Low Tilt Angle Research Articles

Experimental optimization of the FSW parameters to weld the dissimilar Al- and Cu-alloys by using additives at their joints

Friction stir welding (FSW) stands as a promising technique for joining materials, offering advantages over conventional methods. This study investigates the influence of tool tilt angle, rotational speed and profile on welded joint characteristics using a design of experiment (DOE) approach. The research objective aims to determine optimal parameter combinations for improved mechanical properties. Methodology entails the systematic variation of tilt angle, rotational speed and tool profile in a DOE setup, with subsequent FSW of samples. Mechanical testing, including tensile, bend and hardness tests, is conducted on 24 samples, with scanning electron microscope (SEM) and microstructure analysis on two specimens. Results reveal that higher tilt angles, rotational speeds and threaded profiles yield increased tensile strength but decreased ductility. Similarly, bend tests show higher fracture loads but reduced deflection before fracture under these conditions. Hardness tests indicate elevated hardness in welded areas, with variations based on input parameters. Main findings highlight the importance of parameter optimization for desired mechanical properties. Lower tilt angles and rotational speeds promote smoother material flow and uniform heating, resulting in consistent microstructure and hardness distribution. In conclusion, this study provides valuable insights for optimizing FSW parameters to achieve desired mechanical properties in welded joints. The combination of a 2° tilt angle, threaded tool profile and 1500 rpm rotational speed demonstrated the highest tensile strength, while a 1° tilt angle, cylindrical tool profile and 1000 rpm rotational speed yielded highest ductility.

Effect of the intraoperative head hypsokinesis on sore throat after thyroid surgery: a randomized controlled trial.

Postoperative sore throat (POST) after thyroidectomy is a major concern.A roll is typically inserted under the shoulder to achieve head hypsokinesis and neck extension to better expose the surgical site during thyroid surgery. However, POST and impaired voice function have been attributed to neck overextension. This study aimed to explore the rational angle of head hypsokinesis that both reduced sore throat intensity and protects voice function after thyroid surgery. A total of 210 patients who underwent thyroidectomy were enrolled and randomized into high-tilt (Group H) and low-tilt angle groups (Group L). The primary outcome was the incidence of POST 6 h after surgery. Secondary outcomes included the severity of postoperative pharyngeal pain, voice function, swallowing pain, and coughing. The incidence of POST 6 h after thyroidectomy was significantly lower in Group L than that in Group H. In addition, the intensity of postoperative sore throat and swallowing pain was more severe in Group H. A lower degree of head hypsokinesis in Group L prevented transient postoperative voice injury. A lower degree of head hypsokinesis effectively mitigated sore throat severity after thyroidectomy and improved postoperative voice function. The trial was registered in the Chinese Clinical Trial Registry on 21 June 2022 (ChiCTR2200061329). The trial is registered at https://www.chictr.org.cn/showproj.html?proj=166254 .

PVSails: Harnessing Innovation With Vertical Bifacial PV Modules in Floating Photovoltaic Systems

AbstractIn the context of offshore floating photovoltaic systems (FPVs), this paper explores the use of bifacial photovoltaic modules installed in the vertical position. The energy harvested from the rear face of vertically configured bifacial PV modules compensates for the reduced production at the front face of the module, and this demonstrates the potential of bifacial technology for offshore applications. By comparison, most existing horizontally tilted bifacial FPV systems gain only a small benefit in production from the rear face of the module due to the minimum radiation received, and what also must be taken into consideration is the negative effect of significant soiling owing to the low tilt angle of the PV modules. Hence, to overcome these drawbacks, we have developed the innovative “PVSail” concept, which explores the deployment of vertical FPV systems on floats, buoys, or poles/minipiles. Floating vertical bifacial PV systems (VBPVs) have huge potential to harness all the energy generation capabilities enhance by reflected light, especially from snow‐covered surfaces in northern regions. Our analysis considers a patented mooring and vertical PV system that allows the VBPV structure to align with the prevailing wind direction to shed wind loads, and our numerical analysis explores the potential of VBPV applied to Catania in Italy and Nigg Bay in the United Kingdom. Our analysis study has revealed that across an azimuth angle range (0°–180°), vertical bifacial modules experience roughly a 9% decrease in energy yield at Catania and about a 5% energy yield gain in higher latitude regions like Nigg Bay. Additionally, increasing the latitude of the installation location of VBPV reduces the energy yield sensitivity to the orientation, that is, azimuth angle. The PVSail concept opens the door to novel deployment possibilities in offshore renewable energy projects.

