Journal articles on the topic 'Speed of Adjustment (SOA)'
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Ataünal, Levent, and Aslı Aybars. "Testing Target-Adjustment and Pecking Order Models of Capital Structure and Estimating Speed of Adjustment." International Journal of Corporate Finance and Accounting 4, no. 1 (January 2017): 1–15. http://dx.doi.org/10.4018/ijcfa.2017010101.
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This article examines the explanation power of the pecking order and target adjustment models on 148 Borsa Istanbul (BIST) firms' capital structure over the period of 2005 to 2015. The article also estimates the speed of adjustment (SOA) to the targeted leverage level. Although a firm's capital structure is jointly determined by both theories, target adjustment model appear to have relatively higher power in explaining capital structures of BIST firms. Estimates of the adjustment speeds suggests that firms move toward their target debt ratios at a fast pace. Adjustment speeds estimated with market leverage were significantly higher (44% - 83%). Share price volatility was found to have a rather short-term impact on market leverage. Firms rapidly revert back to their targets and offset these fluctuations within few years. Adjustment speed estimates vary with the estimation method. System generalized methods of moment estimator (GMM-SYS) provided the slowest SOA estimation whereas firm-fixed effects estimators imparted the fastest adjustment speed.
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Outla, Adil, and Moustapha Hamzaoui. "Speed of adjustment over entry and exit dynamics." International Journal of Organizational Analysis 26, no. 3 (July 9, 2018): 470–89. http://dx.doi.org/10.1108/ijoa-07-2017-1193.
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Purpose This paper aims to provide a theoretical conception that establishes growth rate dynamics for co-operatives and studies Moroccan co-operatives’ start-ups and closures, by analyzing the co-operatives’ growth rate speed of adjustment (SOA). Design/methodology/approach This paper documents the basic patterns of entry and exit flow for agricultural, artisanal, housing and fishery co-operatives; highlights, with econometric tests, whether co-operatives’ growth rate is mean reverting or a unit root random walk; and estimates the growth rate adjustment speed, using a quadratic interval reverting model to capture both the upward and downward speeds of adjustment. Findings The empirical results indicate that co-operatives’ growth rate is significantly mean reverting for all sectors. Also, it concludes that the upward and downward adjustment speeds are significantly different within and between sectors, with negative indicator for artisanal co-operatives. The paper discusses these results, which are of interest to academics and policymakers. Research limitations/implications The study does not investigate the causes of the growth rate SOA. Further, in-depth work with the results of this study would help scholars and policymakers to get close to the accurate research questions that characterize the mean reverting and affects the adjustment processes for Moroccan co-operatives. Practical implications The suggested model – with upward and downward adjustment speeds– could be valuable for policymakers’ strategies on co-operatives’ emergence. Social implications The paper moves policymakers closer to social work and socio-economic trends to explain the empirical regularities of co-operatives’ dynamics. The model could be of value to avoid a volatile rate of entries and exits, to ensure continuity, to avoid fast failure of co-operative memberships and then to achieve the social inclusion. Originality/value The paper provides empirical evidence and results for co-operatives’ start-ups and closures adjustment speed and determines the conditions in which government policy must be clarified and specified. To the best of the authors’ knowledge, this paper is the first empirical analysis for the co-operatives’ SOA over entry and exit dynamics.
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Kim, Mi-Ok, Sangkwon Cha, and Hyung-Rok Jung. "Cash Holding Policy and Competitive Strategy." Korean Accounting Information Association 40, no. 3 (September 30, 2022): 1–26. http://dx.doi.org/10.29189/kaiaair.40.3.1.
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[Purpose] We investigated the relation between competitive strategy and cash holding process, focusing on the level of cash holdings, the speed of adjustment in cash, and the direction of SOA.
[Methodology] From 2002 to 2017, empirical analysis was conducted targeting the domestic capital market. Here, the research methodology of Bentley et al.(2013) was used for the competitive strategy, and the method of Opler et al.(1999) was used for the cash holding policy.
[Findings] we find that competitive strategy is associated with cash holding process including cash holding levels, speed of adjustment in cash, and the direction of SOA. Firms pursuing differentiation strategy is negatively associated with cash holding level, which indicates the strategy partially affect the cash holding level. Secondly, we find that average firms’ SOA is 37.7% and the SOA of firms with competitive is 43.8.%. Lastly, we find that asymmetry speed of adjustment in cash depending on the direction of deviation from the target as we expected.
[Implications] This study contributes to expanding the perception of the field of management accounting research in that it empirically analyzes the strategy execution premium as the relationship between the competitive strategy measurable by corporate financial information and the cash holding policy, which is one of the operational processes.
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Yin, Qie Ellie, and Jay R. Ritter. "The Speed of Adjustment to the Target Market Value Leverage Is Slower Than You Think." Journal of Financial and Quantitative Analysis 55, no. 6 (August 6, 2019): 1946–77. http://dx.doi.org/10.1017/s0022109019000516.
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In the capital structure literature, speed of adjustment (SOA) estimates are similar whether book or market leverage is used. This robustness is suspect, given the survey evidence that firms target their book leverage and the empirical evidence that they don’t issue securities to offset market leverage changes caused by stock price changes. We show that existing market SOA estimates are substantially upward biased due to the passive influence of stock price fluctuations. Controlling for this bias, the SOA estimate is 16% for book leverage and 10% for market leverage, implying that the trade-off theory is less important than previously thought.
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Imas Iyoha, Agbonrha-Oghoye, Godwin Ohiokha, David Umoru, Sadiq Oshoke Akhor, and Grace Abohiri Igele. "Target capital structure for managerial decision making: Dynamics and determinants." Investment Management and Financial Innovations 19, no. 3 (September 23, 2022): 322–34. http://dx.doi.org/10.21511/imfi.19(3).2022.27.
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The study examines the dynamics and determinants of target capital structures among manufacturing firms listed on the Nigeria Stock Exchange during the period from 2012 to 2021. The study is motivated by the disparity in the Speed of Adjustment (SOA) to target leverage, which is influenced by firm-specific attributes largely dependent on macroeconomic indices. Therefore, understanding the determinants of SOA to target leverage is germane because no two macro-economic environments are the same. A longitudinal research design is used with a population of 75 manufacturing firms. The sample consists of 42 firms, drawn using a simple random technique. Secondary data is sourced from the annual report. Generalized Method of Moments is the estimation technique. The result shows that manufacturing firms adjust to a target capital structure with a high speed of 72%. This confirms the application of dynamic trade-off theory among listed manufacturing firms in Nigeria. Profitability, firm size, and asset tangibility are significant determinants of SOA to a target capital structure, confirming pecking order, agency, and static trade-off theories, respectively. Tax shelter and growth were not significant determinants. The study concludes that there is evidence of dynamic adjustment to the optimal capital structure of listed manufacturing firms in Nigeria. Governments and policymakers in firms should make effective policies that aid speedy access to long-term funds by these firms to increase their SOA to target capital structure.
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Rani, Neelam, Surendra S. Yadav, and Naliniprava Tripathy. "Capital structure dynamics of Indian corporates." Journal of Advances in Management Research 17, no. 2 (November 11, 2019): 212–25. http://dx.doi.org/10.1108/jamr-12-2017-0125.
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Purpose The purpose of this paper is to examine the capital structure determinants and speed of adjustment (SOA) toward the target capital structure of firms. Design/methodology/approach The study has used the generalized method of moments (GMM) model and two-stage least squares (TSLS) to the panel data of 3,310 Indian firms, from January 2000 to March 2018, to determine the adjustment speed toward target capital structure. Further, the study employed a fully modified ordinary least square technique to shed light on the dynamic nature of the adjustment process. Findings The results of the GMM estimations indicate that Indian firms are adjusting their capital structure toward the target rate of 10.38 percent per year. Similarly, the findings of TSLS estimate specify a SOA of 15.49 percent per year. The low adjustment speed suggests the prevalence of higher adjustment costs of Indian firms. Research limitations/implications Future research can be undertaken by including certain macroeconomic factors such as GDP, inflation and the interest rate, which also affect the SOA since firms are pretentious by market conditions while designing capital structure for firms. Practical implications In the current financial and regulatory set-up when there are frequent perturbations in the capital market, the study will be valuable for regulators, firms and academicians. The work would enable the concerned stakeholders to manage their scare resources and capital effectively by a better way to make informed decisions. It will facilitate managers of young companies to identify and regulate the factors that are more pertinent for them to make flexible financial decisions concerning the capital structure. Originality/value The study amplifies on previous studies and provides new insights on the speed of the adjustment process of Indian firms, helping to modify and refine their capital structures toward the optimum capital structure. This will not only enhance the financial flexibility in the capital structure of Indian corporates but also be of great value to the policymakers and other stakeholders.
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Mirota, Fryderyk. "The use of meta-analysis in research on corporate cash holdings speed of adjustment." Wiadomości Statystyczne. The Polish Statistician 64, no. 5 (May 28, 2019): 48–73. http://dx.doi.org/10.5604/01.3001.0013.8505.
