Engineering Spiking Neurons Using Threshold Switching Devices for High-Efficient Neuromorphic Computing

Inspired by the human brain, the spike-based neuromorphic system has attracted strong research enthusiasm because of the high energy efficiency and powerful computational capability, in which the spiking neurons and plastic synapses are two fundamental building blocks. Recently, two-terminal threshold switching (TS) devices have been regarded as promising candidates for building spiking neurons in hardware. However, how circuit parameters affect the spiking behavior of TS-based neurons is still an open question. Here, based on a leaky integrate-and-fire (LIF) neuron circuit, we systematically study the effect of both the extrinsic and intrinsic factors of NbOx -based TS neurons on their spiking behaviors. The extrinsic influence factors contain input intensities, connected synaptic weights, and parallel capacitances. To illustrate the effect of intrinsic factors, including the threshold voltage, holding voltage, and high/low resistance states of NbOx devices, we propose an empirical model of the fabricated NbOx devices, fitting well with the experimental results. The results indicate that with enhancing the input intensity, the spiking frequency increases first then decreases after reaching a peak value. Except for the connected synaptic weights, all other parameters can modulate the spiking peak frequency under high enough input intensity. Also, the relationship between energy consumption per spike and frequency of the neuron cell is further studied, leading guidance to design neuron circuits in a system to obtain the lowest energy consumption. At last, to demonstrate the practical applications of TS-based neurons, we construct a spiking neural network (SNN) to control the cart-pole using reinforcement learning, obtaining a reward score up to 450. This work provides valuable guidance on building compact LIF neurons based on TS devices and further bolsters the construction of high-efficiency neuromorphic systems.

Bidirectional switchable beam splitter/filter based graphene loaded Si ring ‎resonators

Using bus waveguides coupled to the graphene-loaded Si-ring resonators (GSRRs) all on a Si-‎on-insulator substrate, we propose a compact bidirectional switchable beam splitter/filter ‎controlled by graphene-based electro-absorptive (refractive) mode modulation. The proposed ‎device consists of a through waveguide coupled to two drop waveguides via two GSRRs. ‎Each GSRR consists of a stack of hBN/graphene/hBN nanolayers sandwiched between two ‎Si-ring resonators. Using a finite difference time domain method, we show that the resonant ‎wavelength of GSRRs can be tuned in the range of 1551.5 < λ <1552.1 nm, linearly with the ‎slope of ~2.46 nm/eV via appropriately changing the graphene chemical potential, ‎electrostatically. The numerical results show that when both GSRRs are in an electro-refractive ‎state and a transverse electric (TE) polarized light beam of an appropriate wavelength is ‎launched into one of the though-ports, ~ 84.5% of the input intensity equally splits between ‎the adjacent drop-ports. The transmission out of the second through-port is less than 0.8%. ‎The numerical results further show that when one GSRR is in an electro-refractive mode, and ‎the other one is in an electro-absorptive state, ~68.4% of the input intensity transmits out of ‎the drop-port adjacent to the former GSRR, and the other ports experience insignificant ‎outputs (<0.7%). The device's structural symmetry makes it a bidirectional tunable, suitable for ‎long-haul optical telecommunication applications.‎

Exact Probability Landscapes of Stochastic Phenotype Switching in Feed-Forward Loops: Phase Diagrams of Multimodality

Feed-forward loops (FFLs) are among the most ubiquitously found motifs of reaction networks in nature. However, little is known about their stochastic behavior and the variety of network phenotypes they can exhibit. In this study, we provide full characterizations of the properties of stochastic multimodality of FFLs, and how switching between different network phenotypes are controlled. We have computed the exact steady-state probability landscapes of all eight types of coherent and incoherent FFLs using the finite-butter Accurate Chemical Master Equation (ACME) algorithm, and quantified the exact topological features of their high-dimensional probability landscapes using persistent homology. Through analysis of the degree of multimodality for each of a set of 10,812 probability landscapes, where each landscape resides over 105–106 microstates, we have constructed comprehensive phase diagrams of all relevant behavior of FFL multimodality over broad ranges of input and regulation intensities, as well as different regimes of promoter binding dynamics. In addition, we have quantified the topological sensitivity of the multimodality of the landscapes to regulation intensities. Our results show that with slow binding and unbinding dynamics of transcription factor to promoter, FFLs exhibit strong stochastic behavior that is very different from what would be inferred from deterministic models. In addition, input intensity play major roles in the phenotypes of FFLs: At weak input intensity, FFL exhibit monomodality, but strong input intensity may result in up to 6 stable phenotypes. Furthermore, we found that gene duplication can enlarge stable regions of specific multimodalities and enrich the phenotypic diversity of FFL networks, providing means for cells toward better adaptation to changing environment. Our results are directly applicable to analysis of behavior of FFLs in biological processes such as stem cell differentiation and for design of synthetic networks when certain phenotypic behavior is desired.

