Basic Cycle Research Articles

Traditional, Mixed-Mode, and Online Instruction for Microbial Metabolism Before and During COVID-19

As COVID-19 restrictions are removed, instructors are faced with two questions: should the course be taught online, via mixed-mode, or through traditional methods, and what effect did online instruction have on students in the course in regards regarding enrolled across eight semesters of metabolism courses using traditional, mixed-mode, and online methods. Post-hoc analysis of a repeated-measures ANOVA determined that while mixed-mode outperformed traditional methods on metabolism exams involving introductory concepts on the first exam (4.47 ±4.24, p= 0.012) and on the cumulative final exam (8.15 ±4.24, p= <0.001), traditional methods were superior to both mixed-mode (9.21 ±4.24, p= <0.001) and online methods (6.37 ±5.76, p= 0.006) at teaching alternative pathways of metabolism and lipid, nucleotide, and amino acid synthesis pathways. All methods showed poor student scores on glycolysis, TCA cycle, oxidative phosphorylation topics. Online methods performed nearly equally to mixed-mode, though there was not a significant difference on the first exam’s content as was found with mixed-mode. It is evident that, based on this study, a different approach to teaching basic central metabolic cycles such as glycolysis, the TCA cycle, and the electron transport chain is necessary to improve student understanding of these topics.

DEVOPS FOR MANUFACTURING SYSTEMS: SPEEDING UP SOFTWARE DEVELOPMENT

AbstractThe increasing importance of software as an essential functional provider in products and processes requires that companies master the development capabilities to continiously and quickly deliver high-quality software features. DevOps (acronym for Development and Operations) is an essential approach to these capabilities, which has so far been used predominantly in software-driven companies. This paper investigates the conditions under which DevOps can also be used in the industrial context of series manufacturing in order to be able to steadily develop and provide software features used in these environments (e.g. for monitoring and maintenance of manufacturing machines). A concept for DevOps for manufacturing systems was developed based on current best practices and the specific situation in the industrial company. The concept was then implemented and validated with experts on the basis of initial development cycles, demonstrating the usefulness of DevOps for manufacturing systems.

Geometric characterization of the persistence of 1D maps

We characterize critical points of 1-dimensional maps paired in persistent homology geometrically and this way get elementary proofs of theorems about the symmetry of persistence diagrams and the variation of such maps. In particular, we identify branching points and endpoints of networks as the sole source of asymmetry and relate the cycle basis in persistent homology with a version of the stable marriage problem. Our analysis provides the foundations of fast algorithms for maintaining a collection of sorted lists together with its persistence diagram.

Risk factors for recurrent tuberculosis in children under modern conditions

In recent years, the situation on the main epidemiological indicators of tuberculosis (TB) in the Russian Federation has clear positive changes, including those among the pediatric population. The criterion of the efficiency of the therapy performed and the quality of a follow-up after completing the basic therapy cycle is the absence of a relapse of the disease and hence the chronization of the process. It is commonly supposed that the appearance of the signs of active TB in individuals who have experienced and cured of TB is a relapse of TB. The paper describes the clinical case of recurrent TB, which shows that the main risk factor for primary TB is the lack of immunization against TB due the perinatal contact of a child with a HIV-infected mother. The provoking factor for a relapse was exogenous TB superinfection due to the development of new cases of the disease in the family in the presence of a child’s long-term already existing contact.

On a wider class of prior distributions for graphical models

AbstractGaussian graphical models are useful tools for conditional independence structure inference of multivariate random variables. Unfortunately, Bayesian inference of latent graph structures is challenging due to exponential growth of $\mathcal{G}_n$ , the set of all graphs in n vertices. One approach that has been proposed to tackle this problem is to limit search to subsets of $\mathcal{G}_n$ . In this paper we study subsets that are vector subspaces with the cycle space $\mathcal{C}_n$ as the main example. We propose a novel prior on $\mathcal{C}_n$ based on linear combinations of cycle basis elements and present its theoretical properties. Using this prior, we implement a Markov chain Monte Carlo algorithm, and show that (i) posterior edge inclusion estimates computed with our technique are comparable to estimates from the standard technique despite searching a smaller graph space, and (ii) the vector space perspective enables straightforward implementation of MCMC algorithms.

