Using Crumb Rubber to Improve the Properties of Concrete from the Sustainability Point of View

In the past decade,the economy of China has been increasing at a remarkable speed,which causes the rapid increase of automobile industry.Researches in past years demonstrated that the incorporation of crumb rubber into concrete reduces the mechanical strength of concrete.However,properties such as plastic shrinkage cracking resistance,dry shrinkage cracking resistance,frost resistance,impact resistance,fatigue resistance etc.are improved due to the deformable feature of crumb rubber.Therefore,it is expected that using crumb rubber in concrete not only improves the properties of the material,but also reduces the environmental pressure of handling waste tires.

Experimental Investigation and Optimization Design of Multi-Support Pipeline System

The design of aircraft hydraulic pipeline system is limited by many factors,such as the integrity of aviation structure or narrow installation space,so the limited clamp support position should be considered.This paper studied the frequency adjustment and dynamic responses reduction of the multi-support pipeline system through experiment and numerical simulation.To avoid the resonance of pipeline system,we proposed two different optimization programs,one was to avoid aero-engine working range,and another was to avoid aircraft hydraulic pump pulsation range.An optimization method was introduced in this paper to obtain the optimal clamp position.The experiments were introduced to validate the optimization results,and the theoretical optimization results can agree well with the test.With regard to avoiding the aero-engine vibration frequency,the test results revealed that the first natural frequency was far from the aero-engine vibration frequency.And the dynamic frequency sweep results showed that no resonance occurred on the pipeline in the engine vibration frequency range after optimization.Additionally,with regard to avoiding the pump vibration frequency,the test results revealed that natural frequencies have been adjusted and far from the pump vibration frequency.And the dynamic frequency sweep results showed that pipeline under optimal clamp position cannot lead to resonance.The sensitivity analysis results revealed the changing relationships between different clamp position and natural frequency.This study can provide helpful guidance on the analysis and design of practical aircraft pipeline.

Shell powder as a novel bio-filler for thermal insulation coatings

The feasibility of employing shell powder as a novel bio-filler to prepare fluorocarbon coating is demonstrated.According to the relevant Chinese standards, the thermal and mechanical properties of the shell powder-filled fluorocarbon coating were evaluated, and compared with those filled by commercial calcium carbonate. All the shell powder-filled coatings can meet the requirements stated in the relevant standards, and with decreasing the particle size of the shell powders, the performance of the thermal insulation coating is enhanced. The coating(SC3) filled by shell powders with an average particle size of 2.81 μm possesses a better thermal insulation performance than the coating(CC) filled by commercial calcium carbonate. The coating SC3 has comparable adhesive force and washing resistance with the coating CC, and in the washing resistance test, after 2000 cycles, the coating SC3 was still able to cover totally their substrates. This work demonstrates a high value-added disposal method for the aquacultural wastes.

Optical pulse repetition rate division using an optoelectronic oscillator

An approach for frequency division of an optical pulse train(OPT) based on an optoelectronic oscillator(OEO) is proposed and experimentally demonstrated. When the OPT is injected into the OEO, a microwave signal with a frequency equaling fractional multiples of the repetition rate of the OPT is generated. This signal is then fed back to the OEO, maintaining its oscillation, while simultaneously serving as the control signal of a Mach–Zehnder modulator(MZM) in the OEO. The MZM acts as an optical switch, permitting specific pulses to pass through while blocking others. As a result, the repetition rate of the OPT is manipulated. A proof-of-concept experiment is carried out. Frequency division factors of 2 and 3 are successfully achieved. The phase noises of the OPT before and after the frequency division are investigated. Compared to previously reported systems, no external microwave source and sophisticated synchronization structure are needed.

Preparation and arc erosion properties of Ag/Ti_2SnC composites under electric arc discharging

New Ag/Ti_2 SnC(Ag/TSC) composites with uniform microstructure were prepared by powder metallurgy. The superior wettability between Ag and Ti_2 SnC was confirmed with a contact angle of 14°. Arc erosion properties of Ag/10 wt%Ti_2 SnC(Ag/10 TSC) and Ag/20 wt%Ti_2 SnC(Ag/20 TSC) contacts were investigated under 400 V/100 A/AC-3 and compared with Ag/CdO contact.The Ag/10 TSC contact exhibited comparable arc erosion property to Ag/CdO contact. The fine arc erosion resistance was attributed to the good wettability between Ti_2 SnC and Ag,the good heat-conducting property of Ag/10 TSC, and the slight decomposition of Ti_2 SnC that absorbed part of electric arc energy. The excessive Ti_2 SnC significantly decreased the thermal conducting property of the Ag/20 TSC composite, resulting in the severe heat accumulation that decomposed Ti_2 SnC and deteriorated arc erosion property. The oxidation behavior of Ti_2 SnC under high electric arc temperature was also studied and then an arc erosion mechanism was proposed to get a comprehensive understanding on the arc erosion property of Ag/TSC composites.

