Offshore Projects Research Articles

Floating offshore wind projects development in South Korea without government subsidies

The South Korean government is encouraging the active participation of power generation companies in the offshore wind power project by announcing the renewable energy certificates (REC) weighting plan. However, from a long-term perspective, the offshore wind power must be able to generate profits without government support to demonstrate its business feasibility and attract the voluntary participation of power generation companies. This is because government support may be subject to change, depending on the internal and external political circumstances of the country. This report calculates the expected costs for a 495 MW floating offshore wind farm in South Korea’s market environment and examines how the feasibility of the project shifts depending on the country’s current REC weights. Furthermore, this study intends to determine whether floating offshore wind power can generate profits without the Korean government’s support by calculating the expected profit in combination with the green hydrogen project. The net present value, levelized cost of energy and internal rate of return (IRR) indexes are calculated according to the project’s specific particularities, such as power purchase agreement, REC weighting, distance from shore and sea depth. Based on this, an index-based comparison is revealed and the margin for profitability for such an investment is discussed. The calculation results revealed that with a decrease in capital expenditures and operating expenditure or an increase in the system marginal price under specific assumptions, the value of IRR increased.

Forecasting supercritical behavior of drill strings in horizontal wells

The determining factor in the current changes in the world energy balance and its structure, as well as the global development of the oil and gas industry, is currently the technological factor. As a result, fundamentally new categories of horizontal and inclined wells appeared and developed. They give a multiple increase in flow rates, as they increase the production area many times over. They are used in the development of offshore projects, in swampy and very difficult areas, to increase oil recovery, restoration of inactive wells.
 New technologies based on the method of horizontal drilling have revolutionized the practice and theory of world oil production, as they have allowed the destruction of offshore oil and gas fields without the construction of expensive offshore foundations and platforms.
 When drilling horizontal wells, as a rule, the main cause of emergencies is the loss of stability of the drill string, its bifurcation protrusion and the maximum frictional interaction with the well wall. The issues of theoretical modeling of the phenomenon of unstable protrusion of columns are associated with significant difficulties, the main of which is due to the need to set the Sturm-Liouville boundary value problem on a large length of drill string. Because for deep wells, the drill string becomes geometrically similar to a human hair, many traditional mathematical methods used to integrate solving equations become poorly convergent in these cases.
 Based on the theory of curvilinear flexible rods, the problem of theoretical modeling of supercritical states of drill strings taking into account their contact interaction with the walls of oil and gas wells is set. Analytical solutions of the problem are constructed, which determine the critical values of external tensile or compressive longitudinal force and torque at a given difference in the diameters of the cavity and the drill string, the zones of supercritical states of drill strings are established.

Life Cycle Monitoring of Offshore Steel Pipe Piles via UWFBG Wireless Sensor Network

Monitoring the stress and deformation state of offshore steel pipe piles is very necessary for complex ocean environments. However, challenges still remain in remotely capturing detailed data on offshore projects. Herein, an ultraweak fiber Bragg gratings- (UWFBGs-) based wireless sensor network was established to obtain the high-precision strain along the piles. The No. 3 offshore wind power safety monitoring project in South Shandong Peninsula, China, used such a fiber-optic monitoring system. From January 1 to June 1, 2022, strain profiles of three offshore steel pipe piles were measured in seconds with a 1 m spatial resolution and a 1 με strain resolution, which clearly show sea level and mud-water interfaces. To assess the pile’s operational condition, the displacement and rotational angle of the mud surface are further calculated. It is discovered that the horizontal deformation at sea has a positive correlation with the wind, waves, and current, meanwhile decreasing with depth. The UWFBG-wireless sensor network can realize dynamic monitoring and early warning, which is promising for the life cycle monitoring of offshore wind turbine steel pipe piles.

