High-capacity Generator Research Articles

A low heat release cladding pump coupler

Few-mode erbium-doped fiber amplifiers (FM-EDFAs) have opened up the possibility of realizing the next generation of high-capacity, high-rate communication systems. However, the leakage of pump light during continuous operation of the FM-EDFA is likely to cause the temperature of the cladding pump coupler to be too high and thus destabilize the amplifier. In this work, a low heat release cladding pump coupler was designed and the corresponding FM-EDFA was constructed. The cladding pump coupler in the 8 h of continuous operation of the FM-EDFA is at 27.8 °C for maximum, 23.7 °C for minimum, and 26 °C for average temperatures, respectively, which are in a low-temperature safe transmission state. The FM-EDFA performance test was performed on this basis, and the results show that when the input pump power is 7 W, the maximum gain fluctuation of each mode of FM-EDFA at 1550 nm in 0∼8 h is only 1.5 dB, the gain of all modes is greater than 23 dB and the differential mode gain (DMG) is less than 2 dB. In addition, the FM-EDFA still has good performance in the C-band after 8 h of continuous operation. The gain for all modes is greater than 21 dB, DMG is less than 2 dB, and wavelength flatness is 3.6 dB. The low heat release cladding pump coupler is conducive to the stable amplification transmission of FM-EDFA, which is of great significance to achieving the upgrading and expansion of the communication system.

Logical rotation of non-separable states via uniformly self-assembled chiral superstructures

The next generation of high-capacity, multi-task optical informatics requires sophisticated manipulation of multiple degrees of freedom (DoFs) of light, especially when they are coupled in a non-separable way. Vector beam, as a typical non-separable state between the spin and orbital angular momentum DoFs, mathematically akin to entangled qubits, has inspired multifarious theories and applications in both quantum and classical regimes. Although qubit rotation is a vital and ubiquitous operation in quantum informatics, its classical analogue is rarely studied. Here, we demonstrate the logical rotation of vectorial non-separable states via the uniform self-assembled chiral superstructures, with favorable controllability, high compactness and exemption from formidable alignment. Photonic band engineering of such 1D chiral photonic crystal renders the incident-angle-dependent evolution of the spatially-variant polarizations. The logical rotation angle of a non-separable state can be tuned in a wide range over 4π by this single homogeneous device, flexibly providing a set of distinguished logic gates. Potential applications, including angular motion tracking and proof-of-principle logic network, are demonstrated by specific configuration. This work brings important insight into soft matter photonics and present an elegant strategy to harness high-dimensional photonic states.

Deepfake: Creation and Detection using Deep Learning

Abstract: The aim of this study is to develop customizedphoto-realistic talking head models, which refers to the creation of systems capable of generating believable video sequences that mimic the speech expressions and facial movements of a specific person. The authors propose a system that can produce talking head models using just a few photographs, a technique known as "few-shot learning," and with minimal training time. This system is capable of generating a plausible outcome using just one photograph, and additional photographs enhance the level of personalization. The authors present a system that can perform few-shot learning by conducting meta-learning on a vast collection of videos, which allows it to address the neural talking head models of new and unseen individuals as adversarial training problems with high-capacity generators and discriminators. The system can personalize both the generator and the discriminator's parameters based on each person, enabling training to be performed quickly with only a few images, despite the need to fine-tune millions of parameters.

Spin-orbit microlaser emitting in a four-dimensional Hilbert space.

A step towards the next generation of high-capacity, noise-resilient communication and computing technologies is a substantial increase in the dimensionality of information space and the synthesis of superposition states on an N-dimensional (N > 2) Hilbert space featuring exotic group symmetries. Despite the rapid development of photonic devices and systems, on-chip information technologies are mostly limited to two-level systems owing to the lack of sufficient reconfigurability to satisfy the stringent requirement for 2(N - 1) degrees of freedom, intrinsically associated with the increase of synthetic dimensionalities. Even with extensive efforts dedicated to recently emerged vector lasers and microcavities for the expansion of dimensionalities1-10, it still remains a challenge to actively tune the diversified, high-dimensional superposition states of light on demand. Here we demonstrate a hyperdimensional, spin-orbit microlaser for chip-scale flexible generation and manipulation of arbitrary four-level states. Two microcavities coupled through a non-Hermitian synthetic gauge field are designed to emit spin-orbit-coupled states of light with six degrees of freedom. The vectorial state of the emitted laser beam in free space can be mapped on a Bloch hypersphere defining an SU(4) symmetry, demonstrating dynamical generation and reconfiguration of high-dimensional superposition states with high fidelity.

