Search

This study aims to improve the non-contact measurement accuracy of roughness of small samples. Therefore, machine vision and virtual sample generation technology are used to detect the roughness of small sample bearing steel (GCr15) in this study. The surface roughness of different specimens is tested with a contact roughness detector. Image acquisition is carried out on the specimen, histogram equalization image enhancement preprocessing is carried out on the image, and sample capacity expansion is carried out on the basis of data enhancement. On this basis, the gray-level co-occurrence matrix (GLCM) is used to extract the image texture features, and a linear regression model of roughness and Energy, Entropy, Homogeneity, Contrast and Correlation is established. Artificial neural networks (ANNs) is used to classify and predict their surface roughness, train the original samples and virtual samples respectively, and compare their prediction accuracy. The results show that the precision of the virtual samples based on resampling and singular value decomposition(SVD) are 10.13% and 21.21% higher than that of the original samples, respectively, and the average error between the predicted value and the measured value of visual roughness is 3.4%. Therefore, the machine vision and virtual sample generation technology are combined to achieve acceptable surface roughness detection of small samples, which provides a theoretical basis for online detection in gear processing.

Acoustic liners are the most commonly used dissipative muffler for aero-engines but remain a challenge to design a broadband acoustic liner under the grazing flow. In this work, a novel neck-embedded meta-liner is proposed for the broadband sound-absorbing under the grazing flow with a wide speed range. The meta-liner is composed of many neck-embedded Helmholtz Resonators, and the idea of bending the subsequent cavity is introduced to improve low-frequency sound absorption performance. The acoustic impedance model of the meta-liner with neck-embedded slit is first detailly established by analyzing the acoustic characteristics of the equivalent elliptical pipe and using the matrix transfer method. Then by designing the local coupling between channels, efficient broadband impedance modulation and broadband matching with air impedance under grazing flow conditions are realized. The proposed meta-liner exhibits the excellent sound attenuation capacity in the frequency domain of 500–3000 Hz under the grazing flow speeds from 0 m s−1 to 98 m s−1 and the sound absorption performance is greatly boosted compared with the traditional Double- Degree-Of-Freedom liner. Features mentioned above have been verified numerically and in a series of comparative experiments. Besides, the thickness of the meta-liner is only 50 mm. Our work provides a possible design reference for the new generation of acoustic liners and has potential applications in noise reduction engineering.

A machined surface has observable fractal characteristics, with infinite local and overall self-similar consistency. Therefore, the fractal theory is considered to provide a better description of the morphological characteristics of rough surfaces, which accurately reflects the randomness and multi-scale characteristics of rough surfaces and it is not comparable with the surface characteristics obtained based on statistical parameters limited by sampling length and device resolution. In this study, the Weierstrass-Mandelbrot (W-M) function was applied to construct a fractal reconstruction surface, and the mixed elastohydrodynamic lubrication model was used to investigate the lubrication characteristics of real and reconstructed surfaces under the same fractal parameters. The effects of the fractal parameters on the fractal surface lubrication characteristics were further analyzed. The results demonstrate that the lateral roughness fractal surface provides greater resistance to the entrained flow of lubricant, which leads to a larger average film thickness, than the longitudinal roughness and isotropic fractal surface. With the increase in fractal dimension, the surface roughness peak density increases, which reduces the surface film thickness by 47%, and the friction coefficient increases by 46%. The lubrication parameter fluctuates slightly with the change in the number of overlapping ridges M of the fractal surface. Generally, M has little effect on the surface lubrication characteristics.

Graphene-based pressure sensors have received extensive attention in wearable devices. However, reliable, low-cost, and large-scale preparation of structurally stable graphene electrodes for flexible pressure sensors is still a challenge. Herein, for the first time, laser-induced graphene (LIG) powder are prepared into screen printing ink, and shape-controllable LIG patterned electrodes can be obtained on various substrates using a facile screen printing process, and a novel asymmetric pressure sensor composed of the resulting screen-printed LIG electrodes has been developed. Benefit from the 3D porous structure of LIG, the as-prepared flexible LIG screen-printed asymmetric pressure sensor has super sensing properties with a high sensitivity of 1.86 kPa−1, low detection limit of about 3.4 Pa, short response time, and long cycle durability. Such excellent sensing performances give our flexible asymmetric LIG screen-printed pressure sensor the ability to realize real-time detection of tiny body physiological movements (such as wrist pulse and pronunciation action). Besides, the integrated sensor array has a multi-touch function. This work could stimulate an appropriate approach to designing shape-controllable LIG screen-printed patterned electrodes on various flexible substrates to adapt the specific needs of fulfilling compatibility and modular integration for potential application prospects in wearable electronics.

