Operating Region Research Articles

Courier satisfaction in rapid delivery systems using dynamic operating regions

Rapid delivery systems where an order is delivered to a customer from a local distribution point within minutes or hours have experienced rapid growth recently and often rely on gig economy couriers. The prime example is a meal delivery system. During an operating day, couriers in such a system are used to deliver orders placed at different restaurants to different customer locations. Operating a rapid delivery network is challenging, primarily due to the high service expectations and the considerable uncertainty in both demand and delivery capacity. We seek to fill a gap in the literature by considering courier satisfaction in a rapid delivery system, which may improve retention/loyalty in a highly competitive environment. Under the premise that couriers prefer to operate in relatively small geographic areas to increase their efficiency, we propose the novel concept of dynamic courier regions: small operating regions for couriers which can be dynamically and temporarily expanded to allow delivery capacity to be shared between neighboring regions when necessary to keep customer service performance metrics high. We propose an optimization-based rolling horizon algorithm for courier management that handles both region resizing and delivery task assignment decisions. Experimental results for realistic settings demonstrate that the proposed algorithm successfully balances customer and courier satisfaction, simultaneously achieving delivery times that are comparable to those of a single operating region and courier satisfaction metrics that are comparable to those achieved by fixed, inflexible regions.

A wideband magnetoelectric dipole antenna for 4G/5G communication

AbstractIn this letter, a wideband magnetoelectric (ME) dipole antenna for 4G/5G communication is proposed. The bandwidth of the antenna is greatly enhanced by loading two pairs of metallic circular loops on the planar electric dipole. With the loops, the antenna impedance bandwidth in terms of 10 dB is improved from 48.3% (1.98–3.24 GHz) to 86.8% (1.465–3.71 GHz), that is, 79.7% bandwidth enhancement is achieved. The surface current of the proposed antenna is analyzed in detail. It shows that when the length of the loops approaches half a wavelength, the loops contribute new resonant modes, thereby increasing the impedance bandwidth. A prototype is fabricated and measured. The measured results are in good agreement with the simulated counterparts. Meanwhile, the antenna gain ranges from 7.42 to 12.8 dBi across the operational frequency region. Stable radiation patterns with low crosspolarization levels are obtained in both E‐ and H‐plane.

Comparative study of multiple-mode collaborative operation strategy and traditional heat and power decoupling technologies for cogeneration system based on GTCC

This study proposes a multiple-mode collaborative operation strategy for the first time, which integrates compressor inlet air heating mode, gas turbine interstage extraction mode, and back pressure heating mode. This operation strategy can improve the peak shaving flexibility of the cogeneration system based on gas turbine combined cycle (GTCC). This article uses Ebsilon software to simulate cogeneration system based on GTCC under different heat and power decoupling technologies and obtain the heat and power operation region. The peak performance of different heat and power decoupling technologies on heating characteristic days are analyzed. Meanwhile, the impact of objective power load changes is studied. The results show that during the whole heating season, compared with the conventional operation mode without heat and power decoupling technology, the multiple-mode collaborative operation strategy, electric boiler (EB) technology, and heat storage tank (HST) technology are adopted, and the renewable energy integration of the cogeneration system based on GTCC are increased by 1.16 × 105 MW, 1.37 × 105 MW and 5.65 × 104 MW, respectively. In addition, When the objective power load is 197.5 MW or 120 MW, taking into account the integration of renewable energy, natural gas consumption, and system benefits, the multiple-mode collaborative operation strategy is the optimal choice.

Machine learning models for maintenance cost estimation in delivery trucks using diesel and natural gas fuels

