scholarly journals One year of measurements in Alderney Race: preliminary results from database analysis

2020 ◽  
Vol 378 (2178) ◽  
pp. 20190625 ◽  
Author(s):  
L. Furgerot ◽  
A. Sentchev ◽  
P. Bailly du Bois ◽  
G. Lopez ◽  
M. Morillon ◽  
...  
Keyword(s):  
Wave Height ◽  
Tidal Energy ◽  
Significant Advance ◽  
Strong Wind ◽  
Mean Flow ◽  
Database Analysis ◽  
Energy Potential ◽  
Wide Range ◽  
Tidal Stream ◽  
One Year

The Alderney Race is assumed to have the largest tidal-stream energy potential in the north-western European coastal seas. Interaction of the powerful tidal stream with strong wind, high waves and irregular bathymetry creates hydrodynamic conditions of extreme complexity, with high levels of turbulence. A comprehensive dataset has been created to improve the understanding of physical processes, turbulence, tidal stream and resource variability at the site. The database contains a large amount of oceanographic and meteorological measurements acquired in Alderney Race in 2017–2018. This exceptionally long period of observations (nearly one year) became possible due to modern tools and strategies of data acquisition. The paper presents some significant results from the database analysis. Among many results, we would like to underline the following: (i) a wide range of variability of mean flow and sea state parameters was documented; (ii) exceptionally large values of current velocity (7 m s −1 ) and significant wave height (8 m) were measured during extreme meteorological conditions; (iii) high-frequency variability of current speed during storm events was also found to be very large, with the standard deviation of velocity reaching 0.3 m s −1 in the bottom boundary layer, and 0.6 m s −1 in the surface layer; and (iv) predominant wind and wave direction relative to the flow impacts the wave height and significantly increases the turbulence kinetic energy of the flow. To our knowledge, this is the largest multi-variable database available on potential tidal energy sites. The results of database analysis can represent a significant advance in environmental conditions and resource characterization and provide advanced information to turbine developers. This article is part of the theme issue ‘New insights on tidal dynamics and tidal energy harvesting in the Alderney Race’.

scholarly journals Tidal Energy: Perspective of Bangladesh

2018 ◽  
Vol 41 (2) ◽  
pp. 201-215
Author(s):  
Mohammad Asadul Haque ◽  
Mst Sujata Khatun
Keyword(s):  
Tidal Energy ◽  
Tidal Range ◽  
Tidal Power ◽  
Power Resources ◽  
Wide Range ◽  
Tidal Data ◽  
Tidal Stream ◽  
Tidal Power Generation ◽  
Ocean Thermal Energy ◽  
Academy Of Sciences

Bangladesh is blessed by the nature with renewable resources that are used all over the world in a wide range but in our country it is limited. The country has vast ocean area with various power resources such as Wave energy, Ocean Thermal Energy Conversion (OTEC) and Tidal energy. In the Bay of Bengal, the tidal range and tidal stream speed indicate the potentiality of tidal power generation in Bangladesh. This paper describes various methods of utilizing tidal power to generate electricity and assess the tidal energy resources of three potential sites of Bangladesh. The tidal data recorded by the Department of Hydrography of The Chittagong Port Authority (CPA) and Bangladesh Inland Water Transport Authority (BIWTA) have been analyzed. This study clearly indicates the bright prospects of tidal power in Bangladesh.Journal of Bangladesh Academy of Sciences, Vol. 41, No. 2, 201-215, 2017

scholarly journals Characteristics of the turbulence in the flow at a tidal stream power site

2013 ◽  
Vol 371 (1985) ◽  
pp. 20120196 ◽  
Author(s):  
I. A. Milne ◽  
R. N. Sharma ◽  
R. G. J. Flay ◽  
S. Bickerton
Keyword(s):  
Turbulence Intensity ◽  
Spring Tide ◽  
Maximum Flow ◽  
Large Degree ◽  
Tidal Energy ◽  
Inertial Subrange ◽  
Mean Flow ◽  
Local Isotropy ◽  
Spectral Models ◽  
Tidal Stream

This paper analyses a set of velocity time histories which were obtained at a fixed point in the bottom boundary layer of a tidal stream, 5 m from the seabed, and where the mean flow reached 2.5 m s −1 . Considering two complete tidal cycles near spring tide, the streamwise turbulence intensity during non-slack flow was found to be approximately 12–13%, varying slightly between flood and ebb tides. The ratio of the streamwise turbulence intensity to that of the transverse and vertical intensities is typically 1 : 0.75 : 0.56, respectively. Velocity autospectra computed near maximum flood tidal flow conditions exhibit an f −2/3 inertial subrange and conform reasonably well to atmospheric turbulence spectral models. Local isotropy is observed between the streamwise and transverse spectra at reduced frequencies of f >0.5. The streamwise integral time scales and length scales of turbulence at maximum flow are approximately 6 s and 11–14 m, respectively, and exhibit a relatively large degree of scatter. They are also typically much greater in magnitude than the transverse and vertical components. The findings are intended to increase the levels of confidence within the tidal energy industry of the characteristics of the higher frequency components of the onset flow, and subsequently lead to more realistic performance and loading predictions.

