Spin Speed Research Articles

Collisionless drag for a one-dimensional two-component Bose-Hubbard model

We theoretically investigate the elusive Andreev-Bashkin collisionless drag for a two-component onedimensional Bose-Hubbard model on a ring. By means of tensor network algorithms, we calculate the superfluid stiffness matrix as a function of intra- and interspecies interactions and of the lattice filling. We then focus on the most promising region close to the so-called pair-superfluid phase, where we observe that the drag can become comparable with the total superfluid density. We elucidate the importance of the drag in determining the long-range behavior of the correlation functions and the spin speed of sound. In this way, we are able to provide an expression for the spin Luttinger parameter $K_S$ in terms of drag and the spin susceptibility. Our results are promising in view of implementing the system by using ultracold Bose mixtures trapped in deep optical lattices, where the size of the sample is of the same order of the number of particles we simulate. Importantly, the mesoscopicity of the system, far from being detrimental, appears to favor a large drag, avoiding the Berezinskii-Kosterlitz-Thouless jump at the transition to the pair-superfluid phase which would reduce the region where a large drag can be observed.

Structure–property relationship of melt spinning polypropylene fibers containing inorganic particulate CaCO3 fillers

Spinning technology using melt extrusion and spin-draw processes transforms polymeric materials into highly oriented, crystallized polymeric fibers. Thermoplastic isotactic polypropylene compound with ground CaCO3 (GCC) and precipitate CaCO3 (PCC) with stearic acid surface coating treatment was used in this study. This product was developed in masterbatch form, which contained 70% GCC in resin and 50% PCC in resin. The resulting (masterbatch pellets) polymer can be spun into fibers through a single-screw extruder. Surface and cross-sectional images of fibers were captured by optical microscopy and scanning electronic microscopy for identifying the organic/inorganic interface of fibers. The melt-spun fibers have a distinctive morphology, the particles impact on spinnability, and productivity in the spunbond will alter the mechanical property, thermal property and optical property of fiber-based products. Processing parameters, including spinning speed, throughput rate and take-up roll velocity, were systematically study to understand the structure formation. Meanwhile, different loading concentrations are applied for varied factor comparison of particle size and shape. The Weibull distribution model is applied for determining the tensile property of fibers containing high GCC dosages of 20–40%. Meanwhile, a few more steps of gauge length are utilized for studying the probability of a weak link in polymer materials. Through a systematic discussion of the GCC and PCC comparison study in changing fiber properties, the impact of the particle size on agglomeration formation is emphasized, as well as the breaking mechanism of fibers.

Study of Cucurbit[7]uril nanocoating on epitaxial graphene to design a versatile sensing platform

Present study aimed to develop nanocoating of cucurbit[7]uril (CB[7]) on surfaces of silicon and epitaxial graphene using drop casting and spin coating techniques. Here, we report a systematic study for the influence of sonication, probe sonication, and centrifugation time on the dispersion of CB[7] in aqueous solutions for the preparation of high-quality CB[7] nanocoating. Spin speed, spin time, and spin acceleration have been optimised to attain uniform films with minimum rms. Atomic force microscopy is used to study morphology, rms, and height of CB[7] nanocoating under different parameters. The presence of CB[7] on the nanocoating and its binding nature was determined by Infrared absorption and X-ray photoelectron spectroscopy. The present method of CB[7] nanocoating preparation is easy, versatile, scalable, and does not need the addition of electrolyte additives. Prepared CB[7] films are high-quality, uniform, and could be used as a novel sensing platform to tether required functional groups.

Highly efficient and stable inorganic CsPbBr3 perovskite solar cells via vacuum co-evaporation

High power conversion efficiency (PCE) and good long-term stability are everlasting pursuit for perovskite solar cells. We present here CsPbBr3 perovskite film deposited by vacuum co-evaporation of CsBr and PbBr2. By optimizing evaporation rate ratio of the two precursor and annealing temperature, perovskite films with large grain and high crystallinity are obtained. Furthermore, by regulating spinning speed of TiO2 precursor solution and thickness of CsPbBr3 film, a best PCE of 9.43% is recorded under 100 mW cm−2 illumination, providing a significant enhancement in contrast with 6.26% of device based on spin-coating method. Additionally, the PCE of resulting perovskite solar cell without encapsulation remains at 96% of initial value after storing for 480 h under humidity of 40% in air. Our findings in this work deliver an effective strategy to fabricate high-performance inorganic perovskite solar cells.

