Cascade Scheme Research Articles

Three types of third-order non-Hermitian interaction of spontaneous six-wave and eight-wave mixing under multi-dressing effects

Non-Hermitian degeneracy, also known as exceptional point, has been recently seen as a new way to engineer the response of open physical systems. Based on natural non-Hermitian atomic coherence, we investigate spontaneous six-wave mixing (SSWM) and eight-wave mixing (SEWM) processes under both parity–time (PT) and anti-parity–time (anti-PT) symmetry, and we obtain high-dimensional coherent channels under third-order energy-level splitting. Finally, we reveal that the third-order non-Hermitian interaction between two dressing fields of the nested scheme is the strongest, and the parallel scheme is the weakest, with the cascade scheme considered intermediate between them. It can also be used to develop quantum memory devices with enhanced sensitivity in the atom-like system.

Development of multilevel cascade layouts to improve performance of SCO2 Brayton power cycles: Design, simulation, and optimization

The multilevel cascade SCO2 Brayton cycles are developed based on the conventional recompression-reheat cycle to enhance thermodynamic performances using the multilevel cascade scheme. Mathematical models are proposed to characterize their thermal cycle efficiency. The results show that for three typical cases, the proposed multilevel cascade cycle with 3 compressors × 3 reheats × 2 turbines improve cycle efficiency by 2.56 %, 3.17 %, and 3.44 % in absolute change, while the other with 3 compressors × 3 reheats × 3 turbines further enhance by 3.17 %, 4.19 %, and 4.17 % in absolute change over the conventional cycle. The latter cycle as the optimal layout is chosen to perform the key parametric analysis. The cycle efficiency increases with increasing high-pressure turbine inlet temperature, while the main compressor inlet temperature has the opposite effect. It increases and then decreases with the high-pressure turbine inlet pressure, the main compressor inlet pressure, and the split ratio of the recompressor, respectively. Finally, the parametric global optimization is conducted to improve the cycle performance more deeply. It is demonstrated that the absolute efficiency can be further increased by 2.62 %, 1.81 %, and 1.09 % for the responding cases. The integrated configurations are also suggested for power generation systems with different applications.

A Method for Reducing Training Time of ML-Based Cascade Scheme for Large-Volume Data Analysis.

We live in the era of large data analysis, where processing vast datasets has become essential for uncovering valuable insights across various domains of our lives. Machine learning (ML) algorithms offer powerful tools for processing and analyzing this abundance of information. However, the considerable time and computational resources needed for training ML models pose significant challenges, especially within cascade schemes, due to the iterative nature of training algorithms, the complexity of feature extraction and transformation processes, and the large sizes of the datasets involved. This paper proposes a modification to the existing ML-based cascade scheme for analyzing large biomedical datasets by incorporating principal component analysis (PCA) at each level of the cascade. We selected the number of principal components to replace the initial inputs so that it ensured 95% variance retention. Furthermore, we enhanced the training and application algorithms and demonstrated the effectiveness of the modified cascade scheme through comparative analysis, which showcased a significant reduction in training time while improving the generalization properties of the method and the accuracy of the large data analysis. The improved enhanced generalization properties of the scheme stemmed from the reduction in nonsignificant independent attributes in the dataset, which further enhanced its performance in intelligent large data analysis.

Polarized spectral properties and 2.3 µm laser performance of the Tm:YVO4 crystal

The polarized spectral properties and ∼2.3 µm high-power continuous-wave laser operation of Tm3+-doped yttrium orthovanadate crystal (Tm:YVO4) are reported. For the 3H4 → 3H5 transition, the stimulated-emission cross-section σSE is 1.01 × 10−20 cm2 at 2276 nm corresponding to a large emission bandwidth of 52 nm (for π-polarization). Pumped by a 794 nm laser diode, the 1.5 at.% Tm:YVO4 laser delivered 5.52 W at 2.29 µm with a slope efficiency of 19.9%, a laser threshold of 8.70 W, and a linear laser polarization (π). The Tm laser operated on the cascade scheme (on the 3H4 → 3H5 and 3F4 → 3H6 transitions) which was mainly responsible for the observed high laser slope efficiency. We also report on the first passively Q-switched Tm:YVO4 laser at 2.3 µm by employing porous nano-grained cuprous selenide (PNG-Cu2Se) as a saturable absorber. The shortest pulse duration and the highest single pulse energy amounted to 706 ns and 3.65 µJ, respectively, corresponding to a pulse repetition rate of 62.8 kHz.

