Semi-cylindrical Shape Research Articles

Study of microchannel structures for measuring emission conductance of indium field emission electric propulsion micro-thrusters

Surface morphology of emitting tip has a significant effect on performance of Liquid-Metal Ion Sources. In this paper, fabrication technics of dynamic micro-electrochemical etching was employed to realize micro-grooves processing of emitting tip surfaces at different depths by regulating roughening time and voltage frequency. Through field emission experiments of indium Field Emission Electric Propulsion micro-thruster, we measured volt–ampere characteristic curves of a batch of emitters with different microchannel structures. By a normalization method, the effect of inconsistency of apex radius between different tips on volt–ampere characteristics was eliminated, and influence law of surface roughness on emission conductance was revealed more clearly. The test results were found to be consistent with the current–voltage characteristics which was deduced from microchannel model based on a semi-cylindrical shape. This study presents an approach for pre-estimating and optimizing the emission conductance through assessment of emitter surface roughness and substantiates the method’s viability.

Conceptual design and optimisation of a novel hybrid device for capturing offshore wind and wave energy

AbstractThe access to the offshore wind resource in the deep sea requires the development of innovative solutions which reduce the cost of energy. Novel technologies propose the hybrid combination of wind and wave energy to improve the synergy between these technologies sharing costs, such as mooring and electrical connexion. This work proposes a novel hybrid wind and wave energy system integrating a floating offshore wind turbine with three-point absorbers wave energy converters (WECs). The WECs are an integral part of the floating structure and contribute significantly to the hydrostatic and dynamic stability of the system. Their geometry is optimised considering a cylindrical, semi-cylindrical and spherical shape for the Pantelleria case study. The cylindrical shape with the largest radius and the lowest height is the optimal solution in terms of reducing structural costs and maximising the performance of the WECs. The in-house hydrostatic stability tool and the time domain model MOST are used to optimise the WECs, with a combined meta-heuristic genetic algorithm with the Kriging surrogate model and a local Nelder–Mead optimization in the final simulations. The power of the WECs is estimated with both linear and variable motor flow hydraulic PTOs to obtain a more realistic electrical power generation. Generally, the hybrid device proved to be more competitive than the floating wind turbine alone, with a LCOE reduction up to 11%. Performance of the hybrid device can be further improved when more energetic sites are considered, as the energy generated by the WECs is higher.

Impact of fibroglandular tissue distribution and breast shape in voxelized breast models for dosimetry in mammography

Objective. This work proposes to study the impact of different voxelized heterogeneous breast models (gaussian centered - GaussC; gaussian lower - GaussL; and fitted equation patient-based on 3D realistic distribution (Fedon et al 2021) - FitPB) for dosimetry in mammography compared to a well-established homogeneous approximation. Influence of breast outer shape also was investigated by comparing semicylindric and anthropomorphic breasts. Approach. By using the PENELOPE (v. 2018) + penEasy (v. 2020) MC code, simulations were performed to evaluate the normalized glandular dose (DgN) and the glandular depth dose (GDD(z)) for different breast characteristics and x-ray beam spectra. Main results. The average DgN overestimation caused by homogeneous tissue approximation was 33.0%, with the highest values attributed to GaussL and FitPB models, where fibroglandular tissue is concentrated deeper in the breast. The observed variation between anthropomorphic and semicylindrical breast shapes was, on average, 5.6%, legitimizing the latter approximation for breast dosimetry. Thicker breasts and lower energy beams resulted in larger overestimation caused by the homogeneous approach, while variations in DgN values among different heterogeneous models were higher for thinner breast and lower energy beams. Moreover, the depth where differences between GDD(z) for different breast models became maximum depends on the axial variation of fibroglandular tissue concentration between each model. The GDD(z) dependence results in a significant variation of the contribution of each breast depth to mean glandular dose (MGD) among the breast models studied. Significance. Intercomparison between different breast models for dosimetry can be useful for estimating more accurate MGD values for population-based dosimetry, for exploring the use of 1D gaussian distribution for breast dosimetry, and for understanding the dose distributions inside the fibroglandular tissues, which could be a novel source of information for risk estimations.

