scholarly journals Practical numerical method for erosion risk prediction on ship propellers

2021 ◽  
pp. 1-22
Author(s):  
Keun Woo Shin ◽  
Poul Andersen
Keyword(s):  
Risk Index ◽  
The Other ◽  
Surface Erosion ◽  
Design Phase ◽  
Blade Surface ◽  
Erosion Risk ◽  
Design Evolution ◽  
Propeller Design ◽  
Cavitation Tunnel ◽  
Order Of Magnitude

It is important to make predictions of cavitation-induced erosion risk on ship propellers in the design phase. Since a cavitation tunnel test on a propeller model coated by soft paint, that is, a standard experimental method for evaluating erosion risk, is costly and time-consuming, numerical methods are necessary for erosion risk predictions. DES is made for cavitating flows around the propeller with a numerically modelled hull wake at the inflow. After achieving a converged solution, an erosion risk index is computed in each cell connecting to the blade surface and accumulated over a propeller rotation. Cavitation simulations are made for two propellers designed for a single-screw ship, of which one showed an erosion indication and the other showed no indication after cavitation tunnel tests with soft paint coating. Three index formulations are compared with the experiment result. The high value region of Index 1 based on the potential energy density of collapsing bubbles corresponds better with the eroded spot indicated by partial and complete paint removals in the experiment than those of the other indices. The maximum value of Index 1 for the non-eroded propeller is lower by more than an order of magnitude than that for the eroded one, whereas the maximum values of the other indices are of the same order of magnitude for both propellers. The validation of Index 1 is in agreement with the criterion that the maximum index needs to be below 1,000 J/m3 for erosion-free propeller designs. The design evolution based on the erosion risk index and propulsive efficiency from CFD shows that it can be a practical tool for a quantitative evaluation of blade surface erosion risk in the propeller design phase.

Comparison of the Potency of 8-L-Arginine, 8-D-Arginine and 8-D-Homoarginine Vasopressin Analogs with Substituted Phenylalanine in Position 2

1994 ◽  
Vol 59 (6) ◽  
pp. 1439-1450 ◽  
Author(s):  
Miroslava Žertová ◽  
Jiřina Slaninová ◽  
Zdenko Procházka
Keyword(s):  
Amino Acid ◽  
Solid Phase Synthesis ◽  
Solid Phase ◽  
Basic Amino Acid ◽  
The Other ◽  
Side Chain ◽  
Inhibitory Potency ◽  
Phase Synthesis ◽  
Other Hand ◽  
Order Of Magnitude

An analysis of the uterotonic potencies of all analogs having substituted L- or D-tyrosine or -phenylalanine in position 2 and L-arginine, D-arginine or D-homoarginine in position 8 was made. The series of analogs already published was completed by the solid phase synthesis of ten new analogs having L- or D-Phe, L- or D-Phe(2-Et), L- or D-Phe(2,4,6-triMe) or D-Tyr(Me) in position 2 and either L- or D-arginine in position 8. All newly synthesized analogs were found to be uterotonic inhibitors. Deamination increases both the agonistic and antagonistic potency. In the case of phenylalanine analogs the change of configuration from L to D in position 2 enhances the uterotonic inhibition for more than 1 order of magnitude. The L to D change in position 8 enhances the inhibitory potency negligibly. Prolongation of the side chain of the D-basic amino acid in position 8 seems to decrease slightly the inhibitory potency if there is L-substituted amino acid in position 2. On the other hand there is a tendency to the increase of the inhibitory potency if there is D-substituted amino acid in position 2.

scholarly journals On the 2PN Periastron Precession of the Double Pulsar PSR J0737–3039A/B

Universe ◽  
2021 ◽  
Vol 7 (11) ◽  
pp. 443
Author(s):  
Lorenzo Iorio
Keyword(s):  
General Relativity ◽  
Present Author ◽  
Moment Of Inertia ◽  
The Other ◽  
Orbital Elements ◽  
Binary Pulsars ◽  
Orbital Phase ◽  
Order Of Magnitude ◽  
General Relativistic ◽  
The Moment

