Loop Configuration Research Articles

Performance Requirements of Membrane Reactors for the Application in Renewable Methanol Synthesis: A Techno‐Economic Assessment

AbstractRenewable energy carriers are expected to play a key role in the defossilization of the energy and chemical sector. For renewable methanol synthesis, membrane reactors (MR) have been tested on a laboratory‐scale with promising results. However, membrane performance requirements that allow an economic benefit for their large‐scale deployment are missing. Therefore, a 1D Python MR model is coupled with an AspenPlus process simulation to conduct a techno‐economic assessment with focus on membrane performance. Two synthesis loop configurations are investigated: one where feed and sweep recycle are operated at the same pressure and one where the sweep recycle operates at atmospheric pressure. The results show that both configurations can offer technical benefits, if sufficiently high product separation can be achieved, but that for a compressed sweep recycle no economic benefits are possible. As a consequence, membranes used for methanol synthesis must endure operation at high pressure differences. Furthermore, the results highlight the critical role of the H2 permeance, which should remain below 1 × 10−9 mol m−2 s−1 Pa−1. From an economic standpoint high water permeation has a more beneficial effect than high methanol permeation.

Conservation and Diversification of tRNA t6A-Modifying Enzymes across the Three Domains of Life.

The universal N6-threonylcarbamoyladenosine (t6A) modification occurs at position 37 of tRNAs that decipher codons starting with adenosine. Mechanistically, t6A stabilizes structural configurations of the anticodon stem loop, promotes anticodon-codon pairing and safeguards the translational fidelity. The biosynthesis of tRNA t6A is co-catalyzed by two universally conserved protein families of TsaC/Sua5 (COG0009) and TsaD/Kae1/Qri7 (COG0533). Enzymatically, TsaC/Sua5 protein utilizes the substrates of L-threonine, HCO3-/CO2 and ATP to synthesize an intermediate L-threonylcarbamoyladenylate, of which the threonylcarbamoyl-moiety is subsequently transferred onto the A37 of substrate tRNAs by the TsaD-TsaB -TsaE complex in bacteria or by the KEOPS complex in archaea and eukaryotic cytoplasm, whereas Qri7/OSGEPL1 protein functions on its own in mitochondria. Depletion of tRNA t6A interferes with protein homeostasis and gravely affects the life of unicellular organisms and the fitness of higher eukaryotes. Pathogenic mutations of YRDC, OSGEPL1 and KEOPS are implicated in a number of human mitochondrial and neurological diseases, including autosomal recessive Galloway-Mowat syndrome. The molecular mechanisms underscoring both the biosynthesis and cellular roles of tRNA t6A are presently not well elucidated. This review summarizes current mechanistic understandings of the catalysis, regulation and disease implications of tRNA t6A-biosynthetic machineries of three kingdoms of life, with a special focus on delineating the structure-function relationship from perspectives of conservation and diversity.

ANALISIS PERBANDINGAN KEANDALAN SISTEM JARINGAN DISTRIBUSI BERKONFIGURASI RADIAL DAN LOOP MENGGUNAKAN METODE SECTION TECHNIQUE

Electric power is needed in all sectors of life because basically, electric power is one of the basic human needs. With the existence of electric power in the daily activities of society and industry, it will also have an impact on increasing electrical energy which is increasing day by day. With the increasing number of consumers, the demand for quality in the supply of electrical energy will increase. So that the reliability of the electric power system is needed in increasing the availability of electricity to consumers. To find out that the distribution of electrical energy is maintained, it is necessary to have a very good level of reliability. The reliability method chosen in determining the reliability index is the Section Technique method. Section Technique is a structured method for analyzing a particular system. The results of calculations using the section technique method on the Arjasa feeder with loop configuration obtained a SAIFI reliability index of 1.5471 times/year, SAIDI of 1.1843 hours/year, and CAIDI of 0.7654 hours/year, while for feeders with radial configuration the SAIFI value is 1.4762 times/year, SAIDI of 5.2587 hours/year and CAIDI of 3.5623 hours/year.