Experimental Study of Geometric Shape and Size of Sill Effects on the Hydraulic Performance of Sluice Gates

The present research was conducted to investigate the effect of sill geometry and sill width on the discharge coefficient and hydraulic jump characteristics. For this purpose, sills with semi-cylindrical, cylindrical, pyramidal, and rectangular cube geometries with widths of 0.075, 0.10, 0.15, and 0.2 m were installed under a sluice gate. Results showed that increasing the sill width increased the sluice gate discharge coefficient compared to the no-sill mode. The results of placing a sill with different geometric shapes under a sluice gate indicate that using a semi-cylindrical sill increases the discharge coefficient. The ranked order of other sills, from the largest to smallest discharge coefficient, is: cylindrical, pyramidal, and rectangular cubic sills, respectively. The results show that the use of a sill increases the energy dissipation. Examining sills of different widths indicates that with increasing width, the increase in velocity and consequent decrease in the depth of the hydraulic jump causes an increase in energy loss. When employing sills of maximum width (b = 0.20 m) for pyramidal, semi-cylindrical, cylindrical, and rectangular shapes, the energy loss increased by 125, 119, 116, and 125% in section A, respectively. The semi-cylindrical sill is most effective in increasing the discharge coefficient, while the pyramidal sill is most effective for increasing energy dissipation.

Optimization of a Management Algorithm for an Innovative System of Automatic Switching between Two Photovoltaic and Wind Turbine Modes for an Ecological Production of Green Energy

Today, renewable energy and energy efficiency are key to limiting global warming and preventing the dangerous effects of climate change. The biggest problem with conventional solar and wind turbine systems is the intermittency of electrical power generation. Even if these two energy sources can be complementary, the space occupied by these hybrid systems remains very important. This work proposes an improved management algorithm for a patented transformable photovoltaic-wind system, which mainly uses two flexible photovoltaic panels which are automatically deformed by an electromechanical system from the planar shape to the semi-cylindrical shape of the Savonius wind turbine blades. When weather conditions change, this system switches to eco-friendly photovoltaic (PV) or wind turbine (WT) mode, allowing a good total power generation from two solar power sources or wind turbine power. The contribution brought for this work relates to the realization and the improvement of the management algorithm to determine a better change to the mode PV or the mode WT. The operation test was simulated in 8760 hours for the year 2021. This developed algorithm allows several theoretical calculations of the power produced from solar radiation and wind speed data, thereafter the algorithm compare and determines the overall power and selects the optimal PV or WT mode. In this study, the overall power generated by the invented system produces more electricity per hour, the power Pt increases by 75.55% compared to the power Pwt, and also the power Pt increases by 68.15% compared to Pvp power.

Thermal effect on curved photovoltaic panels: Model validation and application in the Tabuk region.

This paper aimed to investigate the temperature effect on photovoltaic (PV) cell parameters. The PV cell parameters such as series and parallel resistances, diode ideality factor, and diode saturation current, are not considered in the reported stepwise modeling. The present work aims to improve available models used in the modeling and simulation of PV modules to support the researcher and power project developer. All the required temperature-dependent parameters are determined to model the simulated PV module with high accuracy using Simulink/MATLAB software. To validate the method, a 36-cell-50W solar panel with different radii of curvature is set up to assess solar power outputs under varying irradiance and temperature conditions. For the present application, the Tabuk region (Saudi Arabia) is chosen based on its location and climatic conditions. The method provided conformity to the measured power outputs for varying Global Horizontal Irradiance (GHI) and temperature conditions. The maximum power output of the PV module increases from 14.4 W to 25.8 W when the received solar power density varies from 307 W/m2 to 526 W/m2 depending on the level of curvature starting from a semi-cylindrical shape to a vaulted shape to a flat shape. The curved PV module shows slightly higher power variation with temperature as compared to the flat one. Above 25°C, the power output is about 20% less at a maximum temperature of 65°C. When the temperature drops below 25°C, the power outputs increase about 6% and 11.5% for corresponding temperatures of 15°C and 5°C, respectively.

