The integration of active cooling systems in super or hypersonic aircraft using endothermic hydrocarbon fuels is considered an effective way to relieve the thermal management issues caused by overheating. When the temperature of aviation kerosene exceeds 150 °C, the oxidation reaction of fuel is accelerated, forming insoluble deposits that could cause safety hazards. This work investigates the deposition characteristic as well as the morphology of the deposits formed by thermal-stressed Chinese RP-3 aviation kerosene. A microchannel heat transfer simulation device is used to simulate the heat transfer process of aviation kerosene under various conditions. The temperature distribution of the reaction tube was monitored by an infrared thermal camera. The properties and morphology of the deposition were analyzed by scanning electron microscopy and Raman spectroscopy. The mass of the deposits was measured using the temperature-programmed oxidation method. It is observed that the deposition of RP-3 is highly related to dissolved oxygen content (DOC) and temperature. When the outlet temperature increased to 527 °C, the fuel underwent violent cracking reactions, and the structure and morphology of deposition were significantly different from those caused by oxidation. Specifically, this study reveals that the structure of the deposits caused by short-to-medium term oxidation are dense, which is different from long-term oxidative deposits.
Continues wave terahertz imaging has been used widely in the field of security inspection and nondestructive examination because of its simplicity and stability. In this presentation, we proposed an image method with continues wave terahertz interferometry to obtain the sample's phase information. In the experiment, a reference terahertz beam was added into the exiting continues wave terahertz imaging system to be a Michelson interferometer. With three maps obtained at three fixed phase-shift positions, a phase image is obtained by using a phase shift algorithm. Afterwards, this phase image is unwrapped to get its accurate phase profile. By this method, a bulk of foam with two height steps structure is imaged. The result shows that the inner structures of samples can be identified clearly and the relative optical depth profiles of samples can be obtained.
The softening technology with heated water of sliced veneers from small diameter logs of Schima superba was studied in this paper The results showed that thetechnology of bending was feasible, and the property of bending of Schima superba could get 1/17 without using metallic board The optimum technology parameters were 80 ℃ of steaming temperature,15 min/mm of steaming time and 25% of early moisture And the relationship model between quality of bending of sample and parameters of softening technology were established,which would provide theoretical basic for practical production
Abstract In this work, a hierarchical DNA–directed self–assembly strategy to construct structure–controlled Au nanoassemblies (NAs) has been demonstrated by conjugating Au nanoparticles (NPs) with internal–modified dithiol single-strand DNA (ssDNA) (Au–B–A or A–B–Au–B–A). It is found that the dithiol–ssDNA–modified Au NPs and molecule quantity of thiol–modified ssDNA grafted to Au NPs play critical roles in the assembly of geometrically controlled Au NAs. Through matching Au–DNA self–assembly units, geometrical structures of the Au NAs can be tailored from one–dimensional (1D) to quasi–2D and 2D. Au–B–A conjugates readily give 1D and quasi–2D Au NAs while 2D Au NAs can be formed by A–B–Au–B–A building blocks. Surface-enhanced Raman scattering (SERS) measurements and 3D finite–difference time domain (3D-FDTD) calculation results indicate that the geometrically controllable Au NAs have regular and linearly “hot spots”–number–depended SERS properties. For a certain number of NPs, the number of “hot spots” and accordingly enhancement factor of Au NAs can be quantitatively evaluated, which open a new avenue for quantitative analysis based on SERS technique.
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