Extreme Tension Research Articles

The Hydrodynamic Similarity between Different Power Levels and a Dynamic Analysis of Ocean Current Energy Converter–Platform Systems with a Novel Pulley–Traction Rope Design for Irregular Typhoon Waves and Currents

In the future, the power of a commercial ocean current energy convertor will be able to reach the MW class, and its corresponding mooring rope tension will be very good. However, the power of convertors currently being researched is still at the KW class, which can bear less rope tension. The main mooring rope usually has a single cable and a single foundation. To investigate the dynamic response and rope tension of an MW-class ocean current generator mooring system, here, a similarity rule is proposed for (1) coefficients without any fluid–structure interaction (FSI) using the Buckingham theorem and (2) ones with FSI. The overall hydrodynamic drag and moment including the hydrodynamic coefficients in these two situations are represented in a Taylor series. Assuming similarity between the commercial MW-class and KW-class ocean current convertors, all hydrodynamic parameters of the MW-class system are estimated based on the known KW-class parameters and based on the similarity formula. In order to overcome the extreme tension of the MW-class system and to provide good stability, in this paper, we propose a pulley–rope design to replace the traditional single-traction-rope design. The static and dynamic mathematical models of this mooring system subjected to the impact of typhoon waves and currents are proposed, and analytical solutions are obtained. We find that the pulley–rope design can significantly reduce the dynamic rope tensions of the mooring system. The effect of the length ratio of the main traction rope, rope A, to the seabed depth on the dynamic tension of stabilizing converter rope D is significant. The length ratio is within a safe range, and the maximum rope dynamic tension is less than the fracture strength. In addition, if the rope length ratio is over the critical value, the larger the ratio, the higher the safety factor of the rope. In summary, the pulley–rope design can be safely used in an MW-level ocean current generator system.

Hydrodynamic analysis of three-module semi-submersible platform and its mooring design

The floating platform consisting of three interconnected semi-submersible modules deployed in shallow water with severe environmental conditions will be subject to very high environmental loads during storms and its position keeping will become a huge challenge. Therefore, it is important to investigate the hydrodynamic characteristics of the platform and design a robust mooring system to meet different demands during the service period of the platform. In this study, the hydrodynamic and motion analyses of the three-module semi-submersible platform were conducted by using both numerical simulation and experimental tests. In addition, a distinctive X-shaped mooring system was designed, which is characterized by relatively low stiffness in the direction of beam sea in which the environmental loads are the highest, and better load sharing among different mooring lines so that the extreme tension is curbed. Model tests were performed in a wave basin to acquire the platform motions and mooring tensions, and comparisons were made between the measurements and numerical predictions. The results of the study verify the feasibility of the three-module connected platform and its mooring system.

Prediction of ultimate tensions in mooring lines for a floating offshore wind turbine considering extreme gusts

The design of mooring line parameter for a floating offshore wind turbine (FOWT) should consider the ultimate limit state. Typhoons should be considered as a threatening condition for mooring design, and the characteristics of transient changing wind should be studied. Currently, few extreme value predictions consider gust features, and extreme mooring tensions may be underestimated in practical FOWT design. We conducted the simulations of the 5 MW wind turbine from the National Renewable Energy Laboratory (NREL) in the environmental conditions of extreme gusts, waves, and currents. Extreme gusts were found to cause dramatic increases in mooring tensions under 100-year typhoon conditions. The average conditional exceedance rate (ACER) method is used to predict extreme mooring tensions. The impacts of simulation duration and sample size on the prediction results are then discussed. The results show that in extreme gust conditions, the tail data of the average conditional exceedance rate of mooring tension presents a different extrapolation trend from stable wind conditions. Short-term predicted values in gust conditions are 14–20% larger than those in stable wind conditions. The research shows the necessity of considering threatening gust conditions in the ultimate limit state design of mooring system of FOWT.

