基于粗糙度轮廓仪的圆柱齿轮齿廓形状偏差测量

齿廓形状偏差是齿轮质量的重要指标,反映了加工设备展成运动和刀具形状的精度,常在齿轮测量中心或三坐标测量机进行测量。论文提出了一种在粗糙度轮廓仪上进行齿廓形状偏差测量的新方法。该方法利用粗糙度轮廓仪获取齿轮齿廓测量数据,根据被测齿轮的参数,建立渐开线圆柱齿轮齿廓的理论几何模型;然后利用正交距离齿廓拟合算法实现齿廓测量数据与理论齿廓模型拟合,得到齿廓偏差曲线;最后根据ISO 1328-2013标准进行齿廓形状偏差评定。实验结果表明,所提出的方法得到的齿廓形状偏差结果具有较好的重复性,齿廓形状偏差的评价结果与齿轮测量中心给出的测量报告结果一致,两者齿廓形状偏差计算结果最大差距不超过0.5μm,验证了该方法的有效性。

海绵城市建设指标与场地规划条件的相关性研究

城市规划设计依托总体规划、区域规划和控制性详细规划等法定规划进行分级别指导和管控城市,目前海绵城市专项规划已经实施编制多年,但在控制性详细规划层面,海绵城市管控指标和场地规划条件存在一定的脱节,不利于推进海绵城市在建设中的落实。文章通过研究武汉市近百个实际项目,首先对其海绵城市建设指标和场地规划条件在空间地理位置上的分析,然后分别对居住型地块和非居住型地块的海绵城市建设指标和场地规划条件进行相关性分析,以期得到二者之间的具体影响因素,为后续街区层面的海绵城市建设提供指导。

Effects of nano-HMX on the properties of RDX-CMDB propellant:Higher energy and lower sensitivity

Batch preparation of nano-HMX was achieved via a mechanical trituration method. The morphology and particle size of nano-HMX and raw RDX were characterized using SEM. Then nano-HMX was used in a formulation of composite modified double base propellant containing RDX. The method is to use nanoHMX to replace the RDX in the formulation by 10% gradually with the total mass content of RDX and HMX unchanged. The burning rate, mechanical sensitivity and mechanical property of propellant strands with different mass content of nano-HMX were tested. The results indicate that the 30% content of nanoHMX has the best comprehensive performance which can be used as an improvement of the existing formula. A possible mechanism of action was discussed.

Preparation and property of CL-20/BAMO-THF energetic nanocomposites

A sol-gel freezing-drying method was utilized to prepare energetic nanocomposites based on 2, 4, 6, 8,10, 12-hexanitro-2, 4, 6, 8, 10, 12-hexaazaisowurtzitane(CL-20) with 3, 3-Bis(azidomethyl) oxetanetetrahydrofuran copolymer(BAMO-THF) as energetic gel matrix. Scanning electron microscopy(SEM),X-ray diffraction(XRD), Raman, Fourier-transform infrared spectroscopy(FT-IR) and differential thermal analyser(DTA) were utilized to characterize the structure and property of the resultant energetic nanocomposites. Compared with raw CL-20, the average particle sizes of CL-20 in CL-20/BAMO-THF energetic nanocomposites were decreased to nano scale and the morphologies of CL-20 were also changed from prismatic to spherical. FT-IR detection revealed that CL-20 particles were recrystallized in BAMO-THF gel matrix during the freezing-drying process. The thermal decomposition behaviors of the energetic nanocomposites were investigated as well. The thermolysis process of CL-20/BAMO-THF nanocomposites was enhanced and the activation energy was lower compared with that of raw CL-20,indicating that CL-20/BAMO-THF nanocomposites showed high thermolysis activity. The impact sensitivity tests indicated that CL-20/BAMO-THF energetic nanocomposites presented low sensitivity performance.