One of the post-Keplerian (PK) parameters determined in timing analyses of several binary pulsars is the fractional periastron advance per orbit kPK. Along with other PK parameters, it is used in testing general relativity once it is translated into the periastron precession ω˙PK. It was recently remarked that the periastron ω of PSR J0737–3039A/B may be used to measure/constrain the moment of inertia of A through the extraction of the general relativistic Lense–Thirring precession ω˙LT,A≃−0.00060∘yr−1 from the experimentally determined periastron rate ω˙obs provided that the other post-Newtonian (PN) contributions to ω˙exp can be accurately modeled. Among them, the 2PN seems to be of the same order of magnitude of ω˙LT,A. An analytical expression of the total 2PN periastron precession ω˙2PN in terms of the osculating Keplerian orbital elements, valid not only for binary pulsars, is provided, thereby elucidating the subtleties implied in correctly calculating it from k1PN+k2PN and correcting some past errors by the present author. The formula for ω˙2PN is demonstrated to be equivalent to that obtainable from k1PN+k2PN by Damour and Schäfer expressed in the Damour–Deruelle (DD) parameterization. ω˙2PN actually depends on the initial orbital phase, hidden in the DD picture, so that −0.00080∘yr−1≤ω˙2PN≤−0.00045∘yr−1. A recently released prediction of ω˙2PN for PSR J0737–3039A/B is discussed.

Evaluation of the Service Performance of Ships

2005 ◽  
Vol 42 (04) ◽  
pp. 177-183
Author(s):  
Poul Andersen ◽  
Anne-Sophie Borrod ◽  
Hervé Blanchot
Keyword(s):  
Input Data ◽  
High Efficiency ◽  
Service Performance ◽  
The Other ◽  
Simple Method ◽  
Propulsive Efficiency ◽  
Order Of Magnitude ◽  
Time Periods

A simple method has been established for the evaluation of the service performance of ships. Input data are easily collected daily on board and transformed to a well-defined condition that makes possible the comparison between ships, for instance, sister ships, and between different time periods of voyages for the same ship. The procedure has been applied to two ships that are identical, with the only exception that one has a conventional propeller, whereas the other one is fitted with a high-efficiency propeller of the KAPPEL type. The results are obtained from a period of 2 years steaming for both vessels. They clearly confirm the increase of propulsive efficiency obtained with the KAPPEL propeller in the order of magnitude of 4%.

Modelling and Analysis of Web-Based CourseWare Systems

2000 ◽  
pp. 155-173
Author(s):  
Lam Chi-Yung ◽  
Cheung Shing-Chi
Keyword(s):  
Information Structure ◽  
Formal Method ◽  
The Other ◽  
Design Phase ◽  
Web Based ◽  
Case Tools ◽  
Computer Aided ◽  
Dynamic Components ◽  
The One ◽  
Computer Aided Software Engineering

Designing reliable Web-based courseware systems is not trivial. Courseware authors need to allow as much flexibility in navigating through the system as possible on the one hand, and to ensure the satisfaction of properties and constraints in the system on the other. The problem is aggravated with facilities like Java applets which incorporate dynamic behaviour into the information structure. These issues motivate the need for designing such systems through rigorous modelling and analysis. We propose a scheme using a formal method called the Calculus of Communicating Systems (CCS) to unify the modelling of the courseware based on its navigational structure, semantics and dynamic components. Properties like ordering constraint, reachability and coverage constraint can be answered after a model is extracted from the implementation. Besides, our approach can be extended to assist in the design phase of the construction process, just like what computer-aided software engineering (CASE) tools do. A hypothetical example is used throughout the chapter as an illustration.

scholarly journals A Systematic Review of the Role of BIM in Building Sustainability Assessment Methods

2020 ◽  
Vol 10 (13) ◽  
pp. 4444 ◽  
Author(s):  
José Pedro Carvalho ◽  
Luís Bragança ◽  
Ricardo Mateus
Keyword(s):  
Systematic Review ◽  
Construction Industry ◽  
Design Process ◽  
Sustainability Assessment ◽  
The Other ◽  
Design Phase ◽  
Building Information Modelling ◽  
Current Role ◽  
Building Information

