压实发射药用发火系统

[课题] 提供对假比重高的压实发射药也可取得稳定的发火及火焰传播性的发火系统。[构成] 使压实发射药发火或传播时的发火压力为50kgf/cm^2以上时的压实发射药用发火系统。

某产品发射率控制分析

分析影响某产品发射率的机构原理,结合射击试验数据总结发射率的调整方法。

Prediction and critical transition mechanism for granite fracture:Insights from critical slowing down theory

Rock fracture warning is one of the significant challenges in rock mechanics.Many true triaxial and synchronous acoustic emission(AE)tests were conducted on granite samples.The investigation focused on the characteristics of AE signals preceding granite fracture,based on the critical slowing down(CSD)theory.The granite undergoes a transition from the stable phase to the fracture phase and exhibits a clear CSD phenomenon,characterized by a pronounced increase in variance and autocorrelation coefficient.The variance mutation points were found to be more identifiable and suitable as the primary criterion for predicting precursor information related to granite fracture,compared to the autocorrelation coefficient.It is noteworthy to emphasize that the CSD factor holds greater potential in elucidating the underlying mechanisms responsible for the critical transition of granite fracture,in comparison to the AE timing parameters.Furthermore,a novel multi-parameter collaborative prediction method for rock fracture was developed by comprehensively analyzing predictive information,including abnormal variation modes and the CSD factor of AE characteristic parameters.This method enhances the understanding and prediction of rock fracture-related geohazards.

Fracture evolution around pre-existing cylindrical cavities in brittle rocks under uniaxial compression

The development of fracture around pre-existing cylindrical cavities in brittle rocks was examined using physical models and acoustic emission technique. The experimental results indicate that when granite blocks containing one pre-existing cylindrical cavity are loaded in uniaxial compression condition, the profiles of cracks around the cavity can be characterized by tensile cracking （splitting parallel to the axial compression direction） at the roof-floor, compressive crack at two side walls, and remote or secondary cracks at the perimeter of the cavity. Moreover, fracture around cavity is size-dependent. In granite blocks containing pre-existing half-length cylindrical cavities, compressive stress concentration is found to initiate at the two sidewalls and induce shear crack propagation and coalescence. In granite blocks containing multiple parallel cylindrical cavities, the adjacent cylindrical cavities can influence each other and the eventual failure mode is determined by the interaction of tensile, compressive and shear stresses. Experimental results show that both tensile and compressive stresses play an important role in fracture evolution process around cavities in brittle rocks.

Simulation of a Silicon LED in Standard CMOS Technology

A reverse bias silicon p-n junction based on light emitting diode is designed in standard 0.6μm industrial CMOS technology.The mechanism of the light emitting of this device is discussed.The device is simulated by the commercial software.I-V characteristic under forward or reverse bias is simulated utilizing the commercial software.The results between simulation and experiment data are compared.The results show that it is a promising device and may find applications in light linking.

钹式换能器制作工艺与实验研究

设计方法与制作工艺是开发低频钹式换能器的核心技术。首先在继承传统压电材料制作工艺的基础上,根据钹式换能器的设计规律,研制了含有低频换能器在内的多套金属帽冲压模具,比较了粘结剂、金属材料等的不同特点,给出了合成钹式阵元的一般性方法,掌握了制作钹式阵元的特殊工艺,由此可开发系列阵元;然后,针对其中的低频阵元,在消声水池实验中分别对阵元的共振频率、发射幅压响应、自由场接收灵敏度等进行了测试。实验结果表明,低频钹式阵元具有较好的接收效果,单个5 kHz钹式阵元在0~40 kHz工作时,其自由场接收灵敏度在-170^-150 dB之间,其发射幅压值135 dB,可通过成阵提高发射指标。研究结果为开发新型钹式声学装置提供了依据。

Alloy Temperature Dependence of Offset Voltage and Ohmic Contact Resistance in Thin Base InGaP/GaAs HBTs

The alloy temperature dependence of Voffset and Rcontact is studied, and an optimal alloy temperature range for the best trade-off between Voffset and Rcontact, is given for thin base HBTs. In addition,the reason for the high Voffset at high alloy temperature is interpreted using Schottky clamped theory. The lower Voffset of our U-shaped emitter HBT than that of traditional strip emitter HBTs is explained.