Dynamic behavior and stability of energy efficient electro-magnetic suspension of rotors involving time delay

Energy efficient contact less suspension of high-speed rotor shafts in application areas such as power-plants and Flywheel Energy Storage Systems (FESS), can be achieved through Active Magnetic Bearings (AMBs). Inevitably, there exists time delay in sensing the rotor displacement and actual application of control force by electromagnets, thus leading to system instability. This paper therefore analyses stability of AMBs, with constant time delay. FESS is modelled as a rigid rotor-AMB system. Performance of two different control laws, (i) PID and (ii) a recently introduced Four-Element (FE) law, are compared. The governing equations are transformed to frequency domain, to exploit Pade's approximation in modeling time delayed value of feedback signal and stability analysis is carried out by analyzing the system poles. This methodology has been verified using experimental results from the existing literature. Numerical simulation of delay differential equations is also used to validate analytical results. The FE control law shows promise in tolerating delay, as compared to conventional PID controller thus leading to AMB system with higher possible spin speed and relaxed sampling constraints on AMB system instrumentation. One of the prospective applications of this work is in design of flywheel energy storage systems for an electric vehicle.

Essential Enzyme Kinetics: A Textbook for Molecular Life Scientists

Energy efficient contact less suspension of high-speed rotor shafts in application areas such as power-plants and Flywheel Energy Storage Systems (FESS), can be achieved through Active Magnetic Bearings (AMBs). Inevitably, there exists time delay in sensing the rotor displacement and actual application of control force by electromagnets, thus leading to system instability. This paper therefore analyses stability of AMBs, with constant time delay. FESS is modelled as a rigid rotor-AMB system. Performance of two different control laws, (i) PID and (ii) a recently introduced Four-Element (FE) law, are compared. The governing equations are transformed to frequency domain, to exploit Pade's approximation in modeling time delayed value of feedback signal and stability analysis is carried out by analyzing the system poles. This methodology has been verified using experimental results from the existing literature. Numerical simulation of delay differential equations is also used to validate analytical results. The FE control law shows promise in tolerating delay, as compared to conventional PID controller thus leading to AMB system with higher possible spin speed and relaxed sampling constraints on AMB system instrumentation. One of the prospective applications of this work is in design of flywheel energy storage systems for an electric vehicle.

Piezoelectric Properties of Mg Doped ZnO Thin Film using Sol-Gel Method and Spin Coating

This reports about the synthesis of Mg doped ZnO thin film using spin-coating techniques through sol-gel method. For studying piezoelectric properties, optical properties and morphology, the prepared Mg doped ZnO thin film samples were characterized using Ultraviolet-Visible Spectroscopy (UV-Vis), Photoluminescence Spectroscopy (PL), X-ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM) and Ultrasonic Vibrator. The particle size was evaluated using Scherrer’s formula from XRD patterns. The results show the crystallite size decreased with increasing Mg concentrations. The optical properties showed that sample exhibit a blue shift in absorption in UV spectra indicating good optical properties. The morphology of grain size microstructure was observed from FESEM with results the grain size of the samples decreased with increasing Mg doping. The piezoelectric properties were evaluated using ultrasonic vibrator and multimeter to obtain potential difference for each sample. The results obtained that potential difference increase with increasing Mg contents and higher rotation of spin speed was used.