Automatic Blade Shape Optimization of a Three-Bladed Modified Savonius Turbine

In this study, the performance of a new wind turbine design derived from a conventional Savonius turbine is optimized by numerical simulation. The new design consists of three blades without passage between them (closed center). The coupling between the CFD codes (ANSYS Fluent) and the optimizer (OPAL) is used through an automatic procedure in-house codes, as documented, for example, in Thévenin et al.’s Optimization and Computational Fluid Dynamics (2008). A single-objective function (output power coefficient, Cp) is considered as the target of the optimization technique and the shape of the blade as an optimization parameter and relies on evolutionary algorithms. An optimal solution can emerge from this optimization study. By comparison between regular design (semi-cylindrical shape blades) and the optimal configuration, a considerable improvement (up to 7.13% at λ = 0.7) of the optimal configuration performance can be obtained in this manner.

КОНСТРУКТИВНЕ РІШЕННЯ ПОКРІВЛІ У ВІЗАНТІЙСЬКИХ ХРАМАХ СЕРЕДНЬО- ТА ПІЗНЬОВІЗАНТІЙСЬКОГО ПЕРІОДІВ

In this article, based on archaeological and hagiographic sources, the features of constructive solutions (techniques of construction and use of building materials) in the temples of the capital and provincial architectural schools of the middle and late Byzantine period were studied. The author focuses on the two main types of roofs of Byzantine temples – tiles and metal plates, the technology of their construction, roof shapes, the use of certain types of building materials and the specifics of using certain types of roofs in different regions of the Byzantine Empire. Each case of application of a certain technique / building material / type of roof is illustrated by the example of archeological finds or preserved mentions in the hagiographic literature. The study found that the most common version of the roof was ceramic tile, due to the cheapness of the material. A popular type for Byzantine roofs was a tile of weakly conical semi-cylindrical, sometimes flattened, shape; trapezoidal tile provided in the design of a wedge-shaped gutter for water drainage on the outside of the tile. It was found that the process of «assembling» the roof took place by connecting the tiles from the top elements (semi-cylindrical shape with a tooth-shaped end), which were driven between the already connected two tiles. During a study of the manufacture of ceramic tiles, it was found that the process was probably similar to the production of plinths (bricks) in the same kilns; instead, the main difference was that at the time of formation, trapezoidal, flat thin frames were used (so that the tile was formed on one side wider and narrower on the other – to overlap each other), and in the drying process these frames with clay were not placed on sand, and on a wooden board. The author also considered other variations of the tile – depending on the building material and shape. Thus, it was found that the material of the tile could not be limited to ceramics: in areas of construction, where there were no resources for the manufacture of ceramic tiles, stone was made and used. The most expensive and strongest variant of a material for a tile – metal – was chosen also because it was easy in processing. Particular emphasis in the study was placed on the use of metal plates for the roof. So the most popular material for this was lead – it melted at low temperatures, easily rolled into sheets (usually rectangular, but there were exceptions). The technique of construction of a roof with lead plates was that when superimposing plates, one overlapped another, for this purpose in places of seams they were bent and rolled. Lead for Byzantine construction was found to have been mined in several regions, including the northern Balkans, Pontus, and Macedonia. It is also noted that the use of lead plates for the roof contributed to the emergence and development of various forms of the roof (for example, the capital’s architectural school preferred a wavy surface).