Numerical Investigation on Mooring Line Configurations of a Semisubmersible Fish Farm for Global Performance

The growth of the aquaculture industry has led to the development of innovative fish farming technologies, such as semisubmersible fish farms which offer significant advantages in terms of scalability and environmental sustainability. The study utilizes a new workflow based on an open-source finite element solver, Code_Aster, to calculate the hydrodynamic dynamic response of a fish farm. The mooring line configuration of a semisubmersible fish farm plays a crucial role in ensuring its stability and overall performance. This study presents a comprehensive numerical investigation aimed at evaluating the influence of different mooring line configurations (i.e., 4 × 1, 4 × 2, and 4 × 3) on the global performance of a semisubmersible fish farm under regular waves and irregular waves conditions. Increasing the number of mooring lines can reduce the mean and extreme tension in individual mooring lines and suppress the horizontal motions, but bring neglectable effects on the rotational responses. The findings from this research provide valuable insights into the optimal mooring line configuration for the global performance of semisubmersible fish farms.

From “Decisive Hostility” to “Cordial Agreement”: “The Times” on the Evolution of Britain’s Image in Russian Press at the Beginning of the 20th Century

The article deals with the reflection of the image of Britain in the analytical reviews of “The Times” newspaper on the pages of the Russian periodical press at the beginning of the 20th century.
 The study covers the period from the turn of the 19th–20th centuries until 1907, when the relations between Russia and Britain transitioned from extreme tension and rivalry in different regions of the world to an alliance within the Triple Entente. At this time, the press became truly massive and exerted a stronger influence than ever on the development of international relations. One of the leading English newspapers, “The Times”, took a largely pro-government stance and reflected the official position on foreign policy issues. It regularly reviewed the publications in the Russian press concerning Anglo-Russian relationship or British politics in general.
 As a result of the analysis of “The Times” reviews, it is possible to show the significance of the British political image, the dynamics of public opinion in the Russian Empire regarding a possible confrontation or Anglo-Russian rapprochement. The Russian press formed among readers a certain perception of Britain in the context of the Anglo-Boer War, the events in the Far East, the process of resolving contradictions, and the conclusion of the 1907 agreement, while the English press reflected on this image. The transformation of rhetoric in the press happened as rapidly as the changes in relations between the two powers.

"Sonny’s Blues": The Dream Variation and Cultural Integration through Music

“Sonny’s Blues” is a chronicle of racial prejudice, diverse dreams, suffering, redemption, and reconciliation. As a tale of conflicting relationships between two brothers in Harlem society, it narrates the narrative of life, liberty and the pursuit of happiness on two opposite sides that the brothers are situated in: the legacy of African-American cultural and mainstream dreams. It is against this background dichotomy that the suffering of Sonny, the African-American protagonist, engendered due to his latent desire to be a jazz musician, is shown. This paper discourses on the existential narrative and its manifestation on society through an individual and answers different questions: why would characters go through extreme familial tension? What aspires them to embody two dissimilar legacies? How does music amidst racism produce a therapeutic effect? How are human predicaments resolved and why do characters go back to their original niche, which their ancestors had created? Hence, this paper aims at how music outcasts the barriers and welcomes avenues of resilience by removing the thundering cloud of stillness and darkness in the blue sky of Harlem.

Data-driven modeling of hydrodynamic loading using NARX and harmonic probing

Optimizing floating wind turbines and their mooring systems requires validated computational models that predict wave-frequency and low-frequency hydrodynamic loads. Low-frequency loads are crucial for determining extreme offsets and tension in mooring lines and are generally described by a quadratic transfer function. The quadratic transfer function, obtained with numerical tools, accurately predicts low-frequency loads in mild sea states. However, since the existing numerical methods are based on potential and perturbation theory, they generally fail to accurately predict low-frequency loads in moderate-to-extreme sea states where current, viscous, and beyond-second-order potential effects become significant. Developing a procedure for empirical transfer function estimation is, therefore, necessary to overcome these limitations. This paper describes an existing framework for estimating any higher-order transfer functions from experimental data. The framework employs a nonlinear auto-regressive model based on Kriging to establish a causal input/output relationship between the wave-elevation and hydrodynamic force histories exerted on the floater. Then, higher-order transfer functions are extracted using harmonic probing. The procedure was validated by estimating the linear surge transfer function of the INO WINDMOOR 12 MW floater using synthetic data. The data-driven results showed an excellent agreement with the theoretically computed transfer function.