Spider silk: A natural marvel of mechanical and structural strength

The spider silk fibers have unique high performance properties that make it a desirable model for artificial fibers and its performance under benign conditions has important implications for biomimicry. It has tensile strengths comparable to steel and some are nearly as elastic as rubber on a weight to weight basis. The spider spins its silk at ambient temperatures, low pressures and with water as solvent. Spiders are ectotherms and the ambient temperature affects the spinning speed and the mechanical and structural properties of the silk spun. The high cytocompatibility and low immunogenicity of spider silk fibers make them well suited for biomaterial products such as nerve conduits. Spider silk proteins have been shown to be soluble in ionic liquids, thus once soluble, they can be processed into new biomaterials such as films, gels, porous sponges, bone tissue engineering. The spider silk chains with a fixed molecular weight decreases exponentially with the UV irradiation time, since UV irradiation causes the chemical bonds in the protein chains to undergo cleavage. This paper reviews related literature on the spider silk spinning process, conditions and their effects on structure, mechanical properties of spider silk and its resistance to UV degradation. As a bonus, a brief review of the biotechnological production of recombinant spider silk us presented.

Highly efficient wide-band-gap perovskite solar cells fabricated by sequential deposition method

Perovskite-based double junction tandem solar cells, including perovskite/silicon, perovskite/perovskite, and perovskite/Cu(In, Ga)Se 2 , have received increasing attention in recent years. While most wide-band-gap perovskite solar cells so far were synthesized by the one-step deposition method which has a simple procedure but is hindered by its narrow antisolvent dripping time window, exploration of other method is in demand. In this study, a highly efficient wide-band-gap perovskite solar cell device with a bandgap of 1.63–1.65 eV has been successfully fabricated using the two-step sequential deposition method by optimizing the solution composition and the spinning speed of the second step. The best solar cell obtained has a power conversion efficiency of 20.35% and a fill factor (FF) of 81.53%, and is believed to be the first wide-band-gap solar cell device fabricated by the sequential deposition method with an efficiency over 20%. The obtained FF value is also pretty high among all reported perovskite solar cells fabricated by sequential deposition method. Our work indicates that sequential deposition method not only can be applied to the traditional narrow-band-gap perovskite solar cells but also has a potential for fabricating highly efficient wide-band-gap perovskite solar cells. A highly efficient wide-band-gap perovskite solar cell device with an energy conversion efficiency of 20.35% and a fill factor of 81.53% has been successfully fabricated using the two-step sequential deposition method by optimizing the solution composition and the spinning speed of the second step. • A highly efficient wide-band-gap perovskite solar cell device was fabricated using sequential deposition method. • The obtained FF value 81.53% is the maximum among all reported perovskite solar cells fabricated by sequential deposition method. • This work has shown the potential of sequential deposition method for fabricating highly efficient and reproducible wide-band-gap perovskite active layers.

Effects of Concentration and Spin Speed on the Optical and Electrical Properties of Silver Nanowire Transparent Electrodes.

In this paper, silver nanowires (AgNWs) with a diameter of 40 nm and a length of 45 μm were dispersed into an ethanol solution to prepare AgNW solutions with concentrations of 1, 2, and 3 mg/mL, respectively. The AgNW solutions were then deposited on a glass substrate using spin-coating at 1000, 2000, and 3000 rpm for 45 s, respectively, to prepare transparent electrodes. The results showed that the distribution of AgNWs on the substrate increased in density with the increase in the AgNW solution concentration and the decrease in spin speed. The effect of concentration on the distribution of AgNWs was greater than that of the spin speed. The transmittance of each electrode was between 84.19% and 88.12% at 550 nm, the average sheet resistance was between 20.09 and 358.11 Ω/sq, the highest figure of merit (FoM) was 104.42, and the lowest haze value was 1.48%. The electrode prepared at 1000 rpm with a concentration of 2 mg/mL and that prepared at 3000 rpm with a concentration of 3 mg/mL were very similar in terms of the average sheet resistance, transmittance at 550 nm, FoM, and haze value; thus, these two electrodes could be considered equivalent. The haze value of the electrode was positively correlated with the spin speed at low concentration, but that relationship became inverse as the concentration rose. For the AgNWs used in this experiment with an aspect ratio of 1125, the concentration of the AgNW solution should reach at least 2 mg/mL to ensure that the FoM of the electrode is greater than 35.