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In empirical research significant diversity of corporate cash holdings speed of adjustment (SOA) estimates can be observed. It is possible that some of the results are affected by publication selection bias. Articles whose results are clearly in line with economic theories may be preferred by authors and reviewers and, consequently, conclusions from this area can be published more frequently. The aim of this article is to verify whether there is a publication selection bias with respect to studies related to corporate cash holdings adjustments and to investigate the sources of heterogeneity in cash holdings SOA estimates. The statistical method used in the study was meta-analysis, which allows a combined analysis of the results from independent research. Meta-analysis enables to verify the occurrence of the publication selection bias and to explain the heterogeneity of the results presented in articles. The study was based on data collected asa result of a review of the literature published between 2003 and 2017. On the basis of information on 402 estimates from 58 different studies it has been shown that the publication selection bias does not occur. The Bayesian Model Averaging was used for modelling. It was identified that the characteristics associated with the data set used in the study, model specification and the estimation method significantly affect the hetero-geneity of corporate cash holdings SOA estimates. This diversity is determined, among others, by the choice of estimation method, length of the period covered by the analysis and characteristics of the market environment of the concerned entities.
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Karpates, Akbar Aldino, and Viverita Viverita. "Speed of Adjustment and Leverage Deviation - Cost of Equity Nexus: Evidence from Emerging Markets and Crisis." GLOBAL BUSINESS FINANCE REVIEW 27, no. 6 (December 31, 2022): 1–15. http://dx.doi.org/10.17549/gbfr.2022.27.6.1.
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Purpose: This study investigates the impact of leverage deviation on the cost of equity under the specifically mentioned condition in ASEAN-5 considering the global financial crisis and the sensitivity of the cost of equity on leverage deviation.
Design/methodology/approach: This study employs the Generalized Least Square (GLS) model and the dynamic panel estimation based on the two-step difference GMM to analyze the data.
Findings: The regression analysis found deviated from the target leverage impact unfavorably on the firm's cost of equity. The results also show that the more sensitive the cost of equity is to the leverage deviation from the target, the faster the adjustment. However, firms will adjust their capital structure for a lower cost during the crisis. Additionally, it shows a compelling behavior in the relation between the sensitivity of the cost of equity to leverage deviation on the leverage speed of adjustments.
Research limitations/implications: The higher sensitivity of the cost of equity is to the leverage deviation from the target, the faster the adjustment. It implies that the disregard of heterogeneity in SOA will mislead the adjustment period to the target leverage.
Originality/value: Using manually collected data, this study provides empirical evidence on the importance of leverage deviation and the sensitivity of the cost of equity and the speed of adjustment to the target debt level to analyze capital structure decision in an enormous leverage usage in ASEAN. Second, this paper presents new evidence of the effect both in normal economic conditions and crisis periods, which is rarely examined in the ASEAN emerging market.
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Warmana, G. Oka, I. Ketut Rahyuda, Ida Bagus Anom Purbawangsa, and Ni Luh Gede Sri Artini. "Investigating Capital Structure Speed of Adjustment (SOA) of Indonesian Companies for Corporate Value." Global Journal of Flexible Systems Management 21, no. 3 (May 24, 2020): 215–31. http://dx.doi.org/10.1007/s40171-020-00235-9.
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Widodo, Puwanto. "DETERMINAN STRUKTUR MODAL DINAMIS : STUDI EMPIRIS DI BURSA EFEK INDONESIA." Inovator 8, no. 2 (September 1, 2019): 1. http://dx.doi.org/10.32832/inovator.v8i1.2506.
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<p><em>Research on dynamic capital structure basically wants to know the existence of targeted leverage as hypothesized by Trade-Off Theory and Speed off Adjustment (SOA). Later developments, the magnitude of the speed of adjustment can be used as a determinant of capital structure theory used by the company. Another problem in dynamic capital structure research is the use of analytical tools that can produce biased and inconsistent predictors. To overcome this, this study uses dynamic panel data with the General Method of Moment (GMM) approach. Samples were taken from non-financial companies listed on the Indonesia Stock Exchange in the 2009-2015 period. The results of the inference show the existence of Dynamic Trade Off Theory and the variables of company characteristics and macroeconomic significantly influence the dynamic capital structure. In addition, it is known that there is an influence of company size and growth Opportunity on the speed of adjustment. Another finding is that he knows that managing profitability follows and Pecking Order Theory.Keyword</em><em>s</em><em> : capital structure, static model, dynamic model</em></p>
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Outla, Adil, and Moustapha Hamzaoui. "Equilibrium and the Adjustment Process in the Number and Scope of Co-operatives in Morocco." Organizations and Markets in Emerging Economies 11, no. 1 (May 29, 2020): 128–51. http://dx.doi.org/10.15388/omee.2020.11.27.
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The paper discusses the government policy that encourages the emergence of co-operatives and analyzes the co-operatives in light of their growth in number. It establishes a static equilibrium and highlights the co-operatives’ adjustment process (dynamic equilibrium).The methodology/approach consists of the development of a theoretical model, using the Nash equilibrium for the co-operative market, and the determination of a static equilibrium. It presents the data which includes variable measurements for the adjustment process for agricultural, artisanal, and fishery co-operatives in order to analyze the stochastic process of entry-and-exit flow of co-operatives. Accordingly, the paper estimates the co-operatives’ growth index speed of adjustment (SOA) as a function of the mean-reversion Ornstein–Uhlenbeck (OU) process.The theoretical results indicate that co-operatives’ earnings depend on the number of co-operatives, market-demand, and the capacity constraint. They also show that the margin for new entrants is a dynamic gap that especially depends on demand, capacity constraint and the profits. The empirical results indicate that co-operatives growth-index process is significantly mean reverting for all sectors, and the speed of adjustment for artisanal co-operatives is significantly higher than for those in agriculture and the fisheries.
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Buvanendra, S., P. Sridharan, and S. Thiyagarajan. "Determinants of Speed of Adjustment (SOA) toward Optimum Capital Structure: Evidence from Listed Firms in Sri Lanka." Journal of Asia-Pacific Business 19, no. 2 (April 2, 2018): 46–71. http://dx.doi.org/10.1080/10599231.2018.1453742.
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Bates, Thomas W., Ching-Hung Chang, and Jianxin Daniel Chi. "Why Has the Value of Cash Increased Over Time?" Journal of Financial and Quantitative Analysis 53, no. 2 (March 19, 2018): 749–87. http://dx.doi.org/10.1017/s002210901700117x.
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The value of corporate cash holdings has increased significantly in recent decades. On average, $1 of cash is valued at $0.61 in the 1980s, $1.04 in the 1990s, and $1.12 in the 2000s. This increase is predominantly driven by the investment opportunity set and cash-flow volatility, as well as secular trends in product market competition, credit market risk, and within-firm diversification. We document a secular decrease in the speed of adjustment (SOA) in cash holdings, particularly for financially constrained firms with cash deficits, suggesting that capital market frictions can account for the trend in the value of cash holdings.
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Abdeljawad, Islam, and Fauzias Mat Nor. "The capital structure dynamics of Malaysian firms: timing behavior vs adjustment toward the target." International Journal of Managerial Finance 13, no. 3 (June 5, 2017): 226–45. http://dx.doi.org/10.1108/ijmf-09-2015-0170.
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Purpose The purpose of this paper is to investigate how the timing behavior and the adjustment toward the target of capital structure interact with each other in the capital structure decisions. Past literature finds that both timing and targeting are significant in determining the leverage ratio which is inconsistent with any standalone framework. This study argues that the preference of the firm for timing behavior or targeting behavior depends on the cost of deviation from the target. Since the cost of deviation from the target is likely to be asymmetric between overleveraged and underleveraged firms, the direction of the deviation from the target leverage is expected to alter the preference toward timing or targeting in the capital structure decision. Design/methodology/approach This study used the GMM system estimators with the Malaysian data for the period of 1992-2009 to fit a standard partial adjustment model and to estimate the speed of adjustment (SOA) of capital structure. Findings This study finds that Malaysian firms, on average, adjust their leverage at a slow speed of 12.7 percent annually and this rate increased to 14.2 percent when the timing variable is accounted for. Moreover, the SOA is found to be significantly higher and the timing role is lower for overleveraged firms compared with underleveraged firms. Overleveraged firms seem to find less flexibility to time the market as more pressure is exerted on them to return to the target regardless the timing opportunities because of the higher costs of deviation from the target leverage. Underleveraged firms place lower priority to rebalance toward the target compared with overleveraged firms as the costs of being underleveraged are lower and hence, these firms have more flexibility to time the market. Research limitations/implications The findings of this study support that firms consider both targeting and timing in their financing decisions. No standalone theory can interpret the full spectrum of empirical results. The empirical work is based on partial adjustment model of leverage; however, this model has been criticized by inability to distinguish between active adjustment behavior and mechanical mean reversion. This is an avenue for future research. Originality/value This study investigates if targeting and timing behaviors are mutually exclusive as theoretically expected or they can coexist. A theoretical explanation and an empirical investigation support the conclusion that firms consider both targeting and timing in their financing decisions. This study provides evidence from Malaysian firms that are characterized by concentrated ownership structure and separation of cash flow rights and control rights of the firm due to pyramid ownership structure. Therefore, it provides evidence on how environmental characteristics may affect the capital structure determinants of the firm.
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Djath, Bughsin’, Johannes Schulz-Stellenfleth, and Beatriz Cañadillas. "Study of Coastal Effects Relevant for Offshore Wind Energy Using Spaceborne Synthetic Aperture Radar (SAR)." Remote Sensing 14, no. 7 (March 31, 2022): 1688. http://dx.doi.org/10.3390/rs14071688.
