Axis Points Research Articles

Double NURBS trajectory generation and synchronous interpolation for five-axis machining based on dual quaternion algorithm

An equidistant double NURBS tool paths (EDNTP) fairing method satisfying the given fitting accuracy is proposed for the linear tool path in work coordinate system (WCS). By utilizing dual-quaternion to describe five-axis tool posture, the linear tool path in WCS is fitted with dual-quaternion B-spline vector function in order to obtain the equidistant double NURBS curves P and Q describing the coordinate points of tool tip and tool axis, respectively. Then, due to the different parameters of the two curves, a parameter synchronization interpolation model based on EDNTP is presented to realize synchronous motion of the two NURBS curve parameters during the interpolation process. The three-axis machining NURBS curve interpolation algorithm is utilized to interpolate the tool tip points NURBS curve of EDNTP for five-axis machining. In terms of parameter synchronization model, interpolation algorithm can be mapped to NURBS curve of tool axis points. Simulation and experimental results show that the proposed algorithm can generate G2 continuous EDNTP satisfying the given fitting accuracy and make the tool interpolate synchronously with the constant cutter length along the EDNTP during the interpolation process and achieve high machining precision which is mainly concentrated on the 10−6 mm series.

Dual-Bézier path smoothing and interpolation for five-axis linear tool path in workpiece coordinate system

The tool path composed of consecutive short linear segments (G01 blocks) is still the widespread tool path representation form in five-axis machining. The inherent shortcoming of linear tool path is first-order discontinuity at the corner, which is the bottleneck to achieve high-speed and high-accuracy machining. In this article, a dual-Bézier path smoothing algorithm for five-axis linear tool path in workpiece coordinate system is proposed. There are three steps involved in our method. First, the corner error distribution model is introduced to assign the given tolerance to the smoothing approximation error constraint and the chord error constraint to ensure the interpolation trajectory error within the given tolerance. Second, segment junctions of the linear tool path in workpiece coordinate system are smoothed by double G2 continuous cubic Bézier curves. One cubic Bézier curve is used to round the corner of the tool tip point path, and the other Bézier curve is used to round the corner of the tool axis point path. This algorithm takes the conditions of approximation error constraint, the parameterized synchronization constraint, and continuous curvature constraint into consideration. Hence, the tangency and curvature continuities are both guaranteed in the new path. Third, an adaptive feedrate scheduling method is introduced to interpolate the new path. Simulation and experiment are performed to verify the effectiveness of the proposed method in five-axis tool path smoothing, speed smoothing, and trajectory accuracy controlling.

On the effect of intrafraction motion in a single fraction step-shoot IMRT.

The authors studied the respiratory motion effect in a single step-shoot intensity modulated radiotherapy (IMRT) to assess the basic properties of the uncertainty in the delivered dose due to the unknown starting phase of the motion. Using computer simulations, the motion-averaged dose for open beams with various field sizes was calculated for two one-dimensional trajectories with different motion amplitudes at 20 equally spaced starting phases. The properties of the standard deviation (SD) of delivered dose were analyzed. The dependence of SD on the field size, motion amplitude, and delivery time was investigated and experimentally validated. To study effect of number of small monitor unit (MU) segments on the dose uncertainty, the authors generated 1000 pairs of multisegment beams such that each pair consists of two beams with the same total MU and different segment MU. The SD at the central axis point was compared for each pair. The authors proved that the direct time-dependent dose accumulation can be calculated using a convolution formula for a single fraction step-shoot IMRT treatment. Single segment simulation showed that the maximum dose uncertainty occurred symmetrically at the beam penumbra for a sinusoidal motion. For other sinusoidal motions (sin(2n) n > 1), the maximum dose uncertainty occurred at asymmetrical locations and may be beyond the penumbra region. The SD of relative dose periodically varied with delivery time with decreasing envelope for both motion trajectories. The SD of absolute dose was a periodic function of the delivery time for a given field size and motion amplitude and was proved to be true for any periodic motion. The SD reduced to zero when the delivery time was an integer multiple of the motion period. Analytical function σA=3βsin(2)π/Tδt-4/3sin(4)π/Tδt+2/3sin(6)π/Tδt was found to fit the delivery time dependence of the SD for motions studied in this paper and was verified with experimental data and an irregular motion. The dose uncertainty increased with motion amplitude and decreased slowly with field size. Simulations for 1000 beam pairs with multiple segments demonstrated that the probability that more small MU segments did not introduce larger dose uncertainty at central axis point for three cutoff small MUs (2.5/5/10) was 55.8%/51.9%/43.4% and 54.6%/54.4%/45%, respectively, for a sin and a sin(4) motion in a conventional treatment. These probabilities became 53.6%/50.9%/47.2% and 51.0%/50.2%/47.8%, respectively, for a hypofractionated treatment. The periodic dependence of the dose uncertainty on the delivery time can be modeled with an analytic function, and the functional form is independent of motion trajectories in this paper. The relation of dose uncertainty between different dose schemes can be obtained using this function. The dose uncertainty at central axis point for a beam with more small MU segments may not be greater than a beam with less small MU segments. By varying the dose rate of each segment such that the delivery time is close to the integer multiples of the motion period, the interplay effect can be reduced.

