Tetris-Style Stacking Process to Tailor the Orientation of Carbon Fiber Scaffolds for Efficient Heat Dissipation

As the miniaturization of electronic devices and complication of electronic packaging,there are growing demands for thermal interfacial materials with enhanced thermal conductivity and the capability to direct the heat toward heat sink for highly efficient heat dissipation.Pitch-based carbon fiber(CF)with ultrahigh axial thermal conductivity and aspect ratios exhibits great potential for developing thermally conductive composites as TIMs.However,it is still hard to fabricate composites with aligned carbon fiber in a general approach to fully utilize its excellent axial thermal conductivity in specific direction.Here,three types of CF scaffolds with different oriented structure were developed via magnetic field-assisted Tetris-style stacking and carbonization process.By regulating the magnetic field direction and initial stacking density,the self-supporting CF scaffolds with horizontally aligned(HCS),diagonally aligned and vertically aligned(VCS)fibers were constructed.After embedding the polydimethylsiloxane(PDMS),the three composites exhibited unique heat transfer properties,and the HCS/PDMS and VCS/PDMS composites presented a high thermal conductivity of 42.18 and 45.01 W m^(−1)K^(−1)in fiber alignment direction,respectively,which were about 209 and 224 times higher than that of PDMS.The excellent thermal conductivity is mainly ascribed that the oriented CF scaffolds construct effective phonon transport pathway in the matrix.In addition,fishbone-shaped CF scaffold was also produced by multiple stacking and carbonization process,and the prepared composites exhibited a controlled heat transfer path,which can allow more versatility in the design of thermal management system.

Application of FLAC3D in supporting engineering of deep foundation ditch

Based on the design principles of economic rationality and safety,multiple-pivot pile anchorage approach was used as the supporting engineering of a tall building with a deep foundation ditch.The designs,such as anchor arm,single pile and the whole,were set up in accordance with the calculations of the internal force from the equivalent beam and Yamagata Kunio methods.Moreover,the rationality of the design was estimated using the stability checks.FLAC3D was used for calculating the accuracy of the design.Using FLAC3D to simulating ditch cutting and supporting processes can obtain the equivalent results as the theory analysis in the displacement of ditch surrounding wall,the stress field and stress distribution.

Application of ultrasonic CT method in nondestructive detection of interior defects in large scale concrete structural member of bridge

The ultrasonic computed tomography(USCT)method is derived from the basic principles of X-ray section scanning.This method records the arriving times of ultrasonic wave between the probes and the sources to calculate the elastic wave velocity values in the section using the arrival times.Through analyzed the distribution of elastic wave velocity in aim area,the information of the strength and the homogeneity of the investigated zone could be got indirectly.The authors introduced the operational principle of USCT and a practical case of using this method to detect the interior defects in large scale concrete structural member.Compared with other exploration methods,this method is more efficient and accurate.

Fabrication of wear-resistant PA6 composites with superior thermal conductivity and mechanical properties via constructing highly oriented hybrid network of SiC-packed BN platelets

Herein,a strong extensional and shearing field was introduced to construct highly oriented hybrid networks of silicon carbide(SiC)-packed boron nitride(BN)platelets to fabricate high-performance wearresistant PA6 composites.Results show that in-plane and through-plane thermal conductivity(TC)of the prepared PA6 composites with a total filler loading of 20 wt.%reached 1.31 and 0.35 W/(m K),352%and 25%higher than those of pure PA6,respectively.It is attributed to the highly oriented hybrid network that facilitates the formation of efficient thermal conductivity pathways.Temperature monitoring results during friction confirm that high TC favors the friction heat dissipation performance.Meanwhile,the yield strength of PA6 composites increased by 39.1%and they still have excellent ductility with an elongation at break of 207.1%.Finally,the wear rate of PA6 composites decreased sharply by 92.5%.This method can be used to manufacture advanced linear bearing and guideway parts,etc。

基于重组酶和终止子的状态调控开关设计

合成生物学研究常用基因开关来调控细胞的状态以实现相应功能。已有的基因开关往往需要持续的输入信号来维持特定的开关状态,开关功能的维持需要持续消耗能量,并且对扰动较为敏感。文中利用了位点特异性重组酶的倒位效应反转终止子,构建了一种转录层次的状态调控开关,使得脉冲信号即可触发开关状态改变,并在下一次信号来临前稳定维持当前状态。应用自下而上的工程化思想,文中先后对重组酶和终止子进行了单独表征和组合表征,探究了二者之间的相互影响,筛选出了相互兼容的组合,成功实现了细胞的单次、二次状态切换。最后,此开关成功地被用于构建生物七段译码器,显示出了其较好的应用潜力。