Enzyme-integrated metal-organic framework platform for cascade detection of α-amylase

As one of the most important industrial enzymes, α-amylase is widely used in food processing, such as starch sugar and fermentation, bringing high added value to industry of more than a trillion dollars. We developed a multi-enzyme system (Glu&Gox@Cu-MOF-74) prepared by embedding α-glucosidase (Glu) and glucose oxidase (Gox) into the biomimetic metal-organic framework Cu-MOF-74 using in situ encapsulation within 15 min at room temperature for efficient and sensitive detection of α-amylase activity. Benefitting from the remarkable peroxidase-mimicking property and rigid skeleton of Cu-MOF-74, the biocatalytic platform exhibited excellent cascade activity and tolerance in various extremely harsh environments compared to natural enzymes. On this basis, a cascade biocatalytic platform was constructed for the detection of α-amylase activity with wide linear range (5–100 U/L) and low limit of detection (1.45 U/L). The colorimetric cascade scheme is important for the sensitive and selective determination of α-amylase in complex fermentation samples, and the detection time is short (∼0.5 h). This work provides new ideas for the detection of α-amylase based on the cascade amplification method.

An Electrocatalytic Cascade Reaction for the Synthesis of Ketones Using CO2 as a CO Surrogate

AbstractThe construction of carbonyl compounds via carbonylation reactions using safe CO sources remains a long‐standing challenge to synthetic chemists. Herein, we propose a catalyst cascade Scheme in which CO2 is used as a CO surrogate in the carbonylation of benzyl chlorides. Our approach is based on the cooperation between two coexisting catalytic cycles: the CO2‐to‐CO electroreduction cycle promoted by [Fe(TPP)Cl] (TPP=meso‐tetraphenylporphyrin) and an electrochemical carbonylation cycle catalyzed by [Ni(bpy)Br2] (2,2′‐bipyridine). As a proof of concept, this protocol allows for the synthesis of symmetric ketones from good to excellent yields in an undivided cell with non‐sacrificial electrodes. The reaction can be directly scaled up to gram‐scale and operates effectively at a CO2 concentration of 10 %, demonstrating its robustness. Our mechanistic studies based on cyclic voltammetry, IR spectroelectrochemistry and Density Functional Theory calculations suggest a synergistic effect between the two catalysts. The CO produced from CO2 reduction is key in the formation of the [Ni(bpy)(CO)2], which is proposed as the catalytic intermediate responsible for the C−C bond formation in the carbonylation steps.

An Electrocatalytic Cascade Reaction for the Synthesis of Ketones Using CO2 as a CO Surrogate.

The construction of carbonyl compounds via carbonylation reactions using safe CO sources remains a long-standing challenge to synthetic chemists. Herein, we propose a catalyst cascade Scheme in which CO2 is used as a CO surrogate in the carbonylation of benzyl chlorides. Our approach is based on the cooperation between two coexisting catalytic cycles: the CO2-to-CO electroreduction cycle promoted by [Fe(TPP)Cl] (TPP=meso-tetraphenylporphyrin) and an electrochemical carbonylation cycle catalyzed by [Ni(bpy)Br2] (2,2'-bipyridine). As a proof of concept, this protocol allows for the synthesis of symmetric ketones from good to excellent yields in an undivided cell with non-sacrificial electrodes. The reaction can be directly scaled up to gram-scale and operates effectively at a CO2 concentration of 10 %, demonstrating its robustness. Our mechanistic studies based on cyclic voltammetry, IR spectroelectrochemistry and Density Functional Theory calculations suggest a synergistic effect between the two catalysts. The CO produced from CO2 reduction is key in the formation of the [Ni(bpy)(CO)2], which is proposed as the catalytic intermediate responsible for the C-C bond formation in the carbonylation steps.

Optimizing the series cascade control structure for nonminimum phase system regulation

AbstractThis work elucidates the control of integrating a nonminimum phase system via a series cascade scheme with fractional‐order P.I. (Proportional–Integral) plus D (Derivative) controller. The traditional Internal Model Control (IMC) is adopted for inner loop controller design. The feedback D controller is synthesized with the outer loop process model, showing the proposed work's universality. The outer loop controller is suggested in the IMC framework after the accountability of fractional‐filter and inverse response compensator. This combination is revealed to enhance performance without compromising robustness. The Riemann sheet principle is explored to compute the stability of the suggested controller. The sensitivity analysis has asserted the robustness. More importantly, the optimal value of controller settings is achieved via the Teaching Learning Based Optimization (TLBO) algorithm. This TLBO algorithm uses an objective function that minimizes Integral Square Error. Two illustrative problems are utilized to examine the recommended control structure's virtue.