THREE-DIMENSIONAL NUMERICAL HYDRODYNAMICAL SIMULATION OF LOW/HARD AND HIGH/SOFT STATES IN ACCRETION DISCS OF MICROQUASARS AND QUASARS ON BASE OF UNDEFINED PRECESSION

In this study, the models of slaved precession of accretion disc and donors radiationdriven wind were performed using three-dimensional numerical astrophysical methods by the example of microquasar Cyg X-1. As is shown, in the course of precession of the accretion disc blown by the donor’s wind the states with high and low temperature (low and high mass accretion rate, respectively) start being generated in the centre of disc. Our computations of disc precession performed on base of undefined precession that means each point of rotation axis of accretion disc makes unclosed difficult curve instead of a circle as it is in case of definite precession. In this case, the transition between states of high and low temperature takes place irregularly and not depend on precession period. The duration of transition between these both states is less than intervals of states on several orders of magnitudes

3-D CFD Modeling of a Slanted Receiver in a Compact Linear Fresnel Plant with Etendue-Matched Mirror Field

Abstract Compact linear Fresnel receivers can be modified to include an etendue conserving mirror field as opposed to a flat field. Etendue can be used as an indicator of the losses within the system and therefore the optical optimization of the mirror field seeks to conserve incoming etendue. This can be done once for peak conditions and subsequently fixed with mirrors rotating throughout the day; or the mirror axis points can also be allowed to move up and down throughout the day, creating new etendue conservation curves. Radiation is modeled using discrete ordinates with no conduction in a two-dimensional and the absorbed radiation flux profiles are subsequently patched onto a three-dimensional slanted receiver as a heat source. The commercial software package ANSYS Fluent v15.0 was used together with the Matlab toolset to study the influence of different mirror fields on the amount of radiation transferred to the collector pipes.

Character shape restoration system through medial axis points in video

Shape restoration for characters in video is challenging because natural scene characters usually suffer from low resolution, complex background and perspective distortion. In this paper, we propose histogram gradient division and reverse gradient orientation in a new way to select Text Pixel Candidates (TPC) for a given input character. We apply a ring radius transform on TPC in different directions, namely, horizontal, vertical, principal and secondary diagonals in a TPC image to obtain respective radius maps, where each pixel is assigned a value that is the radius to the nearest TPC. This helps in finding Medial Axis Points (MAP) by searching for the maximum radius values from their neighborhoods in a radius image. The union of all the medial axis points obtained from the respective directions at each location is considered as Candidate Medial Axis Points (CMAP) of the character. Then color difference and k-means clustering are proposed to eliminate false CMAP, which outputs Potential Medial Axis Points (PMAP). We finally propose a novel way to restore the shape of the character from the PMAP. The method is tested on a video dataset and the benchmark ICDAR 2013 dataset to show its effectiveness for complex background and low resolution. Experimental results show that the proposed method is superior to the existing methods in terms of shape restoration error and recognition rate.

Weight-bearing-line analysis in supramalleolar osteotomy for varus-type osteoarthritis of the ankle.

