MZI/FPI Fiber Optic Dual-parameter Sensor Based on a Double Cone and Air Cavity Structure(Invited)

This paper proposes a Mach Zehnder/Fabry Perot Interferometer(MZI/FPI)fiber sensor based on Single-mode Fiber(SMF)and Hollow-core Fiber(HCF),which has high sensitivity to temperature and lateral loads.The proposed device consists of two single-mode fiber cones formed by manually controlling the fusion splicer and an air cavity formed by fusing a section of hollow-core fiber.The structure of the sensor is a double cone cascaded air cavity.At the beginning of the design,we compared the basic transmission spectra of single cone structure and double cone structure experimentally,and therefore chose to use double cone structure and air cavity cascade.Light undergoes its first reflection at the first interface between the single-mode fiber and the air cavity structure,and its second reflection at the second interface between the air cavity structure and the single-mode fiber.The two reflected light waves produced by the two reflections form FP interference,which can be used to measure lateral loads.The transmitted light is excited through the first cone,and a portion of the core mode light is excited to the cladding,while another portion of the core mode light continues to propagate in the core.The light couples at the second cone,and the cladding mode light couples back into the core,forming MZ interference with the core mode light,which can be used to measure temperature.The use of hollow-core fiber to form an air cavity has little effect on transmitted light,while avoiding the problem of crosstalk in dual parameter measurements.By designing temperature and lateral load experiments,this article verifies the sensitivity characteristics of this sensor to temperature and lateral loads.A significant redshift phenomenon was observed in the temperature experiment.A significant redshift phenomenon also occurred in the lateral load experiment.Through wavelength demodulation,the experimental results show that the wavelength sensitivity of the sensor to temperature is 56.29 pm/℃in the range of 30℃to 80℃.The wavelength sensitivity of the sensor to lateral loads is 1.123 nm/N in the range of 0~5 N.In addition,we have prepared multiple sets of fiber optic sensors with this structure and conducted repeated experiments to verify that the sensing performance of this structure of fiber optic sensors for temperature and lateral load is relatively stable.Also,the different waist diameters of cones will have a certain impact on the transmission spectrum of MZ,while the length of the air cavity will also have a certain impact on the reflection spectrum of FP.This article lists some fiber optic sensors for dual parameter measurement of temperature and lateral load.Compared with the listed sensors,the fiber optic sensor proposed in this article has better sensitivity to temperature and lateral load.And the fiber optic sensor proposed in this article has a simple manufacturing process,low production cost,and good performance,which has certain prospects in scientific research and industrial production.

Shear mechanical properties and frictional sliding responses of rough joint surfaces under dynamic normal displacement conditions

A comprehensive understanding of the dynamic frictional characteristics in rock joints under high normal load and strong confinement is essential for ensuring the safety of deep engineering construction and mitigating geological disasters.This study conducted shear experiments on rough rock joints under displacement-controlled dynamic normal loads,investigating the shear behaviors of joints across varying initial normal loads,normal loading frequencies,and normal loading amplitudes.Experimental results showed that the peak/valley shear force values increased with initial normal loads and normal loading frequencies but showed an initial increase followed by a decrease with normal loading amplitudes.Dynamic normal loading can either increase or decrease shear strength,while this study demonstrates that higher frequencies lead to enhanced friction.Increased initial normal loading and normal loading frequency result in a gradual decrease in joint roughness coefficient(JRC)values of joint surfaces after shearing.Positive correlations existed between frictional energy dissipation and peak shear forces,while post-shear joint surface roughness exhibited a negative correlation with peak shear forces through linear regression analysis.This study contributes to a better understanding of the sliding responses and shear mechanical characteristics of rock joints under dynamic disturbances.

