Gain Property Research Articles

Submodular batch scheduling on parallel machines

AbstractThis article studies a submodular batch scheduling problem motivated by the vacuum heat treatment. The batch processing time is formulated by a monotone nondecreasing submodular function characterized by decreasing marginal gain property. The objective is to minimize the makespan. We show the NP‐hardness of the problem on a single machine and of finding a polynomial‐time approximation algorithm with the worst‐case performance ratio strictly less than for the problem on parallel machines. We introduce a bounded interval to model the batch processing time using two parameters, that is, the total curvature and the quantization indicator. Based on the decreasing marginal gain property and the two parameters, we make a systematic analysis of the full batch longest processing time algorithm and the longest processing time greedy algorithm, and propose the instances with the bound of batch capacity for these two algorithms for the submodular batch scheduling problem. Moreover, we prove the submodularity of batch processing time function of the existing batch models including the parallel batch, serial batch, and mixed batch models. We compare the worst‐case performance ratios in the existing batch models with those deduced from our work in the submodular batch model. In most situations, the worst‐case performance ratios deduced from our work are comparable to the best‐known worst‐case performance ratios with tailored examinations.

∼2μm luminescence and energy transfer mechanism in highly Ho3+/Tm3+ co-doped bismuth glass

Highly Ho3+/Tm3+ co-doped Bi2O3-B2O3-Al2O3-BaF2 glasses were fabricated using the melt-quenching technique. The emission, radiation, and gain characteristics of the glass samples at the wavelength of 2.0 μm were examined analyzed. An intense and broad 2.0 µm emission, resulting from the 3F4→3H6 transition of Tm3+ and the 5I6→5I7 transition of Tm3+, was detected under the stimulation of 808 nm LD. The gain coefficient of Ho3+ in Ho3+/Tm3+ co-doped glass reaches 7.81 cm−1(at 2050 nm), which is 7.5 times as high as that of tellurite glass. Meanwhile, the large σemi × Δλeff(39.84 × 10-26 cm3) and σemi × τrad(16.10 × 10-21 cm2 ms) indicated BBTH4 glass possessed a large gain property and broadband. The energy transfer process of Tm3+: 3F4 ↔ Ho3+:5I7 was analyzed, the CD-A is 90 times larger than the CA-D. The Ho3+/Tm3+ co-doped Bi2O3-B2O3-Al2O3-BaF2 glasses show potential as broadband mid-infrared emission gain material.

Integrated erbium-doped waveguide amplifier on lithium niobate on insulator

The erbium-doped lithium niobate on insulator (Er:LNOI) has garnered significant attention as it combines outstanding gain property with integration capabilities, making it a promising solution for active devices on the versatile LNOI platform. This also paves a way for the development of appealing erbium-doped waveguide amplifiers. Here, we demonstrate an efficient integrated Er:LNOI micro-waveguide amplifier directly compatible with the lens fiber. In a 5.6-cm-long Er:LNOI micro-waveguide, we demonstrate a maximum internal net gain of 18.8 dB for 1531-nm signal light with 1460-nm pumping. Moreover, the maximum output signal power surpasses 20 mW, thereby confirming the practicality of the Er:LNOI micro-waveguide amplifier.

Realization of broadband ∼1.8 μm luminescence by level population inversion in Tm3+ doped tellurite glass for laser applications

This study aims to investigate the characteristics of Tm3+ doped TeO2–B2O3–Al2O3Na2O glass. The structures that exist in host glass were obtained from the Raman spectrum. Due to the introduction of sodium and aluminum, the TeOTe bond is broken, and the amount of bridge oxygen is reduced, causing the transformation of [TeO4] structural units to [TeO3+1] and [TeO3] structural units. The spectrum characteristics of Tm3+ in the samples were predicted by theoretical calculations. Prepared Tm3+ doped glass has large Ω2 and small Ω6, which is connected to the ligand field's asymmetry and the stiffness of the network. Furthermore, under the excitation of 808 nm laser diode, broadband ∼1.8 μm fluorescence was observed and the effective fluorescent bandwidth Δλeff of 1830 nm emission in the glass is about 234 nm. For the sample with 0.5 mol% Tm2O3, the large values of emission cross-section product (9.08 × 10−21 cm2) and σemi × Δλeff product (21.25 × 10−26 cm3) indicate a good gain property as well as a good gain bandwidth. Eventually, the energy migration process and cross-relaxation process between thulium ions were analyzed. The micro-parameter of the CR process is 4.049 × 10−40 cm6/s. Hence, the results indicate that the prepared Tm3+ doped glass could be a potential candidate for ∼2 μm mid-infrared laser devices.