We determined the preoperative and postoperative passing points of the mechanical axis of the lower limb at the level of the tibial plafond using a new method involving a full-length standing posteroanterior radiograph that includes the calcaneus (a hip-to-calcaneus radiograph) and correlated them to the clinical results after supramalleolar osteotomy for ankle osteoarthritis. We reviewed the hip-to-calcaneus radiographs of fifty lower limbs of forty-one patients treated for lower limb malalignment at our institution. The mechanical axis point of the ankle was the point at which the mechanical axis divides the coronal length of the plafond, expressed as a percentage. Four independent observers performed all measurements twice. Supramalleolar tibial osteotomy was performed in twenty-seven ankles (twenty-four patients) to treat moderate varus-type osteoarthritis of the ankle. The mean follow-up period was 2.8 years (range, two to 5.3 years). Clinical assessment was based on the American Orthopaedic Foot & Ankle Society (AOFAS) scale. Interobserver and intraobserver reliability in identifying the mechanical ankle joint axis point were very high. The mean postoperative mechanical axis point was 50% (range, 13% to 70%) in ankles for which the preoperative point was ≤0%, whereas the mean postoperative point was 81% (range, 48% to 113%) in ankles for which the preoperative point was >0%. The mean change in AOFAS score was significantly less for patients with a preoperative point of ≤0% than for those with a preoperative point of >0% (p=0.004). Improvement was significantly greater in ankles with a postoperative mechanical ankle joint axis point of ≥80% than in ankles with a postoperative mechanical ankle joint axis point of <60% (p=0.030). Traditional tibial correction resulted in great variation in the locations of the postoperative mechanical ankle joint axis point. In ankles with the preoperative point more medial than the tibial plafond, the point was insufficiently moved to the lateral side, and the clinical outcomes were less satisfactory.

The ‘Bhojpuriya’ Mumbaikar

Using Cultural Studies as the framework, this study investigates how north Indian migrants living in Kandivali east, Mumbai, exercise agency and appropriate Bhojpuri media texts to maintain their regional identity. Bhojpuri, a dialect of Hindi, has emerged as the lingua franca of these migrants hailing from the Indian states of Uttar Pradesh and Bihar. Beleaguered by the identity politics of the host city, the migrants turn to the Bhojpuri media to sustain the shared cultural beliefs that permeate their social relations. Familiar images in the media texts ensure continuity with tradition, feeding the resurgent pride of the community. The migrants’ aggressive defence of all things Bhojpuri, as well as their desire to sanitise Bhojpuri media of its bawdiness, is a manifestation of their embattled identities seeking validation. This article examines how the Bhojpuri media are intertwined with the migrants’ everyday realities. The media reinforce gender roles, alleviate anxieties and gratify desires vicariously. Media representations meld cultural memory with the migrants’ newly acquired understanding of the metropolis. In the process, hybrid identities are being fashioned by people on different points of the socio-economic axis.

Evaluation of arch form between Vietnamese and North American Caucasians using 3-dimensional virtual models.

The purpose of this study was to investigate the three-dimensional (3D) morphologic differences in the mandibular arch of Vietnamese and North American White subjects. The sample included 113 Vietnamese subjects (41 Class I, 37 Class II and 35 Class III) and 96 White subjects (29 Class I, 30 Class II and 37 Class III). The samples were regrouped according to arch form types (tapered, ovoid, and square) to compare the frequency distribution of the three arch forms between ethnic groups in each angle classification. The facial axis point of each tooth was digitized on 3D virtual models. Four linear and two ratio variables were measured. In comparing arch dimensions, the intercanine and intermolar widths were wider in Vietnamese than in Whites (p < 0.001, p = 0.042, respectively). In the White group, there was even frequency distribution of the three arch forms. However, in the Vietnamese group, the square arch form was the most frequent followed by tapered and ovoid arch forms. The arch forms of Whites were narrower than Vietnamese. In North American Whites, the distribution of the arch form types showed similar frequency. In Vietnamese, the square arch form was more frequent.

Self-adjoint Dirac type Hamiltonians in one space dimension with a mass jump

Physical self-adjoint extensions and their spectra of the one-dimensional Dirac type Hamiltonian operator, in which both the mass and velocity are constant except for a finite jump at one point of the real axis, are found correctly. Different boundary conditions on envelope wave functions are studied and the limiting case of equal masses (with no mass jump) is reviewed. Transport across one-dimensional heterostructures described by the Dirac equation is considered.

