Two-point Analysis Research Articles

An Analytical Model of Four-Point Contact Rolling Element Ball Bearings

The purpose of this work is to establish an analytical model and standard way to predict the performance characteristics of a four-point contact, or gothic arch type, rolling element ball bearing. Classical rolling element bearing theory, as developed by Jones, has been extended to include the complex kinematics of the four-point contact bearing; thereby providing complete elementwise attitude and internal load distribution of the bearing under operating conditions. Standard performance parameters, such as element contact stresses, contact angles, inner ring deflections, nonlinear stiffness's, torque, and L10 life, are solved explicitly via standard Newton–Raphson techniques. Race control theory is replaced with a minimum energy state theory to allow both spin and slip to occur at the ball-to-raceway contact. The developed four-point model was programed within the orbis software program. Various test cases are analyzed and key analytical results are compared with the Jones four-point contact ball bearing analysis program, the Wind Turbine Design Guideline, DG03, and traditional two-point (angular contact) analysis codes. Model results for the internal distribution of ball loads and contact angles match the Jones program extremely well for all cases considered. Some differences are found with the DG03 analysis methods, and it is found that modeling a four-point contact bearing by overlaying two opposed angular contact bearings can result in gross errors.

Estimating sparse precision matrices

We apply a method recently introduced to the statistical literature to directly estimate the precision matrix from an ensemble of samples drawn from a corresponding Gaussian distribution. Motivated by the observation that cosmological precision matrices are often approximately sparse, the method allows one to exploit this sparsity of the precision matrix to more quickly converge to an asymptotic 1/sqrt(Nsim) rate while simultaneously providing an error model for all of the terms. Such an estimate can be used as the starting point for further regularization efforts which can improve upon the 1/sqrt(Nsim) limit above, and incorporating such additional steps is straightforward within this framework. We demonstrate the technique with toy models and with an example motivated by large-scale structure two-point analysis, showing significant improvements in the rate of convergence.For the large-scale structure example we find errors on the precision matrix which are factors of 5 smaller than for the sample precision matrix for thousands of simulations or, alternatively, convergence to the same error level with more than an order of magnitude fewer simulations.

A high-dimensional linkage analysis model for characterizing crossover interference.

Linkage analysis has played an important role in understanding genome structure and evolution. However, two-point linkage analysis widely used for genetic map construction can rarely chart a detailed picture of genome organization because it fails to identify the dependence of crossovers distributed along the length of a chromosome, a phenomenon known as crossover interference. Multi-point analysis, proven to be more advantageous in gene ordering and genetic distance estimation for dominant markers than two-point analysis, is equipped with a capacity to discern and quantify crossover interference. Here, we review a statistical model for four-point analysis, which, beyond three-point analysis, can characterize crossover interference that takes place not only between two adjacent chromosomal intervals, but also over multiple successive intervals. This procedure provides an analytical tool to elucidate the detailed landscape of crossover interference over the genome and further infer the evolution of genome structure and organization.

Search for spatial and temporal collective effects in the ANTARES neutrino telescope data

We investigate potential collective effects in the spatial and temporal domains in ANTARES data sets. On the one hand, we apply a two-point correlation analysis to look for inhomogeneities in the arrival directions of the high energy muon neutrino candidates detected between 2007 and 2012. This enables us to provide constraints on models of a population of point sources too faint to be detected by a likelihood-based method. On the other hand, we perform a search for ANTARES neutrino events in temporal coincidence with IceCube High-Energy Starting Events located within 45 ∘ from the Galactic Center. This study, also based on a two-point correlation function, is sensitive to transient emission and does not a prior on either the burst timing structure or on the electromagnetic emission. Therefore, it provides an effective way to acquire information on the possible origin of the IceCube astrophysical signal from transient sources.

