Centroid Position Research Articles

Method of differential privacy protection for web-based communities based on adding noise to the centroid of positions

The research of location privacy protection has a very important significance for the emergence and sustenance of web-based communities in the big data era. The method of differential privacy for position is a privacy model strictly for the measurement of privacy. However, under the privacy protection for multi-positions, it will bring much bigger errors by adopting the method of adding noise to protect the privacy of multi-positions. In this paper, the author puts forward a new method of differential privacy for multi-positions based on mechanism of adding noise to the centroid of positions and compares with the independent mechanism of adding noise. The experiment shows that the centroid mechanism of adding noise is better than the mechanism of independently adding noise.

Analysis on the change of GF-7 satellite laser altimeter spot centroid position

Analysis on the change of GF-7 satellite laser altimeter spot centroid position

Modelling and characteristics of hybrid coupling hydro-pneumatic suspension for a seven-axle vehicle

A hybrid coupling scheme of parallel connection and contralateral cross-linking was proposed based on the characteristics of high centroid position and low rollover threshold on hydro-pneumatic suspension (HPS) for a seven-axle elevated platform vehicle. A dynamic model with 20 DOFs which can comprehensively reflect vehicle coupling vibration including vertical-lateral-longitudinal-transverse and the joint simulation model of Simulink and AMESim were established based on the structural characteristics of the vehicle. Furthermore, the random road surface model linking the wheels was constructed by filter shaping white noise. Based on the model of hybrid coupling HPS, the study of joint simulation and test on the whole vehicle were conducted, and improved ant colony algorithm (IACA) was applied to the multi-objective optimisation study of HPS parameter matching. The comparison between simulation and test data shows that the weighted acceleration PSD curve is in good agreement, and the relative error of weighted acceleration RMS is small, which indicated that the theoretical model was accurate. The results of simulation and testing show that the optimal parameter matching scheme output by IACA can improve vehicle ride comfort and stability to a significant extent.

Vision-based Size Estimation and Centroid Positioning of Partially Occluded Fruits

The objective of this study was to propose a simple and efficient image processing algorithm for estimating the size and centroid of partially occluded round fruits. In the proposed method, the size and centroid of partially occluded fruit were estimated based on the mathematical properties of the arc-radius. The experimental tests were conducted in a laboratory with orange, Sunkist, apple, and tomato fruits by setting different occlusion conditions. The occlusion percentage was varied between 0% and 90%. The accuracy and processing time of the proposed method were compared with that of the widely-used conic-section circle fitting method. The results showed that the proposed method resulted in an overall accuracy of 95.1% and processing time of 0.66 s, as opposed to 60.2% and 0.68 s, respectively, using the conic-section equation. Compared with the conic-section equation, the proposed method was able to give a more robust prediction, even for low resolution images.

Evaluation of patient-specific MR distortion correction schemes for improved target localization accuracy in SRS.

This work aims at promoting target localization accuracy in cranial stereotactic radiosurgery (SRS) applications by focusing on the correction of sequence-dependent (also patient induced) magnetic resonance (MR) distortions at the lesion locations. A phantom-based quality assurance (QA) methodology was developed and implemented for the evaluation of three distortion correction techniques. The same approach was also adapted to cranial MR images used for SRS treatment planning purposes in single or multiple brain metastases cases. A three-dimensional (3D)-printed head phantom was filled with a 3D polymer gel dosimeter. Following treatment planning and dose delivery, volumes of radiation-induced polymerization served as hypothetical lesions, offering adequate MR contrast with respect to the surrounding unirradiated areas. T1-weighted (T1w) MR imaging was performed at 1.5T using the clinical scanning protocol for SRS. Additional images were acquired to implement three distortion correction methods; the field mapping (FM), mean image (MI) and signal integration (SI) techniques. Reference lesion locations were calculated as the averaged centroid positions of each target identified in the forward and reverse read gradient polarity MRI scans. The same techniques and workflows were implemented for the correction of contrast-enhanced T1w MR images of 10 patients with a total of 27 brain metastases. All methods employed in the phantom study diminished spatial distortion. Median and maximum distortion magnitude decreased from 0.7mm (2.10ppm) and 0.8mm (2.36ppm), respectively, to <0.2mm (0.61ppm) at all target locations, using any of the three techniques. Image quality of the corrected images was acceptable, while contrast-to-noise ratio slightly increased. Results of the patient study were in accordance with the findings of the phantom study. Residual distortion in corrected patient images was found to be <0.3mm in the vast majority of targets. Overall, the MI approach appears to be the most efficient correction method from the three investigated. In cranial SRS applications, patient-specific distortion correction at the target location(s) is feasible and effective, despite the expense of longer imaging time since additional MRI scan(s) need to be performed. A phantom-based QA methodology was developed and presented to reassure efficient implementation of correction techniques for sequence-dependent spatial distortion.