scholarly journals On Tidal Current Velocity Vector Time Series Prediction: A Comparative Study for a French High Tidal Energy Potential Site

2019 ◽  
Vol 7 (2) ◽  
pp. 46 ◽  
Author(s):  
Tony El Tawil ◽  
Nicolas Guillou ◽  
Jean-Frédéric Charpentier ◽  
Mohamed Benbouzid
Keyword(s):  
Time Series ◽  
Numerical Model ◽  
Linear Approximation ◽  
Current Velocity ◽  
Tidal Current ◽  
Tidal Energy ◽  
Energy System ◽  
Energy Potential ◽  
Tidal Current Velocity ◽  
Tidal Stream

Estimating the energy potential of tidal stream site is a key feature for tidal energy system deployment. This paper aims to compare two methods of prediction of tidal current velocities. The first one is based on the use of a fully three-dimensional (3D) numerical approach. However, while being accurate, the numerical model is highly time-consuming. The second method is based on a linear approximation of the tidal current, which only requires preliminary knowledge of local current velocities time series during two typical tidal cycles. This second method allows a very quick evaluation of the tidal stream resource during a long time period. The proposed comparison is done in three different locations of a high potential tidal energy site in west of France. It is carried out in terms of current velocity and energy harnessing for several turbines technology options (with and without yaw). The achieved results show that the linear approximation gives satisfactory evaluation of the tidal stream potential and can be a very interesting tool for preliminary site evaluation and first technology options selection. However, the fully 3D numerical model can obviously be very useful in more advanced steps of a project.

scholarly journals Reassessment of tidal energy potential in India and a decision-making tool for tidal energy technology selection

2017 ◽  
Vol 8 (2) ◽  
pp. 85-97 ◽  
Author(s):  
K Murali ◽  
V Sundar
Keyword(s):  
Energy Conversion ◽  
Clean Energy ◽  
Tidal Energy ◽  
Technology Selection ◽  
Tidal Range ◽  
Energy Technology ◽  
Ocean Energy ◽  
Tidal Power ◽  
Energy Potential ◽  
Tidal Stream

Oceans have significant renewable energy options to provide environmental friendly and clean energy. Technology for ocean energy systems and the feasibility for extraction of the same is an important area on which research is being focused worldwide. This article covers a detailed review of available tidal energy conversion technologies and case studies, with specific focus on tidal power potential in India. The proven option for tidal energy conversion is barraging. Recently, open-type turbine (usually known as tidal stream turbines) has been studied by several researchers and pilot demonstrations have been made. While conventional turbines of 10–20 MW rating are used in barrages, the application of tidal stream turbines of 0.5–2.0 MW has been demonstrated in water depths between 40 and 60 m. A new scale is proposed for categorizing the tidal energy potential in terms of tidal velocity and tidal range which could be used to categorize the potential sites and their ranking. A new systematic approach proposed for the assessment of tidal energy conversion potential can facilitate the suitability of either tidal stream energy or tidal barrage for a location. Within this, one could also decide the site could be developed as a major project or minor project. Therefore, the present work will be useful for engineers and decision makers in technology selection investment potential identification.

Estimation of the Energy Potential of the Euripus' Gulf Tidal Stream Using Channel Sea-surface Slope

2015 ◽  
Vol 3 (4) ◽  
pp. 23-42 ◽  
Author(s):  
Aphrodite Ktena ◽  
Christos Manasis ◽  
Dimitrios Bargiotas ◽  
Vasilis Katsifas ◽  
Takvor Soukissian ◽  
...  
Keyword(s):  
Sea Level ◽  
Tidal Energy ◽  
Energy Yield ◽  
Energy Extraction ◽  
Low Velocity ◽  
Energy Potential ◽  
Yield Data ◽  
Island Communities ◽  
Tidal Stream ◽  
Harmonic Analysis Method

Potential energy extraction from tidal currents is investigated in this work. Recordings on the streams' velocity and the sea level in the Euripus' strait in Evia, Greece are used to calculate the energy yield. Data on sea level measurements were used to extract information for the current velocity profile through harmonic analysis method. Requirements, limitations and possible new designs that will improve the energy extraction from the low velocity tidal current of the area are discussed. Also, exploitation of tidal energy in cooperation with RES microgrid is proposed for areas where the abundance of sun, wind, island communities and coast areas such as the Mediterranean.