Tri-Generation System Configuration Selection Based on Energy and Exergy Analyses

A tri-generation system combining cooling, heating, and power generation can contribute to increased system efficiency and thereby reduce greenhouse gas emissions. This study proposed a novel concept using 100-kW polymer electrolyte membrane fuel cells (PEMFCs) as the basis for a tri-generation system with an integrated heat pump and adsorption chiller for greenhouse use. Three configurations of heat pump loop were designed to recover the waste heat from PEMFCs and used either for direct heating or cooling power generation in adsorption cooling. Analyses were carried out in terms of primary energy rate (PER) and exergy efficiencies. Of those investigated, the layout with a heat pump and internal heat exchanger demonstrated the best performance, with PERs of the cooling and heating modes at 0.94 and 0.78, respectively. Additionally, the exergy analysis revealed that the exergies are mostly destroyed at the expansion valve and evaporator due to differences in pressure and temperature. These differences are minimized when the system layout contains a cascade heat pump loop or an internal heat exchanger, thus resolving the problem of exergy destruction. As a result, the total exergy destruction in the system was decreased from 61.11% to 49.18% and 46.60%, respectively. Furthermore, the proposed configurations showed 36.1% and 31.4% lower values in terms of energy consumption compared with relevant works in the heating mode and cooling mode, respectively.

An adaptive memetic algorithm for the bidirectional loop layout problem

Given a set of facilities, a set of positions arranged in a loop configuration and a flow cost matrix, the bidirectional loop layout problem (BLLP) is to find a facility-to-position assignment with the minimum sum of the products of flow costs and facility distances. The flow cost between two facilities is the unit cost of transporting items between two facilities, and the distance between two positions is shorter in the clockwise or counterclockwise direction in the loop. The BLLP is a relevant model for manufacturing systems; however, as the problem is known to be NP-hard, solving the problem is computationally challenging. This paper presents a memetic algorithm for BLLP that features an adaptive crossover selection and a dedicated 3-phase local search. Experiments of the proposed algorithm are conducted on 65 benchmarks, demonstrating a competitive performance compared with the current best algorithms. Additional experiments are conducted to study the impacts of the essential components of the algorithm.

Machine learning based system identification of a realistic heat integrated distillation column using particle swarm optimization

In the petrochemical industry, heat integration is one of the most commonly used methods for saving energy in the distillation column. The component of the liquid mixture can be estimated by correctly modeling or identifying the respective heat integrated distillation column (HIDC). Previously, system identification for HIDC has been performed using steady state data in an open loop configuration. However, the data obtained from steady state does not characterize realistic HIDC. Complex nonlinear modeling is required to account for the nonlinearities present in HIDC. In this study, a unique approach is presented to identify a dynamic closed-loop HIDC system using Support Vector Regression (SVR). Here, HYSYS is used to simulate HIDC in a fairly realistic environment and the resulting data is used in MATLAB for system identification. Particle Swarm Optimization (PSO) is used to optimize the SVR parameters, which gives better results than conventional metaheuristic optimization approaches. The proposed approach is also verified by accurately estimating the mole fraction of benzene-toluene mixtures in a dynamic HIDC. In terms of root mean square error (RMSE) and regression coefficients (R), the proposed strategy outperforms artificial neural networks (ANN) and radial basis function (RBF) models. The proposed technique reduces the RMSE by 80% and 47% compared to ANN for the mole fractions of benzene and toluene, respectively.

Lateral directional geometric control for small fixed-wing aircraft

This paper presents a solution to the path following problem for fixed-wing aircraft on the cartesian plane. The solution considers the lateral-directional aircraft dynamics, the geometric structure of the aircraft kinematics, and an inner-outer control loop configuration. Numerical simulations employing Matlab-Simulink and the flight simulator X-Plane are presented to verify the performance of the proposed control algorithm.