Modeling the optimal condition for drying rumen contents using a solar greenhouse dryer

The ruminal content is a biomass waste obtained from the benefit of cattle. This biomass can be used as a fuel for generating part of the thermal energy that is required in the slaughterhouse processes. For this purpose, the ruminal content must be subjected to several pretreatments to facilitate its use as a fuel. The combustion efficiency of the ruminal content is affected by the particle size and the size distribution, as well as the moisture content. The ruminal content has a high moisture content that must be reduced from around 60% to values below 15% (by mass) within a few days so that the conversion efficiency and heating value are not affected. To dry the rumen content, low-cost natural drying systems can be utilized. A numerical approach for the solar greenhouse dryer performance was analyzed for typical local solar irradiation and natural convection conditions, at the greenhouse site of installation. To analyze the rumen content, at variable drying temperatures ranging from 40 °C to 70 °C, a thin layer model was used. Within the temperature range evaluated, the ruminal content effective diffusivity varied from 1.6 × 10−13 to 5.6 × 10−13 m2/s. The dryer was designed as a semi-cylindrical shape with a loading capacity of about 10 000 kg. A set of ordinary differential equations was formulated for modeling and simulating the heat transfer and drying phenomena inside the greenhouse dryer. The method of finite differences was used for solving the system of equations. The estimated drying time of the ruminal content was around 6 days (d) and the final product moisture was 14.10%.

Experimental and theoretical analysis of hybrid concentrated photovoltaic/thermal system using parabolic trough collector

In the current work, a hybrid concentrated photovoltaic thermal system was designed and coupled with a parabolic trough collector and investigated theoretically and experimentally for combined heat and power output. In the design, a photovoltaic module was mounted on a flat surface of parabolic trough absorber tube having semi cylindrical shape. A provision was made to cool photovoltaic panel from both the surfaces by flowing water through the absorber tube as well as the annulus of between absorber tube and glass cover. The model was developed using first law of the thermodynamics and then validated using experimental data generated through the fabricated setup. During the experimentation, the annulus flow rate was varied from 0.008 kg/s, 0.017 kg/s and 0.025 kg/s and inner flow rate was varied from 0.075 kg/s, 0.083 kg/s and 0.091 kg/s. The field testing results showed the mean overall efficiency of system obtained as 61.42%, 64.61% and 66.36% for inner tube flow rate of 0.075 kg/s, 0.083 kg/s and 0.091 kg/s respectively for annulus flow rate of 0.008 kg/s. The theoretical results of hybrid system obtained from the simulation are in good agreement with the experimental data. In the end environmental cost analysis was also carried out for the proposed system.

Simulation Analysis of Combined Flow over and under Semi-Cylindrical Structure

Combined flow over and under structure may solve the problem of the deposit of suspension materials in channels. Semi-cylindrical shape reduces the curvature of streamlines which reflected on its performance. To study how this shape performs, experimental and simulation has been done. The laboratory models were of four different diameters and four different gate openings. The same physical structures have been modeled in commercial software, FLOW-3D®, by employing RNG k- ε turbulence model. The verification has been based on measured flow profile and discharge. Simulation outputs indicate that a separation zone located at a distance from the structure became farther when the diameter and gate opening decreases, also the separation portions and their thickness are related to the incoming discharge. The location height of separation zone tends to be lower when there is an increase in flow discharge and it is located at half the total depth when two flow portions are equal. The weir flow in this system shows a better performance than traditional weir by at least 33%, while the gate out flow is less than free flow of the same total head by 70% to 90%. Within the limitation of this work, two mathematical models for predicting discharge coefficient have been proposed for the weir and gate respectively, moreover a model for predicting relative discharge of weir to gate, and one mathematical model for the dimensionless total discharge.

Separation Efficiency of Mixtures by Distillation using Structured Noncircular Packings

The paper presents experimental results on separation of a binary mixture in distillation columns with semi-cylindrical and square shapes of cross-section. The cross-sectional areas of non-cylindrical columns are close to area of a round column with the diameter of 0.6 m. The structured package with corrugation angles of 45° and 60° and specific area of 500 m2/m3 was studied. Pressure drop on the packings with non-cylindrical cross-section before loading point is almost the same as for a round column. HETP at low vapor loads of the column does not depend on the shape of the columns cross-section. At high vapor loads, HETP for the structured packings in square and semi-cylindrical columns increases by 20–30% as compared to the round column. The main regularities in terms of the influence of the liquid and vapor flows, other operating parameters obtained for round column, are also valid for columns with noncircular geometry.