电路设计中共射电路的应用方法

三极管共发射极放大电路有两种结构,其中分压式共发射极放大电路主要用于信号的放大,而串联式共发射极放大电路主要用于信号的传输与控制。

Stress-strain-acoustic responses in failure process of coal rock with different height to diameter ratios under uniaxial compression

Residual coal pillars play an important role in mining the adjacent coal seam safely,managing the gobs and maintaining the stability of abandoned coal mines.The height to diameter ratio(H/D)affects the stability of residual coal pillars.In this study,uniaxial compressive tests of coal specimens with five H/D(2.0,1.5,1.0,0.8 and 0.6)were performed,and the stress,strain and acoustic emission(AE)were monitored.Results show that the uniaxial compressive strength(UCS)and peak strain increase with H/D decreasing.An empirical equation is proposed to calculate the UCS based on the H/D.The AE activities during coal failure process can be separated into four periods.The span of quiet period and rapid decline period shorten with H/D decreasing.The smaller the H/D is,the more complicated the failure characteristics of coal will be.The failure form of coal with H/D of 2.0,1.5,and 1.0 is primarily shear failure,while splitting failure along the axial direction is the mainly mode when H/D is 0.8 or 0.6.The initiation,expansion,aggregation and connection of micro-cracks can be reflected by the real-time spatial evolution of AE event points.

True triaxial hydraulic fracturing test and numerical simulation of limestone

Hydraulic fracturing,as a key technology of deep energy exploitation,accelerates the rapid development of the modern petroleum industry.To study the mechanisms of hydraulic fracture propagation and rock failure mode of the vertical well hydraulic fracturing,the true triaxial hydraulic fracturing test and numerical simulation are carried out,and the influence of the principal stress difference,water injection displacement,perforation angle and natural fracture on fracture propagation is analyzed.The results show that the fracture propagation mode of limestone is mainly divided into two types:the single vertical fracture and the transverse-longitudinal crossed complex fracture.Under high displacement,the fracturing pressure is larger,and the secondary fracture is more likely to occur,while variable displacement loading is more likely to induce fracture network.Meanwhile,the amplitude of acoustic emission(AE)waveform of limestone during fracturing is between 0.01 and 0.02 mV,and the main frequency is maintained in the range of 230−300 kHz.When perforation angleθ=45°,it is easy to produce the T-type fracture that connects with the natural fracture,while X-type cracks are generated whenθ=30°.The results can be used as a reference for further study on the mechanism of limestone hydraulic fracturing.

Acoustic emission characteristics of rock under impact loading

Acoustic emission tests were performed using a split Hopkinson pressure bar system(SHPB) on 50-mm-diameter bars of granite, limestone, sandstone and skarn. The results show that the amplitude distribution of hits is not well centralized around 50 d B, and that some hits with large amplitudes, usually larger than 70 d B, occur in the early stages of each test, which is different from the findings from static and low-loading-rate tests. Furthermore, the dominant frequency range of the recorded acoustic emission waveforms is between 300 k Hz and 500 k Hz, and frequency components higher than 500 k Hz are not significant. The hit with the largest values of amplitude, counts, signal strength, and absolute energy in each test, displays a waveform with similar frequency characteristics and greater correlation with the waveform obtained from the elastic input bar of the split Hopkinson pressure bar system compared with the waveforms of the other hits. This indicates that the hit with the largest values of amplitude, counts, signal strength, and absolute energy is generated by elastic wave propagation instead of fracture within the rock specimen.