The maintenance costs can represent about 15%–60% of the cost of produced goods depending on the type of goods transported. To comply with stringent emissions regulations, diesel engines are incorporated with complex after-treatment systems that demand increased maintenance. The availability of alternative fuels such as natural gas and propane has fostered the natural gas and propane powertrain systems as well as electrification options for heavy- and medium-duty vehicles. A critical barrier to adopting alternative fuel vehicles has been the lack of knowledge on comparative vehicle maintenance/repair costs with conventional diesel. Moreover, the region of operation, the type of vehicle operation, and seasonal temperature changes also affect the duty cycle which impacts the maintenance and repair costs. This study focuses on estimating the cost-per-mile for heavy-duty vehicles using machine learning models such as random forest, xgboost, neural networks, and a super-learner model. The super-learner model achieved an error as low as 0.0068 $/mile for mean absolute error and 0.0086 $/mile for root mean square error with a coefficient of determination/R-Squared of 97.28%. Specifically, the paper investigates the data collected from the maintenance and repair costs associated with delivery trucks using diesel and natural gas fuels. Since the availability of data is the major constraint, we leveraged the data collected by West Virginia University and the partnership with fleet companies. This allows for additional information related to maintenance costs and fleet-specific maintenance practices of alternative fuel vehicles. This study promotes clean fuel technologies and enables fleet management companies to adopt alternative fuel vehicles in case of similar or lower cost of maintenance compared to diesel vehicles resulting in reduced emissions and total cost of ownership.

Characterization and modeling of threshold voltage for organic and amorphous thin-film transistors

This work portrays the study and analysis of several extraction techniques that are typically used to ascertain the threshold voltage of organic thin-film transistors (OTFTs) and oxide-based transistors. This study evaluates the effects of physical and electrical parameters such as channel length, doping concentration, temperature, and trap on the threshold voltage (VTH) of both p-type and n-type bottom gate top contact (BGTC) OTFTs using graphical method. The methods employed in the present work to extract the threshold voltage are determined in the linear region of operation and are derived from the drain current (IDS) and the gate-source voltage (VGS) transfer characteristics. To compare and analyze the threshold voltage, various techniques such as the linear extrapolation method (ELR), constant current method (CC), transconductance linear extrapolation method (GMLE), second derivative method (SD), ratio method (RM), Inverse Ratio method (VX), and transition method (TM) are employed in the present work. In addition to DC characterization, the capacitance-voltage (C-V) method was also used to extract and compare the threshold voltage using all the conventional techniques listed above. 2-D numerical simulations were performed to assess the validity and usefulness of the various methodologies used for the extraction of the threshold voltage.

Analytical Quality by Design-Compliant Development of a Cyclodextrin-Modified Micellar ElectroKinetic Chromatography Method for the Determination of Trimecaine and Its Impurities.

In 2022, the International Council for Harmonisation released draft guidelines Q2(R2) and Q14, intending to specify the development and validation activities that should be carried out during the lifespan of an analytical technique addressed to assess the quality of medicinal products. In the present study, these recommendations were implemented in Capillary Electrophoresis method development for the quality control of a drug product containing trimecaine, by applying Analytical Quality by Design. According to the Analytical Target Profile, the procedure should be able to simultaneously quantify trimecaine and its four impurities, with specified analytical performances. The selected operative mode was Micellar ElectroKinetic Chromatography employing sodium dodecyl sulfate micelles supplemented with dimethyl-β-cyclodextrin, in a phosphate-borate buffer. The Knowledge Space was investigated through a screening matrix encompassing the composition of the background electrolyte and the instrumental settings. The Critical Method Attributes were identified as analysis time, efficiency, and critical resolution values. Response Surface Methodology and Monte Carlo Simulations allowed the definition of the Method Operable Design Region: 21-26 mM phosphate-borate buffer pH 9.50-9.77; 65.0 mM sodium dodecyl sulfate; 0.25-1.29% v/v n-butanol; 21-26 mM dimethyl-β-cyclodextrin; temperature, 22 °C; voltage, 23-29 kV. The method was validated and applied to ampoules drug products.

