Energy dissipation mechanism and ballistic characteristic optimization in foam sandwich panels against spherical projectile impact

This study systematically examines the energy dissipation mechanisms and ballistic characteristics of foam sandwich panels(FSP)under high-velocity impact using the explicit non-linear finite element method.Based on the geometric topology of the FSP system,three FSP configurations with the same areal density are derived,namely multi-layer,gradient core and asymmetric face sheet,and three key structural parameters are identified:core thickness(t_(c)),face sheet thickness(t_(f))and overlap face/core number(n_(o)).The ballistic performance of the FSP system is comprehensively evaluated in terms of the ballistic limit velocity(BLV),deformation modes,energy dissipation mechanism,and specific penetration energy(SPE).The results show that the FSP system exhibits a significant configuration dependence,whose ballistic performance ranking is:asymmetric face sheet>gradient core>multi-layer.The mass distribution of the top and bottom face sheets plays a critical role in the ballistic resistance of the FSP system.Both BLV and SPE increase with tf,while the raising tcor noleads to an increase in BLV but a decrease in SPE.Further,a face-core synchronous enhancement mechanism is discovered by the energy dissipation analysis,based on which the ballistic optimization procedure is also conducted and a design chart is established.This study shed light on the anti-penetration mechanism of the FSP system and might provide a theoretical basis for its engineering application.

Mechanical Behavior of Panels Reinforced with Orthogonal Plant Fabrics: Experimental and Numerical Assessment

The construction sector is one of the main sources of pollution,due to high energy consumption and the toxic substances generated during the processing and use of traditional materials.The production of cement,steel,and other conventional materials impacts both ecosystems and human health,increasing the demand for ecological and biodegradable alternatives.In this paper,we analyze the properties of panels made from a combination of plant fibers and castor oil resin,analyzing the viability of their use as construction material.For the research,orthogonal fabrics made with waste plant fibers supplied by a company that deals with the manufacture of furniture and craft products were used.These fabrics were made with strips of plant fibers of the Calamus rotang,Bambusa vulgaris,Heteropsis flexuosa,and Salix viminalis species.To improve their compatibility with the castor oil resin,a cold argon plasma treatment was applied.The effect of the treatment on the properties of the fibers and the panels was analyzed.The density,water absorption capacity,and swelling percentage were evaluated.Tensile,compression,static bending,and linear buckling tests were carried out.The study found that panels made with treated fiber fabrics exhibited a reduction of approximately 10%in absorption capacity and up to 35%in swelling percentage values.Panels made with Bambusa vulgaris fabrics exhibited the highest strength and stiffness values.Numerical models were constructed using commercial finite element software.When comparing the numerical results with the experimental ones,differences of less than 15%were seen,demonstrating that the models allow adequately predicting the analyzed properties.On comparing the values obtained with the characteristic values of oriented strand board,the results suggest that panels made with unconventional materials could replace commercial panels traditionally made with wood-based fibers and particles and other composite materials in several applications in the construction industry.

Impact of Different Rooftop Coverings on Photovoltaic Panel Temperature

Photovoltaic(PV)panels are essential to the global transition towards sustainable energy,offering a clean,renewable source that reduces reliance on fossil fuels and mitigates climate change.High temperatures can significantly affect the performance of photovoltaic(PV)panels by reducing their efficiency and power output.This paper explores the consequential effect of various rooftop coverings on the thermal performance of photovoltaic(PV)panels.It investigates the relationship between the type of rooftop covering materials and the efficiency of PV panels,considering the thermal performance and its implications for enhancing their overall performance and sustainability.The study compares four rooftop covering materials:wooden flakes packs(both dry and wet),polystyrene,and woolen insulation.The measurements were implemented under Iraqi weather conditions.The comparison was based on the PV panels’thermal behavior and its impact on conversion efficiency.The results revealed that covering the roof beneath the installed PV panels reduces their temperature and increases efficiency.The best performance was observedwhen placingwetwooden flakes beneath the panels,with an efficiency increase of 5%.Moreover,thewoolen insulation offered an efficiency rise of 12%near sunset.Themain outcome of thiswork is that the wet–wooden–flakes showed the best performance improvement of the PV panels.