Three‐Dimensional Porous Carbon Framework Confined Si@TiO2 Nanoparticles as Anode Material for High‐Capacity Lithium‐Ion Batteries

AbstractSilicon‐based lithium‐ion battery anodes, in recent years, have caught widespread interest seeing their great theoretical capacity, low charge‐discharge potentials, and ample natural storage. However, poor electrochemical performance is typically observed, attributed mainly to significant volume expansion, unstable solid‐electrolyte interphase, and low intrinsic electronic/ionic conductivity. Numerous attempts have been reported to revamp its electrochemical performance, including the capacity cycle stability and cycle life. Herein, we reported the synthesis of three‐dimensional (3D) Si@TiO2@C nanohybrids adopting a facile three‐step synthesis strategy. Compared with Si@C and C (derived from polyaniline) electrodes, the well‐designed Si@TiO2@C electrode delivered a momentous enhancement in the electrochemical performance thanks to the presence of robust TiO2 shell and polyaniline‐derived porous carbon skeleton to cope with volume changes of silicon during lithiation and promote the electric conductivity of the overall electrode. The Si@TiO2@C hybrid electrode delivered a high initial discharge capacity of 1748.6 mA h g−1 at 100 mA g−1 and a stable reversible capacity of 1112.5 mA h g−1 at 100 mA g−1 after 500 cycles, with the coulomb efficiency of 98.8 %. Moreover, the electrode showed a high reversible capacity of 508.9 mA h g−1 even at 500 mA g−1 at the 500th cycle with the coulomb efficiency of 99.1 %. This work showed the paramount role of TiO2 shell and 3D porous carbon skeleton, being a promising future for designing the next generation of high capacity, long cycle stable anode materials for lithium‐ion batteries.

Design of Generator Stator Protection 100% Using Overvoltage and Undervoltage Schemes

Nowadays, there are still many high capacity generators have not yet protected completely from their internal ground faults. They still rely on differential and over current relays. It is seen that this relay will reduce their sensitivities when applied to generators with high impedance grounding systems. To overcome such problem, a combination protection scheme of the neutral overvoltage (59N) and neutral undervoltage third harmonics (27N3) is developed. This paper aims to design the protection scheme for high capacity generators. This paper demonstrates the designing of neutral grounding transformer (NGT) system, the relay settings and reviewing of their sensitivities. To clarify the concepts this study uses a generator 802 MVA, 22.8 kV as object. The results show that the protection scheme is very effective to protect 100% of generator stator with relays overlapping of 31.5%. It needs NGT transformer with capacity of only 28.33 kVA, 15000/240 V, and the secondary resistor of 0.38,117 kW. This paper can hopefully be used as one reference for protection system engineers to design or develop protection schemes in their fields especially whose generator has not equipped yet with such protection scheme.

Chemically Prelithiated Hard-Carbon Anode for High Power and High Capacity Li-Ion Batteries.

Hard carbons (HC) have potential high capacities and power capability, prospectively serving as an alternative anode material for Li-ion batteries (LIB). However, their low initial coulombic efficiency (ICE) and the resulting poor cyclability hinder their practical applications. Herein, a facile and effective approach is developed to prelithiate hard carbons by a spontaneous chemical reaction with lithium naphthalenide (Li-Naph). Due to the mild reactivity and strong lithiation ability of Li-Naph, HC anode can be prelithiated rapidly in a few minutes and controllably to a desirable level by tuning the reaction time. The as-formed prelithiated hard carbon (pHC) has a thinner, denser, and more robust solid electrolyte interface layer consisting of uniformly distributed LiF, thus demonstrating a very high ICE, high power, and stable cyclability. When paired with the current commercial LiCoO2 and LiFePO4 cathodes, the assembled pHC/LiCoO2 and pHC/LiFePO4 full cells exhibit a high ICE of >95.0% and a nearly 100% utilization of electrode-active materials, confirming a practical application of pHC for a new generation of high capacity and high power LIBs.

5-V plateau observed for Li-rich Li1 + xMn2 − xO4 stoichiometric spinels containing low-temperature-grown Li2MnO3 as an impurity phase

