Tilt Angle Dependence Research Articles

Influence of chalcopyrite nanoplatelets on nematic phases of bend-shaped dimeric molecules: Phase diagram, birefringence, and reorientation transition

We investigated the influence of chalcopyrite (CuFeS2) nanoplatelets on the ordering of uniform and twist-bend nematic phases of achiral bend-shaped dimers, employing polarized optical microscopy, optical and electro-optical measurements. Specifically, aliphatic amine surface-functionalized hydrophobic chalcopyrite nanoplatelets were synthesized and characterized by XRD, TEM, and IR-vis-UV spectroscopy. Nanocomposites of the liquid crystal compound 1”,9”-bis(4-cyanobiphenyl-4'-yl)nonane (CB9CB) with the nanoplatelets were prepared. The study encompasses an assessment of the thermodynamic stability of the nanocomposites, constructing the corresponding phase diagram as a function of temperature and nanoplatelet mass fraction. Large phase temperature shifts were observed for minute mass fractions of NPs. Birefringence measurements were performed to investigate the orientational order parameter and the conical tilt angle's dependence on the mass fraction of the nanoplatelets and the temperature. Additionally, we measured a Fréedericksz-like reorientation transition voltage threshold and switching times as functions of the mass fraction and temperature. A huge increase of the voltage threshold was measured in the twist-bend nematic phase. The dependence of the viscoelastic coefficient ζ on NPls' mass fraction was investigated. The splay elastic constant of the helicoidal structure was estimated, using a coarse grain approximation, to be two orders of magnitude higher than in the uniform nematic phase. Finally, in the twist-bend nematic phase, the impact of temperature and nanoplatelets mass fraction on the hysteresis loop of the reorientation transition was investigated.

Thermodynamic model for electro-optical properties of antiferroelectric phase in mesogen W-330-3 and W-331-3

ABSTRACT A thermodynamic model developed by our group has been employed to explore the electro-optical properties of the chiral antiferroelectric smectic C (Sm C A ∗ ) phase. In the present study, the temperature dependence of tilt angle and spontaneous polarization of binary ferroelectric mixtures represented as W-330-3 and W-331-3 exhibiting ferroelectric Sm C* and antiferroelectric Sm C A ∗ phase has been investigated. Within the framework of this model, the free-energy density characterizing the system featuring the Sm C A ∗ phase is expressed as a series expansion that incorporates all pertinent degrees of freedom: tensor orientational order Q ij , scalar smectic order ψ, polarization vector P, wave vector q of the helix and the resulting coupling terms between these order parameters. The values of Landau coefficients featured in the expansion series are derived from experimental data (tilt angle and spontaneous polarization) of W-330-3 and W-331-3. A substantial agreement between the theoretical predictions and experimental observations has been found.

Optimal Design of Tilted Building Envelope Considering Air Conditioning Energy Demand, Daylight Utilization and Glare Protection—Case Study

An important energy-saving method to optimize building envelope design is the integration of local climate characteristics. This study attempts to find sloped facade configurations to balance air conditioning energy demand and daylight utilization for four directions in an area with a hot climate. Tilt angle dependence of the air conditioning energy demand, useful daylight illuminance (UDI) and daylight glare index (DGI) are selected to investigate the acceptance thresholds of the tilt angle. The final facade’s configuration is achieved by employing the graphical optimization method. An acceptable solution that balances better daylight performance and less energy consumption by air conditioning is developed. Due to the considered city being located in a low-latitude area with great daylight availability as well as a fully dimmable light control strategy, unbearable glare reduction can be achieved by benefiting from the sloped facades, without necessarily sacrificing much usable daylight. Meanwhile, there is no obvious increase in the demand for lighting energy consumption, and a good outward view is preserved. The sloped rather than vertical facade provides natural solar shading to the east-, south- and west-oriented windows while allowing low-angle winter solar heat to warm the building space. Tilt angles between 35°and 40° are preferred for the east facade, and smaller tilt angles of between 30°and 35° are recommended for the south facade. Larger tilt angles of between 40°and 45° are preferred for the west facade. However, the north-facing facade’s outward tilt would cause an undesirable increase in air conditioning energy demand. The annual air conditioning energy demand of the east-, south- and west-facing space is found to separately decrease by 7.1%, 7.3% and 9.9%, respectively, benefiting from the sloped facades.

