Curvature Variability Study for Small- and Large-Scale Linear Fresnel Solar Fields: A Step Toward Optimization

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Sara Benyakhlef ◽  
Ahmed Al Mers ◽  
Ossama Merroun ◽  
Abdelfattah Bouatem ◽  
Hamid Ajdad ◽  
...  

Reducing levelized electricity costs of concentrated solar power (CSP) plants can be of great potential in accelerating the market penetration of these sustainable technologies. Linear Fresnel reflectors (LFRs) are one of these CSP technologies that may potentially contribute to such cost reduction. However, due to very little previous research, LFRs are considered as a low efficiency technology. In this type of solar collectors, there is a variety of design approaches when it comes to optimizing such systems. The present paper aims to tackle a new research axis based on variability study of heliostat curvature as an approach for optimizing small and large-scale LFRs. Numerical investigations based on a ray tracing model have demonstrated that LFR constructors should adopt a uniform curvature for small-scale LFRs and a variable curvature per row for large-scale LFRs. Better optical performances were obtained for LFRs regarding these adopted curvature types. An optimization approach based on the use of uniform heliostat curvature for small-scale LFRs has led to a system cost reduction by means of reducing its receiver surface and height.

Water ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1154
Author(s):  
Chao-Chih Lin ◽  
Hund-Der Yeh

This research introduces an inverse transient-based optimization approach to automatically detect potential faults, such as leaks, partial blockages, and distributed deteriorations, within pipelines or a water distribution network (WDN). The optimization approach is named the Pipeline Examination Ordinal Symbiotic Organism Search (PEOS). A modified steady hydraulic model considering the effects of pipe aging within a system is used to determine the steady nodal heads and piping flow rates. After applying a transient excitation, the transient behaviors in the system are analyzed using the method of characteristics (MOC). A preliminary screening mechanism is adopted to sift the initial organisms (solutions) to perform better to reduce most of the unnecessary calculations caused by incorrect solutions within the PEOS framework. Further, a symbiotic organism search (SOS) imitates symbiotic relationship strategies to move organisms toward the current optimal organism and eliminate the worst ones. Two experiments on leak and blockage detection in a single pipeline that have been presented in the literature were used to verify the applicability of the proposed approach. Two hypothetical WDNs, including a small-scale and large-scale system, were considered to validate the efficiency, accuracy, and robustness of the proposed approach. The simulation results indicated that the proposed approach obtained more reliable and efficient optimal results than other algorithms did. We believe the proposed fault detection approach is a promising technique in detecting faults in field applications.


Author(s):  
Satoshi Gamou ◽  
Koichi Ito ◽  
Ryohei Yokoyama

The relationships between unit numbers and capacities to be installed for microturbine cogeneration systems are analyzed from an economic viewpoint. In analyzing, an optimization approach is adopted. Namely, unit numbers and capacities are determined together with maximum contract demands of utilities such as electricity and natural gas so as to minimize the annual total cost in consideration of annual operational strategies corresponding to seasonal and hourly energy demand requirements. This optimization problem is formulated as a large-scale mixed-integer linear programming one. The suboptimal solution of this problem is obtained efficiently by solving several small-scale subproblems. Through numerical studies carried out on systems installed in hotels by changing the electrical generating/exhaust heat recovery efficiencies, the initial capital cost of the microturbine cogeneration unit and maximum energy demands as parameters, the influence of the parameters on the optimal numbers and capacities of the microturbine cogeneration units is clarified.


2018 ◽  
Vol 10 (12) ◽  
pp. 4588 ◽  
Author(s):  
Yanran Fu ◽  
Tao Luo ◽  
Zili Mei ◽  
Jiang Li ◽  
Kun Qiu ◽  
...  

Dry anaerobic digestion technology (DADT) is considered a highly feasible way to treat agricultural straw waste; however, most practical operations are always in low efficiency, due to the poor fluidity behavior and complex lignocellulosic structure of straw, which is not easily decomposed by anaerobic bacteria. Hence, it is necessary to further investigate the operation boundary, in order to increase biogas production efficiency for effective applications. In this paper, typical DADTs are reviewed and their suitability for application in China is analyzed. The advantages and disadvantages of different anaerobic digestion processes are evaluated considering pretreatment, organic loading rate, anaerobic digestion temperature, and homogenization of the feedstock and inoculate. The suitability of the DADTs is evaluated considering the accessibility of straw resources and the convenience of biogas use. It is concluded that batch anaerobic digestion processes would be more suitable for the development of southern China due to the prevalence of small-scale agriculture, while continuous anaerobic digestion would be preferable in the north where large-scale agriculture is common. However, the DADTs discussed here need to broad application in China.


