Segmented Scheme Research Articles

A segmented protection scheme based on maximum bandwidth sharing in F5G

A segmented protection scheme based on maximum bandwidth sharing in F5G

SLAP: Segmented Reuse-Time-Label Based Admission Policy for Content Delivery Network Caching

‘‘Learned” admission policies have shown promise in improving Content Delivery Network (CDN) cache performance and lowering operational costs. Unfortunately, existing learned policies are optimized with a few fixed cache sizes while in reality, cache sizes often vary over time in an unpredictable manner. As a result, existing solutions cannot provide consistent benefits in production settings. We present SLAP , a learned CDN cache admission approach based on segmented object reuse time prediction. SLAP predicts an object’s reuse time range using the Long-Short-Term-Memory model and admits objects that will be reused (before eviction) given the current cache size. SLAP decouples model training from cache size, allowing it to adapt to arbitrary sizes. The key to our solution is a novel segmented labeling scheme that makes SLAP without requiring precise prediction on object reuse time. To further make SLAP a practical and efficient solution, we propose aggressive reusing of computation and training on sampled traces to optimize model training, and a specialized predictor architecture that overlaps prediction computation with miss object fetching to optimize model inference. Our experiments using production CDN traces show that SLAP achieves significantly lower write traffic (38%-59%), longer SSDs lifetime (104%-178%), a consistently higher hit rate (3.2%-11.7%), and requires no effort to adapt to changing cache sizes, outperforming existing policies.

A Segmented Iterative Learning Scheme-Based Distributed Fault Estimation for Switched Interconnected Nonlinear Systems.

In this article, a distributed fault estimation (DFE) approach for switched interconnected nonlinear systems (SINSs) with time delays and external disturbances is proposed using a novel segmented iterative learning scheme (SILS). First, through the utilization of interrelated information among subsystems, a distributed iterative learning observer is developed to enhance the accuracy of fault estimation results, which can realize the fault estimation of all subsystems under time delays and external disturbances. Simultaneously, to facilitate rapid fault information tracking and significantly reduce sensitivity to interference, a new SILS-based fault estimation law is constructed by combining the idea of segmented design with the method of variable gain. Then, an assessment of the convergence of the established fault estimation methodology is conducted, and the configurations of observer gain matrices and iterative learning gain matrices are duly accomplished. Finally, simulation results are showcased to demonstrate the superiority and feasibility of the developed fault estimation approach.

Segmented Hash-Based Privacy-Preserving Image Retrieval Scheme in Cloud-Assisted IoT

Segmented Hash-Based Privacy-Preserving Image Retrieval Scheme in Cloud-Assisted IoT

Maximum Efficiency Tracking and ZVS Realization for Wide Output Voltage Range Employing Segmented TPS Modulation Scheme

The efficiency of wireless power transfer (WPT) systems is highly dependent on the load and dc voltage gain, which may change in a wide range in electric vehicle (EV) charging applications. Besides, existing control triple-phase-shift (TPS) strategies aimed at power regulation, zero-voltage switching (ZVS) realization and maximum efficiency point tracking (MEPT) have limitations when applied to the wide output voltage application. To fill this gap, a segmented TPS modulation scheme is proposed. Considering wide-range ZVS, three different working modes are derived to achieve MEPT over the wide output voltage range. The proposed modulation scheme employs closed-loop control by integrating different working modes. In addition, the efficiency-oriented seamless transition method among different working modes is described, which can avoid the transient oscillation at the boundary of the mode transition. The proposed modulation scheme's on-state loss and switching loss are compared to the traditional TPS modulation scheme. Finally, a 1.5 kW prototype has been built to verify effectiveness of the proposed modulation scheme within the wide voltage range, and the measured efficiency can be increased by up to 0.82% in the deep buck mode and 2.20% in the deep boost mode.

3D printed crack-free SiOC(Fe) structures with pyrolysis-induced carbon nanowires for enhanced wave absorption performance

High-performance SiOC(Fe) wave-absorbing ceramics, containing a large number of carbon nanowires, were successfully prepared using a combination of photopolymerization 3D printing technology and the polymer-derived ceramic pyrolysis method. By employing an optimized segmented slow heating scheme with extended holding time, the pyrolysis of SiOC(Fe) ceramics at 1000 °C facilitated the growth of carbon nanowires, Fe3C and SiO2 grains. These carbon nanowires were interlaced and interconnected within the samples, forming abundant conductive networks. This highly conducive network efficiently converted electromagnetic energy into thermal energy, effectively dissipating electromagnetic waves, and consequently enhancing the microwave absorption performance of ceramics. Moreover, this approach not only reduced ceramic cracks but also improved the dielectric loss performance of the materials, achieving a minimum reflectivity value of −35.72 dB. The SiOC(Fe) ceramics added with 5 wt% VcFe effectively enhanced the magnetic loss of the material, reduced the difference between the relative complex permeability (μr) and the relative complex dielectric constant (εr), and improved the impedance matching between the material surface and air, thereby further improving its microwave absorption performance. This resulted in an increase in the maximum effective absorption bandwidth of the material to 12.7 GHz at 5 mm. This study offers a promising solution for the preparation of ceramic matrix composite materials incorporating carbon nanowires, magnetic particles and ceramic precursors, which would be potentially valuable for radar detection and sensor applications.