Correlation driven topological nodal ring ferromagnetic spin gapless semimetal: CsMnF4

The observation of in-plane ferromagnetism in layered magnetic materials in conjunction with the topological nodal-ring dispersion in a spin gapless semimetal with 100 % spin polarization has a fertile ground for novel physics, rich scientific significance and for the next-generation advanced spintronic and topological devices. Topological nodal ring spin gapless semimetals with large band gap in the other spin channel prevents the spin leakage and are excellent spintronic materials. On the basis of density functional theory (DFT), we have studied the layered magnetic perovskite, CsMnF4 which is predicted to be a ferromagnetic insulator though the fellow compounds like AMnF4 (A = Na, K, Rb) are anti-ferromagnetic in nature. DFT + U calculations reveal that this layered system undergoes a transition from an insulating to half-semimetallic nature with decreasing on-site Hubbard Coulomb interaction, U. For U = 2.5 eV, we observe the topological nature in the system with the emergence of four Mexican hat like dispersions associated with band-flipping. Also, we calculated the magneto-crystalline anisotropic energy with inclusion of spin–orbit coupling (SOC) and found that the system consists of in-plane ferromagnetism. Transport properties infer huge anisotropy of one order of magnitude between ’a’ and ’c’ axes. Interestingly, the estimated Fermi velocities are 2.66 × 105 and 2.24 × 105 m s−1 for Z(=0) and Z(=0.5) plane respectively and are comparable to that of graphene, which might fetch applications in high speed spin electronic devices. The topological phase observed is robust to SOC and the band-crossings associated with nodal rings could be preserved by additional symmetry as the time-reversal symmetry breaks in magnetic systems. The nearly charge compensation observed from Fermi surfaces might fetch memory device applications.

A Study on Stator Design for Electromagnetic Noise Reduction in Washing Machine Motor

Received:11 november 2020; Accepted: 27 December 2020; Published online: 05 April 2021
 Abstract : For low cost, spoke type ferrite magnet motors with small air gap are using to washing machine. At that time, a noise problem occurs, so a design to reduce the noise is required. In the washing machine, set noise increased due to the reduction of air gap of motor at high speed spin mode. Not only the overall noise, but also the harmonics noises are greatly increased at set. As a result of set noise test and noise analysis through finite elements method, a stator tooth shoe shape in which the magnetic flux changes rapidly is cause of noise. Its shape creates many harmonics of load torque. The harmonics component of the load torque increases the overall noise of the set. The harmonics noise of the set has a large correlation with radial force component as well as the torque ripple. Especially, it is found that the harmonics noise of the set is related to harmonics component of load torque and the harmonics component of the radial force at stator tooth. The noise is reduced by applying the new design of stator tooth shoe that can minimize the change in magnetic flux through the noise cause analysis. Through this research, the harmonics noise as well as overall noise are reduced at small airgap motor. Therefore, it is possible to develop cost reduction motor for washing machine.

Assembly of Nanofluidic MXene Fibers with Enhanced Ionic Transport and Capacitive Charge Storage by Flake Orientation.

MXenes are an emerging class of highly conductive two-dimensional (2D) materials with electrochemical storage features. Oriented macroscopic Ti3C2Tx fibers can be fabricated from a colloidal 2D nematic phase dispersion. The layered conductive Ti3C2Tx fibers are ideal candidates for constructing high-speed ionic transport channels to enhance the electrochemical capacitive charge storage performance. In this work, we assemble Ti3C2Tx fibers with a high degree of flake orientation by a wet spinning process with controlled spinning speeds and morphology of the spinneret. In addition to the effects of cross-linking of magnesium ions between Ti3C2Tx flakes, the electronic conductivity and mechanical strength of the as-prepared fibers have been improved to 7200 S cm-1 and 118 MPa, respectively. The oriented Ti3C2Tx fibers present a volumetric capacitive charge storage capability of up to 1360 F cm-3 even in a Mg-ion based neutral electrolyte, with contributions from both nanofluidic ion transport and Mg-ion intercalation pseudocapacitance. The oriented 2D Ti3C2Tx driven nanofluidic channels with great electronic conductivity and mechanical strength endows the MXene fibers with attributes for serving as conductive ionic cables and active materials for fiber-type capacitive electrochemical energy storage, biosensors, and potentially biocompatible fibrillar tissues.

