Methods to Evaluate and Measure Power of Pneumatic System and Their Applications

Pneumatic system has been widely used throughout industry, and it consumes more than billions kW h of electricity one year all over the world. So as to improve the efficiency of pneumatic system, its power evaluation as well as measurement methods should be proposed, and their applicability should be validated. In this paper, firstly, power evaluation and measurement methods of pneumatic system were introduced for the first time. Secondly, based on the proposed methods, power distributions in pneumatic system was analyzed. Thirdly, through the analysis on pneumatic efficiencies of typical compressors and pneumatic components, the applicability of the proposed methods were validated. It can be concluded that, first of all, the proposed methods to evaluation and measurement the power of pneumatic system were efficient. Furthermore, the pneumatic power efficiencies of pneumatic system in the air production and cleaning procedure are respectively about 35%–75% and 85%–90%. Moreover, the pneumatic power efficiencies of pneumatic system in the transmission and consumption procedures are about 70%–85% and 10%–35%. And the total pneumatic power efficiency of pneumatic system is about 2%–20%, which varies largely with the system configuration. This paper provides a method to analyze and measure the power of pneumatic system, lay a foundation for the optimization and energy-saving design of pneumatic system.

Tuning Atomically Dispersed Fe Sites in Metal–Organic Frameworks Boosts Peroxidase‑Like Activity for Sensitive Biosensing

Although nanozymes have been widely developed,accurate design of highly active sites at the atomic level to mimic the electronic and geometrical structure of enzymes and the exploration of underlying mechanisms still face significant challenges.Herein,two functional groups with opposite electron modulation abilities(nitro and amino)were introduced into the metal–organic frameworks(MIL-101(Fe))to tune the atomically dispersed metal sites and thus regulate the enzymelike activity.Notably,the functionalization of nitro can enhance the peroxidase(POD)-like activity of MIL-101(Fe),while the amino is poles apart.Theoretical calculations demonstrate that the introduction of nitro can not only regulate the geometry of adsorbed intermediates but also improve the electronic structure of metal active sites.Benefiting from both geometric and electronic effects,the nitro-functionalized MIL-101(Fe)with a low reaction energy barrier for the HO*formation exhibits a superior POD-like activity.As a concept of the application,a nitro-functionalized MIL-101(Fe)-based biosensor was elaborately applied for the sensitive detection of acetylcholinesterase activity in the range of 0.2–50 mU mL−1 with a limit of detection of 0.14 mU mL−1.Moreover,the detection of organophosphorus pesticides was also achieved.This work not only opens up new prospects for the rational design of highly active nanozymes at the atomic scale but also enhances the performance of nanozyme-based biosensors.

Novel assisted cough system based on simulating cough airflow dynamics

Cough is a defensive behavior that protects the respiratory system from infection and clears airway secretions.Cough airflow dynamics have been analyzed by a variety of mathematical and experimental tools.In this paper,the cough airflow dynamics of 42 subjects were obtained and analyzed.An identification model based on piecewise Gauss function for cough airflow dynamics is proposed through the dimensionless method,which could achieve over 90%identification accuracy.Meanwhile,an assisted cough system based on pneumatic flow servo system is presented.The vacuum situation and feedback control are used to increase the simulated peak cough flow rate,which are important for airway secretion clearance and to avoid airway collapse,respectively.The simulated cough peak flow could reach 5 L/s without the external assistance such as manual pressing,patient cooperation and other means.Finally,the backstepping control is developed to generate a simulated cough airflow that closely mimics the natural cough airflow of humans.The assisted cough system opens up wide opportunities of practical application in airway secretion clearance for critically ill patients with COVID 2019 and other pulmonary diseases.

脑机接口——脑信息读取与脑活动调控技术

脑机接口(brain-computer interface,BCI)技术通过建立大脑与外部设备之间直接的信息交流和信号控制通道,实现脑思维活动与外界通信和交互作用,从而进行脑信息读取、外部执行设备的控制,以及脑活动的调整和控制.脑机接口是一种多学科融合的交叉技术,涉及神经科学、计算机科学、通信与信息处理技术、人工智能技术等,展现了广阔的发展和应用前景,包括医疗与康复、科学与教育、自动驾驶、工业控制等.同时,脑机接口技术的发展和应用面临重要的技术以及法律和伦理方面的挑战.本文简要介绍脑机接口技术的基本原理和组成,从信号获取、神经解码和认知脑机接口等关键技术角度阐述了国内外研究现状:从技术角度,讨论了脑机接口技术面临生物兼容性、通信速率、信号获取和处理、神经解码、安全等方面的挑战;从伦理和法制角度,指出该技术面临隐私、自由意志、身份认同和社会公平等方面的挑战.最后,展望了脑机接口技术未来的研究方向和应用前景.