Thermodynamic model to study the structural and electro-optical properties of chiral antiferroelectric smectic C phase exhibited by mesogenic homologous series 3FnHBM6(s) and W-316 mixture

ABSTRACT Using a thermodynamic model developed by us to study the structural and electro-optical properties of Sm C A ∗ phase, we investigate the temperature dependence of helical pitch, tilt angle and spontaneous polarization of a homologous series of fluorinated biphenyl benzoate esters (3FnHBM6, n = 2, 5, 7) and one of the series W-316-3 obtained from the mixture of two chiral liquid crystalline compounds 6F2OBi and 3F6HBM6. The free-energy density of the system exhibiting Sm C A ∗ phase is written as an expansion series in terms of all the relevant degrees of freedom: Q i j , ψ, P, q and the resulting coupling terms between these order parameters. The values of Landau coefficients are determined from the experimental data of antiferroelectric mesogens 3FnHBM6 (n = 2, 5, 7) and W-316-3 in the Sm C A ∗ phase. Using these coefficients, the electro-optical and structural properties have been studied. We have found good agreements between the theoretical and experimental results.

Evaluation of direct beam energy received by convex solar collectors and their optimal orientations

We use analytical and numerical methods to evaluate the daily beam energy received by some convex surfaces. Spherical, hemispherical, cylindrical, and semi-cylindrical convex surfaces with arbitrary tilt angles have been investigated and compared with a flat surface of unit area. Diffusive irradiations (sky and ground) were not considered. For hemispherical and semi-cylindrical surfaces, the optimal orientations at which the received beam energy is maximal were obtained for each day of the year. The dependence of the optimal tilt angle on the day of the year is qualitatively the same as for the flat surface. Clear sky condition has been assumed to hold in this work. It is shown that a flat surface per unit of its area receives highest beam energy among other convex surfaces whereas a sphere receives the least amount. Furthermore, the received daily beam energy per unit of the ground-occupied area has been calculated. In this case, a cylindrical surface with a range of values of radius to height ratio receives the highest amount of energy whereas a flat surface receives the least. This aspect becomes noticeable in places where there are some limits, e.g., land price or any other limitation on the available surface area.

A simulated study on the performance evaluation of amorphous silicon solar PV module for temperature, irradiance and tilt angle dependence

The performance of an amorphous silicon solar PV module is tested at various irradiance levels, operation temperatures and tilt angles using a solar simulator. Electrical efficiency, V-I characteristics and power conditioning curves are generated at various solar irradiance levels of 400, 700 and 1000 W/m2, cell operation temperature range of 40 to 100°C and various panel tilt angles of 0°, 15°, 30°, 45° and 60° with horizontal. Solar equations are used to compute the maximum swing angle of the sun away from the normal position of the panel at noon (l) during different months and latitudes. Analogy between the simulated study and l (for real operation conditions) for polar mounted inclinations of PV panels, winter & summer maximization inclinations of the PV panels and south facing vertical walls/windows for different months of the year and at various latitudes is established and the effect of l on the percent reduction in maximum power produced (Pmp) by the PV solar panel is studied. The tilt angle dependence shows that the panel produces highest Pmp at l = 0° (tilt angle of the panel when the light source is normal to the panel surface). It is also observed that Pmp decreases by about 9%, 14 % and 19% when l is 15°, 30° and 45° respectively as compared to the normal position of the panel. Newton-Raphson’s technique is used to theoretically compute Imp, Vmp & Pmp and compared with the experimental values generated using the solar simulator within less than 5% deviation.

A simulated study on the performance evaluation of amorphous silicon solar PV module for temperature, irradiance and tilt angle dependence

A simulated study on the performance evaluation of amorphous silicon solar PV module for temperature, irradiance and tilt angle dependence

Atomistic simulation of shear deformation at bcc-Fe grain boundary and precipitation strengthening by Cr23C6

We investigate the temperature and the tilt angle dependence of the shear deformation behavior at a body-centered cubic (bcc)-Fe grain boundary (GB) by utilizing classical molecular dynamics simulations. We found that the shear deformation at a [001] axial bcc-Fe GB accommodates GB migration. The critical shear stress needed to induce GB migration was found to decrease with an increase in the temperature or molecular dynamics simulation time, because GB migration is a thermally activated process. The tilt angle dependence of the critical shear stress is successfully explained by the presence of a specific structure unit composed of under-coordinated atoms. It was suggested that Cr 23 C 6 precipitation within the bcc-Fe crystal decreases the critical stress required to generate dislocations, because of the interface between the precipitation and parent phases. On the other hand, Cr 23 C 6 precipitation on a [001] axial bcc-Fe GB was found to increase the critical shear stress, while the precipitation didn’t change the shear deformation mechanism. The degree of strengthening was verified by theoretical equation to evaluate the shear strengthening by the ordered precipitates.