Slip casting and pressureless sintering of Ti3AlC2

Slip casting and subsequent pressureless sintering(PLS)allow the preparation of complex-shaped and large-sized Ti3AlC2 components for many potential applications.The behaviors of the suspensions,green compacts,and sintered samples of Ti3AlC2 were studied in this paper.The optimized condition of 1 wt%of arabic gum as dispersant at pH=10 results in a Ti3AlC2 suspension for slip casting Ti3AlC2 green compacts without macro defects or cracks.The sintering temperature and Al4C3 embedding powder are found to dominate the properties of the sintered Ti3AlC2 samples.The Ti3AlC2 sample sintered at 1450℃for 1.5 h with Al4C3 embedding powder reaches the best properties,namely 95.3%relative density,hardness of 4.18 GPa,thermal conductivity of 29.11W·m-1·K-1,and electrical resistivity of 0.39μΩ·m.The findings in this work may pave the way for the application of MAX phases with large size and complex shape.

Modulation format identification in fiber communications using single dynamical node-based photonic reservoir computing

We present a simple approach based on photonic reservoir computing(P-RC)for modulation format identification(MFI)in optical fiber communications.Here an optically injected semiconductor laser with self-delay feedback is trained with the representative features from the asynchronous amplitude histograms of modulation signals.Numerical simulations are conducted for three widely used modulation formats(on–off keying,differential phase-shift keying,and quadrature amplitude modulation)for various transmission situations where the optical signal-to-noise ratio varies from 12 to 26 d B,the chromatic dispersion varies from-500 to 500 ps/nm,and the differential group delay varies from 0 to 20 ps.Under these situations,final simulation results demonstrate that this technique can efficiently identify all those modulation formats with an accuracy of>95%after optimizing the control parameters of the P-RC layer such as the injection strength,feedback strength,bias current,and frequency detuning.The proposed technique utilizes very simple devices and thus offers a resource-efficient alternative approach to MFI.

Optical single sideband polarization modulation for radio-over-fiber system and microwave photonic signal processing

An approach to implementing optical single sideband(OSSB)polarization modulation,which is a combination of two orthogonally polarized OSSB modulations with complementary phase differences between the optical carrier and the sideband,is demonstrated based on two cascaded polarization modulators(PolMs).The two PolMs are driven by two RF signals that are 90°out of phase.By properly adjusting the polarization state between the two PolMs,OSSB polarization modulation with large operation bandwidth can be realized.An experiment is performed.OSSB polarization modulation with an operation bandwidth from 2 to 35 GHz is successfully demonstrated.The spectral profile of the OSSB polarization-modulated signal is observed through an optical spectrum analyzer,and its complementary phase properties are analyzed by sending the signal to a photodetector(PD)for square-law detection.Due to the complementary phase differences between the optical carrier and the sideband along the two polarization directions,no microwave frequency component is generated after the PD.The generated OSSB polarization-modulated signal is transmitted through 25 and 50 km single-mode fiber with 50 Mbaud 16 quadrature amplitude modulation baseband data to investigate the transmission performance of the proposed system in radio-over-fiber applications,and very small error vector magnitude degradation is observed.OSSB polarization modulation is also employed to realize a microwave photonic phase shifter.A full-range tunable phase shift is obtained for 2 and 35 GHz microwave signals.

Confining effect of oxide film on tin whisker growth

Spontaneous tin whisker growth has been mysterious and catastrophic for more than half century. The difficulty in the research on this topic consists of the randomness of the whisker growth, the slow growth rate and many other tricky factors. Herein, with Ti2SnC-Sn as a new platform, fast tin whisker growth is realized to facilitate the research. The whisker morphology is found to be modulated by oxide film. A striated whisker morphology forms as growing in air, whereas a faceted morphology forms in vacuum.Furthermore, the evolution to the faceted morphology is attributed to the reconstruction of the whisker surface driven by surface energy reduction. The findings might open a new avenue to uncover the myths of this long-standing issue, and thus develop a long-awaited lead-free tin whisker mitigation strategy.

Spontaneous Growth of Metal Whiskers on Surfaces of Solids:A Review

Spontaneous metal whisker growth phenomenon has been studied for -70 years, but still resists in- terpretations, which has haunted the electronics-rich systems from the birth of the industry since whiskers may lead to short circuits and hence other disasters. In addition to reliability problems, threat of Pb whiskers to human health is also significant due to the toxicity of the element and its geometry as well as its nanometer size. This issue becomes more attention drawing and urgent due to the restrictions on Pb use in ELI, Japan etc., which phases out the Pb-addition practice to mitigate Sn whiskers. This paper reviews the origin of the whiskering phenomenon and whisker-induced problems, ranging from early in the World War II to the present; details the development of this issue in the electronics-rich systems including the phenomenon, problems and remedies; pictures the long history of the developments of the growth mechanisms and models which are full of hardship and contradictions. New aspects on the spontaneous whisker growth in some different substrates, such as in brasses and MAX phase materials are reviewed in more details. The latter was found to be a promising system to understand the whisker growth phenomenon, with new growth models proposed that may shed new light to the intricate battle field of the metal whisker research in general.