ICI in W-band OFDM RoF systems.

Target Tracking Based on Correlation Filter for Scale Offset

Existing scale estimation methods mainly use fixed-size tracking box for target tracking. However, when the moving direction of the target changes from near to far or from far to near, the size of the current tracking box cannot adapt to the scale change. In order to overcome the disadvantage of invariant size of tracking box in the scale change, this paper proposes a scale offset estimation method based on correlation filter by combining the state of previous frame and current frame of the target. Select the scale proposal box in the scale layer, and adjust the position and size of the actual tracking box in real time according to the size of the proposal box, target position and scale offset. In this paper, OTB-100 is used as the dataset. The obtained tracking results show that our algorithm Ours has better tracking performance than the existing others tracking algorithm in scale variation, and it has better tracking effect and stronger robustness in drift and occlusion events.

Retroreflective Transceiver Array Using a Novel Calibration Method Based on Optimum Phase Searching

The retrodirective or retroreflective method has been used as a radio-frequency beamforming method for massive antenna array, for wireless communication systems, radars, and microwave power transfer (MPT) systems. In particular, the retroreflective method is suitable for optimum beamforming for both near- and far-field zones. Each transmitter (Tx) and receiver (Rx) circuit in the Tx array has its own phase offset, which should be calibrated for optimum retroreflective operation. This article presents a simple and effective phase offset calibration method for the retroreflective beamforming arrays using a one-by-one basis optimum phase searching method with a receiver at a reference point. To verify the proposed calibration method for a massive retroreflective beamforming array, a 5.2 GHz shortand mid-range (≤4 m) MPT system, including a Tx array based on 8 × 8 antennas and an Rx using six antennas (five rectennas for power reception, and 1 additional for pilot transmission) for charging mobile handsets was designed and implemented. Optimal retroreflective beamforming from the Tx array, which was calibrated using the proposed method, was experimentally verified for elevation angles of within ±45 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sup> for both xz- and yz-planes. The implemented Tx and Rx circuits achieved a received dc power of about 100 mW at a distance of 4 m.

Determination of dowel-bearing strength of laminated bamboo at elevated temperatures

The Eurocode Yield Model to calculate the load capacity of dowel-type fastener connections is commonly adopted at normal temperature and in fire. The dowel-bearing strength of bamboo and timbers are required for the use of the calculation method. A total of 100 laminated bamboo specimens are employed to study the effect of temperature and grain direction on the dowel-bearing strength by the steady-state test method. With the temperature increasing from 20 °C to 250 °C, the embedding strength decreases gradually for both grain directions. But due to the evaporation of inherent water and glass transition of hemicellulose and lignin, the load-displacement curves of laminated bamboo have a turning point at 100 °C and 150 °C. For laminated bamboo perpendicular to grain, the embedding load rises linearly with the displacement, and a continuous increase is witnessed after yielding. And it shows obvious brittleness regardless of the increase in temperature. Four different typical failure modes have been observed, each two for one kind of grain directions. The yielding load of laminated bamboo is determined by the 5% diameter off-set method in different temperature ranges. By comparing different national standards and literature, the formula for embedding strength and the reduction factor with temperature are established at normal and elevated temperatures. This paper gives a valuable reference to calculate the bearing capacity of a dowel-type connection and predict structural performance under fire exposure.

Domains and trends in AVO

Amplitude Versus Offset methods make use of different domains to display rock properties and seismic amplitudes. A transformation from one domain to another will in general either create a trend or change an existing trend. Trends created by a transformation do not add any information about properties of the input data and I call these transformation trends. Whereas a strong transformation trend results when displaying seismic data in the Intercept Gradient domain, a trend is also created, though a much weaker one, when converting compressional and shear velocities and density to the same Intercept Gradient domain. Points and trendlines transfer in different ways. If a trend seen in one domain is (for example) a lithology trend, such as the trend often seen in crossplots of Vp and Vs, then a trend resulting from the same data in another domain will not be a lithology trend.