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Coastal wind speed gradients relevant for offshore windfarming are analysed based on synthetic aperture radar (SAR) data. The study concentrates on situations with offshore wind directions in the German Bight using SAR scenes from the European satellites Sentinel-1A and Sentinel-1B. High resolution wind fields at 10 m height are derived from the satellite data set and respective horizontal wind speed gradients are investigated up to about 170 km offshore. The wind speed gradients are classified according to their general shape with about 60% of the cases showing an overall increase of wind speeds with growing distance from the coast. About half of the remaining cases show an overall wind speed decrease and the other half a decrease with a subsequent increase at larger distances from the coast. An empirical model is fitted to the horizontal wind speed gradients, which has three main parameters, namely, the wind speed over land, the equilibrium wind speed over sea far offshore, and a characteristic adjustment length scale. For the cases with overall wind speed increase, a mean absolute difference of about 2.6 m/s is found between wind speeds over land and wind speeds far offshore. The mean normalised wind speed increase with respect to the land conditions is estimated as 40%. In terms of wind power density at 10 m height this corresponds to an absolute average growth by 0.3 kW/m2 and a normalised increase by 160%. The distance over which the wind speed grows to 95% of the maximum wind speed shows large variations with maximum above 170 km and a mean of 67 km. The impact of the atmospheric boundary layer stability on horizontal wind speed gradients is investigated using additional information on air and sea temperature differences. The absolute SAR-derived wind speed increase offshore is usually higher in unstable situations and the respective adjustment distance is shorter. Furthermore, we have found atypical cases with a wind speed decrease offshore to be often connected to stable atmospheric conditions. A particular low-level jet (LLJ) situation is analysed in more detail using vertical wind speed profiles from a wind LIDAR system.
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Widodo, Purwanto, and Juardi Juardi. "Determinan Leverage Optimal Di Bursa Efek Indonesia." Majalah Ilmiah Bijak 17, no. 1 (April 1, 2020): 94–107. http://dx.doi.org/10.31334/bijak.v17i1.829.
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Research on capital structure, recently characterized by the use of dynamic capital structure. The use of dynamic capital structure basically wants to know the existence of optimal leverage as hypothesized by Trade-Off Theory and Speed off Adjustment (SOA) to optimal leverage. This research tries to overcome this problem, by using dynamic panel data by using company characteristics and macroeconomic factors. The use of General Method of Moment (GMM) to overcome the problem of econometrics due to the use of dynamic models. Samples taken from manufacturing companies listing on the Indonesia Stock Exchange 2009-2015. The inference model and the determinant behavior of capital structure can be explained by Trade-Off Theory and Pecking Order Theory. The variable characteristics of the company and macro economy are significant and are marked according to the hypothesis. The findings of this study include: the influence of profitability, size, tangibility, growth opportunity and business risk. In addition, on average companies in Indonesia can increase their debt to utilize tax shields
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Algamluoli, Ammar Falah, and Nizar Hadi Abbas. "Speed controller design for three-phase induction motor based on dynamic adjustment grasshopper optimization algorithm." International Journal of Electrical and Computer Engineering (IJECE) 11, no. 2 (April 1, 2021): 1143. http://dx.doi.org/10.11591/ijece.v11i2.pp1143-1157.
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Three-phase induction motor (TIM) is widely used in industrial application like paper mills, water treatment and sewage plants in the urban area. In these applications, the speed of TIM is very important that should be not varying with applied load torque. In this study, direct on line (DOL) motor starting without controller is modelled to evaluate the motor response when connected directly to main supply. Conventional PI controller for stator direct current and stator quadrature current of induction motor are designed as an inner loop controller as well as a second conventional PI controller is designed in the outer loop for controlling the TIM speed. Proposed combined PI-lead (CPIL) controllers for inner and outer loops are designed to improve the overall performance of the TIM as compared with the conventional controller. In this paper, dynamic adjustment grasshopper optimization algorithm (DAGOA) is proposed for tuning the proposed controller of the system. Numerical results based on well-selected test function demonstrate that DAGOA has a better performance in terms of speed of convergence, solution accuracy and reliability than SGOA. The study results revealed that the currents and speed of TIM system using CPIL-DAGOA are faster than system using conventional PI and CPIL controllers tuned by SGOA. Moreover, the speed controller of TIM system with CPIL controlling scheme based on DAGOA reached the steady state faster than others when applied load torque.
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Chen, Song, Kailin Jian, and Xianghe Peng. "Cylindrical Magnetorheological Fluid Variable Transmission Controlled by Shape-Memory Alloy." Science and Technology of Nuclear Installations 2012 (2012): 1–6. http://dx.doi.org/10.1155/2012/856082.
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Centrifugal fan is an important component of a ventilation system in a nuclear power plant. In this paper, we proposed a magnetorheological speed-adjustment system controlled by shape-memory alloy for centrifugal fan. A theoretical analysis of the effect of the applied magnetic field on the viscoplastic flow between two cylinders in the speed-adjustment system is presented. The expressions for the velocity in viscoplastic flow and the torque transmitted by MR fluids are derived. A sliding mode SMA switch is proposed to modify the magnetic field acting on working gap under thermal effect. The results indicate that with the increases of applied magnetic field, the torque transmitted by MR fluid goes up rapidly.
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Sun, Jianxiang, Suping Zhang, Christopher J. Nowotarski, and Yuxi Jiang. "Atmospheric Responses to Mesoscale Oceanic Eddies in the Winter and Summer North Pacific Subtropical Countercurrent Region." Atmosphere 11, no. 8 (August 3, 2020): 816. http://dx.doi.org/10.3390/atmos11080816.
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In the winter and summer North Pacific Subtropical Countercurrent region, the atmospheric responses to 20,000+ mesoscale oceanic eddies (MOEs) are examined using satellite and reanalysis data from 1999 to 2013. The composite results indicate that surface wind speed, cloud, and precipitation anomalies are positively correlated with sea surface temperature anomalies in both seasons. The surface wind speed anomalies and convective precipitation anomalies show dipolar structures centering on MOEs in winter and on unipolar structures in summer. In both seasons, the vertical mixing mechanism plays an obvious role in the atmospheric responses to MOEs. In addition, the distributions of sea level pressure anomalies in winter reflects the effects of the pressure adjustment mechanism. Due to the seasonal variations in the atmospheric background state and the MOEs, the sensitivities of surface wind speeds, clouds, and precipitation responses to MOEs in summer are over 30% higher than those in winter.
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Chen, Guanxu, Yang Liu, Yanxiong Liu, Ziwen Tian, Jingnan Liu, and Menghao Li. "Adjustment of Transceiver Lever Arm Offset and Sound Speed Bias for GNSS-Acoustic Positioning." Remote Sensing 11, no. 13 (July 5, 2019): 1606. http://dx.doi.org/10.3390/rs11131606.
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Global Navigation Satellite System––Acoustic (GNSS-A) positioning is the main technique for seafloor geodetic positioning. A transceiver lever arm offset and sound velocity bias in seawater are the main systematic errors of the GNSS-A positioning technique. Based on data from a sea trial in shallow water, this paper studies the functional model of GNSS-A positioning. The impact of the two systematic errors on seafloor positioning is analysed and corresponding processing methods are proposed. The results show that the offset in the lever arm measurement should be parameterised in the observation equation. Given the high correlation between the vertical lever arm offset and the vertical coordinate of the seafloor station, a sample search method was introduced to fix the vertical offset correction. If the calibration of the sound velocity profiler cannot be ensured, the correction parameter of the sound velocity bias should be solved. According to the refined functional model and corrections, the position of a seafloor station in shallow water can be determined with a precision of better than 1 cm.
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Halliwell, G. R., S. Gopalakrishnan, F. Marks, and D. Willey. "Idealized Study of Ocean Impacts on Tropical Cyclone Intensity Forecasts." Monthly Weather Review 143, no. 4 (March 31, 2015): 1142–65. http://dx.doi.org/10.1175/mwr-d-14-00022.1.
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Abstract Idealized coupled tropical cyclone (TC) simulations are conducted to isolate ocean impacts on intensity forecasts. A one-dimensional ocean model is embedded into the Hurricane Weather Research and Forecasting (HWRF) mesoscale atmospheric forecast model. By inserting an initial vortex into a horizontally uniform atmosphere above a horizontally uniform ocean, the SST cooling rate becomes the dominant large-scale process controlling intensity evolution. Westward storm translation is introduced by bodily advecting ocean fields toward the east. The ocean model produces a realistic cold wake structure allowing the sensitivity of quasi-equilibrium intensity to storm (translation speed, size) and ocean (heat potential) parameters to be quantified. The atmosphere provides feedback through adjustments in 10-m temperature and humidity that reduce SST cooling impact on quasi-equilibrium intensity by up to 40%. When storms encounter an oceanic region with different heat potential, enthalpy flux adjustment is governed primarily by changes in air–sea temperature and humidity differences that respond within 2–4 h in the inner-core region, and secondarily by wind speed changes occurring over a time interval up to 18 h after the transition. Atmospheric feedback always acts to limit the change in enthalpy flux and intensity through adjustments in 10-m temperature and humidity. Intensity change is asymmetric, with a substantially smaller increase for storms encountering larger heat potential compared to the decrease for storms encountering smaller potential. The smaller increase results initially from the smaller wind speed present at the transition time plus stronger limiting atmospheric feedback. The smaller wind speed increase resulting from these two factors further enhances the asymmetry.