A Novel Arc Segmentation Approach for Document Image Processing

In document image processing, arc segmentation plays an important role in vectorization and graphic recognition. Moreover, the unsatisfactory results of several recent arc segmentation contests indicate that conventional methods are inadequate. This paper proposes a new arc segmentation algorithm called SymCAve (an acronym for Symmetry axis, Circle fitting and Average distribution points). First, we locate several seed points and adopt three strategies to ensure that the seed points are proper; then we calculate the center and radius utilizing the seed points. Second, the coordinates of the center and radius are adjusted by employing symmetry axes. Third, the average distribution points method is used to verify whether the points on the circumference are all black pixels. It is a complete circle if all of the points are black pixels. Otherwise, it is a partial circle if some of the points are black pixels and are continuous. Based on this information, the start and end angles of the partial circle can be determined. Finally, these arcs are verified to ensure that the results are accurate. Images and the evaluation tool were obtained from the GREC Workshop's Arc Segmentation contests, to test the systematic performance of the SymCAve algorithm. The experiments demonstrate that the proposed method can provide promising results. However, the algorithm has some drawbacks: it cannot detect a line with width of one pixel, small angles, and any large radius arcs. It is suited for segmenting images with appropriate symmetry axes.

Application of Commensurability in Earthquake Prediction

This article introduces application of the expanding commensurability in earthquake prediction. The results show that most of the world’s major earthquake occurred at their commensurable points of time axis. An EQ 7.0 occurred in Lushan of China on 2013-04-20 and an EQ 8.2 occurred in Iquique of northern Chile on 2014-04-01 all occurred at their commensurable points of time axis. This once again proves that the commensurability provides an important scientific basis for the prediction of major earthquakes, which will occur in the area in future.

Urban Sustainable Development Solutions by Creating Dynamic Tourism Pedestrian Passagea in Historical Textures (Case Study: Sepah Street in Qazvin)

Abstract. One of the solutions to achieve sustainable growth in urban areas, attracting tourists and creating local and national revenue solution, is to provide a chance of visiting the urban historical attractions in the form of pedestrian tourism axis. Creating this axis provides a chance to preserve and mend historical sites and revive urban environment. Also in addition to reduction of traffic and air pollution issue, helps tourists to better understand historical attractions and increases security sense with the absence of cars. This can boost tourism sustainable development in urban areas with an approach towards preserving historical attraction. This can also positively affect tourist sight clarity, urban identity and communal image. But creating pedestrian axis must not impact the lively and active aspects of the environment. Thus, with an evaluation of Khayyam pedestrian and using field method and interview, the weak and strong points of Sepah axis was evaluated and solutions for creating active tourism pedestrian were extracted. The method to the present study was descriptive-analytic. Data was gathered in library and by field method and finally it turned out that changing required professions in tourism, conversing urban views, repairing and rebuilding historical sites to gain a higher visual quality, building welfare equipments and many other changes, make it possible to create dynamic tourism pedestrian in the site.

Feature Line Method of Tool Axis Trajectory Planning for Non-developable Ruled Surface Flank Milling with Conical Tools

Aiming to the problem of complex tool axis trajectory planning for flank milling non-developable ruled surface with conical milling tools,an intuitive and simple tool axis trajectory generation method is presented. According to the properties of conical surface,the normal mapping curve is defined,i.e. the set of points which are the normal projection of all points of tool axis on the design curved surface,so that the problem of tool envelope surface approximating to design surface,is convert into the least squares approximation problem of normal mapping curve to characteristic curve for every tool position,and the generation method of ideal feature line of single tool position before the formation of tool envelope surface is given. Using the two-offsetting method the initial tool position is generated. Then based on this,the tool axis pose can be described by a function of three rotational and three translational motion parameters,consequently,a non-dominant function between single tool position optimization condition and six motion parameters is built. In the solving process,the experimental design method of Latin hypercube is used,and through analyzing and optimizing the influence factors of calculation,the optimal tool position is obtained,and then the optimized tool axis trajectory surface is obtained. The actual example calculation showed that the envelope error of optimized tool axis is reduced significantly,and the calculation results are stable. This method provides the theoretical basis for flank milling non-developable ruled surface with conical tools.

Changes in anteroposterior position and inclination of the maxillary incisors after surgical-orthodontic treatment of skeletal class III malocclusions.

