The Simplified Method for the Wave Loads Statistical Characteristics Estimation in Stationary Confused Seas

2004 ◽  
Author(s):  
I. F. Davydov ◽  
G. V. Egorov ◽  
V. V. Kozlyakov
Keyword(s):  
Three Dimensional ◽  
Correlation Coefficients ◽  
Statistical Characteristics ◽  
Wave Loads ◽  
Short Term ◽  
Shape Stability ◽  
Response Characteristics ◽  
Combined Stresses ◽  
Definition Of

Practically relevant procedures of construction of the short-term and long-term distributions of wave loads and combined stresses at two- and three-dimensional waves is based on the rather cumbersome schemes of definition of the standards “σyi”, effective periods “Tyie” and correlation coefficients “ryiyi” of wave loads “yi”. These calculations can be made more visible and essentially simplified on the basis of the shape stability of the doubly-normalized amplitude-frequency (AFC) and mutual-frequency response characteristics (MFRC). All specific features of these characteristics are determined by their maximum values and frequencies of maxima. In the report the convenient formulae for estimation of σyi, Tyie and ryiyj are derived, and graphs of functions, determining them, for different wave loads are plotted. These relations allow to reveal major influencing factors and use them for construction of the short-term and long-term spectra of wave loads and stresses for full transport ships (CB > 0.75), including FPSO ships, for which non-linear and dynamic effects are expressed rather weakly.

The Research of Statistic Prediction for Wave Loads Based on Three Dimensional Method

2013 ◽  
Author(s):  
Yihan Zhang ◽  
Huilong Ren ◽  
Hui Li ◽  
Xiaoyu Li
Keyword(s):  
Structural Strength ◽  
Wave Spectrum ◽  
Three Dimensional ◽  
Frequency Interval ◽  
Wave Loads ◽  
Short Term ◽  
Empirical Formulas ◽  
Strength Assessment ◽  
Term Prediction

The exact prediction of wave loads for ship or other marine structure is the key to its design and the assessment of structural strength, reliability and security. The short-term and long-term prediction of wave loads are always used in direct calculation for structural strength, fatigue strength assessment and so on based on spectral analysis method. In this paper, the numerical calculation method for statistic prediction is discussed firstly, including the Weibull distribution fitted method and the stack method. Further more, it is necessary to find a quick solution in order to improve the efficiency to compute the nonlinear equation in the second method. Then, some main factors that may influence the long-term or short-term prediction are discussed, such as wave spectrum, wave scatter diagram, incident wave angle interval and frequency interval. Finally, the wave loads prediction for a series of typical bulk carriers and oil tankers are calculated by the uniform predict method discussed above base on three dimensional wave loads calculation theory. The results showed that the method used in this paper can predict the statistic value of wave loads induced by irregular incident waves conveniently and efficiently. A rule to choose a series of uniform factors is confirmed for statistic prediction and some empirical formulas for long-term value of wave bending moment are concluded which are very useful in marine engineering.

Analysis of Motions of a Semisubmersible in Sea Waves

1982 ◽  
Vol 104 (1) ◽  
pp. 29-38
Author(s):  
F. Z. Sun
Keyword(s):  
Transfer Functions ◽  
Three Dimensional ◽  
Theoretical Data ◽  
Statistical Characteristics ◽  
Sea Waves ◽  
Regular Waves ◽  
Short Term ◽  
Equivalent Wave ◽  
Processing Techniques

The forces acting on a three-dimensional cylinder with arbitrary symmetrical cross section are derived taking into account viscous effect and applying linear-processing techniques. Then general expressions for the hydrodynamic forces, motion equation and its solution for a semisubmersible platform in regular waves are obtained. Based on linear theory of statistical analysis, it is proposed to employ the concept of “equivalent wave height” for the calculation of transfer functions with which both the short-term and long-term distribution and statistical characteristics of the motion of a semisubmersible may be estimated. A computer program has been developed. Comparison between model experimental and theoretical data has shown satisfactory agreement.

An Approach to the Estimation of Structural Design Loads of Turret Moored FPSO Tankers

2003 ◽  
Author(s):  
Huilong Ren ◽  
Chang Doo Jang
Keyword(s):  
Structural Design ◽  
Three Dimensional ◽  
Wave Loads ◽  
Short Term ◽  
Efficient Calculation ◽  
Restoring Forces ◽  
Design Loads ◽  
The Given ◽  
Equations Of Motions

A practical approach to determine the structural design loads of turret moored FPSO (Floating Production Storage and Offloading) tankers is suggested in this paper. The linearized restoring forces acting on the ship hull by the mooring system are calculated according to the catenary theory. The effect of the restoring forces is included in the equations of motions of the ship in the form of linear stiffness coefficients. The hydrodynamic coefficients are calculated by the three-dimensional potential flow theory. The equations of motions are solved in frequency domain, and the motions and wave loads responses can be obtained. Then the short-term and long-term analyses are carried out for the wave loads of this kind of ship. With a 250m turret moored FPSO tanker as an example, according to the given environmental sea states data, headings, exceeding probability for the FPSO tanker, the structural design loads are calculated and compared with those obtained from rules for traditional tankers with the same dimensions. By the present approach, it is possible to perform a practical and efficient calculation of structural design loads of actual turret moored FPSO tankers.