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Choi, Andrew, Hyeonseok Han, and Dong Sung Kim. "A programmable powerful and ultra-fast water-driven soft actuator inspired by the mutable collagenous tissue of the sea cucumber." Journal of Materials Chemistry A 9, no. 29 (2021): 15937–47. http://dx.doi.org/10.1039/d1ta02566j.
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Composition/dimensional adjustment of a bulk PNIPAAm-based water-driven soft actuator tuned actuation force/speed in wide ranges at maximum of 2 N and 3 s−1, respectively, demonstrating immediate potentials in soft robotics and biomedical appliance.
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Mrzygłód, Urszula, Sabina Nowak, Magdalena Mosionek-Schweda, and Jakub M. Kwiatkowski. "What drives the dividend decisions in BRICS countries?" Oeconomia Copernicana 12, no. 3 (September 27, 2021): 593–629. http://dx.doi.org/10.24136/oc.2021.020.
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Research background: We examine the dividend payout policies across companies listed on the main stock exchanges in Brazil, Russia, India, China, and South Africa (BRICS). Unlike the highly developed capital markets, the literature regarding dividend policy on BRICS? stock exchanges is scarce.
Purpose of the article: The purpose of this paper is threefold: verification of the existence of dividend smoothing pattern; selection of the significant drivers that affect both dividend levels and dividend smoothing; examination of differences between dividend policy of cross- and single-listed companies.
Methods: Based on a dataset of 564 companies that paid dividends for at least 11 consecutive years in the period of 1995?2015, we apply a GMM two-step estimator to assess the speed of dividend adjustment (SOA) coefficient. Further we employ the linear panel regression to indicate the individual and market determinants of the dividend levels and SOAs. In the latter case, we base on time series of the SOAs obtained from the rolling estimation technique. Finally, we conduct separate estimations for cross-listed companies.
Findings & value added: We confirm a moderate level of dividend smoothing within BRICS countries. Among the firm-level characteristics affecting the SOA the most important are: ownership dispersion, age and size of a firm, retained earnings, leverage, long term debt, asset tangibility, liquidity risk ratio, and issuing the depositary receipts (DR). Two relevant market factors are found: market capitalisation and turnover in relation to GDP. Similar characteristics have a significant impact on dividends? levels in the entire sample, whereas in the subsample of cross-listed companies fewer variables are significant. Our paper is the first comprehensive attempt to investigate the dividend policy and determinants of dividend smoothing among BRICS countries.
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Magerakis, Efstathios, and Dimitris Tzelepis. "The impact of business strategy on corporate cash policy." Journal of Applied Accounting Research 21, no. 4 (June 23, 2020): 677–99. http://dx.doi.org/10.1108/jaar-05-2019-0077.
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PurposeThe purpose of this study is to explore the association between cash holdings and business strategy for nonfinancial and nonutility US firms over the period from 1970 to 2016.Design/methodology/approachThe authors have used Miles and Snow's (1978, 2003) theoretical background and followed Bentley et al. (2013) to construct a strategy index. Thus, the authors have distinguished two extreme corporate strategies, prospectors and defenders, based on a firm's resource allocation and investment behavior patterns. Following the methodology of Bates et al. (2009), the authors have used the multiple regression analysis to explore the relationship between business strategy and corporate cash holdings.FindingsThe empirical results show that business strategy is positively related to cash holdings. Prospectors are more likely to hold higher cash levels than defenders. Furthermore, the authors have found that cash holding's speed of adjustment (SOA) is slower for prospectors than for defenders, suggesting that business strategy influences cash holding's trend. Interestingly, the results show that the market value of cash increases significantly only for the firms that pursue a defender strategy.Research limitations/implicationsThe results of this work have valuable implications for researchers, by unveiling the relationship between corporate strategy and firm's cash holdings. This study, however, is limited to a sample of US firms; empirical evidence based on international samples of firms would add value to the current literature.Practical implicationsThe findings could be useful to financial managers and investment strategists, who seek to maximize firm value through the adoption of an effective liquidity policy. What is more, this study provides support for the view that strategic choice and optimal cash management are of great importance for firms' market value.Originality/valueThis study enriches the knowledge of business strategy's impact on financing policy of firms and contributes to the empirical literature of cash holdings' determinants. In addition, it complements previous studies on US firms by documenting the effect of business strategy on the SOA in cash holdings and firm value.
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Gorb, Sergii, Maksym Levinskyi, and Mykola Budurov. "Sensitivity Optimisation of a Main Marine Diesel Engine Electronic Speed Governor." Scientific Horizons 24, no. 11 (February 23, 2022): 9–19. http://dx.doi.org/10.48077/scihor.24(11).2021.9-19.
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Electronic speed governors have become widespread on marine diesel engines. In comparison with hydromechanical ones, they have an additional setting parameter – input signal sensitivity. This parameter allows changing the response of governors to high-frequency disturbances. In camshaft diesel engines, such disturbances are generated when the cams run over fuels pump push rods, while in ME (MAN Energy Solutions) or RT-flex (Wärtsilä) engines they result from the use of inductive sensors with a serrated tape on the diesel shaft for speed measurement. If the engine is used as a main engine on vessels, the governor’s sensitivity additionally allows governors to vary the response to propeller shaft resistance moment fluctuations in sea waves conditions. In practice the value of sensitivity of electronic speed governors of main marine engines is selected intuitively. As a result, the adjustment of governors doesn’t provide satisfactory stability of speed modes at the change of sea conditions. The study aims to develop a methodology for adjusting the sensitivity of main engines electronic speed governors with considering the stochasticity of the load on the diesel engine in sea waves state. The study was carried out using the systems of automatic speed control model, which is based on the assumption of relatively small deviations of diesel engine shaft rotation speed and load parameters at sea waves conditions. Considering the character and magnitude of change of load on diesel engine at sea waves conditions depend on many variables of external conditions (waves levels, course of a vessel in relation to wind-wave conditions, wind gusts, vessel’s loading condition, given speed of a vessel), any set value of sensitivity of electronic speed governors appears to be optimum only for a particular case of vessel movement in sea waves state. The scientific novelty is defined by the fact that recommendations on the choice of governor sensitivity are determined with considering stochasticity of propeller shaft resistance moment fluctuations at sea waves conditions, that increased accuracy, and validity of recommendations. The practical significance of the research consist in the increase of stability of speed modes of the main engine with electronic speed governor at various sea waves conditions
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Wang, Lin-Lin, Hong-Jian Wang, Li-Xin Pan, and Jun-Xi Guo. "Active Disturbance Rejection Fuzzy Controller for Roll Stabilization of Autonomous Underwater Vehicle under Wave Disturbance." Discrete Dynamics in Nature and Society 2015 (2015): 1–10. http://dx.doi.org/10.1155/2015/835126.
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Considering the case of autonomous underwater vehicle navigating with low speed near water surface, a new method for designing of roll motion controller is proposed in order to restrain wave disturbance effectively and improve roll stabilizing performance under different sea conditions. Active disturbance rejection fuzzy control is applied, which is based on nonlinear motion model of autonomous underwater vehicle and the principle of zero-speed fin stabilizer. Extended state observer is used for estimation of roll motion state and unknown wave disturbance. Wave moment is counteracted by introducing compensation term into the roll control law which is founded on nonlinear feedback. Fuzzy reasoning is used for parameter adjustment of the controller online. Simulation experiments on roll motion are conducted under different sea conditions, and the results show better robustness improved by active disturbance rejection fuzzy controller of autonomous underwater vehicle navigating near water surface.
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Hayakawa, Hiroki, and Tomohiro Yendo. "Projection type 3D display using spinning screen." Electronic Imaging 2020, no. 2 (January 26, 2020): 99–1. http://dx.doi.org/10.2352/issn.2470-1173.2020.2.sda-099.
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We propose 3D display that scans light rays from projector and enables stereoscopic display by arranging a number of long and thin mirror scanners with a gap and spinning each mirror scanner. This proposal aims at large-screen 3D display that allows multiple people to observe simultaneously with the naked eye. In previous study, multi-projection type 3D display was proposed as largescreen 3D display. However, many projectors make installation and adjustment complicated. Therefore, we have proposed 3D display that can display large screen with single projector in the past. However, there is a problem that the screen vibrates due to the screen swing mechanism, the scanning speed cannot be increased, and the displayed image appears to flicker. Our new proposed method can reduce the screen vibration by the spin mechanism, increase the scanning speed, and prevent the displayed image from flickering. Computer simulation was performed to confirm the principle of the proposed method, and it was confirmed that appropriate parallax could be presented. The necessary conditions and problems when manufacturing the actual machine were considered, and the prototype was designed.
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Haldun Ünalmis, Ö. "Flow Measurement Optimization Using Surface Measurements and Downhole Sound Speed Measurements from Local or Distributed Acoustic Sensors." SPE Production & Operations 36, no. 02 (March 24, 2021): 437–50. http://dx.doi.org/10.2118/201313-pa.