Recent progress on transition metal oxides and carbon-supported transition metal oxides as catalysts for thermal decomposition of ammonium perchlorate

As a main oxidizer in solid composite propellants,ammonium perchlorate(AP)plays an important role because its thermal decomposition behavior has a direct influence on the characteristic of solid composite propellants.To improve the performance of solid composite propellant,it is necessary to take measures to modify the thermal decomposition behavior of AP.In recent years,transition metal oxides and carbon-supported transition metal oxides have drawn considerable attention due to their extraordinary catalytic activity.In this review,we highlight strategies to enhance the thermal decomposition of AP by tuning morphology,varying the types of metal ion,and coupling with carbon analogue.The enhanced catalytic performance can be ascribed to synergistic effect,increased surface area,more exposed active sites,and accelerated electron transportation and so on.The mechanism of AP decomposition mixed with catalyst has also been briefly summarized.Finally,a conclusive outlook and possible research directions are suggested to address challenges such as lacking practical application in actual formulation of solid composite propellant and batch manufacturing.

Genetic polymorphism of mitochondrial DNA HVS-I and HVS-II of Chinese Tu ethnic minority group

We analyzed the two hypervariable segments HVS-I and HVS-II of 108 Chinese Tu ethnic minority group samples for forensic and population genetics purposes, Comparing with Anderson sequence, 79 polymorphic loci in HVS-I and 40 in HVS-II were found in Chinese Tu ethnic minority group mtDNA sequences, and 90 and 64 haplotypes were then defined. Haplotype diversity and the mean pairwise differences were 0.9903±0.0013 and 5.7785 in HVS-I, and 0.9777±0.0013 and 3.5819 in HVS-II, respectively. By analyzing the hypervariable domain from nucleotide 1,6180 to 1,6193 in HVS-I, we defined some new types of sequence variations. We also compared the relationship between Tu population and other populations using mtDNA HVS-I sequences. According to Rst genetic distances, the phylogenetic tree showed that the Tu population, the Xi＇an Han population, the Chinese Korean, and the Mongol ethnic group were in a clade. This indicated a close genetic relationship between them. There were far relations between the Tu population and other Chinese southern Han populations, Siberian, European, African, and other foreign populations. The results suggest that Tu population has a multi-origin and has also merged with other local populations.

miR-3937在多发性骨髓瘤中的表达水平及临床诊断中的潜在应用价值

目的分析多发性骨髓瘤(MM)患者血浆中hsa-miR-3937的表达水平及其潜在的临床应用价值。方法利用GEO数据库中公开数据集筛选MM患者血浆中的差异表达基因,并通过实时荧光定量PCR方法对MM患者血浆与健康对照组预测差异miRNAs表达量进行验证。然后利用受试者工作特征曲线(ROC)分析了hsa-miR-3937诊断MM的敏感性和特异性,并通过Spearman法分析了MM患者血浆miR-3937与临床检验指标的相关性,评估其潜在的临床应用价值。结果MM患者血浆中hsa-miR-3937表达量明显高于健康对照组(P<0.01)。hsa-miR-3937的ROC曲线下面积显示hsa-miR-3937基因在诊断MM上具有较高的灵敏度和特异度。同时,通过数据还发现hsa-miR-3937表达量与血清M蛋白、骨髓中浆细胞比例呈正相关。结论实验数据结果表明hsa-miR-3937在MM患者血浆中特异性高表达,作为临床上新的诊断性标志物具有较高的灵敏度和特异度,有望成为临床潜在的新型诊断性分子标志物。

Enzyme‐like mechanism of selective toluene oxidation to benzaldehyde over organophosphoric acid‐bonded nano‐oxides

The completely selective oxidation of toluene to benzaldehyde with dioxygen,without the need touse H_(2)O_(2),halogens,or any radical initiators,is a reaction long desired but never previously successful.Here,we demonstrate the enzyme‐like mechanism of the reaction over hexadecylphosphateacid(HDPA)‐bonded nano‐oxides,which appear to interact with toluene through specific recognition.The active sites of the catalyst are related to the ability of HDPA to change its bonding to theoxides between monodentate and bidentate during the reaction cycle.This greatly enhances themobility of the crystal oxygen or the reactivity of the catalyst,specifically in toluene transformations.The catalytic cycle of the catalyst is similar to that of methane monooxygenase.In thepresence of catalyst and through O_(2)oxidation,the conversion of toluene to benzaldehyde is initiatedat 70°C.We envision that this novel mechanism reveals alternatives for an attractive route to designhigh‐performance catalysts with bioinspired structures.