POLARBEAR constraints on cosmic birefringence and primordial magnetic fields

We constrain anisotropic cosmic birefringence using four-point correlations of even-parity E-mode and odd-parity B-mode polarization in the cosmic microwave background measurements made by the POLARization of the Background Radiation (POLARBEAR) experiment in its first season of observations. We find that the anisotropic cosmic birefringence signal from any parity-violating processes is consistent with zero. The Faraday rotation from anisotropic cosmic birefringence can be compared with the equivalent quantity generated by primordial magnetic fields if they existed. The POLARBEAR nondetection translates into a 95% confidence level (C.L.) upper limit of 93 nanogauss (nG) on the amplitude of an equivalent primordial magnetic field inclusive of systematic uncertainties. This four-point correlation constraint on Faraday rotation is about 15 times tighter than the upper limit of 1380 nG inferred from constraining the contribution of Faraday rotation to two-point correlations of B-modes measured by Planck in 2015. Metric perturbations sourced by primordial magnetic fields would also contribute to the B-mode power spectrum. Using the POLARBEAR measurements of the B-mode power spectrum (two-point correlation), we set a 95% C.L. upper limit of 3.9 nG on primordial magnetic fields assuming a flat prior on the field amplitude. This limit is comparable to what was found in the Planck 2015 two-point correlation analysis with both temperature and polarization. We perform a set of systematic error tests and find no evidence for contamination. This work marks the first time that anisotropic cosmic birefringence or primordial magnetic fields have been constrained from the ground at subdegree scales.Received 8 September 2015DOI:https://doi.org/10.1103/PhysRevD.92.123509© 2015 American Physical Society

Complete self-preservation along the axis of a circular cylinder far wake

Self-preservation (SP) analyses are applied to the mean momentum and the scale-by-scale energy budget equations in the far wake of a circular cylinder. The scale-by-scale SP analysis, which is a two-point analysis, complements the SP analysis of the mean momentum equation. Power-law variations are derived for different length scales (e.g. the Taylor microscale and the Kolmogorov length scale) and velocity scales (e.g. the root mean square and the Kolmogorov velocity scale). Further, the SP solutions for the scale-by-scale energy budget equation are exploited to develop an exact relation to estimate the mean turbulent kinetic energy dissipation rate $\bar{{\it\epsilon}}$ on the wake axis. These SP solutions and the new $\bar{{\it\epsilon}}$ relation are well supported by hot-wire data in the far wake at a Reynolds number of 2000 based on the free stream velocity and the cylinder diameter. On the far-wake axis, both the energy spectra and the structure functions exhibit an almost perfect collapse over all wavenumbers and separations, irrespective of the set of scaling variables used for normalisation. This is consistent with a complete self-preservation (i.e. SP is satisfied at all scales of motion) in the far wake.

UNVEILING A RICH SYSTEM OF FAINT DWARF GALAXIES IN THE NEXT GENERATION FORNAX SURVEY

We report the discovery of 158 previously undetected dwarf galaxies in the Fornax cluster central regions using a deep coadded $u, g$ and $i$-band image obtained with the DECam wide-field camera mounted on the 4-meter Blanco telescope at the Cerro Tololo Interamerican Observatory as part of the {\it Next Generation Fornax Survey} (NGFS). The new dwarf galaxies have quasi-exponential light profiles, effective radii $0.1\!<\!r_e\!<\!2.8$ kpc and average effective surface brightness values $22.0\!<\!\mu_i\!<\!28.0$ mag arcsec$^{-2}$. We confirm the existence of ultra-diffuse galaxies (UDGs) in the Fornax core regions that resemble counterparts recently discovered in the Virgo and Coma galaxy clusters.~We also find extremely low surface brightness NGFS dwarfs, which are several magnitudes fainter than the classical UDGs. The faintest dwarf candidate in our NGFS sample has an absolute magnitude of $M_i\!=\!-8.0$\,mag. The nucleation fraction of the NGFS dwarf galaxy sample appears to decrease as a function of their total luminosity, reaching from a nucleation fraction of $>\!75\%$ at luminosities brighter than $M_i\!\simeq\!-15.0$ mag to $0\%$ at luminosities fainter than $M_i\!\simeq\!-10.0$ mag. The two-point correlation function analysis of the NGFS dwarf sample shows an excess on length scales below $\sim\!100$ kpc, pointing to the clustering of dwarf galaxies in the Fornax cluster core.