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Summary The litmus test for downhole multiphase flowmeters is to compare the measured phase flow rates with the rates from a test separator or other surface measurement systems. In most cases, the composition of the measurand is required for flowmeters. This is typically obtained from bottomhole fluid samples. Extracting and analyzing fluid samples is an expensive process mostly done at the initial stages of field development. In some cases, the composition may be old or unavailable, leading to subpar flowmeter performance compared to surface systems. In this work, it is shown that when the data from a surface system such as a test separator are used in conjunction with the mixture sound speed measured downhole, it is possible to optimize a downhole multiphase flowmeter system without obtaining new fluid samples. The optimization process is independent of the downhole measurement device because the required flow-velocity and sound-speed measurements may be obtained from separate devices. For example, the fluid bulk velocity and mixture sound speed can be measured by a local measurement device and a distributed acoustic sensing (DAS) system, respectively. The main challenge in a flow-velocity/sound-speed measurement system is determining individual phase sound speeds so that the mixture phase fraction can be correctly determined using Wood’s mixture sound speed model. The phase fraction from the separator tests can be used as the target value to optimize the performance of the system. The system has two operation modes. In optimization mode, the individual phase sound speeds are calculated backward using the predicted phase fractions from surface measurements. Pressure and temperature variations at measurement locations, as well as pipe compliance effects, are accounted for during the process. After the adjustment of individual phase sound speeds, steady-state operation mode takes over, and a forward calculation is implemented using the same model. The final phase fraction agrees well with the actual value and can be improved further with an iterative approach. This novel method is demonstrated in a North Sea case history. A downhole optical flowmeter in a North Sea field measured mixture velocity and sound speed. Well-test results indicated that water cut from the flowmeter was underreported and phase flow rates did not match test-separator rates. Instead of halting production and going through a fluid sample analysis cycle, the test-separator water cut was used as the target value to optimize oil phase sound speed using Wood’s model in the optimization mode. The difference between the initial and optimized oil sound speeds was extrapolated to other pressure and temperature conditions, and steady-state operation mode showed that separator tests and flowmeter measurements closely matched. Subsequent flowmeter and test-separator data confirmed excellent agreement. Using surface measurements and downhole mixture sound speed to optimize phase flow rates is a novel method that has not been previously demonstrated. This method is independent of device type, is broadly applicable, and improves the understanding of multiphase flow measurement.
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Wang, Aiming, Yujie Bi, Yu Feng, Jie Yang, Xiaohan Cheng, and Guoying Meng. "Continuous Rotor Dynamics of Multi-Disc and Multi-Span Rotors: A Theoretical and Numerical Investigation of the Identification of Rotor Unbalance from Unbalance Responses." Applied Sciences 12, no. 8 (April 11, 2022): 3865. http://dx.doi.org/10.3390/app12083865.
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Rotor unbalance identification plays a critical role in balancing rotors. In this paper, concerned with multi-disc and multi-span rotor-bearing systems, two novel algorithms called the Single Direction Algorithm (SDA) and the Two Orthogonal Direction Algorithm (TODA) are proposed for identifying rotor unbalance from unbalance responses. A matrix method is proposed to solve the problem of the equations being non-linear transcendental, there being too many unknown variables in the equations, and rotor unbalances and bearing coefficients being coupled together. The unbalance responses at all the eccentric discs are necessary for identifying their unbalances. Numerical simulations are conducted to validate the proposed methods. Moreover, an adjustment point is found, and a proper sensor resolution is suggested to achieve high identification accuracy by means of numerical studies. In addition, the identification accuracy of SDA is better than TODA, and SDA is more practical and suitable for medium-speed and high-speed rotors. The proposed algorithms have the flexibility to incorporate any number of bearings and discs and provide a technique for monitoring rotor unbalance without test runs or external exciters.
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Su, Chien-Han, and Jean-Fu Kiang. "Effects of Sea-Surface Temperature, Cloud Vertical Structure and Wind Speed on Temperature Change between Hiatus and Post-Hiatus Periods in Tropical Western Pacific." Atmosphere 13, no. 12 (December 19, 2022): 2130. http://dx.doi.org/10.3390/atmos13122130.
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A region in the tropical western Pacific is selected to study the notable change in temperature between the recent warming hiatus period and the post-hiatus period. In total, three probable factors, namely sea-surface temperature (SST), cloud vertical structure (CVS) and wind speed, which may account for the temperature change are found to exhibit noticeable differences between these two periods. A one-dimensional atmospheric radiative transfer model, incorporating convective adjustment and energy exchange with the ocean, is developed to simulate the diurnal pattern of temperature profile under the influence of the three probable factors in the two concerned periods. Virtual profiles of sea-surface temperature, cloud vertical structure and wind speed in both periods are developed from data available in the literature. Diurnal patterns of temperatures near the air–sea interface are computed with the proposed model over a sufficient number of days. The simulated temperatures under different combinations of factors, in either the hiatus or post-hiatus period, are statistically analyzed to gain insights about the separate and combined effects of these three factors on causing climate change.
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Acevedo-Fontanez, Adrianna, Ryan Cvejkus, Allison Kuipers, Joseph Zmuda, Caterina Rosano, and Iva Miljkovic. "SKELETAL MUSCLE ADIPOSITY IS ASSOCIATED WITH LOWER COGNITION IN AFRICAN CARIBBEAN WOMEN." Innovation in Aging 6, Supplement_1 (November 1, 2022): 610–11. http://dx.doi.org/10.1093/geroni/igac059.2275.
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Abstract Objective Skeletal muscle adiposity (SMA) increases with aging and is recognized as a major risk factor for cardiometabolic diseases, disability, and mortality among older adults. Obesity is related to dementia and cognitive decline yet the relationship between SMA and cognition remains ill defined. The objective of this study was to assess SMA and cognitive function among African Caribbean women.Design and Methods Cross-sectional analysis of 448 African Caribbean women in the Tobago Health Study (mean age, 55 years; range, 39-84 years). Cognition was assessed by the Digit Symbol Substitution Test (DSST), a test of information processing speed with a range of 0-90; higher scores suggest better cognitive function (faster information processing speed). Calf SMA (muscle density) was assessed with computed tomography (Stratec XCT-2000). Linear regression was used to assess the association of SMA with DSST adjusted for age, education, muscle area, waist circumference, alcohol intake, smoking, physical activity, diabetes, and hypertension. Results Participants had a BMI of 30.7 kg/m2. Mean (SD) DSST scores and SMA were 39.2 (13.1) and 71.7 (5.3) mg/cm3, respectively. After full adjustment, we found that one SD greater skeletal muscle adiposity was associated with a 1.40 lower DSST score (p-value=0.025). Conclusions Our findings suggest that in African Caribbean women, greater SMA is associated with slower information processing speed, an early indicator of future dementia risk. Future studies using an expanded battery of cognitive tests and longitudinal follow-up should further advance our understanding of the role of SMA and dementia risk among African ancestry populations.
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Piotrovskii, Dmitri, Alexander Kukolev, and Sergei Podgornyi. "Sine waves frequency identification system modeling based on artificial network operation." Digital Technology Security, no. 2 (June 25, 2021): 20–31. http://dx.doi.org/10.17212/2782-2230-2021-2-20-31.
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Sine wave contribution can be observed in many casual periodic processes- starting with nature and finishing with complex hand-made processes like social, economic, technical and biological. This sphere of science have been staying under strict society attention thus having promoted and developed different theories, based on discrete Fourier transform, least squares methods and so on. Technical problem in question can be represented by the list of different processes of wave nature, e.g. sound and light occurrence, wave motion of different mediums. One of the most actual problems in question examples is marine sine wave impact identification for the marine ship main engine speed of rotation adjustment– the process, where control object inevitably is subject to load impact fluctuations. Especially evident this object can be concerned for the Northern Sea Route area, where climate severity is next to the states freights turnover increase desire. In this case marine main engine speed of rotation adjustment without specific control algorithm can be considered to be ineffective because of efficiency drops, increased parts and facilities run-outs. That is why, due to neural networks integration trend into industry processes, we tried to attempt building a separate neural network for defining the frequency of a noisy low-frequency sine wave. The obtained results [1] proved sine waves frequency identification possibility with the help of artificial network, however accuracy was found to be unacceptable because of sketchy algorithm elaboration and small learning array size.
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Xu, Haiming, Hiroki Tokinaga, and Shang-Ping Xie. "Atmospheric Effects of the Kuroshio Large Meander during 2004–05*." Journal of Climate 23, no. 17 (September 1, 2010): 4704–15. http://dx.doi.org/10.1175/2010jcli3267.1.
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Abstract In the summer of 2004, the Kuroshio took a large meander path south of Japan for the first time since 1991, and this large meander event persisted until the next summer. Satellite observations and numerical model simulations are used to study the effect of this large meander event on the atmosphere. The large meander leaves a cool water pool between the Kuroshio and Japanese coast. Sea surface temperature (SST) in the cool water pool is about 2°–3°C colder than the surroundings during winter and spring, whereas the SST signature substantially weakens in summer. A local reduction of wind speed is found over the cool water pool, and the positive SST–wind speed correlation is indicative of ocean forcing of the atmosphere. Cloud liquid water (CLW) content and precipitation also decrease over the cool SST pool. A regional atmospheric model successfully simulates atmospheric response to the Kuroshio large meander. The model experiments suggest that the reduced surface wind speed and precipitation are due to the large meander-induced SST cooling. Analysis of the surface perturbation momentum budgets shows the importance of the pressure adjustment mechanism in surface wind response to the cold SST anomalies.