Effects of graphene on the smectic-A to chiral smectic-C* phase transition

ABSTRACT The smectic-A to chiral smectic-C* (SmA–SmC*) phase transition in the mixture of graphene nanoparticles and ferroelectric liquid crystal is studied. Combination of Flory–Huggins free energy of isotropic mixing and Landau theory is applied to explain the effects of graphene nanoparticles on the SmA–SmC* phase transition. The temperature and concentration of graphene nanoparticles dependence of tilt angle, spontaneous polarization and dielectric susceptibility in the smectic-C* phase of the SmA–SmC* phase transition are discussed. A qualitative agreement between theoretical results and experimental results is found.

Substrate Roughness and Tilt Angle Dependence of Sum-Frequency Generation Odd–Even Effects in Self-Assembled Monolayers

Substrate Roughness and Tilt Angle Dependence of Sum-Frequency Generation Odd–Even Effects in Self-Assembled Monolayers

Dynamics of low energy electrons transmitting through straight glass capillary: Tilt angle dependence

<sec>It is a hot topic that using glass capillary to focus and shape the charged particle beam, for it is inexpensive and simple. There are the cases that single glass capillaries are used to make the microbeam of the positive ions. When it comes to electrons, their transmitting through insulating capillaries is complex and the attempt to use the glass capillary to produce electron beams in the size of micrometer needs further exploring.</sec><sec>In this paper, the charging-up process of the 900-eV electrons transmitting through a glass capillary with the grounded conductive-coated outer surface is reported. Two-dimensional angular distributions of the transmitted electrons and their time evolutions are measured for the cases of various tilt angles of glass tube. It is found that there are a considerable number of transmitted electrons at the tilt angle exceeding the geometrical opening angle (1°) of the glass tube. The intensity of transmitted electrons for large tilt angle (i.e. –1.15°) can be considered as first falling to zero, then keeping zero for a long time, finally rising to a certain stable value. Correspondingly, the angular distribution center experiences moving towards negative-positive-negative-settled. The energy losses are measured for various tilt angles. The larger the tilt angles, the larger the energy loss of transmitted electrons is. To better understand the physics behind the observed phenomena, the simulations of the energy loss for transmitted electrons at various tilt angles are performed by the Monte Carlo method. The comparation between the simulated energy losses and the measured energy losses shows that the experimental results are well explained by multiple deflections from the wall.</sec>

Nematic Structures under Conical Anchoring at Various Director Tilt Angles Specified by Polymethacrylate Compositions.

Dependence of the director tilt angle of nematic liquid crystal (LC) under conical anchoring from the two-component polymer mixture composition has been studied. We varied the ratio of poly(isobutyl methacrylate) (PiBMA), which specifies a conical anchoring for the nematic liquid crystal LN-396, and poly(methylmethacrylate) (PMMA) assigning a tangential alignment for the same nematic. An oblique incidence light technique to determine a tilt angle has been used. It has been shown that the tilt angle increases from to when PiBMA:PMMA ratio changes in the range 30:70 to 100:0. The specific optical textures viewed under the polarizing microscope and proper orientational structures have been considered for various compositions of the polymer films. An electric field action on the formed orientational structures has been investigated. The obtained results are promising for the application in various electro-optical LC devices with a conical anchoring in which the director tilt angle is a crucial parameter: a controlled diffraction gratings, an electrically operated achromatic rotators of linear light polarization, etc.