Proposal of Design Method of Light-Entering Face of LED Backlight to Improve Luminance Distribution

In this study, We studied design method to reduce scattering reflection by adding a three - dimensional structure to light guide plate of LED backlight widely used in small and portable devices. In order to improve the efficiency of the light-incident part, a three-dimensional structure is used in which a repetitive structure of a prism shape and a semi-cylindrical shape is repeatedly added to the light-entering face in light-guide plate. As a result of the study, it was found that uniform luminance values were obtained in the light-incident portion and the backlight when a repetitive pattern of a semi-cylindrical shape was added as compared with a case in which a prism shape was added. Particularly, when a rectangular lens with a semi-cylindrical shape is added, the average value of the total luminance is increased by about 15% from 7278 lm to 8324 lm as compared with a general light guide plate.

An Angular Displacement Sensor With a Curved Two-Metal-Layer CPW Loaded by an EBG Structure

This paper presents a microwave angular displacement sensor that consists of a curved two-metal-layer coplanar waveguide (TML CPW) loaded by an electromagnetic bandgap structure (two semi-cylindrical periodic air-gap structures of dielectrics, allocated at the top and bottom of the curved TML CPW). Rotating one of the dielectrics against the other one, produces a variation in the depth of the stopband at the central frequency. The magnitude change is proportional to the angle of the rotation. The curved TML CPW line with the length of 140 mm is fabricated on a $254~\mu \text{m}$ thick RO3010 Rogers substrate ( $\varepsilon _{r} = 10.2$ and $\tan \delta = 0.0022$ ), which is arched in a semi-cylindrical shape with a radius of 50 mm. The periodic air-gap structures, in order to create the electromagnetic bandgap, are manufactured by laser cutting of an optically transparent polycarbonate ( $\varepsilon _{r} = 2.8$ and $\tan \delta =0.01$ ) in semi-cylindrical shapes. The analysis, finite element method simulation, realization, and measurements have been performed for the sensor with 15 unit cells. An average sensitivity and a dynamic range of about 3 dB/deg and 5° degrees, respectively, have been obtained at 10.2 GHz. The fixed operating frequency and the wide bandwidth of the sensor (>1 GHz) will simplify the design and fabrication of the data readout circuit. The impact of the structure curvature on the sensor response is also investigated as an important practical issue.

IRRADIATOR SYSTEM FOR MANGANESE SULFATE BATH EFFICIENCY MEASUREMENTS USING A PLUTONIUM-BERYLLIUM NEUTRON SOURCE.

This study describes the use of a neutron irradiator system based on a plutonium-beryllium neutron source for MnSO4 solution activation for use to determine the MSB system efficiency. Computational simulations using Monte Carlo code were performed to establish the main characteristics of the irradiator system. Among the simulated geometries and volumes, semi-cylindrical shape with 84.5 cm3 of MnSO4 solution yielded the best option to be built. Activity measurements were performed with a high-pure germanium detector to validate the new irradiation system. Results showed an average efficiency and uncertainty of the experimental standard deviation of the mean: 5.742 × 10-4 ± 0.036 × 10-4 (coverage factor k = 1), for MSB system. Efficiency value obtained shows good correlation to other published methods (i.e. a relative difference of 0.07%). This alternative metrological method demonstrated the utility of neutron sources for the irradiation of solutions in metrology laboratories providing a cost-efficient alternative to nuclear reactors or particle accelerators.