Catalytic CO2 Desorption Study of Tri-Solvent MEA-EAE-DEEA with Five Solid Acid Catalysts

To achieve the CO2 emission control as the urgent task of Carbon Peak and Carbon Neutrality, the CO2 desorption experiments were performed with a new tri-solvent MEA-EAE(2-(ethylamino)ethanol)-DEEA(N, N-diethylethanolamine) with five solid acid catalysts: blended catalysts of γ-Al2O3/H-ZSM-5 = 2:1, H-Beta (Hβ), H-mordenite, HND-8, and HND-580 as H2SO4 replacement. A series of sets of experiments were performed in a typical recirculation process by means of both heating directly at 363 K and temperature programming method within 303~358 K to evaluate the key parameters: average desorption rate (ADR), heat duty (HD), and desorption factors (DF). After analyses, the 0.5 + 2 + 2 mol/L MEA-EAE-DEEA with catalyst HND-580 possessed the best CO2 desorption act at relatively low amine regeneration temperatures with minimized HD and the biggest DF among the other catalysts. Comparing with other tri-solvents + catalysts studied, the order of DF was MEA-BEA-DEEA + HND-8 > MEA-EAE-DEEA + HND-580 ≈ MEA-EAE-DEEA + HND-8 > MEA-EAE-AMP + HND-8. This combination has its own advantage of big cyclic capacity and wider operation region of CO2 loading range of lean and rich amine solution (αlean~αrich), which is applicable in an industrial amine scrubbing process of a pilot plant in carbon capture.

Analytical and Normalized Equations to Implement the Optimized Triple Phase-Shift Modulation Strategy for DAB Converters

A fully normalized algorithm to implement the optimal triple-phase shift (TPS) modulation strategy of the dual active bridge converter is proposed in this paper. The algorithm evaluates three simple expressions that fit the optimal solutions obtained in recent works, which allows the algorithm to be implemented in real-time and valid for the whole operating range. As a result, the converter operates under zero voltage switching conditions and minimizes conduction losses. In addition, the algorithm considers the minimum current required to guarantee zero voltage switching condition that faces undesired dead-band of switching devices effect. The proposal achieves soft transition between any operation region and fast closed-loop response with no stability concern, presenting robustness under leakage inductance deviation. Finally, the algorithm presented in this paper is verified with a 4 kW experimental prototype. Experimental results show that the algorithm proposed can be evaluated with less than 2.8 μs and allows soft transition between any operation region to be achieved. Besides, fast closed-loop changes of 750 μs through all the operating ranges, keeping minimum RMS current under zero voltage switching, are shown.

Multiobjective Optimization and Multiphysics Design of a 5 MW High-Speed IPMSM Used in FESS Based on NSGA-II

The flywheel energy storage system (FESS) has high-power density and fast response speed, hence it is widely used as a pulse power supply. For the high-speed permanent magnet synchronous machine (HSPMSM) used in high-power FESS, there are two technical problems that need to be solved, including huge centrifugal forces of the rotor at a high-speed operation region and large phase currents at a low-speed operation region. In this paper, a 5 MW high-speed interior PMSM (HSIPMSM) is designed for FESS. The design goal of this electric machine is to reduce the maximum phase current at the lowest speed as much as possible while ensuring the rotor mechanical strength. Based on the response surface (RS) model and non-dominated sorting genetic algorithm II (NSGA-II), the multiobjective design of the HSIPMSM is accomplished using 29 groups of multiphysical field finite element analysis (FEA) sampling experiments. The computational cost is effectively reduced. In addition, the constant power optimal trajectory and control switching speed of the HSIPMSM are analyzed and discussed, and the reason that the constant power flux weakening region of the designed HSIPMSM is not wide and the maximum torque per ampere (MTPA) mode is adopted at a low-speed operation region is further illustrated.

Metal–Ferroelectric–Semiconductor Tunnel Junction: Essential Physics and Design Explorations

The essential physics of the ferroelectric tunnel junction (FTJ) is assessed with technology computer-aided design (TCAD) simulations and analytical models. With experimental data calibrations, a TCAD simulation framework including electrostatic potentials, ferroelectric (FE) polarizations, and nonlocal tunneling is built. Full regions of the FTJ operations, including the read/write, are then explored. Key parameters such as the memory state threshold voltages ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {mth}}$ </tex-math></inline-formula> ) and the region boundary voltages are defined, and their model formulations are developed. With the essential physics captured, FTJ figure-of-merits (FoMs) are accessed with not only tunneling electroresistance (TER), but also power consumption. Design parameters from FE layer thickness, polarizations, and coercive field to silicon doping and metal work functions are studied, with their impacts on key FTJ FoMs evaluated.