Automatic design for trimming die insert of automotive panel

Trimming inserts with complicated geometric features are widely used in the manufacture of automotive panels. The number of trimming inserts for a typical automotive panel is usually more than 20, even up to 100. The design of trimming inserts is a complex and time-consuming process, which significantly affects the development period and quality of automotive panels. However, the design of trimming insert needs to handle a lot of complex geometrical problems, such as 3D curve offset problems. The current commercial CAD software cannot provide a complete and effective solution to the problem, where a lot of tedious human-intersections are needed. This paper presents a systematic methodology which includes the automation of trimming lines division and trimming inserts design. An automatic-decomposition algorithm is presented to divide the trimming lines into short segments. Then the trimming insert is designed for each divided trimming segment. In order to automate the design of trimming insert, a bulking-fairing algorithm is introduced to fair planar curves to meet physical constraints, and a robust 3D curve offset method is proposed to generating 3D offset curves to overcome the main limitation of existing methods. Lastly, the path-interference-check algorithm is presented to check if the interference occurs during the trimming process. This system is implemented and has applications in industry. Case studies and industrial applications have demonstrated the system’s powerful ability in design trimming inserts of automotive panel, and the efficiency for insert design could be improved by 80% at least.

Effect of laser offset on microstructure and mechanical properties of laser welding of pure molybdenum to stainless steel

Direct welding of Mo and stainless steel is exceptionally difficult due to intrinsic brittleness of Mo and the formation of brittle Fe-Mo phases. To explore the feasibility of welding of Mo and stainless steel, the laser offset method was used in this study. Experimental results show that the offset of the laser beam toward stainless steel has a positive effect for the quality of Mo/Fe dissimilar joint. As the laser beam shifts from the Mo side to the stainless steel side, the formation of welding defects and Fe-Mo intermetallic compounds (IMCs) are effectively restricted because of the decrease amount of molten Mo. The decrease of Fe-Mo IMCs contributes to the reduction of hardness in the joints. With an increase of laser offset, the thickness of Fe-Mo IMCs layer decreased, consequently the tensile strength of joints increased first and then decreased in the laser offset range of 0.2–0.5 mm. The highest tensile strength of the joints is 290 MPa at the laser offset of 0.3 mm. All joints failed in the Fe-Mo IMCs layer with brittle fracture mode during tensile tests, indicating the weakest zone of the joint was Fe-Mo IMCs layer. A sound weld of Mo and stainless steel can be obtained if an appropriate thickness of Fe-Mo IMCs layer is produced by adjusting the laser offset.

Assessing Error in Locations of Conspicuous Wildlife Using Handheld GPS Units and Location Offset Methods

ABSTRACTCollecting spatially explicit locations of individual animals often is an important part of the study of habitat use. Obtaining accurate locations without disturbing an individual can be difficult for small species and may be limited for species of conservation concern, such as piping plover (Charadrius melodus), where a close approach is undesirable because of the potential for disturbance. To reduce disturbance while estimating an animal's location, an observer can collect their location using Global Positioning System (GPS) and offset that position using a distance and azimuth. Typically, error is not considered when these locations are determined, despite the potential effects of inaccuracy on habitat association results. Therefore, our objectives were to quantify potential error using the offset method and then evaluate how that error may manifest. During the plover breeding season in 2017 (Apr through Sep), we tested the error of Trimble GPS units compared with benchmark locations to assess the accuracy of locations derived from these units. We then assessed the error associated with offset locations of a small target using Trimble GPS units, laser rangefinders, and 2 compass types. Finally, we determined the potential consequence of unaccounted error in our system by comparing the difference between point locations and land‐cover data using our estimated error as a point buffer. Average error of the GPS units at benchmark locations was 0.95 m. The mean error of the offset locations increased with increasing observer distance from the decoy location (from = 2.9 m to 7.6 m at distances of 20 m and 100 m, respectively). Error also increased with increasing error in the distance and azimuth measurements, and was greater using a digital GPS compass as compared with a handheld magnetic compass corrected for magnetic declination. In addition, potential misclassification of land‐cover type increased with increasing potential location error. When modeling animal locations, the error of point locations using this method, especially for land‐cover at the point location, should be accounted for using appropriately sized position buffers. Using this location collection method, we can increase our knowledge and study of conspicuous species to ensure that we consider habitats used throughout the species' life stages. © 2020 The Wildlife Society.

Study of the biaxial fatigue behaviour and overloads on S355 low carbon steel

This work aimed to study the fatigue behaviour of S355 low carbon steel under uniaxial and biaxial loading conditions and to measure the overload effects under both types of loads. The analysis is performed with a local strain approach and with damage tolerance approach. Local strain based investigation was based on Fatemi-Socie critical plane model. This allows the life reduction caused by growing the crack from a stress raiser to be quantified. The fatigue life reduction caused by applying simultaneously torsional and tension loads was also evaluated with Fatemi-Socie model. In addition, the crack opening displacement (COD) and the effective stress intensity factor (SIF) were evaluated experimentally via full-field technique of digital image correlation (DIC). Both COD and SIF have been useful to understand the transient effects caused by a 40% overload under the two types of load. In addition, COD measurements allowed the offset compliance method for evaluating the opening load to be applied on a cylindrical specimen subjected to tension load. SIF estimation was also useful to quantify the mode mixity (I + II) developed during the experiment under the two types of load.