Radial Variation in Sap Flux Density as a Function of Sapwood Thickness in Two Eucalyptus ( Eucalyptus urophylla ) Plantations

Radial variation in sap flux density (SFD) as a function of sapwood thickness is of importance in accurately estimating sap flux through sapwood area which, in turn, decides the precision of heat pulse application. However, until now, only a few studies have evaluated the magnitude and significance of sampling errors associated with radial gradients in SFD, which were based on the small monitoring measurement data from a few trees. Based on one year of heat pulse observation of two 3 - 4 years old Eucalyptus urophylla S. T.,P Blake plantations in Leizhou Peninsula, Guangdong Province, China, a way of data processing was developed to treat with the lots of SFD data measured from 39 trees. It was found that the radial variation in SFD as a function of sapwood thickness in the two eucalyptus plantation sites could be expressed as y = 3. 667 5x(3) - 7.295 5x(2) + 3.682 6x + 0. 567 4 (R-2 = 0. 939 1, n = 80, P = 0.01), where y is the ratio of SFD of a sensor to the average of four data in different depths, x is the ratio of a sensor depth to tire radial sapwood thickness. It was the same (as in the following equation) in Jijia site, y = 5.006 2x(3) - 9.116 1x(2) + 4. 454 4x + 0.463 4 (R-2 = 0. 806 9, n = 72, P = 0.01) in Hetou site. From cambium to heartwood, SFD showed some increases at first and then decreases continuously. However, because die trees were very young, the maximum SFD was only 0. 33 - 0. 36 times more than the minimum.

Anisotropy measurements and characterization of the Qingshankou shale

Qingshankou shale(Gulong area,China)exhibits strong acoustic anisotropy characteristics,posing significant challenges to its exploration and development.In this study,the five full elastic constants and multipole response law of the Qingshankou shale were studied using experimental measurements.Analyses show that the anisotropy parametersϵandγin the study region are greater than 0.4,whereas the anisotropy parameterδis smaller,generally 0.1.Numerical simulations show that the longitudinal and transverse wave velocities of these strong anisotropic rocks vary significantly with inclination angle,and significant differences in group velocity and phase velocity are also present.Acoustic logging measures the group velocity in dipped boreholes;this differs from the phase velocity to some extent.As the dip angle increases,the longitudinal and SH wave velocities increase accordingly,while the qSV-wave velocity initially increases and then decreases,reaching its maximum value at a dip of approximately 40°.These results provide an effective guide for the correction and modeling of acoustic logging time differences in the region.

基于MEMS三轴加速度传感器的摔倒检测

摔倒作为人体活动的一部分,是影响人体健康的一大因素,尤其对病人和老年人而言,摔倒检测至关重要。基于MEMS三轴加速度传感器采集的人体活动加速度信号,提出了一种基于固定阈值的信号幅度向量滑动平均法SVMSA。该方法根据人体活动时的加速度信号特征,利用预先设定的阈值对加速度信号幅度向量SVM的滑动平均SVMSA进行判决,同时使用差分信号幅度域DSMA区分快速跑步等剧烈运动,准确实现了人体的摔倒检测。主要优势在于分析并区别了人体快速跑步等剧烈运动对摔倒检测的影响。通过对8位实验者的测试,该算法实现了94.4%的精确度。实验表明该算法能够较为准确地实现人体的摔倒检测。

Effect of Site Factor on Plant Community Characteristic in Closed Watershed in Loess Hilly and Gully Region

[Objective] The aim was to study the effect of site factor on plant community characteristic in closed watershed in loess hilly and gully region.[Method] Based on the investigation of vegetation in the closed watershed of Wuqi County in Shaanxi Province,the difference of plant community characteristic and species diversity under various site types was researched in our paper.[Result] In the investigation area,xerophytic herb was the main community,with sole species composition and simple community structure.Zonal vegetations were Artemisia sacrorum and Artemisia giraldii community;for plant diversity,the order of diversity index was ridge topgully bottomridge slopegully slope in various landform positions and semi-shady slopeshady slopesemi-sunny slopesunny slope in various slope aspects;with the increase of gradient,the diversity index of sunny slope changed with ＂S＂ type,and it reached maximum value at 37°.[Conclusion] Our study could provide theoretical foundation for vegetative restoration in loess hilly and gully region.