Experimental study of the flow structures of 3D turbulent offset jets

ABSTRACTThree-dimensional turbulent offset jets were investigated using a particle image velocimetry technique. Detailed measurements were performed for offset height ratios of 0, 2 and 4. The presence of backflow influenced the distribution of the mean velocity and Reynolds stresses. A two-point correlation analysis was used to investigate the spatial distribution of large-scale structures within the inner shear layer of the flow domain. The results revealed that large-scale structures dominate the inner layer of the self-similarity region. Proper orthogonal decomposition was performed on the fluctuating velocity field within the symmetry and lateral planes using the snapshot approach. Results from the reconstructed field provided insight into the contributions of the most energetic structures to the turbulence statistics. The energetic structures contributed more to the Reynolds shear stress and streamwise turbulence intensity, while contributing less to the wall-normal turbulence intensity.

The ALHAMBRA survey: Estimation of the clustering signal encoded in the cosmic variance

The relative cosmic variance ($\sigma_v$) is a fundamental source of uncertainty in pencil-beam surveys and, as a particular case of count-in-cell statistics, can be used to estimate the bias between galaxies and their underlying dark-matter distribution. Our goal is to test the significance of the clustering information encoded in the $\sigma_v$ measured in the ALHAMBRA survey. We measure the cosmic variance of several galaxy populations selected with $B-$band luminosity at $0.35 \leq z < 1.05$ as the intrinsic dispersion in the number density distribution derived from the 48 ALHAMBRA subfields. We compare the observational $\sigma_v$ with the cosmic variance of the dark matter expected from the theory, $\sigma_{v,{\rm dm}}$. This provides an estimation of the galaxy bias $b$. The galaxy bias from the cosmic variance is in excellent agreement with the bias estimated by two-point correlation function analysis in ALHAMBRA. This holds for different redshift bins, for red and blue subsamples, and for several $B-$band luminosity selections. We find that $b$ increases with the $B-$band luminosity and the redshift, as expected from previous work. Moreover, red galaxies have a larger bias than blue galaxies, with a relative bias of $b_{\rm rel} = 1.4 \pm 0.2$. Our results demonstrate that the cosmic variance measured in ALHAMBRA is due to the clustering of galaxies and can be used to characterise the $\sigma_v$ affecting pencil-beam surveys. In addition, it can also be used to estimate the galaxy bias $b$ from a method independent of correlation functions.

Cosmological constraints from weak lensing peak statistics with Canada-France-Hawaii Telescope Stripe 82 Survey

We derived constraints on cosmological parameters using weak lensing peak statistics measured on the ∼ 130 deg2 of the Canada–France–Hawaii Telescope Stripe 82 Survey. This analysis demonstrates the feasibility of using peak statistics in cosmological studies. For our measurements, we considered peaks with signal-to-noise ratio in the range of ν = [3, 6]. For a flat Λ cold dark matter model with only (Ωm, σ8) as free parameters, we constrained the parameters of the following relation Σ8 = σ8(Ωm/0.27)α to be Σ8 = 0.82 ± 0.03 and α = 0.43 ± 0.02. The α value found is considerably smaller than the one measured in two-point and three-point cosmic shear correlation analyses, showing a significant complement of peak statistics to standard weak lensing cosmological studies. The derived constraints on (Ωm, σ8) are fully consistent with the ones from either WMAP9 or Planck. From the weak lensing peak abundances alone, we obtained marginalized mean values of |$\Omega _{\rm m}=0.38^{+0.27}_{-0.24}$| and σ8 = 0.81 ± 0.26. Finally, we also explored the potential of using weak lensing peak statistics to constrain the mass–concentration relation of dark matter haloes simultaneously with cosmological parameters.

