- 标题
- 摘要
- 关键词
- 实验方案
- 产品
过滤筛选
- 2019
- 2018
- Heat Trap
- outgassing
- lifetime
- Carbon nanotubes
- current stability
- cathode
- thermionic emission
- photovoltaic
- monocrystalline
- Heat mapping
- Nanomaterials and Technology
- Electrical Engineering and Automation
- University of British Columbia
- Univesitas Budi Luhur
- Institut Teknologi Sepuluh Nopember
-
Parametric study of laser cutting of carbon fibre reinforced polymer (CFRP) and the effect of fibre orientation on cutting quality
摘要： Laser cutting of CFRP was performed using 2 kW fibre laser. A detailed analysis of the effect of various laser processing parameters on the cutting of CFRP was carried out. The present work considers mainly laser power (W), scan speed (mm/min), gas pressure (bar) and duty cycle (%) as the process parameters with average kerf width and heat affected zone (HAZ) as the output parameters. Cutting of the fibres at 90o with respect to fibre orientation was performed. The SEM and EDS analysis were also performed to understand the cut quality, matrix melting, fibre pullout and vaporisation phenomena of the matrix in the heat affected zone (HAZ). Laser cutting of CFRP with a minimum kerf width of around 184 μm was observed for 800 W, 600 mm/min, 3 bar and 25% duty cycle while HAZ in this parameter was around 1561 μm. Kerf width and HAZ directly increase with an increase in laser power, gas pressure and duty cycle, but they reduce with increase in scan speed. SEM images confirm that the CFRP cutting process generates relatively burr-free fibre edges. Matrix recession and delamination (fibre pullout) were identified as the major quality defects occurring in the laser cutting process of CFRP.
关键词： fibre delamination,matrix melting,heat affected zone,laser cutting,fibre consolidation,kerf width,CFRP
更新于2025-11-28 14:24:20
-
Effect of Heat Input on Porosity Defects in a Fiber Laser Welded Socket-Joint Made of Powder Metallurgy Molybdenum Alloy
摘要： Porosity defects are still a challenging issue in the fusion welding of molybdenum and its alloys due to the pre-existing interior defects associated with the powder metallurgy process. Fiber laser welding of end plug and cladding tube made of nanostructured high-strength molybdenum (NS-Mo) alloy was performed in this work with an emphasis on the role of welding heat input. The distribution and morphology of porosity defects in the welded joints were examined by computed tomography (CT) and scanning electron microscopy (SEM). Preliminary results showed that laser welding of NS-Mo under low heat input significantly reduced the porosity defects in the fusion zone. The results of computed tomography (CT) showed that when the welding heat input decreased from 3600 J/cm (i.e., 1200 W, 0.2 m/min) to 250 J/cm (i.e., 2500 W, 6 m/min), the porosity ratio of the NS-Mo joints declined from 10.7% to 2.1%. Notable porosity defects under high heat input were related to the instability of the keyhole, expansion and the merging of bubbles in the molten pool, among which the instability of the keyhole played the dominant role. The porous defects at low heat input were generated as bubbles released from the powder metallurgy base metal (BM) did not have enough time to overflow and escape.
关键词： fiber laser welding,molybdenum alloy,porosity defects,heat input
更新于2025-11-28 14:24:20
-
Precipitates evolution in the heat affected zone of Mg-Gd-Y-Zr alloy in T6 condition during laser welding
摘要： The precipitates evolution in the heat affected zone of laser-welded Mg-Gd-Y-Zr alloy in T6 condition was investigated based on the TEM observation. Some oval and long-rod shape precipitates along [2110]α were observed, which were not involved in precipitation sequence. Compared with isothermal aged precipitates, the overaged β′ phase presented same morphology and size, while size of needle-shape β became much smaller. The width of complete dissolution zone of the β′ is smaller than that of partial dissolution and transformation zone.
关键词： Precipitates evolution,Heat affected zone,Mg-Gd-Y-Zr alloys,Laser welding
更新于2025-11-28 14:24:20
-
Microstructure modelling of laser metal powder directed energy deposition of Alloy 718
摘要： A multi-component and multi-phase-field modelling approach, combined with transformation kinetics modelling, was used to model microstructure evolution during laser metal powder directed energy deposition of Alloy 718 and subsequent heat treatments. Experimental temperature measurements were utilised to predict microstructural evolution during successive addition of layers. Segregation of alloying elements as well as formation of Laves and δ phase was specifically modelled. The predicted elemental concentrations were then used in transformation kinetics to estimate changes in Continuous Cooling Transformation (CCT) and Time Temperature Transformation (TTT) diagrams for Alloy 718. Modelling results showed good agreement with experimentally observed phase evolution within the microstructure. The results indicate that the approach can be a valuable tool, both for improving process understanding and for process development including subsequent heat treatment.
关键词： Modelling,Heat Treatment,Phase-field,Thermal Cycle,DED
更新于2025-11-21 11:18:25
-
A dynamic model based on response factor method and seasonal performance analysis for integration of flat plate solar collector with building envelope
摘要： Integrating solar thermal collectors into building envelopes (e.g. walls or roofs) is very promising due to no need of additional site to place solar collectors. When a solar collector is integrated with a building, the working conditions for both the solar collector and the building envelope are changed. This paper proposed a new dynamic thermal model based on the response factor method. The new model combines the conventional analysis method for solar collectors with building envelopes, therefore it is easy to be understood and is more convenient to be realized by programming in a computer than state space model. The calculated results by the dynamic model agreed well with those calculated by the state space model and the measured experimental data, suggesting a satisfying validity of the model proposed. The seasonal performance of a solar wall (integrating of solar collectors and walls) in Beijing was studied by the new model. The results showed that: (1) In winter, the useful heat gain by the solar wall was always a little higher than the separate wall by about 6.7–8.8%, and the heat loss through solar wall is reduced by 90% or more, this is very favorable to reduce space heating load. (2) In summer, the useful heat gain of solar wall was higher than the separate collector by about 2.1–10.2%, the heat transferred through walls was less or higher than the separate wall depending on the inlet water temperature.