Advancements in Photovoltaic Panel Fault Detection Techniques

This paper examines the progression and advancements in fault detection techniques for photovoltaic (PV) panels, a target for optimizing the efficiency and longevity of solar energy systems. As the adoption of PV technology grows, the need for effective fault detection strategies becomes increasingly paramount to maximize energy output and minimize operational downtimes of solar power systems. These approaches include the use of machine learning and deep learning methodologies to be able to detect the identified faults in PV technology. Here, we delve into how machine learning models, specifically kernel-based extreme learning machines and support vector machines, trained on current-voltage characteristic (I-V curve) data, provide information on fault identification. We explore deep learning approaches by taking models like EfficientNet-B0, which looks at infrared images of solar panels to detect subtle defects not visible to the human eye. We highlight the utilization of advanced image processing techniques and algorithms to exploit aerial imagery data, from Unmanned Aerial Vehicles (UAVs), for inspecting large solar installations. Some other techniques like DeepLabV3 , Feature Pyramid Networks (FPN), and U-Net will be detailed as such tools enable effective segmentation and anomaly detection in aerial panel images. Finally, we discuss implications of these technologies on labor costs, fault detection precision, and sustainability of PV installations.

Composite Panels from the Combination of Rice Husk and Wood Chips with a Natural Resin Based on Tannins Reinforced with Sugar Cane Molasses Intended for Building Insulation: Physico-Mechanical and Thermal Properties

The objective of this work is to develop new biosourced insulating composites from rice husks and wood chips that can be used in the building sector. It appears from the properties of the precursors that rice chips and husks are materials which can have good thermal conductivity and therefore the combination of these precursors could make it possible to obtain panels with good insulating properties. With regard to environmental and climatic constraints, the composite panels formulated at various rates were tested and the physico-mechanical and thermal properties showed that it was essential to add a crosslinker in order to increase certain solicitation. an incorporation rate of 12% to 30% made it possible to obtain panels with low thermal conductivity, a low surface water absorption capacity and which gives the composite good thermal insulation and will find many applications in the construction and real estate sector. Finally, new solutions to improve the fire reaction of the insulation panels are tested which allows to identify suitable solutions for the developed composites. In view of the flame tests, the panels obtained are good and can effectively combat fire safety in public buildings.

A Modified Principal Component Analysis Method for Honeycomb Sandwich Panel Debonding Recognition Based on Distributed Optical Fiber Sensing Signals

The safety and integrity requirements of aerospace composite structures necessitate real-time health monitoring throughout their service life.To this end,distributed optical fiber sensors utilizing back Rayleigh scattering have been extensively deployed in structural health monitoring due to their advantages,such as lightweight and ease of embedding.However,identifying the precise location of damage from the optical fiber signals remains a critical challenge.In this paper,a novel approach which namely Modified Sliding Window Principal Component Analysis(MSWPCA)was proposed to facilitate automatic damage identification and localization via distributed optical fiber sensors.The proposed method is able to extract signal characteristics interfered by measurement noise to improve the accuracy of damage detection.Specifically,we applied the MSWPCA method to monitor and analyze the debonding propagation process in honeycomb sandwich panel structures.Our findings demonstrate that the training model exhibits high precision in detecting the location and size of honeycomb debonding,thereby facilitating reliable and efficient online assessment of the structural health state.

Comprehensive Examination of Solar Panel Design: A Focus on Thermal Dynamics

In the 21st century, the deployment of ground-based Solar Photovoltaic (PV) Modules has seen exponential growth, driven by increasing demands for green, clean, and renewable energy sources. However, their usage is constrained by certain limitations. Notably, the efficiency of solar PV modules on the ground peaks at a maximum of 25%, and there are concerns regarding their long-term reliability, with an expected lifespan of approximately 25 years without failures. This study focuses on analyzing the thermal efficiency of PV Modules. We have investigated the temperature profile of PV Modules under varying environmental conditions, such as air velocity and ambient temperature, utilizing Computational Fluid Dynamics (CFD). This analysis is crucial as the efficiency of PV Modules is significantly impacted by changes in the temperature differential relative to the environment. Furthermore, the study highlights the effect of airflow over solar panels on their temperature. It is found that a decrease in the temperature of the PV Module increases Open Circuit Voltage, underlining the importance of thermal management in optimizing solar panel performance.