Thermo-economic optimization and comparative analysis of different organic flash cycles for the supercritical CO2 recompression Brayton cycle waste heat recovery

It is well known that the energy efficiency of the supercritical carbon dioxide recompression Brayton cycle (sCO2RBC) can be improved by employing the bottoming cycles to recover its large waste heat. To achieve better performance, three bottoming cycles with a good temperature matching with the sCO2 stream, namely the basic organic flash cycle (BOFC), the regenerative organic flash cycle (ROFC), and the organic flash Rankine cycle (OFRC), are employed to combine with the sCO2RBC in this work. The parametric analysis is performed to determine the variation trends of systems’ thermodynamic and exergoeconomic performance with five important parameters. The single-objective optimization is conducted for the sCO2RBC/BOFC, sCO2RBC/ROFC and sCO2RBC/OFRC systems with six organic fluids. The single-objective optimization results show that the highest exergy efficiency of the sCO2RBC/OFRC is higher than that of the rest combined sCO2RBC/OFCs by up to 1.95%. And the lowest total product unit cost for the sCO2RBC/OFRC is up to 0.93% lower than that of the rest combined sCO2RBC/OFCs. Finally, a comparative analysis is performed for the three combined sCO2RBC/OFCs, sCO2RBC/ORC and stand-alone sCO2RBC systems under the multi-objective optimization conditions. Results show that the integrated systems can improve the ηex by 4.62–6.06% and reduce the cp,tot by 2.68–3.14% when taking the sCO2RBC system as the baseline system. The sCO2RBC/OFCs and sCO2RBC/ORC are recommended to use R1336mzz(Z) and R245fa as working fluids, respectively. Moreover, the sCO2RBC/OFRC system achieves an improvement of 0.41%–1.37% in exergy efficiency with a comparable total product unit cost, compared to other aforementioned integrated systems.

Comparison of three arrangements of internal combustion engine-driven energy systems boosted with PEM fuel cell towards net-zero energy systems

The current works aim is performance improvement of different integrated energy systems towards net-zero energy which is driven by a set of Internal Combustion Engine (ICE) through adding some components like fuel cell and thermoelectric generator (TEG) in new arrangements introduced and analyzed. The novelty of the present work is the proposal of the new arrangement of energy conversion systems. In this study the basic cycle (cycle 1) is including an ICE, Kalina cycle, Humidification and Dehumidification (HDH) unit, in cycle 2, the HDH is eliminated while a fuel cell is added to the system and in the cycle 3, in addition to fuel cell and having HDH unit in the system, a thermoelectric generator (TEG) has been used instead of condenser to recover more wasted thermal energy. The performance of all proposed systems is analyzed from energy, exergy, and exergo-economic aspects. It is demonstrated that from an energetic viewpoint, cycle 3 has the better performance with an energy efficiency, and net output power of 37% and 391.7 kW, respectively. That is while from an exergetic viewpoint cycle 2 with exergy destruction of 257.1 kW has superior exergetic performance. The results of current work can provide a precise basis for designing an efficient energy system with a higher thermal performance.

THERMODYNAMIC ANALYSIS OF RECUPERATIVE AND REHEAT BASED ON ORGANIC RANKINE CYCLE FOR HIGH-TEMPERATURE WASTE HEAT RECOVERY

Heat recovery from available waste heat is an essential method in renewable energy processes due to the ability to generate electricity by using Organic Rankine Cycles (ORC). The process model is developed with the Cycle Tempo software. Fluid properties were analyzed with Reference Fluid Properties (REFPROP) software. This research presents a thermodynamic comparison of the Basic Organic Rankine Cycle (BORC) and Recuperative Organic Rankine Cycle (RORC) for waste heat recovery applications using pure refrigerants R-141b, R-245fa, R-123, and R-21. By performing simulations for heat source high-temperatures ranging from 160 to 200 °C. The comparison between BORC and RORC performance parameters and refrigerant properties was evaluated on the heat source temperature. Research shows that RORC produces higher thermal efficiency but has lower irreversibility than BORC. RORC has a maximum thermal efficiency of 12.67%, and BORC has a thermal efficiency of 11.49% for refrigerant R-141b at a flue gas temperature of 160 °C. The thermal efficiency of the ORC increases as the temperature of the heat source increases.

