Big Angles Research Articles

Rational Design Dithieno[3,2-f:2',3'-h]Quinoxaline-Based Polymers with Optimized Molecular Configuration and Charge Transfer for High-Performance All-Polymer Solar Cells.

Due to poor planarity and weak intermolecular interactions of acceptor units which have two-dimensional configuration, the development of related polymers is slow. In this work, we synthesized a dithieno[3,2-f:2',3'-h]quinoxaline-based unit substituted with fluorinated thiophene, which can effectively expand the area of the acceptor unit. Then, it paired with three different benzodithiophene-based donor units, and three new polymers of PQTF-BT, PQTF-BTCl and PQTF-DTCl were obtained. PQTF-BT with thiophene side chain exhibits appropriate aggregation and crystallization performance, and the PQTF-BT:PY-IT all-polymer solar cells exhibit high device efficiency of 15.54 %. Meanwhile, PQTF-BTCl with chlorination strategy on thiophene side chain further enhances the open-circuit voltage of related devices. However, it has negative impact on the miscibility and charge transfer of the material, leading to a poor efficiency of 8.71 % in the PQTF-BTCl:PY-IT device. To reinforce miscibility, PQTF-DTCl with expanded backbone planarity was further studied. However, the big dihedral angles of the donor side chains disrupted the effective stacking of the molecules, resulting in great recovery of device performance to 13.42 %. This work provides research ideas for the design of polymers with two-dimensional configuration side chain and match selection of donor units.

Effect of Rare Earth Ce on Structure and Properties in 7CrSiMnMoV Die Steel Castings

In this study, rare earth (RE) Ce is used to modify the interaction between atoms in 7CrSiMnMoV die steel castings. The tensile properties are performed, and strengthening mechanism are analyzed by investigated fracture surface, and microstructure by optical microscopy (OM) and scanning electron microscope‐energy dispersive spectrometer (SEM‐EDS). And ab initio molecular dynamics (AIMD) is used to simulate the effect of the Ce element on the local atomic structure of the FeCeC system alloy steel. The results indicate the strength can increase from 722.55 to 1074.27 MPa, and the elongation can increase from 24.86% to 44.22% with a RE Ce concentration of 0.009%. It is attributed to that doping of Ce can inhibit the formation of network eutectic cementite, refine the lamellar spacing of pearlite, and even form granular cementite and martensite structures. AIMD simulation results show that C atoms tend to be surrounded by Fe, and the strong chemical bonds of FeC make the Fe‐centered C more stable with an increase in RE Ce concentration. And doping Ce can introduce new local topological and chemical orderings such that the FeCFe triplets predominantly form small and big angles shifting from near 75° and 136° to 47° and 81°, respectively.

Modeling the Hydraulic Fracturing Processes in Shale Formations Using a Meshless Method

Complex bedding properties and in situ stress conditions of shale formation lead to complex hydraulic fracturing morphologies. However, due to the limitations of traditional numerical methods, the simulation of hydraulic fracturing in shale formation still needs further development. Based on this, the liquid–solid interaction modes and the SPH governing equations considering liquid–solid interaction force have been introduced. The smoothing kernel function in the traditional SPH method is improved by introducing the fracture mark ξ, which can realize the simulation of rock hydraulic fracturing processes. The stress boundary of the SPH method is applied by stress mapping of “stress particles”, and the feasibility and correctness of the method are verified by two numerical examples. Then, the simulation of hydraulic fracturing processes of bedding shale formations are carried out. With the increase of horizontal stress ratio, the total number of damaged particles decreases, but the initiation and extension pressure increase gradually. The initiation stress of small bedding dip angles (θ < 45°) is larger than that of big bedding dip angles (θ > 45°). The hydraulic fracture propagation range at low horizontal stress ratio is wider and the fracture is along the direction of maximum principal stress, while the hydraulic fracture propagation range at high horizontal stress ratio is limited to the perforation. The hydraulic fracture will propagate through the bedding with small dip angles. However, when the bedding dip angle is larger, the hydraulic fracture will propagate along the bedding direction.