Health diagnosis of ultrahigh arch dam performance using heterogeneous spatial panel vector model

Currently,more than ten ultrahigh arch dams have been constructed or are being constructed in China.Safety control is essential to long-term operation of these dams.This study employed the flexibility coefficient and plastic complementary energy norm to assess the structural safety of arch dams.A comprehensive analysis was conducted,focusing on differences among conventional methods in characterizing the structural behavior of the Xiaowan arch dam in China.Subsequently,the spatiotemporal characteristics of the measured performance of the Xiaowan dam were explored,including periodicity,convergence,and time-effect characteristics.These findings revealed the governing mechanism of main factors.Furthermore,a heterogeneous spatial panel vector model was developed,considering both common factors and specific factors affecting the safety and performance of arch dams.This model aims to comprehensively illustrate spatial heterogeneity between the entire structure and local regions,introducing a specific effect quantity to characterize local deformation differences.Ultimately,the proposed model was applied to the Xiaowan arch dam,accurately quantifying the spatiotemporal heterogeneity of dam performance.Additionally,the spatiotemporal distri-bution characteristics of environmental load effects on different parts of the dam were reasonably interpreted.Validation of the model prediction enhances its credibility,leading to the formulation of health diagnosis criteria for future long-term operation of the Xiaowan dam.The findings not only enhance the predictive ability and timely control of ultrahigh arch dams'performance but also provide a crucial basis for assessing the effectiveness of engineering treatment measures.

On Structure,production,and market of bamboo-based panels in China

Since bamboo has the advantages of straight grain, beautiful color, high strength and toughness, and excellent abrasion resistance, bamboo-based panels have been widely used in the fields of vehicle, construction, ship building, furniture, and decoration to partly take the place of wood, steel, plastic etc in China. This paper briefly described the basic component units, including strip, sliver, and particle, of bamboo-based panel and pointed out that to design the structure of bamboo-based panels should follow the principle of symmetric structure, surface forming method, and structuring principle of equalizing stress. According to the processing methods and formation of component units, the authors classified the bamboo-based panels in China into 13 types and presented the manufacturing technique and uses of the bamboo products, such as plybamboo, bamboo flooring, and bamboo-wood composite products in detail. In the last part of the paper, much information were offered on the output, market, and selling prospect of each type of bamboo-based panels.

Cooling performance analysis of radiant panel at different positions

The influence of the panel position on the cooling performance of a radiant panel is analyzed.The coupled simulation of convection and radiation is set up by a computational fluid dynamics（CFD）method.The simulations with different panel positions and different indoor heat sources are used to calculate the cooling capacity of the radiant panel and the indoor thermal environment.The simulation results are in good agreement with the experimental results.The results show that when the indoor heat source temperature is low,the convective heat flux is the main influence factor of the cooling capacity and the radiant panel should be placed on the wall or on the ceiling.Otherwise,when the indoor heat source temperature is high,the radiation heat flux is the main factor and the radiant panel should be placed as near to the heat sources as possible.

How R&D investment promotes green technology innovation in the context of digitalization?-An empirical analysis based on provincial panel data

Green technology innovation is an important driving force and source to promote my country’s high-quality development,and it is the core path to achieve sustainable development.This paper uses my country’s provincial panel data from 2016 to 2019 to study the impact mechanism of R&D investment on green technology innovation,and introduces the level of digitization,using the panel threshold model to discuss its role in the impact mechanism of R&D investment on green technology innovation.The study found that when the level of digitalization in a region is low,increasing R&D investment does not necessarily improve the ability of green technology innovation;when the level of digitalization is relatively high,R&D investment has a positive role in promoting green technology innovation.Therefore,it is necessary to improve policies to encourage enterprises to increase investment in research and development;at the same time,it is necessary to promote the coordinated development of digital foundation,digital investment,digital literacy,digital economy and digital application,and promote the deep integration of digitalization and green technology innovation.

