基音检测的一种时域方法

提出基音检测的一种新的时域方法,直接利用波形的形状特征,进行波形之间的匹配估计,从而提取出一帧语音信号的平均基音周期。实验证明该方法运算量小、准确率高,能满足实时处理的需要。     

节矩法测量火炮身管弯曲度的数学模型

用解析的方法建立了节矩法测量火炮身管弯曲度的数学模型,讨论了模型的可解性。并验证了模型的正确性。     

时序电路故障可测性分析

对不可测故障进行测试产生是影响时序电路测试产生效率的一个重要因素。文中提出了一种基于简化可控性计算的识别时序电路中不可测故障的算法,运用该算法无须搜索便可识别出时序电路中相当一部分不可测故障。针对ISCAS89电路的实验结果也验证了其有效性。     

Blast resistance evaluation of urban utility tunnel reinforced with BFRP bars

To improve corrosion-resistance of shallow-buried concrete urban utility tunnels(UUTs),basalt fiber reinforced polymer(BFRP)bars are applied to reinforce UUTs.As the UUT must have excellent survival capability under accidental explosions,a shallow-buried BFRP bars reinforced UUT(BBRU)was designed and constructed.Repetitive blast experiments were carried out on this BBRU.Dynamic responses,damage evolutions and failure styles of the BBRU under repetitive explosions were revealed.The tunnel roof is the most vulnerable component and longitudinal cracks develop along the tunnel.When the scaled distance is larger than 1.10 m/kg1/3,no cracks are observed in the experiments.When the BBRU is severely damaged,there are five cracks forming and developing along the roof.The roof is simplified as a clamped-supported one-way slab,proved by the observation that the maximum strain of the transverse bar is much larger than that of the longitudinal bar.Dynamic responses of the roof slab are predicted by dynamic Euler beam theory,which can consistently predict the roof displacement under large-scaled-distance explosion.Compared with the UUT reinforced with steel bars,the BBRU has advantages in blast resistance with smaller deflections and more evenly-distributed cracks when the scaled distance is smaller than 1.260 m/kg1/3 and the steel bars enter plastic state.Longer elastic defamation of the BFRP bars endows the UUT more excellent blast resistance under small-scaled-distance explosions.     

Experimental investigation on enhanced damage to fuel tanks by reactive projectiles impact

Enhanced damage to the full-filled fuel tank,impacted by the cold pressed and sintered PTFE/AL/W reactive material projectile(RMP)with a density of 7.8 g/cm3,is investigated experimentally and theoretically.The fuel tank is a rectangular structure,welded by six pieces of 2024 aluminum plate with a thickness of 6 mm,and filled with RP-3 aviation kerosene.Experimental results show that the kerosene is ignited by the RMP impact at a velocity above 1062 m/s,and a novel interior ignition phenomenon which is closely related to the rupture effect of the fuel tank is observed.However,the traditional steel projectile with the same mass and dimension requires a velocity up to 1649 m/s to ignite the kerosene.Based on the experimental results,the radial pressure field is considered to be the main reason for the shear failure of weld.For mechanism considerations,the chemical energy released by the RMP enhances the hydrodynamic ram(HRAM)effect and provides additional ignition sources inside the fuel tank,thereby enhancing both rupture and ignition effects.Moreover,to further understand the enhanced ignition effect of RMP,the reactive debris temperature inside the kerosene is analyzed theoretically.The initiated reactive debris with high temperature provides effective interior ignition sources to ignite the kerosene,resulting in the enhanced ignition of the kerosene.     

A novel launch dynamics measurement system for multiple launch rocket system and comparative analysis with numerical simulations

In this paper,a novel launch dynamics measurement system based on the photoelectric sensor pair is built.The actual muzzle time(i.e.a time duration that originates from the initial movement to the rocket's departure from the muzzle)and the muzzle velocity are measured.Compared with the classical methods,the actual muzzle time is obtained by eliminating the ignition delay.The comparative analysis method is proposed with numerical simulations established by the transfer matrix method for multibody systems.The experiment results indicate that the proposed measurement system can effectively measure the actual muzzle time and reduce the error of classical methods,which match well with the simulation results showing the launch dynamics model is reliable and helpful for further analysis and design of the MLRS.     

