Influence of Plasma Modified Carbon Nanotubes on the Resistance Sensitiveness of Cement

The surface of carbon nanotubes(CNTs)was modified by plasma to improve the dispersion,conductivity and adsorption properties of carbon nanotubes.Cement-based composites made with plasmatreated carbon nanotubes(P-CNTs)at different perntages were tested under repeated cyclic axial compressive stress by four electrode methods to measure the electric resistance.Those made with CNTs without plasma treatment as controls were tested also.The results showed that electric resistance change values of the cement mortar with P-CNT and CNT were all monatomic corresponding to the cyclic loading.When the water-cement ratio of the mortar was fixed,increasing of the P-CNT/CNT content would increase the resistance change value of the mortars added with P-CNT/CNT,and the sensitivity performance.It has certain engineering application value.

Relationship between changes of endogenous ABA level and resistance in hybrid rice under temperature stress

We studied the relationship between endogenous ABA and resistance to temperature stress in seedlings of hybrid rice. The hybrid rice Combinations Shanyou 63, Shanyou 287, Weiyou 63, and Weiyou 287 were treated under 2℃ and 42℃ respectively for 48 h. Endogenous ABA concentrations were obtained by gas chromatography with electron capture detector (GC-ECD) and a nickel labelled external standard. Leakage of electrolytes were determined. At optimal temperature (27℃), there was difference between the level of endogenous ABA and the leakage of electrolytes in hybrid rice combinations, which attributed to genetic difference. ABA level in Weiyou system was higher than that in Shanyou, and there were distinctions between Shanyou system itself (see table). At 2℃, the ABA content of rice seedling was increased. ABA level of Weiyou system maintained higher than Shanyou system at 27℃. The leakage quantities of

Protein changes in rice seedlings during the enhancement of chilling resistance by different stress pretreatment

The changes of proteins in the rice (Oryzasativa L.) Tesanai 2 seedling under salt (NaCl,4 g/L), heat shock (42℃, 3h ), and cold(14℃, 3d ) pretreatments were compared toexplore the mechanism of the cross adaptationto different environmental stresses. The chill-ing resistance of rice seedling after 1℃, 150pmol·msPFD(photo flux density) for 2d was enhanced distinctly by salt, heat shock,

Experimental study on shear properties and resistivity change of soil-rock mixture

The deterioration of shear resistance in rock and soil masses has resulted in numerous severe natural disasters,highlighting the significance of long-term monitoring for disaster prevention and mitigation.This study explores the use of a non-destructive method to quickly and accurately evaluate the shear properties of soil-rock mixture.The shear stress,shear strain,and resistivity of the soil-rock mixture were tested simultaneously using a combination of direct shear and resistivity tests.The test results show that the resistivity of the soil-rock mixture gradually decreases with increasing shear strain.The resistivity of all specimens ranged approximately from 60 to 130Ω.m throughout the shear process.At the end of the shear test,the vertical failure resistivity showed an irregular“W”shape with increasing rock content.It exhibited a significant negative linear functional relationship with the shear strength.With reference to the determination of cohesion and internal friction angle on the shear strength envelope,the horizontal angle of the vertical failure resistivity-normal stress curve is defined as the resistivity angle,and the intercept of the curve is the resistivity at the initial moment of shear.It has been observed that the resistivity angle is negatively and linearly correlated with the internal friction angle.At the same time,there is a linear growth relationship between resistivity at the initial moment of shear and cohesion.It has been demonstrated that an increase in rock content contributes to a general escalation in both the average structure factor and average shape factor.Meanwhile,a decrease in the anisotropy coefficient has also been noted.These alterations are indicative of the extent of microstructural transformations occurring during the deformation process of the soil-rock mixture.The research results verify the feasibility of real-time deformation monitoring and characterization of shear strength parameters using resistivity.

Effect of Raw Bauxite Addition on Thermal Behaviour of Ultra-low Cement Al_2O_3-SiO_2 Castables

This work investigated the thermo-gravimetric （TG） change and explosion resistance of ultra-low cement Al2O3 - SiO2 castables added with 0, 5%, 10%, 15% and 20% of 474 μm raw bauxite powders containing 72.8% Al2O3, respectively. The castables were prepared using white fused alumina as aggregate, powders of white fused alumina, fused mullite,α-Al2O3 ultrafines, 3% CA cement and 5% microsilica as the matrix portion. TG change of the castables was investigated by a thermo-gravimetric analyzer for large size specimen. When the raw bauxite addition is less than 10%, the mass-losing behavior of the castables is similar to that without raw bauxite, tending to reach a constant mass around 400 ℃ , before which the mass-loss is mild and producing little destructive influence. With more than 10% raw bauxite addition, however, the mass-loss increases significantly, and the temperature to reach a constant mass increases to 600 ℃ or higher, unfavorable to structural stabilization. With the raw bauxite addition up to 20% , no negative influence on explosion resistance is found.