Nest-type NCM ■ Pt/C with oxygen capture character as advanced electrocatalyst for oxygen reduction reaction

A unique nest-type catalyst has been designed with a nest of oxygen capture surrounding catalytic Pt centers, which shows much promoted performance, on the base of Pt/C catalyst, for oxygen reduction reaction(ORR). The nest is constructed with nitrogen-doped carbon matrix(NCM), derived from the controlled carbonization of PANI precursor, to cover Pt/C catalyst. The unique structure of the catalyst(denoted as NCM■ Pt/C) has many merits. Firstly, it can capture oxygen both in air and in acidic electrolyte. Compared with naked Pt/C, it is found that, in air, the oxygen concentration within the porous nest of NCM surrounding Pt/C particles is ~13 times higher than atmospheric oxygen concentration and, in acidic electrolyte, the concentration of activated oxygen over the catalyst NCM■ Pt/C rise to~1.9 times. Secondly, the NCM nest offers a special electronic modulation on Pt centers toward modified ORR kinetics and then catalytic performances. With these merits, compared with Pt/C, the NCM■ Pt/C catalyst shows 3.2 times higher turnover frequency value and 2.9 times enhanced specific activity for ORR with half-wave potential at 0.894 V. After 50,000 sweeping cycles, the NCM■ Pt/C catalyst retains~66% mass activity and still has advantages over the fresh Pt/C catalyst. We envision that the nest-type catalyst provides a new idea for progress of practical Pt/C ORR catalyst.

Preparation and study of ultrafine flake-aluminum with high reactivity

To achieve aluminum particles with ultrafine granularity and high reactivity,the mechanical ball-milling method was adopted and three kinds of coatings,including stearic acid(SA),viton and dinitrotoluene(DNT),were added.The effects of milling time and different coatings on granularity and reactivity of ultrafine aluminum particles were studied.The structures of prepared ultrafine aluminum were characterized by scanning electron microscopy,X-ray particle diffraction and the thermal properties were analyzed by TG/DSC.Besides,the reactivity of prepared ultrafine aluminum particles was comprehensively analyzed and judged according to several thermodynamic parameters,the maximal oxidation rate,the oxidation degree of aluminum and the enthalpy change.The results revealed that aluminum particles prepared by the mechanical ball milling method were all flake-like and the particle sizes were below5 mm with nanometer-scale thickness.And the crystal form of aluminum was found to be unchanged.Besides,the ultrafine flake aluminum coated with stearic acid after milling for 5 h showed the highest reactivity with 56.1% of oxidation degree before 660℃,0.945 mg/℃ of maximal oxidation rate and 20491 J/g of enthalpy change.

A review:Multi-hierarchy design strategy of electrocatalysts for energy molecule conversion

Under the new energy resource structure,electrocatalysts are key materials for the development of proton membrane fuel cells,electrolysis of aquatic hydrogen devices,and carbon dioxide reduction equipment,to address energy shortages and even environmental pollution issues.Although controlling the morphology or doping with heteroatoms for catalyst active centers have accelerated the reaction rate,it is difficult to solve the problems of multiple by-products,and poor stability of catalytic sites.From this,it will be seen that single regulation of metal active centers is difficult to comprehensively solve application problems.Orderly assembly and coordination of catalyst multi-hierarchy structures at the mesoscale above the nanometer level probably be more reasonable strategies,and numerous studies in thermal catalysis have supported this viewpoint.This article reviews the multi-hierarchy design of electrocatalyst active centers,high-energy supports,and peripheral structures in recent years,providing unconventional inspiration about electrocatalyst creation,which perhaps serves as a simple tutorial of electrocatalysis exploration for abecedarian.

Efficient Dynamic Locomotion of Quadruped Robot via Adaptive Diagonal Gait

Quadruped animals in the nature realize high energy efficiency locomotion by automatically changing their gait at different speeds.Inspired by this character,an efficient adaptive diagonal gait locomotion controller is designed for quadruped robot.A unique gait planning method is proposed in this paper.As the speed of robot varies,the gait cycle time and the proportion of stance and swing phase of each leg are adjusted to form a variety of gaits.The optimal joint torque is calculated by the controller combined with Virtual Model Control(VMC)and Whole-Body Control(WBC)to realize the desired motion.The gait and step frequency of the robot can automatically adapt to the change of speed.Several experiments are done with a quadruped robot made by our laboratory to verify that the gait can change automatically from slow-trotting to flying-trot during the period when speed is from 0 to 4 m/s.The ratio of swing phase is from less than 0.5 to more than 0.5 to realize the running motion with four feet off the ground.Experiments have shown that the controller can indeed consume less energy when robot runs at a wide range of speeds comparing to the basic controller.

