1,799 research outputs found
Accelerated Testing Method for PEM Fuel Cell based Uninterrupted Power Supply Systems
Proton exchange membrane fuel cell based power systems are on the verge of commercialization for a number of niche applications where batteries are traditionally used. Uninterrupted power supply (UPS) for wireless communication towers and broadband network relay utilities is one of the targeted application of fuel cell power systems with capacity ranging from one to serveral kilowatts. It is believed that fuel cell based UPS systems can offer considerable advantage when extended backup time is desirable. In order to replace the well-known battery based UPS systems, the reliability and perofrmance of fuel cell based UPS system need to be thoroughly evaluated by preferrably independent testing laboratories. Accelerated testing is frequently needed in light of the time constraints in typical product development cycles
Crystal structure and electronic structure of quaternary semiconductors CuZnTiSe and CuZnTiS for solar cell absorber
We design two new I2-II-IV-VI4 quaternary semiconductors CuZnTiSe and
CuZnTiS, and systematically study the crystal and electronic structure
by employing first-principles electronic structure calculations. Among the
considered crystal structures, it is confirmed that the band gaps of
CuZnTiSe and CuZnTiS originate from the full occupied Cu 3
valence band and unoccupied Ti 3 conducting band, and kesterite structure
should be the ground state. Furthermore, our calculations indicate that
CuZnTiSe and CuZnTiS have comparable band gaps with
CuZnTSe and CuZnTS, but almost twice larger absorption
coefficient . Thus, the materials are expected to be candidate
materials for solar cell absorber.Comment: 4 pages, 4 figure
Boundedness of Multiparameter Forelli-Rudin Type Operators on the Product of Unit Balls of
In this work, we provide a complete characterization of the boundedness of
two classes of multiparameter Forelli-Rudin type operators from one mixed-norm
Lebesgue space to another space , when , equipped with possibly different weights. Using
these characterizations, we establish the necessary and sufficient conditions
for both boundedness of the weighted multiparameter
Berezin transform and boundedness of the weighted
multiparameter Bergman projection, where denotes the mixed-norm
Bergman space. Our approach presents several novelties. Firstly, we conduct
refined integral estimates of holomorphic functions on the unit ball in
. Secondly, we adapt the classical Schur's test to different
weighted mixed-norm Lebesgue spaces. These improvements are crucial in our
proofs and allow us to establish the desired characterization and sharp
conditions.Comment: 42 page
The Boundedness and Exponential Stability Criterions for Nonlinear Hybrid Neutral Stochastic Functional Differential Equations
Neutral differential equations have been used to describe the systems that not only depend on the present and past states but also involve derivatives with delays. This paper considers hybrid nonlinear neutral stochastic functional differential equations (HNSFDEs) without the linear growth condition and examines the boundedness and exponential stability. Two illustrative examples are given to show the effectiveness of our theoretical results
Estimating Properties of Solid Particles Inside Container Using Touch Sensing
Solid particles, such as rice and coffee beans, are commonly stored in
containers and are ubiquitous in our daily lives. Understanding those
particles' properties could help us make later decisions or perform later
manipulation tasks such as pouring. Humans typically interact with the
containers to get an understanding of the particles inside them, but it is
still a challenge for robots to achieve that. This work utilizes tactile
sensing to estimate multiple properties of solid particles enclosed in the
container, specifically, content mass, content volume, particle size, and
particle shape. We design a sequence of robot actions to interact with the
container. Based on physical understanding, we extract static force/torque
value from the F/T sensor, vibration-related features and topple-related
features from the newly designed high-speed GelSight tactile sensor to estimate
those four particle properties. We test our method on very different daily
particles, including powder, rice, beans, tablets, etc. Experiments show that
our approach is able to estimate content mass with an error of g, content
volume with an error of ml, particle size with an error of mm, and
achieves an accuracy of % for particle shape estimation. In addition, our
