“LIQUEFACTION” AND “DYNAMIC SEPARATION” DIFFERENT ASPECTS OF THE SAME PROBLEM

2021 ◽  
Vol 161 (A4) ◽  
Author(s):  
S Ferauge ◽  
W Jacobs ◽  
K De Baere
Keyword(s):  
Free Surface ◽  
Real World ◽  
Working Group ◽  
Surface Effect ◽  
Separation Mechanism ◽  
Worst Case ◽  
Bauxite Ore ◽  
Solid Bulk ◽  
Bad Weather ◽  
The Stability

In 2015 the Bulk Jupiter sank during bad weather loaded with bauxite. Nearly automatically everybody considered “liquefaction” to be the prime cause of this accident. Liquefaction is a phenomenon where solid bulk cargo, triggered by the ship movements, starts to behave has a high density viscous liquid in the holds. The stability is negatively influenced by the free surface effect and further research, especially by the Global Bauxite Working Group or GBWG showed that bauxite ore simply will not liquefy even under the worst case shipping conditions. Evidence from real world shipments of bauxites shows that instabilities due to moisture cannot be explained by liquefaction phenomena, but can be under a “dynamic separation” mechanism of instability. Both liquefaction and dynamic separation are caused by an excessive moisture of the bauxite cargo. However, the influence on the stability of the ship is fundamentally different.

“Liquefication” and “Dynamic Separation” Different Aspects of the Same Problem

2019 ◽  
Vol 161 (A4) ◽  
Keyword(s):  
Free Surface ◽  
Real World ◽  
Working Group ◽  
Surface Effect ◽  
Separation Mechanism ◽  
Worst Case ◽  
Bauxite Ore ◽  
Solid Bulk ◽  
Bad Weather ◽  
The Stability

In 2015 the Bulk Jupiter sank during bad weather loaded with bauxite. Nearly automatically everybody considered “liquefaction” to be the prime cause of this accident. Liquefaction is a phenomenon where solid bulk cargo, triggered by the ship movements, starts to behave has a high density viscous liquid in the holds. The stability is negatively influenced by the free surface effect and further research, especially by the Global Bauxite Working Group or GBWG showed that bauxite ore simply will not liquefy even under the worst case shipping conditions. Evidence from real world shipments of bauxites shows that instabilities due to moisture cannot be explained by liquefaction phenomena, but can be under a “dynamic separation” mechanism of instability. Both liquefaction and dynamic separation are caused by an excessive moisture of the bauxite cargo. However, the influence on the stability of the ship is fundamentally different.

scholarly journals Influence of flooding compartments on the stability safety of the training warship

2017 ◽  
Vol 42 (1) ◽  
pp. 75-92
Author(s):  
Waldemar Mironiuk
Keyword(s):  
Free Surface ◽  
Surface Effect ◽  
Calculation Algorithm ◽  
Computational Stability ◽  
The Stability ◽  
Stability Issues ◽  
Metacentric Height

Abstract The paper presents computational stability issues with a flooded ship compartment situated on boat deck. As the main criteria for stability of the warship, calculation algorithm of metacentric height and righting levers have been defined, with a free surface effect taken into account. Based on the results of the calculations presented in tabular and graphical forms, suitable conclusions have been drawn up.

scholarly journals Hydrostatic Stability of Compartmented Structures Supported by Air Cushions

2009 ◽  
Vol 53 (03) ◽  
pp. 151-158 ◽  
Author(s):  
Krish P. Thiagarajan
Keyword(s):  
Free Surface ◽  
Correction Factor ◽  
First Principles ◽  
Surface Effect ◽  
Operating Conditions ◽  
Forward Speed ◽  
Air Cushion ◽  
The Stability ◽  
Metacentric Height ◽  
Water Plug

This paper presents theoretical formulations to evaluate the restoring moment of structures supported by air cushions at zero forward speed. The air cushion is assumed to be enclosed within a number of compartments that are open to sea. The height of the water plug within the compartments is thus an important parameter. The theory, developed from first principles, is verified against data from inclining experiments conducted on a nine-compartment air cushion supported structure at different drafts and water plug heights. The theory shows that the air cushion affects the stability in two conflicting ways: favorable decrease in the vertical center of gravity caused by the water plug effect and unfavorable enhancement of the internal free surface effect. The net effect on stability depends on the operating conditions as well as on the scale of the structure being considered. A correction factor for the metacentric height incorporating the air cushion effects is proposed.

scholarly journals Asymmetry underlies stability in power grids

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ferenc Molnar ◽  
Takashi Nishikawa ◽  
Adilson E. Motter
Keyword(s):  
Symmetry Breaking ◽  
Real World ◽  
Power Grids ◽  
Stable Operation ◽  
World Systems ◽  
Symmetric State ◽  
Network Systems ◽  
Additional Improvement ◽  
The Stability ◽  
General Method

AbstractBehavioral homogeneity is often critical for the functioning of network systems of interacting entities. In power grids, whose stable operation requires generator frequencies to be synchronized—and thus homogeneous—across the network, previous work suggests that the stability of synchronous states can be improved by making the generators homogeneous. Here, we show that a substantial additional improvement is possible by instead making the generators suitably heterogeneous. We develop a general method for attributing this counterintuitive effect to converse symmetry breaking, a recently established phenomenon in which the system must be asymmetric to maintain a stable symmetric state. These findings constitute the first demonstration of converse symmetry breaking in real-world systems, and our method promises to enable identification of this phenomenon in other networks whose functions rely on behavioral homogeneity.