3D CEST MRI with an unevenly segmented RF irradiation scheme: A feasibility study in brain tumor imaging.

To integrate 3D CEST EPI with an unevenly segmented RF irradiation module and preliminarily demonstrate it in the clinical setting. A CEST MRI with unevenly segmented RF saturation was implemented, including a long primary RF saturation to induce the steady-state CEST effect, maintained with repetitive short secondary RF irradiation between readouts. This configuration reduces relaxation-induced blur artifacts during acquisition, allowing fast 3D spatial coverage. Numerical simulations were performed to select parameters such as flip angle (FA), short RF saturation duration (Ts2), and the number of readout segments. The sequence was validated experimentally with data from a phantom, healthy volunteers, and a brain tumor patient. Based on the numerical simulation and l-carnosine gel phantom experiment, FA, Ts2, and the number of segments were set to 20°, 0.3 s, and the range from 4 to 8, respectively. The proposed method minimized signal modulation in the human brain images in the kz direction during the acquisition and provided the blur artifacts-free CEST contrast over the whole volume. Additionally, the CEST contrast in the tumor tissue region is higher than in the contralateral normal tissue region. It is feasible to implement a highly accelerated 3D EPI CEST imaging with unevenly segmented RF irradiation.

A method for pole figure measurements via a dynamic segmented spiral scheme

A new method for pole figure measurement is described, entitled a dynamic segmented spiral scheme. Compared with the schemes currently in use, the dynamically segmented spiral scheme is shown to have advantages in terms of evenness of pole figure coverage and phase fraction accuracy. The phase fraction accuracy is shown to be robust for a variety of texture components commonly encountered in steels and for texture sharpness exceeding what is commonly encountered for rolled sheet steels. This scheme provides a promising alternative to conventional methods of simultaneous texture and phase fraction measurement.

Stepwise correction of ECMWF ensemble forecasts of severe rainfall in China based on segmented hierarchical clustering

Ensemble forecast plays a vital role in numerical weather prediction. Hence, effectively extracting useful information from ensemble members to improve precipitation forecasting skills has always been an important issue. Using the ensemble forecast data on precipitation from the ECMWF-GEPS (Global Ensemble Prediction System), we propose a stepwise correction method, based on segmented hierarchical clustering (SHC), for forecast of daily precipitation. This method employs a segmented correction scheme, thereby generating more probabilistic forecast information and improving forecasts. Validations of the SHC method have been performed by comparison with two other methods, namely the ensemble-mean (EM) method and the direct hierarchical clustering (HC) method. Our results showed that deterministic forecast via SHC improved the ability to forecast heavy precipitation in short- and medium-range forecast timeframes. Therefore, SHC performed better than either EM or HC by effectively extending lead time to impending severe rainfall by 2–3 days relative to the other two methods. SHC also demonstrated better performance than the other methods through continuous forecast verification in summer 2021, and even had better effects in the forecast of multiple heavy-precipitation cases, including the Zhengzhou extreme rainfall on 20 July 2021. Overall, the SHC method has great potential for improving ensemble rainfall forecasts in the current operational system.

Detuning modulated composite segments for robust optical frequency conversion

The creation of efficient broadband frequency conversion devices while maintaining robustness to manufacturing and setup errors is crucial for accurate multiphoton spectroscopy, broadband imaging and the design of robust optical sources. Traditionally, nonlinear optical conversion processes are either efficient but narrowband or broadband but with low photon conversion yield. Several methods have been introduced in recent years to obtain both with great success, among them we can find adiabatic frequency conversion and Shaka–Pines composite segmented design. Here, we expand the composite design and introduce the detuning modulated composite segmented (DMCS) scheme in nonlinear optics, which offers a broadband, efficient and robust method for frequency conversion. We also present the constant-length DMCS scheme, which offers multiple efficient and robust wavelength regimes for broadband upconversion. We apply these schemes to a system of quasi-phase-matching crystal for the sum frequency generation process, and demonstrate the high robustness and bandwidth of the composite schemes. We show that these schemes are robust to temperature and crystal length variations and can have a superior conversion bandwidth under length and power constraints compared to other conversion schemes, such as periodically poled and adiabatic chirped crystals. We believe that the new family of DMCS schemes will have many uses in applications of frequency conversion, due to their robustness, low energy demand and compact size.