Sunspot tilt angles revisited: Dependence on the solar cycle strength

Context. The tilt angle of sunspot groups is crucial in the Babcock-Leighton (BL) type dynamo for the generation of the poloidal magnetic field. Some studies have shown that the tilt coefficient, which excludes the latitudinal dependence of the tilt angles, is anti-correlated with the cycle strength. If the anti-correlation exists, it will be shown to act as an effective nonlinearity of the BL-type dynamo to modulate the solar cycle. However, some studies have shown that the anti-correlation has no statistical significance. Aims. We aim to investigate the causes behind the controversial results of tilt angle studies and to establish whether the tilt coefficient is indeed anti-correlated with the cycle strength. Methods. We first analyzed the tilt angles from Debrecen Photoheliographic Database (DPD). Based on the methods applied in previous studies, we took two criteria (with or without angular separation constraint Δs > 2.​​°5) to select the data, along with the linear and square-root functions to describe Joy’s law, and three methods (normalization, binned fitting, and unbinned fitting) to derive the tilt coefficients for cycles 21–24. This allowed us to evaluate different methods based on comparisons of the differences among the tilt coefficients and the tilt coefficient uncertainties. Then we utilized Monte Carlo experiments to verify the results. Finally, we extended these methods to analyze the separate hemispheric DPD data and the tilt angle data from Kodaikanal and Mount Wilson. Results. The tilt angles exhibit an extremely wide scatter due to both the intrinsic mechanism for its generation and measurement errors, for instance, the unipolar regions included in data sets. Different methods to deal with the uncertainties are mainly responsible for the controversial character of the previous results. The linear fit to the tilt-latitude relation of sunspot groups with Δs > 2.​​°5 of a cycle carried out without binning the data can minimize the effect of the tilt scatter on the uncertainty of the tilt coefficient. Based on this method the tilt angle coefficient is anti-correlated with the cycle strength with strong statistical significance (r = −0.85 at 99% confidence level). Furthermore, we find that tilts tend to be more saturated at high latitudes for stronger cycles. The tilts tend to show a linear dependence on the latitudes for weak cycles and a square-root dependence for strong cycles. Conclusions. This study disentangles the cycle dependence of sunspot group tilt angles from the previous results that were shown to be controversial, spurring confusion in the field.

A Temperature Independent Inclinometer Based on a Tapered Fiber Bragg Grating in a Fiber Ring Laser.

We demonstrate a new concept for an all-fiber inclinometer based on a tapered fiber Bragg grating (tFBG) in a fiber ring laser (FRL) with the capability of measuring the tilt angle and temperature simultaneously. The sensor performance is analyzed theoretically and investigated experimentally. The dependence of tilt angle on the spectral response in variable temperature conditions was measured. Two inclinometers with different lengths have been fabricated and characterized in FRL. The sensitivity is 0.583 dB/° and 0.849 dB/°, respectively, in the range of 0° to 90°. Thanks to the FRL system, narrow 3-dB bandwidth (<0.1 nm) and high optical signal-to-noise ratio (~60 dB) are achieved. The tFBG in the FRL system can be used for working as a temperature insensitive inclinometer. The results suggested that the proposed inclinometer has the advantages of compact size and convenient manufacture, enhancing its potential for application prospect.

Deep levels in ion implanted n-type homoepitaxial GaN: Ion mass, tilt angle and dose dependence

Ion implantation is a fundamental processing step in electronic device manufacturing. However, it can give rise to electrically active defects, in the crystal, that can undermine the functionality of devices. In this study, we carried out an electrical characterization study of defects in ion implanted n-type GaN. We found several levels in the 0.2–1.2 eV below the conduction band edge. The nature of these defects is discussed in the light of the ion mass, tilt angle and dose dependence of the concentration of the detected levels.

Experiments of keV negative ions transmitted through straight and tapered glass capillaries: tilt angle dependence

In this study, experiments are performed to study the transmission of 15 keV C− ions through straight and tapered borosilicate glass capillaries. The tilt angle is varied from 0° to 0.8°. In a straight capillary, the transmitted ions produced only one spot on the detector, and its intensity declined with increasing tilt angle. In this case, almost 98% of the transmitted particles maintained their initial charge. However, in the tapered capillary, the transmitted particles formed a different pattern composed of a core and a halo. The negative ion fractions of the core and the halo were 97.5% and 42.5% at a 0° tilt angle, respectively. Therefore, the particles formed the halo by scattering after colliding with the inner surface of the capillary, and most of them were neutralized. As the tilt angle increased, the intensity and negative ion fraction of the transmitted particles declined, and the halo gradually became quite asymmetric. These results indicate that the scattering process plays a role in the transmission.

Dipole Tilt Effect on Magnetopause Reconnection and the Steady‐State Magnetosphere‐Ionosphere System: Global MHD Simulations

AbstractThe Earth's dipole tilt angle changes both diurnally and seasonally and introduces numerous variabilities in the coupled magnetosphere‐ionosphere system. By altering the location and intensity of magnetic reconnection, the dipole tilt influences convection on a global scale. However, due to the nonlinear nature of the system, various other effects like dipole rotation, varying interplanetary magnetic field (IMF) orientation, and nonuniform ionospheric conductance can smear tilt effects arising purely from changes in coupling with the solar wind. To elucidate the underlying tilt angle dependence, we perform magnetohydrodynamic (MHD) simulations of the steady‐state magnetosphere‐ionosphere system under purely southward IMF conditions for tilt angles from 0–90°. We identify the location of the magnetic separator in each case and find that an increasing tilt angle shifts the 3‐D X line southward on the magnetopause due to changes in magnetic shear angle. The separator is highly unsteady above 50° tilt angle, characteristic of regular flux transfer event (FTE) generation on the magnetopause. The reconnection rate drops as the tilt angle becomes large, but remains continuous across the dayside such that the magnetosphere is open even for 90°. These trends map down to the ionosphere, with the polar cap contracting as the tilt angle increases, and region I field‐aligned current (FAC) migrating to higher latitudes with changing morphology. The tilt introduces a north‐south asymmetry in magnetospheric convection, thus driving more FAC in the Northern (sunward facing) hemisphere for large tilt angles than in the Southern independent of conductance. These results highlight the strong sensitivity to onset time in the potential impact of a severe space weather event.