Multipoint observation of anisotropy and intermittency in solar-wind turbulence

Using high-resolution magnetic-field Cluster observations, we have investigated the magnetic-field anisotropy via the second- and fourth-order structure functions over a wide range of scales reaching below the subproton scale. The magnetic-field increments have been computed from single- and two-spacecraft measurements. The two-satellite technique allows us to study the increments as a function of an actual space lag. Both single- and two-point analyses show that the magnetic field is anisotropic even at small time/spatial scales. The single-spacecraft data also shows that the degree of anisotropy does not change with the scale at proton and subproton scales. It is also pointed out that the degree of magnetic-field anisotropy tends to be overestimated in the single-spacecraft data analysis. This is particularly evident at small scales and it depends on the angle between the spacecraft separation and the flow direction. From the fourth-order moment of the probability density function of the magnetic-field increments we have also investigated the presence of intermittency in the fluctuations. Even though to a different degree, intermittency was present over the entire range of scales, with an indication of scale invariance at subproton scales.

Multimodal Instability in the Weakly Underexpanded Elliptic Jet

Particle image velocimetry and schlieren imaging are used to study the interrelationship between the hydrodynamic and acoustic fields of a screeching underexpanded elliptical jet. An elliptical jet with an aspect ratio equal to two is studied at a nozzle pressure ratio of 2.2. Two-point correlation analysis of the schlieren image sets suggests that the flow is dominated by a flapping mode about the major axis plane, however, a proper orthogonal decomposition of the transverse velocity field suggests that there is also a helical mode that becomes dominant further downstream. The flapping mode appears to grow, saturate, and decay more rapidly and is associated with the production of discrete acoustic tones in the form of jet screech, whereas no discrete tone sound production is observed from the helical mode. It is suggested that the lack of tonal generation by the helical mode is linked to its slower growth; it does not produce coherent fluctuations in shear layer vorticity in the vicinity of the jet shock cells.

&amp;#8220;ETNOINTELECTUALIDAD&amp;#8221;: CONSTRUCCIÓN DE &amp;#8220;SUJETOS LETRADOS&amp;#8221; EN AMÉRICA LATINA, 1980-2010

This paper studies the processes of historical social construction of “indigenous intellectuals”, one of the most important and complex stages for ethnic movements in Latin America: redemocratization, the opening of markets and high participation of the grassroots mobilization processes. Thus, this proposition develops a two-point analysis: firstly, the definition and selfdefinition which is made by an indigenous intellectual and, on the other hand, the problems facing this etnointellectual in a scientific and Western semantic framework.

Flow characteristics within the recirculation region of three-dimensional turbulent offset jet

ABSTRACTThe present study investigates the flow characteristics within the recirculation region of three-dimensional offset jets using a particle image velocimetry technique. Measurements were performed for four nozzle offset height ratios of 0, 2, 4 and 8. The discharged jet entrained the ambient fluid as depicted by streamlines superimposed on the mean velocity contours. Analysis of the flow field showed that the maximum streamwise mean velocity decay rate increased with increasing offset height ratio. Wall-normal spread rates of 0.066 and 0.016 were obtained for jets with offset height ratios of 0 and 2, respectively, and lateral spread rates of 0.116, 0.114 and 0.096 for jets with offset height ratios of 0, 2 and 4, respectively. The reattachment lengths of the jets increased with increasing offset height ratio. Profiles of the mean velocities, Reynolds stresses and some of the budget terms (specifically, production, diffusion and convective terms) of the turbulent kinetic energy have been investigated. It was observed that increasing the offset height ratio influenced the distribution of these quantities within the recirculation region. A two-point velocity correlation analysis was performed to analyse the flow structures within the recirculation region. The two-point correlation revealed some large-scale structures which were observed to increase in size as the offset height ratio increased. The two-point correlation analysis also revealed that the estimated integral length scales within the recirculation region of the flow increased with increasing offset height ratio.

Space-frequency analysis with parallel computing in a phase-sensitive optical time-domain reflectometer distributed sensor.

