Experimental Study of Leakage Monitoring of Diaphragm Walls Based on Distributed Optical Fiber Temperature Measurement Technology.

In geotechnical engineering seepage of diaphragm walls is an important issue which may cause engineering disasters. It is therefore of great significance to develop reliable monitoring technology to monitor the leakage. The purpose of this study is to explore the application of a distributed optical fiber temperature measurement system in leakage monitoring of underground diaphragm walls using 1 g model tests. The principles of seepage monitoring based on distributed optical fiber temperature measurement technology are introduced. Fiber with heating cable was laid along the wall to control seepage flow at different speeds. The temperature rise of the fiber during seepage was also recorded under different heating power conditions. In particular the effect of single variables (seepage velocity and heating power) on the temperature rise of optical fibers was discussed. Test results indicated that the temperature difference between the seepage and non-seepage parts of diaphragm wall can be monitored well using fiber-optic external heating cable. Higher heating power also can improve the resolution of fiber-optic seepage. The seepage velocity had a linear relationship with the final stable temperature after heating, and the linear correlation coefficient increases with the increase of heating power. The stable temperature decreased with the increase of flow velocity. The findings provide a basis for quantitative measurement and precise location of seepage velocity of diaphragm walls.

Dynamic Characteristics of Rubber Reinforced Expansive Soil (ESR) at Positive and Negative Ambient Temperatures.

Using tire waste rubber reinforced expansive soil (ESR) can modify its poor engineering characteristics. The damping properties of ESR at different temperatures may vary dramatically. Two kinds of rubber Ra (large particle size) and Rb (small particle size) are mixed with expansive soil according to gradient ratio. The backbone curves, dynamic shear modulus, and damping ratio of expansive soil in varying temperature fields of 20 °C, -5 °C, and -15 °C are investigated. The Hardin-Drnevich model can well fit the backbone curves of ESR specimens in various temperature fields. Dynamic triaxial results show that 5-10% Ra rubber can withstand higher shear stress in all temperature fields; Rb rubber can increase the dynamic shear modulus of expansive soil and reach the peak value with 10% rubber content. The damping ratio can be significantly improved by using 10% Ra rubber at room temperature, while the ESR damping ratio in a temperature field of -5 °C does not change significantly with increasing shear strain or even decreases; Ra increases the damping ratio of expansive soils in the temperature field of 15 °C while small particle size Rb decreases the damping ratio of expansive soils. The experimental results validate the effectiveness of ESR in the frozen soil area. In an engineering sense, local temperature needs to be considered to use an appropriate ESR, which can provide effective seismic isolation and damping.

Inhibition performance of halogen-substituted benzaldehyde thiosemicarbazones as corrosion inhibitors for mild steel in hydrochloric acid solution.

Halogen-substituted benzaldehyde thiosemicarbazone derivatives were synthesized and their inhibition performance for mild steel in hydrochloric acid solution were investigated systematically using weight loss measurements, electrochemical techniques, scanning electron microscopy and quantum chemical calculations. Results of weight loss measurements indicated that all these compounds exhibited excellent inhibition performance and the inhibition efficiency increased with increasing inhibitor concentrations. Polarization results revealed that the synthesized benzaldehyde thiosemicarbazone derivatives were mixed-type inhibitors. Adsorption of these compounds onto a mild steel surface was mainly chemisorption and complied with the Langmuir adsorption isotherms. Both theoretical calculations and experimental measurements suggested that the inhibition efficiency of these compounds followed the order of Br-BT > Cl-BT > F-BT > H-BT.

Effects of sulfation on hematite for selective catalytic reduction of nitrogen oxides with ammonia.

Hematite (α-Fe2O3) is a promising candidate for NH3 selective catalytic reduction (NH3-SCR) of NOx due to its good sulfur resistance. However, the activity of pure α-Fe2O3 is very low. In this work, α-Fe2O3 obtained excellent N2 selectivity and medium-high temperature activity via a simple surface sulfation method. The α-Fe2O3-350 (sulfated at 350 °C) sample showed an NO conversion rate of ~ 100% in the range of 275-350 °C and exhibited excellent H2O and SO2 resistance ability at 300 °C. Furthermore, pure α-Fe2O3 was used as a model catalyst to fully uncover the effect of sulfation on FeOx-based catalysts in NH3-SCR reactions. Structural characterization indicated that the degree of surface sulfation of the catalyst would be deepened with increasing temperature, and the states of sulfate species on α-Fe2O3 changed from surface sulfates to bulk-like sulfates. Although sulfation treatment reduced the redox properties of α-Fe2O3, it significantly increased its surface acidity and thus the activity. Excessive bulk-like sulfates induced a decrease in activity. Sulfation inhibited the adsorption of NOx on the α-Fe2O3 catalyst surface and reduced the thermal stability of nitrates at medium-high temperature. Thus, the Langmuir-Hinshelwood (L-H) mechanism was inhibited, and the reaction mainly followed the Eley-Rideal (E-R) mechanism.