Optimal intensity measures for longitudinal seismic response of tunnels

To study the ground motion intensity measures(IMs)suitable for the design of seismic performance with a focus on longitudinal resistance in tunnel structures,21 different seismic intensity parameters are selected for nonlinear calculation and analysis of tunnel structures,in order to determine the optimal IM for the longitudinal seismic performance of tunnel structures under different site conditions.An improved nonlinear beam-spring model is developed to calculate the longitudinal seismic response of tunnels.The PQ-Fiber model is used to simulate the longitudinal nonlinear behavior of tunnel structures and the tangential interactions between the tunnel and the soil is realized by load in the form of moment.Five different site types are considered and 21 IMs is evaluated against four criteria:effectiveness,practicality,usefulness,and sufficiency.The results indicate that the optimal IMs are significantly influenced by the site conditions.Specifically,sustained maximum velocity(V_(SM))emerges as the optimal IM for circular tunnels in soft soil conditions(CaseⅠsites),peak ground velocity(V PG)is best suited for CaseⅡsites,sustained maximum acceleration(A_(SM))is ideal for both CaseⅢand CaseⅤsites,and peak ground acceleration(A PG)for CaseⅣsites.As site conditions transition from CaseⅠto CaseⅤ,from soft to hard,the applicability of acceleration-type intensity parameters gradually decreases,while the applicability of velocity-type intensity parameters gradually increases.

Phase field model for strong interfacial energy anisotropy of HCP materials

Based on the Karma model and the Eggleston regularization technique of the strong interfacial energy anisotropy, a phase-field model was established for HCP materials. An explicit finite difference numerical method was used to solve phase field model and simulate the dendrite growth behaviors of HCP materials. Results indicate that the dendrite morphology presents obvious six-fold symmetry, and discontinuity in the variation of interface orientation occurs, resulting in a fact that the corners were formed at the tips of the main stem and side branches. When the interfacial energy anisotropy strength is lower than the critical value（1/35）, the steady-state tip velocity of dendrite increases with anisotropy as expected. As the anisotropy strength crosses the critical value, the steady-state tip velocity drops down by about 0.89%. With further increase in anisotropy strength, the steady-state tip velocity increases and reaches the maximum value at anisotropy strength of 0.04, then decreases.

Modified MK model combined with ductile fracture criterion and its application in warm hydroforming

A modified MK model combined with ductile fracture criterion（DFC-MK model） is proposed to compute the forming limit diagrams（FLDs） of 5A06-O aluminum alloy sheet at different temperatures.The material constant（C） of ductile fracture criterion and initial thickness imperfection parameter（f0） at various temperatures are determined by using a new computing method based on wide sheet bending test.The FLDs at 20 and 200 °C are calculated through the DFC-MK model.The DFC-MK model,which includes the influence of through-thickness normal stress,is written into the subroutine VUMAT embedded in Abaqus/ Explicit.The cylindrical cup hydroforming tests are carried out to verify the model.The results show that compared with experimental observations,the predicted FLDs based on DFC-MK model are more accurate than the conventional MK model;the errors between the simulations and experiments in warm hydroforming are 8.23% at 20 °C and 9.24% at 200 °C,which verify the effectiveness of the proposed model.

Effect of Transplanting Density on Rice Yield,Nitrogen Uptake and ^(15)N-fertilizer Fate

[Objective] The aim of this study was investigated the rice yield, nitrogen uptake and ^15-fertilizer fate at different transplanting density to provide scientific ba- sis for improving the yield of rice and applying reasonably fertilizer. [Method] A field experiment was carried out to study the effect of different transplanting density on rice yield, nitrogen （N） absorption, sources of N uptake by rice and the N balance in the plant-soil systems by using ^15-labelled urea. [Result] There were no significant differences in rice yields and total N uptakes by rice between treatments 30 cm × 30 cm and 40 cm × 40 cm, but the yield of rice and total N absorption in the two treatments were remarkably higher than those in 50 cm × 50 cm treatment. The amounts of total N uptake by rice were in the range of 112.3-162.7 kg/hm2 in the three transplanting densities. The result showed that about 1/3 of the total N uptake by rice was supplied by application fertilizer and the other 2/3 was obtained from the soil N pool. The ^15N-labelled urea absorbed by rice, residual in soil and lost accounted for 16.3%-26.1%, 17.0%-20.9% and 53.0%-66.7% of the total fertilizer, respectively. A great deal of ^15N-labelled urea was lost during the rice growing season. [Conclusion] Considering the rice yield and environmental protection, the transplanting density of 30 cm×30 cm was recommended in the hilly area of Sichuan basin in the southwest China.