COMPETITIVE STATUS OF UKRAINE

2017 ◽  
Author(s):  
Olena Zayats ◽  
Keyword(s):  
National Economy ◽  
Financial System ◽  
Product Market ◽  
Global Competitiveness ◽  
Innovation Potential ◽  
Wide Range ◽  
Ict Adoption ◽  
World Economic ◽  
Global Competitiveness Index ◽  
One Year

The article examines the competitive status and competitive positions of Ukraine. It proves that in the current context the competitive status of the national economy is determined by the presence of a strong global competitive force that provides dynamic growth based on innovation potential, developed institutions, infrastructure, ICT adoption, macroeconomic stability, health, skills, product market, labor market, financial system, market size, business dynamism rather than by traditional factors (natural resources, geopolitical situation). It has been identified that a wide range of factors in global competitive force establishment suggests the complexity of its assessment. It has been noted that in world economic practice the Global Competitiveness Index of the World Economic Forum is predominantly used to assess the competitive status of the national economy. It has been determined that according to this index, in the overall ranking among 141 countries in 2019, Ukraine ranked 85th (2009-2010 – 82/133; 2018 – 83/140). The article analyzes of the competitive status of Ukraine in the international arena in terms of twelve pillars of the studied index and in the context of components of the said pillars. The dynamics of Ukraine's global competitive force in recent years shows that there has not been any build up. However, if one analyzes it in terms of the criteria of the global competitive force of the domestic economy, their assessment is volatile: the main regression can be traced in the sphere of the financial system, where Ukraine dropped by 19 positions in one year (2018 – 117/140, 2019 – 136/141), and the greatest progress is observed in the product market, where Ukraine rose by 16 positions in one year (2018 – 73/140, 2019 – 57/141). Analysis of the components of Ukraine’s global competitive force criteria shows that the worst positions in terms of such components are as follows: non-performing loans (% of gross total loans) – 139/141 and soundness of banks – 131/141. The best positions are in terms of the following components: costs of starting a business – 14/141 and attitude towards entrepreneurial risk – 18/141.

scholarly journals Quantifying the Effects of Wave—Current Interactions on Tidal Energy Resource at Sites in the English Channel Using Coupled Numerical Simulations

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3625
Author(s):  
Jon Hardwick ◽  
Ed B. L. Mackay ◽  
Ian G. C. Ashton ◽  
Helen C. M. Smith ◽  
Philipp R. Thies
Keyword(s):  
Wave Model ◽  
Tidal Energy ◽  
English Channel ◽  
Flow Conditions ◽  
Mean Flow ◽  
Radiation Stress ◽  
Large Wave ◽  
Stress Gradients ◽  
The Mean ◽  
Flow Power

Numerical modeling of currents and waves is used throughout the marine energy industry for resource assessment. This study compared the output of numerical flow simulations run both as a standalone model and as a two-way coupled wave–current simulation. A regional coupled flow-wave model was established covering the English Channel using the Delft D-Flow 2D model coupled with a SWAN spectral wave model. Outputs were analyzed at three tidal energy sites: Alderney Race, Big Roussel (Guernsey), and PTEC (Isle of Wight). The difference in the power in the tidal flow between coupled and standalone model runs was strongly correlated to the relative direction of the waves and currents. The net difference between the coupled and standalone runs was less than 2.5%. However, when wave and current directions were aligned, the mean flow power was increased by up to 7%, whereas, when the directions were opposed, the mean flow power was reduced by as much as 9.6%. The D-Flow Flexible Mesh model incorporates the effects of waves into the flow calculations in three areas: Stokes drift, forcing by radiation stress gradients, and enhancement of the bed shear stress. Each of these mechanisms is discussed. Forcing from radiation stress gradients is shown to be the dominant mechanism affecting the flow conditions at the sites considered, primarily caused by dissipation of wave energy due to white-capping. Wave action is an important consideration at tidal energy sites. Although the net impact on the flow power was found to be small for the present sites, the effect is site specific and may be significant at sites with large wave exposure or strong asymmetry in the flow conditions and should thus be considered for detailed resource and engineering assessments.

scholarly journals Novel Protein-Repellent and Antibacterial Resins and Cements to Inhibit Lesions and Protect Teeth

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Li Cao ◽  
Junling Wu ◽  
Qiang Zhang ◽  
Bashayer Baras ◽  
Ghalia Bhadila ◽  
...  
Keyword(s):  
Orthodontic Treatment ◽  
The Novel ◽  
Dental Resin ◽  
Biofilm Growth ◽  
New Class ◽  
Dental Resins ◽  
Wide Range ◽  
Oral Biofilms ◽  
One Year

