Ballistic Penetration Damage of Hybrid Thermoplastic Composites Reinforced with Kevlar and UHMWPE Fabrics

Polymer matrix types of fiber hybrid composites are key factors to improve ballistic impact damage tolerances.Here we report ballistic penetration damages of Kevlar/ultra-high molecular weight polyethylene(UHMWPE)hybrid composites with thermoplastic polyurethane(PU)matrix.The hybrid composites were penetrated by fragment-simulating projectiles(FSPs)using an air gun impact system.The effects of stacking sequences on the ballistic performance of hybrid composites were analyzed.Two types of specific energy absorption(the energy absorption per unit area density and the energy absorption per unit thickness)were investigated.It was found that the main damage modes of PU hybrid composites were fiber breakage,matrix damage,fiber pullout and interlayer delamination.The instantaneous deformation could not be used as a reference index for evaluating the ballistic performance of the target plate.The energy absorption process of the PU hybrid composites showed a nonlinear pattern.The hybrid structure affected the specific energy absorption of the materials.

Microstructure and mechanical properties of TC4 titanium alloy K-TIG welded joints

The 12 mm-thick Ti−6Al−4V(TC4)titanium alloy plates were welded using keyhole tungsten inert gas(K-TIG)welding at various heat inputs.The microstructure,grain boundary(GB)characteristics and mechanical properties of the weld metal zone(WMZ)were analyzed.The test results show that the K-TIG welds are well formed,and no obvious defects are observed when the heat input is 2.30−2.62 kJ/mm.When the heat input gradually increases,αlaths increase in length,andα′phase and residualβphase are reduced.The electron backscatter diffraction(EBSD)test results indicate that the high-angle GB proportion in the WMZ increases with the increase of heat input.The tensile strength of the WMZ gradually decreases and the elongation of the WMZ increases when the heat input increases from 2.30 to 2.62 kJ/mm.The impact toughness of the WMZ increases as the heat input increases.

Evaluating instrumented Charpy impact strain signals using curve fitting equations

An effective and simple way to develop equations from impact strain signals was proposed.Little research has been performed in this area,but this equation is very important for evaluating input signals in finite element analysis impact tests and for obtaining additional information on material deformation and fracture processes under impact loading.For this purpose,dynamic impact responses were examined through signals obtained from a strain gauge installed on an impact striker connected to a data acquisition system.Aluminium 6061-T6 was used to extract strain responses on the striker during Charpy impact testing.Statistical analysis was performed using the I-kaz method,and curve fitting equations based on the equation for vibration response under a non-periodic force were used to evaluate the Charpy impact signals.The I-kaz coefficients and curve fitting equations were then compared and discussed with related parameters,such as velocities and thicknesses.Velocity and thickness were found to be related to the strain signal patterns,curve fitting equations and I-kaz coefficients.The equations developed using this method had R2 values greater than 97.7%.Finally,the constructed equations were determined to be suitable for evaluating Charpy impact strain signal patterns and obtaining additional information on fracture processes under impact loading.

Mitigation of blast loadings on structures by an anti-blast plastic water wall

Seven in-situ tests were carried out in far field to study the blast mitigation effect of a kind of water filled plastic wall. Test results show that the mitigation effect of water filled plastic wall is remarkable. The maximum reduction of peak reflected overpressure reaches up to 94.53%, as well as 36.3% of the minimum peak reflected overpressure reduction in the scaled distance ranging from 1.71 m/kg1/3 to 3.42 m/kg1/3. Parametric studies were also carried out. The effects of the scaled gauge height, water/charge scaled distance(the distance between the explosive charge and the water wall), water wall scaled height and water/structure scaled distance(the distance between the water wall and the structure) were systematically investigated and compared with the usual rigid anti-blast wall. It is concluded that these parameters affect the mitigation effects of plastic water wall on blast loadings significantly, which is basically consistent to the trend of usual rigid anti-blast wall. Some formulae are also derived based on the numerical and test results, providing a simple but reliable prediction model to evaluate the peak overpressure of mitigated blast loadings on the structures.

