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Wind-induced interference effect commonly occurs among arched plastic greenhouse group. To describe such influence and finally determine the wind load shape coefficients considering the interference effects, we conducted a series of numerical simulations based on computational fluid dynamics (CFD). Combining the Reynolds-averaged N-S equations and the Realizable k-ε turbulence model, the surface wind pressure characteristics of the models for single greenhouse and greenhouse group under different wind direction angles and distances were studied separately. In combination with the actual production, 5 rows and 6 columns symmetrical layout was adopted as the greenhouse group’s model with different gap distances (2, 4, 6, 8, 10 and 12 m) and wind direction angles (0, 30, 45, 60 and 90 degrees). In order to achieve quantitative analysis of the wind-induced interference effects, the interference factor was introduced in this paper as an important contrast parameter. According to the characteristics of the greenhouse structure, the greenhouse partition was reasonably set to realize the key research of wind pressure characteristics in wind-sensitive areas. In the numerical wind tunnel simulation, unstructured grids suitable for greenhouse group’s model were used to divide the computational domain. The calculation parameters such as blocking ratio, inlet and outlet conditions, and near-wall treatments and so on were appropriately set. By comparing with wind tunnel test results of similar models, the present numerical simulations were verified. According to the simulation results, the arrangement of greenhouse group causes the wind-induced interference effects, which will change wind pressure characteristics of the greenhouses. The effects can result in amplification effects (the outer area of the greenhouse group) and the shielding effects (the middle area of the greenhouse group), among which the amplification effects threatens the safety of the structure and cannot be ignored. The interference effects is significantly affected by the wind direction angle and the gap distance, and specifically it decreases with the increase of distance, and tends to be stable when the distance between greenhouses is about 10 m. Based on the analysis of the variation law of the mean wind pressure coefficients and wind direction angles on the greenhouse group’s roofs, it is obvious that the interference effects weakens the wind pressure ventilation ability of the greenhouse group as a whole. From the point of view of advantageous to wind pressure ventilation, the suggestions on planning and layout of the greenhouse group are put forward, that is, the long axis direction of the greenhouses should be perpendicular to the dominant wind direction in summer of the area where the greenhouse group is located and the gap distance should be increased appropriately. Finally, according to the wind-induced interference effects, the wind load shape coefficients for arched plastic greenhouses (the rise-span ratio is 3:8) are given, which are convenient for design. The wind load shape coefficients of greenhouses which are located in the outer area of the greenhouse group: At 0 wind direction angle, +0.41 on the windward side, -0.78 on the middle roof, -0.26 on the leeward side and -0.48 on both sides of gables; at 90 degrees wind direction angle, +0.36 on the windward gable, -0.44 on the roof. The wind load shape coefficients of greenhouses which are located in the middle area of the greenhouse group: At 0 wind direction angle, +0.30 on the windward side, -0.71 on the middle roof, -0.26 on the leeward side and -0.48 on both sides of gables; at 90 degrees wind direction angle, +0.34 on the windward gable, -0.35 on the roof. Wind-induced interference effects exists in arched plastic greenhouses arranged in group, and wind pressure changes on the greenhouses caused by wind-induced interference effects should be considered in design. [ABSTRACT FROM AUTHOR]

The rapidly increasing penetration of renewable energies has introduced severe challenges to power system frequency controls due to the highly intermittent and uncertain power output of renewable energies. This study proposes a proactive frequency control method to control traditional synchronous generators in advance in anticipation of sudden power fluctuation. Therefore, the frequency deviations can be well mitigated by such early‐acted control signal. In order to obtain this new control reference, an ensemble‐forecasting model based on the extreme learning machine algorithm is designed to predict ultra‐short‐term power fluctuations, which serves as an extra signal for automatic generation control. The proposed method was verified on an equivalent model of the Singapore power system with various types of generations and loads. The simulation results clearly demonstrate the accuracy of the forecasting model and the advantages of the proposed control method. The proposed method can also reduce the frequency charging/discharging of energy storage systems, which can effectively extend their lifetime. [ABSTRACT FROM AUTHOR]