A strategy to decelerate and capture a spinning object by a dual-arm space robot

With the increasing requirement of grasping the non-cooperative objects in space by space robots, this paper introduces a new strategy operated by a dual-arm space robot. The strategy includes path planning to capture a spinning target, hybrid control of the motion and the contact force for the end-effectors, coordinated control of the base attitude, and parameter identification of the spinning target during the capture phase. Notably, a pair of proper contact forces can be applied to the two grasp points of the spinning target by the two manipulators, which can decelerate the spinning speed of the target and be utilized to identify the target's moment of inertia around its spinning axis. Considering the non-cooperative situation with the spinning target like a defunct satellite, the uncertainties of the space robot and the target, such as parameters of mass and moment of inertia, are concerned in the design of the Sliding Mode Controller (SMC) with good robustness. Moreover, due to the coupling movement of the base and arms of a dual-arm space robot, the base attitude will be simultaneously maintained by the mounted reaction wheels during the capture operation for good communications and effective solar energy collection. The post-capture process is also presented in the paper to bring the entire system of the space robot and the target into stationary status. To compare the system performance against the uncertainties by different controllers, PID-type Computed Torque Controller (CTC) and SMC are designed together for comparison. When the uncertainties of the mass and the moment of inertia are applied to the system, the simulation results show that SMC has better performance against the uncertainties by delivering higher accuracy of the tracking errors to the desired trajectories than CTC.

Application of centrifugation technology for production of chhana – An Indian soft cheese

The present study was aimed at applying centrifugation for the rapid removal of whey from chhana and investigating the effect of processing parameters on various attributes of chhana. A prototype model based on centrifugation was developed for rapid whey removal from chhana. The optimised spin speed and centrifugation time for manufacturing chhana using the developed system were 80 rpm and 7 min, respectively. Whey removal at centrifugation speed of 39.09 rpm for 2.57 min resulted in production of soft chhana with minimum hardness value (2.054 N).

Dynamics and stability analysis of an axially functionally graded hollow rotor partially filled with liquid

The dynamics and stability of an axially functionally graded (AFG) hollow rotor partially filled with liquid are performed in this paper. Based on the Euler-Bernoulli beam theory, the governing equation of transverse vibration of an AFG liquid-filled rotor is derived using Hamilton principle. For the exponentially graded liquid-filled rotor with simply supports, the exact whirl frequency equation and the stability prediction model are obtained analytically. The validity of the present analysis is demonstrated by comparing with the existing data in the literature. Using the obtained analytical models, the effects of parameters including gradient parameter, mass ratio and cavity ratio on the whirl speed, critical spinning speed and system stability are put into evidence through a set of parametric studies. The results show that these parameters play an important role in the whirl speed and stability of the rotor system. Furthermore, the obtained results also indicate that the critical spinning speed of an AFG liquid-filled rotor is strongly dependent on the mass ratio and gradient parameter.

Study of the Optical and Structural Properties of PbI2 Thin Films Prepared by Spin Coating Technique at Room Temperature

Lead iodide thin films were deposited on a glass substrate using a spin coating technique. Powder of with a concentration (0.2M) was dissolved in a solution of Dimethylformamide (DMF). the thickness of the prepared films was controlled through the time of deposition and the spinning speed. the X-ray patterns show that the PbI2 thin films have hexagonal structures The bandgap of the thin films was measured optically and found to be about 2.45 eV. The FTIR measurements depicted the vibration modes from 1650 to 700 cm−1; the energy bandgap from the diffused reflectivity measurements was 2.4 eV; which is in a good agreement with energy gap from Tauc plot. (FESEM) images shows the nano rod shape of particles with large pores and non uniform distribution of particles