Input‐to‐state practical stability for nonautonomous nonlinear infinite‐dimensional systems

AbstractIn this article, we are concerned with the input‐to‐state practical stability (ISpS) of nonautonomous nonlinear infinite‐dimensional systems. Sufficient conditions of ISpS are provided based on Lyapunov functions and a nonlinear inequality. We characterize ISpS in terms of uniform practical asymptotic gain property. We show that for a class of admissible inputs the existence of an ISpS‐Lyapunov function implies the ISpS of a system in Banach spaces. These results are used to study the input‐to‐state practical stability of a certain class of nonautonomous semilinear evolution equations. Furthermore, we provide a small‐gain theorem for nonautonomous nonlinear interconnected systems. An example is used to illustrate the application of the developed method.

Saturating PI Control of Stable Nonlinear Systems Using Singular Perturbations

This article presents an antiwindup propor- tional-integral (PI) controller, using a saturating integrator, for a single-input and single-output (SISO) stable nonlinear plant, whose steady-state input–output map is increasing. We prove that, under reasonable assumptions, there exists an upper bound on the controller gain such that for any constant reference input, the corresponding equilibrium point of the closed-loop system is exponentially stable, with a “large” region of attraction. When the state of the closed-loop system converges to this equilibrium point, then the tracking error tends to zero. The closed-loop stability analysis employs Lyapunov methods in the framework of the singular perturbations theory. Finally, we show that if the plant satisfies the asymptotic gain property, then the closed-loop system is globally asymptotically stable for any sufficiently small controller gain. The effectiveness of the proposed PI controller is proved by showing how it performs as part of the control algorithm of a synchronverter (a special type of dc to ac power converter).

A High Power Density Wide Range DC–DC Converter for Universal Electric Vehicle Charging

This article presents a single stage isolated bidirectional DC–DC converter comprising of LCL-T resonant network for universal electric vehicle (EV) charging. Fixed frequency operation along with phase-shift control enables easier design of passive components, while achieving high efficiency across wide output voltage range. Furthermore, to increase the switching frequency and consequently the power density, gallium nitride (GaN) switches are explored in the proposed solution. In order to facilitate use of commercially available 650 V GaN transistors, a multi-level inverter and a reconfigurable rectifier architecture is utilized along with LCL-T resonant network, accommodating an input voltage of 800 V, generated from an universal three phase ac input supply, and an output voltage ranging from 150 V to 950 V catering to large variation of battery voltages from different vehicle manufacturers. The constant input voltage-to-output current gain property of LCL-T network, along with an efficient phase-shift modulation proposed in this paper enable soft switching of all transistors with minimum circulating currents over constant current (CC), constant power (CP), and constant voltage (CV) modes of battery charging. Experimental results are provided for a single-phase DC–DC converter prototype utilizing 650 V GaN transistors operating from an 800 V DC bus and providing a very wide output voltage from 150 V to 950 V at 6.6 kW maximum power at a constant switching frequency of 500 kHz. The prototype achieves two peak efficiency points of 98.2% and maintains <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$&gt;$</tex-math></inline-formula> 97% efficiency across the entire output voltage range at a power density of 120 W/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> (7.3 kW/L).

Uniform attractors in sup-norm for semi linear parabolic problem and application to the robust stability theory

In this paper we establish the existence of the uniform attractor for a semi linear parabolic problem with bounded non autonomous disturbances in the phase space of continuous functions. We applied obtained results to prove the asymptotic gain property with respect to the global attractor of the undisturbed system.