Behavior of hybrid FRP-concrete-steel double-skin tubular beams with ultra-high strength concrete and PBL shear connectors under bending

Hybrid double-skin tubular beams (DSTBs) with the external fiber-reinforced polymer (FRP) tube-annular concrete-inner steel tube configuration have excellent mechanical performance and corrosion resistance, but are prone to slip problems. In this study, perfobond shear connectors (PBLs) are proposed to reduce the slip between infilled concrete and inner steel tube. Moreover, using ultra-high strength concrete (UHSC) as the annular material could further improve the structural performance and magnify the lightweight merit of hybrid DSTBs, while hybrid DSTBs with PBLs and UHSC have not been investigated yet. To this end, three-point bending experiments were conducted to hybrid DSTBs with PBLs and UHSC to study the flexural behavior. The mid-span load–deflection curves revealed a three-branched behavior: (i) a first linear ascending branch up to the first yielding at the extreme tension fiber of inner steel tube; (ii) a transition branch to the peak load with a significant slope deterioration when infilled concrete in the compression side reached the unconfined failure strain; (iii) a post-peak residual branch characterized by progressive load reductions over a number of load plateaus. The adoption of UHSC could significantly delay the plastic hinge formation in inner steel tube, and meanwhile improve the bond with PBLs. Thus, the slips between infilled concrete and inner steel tube were minimal (less than 0.2 mm) for most of the specimens, except for those with foamy sheet insertions between PBLs (at around 1 mm). In the end, the design loads of the hybrid DSTBs were predicted by a sectional analysis with high level of accuracy (average error at 6%).

A Conceptual Study on Rajyakshma through Ayurveda

One of the Asthamahagadas described by Acharya Charaka and known as the "king of the disease" is Rajyakshma. Due to its multisystem involvement and syndromic expression, it has traditionally been difficult to identify and treat. Therefore, it is crucial to fully comprehend Nidana and Samprapti prior to making treatment plans. Rajayakshma has been linked to numerous immunodeficiency syndromes. However, a closer look at the symptoms reveals that it more closely resembles a multisystem respiratory disease. As well as being classified as an Aupsargika Vyadhi, the ailment also had a number of predisposing elements or Chaturvidha Nidana. Tridoshas and Sapta Dhatu are induced as a result of Nidana indulgence. In the present period, pulmonary tuberculosis can be linked to Rajyakshma, which affects the Pranavaha Srotasa. Although the pathophysiology of Rajayakshma and pulmonary tuberculosis differ, their clinical profiles are remarkably similar. Western medicine focuses primarily on infectious diseases, how they spread, various diagnostic techniques, and WHO-recommended antibiotics. The paper's main goals are to fully convey the fundamental ideas of Rajayakshma's Hetu and Samprapti and how they affect the Pranavaha Srotasa in relation to pulmonary tuberculosis. Rajayakshma is considered the king of all diseases. It is formed with two words: Raja (king) and Yakshma (decay), which means fraying condition of huge magnitude. The symptoms of Rajayakshma include Sahasa (extreme tension and strain), Vegasandharana (restraining natural impulses), Kshaya (decreasing Dhathu), and Vishamashana (resisting natural urges). It is a Shosha that Madhyama Rogamarga Vyadhi has manifested. The Tridosha and the Sapta Dhatu are impacted by the emergence of Ekadasha Roopa. The Nidana and the Samprapti are given a lot of attention in the classics of Ayurveda, since they are crucial to comprehending Chikitsa. Chikitsa is Nidana Parivarjana and Samprapti Vighatana; it is nothing. Rajayakshma's knowledge was compiled by exhaustively searching the primary Ayurvedic literature. Rajayakshma is a rare illness, and the disease hierarchy is as described by Sahasajanaya Rajayakshma and Vega Sandarana. Janya Rajayakshma, Kshaya Janya Rajayakshma, and Vishamashana Janya Rajayakshma is one of the four categories involved in Nidana. In modern medicine, Rajyakshma may correlate with pulmonary tuberculosis. Though there is a difference in the pathogenesis of tuberculosis and Rajyakshma, the clinical picture of both is quite similar.

