Big Disk Research Articles

All-optical multichannel switch and slow light based on dynamically tunable plasmon-induced transparency

The triple plasmon-induced transparency (PIT) effect based on a metal–insulator–metal waveguide structure comprising two groups of big and small disk resonators (BSDRs) is investigated theoretically and numerically. As a tool employed to explain the PIT, N-order coupled mode theory (CMT), is established, and the calculated results of the triple-PIT effect exhibit excellent consistency with finite-difference time-domain simulations. The influence of the separation between the small disk resonators on the triple-PIT response is discussed in detail through the dynamical equation. Further research shows that the central wavelengths of the triple-PIT transmission window can be adjusted with extremely low pump intensity and ultrafast optical response when monolayer graphene covers the surface of the BSDRs. Meaningfully, light traveling at resonant wavelengths can be effectively slowed down, with the highest group index reaching 368. Based on the PIT effect, a low-power and ultrafast switch is realized with a modulation amplitude of more than 93% at the corresponding wavelengths of the eight depressions. Thus, not only do the insights put forward new ideas, to the best of our knowledge, for highly tunable optoelectronic devices, but the results from the N-order CMT also offer new theory progress and references in the plasmonic waveguide structures.

Circumbinary Accretion: From Binary Stars to Massive Binary Black Holes

We review recent works on the dynamics of circumbinary accretion, including time variability, angular momentum transfer between the disk and the binary, and the secular evolution of accreting binaries. These dynamics impact stellar binary formation/evolution, circumbinary planet formation/migration, and the evolution of (super)massive black hole binaries. We discuss the dynamics and evolution of inclined/warped circumbinary disks and connect with observations of protoplanetary disks. A special kind of circumbinary accretion involves binaries embedded in big disks, which may contribute to the mergers of stellar-mass black holes in AGN disks. Highlights include the following: ▪Circumbinary accretion is highly variable, being modulated at P b (the binary period) or ∼5P b, depending on the binary eccentricity e b and mass ratio q b.▪The inner region of the circumbinary disk can develop coherent eccentric structure, which may modulate the accretion and affect the physical processes (e.g., planet migration) taking place in the disk.▪Over long timescales, circumbinary accretion steers binaries toward equal masses, and it does not always lead to binary orbital decay. The secular orbital evolution depends on the binary parameters (e b and q b) and on the thermodynamic properties of the accreting gas.▪A misaligned disk around a low-eccentricity binary tends to evolve toward coplanarity due to viscous dissipation. But when e b is significant, the disk can evolve toward “polar alignment,” with the disk plane perpendicular to the binary plane.

Spontaneous preference for unpredictability in the temporal contingencies between agents' motion in naive domestic chicks.

The ability to recognize animate agents based on their motion has been investigated in humans and animals alike. When the movements of multiple objects are interdependent, humans perceive the presence of social interactions and goal-directed behaviours. Here, we investigated how visually naive domestic chicks respond to agents whose motion was reciprocally contingent in space and time (i.e. the time and direction of motion of one object can be predicted from the time and direction of motion of another object). We presented a 'social aggregation' stimulus, in which three smaller discs repeatedly converged towards a bigger disc, moving in a manner resembling a mother hen and chicks (versus a control stimulus lacking such interactions). Remarkably, chicks preferred stimuli in which the timing of the motion of one object could not be predicted by that of other objects. This is the first demonstration of a sensitivity to the temporal relationships between the motion of different objects in naive animals, a trait that could be at the basis of the development of the perception of social interaction and goal-directed behaviours.

Current Flow in a Cylindrical Nanopore with an Object-Implications for Virus Sensing.