How temperature and hydrostatic pressure impact organic room temperature phosphorescence from H-aggregation of planar triarylboranes and the application in bioimaging

Highly efficient persistent organic room temperature phosphorescence(RTP) has attracted increasing attention because of promising applications in fields of chemical sensors, optoelectronic devices, information security, and bioimaging, etc. Wherein,the crystal engineering of H-aggregation offers stabilization for long-lived triplet exciton for RTP, but the related research is rare because of the scarcity of ideal phosphorescent H-aggregate. Herein, we designed planar tricoordinate organoboron derivatives with molecular arrangement in ideal H-aggregation. The integration of Br atom can largely enhance RTP efficiency through increasing SOC effect, while the antiparallel molecular arrangement causes annihilation of triplet exciton. Thanks to good selfassembly property, their RTP can even be observed in PMMA matrix with doping ratio of merely 1 wt%. We further found that the cryogenic temperature contributes to stabilizing triplet exciton in H-aggregation, leading to red-shifted phosphorescence. By applying high hydrostatic pressure, the phosphorescence was largely enhanced and redshifted, demonstrating the crucial role of H-aggregation on RTP property. In phosphorescent tissue imaging of live mouse, nanoparticles of BrBA exhibited high contrast image via eliminating the interference of autofluorescence.

Protein trap-engineered metal-organic frameworks for advanced enzyme encapsulation and mimicking

Immobilizing enzymes within metal-organic frameworks(MOFs)enables enzymes to against extreme environments.However,these MOF shells are just like armors,protective but heavy,which shield the enzymes from threats while locking them in the cage.The exploitation of immobilization strategy and intrinsic property of MOFs themselves is of great significance.Here,we proposed a functional protein trap strategy for efficient enzyme encapsulation.The ferrocenedicarboxylic acid(Fc)was used to induce the formation of defect-rich Co-based MOFs(CoBDC-Fc).As result,the engineered protein trap can not only improve the enzyme loading but also accelerate catalytic efficiency.Specifically,the atomically dispersed Fc sites serve as cocatalysts/cofactors and even change the conformation of enzymes in the construed microenvironment.Furthermore,the obtained CoBDC-Fc/enzyme exhibits excellent recyclability and tolerance to inhospitable conditions.Benefited by these,the CoBDC-Fc/enzyme/antigen composites were further prepared for cascade enzyme-linked immunosorbent assay of prostate-specific antigen with satisfactory sensitivity.

Nanozymes enable sensitive food safety analysis

Food safety has become a subject of major concern in controlling food contamination and supervision.Effective detection and analysis methods need to be urgently exploited to cope with this grand global challenge.Among conventional methods for food safety analysis,enzyme-based biosensing methods serve a critical role in the monitoring of food safety.However,some long-lasting challenges,like high cost and low stability,hinder enzymebased biosensing systems.In this regard,nanozymes with superior enzyme-like activity and special physical and chemical characteristics gradually emerge as excellent tools for quality and safety analysis in agricultural fields.In this review,recent advances made in the food safety analysis based on nanozymes are summarized.Firstly,an introduction of nanozymes containing their definition,classification,and modulation is provided.Subsequently,four main sensing modes used in nanozyme-based biosensing are discussed in detail.Taking advantage of nanozyme-based biosensing platforms,great achievements made in food safety are highlighted,where biological hazards,heavy metal ions,antibiotics,pesticide residues,and additives are involved.At last,personal views of the progress and perspective in this evolving field are proposed.This review not only shows great reference significance for the construction and application of nanozyme-based analysis methods but also promotes solutions to some challenges existing in food safety.

Highly effective and reproducible surface-enhanced Raman scattering substrates based on Ag pyramidal arrays

Close-packed Ag pyramidal arrays have been fabricated by using inverted pyramidal pits on Si as a template and used to generate plentiful and homogeneous surface-enhanced Raman scattering （SERS） hot sites. The sharp nanotip and the four edges of the Ag pyramid result in strong electromagnetic field enhancement with an average enhancement factor （EF） of 2.84 × 10^7. Moreover, the features of the close-packed Ag pyramidal array can be well controlled, which allows SERS substrates with good reproducibility to be obtained. The relative standard deviation （RSD） was lower than 8.78% both across a single substrate and different batches of substrates.