Curing Behaviors and Thermal Properties of Dimer Fatty Acid （DFA） Modified Multifunctional Epoxy Resin

In order to improve the toughness of the cured aromatic tetrafunctional epoxy resins, a dlmer rarboxylic acid named dlmer fatty acid （DFA） was used to modify an aromatic tetrafunctional epoxy, N, N, N＇, N＇-tetraglycidyl-2,2-bis [ 4-（ 4-aminophcuoxy ） phenyl ] propane （TGBAPP）. The curing behaviors of DFA- TGBAPP/MNA （ methyl nadic anhydride） systems were studied by differential scanning calorimetry （DSC） method. And the thermal properties of the cured epoxy resin were investigated with the thermo-gravimetric analysis （TGA） and dynamic mechanical analysis （DMA）. Besides, the toughness was characterized with the impact strength tested by charpy impact testing. The results indicated that the modification would improve the curing reactions, and the curing temperatures were decreased with the increasing content of DFA. The thermal properties were not influenced obviously, and the toughness could be improved when the epoxy resin was modified with DFA.

Performance analysis of UWB radio systems under cassa impulsive noise environment

The performance of UWB (Ultrawide Bandwidth) radio systems under class A impulsive noise environment is studied in this paper. First, while employing the Middleton’s class A model as a model of impulsive noise, the statistical characteristics of in-phase and quadrature components of impulsive noise is investigated. It is proven that, unlike Gaussian noise, they are dependent especially due to the fact that impulsive indices are small. Next, using this above dependence, a novel UWB radio receiver designed for impulsive noise is proposed and the exact expression for the average BER (Bit Error Rate) of this receiver as a function of SNR (Signal to Noise Power Ratio) and threshold value is derived. Then, the optimum threshold value is discussed and the performance of UWB radio systems with the proposed receiver designed for impulsive noise and with the conventional receiver designed for Gaussian noise under impulsive noise environment is estimated. Numerical results are compared and show that the influence of impulsiveness index and threshold value on the performance of UWB radio systems is quite large and that the performance achieved by the proposed UWB radio receiver is much superior to that of the conventional UWB radio receiver under class A impulsive noise environment.

Finite element and experimental analysis for cold tube-bending of a power station boiler

Combining the computer simulation, theoretical analysis and experiments, this paper studies the process of tube-bending production of a power station boiler. The FEM-numerical simulation system was set up to study the performance features in the process of manufacturing cold tube-bending, such as ovality, thinning ratio of wall and the equipment driven force. Experiments were carried out in Harbin boiler factory. The parametric FEM model can simulate the force and quality parameters for tube-bending process and the error is within 5%. Experiments have demonstrated that the results achieved by this system are more useful and economical than those obtained through trial-produce method. It greatly reduces the production cost using computer simulation than conducting lots of experiments.

An Intertextual Study of Ironies From Father-Daughter Conflicts in King Lear and A Thousand Acres

As one of Shakespeare＇s four great tragedies, King Lear stands as a classic masterpiece firmly in world literary history. The Lear story goes through many retellings, among which Jane Smiley＇s A Thousand Acres proves to be a successful one. Though exhibited from different perspectives, the two stories have something in common the ironies arising from father-daughter conflicts. In the way of an intertextual comparison, the paper analyzes the ironies from father-daughter conflicts with an aim of digging out deep meaning from behind in a new angle. It f＇mds out that the ironies shared by the two works help to increase the tragic atmosphere and reveal a lot of truths underneath the lines.

To Improve the Accuracy of Laser Pulse Range Finding by Time Scale-Up

A method of improving the accuracy of laser pulse range finding from ±10 m to ±1 m inexpensively by means of time scale up is described. Time scale up can stretch the entire flight time by a factor of 1 000 and then the stretched result is counted to calculate the distance. The use of this technique decreases the resolution of counting from nanosecond to microsecond, therefore a separate counting oscillator followed by an interpolation operation is unnecessary. This technique can improve the accuracy of laser pulse range finding inexpensively and effectively.