The purpose of this study was to evaluate and compare the anteroposterior (AP) position and inclination of the maxillary incisors in subjects with class I normal occlusion and a harmonious profile with patients with skeletal class III malocclusions, and to investigate the changes in maxillary incisor inclination and AP position after surgical-orthodontic treatment in class III patients. Sixty-five subjects (35 female and 30 male; mean age: 21.8 ± 3.89 years) with normal profiles and class I skeletal and dental patterns were selected as a control sample. Sixty-seven patients (38 female and 29 male; mean age: 21.3 ± 3.31 years) with skeletal and dental class III malocclusions who sought surgical-orthodontic treatment were used as the study sample. Subjects were asked to smile and profile photographs were taken with the head in a natural position and the maxillary central incisors and the forehead in full view; cephalograms were taken and superimposed on the profile pictures according to the outline of the forehead and nose. Forehead inclination, maxillary incisor facial inclination and the AP position of the maxillary central incisor relative to the forehead (FAFFA) were measured on the integrated images and statistical analyses were performed. In both groups, there were no significant male/female differences in either the maxillary central incisor inclination or AP position. Female subjects had a significantly steeper forehead inclination compared with males (P < 0.001) in both groups. After combined surgical-orthodontic treatment, the significant labial inclination (P < 0.001) and posterior positioning (P < 0.001) of the maxillary central incisors had been corrected to close to normal range (P > 0.05). In the control group, 84.6% had the facial axial point (FA) of their maxillary central incisors positioned between lines through the forehead facial axis (FFA) point and the glabella. In the study group, however, 79.1% had the maxillary central incisors positioned posterior to the line through the FFA point and the difference with the control group was statistically significant (P < 0.001). The position of the maxillary central incisors was strongly correlated with forehead inclination in the control sample (r(2) = 0.456; P < 0.01), but only a poor correlation was detected in the class III group (r(2) = 0.177; P > 0.05). With the integrated radiograph-photograph method, the lateral cephalogram was reoriented, which makes it possible to accurately measure the variables on profile photographs. The AP position and inclination of the maxillary central incisors relative to the forehead plays an important role in the esthetics of the profile during smiling and could be an important variable to be considered during diagnosis and treatment planning.

Effect of anatomical landmark perturbation on mean helical axis parameters of in vivo upper costovertebral joints

The literature concerning quantification of costovertebral joint (CVJ) motion under in vivo conditions is scarce. Most papers concerning this topic are related to ex vivo loading conditions. In vivo protocols are available from the literature to determine rib and vertebra kinematics but new developments are needed to improve data processing concerning CVJ behaviour obtained from discrete breathing positions showing limiting ranges-of-motion and sensitive to noise. Data from previous work were used to implement a method analyzing mean helical axis (MHA) and pivot point parameters of the CVJ complexes. Several levels of noises were estimated within Monte-Carlo simulations to optimize MHA results. MHA parameters were then used to transform and define a CVJ-specific local coordinate system. This study proposes an improvement for CVJ kinematics processing and description from in vivo data obtained from computed tomography. This methodology emphasizes the possibility to work with variability of MHA parameters using Monte-Carlo procedures on anatomical landmark coordinates and to define a local coordinate system from this particular joint behaviour. Results from the CVJ joint model are closer to a hinge joint (secondary motions inferior to 3°) when anatomical frames are expressed from MHA orientation. MHA orientation and position data obtained from the proposed method are relevant according to angular dispersion obtained (from 7.5° to 13.9°) and therefore relevant to define behaviour of CVJ.

Dosimetric properties of fluoroscopic EPID for transit dosimetry

AbstractThe aim of this work was to evaluate dose response of fluoroscopic EPID for transit dosimetry applications. Properties studied included warm up time, build-up thickness evaluation, dose history, linearity, stability, and short and long-term reproducibility of EPID response, as well as field size dependence.Pixel value matrices of electronic portal images in DICOM format were analysed in central and 8 off axis points using customised written codes in Matlab. In order to do this, nine 26×26 pixel matrices were selected as regions of interest, the regions represented by these arrays were 1×1 and 0·65×0·65 cm2 at the EPID and isocentre level, respectively.Necessary warm up time for stable operation of EPID is 30 minutes, and there is no need for extra build-up layer to increase the dose response. Linearity tests indicate charged coupled device camera of EPID saturates at 50 cGy level, and does not have linear relationship with dose. Reproducibility and stability of the measurements were excellent and the detector showed same signal with a maximum deviation of &lt;0·3% both in short and long terms. Results of dosimetric evaluation have shown the TheraView fluoroscopic EPID can be used for transit dosimetry purposes.