Microgrids are usually based on single voltage levels, supporting a number of distributed generation sources and loads. This paper describes a multi-tier DC microgrid, with multiple voltage levels able to source and supply different power demands. A universal droop controller is developed for this multi-tier microgrid, able to connect uni- and bi-directional elements on to the grid. Simulations are used to demonstrate the functionality of the controller to allow autonomous load sharing based on decentralised control, with bi-directional power transfer between tiers to balance supply and demand at each level. Power can also be directly sent from one element of the microgrid to another, which is demonstrated through simulation, allowing for integration with future peer-to-peer energy trading systems. [ABSTRACT FROM AUTHOR]

Along with the upscaling tendency, lighter and so more flexible wind turbine blades are introduced for reducing material and manufacturing costs. The flexible blade deforms under aerodynamic loads and in turn affects the flow field, arising the aeroelastic problems. In this paper, the impacts of blade flexibility on the wind turbine loads, power production, and pitch actions are discussed. An advanced aeroelastic model is developed for the study. A free wake vortex lattice model instead of the traditionally used blade element momentum (BEM) method is used to calculate the aerodynamic loads, and a geometrically exact beam theory is adopted to compute the blade structural dynamics. The flap, lead-lag bending, and torsion degrees-of-freedom (DOFs) are all included and nonlinear effects due to large deflections are considered. The National Renewable Energy Laboratory (NREL) 5 MW reference wind turbine is analyzed. It is found that the blade torsion deformations are significantly affected by both the aerodynamic torsion moment and the sectional aerodynamic center offset with respect to the blade elastic axis. Simulation results further show that the largest bending deflection of the blade occurs at the rated wind speed, while the torsion deformation in toward-feather direction continuously increases along with the above-rated wind speed. A significant reduction of the rotor power is observed especially at large wind speed when considering the blade flexibility, which is proved mainly due to the blade torsion deformations instead of the pure-bending deflections. Lower pitch angle settings are found required to maintain the constant rotor power at above-rated wind speeds. [ABSTRACT FROM AUTHOR]

Copyright of Guangdong Architecture Civil Engineering is the property of Guangdong Architecture Civil Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A comparison between the rolling loads calculated through the theoretical models of Sims, Orowan-Pascoe and Ekelund is performed in order to verify the performance of the models compared to the real values recorded during the processing of plain carbon-manganese steels and niobium steels during the finish rolling in the hot strip mill. To determine the hot deformation resistance, the equations of Shida, Poliak & Siciliano, Siciliano, Marini & Bruna, Siciliano, Leduc & Hensger, Misaka and Siciliano & Jonas are used. In the direct comparison between the calculated values and the actual values the best level of precision is obtained when the load prediction models are combined with the Shida equation, respectively Sims, Orowan-Pascoe and Ekelund. In order to better adjust calculated loads to the reality of the industrial process, adjustment factors are proposed for each of the seven stands of the finishing mill. With the application of the adjustment factors, the load prediction equations presented global mean errors in the finishing mill, varying between 4.3 and 5.6% for C-Mn steels and 4.6 and 6.3% for niobium steels. [ABSTRACT FROM AUTHOR]

Plants live in constantly moving fluid, whether air or water. In response to the loads associated with fluid motion, plants bend and twist, often with great amplitude. These large deformations are not found in traditional engineering application and thus necessitate new specialized scientific developments. Studying fluid–structure interaction (FSI) in botany, forestry, and agricultural science is crucial to the optimization of biomass production for food, energy, and construction materials. FSIs are also central in the study of the ecological adaptation of plants to their environment. This review paper surveys the mechanics of FSI on individual plants. I present a short refresher on fluid mechanics then dive into the statics and dynamics of plant–fluid interactions. For every phenomenon considered, I examine the appropriate dimensionless numbers to characterize the problem, discuss the implications of these phenomena on biological processes, and propose future research avenues. I cover the concept of reconfiguration while considering poroelasticity, torsion, chirality, buoyancy, and skin friction. I also assess the dynamical phenomena of wave action, flutter, and vortex-induced vibrations. [ABSTRACT FROM AUTHOR]