Efficiency optimized fuel supply strategy of aircraft engine based on air-fuel ratio control

Accurate fuel injection control of aircraft engine can optimize the energy efficiency of UAV power system while meeting the propeller speed requirement. Traditional injection control method such as open-loop calibration causes instability of fuel supply which brings the risk of power loss of UAV. Considering that the closed-loop control of AFR can ensure a stable fuel feeding, this paper proposes an AFR control based fuel supply strategy in order to improve the efficiency of fuel-powered UAV while obtaining the required engine speed. According to the optimum fuel injection results, we implement fuzzy-PID method to control the set AFR in different situations. Through simulation and experiment studies, the results indicate that, to begin with, the calibrated mathematical model of the aircraft engine is effective. Next, this fuel supply strategy based on AFR control can normally realize the engine speed regulation, and the applied control algorithm can eliminate the overshoot of AFR throughout all the working progress. What is more,the fuel supply strategy can averagely shorten the response time of the engine speed by about two seconds. In addition, compared with the open-loop calibration, in this work the power efficiency is improved by 9% to 33%. Last but not the least, the endurance can be improved by 30 min with a normal engine speed. This paper can be a reference for the optimization of UAV aircraft engine.

Surface-state triggered solvatochromism of carbonized polymer dot and its two-photon luminescence

This study reports a new nitrogen-doped carbonized polymer dot(CPD)-based solvatochromic probe.Its color-changing for different solvents was explored in detail by the measurements of photophysical parameters(involving Stokes shifts,fluorescence quantum yield,fluorescence lifetime,radiative decay rate constant,and non-radiative decay rate constant)and the following analyses according to Lippert–Mataga equation and Kamlet–Taft model.The hydrogen bonding effect of the CPD in protonic solvents was semi-quantitatively assessed.It takes charge of the solvatochromic phenomenon,especially in proton solvents.Interestingly,this CPD exhibits two-photon solvatochromism.Moreover,the relations between the photophysical parameters and the surface states of CPD in aprotic and proton solvents were depicted.The results reveal the nitrogen doping in the CPD impacts the up-and down-conversion solvatochromic features from the comparison between N-free and N-doped CPDs in many characterizations.In addition,this N-doped CPD was dispersed into polymer matrices to fabricate tunable solid-state luminescent films,which is another model for evidencing the interactions of the CPD with surroundings.This study is of significance in understanding the surface-state controlled luminescence in the CPDs,and will be beneficial for developing new smart,responsive carbon-based nanoprobes.

Atomically dispersed N-coordinated Fe-Fe dual-sites with enhanced enzyme-like activities

Replacement of enzymes with nanomaterials such as atomically dispersed metal catalysts is one of the most crucial steps in addressing the challenges in biocataiysis.Despite the breakthroughs of single-atom catalysts in enzyme-mimicking,a fundamental investigation on the development of an instructional strategy is still required for mimicking biatomic/multiatomic active sites in natural enzymes and constructing synergistically enhanced metal atom active sites.Herein,Fe_(2)NC catalysts with atomically dispersed Fe-Fe dual-sites supported by the metal-organic frameworks-derived nitrogen-doped carbon are employed as biomimetic catalysts to perform proof-of-concept investigation.The effect of Fe atom number toward typical oxidase(cytochrome C oxidase,NADH oxidase,and ascorbic acid oxidase)and peroxidase(NADH peroxidase and ascorbic acid peroxidase)activities is systematically evaluated by experimental and theoretical investigations.A peroxo-like O_(2) adsorption in Fe_(2)NC nanozymes could accelerate the O-O activation and thus achieve the enhanced enzyme-like activities.This work achieves the vivid simulation of the enzyme active sites and provides the theoretical basis for the design of high-performance nanozymes.As a concept application,a colorimetric biosensor for the detection of S^(2-) in tap water is established based on the inhibition of enzyme-like activity of Fe_(2)NC nanozymes.

Modulation of hot regions in waveguide-based evanescent-field-coupled localized surface plasmons for plasmon-enhanced spectroscopy

Coupling efficiency between the localized surface plasmons(LSPs) of metal nanoparticles(NPs) and incident light dominates the sensitivities of plasmon-based sensing spectroscopies and imaging techniques, e.g., surfaceenhanced Raman scattering(SERS) spectroscopy. Many endogenous features of metal NPs(e.g., size, shape,aggregation form, etc.) that have strong impacts on their LSPs have been discussed in detail in previous studies.Here, the polarization-tuned electromagnetic(EM) field that facilitates the LSP coupling is fully discussed.Numerical analyses on waveguide-based evanescent fields(WEFs) coupled with the LSPs of dispersed silver nanospheres and silver nano-hemispheres are presented and the applicability of the WEF-LSPs to plasmon-enhanced spectroscopy is discussed. Compared with LSPs under direct light excitation that only provide 3–4 times enhancement of the incidence field, the WEF-LSPs can amplify the electric field intensity about 30–90 times(equaling the enhancement factor of 10~6–10~8 in SERS intensity), which is comparable to the EM amplification of the SERS"hot spot" effect. Importantly, the strongest region of EM enhancement around silver nanospheres can be modulated from the gap region to the side surface simply by switching the incident polarization from TM to TE, which widely extends its sensing applications in surface analysis of monolayer of molecule and macromolecule detections. This technique provides us a unique way to achieve remarkable signal gains in many plasmon-enhanced spectroscopic systems in which LSPs are involved.

