Helium isotope separation by bi-layer membranes of g-C3N4

The problem of helium isotope separation via bi-layer membranes of graphitic carbon nitride g-C3N4 has been studied. The probability of passing isotopes through the membrane is derived from solving the Schrödinger integral equation using Hermite polynomials. The potential energy of the membrane is calculated based on modified Lennard-Johnes potential. The separation degree of the 3He/4He reaches the value of 1045 due to the resonant effect.

Disynaptic Effect of Hilar Cells on Pattern Separation in A Spiking Neural Network of Hippocampal Dentate Gyrus

We investigate the disynaptic effect of the hilar cells on pattern separation in a spiking neural network of the hippocampal dentate gyrus (DG). The principal granule cells (GCs) in the DG perform pattern separation, transforming similar input patterns into less-similar output patterns. In our DG network, the hilus consists of excitatory mossy cells (MCs) and inhibitory HIPP (hilar perforant path-associated) cells. Here, we consider the disynaptic effects of the MCs and the HIPP cells on the GCs, mediated by the inhibitory basket cells (BCs) in the granular layer; MC → BC → GC and HIPP → BC → GC. Disynaptic inhibition from the MCs tends to decrease the firing activity of the GCs. On the other hand, the HIPP cells disinhibit the intermediate BCs, which leads to increasing the activity of the GCs. By changing the synaptic strength K(BC, X) [from the presynaptic X (= MC or HIPP) to the postsynaptic BC] from the default value K(BC, X)*, we study the change in the pattern separation degree Sd. When decreasing K(BC, MC) or independently increasing K(BC, HIPP) from their default values, Sd is found to decrease (i.e., pattern separation is reduced). On the other hand, as K(BC, MC) is increased or independently K(BC, HIPP) is decreased from their default values, pattern separation becomes enhanced (i.e., Sd increases). In this way, the disynaptic effects of the MCs and the HIPP cells on the pattern separation are opposite ones. Thus, when simultaneously varying both K(BC, MC) and K(BC, HIPP), as a result of balance between the two competing disynaptic effects of the MCs and the HIPP cells, Sd forms a bell-shaped curve with an optimal maximum at their default values. Moreover, we also investigate population and individual behaviors of the sparsely synchronized rhythm of the GCs, and find that the amplitude measure Ma (representing population synchronization degree) and the random-phase-locking degree Ld (denoting individual activity degree) are strongly correlated with the pattern separation degree Sd. Consequently, the larger the synchronization and the random phase-locking degrees of the sparsely synchronized rhythm is, the more the pattern separation becomes enhanced.

Simulation of drawing process based on fiber arrangement in the sliver with straightness and separation degree

Sliver irregularity, straightness and separation degree of fibers are three crucial factors in sliver quality. Considering the straightness and separation degree, the drafting model based on the fiber arrangement in the sliver was applied to simulate the drawing process. First, the fiber arrangement in the carding sliver was developed. Then, the drafting process was divided into the low-velocity stage, straightening stage and high-velocity stage to carry out the redistribution of the fiber arrangement so that the sliver quality after drafting can be recalculated from the new fiber arrangement after the drafting procedure. Combining the doubling procedure, the simulated sliver quality of each drawing process was demonstrated to be close to the actual values, taking the straightness and separation degree into consideration. The relative errors between the simulated straightness and percentage of separated fibers and the tested one were all less than 10%. The prediction accuracy of sliver irregularity was raised by about 40%. In addition, the simulated results strongly confirmed the theory that the drawing process has an influence on straightening the hooked fibers, separating the fiber in the assembly and improving the sliver evenness, which cannot be reflected in previous models.

A new adaptive variable step size natural gradient BSS algorithm

The traditional blind source separation (BSS) algorithm is mainly used to deal with signal separation under the noiseless model, but it does not apply to data with the low signal to noise ratio (SNR). To solve the problem, an adaptive variable step size natural gradient BSS algorithm based on an improved wavelet threshold is proposed in this paper. Firstly, an improved wavelet threshold method is used to reduce the noise of the signal. Secondly, the wavelet coefficient layer with obvious periodicity is denoised using a morphological component analysis (MCA) algorithm, and the processed wavelet coefficients are recombined to obtain the ideal model. Thirdly, the recombined signal is pre-whitened, and a new separation matrix update formula of natural gradient algorithm is constructed by defining a new separation degree estimation function. Finally, the adaptive variable step size natural gradient blind source algorithm is used to separate the noise reduction signal. The results show that the algorithm can not only adaptively adjust the step size according to different signals, but also improve the convergence speed, stability and separation accuracy.

