When flooding with viscous Polymers, due to the increase in viscosity and decrease in permeability (for polymers that absorb on the rock surface), the mobility ratio compared to water flooding becomes more favorable. Therefore the volumetric sweep efficiency increases and the recovery of the reservoir on a macro scale increases also. Most people think that polymer flooding does not increase the recovery at a micro scale. But numerous results in this work do not support this conclusion. From cores in the lab, the effect of flooding with viscous-elastic polymers on different types of residual oil after water flooding was studied. The different types of residual oil are:oil film on the rock surface;oil in "dead ends";oil in pores throats retained by capillary forces;oil un-swept in micro scale heterogeneous portions of the core. It could be seen that all types of micro-scale residual oil were reduced after flooding with viscous-elastic polymers. Due to the elastic nature of the polymer, the velocity distribution in the pores are quite different from Newtonian Fluids and the polymer could also exert a very strong "pulling effect" on different types of residual oil. The study pointed out that the relationship between Capillary Number and Recovery of cores for Newtonian Fluids does not apply to fluids with elastic properties. In the study, it was seen that the increase in micro scale recovery was related to the elastic properties of the polymer fluids. Different polymer fluids had quite different elastic properties. Some had practically no elasticity. Therefore, when selecting polymers for flooding, its elastic properties must be considered. The difference in incremental recovery can be more than 6% OOIP (original oil in place), which is substantial, it can make a polymer flood successful (both technically and economically) or not. The above conclusions can also be confirmed by pressure coring data and field results of large scale polymer (PAM) flooding in Daqing Oil Field, which is obtaining an incremental oil recovery of more than 13% OOIP. This magnitude of incremental oil recovery can not be explained by just an increase in volumetric sweep efficiency. The above conclusionscan explain why some polymer floods were successful or not;should be considered when selecting polymer floods and,should be able to increase the incremental oil of future polymer floods. The rheology of viscous-elastic fluids in porous media is very much different from fluids with no elasticity. Much work needs to be done in this field. Many conclusion obtained by studies on Newtonian Fluids need to be re-assessed when used on visco-elastic fluids. Introduction The relationship between Capillary Number and Recovery when flooding cores with Newtonian Fluids is well-established[1]. It is known that to obtain substantial increase in recovery at a micro scale in cores, the Capillary Number needs to be increased several thousand times, but the increase when flooding with polymers, compared to with water, usually is less than one hundred. Therefore, most people think that polymer flooding does not increase the recovery at a micro scale. However, in the lab, the recovery from natural and artificial consolidated cores were mostly 5~8% OOIP higher when polymer flooded than water flooded. The same results were obtained by flooding glass-etched cores. The end point (oil saturation when water cut reaches 100%) of relative permeability curves were 6~8% lower for polymer flooding than by water flooding. Pressure cores in polymer flooded portions of the reservoir showed residual oil saturation much lower than could be obtained by water flooding.

After chemical or nuclear leakage or explosions, finding survivors is a huge challenge. Although human bodies can be found by smart vehicles and drones equipped with cameras, it is difficult to verify if the person is alive or dead this way. This paper describes a continuous wave radar sensor for remotely sensing the vital signs of human subjects. Firstly, a compact and portable 24 GHz Doppler radar system is designed to conduct non-contact detection of respiration signal. Secondly, in order to improve the quality of the respiration signals, the self-correlation and adaptive line enhancer (ALE) methods are proposed to minimize the interferences of any moving objects around the human subject. Finally, the detection capabilities of the radar system and the signal processing method are verified through experiments which show that human respiration signals can be extracted when the subject is 7 m away outdoors. The method provided in this paper will be a promising way to search for human subjects outdoors.

This study employed the process of removing bamboo green and bamboo brooming from Neosinocalamus affinis in the production of laminated bamboo-bundle veneer lumber (BLVL) with a thickness of 28 mm. The effect of the removing extent of bamboo green on dimensional stability, modulus of rupture, modulus of elasticity and horizontal shearing strength of BLVL was discussed. The results show a rising trend for the lightness (L*) as well as red hue (a*) and yellow hue (b*) with increasing extent of removing bamboo green, The higher the extent of removing bamboo green, the less wax and SiO 2 remained on the bamboo surface, the smaller the contact angle of bamboo-bundle and the better the dimensional stability of the corresponding BLVL. As the removing extent of bamboo green increased, BLVL exhibited a slightly decreasing value of modulus of rupture, modulus of elasticity and horizontal shear strength prior to the 28 h cycling treatment, while less strength reduction was observed after the treatment. The ones without removal of bamboo green suffered most severe strength reduction. In terms of horizontal shearing strength, A, B, C, D could meet the standard requirement of GB/T 20241-2006, while A, B and C, except for D, could reach the 9 V-12H level according to Bamboo Scrimber standard.

The objective of this study was to evaluate the uniformity of density distribution for Bamboo-bundle Laminated Veneer Lumber (BLVL) and its relationship to the stability of mechanical performance. A novel assembly style called one-piece veneer formation technology was developed to enhance the density uniformity, and four different density levels for BLVL were examined by X-ray scanning. The results indicated that the homogeneity of density, the stability of mechanical performance, and the mechanical properties for BLVL could be effectively improved by assembling the bamboo bundles into layers and then combining the layers to make the lumber. The density uniformity in width and thickness directions increased with increasing target density. A negatively linear correlation between density and Coefficient of Variation (COV) of MOR and shearing strength was observed. Partial correlation analysis revealed that when controlling for the variability of density, the linear relationship between density and the COV of MOR became insignificant, and the degree of linear correlation between density and the COV of shearing strength decreased.

As one of the most renewable and sustainable resources on Earth, bamboo with its high flexibility has been used in the fabrication of a wide variety of composite structures due to its properties. A bamboo-based winding composite (BWC) is an innovative bamboo product which has revolutionized pipe structures and their applications throughout China as well as improving their impact on the environment. However, as a natural functionally graded composite, the flexibility mechanism of bamboo has not yet been fully understood. Here, the bending stiffness method based on the cantilever beam principle was used to investigate the gradient and directional bending flexibility of bamboo (Phyllostachys edulis) slivers under different loading Types during elastic stages. Results showed that the graded distribution and gradient variation of cell size of the fibers embedded in the parenchyma cells along the thickness of the bamboo culm was mainly responsible for the exhibited gradient bending flexibility of bamboo slivers, whereas the shape and size difference of the vascular bundles from inner to outer layers played a critical role in directional bending flexibility. A validated rule of mixture was used to fit the bending stiffness under different loading Types as a function of fiber volume fraction. This work provides insights to the bionic preparation and optimization of high-performance BWC pipes.