scholarly journals Remember like humans

2017 ◽  
Vol 14 (1) ◽  
pp. 172988141769231 ◽  
Author(s):  
Ning An ◽  
Shi-Ying Sun ◽  
Xiao-Guang Zhao ◽  
Zeng-Guang Hou
Keyword(s):  
Short Term Memory ◽  
Three Dimensional ◽  
Sensory Memory ◽  
Long Term Memory ◽  
Observation Model ◽  
Two Dimensional ◽  
Short Term ◽  
Term Memory ◽  
Memory Register

Visual tracking is a challenging computer vision task due to the significant observation changes of the target. By contrast, the tracking task is relatively easy for humans. In this article, we propose a tracker inspired by the cognitive psychological memory mechanism, which decomposes the tracking task into sensory memory register, short-term memory tracker, and long-term memory tracker like humans. The sensory memory register captures information with three-dimensional perception; the short-term memory tracker builds the highly plastic observation model via memory rehearsal; the long-term memory tracker builds the highly stable observation model via memory encoding and retrieval. With the cooperative models, the tracker can easily handle various tracking scenarios. In addition, an appearance-shape learning method is proposed to update the two-dimensional appearance model and three-dimensional shape model appropriately. Extensive experimental results on a large-scale benchmark data set demonstrate that the proposed method outperforms the state-of-the-art two-dimensional and three-dimensional trackers in terms of efficiency, accuracy, and robustness.

scholarly journals When is a Learning Object not an Object: A first step towards a theory of learning objects

2002 ◽  
Vol 3 (2) ◽  
Author(s):  
Mike Sosteric ◽  
Susan Hesemeier
Keyword(s):  
Economies Of Scale ◽  
Learning Objects ◽  
Short Term ◽  
Object A ◽  
Smart Learning ◽  
Smart Learning Environments ◽  
Adequate Definition ◽  
Definition Of ◽  
Conceptual Confusion

<p> For some, “learning objects" are the “next big thing” in distance education promising smart learning environments, fantastic economies of scale, and the power to tap into expanding educational markets. While learning objects may be revolutionary in the long term, in the short term, definitional problems and conceptual confusion undermine our ability to understand and critically evaluate the emerging field. This article is an attempt to provide an adequate definition of learning objects by (a) jettisoning useless theoretical links hitherto invoked to theorize learning objects, and (b) reducing the definition of learning objects to the bare essentials. The article closes with suggestions for further research and further refinement of the definition of learning objects. </P>

scholarly journals Systema Temporis: A Time-Based Dimensional Framework for Consciousness and Cognition

2019 ◽  
Author(s):  
Lachlan Kent ◽  
George Van Doorn ◽  
Britt Klein
Keyword(s):  
Time Perception ◽  
Dimensional Structure ◽  
Two Dimensional ◽  
Dimensional Approach ◽  
Short Term ◽  
Hierarchical Framework ◽  
Time Consciousness ◽  
Emotion And Memory ◽  
Definition Of

This study uses a combined categorical-dimensional approach to depict a hierarchical framework for consciousness similar to, and contiguous with, factorial models of cognition (cf., intelligence). On the basis of the longstanding definition of time consciousness, the analysis employs a dimension of temporal extension, in the same manner that psychology has temporally organised memory (i.e., short-term, long-term, and long-lasting memories). By defining temporal extension in terms of the structure of time perception at short timescales (&lt; 100 s), memory and time consciousness are proposed to fit along the same logarithmic dimension. This suggests that different forms of time consciousness (e.g., experience, wakefulness, and self-consciousness) are embedded within, or supported by, the ascending timescales of different modes of memory (i.e., short-term, long-term, etc.). A secondary dimension is also proposed to integrate higher-order forms of consciousness/emotion and memory/cognition. The resulting two-dimensional structure accords with existing theories of cognitive and emotional intelligence.