Interest is growing in nanopores as real-time, low-cost, label-free virus size sensors. To optimize their performance, we evaluate how external electric field and ion concentrations and pore wall charges influence currents and object (disk) radius-current relationship using simulations. The physics was described using the Poisson-Nernst-Planck and Navier–Stokes equations. In a charged cylindrical nanopore with a charged disk, elevated external electric field produces higher (and polarity independent) ion concentrations and greater ion current (largely migratory). Elevated external ion concentrations also lead to higher concentrations (mainly away from the pore wall), greater axial electric field especially in the disk-pore wall space, and finally larger current. At low concentrations, current is disk radius independent. The current rises as concentrations increase. Interestingly, the rise is greater for larger disks (except when the pore is blocked mechanically). Smaller cross-sectional area for current flow or volume exclusion of electrolyte by object thus cannot be universally accepted as explanations of current blockage. Ion current rises when pore wall charge density increases, but its direction is independent of charge sign. Current-disk radius relationship is also independent of pore wall charge sign. If the pore wall and disk charges have the same sign, larger current with bigger disk is due to higher counter-ion accumulation in the object-pore wall space. However, if their signs are opposite, it is largely due to elevated axial electric field in the object-pore wall space. Finally in uncharged nanopores, current diminishes when disk radius increases making them better sensors of virus size.

Three-band plasmon induced transparency effect based on four-disk resonator coupled waveguide system

In order to reduce power consumption and realize ultrafast response time and dynamic tunability, a plasmonic waveguide system based on four disk resonators is designed. A plasmon induced transparency effect is theoretically analyzed by using two different methods: one is the direct destructive interference between bright mode resonator and dark mode resonator, and the other is the indirect coupling through a plasmonic waveguide. Owing to the giant effective nonlinear Kerr coefficient of the graphene-Ag composite material structure and the enhancement characteristics of slow light response to optical Kerr effect, the pump intensity of PIT system for changing the phase shift of transmission spectrum is greatly reduced. An ultrafast response time of 1 ps is achieved, and 0.4π, 0.8π, 1.2π, 1.6π and 2π-phase shift of the transmission spectrum in the plasmon induced transparency system are achieved with the intensity of the pump light as low as 2.34, 4.68, 7.02, 9.36, 11.7 MW/cm<sup>–2</sup>, respectively. In this work, a plasmonic waveguide coupled directly by two small disk resonators is employed, because two small disk resonators play a role of the slit between the waveguide and the resonators, and also act as two separate resonators side-coupled with a plasmonic waveguide, which leads to the more efficient coupling of electromagnetic energy in the waveguide into the big disk resonators to form resonance and easier storage of light in the resonator. The triple-band plasmon induced transparency (PIT) effect and slow light properties of the model are analyzed by the expression of the deduced theoretical transmittance based on the coupled mode theory, indicating that they are very consistent with the finite-difference time-domain simulations. The results show that the transmission peak of the system is over 80% and the maximum group index is as high as 368. Furthermore, the disk resonators are easy to fabricate and the size of the entire PIT structure is < 0.5 μm<sup>2</sup>, which is beneficial to the design of optoelectronic device on-chip integration. The research results have important application prospects in highly integrating optical circuits and networks, and also provide the ideas for the design and fabrication of multi-channel optical filter and light storage devices with low power consumption, ultrafast nonlinear response, ultracompact and dynamical tunability.

Revealing the structure of the lensed quasar Q 0957+561

Aims. We aim to use signatures of microlensing induced by stars in the foreground lens galaxy to infer the size of the accretion disk in the gravitationally lensed quasar Q 0957+561. The long-term photometric monitoring of this system (which so far has provided the longest available light curves of a gravitational lens system) permits us to evaluate the impact of uncertainties on our recently developed method (controlled by the distance between the modeled and the experimental magnitude difference histograms between two lensed images), and thus to test the robustness of microlensing-based disk-size estimates. Methods. We analyzed the well-sampled 21-year GLENDAMA optical light curves of the double-lensed quasar and studied the intrinsic and extrinsic continuum variations. Using accurate measurements for the time delay between the images A and B, we modeled and removed the intrinsic quasar variability, and from the statistics of microlensing magnifications we used a Bayesian method to derive the size of the region emitting the continuum at λrest = 2558 Å. Results. Analysis of the Q 0957+561 R-band light curves show a slow but systematic increase in the brightness of the B relative to the A component during the past ten years. The relatively low strength of the magnitude differences between the images indicates that the quasar has an unusually big optical accretion disk of half-light radius: R1/2 = 17.6±6.1 √(M/0.3 M⊙) lt-days.

