Fatigue Strength Assessment of Propellers by Means of Weakly Coupled CFD and FEM Analyses

2014 ◽  
Author(s):  
Chiara Bertoglio ◽  
Stefano Gaggero ◽  
Cesare M. Rizzo ◽  
Michele Viviani
Keyword(s):  
High Efficiency ◽  
Added Value ◽  
General Requirement ◽  
Strength Assessment ◽  
Radiated Noise ◽  
Design Procedures ◽  
Continuous Review ◽  
Propeller Design ◽  
Weakly Coupled ◽  
New Challenges

Propeller design considerably evolved during years, continuously imposing new challenges to the designer, from usual high efficiency and avoidance of erosive cavitation up to reduction of radiated noise and pressure pulses for “high added value” ships. New more stringent limits, together with a general requirement for performances optimization, leads to the need of a continuous review of design procedures which, in some cases, still rely on rather “old-fashioned” approaches. The aim of this paper is to analyse in detail the importance of considering fatigue phenomena in the propeller design, proposing a procedure for the evaluation in time of the stress field acting on a blade during one revolution, which is then considered for fatigue assessment.

scholarly journals COHERENT PROPAGATION OF LASER BEAMS IN MCF FIBERS

2019 ◽  
Vol 47 (1) ◽  
pp. 21-23
Author(s):  
A.A. Balakin ◽  
S.A. Skobelev ◽  
A.V. Andrianov ◽  
E.A. Anashkina ◽  
A.G. Litvak
Keyword(s):  
Solid State ◽  
Optical Fibers ◽  
High Efficiency ◽  
Radiation Power ◽  
Experimental Studies ◽  
Pump Energy ◽  
Total Power ◽  
Beam Power ◽  
Self Focusing ◽  
Weakly Coupled

The successful development of fiber-optic technologies in recent decades has stimulated research on the replacement of components of solid-state laser systems with fiber components, which can drastically change the attractiveness of the corresponding applied developments. Yielding on the energy characteristics of solid-state systems, fiber lasers and nonlinear optical devices have high efficiency of conversion of pump energy to radiation energy associated with waveguide geometry, high quality of the spatial profile of the laser beam, as well as low cost, compactness, lack of alignment in work process. Note that the maximum achievable radiation power in a single fiber is limited primarily by the process of self-focusing, which leads to fiber damage. The use of a multi-core fiber (MCF), consisting of identical equidistant weakly coupled optical fibers, makes it possible to realize initially coherent propagation of laser radiation with a total power noticeably higher than it can be transmitted in a single optical fiber. However, as theoretical and experimental studies have shown, such systems have its own critical power (Balakin et al., 2016) whereby the self-focusing of the quasihomogeneous distribution of the wave field and its separation into a set of incoherent structures occurs. Therefore, we have considered a small-sized optical system of 2N identical weakly coupled optical fibers arranged in a ring (Balakin et. al., 2018). In such systems, it is possible to find stable distributions of intense wave beams, which allow coherent radiation transport over long distances. The total radiation power in the found distributions can significantly (up to 2N times) exceed the critical self-focusing power in continuous media. This manifests itself most clearly for the distribution of un ~ (-1)n with antiphase fields in neighboring waveguides, which is stable at an arbitrary wave beam power. Direct numerical simulation of a nonlinear wave equation confirms the stability of the field distributions found. The research was supported by the RAS Presidium Program «Nonlinear dynamics: fundamental problems and applications».

scholarly journals Branded Apps in Spain as a Means of Communicating Trends in Fashion

2016 ◽  
Vol 10 (2) ◽  
pp. 58 ◽  
Author(s):  
Zahaira Fabiola González Romo ◽  
Ruth Contreras-Espinosa ◽  
Irene García Medina
Keyword(s):  
Mass Media ◽  
Mobile Phones ◽  
Mobile Applications ◽  
New Technologies ◽  
Added Value ◽  
New Challenges