Method to Realize the Tilt Monitoring and Instability Prediction of Hazardous Rock on Slopes

Hazardous rock refers to an unstable rock block that is cut by weak structural planes and gradually separates from the slope. Hazardous rock generally collapses rapidly, and at present, it is challenging to effectively identify the separation degree of the rock and accurately predict its sudden failure. In this study, focusing on a hazardous rock with tilt behavior, a microelectromechanical system (MEMS) acceleration sensor is used in combination with the calculation principle of the included angle of the space vector to establish a microtilt angle monitoring method. A physical model test is designed, in which a thermally sensitive material (with heat-sensitive strength) is adopted as the weak structural plane of the hazardous block, and the change in the tilt angle during the process of block instability is monitored at a sampling frequency of 1000 Hz. The test results show that the accelerated evolution of the tilt angle is a precursor to hazardous rock failure. In the rapid acceleration stage, the reciprocal of the tilt angle rate is approximately linear with time, and a correlation equation is obtained. Assuming that the change rate of the tilt angle is approximately infinite, the failure time of hazardous rock can be predicted using the correlation equation. In addition, the effectiveness of the instability prediction method based on microtilt angle monitoring is verified by analyzing the long-term monitoring data of hazardous rock.

Grading of Scots Pine Seeds by the Seed Coat Color: How to Optimize the Engineering Parameters of the Mobile Optoelectronic Device

Research Highlights: There is a problem of forest seeds quality assessment and grading afield in minimal costs. The grading quality of each seed coat color class is determined by the degree of its separation with a mobile optoelectronic grader. Background and Objectives: Traditionally, pine seeds are graded in size, but this can lead to a loss of genetic diversity. Seed coat color is individual for each forest seed and is caused to a low error in identifying the genetic features of seedling obtained from it. The principle on which the mobile optoelectronic grader operates is based on the optical signal detection reflected from the single seed. The grader can operate in scientific (spectral band analysis) mode and production (spectral feature grading) mode. When operating in production mode, it is important to determine the optimal engineering parameters of the grader that provide the maximum value of the separation degree of seed-color classes. For this purpose, a run of experiments was conducted on the forest seeds separation using a mobile optoelectronic grader and regression models of the output from factors were obtained. Materials and Methods: Scots pine (Pinus sylvestris L.) seed samples were obtained from cones of the 2019 harvest collected in a natural stand. The study is based on the Design of Experiments theory (DOE) using the Microsoft Excel platform. In each of three replications of each run from the experiment matrix, a mixture of 100 seeds of light, dark and light-dark fraction (n = 300) was used. Results: Interpretation of the obtained regression model of seed separation in the visible wavelength range (650–715 nm) shows that the maximum influence on the output—separation degree—is exerted by the angle of incidence of the detecting optical beam. Next in terms of the influence power on the output are paired interactions: combinations of the wavelength with the angle of incidence and the wavelength with the grader’s seed pipe height. The minimum effect on the output is the wavelength of the detecting optical beam. Conclusions: The use of a mobile optoelectronic grader will eliminate the cost of transporting seeds to and from forest seed centers. To achieve a value of 0.97–1.0 separation degree of Scots pine seeds colored fractions, it is necessary to provide the following optimal engineering parameters of the mobile optoelectronic grader: the wavelength of optical radiation is 700 nm, the angle of incidence of the detecting optical beam is 45° and the grader’s seed pipe height is 0.2 m.

Electropulse method of selective destruction of abrasive electrocorundum tool

In laboratory conditions the efficiency of electropulse disintegration of scrap abrasive wheels made of electrocorundum has been investigated. It is shown that at the chosen parameters of the process of selective destruction of abrasive scrap, the separation degree of electrocorundum grains, coarseness of which almost corresponds to the initial fraction, is more than 50%.

Yaw control of a flying-wing unmanned aerial vehicle based on reverse jet control

Due to its layout, there are difficulties in realizing heading attitude control of a flying-wing unmanned aerial vehicle. In this paper, a reverse jet control scheme has been designed: (1) to replace the resistance rudders that are used for the yaw control of a conventional flying-wing unmanned aerial vehicle, (2) to assist and optimize heading attitude control, eliminate the adverse effects of the control surface and enhance stealth performance, and (3) to promote the use of rudderless flight for flying-wing unmanned aerial vehicles. To explore the control mechanism and the flow field of the reverse jet scheme, three-dimensional numerical simulations and low-speed wind tunnel experiments were carried out. First, the numerical simulations evaluated the feasibility and effectiveness of the reverse jet control scheme and explored and optimized the excitation parameters for the scheme. Then the forces were measured in a wind tunnel, and particle image velocimetry experiments were carried out. A reverse jet actuator was independently designed to verify the results of the numerical simulation. The results show that when the reverse jet excitation is applied, the jet obstructs the mainstream, destroys the flow field at the excitation position, and causes early separation of the flow, which increases the pressure drag on the wings and produces a control effect. The control effect mainly depends on the separation degree of the leeward surface. The larger the jet momentum coefficient is, the smaller the jet angle is, and the closer the excitation position is to the leading edge, the greater the separation degree of the leeward surface is, the better the heading attitude control effect is.