Advanced Security in Geo Social Applications

In real world geo social applications become more useful. But there is lot of misuse by the personal information. There are many number of security issues in the geo social applications. LocX is new technique which is used to provide the security in geosocial applications. In this process, searching of location axis points are sent to update the server. In this LocX, user will share the secret key prior to location sharing, this will provide through mail or messages. This is not compatible with high range geosocial applications. Here one user will have the secret key of his K friends. LocX is the better technique but it is not suitable for high end geo social applications. In this paper, attribute based encryption instead of sharing secret key. Using this performance overhead and easy to use.

Measurement of the buccolingual inclination of teeth: Manual technique vs 3-dimensional software

In this study, we aimed to measure the inclination of teeth on dental casts by a manual technique with the tooth inclination protractor (TIP; MBI, Newport, United Kingdom) and a newly designed 3-dimensional (3D) software program. The correlation of the 2 techniques was evaluated, and the reliability of each technique was assessed separately. This study was conducted on 36 dental casts of normal, well-aligned Class I occlusions; we assessed 432 teeth. All casts had a normal Class I occlusion. After determining the facial axis of the clinical crown and the facial axis points on the dental casts, we measured the inclinations of the incisors and posterior teeth up to the first molars in each dental arch relative to Andrews' occlusal plane and the posterior occlusal plane using the TIP. Moreover, the casts were scanned by a structured-light 3D scanner. The inclination of teeth relative to the occlusal plane was determined using the new software. To assess the reliability, measurements of all teeth from 15 casts were repeated twice by the 2 methods. Intraclass correlation coefficient and Dahlberg's formula were used for calculation of correlation and reliability. Overall, the 2 techniques were not significantly different in the measurements of the inclinations of the teeth in both jaws. The ranges of Dahlberg's formula were 3.1° to 5.8° for the maxilla and 3.3° to 5.9° for the mandible. The overall correlation of the 2 techniques according to the intraclass correlation coefficient was 0.91. For calculation of reliability, the intraclass correlation coefficients for the TIP and the 3D method were 0.73 and 0.82, respectively. The TIP and the 3D software showed a high correlation for measurement of the inclinations of maxillary and mandibular teeth relative to the occlusal plane. Also, the reproducibility of the measurements in each method was high.

A novel role for histone deacetylase 6 in the regulation of the tolerogenic STAT3/IL-10 pathway in APCs.

APCs are critical in T cell activation and in the induction of T cell tolerance. Epigenetic modifications of specific genes in the APC play a key role in this process, and among them histone deacetylases (HDACs) have emerged as key participants. HDAC6, one of the members of this family of enzymes, has been shown to be involved in regulation of inflammatory and immune responses. In this study, to our knowledge we show for the first time that genetic or pharmacologic disruption of HDAC6 in macrophages and dendritic cells results in diminished production of the immunosuppressive cytokine IL-10 and induction of inflammatory APCs that effectively activate Ag-specific naive T cells and restore the responsiveness of anergic CD4(+) T cells. Mechanistically, we have found that HDAC6 forms a previously unknown molecular complex with STAT3, association that was detected in both the cytoplasmic and nuclear compartments of the APC. By using HDAC6 recombinant mutants we identified the domain comprising amino acids 503-840 as being required for HDAC6 interaction with STAT3. Furthermore, by re-chromatin immunoprecipitation we confirmed that HDAC6 and STAT3 are both recruited to the same DNA sequence within the Il10 gene promoter. Of note, disruption of this complex by knocking down HDAC6 resulted in decreased STAT3 phosphorylation--but no changes in STAT3 acetylation--as well as diminished recruitment of STAT3 to the Il10 gene promoter region. The additional demonstration that a selective HDAC6 inhibitor disrupts this STAT3/IL-10 tolerogenic axis points to HDAC6 as a novel molecular target in APCs to overcome immune tolerance and tips the balance toward T cell immunity.