MPC-Based Startup Current Shaping Strategy With State-Space Model of DAB in DC Distribution System

The popularity of renewable energy sources and load structure changes make the development of dual active bridge (DAB) dc–dc converters in the dc distribution system. However, due to the fast start and the large output capacitors, DAB converters suffer from inrush current. This article aims to design a current shaping scheme with a fast dynamic response to startup quickly and control the inrush current. First, the state-space average model of the startup process and its simplification are analyzed. It presents a theoretical basis for the widely used vary-frequency segmented startup scheme. Then, the model predictive control with the current shaping (MPC-CS) scheme that features fast dynamic response is presented. Also, single objective cost function, demarcation method between operating modes, and enhanced preprocessing modules are introduced to address the difficulties increased by the high switching frequency using wide bandgap devices. Finally, evaluations and comparisons among two typical schemes and MPC-CS scheme are carried out on simulations and a full-silicon-carbide-based DAB converter with the distributed heterogeneous controllers, which verify the practicality of the MPC-CS.

Relativistic Segmented Correlation Consistent Basis Sets for the 5p and 6p Elements.

The relativistic all-electron triple-ζ (TZ) and quadruple-ζ (QZ) correlation-consistent basis sets for the 5p and 6p elements were reoptimized to have a segmented contraction scheme. Properties computed with the segmented basis sets using the coupled-cluster level of theory with single, double, and perturbative triple excitations closely match the results obtained using the generally contracted analogues. Deviations in the ionization potentials and electron affinities computed using the segmented basis sets compared with those computed with the generally contracted basis sets are within 1 kcal mol-1. The relative deviation in the computed bond lengths for a selection of diatomic molecules is within 0.02 Å, and the computed harmonic vibrational frequencies differ by less than 3%. The mean absolute deviations (MADs) in the computed bond dissociation energies are 1.01 and 1.31 kcal mol-1 for the TZ and QZ basis sets, respectively, when only the valence electrons are correlated and 0.14 and 0.10 kcal mol-1 for the TZ and QZ basis sets, respectively, when the valence and outer-core electrons are correlated. The segmented basis sets also retain the systematically convergent behavior intrinsic to the correlation-consistent family of basis sets while affording speedups for the average time required to form the Fock matrix from 32.8 to 82.9× compared to the time required with the generally contracted versions when used with integral algorithms employed by many computational chemistry software packages.

Stable single transverse mode excitation in 50 µm core fiber using a photonic-lantern-based adaptive control system.

We report on the generation of single transverse mode output in large-mode-area fiber with a core diameter of 50 µm using a 3×1 photonic-lantern-based adaptive spatial mode control system. We have designed and fabricated the photonic lantern composed of a single mode fibers bundle taper region and a multi-segment multimode fiber splicing region. From simulation and experiments, we demonstrate that the quality of the output beam is significantly influenced by the size of the fibers bundle's waist and the segmented splicing scheme of the multimode fiber. Stable single transverse mode output is achieved at 1064 nm with M2 ∼1.4, which will provide a possible technical solution to increase the mode instability threshold in high power large-mode-area fiber systems.

A segmental pump-motor control scheme to attain targeted speed under varying load demand of a hydraulic drive used in heavy earth movers

The work presents a segmented pump-motor control scheme of a closed-loop hydraulic drive used in mining equipment. It analyses the dynamics of the drive through modeling and simulation. The system model integrates a control scheme for modulating the displacement of the pump and the hydro-motor of the hydraulic drive. The model also considers the state-dependent non-linear losses as well as the transient behaviors of the pump and the hydro-motor. The experimental results validate the model for various working conditions of the equipment. The model simulation also analyses the perturbation of critical parameters and control gain on the system's performance for a wide range of operating conditions of the mining equipment. The study performed in this research work will be expedient for the preliminary design and assortment of similar hydraulic drive used in the mobile equipment.

Numerical investigation of dynamic characteristics for expansion power generation system of liquefied air energy storage

Liquefied air energy storage (LAES), as a type of compressed air energy storage, has comprehensive advantages. It is suitable for various situations regarding electric energy storage, such as generation, transmission, and user-side applications. It is necessary to learn the operating characteristics of LAES for safe, stable, and controllable operations. In this study, a dynamic model of a 12.5 MW LAES system is established and used to simulate various operating conditions in the expansion phase. The results show that the startup period and rotating speed overshoot of the expander affect each other during the startup process. This can be balanced using a segmented startup scheme, so that the rotating speed overshoot can be controlled within a permissible safe range while shortening the startup period as much as possible. When the segmented startup scheme is “9000 rpm/min–3000 rpm/min,” the startup time is shortest, at 145 s. A ±0.03 Hz dead zone for frequency regulation is considered in the application of the LAES system to the primary frequency regulation of power grid to avoid frequent regulation of the control system, and the primary frequency regulation process is controlled to be within 20 s, meeting the requirements of the power grid. As the action of the emergency closing valve of the protection system in the process of power generation is triggered by the off-grid of the expansion generator owing to an unexpected event, the delay time of the valve action must be controlled to remain within the permissible safe range. This ensures that the expansion generator is safe, and avoids the rotor over-speed caused by the delay of the valve action. The dynamic model and its simulation results can be used to support operation control strategies for LAES systems for primary frequency regulation.