High-resolution scenario building support for offshore grid development studies in a geographical information system

On the roadmap to reach the climate targets, Europe is committed to increase offshore wind power generation substantially from today towards 2050. This raises the question, what infrastructure layout efficiently integrates offshore wind power into the transmission grid. It is commonly addressed via scenario based optimisation studies to benchmark arbitrarily defined grid topology layouts such as radial connections of wind farms to shore against multi terminal offshore hubs or hybrid interconnectors. This paper proposes a new workflow to improve the design and calibration of topology scenarios for offshore grid studies with help of an automated process in a geographical information system. Against the backdrop of the recently adopted maritime spatial plans by EU member states, a high-resolution and large scale search graph of the future offshore grid is created with a multi-criteria analysis. Complexity reduction techniques are proposed to simplify this graph for subsequent investment optimisation studies. It is found that respecting the geographic reality of the heavily managed sea space not only reduces uncertainty for future offshore projects for more accurate cost estimates and cable trajectories. The consideration of designation areas in the sea also consolidates future grid planning options into common paths of transmission which facilitates the identification of relevant scenarios for analysis. It can be shown, that the commonly chosen benchmark of an “all radial” connection of wind farms to shore is a questionable choice to which an alternative is provided. The strategic relevance of the existence of spatial planning and access to high-resolution data for an improved grid development is demonstrated at the example of Baltic and North Sea.

Identification of 4D-BIM Barriers in Offshore Construction Projects Using Fuzzy Structural Equation Modeling

Planners face many obstacles during the planning phase of any new project, especially project scheduling due to the numerous details and complexity of each uniquely designed project; previous experience in similar projects and traditional scheduling methods are not sufficient. The 4D-BIM schedule is the best solution, as it can be integrated with other modern technologies such as UAS, which improves project scheduling by allowing the project team to access project plans, details, and time-related information to simulate construction sequences. Despite the benefits of using 4D-BIM, planners prefer traditional planning and scheduling methods because of the barriers to using modern technologies. This research proposes a structural equation model focusing on estimating the weights of BIM barriers in offshore construction projects, including: the investigation of barriers keeping the construction industry standing at 3D-BIM; the relationships between them; and the evaluation of the probability and impact of each, using fuzzy theory. To validate the proposed model, a case study of an offshore project was conducted. The most important latent variables were awareness, risk, demand, and management, while the most prominent observed variables were the uncertainty of the return on investment and the lack of experienced users. This research guides project managers on actions that can be taken for each key variable to enhance and develop the use of 4D-BIM in project scheduling.

The Practice and Development of T-Bar Penetrometer Tests in Offshore Engineering Investigation: A Comprehensive Review

In recent years, the development of marine hydrocarbon resources has led to an increased demand for research on the marine soil bearing capacity and cyclic loading effect in marine engineering design. Because of the difficulties and high costs involved in obtaining high-quality soil samples from offshore sites, in situ testing techniques have become the preferred method of determining design parameters in offshore geotechnical engineering projects. This paper provides a review of the current state of marine penetrometer deployment technology used in offshore engineering investigations and presents a summary of the T-bar penetrometer test for measuring marine soft clay. The existing literature research on penetration mechanisms, numerical simulations, laboratory experiments, and field tests of the T-bar penetrometer in the field of marine geotechnical engineering are analyzed. Finally, the potential difficulties, challenges, and prospects of the T-bar penetrometer tests are discussed.

Harnessing Offshore Wind in Canada: The Regulatory Landscape for Offshore Wind Development and Lessons Learned from the United Kingdom, Denmark, and the United States

Abstract Offshore wind is a key renewable energy source which can lessen depend-ency on fossil fuels and help meet global decarbonization targets. Countries such as the United Kingdom, Denmark, and recently the United States of America, have success in operationalizing offshore wind developments. Canada, despite vast ocean resources, does not have any offshore wind projects. One reason for this can be attributed to the lack of policies to sup-port development of offshore wind projects. To date, there has been no research conducted on the legal regime for developing an offshore wind energy project in Canada. This research focuses on identifying which ear-ly-stage permits are required for offshore wind development federally and provincially, utilizing Nova Scotia as a provincial example. This article iden-tifies the relevant Canadian legislation, regulations, and decision-makers as well as makes suggestions to improve Canada’s regime. To identify regula-tory improvements that Canada could utilize, the regimes of the UK, Den-mark, and the USA are examined with a focus on their initial permit pro-cess. The proposed policy improvements relate to matters of environmental and impact assessments, seabed acquisition and licensing, as well as the administrative processes for granting required permits and consents.