The Measurement of Thickness and Velocity of Our Galaxy

Many of the ancient astronomers have emerged and made great progress in the measuring the scale and motion of our galaxy. With rapidly developed technology, we have a more ambitious goal for putting our eyesight out of the Earth. The radius of our galaxy can be easily detected via the observation of Doppler effect. The motion of our galaxy, and the thickness of the galactic plan, however, would be relatively difficult, either because what we want to know is not stable, or because no direct evidence helps. Now with the help of radio astronomy, the most efficient tool on astronomical measuring, we are able to find out how thick our galaxy really is.
 
 Here this paper includes the method of measuring the thickness of our galaxy via the using of radio astronomy and the Doppler effect. The whole measuring is based on an 18-meter telescope which receives only radio waves with its wavelength as 21cm. 21cm is the wavelength of the radiation released while interaction between the nuclei and the electron occurs. The signal is very useful for detecting matter in space. Since diffraction is unavoidable when receiving signals on the big disk, we used the measuring of FWHM (Full width at Half Maximum) to find out the real width of the signal in the thickness measurement part when the signal is supposed to be uniformly distributed in a special range, which indicates our galactic thickness. Although we have given out a relatively precise answer at the end, unknown factors, such as the idea of precise border of our galaxy, still has a great impact on it that we could not solve. So the result, especially the thickness measuring, provides a method to measure the structure and scale of our galaxy via radio astronomy generally.

Investigation on the influence of aerostatic pressure upon surface generation in flycutting

Single-point diamond flycutting is an important technology for cutting flat KH2PO4 (potassium dihydrogen phosphate) crystals of large size. However, there always exist some undesirable waviness errors on the machined surface, which can directly reduce the optical performance of the potassium dihydrogen phosphate crystals. This article presents a kind of low-frequency waviness errors with wavelength about 26 mm along the feeding direction in single-point diamond flycutting, which has not been described yet. In order to find the main source of the mentioned waviness errors, the relationship between the displacement of the cutting tool and the aerostatic pressure was quantitatively studied for the first time. And then, surface simulation considering the aerostatic pressure fluctuations was carried out based on the relationship. Besides, a novel method that can achieve online submicron feeding along axial direction in single-point diamond flycutting without complex structure was proposed considering the spindle motion errors, the spindle dynamic characteristics and the aerostatic pressure. The experimental results validate that the mentioned waviness errors are mainly generated by the bolt stretched phenomenon and deformation of the big disk flycutting head due to the aerostatic pressure fluctuations. And the proposed method can achieve a cutting depth of about 120 nm when the aerostatic pressure increases from 0.52 to 0.56 MPa, which can reduce the cutting force and is beneficial for the performance of single-point diamond flycutting.

The Bright γ-ray Flare of 3C 279 in 2015 June: AGILE Detection and Multifrequency Follow-up Observations

Abstract We report the AGILE detection and the results of the multifrequency follow-up observations of a bright γ-ray flare of the blazar 3C 279 in 2015 June. We use AGILE and Fermi gamma-ray data, together with Swift X-ray andoptical-ultraviolet data, and ground-based GASP-WEBT optical observations, including polarization information, to study the source variability and the overall spectral energy distribution during the γ-ray flare. The γ-ray flaring data, compared with as yet unpublished simultaneous optical data that will allow constraints on the big blue bump disk luminosity, show very high Compton dominance values of ∼100, with the ratio of γ-ray to optical emission rising by a factor of three in a few hours. The multiwavelength behavior of the source during the flare challenges one-zone leptonic theoretical models. The new observations during the 2015 June flare are also compared with already published data and nonsimultaneous historical 3C 279 archival data.