We design a double quantum-dot (QD) shuttle (DQDS) model including two rigidly connected QDs that are softly linked to two leads via deformable organic materials. Based on the full quantum mechanical approaches we explore the influences on the electron transport induced by the electrical and mechanical degrees of freedom. First of all the modified rate equations of the DQDS are derived theoretically and then a numerical investigation on the quantum transport through the DQDS is performed. For the classical DQDS, the time-dependent evolutions of the electron-occupation probabilities and the currents flowing through the DQDS show the periodic oscillations with their periods determined by the oscillation period of the DQDS. Both the mechanical oscillation amplitude and the interdot coupling can play crucial roles in adjusting the peak shapes of the currents and the probabilities. For the quantum DQDS, the current and electron-occupation probabilities of the DQDS evolve into a stationary state as time goes on, with no periodical oscillations observed. As a consequence, the sharp differences of the time-dependent properties between the classical and quantum DQDS systems are clearly demonstrated, which should be greatly helpful in designing new nanoelectromechanical devices. Also, this work is of great significance to understanding the kind of rigidly connected QD shuttle systems that have more than two QDs.

In order to study the geochemical characteristics, origin and its hydrocarbon potential of the Upper Cretaceous marine source rocks in the Rio Muni Basin, Equatorial Guinea, 62 debris samples of the Anduak-1 well in the Rio Muni Basin were collected to Rock-Eval pyrolysis, whole rock organic petrology analysis. This study revealed that the OM in the upper Cretaceous source rock is early mature - mature, with moderate abundance and fair quality (mainly type II and III). The organic matter has a mixed marine–terrestrial origin and deposited in the marine environment, the plant debris were probably suffered from a long-distance transportation via fluvial or else forces. The main hydrocarbon generation phase of the type III kerogen was more duration than type II, initial hydrocarbon generation was earlier, and ending hydrocarbon generation time was late. Comprehensive studies demonstrated that it has a good hydrocarbon potential to the upper Cretaceous marine shale, and is an unneglectable hydrocarbon source rock.

Scholars pay more and more attention to the spoken dialogue system after the emergence of deep learning technology. The task-based dialogue system has become one of the most important branches in the field of spoken dialogue systems. Dialogue management is the core of the task-based dialogue system, and its research theory and technology have been gained extensive attention. This paper summarizes the research progress and current situation of task-based dialogue system and dialogue management strategy. Firstly, it summarizes the status of the task-based dialogue system models and compares their advantages and disadvantages. Then it focuses on the analysis of various dialogue management research strategies from the perspective of model theory and research methods. Finally, it looks forward to the future research direction of task-oriented dialogue system combined with dialogue management.

Kondo transport properties through a Kondo-type quantum dot (QD) with a side-coupled triple-QD structure are systematically investigated by using the non-equilibrium Green's function method. We firstly derive the formulae of the current, the linear conductance, the transmission coefficient, and the local density of states. Then we carry out the analytical and numerical studies and some universal conductance properties are obtained. It is shown that the number of the conductance valleys is intrinsically determined by the side-coupled QDs and at most equal to the number of the QDs included in the side-coupled structure in the asymmetric limit. In the process of forming the conductance valleys, the side-coupled QD system plays the dominant role while the couplings between the Kondo-type QD and the side-coupled structure play the subsidiary and indispensable roles. To testify the validity of the universal conductance properties, another different kinds of side-coupled triple-QD structures are considered. It should be emphasized that these universal properties are applicable in understanding this kind of systems with arbitrary many-QD side structures.

