3,175 research outputs found
Study on the non-uniform contact between the shaft-taper hole and toolholder for a high speed spindle
The drawbar mechanism of a motor built-in high speed spindle with ATC is to provide the clamping force to grip the toolholder for high speed cutting. The connection status between the shaft-taper hole and toolholder is important on the spindle design and manufacture. In this paper, contact analyses of the toolholder and shaft-taper hole using contact elements are conducted. The stresses distribution between the toolholder and shaft-taper hole is then obtained and is used for the subsequent finite element modal analysis. The finite element modal analysis results are verified by the experimental modal testing to guarantee the accuracy of finite element model. Non-uniform contact conditions between the shaft-taper hole and toolholder is addressed especially in this study. Different intensities of resistance to the cutting torque due to different clamping forces, coefficients of friction, contact types and contact rates are provided. The deformations on the shaft and toolholder are also studied in this paper. The results are helpful to design a motor built-in high speed spindle with a suitable clamping force for providing the necessary torque to resist the cutting force and to give a suggestion on the manufacture of toolholder and shaft-taper hole
Null and time-like geodesics in Kerr-Newman black hole exterior
We study the null and time-like geodesics of the light and the neutral
particles respectively in the exterior of Kerr-Newman black holes. The geodesic
equations are known to be written as a set of first-order differential
equations in Mino time from which the angular and radial potentials can be
defined. We classify the roots for both potentials, and mainly focus on those
of the radial potential with an emphasis on the effect from the charge of the
black holes. We then obtain the solutions of the trajectories in terms of the
elliptical integrals and the Jacobian elliptic functions for both null and
time-like geodesics, which are manifestly real functions of the Mino time that
the initial conditions can be explicitly specified. We also describe the
details of how to reduce those solutions into the cases of the spherical
orbits. The effect of the black hole's charge decreases the radii of the
spherical motion of the light and the particle for both direct and retrograde
motions. In particular, we focus on the light/particle boomerang of the
spherical orbits due to the frame dragging from the back hole's spin with the
effect from the charge of the black hole. To sustain the change of the
azimuthal angle of the light rays, say for example during the
whole trip, the presence of the black hole's charge decreases the radius of the
orbit and consequently reduces the needed values of the black hole's spin. As
for the particle boomerang, the particle's inertia renders smaller change of
the angle as compared with the light boomerang. Moreover, the
black hole's charge also results in the smaller angle change of
the particle than that in the Kerr case. The implications of the obtained
results to observations are discussed.Comment: 50 pages, 18 figure
Investigation of clamping force for a high-speed shaft with toolholder using contact element analysis
The main characteristic of a motor built-in high speed spindle with ATC is to perform high-speed cutting. The drawbar mechanism of spindle provides the clamping force to grip the toolholder for machining. Poor connection between the shaft-taper hole and toolholder will cause the danger of toolholder to loose and slip. In this study, a solid modeling method is adopted to investigate the effects of clamping force provided by the drawbar mechanism. Contact analyses of the toolholder and shaft-taper hole using contact elements are conducted. The stresses distribution between the toolholder and shaft-taper hole is then obtained. The effects of pre-stress are then adopted for subsequent finite element modal analysis. The finite element modal analysis results are verified by the experimental modal testing. The results presented herein indicate that it is effective in simulating and analyzing the contact relationship between the toolholder and shaft-taper hole by using contact elements. Also, it is proved that the shaft-toolholder system can provide different friction torque to resist the cutting force due to different clamping forces and coefficients of friction
Experimental demonstration of measurement-device-independent measure of quantum steering
Within the framework of quantum refereed steering games, quantum steerability can be certified without any assumption on the underlying state nor the measurements involved. Such a scheme is termed the measurement-device-independent (MDI) scenario. Here, we introduce a measure of steerability in an MDI scenario, i.e., the result merely depends on the observed statistics and the quantum inputs. We prove that such a measure satisfies the convex steering monotone. Moreover, it is robust against not only measurement biases but also losses. We also experimentally estimate the amount of the measure with an entangled photon source. As two by-products, our experimental results provide lower bounds on an entanglement measure of the underlying state and an incompatible measure of the involved measurement. Our research paves a way for exploring one-side device-independent quantum information processing within an MDI framework
CVD-grown monolayer MoS2 in bioabsorbable electronics and biosensors
Transient electronics entails the capability of electronic components to dissolve or reabsorb in a controlled manner when used in biomedical implants. Here, the authors perform a systematic study of the processes of hydrolysis, bioabsorption, cytotoxicity and immunological biocompatibility of monolayer MoS2
Detecting Variability in Massive Astronomical Time-Series Data I: application of an infinite Gaussian mixture model
We present a new framework to detect various types of variable objects within
massive astronomical time-series data. Assuming that the dominant population of
objects is non-variable, we find outliers from this population by using a
non-parametric Bayesian clustering algorithm based on an infinite
GaussianMixtureModel (GMM) and the Dirichlet Process. The algorithm extracts
information from a given dataset, which is described by six variability
indices. The GMM uses those variability indices to recover clusters that are
described by six-dimensional multivariate Gaussian distributions, allowing our
approach to consider the sampling pattern of time-series data, systematic
biases, the number of data points for each light curve, and photometric
quality. Using the Northern Sky Variability Survey data, we test our approach
and prove that the infinite GMM is useful at detecting variable objects, while
providing statistical inference estimation that suppresses false detection. The
proposed approach will be effective in the exploration of future surveys such
as GAIA, Pan-Starrs, and LSST, which will produce massive time-series data.Comment: accepted for publication in MNRA
The Results of Cervical Nucleoplasty in Patients with Cervical Disc Disorder: A Retrospective Clinical Study of 22 Patients
Nucleoplasty is a minimally invasive spinal surgery using a Coblation Ⓡ technique that creates small voids within the disc. The purpose of this study was to evaluate the efficacy of cervical nucleoplasty in patients with cervical disc disorder. Methods: Between March 2008 and December 2009, 22 patients with cervical disc disorders were treated with cervical nucleoplasty after failed conservative treatment. All procedures were performed under local anesthesia, and fluoroscopic guidance and voids were created in the disc with the Perc TM DC Spine Wand TM. Clinical outcomes were evaluated by the Modified Macnab criteria and VAS score at preprocedure, postprocedure 1 month, and 6 months. Results: Six patients had one, eight patients had two and eight patients had three discs treated; a total of 46 procedures was performed. Mean VAS reduced from 9.3 at preprocedure to 3.7 at postprocedure 1 month and to 3.4 at postprocedure 6 months. There was no significant complication related to the procedure within the first month. Outcomes were good or excellent in 17/22 (77.3%) cases. Postprocedure magnetic resonance imaging was acquired in two patients after two months showing morphologic evidence of volume reduction of protruded disc material in one patient but not in the other. Conclusions: Percutaneous decompression with a nucleoplasty using a Coblation Ⓡ technique in the treatment of cervical disc disorder is a safe, minimally-invasive and less uncomfortable procedure, with an excellent short-term clinical outcome. (Korean J Pain 2011; 24: 36-43
Post-translational regulation enables robust p53 regulation
The tumor suppressor protein p53 plays important roles in DNA damage repair, cell cycle arrest and apoptosis. Due to its critical functions, the level of p53 is tightly regulated by a negative feedback mechanism to increase its tolerance towards fluctuations and disturbances. Interestingly, the p53 level is controlled by post-translational regulation rather than transcriptional regulation in this feedback mechanism
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