The redox reaction of tetravalent Mn4+ ions has attracted much interest since it is considered that this reaction is closely related to the generation of high capacity in layered cathodes with excess lithium.We considered that to investigate materials, which include tetravalent Mn4+ ions and have a different crystal structure from Li2MnO3, is valuable for understanding the reaction mechanism. The result will reveal whether Mn4+ ion in the Li2MnO3 structure is essential or only existence of Mn4+ ion is sufficient for appearance of the high capacity. In this work, we investigated Li-rich Li1+xMn2−xO4 (x=0.20, 0.25, 0.30, 0.33) stoichiometric spinels. For a Li content of x=0.33, a capacity of 50mAhg−1 was observed in 5-V region. It is possible that the Li-rich spinel includes a small amount of Li2MnO3 impurity, which exhibits the 5-V plateau. No significant changes in lattice constants are observed from x=0.25 to 0.33, which indicates generation of Li2MnO3. We estimated the amount as 9.2wt.% for x=0.33 by standard addition analysis, and true Li concentration of the spinel component as 0.23. However, the observed 5-V capacity cannot be attributed to only the impurity phase of Li2MnO3, because the specific capacity must exceed 540mAhg−1 to explain it. It is considered that the observed 5-V capacity is caused by two components of the Li-rich spinel and the other phase like a composite material of Li2MnO3/Li-rich spinel. The 5-V capacity for the pure spinel component estimated by extrapolating the 5-V capacity vs. impurity-concentration plot is 7.9mAhg−1.

Reactions of graphene supported Co3O4 nanocubes with lithium and magnesium studied by in situ transmission electron microscopy

Reaction beyond intercalation and the utilization of metal ions beyond lithium-ions are two promising approaches for developing the next generation of high capacity and low cost energy storage materials. Here, we use graphene supported Co3O4 nanocubes and study their reaction with lithium, magnesium and aluminum using in situ transmission electron microscopy. On lithiation, the Co3O4 nanocubes decompose to Co metal nanoparticles (2 to 3 nm) and embed in as-formed Li2O matrix; conversely, the CoO nanoparticles form on the Co site accompanying the decomposition of Li2O in the delithiation process. The lithiation process is dominated by surface diffusion of Li+, and graphene sheets enhance the Li+ diffusion. However, upon charge with magnesium, the Mg2+ diffusion is sluggish, and there is no sign of conversion reaction between Mg and Co3O4 at room temperature. Instead, a thin film consisting of metal Mg nanoparticles is formed on the surface of graphene due to a process similar to metal plating. The Al3+ diffusion is even more sluggish and no reaction between Al and Co3O4 is observed. These findings provide insights to tackle the reaction mechanism of multivalent ions with electrode materials.

Torque Performance Study of Magnus Wind Turbine

Current wind turbine technology cannot operate in low wind velocity conditions to produce adequate torque for high capacity generators. This Magnus Wind Turbine (MWT) experiment aims to study the torque performance in relationship with the frequency of rotation of the cylinder blade. The experiment started with the design and fabrication of the MWT through computational calculation and simulation. This study solves the relationship gap between the torque generated and the rotation frequency of the cylinder blade by building upon previous research where only one type of rotation frequency of the cylinder blade was used. The research is done inside a wind tunnel by attaching a spring balance to the rotor shaft through a rope. The spring balance stops the rotor shaft from rotating at certain positions and the corresponding torques were measured, while the rotation frequency of the cylinder blade and wind velocity are controlled. The results show a positive trend that the torque generated will increases as rotation frequency of the cylinder blade and wind velocity are increased. Therefore, the results indicate the possibility that a higher torque can be produced by MWT in countries with low wind velocity.

Research on Electrical Power System with Analysis of Fault Operation State Magnetic Field about DFIG in Wind Power

Doubly-fed Induction Generator (DFIG) is an important equipment in electrical power system. Operation state of DFIG is complex: it works at subsynchronism, synchronization and hypersynchrony state. Electromagnetic field is various. There is winding on stator and rotor, it’s more possible for fault to happen. Text discuss structure of DFIG, finite element method (FEM) model including stator rotor and air-gap is created, typical magnetic field is calculated including normal operation state, turn-to-turn and single-phase short-circuit happened, result is analysed, distribution discipline of multiple magnetic field is obtained. It provide the evidence to early failure prediction, basic data to develop and design high-capacity generator, optimize structure and magnetic field analysis of DFIG.

Generation of high capacity, high density bubble domain patterns using electron beam technology

Three mask fabrication techniques capable of producing megabit capacity chip mask sets have been investigated: photocomposition, electron beam raster scan, and electron beam vector scan. Details of the technique used for photocomposition are described to illustrate the difficulties of obtaining 1 μm resolution over 1×1 cm2 chip areas with reasonable throughput. These difficulties may be circumvented by using electron beam pattern generation. Details of the experimental vector scan system used are presented and a comparison made of results obtained using the three techniques.

Abdominal compression during angiography to increase radiographic quality.

Rapid serial filming usually requires short exposures, e.g., 0·1 second at the rate of three films per second—a limit determined by the time interval when the film is motionless in the changer. If high capacity generators are not available to give adequate mAs, the only method of producing films of adequate density is to increase the kilovoltage. This technique results in low contrast radiographs and poor quality contrast density. The obese patient is particularly difficult to examine because of this problem.