A proposed hybrid neural network for position control of a walking robot

The use of a proposed recurrent neural network control system to control a four-legged walking robot is presented in this paper. The control system consists of a neural controller, a standard PD controller, and the walking robot. The robot is a planar four-legged walking robot. The proposed Neural Network (NN) is employed as an inverse controller of the robot. The NN has three layers, which are input, hybrid hidden and output layers. In addition to feedforward connections from the input layer to the hidden layer and from the hidden layer to the output layer, there is also a feedback connection from the output layer to the hidden layer and from the hidden layer to itself. The reason to use a hybrid layer is that the robot’s dynamics consists of linear and nonlinear parts. The results show that the neural-network controller can efficiently control the prescribed positions of the stance and swing legs during the double stance phase of the gait cycle after sufficient training periods. The goal of the use of this proposed neural network is to increase the robustness of the control of the dynamic walking gait of this robot in the case of external disturbances. Also, the PD controller alone and Computed Torque Method (CTM) control system are used to control the walking robot’s position for comparison.     

On stabilization of systems with delay

The optimization of the parameters of a controller of given structure for a controlled unstable scalar system with delay is studied. First, the original system with delay is approximated by a system without delay. To this end, the exponent is approximated by a fractional rational function. Since the structure of the controller is fixed, the quality of the approximation is assessed by comparing the stability domains of the original and approximating systems (in the space of controller coefficients). Next, the coefficients of the controller for the reduced system are optimized. The performance of the controller thus synthesized can be assessed by mathematically modeling the original system (with delay) whose feedback is determined by the controller coefficients found. The approach is exemplified by stabilizing an inverted mathematical pendulum with a PD controller. This example is used to examine the issue of synthesis of a robust controller __________ Translated from Prikladnaya Mekhanika, Vol. 44, No. 10, pp. 86–100, October 2008.     

Synthesis and properties of novel polymers based on PD electron-withdrawing unit

In this article, we designed and synthesized a series of 5-(2,6-dimethyl-4H-pyran-4-ylidene)-1,3-diethyl-2-thioxodihydropyrimidine-4,6(1H, 5H)-dione(PD) unit based polymers(PFTDT, CZTDT, PHTDT and THTDT) for the first time. In these polymers, fluorene, 2,7-carbazole, phenothiazine and thiophene are employed as electron-donating groups and PD as electron-withdrawing group. TGA measurements demonstrated that these polymers possess good thermal stability(all above 377 °C). Very broad absorption spectrum was also obtained from the polymer THTDT(300?850 nm). CV characterization found that these polymers owned low highest occupied molecular orbital(HOMO) energy levels(?5.39 e V for THTDT, ?5.49 e V for CZTDT and ?5.78 e V for PFTDT) except for PHTDT(?5.17 e V). The geometry and electronic properties of PFTDT, CZTDT, PHTDT and THTDT were investigated by means of theoretical calculation. All the above advantages demonstrate that PD based polymers could be candidates for electronic devices.     

fMRI study of motor cortex activity modulation in early Parkinson's disease

Parkinson's disease is a neurological disorder associated with the disfunction of dopaminergic pathways of the basal ganglia, mainly resulting in a progressive alteration in the execution of voluntary movements. We present a functional magnetic resonance imaging (fMRI) study on cortical activations during simple motor task performance, in six early–stage hemiparkinsonian patients and seven healthy volunteers. We acquired data in three sessions, during which subjects performed the task with right or left hand, or bimanually. We observed consistent bilateral activations in cingulate cortex and dorsolateral prefrontal cortex of Parkinsonian subjects during the execution of the task with the affected hand. In addition, patients showed both larger and stronger activations in motor cortex of the affected hemisphere with respect to the healthy hemisphere. Compared with the control group, patients showed a hyperactivation of the dorsolateral prefrontal cortex of the affected hemisphere. We concluded that a presymptomatic reorganization of the motor system is likely to occur in Parkinson's disease at earlier stages than previously hypothesized. Moreover, our results support fMRI as a sensitive technique for revealing the initial involvement of motor cortex areas at the debut of this degenerative disorder.     

Selective recognition of Ca ions using novel polymeric phenols

The research described here elucidates the fundamental interactions of various cations with phenolic moieties constituting the side chains of novel copolymers. The phenolic group was chosen because similar interactions of the tyrosine (Tyr) moiety in proteins with alkaline earth cations are of particular interest for some biochemical systems where both the alkaline earth cations and the aromatic compounds are abundant. The present study has revealed the preferred binding site for our polymeric systems.     