Apps are of great interest and curiosity for the users of mobile phones, being already highly unloaded and used for the users of smartphones. The fashion mobile applications represent only a fraction of the mobile global applications (almost 0,2 %), nevertheless they are starting to deserve special attention from designers and researchers in this area. Brands want to know about the new trends in the market to be able to continue surprising and impressing their public. In this study, we seek to identify the most relevant aspects of the applications that help to improve the image of the Spanish prêt-à-porter fashion brands such as Zara, Pull and Bear, Stradivarius, Shana, Bimba y Lola,... The study considers the position in the ranking of downloads, the category, the opinions, valuations of the users and the criteria described by Jami Lawrence (2010): amusement, saving of time and / or comfort in the use. Findings: In this analysis, we seek to identify the most relevant aspects of the applications that help to improve the image of the brand, in this particular case of the Spanish prêt-à-porter fashion brands. - It is indispensable that the applications entertain the user, save time and / or comfort, we have observed that they are these characteristics those that are valued by the users. - Another factor that is valued in the applications, is that the application should make sense for the user and to have an added value that doesn't necessarily have to be related with the nature of the brand. - But it is important that applications to be developed have to be coherent with the identity of the brand. As in any other area, the appearance of new mass media, like the mobile, is the introduction of new challenges. – Finally, it is important for the brand to adapt constantly to the new technologies, but we must not forget that a precarious incorporation and badly developed app it can be more harmful than beneficial.

Effective Decision Making in Simple and Combined Cycle Schemes at the Turn of the Millennium

1999 ◽  
Author(s):  
Stéphane Gayraud ◽  
Riti Singh
Keyword(s):  
Decision Making ◽  
Gas Turbines ◽  
High Efficiency ◽  
Combined Cycle ◽  
Market Potential ◽  
Load Following ◽  
Cost Planning ◽  
New Challenges ◽  
Effective Decision Making ◽  
Save Energy

The electricity supply industry is being restructured all over the world. Privatisation, with the emergence of Independent Power Projects (IPPs), especially in developing countries, and liberalisation of the power generation market are changing decision-making processes in a radical way. New challenges of deregulation and customer demands, and economic instabilities in south-east Asia, oblige electric utilities to face a double jeopardy: least-cost planning and least-risk investments. Consumers are encouraged to save energy and emission reduction policies are implemented to promote utilisation of high efficiency, clean power production technologies. The aim of this paper is to introduce the concept of life cycle risk management and Decision Support System (DSS) for open and combined cycle schemes, highlighting the market potential for Flexible Mid-size Gas Turbines (FMGT) in mid-merit applications. The DSS that has been developed at Cranfield University includes: plant simulation program, providing design and off-design performance, maintenance planning, component degradation, and load-following models. In addition several economic techniques based upon engineering finance and project accounting make power plant economic appraisals possible. The DSS also provides a Monte Carlo risk analysis in order to deal with technical and economic uncertainties in a very effective way. Case studies will stress several parameters that planners have to carefully assess when making decision in the context of the coming millennium, bringing all sorts of new challenges and areas of uncertainty that will be discussed in the paper.

Computation of Hydrodynamic Load and Strength Assessment of Highly Skewed Propeller

2016 ◽  
Author(s):  
Sachin S. Awasare ◽  
Ram Kumar Joga ◽  
Sharad S. Dhavalikar ◽  
Apurba R. Kar
Keyword(s):  
Navier Stokes ◽  
Hydrodynamic Load ◽  
Hydrodynamic Analysis ◽  
Blade Loading ◽  
Strength Assessment ◽  
Propeller Design ◽  
Blade Thickness ◽  
Static Approach ◽  
Ship Classification

Ship Classification societies have rule requirements for assessment of propeller strength in terms of minimum blade thickness, however these rules generally covers only propellers of conventional geometry. In case of nonconventional (e.g. highly skewed) propellers, class societies ask for direct and detailed stress analysis for examination and approval. This paper introduces a procedure/strategy for assessing the strength of highly skewed propeller by determination of hydrodynamic load and consequent structural stress. The hydrodynamic analysis is performed separately using Reynolds Averaged Navier Stokes (RANS) solver STARCCM+ and structural analyses by finite element solver ANSYS. The hydrodynamic pressures as computed by CFD are transferred to the propeller model to calculate the resulting stationary stresses for maximum and minimum blade loading, using a quasi-static approach. The significance of root fillet in propeller design is demonstrated by comparing blade stress results with and without fillet at blade root. The stress concentration as a function of geometry and loading is also represented by the presented examples. The proposed method can assist the designer or reviewer to assess adequacy of strength of solid propellers as well as composite propellers of any geometrical configuration.