The optimal dispatch of microgrids is greatly challenged by various uncertainties, introduced by dynamic power fluctuations in loads and variations in renewable energy sources. To depress the over‐conservativeness of traditional robust optimisation, this study puts forward a two‐stage coupled robust and stochastic optimal (CRSO) dispatching model with mixed integer recourse for the islanded hybrid AC/DC microgrid. The CRSO model comprehensively considers the uncertainties in source–load power and bidirectional converter overhauling, and the stochastic source–load uncertainty sets are constructed by interval partitioning methods. The CRSO model optimises the binary states of the diesel generator and the bidirectional converter in the first stage, and the second stage obtains the flexible operating states and power of each unit. The daily worst‐case operation cost is minimised by the nested column‐and‐constraint generation algorithm. Numerical simulations have validated the rationality and superiority of the developed dispatching model and its solution method. [ABSTRACT FROM AUTHOR]

• Coherent turbulent structures affect floater loading mainly in high-wind conditions. • Failing to model lateral coherence can lead to an overestimation of predicted loads. • Kaimal generally performs better than Mann in high-wind, high-load scenario. • Loads on the mooring system are most sensitive to atmospheric stability in low winds. • Loads on the blade root are most sensitive to atmospheric stability in high winds. The two turbulence-generation models [Kaimal Spectrum Exponential Coherence (KSEC) and Mann] specified in the international standard for wind turbine design assume neutral atmospheric conditions and are based on statistical and spectral methods. Mainly due to the lack of physics, the flow fields simulated with these models ultimately differ in their underlying structure, especially in terms of the spatial coherence of longitudinal velocity perturbations. While this may not be critical for smaller wind turbine rotors, it becomes important when rotor sizes increase. Furthermore, it might be especially important in the context of floating technologies as they are more sensitive to large turbulent coherent structures. Previous work found that these differences between KSEC and Mann can propagate to loads predictions and thereby affect the design space of the entire wind turbine system. It is therefore crucial to determine in which ways these two models are underperforming. Up until now, validation of these models had only been done in the vertical direction because it is extremely difficult to obtain atmospheric turbulence measurements separated laterally, and sampled at heights relevant to wind energy. In this work, we address the lack of measurements by using high-fidelity, high-resolution simulation data as a reference. We perform hour-long, large-eddy simulations of turbulent velocity fields that are stability-dependent and contain three-dimensional coherent structures. These flow fields are then used to investigate which stochastic model is a better predictor of loads on a realistic spar-system floating offshore wind turbine, and to quantify how the assumption of neutral stratification propagates to short-term load estimates. Both stochastic turbulence models are found to overpredict fatigue loading in high-wind scenarios (in some cases, by more than 25%) and underpredict it when the wind speed is low (by as much as 20%). The KSEC model matches the high-fidelity flow fields more closely than Mann at high wind speeds, and the opposite is true at low wind speeds. Finally, turbine loading is found to be sensitive to atmospheric stability even when the turbulence intensity remains fairly constant. This sensitivity is most pronounced at low wind speeds, when fatigue load estimates on the spar system can differ by 40%. [ABSTRACT FROM AUTHOR]

Copyright of Food Research & Development is the property of Food Research & Development Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study proposes a time‐based security (TBS) evaluation mechanism for radial microgrids (MGs) short‐term operation. In the proposed framework, system security is modelled using time‐based sensitivity analysis in the load points. Occurring branch contingencies in a radial MG creates some islands with oscillating frequencies. The settling time of frequency oscillation, as the successful islanding time, and the island's capability to continue the load supply are considered in TBS assessment. A system frequency response model and the stored energy of storages are used to calculate the two mentioned factors. Depending on the loads' sensitivities to the successful islanding time and the service continuity duration, they are exposed to extreme damage. In the case of branches' sudden outages, it may be impossible to operate the MG without any extreme damage of loads, due to the capacity shortage in the island, dynamic behaviours of the MG and inadequate stored energy of storages. Under these conditions, the load shedding unit participates considering the customer damage function. To evaluate the performance of the proposed security assessment mechanism, the 123‐bus distribution test system is precisely analysed. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the effect of muscle imbalance on motion of back squat. The isokinetic muscle strength of the 8 subjects was recorded for the knee flexion/extension by the cybex 770 dynamometer. Each subject performed 3 back squats with the long barbell with an intensity of 25% body weight(BW), 50%BW, 100%BW, 125%BW. During the back squat through the recorded kinematic data the subjects' maximum flexion and extension knee angle, center of mass displacement and V-COP were calculated for evaluation of the stability of the movement. For the statistical analysis independent t-test was used. Knee flexion angle and COM displacement are dominated by the reciprocal muscle ratio. V-COP factor was dominated by bilateral extension deficit. Based on the results we can know that as the intensity of the squat increased to a level control was difficult because the muscles' imbalance influenced the movement. [ABSTRACT FROM AUTHOR]

