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In experimental studies, single-wave mode and two counter-rotating wave mode are often observed in rotating detonation combustors. To investigate the mechanism behind different propagation modes, high-resolution numerical simulations of two-dimensional detonation in hydrogen/air mixtures are conducted by solving the reactive Navier–Stokes equations with a detailed chemical mechanism. The numerical results show that the occurrence of the dual-wave detonation propagation mode is positively influenced by an increase in both the channel width and the initial pressure. The dual-wave modes are observed when increasing the channel width, and it is found that the dual-wave modes are caused by increasing the residual premixed gas height near the inner wall. When increasing the initial pressure, the initial peak detonation heat release increases, which leads to the increase in the hot spot intensity formed, and it is found that the dual-wave modes are mainly caused by the interactions between the initial detonation wave and the inner wall. However, the initial equivalent ratio appears to have a relatively minor impact on the detonation propagation mode due to a relatively narrow range variation of physical properties. The peak heat release rate exerts a greater influence on the change of the propagation mode than the induction time does through a wider range test on rotating detonation engines' working condition. Moreover, the velocities and the cell sizes of detonation waves propagating in different directions with different channel widths are also analyzed, revealing that the characteristics of the detonation waves propagating in different directions are nearly the same. [ABSTRACT FROM AUTHOR]

During the production of underground engineering, investigating the mechanical behaviors of rock materials after high temperature damage is of great importance for controlling the stability of the underground structure. In this paper, for revealing the deformation and energy evolution laws of rock materials after high temperature damage under cyclic loading, a series of uniaxial compressive and cyclic loading experiments were conducted on sandstone after various high temperature damages, i.e., 200, 300, 400, 500, 600, 700, 800, and 900°C, to study the effect of high temperature on primary wave velocity, microstructure, deformation, strength, energy, etc. It can be observed that the primary wave velocity and microstructure weakened seriously with the development of high temperature damage and the uniaxial compressive strength of samples increases toward the maximum value with a high temperature damage of 300°C and then decreases gradually. The energy proportion index was established to characterize the influence of high temperature damage and cyclic stress levels on energy evolution laws of samples. With an increase in temperature, compared with input energy, elastic strain energy proportion decreases and dissipated energy proportion rises up, which indicate that the property of samples transforms from elasticity to plasticity. Finally, the variation laws between the burst tendency of the sample and high temperature damage were well described by presenting the average elastic energy index, which provides references for studying failure characteristics of rock materials. [ABSTRACT FROM AUTHOR]

In this study, the application of micro-leverage in the monolithically all-quartz resonant accelerometer is proposed. The magnification of the micro-leverage structure used for a large size double-ended tuning fork (DETF) was analyzed. The effect of DETF's dimension both on its own force–frequency sensitivity and micro-leverage's magnification was investigated. Through the study of the relationship between DETF's force–frequency sensitivity and micro-leverage's magnification, the effect of micro-leverage and the DETF system on the sensitivity of the accelerometer was obtained. The problem of big error in theoretical calculation of micro-leverage magnification was solved because the structural arrangement of the output beam was ignored in the derivation process. The correctness of the analysis was verified by theoretical calculation, simulation, and the experiment. The equivalent structures of tension (compression) stiffness and flexural stiffness of the micro-leverage output beam were obtained by analyzing and simplifying the composite structure of the link beam and DETF. By simplifying the mechanical model of micro-leverage, the amplification factor K of micro-leverage is deduced to be 23. Therefore, the theoretical sensitivity of the sensor is 15.6 Hz/g. The experimental results show that the sensitivity of the accelerometer with the micro-leverage is 16.1 Hz/g, which is close to the theoretical analysis results. [ABSTRACT FROM AUTHOR]

Differential molecular diffusion (DMD) is a fundamental physical phenomenon that occurs in many fluid flow problems such as turbulent reactive flows. Because DMD is a small-scale event, its modeling is intrinsically challenging, and hence in practical applications, it is more feasible to develop phenomenological models for treating the effect of DMD. In order to develop these phenomenological models, a set of model constraints based on physical observations are needed in order to constrain the model development to yield consistent results with the physical observations. In this work, we adopt an existing power-law Reynolds number scaling of DMD as the model constraints and examine the turbulence modeling requirement of DMD in order to yield the desired scaling. The Reynolds-averaged Navier-Stokes simulations are employed as the modeling framework, and a turbulent mixing layer test case is used as a test case. Perturbation analysis is conducted to examine the model consistency in order to yield the power-law scaling for DMD in the mixing layer test case. It is found that a differential mixing time scale model is needed to yield the power-law scaling, and the commonly used equal mixing time scale model cannot produce the scaling correctly. Numerical simulations of the turbulent mixing problem are also performed to further demonstrate the turbulence modeling requirement for producing the desired power-law scaling of DMD. [ABSTRACT FROM AUTHOR]

We use low temperature scanning laser microscope (LTSLM) to study the Joule power distribution of superconducting (SC) terahertz (THz) modulator. The LTSLM scanning images record the SC state transformation process under different DC bias voltages. The change of THz transmission spectra can be well explained by the thermal effect in the devices observed by LTSLM. Hotspots are present in one THz modulator and the transmission spectra changes a lot after the hotspots show up. According to theoretical analysis, the appearance of hotspot may be helpful for improving the modulation speed. These results will be useful to understand the mechanism of SC THz modulator and design higher performance THz moduators. [ABSTRACT FROM AUTHOR]