The comparison of gains prescribed for digital behind-the-ear hearing aids using the manufacturer-specific and conventional prescriptive formulas

Background and Aim: There are several prescriptive formulas for covering a variety of hearing loss, each of which applies relatively different amplifications at different frequencies. This study aims to compare the gains prescribed for digital behind-the-ear (BTE) hearing aids by the Desired Sensation Level Multi-Stage [Input/Output] (DSLm[I/O]), National Acoustic Laboratories-non linear2 (NAL-NL2) and manufacturer-specific formulas at different levels of input intensity. Methods: The gain values in 12-channel BTE hearing aids prepared from four companies (Oticon, Phonak, ReSound and Siemens) were measured at three levels of input intensity (45, 65, and 85 dB SPL) and at a frequency range of 250−8000 Hz for two moderately severe flat and mild sloping to severe hearing losses by using the DSLm[I/O], NAL-NL2 and manufacturerspecific formulas in the Frye FP35 test box. Results: There was no significant difference between the four selected hearing aids in terms of prescribed gain values using the prescriptive formulas (p > 0.05). Conclusion: The DSLm[I/O] formula prescribes higher gain in the 12-channel BTE hearing aids from Oticon, Phonak and Siemens companies at all input intensities and frequencies for moderately severe flat and mild sloping to severe hearing losses compared to the NAL-NL2 formula and manufacturer-specific formulas (Voice Aligned Compression (VAC), Adaptive Phonak, Connexx Fit and audiogram+). Keywords: National acoustic laboratories-non linear2; desired sensation level multi-stage [input/output]; gain; frequency; intensity levels

Application of BP Neural Network Model in the Evaluation of Urban Land Intensive Utilization

Using BP neural network model to analyze the urban land development status of Zhengzhou City from 2013 to 2017, the evaluation grades are divided into over-utilization, intensive use, moderate utilization and extensive utilization, and from the land input intensity, land use intensity and a total of nine indicators were selected for evaluation in three aspects of land output benefits. The results show that the urban land intensive degree of Zhengzhou City during the five years from 2013 to 2017 is 0.3039, 0.5118, 0.6189, 0.6914, 0.8509, and the intensive degree is gradually increased every year. The degree of intensive use is gradually increased every year, the evaluation level has risen from extensive use to intensive use, and the intensity of land intensive use has continued to increase.

Spatiotemporal changes caused by the intensive use of sea areas in the liaoning coastal economic zone of China

Oceans and their resources are experiencing immense pressure because of human exploitation. The intensive use of sea areas has become an important method in solving the contradiction between ocean supply and demand, thereby ensuring sustainable marine economy development, tapping potential sea-area utilization, reasonably allocating sea-area utilization structures, and increasing marine economic benefits. This paper explores the definition and connotation of intensive sea-area use and constructs an evaluation index system based on marine input intensity, marine utilization structure, marine economic benefit, and marine ecological environment. Multi-objective variable fuzzy set theory and fuzzy decision analysis methods were used to evaluate the intensive sea-area utilization in the Liaoning Coastal Economic Zone of China during 2004–2016. The spatial differentiation characteristics of intensive sea-area use were analysed using cluster analysis. The research result showed that: (1) Intensive utilization level of the Liaoning coastal economic zone has gradually increased, while it is still in a moderately weak level; (2) Sea area intensive utilization varied in degrees and fluctuates in the six cities under the jurisdiction of the Liaoning coastal economic zone; and (3) Marine input intensity, marine utilization structure, marine economic benefit, and marine sustainability indexes have increased in the cities, thereby exhibiting improvements in the Liaoning coastal economic zone.

The use of various genetically engineered biological drugs and selective immunosuppressants within the current provider-payment model of russian diagnosis-related groups

Diagnosis-Related Groups (DRG) for the payment for biological therapy were created at the stage of the pilot project and their coefficients of input intensity were not revised since then. The expansion of the range of genetically-engineered biological drugs (GEBD) and the development of new indications for biological therapy and new groups of expensive drugs (like selective immunodepressants, SI) determine the necessity in the differentiated payment for the therapy with GEBD and SI. However, at the federal level, this will be possible only after the approval of the clinical recommendations.Aim. The study aimed to identify possible applications of different GEBD and SI within the current provider-payment model of the Russian diagnosis-related group in terms of bronchial asthma (BA) and inflammatory bowel disease (IBD) - Crohn's disease and ulcerative colitis.Materials and methods. The expenses on GEBD and SI for one case of hospitalization were calculated and compared with the imposed tariffs. For the evaluation of the possibility of the provision of an expensive treatment within the existing DRG model, the authors modeled the distribution of patients with BA and IBD by different pharmaceutical treatment plans in the current practice and cases of an increase in the share of indications of more expensive therapy. The authors identified the number of patients that could have been treated without an increase in the costs of compulsory medical insurance (CHI). The authors proposed the subgroups for the differentiated payment for the treatment of BA and IBD with GEBD and SI.Results. Few variants of treatment with GEBD and SI were characterized by the costs of drugs that would exceed an average payment rate for DRG st36.003 and ds36.004 in 2020. In the model, an increase in the share of patients that received the most expensive drugs of all the registered GEBD and SI in the RF for the treatment of BA and IBD did not lead to an increase in the costs for CHI. It is possible to maintain the initial volume of the financing and increase the number of patients that receive GEBD and SI due to a decrease in the number of hospitalizations. The authors identified approximate values of the coefficient of input intensity (CII) for the subgroups that can be formed for the differentiated payment for pharmaceutical treatment with GEBD and SI.Conclusion. Despite the fact that without the recalculation of CII, there were numerous changed introduced into DRGs st36.003 and ds36.004 “Treatment with GEBD and SI” and the spectrum of the associated clinical situations expanded, it was possible to maintain the possibility of the payment for the therapy with different drugs, including the most expensive ones without an increase in the costs for the CHI system. Still, the results of the present study indicate the necessity in the optimization of the system of payment for medical care with genetically-engineered biologic drugs and selective immunodepressants through the implementation of a differentiated approach to the payment at the federal level.