City Profile: Datong, China

2019 ◽  
Vol 10 (2) ◽  
pp. 176-192
Author(s):  
Chenguang Li ◽  
Tao Sun ◽  
Lei ZHAI ◽  
Ke Yuan
Keyword(s):  
North China ◽  
Resource Dependence ◽  
High Efficiency ◽  
Industrial Structure ◽  
Abrupt Change ◽  
Consumption Pattern ◽  
Financial Risks ◽  
Balanced Development ◽  
New Challenges ◽  
Huge Investment

Small- and medium-sized cities have not received enough scholarly attention in China. In fact, these cities have a larger share of urban population than large-sized cities. Therefore, the paper focuses on one such typical medium-sized city in North China named Datong; a resource-reliant city with a long history but undergoing a difficult phase of transformation. Its industrial structure is upgrading from unitary resource-dependence to balanced development, but it is also accompanied by recessive unemployment and a depressed consumption pattern of its residents. Datong’s urban planning generally reflects the ideas of its leaders and often demonstrates high efficiency and execution. However, abrupt change in the leadership has brought new challenges such as constant adjustment and restructuring along with huge investment and financial risks to cities. This model also fully illustrates the self-repairing and error-correcting ability, which is guiding Datong towards sustainable development.

scholarly journals Production of high added value products from sweet sorghum using high efficiency bioprocesses

2015 ◽  
Author(s):  
Λεωνίδας Μάτσακας
Keyword(s):  
Sweet Sorghum ◽  
High Efficiency ◽  
Added Value