A Wideband Circularly Polarized Dielectric Patch Antenna With a Modified Air Cavity for Wi-Fi 6 and Wi-Fi 6E Applications

In this letter, a novel wideband circularly polarized (CP) dielectric patch antenna (DPA) featuring low profile and relatively high gain property is investigated for Wi-Fi 6 and Wi-Fi 6E applications. Multiple modes of the feeding structure are excited which produces a wide impedance bandwidth (IBW). The introduction of FR4 branches in the air cavity helps to achieve a wider IBW of 48.3% (4.63–7.58 GHz). The E-field inside the air cavity acquires perturbation from the coupling of two dielectric patches (DP), which contributes to obtaining better CP performance. It can help achieve a wide axial ratio bandwidth of 35.3% ranging from 5.15 to 7.36 GHz for the proposed DPA. As the upper dielectric patch works as a director, a measured peak gain is increased to 8.47 dBic. Based on the multilayer PCB structure, the high permittivity dielectric patches loaded are packaged inside the FR4 substrates and fixed by branches. Therefore, a low-profile DPA with a height of 0.13 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is obtained and exhibits self-packaging for DP elements.

Automatic Time Picking for Weak Seismic Phase in the Strong Noise and Interference Environment: An Hybrid Method Based on Array Similarity.

The extraction of travel-time curve of seismic phase is very important for the subsequent inference of the structural properties of underground media in seismology. In recent years, with the increase in the amount of data, manual processing is facing significant challenges, and automatic signal processing has gradually become the mainstream. According to the similarity of array signals and considering the elimination of outliers, we propose an improved multi-channel cross-correlation method using the L1 norm measure to obtain preliminary results, which builds on a new controllable measurement mode. Then, the post-correction step is carried out in combination with the signal gain property of beamforming technique. Based on these two methods, this paper proposes a new scheme of automatic arrival time picking. We apply the scheme to actual data to verify the effects of the two methods step by step. The entire scheme achieves fine results: direct water waves, seismic waves refracted by the crust and seismic waves reflected by the upper mantle are automatically detected. In addition, compared with the two traditional methods, the scheme proposed in this paper has a better overall effect and a reasonable computation cost.

Drag reduction of blowing-based active control in a turbulent boundary layer

Direct numerical simulations are conducted to gain insight into the blowing-based active control in a spatially developing turbulent boundary layer at a low Reynolds number. The drag reduction properties and mechanisms of different blowing velocity distribution forms under constant wall-normal mass flux are comparatively studied, including uniform blowing and blowing-only opposition control (BOOC). After the application of blowing control, the self-similarity of the Reynolds shear stress is influenced. The property of drag reduction and control gain of the blowing-based active control schemes in the turbulent boundary layer is similar to that in turbulent channel flow, i.e., the BOOC scheme can achieve higher drag reduction than uniform blowing, but the control gain reduces. Due to the coexistence of the opposition effect and the induction effect, the negative wall-normal velocity fluctuations accompanied by the sweep motion are induced to form small-scale flow structures in the near-wall region. The decomposition of the skin-friction drag coefficient shows that the changes of each contribution term are basically the same for different blowing schemes, except that the BOOC scheme has a more substantial influence on mean convection and spatial development. According to the property that the drag reduction of the BOOC scheme with additional threshold limitation is equivalent to that without the restriction, it can be determined that the effect of blowing-based active control is mainly based on the temporal and spatial averaging effects of blowing, including the opposition effect and the induction effect.

A novel approach of developing all-optical frequency encoded dibit-based Peres gate using reflective semiconductor optical amplifier

In recent trends, digital systems in the light of power dissipation are a crucial issue. In computing, the computational process of reversible logic is bijective and can decrease the rising issue of power dissipation. In reversible circuit design, Peres gate considered as one of the fundamental reversible gate. Therefore, a Peres gate using Add/Drop Multiplexer (ADM) and Reflective Semiconductor Optical Amplifier (RSOA) is proposed in this paper. Frequency encoding scheme and dibit-based logic are incorporated here. In long range transmission, frequency encoding bears huge benefits in respect with the other encoding techniques. This encoding technique may decrease the probability of bit error. Due to the high gain and low noise property of RSOA, the proposed design can perform operations like computation, data processing, etc. at ultra-high speed with low noise. MATLAB Simulink (R2018a) software has been used to verify the operation of the proposed design.