For a phase-sensitive optical time-domain reflectometer (ϕ-OTDR) distributed sensor system, space-frequency analysis can reduce the false alarm by analyzing the frequency distribution compared with the traditional difference value method. We propose a graphics processing unit (GPU)-based parallel computing method to perform multichannel fast Fourier transform (FFT) and realize the real-time space-frequency analysis. The experiment results show that the time taken by the multichannel FFT decreased considerably based on this GPU parallel computing. The method can be completed with a sensing fiber up to 16 km long and an entry-level GPU. Meanwhile, the GPU can reduce the computing load of the central processing unit from 70% down to less than 20%. We carried out an experiment on a two-point space-frequency analysis, and the results clearly and simultaneously show the vibration point locations and frequency components. The sensor system outputs the real-time space-frequency spectra continuously with a spatial resolution of 16.3 m and frequency resolution of 2.25 Hz.

Investigation of Kelvin-Helmholtz instability in the stable boundary layer using large eddy simulation

We conducted a large eddy simulation of the stable boundary layer in order to investigate the coherent structure of the Kelvin–Helmholtz instability (KHI). The simulations were performed using the initial conditions based on the Beaufort Sea Arctic Stratus Experiment. We used the Richardson criteria and the linear stability analysis methods to detect the KHI and to adopt the eigenvalue and the two-point correlation methods to identify the vortex cores near the KHI region. In the two-point correlation analysis, the rotating configuration of the KHI varied in angles and lengths, according to the difference in the distance to the inversion layer. These vortex cores were divided into four components in different directions, defined by the signs of the x and y vorticities (Wx and Wy, respectively), and the vortex cores of the two components related to the negative Wy were elongated along the streamwise direction. The ratio between the sweeps and the ejections exhibited a linear trend as the boundary layer became more stable. Also, the sweep motion was dominant to the ejection motion for a high-stability index of 1.63. Furthermore, the plot of the vortex angles versus the stability index illustrated a linear relationship, indicating that the varying trends of the vortex angles were independent from the distance to the inversion layer in a sensitivity study of the vortex angle.

Consequences of self-preservation on the axis of a turbulent round jet

AbstractOn the basis of a two-point similarity analysis, the well-known power-law variations for the mean kinetic energy dissipation rate $\overline{\epsilon }$ and the longitudinal velocity variance $\overline{u^2}$ on the axis of a round jet are derived. In particular, the prefactor for $\overline{\epsilon } \propto (x-x_0)^{-4}$, where $x_0$ is a virtual origin, follows immediately from the variation of the mean velocity, the constancy of the local turbulent intensity and the ratio between the axial and transverse velocity variance. Second, the limit at small separations of the two-point budget equation yields an exact relation illustrating the equilibrium between the skewness of the longitudinal velocity derivative $S$ and the destruction coefficient $G$ of enstrophy. By comparing the latter relation with that for homogeneous isotropic decaying turbulence, it is shown that the approach towards the asymptotic state at infinite Reynolds number of $S+2G/R_{\lambda }$ in the jet differs from that in purely decaying turbulence, although $S+2G/R_{\lambda } \propto R_{\lambda }^{-1}$ in each case. This suggests that, at finite Reynolds numbers, the transport equation for $\overline{\epsilon }$ imposes a fundamental constraint on the balance between $S$ and $G$ that depends on the type of large-scale forcing and may thus differ from flow to flow. This questions the conjecture that $S$ and $G$ follow a universal evolution with $R_{\lambda }$; instead, $S$ and $G$ must be tested separately in each flow. The implication for the constant $C_{\epsilon 2}$ in the $k-\overline{\epsilon }$ model is also discussed.