Contrast enhancement of medical ultrasound imaging with reversal phase-inversion pulse technology

A new ultrasound contrast imaging technique was proposed for eliminating the harmonic components from the emission signal transmitted by the broadband ultrasonic system.Reversal phase-inversion pulse was used for the first time to separate the contrast harmonics from the harmonics in the emission signal to improve the detection of contrast micro-bubbles.Based on the nonlinear acoustic theory of finite-amplitude effects and the associated distortion of the propagating wave,the Bessel-Fubini series model was applied to describe the nonlinear propagation effects of the reversal phase-inversion pulse,and the Church's equation for zero-thickness encapsulation model was used to produce the scattering-pulse of the bubble.For harmonic imaging,the experiment was performed using a 64-element linear array,which was simulated by Field II.The results show that the harmonic components from the emission signal can be completely cancelled,and the harmonics generated by the nonlinear propagation of the wave through the tissue,can be reduced by 15-30 dB.Compared with the short pulse,the reversal phase-inversion pulse can improve the contrast and definition of the harmonic image significantly.

Efficient energy absorption of functionally-graded metallic foam-filled tubes under impact loading

The deformation behavior and crashworthiness of functionally-graded foam-filled tubes(FGFTs)under drop-weight impact loading were investigated.Closed cell aluminum,A356 alloy and zinc foams fabricated by the liquid state processing were used as axial grading fillers for the manufacture of single-layer and multilayer structures with different configurations.The results indicate that the deformation of multilayer foam filled tubes initiates from the low-strength components,and then propagates in the high-strength components through the gradual increment of stress.The use of more A356 alloy and aluminum foam layers provides greater specific energy absorption(SEA)for the graded structures,whereas the high-strength zinc foam has no positive effect on the crash performance.The progressive collapse of graded structures consisting of the aluminum and A356 alloy foams occurs in a symmetric mode under quasi-static and drop-weight impact conditions.However,the zinc foam causes a combination of symmetric and extension modes as well as greater localized deformation under dynamic loading and greater local rupture in quasi-static loading condition.The Al−A356 foam-filled tubes with a combination of the highest SEA(10 J/g)and the lowest initial peak stress(σmax of 10.2 MPa)are considered as the best lightweight crashworthy structures.

Effects of Pulse Ultrasound on Adsorption of Geniposide on Resin 1300 in a Fixed Bed

The effects of pulse ultrasound with different pulse parameters on the breakthrough curves of Geniposide on Resin 1300 were studied. The mass transfer model describing the adsorption process was constructed. Adsorption capability and the overall mass-transfer coefficient were obtained by fitting the constructed mass-transfer model and the experimental data. The effects of pulse ultrasound on adsorption of Geniposide on Resin1300 in a fixed bed were studied and compared. Amount of Geniposide adsorbed on Resin 1300 in the presence of ultrasound is lower than that in the absence of ultrasound, but the mass-transfer rate with ultrasonic irradiation is higher than that without ultrasound. Furthermore, mass transfer rate is enhanced by pulse modulation. In the conditions studied, the adsorption equilibrium constant decreases with increasing ultrasonic power, while the overall mass-transfer co-efficient increases. With increasing pulse duty ratio, adsorption equilibrium constant decreases initially, reaches a minimum when pulse duty ratio is 0.5, and then increases. On the contrary, the overall mass-transfer coefficient in-creases initially and reaches a maximum when pulse ratio is 0.5, and then decreases. Effects of pulse period on ad-sorption equilibrium and mass transfer rate reached the peak at pulse period of 28.6 ms.

Strategic Environmental Assessment:A New Tool for Ecological Urbanization of Coastal Cities in China

Recently, there has been growing concerns about environmental issues related to urbanization in China. The intense natural resources utilization and increasing population has brought great pressure, especially in coastal areas, consequently affecting the sustainable development of coastal cities. In 2002, Environmental Impact Assessment Act (EIA Act) was enacted in China. Environmental impact assessment targeted at planning, one level of strategic environmental assessment (SEA), thus became a legislative requirement. This paper considers SEA to be one of the important approaches not only to control coastal pollution, but also to conserve coastal ecosystems and finally to achieve sustainable development during urbanization, thus it will be a set an example for other areas of China. The experience of SEA in Xiamen, a coastal city in southeast China, illustrates the potentials of SEA. This paper first briefly introduces the concept and potentials of SEA, then compares two SEA cases and a project EIA case in Xiamen, and finally identifies the key characteristics of SEA.