While silicon anodes hold promise for use in lithium-ion batteries owing to their very high theoretical storage capacity and relatively low discharge potential, they possess a major problem related to their large volume expansion that occurs with battery aging. The resulting stress and strain can lead to mechanical separation of the anode from the current collector and an unstable solid electrolyte interphase (SEI), resulting in capacity fade. Since capacity loss is in part dependent on the cell materials, two different electrodes, Lithium Nickel Oxide or LiNi0.8Co0.15Al0.05O2 (NCA) and LiNi1/3Mn1/3Co1/3O2 (NMC 111), were used in combination with silicon to study capacity fade effects using simulations in COMSOL version 5.5. The results of these studies provide insight into the effects of anode particle size and electrolyte volume fraction on the behavior of silicon anode-based batteries with different positive electrodes. It was observed that the performance of a porous matrix of solid active particles of silicon anode could be improved when the active particles were 150 nm or smaller. The range of optimized values of volume fraction of the electrolyte in the silicon anode were determined to be between 0.55 and 0.40. The silicon anode behaved differently in terms of cell time with NCA and NMC. However, NMC111 gave a high relative capacity in comparison to NCA and proved to be a better working electrode for the proposed silicon anode structure.

The vibration serviceability of footbridges has evolved from the adoption of a single pedestrian crossing in the resonance condition to load cases in which several pedestrians cross the structure simultaneously. However, in spite of this improvement, pedestrians continue to be considered as applied loads in codes of practice. Recent research has pointed out that modeling pedestrians as dynamic systems is a step further in the search for a more realistic design approach. This is explored in this paper, focusing on the case of vertical vibration. A two-span cable-stayed test structure was selected, and accelerations were measured from single and group crossings, both at the structure and at a pedestrian’s waist. Numerical simulations considering the pedestrians modeled as loads only and also as dynamic systems were implemented, and numerical and experimental time response vibration signatures were compared. Reductions of up to 25% and 20% in peak and RMS acceleration, respectively, were obtained when pedestrians were modeled as dynamic systems, in comparison with the less realistic model of pedestrians as loads only. Such reductions were shown to depend on the number of pedestrians involved in the group. The results, thus, highlight that pedestrian–structure interaction is an asset for the vibration serviceability design of footbridges.