Response surface methodology for characterization of wind effect on combined convective loss from a bicylindrical cavity receiver

To assess the combined convective loss of a bicylindrical cavity receiver, an investigation was conducted using response surface methodology under varying wind directions, speeds, and cavity tilt angles. The study revealed that wind direction has a more substantial influence on the combined Nusselt number than cavity tilt angle. For all wind speeds and cavity tilt angles, the head-on wind direction results in a higher combined convective loss compared to back-on and side-on wind directions. Wind speed significantly affects the combined Nusselt number at higher cavity tilt angles for the back-on and side-on winds, with the effect diminishing at lower tilt angles. Increasing the tilt angle of the cavity leads to a greater change in the combined Nusselt number as wind speed increases. A quadratic model was developed to predict the combined Nusselt number, which achieves reasonable agreement between the predicted and experimental values, with a deviation of up to 12.5%.

Instabilities of rotating inclined buoyancy layers.

The boundary layer near a cooled inclined plate, which is immersed in a stably stratified fluid rotating about an axis parallel to the direction of gravity, is a model for katabatic flows at high latitudes. In this paper the base flow of such an inclined buoyancy layer is solved analytically for arbitrary Prandtl numbers. By applying linear stability analyses, five unstable modes are identified for both the fixed temperature and the isoflux boundary conditions, i.e., the stationary longitudinal roll (LR) mode, the oblique roll with low streamwise wave-number (OR-1) and high streamwise wave-number (OR-2) modes, and the Tolmien-Schlichting (TS) wave with low streamwise wave-number (TS-1) and high streamwise wave-number (TS-2) modes. It is indicated that the Coriolis effect induced by the rotation leads the critical modes to be three dimensional, and a larger tilt angle of the plate and stronger Coriolis effect cause both TS wave modes to be more unstable for both thermal boundary conditions. When the Coriolis effect is considered, the OR-1 and OR-2 modes are the most unstable mode at low and high tilt angles, respectively, but the TS-1 wave mode may be the most unstable one when the plate is nearly vertical. In addition, the spanwise phase velocities of the TS wave modes change directions as the tilt angle passes some threshold values for both thermal boundary conditions except for the TS-1 wave mode with a fixed temperature boundary condition, which propagates in the same spanwise direction for all explored tilt angles.

Area average heat transfer from a vertical flat plate impinged by circular inclined jet

ABSTRACT The inclined impinging jets owing to higher efficiency are widely used to disperse concentrated and transient heat loads. The temperature and heat transfer characteristics of jet cooling vertical hot plate at different inclinations are experimentally investigated. Experiments are performed to investigate the area average heat transfer over a flat surface of 600 × 300 mm2 placed at different location (z) of 3−20 d from the jet. The investigation is employed for Reynolds number based on hydraulic diameter of 11.5 mm ranging from 10,000 to 75,000. The orientation of the jet varies from 15° to 75°. The study aims to investigate the influence of jet orientation at different area locations on the surface from the point of impingement. The effect in stagnation region with different jet tilt is investigated. The area average temperature variation and characteristic temperature contours with increasing surface area and inclination is delineated. The characteristics of heat transfer on the surface’s periphery are studied. Heat transfer increases by 40% at lower tilt angle as the jet is displaced from 20 to 6 d, whereas the maximum average Nu occurs at higher inclination. The available Nusselt numbers in inclined jet are compared with present experimental results. A new empirical correlation is developed for a complete range of z/d, Re and large radial span.