Pitfalls and Opportunities in the Execution of Quality by Design in Analytical Sciences

Abstract: Quality by Design (QbD) is a systematic approach integrated with quality risk management. It uses different design approaches followed by statistical analysis to yield a quality product. Now, the pharmaceutical industries are intrested in the application of QbD principles to analytical methods and term it as Analytical QbD (AQbD), which does not essentially mean less analytical testing; to a particular extent, it means the right analysis at the right time, supported by science and risk evaluation which ensures that the analytical method can be improved throughout its life cycle. However, for that, the analyst must have sound knowledge of Analytical Target Profile (ATP), method performance characteristics, risk assessment, choice of Design of Experiment (DoE), optimization of Method Operable Design Region (MODR). Some papers have cited the importance, regulatory flexibility, theoretical aspects, and statistical analysis of AQbD, but only a few discuss the core issue of gradual implementation of QbD in analytical sciences. For seamless transition, researchers need clarification on AQbD terminologies, acceptable methods, criteria to embrace critical quality attributes (CQAs), and standards to judge the adequacy of controls. This paper summarizes the challenges and solutions for the implementation of AQbD.

Rethinking Linear Modulation Range of Modular Multilevel Converters

The linear modulation problem of modular multilevel converter (MMC) is considerably complicated by capacitor voltage ripples (CVRs) and circulating current suppression control (CCSC). This study examines the linear modulation range of MMC and its influence on parameter design and operating characteristics, taking into account the CVR effect and CCSC. The deviation between the actual voltage output and the reference is revealed and analyzed, and the analytical expression of this deviation is determined. The effects of CCSC on linear modulation are also revealed. Based on the study, a set of equations are proposed to determine the exact reference wave while accounting for the CVR effect and CCSC and precisely assess linear modulation. Subsequently, the linear modulation range of MMC, which is defined as the maximum selectable valve-side voltage that can satisfy whole operating region linear modulation (WOR-LM) in this study, can be exactly determined. Furthermore, how the CVR effect and CCSC influence the linear modulation range, parameter design, and operating characteristics are analyzed using case studies. The proposed theory and method are also verified through simulation and experimental results.

On Optimizing the Conditional Value-at-Risk of a Maximum Cost for Risk-Averse Safety Analysis

The popularity of Conditional Value-at-Risk (CVaR), a risk functional from finance, has been growing in the control systems community due to its intuitive interpretation and axiomatic foundation. We consider a nonstandard optimal control problem in which the goal is to minimize the CVaR of a maximum random cost subject to a Borel-space Markov decision process. The objective represents the maximum departure from a desired operating region averaged over a given fraction of the worst cases. This problem provides a safety criterion for a stochastic system that is informed by both the <i>probability</i> and <i>severity</i> of the potential consequences of the system&#x0027;s behavior. In contrast, existing safety analysis frameworks apply stage-wise risk constraints or assess the probability of constraint violation without quantifying the potential severity of the violation. To the best of our knowledge, the problem of interest has not been solved. To solve the problem, we propose and study a family of stochastic dynamic programs on an augmented state space. We prove that the optimal CVaR of a maximum random cost enjoys an equivalent representation in terms of the solutions to these dynamic programs under appropriate assumptions. For each dynamic program, we show the existence of an optimal policy that depends on the dynamics of an augmented state under the assumptions. In a numerical example, we illustrate how our safety analysis framework is useful for assessing the severity of combined sewer overflows under precipitation uncertainty.

A Weather-Independent and Renewable Power Supply With Wireless Power Transfer Feature for Powering Online Monitoring Systems in Smart Grid

The merge of the power and information infrastructures in smart grid requires increasing number of sensors and online monitoring systems on the high-voltage (HV) transmission towers. These systems are traditionally powered by small solar panels or wind turbines that are weather-dependent. This new contribution involves a full analysis of a complete weather-independent power supply to replace existing approaches. For the first time, the complete system comprising the energy harvesting, wireless power transfer (WPT) and output power stages is practically evaluated using printed circuit board (PCB) resonators embedded in a 35-kV composite insulator. We leverage the nearly constant current, transresistance, and voltage gains characteristics of the PCB domino-resonator structure under different self-oscillating frequencies and propose a coordinated control scheme of transmitter-side and receiver-side converters to regulate the constant current (CC) or constant voltage (CV) through entire charging process. Any current surge caused by the burst operation of the active rectifier on the receiver side triggers a transition between different self-oscillating operations on the transmitter side, leading to operating region extension of the active rectifier. Thus, the proposed system can easily adjust the output to follow different battery charging profiles without wireless communication between the transmitter and receiver.