Skin-inspired interface modification strategy toward a structurefunction integrated hybrid smart fabric system with self-powered sensing property for versatile applications

Fabric-based composites with superior mechanical properties and excellent perceptive function are highly desirable.However,it remains a huge challenge to attain structure-function integration,especially for hybrid fabric composites.Herein,a skin-inspired interface modification strategy is proposed toward this target by constructing a hybrid smart fabric system consisting of two types of smart fabrics:carbon nanotube(CNT)/MXene-modified aramid fabrics and zinc oxide nanorod(ZnO NR)-modified carbon fabrics.Based on that,flexible piezoelectric pressure sensors with skin-like hierarchical perception interfaces are fabricated,which demonstrate superb sensitivity of 2.39 V·kPa^(-1)and are capable of various wearable monitoring tasks.Besides,the interface-modified hybrid fabric reinforced plastics can also be fabricated,which are proven to possess 13.6%higher tensile strength,10.1%elastic modulus.More impressively,their average energy absorption can be improved by 111.9%,accompanied with inherent damage alert capability.This offers a paradigm to fabricate structure-function integrated hybrid smart fabric composites for the smart clothing and intelligent aerial vehicles.

Predicting influenza-like illness trends based on sentinel surveillance data in China from 2011 to 2019:A modelling and comparative study

Background Influenza is an acute respiratory infectious disease with a significant global disease burden.Additionally,the coronavirus disease 2019 pandemic and its related non-pharmaceutical interventions(NPIs)have introduced uncertainty to the spread of influenza.However,comparative studies on the performance of innovative models and approaches used for influenza prediction are limited.Therefore,this study aimed to predict the trend of influenza-like illness(ILI)in settings with diverse climate characteristics in China based on sentinel surveillance data using three approaches and evaluate and compare their predictive performance.Methods The generalized additive model(GAM),deep learning hybrid model based on Gate Recurrent Unit(GRU),and autoregressive moving average-generalized autoregressive conditional heteroscedasticity(ARMA—GARCH)model were established to predict the trends of ILI 1-,2-,3-,and 4-week-ahead in Beijing,Tianjin,Shanxi,Hubei,Chongqing,Guangdong,Hainan,and the Hong Kong Special Administrative Region in China,based on sentinel surveillance data from 2011 to 2019.Three relevant metrics,namely,Mean Absolute Percentage Error(MAPE),Root Mean Squared Error(RMSE),and R squared,were calculated to evaluate and compare the goodness of fit and robustness of the three models.Results Considering the MAPE,RMSE,and R squared values,the ARMA—GARCH model performed best,while the GRU-based deep learning hybrid model exhibited moderate performance and GAM made predictions with the least accuracy in the eight settings in China.Additionally,the models’predictive performance declined as the weeks ahead increased.Furthermore,blocked cross-validation indicated that all models were robust to changes in data and had low risks of overfitting.Conclusions Our study suggested that the ARMA—GARCH model exhibited the best accuracy in predicting ILI trends in China compared to the GAM and GRU-based deep learning hybrid model.Therefore,in the future,the ARMA—GARCH model may be used to predict ILI trends in public health practice across diverse climatic zones,thereby contributing to influenza control and prevention efforts.

NP-MBO:A newton predictor-based momentum observer for interaction force estimation of legged robots

Swift perception of interaction forces is a crucial skill required for legged robots to ensure safe human-robot interaction and dynamic contact management.Proprioceptive-based interactive force is widely applied due to its outstanding cross-platform versatility.In this paper,we present a novel interactive force observer,which possesses superior dynamic tracking performance.We propose a dynamic cutoff frequency configuration method to replace the conventional fixed cutoff frequency setting in the traditional momentum-based observer(MBO).This method achieves a balance between rapid tracking and noise suppression.Moreover,to mitigate the phase lag introduced by the low-pass filtering,we cascaded a Newton Predictor(NP)after MBO,which features simple computation and adaptability.The precision analysis of this method has been presented.We conducted extensive experiments on the point-foot biped robot BRAVER to validate the performance of the proposed algorithm in both simulation and physical prototype.