Design and evaluation of performance tester for yaw brakes in wind turbines

In this study, a new type of test equipment is proposed to verify the performance of yaw brakes. A Nacelle, one of the wind turbine unit, rotates every 15 minutes to adjust its position to perpendicular to the blowing wind, which is known for yawing motion. The nacelle contains a main shaft, a gear box, and a generator, so that the size and weight are huge. A yaw brake system is the main device to stop the rotating nacelle during the yawing motion. A big disc of which the diameter is about 2 meters and several brakes are installed at the bottom part of the nacelle. Due to the difficulty of the size, the performance test for the yaw brake is very difficult. New tester is designed using a partial disk to simulate the disk brakes in the nacelle, as well as the application of braking force by a hydraulic actuator located at double the radius of the disk in order to reduce the hydraulic power. The stresses and strains are calculated through CAE analysis, and the values are compared with those from strain gage tests. After verifying the performance of the tester and testing two kinds of brake pads, it is found that alumina and chromite increase the friction coefficients but produce vibration and sound noise.

Short communication: Many missing rings in old Canary pines can be related with age, fires and traditional uses

Aim and area of study: In the present paper we estimated the age of four monumental Pinus canariensis of Gran Canaria (Canary Islands, Spain) by means of tree-ring analysis. Many tree-ring series have been accurately studied and many missing rings have been determined.Material and methods: The trees were dead and the samples analysed were big disks. We measured numerous radii and crossdated the individual tree-ring series, paying particular attention to the existence and location of missing rings. We have distinguished between missing outer rings (MORs) and missing inner rings (MIRs) and analysed the possible causes of both.Main results: We determined an average of 8.8% total missing rings (MRs) for these long-lived trees, with a maximum of 96 MRs in a series of over 500. We have tried to establish a tree-ring chronology on Gran Canaria Island, also having the tree-ring series from Inagua site, but the long individual tree-ring series analysed do not crossdate between them. Research highlights: We consider the Canary pine a species hard to conducting dendroecological studies, especially if the samples come from managed old trees, in which a large amount of known and potentially unknown missing rings can hampered dating. Even knowing the difficulties involved in dendrochronological analyses of P. canariensis, we can confirm that it is a long-lived species, which can grow to over 500 years, and some of whose growth changes could be associated with certain historical and ecological events.

Study on permanent holographic recording in trimethylol propane triacrylate-based photopolymer films with high diffraction efficiency

We investigate permanent hologram recording in a photosensitive material with high diffraction efficiency (DE) of ∼90%. We successfully recorded three-dimensional (3D) object information, gratings, and “hogel” images in this photopolymer film without postprocessing. In addition, we study multiplexed hologram storage in this material. Because of its high resolution, high DE, and lack of need for electric field and postprocessing, this photopolymer may be suitable for analog hologram, digital hologram, and big data permanent storage. Our study proposes a potential holographic recording material to apply in large size static 3D holographic displays, including analog hologram storage, digital hologram prints, holographic anticounterfeiting, and big data holographic disks.

Simultaneous identification of bearing dynamic coefficients in a water-gas lubricated hydrostatic spindle with a big thrust disc

A water-gas lubricated hydrostatic spindle system with big thrust disc, supported by a water-lubricated journal bearing and a gaslubricated thrust bearing, is developed to improve spindle stiffness and to reduce friction power of spindle. A new identification algorithm is derivated to identify simultaneously the eighteen dynamic coefficients of the coupled journal and thrust bearings. A comparison with the available experimental results reveals that the bearing coefficients is well estimated by the present theoretical model. The results also indicate that, the estimated bearing parameters by regularization solution are in good agreement with the assumed values; while it has opposite effect by directed solution for discrete ill-posed problems. It is concluded that, the identification accuracy of bearing parameters is govern by the measured errors; contrast to unbalance mass error and unbalance phase error, the displacement error leads the maximal percentage deviations of estimated coefficients.