To study the disintegration behavior and characterization indexes of Modified Graded Carbonaceous Mudstone (MGCM), soaking disintegration tests of MGCM under vertical loading and cyclic drying-wetting were carried out with a disintegration test instrument which self-designed by our team. The grain size distribution of MGCM during drying-wetting cycles was analysed. Standard basal entropy, as an important parameter of grading entropy that quantitatively characterizes distribution curves, was introduced to characterize the disintegration behavior of MGCM and correlated with the comprehensive evaluation index, namely, disintegration ratio. The results show that as the number of drying-wetting cycles increases, the Graded Carbonaceous Mudstone (GCM) blocks disintegrate rapidly and the fine-grain content increases. With an increase in vertical load, the particles disintegrate more completely. The contents of each particle group in the GCM test groups stabilize after 9, 7, and 4 drying-wetting cycles under vertical loads of 0, 100, and 200 kPa, respectively. Under the same vertical load of 200 kPa, the contents of each particle group in MGCM test groups with Polyurea (PU) content 0, 5, and 10 wt% stabilize after 4, 6, and 8 drying-wetting cycles, respectively. The inclusion of PU can effectively retard the disintegration of GCM, and the effect is more pronounced with 5 wt% PU content compared to 10 wt%. However, it is also susceptible to the deterioration of PU layer caused by mechanical screen. The grading entropy model of MGCM under loading and cyclic drying-wetting is established. There is a significant positive, linear correlation between the standard basal entropy and the disintegration ratio. A smaller standard basal entropy to a smaller disintegration ratio, indicating a greater degree of particle disintegration and fragmentation. The standard basal entropy can characterize the disintegrated particles of MGCM with different PU content under vertical loading and drying-wetting cycles. The standard basal entropy of GCM decreases rapidly initially and then stabilizes as the number of drying-wetting cycles increases. The standard basal entropy decreases exponentially as the vertical load increases. The results provide a new quantitative index for analyzing the grading characteristics of MGCM following disintegration, which are valuable for engineering construction and disaster prevention in carbonaceous mudstone areas. [Display omitted] • Soaking disintegration tests were performed on Modified Graded Carbonaceous Mudstone (MGCM) under vertical loading and cyclic drying-wetting. • Polyurea (PU) can effectively retard the disintegration of GCM, and the effect is more pronounced at 5 wt% content. • The standard basal entropy can characterize the disintegrated particles of MGCM with different PU contents under vertical loading and drying-wetting cycles. [ABSTRACT FROM AUTHOR]

Structural design codes of different countries provide engineers with data and procedures for design of the various structural components. Building design codes from USA, Europe, and Egypt are considered. Comparisons of the provisions for actions (loads), and for the resistance (strength) of sections in flexural and compressive axial loading are carried out. Several parameters are considered including variable actions for occupancy and different material strengths. The comparison is made considering both concrete and steel structures. Issues and consequences of mixing actions from one code and resistance from another code are also discussed.

Purpose: to study influence of regional factors and intensive educational process on cardio-haemo-dynamic and vegetative characteristics in conditions of individual differentiated classes. Material: in the research 80 student (of 17-18 years’ age) participated; they were divided into group of the tested (n=40) and group of comparison (n=40). Results: we showed physiological influence on bloodstream regulation and weakening of activity in conditions of individual-differentiated classes. The content of programs of informational, sports-health related, physical culture and prophylaxis measures resulted in students’ different speed characteristics (in bloodstream links and in its regulation). In conditions of annual educational process the students had balance of sympathetic and para-sympathetic regulation of central and periphery bloodstream. It depends on weather factors of year seasons, on examination sessions. Conclusions: in conditions of educational process adaptation-compensatory shifts are conditioned by dominating segmental regulation with participation of bloodstream links and regulatory supra-segmental influences. We also observed manifestation of influence of separate autonomous regulation factors.

The exploitation of distributed renewable energy sources leads to a low-carbon energy transition, mainly based on the optimal integration of hydro, PV and wind power plants with the remaining high-performance fossil-fuel power stations. In the last twenty years, European Union (EU) countries have shown a significant increase of the power installed in new PV and wind power plants, together with the refurbishment of small and medium size hydro stations. In particular, in Italy, PV and wind energy production has strongly increased and nowadays there are regions characterized by a very green energy mix. In this new scenario, energy storage becomes a viable solution to mitigate the variability of renewable energy sources thus optimizing the network operation. The present paper is focused on the Liguria region, in the North of Italy and in particular on the Bormida Valley where nowadays more than the half of the annual electricity consumption is covered by the renewable energy local production. The paper describes the current energy situation and proposes an optimization tool to investigate the possibility of installing new PV and wind power plants, as well as energy intensive storage units based on sodium-sulphur batteries; moreover, different scenarios are analyzed through the definition of economic and environmental key performance indicators.

The experimental measuring of working loads upon the parts of rotating excavator is a complicated procedure given the complexity of the construction of the excavator and the specificity of exploitation conditions. Therefore, there are no uniform solutions and methods for this purpose, and any proposed solution is of great benefit to excavator users, as well to science studying this issue. This paper presents a preset methodology for measuring working loads of the clamp dogs on the carrying structure of the working wheel at the excavator used in surface coal mining. This methodology uses the default settings implicit to the strain gage method, which records the stresses resulting from external loads occurring within the clamp dogs’ material using strain gages and measuring equipment. Within this concept, the paper shows the manner of determining the measuring points and setting up the strain gages on both clamp dogs, the connecting with the measuring installation and the equipment. Employing diagrams, the paper presents the measurement results of static and dynamic loads, as well as induced stress state by them.