Discrete element analysis on press and fracture mechanism of propellant grain

To analyze fracture mechanism of propellant grain and study the mechanical properties of propellant grain, the press and fracture processes of propellant grain with and without initial defects are modeled using the discrete element method. On the basis of the appropriate constitutive relationships, the discrete element model of the propellant grain was established. Compared with experimental measurements, the micro-parameters of the bonded-particle model of the propellant grain under unconfined uniaxial compression tests were calibrated. The propellant grains without initial defects, with initial surface defects, and with initial internal defects were studied numerically through a series of unconfined uniaxial compression tests. Results show that the established discrete element model is an efficient tool to study the press and fracture processes of the propellant grain. The fracture process of the propellant grain without initial defects can be divided into the elastic deformation phase, crack initiation phase, crack stable propagation phase, and crack unstable propagation phase. The fracture mechanism of this grain is the global shear failure along the direction of the maximum shear stress. Initial defects have significant effects on both the fracture mechanism and peak strength of the propellant grain. The major fracture mechanism of the propellant grain with initial surface defects is local shear failure, whereas that of the propellant grain with initial internal defects is global tensile failure. Both defects weaken the peak strengths of the propellant grain. Therefore, the carrying and filling process of the propellant grain needs to minimize initial defects as far as possible.

Progressive fracture processes around tunnel triggered by blast disturbances under biaxial compression with different lateral pressure coefficients

To investigate the progressive fracture processes around a tunnel triggered by static stress and dynamic disturbance,experiments and numerical simulations were performed.The results show that the spatial distributions of acoustic emission(AE)events become very different as lateral pressure coefficients change.The combined effect of static stress and dynamic disturbance causes the damage around the tunnel,and initial stress conditions control the damage morphology.The blast disturbance cannot fundamentally change the damaged area but will deepen the extent of damage and accelerate the failure speed.The more significant the difference between the vertical and horizontal stresses is,the higher the impact on the tunnel by the dynamic disturbance is.The AE activity recovers to a relatively stable state within a short time after the blast and conforms to power-law characteristics.

Innovation and Outlook of the New Generation of Cryogenic and Quick-Launch Launch Vehicle

This paper introduces a launch vehicle scheme for the new generation of cryogenic and quick-launch launch vehicle(LM-6). The main technical innovations of LM-6 launch vehicle include the capability of twenty satellites launched by one vehicle, high-pressure staged combustion cycle engine and oxygen tank self-pressurization, sandwich bulkhead tank with 200 K temperature difference, and 7-day quick-launch using the "three horizontals" test and launch mode with integral transportation and erection. The future development of the quick-launch launch vehicle is predicted based upon the need for vehicle mission coverage improvement, better response speed, and stronger market competiveness.

Research on propagation law of AE wave in coal seam

Based on mechanism of AE creation, put forward sphere cavity model, and deduced wave Equation of AE wave radiated by the AE source in detail, and analyzed the propagation attenuation law of AE stress wave in coal （rock） strata. Displacement function of AE wave indicates that displacement field can be divided into two parts. Firstly, displacement of particle is approaching to the source intensity function in zone near the AE source. Secondly, in zone far away from the AE source, displacement of particle is approaching to the derivative of source intensity function. AE wave changes gradually in the spreading process, and notable change of the wave form happens when wave propagates far away from the AE source.

Research on CMOS Mm-Wave Circuits and Systems for Wireless Communications

This paper lenges in the design of discusses some chal- millimeter-wave （mln- wave） circuits and systems for 5th generation （5G） wireless systems in CMOS process. The properties of some passive and active devices such as inductors, capacitors, transmission lines, translbrmers and transistors in mm-wave frequency band are discussed. Self-healing technique dealing with PVT variation, res- onant mode switching technique to enhance frequency tuning range of voltage controlled oscillator （VCO） and dual mode technique for power amplifier （PA） efficiency enhancement are introduced. At last, A fully-integrated 60 GHz 5 Gb/s QPSK transceiver with the transmit/receive （T/R） switch in 65nm CMOS process is introduced. The measured error vector magnitude （EVM） of the TX is -21.9 dB while the bit error rate （BER） of the RX with a -52 dBm sine-wave input is below 8e-7 when transmitting/receiving 5 Gb/s data. The transceiver is powered by 1.0 V and 1.2 V supply （except the phase-frequency detector and charge-pump in the frequency synthesizer which are powered by 2.5 V supply） and con- sumes 135 mW in TX mode and 176 mW in RX mode.