Piezoresistive Sensors Based on Carbon Nanotube Films

Piezoresistive effect of carbon nanotube films was investigated by athree-point bending test. Carbon nanotubes were synthesized by hot filament chemical vapordeposition. The experimental results showed that the carbon nanotubes have a striking piezoresistiveeffect. The relative resistance was changed from 0 to 10.5 X 10^(-2) and 3. 25 X 10^(-2) for dopedand undoped films respectively at room temperature when the microstrain under stress from 0 to 500.The gauge factors for doped and undoped carbon nanotube films under 500 microstrain were about 220and 67 at room temperature, respectively, exceeding that of polycrystalline silicon (30) at 35℃.The origin of the resistance changes in the films may be attributed to a strain-induced change inthe band gap for the doped tubes and the defects for the undoped tubes.

Synthesis of N-Alkane Mixture Microcapsule and Its Application in Low-Temperature Protective Fabric

We investigated synthesis and characterization of melamine-urea-formaldehyde（MUF） microcapsules containing n-alkane mixture as phase change core material for thermal energy storage and low-temperature protection. The phase change microcapsules（microPCMs） were prepared by an in situ polymerization using sodium dodecyl sulfate（SDS） and polyvinyl alcohol（PVA） as emulsifiers. Surface morphology, particle size, chemical structure, and thermal properties of microPCMs were, respectively, characterized by using scanning electron microscopy（SEM）, field emission scanning electron microscopy（FESEM）, Fourier transform infrared spectroscopy（FT-IR）, differential scanning calorimetry（DSC）, and thermal gravimetric analysis（TGA）. Low-temperature resistance performances were measured at-15,-30,-45, and-60 ℃ after microPCMs were coated on a cotton fabric by foaming technology. The results showed that spherical microPCMs had 4.4 μm diameter and 100 nm wall thickness. The melting and freezing temperatures and the latent heats of the microPCMs were determined as 28.9 and 29.6 ℃ as well as 110.0 and 115.7 J/g, respectively. Encapsulation of n-alkane mixture achieved 84.9 %. TGA analysis indicated that the microPCMs had good chemical stability below 250 ℃. The results showed that the microencapsulated n-alkane mixture had good energy storage potential. After the addition of 10 % microPCMs, low-temperature resistance duration was prolonged by 126.9%, 145.5%, 128.6%, and 87.5% in environment of-15,-30,-45 and-60 ℃, respectively as compared to pure fabric. Based on the results, phase change microcapsule plays an effective role in lowtemperature protection field for the human body.

Impact localization of composite laminates based on weight function compensation localization algorithm of thin film sensors

Composite structures are sensitive to impact damage in practical engineering.Electric resistance change method(ERCM)is an ideal technique for damage monitoring of composite structures.Due to the anisotropy of fiber-resin matrix composites,impact location monitoring is difficult,and research on impact location of fiber composite laminates(FRPs)is limited.A preparation method of MXene/CNT/CuNps thin film sensor is proposed.According to the modeling simulation and theoretical calculation,the resistance change characteristics of the thin film sensor are obtained,the relationship between the impact distance and the resistance change is established,and the sensor array is designed.A three-point localization algorithm and a weight function compensation localization algorithm are proposed,which can improve the imaging accuracy of the impact position.The impact point location was observed and analyzed using ultrasonic C-scan technology.The results show that the weight function compensation positioning algorithm can accurately locate the impact of the composite structure,and the error in the X direction is 7.1%,the error in the Y direction is 0.03%,which verifies the effectiveness of the method.

Observation of an EPIR Effect in Nd_(1-x)Sr_xMnO_3 Ceramics with Secondary Phases

Nd1-xSrxMnO3 （x ： 0.3, 0.5） ceramics containing a secondary phase are synthesized by high-energy ball milling and post heat-treatment method. The 4-wire and 2-wire measuring modes are used to investigate the transport character of the grain/phase boundary （inner interface） and electrode-bulk interface （outer interface）, respectively, and the results indicate that there is a similar nonlinear I-V behaviour for both of the inner and outer interfaces, however, the electric pulse induced resistance change （EPIR） effect can only be observed at the outer interface.