Price prediction of power transformer materials based on CEEMD and GRU

The rapid growth of the Chinese economy has fueled the expansion of power grids.Power transformers are key equipment in power grid projects,and their price changes have a significant impact on cost control.However,the prices of power transformer materials manifest as nonsmooth and nonlinear sequences.Hence,estimating the acquisition costs of power grid projects is difficult,hindering the normal operation of power engineering construction.To more accurately predict the price of power transformer materials,this study proposes a method based on complementary ensemble empirical mode decomposition(CEEMD)and gated recurrent unit(GRU)network.First,the CEEMD decomposed the price series into multiple intrinsic mode functions(IMFs).Multiple IMFs were clustered to obtain several aggregated sequences based on the sample entropy of each IMF.Then,an empirical wavelet transform(EWT)was applied to the aggregation sequence with a large sample entropy,and the multiple subsequences obtained from the decomposition were predicted by the GRU model.The GRU model was used to directly predict the aggregation sequences with a small sample entropy.In this study,we used authentic historical pricing data for power transformer materials to validate the proposed approach.The empirical findings demonstrated the efficacy of our method across both datasets,with mean absolute percentage errors(MAPEs)of less than 1%and 3%.This approach holds a significant reference value for future research in the field of power transformer material price prediction.

ASYMPTOTIC ANALYSIS OF MODE Ⅱ STATIONARY GROWTH CRACK ON ELASTIC-ELASTIC POWER LAW CREEPING BIMATERIAL INTERFACE

A mechanical model was established for modeⅡinterfacial crack static growing along an elastic_elastic power law creeping bimaterial interface. For two kinds of boundary conditions on crack faces, traction free and frictional contact, asymptotic solutions of the stress and strain near tip_crack were given. Results derived indicate that the stress and strain have the same singularity, there is not the oscillatory singularity in the field; the creep power_hardening index n and the ratio of Young's module notably influence the crack_tip field in region of elastic power law creeping material and n only influences distribution of stresses and strains in region of elastic material. When n is bigger, the creeping deformation is dominant and stress fields become steady,which does not change with n. Poisson's ratio does not affect the distributing of the crack_tip field.

The crack tip fields of Mode Ⅱ stationary growth crack on bimaterial interface

A mechanical model is established for mode II interfacial crack static growing along an elastic-elastic power law creeping bimaterial interface. For frictional contact of boundary conditions on crack faces, asymptotic solutions of the stresses and strains of near tip-crack are got. It was shown that in stable creep growing phase, elastic deformation and viscous deformation are equally dominant in the near-tip field, the stress and strain have the same singularity and there is not the oscillatory singularity the field. Through numerical calculation , it is shown that the frictional coefficient η notably influence the crack-tip field.

Titanylphthalocyanine as hole transporting material for perovskite solar cells

Titanylphthalocyanine （TiOPc） as hole transporting material （HTM） was successfully synthesized by a simple process with low cost. Perovskite solar cells using the TiOPc as HTM were fabricated and characterized. TiOPc as HTM plays an important role in increasing the power conversion efficiency （PCE） by minimizing recombi- nation losses at the perovskite/Au interface because TiOPc as HTM can extract photogenerated holes from the perovskite and then transport quickly these charges to the back metal electrode. In the research, the β-TiOPc gives a higher PCE than α-TiOPc for the devices due to sufficient transfer dynamics, The β-TiOPc was applied in perovskite solar cells without clopping to afford an impressive PCE of 5.05% under AM 1.5G illumination at the thickness of 40 nm which is competitive with spiro-OMeTAD at the same condition. The present work suggests a guideline for optimizing the photovoltaic properties ofperovskite solar cells using the TiOPc as the HTM.

Analysis of bulging process of aluminum alloy by overlapping sheet metal and its formability

The influences of strength coefficient K, work hardening exponent n and thickness t of the overlapping sheet on bulging process are analyzed based on hardening material model. Also, bulging experiments are carried out by taking the aluminum alloy LF21 as formed sheet metal, and selecting overlapping sheet with different thicknesses and material properties, by which accuracy of the above analysis result is verified in the aspects of geometric shape, thickness distribution and limit bulging height. The results show that higher strength coefficient K, larger work hardening exponent n and proper thickness of the overlapping sheet are helpful to improve the formability and forming uniformity of formed sheet metal.

Vibrational power flow analysis on combined plates partially covered layer of discontinuous material

Vibrational power flow on combined plates with a change in mass and stiffness or with viscoelastic damping layer used widely in engineering is studied. The expressions of flexural displacement and other physical quantities are obtained using Laplace transformation and transfer matrix approach, then influences of changes in mass and stiffness of discontinuous material and the free damping layer on the input power flow and the transmitted power flow are discussed. The conclusions provide theory basis for structural optimization design and reducing noise and vibration

On the use of ferroelectric material LiNbO3 as novel photocatalyst in wastewater-fed microbial fuel cells

In this work, the use of lithium niobate （LiNbO3）, a ferroelectric and photocatalyst material, is investi- gated as a new type of cathode catalyst for wastewater-fed single-chamber microbial fuel cells （MFCs）. Carbon cloth electrodes coated with LiNbO3 were studied with and without UV-vis irradiation to assess its photocatalytic behavior in these devices. The synthesized phase of LiNbO3 was characterized by X- ray diffraction, differential scanning calorimetry, particle size distribution, and transmission electron microscopy analyses. The MFC containing a LiNbO3-based cathode exhibited a maximum open circuit potential and power output of 400 mV and 131 mW/m^3, respectively, under irradiation. This cathode configuration also achieved the maximum chemical oxygen demand removal of 84% after 120 h of MFC operation. These results show that ferroelectric materials such as LiNbO3 could be used as cathode cat- alysts in MFC devices. As a complementary analysis, the removal of the heavy metals detected in the wastewater was also monitored.

D-A structural protean small molecule donor materials for solution-processed organic solar cells

Under the synergistic effect of molecular design and devices engineering, small molecular organic solar cells have presented an unstoppable tendency for rapid development with putting forward donor- acceptor （D-A） structures. Up to now, the highest power conversion efficiency of small molecules has exceeded 11%, comparable to that of polymers. In this review, we summarize the high performance small molecule donors in various classes of typical donor-acceptor （D-A） structures and discuss their relationships briefly.

Organic functional materials based buffer layers for efficient perovskite solar cells

In this review, we highlight the recent development of organic π-functional materials as buffer layers in constructing efficient perovskite solar cells（PVSCs）. By following a brief introduction on the PVSC development, device architecture and material design features, we exemplified the exciting progresses made in field by exploiting organic π-functional materials based hole and electron transport layers（HTLs and ETLs） to enable high-performance PVSCs.