Long-term N addition leads to microbial C, but not N limitation of poplar plantation soils in eastern China

Soil extracellular enzymes are vital to regulating soil carbon (C) and nutrient cycling, and hence affecting soil function. However, how soil enzymes activity will respond to increasing global nitrogen (N) deposition, remains poorly understood. In this study, we applied five N addition treatments (0, 5, 10, 15, and 30 g m−2 yr−1) at a coastal China poplar plantation to explore the activity of the five soil enzymes associated with C, N, and phosphorus (P) cycling and nutrient limitation of soil microbes from 2018 to 2020. We found that N addition significantly increased C, decreased N and showed no significant impact on P acquisition enzyme activity. We also found that N addition aggravated soil microbial C limitation but did not significantly change the N limitation. Both soil microbial C and N limitation were eased with time (year). Best subset regression analysis (BSS) showed that dissolved organic C, soil pH, and microbial biomass C were the dominant drivers of C, N, and P acquisition enzyme activity, respectively. Also, BSS showed that soil available N explained the greatest proportion of variation in positive soil microbial C and negative N limitation. Our study provides evidence for changes in soil enzymes activity and microbial nutrients limitation, as well as contributes to the theoretical basis for soil microbial nutrient cycling with elevated N deposition.

Impact of effective refractory period personalization on prediction of atrial fibrillation vulnerability

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – EU funding. Main funding source(s): European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska- Curie grant agreement Introduction Although the effective refractory period (ERP) is one of the main electrophysiological properties governing atrial tachycardia (AT) maintenance, ERP personalization is rarely performed when creating patient-specific computer models of the atria to inform clinical decision making. State-of-the-art models usually do not consider physiological ERP gradients but assume a homogeneous ERP distribution. This assumption might have an influence on the ability to induce reentries in the model. Aim To evaluate the impact of incorporating clinical ERP measurements when creating in silico personalized models to predict vulnerability to atrial fibrillation (AF). Methods Clinical ERP measurements were obtained from three patients from multiple locations in the atria. The protocol for ERP identification consisted of trains of 7 S1 stimuli with a basic cycle length of 500ms followed by an S2 stimulus with a coupling interval between 300 and 200ms in decrements of 10ms until loss of capture. The atrial geometries from the electroanatomical mapping system were used to generate personalized atrial models. To reproduce patient-specific ERP, the established Courtemanche cellular model was gradually reparameterized from control conditions to a setup representing AF-induced remodeling. Three different approaches were studied: 1) a control scenario with no ERP personalization 2) a discrete split where each region had a single ERP value and 3) a continuous ERP distribution by interpolation of measured ERP data (Fig. 1). Arrhythmia vulnerability was assessed by virtual S1S2 pacing from different locations separated by 3cm. The number and location of inducing points and type of arrhythmia were determined for the three approaches. The mean conduction velocity was set to 0.7 m/s and the electrical propagation in the atria was modeled by the monodomain equation and solved with openCARP. Results Incorporating patient-specific ERP as a continuous distribution did not induce any reentrant activity. A summary of induced ATs is shown in Table 1. For patient A, AF was induced from 3 different locations with the control setup, whereas 9 ATs were induced with the regional method, of which 4 were AF and 5 macro reentries. For patient B, AF was induced from 1 point with the control setup; whereas with the regional approach, AF was induced at 4 points. For patient C, only one macro reentry was induced with the regional method. Conclusion Incorporation of patient-specific ERP values has an impact on the assessment of AF vulnerability. Furthermore, the type of personalization affects the likelihood of AF inducibility. The incorporation of more detailed ERP distributions may lead to a more accurate prediction of AF trigger points and could in the future inform patient-specific therapy planning. Larger cohorts need to follow to demonstrate the role of incorporating clinical patient-specific ERP values into personalized models for predicting AF vulnerability.