Azimuthally-Differential Pion Femtoscopy in Cu + Au and Au + Au Collisions at $$\sqrt {{{s}_{{NN}}}} $$ = 200 GeV in the STAR Experiment

Anisotropic flow is sensitive to the properties of the systems created in heavy-ion collisions. Azimuthally-sensitive femtoscopy with respect to the first-order event plane is coupled with the directed flow, and probes the space-time structure of the particle-emitting source. The knowledge of the source tilt can give a helpful experimental handle on the origin of the anisotropic flow. In addition, the tilt angle dependence on different collision systems at the same energy can provide constraints on theoretical models. In the experiment, this information can be extracted by measuring pion femtoscopic radii as a function of the pair emission angle with respect to the first-order event plane. In this work, we present comparisons between the results of the radius oscillations of the pion-emitting sources at $$\sqrt {{{s}_{{NN}}}} $$ = 200 GeV in symmetric (Au + Au) and asymmetric (Cu + Au) collisions measured with the STAR experiment, and those estimated in the UrQMD model.

No Tilt Angle Dependence of Grain Boundary on Mechanical Strength of Chemically Deposited Graphene Film

No Tilt Angle Dependence of Grain Boundary on Mechanical Strength of Chemically Deposited Graphene Film

Micro Optical-Interference-Plate Featuring Highly Efficient Diamagnetic Rotation of Biogenic Crystals

Optical interference, which enhances or reduces intensity of light propagating, is very important for many kinds of shape analysis methods. It will be available to detect a morphology change in micro- to nano-scale by using optical interference when we can obtain a new optical material from the animal kingdom. This paper focused on the light interference in biogenic guanine crystals which is derived from fish skin/scale. So far, it has been reported that two cross-stacked guanine crystals show stripe patterns which are produced by the optical interference between guanine crystals [1]. In this study, we have found that a very clear moire effect pattern is generated on a single guanine crystal plate combining with the mirror surface substrate. The observation system is consisted with telecentric lens and coaxial vertical illumination using blue LED. Guanine crystals in water are set on a mirror polishing Si substrate. Figure 1(a) shows the optical image of guanine crystal plates in water using our observation system. It can be clearly seen that homogeneous light and shade stripe patterns are observed on the plates when the surface of the guanine plates are parallel to the Si substrate reflecting that their very flat surface morphology. By contrast, when the guanine crystals in water are set on the substrates having the diffused reflection surface such as the black vinyl tape and Teflon plate, the light and shade stripe pattern is not observed on the single guanine crystal but observed on two crossstacked crystals as reported before (Fig.1(b)). These results suggest that moire pattern on the guanine crystal plate is perturbed or disappears when the substance or the defect which changes the reflective state of the light exists under the crystal plate. Next, we have investigated the response of guanine crystal to the magnetic field by using the moire pattern to determine that the guanine plate is parallel to the substrate. Furthermore, it makes possible to estimate the quite small angle between the guanine crystals and substrate surface from the pattern period of moire stripes measured by optical observation system. The time dependences of the ratio of guanine crystals oriented in the horizontal magnetic field direction are measured by changing the magnetic field amplitude as shown in Fig.2. The experimental procedure is as follows: First, the horizontal magnetic field of 500 mT is applied and guanine crystals are aligned as the long axis of the guanine plate is parallel to the field (step A). Next, the vertical magnetic field of 200 mT is applied in order to align guanine crystals as the long axis of guanine plate is orthogonal to the field and the moire pattern disappear (step B) [2]. From this state, the horizontal magnetic field which is orthogonal to the first horizontal filed is applied and moire patterns appear again (step C). As shown in the figure, the guanine crystal plates quickly oriented to the horizontal direction with the magnetic field of 350 mT or more. This suggests that the magnetic field operates moire pattern switching which is effective to obtain a reference signal. The dependence of orientation time of guanine crystal upon the angle between the long axis of guanine plate and horizontal magnetic field and the tilt angle dependence of reflection brightness from the guanine plate will also be presented.