Intelligent Deepwater Solutions Hub Maximizes Value Across Asset Life Cycle

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 211453, “Intelligent Deepwater Advanced Solutions Hub for Value Maximization Throughout Asset Life Cycle,” by Sam Ryu, Carmela Chaney, and Wei Xu, ExxonMobil, et al. The paper has not been peer reviewed. _ Challenges posed by life-cycle management of an offshore asset, multidisciplinary systems engineering, and competing project objectives provide an opportunity for a new approach to maximize value. The objective of the complete paper is to introduce the operator’s intelligent Deepwater Advanced Solutions Hub (iDASH) approach, wherein various engineering tools are integrated strategically to improve decision quality. Introduction The complexities inherent in producing offshore oil and gas mean that creation of an optimal solution for all phases of the project life cycle is a serious challenge. Market research has suggested that the oil and gas industry could benefit from increased systems engineering with an approach that looks beyond first application, integrates requirements, and supports the identification of changes for new applications. The industry has been slow to adopt digitalization, with one of the lowest levels of digital maturity compared with other sectors. For the purposes of this paper, offshore oil and gas development can be broken into four phases after a field is evaluated to be commercially viable: concept selection, definition and execution, operations, and decommissioning. Each phase has unique objectives and challenges. During concept selection, generation of creative multiple alternatives for deepwater full-field development is a challenge because each offshore project is unique and requires time-consuming discussion cycles involving high uncertainty, multidisciplinary input, and constraints identified from a wide range of technical specialties. Once detailed design and execution begin, the objective becomes value preservation. Collaboration between the operator’s project management and contractors becomes a resource-intensive process. After startup, the objective moves toward value realization. Handover from project teams to operations can be time-consuming, leaving key pieces of data missing. Unexpected downtime, integrity issues, or process conditions can erode value and delay project payback. Operations also present an opportunity to process and implement feedback and lessons learned. The authors divide engineering tools into four pillars within the discussed iDASH approach: iConcept (concept-selection tools), iDesign (definition and execution tools), iOperate (operation tools), and iDecom (decommissioning tools), offering different value to each stage of value maximization, reducing capital expenditure (CAPEX) and maximizing net present value (NPV), achieving balance with other important objectives. These four pillars are expanded upon and illustrated with use cases in the complete paper. Finally, strong data integration is the foundation of this platform, enhancing interdisciplinary work, ideation cycle time, and decision traceability. Making Quality Decisions With Multiple Alternatives iConcept is a digital suite focusing on addressing challenges at the concept-selection stage. The centralized suite includes a variety of different tools developed both internally and externally based on data analytics, artificial intelligence (AI), and decision science that aim to improve decision quality. One of the key tools being leveraged is called the Field Layout Concept Optimizer. Through its use, a team can evaluate multiple alternative deepwater field developments rapidly to enable quick turnaround for quality decision-making. Multiple disciplines are integrated to reduce human bias.

A geospatial method for estimating the levelised cost of hydrogen production from offshore wind

This paper describes the development of a general-purpose geospatial model for assessing the economic viability of hydrogen production from offshore wind power. A key feature of the model is that it uses the offshore project's location characteristics (distance to port, water depth, distance to gas grid injection point). Learning rates are used to predict the cost of the wind farm's components and electrolyser stack replacement. The notional wind farm used in the paper has a capacity of 510 MW. The model is implemented in a geographic information system which is used to create maps of levelised cost of hydrogen from offshore wind in Irish waters. LCOH values in 2030 spatially vary by over 50% depending on location. The geographically distributed LCOH results are summarised in a multivariate production function which is a simple and rapid tool for generating preliminary LCOH estimates based on simple site input variables.

Assessment of turbulence intensity estimates from floating lidar systems

In the pre-construction phase of offshore wind energy projects floating lidar systems (FLS) are used for wind site assessment. Their measurements of mean wind speed and direction have proven to be accurate according to existing standards. But for the assessment of turbulence intensity (TI), a widely-accepted procedure and acceptance criteria are missing. This study investigates different evaluation methods, namely linear regression analysis and the key performance indicators (KPIs) presented by the Consortium for Advancing Remote Sensing (CFARS). The assessment is based on data from an offshore trial of the Fugro SEAWATCH Wind Lidar Buoy (SWLB) against the meteorological mast and a collocated fixed profiling wind lidar at Blyth, UK. The results show that the accuracy of TI estimates from FLS can be evaluated well, when the KPIs mean bias error (MBE) and representative TI error suggested by CFARS are used. We propose best-practice acceptance thresholds of ±1% for MBE and ±1.5% for the representative TI error. The motion-compensation approach of the SWLB works well and after compensation, its TI data are similar to the data from the fixed reference lidar. The impact of lidar-specific effects is minor in the analyzed data set and near-to-zero biases are found for all measurement elevations and wind speed bins in comparison to mast data.