The drive for increasing flight efficiency is resulting in wing designs that are of higher aspect ratios, lower in weight, increased wingspans and, consequently, require greater attention in the disciplines of aeroelastics and loads. This trend in aircraft design, along with past research experience with flexible aircraft, motivate a review of assumptions in gust models; especially, that of the gust maintaining a uniform spanwise profile. In this paper, the authors investigate the use of spanwise varying 1−cos gust models for loads prediction using a non-linear aeroelastic model of a conventional large transport aircraft. The comparison between a test case using conventional uni-dimensional approach and another, using multidimensional gusts, illustrates the impact of stepping away from traditional discrete tuned gust processes and adding a spanwise varying gust component. A methodology for processing and analysing the loads data arising due to the added dimension is also developed and both envelope and correlated loads are considered. Gust characteristics and resulting load factor are, respectively, considered for comparison between the two models, as both metrics define realistic gust encounters. In this case, it has been shown that spanwise variation of gust profiles leads to lower envelope loads if viewed in terms of conventional gust gradients. However, higher envelope loads are found if the maximum load factors are matched. [ABSTRACT FROM AUTHOR]

Recycled aggregate concrete has obtained worldwide attention as an important part of sustainability. In the aspect of durability of recycled concrete under coupling multi-factors, a number of devices were designed and installed to investigate the durability of recycled concrete. In previous studies, the concrete specimen was tightened by the screws to apply a prestress with the jack, and then specimen was put in the devices for the durability test, which was difficult to operate and prone to stress loss. In this paper, in order to better research the durability of concrete under coupling multi-factors, we designed a coupling mechanism of alternated with loading and freeze-thaw cycles in salt-solution to replace the traditional mold loading to accurately simulate the simultaneous interaction of freezing thawing, corrosion and load. The coupling protocol was designed with repetitive load and 25 time’s freeze-thaw cycles alternately 2 times in the salt-solution, in which the maximum stress level (the applied stress to 28 days compressive strength) of repetitive load is 0, 40%, 70%. The specific operation was that specimens were loaded repetitively for the first time, then they were freeze-thawed in the salt-solution for 25 time’s cycles, after that, they were repetitively loaded again, and freeze-thawed in the salt-solution for another 25 time’s cycles. The experiment on compressive strength and microhardness of recycled concrete and natural concrete under coupling action was carried out. In the macroscopic test, compressive strength loss of each specimen was measured under the above mentioned coupling protocols. At the same time, the microhardness across the ITZs between the coarse aggregate and the cement matrix was measured before and after 50 freeze-thawing cycles for the control specimens. The macro test results showed that the stress level of the coupling action increased from 40% to 70%, the compressive strength loss of both recycled concrete and natural concrete increased from 1.8% and 71.3% to 27.2% and 100% respectively. It is implied that the durability of recycled concrete under coupling action is better than that of natural concrete, and the loading mechanism with high stress level will accelerate the deterioration of both recycled concrete and natural concrete. The micro test results showed that the microhardness values gradually increased with the increases of distance from the interface of natural aggregate and cement paste, the microhardness losses were 8.1% and 23.8% of the interface of both recycled aggregate and natural aggregate before and after the coupling action respectively. It can be seen that the interface transition zone was the weakest part of the concrete, and the decreasing rate of microhardness of the interface transition zone in natural aggregate specimens was faster than that of recycled aggregate after 50 time’s freeze-thaw cycles in salt-solution. The environmental scanning electron microscope (ESEM) test results indicated that the bond strength and plastic deformation ability of interface of natural aggregate are better than that of recycled aggregate before freeze-thaw cycles, while the ability to resist freeze-thaw at the interface transition zone of recycled aggregate was better than natural aggregate after freeze-thaw cycles. The related results can provide an insight into the long-term performance of recycled concrete subjected to harsh environmental conditions and thus to promote practical application of recycled aggregate concrete in the future. [ABSTRACT FROM AUTHOR]