We investigate the quantum transport properties through a special kind of quantum dot (QD) system composed of a serially coupled multi-QD-pair (multi-QDP) chain and side-coupled Majorana bound states (MBSs) by using the Green functions method, where the conductance can be classified into two kinds: the electron tunneling (ET) conductance and the Andreev reflection (AR) one. First we find that for the nonzero MBS-QDP coupling a sharp AR-induced zero-bias conductance peak with the height of e 2/h is present (or absent) when the MBS is coupled to the far left (or the other) QDP. Moreover, the MBS-QDP coupling can suppress the ET conductance and strengthen the AR one, and further split into two sub-peaks each of the total conductance peaks of the isolated multi-QDPs, indicating that the MBS will make obvious influences on the competition between the ET and AR processes. Then we find that the tunneling rate Γ L is able to affect the conductances of leads L and R in different ways, demonstrating that there exists a Γ L-related competition between the AR and ET processes. Finally we consider the effect of the inter-MBS coupling on the conductances of the multi-QDP chains and it is shown that the inter-MBS coupling will split the zero-bias conductance peak with the height of e 2/h into two sub-peaks. As the inter-MBS coupling becomes stronger, the two sub-peaks are pushed away from each other and simultaneously become lower, which is opposite to that of the single QDP chain where the two sub-peaks with the height of about e 2/2h become higher. Also, the decay of the conductance sub-peaks with the increase of the MBS-QDP coupling becomes slower as the number of the QDPs becomes larger. This research should be an important extension in studying the transport properties in the kind of QD systems coupled with the side MBSs, which is helpful for understanding the nature of the MBSs, as well as the MBS-related QD transport properties.

We report the measured results of non-resonant nonlinearity by degenerate four-wave mixing for Cu2O nanoparticles having central diameter of 9 nm. The value of χ(3) obtained in a 10 ns pulse experiment is 8.48 × 10-10 esu, and the nonlinear response time of the sample is estimated to be in the order of nanosecond.

The upgrade of Beijing Synchrotron Radiation Facility (BSRF) needs two-dimensional position-sensitive detection equipment to improve the experimental performance. Gas Electron Multiplier (GEM) detector, in particular, pixel-based GEM detector has good application prospects in the domain of synchrotron radiation. The read-out of larger scale pixel-based GEM detector is difficult for the high density of the pixels (PAD for collecting electrons). In order to reduce the number of cables, this paper presents a read-out scheme for pixel-based GEM detector, which is based on System-in-Package technology and ASIC technology. We proposed a circuit structure based on capacitor switch array circuit, and design a chip GEM400, which is a 400 channels ASIC. The proposed circuit can achieve good stability and low power dissipation. The chip is implemented in a 0.35 mu m CMOS process. The basic functional circuitry in ths chip includes analog switch, analog buffer, voltage amplifier, bandgap and control logic block, and the layout of this chip takes 5mm x 5mm area. The simulation results show that the chip can allow the maximum amount of input charge 70pC on the condition of 100pF external integrator capacitor. Besides, the chip has good channel uniformity (INL is better than 0.1%) and lower power dissipation.

This paper investigates Kondo transport properties in a quadruple quantum dot (QD) based on the slave-boson mean field theory and the non-equilibrium Green's function. In the quadruple QD structure one Kondo-type QD sandwiched between two leads is side coupled to two separate QD structures: a single-QD atom and a double-QD molecule. It shows that the conductance valleys and peaks always appear in pairs and by tuning the energy levels in three side QDs, the one-, two-, or three-valley conductance pattern can be obtained. Furthermore, it finds that whether the valley and the peak can appear is closely dependent on the specific values of the interdot couplings and the energy level difference between the two QDs in the molecule. More interestingly, an extra novel conductance peak can be produced by the coexistence of the two different kinds of side QD structures.

Nit clusters containing 10 to less than 1000 metal sodium atoms and blisters containing xenon inclusions were formed in NaCl crystal specimens prepared by xenon ion implantation to single crystal NaCl with fluences more than or equal to 2 x 10(16)/cm(2) at the energy of 36 keV. Experiments indicated that on the condition of xenon ion fluences more than or equal to 1 x 10(17)/cm(2) the xenon inside the inclusions formed in NaCl crystal specimens is in solid state and the solid state molecules NaXe are formed through the combination of Xe with Na in Na clusters. The chemical shift of Na-23 in solid state molecules NaXe relative to Na-23 in single crystal NaCl was measured and is equal to -17 ppm.