Optimal fractional-order series cascade controller design: A refined Bode’s ideal transfer function perspective

In process industries, cascade control is comprehensively used for disturbance attenuation. This manuscript presents the control of the non-minimum phase (NMP) system with dead time via a series cascade scheme. An improved fractional-filter-based control scheme encompassing inverse and dead time compensators with analytical tuning is proposed. The design hinges on an enhanced Bode’s ideal transfer function, which incorporates delay and NMP zero to deal with the system’s NMP and dead time. Particle swarm optimization (PSO) is utilized to obtain the optimal assessment of fractional filter-based controller settings by minimizing an objective function. Two benchmark problems are presented to test the efficacy of the recommended controller. The Riemann surface and sensitivity examination are used to realize the stability and robustness of the feedback design. Numerical simulations exhibit the superiority of the suggested controller for closed-loop results.

Crosstalk of CGMP and CAMP in the vertebrate phototransduction cascade

The conventional phototransduction cascade suggests that cyclic guanosine monophosphate (cGMP) functions as the chief secondary messenger while intracellular calcium concentration dominates as the central feedback modulator. Countless years and several scientific institutions have led to this conclusion, and it stands as the most extensively researched and explicit among all sensory transduction schemes. However, experimental evidence suggests that our understanding of the phototransduction cascade mechanisms remains significantly incomplete [1]. According to the canonical cascade scheme, all transients should be completed within a second once the light stimulus is no longer present. However, our data indicates that there are long-lasting changes in cell sensitivity and dark current parameters after the stimulus, which can last for more than 10 s. Phenomena that deviate from the standard phototransduction cascade behavior can potentially be clarified by an alternative regulatory mechanism that is based on cyclic adenosine monophosphate (cAMP). Previous research has provided convincing evidence that the intracellular levels of cAMP can significantly impact the functioning of the phototransduction cascade on both slow (day) [2] and relatively fast (minutes) [3] time scales. Additionally, there is phenomenological evidence indicating the existence of other regulatory signaling pathways in the phototransduction cascade without a corresponding mechanism in the classical phototransduction scheme, including inositol triphosphate (IP3) and diacylglycerol (DAG). We investigate whether cAMP, IP3, and DAG regulate the phototransduction cascade during photoresponse. For this regulatory effect to occur, there must be a change in the signaling molecule concentration during the process. These processes occur in less than a second, and it is crucial for the presence of the regulatory effect. Given that traditional fluorescence methods cannot measure the concentration of any signaling molecule in the retina, a hardware-software setup has been developed that allows cryofixation of retinal samples at the required speed. The setup permits fixing up to six samples in a series with a delay of no more than 80 milliseconds after light stimulation. The concentration of signal molecules is assessed using high-performance liquid chromatography coupled with high-resolution tandem mass spectrometry. The results demonstrate a 4.5-fold elevation in cAMP concentration 1.1 s after switching on a light with an intensity close to saturation. The concentration of cAMP is directly proportional to the intensity of the stimulating light; there is no increase in cAMP at lower light intensities. No noteworthy changes in IP3 and DAG concentration were detected in response to light stimulation. The findings align with existing literature on the kinetics of light-triggered protein kinase A (PKA) activity [3], which indicated an initial decrease followed by an increase in PKA activity. These results could potentially inform the revision and expansion of the phototransduction cascade model.

Experimentally validated frequency shifted internal model cascade control strategy for magnetic levitation system