Defect-rich and ultrathin nitrogen-doped carbon nanosheets with enhanced peroxidase-like activity for the detection of urease activity and fluoride ion

Although carbon nanozymes have attracted great interest due to their good biocompatibility, low cost,and high stability, designing high-active carbon nanozymes still faces great challenges. Herein, ultrathin nitrogen-doped carbon nanosheets with rich defects(d-NC) were prepared through a high-temperature annealing process, using potassium chloride and ammonium chloride as templates. Owing to the large specific surface area, rich defects and the high exposure of active sites, the proposed d-NC nanozymes exhibited excellent peroxidase-like activity. The d-NC nanozymes possess maximal reaction velocity and their specific activity is 9.4-fold higher than that of nitrogen-doped carbon nanozymes, indicating that the induced defects can boost the catalytic performance. Benefited from the good peroxidase-like activities of d-NC nanozymes, the colorimetric sensing platforms were constructed for the detection of urease activity and fluoride ion, exhibiting satisfactory stability and selectivity. This study not only offers a way to synthesize carbon nanozymes with improved enzyme-like activities but also broadens their applications in colorimetric biosensing.

Fine-Tuning Pyridinic Nitrogen in Nitrogen-Doped Porous Carbon Nanostructures for Boosted Peroxidase-Like Activity and Sensitive Biosensing

Carbon materials have been widely used as nanozymes in bioapplications,attributing to their intrinsic enzyme-like activities.Nitrogen(N)-doping has been explored as a promising way to improve the activity of carbon material-based nanozymes(CMNs).However,hindered by the intricate N dopants,the real active site of N-doped CMNs(N-CMNs)has been rarely investigated,which subsequently retards the further progress of high-performance N-CMNs.Here,a series of porous N-CMNs with well-controlled N dopants were synthesized,of which the intrinsic peroxidase(POD)like activity has a positive correlation with the pyridinic N content.Density functional theory calculations also reveal that pyridinic N boosts the intrinsic POD-like activity of N-CMNs.Pyridinic-N dopant can effectively promote the first H_(2)O desorption process in comparison with the graphitic and pyrrolic N,which is the key endothermic reaction during the catalytic process.Then,utilizing the optimized nanozymes with high pyridinic N content(NP-CMNs)and superior POD-like activity,a facile total antioxidant capacity(TAC)assay was developed,holding great promise in the quality assessment of medicine tablets and antioxidant food for healthcare and healthy diet.

Boosting a sub-10 nm nanogap array by plasmon-triggered waveguide resonance

Gap-type metallic nanostructures are widely used in catalytic reactions,sensors,and photonics because the hotspot effect on these nanostructures supports giant local electromagnetic field enhancement.To achieve hotspots,researchers devote themselves to reducing gap distances,even to 1 nm.However,current techniques to fabricate such narrow gaps in large areas are still challenging.Herein,a new coupling way to boost the sub-10 nm plasmonic nanogap array is developed,based on the plasmon-triggered optical waveguide resonance via near-field coupling.This effect leads to an amplified local electromagnetic field within the gap regions equivalent to narrower gaps,which is evidenced experimentally by the surface-enhanced Raman scattering intensity of probed molecules located in the gap and the finite-difference time-domain numerical simulation results.This study provides a universal strategy to promote the performance of the existing hotspot configurations without changing their geometries.

Surface-enhanced Raman scattering(SERS)based on surface plasmon resonance coupling techniques

Surface plasmon resonance(SPR)can provide a remarkably enhanced electromagetic field around metal surface.It is one of the enhancement models for explaining surface-enhanced Raman scattering(SERS)phonomenon.With the development of SERS theories and techniques,more and more studies referred to the configurations of the optical devices for coupling the excitation and radiation of SERS,including the prism-coupling,waveguide-coupling,and grating-coupling modes.In this review,we will summarize the recent experimental improvements on the surface plasmoncoupled SERS.