Theatrical Hybridity, Thy Name Is Conflict： A Case Study on Holo Taiwan Residents Opera Troupe＇s Tai Tzu Fu Chou （The Prince＇s Vengeful Plan）

Holo Taiwan Residents Opera Troupe has produced a series of intercultural performances in Taiwan Residents Opera since the troupe adapted Nikolai Vasilievich Gogol＇s （1809-1852） The Government Inspector in 1996. In fact, there is a huge controversy over these intercultural performances which fuse western drama with traditional Taiwan Residents performing art because such a kind of theatrical hybridity lacks the spirit of the original and damages the aesthetics of native performing art practice. In 2002, Holo adapted William Shakespeare＇s Hamlet into a six-hour-long performance, Tai Tzu Fu Chou （The Prince＇s Vengeful Plan）, which the troupe tried to explore new source for traditional Taiwan Residents Opera and expected to bring something new to Taiwan Residents audience. However, The Prince＇s Vengeful Plan is considered ＂cultural collage＂ as well as an unsuccessful intercultural performance. Besides, The Prince＇s Vengeful Plan is accused to blaspheme Shakespeare because the performance merely maintains the frame of the original and distorts the spirit of the original. According to Rustom Bharucha, the most problematic aspect of intercultural performance is ＂de-historicizing tendency＂, and such a condition explains why Holo＇s The Prince＇s Vengeful Plan cannot transcend the original. In order to detect the problems of intercultural adaptation in Holo＇s The Prince Vengeful Plan, we cover the related issues in three aspects： （1） to discuss the development of Taiwan Residents Opera in Taiwan; （2） to explore the cultural conflicts when the text of the source culture is adapted into the performance of the target culture; and （3） to see how and why the spirit and aesthetics of Shakespeare＇s verses in Hamlet are distorted in Holo＇s theatrical adaptation. After that, we expect to conclude the impossibility of adapting Shakespeare＇s play into traditional Taiwan Residents Opera in the case of Holo＇s The Prince＇s Vengeful Plan.

The Representation of a Broadband Vector Field

Compared to a scalar pressure sensor, a vector sensor can provide a higher signal-to-noise ratio （SNR） signal and more detailed intbrmation on the sound field. Study on vector sensors and their applications have become a hot topic. Research on the representation of a vector field is highly relevant for extending the scope of vector sensor technology. This paper discusses the range-frequency distribution of the vector field due to a broadband acoustic source moving in a shallow-water waveguide as the self noise of a surface ship, and the vector extension of the waveguide impulse response measured over a limited frequency range using an active source of known waveform. From theory analysis and numerical simulation, the range-frequency representation of a vector field exhibits an interference structure qualitatively similar to that of the corresponding pressure field but, being quantitatively different, provides additional information on the waveguide, especially through the vertical component. For the range-frequency representation, physical quantities that can better exhibit the interference characteristics of the wavegaide are the products of pressure and particle velocity and of the pressure and pressure gradient. An image processing method to effectively detect and isolate the individual striations from an interference structure was reviewed briefly. The representation of the vector impulse response was discussed according to two different measurement systems, also known as particle velocity and pressure gradient. The vector impulse response representation can not only provide additional information from pressure only but even more than that of the range-frequency representation.