Comparative study of low frequency noise and hot-carrier reliability in SiGe PD SOI pMOSFETs

The stress effect of SiGe pMOSFETs has been investigated to understand the electrical properties of devices fabricated on the Si bulk and PD SOI substrates. A comparison of the drain saturation current (I_D.sat) and maximum transconductance (g_m,max) in both the SiGe bulk and the SiGe PD SOI devices clearly shows that the SiGe PD SOI is more immune from hot-carriers than the SiGe bulk. The stress-induced leakage current (SILC) is hardly detectable in ultra-thin oxide, because the increasing contribution of direct tunneling is comparable to the trap-assisted component. The SiGe PD SOI revealed degraded properties being mainly associated with the detrimental silicon-oxide interface states of the SOI structure.     

Heterogenous catalysis in fine chemistry: the Heck reaction on Pd/SiO<Subscript>2</Subscript> catalysts

The preparation conditions to obtain a Pd/SiO₂ catalyst effective in the Heck reaction between para-substituted halogenobenzene and alkylacrylate have been studied. The impregnation of SiO₂, functionalised with a thiourea derivative, with a Pd(CH₃COO)₂ solution resulted in an active, but unstable catalyst. The catalyst became stable after calcination, but its activity appeared to be strongly dependent on the calcination temperature. IR spectra of adsorbed CO indicated that such a dependence should result from differences in the surface structure of the supported particles.     

Numerical investigation of ice breaking by a high-pressure bubble based on a coupled BEM-PD model

In this paper, by combining the boundary element method (BEM) and peridynamics (PD), a bubble-ice interaction model is established, which can investigate the dynamic interactions between a high-pressure bubble and an ice plate with particular focus on the mechanical behaviors of ice breaking. The bubble dynamics are solved by BEM based on the potential flow theory. Ice cracks initiation and propagation are simulated by the bond-based peridynamics which is validated by a three-point bending test. The fluid–structure interaction (FSI) is achieved by matching the normal velocity and hydrodynamic loads at the fluid–structure interface. To validate the proposed FSI model, an experiment is carried out in which an oscillating bubble is generated under an ice plate by underwater discharge system. The whole interaction process is captured by a Phantom V711 high-speed camera. Qualitative agreements are achieved between the numerical and experimental results. The underlying mechanism of cracks initiation, propagation, branching, and coalescence of the ice plate is found to highly depend on three parameters, i.e., bubble–ice distance, ice thickness and bubble size. The present study is expected to provide further assists in the understanding of ice breaking problems.     

一种基于瞳面相位差的波前传感器相位恢复

根据瞳面相位差波前传感器的特点,提出把模式分解和随机并行梯度下降算法结合起来实现波前相位的恢复.以32单元变形镜的初始面形和Roddier提出的相位生成方法随机产生的一帧相屏为研究对象,分析所提出的相位恢复算法的性能.结果表明,两种情况下的畸变波前都得到了很好的恢复.当像差仅含有低阶成分时,使用模式分解法就可获得令人满...     

Therapeutic Intervention of COVID-19 by Natural Products: A Population-Specific Survey Directed Approach

To date very few promising leads from natural products (NP) secondary metabolites with antiviral and immunomodulatory properties have been identified for promising/potential intervention for COVID-19. Using in-silico docking studies and genome based various molecular targets, and their in vitro anti-SARS CoV-2 activities against whole cell and/or selected protein targets, we select a few compounds of interest, which can be used as potential leads to counteract effects of uncontrolled innate immune responses, in particular those related to the cytokine storm. A critical factor for prevention and treatment of SARS-CoV-2 infection relates to factors independent of viral infection or host response. They include population-related variables such as concurrent comorbidities and genetic factors critically relevant to COVID-19 health disparities. We discuss population risk factors related to SARS-CoV-2. In addition, we focus on virulence related to glucose-6-phosphate dehydrogenase deficiency (G6PDd), the most common human enzymopathy. Review of data on the response of individuals and communities with high prevalence of G6PDd to NP, prompts us to propose the rationale for a population-specific management approach to rationalize design of therapeutic interventions of SARS-CoV-2 infection, based on use of NP. This strategy may lead to personalized approaches and improve disease-related outcomes.