Strategic PV expansion and its impact on regional electricity self-sufficiency: Case study of Switzerland

Solar photovoltaics (PV) will play an important role in decarbonising the energy system. To date, most assessments of PV transition pathways focus on least-cost aspects, without neither considering the time needed to achieve a substantial PV deployment, nor the impacts on regional electricity supply equality. In this work, we propose two alternative PV expansion strategies for Switzerland: The first strategy prioritises the most productive roofs and reaches national PV targets by exploiting the minimum number of rooftops, while the second strategy aims at maximising regional self-sufficiency as proxy of PV supply equality. Both strategies are assessed for several PV expansion scenarios using real hourly PV potential data for the entire Swiss building stock. The scenarios are compared to hourly electricity demand profiles for the residential and service sector. Results suggest that when employing the first strategy, at least 46% of suitable rooftops – mostly large roofs with low tilt angles – are needed to reach Switzerland’s 2050 PV expansion target of 35 TWh. For the projected electricity demand in 2050, this leads to annual electricity self-sufficiency in about 40% of Swiss districts. This percentage can be increased to over 70% by following strategy two to maximise self-sufficiency – which may feature several economic and societal advantages – at the cost of covering 86% of suitable rooftops with PV. The findings may support policy makers and local utilities to find efficient and equitable pathways for a decentralised PV expansion, while at the same time reaching the ambitious national renewable energy targets within due time.

Performance Evaluation of an Installed On-Grid Photovoltaic System at Bamako

The primary goal of this paper is to analyze the performance of an installed on-grid photovoltaic 100 kW system installed on the roof of a building at the Institute of Applied Sciences, University of Sciences, Techniques and Technologies of Bamako. The system under consideration is part of a pilot project of a grid-connected system in Mali by the Renewable Energies Agency (AER). The PV system is located at 12.62°N latitude and -7.99°W longitude. It is composed of 313 monocrystalline modules of 320W for an installed power of approximately 101kWp and they are fixed on support inclined at 6 degrees orientated East-West. The system was monitored from March 2020 to February 2021. Within this period, the photovoltaic system supplied 114801.57 kWh to the grid with the final yield varying between 2.41 to 4.09 kWh/kWp/day. Additionally, the ratio of performance in this one year ranged from 53% to 89%. The annual capacity factor and efficiency are 13% and 10%, respectively. The main roots of this bad performance of the system are analyzed. The system performance is significantly affected by the soiling effects which are in other words attributed to meteorological and environmental parameters mainly dust accumulation and ambient temperature, as well as, factors like inclination (low tilt angle (6°)), the east and west orientation of the panels and finally lack of cleaning frequencies.

Comparison of the Power Extraction Performance of an Oscillating Hydrofoil Turbine with Different Deflector Designs

The unsteady RANS equations for a two-dimensional hydrofoil were solved using ANSYS Fluent to model and simulate the hydrofoil at a constant Reynolds number, Re, of 2 × 105 and a fixed reduced frequency, f*, of 0.14. The simulations were performed by varying parameters, such as the number of deflectors N, tilt angle of the deflectors β, and vertical spacing of the deflectors J* = J/c, to determine the effect of the upstream deflector’s position on the hydrofoil’s performance. The results demonstrated that the deflector was effective at redirecting the separated flow away from the edges, which was then amplified downstream before colliding with the leading edge of the oscillating hydrofoil to increase power extraction. The performance of the oscillating hydrofoil was highly reliant on all three studied parameters. The hydrofoil with two deflectors (N = 2) displayed marginally superior power extraction capability compared to the hydrofoil with a single deflector (N = 1). Furthermore, the hydrofoil with the rightward inclined deflector at a low tilt angle (−5° ≥ β ≥ −10°) exhibited relatively better power extraction performance than the others. The best deflector design increased the hydrofoil’s cycle-averaged power coefficient by approximately 32% compared to a hydrofoil without a deflector. The vortex structures revealed that the flow evolution and power extraction performance were dependent on the size, robustness, and growth rate of the leading edge vortex (LEV) as well as the timing of LEV separation. The power extraction efficiency of an oscillating hydrofoil increased in the mid downstroke and upstroke due to the formation of a more robust LEV when the hydrofoil–deflector interaction was advantageous, but it dropped in the wing reversal due to the early separation of the LEV when the hydrofoil–deflector interaction was counterproductive.