Building Information Modelling (BIM) is creating new opportunities for the Architecture, Engineering and Construction industry. One of them is the integration of the Building Sustainability Assessment (BSA) during the design process. Currently, an approach for using BIM to foster and optimise the application of BSA methods has not been clearly established yet, creating a knowledge gap on the application of BIM for sustainability assessment purposes. Thus, this paper analyses the current role of BIM to evaluate three BSA methods—LEED, BREEAM and SBTool. The current BIM applicability is assessed by performing a systematic review, where the criteria being assessed and the applied BIM software are identified. A comparison is made to determine which BSA method can currently take more advantage from BIM and to identify the number of assessed criteria from each one. Furthermore, the attractiveness of a BIM-based assessment for SBTool is analysed, facing the actual BIM scenario for LEED and BREEAM. Despite the restrictions, BIM use is increasing for sustainability purposes. Most of the analysed studies and identified software are still focused on the use of LEED for assessing sustainability during the design phase. However, BIM software capabilities can also support the assessment of the other BSA methods so that process replicability can happen. Among the most addressed criteria, the energy and material-related categories are the most eminent. Autodesk Revit is the most-used software. A BIM-based assessment for SBTool will have enough attractiveness. It can assess, at least, the same percentage of criteria as the other schemes, creating new opportunities to enhance building sustainability.

scholarly journals The Near-Synchronous Polar Candidate V4633 Sgr (Nova Sagittarii 1998)

2004 ◽  
Vol 190 ◽  
pp. 176-177
Author(s):  
Y. Lipkin ◽  
E. M. Leibowitz
Keyword(s):  
Angular Momentum ◽  
Momentum Transfer ◽  
White Dwarf ◽  
Moment Of Inertia ◽  
The Other ◽  
Angular Momentum Transfer ◽  
Classical Nova ◽  
Order Of Magnitude ◽  
Photometric Monitoring ◽  
The Moment

AbstractThe classical nova V4633 Sgr (1998) exhibits two photometric periodicities. The shorter period (P1=3.01 hr) is stable, while the other one, longer by ~2.5%, has decreased monotonically since shortly after the nova eruption, with Ṗ2 ≈ –10−6 (Lipkin et al. 2001).Here we report on results of photometric monitoring of the star in 2001 and 2002. During our observations, the longer period decreased more, and in 2002 it was only 1.8% longer than P1 The decrease rate (Ṗ2) in 2001-2002 was an order of magnitude smaller than in 1998-2000.These new results support the Near-Synchronous Polar classification which was suggested for V4633 Sgr (Lipkin et al. 2001). In this model, the longer period of V4633 Sgr is the spin of the white dwarf, and its variation since 1998 reflects changes in the moment of inertia of the white dwarf, and angular momentum transfer in the system following the nova eruption.

scholarly journals Topological susceptibility with a single light quark flavour

2018 ◽  
Vol 175 ◽  
pp. 14017 ◽  
Author(s):  
Julien Frison ◽  
Ryuichiro Kitano ◽  
Norikazu Yamada
Keyword(s):  
Quark Mass ◽  
Continuum Limit ◽  
Light Quark ◽  
The Other ◽  
Theoretical Argument ◽  
Up Quark ◽  
Order Of Magnitude ◽  
Quark Flavour ◽  
Definition Of ◽  
The Continuum

One of the historical suggestions to tackle the strong CP problem is to take the up quark mass to zero while keeping md finite. The θ angle is then supposed to become irrelevant, i.e. the topological susceptibility vanishes. However, the definition of the quark mass is scheme-dependent and identifying the mu = 0 point is not trivial, in particular with Wilson-like fermions. More specifically, up to our knowledge there is no theoretical argument guaranteeing that the topological susceptibility exactly vanishes when the PCAC mass does. We will present our recent progresses on the empirical check of this property using Nf = 1 + 2 flavours of clover fermions, where the lightest fermion is tuned very close to [see formula in PDF] and the mass of the other two is kept of the order of magnitude of the physical ms. This choice is indeed expected to amplify any unknown non-perturbative effect caused by mu ≠ md. The simulation is repeated for several βs and those results, although preliminary, give a hint about what happens in the continuum limit.

scholarly journals Erosion risk assessment and identification of susceptibility lands using the ICONA model and RS and GIS techniques

2020 ◽  
Author(s):  
Hossein Esmaeili Gholzom ◽  
Hassan Ahmadi ◽  
Abolfazl Moeini ◽  
Baharak Motamed Vaziri
Keyword(s):  
Land Cover ◽  
Catchment Area ◽  
The Other ◽  
Rock Outcrops ◽  
Risk Class ◽  
Erosion Risk ◽  
Gis Techniques ◽  
Rs And Gis ◽  
Other Hand ◽  
Very High