Predictive Value of Assessing Vehicle Interior Design Ergonomics in a Virtual Environment

2004 ◽  
Vol 4 (2) ◽  
pp. 109-113 ◽  
Author(s):  
Thomas Reuding ◽  
Pamela Meil
Keyword(s):  
Virtual Environments ◽  
Interior Design ◽  
Real World ◽  
Predictive Value ◽  
Work Processes ◽  
Complex Activity ◽  
Vehicle Interior ◽  
Design Work ◽  
The Real ◽  
The Stability

The predictive value and the reliability of evaluations made in immersive projection environments are limited when compared to the real world. As in other applications of numerical simulations, the acceptance of such techniques does not only depend on the stability of the methods, but also on the quality and credibility of the results obtained. In this paper, we investigate the predictive value of virtual reality and virtual environments when used for engineering assessment tasks. We examine the ergonomics evaluation of a vehicle interior, which is a complex activity relying heavily on know-how gained from personal experience, and compare performance in a VE with performance in the real world. If one assumes that within complex engineering processes certain types of work will be performed by more or less the same personnel, one can infer that a fairly consistent base of experience-based knowledge exists. Under such premises and if evaluations are conducted as comparisons within the VE, we believe that the reliability of the assessments is suitable for conceptual design work. Despite a number of unanswered questions at this time we believe this study leads to a better understanding of what determines the reliability of results obtained in virtual environments, thus making it useful for optimizing virtual prototyping processes and better utilization of the potential of VR and VEs in company work processes.

Three-component analysis of regional seismograms

1990 ◽  
Vol 80 (6B) ◽  
pp. 2032-2052 ◽  
Author(s):  
D. C. Jepsen ◽  
B. L. N. Kennett
Keyword(s):  
Free Surface ◽  
Time Window ◽  
Seismic Station ◽  
P Wave ◽  
Sh Waves ◽  
Near Surface ◽  
Source Discrimination ◽  
Decomposition Scheme ◽  
Phased Array Techniques ◽  
The Stability

Abstract Both phased array techniques for single-component sensors and vectorial analysis of three-component recordings can provide estimates of the azimuth and slowness of seismic phases. However, a combination of these approaches provides a more powerful tool to estimate the propagation characteristics of different seismic phases at regional distances. Conventional approaches to the analysis of three-component seismic records endeavor to exploit the apparent angles of propagation in horizontal and vertical planes as well as the polarization of the waves. The basic assumption is that for a given time window there is a dominant wavetype (e.g., a P wave) traveling in a particular direction arriving at the seismic station. By testing a range of characteristics of the three-component records, a set of rules can be established for classifying much of the seismogram in terms of wavetype and direction. It is, however, difficult to recognize SH waves in the presence of other wavetypes. Problems also arise when more than one signal (in either wavetype or direction) arrive in the same window. The stability and robustness of the classification scheme is much improved when records from an array of three-component sensors are combined. For a set of three-component instruments forming part of a larger array, it is possible to estimate the slowness and azimuth of arrivals from the main array and then extract the relative proportions of the current P-, SV-, and SH-wave contributions to the seismogram. This form of wavetype decomposition depends on a model of near-surface propagation. A convenient choice for hard-rock sites is to include just the effect of the free surface, which generates a frequency-independent operation on the three-component seismograms and which is not very sensitive to surface velocities. This approach generates good estimates of the character of the S wavefield, because the phase distortion of SV induced by the free surface can be removed. The method has been successfully applied to regional seismograms recorded at the medium aperture Warramunga array in northern Australia, and the two small arrays NORESS and ARCESS in Norway, which were designed for studies of regional phases. The new wavefield decomposition scheme provides results in which the relative proportions of P, SV, and SH waves as a function of time can be compared without the distortion imposed by free surface amplification. Such information can provide a useful adjunct to existing measures of signal character used in source discrimination.

