scholarly journals Long Term Analysis of Semi Submersible Offset

2017 ◽  
Author(s):  
Sindre S. Sandbakken ◽  
Sverre Haver ◽  
Kjell Larsen
Keyword(s):  
Method Of Moments ◽  
Response Surfaces ◽  
Maximum Response ◽  
Reasonable Accuracy ◽  
Short Term ◽  
Peak Period ◽  
Peak Over Threshold ◽  
Term Analysis ◽  
Short Term Variability

During the design of risers, it is necessary to calculate the 100-year (ULS) top-end motion with reasonable accuracy. The ULS offset is usually taken as the most probable 3-hour maximum response in a storm modeled with 100-year wind and 100-year waves when current forces are neglected. This design approach is assumed to be conservative. In this paper, the level of conservatism is considered by performing a Peak Over Threshold (POT) and All Sea States (ASS) stochastic long term analysis. The 3-hour maximum offset is assumed to be Gumbel distributed for the POT and ASS analysis. Gumbel parameters are estimated using method of moments for all metocean combinations. Response surfaces are established as a function of wind speed, W, significant wave height, Hs, and spectral peak period, Tp, to represent the short term variability of the response problem. The long term distribution of the most probable maximum response is established for the POT analysis. Similarly, a long term probabilistic model for W, Hs and Tp is established for the ASS analysis. Finally, the long term analyses are performed by combining the short term and long term variabilities using IFORM.

LOCA analysis of BWR-4/Mark-I nuclear power plant with TRACE

Kerntechnik ◽  
2021 ◽  
Vol 86 (2) ◽  
pp. 128-142
Author(s):  
J.-J. Huang ◽  
S.-W. Chen ◽  
J.-R. Wang ◽  
C. Shih ◽  
H.-T. Lin
Keyword(s):  
Nuclear Power ◽  
Coupled Model ◽  
Short Term ◽  
Containment System ◽  
Loss Of Coolant Accident ◽  
Main Steam Line ◽  
Main Steam ◽  
Temperature Responses ◽  
Term Analysis

Abstract This study established an RCS-Containment coupled model that integrates the reactor coolant system (RCS) and the containment system by using the TRACE code. The coupled model was used in both short-term and long-term loss of coolant accident (LOCA) analyses. Besides, the RELAP5/CONTAN model that only contains the containment system was also developed for comparison. For short-term analysis, three kinds of LOCA scenarios were investigated: the recirculation line break (RCLB), the main steam line break (MSLB), and the feedwater line break (FWLB). For long-term analysis, the dry-well and suppression pool temperature responses of the RCLB were studied. The analysis results of RELAP5/CONTAN and TRACE models are benchmarked with those of FSAR and RELAP5/GOTHIC models, and it appears that the results of the above four models are consistent in general trends.

Strength Performance of Steel Catenary Riser Using Short Term and Long Term Analysis Methodologies

2016 ◽  
Author(s):  
Feng Wang ◽  
Roger Burke ◽  
Anil Sablok ◽  
Kristoffer H. Aronsen ◽  
Oddgeir Dalane
Keyword(s):  
Bending Moment ◽  
Current Profile ◽  
Short Term ◽  
Sea State ◽  
Strength Performance ◽  
Steel Catenary Riser ◽  
Analysis Methodology ◽  
Riser Design ◽  
Term Analysis

Strength performance of a steel catenary riser tied back to a Spar is presented based on long term and short term analysis methodologies. The focus of the study is on response in the riser touch down zone, which is found to be the critical region based on short term analysis results. Short term riser response in design storms is computed based on multiple realizations of computed vessel motions with various return periods. Long term riser response is based on vessel motions for a set of 45,000 sea states, each lasting three hours. The metocean criteria for each sea state is computed based on fifty six years of hindcast wind and wave data. A randomly selected current profile is used in the long term riser analysis for each sea state. Weibull fitting is used to compute the extreme riser response from the response of the 45,000 sea states. Long term analysis results in the touch down zone, including maximum bending moment, minimum effective tension, and maximum utilization using DNV-OS-F201, are compared against those from the short term analysis. The comparison indicates that the short term analysis methodology normally followed in riser design is conservative compared to the more accurate, but computationally more expensive, long term analysis methods. The study also investigates the important role that current plays in the strength performance of the riser in the touch down zone.

scholarly journals Fetal Vibroacoustic Stimulation in Computerized Cardiotocographic Analysis: The Role of Short-Term Variability and Approximate Entropy