Towards development of sustainable metallic superhydrophobic materials

In the present study, an environment friendly, scalable, and cost-effective approach is proposed, combining thermo-mechanical and microwave-assisted hydrothermal processing techniques, resulting in the augmentation of nanoscale structures on metallic surfaces. The thermo-mechanical processing of the aluminium alloy performed at different strain rates resulted in significant grain refinement (∼ 1 µm for processed and ∼ 30 µm for unprocessed samples). After hydrothermal treatment, highly dense and networked nanostructured morphology was evoked by refined grains. Post silanization, samples exhibited high contact angle (θs > 155°) with a low tilt angle (θt < 10°) and CAH (< 5°). The low adhesion with water (∼ 16 µN) for the processed sample (∼ 50 μN for unprocessed) with utmost refined grains is attributed to the high interfacial energy of Cassie state (EC−B>1.0J) due to effective entrapment of air. The processed samples were highly de-wetting and mechanically resilient owing to the strong negative capillary pressure (PC > 1100 kPa) generated by highly dense networked nanostructures. As a result of thermo-mechanical processing, samples displayed higher resilience to abrasion, simulated rain, and long-term immersion tests with low tilt angles (θt < 10°) and CAH (< 5 °). This paper provides a practical approach to achieve anti-wetting surfaces in various industrial settings.

Development of self-cleaning polydimethylsiloxane/nano-calcium carbonate-titanium dioxide coating with fog-resistance response for building glass

PurposeThis paper introduced the simple synthesis process of self-cleaning coating with fog-resistance property using hydrophobic polydimethylsiloxane (PDMS) polymer and nano-calcium carbonate (nano-CaCO3) and titanium dioxide (TiO2).Design/methodology/approachThe synthesis method of PDMS/nano-CaCO3-TiO2 is based on sol-gel process. The crosslinking between PDMS and nanoparticles is driven by the covalent bond at temperature of 50°C. The 3-Aminopropyltriethoxysilane is used as binder for nanoparticles attachment in polymer matrix. Two fabrication methods are used, which are dip- and spray-coating methods.FindingsThe prepared coated glass fulfilled the requirement of standard self-cleaning and fog-resistance performance. For the self-cleaning test BS EN 1096-5:2016, the coated glasses exhibited the dust haze value around 20%–25% at tilt angle of 10°. For the antifog test, the coated glasses showed the fog haze value were below 2% and the gloss value were above 85%. The obtained results completely achieved the standard antifog value ASTM F659-06 protocol.Research limitations/implicationsFindings will provide an infrastructure support for the building glass to enhance building’s energy efficiency, cleaning performance and friendly environment.Practical implicationsThis study proposed the simple synthesis method using hydrophobic polymer and nano-CaCO3 and nano-TiO2, which can achieve optimum self-cleaning property at low tilt angle and fog-resistance performance for building glass.Social implicationsThe research findings have high potential for building company, cleaning building company and government sector. The proposed project capable to reduces the energy consumption about 20% per annum due to labor cost, time-consuming and safety during manual cleaning.Originality/valueThe novel method to develop self-cleaning coating with fog-resistance using simple synthesis process and fabrication method for building glass application.

