The nominal operation cell temperature (NOCT) is one of the most critical parameters for a photovoltaic (PV) module. We find that for the emerging types of glass/glass and insulating glass modules, the measurement error between the IEC61215 method and the thermocouple direct measurements on the actual cell can be as high as 15°C. To address this problem, a new NOCT measurement method for building-integrated photovoltaic (BIPV) modules is proposed. In the new method, the standard reference environment has the same total irradiance (800 W/m ² ), ambient temperature (20°C), and wind speed (1 m/s) as IEC61215 but with a closed circuit and a resistive load to ensure the module operates at the maximum power point. This takes into account both the photoelectrical and photothermal conversion effect simultaneously. The cell temperature is measured directly using several thermocouples encapsulated into the BIPV modules at a certain sampling point. The average cell operating temperature for the whole module is further determined by the infrared thermovision measurements after calibration. In addition, the simulated BIPV house was built to simulate the actual installation environment. It is verified that this new method is more accurate to test the NOCT for BIPV modules.

Closed-cell AlCu5Mn alloy foam with porosity range of ~45–90% were fabricated by the melt-foaming route. The pore structure of the fabricated Al alloy foam was analyzed and the coupling effect of porosity and cell size on the quasi-static compression behavior of the foam was investigated. The results show that the cell size of the foam decreases with the porosity decline from the view of the contribution rate to the porosity and the hierarchical pore structure characteristics becomes obvious when the foam porosity is low; the compression stress–strain curves of the foams with high porosity (>74%) are serrated due to the large cell size being easy to deform and more strain needed to let the stress recover. Meanwhile, the compression curve of the foams with low porosity (<74%) are smooth without serration, which is attributed to the hierarchical pore structure and less strain needed to let the stress recovery.

Diamondene, a carbon nanomaterial containing both sp² and sp³ carbon atoms, is obtained by compressing two or more layers of graphene. By curving rectangular diamondene and matching the unsaturated C–C bonds on the two unbent edges, a nanotube is built. We build two diamondene nanotubes (DNTs) with different radii and test their strengths under uniaxial tension. From the stress–strain curves, we discover that DNTs exhibit softening followed by hardening. The mechanism is as follows: the bond lengths and bond angles impart different stiffnesses to the tube at different axial strains. Molecular dynamics simulations demonstrate that the feature of the softening–hardening process is independent of either the tube radii or the system temperature. The critical strain for the tensile strength of a DNT becomes lower at a higher temperature. This is caused by thermal vibration of the atoms in the tubes. At the same temperature, for a DNT with a larger radius, the value of critical strain is higher. These properties will be beneficial for the potential applications of DNTs in nanodevices.

Molecular dynamics simulations are performed to analyze the uniaxial tensile deformation behaviors of nanotwinned copper bulk containing pre-existing multiple spherical/ellipsoidal voids. The effects of twin-boundary spacing, initial void size, void fraction, void shape, void orientation angle and loading orientation on the mechanical properties are examined by considering the stress-strain response and dislocation activity. Results illuminate that the coherent twin boundary can significantly enhance the strength of bulk copper. The critical stress for dislocation emission in the copper specimen depends mainly on the size of voids, which can influence the yield stress of nanotwinned copper. Less stress is required to emit dislocations from larger voids than smaller ones. In general, the larger initial void porosity is accompanied by smaller elastic modulus and critical stress. Furthermore, it is found that different dislocation patterns can be triggered under different loading orientations.

Porous metals are a new ultra-light material with high specific stiffness, specific strength, and good energy absorption properties. The elastic modulus and plateau stress of porous metals are essential parameters. There have been many studies on the effects of the matrix material, porosity, and pore size on the elastic modulus and plateau stress of porous metals, but few studies can be found on the impact of pore arrangement. The pore arrangement of porous metals cannot be quantitatively described, and the design space of a porous metal structure under the same porosity is vast. With the powerful learning and prediction ability of neural networks, the influence of pore arrangement can be better understood. In this paper, a convolutional neural network was used to explore the impact of pore arrangement on both the elastic modulus and plateau stress of a porous aluminum alloy. Firstly, a finite element method was used to simulate the compression of a porous aluminum alloy to obtain a training sample library. Secondly, a convolutional neural network was built to positively predict the elastic modulus and plateau stress of the porous aluminum alloy. Partial samples were used to select the best training model from five convolutional neural network candidates. Dropout, Batch Normalization, and L2 regularization methods were used to alleviate the over-fitting phenomenon in training. All data in the database were then trained and predicted, and the predicted goodness of fit of the elastic modulus and plateau stress were 0.8785 and 0.5922, respectively. A search method based on the convolutional neural network was then used to iteratively search the database. Under the condition of using a small amount of data, the pore structure with the best elastic modulus and plateau stress in the database could be determined, and the inverse design of a structure with high elastic modulus and plateau stress could be realized.