Acid gas preparation for enhanced oil recovery: techno-economic analysis of different dehydration processes

ABSTRACT The natural gas treatment plant is one source of CO2 emissions into the atmosphere. To tackle this issue, it is probable to inject CO2 into the wells and it can be used for enhanced oil recovery (EOR) application. However, the main setback is the high content of water in acid gas that could be converted to hydrate at high pressure in the pipelines. In this article, two different processes (solvent extraction, stripping gas) with two different solvents mono ethylene glycol (MEG), Tri ethylene glycol (TEG), are simulated in Aspen HYSYS. The stripping gas method is more efficient in terms of energy consumption, consuming 31.8% and 56.8% less energy than solvent extraction method for MEG and TEG solvents, respectively. Hydrate formation analyses showed that applying MEG as a solvent in the stripping gas method leads to a safer operation region. Economic evaluation depicts that the stripping gas method saves the total annual cost by 22.2% compared to solvent extraction.

Examination of fast frequency response capacity requirements considering frequency ride-through capabilities in distributed generators with legacy inverters

Given the rapid increase in inverter-based distributed generators (IBDGs), their response and subsequent impacts on power system stability during abnormal power system conditions are becoming important. Recent events have shown that an unexpected loss of IBDGs triggered by their outdated frequency ride-through (FRT) capability can occur, which in turn can lead to a power system frequency below the secure operation region. As FRT characteristics of IBDGs are dependent on their time of installation and capability to update FRT parameters, IBDGs with different ride-through characteristics are mixed within the power system. In this study, the potential impacts of FRT capabilities of IBDGs with legacy inverters have been investigated. The analysis was conducted considering the penetration level of IBDGs and complying with FRT characteristics. Furthermore, the required amount of fast frequency response resources, which are generally provided by battery energy storage systems, was evaluated along with the secure operating envelope that can aid in future power system planning. Case studies on modified New England 10-machine test system and Korean power system were conducted to validate the effectiveness of the analysis.

Flexible operation, optimisation and stabilising control of a quench cooled ammonia reactor for power-to-ammonia

This paper discusses the operation of an ammonia reactor for a Power-to-Ammonia (P2A) plant. We develop a dynamic model for an ammonia reactor system consisting of a three-bed quench cooled adiabatic reactor and a feed-effluent heat exchanger. The reactor bed model is formulated as a differential algebraic equations (DAE) system. We use the thermodynamic software Thermolib for rigorous modelling of the thermodynamic functions in the high pressure ammonia reactor. We present a case study of an ammonia synthesis loop in a P2A plant connected to a 250 MW renewable energy source with a capacity factor of 0.4. Static optimisation and stability analysis are performed for the reactor system, which located the optimal operating point close to instability. The dynamic simulations confirm the unstable operating regions as severe oscillations arise. A fluctuating energy supply from renewable sources requires the ammonia reactor to operate over a wide operating window from 20%–120% of nominal capacity. We formulate a realistic strategy for varying the supply of H2 and N2 (load) to the synthesis loop depending on the available energy. Open-loop simulations show that varying the synthesis feed flow cause oscillations in the ammonia reactor system. Therefore, we propose a regulatory control structure for stabilising the ammonia reactor. The optimisation algorithm determines the reactor set-point state by updating at changes to the synthesis loop load. Hereby, we achieved fast control and close tracking of the set-points for the ammonia reactor.