Deepening Insights into Near‐Infrared Excited‐State Intramolecular Proton Transfer Lasing: The Charm of Resonance‐Assisted Hydrogen Bonds

AbstractExcited‐state intramolecular proton transfer (ESIPT)‐active organic semiconductor materials, characterized by a or several resonance‐assisted hydrogen bonds (RAHBs), are supposed to be ideal candidates for achieving high‐performance near‐infrared (NIR) lasers. However, according to the energy gap law, the development of ESIPT‐active gain materials is still limited by the serious nonradiative decays. Herein, it is demonstrated that RAHBs can activate ESIPT lasing by inhibiting nonradiative decays. A new ESIPT‐active material 1,5‐dihydroxy‐2,6‐diphenylanthraquinone (DP‐DHAQ) containing two centrosymmetric RAHBs is developed, which exhibits a ≈100‐fold higher radiative decay rate (kr = 1.1 × 1010 s–1) in doped polystyrene (PS) film than that of 1‐hydroxy‐5‐methoxy‐2,6‐diphenylanthraquinone (DP‐HMAQ) and 1,5‐dimethoxy‐2,6‐diphenylanthraquinone (DP‐DMAQ), in which one and two RAHBs are broken, respectively, by introducing methyl groups. Both DP‐DHAQ and DP‐HMAQ can form four‐level systems based on the ESIPT processes, but only DP‐DHAQ doped PS microspheres exhibit laser emission at 710 nm under the test conditions. It is worth mentioning that single‐crystal microplates of DP‐DHAQ can realize NIR laser emission at 725 nm. The results suggest that RAHBs can effectively activate the gain property of ESIPT‐active materials, which deepens insights into NIR ESIPT lasing and provides a new proposal for the design of organic laser‐active molecules.

Low Threshold and Ultrastability of One-Step Air-Processed All-Inorganic CsPbX3 Thin Films toward Full-Color Visible Amplified Spontaneous Emission

All-inorganic perovskites (CsPbX3) with the merits of high stability and remarkable optical gain property are attractive for achieving on-chip coherent light sources. Unfortunately, traditional solution-processed CsPbX3 films suffer from inevitable poor surface integrity and pinhole defects, severely hindering their optical properties. Here, from the perspective of precursor solution chemistry, we use an ionic liquid solvent methylammonium acetate (MAAc) to fabricate compact, pinhole-free, and smooth CsPbX3 thin films in a one-step air process without antisolvent treatment. Optically pumped amplified spontaneous emission (ASE) with a straightforward visible spectral tunability (418-725 nm) is achieved under both nanosecond and femtosecond laser excitation. For the representative CsPbBr3 films, the threshold reaches down to 11.4 μJ cm-2 under nanosecond laser pumping, which is comparable to the value under one-photon femtosecond pumping. The long gain lifetime up to 258.2 ps is revealed by transient absorption spectroscopy. Most importantly, the films show excellent optical stability and humidity stability with no obvious degradation under the pulsed laser irradiation for more than 210 min, stable ASE output under 95% high humidity, and conspicuous ASE after 1000 h of storage in air condition without encapsulation. These results demonstrate that the method of fabricating inorganic perovskite films with an ionic liquid solvent is promising in developing high-performance full-color visible lasers.

Ultrafast Antisolvent Growth of Single-Crystalline CsPbCl3 Microcavity for Low-Threshold Room Temperature Blue Lasing.

All-inorganic perovskite CsPbCl3 has recently attracted considerable attention due to its great potentials for the development of high-efficiency, deep-blue optoelectronic devices. Particularly, single-crystalline CsPbCl3 planar microstructures provide good platforms for both fundamental studies and nanophotonics applications from lasers and detectors to amplifiers. In this study, we report an ultrafast antisolvent deposition route to fabricate single-crystalline CsPbCl3 microplatelets (MPs). The as-grown MPs exhibit uniform morphology, strong emission, and outstanding gain property. Room temperature photoluminescence lasing is realized at 428 nm with a low threshold of 11.5 μJ cm-2 and high net optical gain up to 720 cm-1. These findings advance fundamental understanding on the fabrication and optoelectronic applications of low-dimensional CsPbCl3 perovskite structures.

