A robust method for performance evaluation of the vapor cell for magnetometry

A robust performance evaluation method for vapor cells used in magnetometers is proposed in this work.The performance of the vapor cell determines the sensitivity of the magnetic measurement,which is the core parameter of a magnetometer.After establishing the relationship between intrinsic sensitivity and the total relaxation rate,the total relaxation rate of the vapor cell can be obtained to represent the intrinsic sensitivity of the magnetometer by fitting the parameters of the magnetic resonance experiments.The method for measurement of the total relaxation rate based on the magnetic resonance experiment proposed in this work is robust and insensitive to ambient noise.Experiments show that,compared with conventional sensitivity measurement,the total relaxation rate affected by magnetic noise below 0.9 n T,pump light frequency noise below 1.5 GHz,pump light power noise below 9%,probe light power noise below 3%and temperature fluctuation of 150±3℃deviates by less than 2%from the noise-free situation.This robust performance evaluation method for vapor cells is conducive to the construction of a multi-channel high-spatial-resolution cardio-encephalography system.

Adaptive Memory Event-Triggered Observer-Based Control for Nonlinear Multi-Agent Systems Under DoS Attacks

This paper investigates the event-triggered security consensus problem for nonlinear multi-agent systems(MASs)under denial-of-service(Do S)attacks over an undirected graph.A novel adaptive memory observer-based anti-disturbance control scheme is presented to improve the observer accuracy by adding a buffer for the system output measurements.Meanwhile,this control scheme can also provide more reasonable control signals when Do S attacks occur.To save network resources,an adaptive memory event-triggered mechanism(AMETM)is also proposed and Zeno behavior is excluded.It is worth mentioning that the AMETM's updates do not require global information.Then,the observer and controller gains are obtained by using the linear matrix inequality(LMI)technique.Finally,simulation examples show the effectiveness of the proposed control scheme.

Fiber resonator using negative-curvature anti-resonant fiber with temperature stability

The coupling efficiency of hollow-core fiber changes with temperature,which leads to the decrease of the finesse(F)of fiber resonator and limits the performance of the resonant fiber optic gyroscope(R-FOG)system.Negative-curvature antiresonant fiber(ARF)can maintain single-mode characteristics under the condition of large mode field diameter,achieve efficient and stable fiber coupling,and significantly improve the consistency of the F of the spatial coupling resonator in variable temperature environment.A new type of ARF with a mode field diameter(MFD)of 25μm is used to fabricate a fiber resonator with a length of 5.14 m.In the range of 25℃-75℃,the average F is 31.45.The ARF resonator is used to construct an R-FOG system that shows long-term bias stability(3600 s)of3.1°/h at room temperature,4.6°/h at 75℃.To our knowledge,this is the best reported index of hollow-core fiber resonator and R-FOG system within the temperature variation range of 50℃ test.

Synergistic creation of highly stable strain-insensitive pressure sensors by in-plane strain modulation and quasi-homogenous interfacial design

The urgent requirement of electronic skin conformably attached to nonplanar surfaces to provide sta-ble monitoring in areas of healthcare,prosthetics,and robotics promotes the development of strain-insensitive/unperturbed pressure sensors.The main challenges lie in:(1)stretchability and conduc-tive stability of flexible electrodes and(2)mechanical stability of heterogeneous interfaces.This study presents a highly stable strain-insensitive pressure sensor achieved by in-plane strain modulation and quasi-homogenous interfacial design.Strain modulation of stretchable electrodes by both periodic mi-crostructured engineering and pre-stretching strategies(called“island-ripple”)was employed to suppress microcracks propagation.The improvement in stretchability and cyclic conductive stability of electrodes was identified by finite element analysis and experimental verification.The pre-stretched microconed stretchable electrode with a low sheet resistance of 0.546sq^(−1) shows a maximum deformation of up to 80%and excellent cyclic conductive stability over 10000 times under 30%strain.Quasi-homogenous interface strategy by the CNTs/PDMS system was employed to enhance the mechanical and electrical sta-bility of the electrode-active materials interface,demonstrating a strong peel strength and shear strength of>40.9 N/m and>124.8 kPa,respectively.The as-prepared strain-insensitive pressure sensor provides constant sensing performance over 5000 stretching-releasing cycles within 20%stretching.In addition,a 4×4 pixel strain-insensitive pressure sensor array with reduced cross-talk circuit design was further integrated to identify the shape and weight of different objects under strains.The stretchability and sta-bility of our sensor enable it to be applied in stretchable electronics with great potential.

Combinatorial screening via high-throughput preparation:Thermoelectric performance optimization for n-type Bi-Te-Se film with high average zT>1

Thermoelectric materials have drawn extensive interest due to the direct conversion between electricity and heat,however,it is usually a time-consuming process for applying traditional“sequential”meth-ods to grow materials and investigate their properties,especially for thermoelectric films that typically require fine microstructure control.High-throughput experimental approaches can effectively accelerate materials development,but the methods for high-throughput screening of the microstructures require further study.In this work,a combinatorial high-throughput optimization solution of material properties is proposed for the parallel screening and optimizing of composition and microstructure,which involves two distinctive types of high-throughput fabrication approaches for thin films,along with a new portable multiple discrete masks based high-throughput preparation platform.Thus,Bi_(2)Te_(3-x)Se_(x)thin film library with 196 throughputs for locating the optimized composition is obtained in one growth cycle.In addition,another thin film library composed of 31 materials with traceable process parameters is built to further investigate the relationship between microstructure,process,and thermoelectric performance.Through high-throughput screening,the Bi_(2)Te_(2.9)Se_(0.1)film with(00l)orientation is prepared with a peak zT value of 1.303 at 353 K along with a high average zT value of 1.047 in the interval from 313 to 523 K.This method can be also extended to the discovery of other functional thin films with a rapid combinatorial screening of the composition and structure to accelerate material optimization.

Realizing p-type performance in low-thermal-conductivity BiSbSe_(3) via lead doping

BiSbSe_(3) is an intrinsic n-type thermoelectric material,which attracts a lot of research interest due to its low lattice thermal conductivity and multiple band structure,and it exhibits excellent thermoelectric properties in the midtemperature region.However,there is little research on p-type BiSbSe_(3).This work realized the successful preparation of p-type BiSbSe_(3) through Pb doping.The thermoelectric transport properties of Pb-doped p-type BiSbSe_(3)were investigated.Pb doping could further reduce the thermal conductivity of BiSbSe_(3).All Pb-doped samples exhibited and maintained stable p-type transmissionthroughout the working temperature range(300-723 K).This work proves that Pb can be successfully used as a p-type dopant for BiSbSe_(3).

Zero field optically pumped magnetometer with independent dual-mode operation

We propose a dual-mode optically pumped magnetometer(OPM)that can flexibly switch between single-beam modulation mode and double-beam DC mode.Based on a 4 mm×4 mm×4 mm miniaturized vapor cell,the double-beam DC mode achieves a sensitivity of 7 fT=Hz^(1/2) with probe noise below 4 fT=Hz^(1/2) and working bandwidth over 65 Hz.This mode is designed to precisely measure the noise floor of a mu-metal magnetic shield.The single-beam modulation mode(sensitivity 20 fT=Hz^(1/2))exhibits bandwidth characteristics suitable for biomagnetic measurements.Thus,our design is suitable for a miniaturized OPM with multiple functions,including magnetic-shield background noise measurement and medical imaging.