Offshore wind in the race for ocean space: A forecast to 2050

This paper reports on recent results on the race for space in our ocean, based on DNVs forecasting efforts into the Blue Economy. We find that the world will see a large increase in the usage of ocean area by offshore installations for energy and food production, with the European area for installations growing close to five-fold to 2050. If not carefully managed, the energy transition in the ocean risks triggering a race for space and conflicts with other stakeholders. By introducing the Spatial Competition Index (SCI), we propose a new indicator to measure the level of competition among ocean industries and nature. SCI forecasts to 2050 reveal that shallow waters close to shore will face significant increases in pressure from ocean industries. This indicates that there is a need for co-existence to be considered in new offshore wind development projects, and for developers to increasingly consider floating structures.

Wind Retrieval from Constellations of Small SAR Satellites: Potential for Offshore Wind Resource Assessment

The planning of offshore wind energy projects requires wind observations over long periods for the establishment of wind speed distributions. In the marine environment, high-quality in situ observations are sparse and restricted to point locations. Numerical modeling is typically used to determine the spatial variability of the wind resource. Synthetic Aperture Radar (SAR) observations from satellites can be used for retrieval of wind fields over the ocean at a high spatial resolution. The recent launch of constellations of small SAR satellites by private companies will improve the sampling of SAR scenes significantly over the coming years compared with the current sampling rates offered by multi-purpose SAR missions operated by public space agencies. For the first time, wind fields are retrieved from a series of StriX SAR scenes delivered by Synspective (Japan) and also from Sentinel-1 scenes delivered by the European Space Agency. The satellite winds are compared with wind speed observations from the FINO3 mast in the North Sea. This leads to root-mean-square errors of 1.4–1.8 m s−1 and negative biases of −0.4 m s−1 and −1.0 m s−1, respectively. Although the Geophysical Model Functions (GMF) applied for wind retrievals have not yet been tuned for StriX SAR observations, the wind speed accuracy is satisfactory. Through conditional sampling, we estimate the wind resource from current and future SAR sampling scenarios where the number of SAR satellites in orbit is increasing over time. We find that hourly samples are needed to fully capture the diurnal wind speed variability at the site investigated. A combination of SAR samples from current missions with samples from clusters of small SAR satellites can yield the necessary number of wind speed samples for accurate wind resource estimation. This is particularly important for sites with pronounced diurnal wind speed variability. An additional benefit of small SAR satellites is that wind speed variability can be mapped at the sub-km scale. The very high spatial resolution is valuable for characterizing the wind conditions in the vicinity of existing offshore wind farms.

Response of harbor porpoises (Phocoena phocoena) to different types of acoustic harassment devices and subsequent piling during the construction of offshore wind farms

Before piling of offshore wind farm foundations, acoustic harassment devices (AHDs) are used to drive harbor porpoises out of the area where they could suffer injuries. Until 2017, a combination of pingers and seal scarer devices (usually SPL = 174-193 dB re 1 μPa (rms) @ 1m at 1 to 20 kHz depending on the device) was prescribed for mitigation purposes in Germany. However, seal scarers led to decreased porpoise detection rates in much larger distances than intended, when 750 m is usually rendered sufficient to avoid injuries. Therefore, devices specifically designed for mitigation purposes were developed and are prescribed since then. These acoustic porpoise deterrents (APDs; e.g. FaunaGuard Porpoise Module; SPL = 172 dB re 1 μPa (rms) @ 1m at 60 to 150 kHz) aim to keep the animals away from offshore construction sites but should not lead to large-scale disturbance as caused by a seal scarer. Although project-specific evaluations indicated that APDs are effective, a cross-project analysis and a comparison with data from previous piling procedures employing seal scarers were still pending. The present study aimed to fill this gap. Between March 2018 and April 2019, harbor porpoise detection rates were monitored acoustically in four offshore wind farm projects using CPODs before, during and after piling at different distances up to 10 km from piling. APD operation led to a significant decrease in detection rates in the vicinity of the device, indicating the displacement of the animals from a small-scale area. Depending on the wind farm, detection rates during APD operation decreased by 30 to 100% at 750 m distance compared to 6 hours before APD operation. Furthermore, reduced detection rates during APD operation were only observed up to about 2.5 km distance even when the APD was switched on for over 40 minutes. Given that the extent of disturbance to harbor porpoises is lower when using an acoustic porpoise deterrent compared to the seal scarer, we consider that preferential use of an acoustic porpoise deterrent is an improvement to mitigation strategies and an important step forward to a less harmful piling procedure.