Thermodynamic analysis of a novel vapor-injection Joule-Thomson refrigeration cycle with a binary hydrocarbon mixture for −86 °C freezer

This paper proposes a novel vapor-injection Joule-Thomson refrigeration cycle with mixed-refrigerant. The introduction of the compressor with vapor-injection can reduce the pressure ratio of each compression stage, thus reducing the compressor power and discharge temperature. The thermodynamic analysis results show that the performance of the novel cycle is better than that of the basic Joule-Thomson cycle. In addition, this paper studies the binary hydrocarbons applied in −86 °C freezers, and find a binary hydrocarbon R601a/R1150 with Superior performance. The mass fractions of R1150 in R601a/R1150 corresponding to the maximum COP of the novel cycle and basic cycle are 0.45 and 0.44, respectively. Moreover, the maximum COP of the novel cycle is 19.25% higher than that of the basic cycle. The comparison results demonstrate that the novel cycle has a great energy-saving potential. In addition, at different condenser outlet temperatures of 16 °C, 25 °C and 32 °C, both cycles have the optimal condensation pressure of 300 kPa, 500 kPa and 650 kPa with respect to COP. For the novel cycle, the compressor injection ratio has little effect on COP. The increase of intermediate pressure can improve cycle performance, but too high intermediate pressure is not conducive to the normal operation of the system. Furthermore, the exergy analysis result shows that the location of the largest exergy destruction rate is in the compressors for both cycles, followed by the recuperators, condensers, evaporators, and capillary tubes.

Thermodynamic analysis of the apci skikda liquefaction process

In this paper, the mixed refrigeration cycle of Skikda APCI (Air Products and Chemicals Inc.) process in Algeria was studied thermodynamically in order to determine the optimal operat-ing conditions. The energy and exergy balance equations for each process component were es-tablished. The distribution of the exergy destruction of the basic cycle equipment revealed that the compressors had the highest exergy destruction rate. The effects of operating conditions on performance coefficient of the cycle (COP) and exergy efficiency of the APCI process were evaluated; mainly the inlet temperature of the compressors, natural gas (NG) temperature af-ter cooling in the main cryogenic heat exchanger (MCHE) and inlet temperature of the mixed refrigerant (MR) expansion valve. The results of the numerical simulation validated using Aspen HYSYS software indicate that the COP and exergy efficiency of the basic cycle are 2.66 and 59.99% respectively. These results can be improved by reducing the inlet temperature of the compressor and the expander as well as that of the NG after cooling in the MCHE. Finally, the results of the optimization performed using the genetic algorithms (GA) are in agreement with those of the literature. They show signs of improvement in the COP and exergy efficiency of the APCI process by 1.48% and 3.64% respectively compared to the basic cycle.

Review of Recent Advances in Transcritical CO2 Heat Pump and Refrigeration Cycles and Their Development in the Vehicle Field

Refrigerant substitution is an urgent need in the context of reducing carbon emissions and slowing global warming. CO2 is now being proposed as a promising solution based on its excellent properties and system performance, especially in low-temperature environments. This paper presents an overview of recent advances in system configuration and operation characteristics to improve the performance of transcritical CO2 heat pump and refrigeration systems. The paper first introduces the basic research background, system cycle, and thermodynamic characteristics. Secondly, CO2 cycle improvements with single modifications and modification combinations are reviewed. Then, some important operation characteristics and control methods are discussed. Additionally, the paper provides a detailed description of the development of transcritical CO2 heat pump and refrigeration systems in the vehicle field. At the end of this review, conclusions and opportunities for future work in this field are presented.