Formulation and evaluation of herbal hair serum-a review

In the mammalian system the hair follicle is known to the most significant organ that determine, appearance, gender distinction, provides intense temperature protection and plays a role in self-defence. The younger generations have begun to suffer extreme hair loss problem due to many reasons. The hair loss is not temporary in most cases. but it results in alopecia. Many people suffering from hair loss is in search of multiple treatments due to extreme anxiety and tension. To improve hair growth and to prevent hair loss, hair root activation is required. Citrus sinensis is used to antidandruff protection hair care. It’s had antibacterial and anti-inflammatory properties. Nigella sativa improves the shine, strength, volume, and texture of hair. Flax seed is full of fatty acids and antioxidants that tend to remove pollutants and dead cells from the scalp. Coconut oil may help to moisturise and seal hair. They can help to prevent dry, flaky scalp and dandruff. This review article focuses on the materials required for the formulation of hair serum and various evaluation tests to evaluate hair serum.

Experimental comparison of a dual-spar floating wind farm with shared mooring against a single floating wind turbine under wave conditions

Shared mooring can potentially be a cost-reduction factor for future floating wind farms. To assess the effect of shared mooring on the response dynamics of floating wind turbines (FWTs), experiments have been conducted for two spar FWTs with a shared mooring configuration and for a single spar FWT with catenary mooring, both at a scale of 1:47. Various regular and irregular wave conditions were tested and only one wave heading was considered. From the test results, the response amplitude operators and response spectra of platform motions and statistics of mooring tensions are compared for the two configurations. In the extreme wave condition, the shared mooring configuration leads to a 40% increase in the platform surge motion compared with the single spar FWT. Still, the absolute offset is within allowable limits prescribed by power cables. The fairlead tensions of the anchor lines are not significantly increased in the shared mooring configurations, but the shared line shows extreme tension peak events that are seldom present in the anchor lines. This study demonstrates the technological promises and challenges of a shared mooring system from an experimental perspective. Results and videos are made available and can be used to validate numerical models.

Manila and their agents in the court: long-distance political communication and imperial configuration in the seventeenth-century Spanish monarchy

ABSTRACTThe first ‘globalization’, which from the sixteenth century united the four parts (or continents) of the world, was first of all accomplished in terms of distance and time. There was extreme tension between the Philippines, the last circle of the Hispanic Empire, and its centre, Madrid. Here, information and instructions took three to five years, round trip. Contemporaries were aware of such tension and the complexities it entailed. For this, the Philippine authorities relied on the so-called procuradores (procurators), a group of deputies entrusted with power of attorney, who travelled across the globe, facing constant dangers, unforeseen difficulties and often long delays. Procuradores travelled a variety of routes, including going directly to Spain (‘La carrera de España’), travelling through the viceroyalty of New Spain and its capital Mexico City or crossing the Indian Ocean. In a global empire like the Spanish Catholic monarchy, authorities had to rely on individuals entrusted with producing and transmitting information, which they had to physically submit in the form of pleas and reports at court. In essence, the monarchs’ decision-making process in the Iberian Peninsula relied on information from the Empire’s local communities. Imperial policy is not therefore developed in one centre or in several centres, but in multilateral exchanges on different scales. This essay highlights three interconnected issues: first, the role of information as resource and crucial asset in the relationship between the King, his agents and his distant subjects; second, the importance of travel and physical presence at the Spanish Court for submitting pleas that, theoretically, could have been sent via letter; finally, the interconnection of religious, political and economic interests in the management of the monarchy’s affairs. The authors conclude with two case studies describing the religious experience of displacement and supplication: the journeys of Diego de Guevara to Fernando Moraga.

The dynamic response of a Spar-type floating wind turbine under freak waves with different properties

In the present work, the dynamic responses of a Spar-type floating offshore wind turbine (SFWT) under freak waves with different properties are simulated and analyzed. The properties of freak wave are represented by changing different decision parameters a1, a2, a3 and a4, corresponding to the ratios of the wave elevations around the freak wave crest (FWC). The improved phase modulation method is adopted to generate the original freak wave (OFW). On the basis, the freak wave elevation is further modulated to increase the decision parameters with different degrees, and the modulated freak waves (MFWs) are obtained. The SFWT motions under the OFW and MFWs are simulated in the time domain. We firstly investigated the influence of freak wave on the SFWT transient dynamic performances, including the surge, heave, pitch motions, the turbine output power and the mooring tensions. Then, the SFWT dynamic response under different MFWs corresponding to the specific factors were analyzed. The results show that the freak wave fluctuation represented by the factor a1 significantly affects the surge, heave, pitch transient motion, output power and extreme mooring tension of the SFWT. The output power of the SFWT decreases less after the FWC with the wave fluctuation increasing. At the same time, the wave fluctuation significantly affects the mooring tension, which greatly increases both near the focus time and the extreme mooring tension time. The height of the previous wave (PW) related to a2 affects the heave motion at the trough after PW impact, which in turn affects the transient heave. a3 represents the height of the next wave (NW) and has little effect on the dynamic performance. The impact height of freak waves represented by a4 has a particularly significant effect on heave. It not only affects the transient motion at the focus time, but also has a significant effect on heave after the freak wave subsides.

