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Author(s):  
Aida Farsi ◽  
Marc A. Rosen

AbstractAn analysis is reported of a geothermal-based electricity-freshwater system in which an organic Rankine cycle is integrated with a multi-effect distillation desalination unit. The system is driven by geothermal hot water extracted from the production well. Mass, energy, entropy, and exergy rate balances are written for all system components, as are energy and exergy efficiency expressions for each subsystem. The exergy destruction rate associated with the temperature and chemical disequilibrium of the freshwater and brine with the reference environment are taken into account to reveal accurate results for irreversibility sources within the desalination process. The developed thermodynamic model is simulated using thermodynamic properties of the working fluids (i.e., ammonia, seawater, distillate, and brine) at each state point. A sustainability analysis is performed that connects exergy and environmental impact concepts. That assessment expresses the extent of the contribution of the system to sustainable development and reduced environmental impact, using exergy methods. Results of the sustainability analysis indicate that, with an increase in the reference environment temperature from 20 to 35 $$^\circ{\rm C}$$ ∘ C , the exergy destruction rate decreases for the multi-effect distillation and organic Rankine cycle systems respectively from 6474 to 4217 kW and from 16,270 to 13,459 kW. Also, the corresponding sustainability index for the multi-effect distillation and organic Rankine cycle systems increases from 1.16 to 1.2 and 1.5–1.6, respectively, for the same increase in reference environment temperature.


2021 ◽  
Vol 11 (23) ◽  
pp. 11554
Author(s):  
Ali Baghernejad ◽  
Amjad Anvari-Moghaddam

Combined cycle systems have an important role in power generation. In the present study, three different configurations of combined Brayton and Rankine cycle system are studied from the perspective of energy, exergy, exergoeconomic and environmental perspectives. Results indicate that it depends on the preferences and criteria of each decision maker to select the best configuration among the three proposed configurations as the final configuration. For the purpose of parametric analysis, the effect of changing various parameters such as compressor pressure ratio, gas turbine inlet temperature on the output work, exergy efficiency, exergy-economic and environmental parameters is studied. In addition, an attempt is made to optimize the performance of combined cycle systems considering three objective functions of exergy efficiency, total cost rate and exergy unit cost of produced electricity.


2021 ◽  
Author(s):  
Ruifen Ren ◽  
Lingling Zhang ◽  
Hao Zhou ◽  
Xueru Jiang ◽  
Yan Liu

Abstract Reactive oxygen species (ROS) and nitric oxide (NO), two common active molecules, are both involved in changes in viability after liquid nitrogen (LN) storage, but the relationship between these two molecules has not been examined in plant cryopreservation until now. In this study, the pollen of Paeonia lactiflora 'Fen Yu Nu' with significantly decreased viability after cryopreservation was used as the material. We studied the effects of the two regulators on each other and their biosynthesis and scavenging indices to explore the interaction between ROS and NO in pollen cryopreservation and its mechanism. The results showed that the contents of ROS and NO increased significantly with the decrease of pollen viability after cryopreservation, and changes in the ROS and NO content had a significant effect on post-LN pollen viability. The ROS content positively regulated the endogenous NO content and had significant effects on the expression level of NOS-like enzyme regulation gene CSU2 and its activity. Down-regulated NO had a positive effect on the ROS content, and it significantly affected the expression of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and its regulatory gene RBOHJ. It also significantly affected catalase (CAT) and substrates related to the ascorbic acid (AsA)-glutathione (GSH) antioxidant cycle system. These results indicate that there was a positive interaction between ROS and NO in pollen cryopreservation. The NOS biosynthesis pathway is one of the ROS-regulated NO pathways, and the NADPH oxidase, CAT and AsA-GSH antioxidant cycle systems are the key sites of regulation of the ROS content by NO.


2021 ◽  
Vol 2 (1) ◽  
Author(s):  
R. Christopher Sheldrick ◽  
Gracelyn Cruden ◽  
Ana J. Schaefer ◽  
Thomas I. Mackie

Abstract Background To “model and simulate change” is an accepted strategy to support implementation at scale. Much like a power analysis can inform decisions about study design, simulation models offer an analytic strategy to synthesize evidence that informs decisions regarding implementation of evidence-based interventions. However, simulation modeling is under-utilized in implementation science. To realize the potential of simulation modeling as an implementation strategy, additional methods are required to assist stakeholders to use models to examine underlying assumptions, consider alternative strategies, and anticipate downstream consequences of implementation. To this end, we propose Rapid-cycle Systems Modeling (RCSM)—a form of group modeling designed to promote engagement with evidence to support implementation. To demonstrate its utility, we provide an illustrative case study with mid-level administrators developing system-wide interventions that aim to identify and treat trauma among children entering foster care. Methods RCSM is an iterative method that includes three steps per cycle: (1) identify and prioritize stakeholder questions, (2) develop or refine a simulation model, and (3) engage in dialogue regarding model relevance, insights, and utility for implementation. For the case study, 31 key informants were engaged in step 1, a prior simulation model was adapted for step 2, and six member-checking group interviews (n = 16) were conducted for step 3. Results Step 1 engaged qualitative methods to identify and prioritize stakeholder questions, specifically identifying a set of inter-related decisions to promote implementing trauma-informed screening. In step 2, the research team created a presentation to communicate key findings from the simulation model that addressed decisions about programmatic reach, optimal screening thresholds to balance demand for treatment with supply, capacity to start-up and sustain screening, and availability of downstream capacity to provide treatment for those with indicated need. In step 3, member-checking group interviews with stakeholders documented the relevance of the model results to implementation decisions, insight regarding opportunities to improve system performance, and potential to inform conversations regarding anticipated implications of implementation choices. Conclusions By embedding simulation modeling in a process of stakeholder engagement, RCSM offers guidance to realize the potential of modeling not only as an analytic strategy, but also as an implementation strategy.


2021 ◽  
Author(s):  
Sergey S Ananyev ◽  
Boris Ivanov ◽  
Alexey Dnestrovskiy ◽  
Andrei S Kukushkin ◽  
Alexander Spitsyn ◽  
...  

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