Quantum computational advantage via 60-qubit 24-cycle random circuit sampling

To ensure a long-term quantum computational advantage,the quantum hardware should be upgraded to withstand the competition of continuously improved classical algorithms and hardwares.Here,we demonstrate a superconducting quantum computing systems Zuchongzhi 2.1,which has 66 qubits in a two-dimensional array in a tunable coupler architecture.The readout fidelity of Zuchongzhi 2.1 is considerably improved to an average of 97.74%.The more powerful quantum processor enables us to achieve larger-scale random quantum circuit sampling,with a system scale of up to 60 qubits and 24 cycles,and fidelity of FXEB=(3·66±0·345)×10^(-4).The achieved sampling task is about 6 orders of magnitude more difficult than that of Sycamore[Nature 574,505(2019)]in the classic simulation,and 3 orders of magnitude more difficult than the sampling task on Zuchongzhi 2.0[arXiv:2106.14734(2021)].The time consumption of classically simulating random circuit sampling experiment using state-of-the-art classical algorithm and supercomputer is extended to tens of thousands of years(about 4·8×104years),while Zuchongzhi 2.1 only takes about 4.2 h,thereby significantly enhancing the quantum computational advantage.

Aerodynamic performance of the flexibility of corrugated dragonfly wings in flapping flight

At low Reynolds numbers,the variable flexibility of flapping insect wings is considered essential in improving the favorable aerodynamic forces.To further explore whether significant aerodynamic coupling exists between the microstructure and passive flexible deformation,this paper proposes three technical comparison airfoils:a corrugated wing with deformation,a symmetric flat plate wing with deformation,and a corrugated wing without deformation.Based on STAR-CCM+software,this paper numerically solves the Navier-Stokes equations using the fluid-structure interaction method.The results show that the aerodynamic performance of the flexible corrugated wing is better than that of the rigid corrugated wing,and its lift and thrust are both improved to a certain extent,and the thrust efficiency of the flexible corrugated wing is significantly higher than that of the flexible flat plate.Although the thrust is improved,a part of the lift is lost,and as the flapping amplitude increases past 35°,the disparity gradually increases.A comparison of the flexible technical airfoils shows that the corrugated structure promotes thrust and retards lift,which is closely related to the formation and dissipation of strong vortex rings during the downstroke phase.On the premise of maintaining typical flapping without falling,dragonflies can fly with skillful efficiency by adjusting the way they flap their wings.The results of this work provide new insight into the formation and role of thrust in flapping maneuvering flight and provide a specific reference for developing new bionic flapping-wing aircraft.

A DELAYED RATIO-DEPENDENT PREDATOR-PREY SYSTEM WITH STAGE-STRUCTURED AND IMPULSIVE EFFECT

In this paper, a delayed ratio-dependent Holling-III predator-prey system with stagestructured and impulsive stocking on prey and continuous harvesting on predator is considered. The authors obtain sufficient conditions of the global attractivity of predator-extinction periodic solution and the permanence of the system. These＇ results show that the behavior of impulsive stocking on prey plays an important role for the permanence of the system. The authors also prove that all solutions of the system are uniformly ultimately bounded. The results show that the biological resource management is effective and reliable. Key words Globally attractivity, impulsive effect, permanence, ratio-dependent, stage-structured.

Shock relations in gases of heterogeneous thermodynamic properties

Shock relations usually found in literatures are derived theoretically under the assumption of homogeneous thermodynamic properties, i.e., constant ratio of specific heats, γ. However, high temperature effects post a strong shock wave may result in thermodynamic heterogeneities and failure to the original shock relations. In this paper, the shock relations are extended to take account of high-temperature effects. Comparison indicates that the present approach is more feasible than other analytical approaches to reflect the influence of γ heterogeneity on the post-shock parameters.

Design of the pulse duty cycle of the pseudolite signal in local area augmentation systems

The short-pulse TDMA signal is an excellent solution to the near-far problem in the pseudolite augmentation systems,and the pulse duty cycle is an important element in the solution.This paper aims at designing the duty cycle of the pseudolite pulse signals with a theoretical method.At first,the scope of the duty cycle is derived theoretically with the object of ensuring the reception of both the pseudolite signals and the satellite signals,and the expression for the theoretical upper limit is given.Then based on the proposed expression,the duty cycles of Galileo pseudolite pulse signals are designed.The theoretical upper limit can guide the design of the short-pulse TDMA pseudolite signals.