Pyrrole-Containing ABA Triblock Brush Polymers as Dual Functional Molecules to Facilely Access Diverse Mesostructured Materials

We report a new type of ABA-type brush-like triblock copolymer (PEGMA-b-PPHMA-b-PEGMA), which is characterized by two hydrophilic end segments (A) and a hydrophobic midblock (B) bearing polymerizable pyrrole moieties. This kind of symmetric triblock copolymers can not only serve as a structure-directing agent for the formation of mesoporous silicates but also function as a polymerizable monomer or carbon source for further chemical conversion to deliver mesostructured polymer or carbon materials within the preformed silicate framework. By utilizing such dual functional macromolecules, rich morphologies of mesostructures are accessible through microphase separation, and the order–order transition among cubic, lamellar, 2D hexagonal, and bicontinuous mesostructures is sensitively achievable by varying the hydrophilic volume fraction of copolymers and TEOS dosage. These features enable facile access to diverse mesostructured silica, polymer, and carbon materials. Remarkably, due to the brush-like polymer architecture and the formation of loop configuration, a widely tunable pore size from mesoscale to macroscale is realizable through using a relatively lower molecular weight copolymer. Importantly, it is found that the brush-like hydrophilic segments of our triblock copolymers can firmly anchor into the silica walls without appreciable escape of copolymer template in commonly used solvents even under reflux extraction, providing a prerequisite for reliable confined chemical transformation into mesostructured polymer and carbon materials. Our work demonstrates that the design and synthesis of functional amphiphilic block copolymers will bring great opportunity for the development of novel mesostructured materials.

Surgical Management of Perigraft Seroma by Graft Wrapping with Local Hemostatic Agents: A Case Report.

A 76-year-old female developed progressive local groin bulging. She received regular hemodialysis using a left-thigh polytetrafluoroethylene arteriovenous graft in the loop configuration. Lower extremity enhanced computed tomography showed a large low-density area around the graft 18 months after its creation, and perigraft seroma (PS) was suspected. The patient underwent PS excision followed by graft wrapping with two local hemostatic agents, oxidized regenerated cellulose, and a fibrin sealant. Local PS recurrence was not detected four months after surgery. We herein describe a surgical case of refractory PS successfully treated by graft wrapping using two local hemostatic agents.

Local Normal Mode Analysis for Fast Loop Conformational Sampling.

We propose and validate a novel method to efficiently explore local protein loop conformations based on a new formalism for constrained normal mode analysis (NMA) in internal coordinates. The manifold of possible loop configurations imposed by the position and orientation of the fixed loop ends is reduced to an orthogonal set of motions (or modes) encoding concerted rotations of all the backbone dihedral angles. We validate the sampling power on a set of protein loops with highly variable experimental structures and demonstrate that our approach can efficiently explore the conformational space of closed loops. We also show an acceptable resemblance of the ensembles around equilibrium conformations generated by long molecular simulations and constrained NMA on a set of exposed and diverse loops. In comparison with other methods, the main advantage is the lack of restrictions on the number of dihedrals that can be altered simultaneously. Furthermore, the method is computationally efficient since it only requires the diagonalization of a tiny matrix, and the modes of motions are energetically contextualized by the elastic network model, which includes both the loop and the neighboring residues.

A NEW METHOD TO ENHANCE THE DIFFERENTIAL PROTECTION OF THE MICROGRID BY SELF-BACKUP PROTECTION

Although the differential protection schemes consider as one of the effective types to protect the microgrid, this method may result in inaccurate performance because of the loss of communication link connecting the two ends of the line or other reasons. Therefore, the use of backup protection can lead to more accurate results. In this paper, self-backup protection is presented to cover the mal-operation of main protection. In this scheme, a new R-ratio method is defined based on the summation of the three-phase currents and the minimum of the three-phase voltages to overcome the low fault current during the islanded microgrid. The proposed scheme can detect all fault types during both operation modes of microgrid, grid-connected and islanded for radial and loop configuration. The validation of the proposed scheme is performed using PSCAD/EMTDC software. The simulation results proved that the proposed scheme could provide adequate protection against various fault types in grid-connected and islanded operation modes for a radial and loop configuration.