Numerical study of the performance for a curved double-skin façade in summer

Recently, curved double-skin façades (CDSFs) have been increasingly used in buildings due to the advantages of aesthetics and structure. However, existing studies mainly focus on planar double-skin facades (PDSFs) and barely address the thermal and ventilation performance of CDSFs. In this study, the influences of geometric parameters, glass material and solar radiation on the thermal and ventilation performance of the CDSF are studied with a CFD model validated by a reduced-scale experiment. The results show that the optimal cavity gap ranges from 0.75 m to 1 m, and the optimal ellipse aspect ratio is 0.5. Moreover, glass material shows a significant influence on the ventilation performance of the CDSF – an enhancement of 8.20%–21.31% more cavity velocity is found by replacing the clear glass with a low-e glass. Further analysis shows that the ventilation performance is more sensitive to the optical properties of glass material, and a higher absorptivity is more conducive to natural ventilation. Solar radiation – solar radiation intensities and solar incident angles - show predominant impacts on the cavity velocities of CDSFs with non-linear relationships. Because of the surface's non-uniformity distribution of solar radiation, solar radiation shows more impact on the cavity velocities of CDSFs than PDSFs. The influence of solar incident angles is found to be more sensitive, especially in the regions of big solar incident angles - the variation rates of cavity velocities for the CDSF under high solar incident angles (>45°) are much larger than that under low solar incident angles (<45°).

Методика розрахунку несучої здатності сонячних панелей як елемента забезпечення енергоефективності будівель

Extensive use of solar panels for providing low-rise buildings with electricity has led to the development of methods for assessing the load-bearing capacity of solar panels, taking into account the size of the panel, the angle of inclination to the horizon and climatic loads in a given geographical area. The solar panels are calculated as plates hinged along the contour. Self-weight loads of the panel, snow, wind and ice loads are determined according to DBN B.1.2-2: 2006 "Loads and impacts" and are reduced to a component that is normal to the plane of the panel. Working formulas were obtained for determining the extreme and operational design values of loads, checking the strength and deflection of panels, as well as the maximum allowable spans according to the criteria of strength and structural rigidity. An example of calculation of solar panels placed at angles of inclination to the horizon from 15° to 75° on the roof of a building in Kropyvnytskyi were performed. Strength checks should be performed on combinations of panel self-weight, snow and maximum wind pressure. Deflection check at small angles of panels inclination is carried out taking into account the same combination of loads, and at big angles of inclination - taking into account only ice load. In all cases, the condition of rigidity is decisive. Permissible span L (smaller size) of a solar panel with 3 mm tempered glass sheathing in the conditions of Kropyvnytskyi varies from 0.68 m to 1.36 m. It increases as the angle of inclination increases and as the B/L ratio approaches to 1. The allowable span varies by 13…16% with length ratio of the larger side of solar panel to the smaller one in the range from 1.4 to 2.0. This allows to take the values of the allowable span, corresponding to the ratio of the parties B/L=2.0 in order to simplify the safety margin. The obtained working formulas and their implementation in the form of a calculation sheet in Microsoft Excel allows to perform similar calculations for other source data. Further research focuses on the establishment of allowable spans of solar panels of typical design in the conditions of each of the regions of Ukraine.

Experimental study and numerical validation on the effect of inclination angle to the thermal performance of solar heat pipe photovoltaic/thermal system

Effect of inclination angle to the thermal performance of a heat pipe photovoltaic/thermal system (HP-PV/T) system was rarely reported. In the present study, a HP-PV/T system was firstly constructed in an Enthalpy Difference Laboratory, where inclination angle was experimentally managed as the only variable. Meanwhile, a comprehensive numerical model for the HP-PV/T system was developed to validate the experiments. Particularly, a 3D model for the inclined heat pipe was also firstly involved. The simulation results show that liquid film thickness within the condenser or the evaporator stabilizes at a constant value at inclining condition. The relative filmwise thermal resistance of the condenser decreases first and then increases with inclination angle; while the evaporator shows an opposite trend to the condenser. The overall thermal resistance of solar heat pipe is mainly determined by the evaporator while the evaporator is mainly determined by the effective height of the liquid pool. The experimental and simulation results both indicate that the optimum inclination angle is 40°. The proposed model agrees well with the experimental results at big inclination angles (≥20°), it is practicable to reveal the influence of inclination angle to the thermal performance of a HP-PV/T system.