A Novel PRPF31 Mutation in a Large Chinese Family with Autosomal Dominant Retinitis Pigmentosa and Macular Degeneration

PurposeThis study was intended to identify the disease causing genes in a large Chinese family with autosomal dominant retinitis pigmentosa and macular degeneration.MethodsA genome scan analysis was conducted in this family for disease gene preliminary mapping. Snapshot analysis of selected SNPs for two-point LOD score analysis for candidate gene filter. Candidate gene PRPF31 whole exons' sequencing was executed to identify mutations.ResultsA novel nonsense mutation caused by an insertion was found in PRPF31 gene. All the 19 RP patients in 1085 family are carrying this heterozygous nonsense mutation. The nonsense mutation is in PRPF31 gene exon9 at chr19:54629961-54629961, inserting nucleotide “A” that generates the coding protein frame shift from p.307 and early termination at p.322 in the snoRNA binding domain (NOP domain).ConclusionThis report is the first to associate PRPF31 gene's nonsense mutation and adRP and JMD. Our findings revealed that PRPF31 can lead to different clinical phenotypes in the same family, resulting either in adRP or syndrome of adRP and JMD. We believe our identification of the novel “A” insertion mutation in exon9 at chr19:54629961-54629961 in PRPF31 can provide further genetic evidence for clinical test for adRP and JMD.

Introducing the Tibial–Dorsalis Pedis Osteocutaneous Shin Flap

The authors investigated the possibility of incorporating a well-vascularized, partial corticotomy of the anterolateral aspect of the tibia "in-series" with a dorsalis pedis fasciocutaneous free flap for oromandibular reconstruction. A cadaveric injection study was performed to characterize the vascular territory of the anterior tibial artery with regard to the surrounding osseous and soft tissue. The two-point breaking strength of the tibia (twist) was examined with fracture strain gauge analysis to determine the threshold of tibia corticotomy that would lead to a pathologic fracture. Finally, the authors performed an in vivo prospective clinical examination of the tibial-dorsalis pedis osteocutaneous shin flap. The perfusion study revealed that the anterior tibial artery provided a rich matrix of musculofascial periosteal blood supply to the anterolateral cortex of the tibia that could potentially support free osseous tibial transfer. Two-point osteotomy fracture strain gauge analysis demonstrated that the threshold of tibia corticotomy that would lead to pathologic fracture of the remaining tibia was greater than 30 percent. The osteocutaneous shin flap was performed in eight patients. The mean follow-up was 61 months. There were no cases of flap loss, salivary fistula, nonunion, or tibia pathologic fracture. All patients achieved ambulation. The authors introduce the osteocutaneous tibial-dorsalis pedis free vascularized flap as a viable option for oromandibular reconstruction. Its most notable advantage is the independent mobility of the skin paddle, in combination with bone stock that replicates mandibular bone dimensions, facilitating primary osseointegration or denture rehabilitation. Therapeutic, IV.

Introducing the Tibial‐Dorsalis Pedis Osteocutaneous Shin Flap: A New Option for Oromandibular Reconstruction

Objectives: The authors investigate the possibility of incorporating a well vascularized, partial corticotomy of the anterolateral aspect of the tibia in-series with a dorsalis pedis fasciocutaneous free flap for oromandibular reconstruction. Methods: The study consisted of three components. A cadaveric perfusion study was performed to characterize the vascular territory of the anterior tibial artery in regard to the surrounding osseous and soft tissue. A two-point breaking strength of the tibia was examined with fracture strain gauge analysis to determine the threshold of tibia corticotomy that would lead to a pathological fracture. Finally, the authors performed an in-vivo prospective clinical examination of the tibial-dorsalis pedis osteocutaneous shin flap. Results: The perfusion study revealed that the anterior tibial artery provided a rich matrix of myofascial periosteal blood supply to the anterolateral cortex of the tibia that could support free osseous tibial transfer. Two-point osteotomy fracture strain gauge analysis demonstrated that the threshold of tibia corticotomy that would lead to fracture of the remaining tibia was 30%. The osteocutaneous shin flap was performed in eight patients for recurrent, radiation failure, oral cavity T4 squamous cell carcinomas. The mean follow-up was 61 months. There were no cases of flap loss, salivary fistula, nonunion, or tibia pathologic fracture. All patients achieved ambulation. Conclusions: The authors introduce the osteocutaneous tibial-dorsalis pedis free vascularized flap as a viable option for oromandibular reconstruction. Its most notable advantage is the independent mobility of the skin paddle, in combination with an osseous reconstruction of the mandibular arch that facilitates primary osseointegration or denture rehabilitation.