Fractional Order Modeling of PWR Pressurizer Dynamics and Fractional Order Nonlinear H∞ Controllers Design in LabVIEW

The novel fractional order intelligent transient dynamics and advanced fractional order nonlinear robust control synthesis scheme of the Pressurized Water Reactor (PWR) pressurizer are addressed in this research work. The Graphical User Interface (GUI) is designed for closed-loop model-based PWR pressurizer dynamical studies in LabVIEW. Based on the demand for power, the reactor power and turbine power are predicted using a fractional order backpropagation algorithm in an open loop configuration. Using turbine power and heater power as input variables, pressurizer level, pressurizer pressure and coolant average temperature as output variables, the open loop multi-input multi-output (MIMO) dynamic model of pressurizer is estimated using fractional order artificial intelligence in LabVIEW. Four fractional order robust nonlinear H∞ sub-controllers are designed for charging flow, spray flow, proportional heaters power and backup heaters power. All the dynamic controller models are in fractional order nonlinear H∞ framework and are designed in LabVIEW. The performance of the proposed design work is evaluated in closed loop configuration at 100 %, 75 % and 15 % in steady state conditions. Dynamic transient analysis is performed from 100% to 90% power reduction scenario and found satisfactory and within design limits and robust bounds.

Sensitive seismic sensors based on microwave frequency fiber interferometry in commercially deployed cables

The use of fiber infrastructures for environmental sensing is attracting global interest, as optical fibers emerge as low cost and easily accessible platforms exhibiting a large terrestrial deployment. Moreover, optical fiber networks offer the unique advantage of providing observations of submarine areas, where the sparse existence of permanent seismic instrumentation due to cost and difficulties in deployment limits the availability of high-resolution subsea information on natural hazards in both time and space. The use of optical techniques that leverage pre-existing fiber infrastructure can efficiently provide higher resolution coverage and pave the way for the identification of the detailed structure of the Earth especially on seismogenic submarine faults. The prevailing optical technique for use in earthquake detection and structural analysis is distributed acoustic sensing (DAS) which offers high spatial resolution and sensitivity, however is limited in range (< 100 km). In this work, we present a novel technique which relies on the dissemination of a stable microwave frequency along optical fibers in a closed loop configuration, thereby forming an interferometer that is sensitive to deformation. We call the proposed technique Microwave Frequency Fiber Interferometer (MFFI) and demonstrate its sensitivity to deformation induced by moderate-to-large earthquakes from either local or regional epicenters. MFFI signals are compared to signals recorded by accelerometers of the National Observatory of Athens, Institute of Geodynamics National Seismic Network and by a commercially available DAS interrogator operating in parallel at the same location. Remarkable agreement in dynamical behavior and strain rate estimation is achieved and demonstrated. Thus, MFFI emerges as a novel technique in the field of fiber seismometers offering critical advantages with respect to implementation cost, maximum range and simplicity.

A Low-Profile Compact Meander Line Telemetry Antenna with Low SAR for Medical Applications