A High Breakdown Voltage Thin SOI Device with a Vertically Linearly Graded Concentration Drift Region

As the thickness of an SOI layer varies,a minimum breakdown voltage is reached when the thickness is about 2μm. The vertical electric field of the SOI LDMOS with a drift region which is vertically linearly graded is constant. The vertically linearly graded concentration drift can be achieved by impurity implanting followed by thermal diffusion. In this way,the vertical breakdown voltage of SOI LDMOS with 2μm thickness SOI layer can be improved by 43%. The on-state resistance is lowered by 24 % because of the higher impurity concentration of the SOI surface.

Wavelet transform and gradient direction based feature extraction method for off-line handwritten Tibetan letter recognition

To improve the recognition accuracy of off-line handwritten Tibetan characters the local gradient direction histograms based on the wavelet transform are proposed as the recognition features.First for a Tibetan character sample image the first level approximation component of the Haar wavelet transform is calculated.Secondly the approximation component is partitioned into several equal-sized zones. Finally the gradient direction histograms of each zone are calculated and the local direction histograms of the approximation component are considered as the features of the character sample image.The proposed method is tested on the recently developed off-line Tibetan handwritten character sample database.The experimental results demonstrate the effectiveness and efficiency of the proposed feature extraction method.Furthermore compared with the detail components the approximation component contributes more to the recognition accuracy.

Effect of slice scope on data slice-based class cohesion metrics

This paper suggests that a single class rather than methods should be used as the slice scope to compute class cohesion. First, for a given attribute, the statements in all methods that last define the attribute are computed. Then, the forward and backward data slices for this attribute are generated by using the class as the slice scope and are combined to compute the corresponding class data slice. Finally, the class cohesion is computed based on all class data slices for the attributes. Compared to traditional cohesion metrics that use methods as the slice scope, the proposed metrics that use a single class as slice scope take into account the possible interactions between the methods. The experimental results show that class cohesion can be more accurately measured when using the class as the slice scope.

Temperature compensation method of silicon microgyroscope based on BP neural network

The temperature characteristics of a silicon microgyroscope are studied, and the temperature compensation method of the silicon microgyroscope is proposed. First, an open-loop circuit is adopted to test the entire microgyroscope＇s resonant frequency and quality factor variations over temperature, and the zero bias changing trend over temperature is measured via a closed-loop circuit. Then, in order to alleviate the temperature effects on the performance of the microgyroscope, a kind of temperature compensated method based on the error back propagation（BP）neural network is proposed. By the Matlab simulation, the optimal temperature compensation model based on the BP neural network is well trained after four steps, and the objective error of the microgyroscope＇s zero bias can achieve 0.001 in full temperature range. By the experiment, the real time operation results of the compensation method demonstrate that the maximum zero bias of the microgyroscope can be decreased from 12.43 to 0.75（°）/s after compensation when the ambient temperature varies from -40 to 80℃, which greatly improves the zero bias stability performance of the microgyroscope.

The surface wave suppression using the second generation curvelet transform

In this paper,we develop a new and effective multiple scale and strongly directional method for identifying and suppressing ground roll based on the second generation curvelet transform.Making the best use of the curvelet transform＇s strong local directional characteristics,seismic frequency bands are transformed into scale data with and without noise.Since surface waves and primary reflected waves have less overlap in the curvelet domain,we can effectively identify and separate noise.Applying this method to prestack seismic data can successfully remove surface waves and,at the same time,protect the reflected events well,particularly in the low-frequency band.This indicates that the method described in this paper is an effective and amplitude-preserving method.