Computational Mathematics in Engineering Careers: Study of Electrical Circuits from the Perspective of Interdisciplinary Teaching

The new challenges of the educational engineering framework pretend to encourage the interdepartmental integration and interaction between basic sciences and the module of applied technology subjects. This paper presents a learning approach of interdisciplinary learning in the teaching of trigonometric functions, with special emphasis on the sinusoidal function, showing how the transformation of this function is related to fundamental concepts in the training of electrical energy engineers. The product of trigonometric functions makes it possible to analyze the instantaneous power of passive linear electric circuits and highlight the importance of studying the phase angle between voltage and current associated with the inductive or capacitive nature of the circuit. The development of the contents in the class contemplates the interdisciplinary and integrative aspect that must be implemented from the basic cycle as a bridge towards the applications of mathematics, articulating the problems of Engineering and the use of technologies in teaching.

Performance comparison of basic and parallel double evaporator Organic Rankine Cycle integrated with solar based supercritical CO2 cycle

Performance comparison of basic organic Rankine cycle (ORC) and parallel double evapora-tor ORC (PDORC) integrated with solar power tower (SPT) driven intercooled cascade sCO2 (supercritical carbon dioxide) cycle was carried out in present study. The intercooled cascade sCO2 cycle/ORC (configuration-1) and the intercooled cascade sCO2 cycle/PDORC (configu-ration-2) were considered for comparison on basis of parametric analysis. The effects of SPT design parameters such as solar irradiation, solar receiver emittance, and concentration ratio on system performance were investigated. It was concluded that the addition of basic ORC and PDORC to the intercooled cascade sCO2 cycle improved the thermal efficiency by 2.26% and 6.66% respectively at solar irradiation of 950 W/m2. In the case of basic ORC and PDORC, the waste heat recovery ratios were 0.1197 and 0.1775, respectively. It was also discovered that configuration-2 performed better than configuration-1 in terms of waste heat recovery. The combined cycle’s performance can be improved even more by lowering solar emittance and increasing the concentration ratio.

ELECTRIC VEHICLE SLIPPAGE PREVENTION SYSTEM BASED ON NEURAL NETWORK CONTROLLER

А functional diagram of the skidding prevention system was built, a mathematical model of an asynchronous electric drive of an electric vehicle was built, and a neuro-regulator was synthesized. The asynchronous motor is selected according to the equivalent power method, and the standard urban WLT cycle is taken as the basic cycle cycle. The mathematical model of the mechanical part is built taking into account the possibility of simulating the slippage of each of the driving wheels separately with different coupling coefficients. The model consists of a power converter, a battery, a speed regulator, a torque regulator, an asynchronous motor, a braking resistor, a unit for generating set signals, a mechanics unit and measuring units. The internal control system is built on the basis of DTC vector control using Matlab blocks. This work uses the NARMA-L2 control block, which is included in the Neural Network ToolboxTM. A simplified model (object model) was built, neural network parameters such as the number of hidden layers, discretization, number of samples, and number of epochs were selected for neural network training. The neural network was trained taking into account the linearized model of the object, which reflects the qualitative type of real processes in the system. Regardless of the linearization of the system, the output signal with a minimal error (about 1%) corresponds to the input. An analysis of the obtained results of network training was carried out. Simulation of system operation without skidding and skidding of one of the wheels was carried out. The simulation results are compared with the error obtained during neural network training, namely the discrepancy between the output and input signals. The model does not take into account side drift, so only the discrepancy in wheel speeds and the linear change in the speed of the electric vehicle can be observed. The possibility of using the traction electric drive using the method of intelligent neural networks in the safety system of the electric vehicle is shown. A conclusion was made about the operability and efficiency of the system using a neurocontroller to prevent one of the possible slippage modes.

