716 research outputs found
On the 2-part of the Birch-Swinnerton-Dyer conjecture for elliptic curves with complex multiplication
Given an elliptic curve E over Q with complex multiplication having good
reduction at 2, we investigate the 2-adic valuation of the algebraic part of
the L-value at 1 for a family of quadratic twists. In particular, we prove a
lower bound for this valuation in terms of the Tamagawa number in a form
predicted by the conjecture of Birch and Swinnerton-Dyer
Elastic modulus of viral nanotubes
We report an experimental and theoretical study of the radial elasticity of tobacco mosaic virus (TMV) nanotubes. An atomic force microscope tip is used to apply small radial indentations to deform TMV nanotubes. The initial elastic response of TMV nanotubes can be described by finite-element analysis in 5 nm indentation depths and Hertz theory in 1.5 nm indentation depths. The derived radial Young\u27s modulus of TMV nanotubes is 0.92 +/- 0.15 GPa from finite-element analysis and 1.0 +/- 0.2 GPa from the Hertz model, which are comparable with the reported axial Young\u27s modulus of 1.1 GPa [Falvo et al., Biophys. J. 72, 1396 (1997)]
Effect of Particle Size Distribution on Fluid Rheology of High Density Drilling Fluid
The control and maintenance of rheological properties is the key technical problem that needs to be solved for high density drilling fluid. The influence of particle size distribution on the rheology of high density drilling fluid is analyzed. In order to identify the best particle size distribution of barite and iron ore, the influence of distribution modulus on the rheology of high density drilling fluid weighted by barite and iron ore is investigated based on the Aflred distribution equation. The experimental results show that weighting materials particle distribution has great effect on rheological properties of high density drilling fluid. When the barite particle distribution modulus n=0.4 and iron ore powder particle distribution modulus n=0.6, the rheology of high density drilling fluid is best, while the low settlement density difference and low HTHP filtrate loss is maintained
CCD photometric study of the W UMa-type binary II CMa in the field of Berkeley 33
The CCD photometric data of the EW-type binary, II CMa, which is a contact
star in the field of the middle-aged open cluster Berkeley 33, are presented.
The complete R light curve was obtained. In the present paper, using the five
CCD epochs of light minimum (three of them are calculated from Mazur et al.
(1993)'s data and two from our new data), the orbital period P was revised to
0.22919704 days. The complete R light curve was analyzed by using the 2003
version of W-D (Wilson-Devinney) program. It is found that this is a contact
system with a mass ratio and a contact factor . The high mass
ratio () and the low contact factor () indicate that the system
just evolved into the marginal contact stage
Clamping Force Distribution within Press Pack IGBTs
Press pack insulated gated bipolar transistors (PP IGBTs) have been gradually used in the high-voltage and high-power-density applications, such as the power system and electric locomotive, with its advantages of double-sided cooling, higher power density, and easy to connect in series compared with traditional wire-bonded power IGBT modules. However, the clamping force is quite important for PP IGBTs because too much clamping fore will cause mechanical damage to the silicon chips and too little clamping force will increase the junction temperature of the silicon chips due to the increased thermal contact resistance. And eventually it leads to thermal damage. Furthermore, the clamping force distribution within PP IGBTs is affected by many factors, and they can be divided into the internal and external factors. The finite element analysis model of the PP IGBTs is established based on the theory of elastic mechanics to obtain the influence of the affect factors, including the external clamping modes, spring design, thermal stress, the machining accuracy, and so on. The contribution of those affect factors to the clamping force distribution is ranked, and this can be a guideline not only for users but also for the manufacturers
EFFECTS OF MONITORING SIGNAL HYSTERESIS ON SPEED REGULATION FOR THE AERO-DERIVATIVE GAS TURBINE
Sensor aging and sensor failure are the common phenomena due to the high temperature and pressure environment for gas turbines, which can lead to hysteresis of monitoring signals. In this paper, a kind of aero-derivative gas turbine is taken as the research object. The hysteresis effects of single monitoring signal and coupling of multiple monitoring signals on speed control are mainly studied, and the analysis is carried out from the perspective of adjustment time, overshoot, fuel quantity and fuel quantity regulation output. The analysis results show that the pressure signal hysteresis will lead to speed suspension. The speed signal hysteresis will change the speed regulation into a multi-step mode. When the monitoring signal hysteresis is coupled, the effect of pressure signal hysteresis is greater than that of speed signal hysteresis. The results of this paper can provide a reference for the optimal design of speed control of aero-derivative gas turbine
A Palladium-Catalyzed 4CzIPN-Mediated Decarboxylative Acylation Reaction of O-Methyl Ketoximes with α-Keto Acids under Visible Light.
This work presents a palladium-catalyzed oxime ether-directed ortho-selective benzoylation using benzoylformic acid as the acyl source with a palladium catalyst and 4CzIPN as the co-catalyst under light. Various non-symmetric benzophenone derivatives were obtained in moderate to good yields. A preliminary mechanism study revealed that the reaction proceeds through a free radical pathway
Industrial Anomaly Detection with Domain Shift: A Real-world Dataset and Masked Multi-scale Reconstruction
Industrial anomaly detection (IAD) is crucial for automating industrial
quality inspection. The diversity of the datasets is the foundation for
developing comprehensive IAD algorithms. Existing IAD datasets focus on the
diversity of data categories, overlooking the diversity of domains within the
same data category. In this paper, to bridge this gap, we propose the
Aero-engine Blade Anomaly Detection (AeBAD) dataset, consisting of two
sub-datasets: the single-blade dataset and the video anomaly detection dataset
of blades. Compared to existing datasets, AeBAD has the following two
characteristics: 1.) The target samples are not aligned and at different
scales. 2.) There is a domain shift between the distribution of normal samples
in the test set and the training set, where the domain shifts are mainly caused
by the changes in illumination and view. Based on this dataset, we observe that
current state-of-the-art (SOTA) IAD methods exhibit limitations when the domain
of normal samples in the test set undergoes a shift. To address this issue, we
propose a novel method called masked multi-scale reconstruction (MMR), which
enhances the model's capacity to deduce causality among patches in normal
samples by a masked reconstruction task. MMR achieves superior performance
compared to SOTA methods on the AeBAD dataset. Furthermore, MMR achieves
competitive performance with SOTA methods to detect the anomalies of different
types on the MVTec AD dataset. Code and dataset are available at
https://github.com/zhangzilongc/MMR.Comment: submit to Computers in Industr
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