Comparison of internal target volumes defined by three-dimensional, four-dimensional, and cone-beam computed tomography images of a motion phantom.

BackgroundTo explore the variations of the gross tumor volume (GTV) from different three-dimensional computed tomography (3DCT) scan modes and the consistency of internal target volume (ITV) between different 3DCT, cone-beam computed tomography (CBCT) and four-dimensional computed tomography (4DCT) scan, a study using a motion phantom simulating sinusoidal movement was conducted.MethodsFor three 3DCT scan modes: the GTV was contoured, and ITVI was generated on the basis of GTV with a 10-mm margin while ITVII and ITVIII with a 0-mm margin on the motion direction. ITVCBCT and ITVMIP were contoured on the images of CBCT and maximum-intensity projection (MIP) reconstructed 4DCT images. The centroid position shifts of ITVs were analyzed. The volume consistency between ITVI, ITVII, ITVIII and ITVMIP were evaluated by calculating the Dice similarity coefficient (Dsc) and the value of Δ Volume (ΔV). Furthermore, the 3DCT and CBCT images from 12 NSCLC patients were retrospectively collected, then the Dsc and ΔV were calculated.ResultsThe mean ± standard deviation of centroid position of ITVI, ITVII and ITVIII were 2.3±4.7, 2.6±4.0, and 1.0±1.4 mm, respectively. The mean ± standard deviation of Dsc between ITVI, ITVII, ITVIII and ITVMIP were 0.78±0.77, 0.86±0.1, and 0.94±0.05, respectively. The ΔV of ITVI, ITVII, ITVIII were 29.67%, 17.22%, and 6.46%, respectively. The ITV from CBCT showed a deduction rate of 3.1–9.3% compared to 4DCT. For the patients, the mean Dsc andΔV between ITVI and ITVCBCT were 0.50 and 60.76%.ConclusionsThe GTV acquired from 3DCT scan mode I possessed great deviation of centroid position and target volume. ITV on the basis of this GTV was significantly larger than ITVMIP. A good similarity was showed between ITVIII and ITVMIP, 4DCT is still a golden standard for the ITV delineation, but in the absence of 4DCT, image from 3DCT scan mode III and KV-CBCT may be considered for ITV delineation with caution.

A Fast Laser Adjustment-Based Laser Triangulation Displacement Sensor for Dynamic Measurement of a Dispensing Robot

Height measurement and location by a laser sensor is a key technology to ensure accurate and stable operation of a dispensing robot. In addition, alternation of dynamic and static working modes of a robot, as well as variation of surface and height of a workpiece put forward strict requirements for both repeatability and respond speed of the location system. On the basis of the principle of laser triangulation, a displacement sensor applied to a dispensing robot was developed, and a fast laser adjustment algorithm was proposed according to the characteristics of static and dynamic actual laser imaging waveforms on different objects. First, the relationship between the centroid position of static waveform and peak intensity for different measured objects was fitted by least square method, and the intersection point of each curve was solved to confirm the ideal peak intensity, and therefore reduce the interference of different measured objects. Secondly, according to the dynamic centroid difference threshold of two adjacent imaging waveforms, the static and dynamic working modes of the sensor were distinguished, and the peak intensity was adjusted to different intervals by linear iteration. Finally, a Z direction reciprocating test, color adaptability test, and step response test were carried out on the dispensing robot platform; the experiments showed that the repeatability accuracy of the sensor was 2.7 um and the dynamic step response delay was 0.5 ms.

Study on the Influence of the Center of Gravity of Fuel Cell City Bus on its Handling Characteristics

The vehicles driven by combustion engine leads to environmental problems because of fossil fuel consumption. In recent years, many policies have adopted to support the development of new energy vehicles, especially battery electric vehicles as the main strategy in China. For the battery electric vehicles, the position of the battery pack can change the centroid position of the vehicle because of its big mass, and it can also change the loading of each tire in the motion, which has important influence on the vehicle handing and stability performance. This article studies the relationship between handling characteristic and the change of centroid position on a fuel cell city bus, and then solves the suitable centroid position of this vehicle which makes the vehicle have satisfied steering characteristic.