关键词： Dynamic model,Building heat transfer,Response factor method,Integration of solar collector with building,Useful heat gains
更新于2025-09-23 15:23:52
-
Optical Energy Characteristics of the Optimal Module of a Solar Composite Parabolic-Cylindrical Plant
摘要： The module of parabolic-cylindrical composite mirror concentrating system (MCS) is created with an optimal aperture angle (U) and relevant optimal size of the focal spot provided by flat mirror elements with the optimal size.
关键词： mirror concentrating systems,heat receiver,focal plane,parabolic-cylindrical concentrator,flat facets,heat carrier
更新于2025-09-23 15:23:52
-
Theoretical Investigation of Thermal Effects in High Power Er <sup>3+</sup> /Yb <sup>3+</sup> - Codoped Double-Clad Fiber Amplifiers for Space Applications
摘要： In this paper, a multiphysics numerical model based on the spatial-dependent rate equations and 3-D non-homogeneous heat conduction model is used to investigate the performance of Er3t/Yb3t-codoped double-clad fiber amplifiers with respect to the constraints associated with space applications. The effects of fiber length, coating thickness, and core radius changes are analyzed. Furthermore, the impact of thermal heating due to the high power optical signals propagating along the fiber on the amplifier gain is examined. The temperature dependence of the refractive index, emission and absorption cross sections, as well as the radiation induced attenuation is derived and modeled. It is observed that the coating thickness affects the temperature distribution along the whole fiber length. Thicker coating mitigates the temperature variation along the fiber as well as it improves the temperature difference between the core center and the outer fiber surface. Moreover, larger core results in higher optical gain and shorter fibers. By numerical results, it is inferred that the thermal effects could strongly degrade the whole amplifier performance.
关键词： heat conduction,rare earth,fiber amplifier,thermal analysis
更新于2025-09-23 15:23:52
-
Heat Response of Global Vegetation Biomes to Ongoing Climate Warming Based on Remote Sensing
摘要： Research is needed by global change scientists on how global vegetation biomes respond to ongoing climate warming. To address this issue, we selected study sites with significant climate warming for diverse vegetation biomes, and used global gridded temperature and remote sensing data over the past 32 years (1982–2013). The results suggested that climate warming in areas above approximately 60° N is relaxing the heat-constraints on vegetation activity, thus promoting plant growth; whereas, in mid to low latitude areas, ongoing climate warming probably imposes negative impacts on vegetation biomes through drought and heat stress. Understanding these potential effects is important for planning adaptation strategies to mitigate the impacts of climate warming, particularly for agro-ecosystems.
关键词： climate warming,heat responses,remote sensing,global vegetation biomes
更新于2025-09-23 15:23:52
-
Consideration of the Impact of the Environmental Conditions when Designing Heat-Receiving Systems of the Solar Cylindrical Parabolic Modules
摘要： The aerohydrodynamic and heat exchange characteristics in the cylindrical heat receiver of a solar cylindrical parabolic concentrating module are investigated. The mathematical model is based on the Navier-Stokes equation system for a laminar flow in a channel. The model is implemented using the control volume method. The created computer algorithm allows carrying out parametric studies and revealing the most rational geometric, dynamic, and power parameters of the process. The proposed model describes the general physical outlines of the heat exchange in a cylindrical heat receiver which allows estimating the influence of the environment—wind velocity, ambient temperature, etc.—on it.
关键词： cylindrical heat receiver,rational geometric, dynamic, and power parameters,solar cylindrical parabolic module,wind velocity,Navier-Stokes equation system,ambient temperature,control volume method
更新于2025-09-23 15:23:52
-
Energy/exergy based-evaluation of heating/cooling potential of PV/T and earth-air heat exchanger integration into a solar greenhouse
摘要： Through the present paper, a solar greenhouse integrated with an Earth-Air Heat Exchanger (EAHE) and Photovoltaic/Thermal collectors (PV/Ts) was theoretically studied in terms of energy and exergy and validated against an experimental study presented in literature i.e. a solar greenhouse with floor area, buried pipe length and PV area of 24m2, 39m and 9.68m2, respectively. The comparisons showed a fairly good agreement between the theoretical and experimental results with a relatively high coefficient of correlation around 95%. Afterwards, the given solar greenhouse was optimized in terms of energy and exergy efficiencies while the results indicated that only length of EAHE pipes showed an optimum value equal to 38m on average. Moreover, the results showed that PV/Ts did not have a significant heating potential for raising the greenhouse air and plant temperatures and only the electricity generation potential of PVs was favorable. However, the EAHE integration seemed promising in raising and lowering the temperatures of greenhouse air by 9°C and 8°C in summer and winter, respectively. Moreover, the Temperature Load Leveling (TLL) due to integration of only EAHE was achieved 46% and 58% in summer and winter, respectively.
关键词： Greenhouse,Heating potential,PV/T,Earth-air heat exchanger
更新于2025-09-23 15:23:52