Влияние положения локального источника объемного тепловыделения полуцилиндрической формы на теплообмен внутри замкнутого контура

Влияние положения локального источника объемного тепловыделения полуцилиндрической формы на теплообмен внутри замкнутого контура

Numerical model of an inflatable solar collector

ABSTRACTThe main objective of this paper is to present a mathematical model to simulate the operation of an inflatable solar air heat collector for grain dryers. The solar collector exhibits a semicylindrical shape when air is injected into the confined space between the walls of the two covers. The mathematical model of the collector is obtained by applying the law of conservation of energy on the four main parts of the collector, absorber plate, two covers, and air that flows inside the equipment. To improve the accuracy of the model, the solar collector was divided into N control volumes, with each one containing the four parts, in such a way that one system with 4N differential equations is obtained. The unknown quantities of this system are the temperatures of the absorber plate, air, and walls of both covers in each control volume. The results allow us to conclude that the collector performance strongly depends on several entrance variables of the model (the air flow and air temperature at the collector entrance) and geometric equipment parameters (the collector length, internal radiation at the inner surface of the cover, and space between both covers). Therefore, the model can be used for optimizing the solar collector.

Low profile superstrate using transformation optics for semicircular radiation pattern of antenna

In this article, a dielectric superstrate inspired from transformation optics is presented. When placed over a patch antenna, this superstrate increases the half power beam width (HPBW) of a classical patch antenna. An appropriate spatial transformation relation with spatial compression and refractive index shift factors has been used to derive an expression for a dielectric material profile. The wave front exiting from the transformed space is optimized for a semicylindrical shape. Then, a discretized version of this profile has been used to design a cuboidal superstrate. Full wave simulations have been presented that essentially show a superstrate device capable of producing a 297° of HPBW in H-plane with a peak directivity of 3.2 dBi at the design frequency. The derived solution can be realized using the standard dielectric materials for real-world applications.

Burrowing habits of two Arthropods; Odenthobutus doriae and Hemilepistus schirasi in desert of Isfahan, Iran

Burrows of O. doriae were in slop areas with one side tumulus, having oval entrance, 12–15 mm in small diameter and 25–45 mm in large diameter with the mean length and depth of 38 and 20.5 cm. Whereas burrows of H. schirasi were approximately in flat regions with round tumulus, having circle entrance, 8–11 mm in diameter and the mean length and depth of 80 cm and 62.5 cm. burrows of O. doriae were built as a simple tunnel at 10 cm of the beginning, then followed by spherical shape, continued to end with the slope of 44 to 50 percent. but H. schirasi has tendency to dig semi cylindrical shape borrow as a tunnel with the slope of 80 to 85 percent. the excavated soil texture for O. doriae burrows was soft soil to gravel. but the tumulus structure for H. schirasi burrows consisted of perfectly regular blocks, 1.5 mm in wide and 3.5 mm in length.

Hydraulic Model of Dam Break Using Navier Stokes Equation with Arbitrary Lagrangian-Eulerian Approach

 Abstract—The liquid flow and the free surface shape during the initial stage of dam breaking are investigated. A numerical scheme is developed to predict the wave of an unsteady, incompressible viscous flow with free surface. The method involves a two dimensional finite element (2D), in a vertical plan. The Naiver-Stokes equations for conservation of momentum and mass for Newtonian fluids, continuity equation, and full nonlinear kinematic free-surface equation, were used as the governing equations. The mapping developed to solve highly deformed free surface problems common in waves formed during wave propagation, transforms the run up model from the physical domain to a computational domain with Lagrangian Eulerian (ALE) finite element modeling technique. fluid columns of semi-cylindrical and hemispherical shapes, and showed that these asymptotic are not valid close to the base, where the fluid velocity is much higher than in the rest of the column. The numerical solution for free surfaces has been developed using three defined theories: 1) Lagrangian; 2) Eulerian; 3) Lagrangian-Eulerian description. For waves in particular, the Lagrangian-Eulerian is superior in terms of handling high distortion in the grids. To have a versatile description of the fluid domain, it is necessary to have a method with the benefits of both Lagrangian and Eulerian descriptions, without their deficiencies. Such a method, developed in the last two decades, is the Arbitrary Lagrangian- Eulerian formulation in which grid points may be moved with the fluid in normal Lagrangian description. This method allows the grids move independent of the fluid motion.