Experimental study of effect of glass cover tilt angle of solar still in winter season of India’s composite climate

• Solar still’s performance in the winter season with nocturnal productivity. • Model-2 (TA 30°) above latitude angle performed good with 1660 ml/m2 yield, 17.25 % efficiency, and 1.1 % exergy efficiency . • Effect of covering condenser surface by insulating material in nocturnal yield. • Low tilt angle causes back drop of condensate into the basin. • Effect of wind velocity on outer surface temperature of condenser in daylight. The present work consists of an experimental investigation to find the effect of the tilt angle of the condenser surface of solar still (SS) on distilled water productivity and efficiency in the winter season in the metrological condition of Varanasi (25.2623°N, 82.9894°E), India. In this experiment, three models were fabricated with different tilt angles having the same basin areas. The first two models were single basin single slope (SBSS) type SS having tilt angles of 25° and 30° in southward facing. The third model was a single basin double slope (SBDS) type SS having a tilt angle of 15° facing toward the east–west direction. Generally, the latitude angle is used as a tilt angle however the present study revealed that the tilt angle varies according to season (sun-earth positioning) and affects productivity. The findings show the temperature difference between basin water and condenser glass cover is limited which is the driving force of the desalination process. The results showed that model-1, 2, and 3 give maximum yield of 760, 925, 320 ml/m 2 of distilled water with maximum thermal and exergy efficiency of 17.15 % and 0.6 %, 17.25 % and 1.1 %, and 7 % and 0.3 % respectively over seven hours span. This investigation also reveals the heat retaining capacity of SS and effect of polystyrene coverage on glass cover that helps to obtain maximum nocturnal yield of 435, 735, 320 ml/m 2 from model-1, 2, and 3 respectively on different days that make total distilled output to 1195, 1660, 560 ml/m 2 on a particular day. In design perspective, the proper selection of tilt angle facilitates the seamless gliding of condensate to collecting troughs that mitigate the loss of condensate that falls into the basin before reaching to trough.

Vapor Lubrication for Reducing Water and Ice Adhesion on Poly(dimethylsiloxane) Brushes

Fast removal of small water drops from surfaces is a challenging issue in heat transfer, water collection, or anti-icing. Poly(dimethylsiloxane) (PDMS) brushes show good prospects to reach this goal because of their low adhesion to liquids. To further reduce adhesion of water drops, here, the surface to the vapor of organic solvents such as toluene or n-hexane is exposed. In the presence of such vapors, water drops slide at lower tilt angle and move faster. This is mainly caused by the physisorption of vapor and swelling of the PDMS brushes, which serves as a lubricating layer. Enhanced by the toluene vapor lubrication, the limit departure volume of water drop on PDMS brushes decreases by one order of magnitude compared to that in air. As a result, the water harvesting efficiency in toluene vapor increases by 65%. Benefits of vapor lubrication are further demonstrated for de-icing: driven by gravity, frozen water drops slide down the vertical PDMS brush surface in the presence of vapor.

A novel hybrid control strategy of wind turbine wakes in tandem configuration to improve power production

The wind turbines that operate in the wake region of the upstream turbines produce less power and may suffer serious structural issues due to highly unsteady flows, which can reduce the life expectancy of the turbines. In this study, a novel hybrid wake control strategy for the wind farm power generation enhancement is proposed, which is based on highly accurate large eddy simulations coupled with the actuator line method. The combined effects of yaw angle and tilt angle control methods on the performance improvement of downstream wind turbines in wind farm layouts have not yet been investigated. This work would be the first attempt to evaluate the hybrid wake-control strategy of tandem wind turbines. It is found that the vortex generation is stronger at lower tilt angles because more parts of the rotor are affected by the wakes of the upstream wind turbine. An optimisation analysis is also provided to find the optimum wake deflection angles of the upstream turbine to maximize the electrical power generation. The results show that an accumulative power production increment of 17.1% is achieved by controlling both yaw angle (θ=30o), and tilt angle (φ=24o). The power obtained in the present study is approximately 6.1% higher than previous wake control techniques. By using the hybrid control strategy, an annual energy production enhancement of 3.7% is achieved, which is higher than the previous wake-controlled wind farm layouts.