Optimal design and thermodynamic evaluation of supercritical CO2 oxy-coal circulating fluidized bed power generation systems

Replacing the steam Rankine cycle with the supercritical CO2 Brayton cycle (sCO2 cycle) has been demonstrated to be an effective way to improve the efficiency of oxy-coal power plants. The present work focuses on the optimal design of the sCO2 oxy-coal circulating fluidized bed (CFB) power generation systems which so far has not received much attention in the research field. A novel triple recompression sCO2 cycle and a new sCO2 oxy-coal CFB boiler configuration with medium-temperature and high-temperature flue gas recirculation have been proposed and evaluated. With the novel boiler configuration and triple recompression cycle, the system efficiency can be increased by about 1.4% points in comparison to the basic system using the basic recompression cycle and the basic boiler configuration. The influences of the cycle minimum temperature, recuperator pinch temperature difference, furnace inlet oxygen concentration, flue gas recirculation flow distribution and coal itself on the sCO2 oxy-coal CFB power generation system performances were thoroughly investigated. The results show that increasing the minimum cycle temperature and the recuperator pinch temperature difference reduces the system efficiency while increasing the oxygen concentration at the furnace inlet and reducing the proportion of the recirculating flue gas as the primary oxidizing gas can boost the system efficiency. Coal itself also has an impact on the system efficiency due to its properties affecting the cycle efficiency, boiler efficiency and auxiliary equipment power consumptions.

Life Cycle Assessment of building energy systems on neighbourhood level based on semantic 3D city models

This study presents a method which allows conducting an energy and emission related Life Cycle Assessment (LCA) and cost-related Life Cycle Cost Assessment (LCC) of large residential building stocks focusing on selected heating system components. Using this method the status quo as well as two refurbishment scenarios for an entire neighbourhood with 196 residential buildings in Munich, Germany, is assessed. Within the status quo and the refurbishment scenarios, among other things, the use of different energy systems and energy standards of the building envelope are investigated. CityGML semantic 3D city models serve as a source of building-specific information for these assessments. The results show that even if all residential buildings are refurbished to passive house standard and powered by renewable energies by 2035, life cycle-based energy demands and emissions will still be present, that counteract the goal of achieving climate neutrality. In addition, the life cycle-based costs exceed the savings achieved by the refurbishment. The developed method is implemented in Java which provides on the one hand a new approach to assessing building stocks on a life cycle basis and on the other hand its transferability. This results in innovative evaluation and assessment possibilities for political and municipal decision-makers.

Superstructure-free synthesis and multi-objective optimization of supercritical CO2 cycles

The optimization of the supercritical CO2 cycle structures is mostly experience-intensive and computation-demanding. Using the superstructure-free method can effectively realize computer-aided intelligent construction and optimization of cycle configurations. In this paper, an improved superstructure-free algorithm is proposed which goes beyond the state-of-the-art methods by expanding the searching space and evaluation matrices. The improved algorithm can intelligently and simultaneously optimize the cycle structure and design parameters by considering both the net power output and specific investment cost as objective functions. By applying the algorithm, several previously unseen cycle structures were retrieved, and the maximum net power output increases by a range of 15.45% to 37.71%. The optimal cycle obtained by entropy weight and TOPSIS analysis of the Pareto solution set is a cascaded configuration of a double compression intercooling cycle and a basic cycle through sharing cooling process, which achieves a net power output of 37.75 kW and a specific investment cost of 5.33 $/W. The improved superstructure-free algorithm can also be applied to other thermodynamic cycles and can greatly contribute to the intelligent configuration design and optimization of similar thermodynamic cycles.

Experimental evaluation of the effect of mechanical subcooling on a hydrocarbon heat pump system

In addition to the progressive movement of countries towards the use of renewable energy sources, efficient energy consumption is another important goal set by the International Energy Agency. In heat pump technology, the use of mechanical subcooling system has a high potential for this purpose. In this experimental study, the impact of using a mechanical subcooling cycle on the performance of a heat pump system is investigated. The system is designed to supply heat at condensing temperatures of 50, 60 and 70 °C. Propane and isobutane are used as low GWP refrigerants in the main and secondary cycles, respectively. The results revealed that both the COP and heating capacity of the system are increased by adding the mechanical subcooling cycle up to 15.1% and 34%, respectively. To express the improvement of the system performance by means of the TEWI index, a reduction of 9–13% is calculated when the mechanical subcooling cycle is included. It is also of interest that the cooling coefficient of performance (COP2) is improved by adjoining a secondary cycle as a liquid subcooler. An optimal power ratio between the basic cycle and the secondary cycle was obtained, which is consistent with the simulation results.