A Double-Layer Multibeam Antenna With 45° Linear Polarization Based on Gap Waveguide Technology

In this article, a double-layer 1-D multibeam antenna based on gap waveguide (GWG) technology is proposed. The bottom layer is the beamforming network (BFN), which is composed of four cruciform couplers and two −45° phase shifters realized by groove GWGs. Four output ports of the BFN are connected to the slot arrays on the top layer through 180° E-plane bends. The output amplitudes of the BFN are −6.3 ± 0.5 dB and the phase errors are within ±14° from 26 to 32 GHz with a bandwidth of 20%. To relieve the grating lobe problem, groove GWGs are transited to ridge GWGs on the top layer and the slot array is fed from ridge GWGs. Due to the topology of the BFN, the slot array is oriented along the diagonal plane and as a result, the multibeam antenna is 45° linearly polarized. To handle the dip emerging in the side beam caused by the finite ground of the BFN, several metal fences working as a soft surface are applied to suppress the edge diffractions. Besides, the gain is increased by 0.78 dB compared to the case without metal fences at 29 GHz. Thanks to the low-loss property of GWG technology, high gain, and high radiation efficiency are obtained. The maximum gain is 17.46 dBi with the beam direction at −11° for Port 1 and 16.51 dBi with the beam direction at 37° for Port 2. The simulated radiation efficiency is above 97% for both Port 1 and Port 2.

Robustness of global attractors: Abstract framework and application to dissipative wave equations

&lt;p style='text-indent:20px;'&gt;We establish local input-to-state stability and the asymptotic gain property for a class of infinite-dimensional systems with respect to the global attractor of the respective undisturbed system. We apply our results to a large class of dissipative wave equations with nontrivial global attractors.&lt;/p&gt;

Framework-Shrinkage-Induced Wavelength-Switchable Lasing from a Single Hydrogen-Bonded Organic Framework Microcrystal.

Porous organic materials (POMs) have shown great potential for fabricating tunable miniaturized lasers. However, most pure-POM micro/nanolasers are achieved via coordination interactions, during which strong charge exchanges inevitably destroy the intrinsic gain property and even lead to optical quenching, hindering their practical applications. Herein, we reported on an approach to realize hydrogen-bonded organic framework (HOF)-based in situ wavelength-switchable lasing based on the framework-shrinkage effect. A flexible HOF with reversible framework shrinkage was constructed from gain blocks with multiple rotors. The framework shrinkage of the HOF induced the in situ regulation on the conformation and conjugation degree of gain blocks, leading to distinct energy-level structures with blue/green-color gain emissions. Inspired by this, the in situ wavelength-switchable lasing from HOF microcrystals was achieved through reversibly controlling the framework shrinkage via the absorption/desorption of guests. The results offer useful insight into the use of flexible HOFs for exploiting miniaturized lasers with on-demand nanophotonics performance.

Adaptive pre-assigned finite-time control of uncertain nonlinear systems with unknown control gains

This paper mainly studies an adaptive finite-time control problem for a kind of uncertain strict feedback systems with unknown control gains. First, the original strict-feedback system is transformed into a pure-feedback system. And then, we propose a modified adaptive finite-time design idea on the basis of the property of pre-assigned finite-time function (PFTF) and Nussbaum gain. The designed controller can make sure that all states converge to an arbitrarily region in finite-time and signals in the closed-loop system are finite-time bounded. Moreover, the presented controller is smooth and the settling time does not rely on the initial values and design parameters. Finally, the simulation study is made to illustrate the innovativeness for the proposed scheme.

Manipulating Stimulated Brillouin Scattering Produced Gain Near Its Threshold via Slow Intensity Modulation

Increasing the threshold of stimulated Brillouin scattering (SBS) by frequency and phase modulation is a productive approach to suppress SBS in optical fiber communications. Generally, the modulation frequency is much higher than the Brillouin-gain bandwidth (about 10 MHz). However, the property of the SBS-produced gain is unclear when the frequency of intensity modulation is much lower than the Brillouin-gain bandwidth. Here, we find that the SBS-produced gain increases remarkably near its threshold under the above conditions. It is due to the nonlinearity feature of the SBS. A numerical simulation of the SBS coupled amplitude equations is studied to explain this phenomenon. We demonstrate that the modulation on/off gain produced by this slow intensity modulation is related to the modulation frequency, the waveguide length, and the modulation waveform. According to these new findings, we design a modulation waveform to boost the SBS-produced gain near its threshold by 35 dB in a 1 km length single-mode fiber. The method presented in this paper is expected to apply in SBS studies when the incident optical power is limited.