A Theoretical Study about Ergodicity Issues in Predicting Contaminant Plume Evolution in Aquifers

A large-time Eulerian–Lagrangian stochastic approach is employed to: (1) estimate centroid position uncertainty of contaminant plumes that originate from instantaneous point sources in statistically stationary and isotropic porous formations; (2) assess the time needed for achieving ergodic conditions, which would allow for the evaluation of local concentration values based on the only ensemble mean distribution; (3) derive the concentration coefficient of variation (CV) as a function of asymptotic macro-dispersion coefficients and centroid trajectory variances. The results indicate that the decay time of plume position uncertainty is so large that there is practically no chance for effective ergodicity. The concentration coefficient of variation is zero at the centroid but rapidly increases when moving away from it. The dissipative effect of local dispersion in the presence of relatively high Péclet numbers is considerably exalted by marked flow field heterogeneity, which confirms the previously postulated synergic, non-additive effect of advection and local dispersion in passive solute dilution. A further result from this study is the derivation of the power law that relates dimensionless concentration micro-scale to dimensionless local dispersive area. The exponent of this power law is the same that appears in the relationship between dimensionless Kolmogorov turbulent micro-scale and flow Reynolds number.

The Effect of Substitutions on Team Tactical Behavior in Professional Soccer

ABSTRACT Player substitutions are one of the main options for the coach to change tactical behavior of his team. Purpose: The present study therefore investigates the effect of player substitutions on tactical behavior in high-performance soccer using positional data. Method: The sample consisted of 659 substitutions from 234 matches played in the German Bundesliga during the season 2016–2017. Substitutions were classified either as neutral (n = 485), defensive (n = 45), or offensive (n = 129) according to the player’s roles. The teams’ tactical behavior before and after each substitution was analyzed using team centroid, inter-team centroid distance, team length and width, length per width (LpW) ratio, stretch index, and space control for the whole pitch and for each third as the dependent variables. Results: The linear mixed model analysis showed different effects for neutral, defensive, and offensive substitutions. Teams displayed significantly lower stretch index after defensive substitutions. LpW ratio increased with neutral and offensive substitutions, while inter-team distance decreased. The position of the team centroid, space control in the middle third and in the attacking third were also greater following an offensive substitution. Conclusions: These findings demonstrate that player substitutions effectively change tactical behavior of teams. Soccer coaches should perform more offensive substitutions to elicit a higher defensive pressure and improve goal-scoring opportunities, especially due to greater space control in the attacking third. In contrast, defensive substitutions can be used to increase defensive effectiveness through increases in team compactness.

Actual time determination of egg freshness: A centroid rate based approach

• The centroid rate changed synchronously with egg freshness during storage. • The egg yolk position continually changed with redistribution and diffusion of water. • The centroid position of eggs directionally moved towards the blunt end. • A rapid, actual-time approach to nondestructively determine egg freshness was reported. Developing rapid and nondestructive technologies to evaluate egg quality is meaningful for both industrial and consumer application. In this work, a novel determination technology based on centroid rate was explored. Egg samples were stored at 25 °C and 50–60 % relative humidity. With increasing of storage time, the water states of eggs changed with an increase in immobilized water and a decrease in free water. The egg yolk continuously moved to the air chamber with redistribution and diffusion of water, causing the centroid position of eggs directionally to move towards the blunt end. Accordingly, the correlation between the centroid rate and Haugh unit (HU) value has been established, and the coefficient of determination (R 2 ) in the predictive model reached 0.961. This suggested that the approach possessed a high accuracy and had a potential to be applied in evaluating egg quality in actual time during storage.

Diagnosis method for open‐circuit faults of six‐phase permanent magnet synchronous motor drive system

This study proposes a diagnosis method for open-circuit faults of six-phase permanent magnet synchronous motor. When the open-circuit fault occurs in the single-bridge arm or the double-bridge arm, wavelet transform extracts the trigger signal of fault, and the z 1 –z 2 plane current component is analysed. Seven kinds of fault modes are defined by analysing the characteristics of the scatter plot of the z 1 –z 2 plane current component. The fractal dimension of the z 1 –z 2 plane current component scatter plot is calculated to accurately quantify the fault modes. Moreover, 13 fault areas are defined by analysing the current centroid position of the z 1 –z 2 plane current component. First, the diagnosis of two particular kinds of fault modes is completed by selecting the fault area. Besides, the diagnosis of the remaining five kinds of fault modes is completed by combining the fault area and the fault mode. The conditions for judging all open-circuit faults are summarised to establish a fault database. All the open faults can be diagnosed by searching the fault database by the proposed method. Finally, the effectiveness of the method is verified by experiments.