Prediction of stiffener buckling in press bend forming of integral panels

In order to predict the buckling of stiffeners in the press bend forming of the integral panel,a method for solving the critical buckling load of the stiffeners in press bend forming process was proposed based on energy method,elastic-plastic mechanics and numerical analysis.Bend to buckle experiments were carried out on the designed press bend dies.It is found that the predicted results based on the proposed method agree well with the experimental results.With the proposed method,the buckling of the stiffeners in press bend forming of the aluminum alloy integral panels with high-stiffener can be predicted reasonably.

Residual Strength of Stiffened LY12CZ Aluminum Alloy Panels with Widespread Fatigue Damage

Experimental and analytical investigations on the residual strength of the stiffened LY12CZ aluminum alloy panels with widespread fatigue damage （WFD） are conducted. Nine stiffened LY12CZ aluminum alloy panels with three different types of damage are tested for residual strength. Each specimen is pre-cracked at rivet holes by saw cuts and subjected to a monotonically increasing tensile load until failure is occurred and the failure load is recorded. The stress intensity factors at the tips of the lead crack and the adjacent WFD cracks of the stiffened aluminum alloy panels are calculated by compounding approach and finite element method （FEM） respectively. The residual strength of the stiffened panels with WFD is evaluated by the engineering method with plastic zone linkup criterion and the FEM with apparent fracture toughness criterion respectively. The predicted residual strength agrees well with the experiment results. It indicates that in engineering practice these methods can be used for residual strength evaluation with the acceptable accuracy. It can be seen from this research that WFD can significantly reduce the residual strength and the critical crack length of the stiffened panels with WFD. The effect of WFD crack length on residual strength is also studied.

Sheet Metal Forming Simulation and Its Application in Stamping Process of Automobile Panels

The paper starts with a brief overview to the necessity of sheet metal forming simulation and the complexity of automobile panel forming, then leads to finite element analysis (FEA) which is a powerful simulation tool for analyzing complex three-dimensional sheet metal forming problems. The theory and features of the dynamic explicit finite element methods are introduced and the available various commercial finite element method codes used for sheet metal forming simulation in the world are discussed,and the civil and international status quo of automobile panel simulation as well. The front door outer panel of one certain new automobile is regarded as one example that the dynamic explicit FEM code Dynaform is used for the simulation of the front door outer panel forming process. Process defects such as ruptures are predicted. The improving methods can be given according to the simulation results. Foreground of sheet metal forming simulation is outlined.

Estimation of demand for wood panels in Iran by the year of 2012.

Considering increasing rate of Iran population and consumption of wood panels, the authors investigated the per capita consump- tion of wood panels during the years from 1997 to 2007. The exponential smoothing method was used to obtain a per capita consumption panern of wood panels in lran for estimating demand of wood panels by the year of 2012. Results show that the consumption of particleboard, fiberboard, and medium density fiberboard in lran will increase by 33%, 72% and 107 %o, respectively, by the year of 2012; however, the consumption of plywood will increase only by 7% by 2012. The deficient amount of wood panels in Iran is estimated over 1400 000 m^3. The results of this study provide the technique reference for planners of wood panel industries in Iran in capital investment decisions.

Method for predicting motion artifacts of plasma display panels

A simulation method is proposed to predict the motion artifacts of plasma display panels （PDPs）. The method simulates the behavior of the human vision system when perceiving moving objects. The simulation is based on the measured temporal light properties of the display for each gray level and each phosphor. Both the effect of subfield arrangement and phosphor decay are involved. A novel algorithm is proposed to improve the calculation speed. The simulation model manages to predict the appearance of the motion image perceived by a human with a still image. The results are validated by a set of perceptual evaluation experiments. This rapid and accurate prediction of motion artifacts enables objective characterization of the PDP performance in this aspect.