The main goal of work was to quantify the nitrogen and phosphorus loads transported by small streams to the Gulf of Gdansk. The research aims to determine wastewater release volumes over time, instead of focusing only on spatial distributions. Another aim is to identify the main determinants potentially affecting water quality in rivers flowing across the city of Sopot. The study area consists of six small river catchments located in the city of Sopot, each with an open flow channel, which lies along the bay. Studies were conducted 12 times per year in the period from March 2014 to February 2015. Laboratory analyses were performed to determine the concentration ofboth total nitrogen and total phosphorus. In order to calculate pollutant loads, discharge was also measured in each of studied rivers. Conducted research has shown that all analyzed streams were characterized by low total nitrogen and total phosphorus concentrations. The mean annual values ranged from 0.60 to 1.28 mgdm3 in case of total nitrogen and from 0.066 to 0.100 mgdm"3 in case of total phosphorus. In 2012, the total nitrogen load from Poland to the Baltic Sea was 210.768.000 kg N while the total phosphorus load was 15.269.000 kg P, which means that streams analyzed in this paper supplied barely 0.002 % of the biogenic load supplied to the Baltic Sea by Poland as a whole. [ABSTRACT FROM AUTHOR]

Abstract Sustainable and cost effective design for tidal current turbines requires knowledge of the complex nature of unsteady loads on turbine components including blades, rotor and support structure. This study investigates experimentally the variation with frequency of rotor thrust and torque loads, of streamwise root bending moment on individual blades and of loads on foundation at the bed. Comparisons between these different load spectra are also established. The impact of absolute rotor angular position on blade and rotor thrust loads is also examined. The study is based on measurements from a 1/15 scale, three-bladed, horizontal axis machine tested in a recirculating flume, in onset flows of 3% and 12% turbulence intensity. It is found that for frequencies below the rotational frequency, load spectra are correlated to spectral density of the onset flow velocity. Above the rotational frequency, loads are mainly affected by turbine operation phenomena. The tower shadowing effect is clearly identified through frequency and angular analysis. Finally, thrust loads as experienced by the rotor alone are for the first time compared with streamwise and transverse foundation loads. Higher frequency loads experienced by the tower are shown to be affected by different vortex shedding regimes associated with different regions of the wake. All the experimental measurements presented in this article can be accessed from http://dx.doi.org/10.7488/ds/2423. [ABSTRACT FROM AUTHOR]

A numerical model of mussel farm in current was developed to analyse its hydrodynamic performance, in which the mussel dropper was simulated as a porous media. The Reynolds-Average Naiver-Stokes (RANS) equation was applied to simulate the flow around the mussel farm, and the Darcy-Forchheimer equation was adopted to consider the effect of the porous media. A slew of physical model tests were used to validate the numerical model. The results indicate that our numerical model is appropriate to investigate the hydrodynamic behaviour of the mussel droppers in current. The hydrodynamic performance of mussel farms in different water depths was numerically investigated. In addition, the influence of the mussel dropper density and the oblique current was analysed comprehensively. The results indicate that the shielding effect of mussel droppers is increased with the increasing water depth. [ABSTRACT FROM AUTHOR]

Records of the ice pressures on the joggle skirt of the coal quay in Spitsbergen were performed over winter seasons in 2013 and 2015. The ice thickness below the quay was above 2m. Ice temperature over the ice thickness and water pressure at the sea bed were measured synchronously. It was discovered that sea water migrates through the ice confined inside the joggle skirt under the influence of tidal changes of the water pressure below the ice. It leads to the formation of floods on the ice surface during high tide. The ice surface becomes dry during low tide. Ice temperature and ice pressure on the joggle skirt are changed according to the semidiurnal cycle. Spectral analysis and correlation analysis are performed to analyse the loads caused by thermal expansion of the ice. A thermo-mechanical model of ice based on elastic-plastic rheology with thermal effect is used in numerical simulations of the observed phenomena. Numerical simulations are performed with finite element software. This article is part of the theme issue 'Modelling of sea-ice phenomena'. [ABSTRACT FROM AUTHOR]