Analysis of the upper tail of the short-term extreme tension distribution of mooring line by the peaks-over-threshold method

The consistency of the upper tail of the extreme response distribution plays an important role in the accuracy of the extreme response prediction. Although the peaks-over-threshold method has a high data utilization of the response time series, the consistency of the upper tail of the extreme response distribution was not thoroughly investigated, especially for the inherent randomness of the short-term sea state. This study aims to estimate the upper tail of the short-term extreme tension distribution of the mooring line considering the short-term variability by the peaks-over-threshold method. The consistency of the extreme tension distribution tail is quantified by a relative error compared with the global maximum method, and the theoretical optimal threshold is defined by minimizing the largest relative error among the tail quantiles for different thresholds. Results from a case study for the mooring line of the fish cage indicate that the effect of the random seed is significant for consistency in the prediction of the distribution tail of the short-term extreme tension. And the generalized Pareto distribution model combined with the L-moments method is recommended for the theoretical optimal threshold. These findings provide some useful suggestions for the preliminary design of the mooring line for offshore structures.

FPSO offloading operational safety study by a multi-dimensional reliability method

In contrast to the well-known bivariate statistical approach, which is known to properly anticipate extreme response levels for two-dimensional systems, the research validates a unique structural reliability method that is particularly appropriate for multi-dimensional structural responses. Traditional dependability techniques that deal with time series don't have an edge when it comes to handling high-dimensional systems and cross-correlation between several dimensions. A Floating Production Storage and Offloading Unit (FPSO) is a tanker that can produce, store and transport hydrocarbon products such as oil. The hawser during the offloading process is an important part used during operations, and a thorough prediction of its extreme tension is essential for operational safety. Failure of the offloading process may lead to great environmental harm and economic loss. This study assessed hydrodynamic forces acting on FPSO vessels in real-world environmental conditions based on the potential flow theory. A brief discussion of the experimental verification of numerical results is also included. The outlined method may be effectively employed during the vessel design phase for choosing the best vessel specifications to reduce potential FPSO hawser tension. The ability to foresee high hawser strains during the FPSO offloading operation is essential for reliability and safety.

Dynamic Mooring Field Experiment and Design of a Wave Energy Converter Platform Test System

Abstract This study evaluated a multi-catenary spread mooring system design of a mobile ocean test berth for wave energy converters (WECs), the Ocean Sentinel (OS) instrumentation buoy, through dynamic simulation, numerical analysis, and comparison with measured field motion data of the OS off the OR coast. First, the accuracy of the numerical employed model based on a fully-coupled method of the OS and its mooring lines was validated by comparing predicted mooring tensions to the field measurements. Then, the anchor movability, fatigue damage, and extreme mooring tension of the OS mooring system were analyzed to assess survivability. Field test results show that the numerical model provided accurate predictions of mooring tensions even under environmental conditions of strong wind, current, and waves. Factors affecting the accuracy are discussed. One mooring anchor was shown to have moved significantly during the ocean field test. Mooring fatigue damage was calculated for different levels of sea states. Design strengths of the mooring lines were calculated and analyzed.