Automated Classification of Snow-Covered Solar Panel Surfaces Based on Deep Learning Approaches

Recently,the demand for renewable energy has increased due to its environmental and economic needs.Solar panels are the mainstay for dealing with solar energy and converting it into another form of usable energy.Solar panels work under suitable climatic conditions that allow the light photons to access the solar cells,as any blocking of sunlight on these cells causes a halt in the panels work and restricts the carry of these photons.Thus,the panels are unable to work under these conditions.A layer of snow forms on the solar panels due to snowfall in areas with low temperatures.Therefore,it causes an insulating layer on solar panels and the inability to produce electrical energy.The detection of snow-covered solar panels is crucial,as it allows us the opportunity to remove snow using some heating techniques more efficiently and restore the photovoltaics system to proper operation.This paper presents five deep learning models,■-16,■-19,ESNET-18,ESNET-50,and ESNET-101,which are used for the recognition and classification of solar panel images.In this paper,two different cases were applied;the first case is performed on the original dataset without trying any kind of preprocessing,and the second case is extreme climate conditions and simulated by generating motion noise.Furthermore,the dataset was replicated using the upsampling technique in order to handle the unbalancing issue.The conducted dataset is divided into three different categories,namely;all_snow,no_snow,and partial snow.The fivemodels are trained,validated,and tested on this dataset under the same conditions 60%training,20%validation,and testing 20%for both cases.The accuracy of the models has been compared and verified to distinguish and classify the processed dataset.The accuracy results in the first case showthat the comparedmodels■-16,■-19,ESNET-18,and ESNET-50 give 0.9592,while ESNET-101 gives 0.9694.In the second case,the models outperformed their counterparts in the first case by evaluating performance,where the accuracy results reached 1.00,0.9545,0.9888,1.00.and 1.00 for■-16,■-19,ESNET-18 and ESNET-50,respectively.Consequently,we conclude that the second case models outperformed their peers.

Three-point bending behavior of aluminum foam sandwich with steel panel

Static three-point bending tests of aluminum foam sandwiches with glued steel panel were performed. The deformation and failure of sandwich structure with different thicknesses of panel and foam core were investigated. The results indicate that the maximum bending load increases with the thickness of both steel panel and foam core. The failure of sandwich can be ascribed to the crush and shear damage of foam core and the delamination of glued interface at a large bending load, The crack on the foam wall developed in the melting foam procedure is the major factor for the failure of foam core. The sandwich structure with thick foam core and thin steel panel has the optimal specific bending strength. The maximum bending load of that with 8 mm panel and 50 mm foam core is 66.06 kN.

Quasi-Horizontal Arrangement of Solar Panels in Equatorial Zones： Problems and Proposed Solutions

Solar panels are oriented to the North （South） when the site is in the South （North） with a tilt angle close to the latitude. In the equatorial zone, the panels are quasi-horizontally arranged. This situation caused some problems： the panel is more rapidly covered with dust or salty mud that decreases its performance and degrades the protective glass. To overcome these difficulties, we evaluated theoretically and practically the energy lost by an incorrect tilt. The results are rather encouraging. Just 1.5% of total energy is lost when we tilted the panel at 10.0°. In practice, we realized that the loss of energy is fewer than we calculated it because of the reflected solar rays.

Fabrication and Testing of Carbon Fiber Reinforced Truss Core Sandwich Panels

Truss core sandwich panels reinforced by carbon fibers were assembled with bonded laminate facesheets and carbon fiber reinforced truss cores. The top and bottom facesheets were interconnected with truss cores. Both ends of the truss cores were embedded into four layers of top and bottom facesheets. The mechanical properties of truss core sandwich panels were then investigated under out-of-plane and in-plane compression loadings to reveal the failure mechanisms of sandwich panels. Experimental results indicated that the mechanical behavior of sandwich structure under in-plane loading is dominated by the buckling and debonding of facesheets.