Rigid elliptical cross-section ogive-nose projectiles penetration into concrete targets

The elliptical cross-section ogive-nose projectile (ECOP) has recently attracted attention because it is well suited to the flattened shape of earth-penetrating weapons. However, the penetration performance of ECOPs has not been completely understood. The objective of this study was to investigate the pene-tration performance of ECOPs into concrete targets using a theoretical method. A general geometric model of ECOPs was introduced, and closed-form penetration equations were derived according to the dynamic cavity-expansion theory. The model was validated by comparing the predicted penetration depths with test data, and the maximum deviation was 15.8％. The increment in the penetration depth of the ECOP was evaluated using the proposed model, and the effect of the major—minor axis ratio on the increment was examined. Additionally, the mechanism of the penetration-depth increment was inves-tigated with respect to the caliber radius head, axial stress, and resistance.     

Interval uncertain optimization for damping fluctuation of asegmented electromagnetic buffer under intensive impact load

Aiming at the problems of demagnetization effect of electromagnetic buffer (EMB) caused by high ve-locity under intensive impact load and the difficulty and error of machining composite thin-walled long tube, a segmented EMB is proposed. The inner tube and air-gap are divided into initial segments and the traversing segments. Through theoretical analysis, impact test and simulation, it can be found that the RRF curve has two peaks. Firstly, in order to reduce the resultant resistance force (RRF) peaks, the sensitivity analysis based on optimal Latin hypercube design (OLHD) and polynomial regression was performed. The results show that the smallest contribution ratio to the dynamic response is the seventh and ninth segments of the inner tube, which are less than 1％. Then, fully considering the uncertain factors, important parameters are selected for uncertain optimization after sensitivity analysis. The in-terval order and interval probability degree methods are used to establish interval uncertain optimiza-tion model of the RRF considering robustness. The model was solved using an interval nested optimization method based on radial basis function (RBF) neural network. Finally, the Pareto front is obtained and numerical simulation is performed to verify the optimal value. It indicates that the two kinds of RRF peak is obviously reduced, and the optimization object and strategy are effective.     

Opening behavior of PELE perforation on reinforced concrete target

Impact velocity (v0), target strength (fc) and target thickness (hc) are important factors affecting opening damage ((D)) of PELE penetration into RC target. In this paper, based on the three influence factors of v0, fc and hc, experimental and numerical simulation studies on PELE penetration into RC target were carried out. The study results show that: (1) Since interaction force (or penetration resistance) between pro-jectile and target is positively correlated with v0 and fc, with the increase of v0 and fc, deformation mode of jacket is changed from small bending deformation to large bending deformation and then to curling deformation. Therefore, the variation of jacket deformation mode causes opening diameter of RC target to increase first and then to decrease. It is found that the two factors approximately satisfy a quadratic function relationship, respectively. (2) For PELE projectile penetrating RC targets with thickness of 80—400 mm, the opening diameter of six sets of RC targets grows from 240 to 500 mm, and hc with (D) approximately satisfy a linear relationship. (3) Based on the above study results, the relationship be-tween two dimensionless parameters (I= (mv20/d31fc) and H= hc/l ) and dimensionless opening diameter ((D)/d1) was determined. Combined with the results of previous research, a dimensionless opening diameter model (D)/d1=f1(Q,G,I)f2(H) was established. By tests verified, the test results are all within ±10％error of the theoretical model, which verifies the accuracy of the model.     

Effect of the end cap on the fragment velocity distribution of a cylindrical cased charge

The prediction of the fragment velocity distribution of a cylindrical cased charge with end caps is one of the key issues to assess the damage efficiency of the warhead. However, limited work has been con-ducted to predict the fragment velocity distributions along the axis of cylindrical cased charges with end caps. This paper presents a study of the velocity distribution of fragments caused by the explosion of a cylindrical cased charge with end caps. The fragment velocity distribution and the end cap velocity were determined by an X-ray radiography method, and the axial fragment distribution was determined by witness plates. It was found that the velocities of fragments, especially near the edge, were increased when the end caps were added, and the position of maximum velocity is closer to the non-detonation end. The fragment velocities were increased, and the fragment projection range was decreased with the increase of the thickness of the end cap. A formula for fragment velocity distributions of a cylindrical cased charge with end caps, which is based on Huang's formula, was proposed by the theoretical analysis and data fitting and validated experimentally. The results indicate that the proposed formula is accurate in predicting the fragment velocity distribution along the axis of a cylindrical cased charge with end caps detonated at one end.