Three-dimensional sound scattering from transversely symmetric surface waves in deep and shallow water using the equivalent source method.

This paper proposes a propagation model to calculate the three-dimensional (3-D) sound scattering from transversely symmetric sea surface waves in both deep and shallow water using the equivalent source method (ESM). The 3-D sound field is calculated by integrating an assembly of two-dimensional (2-D) transformed fields with different out-of-plane wavenumbers through a cosine transform. Each 2-D solution is calculated using the ESM incorporating a complex image method that can efficiently and accurately solve the 2-D water/seabed Green's function. The oscillatory cosine integral is accurately calculated using a segmented integral scheme requiring relatively few 2-D solutions, which can be further improved through the use of parallel computation. The model is validated by comparison with a 3-D Helmholtz-Kirchhoff method for deep water and a finite element method for a shallow water wedge with both a fluid and an elastic seabed. The model is as accurate as the finite element approach but more numerically efficient, which enables Monte Carlo simulations to be performed for random rough surfaces in order to study the scattering effects at a reasonable computational cost. Also, 3-D pulse propagation in the shallow water wedge is demonstrated to understand the out-of-plane scattering effects further.

A New Coupling Structure and Position Detection Method for Segmented Control Dynamic Wireless Power Transfer Systems

In this letter, a new coupling structure for dynamic wireless power transfer (DWPT) systems is proposed. Bipolar coils are symmetrically placed on the transmitter unipolar coils, resulting in natural decoupling between the bipolar coils and the unipolar coils. This special structure can mitigate the self-couplings between the adjacent unipolar transmitter coils and hence facilitate the design of the compensation circuit. Another remarkable advantage of this design is that it can lead to a stable mutual coupling between the transmitter array and the receiver when the receiver moves along the transmitter, making it a natural fit for DWPT applications. Furthermore, to reduce the electromagnetic interference and power loss, an automatic segmented control scheme is implemented, and a position detection method by monitoring the primary current is developed. The feasibility of the proposed coupling structure and the position detection method are verified on a laboratory prototype with 72-V output voltage. The experimental results show that the power fluctuation is within ±2.5%, and system efficiency is around 90%. (This letter is accompanied by a video demonstrating the experimental test).

A Novel Segmented Component Injection Scheme to Minimize the Oscillation of DC-Link Voltage Under Balanced and Unbalanced Conditions for Vienna Rectifier

This paper investigates a Vienna rectifier as a charger for series-connected battery packs. Focusing on carrier-based pulsewidth modulation (CBPWM), the ripple current flowing through the neutral point (NP) results in the voltage oscillation if the loads are resistive. To reduce the ripple of average NP current with mitigated distortion under balanced and unbalanced dc-link voltages conditions, a novel CBPWM with segmented component injection scheme (SCIS) is proposed in this paper. After dc component injection, continuous intervals for optimized component injection and clamping intervals for compensation component injection are identified. Optimized components are calculated originally based on unbalanced factor to make the average NP current zero-size in one switching period. Moreover, unique compensation components generate suitable NP current to shape the sinusoidal input currents according to the circuit analysis. In consequence, the SCIS not only keeps the input current with low-harmonic distortion, but also minimizes the oscillation of dc-link voltage under balanced and unbalanced conditions. In addition, the value of the NP current during the clamping intervals is analyzed under various operating conditions. The effectiveness and the performance of the proposed SCIS are verified by simulation and experiments.

Does physical activity associated with chronic food restriction alleviate anxiety like behavior?

We present a method for improving the signal-to-noise ratio in photothermal microscopy by optimizing the detection aperture in the spatially segmented balanced detection scheme. Experimental studies show a 1.44-fold improvement in the signal-to-noise ratio compared with the previous scheme. Consequently, the ratio is 9.6 times larger than that in conventional detection. The proposed method is implemented in a laser scanning photothermal microscope using low-cost compact laser diodes as the light source.

Generalized Segmented Bit-Flipping Scheme for Successive Cancellation Decoding of Polar Codes With Cyclic Redundancy Check

Generalized Segmented Bit-Flipping Scheme for Successive Cancellation Decoding of Polar Codes With Cyclic Redundancy Check