Microchips that perform single cell capture, array, and identification have become powerful tools for single cell studies, which can reveal precise underlying mechanisms among bulk cell populations. However, current single cell capture and on-chip immunostaining methods consume more time and reagent than desired. To optimize this technology, we designed a novel trap structure for single cell capture, array, and release, and meanwhile an oscillatory method was used to perform rapid on-chip cell immunostaining. The trap structure array used equal distribution of lateral flow to achieve single cell array in high velocity flows and decrease the risk of clogging. A length of glass capillary with a sealed bubble was inserted into the outlet so that it could act in a manner analogous to that of a capacitor in an RC circuit. By applying one periodic air pressure to the inlet, oscillation motion was generated, which significantly enhanced the on-chip reaction efficiency. In addition, the oscillation performance could be easily regulated by changing the length of the capillary. The trapped cells could maintain their positions during oscillation; hence, they were able to be tracked in real time. Through our trap microchip, 12 μm microbeads were successfully trapped to form a microarray with a capture efficiency of ∼92.7% and 2 μm microbeads were filtered. With an optimized oscillation condition (Ppush = 0.03 MPa, f = 1 Hz, L = 3 cm), fast on-chip immunostaining was achieved with the advantages of less time (5 min) and reagent (2 μl) consumption. The effectiveness of this method was demonstrated through quantitative microbead and qualitative Caco-2 cell experiments. The device is simple, flexible, and efficient, which we believe provides a promising approach to single cell heterogeneity studies, drug screening, and clinical diagnosis. [ABSTRACT FROM AUTHOR]

In this paper, the weighting techniques are directly acted on traditional 1D sinusoidal electromagnetic bandgap (EBG) structures. The proposed 1D weighted EBG band-stop filter is theoretically designed by using coupled-mode theory, and the coupling coefficient amplitudes of the 1D sinusoidal EBG structure are directly weighted using window functions. The passband ripple, reflected sidelobes, and bandwidth of the band-stop filter are improved using weighted window functions, and the bandgap depth is adjusted by changing the amplitude factor of weighting functions. For validation, the fabrication and measurements have also been done for the proposed filter. The measurement and simulation results have a close match, and the design concept is verified. [ABSTRACT FROM AUTHOR]

This paper describes the design, fabrication, and testing of an integrated packaged sensor that is composed of a micro resonant accelerometer and a temperature sensor. The resonant accelerometer with differential configuration consists of double quartz resonators and a silicon substrate. When acceleration is applied along the sensing axis, the inertial force induced by the proof mass will transfer force to the resonators, which causes an opposite frequency shift of the dual quartz resonators. The loaded acceleration can be measured through detecting the differential frequency shift. The symmetric differential configuration response to spurious effects of thermal loading and inelastic effect causing prestress in the resonators is similar, which can be reduced by detecting the differential frequency, effectively. However, during the manufacture and packaging process, the otherness of residual stress in two quartz resonators results in that the response of resonators to temperature variation is not strictly the same. In other words, this temperature drift cannot be eliminated by the structure design. Thus, a temperature sensor and an accelerometer were packaged in a shell together. These novel integrated sensors can measure acceleration and temperature simultaneously. With the testing temperature data, a novel temperature compensation that is a combination of the variable coefficient regression and least squares support vector machine is used for improving the performance of the accelerometer. By means of this compensation and field programmable gate array, a real-time and online compensation is achieved. The tumble testing results indicate that the sensitivity of the accelerometer is ∼16.97 Hz/g. With the temperature compensation, the output drift of the scale factor is improved by 0.605 Hz/g in the full temperature range, which is from 0.072 Hz/g to 0.015 Hz/g. The drift of zero bias is improved from 345 mg to 1.9 mg. [ABSTRACT FROM AUTHOR]

A high sensitivity quartz resonant pressure sensor with differential output and self-correction is proposed. Although compared to other resonant devices, quartz resonators have less influence on external environmental factors due to their own high quality factor Q; the influence of external environment such as temperature, vibration, and humidity cannot be ignored in high-precision applications. These errors need to be eliminated or compensated. Therefore, this paper divides the core unit of the sensor into two parts: the working unit and the reference unit. The working unit provides the differential outputs which not only improves the sensitivity but also suppresses some interference such as time drift and temperature drift, and it is rarely used in quartz resonant pressure sensors. The reference unit can effectively detect and offset the interference of temperature and vibration which is named as self-correction, and it can also provide temperature measurement. Double-ended tuning fork quartz resonators used in both units are manufactured by micromachining technology. Bellows and flexible mechanisms used as pressure conversion units are manufactured using modern mechanical technology. The test results show that the sensor has the conformity accuracy of the fitting formula of 0.0148% full scale (FS), the good basic accuracy of 0.06% FS, and the high sensitivity of 36.58 Hz/kPa which meets well with the theoretical result. It is shown by the experiments that the reference unit can effectively correct the interference of temperature and vibration. The theoretical analysis and experimental results prove the feasibility of the resonant pressure sensor which can meet the application requirements of pressure measurement in the high-tech industries. [ABSTRACT FROM AUTHOR]