Experimental study of the freeze thaw characteristics of expansive soil slope models with different initial moisture contents.

This paper presents an experimental investigation on the effect of freeze-thaw cycling on expansive soil slopes with different initial moisture contents. Clay soil from Weifang, China, was remolded and selected to build the expansive soil slope for the indoor slope model tests. A total of five freeze-thaw cycles were applied to the three expansive soil slopes with different moisture contents ranging from 20 to 40%. Variations of the crack developments, displacements, soil pressures and moisture contents of the expansive soil slope with different initial moisture contents during the freeze-thaw cycling were reported and discussed. The results indicate that higher moisture contents can slow the development of cracks and that the soil pressure increases with decreasing temperature. The soil pressure of slope decreases after freeze-thaw cycle, and the change amplitude of soil pressure after freeze-thaw is proportional to water content. The slopes with a moisture content of 20% and 30% shrinks during freezing and expands during thawing, which was named ES-FSTE Model, while the slope with a 40% moisture content shows the opposite behavior. During freeze-thaw cycles, moisture migrates to slope surface. As initial moisture contents increase, the soil heat transfer rate and bearing capacity decreases after five freeze-thaw cycling.

(E)-N'-[1-(4-Bromo-phen-yl)ethyl-idene]benzohydrazide.

The asymmetric unit of the title compound, C(15)H(13)BrN(2)O, contains two independent mol-ecules with different conformations; the two aromatic rings form dihedral angles of 32.4 (4) and 27.5 (4)° in the two mol-ecules. In the crystal structure, inter-molecular N-H⋯O hydrogen bonds link mol-ecules into chains propagating in [100].

(E)-N'-(4-Methoxy-benzyl-idene)benzohydrazide.

In the title mol-ecule, C(15)H(14)N(2)O(2), the dihedral angle between the benzene rings is 5.93 (17)°. In the crystal, inter-molecular N-H⋯O hydrogen bonds link the mol-ecules into chains propagating in [010].

Improving the phase stability and cycling performance of Ce2Ni7-type RE-Mg-Ni alloy electrodes by high electronegativity element substitution.

In the present work, a high electronegativity element substitution strategy was employed to obtain a better corrosion resistance and cycling performance of Ce2Ni7-type La0.83-xYxMg0.17Ni3.1Co0.3Al0.1 (x = 0.0-0.6) alloys. The abundance of the Ce2Ni7-type phase increased as x increased from 0 to 0.2 but it decreased with a further increase in x up to 0.6. The alloy with x = 0.2 further showed a superior discharge capacity (400.6 mA h g-1) and high cycling stability (S320 = 75%). We found that the Y (electronegativity value χY = 1.22 > χLa = 1.10) element could play an essential role in enhancing the anti-corrosion of alloys based on a theoretical framework of the electronegativity of rare earth elements, thus leading to an excellent cycle lifetime of the alloys. The new alloying designs are expected to provide viable La-Mg-Ni-based intermetallic compounds as anode materials for commercial Ni-MH batteries.

In Situ Growth of Nanowires and Fabrication of Nanogap Electrode Pairs by Selective Chemical Deposition with the Assistance of an External Magnetic Field.

We have successfully had nanowires in situ grow on the tip of an electrode by selective chemical deposition with the assistance of an external magnetic field. The nanowires are a few microns in length and just a few hundred nanometers in diameter. At the same time, the lateral extent of electrode was not increased obviously. This method combined the lithography technique, self-assembly monolayer (SAM), chemical deposition and the external magnetic field to get nanowires in situ grow on the tip of an electrode. So we can control the growth direction of nanowires along the specified direction at desired locations. Finally, we have fabricated the nanogap electrode pairs by means of the properties of nanowires with grown on the tip of elelctrode in magnetic field.