Recall of Familiar Objects and Projected Color Photographs of Objects by Mentally Retarded Individuals of Comparable Mental Age

1976 ◽  
Vol 42 (1) ◽  
pp. 139-145
Author(s):  
Andrew L. Shotick ◽  
A. Bartow Ray ◽  
C. Lewis Addison
Keyword(s):  
Memory Span ◽  
Three Dimensional ◽  
Mentally Retarded ◽  
Short Term ◽  
Delayed Recall ◽  
Mental Age ◽  
Mentally Retarded Children ◽  
Cue Availability ◽  
Familiar Objects

The effects of cue-availability on short-term and long-term recall of 40 mentally retarded children were investigated. Subjects were chosen on the basis of comparable mental age (approximately 90 mo.) and randomly assigned to either an objects (high cues) group or slides (low cues) group. 52 familiar objects served as stimuli for the objects group and projected color photographs of the objects were presented to the slides group. In the short-term recall session the subjects were shown stimuli grouped into eight trials and asked to recall the names of the stimuli in each trial ten seconds after presentation. Delayed recall was obtained 48 hr. later in a free recall session. The objects group scored significantly higher than the slides group on memory span ( p < .01), short-term recall ( p < .001), and delayed recall ( p < .025). The facilitation of recall achieved by using three-dimensional stimuli was clearly demonstrated, and the relative degree of facilitation was comparable for both short- and long-term recall.

Numerical Analysis of Ship Wave Loads and Structure Strengthen Analysis on a Wind Power Installation Ship

2011 ◽  
Vol 90-93 ◽  
pp. 2521-2527
Author(s):  
Gang Qiang Li ◽  
Yan Yan Zhao ◽  
Yong He Xie
Keyword(s):  
Wind Power ◽  
Structural Design ◽  
Three Dimensional ◽  
Load Condition ◽  
Wave Loads ◽  
Element Simulation ◽  
Wind Power Installation ◽  
Wave Induced ◽  
Term Response

In a typical load condition of wind power equipment Installation ship, using the three-dimensional potential flow theory to prediction the long-term response of wave induced loads. then using the main load control parameters as a basis for the design wave selection, then application of DNV's SESTRA program make the wave-induced directly to the structure to finite element simulation. The results show that the hull structural design can meet the requirements.

Empirical Procedures for Long-Term Prediction of Fatigue Damage for an Instrumented Marine Riser

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
C. Shi ◽  
L. Manuel ◽  
M. A. Tognarelli
Keyword(s):  
Fatigue Damage ◽  
Field Measurements ◽  
Damage Estimation ◽  
Current Profile ◽  
Short Term ◽  
Response Characteristics ◽  
Damage Rate ◽  
Using Data ◽  
Analytical Approaches

Slender marine risers used in deepwater applications can experience vortex-induced vibration (VIV). It is becoming increasingly common for field monitoring campaigns to be undertaken wherein data loggers such as strain sensors and/or accelerometers are installed on such risers to aid in VIV-related fatigue damage estimation. Such damage estimation relies on the application of empirical procedures that make use of the collected data. This type of damage estimation can be undertaken for different current profiles encountered. The empirical techniques employed make direct use of the measurements and key components in the analyszes (such as participating riser modes selected for use in damage estimation) are intrinsically dependent on the actual current profiles. Fatigue damage predicted in this manner is in contrast to analytical approaches that rely on simplifying assumptions on both the flow conditions and the response characteristics. Empirical fatigue damage estimates conditional on current profile type can account explicitly even for complex response characteristics, participating riser modes, etc. With significant amounts of data, it is possible to establish “short-term” fatigue damage rate distributions conditional on current type. If the relative frequency of different current types is known from metocean studies, the short-term fatigue distributions can be combined with the current distributions to yield integrated “long-term” fatigue damage rate distributions. Such a study is carried out using data from the Norwegian Deepwater Programme (NDP) model riser subject to several sheared and uniform current profiles and with assumed probabilities for different current conditions. From this study, we seek to demonstrate the effectiveness of empirical techniques utilized in combination with field measurements to predict the long-term fatigue damage and the fatigue failure probability.

Reliability and reproducibility of a clinical application of a simple technique for repeated circumferential leg measurements

2010 ◽  
Vol 26 (1) ◽  
pp. 14-19 ◽  
Author(s):  
A te Slaa ◽  
P Mulder ◽  
D Dolmans ◽  
P Castenmiller ◽  
G Ho ◽  
...  
Keyword(s):  
Simple Technique ◽  
Correlation Coefficients ◽  
Repeated Measurements ◽  
Medium Term ◽  
Short Term ◽  
Intra Class Correlation ◽  
Long Period ◽  
Simple Instrument ◽  
Reproducible Method

Objective The aim of this study is to determine the reliability and reproducibility of repeated tape measurements to assess the leg circumference during a long period. Methods A tape measure is a simple instrument that is applicable in the presence of oedema. Measurements were performed by four observers on 11 volunteers. Four measurements were done in the first week (short term), a fifth measurement at two weeks (medium term) and a sixth measurement was done at 12 weeks (long term). Results The short-, medium- and long-term intra-class correlation coefficients for repeated measurements were 0.90, 0.89 and 0.78, respectively. The short-term and long-term reproducibility indices equalled 4.4% and 6.5%. If only a single observer would be involved, the short-term intra-class correlation coefficients would improve to 0.94 (reproducibility index 3.3%). Conclusion Tape measurements have been proved to be a reliable and reproducible method to asses the lower limb circumference.

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