Orthodontic treatment is increasingly popular as people worldwide seek esthetics and better quality of life. In orthodontic treatment, complex appliances and retainers are placed in the patients’ mouths for at least one year, which often lead to biofilm plaque accumulation. This in turn increases the caries-inducing bacteria, decreases the pH of the retained plaque on an enamel surface, and causes white spot lesions (WSLs) in enamel. This article reviews the cutting-edge research on a new class of bioactive and therapeutic dental resins, cements, and adhesives that can inhibit biofilms and protect tooth structures. The novel approaches include the use of protein-repellent and anticaries polymeric dental cements containing 2-methacryloyloxyethyl phosphorylcholine (MPC) and dimethylaminododecyl methacrylate (DMAHDM); multifunctional resins that can inhibit enamel demineralization; protein-repellent and self-etching adhesives to greatly reduce oral biofilm growth; and novel polymethyl methacrylate resins to suppress oral biofilms and acid production. These new materials could reduce biofilm attachment, raise local biofilm pH, and facilitate the remineralization to protect the teeth. This novel class of dental resin with dual benefits of antibacterial and protein-repellent capabilities has the potential for a wide range of dental and biomedical applications to inhibit bacterial infection and protect the tissues.

Cognitive impairment in long-term benzodiazepine users

1988 ◽  
Vol 18 (2) ◽  
pp. 365-374 ◽  
Author(s):  
Susan Golombok ◽  
Parimala Moodley ◽  
Malcolm Lader
Keyword(s):  
Neuropsychological Tests ◽  
Matched Control ◽  
Control Group ◽  
Therapeutic Practice ◽  
The Past ◽  
Visual Spatial ◽  
Wide Range ◽  
High Doses ◽  
One Year

SynopsisIn view of the very extensive and often prolonged use of benzodiazepines in therapeutic practice, this study was designed to investigate whether or not cognitive ability is impaired in longterm benzodiazepine users, and to determine the nature and extent of any deficit. Fifty patients currently taking benzodiazepines for at least one year, thirty-four who had stopped taking benzodiazepines, and a matched control group of subjects who had never taken benzodiazepines or who had taken benzodiazepines in the past for less than one year were administered a battery of neuropsychological tests designed to measure a wide range of cognitive functions. It was found that patients taking high doses of benzodiazepines for long periods of time perform poorly on tasks involving visual-spatial ability and sustained attention. This is consistent with deficits in posterior cortical cognitive function.

scholarly journals Oropharyngeal histoplasmosis: report of eleven cases and review of the literature

2011 ◽  
Vol 44 (1) ◽  
pp. 26-29 ◽  
Author(s):  
Vicente Sperb Antonello ◽  
Vanice Ferrazza Zaltron ◽  
Marcela Vial ◽  
Flávio Mattos de Oliveira ◽  
Luiz Carlos Severo
Keyword(s):  
Medical Records ◽  
Histoplasma Capsulatum ◽  
Systemic Mycosis ◽  
Database Analysis ◽  
Laboratory Findings ◽  
Active Pulmonary Tuberculosis ◽  
Disseminated Histoplasmosis ◽  
Amphotericin B Deoxycholate ◽  
One Year ◽  
Hiv Seropositive

INTRODUCTION: Histoplasmosis is a systemic mycosis endemic in Brazil, especially in the State of Rio Grande do Sul, where Histoplasma capsulatum was isolated from the soil. H. capsulatum may compromise unusual areas, including the oropharynx, particularly in patients presenting disseminated histoplasmosis; which is associated with a state of immunosuppression, such as AIDS. METHODS: During database analysis of a total of 265 cases of histoplasmosis, the medical records of 11 patients with histological or microbiological diagnoses of oral histoplasmosis (OH) between 1987 and 2008 were retrospectively reviewed. RESULTS: This work reports 11 cases of OH, the majority presenting histopathological or microbiological evidence of disseminated histoplasmosis (DH). In the patients with DH, OH was the first manifestation of histoplasmosis. Five of the 11 patients discussed were HIV-seropositive with clinical and laboratory findings of AIDS. Four patients presented active pulmonary tuberculosis concomitant with histoplasmosis. Treatment was based on the use of itraconazole and amphotericin B deoxycholate. Eight patients responded successfully to therapy after one year, two did not come back for reevaluation and one died despite adequate therapy. CONCLUSIONS: Oral histoplasmosis is closely associated with immunosuppression status, especially in patients presenting AIDS; moreover, in many cases, OH is the first sign of disseminated histoplasmosis.

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