A Trot and Flying Trot Control Method for Quadruped Robot Based on Optimal Foot Force Distribution

In order to enhance the dynamic motion capability of the bionic quadruped robot,a flying trot gait control method based on full-scale virtual model and optimal plantar force distribution is proposed.A stable flying trot gait is accomplished by mapping the robot torso motion to the foot trajectory.The force distribution calculated by the torso virtual model is converted into a quadratic optimization problem and solved in real time by the open source library Gurobi.The transition between the trot gait and the flying trot gait is achieved by coordinating leg motion phases.The results of the dynamic simulation verify that the proposed method can realize the 3D stable flying trot gait.Compared against the trot gait,the flying trot gait can improve the speed of the quadruped robot.Combine the trot gait and the flying trot gait,the quadruped robot can move efficiently and adapt to complex terrains.

RELAP5程序预测第一类密度波不稳定边界的能力验证

为估算低温核供热堆的第一类密度波不稳定(Type-ⅠDWO)边界,以确定其微沸腾运行模式的参数区间,本文建立了低温核供热堆NHR200相似性实验回路HRTL200的RELAP5数值模型。通过对比模拟结果与实验结果,评价了RELAP5/MOD3.2程序模拟Type-ⅠDWO的一般特性以及预测不稳定边界的能力,分析了进、出口阻力系数、相间摩擦对模拟结果的影响。结果表明,RELAP5程序模拟Type-ⅠDWO的一般特性与实验符合较好;运行压力不高于25 bar(1 bar=10^(5) Pa)时,程序计算的不稳定边界的过冷度边界值与实验值偏差在3 K以内;运行压力大于30 bar时,采用准确的相间摩擦关系式可以改善预测结果。因此,选取与回路相匹配的相间摩擦关系式后,RELAP5程序可以用于模拟和预测Type-ⅠDWO。

Sequence-length variation of mtDNA HVS-I C-stretch in Chinese ethnic groups

The purpose of this study was to investigate mitochondrial DNA (mtDNA) hypervariable segment-I (HVS-I) C-stretch variations and explore the significance of these variations in forensic and population genetics studies. The C-stretch sequence variation was studied in 919 unrelated individuals from 8 Chinese ethnic groups using both direct and clone sequencing ap-proaches. Thirty eight C-stretch haplotypes were identified, and some novel and population specific haplotypes were also detected. The C-stretch genetic diversity (GD) values were relatively high, and probability (P) values were low. Additionally, C-stretch length heteroplasmy was observed in approximately 9% of individuals studied. There was a significant correlation (r=-0.961, P<0.01) between the expansion of the cytosine sequence length in the C-stretch of HVS-I and a reduction in the number of up-stream adenines. These results indicate that the C-stretch could be a useful genetic maker in forensic identification of Chinese populations. The results from the Fst and dA genetic distance matrix, neighbor-joining tree, and principal component map also suggest that C-stretch could be used as a reliable genetic marker in population genetics.

Connexin 36 Mediates Orofacial Pain Hypersensitivity Through GluK2 and TRPA1

Trigeminal neuralgia is a debilitating condition,and the pain easily spreads to other parts of the face.Here,we established a mouse model of partial transection of the infraorbital nerve(pT-ION)and found that the Connexin 36(Cx36)inhibitor mefloquine caused greater alleviation of pT-ION-induced cold allodynia compared to the reduction of mechanical allodynia.Mefloquine reversed the pT-IONinduced upregulation of Cx36,glutamate receptor ionotropic kainate 2(GluK2),transient receptor potential ankyrin 1(TRPA1),and phosphorylated extracellular signal regulated kinase(p-ERK)in the trigeminal ganglion.Cold allodynia but not mechanic al allodynia induced by pT-ION or by virusmediated overexpression of Cx36 in the trigeminal ganglion was reversed by the GluK2 antagonist NS 102,and knocking down Cx36 expression in Nav1.8-expressing nociceptors by injecting virus into the orofacial skin area of Nav1.8-Cre mice attenuated cold allodynia but not mechanic al allodynia.In conclusion,we show that Cx36 contributes greatly to the development of orofacial pain hypersensitivity through GluK2,TRPA1,and p-ERK signaling.