Author(s):  
Ana Rísia Soares Camêlo ◽  
Lindemberg Medeiros de Araujo

Este trabalho tem o objetivo de analisar como os moradores das comunidades localizadas na área litorânea dos municípios de Passo de Camaragibe, São Miguel dos Milagres e Porto de Pedras, percebem a turistificação do seu lugar. Nessa parte do litoral norte de Alagoas, com 23 km lineares de extensão, e denominado localmente de Rota Ecológica, existem 13 pousadas sofisticadas, com uma oferta que se enquadra no eixo do turismo alternativo. Com características de sofisticação e exclusividade, combinadas com preocupação ambiental e práticas que valorizam a cultura local, essas pousadas apresentam aspectos que as ligam à concepção de pousadas de charme, com uma delas – Pousada do Toque – sendo membro da Associação [Nacional] de Hotéis Roteiros de Charme. Portanto, enquanto no restante do litoral alagoano a turistificação tem tido como base o turismo de massa, com resorts e outros grandes equipamentos turísticos, a oferta da Rota Ecológica tem como base uma forma de desenvolvimento turístico alternativo, com fortes traços de sustentabilidade. A metodologia adotou uma abordagem qualitativa, com o uso de entrevistas abertas e entrevistas semiestruturadas junto a moradores antigos da área de estudo e observação direta. O estudo constatou que os entrevistados percebem mudanças na rotina da vida das comunidades relacionadas à chegada das pousadas. Na condição de antigos moradores do lugar, os olhares e sentimentos dos entrevistados indicam contradições, quando eles percebem ao mesmo tempo aspectos positivos, mas também problemas decorrentes da turistificação do seu lugar. O trabalho identifica questões que oferecem novas oportunidades de pesquisa sobre a turistificação desta parte do território alagoano. Local perception on tourism in the Rota Ecológica (AL, Brazil) ABSTRACT The objective of this work is to analyse how residents of communities of the coastal area of the municipalities of Passo de Camaragibe, São Miguel dos Milagres, and Porto de Pedras perceive the touristification of their place. In this part of the Alagoas’ littoral, with an extension of 23 km, which is locally called Rota Ecológica, there are 13 sophisticated small-scale luxury hotels with an alternative tourism offer. These hotels combine sophistication, exclusiveness, environmental concern, and practices that value the local culture in a way that link them up to the concept of charm. One of them, the Pousada do Toque, is a member of the national-scale Associação de Hotéis Roteiros de Charme. So, while the touristification of the rest of the Alagoas’ state is based on mass tourism, with resorts and other large-scale tourism equipments, the offerings of the Rota Ecológica are based on alternative tourism, embedding strong sustainability elements. The study adopted a qualitative approach, with open interviews and semi-structured interviews which were run with residents that have lived in the region since before the arrival of the above-mentioned luxury hotels in the region and direct field observation. Results show that the interviewees perceive changes to the daily routines of their communities that in their views are a consequence of the tourism of these hotels. In the condition of long-standing residents of the region, the perceptions and feelings of the interviewees reveal contradictions in that they perceive both positive and negative aspects which result from the touristification of their place. In this work questions are identified that show new research opportunities regarding the touristification of this part of the territory of Alagoas state. KEYWORDS: Ecological Route; Touristification; Perception; Place.


2021 ◽  
Author(s):  
Raymond Pavloski

<p>Demonstrating that an understanding of how neural networks produce a specific quality of experience has been achieved would provide a foundation for new research programs and neurotechnologies. The phenomena that comprise cortical prosthetic vision have two desirable properties for the pursuit of this goal: 1) Models of the subjective qualities of cortical prosthetic vision can be constructed; and 2) These models can be related in a natural way to models of the objective aspects of cortical prosthetic vision. Sense element engagement theory portrays the qualities of cortical prosthetic vision together with coordinated objective neural phenomena as constituting sensible spatiotemporal patterns that are produced by neural interactions. Small-scale neural network simulations are used to illustrate how these patterns are thought to arise. It is proposed that simulations and an electronic neural network (ENN) should be employed in devising tests of the theory. Large-scale simulations can provide estimates of parameter values that are required to construct an ENN. The ENN will be used to develop a prosthetic device that is predicted by the theory to produce visual forms in a novel fashion. According to the theory, confirmation of this prediction would also provide evidence that this ENN is a sentient device.</p>


2022 ◽  
Vol 10 (1) ◽  
pp. 35-56 ◽  
Author(s):  
Habeeb A. H. R. Aladwani ◽  
Mohd Khairol Anuar Ariffin ◽  
Faizal Mustapha

Large-scale wind turbines mostly use Continuously Variable Transmission (CVT) as the transmission system, which is highly efficient. However, it comes with high complexity and cost too. In contrast, the small-scale wind turbines that are available in the market offer a one-speed gearing system only where no gear ratios are varied, resulting in low efficiency of harvesting energy and leading to gears failure. In this research, an unsupervised machine-learning algorithm is proposed to address the energy efficiency of the automatic transmission system in vertical axis wind turbines (VAWT), to increase its efficiency in harvesting energy. The aim is to find the best adjustment for VAWT while the automatic transmission system is taken into account. For this purpose, the system is simulated and tested under various gear ratios conditions while a centrifugal clutch is applied to automatic gear shifting. The outcomes indicated that the automatic transmission system could successfully adjust the spinning in line with the wind speed. As a result, the obtained level of harvested voltage and power by VAWT with the automatic transmission system are improved significantly. Consequently, it is concluded that automatic VAWTs, equipped with the machine-learning capability can readjust themselves with the wind speed more efficiently.


