Subjects: Materials Science >> Materials Science (General) submitted time 2023-02-14 Cooperative journals: 《桂林电子科技大学学报》
Abstract： In order to improve the thermal conductivity of thermal interface materials, reduced graphene oxide/copper composite
materials were prepared by electrophoretic deposition, and the effects of reduced graphene oxide/copper, multilayer
graphene and nano-silver on the thermal conductivity of epoxy resin were compared and analyzed. The microscopic morphology
of the reduced graphene oxide/copper composite material was characterized by scanning electron microscopy. Thermal
constant analyzer, digital viscometer and contact thermal resistance tester were used to control and test the thermal conductivity,
viscosity and interface thermal resistance of epoxy resin-based composite thermal interface materials. The results
show that the experiment successfully prepared reduced graphene oxide/copper, and the metal copper particles were evenly
distributed between graphene sheets; in addition, the thermal conductivity of reduced graphene oxide/copper, multilayer
graphene, and nano-silver to epoxy resin both have improved. When the mass fraction of the reduced graphene oxide/copper
composite material is 30%, the thermal conductivity of the epoxy resin-based composite thermal interface material is increased
by 4.5 times. Under a pressure of 0.9 MPa, the interface contact thermal resistance is 37.06 mm2·K·W-1, which
is 35.9% lower than when no interface material is added (the interface contact thermal resistance is 57.84 mm2·K·W-1
when no thermal interface material is added.). High thermal conductivity materials can increase the thermal conductivity of
epoxy resin-based thermal interface materials and significantly improve the heat transfer performance of the contact surface.
Subjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics submitted time 2022-09-26 Cooperative journals: 《桂林电子科技大学学报》
Abstract： As a heat pipe occupying a place in the field of heat transfer, the PHP is widely used in electronic heat dissipation
equipment,and regarded to be one of the heat dissipation components that have great development prospects under the conditions
of extra high heat flow density and power consumption. With the maturity of nanotechnology, Nano fluid has also become
an innovative research in the traditional field of heat dissipation and heat transfer. Therefore, it is extremely important
to explore the change mechanism and change law of the operation and thermal characteristics of the pulsating heat pipe in different
magnetic field environments. Through the use of an external magnetic field to strengthen the experimental research on
the heat transfer of the nano-magnetic fluid pulsating heat pipe, a visualization experiment platform for heat transfer testing
of the nano-magnetic fluid pulsating heat pipe was built. The temperature distribution and heat transfer rate of the plate-type
pulsating heat pipe under the action of the magnetic field size of 25, 5, 1 and 0 mT and different magnetic field directions are
respectively measured. The influence of factors such as nano-magnetic fluid, heat load power consumption, magnetic induction
intensity and magnet placement position on its heat transfer performance is studied. The experimental results show that
the use of Fe3O4/ethanol nanofluid as the working fluid can significantly enhance the heat transfer performance of the pulsating
heat pipe under the action of a magnetic field. Especially under high heat flux loading, this can provide a reference for
the working conditions of ultra-high heat flux density and power consumption.
Subjects: Mechanical Engineering >> Mechanical Manufacture and Automation submitted time 2022-09-26 Cooperative journals: 《桂林电子科技大学学报》
Abstract：
To test the rationality of the power system for a fuel cell commercial vehicle, the models of energy source (including fuel cell stack and battery pack), electric motor system (including electric motor and its controller) and driveline are built in Matlab. A global optimization energy management strategy based on dynamic programing is adopt to analysis the vehicle’s fuel economy with the European typical drive cycle under three load modes (including no-load, half-load and fullload). Simulation results show that the energy source employed satisfy the vehicle’s power requirements at the selected drive cycle, while with the increase of on-board load, the terminal SOC of battery gradually deviates from the initial value, which will limit the commercial vehicle’s dynamic performance in the long term cycles with a large on-board load. Verification results for the vehicle point that great power on-board fuel cell stack should be considered in the following research and vehicle verification.
Subjects: Agriculture, Forestry,Livestock & Aquatic Products Science >> Basic Disciplines of Agriculture submitted time 2017-11-07 Cooperative journals: 《中国生态农业学报》
Abstract：本文研究了作物、果树间作模式下果树树冠结构对间作作物区域光环境的影响, 为果粮间作模式下适宜果树高光效树形结构的确定提供理论依据。以南疆地区扁桃(10 a)||冬小麦间作种植模式为研究对象, 扁桃树形分为疏散分层形、开心形、高干形、小冠半圆形4 个树形处理, 以非间作的冬小麦大田为对照, 于冬小麦灌浆期对间作区域不同波段辐射强度、光谱组成和光合有效辐射(PAR)日变化规律进行分区测定。结果表明:1)各树形对应间作区域光环境优劣程度从高至低依次为小冠半圆形、高干形、开心形、疏散分层形, 几个树形处理间作区域总辐射强度平均值分别为对照的55.63%、46.54%、37.87%和28.76%, 光合有效辐射强度依次为自然光对照的55.84%、44.57%、35.52%和26.40%; 2)与自然光对照相比, 间作区域各波段光照辐射强度均有不同程度降低, 其中PAR、蓝紫光、黄绿光和红橙光区域消减幅度高于总辐射平均值, 紫外、近红外和远红外区域消减幅度低于总辐射平均值。以疏散分层形西侧冠下区为例, 该区域总辐射消减为自然光的11.37%,蓝紫光、黄绿光、红橙光和光合有效辐射分别消减至对照的7.98%、8.42%、8.62%和8.30%; 紫外光、近红外和远红外分别消减至对照的12.30%、15.94%和23.00%; 3)光质参数中“红橙光/远红外”比值对树冠结构特征变化敏感度高, 变异系数为23.34%, 可作为对间作区域光环境评价的主要指标; 4)冠幅、干高、树高、有无主干等树冠结构指标对间作区域特别是东侧区域的PAR 日变化趋势影响大。综合以上结果, 南疆扁桃||冬小麦间作模式下, 控冠、提干、落头等整形修剪措施能够改善间作区域的光照条件, 以采用小冠半圆形树形间作区域光环境最优。
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