Big Data, Internet Privacy and the Vulnerabilities of the African Regulatory Landscape

Social media generates massive amount of big data from users, the penetration of these platforms in Africa creates meaningful insights around customer needs and behaviour from the data. This helps to create new businesses that rebalance the technology and wealth gap in the continent. With every gigabytes of data generated brings about exploitation of customer data. Data Privacy becomes a focal point of concern. The global approaches to privacy for the users of social media platforms is still evolving but two jurisdictions have set a standard. The European General Data Protection Regulation (GDPR) and the Californian Consumer Privacy Act (CCPA) have provisions that are built on sustaining consumer consent and enabling consumers to be forgotten or have their consented data deleted at their own request. More so the exponential growth of the internet in Africa highlights the explosion of big data and there is a need to study its regulatory approaches in relation to the global best practices symbolized by the GDPR and the CCPA. The Paper reviews the African regulatory landscape and its approach to Big Data and possible vulnerable angles that exposes data of Africans on these social media platforms. It is clear that in spite of a continental treaty and a reasonable number of African countries with Data Privacy laws, these laws are in most of the countries either not built on strong legal grounds or lack an independent enforcement mechanism. Therefore the African approach leaves a lot of open issues and there is a need for a continental consensus on the best approach that will push through national legislations crept on a unifying continental model. Keywords : Big Data, Privacy, Regulatory, Social Media, Data analytics, Guidelines, rights DOI: 10.7176/EJBM/12-17-14 Publication date: June 30th 2020

WTLS iterative algorithm of 3D similarity coordinate transformation based on Gibbs vectors

The 3D similarity coordinate transformation is fundamental and frequently encountered in many areas of work such as geodesy, engineering surveying, LIDAR, terrestrial laser scanning, photogrammetry, machine vision, etc. The algorithms of 3D similarity transformation are divided into two categories. One is a closed-form algorithm that is straightforward and fast. However, it cannot provide the accuracy information for the transformation parameters. The other category of algorithm is iterative, and this can offer the accuracy information for the transformation parameters. However, the latter usually needs a good initial value of the unknown. Considering the accuracy information for transformation parameters is essential or indispensable from the viewpoint of uncertainty, this contribution proposes a weighted total least squares (WTLS) iterative algorithm of the 3D similarity coordinate transformation based on Gibbs vectors. It is fast in terms of fewer iterations, reliable and does not need good initial values of transformation parameters. Two cases including the registration of LIDAR points with big rotation angles and a geodetic datum transformation with small rotation angles are demonstrated to validate the new algorithm.

STRUCTURAL MODEL OF VISUAL PERCEPTION IN SPECTACULAR HALLS AND CONSTRUCTIONS

In work the structural model of visual perception in spectacular halls and constructions is proposed. By means of the analysis of scientific and standard literature on design of spectacular halls and constructions elements of structure and communication between them are determined. The structural model in fact is the oriented graph in space of concepts. In total the graph contains 21 tops and 24 edges.The top the column "Hall Function or Constructions" defines features of functional process, the sizes of the minimum subject of observation, the observation subject sizes, its form and mobility. Features of functional process influence limit approach of the observer to subject to observation, as well as a cone of clear vision which in turn is defined by the angles of clear vision.Limit removal of the observer from subject to observation is influenced by the sizes of the minimum subject of observation (for example, a soccer characteristic of the technical equipment (for example, the projector at cinema), and the appointed separate corner which purpose cause a separate corner, the observation subject sizes, its form and mobility.Removal of the observer concerning a perpendicular to subject to observation in its geometrical center defines the angles of vision and coverage, which influence distortion of a form of a subject to observation, habitual for the observer. At the big angles of vision the form can be distorted to unrecognizability (the human brain cannot correct it any more).Limit removal and approach, the angles of vision and coverage and also brightness and color of a subject to observation, background on which it is visible, a condition of air between subject to observation and the observer (smoke, fog, a rain, snow), possibility of a human brain to a certain limit to correct distortion of a form of a subject to observation directly influence visual perception.