2020 ◽  
Vol 494 (3) ◽  
pp. 4203-4225 ◽  
Author(s):  
J F Mahlmann ◽  
A Levinson ◽  
M A Aloy

ABSTRACT Black hole – accretion disc systems are the central engines of relativistic jets from stellar to galactic scales. We numerically quantify the unsteady outgoing Poynting flux through the horizon of a rapidly spinning black hole endowed with a rotating accretion disc. The disc supports small-scale, concentric, flux tubes with zero net magnetic flux. Our general relativistic force-free electrodynamics simulations follow the accretion on to the black hole over several hundred dynamical time-scales in 3D. For the case of counter-rotating accretion discs, the average process efficiency reaches up to 〈ϵ〉 ≈ 0.43, compared to a stationary energy extraction by the Blandford/Znajek process. The process efficiency depends on the cross-sectional area of the loops, i.e. on the product l × h, where l is the radial loop thickness and h its vertical scale height. We identify a strong correlation between efficient electromagnetic energy extraction and the quasi-stationary setting of ideal conditions for the operation of the Blandford/Znajek process (e.g. optimal field line angular velocity and fulfillment of the so-called Znajek condition). Remarkably, the energy extraction operates intermittently (alternating episodes of high and low efficiency) without imposing any large-scale magnetic field embedding the central object. Scaling our results to supermassive black holes, we estimate that the typical variability time-scale of the system is of the order of days to months. Such time-scales may account for the longest variability scales of TeV emission observed, e.g. in M87.


2020 ◽  
Vol 10 (16) ◽  
pp. 5554
Author(s):  
Yutong Liu ◽  
Chengxuan Cao

Passenger demand for railway transportation rapidly increases in peak periods, and the transport capacity for existing trains is not sufficient. Railway companies usually adopt the strategy of adding additional trains in peak periods to meet the higher passenger demand. Designing a good operational plan for additional trains becomes a challenge for operators, though. A new optimization approach for designing an operational plan for additional trains is proposed in this paper. The number of trains, the operational plan, the stop plan, and the timetable for each train can be considered simultaneously in the new optimization approach, which will make it easier to design an operational plan for additional trains. A multi-objective nonlinear model with three objectives of minimizing total running distance, dwelling time, and unsatisfied passengers is proposed. Big-M is introduced to transform the nonlinear model into a linear model. The solver CPLEX is used to solve the transformed linear model and obtain the optimal operational plan. Small-scale numerical experiments are implemented to show the effectiveness of the optimization approach. The large-scale case of the Beijing‒Shanghai railway corridor is studied to demonstrate that the optimization approach can be applied to real-word and large-scale situations.


2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Wenqian Liu ◽  
Xiaoning Zhu ◽  
Li Wang ◽  
Baicheng Yan ◽  
Xuewei Zhang

As the core operational issue in container terminals, yard crane scheduling problem directly affects the overall operation efficiency of port connecting highway or railway transportation and sea transportation. In practice, the scheduling of yard cranes is subject to many uncertain factors, so the scheme may be inapplicable and needs to be adjusted. From the perspective of proactive strategy, considering fluctuations in arrival time of external trucks as well as varied handling volume of yard cranes, a stochastic programming model is established in this paper to obtain a fixed scheme with the minimum expected value of yard crane makespan and total task waiting time over all the scenarios. The scheme does not require rescheduling when facing different situations. Subsequently, two algorithms based on certain rules are proposed to obtain the yard crane operation scheme in the deterministic environment, which are taken as the basic solution in the uncertain conditions, and then a tailored genetic algorithm is adopted to find the optimal solution with good adaptability to the uncertain scenarios. Finally, we use small-scale examples to compare the performance of algorithms in the deterministic and uncertain environment and then analyze the relationship between different yard crane configurations and the number of tasks. Large-scale experiments are performed to study the operation efficiency of the storage yard with different handling volumes assigned to each yard crane.


2018 ◽  
Vol 45 ◽  
pp. 161-173
Author(s):  
Kathryn M. de Luna

Abstract:This short essay explores Jan Vansina’s contributions to the study of Africa’s early pasts. In particular, it explores the impact of sustained ethnographic fieldwork on Vansina’s narrative style, which often imagined for deeper pasts the sorts of small-scale social interactions definitive of most experiences of fieldwork. This narrative style produced a tension between Vansina’s interest in large-scale institutions and historical processes and the smaller-scale social interactions sustaining them, offering us new research topics. Attention to the historical significance of the sorts of intimate interactions imagined by Vansina requires new approaches to the variety of archives he compelled us to consider in the pages of this journal.


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