Hydrodynamics of cholinium chloride-based aqueous biphasic systems (ABS): A key study for their industrial implementation

Aqueous biphasic systems (ABS) have been widely studied for extraction and purification processes. Although they are considered biocompatible, amenable, and sustainable separation platforms, their application on an industrial scale remains impractical without proper scaling and integration into existing processes. To better understand the hydrodynamics of ABS formation, three cholinium chloride ([Ch]Cl)-based ABS composed of polypropylene glycol with a molecular weight of 400 g.mol−1 (PPG-400), tripotassium phosphate (K3PO4), and dipotassium hydrogen-phosphate (K2HPO4) were studied. The hydrodynamics of phase separation of ABS composed of PPG-400/[Ch]Cl, [Ch]Cl/K3PO4 and [Ch]Cl/K2HPO4 was studied by analysing the relationship between the mixing time (Tm) and the phase settling time (Ts), at 25 °C and 50 °C. The results showed that Ts is independent of Tm, which is very long for the polymer/salt systems (Ts > 6 h), while for salt/salt ABS, a very fast phase settling was observed (Ts < 150 s). The hydrodynamics of each salt/salt system was then correlated with the physicochemical properties of the coexisting phases and the nature of the phase-forming compounds. The increase in the salting-out effect of the inorganic salts, and the consequent larger differences between the compositions of the coexisting phases, improved the hydrodynamics of the [Ch]Cl-based ABS. With the increase of the tie-line lengths, the composition of the phases stabilized, resulting also in more stable physicochemical properties in each phase and constant Ts. The correlations obtained in this work allow the definition of the best operating region within the biphasic (liquid-liquid) region of [Ch]Cl/salt-based ABS as being the largest TLLs within the LLE region. The definition of these criteria and region of operation is crucial for the design and industrial implementation of these types of LLE processes using conventional mixer-settler units.

Experimental characterization, parameter identification and numerical sensitivity analysis of a novel hybrid sensible/latent thermal energy storage prototype for industrial retrofit applications

Hybrid design combinations of sensible and latent heat thermal energy storage (TES) leverage the advantages and reduce the disadvantages of both types. Thus, the range of application of said individual storage types is extended and crucial retrofit opportunities are enabled. Such hybrid TES concept consisting of a Ruths steam storage (RSS) and a surrounding layer of storage containers filled with an eutectic mixture of sodium nitrate (NaNO3) and lithium nitrate (LiNO3) as phase change material (PCM) was for the first time realized and investigated during operation in a steel production plant.In this work, the hybrid TES prototype is characterized with the help of detailed modelling and real measurement results. Uncertain model parameters are identified via parameter optimization and the numerical models show satisfactory validation results. Additional 30% of thermal energy could be stored in the PCM containers retrofitted to the lab-scale RSS. Charging/discharging times and specific thermal power of the PCM containers were roughly measured as 8h and 12h and 560kWm−3/−802kWm−3, respectively, in the typical operation region. A sensitivity analysis of the performance indicators reveals potential but also engineering challenges for following generations of the hybrid TES concept. Compared to the achieved experimental results, charging/discharging power could be increased by up to 10 and 5 times, respectively, in the future by adequate measures to increase heat transfer between both storage types.

Metaheuristic Framework for Material Screening and Operating Optimization of Adsorption-Based Heat Pumps.

The current methods applied to material screening for adsorption-based heat pumps are based on a fixed set of temperatures or their independent variation, providing a limited, insufficient, and unpractical evaluation of different adsorbents. This work proposes a novel strategy for the simultaneous optimization and material screening in the design of adsorption heat pumps by implementing a meta-heuristic approach, particle swarm optimization (PSO). The proposed framework can effectively evaluate variable and broad operation temperature intervals to search for viable zones of operation for multiple adsorbents at once. The criteria for selecting the adequate material were the maximum performance and the minimum heat supply cost, which were considered the objective functions of the PSO algorithm. First, the performance was assessed individually, followed by a single-objective approximation of the multi-objective problem. Next, a multi-objective approach was also adopted. With the results generated during the optimization, it was possible to find which adsorbents and temperature sets were the most suitable according to the main objective of the operation. The Fisher-Snedecor test was applied to expand the results obtained during PSO application and a feasible operating region built around the optima, enabling the arrangement of close-to-optima data into practical design and control tools. This approach allowed for a fast and intuitive evaluation of multiple design and operation variables.