A low-profile Compact Meander Line Telemetry Antenna (CMLTA) operating at 402.5 MHz for the Medical Implant Communication System (MICS) band medical applications is introduced. The proposed antenna focuses specifically on pacemaker telemetry applications. The meander line technique with an open loop configuration and simple transmission line feeding mechanism has been used for achieving the compact design. Based on the theory of surface current distribution, the proposed technique provides the opportunity to increase the electrical dimensions while decreasing the physical dimensions of the antenna. Further design optimization is carried out to optimize the overall antenna size to a maximum volume of 4080 mm3. By introducing CMLTA, the size of the antenna is reduced by 79% as compared to the previous work. The proposed antenna demonstrated satisfactory performance with 10 dB bandwidth of 6.17%, a maximum gain of -22 dBi and an EIRP of -25.28 dBi. The analysis of Specific Absorption Rate under premise use of 1 W input power provided the maximum 1 g and averaged 10 g SAR of 74.7 W/kg and 17.7 W/kg, respectively, demonstrating a satisfactory level according to the IEEE standard safety guidelines. Fabrication and measurements are carried out where measured results are found to be in good agreement with the simulated results. With the optimized dimensions, satisfactory gain, EIRP, and SAR performance, the proposed CMLTA is deemed suitable for pacemaker telemetry applications for effective communication.

Development of an Open-Source Testbed Based on the Modbus Protocol for Cybersecurity Analysis of Nuclear Power Plants

The possibility of cyber-attacks against critical infrastructure, and in particular nuclear power plants, has prompted several efforts by academia. Many of these works aim to capture the vulnerabilities of the industrial control systems used in these plants through computer simulations and hardware in the loop configurations. However, general results in this area are limited by the cost and diversity of existing commercial equipment and protocols, as well as by the inherent complexity of the nuclear plants. In this context, this work introduces a testbed for the study of cyber-attacks against a realistic simulation of a nuclear power plant. Our approach consists in surveying issues regarding realistic simulations of nuclear power plants and to design and experimentally validate a software testbed for the controlled analysis of cyberattacks against the simulated nuclear plant. The proposal integrates a simulated Modbus/TCP network environment containing basic industrial control elements implemented with open-source software components. We validate the proposed testbed architecture by performing and analyzing a representative cyberattack in the developed environment, thus showing the principles for the analysis of other possible cybernetic attacks.

An improved platform for cultured neuronal network electrophysiology: multichannel optogenetics integrated with MEAs.

Cultured neuronal networks (CNNs) are powerful tools for studying how neuronal representation and adaptation emerge in networks of controlled populations of neurons. To ensure the interaction of a CNN and an artificial setting, reliable operation in both open and closed loops should be provided. In this study, we integrated optogenetic stimulation with microelectrode array (MEA) recordings using a digital micromirror device and developed an improved research tool with a 64-channel interface for neuronal network control and data acquisition. We determined the ideal stimulation parameters including light intensity, frequency, and duty cycle for our configuration. This resulted in robust and reproducible neuronal responses. We also demonstrated both open and closed loop configurations in the new platform involving multiple bidirectional channels. Unlike previous approaches that combined optogenetic stimulation and MEA recordings, we did not use binary grid patterns, but assigned an adjustable-size, non-binary optical spot to each electrode. This approach allowed simultaneous use of multiple input-output channels and facilitated adaptation of the stimulation parameters. Hence, we advanced a 64-channel interface in that each channel can be controlled individually in both directions simultaneously without any interference or interrupts. The presented setup meets the requirements of research in neuronal plasticity, network encoding and representation, closed-loop control of firing rate and synchronization. Researchers who develop closed-loop control techniques and adaptive stimulation strategies for network activity will benefit much from this novel setup.

Analysis of Operation Conditions of Ca(OH)2 Entrained Carbonator Reactors for CO2 Capture in Backup Power Plants.