Facile structure-modification of xanthenone based OLED emitters exhibiting both aggregation induced emission enhancement and thermally activated delayed fluorescence

Four new donor-acceptor compounds were designed, synthesized and investigated by theoretical and experimental approaches aiming to estimate effect of the structure of a donor on the properties of potential OLED emitters. Because of the different electron-donating abilities of the nitrogen-containing heterocycles, derivatives of xanthenone containing di-tert-butyl-carbazolyl, di-tert-butyl-acridanyl, di-tert-butyl-phenothiazinyl and penoxazinyl moieties exhibited different photophysical behavior. Because of big dihedral angles between the donors and acceptor as well as because of possibility of rotation around N–C bond, the designed compounds were characterized by thermally activated delayed fluorescence and aggregation induced emission enhancement effect. Twice higher photoluminesce quantum yields reaching 38% in doped films were obtained for compounds containing di-tert-butyl-carbazolyl and di-tert-butyl-acridanyl moieties as compared to those observed for compounds with the donors containing S and O heteroatoms. Strong effect of the donor substituents on charge injection (ionization potentials were in the range of 5.67–5.96 eV) and charge-transporting properties (hole and electron mobilities were in a wide range from 6.3 × 10−8 to 6.3 × 10−4 cm2V−1s−1 at electric field of 2.5 × 105 V cm−1) was detected. The differently substituted compounds were utilized as emitters in OLEDs. Higher maximum values of external quantum efficiency (up to 3.5%) were observed for OLEDs based on emitters with nitrogen containing donors relative to estimated for OLEDs based on emitters containing di-tert-butyl-phenothiazinyl and penoxazinyl moieties.

Iterative solution of Helmert transformation based on a unit dual quaternion

The rigid motion involving both rotation and translation in the 3D space can be simultaneously described by a unit dual quaternion. Considering this excellent property, the paper constructs the Helmert transformation (seven-parameter similarity transformation) model based on a unit dual quaternion and then presents a rigid iterative algorithm of Helmert transformation using a unit dual quaternion. Because of the singularity of the coefficient matrix of the normal equation, the nine parameter (including one scale factor and eight parameters of a dual quaternion) Helmert transformation model is reduced into five parameter (including one scale factor and four parameters of a unit quaternion which can represent the rotation matrix) Helmert transformation one. Besides, a good start estimate of parameter is required for the iterative algorithm, hence another algorithm employed to compute the initial value of parameter is put forward. The numerical experiments involving a case of small rotation angles i.e. geodetic coordinate transformation and a case of big rotation angles i.e. the registration of LIDAR points are studied. The results show the presented algorithms in this paper are correct and valid for the two cases, disregarding the rotation angles are big or small. And the accuracy of computed parameter is comparable to the classic Procrustes algorithm from Grafarend and Awange (J Geod 77:66–76, 2003), the orthonormal matrix algorithm from Zeng (Earth Planets Space 67:105, 2015), and the algorithm from Wang et al. (J Photogramm Remote Sens 94:63–69, 2014).

All-dielectric metasurfaces for circularly polarized beam-splitters with high conversion efficiency and broad bandwidth

Metasurface can arbitrarily control the polarization states of incident light and has attracted signicant attention. However, the transmission eciency of cross-polarization conversion of transmissive type metallic metasurfaces for polarized beam-splitters reported to date are low, especially the transmission eciency of cross-polarization conversion by single-layer metallic metasurfaces has a low theoretical upper limit of 25%, whose low value severely works against the application requirements. In this work, we propose two beam-splitters based on single-layer anomalous silicon metasurfaces, which can realize high conversion eciency and broad bandwidth wavefront control. A broadband half-wave plate and the high-eciency beam splitting of quarter-wave plate with circularly polarization beam are both achieved. Moreover, with big incident angles, the metasurface still maintains high-eciency performance.

Solving power transmission line routing problem using improved genetic and artificial bee colony algorithms

In engineering studies, finding the best route from a start point to an end point on pixel-based weighted maps is a big problem for researchers. For this problem many methods and algorithms have been developed until now. The “cost distance” (CD) and “cost path” (CP) tools that are used by a modified Dijkstra’s algorithm and used by Environmental Systems Research Institute’s (ESRI) ArcGIS Desktop 10 software are very fast and most preferred solutions for route optimization problems. Despite the advantages of these tools, they have the disadvantage of making a lot of curves with big angles. Especially in some engineering studies like power transmission lines’ routing, the angle of the curves of the lines should not have big values. For overcoming this problem both genetic algorithm (GA) and artificial bee colony (ABC) algorithm that have been improved and adapted for the problem were used as powerful optimizers to find the best routes with fewer curves in those kinds of optimum route problems. New functions like smart direction sensing and improved random functions were developed for application of GA and ABC algorithms in power transmission lines routing studies. This study showed that the ABC algorithm’s performance is better than GA. The accuracy of the algorithms was proven by comparing the results with the CD–CP tools’ results. The experimental results showed that the improved algorithms gave better performance than Dijkstra’s algorithm.