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Maria Laura Annunziata ◽  
Mariamaddalena Scala ◽  
Natascia Giuliano ◽  
Salvatore Tagliaferri ◽  
Olga Carmela Maria Imperato ◽  
...  
Keyword(s):  
High Risk ◽  
Perinatal Outcomes ◽  
Approximate Entropy ◽  
Computer Assisted ◽  
Short Term ◽  
Fetal Movements ◽  
The Impact ◽  
Short Term Variability

The aim of this study was to evaluate the impact of vibroacoustic stimulation (VAS) on computerized cardiotocography short-term variability (STV) and approximate entropy (ApEn) in both low- and high-risk pregnancies. VAS was performed on 121 high- and 95 low-risk pregnancies after 10 minutes of continuous quiet, while their FHR parameters were monitored and recorded by cCTG analysis. Fetal heart rate was recorded using a computer-assisted equipment. Baseline FHR, accelerations, decelerations, STV, long-term irregularity (LTI), ApEn, and fetal movements (FMs) were calculated for defined observational periods before VAS and after 10 minutes. Data were also investigated in relationship with the perinatal outcome. In each group of patients, FHR after VAS remained almost unmodified. Fetal movements significantly increased after VAS in both groups. Results show that only in the high-risk pregnancies, the increase of STV and the decrease of ApEn after VAS were significantly associated with favorable perinatal outcomes.

scholarly journals Modelling large timescale and small timescale service variability

2019 ◽  
Vol 293 (1) ◽  
pp. 123-140
Author(s):  
Marco Gribaudo ◽  
Illés Horváth ◽  
Daniele Manini ◽  
Miklós Telek
Keyword(s):  
Service Time ◽  
Large Scale ◽  
Service Time Distribution ◽  
Efficient Computation ◽  
Short Term ◽  
Service Unit ◽  
Long Term Effect ◽  
Short And Long Term ◽  
Short Term Variability

Abstract The performance of service units may depend on various randomly changing environmental effects. It is quite often the case that these effects vary on different timescales. In this paper, we consider small and large scale (short and long term) service variability, where the short term variability affects the instantaneous service speed of the service unit and a modulating background Markov chain characterizes the long term effect. The main modelling challenge in this work is that the considered small and long term variation results in randomness along different axes: short term variability along the time axis and long term variability along the work axis. We present a simulation approach and an explicit analytic formula for the service time distribution in the double transform domain that allows for the efficient computation of service time moments. Finally, we compare the simulation results with analytic ones.

SPOTing long-term changes in vegetation over short-term variability

2012 ◽  
Vol 28 (1) ◽  
pp. 2-24 ◽  
Author(s):  
Nisha Bao ◽  
Alex Lechner ◽  
Andrew Fletcher ◽  
Peter Erskine ◽  
David Mulligan ◽  
...  
Keyword(s):  
Short Term ◽  
Long Term Changes ◽  
Short Term Variability

scholarly journals XMM-Newton observations of eleven intermediate polars and possible candidates

2020 ◽  
Vol 639 ◽  
pp. A17
Author(s):  
H. Worpel ◽  
A. D. Schwope ◽  
I. Traulsen ◽  
K. Mukai ◽  
S. Ok
Keyword(s):  
Optical Data ◽  
Plasma Emission ◽  
Short Term ◽  
X Ray ◽  
Hot Plasma ◽  
Intermediate Polars ◽  
Orbital Periods ◽  
Firm Evidence ◽  
Short Term Variability

Aims. We aim to identify new intermediate polars (IPs) in XMM-Newton observations from a list of promising candidates. By selecting targets not previously known to be X-ray bright, we aim to uncover evidence for an X-ray underluminous IP subpopulation. Methods. We performed period searches on the XMM-Newton X-ray and optical data of our targets to seek both the spin and orbital periods, which differ in IPs. We also investigated the X-ray spectra to find the hot plasma emission shown by these objects. With archival Swift data we coarsely investigated the long-term X-ray variability, and with archival optical data from a variety of catalogues, we compared the optical to X-ray luminosity to identify X-ray faint objects. This paper presents the first XMM-Newton observation of the prototype IP, DQ Her. Results. We find firm evidence for HZ Pup, V349 Aqr, and IGR J18151-1052 being IPs, with likely white dwarf spin periods of 1552, 390, and 390 s, respectively. The former two have luminosities typical of IPs, and the latter is strongly absorbed and with unknown distance. GI Mon and V1084 Her are apparently non-magnetic CVs with interesting short-term variability unrelated to WD spin. V533 Her is probably a magnetic CV and remains a good IP candidate, while V1039 Cen is possibly a polar. The remaining candidates were too faint to allow for any firm conclusions.

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