Beyond the Known: Detecting Novel Feasible Domains Over an Unbounded Design Space

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
Wei Chen ◽  
Mark Fuge
Keyword(s):  
Real World ◽  
Adaptive Sampling ◽  
Design Space ◽  
Fundamental Problem ◽  
Domain Boundary ◽  
Sampling Technique ◽  
Standard Test ◽  
Worst Case ◽  
Trade Offs ◽  
Design Variables

To solve a design problem, sometimes it is necessary to identify the feasible design space. For design spaces with implicit constraints, sampling methods are usually used. These methods typically bound the design space; that is, limit the range of design variables. But bounds that are too small will fail to cover all possible designs, while bounds that are too large will waste sampling budget. This paper tries to solve the problem of efficiently discovering (possibly disconnected) feasible domains in an unbounded design space. We propose a data-driven adaptive sampling technique—ε-margin sampling, which learns the domain boundary of feasible designs and also expands our knowledge on the design space as available budget increases. This technique is data-efficient, in that it makes principled probabilistic trade-offs between refining existing domain boundaries versus expanding the design space. We demonstrate that this method can better identify feasible domains on standard test functions compared to both random and active sampling (via uncertainty sampling). However, a fundamental problem when applying adaptive sampling to real world designs is that designs often have high dimensionality and thus require (in the worst case) exponentially more samples per dimension. We show how coupling design manifolds with ε-margin sampling allows us to actively expand high-dimensional design spaces without incurring this exponential penalty. We demonstrate this on real-world examples of glassware and bottle design, where our method discovers designs that have different appearance and functionality from its initial design set.

Irreversible Adsorption Erases the Free Surface Effect on the Tg of Supported Films of Poly(4-tert-butylstyrene)

2017 ◽  
Vol 6 (4) ◽  
pp. 354-358 ◽  
Author(s):  
Natalia G. Perez-de-Eulate ◽  
Michele Sferrazza ◽  
Daniele Cangialosi ◽  
Simone Napolitano
Keyword(s):  
Free Surface ◽  
Surface Effect ◽  
Irreversible Adsorption

Visual Memory for Objects in Natural Scenes: From Fixations to Object Files

2005 ◽  
Vol 58 (5) ◽  
pp. 931-960 ◽  
Author(s):  
Benjamin W. Tatler ◽  
Iain D. Gilchrist ◽  
Michael F. Land
Keyword(s):  
Real World ◽  
Visual Memory ◽  
Natural Scenes ◽  
Position Information ◽  
Object Property ◽  
Immediate Recall ◽  
Object Files ◽  
Stability Data ◽  
The Stability ◽  
Types Of Information

Object descriptions are extracted and retained across saccades when observers view natural scenes. We investigated whether particular object properties are encoded and the stability of the resulting memories. We tested immediate recall of multiple types of information from real-world scenes and from computer-presented images of the same scenes. The relationship between fixations and properties of object memory was investigated. Position information was encoded and accumulated from multiple fixations. In contrast, identity and colour were encoded but did not require direct fixation and did not accumulate. In the current experiments, participants were unable to recall any information about shape or relative distances between objects. In addition, where information was encoded we found differential patterns of stability. Data from viewing real scenes and images were highly consistent, with stronger effects in the real-world conditions. Our findings imply that object files are not dependent upon the encoding of any particular object property and so are robust to dynamic visual environments.

scholarly journals Recommendations for the Protocol of functional examination of the anorectal zone and disorders classification: the International Anorectal Physiology Working Group consensus and Russian real-world practice

2020 ◽  
Vol 92 (12) ◽  
pp. 105-119
Author(s):  
O. Yu. Fomenko ◽  
S. V. Morozov ◽  
S. Mark Scott ◽  
H. Charles Knowles ◽  
D. A. Morozov ◽  
...  
Keyword(s):  
Real World ◽  
Working Group ◽  
Anorectal Function ◽  
Anorectal Physiology ◽  
Rectal Sensation ◽  
High Resolution Manometry ◽  
Additional Information ◽  
Wide Range ◽  
Balloon Expulsion ◽  
Function Testing

This manuscript summarizes consensus reached by the International Anorectal Physiology Working Group (IAPWG) for the performance, terminology used, and interpretation of anorectal function testing including anorectal manometry (focused on high-resolution manometry), the rectal sensory test, and the balloon expulsion test. Based on these measurements, a classification system for disorders of anorectal function is proposed. Aim to provide information about methods of diagnosis and new classification of functional anorectal disorders to a wide range of specialists general practitioners, therapists, gastroenterologists, coloproctologists all who face the manifestations of these diseases in everyday practice and determine the diagnostic and therapeutic algorithm. Current paper provides agreed statements of IAPWG Consensus and comments (in italics) of Russian experts on real-world practice, mainly on methodology of examination. These comments in no way intended to detract from the provisions agreed by the international group of experts. We hope that these comments will help to improve the quality of examination based on the systematization of local experience with the use of the methods discussed and the results obtained. Key recommendations: the International Anorectal Physiology Working Group protocol for the performance of anorectal function testing recommends a standardized sequence of maneuvers to test rectoanal reflexes, anal tone and contractility, rectoanal coordination, and rectal sensation. Major findings not seen in healthy controls defined by the classification are as follows: rectoanal areflexia, anal hypotension and hypocontractility, rectal hyposensitivity, and hypersensitivity. Minor and inconclusive findings that can be present in health and require additional information prior to diagnosis include anal hypertension and dyssynergia.

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