Multi-audience tracking with RGB-D camera on digital signage

Digital signage is widely utilized in digital-out-of-home (DOOH) advertising for marketing and business. Recently, the combination of the digital camera and digital signage enables the advertiser to gather the audience demographic for audience measurement. Audience measurement is useful for the advertiser to understand the audience's behavior and improve their business strategies. When an audience is facing the digital display, the vision-based DOOH system will process the audience's face and broadcast a personalized advertisement. Most of the digital signage is available in an uncontrolled environment of public areas. Thus, it poses two main challenges for the vision-based DOOH system to track the audience's movement, which are multiple adjacent faces and occlusion by passer-by. In this paper, a new framework is proposed to combine the digital signage with a depth camera for tracking multi-face in the three-dimensional (3D) environment. The proposed framework extracts the audience's face centroid position (x, y) and depth information (z) and plots into the aerial map to simulate the audience's movement that is corresponding to the real-world environment. The advertiser can further measure the advertising effectiveness through the audience's behavior.

Falling Detection Research Based on Elderly Behavior Infrared Video Image Contours Ellipse Fitting

Throughout the world, the proportion of the elders in the total population is increasing dramatically, and home-based care has become the most important form of old-age care. Falling is the most common cause of accidents among the elders at home that poses a huge threat to their health and lives. In order to protect the privacy of the elders an accidental falling detection algorithm for the elders in the home has been proposed in this paper. First, contour-based infrared motion video images are used instead of high-definition cameras to collect the elderly behaviors to protect their privacy. Second, ellipse fitting is performed on the infrared video images of the five behaviors including standing, sitting, squatting, bending and falling. The five geometric characteristic variables of the contour-fitting ellipses including the number of ellipses, centroid positions, ellipsoidal areas, horizontal inclinations and long-short axis ratios of the images, have been extracted. Next, an LSTM model is established using the above variables as inputs for feature extraction and classification. Finally, infrared video images of different types of active behaviors of the elders aged from 50 to 70 years have been selected as IFD database for classification detection. Sixty percent of the IFD images are used as training datasets, and 40% of the IFD images are used as test datasets, and compared with the classification detection of URFD datasets which contains optical RGB HD video images of the different behaviors. The experimental results show the effectiveness of the algorithm proposed in this paper which combines the contour ellipse fitting of the infrared video images and the LSTM feature extraction. The average correct classification rate of the normal and falling down behaviors of the elders is above 95%, which is comparable to the optical RGB datasets. The precision of behavior recognition can effectively protect the privacy of the elders, and provide protection for the accidental falling detection of the elders living alone.

The impact of centroid connectors on transit assignment outcomes

In transit modeling, access and egress conditions are often overlooked. The most common modeling technique of these conditions relies on the use of centroid connectors. This definition often uses the geographic position of zone centroids and sets constraints on the maximum number and length of connectors. This definition is subject to spatial aggregation issues and has already been proven to bias car assignment outcomes. The impact on transit assignment outcomes has not yet been demonstrated. The current paper investigates the statistical impact of connectors on transit assignment outcomes in an urban model of Lyon in France. Findings suggest that transit ridership, total passenger-kilometers and transit transfers are dependent on the definition of centroid connectors. Setting arbitrary values for the maximum number and length of connectors statistically affects transit results. The pattern and magnitude of this impact vary, however, between transit modes. The bus and rapid bus systems have been shown to be more sensitive towards the definition of connectors than the subway and the light rail systems. These findings question, to a certain extent, the validity and reliability of transit modeling outcomes.

Radio Echo in the Turbulent Corona and Simulations of Solar Drift-pair Radio Bursts

Abstract Drift-pair bursts are an unusual type of solar low-frequency radio emission, which appear in the dynamic spectra as two parallel drifting bright stripes separated in time. Recent imaging spectroscopy observations allowed for the quantitative characterization of the drifting pairs in terms of source size, position, and evolution. Here, the drift-pair parameters are qualitatively analyzed and compared with the newly developed Monte Carlo ray-tracing technique simulating radio-wave propagation in the inhomogeneous anisotropic turbulent solar corona. The results suggest that drift-pair bursts can be formed due to a combination of refraction and scattering processes, with the trailing component being the result of turbulent reflection (turbulent radio echo). The formation of drift-pair bursts requires an anisotropic scattering with the level of plasma density fluctuations comparable to that in type III bursts, but with a stronger anisotropy at the inner turbulence scale. The anisotropic radio-wave scattering model can quantitatively reproduce the key properties of drift-pair bursts: the apparent source size and its increase with time at a given frequency, the parallel motion of the source centroid positions, and the delay between the burst components. The trailing component is found to be virtually cospatial and following the main component. The simulations suggest that drift-pair bursts are likely to be observed closer to the disk center and below 100 MHz due to the effects of free–free absorption and scattering. The exciter of drift pairs is consistent with propagating packets of whistlers, allowing for a fascinating way to diagnose the plasma turbulence and the radio emission mechanism.