Live fast, die young and make a really big disc:

Live fast, die young and make a really big disc:

Pseudo-hyperbolic distance and Gleason parts of the algebra of bounded hyper-analytic functions on the big disk

Let $G$ be the compact group of all characters of the additive group of rational numbers, and let $H_G^\infty$ be the Banach algebra of so-called bounded hyper-analytic functions on the big-disk $\Delta_G$. We characterize the pseudo-hyperbolic distance of the algebra $H_G^\infty$ in terms of the pseudo-hyperbolic distance of the algebra $H^\infty$ and establish relationships between Gleason parts in $M(H_G^\infty)$ and $M(H^\infty)$.

Efficient Storage Management over Cloud using Data Compression without Losing Searching Capacity

Nowadays due to social media, people may communicate with each other, share their thoughts and moments of life in form of texts, images or videos. We are uploading our private data in terms of photos, videos, and documents on internet websites like Facebook, Whatsapp, Google+ and Youtube etc. In short today world is surrounded with large volume of data in different form. This put a requirement for effective management of these billions of terabytes of electronic data generally called BIG DATA. Handling large data sets is a major challenge for data centers. The only solution for this problem is to add as many hard disk as required. But if the data is kept in unformatted the requirement of hard disk will be very high. Cloud technology in today is becoming popular but efficient storage management for large volume of data on cloud still there is a big question. Many frameworks are available to address this problem. Hadoop is one of them. Hadoop provides an efficient way to store and retrieve large volume of data. But Hadoop is efficient only if the file containing data is large enough. Basically Hadoop uses a big hard disk block to store data. And this makes it inefficient in the area where volume to data is large but individual file is small. To satisfy both challenges to store large volume of data in less space. And to store small unit of file without wasting the space. We require to store data not is usual form but in compressed form so that we can keep the block size small. But if we do so it added one more dimension of problem. Searching the content in a compressed file is very in-efficient. Therefore we require an efficient algorithm which compress the file without disturbing the search capacity of the data center. Here we will provide the way how we can solve these challenges. Keywords : Cloud, Big DATA, Hadoop, Data Compression, MapReduce

Manipulation of magnetic vortex parameters in disk-on-disk nanostructures with various geometry.

Magnetic nanostructures in the form of a sandwich consisting of two permalloy (Py) disks with diameters of 600 and 200 nm separated by a nonmagnetic interlayer are studied. Magnetization reversal of the disk-on-disk nanostructures depends on the distance between centers of the small and big disks and on orientation of an external magnetic field applied during measurements. It is found that manipulation of the magnetic vortex chirality and the trajectory of the vortex core in the big disk is only possible in asymmetric nanostructures. Experimentally studied peculiarities of a motion path of the vortex core and vortex parameters by the magneto-optical Kerr effect (MOKE) magnetometer are supported by the magnetic force microscopy imaging and micromagnetic simulations.

Glass for high-peak power high-energy generators and radiation amplifiers

The quality-related factors of neodymium- and copper-containing phosphate glass for big disc and high-aperture rod active elements of high-peak power high-energy radiation amplifiers and generators have been considered. The functionally important parameters of the mentioned glass are given.

Douglas Algebras on the Boundary of the Big Disk

Let G be the compact group of all characters of the additive group of rational numbers, and let H ∞ G be the Banach algebra of so called bounded hyper- analytic functions on the big-diskG. We give a sufficient condition for an algebra between H ∞ G and L ∞ be a Douglas algebra.

Magnetic Bistability of the “Small Disk on Big Disk” Structure

On the basis of the micromagnetic simulations we reveal that in the small disk on big disk (d+D) nanostructure it is possible the sustained existence of a single-domain and vortex configurations of magnetization. The presence of the metastable state is possible due to the energy barrier, which is caused by magnetostatic interaction between disks. Switching between states can be performed by the external high frequency excitation. Magnetization switching of the small disk on big disk nanostructure is determined by the interaction of the vortex core in big disk with z-component of the magnetization of small disk.