Low-complexity compensation of sampling offset with cross-correlation and early-late gate for OFDM receivers

This paper proposes a method for compensation of sampling offset for orthogonal frequency division multiplexing (OFDM) used in wireless local area networks (WLAN). Sampling offset is a typical transmission interference used in OFDM systems that introduce large error when synchronized data is demodulated. In this regard, an appropriate offset compensation method with a simple structure can be adopted to mitigate the impacts of sampling offset by using cross-correlation and early-late gate compensation methods for OFDM receivers instead of conventional methods that use algorithms with analog and mixed mode loops implementations. When bit error rate (BER) is at 10-3, simulation with the method without sampling offset compensation showed a signal noise rate (SNR) curve of about 25 dB, while the SNR curve of the method with offset compensation as proposed in this paper is about 26 dB. The comparisons show that the proposed system sacrifices performance by 1 dB to realize the benefit of compensating sampling offset. This sacrifice of 1 dB in performance is within the system’s tolerance range. Furthermore, the method overcomes the impact of sampling offset without additional hardware resource in WLAN applications.

Time-Series SBAS Pixel Offset Tracking Method for Monitoring Three-Dimensional Deformation in a Mining Area

The ground surface deformation caused by mining damages the ecological environment and severely hinder economic development in the mining area. The acquisition of three-dimensional ground surface deformation in a mining area helps to improve understanding of the process and mechanism of ground surface deformation caused by mining and helps to prevent and control this type of disaster. In this paper, eleven TerraSAR-X images and five Radarsat-2 images covering the 52304 working face in the Daliuta mining area were used to obtain the time-series line-of-sight (LOS) direction deformation and azimuth direction deformation based on different SAR platforms by application of the small baseline subset (SBAS) pixel offset tracking method. According to the three-dimensional solution principle of multiplatform SAR images and 72 GPS points, the accuracy of deformation in the east-west direction is 0.22 m, while the accuracy in the north-south direction is 0.21 m, with an accuracy of subsidence of 0.34 m.

The clinical impact of phase offset errors and different correction methods in cardiovascular magnetic resonance phase contrast imaging: a multi-scanner study

BackgroundCardiovascular magnetic resonance (CMR) phase contrast (PC) flow measurements suffer from phase offset errors. Background subtraction based on stationary phantom measurements can most reliably be used to overcome this inaccuracy. Stationary tissue correction is an alternative and does not require additional phantom scanning. The aim of this study was 1) to compare measurements with and without stationary tissue correction to phantom corrected measurements on different GE Healthcare CMR scanners using different software packages and 2) to evaluate the clinical implications of these methods.MethodsCMR PC imaging of both the aortic and pulmonary artery flow was performed in patients on three different 1.5 T CMR scanners (GE Healthcare) using identical scan parameters. Uncorrected, first, second and third order stationary tissue corrected flow measurement were compared to phantom corrected flow measurements, our reference method, using Medis QFlow, Circle cvi42 and MASS software. The optimal (optimized) stationary tissue order was determined per scanner and software program. Velocity offsets, net flow, clinically significant difference (deviation > 10% net flow), and regurgitation severity were assessed.ResultsData from 175 patients (28 (17–38) years) were included, of which 84% had congenital heart disease. First, second and third order and optimized stationary tissue correction did not improve the velocity offsets and net flow measurements. Uncorrected measurements resulted in the least clinically significant differences in net flow compared to phantom corrected data. Optimized stationary tissue correction per scanner and software program resulted in net flow differences (> 10%) in 19% (MASS) and 30% (Circle cvi42) of all measurements compared to 18% (MASS) and 23% (Circle cvi42) with no correction. Compared to phantom correction, regurgitation reclassification was the least common using uncorrected data. One CMR scanner performed worse and significant net flow differences of > 10% were present both with and without stationary tissue correction in more than 30% of all measurements.ConclusionPhase offset errors had a significant impact on net flow quantification, regurgitation assessment and varied greatly between CMR scanners. Background phase correction using stationary tissue correction worsened accuracy compared to no correction on three GE Healthcare CMR scanners. Therefore, careful assessment of phase offset errors at each individual scanner is essential to determine whether routine use of phantom correction is necessary.Trial registrationObservational Study