Method of the Determination of Exterior Orientation of Sensors in Hilbert Type Space.

The following article presents a new isometric transformation algorithm based on the transformation in the newly normed Hilbert type space. The presented method is based on so-called virtual translations, already known in advance, of two relative oblique orthogonal coordinate systems—interior and exterior orientation of sensors—to a common, known in both systems, point. Each of the systems is translated along its axis (the systems have common origins) and at the same time the angular relative orientation of both coordinate systems is constant. The translation of both coordinate systems is defined by the spatial norm determining the length of vectors in the new Hilbert type space. As such, the displacement of two relative oblique orthogonal systems is reduced to zero. This makes it possible to directly calculate the rotation matrix of the sensor. The next and final step is the return translation of the system along an already known track. The method can be used for big rotation angles. The method was verified in laboratory conditions for the test data set and measurement data (field data). The accuracy of the results in the laboratory test is on the level of 10−6 of the input data. This confirmed the correctness of the assumed calculation method. The method is a further development of the author’s 2017 Total Free Station (TFS) transformation to several centroids in Hilbert type space. This is the reason why the method is called Multi-Centroid Isometric Transformation—MCIT. MCIT is very fast and enables, by reducing to zero the translation of two relative oblique orthogonal coordinate systems, direct calculation of the exterior orientation of the sensors.

Nonlinear Multi-Frequency Dynamics of Wind Turbine Components with a Single-Mesh Helical Gear Train

A complex nonlinear model for a single-mesh helical gear train is developed by including a time-varying mesh stiffness, axial vibrations, torsional vibrations, shaft and bearing damping, generator back EMF (Electromotive Force) and gear backlashes. With the help of a time series and Fast Fourier Transform (FFT) frequency spectrum, the effects of these nonlinear terms on the wind turbine and generator rotational speeds are studied under different excitation conditions by numerically integrating the associated equations using the RK4 algorithm. Results show that for lightly damped oscillations, an extra harmonic is induced in the generator dynamics due to contributions from internal excitations. However, this extra vibration can be suppressed at higher damping. Big helical angles will generally induce heavy nonlinear vibrations in the turbine and generator; a smaller mesh frequency will induce extra noise in the generator; and the external excitation due to wind gust has a greater influence on the nonlinearity of the wind turbine dynamics as compared to the internal excitations due to static transmission errors, time-varying mesh stiffness and the generator back EMF.

Doppler spectrum simulation of nonlinear ocean covered by oil film

In recent years, marine oil spill has become an important disaster for marine environment. Marine oil spill quantity is an important indicator for evaluating the threat of oil spill. This paper focuses on the Doppler spectrum of one-dimensional (1D) nonlinear ocean covered by oil film. Oil film damps the capillary wave of the ocean, which leads to a smooth profile of the ocean covered by the film. The paper is devoted to the detailed analysis of the electromagnetic magnetic wave scattering from a sea that is covered with oil. More precisely, it focuses on the case of homogeneous oil slicks. This allows better detection of oil spills, as well as possibly an estimation of the amount of oil spilled, as the scattering coefficient depends on the layer thickness. The 1D Creamer nonlinear ocean is proposed based on the PM spectra. The Marangoni damping effect is considered for modeling the contaminated rough ocean surface. First, the influence of oil film on the ocean surface spectrum and geometrical structure are examined briefly in the present study. On this basis, the influence of oil film on the Doppler spectrum signature (in L-band) of the backscattered echo of the clean and contaminated rough ocean are studied in detail based on the iterative physical optics. The results of the Doppler spectrum signature including Doppler shift and spectral bandwidth of the backscattered echo from Creamer nonlinear ocean surface are different from those of the linear ocean surface especially at the big and moderate incident angles, which shows that it is necessary to adopt the Creamer nonlinear model in the paper. The simulation results show that the Doppler spectrum signatures including Doppler shift and spectral bandwidth of the echo from ocean covered by oil film are significantly affected by sea slicks. The influence of some important parameters, such as wind speed, oil-damping values and incident angles on Doppler spectrum signature is investigated and discussed in detail. Moreover, simulation results indicate that the Doppler spectrum signature is a promising technique for the remote sensing of oil films floating on sea surfaces.