method can generalize to unseen particles with unknown volumes. By estimating
these particle properties, our method can help robots to better perceive the
granular media and help with different manipulation tasks in daily life and
industry.Comment: 8 pages, 14 figure
Searching for Stable Si\u3csub\u3en\u3c/sub\u3eC\u3csub\u3en\u3c/sub\u3e Clusters: Combination of Stochastic Potential Surface Search and Pseudopotential Plane-Wave Car-Parinello Simulated Annealing Simulations
To find low energy SinCn structures out of hundreds to thousands of isomers we have developed a general method to search for stable isomeric structures that combines Stochastic Potential Surface Search and Pseudopotential Plane-Wave Density Functional Theory Car-Parinello Molecular Dynamics simulated annealing (PSPW-CPMD-SA). We enhanced the Sunders stochastic search method to generate random cluster structures used as seed structures for PSPW-CPMD-SA simulations. This method ensures that each SA simulation samples a different potential surface region to find the regional minimum structure. By iterations of this automated, parallel process on a high performance computer we located hundreds to more than a thousand stable isomers for each SinCn cluster. Among these, five to 10 of the lowest energy isomers were further optimized using B3LYP/cc-pVTZ method. We applied this method to SinCn (n = 4–12) clusters and found the lowest energy structures, most not previously reported. By analyzing the bonding patterns of low energy structures of each SinCn cluster, we observed that carbon segregations tend to form condensed conjugated rings while Si connects to unsaturated bonds at the periphery of the carbon segregation as single atoms or clusters when n is small and when n is large a silicon network spans over the carbon segregation region
Osthole represses growth of multiple myeloma cells by regulating PI3K/AKT and ERK pathways
Purpose: To identify the effects of osthole on the growth of multiple myeloma cells and determine the probable molecular mechanism of action.
Methods: 3-(4, 5-Dimethyl-2-thiazolyl)-2, 5-diphenyl-2-H-tetrazolium bromide (MTT) assay was used to measure multiple myeloma cell viability. Flow cytometry was used for the evaluation of cell cycle and apoptosis. For protein expression measurement, western blot analysis was employed.
Results: The results show that osthole dose- and time-dependently suppressed the viability of multiple myeloma cells (p < 0.01). Osthole also dose-dependently initiated multiple myeloma cell cycle arrest in G0/G1 phase (p < 0.05) and induced multiple myeloma cell apoptosis (p < 0.01). Moreover, western blotting revealed a significant reduction in cyclin D1 (p < 0.01) and induction in p21, cleaved caspase 3 and cleaved poly (ADP-ribose) polymerase (p < 0.01). Furthermore, osthole treatment significantly downregulated the phosphorylation levels of protein kinase B (AKTT308), AKTS473, and extracellular regulated protein kinase 1/2 (ERK1/2).
Conclusion: These findings demonstrated that osthole inhibited viability and induced cell cycle arrest and apoptosis of multiple myeloma cells by regulating PI3K/AKT and ERK pathways. Osthole may be considered as a potential anticancer agent for the therapy of multiple myeloma
Heat Transfer of Helix Energy Pile: Part 2—Novel Truncated Cone Helix Energy Pile
Owing to the fact that severe thermal interferences exist in the radial and generatrix directions of the traditional cylinder helix energy pile due to the limited thermal heat capacity of the pile and small ratio between coil pitch and radius of pile, therefore, a novel truncated cone helix energy pile (CoHEP) is presented to weaken the thermal interferences and improve the heat transfer efficiency. Further, both the analytical solution model and numerical solution model for CoHEP are built to discuss the dynamic characteristics of thermal interferences and heat transfer performance. The results indicate that the thermal interference of CoHEP is dynamic. The thermal interference in the upper part of the CoHEP is much smaller than the traditional CyHEP. And in general the heat flux per unit pipe length of the novel CoHEP is larger than that of the traditional CyHEP. Heat flux per unit pipe length of the CoHEP increases linearly with inlet water temperature. For the same inlet water temperature, the thermal short circuit is serious at the bottom of the CoHEP, and it’s weak in the upper part of CoHEP. Also it’s obvious that as the inlet water temperature increases, the thermal short circuit becomes more serious
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