A General Fast Power Flow Algorithm for Transmission and Distribution Networks

Fast power flow calculation is generally required in static security analysis and power system optimal planning. And the classical DC power flow algorithm, due to its simple mathematical model, linearized equation, and rapid solving speed, is widely utilized. However, the classical DC power flow algorithm has been found to be only suitable for high voltage transmission networks with small branch impedance ratio. To address this issue, a general fast power flow algorithm is proposed. Utilizing this method, the classical DC power flow algorithm is firstly performed to obtain the initial values of the branch active power flow. And the nodal voltage angles are then calculated by the established node-injected reactive power equations. Secondly, through the identical transformation and approximate treatment of the node power flow equation, a voltage offset calculation method for PQ nodes is proposed. Finally, the active power flow and active power loss can be calculated based on the corrected phase angles and node voltages. Simulation studies on standard IEEE power systems, such as the IEEE 33-bus and IEEE 118-bus systems, etc., were conducted by the presented algorithm, compared with those by the back/forward sweep, classical DC power flow and Newton-Raphson algorithms. It is indicated that, the proposed power flow algorithm has the superiority in satisfactory calculation speed and non-sensitivity on the network impedance ratio.

A Novel High-Gain Sum and Difference Conical Beam-Scanning Reflector Antenna

A novel sum and difference (SD) conical beam-scanning reflector antenna is proposed in this paper. The reflector surface, illuminated by two omnidirectional horns, is a body of revolution obtained by revolving the generating parabola about a symmetry axis. The horns stacked along the symmetry axis of the reflector are fed by a nest coaxial waveguide. Teflon lens is used to improve the side lobe levels and reflection coefficients of the feed horns. By tilting the generating parabola and using the offset feeding method, two conical beams, with different beam pointing angles, were generated. A compact feed network was also designed to feed the two horns, which includes two rectangular TE10 mode-to-coaxial TEM mode transitions and a Magic-T to implement SD beams. The scanning performance of conical beams can be achieved by mechanically moving the feed antennas along the symmetry axis and taking full advantage of offset focus characteristic of the parabolic reflector. The error in angle measurement was also discussed. The SD conical beam-scanning antenna was formed by a parabolic dish with a radius of 18 λ operating at 24 GHz. The proposed antenna was designed, simulated, and fabricated. The measured results show that the difference beam null-depth is -25 dB and the sum beam gain is 15 dBi at 40°. The sum beam gain varies by less than 1.5 dB across the scan coverage from 30.8° to 45.2°. The measured results are found to be in good agreement with the simulated ones.

Blind Weighted Least-Squares Frequency Offset Estimation Method for LTE Machine-Type Communications

A key challenge associated with cellular-based machine-type communication (MTC) is to provide better coverage enhancement (CE) along with low power consumption for MTC user equipments (UEs). Due to the limitation on total power allowed for transmission, it is required to estimate frequency error in very low signal-to-noise ratio condition. In this article, an effective frequency offset estimation method is presented for MTC in a long term evolution system. The proposed method applies the repetitive nature of the MTC physical broadcast channel to the weighted least-squares estimation technique. Both analytical and simulation results are provided to corroborate the feasibility of the proposed method. It is shown that the proposed estimation scheme is more efficient for CE of MTC UEs, compared to the existing method.

Highly sensitive optical fiber temperature sensor based on the thermal shift of the liquid–air interface

A highly sensitive optical fiber temperature sensor based on the thermal shift of the liquid–gas interface is proposed. A section of silica capillary tube (SCT) was spliced to a single mode fiber, and a small quantity of liquid polydimethylsiloxane was filled into the innermost part of SCT by using the offset capillarity method. Then, the end of the SCT was sealed by solidified UV curable adhesive. As a result, a liquid Fabry–Perot (FP) cavity, an air FP cavity, and a liquid–gas interface were formed simultaneously in the SCT. The lengths of the two cavities changed synchronously and complementarily along with the thermal shift of the liquid–air interface, which resulted in the opposite wavelength shifts of the corresponding FP interference fringes. The temperature sensitivities are 1.67 and −0.32 nm / ° C, respectively. A differential sensitivity of 1.99 nm/°C can be achieved by monitoring the two kinds of fringes synchronously.