Magnetic levitation systems (MLS) provide friction-less, dependable, quick, and affordable operations in a variety of real life applications. One of the often-employed control strategies for the MLS is traditional cascade control, which uses internal model control (IMC)-based proportional–integral–derivative (PID) and proportional–integral (PI) controllers in its primary and secondary loops, respectively. Though this control structure succeeds in achieving levitation, it falls short in terms of set point tracking and disturbance rejection performance. To overcome this limitation, a bi-loop frequency shifted IMC proportional–derivative (FSIMC-PD) strategy is used in the primary loop retaining the conventional IMC-based PI controller in the secondary loop. Routh stability constraints are used to build the PD controller for stabilizing the MLS. Once the MLS is stabilized, an FSIMC-based PID controller for reference tracking is designed for the outer loop. In addition to simulation-based performance comparison of IMC-based PID-PI cascade scheme and the proposed scheme, experimental validation is also carried out on a laboratory scaled MLS setup. Furthermore, performance evaluation based on metrics like the integral of absolute error, integral of square error, integral of time weighted absolute error, total variation of the control signal and its maximum value are also carried out to vindicate the effectiveness of the suggested design. Robust stability analysis is carried out in addition to Nyquist stability considerations to vindicate that the FSIMC-based design is capable of yielding stable closed-loop response amid uncertainties in plant model parameters.

Method of adaptation of cascade codes to ensure reliability of information transmission of wireless data transmission systems

The article proposes a method of structural adaptation of cascade codes, designed to ensure the specified reliability of information transmission of wireless data transmission systems in the event of interference, due to the dynamic synthesis of combined structures of cascade codes under conditions of a priori uncertainty. The essence of the method is to identify the internal structure of the code, due to which the structure of the component codes of the turbo code is determined. It was developed using the gradient method due to the implementation of a multi-step iterative procedure for finding optimal system parameters. Implementation of the method allows to ensure the reliability of information transmission of wireless data transmission systems. To check the effectiveness of the method of structural adaptation of cascade codes, a simulation model was developed in the C++ programming language in the Visual Studio 2019 software environment, and wireless data transmission systems were simulated. The simulation results show that the combined structure of building cascade codes together with OFDM technology allows you to independently adapt the coding rate of each of the coding stages depending on the results of the analysis of the reliability of information in this cascade, which leads to the provision of the specified reliability of information transmission, while the BSPD bandwidth is reduced by 4–12% against 20–35% of known results. The use of Reed-Solomon codes in a sequential cascade scheme with turbo codes due to the adaptation of the coding rate of this cascade design allows obtaining an energy gain of 0.5–0.7 dB without increasing the bandwidth of the transmission system compared to systems that use only turbo codes. The obtained results are of significant relevance and can be implemented in the development of information transmission systems to ensure the reliability of data transmission, both in peacetime and in conditions of armed aggression of the Russian Federation against Ukraine.

Adaptive Fed-batch Control of Escherichia coli Fermentation for Protein Production

A new adaptive linearizing control algorithm that stabilizes the carbon source concentration in a desired value is proposed. This algorithm is applied to recombinant protein production by Escherichia coli. A model for control of the investigated process is derived. The model identification is made based on experimental data of the batch phase of the process. The operating model includes two sub-models. Each of them describes one of the two physiological states through which the process passes. Switching from one model to another depends on the sign of a key parameter obtained from the acetate measurements. A cascade scheme of software sensors for the estimation of two biomass growth rates included in the structure of the proposed control algorithm is derived. Simulation studies of the developed closed system have been carried out. The results of the impact of an open-loop control system on the same object are compared.

Hardware-in-the-Loop Scheme of Linear Controllers Tuned through Genetic Algorithms for BLDC Motor Used in Electric Scooter under Variable Operation Conditions

Outrunner brushless DC motors (BLDC) are a type of permanent magnet synchronous motor (PMSM) widely used in electric micro-mobility vehicles, such as scooters, electric bicycles, wheelchairs, and segways, among others. Those vehicles have many operational constraints because they are driven directly by the user with light protective wearing. Therefore, to improve control strategies to make the drive safer, it is essential to model the traction system over a wide range of operating conditions in a street environment. In this work, we developed an electro-mechanical model based on the Hardware-in-the-Loop (HIL) structure for a two-wheeler electric scooter, using the BLDC motor to explore its response and to test linear controllers for speed and torque management under variable operating conditions. The proposed model includes motor parameters, power electronics component characteristics, mechanical structure, and external operating conditions. Meanwhile the linear controllers will be adjusted or tuned though a heuristic approach based on Genetic Algorithms (GAs) to optimize the system’s response. The HIL scheme will be able to simulate a wide range of conditions such as user weight, slopes, wind speed changes, and combined conditions. The designed model can be used to improve the design of the controller and estimate mechanical and electrical loads. Finally, the results of the controller tests show how the proposed cascade scheme, tuned through the GA, improves the system behavior and reduces the mean square error with respect to a classical tuning approach between 20% and 60%.

