2,794 research outputs found
Development of the technological process for the production of the electrostatic curved beam actuator for pneumatic microvalves
This work focuses on the development of an effective technological process for the production of the electrostatic curved beam actuator capable to be used as a driving element in different devices such as microswitches or microvalves. Main attention was drawn to the investigation of electroplating technique as a critical process in the microactuator fabrication as well as to the design of the actuator. In addition, usability of ceramic substrates for the microactuator and microvalve production was examined. The idea behind it was that ceramic substrates can be preprocessed and delivered already with necessary electrical connections on it. This would make the entire production process simpler and cheaper. Several types of polished alumina (Al2O3) substrates were used for this purpose. Electrostatic actuation principle was chosen for its good scaling properties to small dimensions, low power consumption, smaller size and higher switching speed. Curved shape of the actuator allows to reduce its pull-in voltage and thus to increase the amplitude of motion as compared to the parallel-plate structures. The material of the actuator is nickel. It was chosen for its good mechanical properties and relative simplicity of processing. Double layer nickel electroplating was used to produce the microactuator. The layers have different stress gradients controlled by current density during the electroplating process, making it possible to achieve the desired bending of the structure. Compared to bimetallic bending cantilever actuators, the curvature of the single-metal beam is less dependable on temperature and aging. Thus, more stable performance under changing working conditions was ensured. In order to avoid sticking of the microactuator to the isolation layer in the closed state, an array of stand-off bumps was added on the back-side of the beam. These bumps reduce the contact area and increase the distance between the actuator and the isolation layer. Fifteen design variants of the actuator differing in length and width were fabricated in order find the most effective solution for given system requirements. Based on the actuators technological process developed in this work, a simple electrostatic microvalve was designed and produced. Final variants of microvalve were fabricated on a standard 380 µm thick silicon wafer. Gas inlet channel as well as the electrodes and the actuator itself are all placed on the same substrate in order to reduce the size and cost of the system. During characterization, mechanical stability of the actuators and microvalves were studied by means of drop, temperature and shear tests in order to prove the reliability of the system. System performance tests proved stable pull-in voltages from 8,6 V to 11,6 V. Maximal gas flow through the valve was 110±5 ml/min at applied differential pressure of 2 bar
Computation of current-voltage characteristics of weak links
Simplified model for current-voltage characteristics of weak links is
suggested. It is based on approach which considers Andreev reflections as
responsible for the dissipative current through the metallic Josephson
junction. The model allows to calculate current-voltage characteristics of weak
links (superconductor - normal metal - superconductor junctions, microbridges,
superconducting nanowires) for different thicknesses of the normal layer at
different temperatures. The current-voltage characteristics of tin microbridges
at different temperatures were computed.Comment: 11 pages, 5 figure
Automated Deep Abstractions for Stochastic Chemical Reaction Networks
Predicting stochastic cellular dynamics as emerging from the mechanistic
models of molecular interactions is a long-standing challenge in systems
biology: low-level chemical reaction network (CRN) models give raise to a
highly-dimensional continuous-time Markov chain (CTMC) which is computationally
demanding and often prohibitive to analyse in practice. A recently proposed
abstraction method uses deep learning to replace this CTMC with a discrete-time
continuous-space process, by training a mixture density deep neural network
with traces sampled at regular time intervals (which can obtained either by
simulating a given CRN or as time-series data from experiment). The major
advantage of such abstraction is that it produces a computational model that is
dramatically cheaper to execute, while preserving the statistical features of
the training data. In general, the abstraction accuracy improves with the
amount of training data. However, depending on a CRN, the overall quality of
the method -- the efficiency gain and abstraction accuracy -- will also depend
on the choice of neural network architecture given by hyper-parameters such as
the layer types and connections between them. As a consequence, in practice,
the modeller would have to take care of finding the suitable architecture
manually, for each given CRN, through a tedious and time-consuming
trial-and-error cycle. In this paper, we propose to further automatise deep
abstractions for stochastic CRNs, through learning the optimal neural network
architecture along with learning the transition kernel of the abstract process.
Automated search of the architecture makes the method applicable directly to
any given CRN, which is time-saving for deep learning experts and crucial for
non-specialists. We implement the method and demonstrate its performance on a
number of representative CRNs with multi-modal emergent phenotypes
A nickel electrostatic curved beam actuator for valve applications
AbstractIn this contribution an electrostatic curved beam actuator for microvalve applications is presented. The actuator consists of two layers of nickel consequently plated upon each other. The resulting double-layer cantilever beam has internal stress gradient due to variation of the electroplating process parameters for each layer. By accurate control of these parameters, desired bending heights were obtained. Compared to bimetallic bending actuators, the curvature of the single-metal beam is less dependable on ambient temperature. Thus, more stable performance under changing working conditions was ensured. In order to avoid sticking during the operation of the variable capacitor, stand-off bumps on the back-side of the actuator beam were provided. The actuator was integrated into an active 2/2-microvalve on a silicon substrate
Automated Code Generation for Lattice Quantum Chromodynamics and beyond
We present here our ongoing work on a Domain Specific Language which aims to
simplify Monte-Carlo simulations and measurements in the domain of Lattice
Quantum Chromodynamics. The tool-chain, called Qiral, is used to produce
high-performance OpenMP C code from LaTeX sources. We discuss conceptual issues
and details of implementation and optimization. The comparison of the
performance of the generated code to the well-established simulation software
is also made
The Relationship Between the Parameters of the Electric and the Acoustic Signal with the Destruction of Concrete Under Cyclic Freeze-Thaw
The paper presents the research results of the effect of formation crack process on the parameters of the electric and acoustic response to impact excitation. The physical basis of mechanoelectric transformations is described. It was found that with increasing number of freeze-thaw cycles observed increase of the attenuation coefficient of energy of the electric and acoustic response by a linear relationship. Differences in the dynamics of change of attenuation coefficient of energy of the electric and acoustic response associated with differences in formation and registration of electric and acoustic response
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