Modeling photovoltaic-electrochemical water splitting devices for the production of hydrogen under real working conditions

Photoelectrochemical splitting of water is potentially a sustainable and affordable solution to produce hydrogen from sun light. Given the infancy stage of technology development, it is important to compare the different experimental concepts and identify the most promising routes. The performance of photoelectrochemical devices is typically measured and reported under ideal irradiation conditions, i.e. 1 sun. However, real-life operating conditions are very different, and are varying in time according to daily and seasonal cycles. In this work, we present an equivalent circuit model for computing the steady state performance of photoelectrochemical cells. The model allows for a computationally efficient, yet precise prediction of the system performance and a comparison of different devices working in real operating conditions. To this end, five different photoelectrochemical devices are modeled using experimental results from literature. The calculated performance shows good agreement with experimental data of the different devices. Furthermore, the model is extended to include the effect of illumination and tilt angle on the hydrogen production efficiency. The resulting model is used to compare the devices for different locations with high and low average illumination and different tilt angles. The results show that including real illumination data has a considerable impact on the efficiency of the PV-EC device. The yearly average solar-to-hydrogen efficiency is significantly lower than the ideal one. Moreover, it is dependent on the tilt angle, whose optimal value for European-like latitude is around 40°. Notably, we also show that the most performing device through the whole year might not necessarily be the one with highest sun-to-hydrogen efficiency for one-sun illumination.

Modelling and Performance Analysis of MgB2 and Hybrid Magnetic Shields.

Superconductors are strategic materials for the fabrication of magnetic shields, and within this class, MgB has been proven to be a very promising option. However, a successful approach to produce devices with high shielding ability also requires the availability of suitable simulation tools guiding the optimization process. In this paper, we report on a 3D numerical model based on a vector potential (A)-formulation, exploited to investigate the properties of superconducting (SC) shielding structures with cylindrical symmetry and an aspect ratio of height to diameter approaching one. To this aim, we first explored the viability of this model by solving a benchmark problem and comparing the computation outputs with those obtained with the most used approach based on the H-formulation. This comparison evidenced the full agreement of the computation outcomes as well as the much better performance of the model based on the A-formulation in terms of computation time. Relying on this result, the latter model was exploited to predict the shielding properties of open and single capped MgB tubes with and without the superimposition of a ferromagnetic (FM) shield. This investigation highlighted that the addition of the FM shell is very efficient in increasing the shielding factors of the SC screen when the applied magnetic field is tilted with respect to the shield axis. This effect is already significant at low tilt angles and allows compensating the strong decrease in the shielding ability that affects the short tubular SC screens when the external field is applied out of their axis.

Effect of Grain Boundaries’ Doping on the Mechanical Properties of Nitrogen-Doped Bicrystalline Graphene

Grain boundaries and doping play an important role in influencing the mechanical behaviour of materials. In this article, Tersoff potential based molecular dynamics simulations were employed to comprehensively investigate the effect of random N doping on the mechanical behaviour of pristine and bicrystalline graphene nanosheets. For bicrystalline nanosheets, three types of grain boundaries with high, transition and low tilt angles, were considered here. Each grain boundary model was doped as a whole nanosheet, only grain boundary area, and/or non-grain boundary area. Our results show that the configurations with doping of grain boundary area showed more deterioration in failure stress and failure strain values than the configurations with doping of the non-grain boundary area. Also, N doped pristine nanosheets and the configurations with non-grain boundary area doping showed a monotonic increase in Young's modulus while a monotonic decreasing-increasing trend was predicted for the rest of the configurations. These results show that the doping of the grain boundary area is more detrimental to the mechanical properties than the doping of the non-grain boundary area. Moreover, even after N doping, the high angle grain boundaries show higher strength as compared to the low angle grain boundaries.