The share of renewables in the energy sector is increasing, and energy storage and backup power combustion systems to cover the periods of time with low renewable energy production are becoming increasingly needed. Flexible calcium looping configurations based on the storage of solids are a promising alternative to capture the CO2 produced in such backup combustion systems. The use of Ca(OH)2 instead of CaO is better suited to these applications due to the faster reaction kinetics and higher carbonation conversions as Ca(OH)2 in powder form can achieve conversions of up to 0.7 in just a few seconds at temperatures of 550–650 °C. To take advantage of these fast reaction kinetics, compact carbonator reactors with short gas–solid contact times (i.e., a few seconds) can be designed. However, the low enthalpy of the carbonation reaction of Ca(OH)2 makes it challenging to find the optimum conditions which maximize the CO2 capture efficiency. In this work, a basic entrained reactor with recent experimental reaction kinetics has been used to determine suitable operational windows for this kind of carbonator. CO2 capture efficiencies above 90% can be achieved for flue gases with low CO2 concentrations (4%v CO2) when they are fed into the carbonator at temperatures of around 500–600 °C while maintaining low FCa/FCO2 ratios (<2) and feeding the sorbent at ambient temperature. When capturing from a flue gas with a higher CO2 concentration (14%v CO2), the sorbent needs to be fed at higher temperatures to effectively capture CO2 in short contact times (i.e., 6 s).

In vitro benchtop mock circulatory loop for heart failure with preserved ejection fraction emulation.

In this work, a novel mock circulatory loop (MCL) is presented that is capable of simulating both healthy cardiac function and Heart Failure with preserved Ejection Fraction (HFpEF). This MCL differs from others presented in the literature as it features two independently actuated heart chambers, representing the left atrium and the left ventricle. This is an important improvement over other designs as it allows for potential HFpEF treatments to be examined, not just in relation to their effect on the left ventricle but also on the left atrium. The aim of this work was to show that novel MCL designs could be developed to allow for testing of new mechanical circulatory support devices for the treatment of HFpEF. Two loop configurations are presented, one featuring hard PVC cylindrical chambers and one that features soft silicone chambers which are anatomically analogous to the native heart. We show that both MCLs are capable of simulating the onset of HFpEF with a sustained increase in diastolic pressure of 62.03% and a sustained decrease in end diastolic volume (EDV) of 14.24%.

Spatiotemporal observation of higher-order modulation instability in a recirculating fiber loop.

We experimentally investigate higher-order seeded modulation instability in an optical fiber experiment. The recirculating loop configuration with round trip losses compensation enables the observation in single-shot of the spatiotemporal evolution of an initially modulated continuous field revealing intricate yet deterministic dynamics. By tuning the modulation period, a continuous transition between perfectly coherent and purely noise-driven dynamics is observed that we characterize by means of a statistical study.

Use of Boost Power Stage for Static Voltage Gain Improvement of a Non-isolated Continuous Input Current Three-Level DC-DC Converter

The work presented in this paper describes the steady state analysis of a non-isolated and continuous conduction mode (CCM) operated three-level DC-DC converter with input boost power stage for achieving high static voltage gain. The proposed converter configuration is a double boost DC-DC conversion scheme. A boost power module consisting of a power switch, an inductor, a pre-charge diode, and a diode rectifier is introduced as the input stage in the conventional three-level DC-DC converter configuration to obtain the DC-DC converter topology suggested in this research work. The role of the input boost power stage is to extend the voltage gain of the conventional three-level boost converter. The proposed topology employs two power switches in addition to a boost power switch with simple control strategy so that the switching losses are reduced. The switches are subjected to low voltage and current stresses. The suggested non-isolated converter is operated under continuous inductor current mode in open loop configuration. The converter configuration has been simulated in MATLAB / SIMULINK platform. The input boost power stage receives a voltage of 24 V from a DC source. With low duty ratio (= 0.8) of the power switches, a DC voltage of around 208 V is obtained at the load end. The passive components of the converter are so designed that the filtering requirements on the DC output voltage and current waveforms are reduced. The voltage gain of the proposed converter is compared with that of the three-level boost converter without input boost power stage. The various modes of operation of the suggested converter are discussed with relevant equivalent circuits. The proposed system is validated using a developed hardware prototype model of 100 W converter with a low cost KA3525A PWM controller. Both simulation and prototype model results demonstrate that the proposed converter suits high voltage gain applications.