Offloading operation bivariate extreme response statistics for FPSO vessel

The Floating Production Storage and Offloading unit (FPSO) is an offshore unit producing and storing crude oil prior to tanker transport. An important design concern is an accurate prediction of risky dynamic hawser tensions during FPSO offloading operations. Bivariate extreme hawser tension contours are important for selecting proper design values. This paper employed the AQWA hydrodynamic software to analyze vessel hydrodynamic wave loads dynamic response, acting on FPSO vessels under realistic sea state conditions. This paper presents an efficient method for estimating FPSO bivariate response statistics based on numerical simulations validated by various experiments. The bivariate Average Conditional Exceedance Rate (ACER2D) method offers an accurate bivariate extreme value probability distribution and return period contours estimation, utilizing available data efficiently. The two-dimensional probability contours, corresponding to low probability return periods, are easily obtained by the ACER2D method. The performance of the presented method has shown that the ACER2D method provides an efficient and accurate prediction of extreme return period contours. The suggested approach may be used for FPSO vessel design, minimizing potential FPSO hawser damage. Bivariate contours yield bivariate design points, as opposed to a pair of uncoupled univariate design points with the same return period as currently adopted in the industry.

Mooring design of offshore aquaculture platform and its dynamic performance

Floating offshore aquaculture platforms, or fish cages, are increasingly becoming popular in recent years in order to meet the world's growing demand for seafood products. These platforms are typically of frame type structures consisting of slender beams, buoyancy tanks and netting surrounding the frame. This unique structural feature leads to complex hydrodynamic properties, and consequently the dynamic performance assessment and mooring system design become more challenging. This paper reports numerical and experimental studies on the mooring system performance of an aquaculture platform under different environmental conditions, including wave and current, in floating operational condition and bottom-sitting survival condition. A method based on the conventional potential flow theory and Morison equation is proposed for the numerical assessment of the hydrodynamic loads on the aquaculture platforms including its frame and net. A mooring system for the position keeping of the platform was designed and its performance analyzed in time domain. A hybrid mooring composition consisting of steel chain and fiber rope in each line was adopted to increase the axial elasticity so that the extreme tension could be reduced. Wave basin model tests were also conducted to obtain the platform motions and mooring tensions, and the comparisons were made between the measured data and the numerical predictions. The results of this study show that the proposed numerical method could be applied to the prediction of the performance of the aquaculture platforms and the mooring system with a reasonable accuracy.

Multibody dynamic modeling and analysis of cable-driven snake robot considering clearance and friction based on ALE method

Cable-driven snake robot (CDSR) is a kind of slender manipulator with excellent maneuverability, which is widely applied in complex spaces. However, several nonlinear factors, such as clearance and contact between cable and hole, can lead to uncertainty of motion and danger of cable under extreme tension, which can affect the performance of the CDSR. In this paper, a multibody dynamic model of CDSR considering both friction and clearance is proposed. The arbitrary Lagrangian Eulerian (ALE) method is used to model the driving cable. The ALE node is constrained in the hole plane and the contact forces are evaluated using nonlinear impact function to describe the cable-hole interaction. Moreover, contact force regularization is adopted to facilitate convergence. A numerical test demonstrates that the clearance model can describe the contact behavior of cable and hole accurately. Moreover, the effect of clearance sizes on CDSR are studied. It shows that the manipulation precision can be dramatically reduced due to the increase of clearance size. Finally, the driving cable slack phenomenon induced by the coupling effect of clearance and friction is revealed. The presented work is expected to be applied for the compensation of feedback control and tension optimization design of CDSR.

Цветовая гамма в «Бриллиантовой руке» Леонида Гайдая

The main motives of the colour composition of the film The Diamond Arm are discussed in the article. The variations of the blue and the semantics of the cold range of colours associated with the world of the main character, Senya Gorbunkov, his unconscious and his fears are analyzed. The development of the motif of pale, light colour shades that appear at moments of dramatic uncertainty, extreme tension and preparation for the upcoming climaxes is traced. Silver and metallic tones are assigned to the secret world of smugglers. The author notes that throughout the film a certain dialogue of cold colours and warm ochre-scarlet colour shades unfolds. At first separate “warm” details inside blue landscapes and “pale” interiors appear, then their spatial presence and energy are enhanced. Ochre and red shades accompany the phenomenon of “dark forces”, whether it is a Soviet house manager Varvara Sergeevna or smugglers. The main red scene of the film is the scene of failed seduction of an honest hero. Thus, the main colour of the revolution is recoded into the colour of eroticism, deception, violence, unfortune. The white colour in the film plays the part of a trickster, revealing ambivalent properties and constantly showing that the whole reality and the person in it are not like what they seem. The colour concept forms a kind of visual melody of the film, adding much more semantic overtones.