Abstract. Soil erosion in Iran due to the destruction of natural resources has intensified in recent years and land use changes have played a significant role in this process. On the other hand, the lack of data in most watersheds to evaluate erosion and sedimentation for finding quick and timely solutions for watershed management has made the use of models inevitable. The purpose of this study was to use the ICONA model and RS and GIS techniques to assess the risk of erosion and to identify areas sensitive to water erosion in the kasilian watershed in northern Iran. The results of this study showed that with very high slope class percentage (20 %–35 %) and sensitivity of shemshak formation to weathering which covers a large part of the watershed, soil erodibility class is high. But there is adequate land cover along with high percentage of natural forest cover, it has mitigated erosion. For this reason, the kasilian watershed is generally classified as low to moderate of erosion risk. Based on the erosion risk map, results show that the moderate class had the highest percentage of erosion risk (26.26 %) at the watershed. On the other hand, the low erosion risk class comprises a significant portion (25.44 %) of the catchment area. Also, 10.92 % of the catchment area contains a very high erosion risk class, with most of it in rangeland and Rock outcrops second. However, the erodibility of the kasilian watershed is currently controlled by appropriate land cover, but the potential susceptibility to erosion is high. If land cover is redused due to inadequate land management, the risk of erosion is easily increased.

Unsteady convective diffusion with interphase mass transfer

1973 ◽  
Vol 333 (1592) ◽  
pp. 115-132 ◽  
Keyword(s):  
Dispersion Model ◽  
Reaction Rates ◽  
The Other ◽  
Time Dependent ◽  
Transport Systems ◽  
Exchange Coefficient ◽  
Dispersion Coefficients ◽  
Interfacial Transport ◽  
Order Of Magnitude ◽  
Proper Values

The theory of miscible dispersion is extended to interphase transport systems. As a specific example miscible dispersion in laminar flow in a tube in the presence of interfacial transport due to an irreversible first-order reaction at the wall is analysed by an exact procedure. A new exact dispersion model which accounts for dispersion with interphase transport is derived from first principles. The new concept of an ‘exchange coefficient’ arises naturally. This coefficient depends strongly on the rate of interfacial transport. Such transport also affects the convection and dispersion coefficients significantly. A general expression is derived which shows clearly the time-dependent nature of the coefficients in the dispersion model. The complete time-dependent expression for the exchange coefficient is obtained explicitly and is independent of the velocity distribution in the flow; however, it does depend on the initial solute distribution. Because of the complexity of the problem only asymptotic large-time evaluations are made for the convection and dispersion coefficients, but these are sufficient to give useful physical insight into the nature of the problem. When the rate of the wall reaction approaches zero the exchange coefficient also approaches zero and the other two coefficients approach their proper values in the absence of interfacial transport. At the other extreme of rapid wall reaction rates, the convection coefficient is more than 50 % larger than its value in the absence of interfacial transport and the dispersion coefficient is an order of magnitude smaller than that for zero interphase transport.

scholarly journals Theories and Applications for Sequencing Randomly Selected Clones

2001 ◽  
Vol 11 (2) ◽  
pp. 274-280
Author(s):  
Michael C. Wendl ◽  
Marco A. Marra ◽  
LaDeana W. Hillier ◽  
Asif T. Chinwalla ◽  
Richard K. Wilson ◽  
...  
Keyword(s):  
Human Chromosome ◽  
The Other ◽  
Chromosome 2 ◽  
Contig Assembly ◽  
Secondary Importance ◽  
Clone Size ◽  
Bac Clones ◽  
Clone Sequencing ◽  
Order Of Magnitude ◽  
Random Approach

Theory is developed for the process of sequencing randomly selected large-insert clones. Genome size, library depth, clone size, and clone distribution are considered relevant properties and perfect overlap detection for contig assembly is assumed. Genome-specific and nonrandom effects are neglected. Order of magnitude analysis indicates library depth is of secondary importance compared to the other variables, especially as clone size diminishes. In such cases, the well-known Poisson coverage law is a good approximation. Parameters derived from these models are used to examine performance for the specific case of sequencing random human BAC clones. We compare coverage and redundancy rates for libraries possessing uniform and nonuniform clone distributions. Results are measured against data from map-based human-chromosome-2 sequencing. We conclude that the map-based approach outperforms random clone sequencing, except early in a project. However, simultaneous use of both strategies can be beneficial if a performance-based estimate for halting random clone sequencing is made. Results further show that the random approach yields maximum effectiveness using nonbiased rather than biased libraries.

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