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Mahrt, L., Dean Vickers, Edgar L. Andreas, and Djamal Khelif. "Sensible Heat Flux in Near-Neutral Conditions over the Sea." Journal of Physical Oceanography 42, no. 7 (July 1, 2012): 1134–42. http://dx.doi.org/10.1175/jpo-d-11-0186.1.
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Abstract The variation of the sea surface sensible heat flux is investigated using data from the Gulf of Tehuantepec Experiment (GOTEX) and from eight additional aircraft datasets representing a variety of surface conditions. This analysis focuses on near-neutral conditions because these conditions are common over the sea and are normally neglected, partly because of uncertain reliability of measurements of the small air–sea temperature difference. For all of the datasets, upward heat flux is observed for slightly stable conditions. The frequency of this “countergradient” heat flux increases with increasing wind speed and is possibly related to sea spray or microscale variations of surface temperature on the wave scale. Upward area-averaged sensible heat flux for slightly stable conditions can also be generated by mesoscale heterogeneity of the sea surface temperature (SST). Significant measurement errors cannot be ruled out. The countergradient heat flux for weakly stable conditions is least systematic for weaker winds, even though it occurs with weak winds in all of the datasets. In an effort to reduce offset errors and different SST processing and calibration procedures among field programs, the authors adjusted the SST in each field program to minimize the countergradient flux for weak winds. With or without this adjustment for the combined dataset, the extent of the upward heat flux for weakly stable conditions increases with increasing wind speed.
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Xu, Mimi, and Haiming Xu. "Atmospheric Responses to Kuroshio SST Front in the East China Sea under Different Prevailing Winds in Winter and Spring." Journal of Climate 28, no. 8 (April 7, 2015): 3191–211. http://dx.doi.org/10.1175/jcli-d-13-00675.1.
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Abstract Atmospheric responses to the Kuroshio SST front in the East China Sea under different prevailing winds are examined using high-resolution observations and numerical modeling. Satellite data reveal a significant in-phase relationship between SST and surface wind speed, indicative of ocean-to-atmosphere influence. The atmospheric response varies according to the relative surface wind direction with respect to the SST front orientation. Under the alongfront condition, low (high) SLP anomalies are found on the warmer (colder) flank of the front, accompanied by surface wind convergence (divergence). Enhanced precipitation and frequent cumulus convection appear over the warm Kuroshio, suggesting an atmospheric response extending into the free troposphere. Under the cross-front condition, when the air blows from cold to warm (warm to cold) SST, divergence (convergence) is located directly over the SST front, and its magnitude is proportional to the downwind SST gradient. Under such prevailing winds, the SST front has little effect on the SLP and precipitation. The Weather Research and Forecasting (WRF) Model is used to investigate the mechanism responsible for the atmospheric adjustment. The results show that under the alongfront condition, large temperature and pressure perturbations in the boundary layer are caused by SST gradients, while stability and turbulent mixing are less affected. By contrast, under the cross-front condition, the perturbations of temperature and pressure are small and shifted downstream, while the SST gradient exerts stronger impact on vertical mixing. The modeling results confirm that the pressure adjustment mechanism contributes more to the atmospheric response under alongfront prevailing winds, while the vertical mixing mechanism dominates the atmospheric adjustment under cross-front winds.
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Legris, Leila, Morten Lindholt Pahus, Takafumi Nishino, and Edgar Perez-Campos. "Prediction and Mitigation of Wind Farm Blockage Losses Considering Mesoscale Atmospheric Response." Energies 16, no. 1 (December 29, 2022): 386. http://dx.doi.org/10.3390/en16010386.
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The engineering wind farm models currently used in industry can assess power losses due to turbine wake effects, but the prediction of power losses due to farm blockage is still a challenge. In this study we demonstrate a new prediction method of farm blockage losses and a possible strategy to mitigate them for a large offshore wind farm in the North Sea, by combining a common engineering wind farm model ’FLORIS’ with the ’two-scale momentum theory’ of Nishino and Dunstan (2020). Results show that the farm blockage losses depend significantly on the ’wind extractability’ factor, which reflects the strength of mesoscale atmospheric response. For a typical range of the extractability factor (assessed using a numerical weather prediction model) the farm blockage losses are shown to vary between about 5% and 15% of the annual energy production (AEP). However, these losses may be mitigated by adjusting turbine operating points taking into account the wind extractability. It is shown that a simple adjustment of the blade pitch angle and tip-speed ratio used below the rated wind speed may increase the AEP by up to about 2%.
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Wang, Ming Hui, Yong Quan Yu, and Bi Zeng. "Neuro-Fuzzy Controller for Rudder Roll Stabilization of Ships." Applied Mechanics and Materials 66-68 (July 2011): 1278–85. http://dx.doi.org/10.4028/www.scientific.net/amm.66-68.1278.
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The uncertainty of ship models and interferences can lead to reduce the effectiveness of conventional roll stabilization controller depending upon accurate mathematical model.This paper proposes the design of neuro-fuzzy controller for rudder roll stabilization. Learning ability of neural network is utilized to optimize the fuzzy controller. Hybrid learning rule which is a combination of backpropagation algorithm and least square estimator is utilized to realized parameter adjustment of fuzzy control rule and membership function in order to improve the adaptive capacity of controller. The simulation tests under various situations such as different navigational speed, sea conditions, wave-to-course angle and ship parameter perturbation are to check the performance of roll stabilizatin controller. Simulation results show that the neuro-fuzzy controller has better robustness and effectiveness for rudder roll stabilization in beam seas.
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Meinvielle, M., J. M. Brankart, P. Brasseur, B. Barnier, R. Dussin, and J. Verron. "Optimal adjustment of the atmospheric forcing parameters of ocean models using sea surface temperature data assimilation." Ocean Science 9, no. 5 (October 17, 2013): 867–83. http://dx.doi.org/10.5194/os-9-867-2013.
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Abstract. In ocean general circulation models, near-surface atmospheric variables used to specify the atmospheric boundary condition remain one of the main sources of error. The objective of this research is to constrain the surface forcing function of an ocean model by sea surface temperature (SST) data assimilation. For that purpose, a set of corrections for ERAinterim (hereafter ERAi) reanalysis data is estimated for the period of 1989–2007, using a sequential assimilation method, with ensemble experiments to evaluate the impact of uncertain atmospheric forcing on the ocean state. The control vector of the assimilation method is extended to atmospheric variables to obtain monthly mean parameter corrections by assimilating monthly SST and sea surface salinity (SSS) climatological data in a low resolution global configuration of the NEMO model. In this context, the careful determination of the prior probability distribution of the parameters is an important matter. This paper demonstrates the importance of isolating the impact of forcing errors in the model to perform relevant ensemble experiments. The results obtained for every month of the period between 1989 and 2007 show that the estimated parameters produce the same kind of impact on the SST as the analysis itself. The objective is then to evaluate the long-term time series of the forcing parameters focusing on trends and mean error corrections of air–sea fluxes. Our corrections tend to equilibrate the net heat-flux balance at the global scale (highly positive in ERAi database), and to remove the potentially unrealistic negative trend (leading to ocean cooling) in the ERAi net heat flux over the whole time period. More specifically in the intertropical band, we reduce the warm bias of ERAi data by mostly modifying the latent heat flux by wind speed intensification. Consistently, when used to force the model, the corrected parameters lead to a better agreement between the mean SST produced by the model and mean SST observations over the period of 1989–2007 in the intertropical band.
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Zhao, Ming, and Isaac M. Held. "An Analysis of the Effect of Global Warming on the Intensity of Atlantic Hurricanes Using a GCM with Statistical Refinement." Journal of Climate 23, no. 23 (December 1, 2010): 6382–93. http://dx.doi.org/10.1175/2010jcli3837.1.
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Abstract A statistical intensity adjustment is utilized to extract information from tropical cyclone simulations in a 50-km-resolution global model. A simple adjustment based on the modeled and observed probability distribution of storm lifetime maximum wind speed allows the model to capture the differences between observed intensity distributions in active/inactive year composites from the 1981–2008 period in the North Atlantic. This intensity adjustment is then used to examine the atmospheric model’s responses to different sea surface temperature anomalies generated by coupled models for the late twenty-first century. In the North Atlantic all simulations produce a reduction in the total number of cyclones, but with large intermodel spread in the magnitude of the reduction. The intensity response is positively correlated with changes in frequency across the ensemble. However, there is, on average, an increase in intensity in these simulations despite the mean reduction in frequency. The authors argue that it is useful to decompose these intensity changes into two parts: an increase in intensity that is intrinsic to the climate change experiments and a change in intensity positively correlated with frequency, just as in the active/inactive historical composites. By isolating the intrinsic component, which is relatively independent of the details of the SST warming pattern, an increase is found in storm-lifetime maximum winds of 5–10 m s−1 for storms with intensities of 30–60 m s−1, by the end of the twenty-first century. The effects of change in frequency, which are dependent on the details of the spatial structure of the warming, must then be superimposed on this intrinsic change.