Cascade control design for supercavitating vehicles with actuator saturation and the estimation of the domain of attraction

Supercavitating vehicles can achieve underwater high-speed motion using supercavitation drag-reduction technology; however, the vehicle-cavity interaction can lead to strong nonlinear characteristics, which pose substantial challenges to the classical control method. This paper proposes a linear matrix inequality (LMI)-based cascade control to realize an efficient depth-tracking task subject to actuator saturation. First, the depth-tracking error cascade scheme is established. Then, the saturation constraint can be represented using the convex hull to obtain a linear-parameter-varying inner-loop model. Finally, the feedback gains can be optimized by using LMIs. Moreover, the domain of attraction can be estimated to obtain the feasible operating range, which can provide an overall guideline for practitioners. We evaluated the proposed method through a comparative simulation, and the results show that it quickly reached the desired depth without overshoot under actuator saturation, indicating the method’s feasibility and efficiency.

Supervised fuzzy control strategy for mean arterial pressure regulation using cascade scheme controller: a continuum approach of hypertension with diabetics

Supervised fuzzy control strategy for mean arterial pressure regulation using cascade scheme controller: a continuum approach of hypertension with diabetics

Relaxation echo

The possibility of generation of a microwave echo-signal due to irreversible phase relaxation in a system of equidistant triplets with a cascade scheme of magnetic-dipole transitions is predicted. The disappearance of relaxation entails the disappearance of this echo-signal. The mechanism of this effect lies in the destructive interference of quantum transitions, which radiate in anti-phase with the same eigen-frequencies. The difference in phase relaxation times for these transitions leads to incomplete damping of the resulting coherence. As a result an echo-signal is generated.

Research on a Novel Combined Cooling and Power Scheme for LNG-Powered Ship

Cold energy recovery in LNG-powered vessels can not only improve the utilization efficiency of energy, but also benefit environmental protection. This paper put forward a new cascade scheme for utilizing flue gas waste heat and LNG cold energy comprehensively. The scheme was integrated by a dual organic Rankine circulation system (ORC), a high- and low-temperature cold storage system (TCS), an air conditioning system (ACS) and a seawater desalination system (SDS). The working medium of the dual ORC system was firstly determined by considering exergy efficiency and economic index simultaneously. On this basis, the adaptive weighted particle swarm optimization algorithm was employed to enhance thermodynamic performance of the scheme with the net output power as the optimization objective. The maximum net power and annual net interest rate can reach 725.78 kW and $115,300, respectively. Furthermore, the economic benefit of the scheme was analyzed by referring to the running track and the operation condition of the target ship. The results showed that the proposed scheme is a potential large-scale cryogenic technology and can bring considerable economic benefits to ship navigation.

ОПТИМІЗАЦІЯ КАСКАДНОЇ СХЕМИ ВИСОКОШВИДКІСНОЇ ЕКСТРУЗІЇ

Plastics are one of the most common materials. Due to its high technical and economical characteristics, this class of materials is used in almost all industries, that is why further growth of the production of plastic products is predicted. Today, the biggest problem in the field of polymer processing by extrusion is to ensure the best possible parameters of resource-energy efficiency of equipment. At the same time, the creating of compounds based on polymers is developing very actively, which requires more flexibility from extrusion lines, since a large number of compositions which differ in their characteristics can be developed on the base of a polymer. The factors listed above have led to cascade extrusion lines become increasingly wide-spread in industry today. Analysis of the extrusion equipment market showed that the schemes with a high-speed double-string extruder at the first stage is more popular. However, the desired mixing quality can be achieved by using a much simpler disc extruder. The article is a review that aims to determine the possibility and feasibility of more efficient arrangement of a cascade scheme for processing composite materials using a disk extruder. Theoretical and experimental studies have shown that melting processes are more efficient in the field of high shear rates at low pressures. Disk extruder is great option for that objective. In this scheme, it is proposed to use a dose feed disk extruder as a homogenizer, and a gear pump as a metering device which allows to reduce pressure and capacity fluctuations before forming device to less than 1%. As a result, it has been determined that the proposed design of the extrusion plant will be more energy efficient than the options on the market and will be able to significantly reduce pressure and performance fluctuations at the inlet to the forming device.

An enhancement in parallel cascade scheme for non-minimum phase system

An enhancement in parallel cascade scheme for non-minimum phase system