Field tests on large-scale instrumented piles driven in chalk: results and interpretation

The design of large open steel piles driven at chalk sites suffers from considerable uncertainty, leading to major difficulties in many significant onshore and offshore projects. This paper describes recent instrumented driving, monotonic testing to failure, and restrike tests conducted on large open steel piles driven in primarily low- to medium-density chalk at a site in North-western France. The experiments are described and interpreted with reference to a high-quality site characterisation, dynamic and static methods of test analysis, and alternative predictive design approaches. Important new conclusions flow regarding driving behaviour, the set-up that took place over up to 65 days after installation and the resistances available under compression and tension loading. Surprisingly large differences are shown between tension and compression shaft capacity, which are postulated to be due to Poisson straining in the steel pile shaft and its interaction with the surrounding chalk mass. The field tests contribute to building a high-quality dataset that allows proposed axial capacity design methods to be tested and potentially refined to provide reliable and representative design tools.

Mechanical properties and hydration of ultra-high-performance seawater sea-sand concrete (UHPSSC) with limestone calcined clay cement (LC3)

Ultra-high-performance seawater sea-sand concrete (UHPSSC) has attracted increasing attentions over the past few years as it exhibits exceptional mechanical and durability properties similar to conventional ultra-high-performance concrete (UHPC). Comparing to conventional UHPC, UHPSSC has great advantages when applied in marine engineering, particularly in offshore projects where construction materials are not easily accessible, and the transportation is costly. Nonetheless, current production of UHPSSC still necessitates large amounts of cement due to its low water/binder ratio. The larger demands of cement in manufacturing UHPSSC/UHPC than ordinary concrete can lead to substantial increase in the carbon emission. Therefore, an eco-friendly UHPSSC is developed in this paper by incorporating a promising ternary binder system (LC3) that consists of limestone (LS), calcined clay (metakaolin) and cement. The influence of the metakaolin (MK) dosage on the mechanical, hydration and microstructure properties of UHPSSC is comprehensively studied by carrying out a variety of experiments including mechanical test, isothermal conduction calorimetry test, TGA, XRD, SEM etc. The results showed that the UHPSSC mixed with LC3 exhibited lower early-age compressive strength than the reference mix, but its long-term strength was better than the reference group owing to the formation of more hydrates at the late age by the pozzolanic reaction of MK and the synergistic reaction between LS, MK and cement. Based on this study, the coupled replacement rate of cement by LS and MK could reach up to 40% without strength compromise. Nonetheless, 20% MK and 10% LS appeared to be the optimum substitution rate (total substitution rate of 30%) where the highest long-term strength was achieved. The main exothermic peak and total heat of hydration normalized per binder weight decreased with the increase of MK content level, but the main peak occurred earlier. Moreover, the addition of seawater can promote the hydration, leading to a greater main exothermic peak.

Offshore wind acceleration in the U.S. Atlantic coast and the 30 GW by 2030 target

There is a growing interest in the United States of America to have a more significant role in the development of offshore wind power. In recent years, the country has begun to shift and drive towards a green economy, investing in clean renewables and technology that will be able to reduce carbon dioxide emissions. It is expected that offshore wind has the potential to become a primary source to supply energy to millions of Americans. In the next 10 years, the Biden administration has set a target to achieve close to 30 GW of offshore wind potential. With the existing offshore wind projects in place, many developers are continuing to make progress, but there are many limiting factors that could decide whether that goal will be achieved. A detailed analysis in the U.S. Atlantic coast was deemed necessary and light was shed to the licensing process towards the goal of 30 GW by 2030.