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Liu, Jing-Wu, Su-Ping Zhang, and Shang-Ping Xie. "Two Types of Surface Wind Response to the East China Sea Kuroshio Front*." Journal of Climate 26, no. 21 (October 16, 2013): 8616–27. http://dx.doi.org/10.1175/jcli-d-12-00092.1.
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Abstract Effects of the sea surface temperature (SST) front along the East China Sea Kuroshio on sea surface winds at different time scales are investigated. In winter and spring, the climatological vector wind is strongest on the SST front while the scalar wind speed reaches a maximum on the warm flank of the front and is collocated with the maximum difference between sea surface temperature and surface air temperature (SST − SAT). The distinction is due to the change in relative importance of two physical processes of SST–wind interaction at different time scales. The SST front–induced sea surface level pressure (SLP) adjustment (SF–SLP) contributes to a strong vector wind above the front on long time scales, consistent with the collocation of baroclinicity in the marine boundary layer and corroborated by the similarity between the thermal wind and observed wind shear between 1000 and 850 hPa. In contrast, the SST modulation of synoptic winds is more evident on the warm flank of the SST front. Large thermal instability of the near-surface layer strengthens temporal synoptic wind perturbations by intensifying vertical mixing, resulting in a scalar wind maximum. The vertical mixing and SF–SLP mechanisms are both at work but manifest more clearly at the synoptic time scale and in the long-term mean, respectively. The cross-frontal variations are 1.5 m s−1 in both the scalar and vector wind speeds, representing the vertical mixing and SF–SLP effects, respectively. The results illustrate the utility of high-frequency sampling by satellite scatterometers.
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Li, Qiang, David M. Farmer, Timothy F. Duda, and Steve Ramp. "Acoustical Measurement of Nonlinear Internal Waves Using the Inverted Echo Sounder." Journal of Atmospheric and Oceanic Technology 26, no. 10 (October 1, 2009): 2228–42. http://dx.doi.org/10.1175/2009jtecho652.1.
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Abstract The performance of pressure sensor–equipped inverted echo sounders for monitoring nonlinear internal waves is examined. The inverted echo sounder measures the round-trip acoustic travel time from the sea floor to the sea surface and thus acquires vertically integrated information on the thermal structure, from which the first baroclinic mode of thermocline motion may be inferred. This application of the technology differs from previous uses in that the wave period (∼30 min) is short, requiring a more rapid transmission rate and a different approach to the analysis. Sources of error affecting instrument performance include tidal effects, barotropic adjustment to internal waves, ambient acoustic noise, and sea surface roughness. The latter two effects are explored with a simulation that includes surface wave reconstruction, acoustic scattering based on the Kirchhoff approximation, wind-generated noise, sound propagation, and the instrument’s signal processing circuitry. Bias is introduced as a function of wind speed, but the simulation provides a basis for bias correction. The assumption that the waves do not significantly affect the mean stratification allows for a focus on the dynamic response. Model calculations are compared with observations in the South China Sea by using nearby temperature measurements to provide a test of instrument performance. After applying corrections for ambient noise and surface roughness effects, the inverted echo sounder exhibits an RMS variability of approximately 4 m in the estimated depth of the eigenfunction maximum in the wind speed range 0 ≤ U10 ≤ 10 m s−1. This uncertainty may be compared with isopycnal excursions for nonlinear internal waves of 100 m, showing that the observational approach is effective for measurements of nonlinear internal waves in this environment.
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Silveira, Ricardo Peterson, Flávio Antônio de Souza Castro, Pedro Figueiredo, João Paulo Vilas-Boas, and Paola Zamparo. "The Effects of Leg Kick on Swimming Speed and Arm-Stroke Efficiency in the Front Crawl." International Journal of Sports Physiology and Performance 12, no. 6 (July 2017): 728–35. http://dx.doi.org/10.1123/ijspp.2016-0232.
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Purpose:To analyze the effects of swimming pace on the relative contribution of leg kick to swimming speed and to compare arm-stroke efficiency (ηF) assessed when swimming with the arms only (SAO) and while swimming front crawl (FCS) using individual and fixed adjustments to arm-stroke and leg-kick contribution to forward speed.Methods:Twenty-nine master swimmers (21 men, 8 women) performed SAO and FCS at 6 self-selected speeds from very slow to maximal. The average swimming speed (v), stroke frequency (SF), and stroke length (SL) were assessed in the central 10 m of the swimming pool. Then, a 2nd-order polynomial regression was used to obtain values of v at paired SF. The percentage difference in v between FCS and SAO, for each paired SF, was used to calculate the relative contributions of the arm stroke (AC) and leg kick (LC) to FCS. Then ηF was calculated using the indirect “paddle-wheel” approach in 3 different ways: using general, individual, and no adjustments to AC.Results:The LC increased with SF (and speed) from –1% ± 4% to 11% ± 1% (P < .05). At the lower FCS speeds, ηF calculated using general adjustments was lower than ηF calculated using individual adjustments (P < .05), but differences disappear at the fastest speeds. Finally, ηF calculated using individual adjustments to LC in the FCS condition did not differ with ηF assessed in the SAO condition at all the investigated speeds.Conclusions:The relative contributions of the arm stroke and leg kick should be individually estimated to reduce errors when calculating arm-stroke efficiency at different speeds and in different swimmers.
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Гонтарев, S. Gontarev, Мошаров, Sergey Mosharov, Корсак, and M. Korsak. "New Phyto-Incubator with Temperature and Illumination Adjustment for Water Ecosystems’ Ecological Parameters Monitoring." Safety in Technosphere 4, no. 4 (August 25, 2015): 3–9. http://dx.doi.org/10.12737/14428.
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During sea ecological expeditions at determination of organic substance formation speed in the course of photosynthesis (sizes of primary production) researchers face need related to creation of special conditions for an exposition of containing the phytoplankton water samples which have been selected at different stations and depths, widely spaced and with different temperature and illumination values. Now for primary production measurement in all marine ecosystems’ photosynthesis zone which has an extent equal to several tens of meters, the standard methods for incubation of containing the phytoplankton water samples in the conditions of constant temperatures and illumination, considerably different from those horizons, where the studied samples were taken, are used. Such a technique based on the water samples incubation at artificial lighting in controlled temperature conditions has been accepted as the main one in the international ecological and monitoring programs (HELCOM, SCOR, etc.). Discrepancy of light and temperature conditions in a sample selection point and in the experiment can lead to distortions at a primary production assessment and light dependences determination. Primary production sizes’ correct determination at photosynthesis zone’s different depths with different temperature and illumination values demands creation of the most approached to the natural conditions for the exposition of containing the phytoplankton water samples. A new phyto-incubator for the water sample incubation at the primary production measurement is described in this paper. The phyto-incubator consists of light and thermo isolated cells with a system of temperature and illumination individual adjustment in each of the cells. The incubation of different samples containing the phytoplankton is carried out in various stabilized conditions on temperature and illumination by a constant light stream, established for each cell separately. Illumination and temperature values can be choose as any of the set range of sizes. Such installation allows to set a "grid" of parameters on temperature and illumination, on exhibiting duration, and to receive predictive estimates for primary production at the change of external conditions. Invention patent No. 2547685 "Incubator and Approach for Water Samples Incubation" has been obtained on the developed incubator. This phyto-incubator type can be also used for various ecological experiments with natural populations of plankton organisms in laboratory conditions.
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Cleary, Ciaran S., and Robert J. Manning. "High speed cross-amplitude modulation in concatenated SOA-EAM-SOA." Optics Express 20, no. 13 (June 12, 2012): 14338. http://dx.doi.org/10.1364/oe.20.014338.
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Elmi, Zeinab, Prashant Singh, Vamshi Krishna Meriga, Krzysztof Goniewicz, Marta Borowska-Stefańska, Szymon Wiśniewski, and Maxim A. Dulebenets. "Uncertainties in Liner Shipping and Ship Schedule Recovery: A State-of-the-Art Review." Journal of Marine Science and Engineering 10, no. 5 (April 21, 2022): 563. http://dx.doi.org/10.3390/jmse10050563.
Full textAbstract:
Each shipping line is expected to establish a reliable operating model, and the design of ship schedules is a key operational consideration. Long-term profits for shipping lines can be expected from a well-designed ship schedule. In today’s liner service design, managing the time factor is critical. Shipping schedules are prone to different unexpected disruptions. Such disruptions would necessitate a near-real-time analysis of port capacity and re-design of the original ship schedule to offset the negative externalities. Ship schedule recovery strategies should be implemented to mitigate the effects caused by disruptions at ports or at sea, which may include, but are not limited to, ship sailing speed adjustment, handling rate adjustment at ports, port skipping, and port skipping with container diversion. A proper selection of ship schedule recovery strategies is expected to minimize deviations from the original ship schedule and reduce delays in the delivery of cargoes to the destination ports. This article offers a thorough review of the current liner shipping research primarily focusing on two major themes: (1) uncertainties in liner shipping operations; and (2) ship schedule recovery in response to disruptive events. On the basis of a detailed review of the available literature, the obtained results are carefully investigated, and limitations in the current state-of-the-art are determined for every group of studies. Furthermore, representative mathematical models are provided that could be further used in future research efforts dealing with uncertainties in liner shipping and ship schedule recovery. Last but not least, a few prospective research avenues are suggested for further investigation.