Σκοπός της παρούσας διδακτορικής διατριβής ήταν η αξιολόγηση της δυνατότητας χρησιμοποίησης του γλυκού σόργου ως πρώτη ύλη για την παραγωγή διαφόρων μορφών βιοκαυσίμων. Αρχικώς αξιολογήθηκε η δυνατότητα παραγωγής βιοαιθανόλης με την χρήση δύο διαφορετικών στρατηγικών (είτε την χρήση όλων των στελεχών του σόργου είτε με την χρήση μόνο του λιγνινοκυτταρινούχου κλάσματος, την βαγάσση). Σε μια προσπάθεια να βελτιωθεί η ενζυμική υδρόλυση της βαγάσσης, μελετήθηκε και βελτιστοποιήθηκε η εφαρμογή υδροθερμική προκατεργασίας με την χρήση μικρομυμάτων. Κάτω απο τις βέλτιστες συνθήκες προκατεργασίας, παρατηρήθηκε υψηλή συγκέντρωση κυτταρίνης (66.84% w/w) καθώς και υψηλή υδρόλυση της κυτταρίνης, η οποία ανήλθε σε 30.42% μετά από 8 ώρες υδρολύσεως. Κατά την διάρκεια των πειραμάτων παραγωγής αιθανόλης, παρατηρήθηκε οτι υδρόλυση 12 ωρών ήταν αρκετή για την αποτελεσματική υδρόλυση της κυτταρίνης, η οποία ανήλθε σε 59.8%. Η συγκέντρωση της αιθανόλης στην ακόλουθη ζύμωση ανήλθε σε 41.4g/L με την παραγωγικότητα να φτάνει σε 1.88g/L·h. Η προσθήκη επιπλέον φρέσκων ενζύμων κατά την έναρξη της ζύμωσης είχε θετική επίδραση στην παραγόμενη αιθανόλη.Κατά την διάρκεια των πειραμάτων όπου χρησιμοποιήθηκαν τα στελέχη του σόργου σε συνθήκες υψηλής συγκέντρωσης στερεών, βρέθηκε οτι η ενσωμάτωση ενός ξεχωριστού σταδίου ενζυμικής υδρόλησης πριν την ζύμωση είχε ως αποτέλεσμα την αύξηση της παραγωγής αιθανόλης καθώς και της παραγωγικότητας. Προκειμένου να βελτιωθεί το στάδιο της υδρολύσεως, μελετήθηκε η συνδυασμένη επίδραση του χρόνου υδρόλυσης και του ενζυμικού φορτίου στην παραγωγικότητα της αιθανόλης. Κάτω από τις βέλτιστες συνθήκες που βρέθηκαν (ενζυμικό φορτίο ίσο με 8.32 FPU/g και χρονική διάρκεια 8.6 ωρών), η παραγωγή αιθανόλης έφτασε τα 62.53 g/L με την παραγωγικότητα να είναι 2.98 g/L·h. Τέλος, κατά την διάρκεια της μελέτης της επίδρασης της αρχικής συγκέντρωσης στερεών, βρέθηκε ότι συγκέντρωση στερεών ίση με 35% w/w οδήγησε στην υψηλή παραγωγή αιθανόλης, στην μέγιστη παραγωγικότητα καθώς και σε έναν από τους υψηλότερους συντελεστές απόδοσης, σε σύγκριση με τις άλλες συγκεντρώσεις που μελετήθηκαν.Λαμβάνοντας υπόψην τα αποτελέσματα σχετικά με την παραγωγή αιθανόλης, καταλήξαμε οτι η χρήση των στελεχών του γλυκού σόργου είναι πιο αποτελεσματική, καθώς λιγότερα στάδια είναι απαραίτητα και η συγκέντρωση της παραγώμενης αιθανόλης ήταν υψηλότερη σε σχέση με την χρήση της βαγάσσης. Για αυτόν τον λόγο αποφασίστηκε να χρησιμοποιηθεί η ίδια διεργασία κατά την διάρκεια των πειραμάτων μελέτης παραγωγής μικροβιακών λιπιδίων τα οποία μπορούν να χρησιμοποιηθούν για την παραγωγή βιοντίζελ. Τρείς ελαιογόνες ζύμες μελετήθηκαν για αυτόν τον σκοπό, πιο συγκεκριμένα οι ζύμες L. starkeyi CBS 1807, T. fermentans CBS 439.83 και R. toruloides CCT 0783. Αρχικώς εξετάστηκε η δυνατότητα των στελεχών του σόργου να υποστηρίξουν την ανάπτυξη των διαφόρων ζυμών παρέχοντας τόσο τον άνθρακα όσο και το απαραίτητο άζωτο. Αυτό πραγματοποιήθηκε μελετώντας την επίδραση που είχε η προσθήκη εξωτερικής πηγής αζώτου στο μέσον της καλλιέργειας. Παρατηρήθηκε ότι η προσθήκη του εξωγενούς αζώτου είχε αρνητική επίδραση και στις τρείς ζύμες, μειώνοντας την παραγωγή μικροβιακού λίπους. Η ικανότητα των στελεχών του σόργου να προσφέρουν τόσο τον απαραίτητο άνθρακα όσο και το απαραίτητο άζωτο είναι πολύ σημαντική για την μείωση του κόστους παραγωγής, καθώς η προσθήκη αζώτου θεωρείται ότι αυξάνει το συνολικό κόστος. Επιπλέον, η ύπαρξη ενός σταδίου ενζυμικής σακχαροποίηση πριν το στάδιο παραγωγής λίπους είχε θετική επίδραση στο παραγώμενο λίπος, ανεξαρτήτως της χρησιμοποιηθέντας ζύμης και της συγκέντρωσης στερεών. Η υψηλότερη συγκέντρωση λίπους παρατηρήθηκε όταν καλλιεργήθηκε η ζύμη R. toruloides σε υπόστρωμα που προέκυψε από συγκέντρωση στερεών ίση με 20% w/w, έχοντας αφαιρέσει τα στερεά, και ανήλθε σε 13.77 g/L. Στο τελικό στάδιο αυτής της μελέτης, έγινε πρόβλεψη των ιδιοτήτων του βιοντίζελ το οποίο θα προέκυπτε αν χρησιμοποιούνταν τα λίπη που προέυψαν απο τις τρείς ζύμες που μελετήθηκαν. Βρέθηκε ότι και οι τρεις παράγουν λιπίδια που θα έδιναν καλές ιδιότητες στο παραχθέν βιοντίζελ.Στο τελικό στάδιο της παρούσας μελέτης, εξετάστηκε η δυνατότητα χρήσης των στελεχών του σόργου για την παραγωγή βιομεθανίου μέσω αναερόβιας χώνευσης. Αρχικώς, μελετήθηκε η επίδραση δύο διαφορετικών κατεργασιών πριν την αναερόβια χώνευση στην απόδοση σε μεθάνιο. Πιο συγκεκριμένα μελετήθηκαν μια ήπια θερμική κατεργασία και μια ενζυμική. Η θερμική κατεργασία βρέθηκε ότι είχε αρνητική επίδραση στην απόδοση σε μεθάνιο. Από την άλλη μεριά, η ενζυμική κατεργασία όταν εφαρμόστηκε σε ένα στάδιο με την αναερόβια χώνευση (προσομοιάζοντας την διεργασία SSF) βελτίωσε την απόδοση σε μεθάνιο από 238mL CH4/g VS σε 274mL CH4/g VS. Σε ένα τελικό στάδιο, εξετάστηκε η συνδυαστική δράση του ενζυμικού φορτίου και του λόγου I/S και βρέθηκε ότι η υψηλότερη απόδοση σε μεθάνιο επιτεύχθηκε για ενζυμικό φορτίο ίσο με 13FPU/g και λόγο I/S ίσο με 0.7 και ανήλθε σε 284.37mL CH4/g VS.