Distortion of a twisted beam passing through a plasma layer.

In this paper, we explore what happens to the intensity profile, phase distribution, and centroid position of a vortex beam (VB) when it passes through a cold collision-less magnetized plasma layer. For this purpose, we utilize angular spectral expansion accompanied by a 4×4 matrix method to obtain the total transmission coefficient, intensity and phase profiles, and centroid shifts of VBs in the output plane. Based on numerical analyses, it is found that the evolution of transverse intensity as well as the distortion of the phase profile of transmitted VBs are greatly affected by variation of radial and angular mode numbers, external magnetic field, plasma number density, and incident angle. In addition, displacement of the VB centroid under variation of angular mode numbers is presented quantitatively. It is expected that the results of this study will give more insight into VB communication, radar probing, and plasma diagnostics.

Research on design and optimization of the pitching float wave energy converter

AbstractWave power generation has been the object of extensive renewable energy research and development all over the world. Concerning the application of a wave energy converter to the harsh environment of the South China Sea, a study of the shape and internal layout of a pitching float wave energy converter was performed based on the mechanism of the oscillating‐float generator. Research methods based on potential flow theory and the use of ANSYS‐AQWA software were applied to predict the hydrodynamic performance and energy conversion of the pitching float wave energy converter. The influence of the float shape, width, side radius, and centroid position on the hydrodynamic performance of the float was analyzed. The results show that the pitching performance of the spherical‐bottom float was the best among the three basic shapes examined. The width of the float had the greatest impact on the pitching performance of the float, and the effect of the radius of the float on the pitching performance was also significant. The pitching performance of the float was improved with the realization of a larger radius in the pitching direction. The centroid position and rotational inertia also had a great impact on the pitching performance of the float. The wave energy converter designed in this study lays the foundation and provides reference for further research on the novel, efficient, and stable wave energy converter.

Single-pixel, single-input-state polarization-sensitive wavefront imaging.

In this Letter, we describe a single-pixel polarization-sensitive imaging technique, capable of generating the birefringence map of a thin specimen by using single-pixel detectors. Spatially modulated light is circularly polarized to illuminate the specimen. The transmitted light through the specimen is then focused via a lens and measured by position-sensitive detectors in two orthogonal polarization channels. The measurement of the irradiance and centroid position of the optical focus and subsequent computations enable the production of polarization-dependent wavefront maps, which can then be utilized to reconstruct sample birefringence information. We demonstrate the feasibility of our method by measuring distribution of optic-axis orientation and phase retardation of various birefringent samples.

Investigation of inter-fraction target motion variations in the context of pencil beam scanned proton therapy in non-small cell lung cancer patients.

PurposeFor locally advanced‐stage non‐small cell lung cancer (NSCLC), inter‐fraction target motion variations during the whole time span of a fractionated treatment course are assessed in a large and representative patient cohort. The primary objective is to develop a suitable motion monitoring strategy for pencil beam scanning proton therapy (PBS‐PT) treatments of NSCLC patients during free breathing.MethodsWeekly 4D computed tomography (4DCT; 41 patients) and daily 4D cone beam computed tomography (4DCBCT; 10 of 41 patients) scans were analyzed for a fully fractionated treatment course. Gross tumor volumes (GTVs) were contoured and the 3D displacement vectors of the centroid positions were compared for all scans. Furthermore, motion amplitude variations in different lung segments were statistically analyzed. The dosimetric impact of target motion variations and target motion assessment was investigated in exemplary patient cases.ResultsThe median observed centroid motion was 3.4 mm (range: 0.2–12.4 mm) with an average variation of 2.2 mm (range: 0.1–8.8 mm). Ten of 32 patients (31.3%) with an initial motion <5 mm increased beyond a 5‐mm motion amplitude during the treatment course. Motion observed in the 4DCBCT scans deviated on average 1.5 mm (range: 0.0–6.0 mm) from the motion observed in the 4DCTs. Larger motion variations for one example patient compromised treatment plan robustness while no dosimetric influence was seen due to motion assessment biases in another example case.ConclusionsTarget motion variations were investigated during the course of radiotherapy for NSCLC patients. Patients with initial GTV motion amplitudes of < 2 mm can be assumed to be stable in motion during the treatment course. For treatments of NSCLC patients who exhibit motion amplitudes of > 2 mm, 4DCBCT should be considered for motion monitoring due to substantial motion variations observed.