Research on High Density Water-Based Drilling Fluid of Complete Tectonic for the Southern Edge of the Junggar Basin

The southern edge of the Junggar basin in China has great potential for oil and gas exploitation. However, during drilling in this area, many borehole problems occurred, which leads to low rate of penetration and long drilling cycle. The main reasons from the geological aspect was that this area was affected by tectonic process, which leaded to development of complete tectonic, formation nappe along fault, big dip angles and poor stability. The Formation E2-3a was dominated by mudstone which was sensitive to water and can easily cause shale hydration expansion and dispersal. The instability of the formation is one of the major causes of borehole collapse and tight hole shrinkage. In order to improve the drilling speed and accelerate the process of exploration of southern edge in Juggar basin, the drilling fluids used in this region are studied based on data of geology and drilling data in this paper, Based on the characteristics of the formation E2-3a, a new high density PRT-organic salt drilling fluid is selected by conducting a large number of laboratory tests. Test results of the inhibitory, sealing and stain resistance of this fluid indicates that it could satisfy the drilling requirement in southern edge of the Junggar basin. And field applications also turned out to be positive, the drilling speed was increased by 22% and drilling cycle was reduced by 4 days.

High-Efficiency All-Dielectric Metasurfaces for Broadband Polarization Conversion

We have presented two polarization convertors based on amorphous silicon metasurfaces. Results show that the cross-polarized transmission of the first polarization convertor is over 90% with over 95% polarization conversion efficiency across the 300-nm bandwidth and maintains high-efficiency performance with big incident angles in this bandwidth. To steer cross-polarized light with an angle according to the generalized Snell’s law, we have created another polarization convertor by choosing several resonators with different geometries in one supercell, achieving full 2π phase control, guiding the co-polarized and cross-polarized transmitted light spatially separated efficiently with broadband operation.

Transmission electron microscopical study of teenage crown dentin on the nanometer scale

This is the first transmission electron microscopic study of teenage crown dentin on the nanometer scale. Samples for TEM were prepared by mechanical thinning and chemical polishing that allowed obtaining the electron transparent foils. It was firstly shown that human dentin possesses the layered morphology: the layers are oriented normally to the main axis of a tooth and have the thickness of ~50nm. HA inorganic phase of teenage crown dentin is in the amorphous state. The cellular structure, which was formed from collagen fibers (diameter is ~5nm), are observed near DEJ region in teenage dentin, whereas bioorganic phase of teenage crown dentin near the pulp camera does not contain the collagen fibers. Cracks in dentin thin foils have sharp tips, but big angles of opening (~30°) with plastic zone ahead crack tip. It means that young crown human dentin exhibits ductile or viscous-elastic fracture behavior on the nanometer scale.

Generalized total least squares prediction algorithm for universal 3D similarity transformation

Three–dimensional (3D) similarity datum transformation is extensively applied to transform coordinates from GNSS-based datum to a local coordinate system. Recently, some total least squares (TLS) algorithms have been successfully developed to solve the universal 3D similarity transformation problem (probably with big rotation angles and an arbitrary scale ratio). However, their procedures of the parameter estimation and new point (non-common point) transformation were implemented separately, and the statistical correlation which often exists between the common and new points in the original coordinate system was not considered. In this contribution, a generalized total least squares prediction (GTLSP) algorithm, which implements the parameter estimation and new point transformation synthetically, is proposed. All of the random errors in the original and target coordinates, and their variance–covariance information will be considered. The 3D transformation model in this case is abstracted as a kind of generalized errors–in–variables (EIV) model and the equation for new point transformation is incorporated into the functional model as well. Then the iterative solution is derived based on the Gauss–Newton approach of nonlinear least squares. The performance of GTLSP algorithm is verified in terms of a simulated experiment, and the results show that GTLSP algorithm can improve the statistical accuracy of the transformed coordinates compared with the existing TLS algorithms for 3D similarity transformation.