Efficiency enhancement in Archimedes screw turbine by varying different input parameters – An experimental study

Archimedes screw is one of the biggest innovations that the human mankind has ever experienced. From the day of its innovation AST has upgraded the lives of the people. Various studies have been done considering various parameters and the results shows that the maximum efficiency is recorded in between 20 and 25 degrees, but the accurate angle hasn’t been shown in any of the study. The experimentation study reveals that the maximum efficiency of 74.27% is recorded at 22 degrees with flow rate of 1 l/s and load of 0.9 kg. Maximum output power of 0.00577 kW was recorded at load 0.9 kg and Flow rate 4 l/s at 25-degree tilt angle. maximum speed of 141 RPM was recorded at load 0.5 kg at Tilt angle of 25 degree and at 4 l/s of flow rate. The results show the feasibility of AST to be installed at low head sites at low tilt angle and at heavy loads.

Optimal Design Strategy of a Solar Reflector Combining Photovoltaic Panels to Improve Electricity Output: A Case Study in Calgary, Canada

This study explores the combination of photovoltaic (PV) panels with a reflector mounted on a building to improve electricity generation. Globally, PV panels have been widely used as a renewable energy technology. In order to obtain more solar irradiance and improve electricity output, this study presents an advanced strategy of a reflector combining PV panels mounted on a building in Calgary, Canada. Based on an experimental database of solar irradiances, the simulation presents an optimal shape designed and tilt angles of the reflector and consequently improves solar radiation gain and electricity outputs. Polished aluminum is selected as the reflector material, and the shape and angle are designed to minimize the interruption of direct solar radiation. The numerical approach demonstrates the improvement in performance using a PV panel tilted at 30°, 45°, 60°, and 75° and a reflector, tilted at 15.5° or allowed to be tilted flexibly. A reflector tilted at 15.5° can improve solar radiation gains, of the panel, by nearly 5.5–9.2% at lower tilt angles and 14.1–21.1% at higher tilt angles. Furthermore, the flexibly adjusted reflector can improve solar radiation gains on the PV panel, by nearly 12–15.6% at lower tilt angles and 20–26.5% at higher tilt angles. A reflector tilted at 15.5° improves the panel’s output electricity on average by 4–8% with the PV panel tilted at 30° and 45° respectively and 12–19% with the PV panel tilted at 60° and 75°, annually. Moreover, a reflector that can be flexibly tilted improves electricity output on average by 9–12% with the PV panel tilted at 30° and 45° and 17–23% with the PV panel tilted at 60° and 75°. Therefore, the utilization of a reflector improves the performance of the PV panel while incurring a relatively low cost.

Ground states of two-dimensional tilted dipolar bosons with density-induced hopping

Motivated by recent experiments with ultracold magnetic atoms trapped in optical lattices where the orientation of atomic dipoles can be fully controlled by external fields, we study, by means of quantum Monte Carlo, the ground-state properties of dipolar bosons trapped in a two-dimensional lattice with density-induced hopping and where the dipoles are tilted along the $xz$ plane. We present ground-state phase diagrams of the above system at different tilt angles. We find that as the dipolar interaction increases, the superfluid phase at half-filling factor is destroyed in favor of either a checkerboard or stripe solid phase for tilt angle $\ensuremath{\theta}\ensuremath{\lesssim}{30}^{\ensuremath{\circ}}$ or $\ensuremath{\theta}\ensuremath{\gtrsim}{30}^{\ensuremath{\circ}}$, respectively. More interesting physics happens at tilt angles $\ensuremath{\theta}\ensuremath{\gtrsim}{58}^{\ensuremath{\circ}}$, where we find that as the dipolar interaction strength increases, solid phases first appear at filling factor lower than 0.5. Moreover, unlike what is observed at lower tilt angles, we find that at half filling, a stripe supersolid intervenes between the superfluid and stripe solid phase.