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Sasgen, I., H. Konrad, E. R. Ivins, M. R. van den Broeke, J. L. Bamber, Z. Martinec, and V. Klemann. "Antarctic ice-mass balance 2002 to 2011: regional re-analysis of GRACE satellite gravimetry measurements with improved estimate of glacial-isostatic adjustment." Cryosphere Discussions 6, no. 5 (September 5, 2012): 3703–32. http://dx.doi.org/10.5194/tcd-6-3703-2012.
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Abstract. We present regional-scale mass balances for 25 drainage basins of the Antarctic Ice Sheet (AIS) from satellite observations of the Gravity and Climate Experiment (GRACE) for the years 2002–2011. Satellite gravimetry estimates of the AIS mass balance are strongly influenced by mass movement in the Earth interior caused by ice advance and retreat during the last glacial cycle. Here, we develop an improved glacial-isostatic adjustment (GIA) estimate for Antarctica using newly available GPS uplift rates, allowing us to more accurately separate GIA-induced trends in the GRACE gravity fields from those caused by current imbalances of the AIS. Our revised GIA estimate is considerably lower than previous predictions, yielding an (upper) estimate of apparent mass change of 48 ± 18 Gt yr−1. Therefore, our AIS mass balance of −103 ± 23 Gt yr−1 is considerably less negative than previous GRACE estimates. The Northern Antarctic Peninsula and the Amundsen Sea Sector exhibit the largest mass loss (−25 ± 6 Gt yr−1 and −126 ± 11 Gt yr−1, respectively). In contrast, East Antarctica exhibits a slightly positive mass balance (19 ± 16 Gt yr−1), which is, however, mostly the consequence of compensating mass anomalies in Dronning Maud and Enderby Land (positive) and Wilkes and George V Land (negative) due to interannual accumulation variations. In total, 7% of the area constitute more than half of the AIS imbalance (53%), contributing −151 ± 9 Gt yr−1 to global mean sea-level change. Most of this imbalance is caused by long-term ice-dynamic speed up expected to prevail in the future.
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Jia, Yinglai, Longjing Chen, Qinyu Liu, Xiaohui Yang, and Yifei Wu. "The Role of Background Wind and Moisture in the Atmospheric Response to Oceanic Eddies During Winter in the Kuroshio Extension Region." Atmosphere 10, no. 9 (September 7, 2019): 527. http://dx.doi.org/10.3390/atmos10090527.
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The role of background wind and moisture in the atmospheric response to oceanic eddies during winter in the Kuroshio Extension (KE) region is examined by numerical experiments (EXPs) using the Weather Research and Forecasting (WRF) model. We designed two sets of parallel experiments (dry and wet EXPs). The dry EXPs exclude the moisture in the air and the evaporation process. Each experiment differs only in the background wind speed during the initial condition. The wet EXPs include humidity in the initial condition and evaporation during the integration; the other settings are the same as the dry EXPs. The atmosphere in the two sets of EXPs are forced by the same mesoscale sea surface temperature anomaly which resembles the oceanic warm eddy in KE region. The results of these EXPs confirm that under weak background wind conditions, the atmospheric secondary circulation over oceanic eddies is driven by the pressure adjustment process due to weak advection. In the case of the dry run, the increase in background wind enhances the sea surface wind (SSW) by increasing vertical mixing. The convergence of SSW induces vertical motion and heating in the boundary layer, which further decreases the instability. The atmospheric secondary circulation in the dry run remains within the boundary layer. In wet EXPs, the atmospheric response is similar to that in dry runs when the background wind is very weak. When the background wind speed is increased to the climatology value (in KE region) or higher, the vertical motion triggers the precipitation process and diabatic heating above the boundary layer, and the heating in turn reinforces the upward flow.
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Zhang, K., C. Zhao, H. Wan, Y. Qian, R. C. Easter, S. J. Ghan, K. Sakaguchi, and X. Liu. "Quantifying the impact of sub-grid surface wind variability on sea salt and dust emissions in CAM5." Geoscientific Model Development Discussions 8, no. 8 (August 27, 2015): 7249–312. http://dx.doi.org/10.5194/gmdd-8-7249-2015.
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Abstract. This paper evaluates the impact of sub-grid variability of surface wind on sea salt and dust emissions in the Community Atmosphere Model version 5 (CAM5). The basic strategy is to calculate emission fluxes multiple times, using different wind speed samples of a Weibull probability distribution derived from model-predicted grid-box mean quantities. In order to derive the Weibull distribution, the sub-grid standard deviation of surface wind speed is estimated by taking into account four mechanisms: turbulence under neutral and stable conditions, dry convective eddies, moist convective eddies over the ocean, and air motions induced by meso-scale systems and fine-scale topography over land. The contributions of turbulence and dry convective eddy are parameterized using schemes from the literature, while the wind variabilities caused by moist convective eddies and fine-scale topography are estimated using empirical relationships derived from an operational weather analysis dataset at 15 km resolution. The estimated sub-grid standard deviations of surface wind speed agree well with reference results derived from one year of global weather analysis at 15 km resolution and from two regional model simulations with 3 km grid spacing. The wind-distribution-based emission calculations are implemented in CAM5. Simulations at 2° resolution indicate that sub-grid wind variability has relatively small impacts (about 7 % increase) on the global annual mean emission of sea salt aerosols, but considerable influence on the emission of dust. Among the considered mechanisms, dry convective eddies and meso-scale flows associated with topography are major causes of dust emission enhancement. With all the four mechanisms included and without additional adjustment of uncertain parameters in the model, the simulated global and annual mean dust emission increase by about 50 % compared to the default model. By tuning the globally constant dust emission scale factor, the global annual mean dust emission, aerosol optical depth, and top-of-atmosphere radiative fluxes can be adjusted to the level of the default model, but the frequency distribution of dust emission changes, with more contribution from weaker wind events and less contribution from stronger wind events.
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Sasgen, I., H. Konrad, E. R. Ivins, M. R. Van den Broeke, J. L. Bamber, Z. Martinec, and V. Klemann. "Antarctic ice-mass balance 2003 to 2012: regional reanalysis of GRACE satellite gravimetry measurements with improved estimate of glacial-isostatic adjustment based on GPS uplift rates." Cryosphere 7, no. 5 (September 25, 2013): 1499–512. http://dx.doi.org/10.5194/tc-7-1499-2013.
Full textAbstract:
Abstract. We present regional-scale mass balances for 25 drainage basins of the Antarctic Ice Sheet (AIS) from satellite observations of the Gravity and Climate Experiment (GRACE) for time period January 2003 to September 2012. Satellite gravimetry estimates of the AIS mass balance are strongly influenced by mass movement in the Earth interior caused by ice advance and retreat during the last glacial cycle. Here, we develop an improved glacial-isostatic adjustment (GIA) estimate for Antarctica using newly available GPS uplift rates, allowing us to more accurately separate GIA-induced trends in the GRACE gravity fields from those caused by current imbalances of the AIS. Our revised GIA estimate is considerably lower than previous predictions, yielding an estimate of apparent mass change of 53 ± 18 Gt yr−1. Therefore, our AIS mass balance of −114 ± 23 Gt yr−1 is less negative than previous GRACE estimates. The northern Antarctic Peninsula and the Amundsen Sea sector exhibit the largest mass loss (−26 ± 3 Gt yr−1 and −127 ± 7 Gt yr−1, respectively). In contrast, East Antarctica exhibits a slightly positive mass balance (26 ± 13 Gt yr−1), which is, however, mostly the consequence of compensating mass anomalies in Dronning Maud and Enderby Land (positive) and Wilkes and George V Land (negative) due to interannual accumulation variations. In total, 6% of the area constitutes about half the AIS imbalance, contributing 151 ± 7 Gt yr−1 (ca. 0.4 mm yr−1) to global mean sea-level change. Most of this imbalance is caused by ice-dynamic speed-up expected to prevail in the near future.
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Lu, Yinheng, Gang Qiao, Chenlu Yang, Yunjiang Zhao, Guang Yang, and Huizhe Li. "A Real-Time Digital Self Interference Cancellation Method for In-Band Full-Duplex Underwater Acoustic Communication Based on Improved VSS-LMS Algorithm." Remote Sensing 14, no. 12 (June 18, 2022): 2924. http://dx.doi.org/10.3390/rs14122924.
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Theoretically, the spectral efficiency of in-band full-duplex underwater acoustic communications (IBFD-UWAC) is twice that of a half-duplex one. However, the actual achievable spectral efficiency of IBFD-UWAC is determined by the performance of the self-interference cancellation (SIC). In addition, the hostile underwater environment poses a challenge to the tracking performance of the SIC due to its complexity and variability. In this paper, we propose a digital SIC method based on the improved variable step-size least mean square (IVSS-LMS) algorithm where we modify the step-size adjustment criterion in the classical LMS filter and establishes a nonlinear relationship with the Sigmoid function to control the step-size using the instantaneous state error, thus improving the robustness and tracking performance of IVSS-LMS. Hardware-in-loop simulation (HLS) based on Simulink® platform verifies the real-time implementability and effectiveness of the proposed IVSS-LMS algorithm. Furthermore, the sea trial results show that the digital SIC method based on the proposed algorithm can be implemented in real-time and the convergence speed, and steady-state performance are significantly improved.