3D density inversion of gravity gradient data using the extrapolated Tikhonov regularization

We use the extrapolated Tikhonov regularization to deal with the ill-posed problem of 3D density inversion of gravity gradient data. The use of regularization parameters in the proposed method reduces the deviations between calculated and observed data. We also use the depth weighting function based on the eigenvector of gravity gradient tensor to eliminate undesired effects owing to the fast attenuation of the position function. Model data suggest that the extrapolated Tikhonov regularization in conjunction with the depth weighting function can effectively recover the 3D distribution of density anomalies. We conduct density inversion of gravity gradient data from the Australia Kauring test site and compare the inversion results with the published research results. The proposed inversion method can be used to obtain the 3D density distribution of underground anomalies.

Infrasound Event Classification Fusion Model Based on Multiscale SE-CNN and BiLSTM

The classification of infrasound events has considerable importance in improving the capability to identify the types of natural disasters.The traditional infrasound classification mainly relies on machine learning algorithms after artificial feature extraction.However,guaranteeing the effectiveness of the extracted features is difficult.The current trend focuses on using a convolution neural network to automatically extract features for classification.This method can be used to extract signal spatial features automatically through a convolution kernel;however,infrasound signals contain not only spatial information but also temporal information when used as a time series.These extracted temporal features are also crucial.If only a convolution neural network is used,then the time dependence of the infrasound sequence will be missed.Using long short-term memory networks can compensate for the missing time-series features but induces spatial feature information loss of the infrasound signal.A multiscale squeeze excitation–convolution neural network–bidirectional long short-term memory network infrasound event classification fusion model is proposed in this study to address these problems.This model automatically extracted temporal and spatial features,adaptively selected features,and also realized the fusion of the two types of features.Experimental results showed that the classification accuracy of the model was more than 98%,thus verifying the effectiveness and superiority of the proposed model.

Biomechanical Characteristics of Rape Stalks

[Objective] To study the correlation between the biomechanical properties of rape stalks and rape stem lodging. [Method] Through axial compression tests to the stalks of 4 different rape varieties, the change rules of maximum stem bearing ca- pacity, maximum compressive strength, elastic modulus and moment of inertia along plant height were analyzed, as well as the effect of different varieties and water contents on the biomechanical property indices of rape stalks. [Result] The maximum loads of rape stalks presented liner decrease trend along with the increase of stem height, and all reached the maximums below the height of 50 cm. The maximum stem compressive strength and elastic modulus of the 4 varieties were increased with ascending height, but in a slow rate with small change, thus the modulus of e- lasticity could be considered as unchanged. The maximum bearing capacity, maxi- mum compressive strength and elastic modulus of dry rape stalks were higher than wet stalks, indicating that the water contents of rape stalks had significant effect on their mechanical properties. According to the actual lodging situations in filed, stalks of variety No. 1 owned the worst biomechanical properties and lodging degree, while the biomechanical properties of No. 6 and F5 were better than No. 1 and No. 9, and they also had stronger lodging-resistance. [Conclusion] The study provides parameters and bases for the design of mechanized production and mechanical deep processing of crops, and can better reveal the physical natures of organisms. The methods used in this study can also be used to screen excellent crop stalks.

Effect of growth rate and diameter on microstructure and hardness of directionally solidified Ti-46Al-8Nb alloy

Bridgman-type directional solidification experiments were conducted for Ti-46Al-8Nb （mole fraction, %） alloy. The effects of the growth rate and the diameter on the microstructure, phase transition and hardness of the alloy were investigated. The results show that with the increase of the growth rate and the decrease of the diameter, the fullyβphase solidification changes to the peritectic solidification, and the final microstructure is composed of theα2/γlamellar structure and a multiphase microstructure （B2 phase,α2/γlamellar structure） respectively, which can be attributed to the solute enrichment resulting from the decreasing diffusion and convection ability. The occurrence of peritectic reaction at high growth rate promotes the solute segregation heavily and the coarse lamellar spacing in Al-and Nb-rich region, which greatly decreases the hardness values and leads to the discontinuity of the hardness curves with the increase of the growth rate. Comparatively, the Ti-46Al-8Nb alloy has lower hardness values than the other applied TiAl-based alloys in previous studies.