Anglers' support for an offshore wind farm: Fishing effects or clean energy symbolism

Rapid expansion of offshore wind energy will have impacts on existing users of marine space, including recreational angling. Because angling has significant economic and cultural significance in ocean and coastal areas, and managers increasingly employ new approaches to manage conflicts between fishing and other uses, it is critical to understand the perspectives of this interest group regarding development of offshore wind energy. Using a mixed-methods approach, this study examines the attitudes of anglers towards the Block Island Wind Farm, the first offshore wind energy development constructed in the United States. Supported by qualitative interviews, a quantitative survey of 199 anglers from Rhode Island, Connecticut, New York, and Massachusetts reveals moderate support for the wind farm. Experience fishing at the wind farm is associated with more positive beliefs regarding the development’s effects on catch-related aspects of fishing; however, beliefs about catch-related effects are not as strong predictors of support as non-catch factors (specifically, visual impacts). Moreover, belief that the wind farm is “symbolic of progress towards clean energy” has the greatest total impact on support and effects of the wind farm, indicating that underlying values and ideologies may have greater influence on angler’s attitudes towards offshore wind projects than effects on the fishing experience. Greater research is needed to understand how general characteristics of anglers affect their attitudes towards offshore renewable energy and other marine governance decisions. Managers must also facilitate greater participation of anglers in offshore wind energy decision-making.

Study on Fine Wave Forecasting for Offshore Wind Farms

In order to ensure the safety of offshore operation and maintenance personnel and the smooth progress of major offshore projects, this paper establishes a prediction model of wave height and wave period based on support vector regression (SVR). First, the observation data of Xiaochangshan meteorological station from August 2021 to July 2021 are used to build a prediction model, and the data are preprocessed, and parameters are optimized. Then, the model trained with nine characteristics is evaluated for error under the test set, and the comparison image between the predicted value and the actual wind wave height and wind wave period is output. Finally, the observation data of the meteorological station in early August 2021 are used for verification of one hour and one day (24 hours). The experimental results show that the model can predict the wave height and wave period of the next hour and day, and the maximum error is not more than 0.4m, which can effectively provide a reasonable technical reference for the short-term prediction of the effective wave height of offshore waves.

Research on the identification and distribution of biofouling using underwater cleaning robot based on deep learning

The rapid identification of biofouling is of great significance to the intelligent operation and maintenance of large ships or other deep-sea and offshore projects. The biofouling's optical imaging properties and its dispersion and concealment bring challenges to the correct segmentation of its images. In this article, a filter-guided inverse dark channel inversion exposure compensation (FIDCE) algorithm is proposed for the ambiguous image by exploring an underwater optical imaging model partially over-exposed and partially under-exposed. Also, MFONet, a pixel-level segmentation model, is proposed. Its backbone feature extraction network includes MobileNetV2—a lightweight CNN model with the Sandglass block as the basic unit, and combines with ASPP enhanced feature extraction module, thereby enhancing the network perception field. In this model, SENet is also used to enhance the deep and shallow feature fusion. In addition, the underwater image evaluation functions are compared to verify the validity of the image processing algorithm mentioned above. According to the results, a more accurate and quicker effect can be observed in the fine-grained identification of biofouling using MFONet. Nowadays, such an algorithm can be used for a priori study of biofouling and the cleaning operation of the robot.

Carbon Footprint of An Offshore Survey by Oil and Gas Service Provider Company

The rapid development of global economy has leaded to climate change issues. The greenhouse gases including carbon dioxide have driven the issues of climate change and become one of the concerns confronting human society. An offshore survey project that carried out by a service provider company in oil and gas industry was chosen for the carbon footprint estimation during the project’s operation in this study. The major objective of this study is to calculate the carbon footprint of the above-mentioned project in terms of CO2, eq and use it as a benchmark or reference for the company, as well as to create an Excel Tool that can be used as a carbon footprint calculator. Greenhouse Gas Protocol methodology is to generate the framework for the project in this study. There have three unavoidable sources: fuel combustion by survey vessel, transportation involved and water consumption during the operation of the project. The emission factors approach is used in this study to quantify the emission of GHGs from the project. Emission factor values will be obtained from the published report that revised by Federal Register of Legislation in 2020. The carbon footprint of the project was calculated to be 130.44 tons of CO2, eq. Scope 1 accounted for 96.05% of the carbon footprint, which comprised fuel combusted by survey vessel.