Damage characteristics of thermally treated granite under uniaxial compression: Insights from active and passive ultrasonic techniques

To explore the effects of thermal treatment on cracking processes in granite, granite samples were thermally treated at 25-400 ℃ and then loaded under uniaxial compression. Active ultrasonic testing and passive acoustic emission(AE) monitoring were combined to monitor the damage characteristics of the samples. The uniaxial compression strength(UCS) of the sample treated at 200 ℃ shows no apparent change compared with that of the nonheated sample, while the UCS increases at 300 °C and decreases at 400 ℃. As the temperature increases from 25 to 400 ℃, the initial P-wave velocity(Vp) decreases gradually from 4909 to 3823 m/s, and the initial Vpanisotropy ε increases slightly from 0.03 to 0.09. As the axial stress increases, ε increases rapidly in the crack closure stage and unstable cracking stage. The attenuation of ultrasonic amplitude spectra also shows an obvious anisotropy. Besides, the main location magnitude of AE events decreases after thermal treatment, and low-frequency AE events and high-amplitude AE events increasingly occur. However, there is insufficient evidence that the treatment temperature below 400 ℃ has a significant effect on the temporal characteristics, source locations, and b-values of AE.

Experimental and numerical simulation of loading rate effects on failure and strain energy characteristics of coal-rock composite samples

The deformation and failure of coal and rock is energy-driving results according to thermodynamics.It is important to study the strain energy characteristics of coal-rock composite samples to better understand the deformation and failure mechanism of of coal-rock composite structures.In this research,laboratory tests and numerical simulation of uniaxial compressions of coal-rock composite samples were carried out with five different loading rates.The test results show that strength,deformation,acoustic emission(AE)and energy evolution of coal-rock composite sample all have obvious loading rate effects.The uniaxial compressive strength and elastic modulus increase with the increase of loading rate.And with the increase of loading rate,the AE energy at the peak strength of coal-rock composites increases first,then decreases,and then increases.With the increase of loading rate,the AE cumulative count first decreases and then increases.And the total absorption energy and dissipation energy of coal-rock composite samples show non-linear increasing trends,while release elastic strain energy increases first and then decreases.The laboratory experiments conducted on coal-rock composite samples were simulated numerically using the particle flow code(PFC).With careful selection of suitable material constitutive models for coal and rock,and accurate estimation and calibration of mechanical parameters of coal-rock composite sample,it was possible to obtain a good agreement between the laboratory experimental and numerical results.This research can provide references for understanding failure of underground coalrock composite structure by using energy related measuring methods.

Experimental investigation on mechanical behaviors of granites after high-temperature exposure

To investigate the influence of temperature on the physical,mechanical and acoustic emission characteristics of granites,uniaxial compression test,variable-angle shear test,acoustic emission signal monitoring and the measurement of physical parameters including mass,size and P-wave velocity were carried out on granite samples treated at temperatures T ranging from 25 to 900℃.The results show that the density and P-wave velocity decrease gradually with increasing T.As the temperature increases,the peak compressive stress decreases while the peak strain increases,due to the fact that a high temperature induces the escaping of waters within granites,the expanding of mineral grains and the generations of fractures.With the increment of T,both the peak shear stress and the cohesion decrease,whereas the frictional angle increases.During the compressing and shearing tests,the maximum acoustic emission counts show a decreasing trend when T increases from 25 to 900℃.When T exceeds 573℃,the crystal lattice structure of quartz changes fromα-phase toβ-phase,decreasing the mechanical behavior of granites to a great extent.In addition,the results also indicate that T=500−600℃ is the critical temperature ramge to characterize the influence of temperature on the physical,mechanical and acoustic emission characteristics of granites.

Model experiment on anti-deformation performance of a self-supporting transmission tower in a subsidence area

A large number of high-voltage power transmission towers have recently been constructed in mining areas prone to subsidence. In order to ensure the safety of the transmission towers and the safe operation of transmission systems, it is imperative to carry out research on the anti-deformation performance of transmission towers. In our study, we performed experiments on the anti-deformation performance of a transmission tower in a subsidence area on a scale model with a geometric scale ratio of 1:5 and analyzed the failure mechanism of the tower members. The results show that, when the axial distance between two supports changes, destabilization failure most likely occurs in the members of the bottom transverse layer because some parts of the main diagonal member bars yield under the action of compression. The failure mechanism of the tower members basically coincides with the lever principle.