Manufacture of unitary/binary ordered arrays employing self-assembled nanocolloid lithography

This paper details the fabrication of unitary and binary nanocolloid arrays using the spin coating technique. Polystyrene spheres of 900 and 100 nm in size were overlaid on the surface of a silicon substrate using a spin coater. To prepare the unitary nanosphere arrays, nanosphere latex spheres of 900 or 100 nm were first mixed with surfactant solution and then spin-coated onto the silicon substrate. For the binary spin coating, both 900 and 100 nm colloidal nanospheres were mixed with surfactant solutions and then concurrently spin-coated. Fabricated nanosphere arrays were evaluated via both scanning electron and atomic force microscopy. The influence of processing parameters, including type of surfactant, nanosphere to surfactant ratio, spin speed, and spin time on the ordering of colloidal array have been identified; after this step is complete, steps can be taken to optimize the process. These steps provide advantages in terms of improved nanosphere array quality.

The Effect of Spin Coating Speed on Structural and Optical Properties of ZnO and ZnO/Dye Thin Films Synthesized by Sol-Gel Spin Coating Method

The ZnO thin films were successfully synthesized using sol-gel spin coating method. The surface other ZnO thin film then were coated with natural dye. Materials used were zinc acetate dehydrate, isopropanol, Diethanolamine and purple heart flower consecutively as based materials, solution, stabilizer, and dye. The ZnO thin films were grown glass by dropping Sol-gel on a surface of FTO glass with spin coating speed variation of 2000, 3000, 4000, and 6000 rpm. The ZnO thin films then successively pre-heated and pot-heated at 250°C and 550°C for 5 hours and holding time of 30 minutes. The source of the dye is boat lily flower was cut into small pieces and put into beaker glass. The sample then crushed with mortar and then milling until it becomes soft. Further, the extract was obtained by immersing it in aquadest, acetate acid, and ethanol with maceration technique. The ZnO thin films then immersed in an extract of dye solution for 24 hours to obtain ZnO/dye thin film. The XRD analysis shows that ZnO thin film size of within 26.5 – 36.9 nm. The optical properties of the ZnO and ZnO/Dye thin films were characterized using UV-Vis spectrometer. The UV-Vis spectrometer results show that there are variations of the ZnO thin film transmission as a result of spin coating speed of the Sol-gel spin coating method. The transmission of ZnO/dye thin films is higher than ZnO thin film and the absorbance of ZnO is higher than ZnO/dye thin films. The band gaps of the ZnO and ZnO/dye thin film were consecutively ranged 3.27 – 3.34 eV and 3.02 – 3.21 eV.

Nonlinear parametric vibration of spinning pipes conveying fluid with varying spinning speed and flow velocity

In this paper, a nonlinear parameter-excited model of spinning pipes conveying fluid is proposed by considering the spinning speed and flow velocity are perturbed periodically, and the stability and nonlinear parametric vibrations of such system are studied analytically and numerically. With taking the viscoelastic material and geometrical nonlinearity due to extensible pipe axis into account, the differential equations governing two transverse vibrations of the pipe are derived by the Hamilton principle. The system stability is then analyzed via the multiple scales method, and the nonlinear responses and spatial vibration shapes are investigated using numerical simulation. The contributions of some significant parameters on the vibrations of the system are discussed in detail. It is revealed that not any other motion but combination parametric resonance with quasi-periodic motion mode can occur in the present system, and it is induced fully by the periodically perturbed fluid. A perturbed spinning motion cannot result in any parametric resonance, however it has an opposite effect on the parametric vibrations as compared to that with constant spinning speed. The flow velocity, nonlinearity and viscoelastic damping all have significant impacts on the present parametric vibrations. Moreover, the pipe performs different aperiodic whirling motions in the first two modes, and the perturbed spinning speed will lead to a gentler motion of the pipe as compared to the case of constant spinning speed.