scholarly journals Branding in Serbian Rural Tourism

2012 ◽  
Vol 4 (11) ◽  
pp. 671-676 ◽  
Author(s):  
Milena Vukić ◽  
Marija Kuzmanović .
Keyword(s):  
World Market ◽  
Rural Tourism ◽  
Added Value ◽  
Know How ◽  
The Road ◽  
Universal Principles ◽  
New Destination ◽  
The World ◽  
New Challenges ◽  
Global World

To become competitive in the global world market, as a relatively new destination for rural tourism, we need to know how to use existing resources and to prove capable of coping with new challenges. The road to this great accomplishment goes through branding, because only with the help of branding it is possible to achieve recognition of Serbian rural product. That, first, implies a reformatory process of searching for our renewed that is redesigned identity, networking of various industries, as well as their integration. In such a context, rural tourism of Serbia should not be isolated within a particular segment of the whole, rather it should master those universal principles upon which the world is organized today, which is a unique and dynamic tourist product, and should be gradually turned into a brand thanks to its added value.

IS DATA SCIENTIST A PROFESSION OF THE PRESENT OR THE FUTURE?

2020 ◽  
Vol 10 (7) ◽  
pp. 1399-1407
Author(s):  
E.V. Bochkova ◽  
◽  
E.A. Avdeeva ◽  
A.V. Usol’tsev ◽  
◽  
...  
Keyword(s):  
Big Data ◽  
Information Technologies ◽  
Data Science ◽  
Modern Society ◽  
Digital Economy ◽  
Added Value ◽  
Management Decision ◽  
High Tech ◽  
Business And Society ◽  
New Challenges

Modern society is characterized by rapid increasing the information volume and increasing its role in various fields of activity: economic, political, social and public ones. The rapid spread and introduction of information technologies, the growth of information data flow pose new challenges to the modern society. Global informatization dictates the need to form an infrastructure for processing and managing Big Data - an array of data, the processing of which requires special skills, knowledge and applications. The formation of the digital economy through the penetration of ICT and the digitalization of production processes contributes to the modernization of traditional industries, trade and procurement procedures, related financial and logistics operations, as well as markets with other sources of added value. Big Data as a new tool for analytics, forecasting and management decision making is becoming a leading asset and resource of the state, business and society as a whole. At the same time, the absence of physical boundaries in the digital space opens up access to big data for all participants in the global space. The national program “Digital Economy of the Russian Federation” is aimed at creating the necessary institutional and infrastructural conditions for the development of high-tech businesses, increasing the competitiveness of the national economy, the quality of life of citizens, and ensuring economic growth. One of the federal projects “Human Resources for the Digital Economy” is aimed at ensuring the training of highly qualified personnel for a modern society with high professional qualifications, skills and abilities to develop and introduce competitive products. Therefore, a Data Science specialist is a profession shaped by the needs of the Russian economy. In this regard, new challenges and methodologies for training IT specialists with the necessary knowledge and skills that meet the requirements of high-tech business are being formed.

Web-Based Organizing in Traditional Brick-and-Mortar Companies

2005 ◽  
pp. 1-30 ◽  
Author(s):  
Jaap Paauwe ◽  
Elaine Farndale ◽  
Roger Williams
Keyword(s):  
Business Models ◽  
Added Value ◽  
The Internet ◽  
Web Based ◽  
Brick And Mortar ◽  
New Business ◽  
New Challenges ◽  
Old Economy ◽  
Business To Business ◽  
New Business Models

This chapter introduces the notion of how old-economy brick-and-mortar firms are adapting their HRM policies and practices and the roles of their HR departments in light of newly introduced Web-based business-to-business transaction practices. It argues that the Internet has introduced three new business models in old-economy companies: the Internet as a marketplace, the Internet as a supply chain integrator, and the Internet as a catalyst for business model redefinition. These innovative ways of organizing are providing HR with opportunities to rise to new challenges and increase their added value to the firm.

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