The aim of this work was to quantify the physical conditions, required for the mobilisation of unexploded ordnance devices (UXO) on the sea floor. As a basis for this, the hydrodynamic processes around UXO were measured in the wind tunnel and the flume tank in terms of conditions, especially Reynolds numbers. From these experiments, the typical shape of a sandy sea floor in the close vicinity of an object, due to current-induced burial was determined. Knowing this, the model for current-induced mobilisation of objects was developed. The model assumes a critical dimensionless Moment Factor M F = a ⋅ R e b , where the parameters a and b had to be investigated. This was accomplished by performing a total number of 287 numerical simulations, wind-tunnel testings and flume tank experiments at different geometric scale factors (1:10, 1:5, 1:2 and 1:1). With the parameter values so determined, the model describes the critical situation of an arbitrary shaped cylinder-like object regarding the incident flow velocity, the immersed mass and the burial depth, as well as the length and the volume-averaged diameter of the object. [ABSTRACT FROM AUTHOR]

Spatial regression models were used to predict yields (kg ha−1 yr−1) of nitrogen (N) and phosphorus (P) discharged from catchments throughout New Zealand under natural and current conditions. The models were derived using loads (kg yr−1) of TN, NO3-N, TP and DRP calculated for 592 river water quality monitoring sites. Anthropogenic increases in yields above natural levels were associated with the proportions of catchments occupied by the intensive agricultural land cover and were unevenly distributed across regions. Anthropogenic increases in national loads of TN, NO3-N, TP and DRP exported to the ocean were 74%, 159%, 48% and 18%, respectively. Increases in loads exported to the ocean varied considerably at smaller scales, with catchments having significant load increases between 4- and 26-fold for N and 6- to 9-fold for P. Predictions of yields and loads reported here have utility in the development of strategies to manage nutrients. [ABSTRACT FROM AUTHOR]

The bodies are studied taking into account the fact that they deform under the action of the tasks. The size of the deformations depends on the elastic characteristics of the material, the shape and dimensions of the body, and the size and mode of application of the loads. In this paper are studied samples of cement mortars which are subjected to tensile stress and is measured the breaking load. [ABSTRACT FROM AUTHOR]

Inducing high thermal loads in machining of difficult-to-cut materials changes the mechanical properties of a machined surface/subsurface. In particular, a thermally affected layer leads to tensile residual stresses and microstructure changes. Nickel-based alloys are hard materials and frequently used in different industries. Since the generation of thermal loads in machining Inconel 718 is evident, in this paper an experimental and numerical investigation were performed to evaluate thermal loads and the depth of the affected layer in the machining of Inconel 718 superalloy. First, the effect of cutting parameters was studied on the average machined surface temperature by experimental tests. Then, the results of experiments were used to validate a 3D numerical model. Using the calibration strategy, the heat transfer coefficient at the chip-tool interface was found to be dependent on the cutting conditions. Next, the effect of the initial workpiece hardness and tool geometry, including tool nose radius and edge radius, was evaluated on thermal loads and the depth of the recrystallized layer. The critical strain criterion was used to estimate the depth of the recrystallized layer and then, the numerical results were compared with experimentally measured depth of the affected layer at different machining parameters. [ABSTRACT FROM AUTHOR]

Knowledge of black carbon (BC) emission factors from ships is important from human health and environmental perspectives. A study of instruments measuring BC and fuels typically used in marine operation was carried out on a small marine engine. Six analytical methods measured the BC emissions in the exhaust of the marine engine operated at two load points (25% and 75%) while burning one of three fuels: a distillate marine (DMA), a low sulfur, residual marine (RMB-30) and a high-sulfur residual marine (RMG-380). The average emission factors with all instruments increased from 0.08 to 1.88 gBC/kg fuel in going from 25 to 75% load. An analysis of variance (ANOVA) tested BC emissions against instrument, load, and combined fuel properties and showed that both engine load and fuels had a statistically significant impact on BC emission factors. While BC emissions were impacted by the fuels used, none of the fuel properties investigated (sulfur content, viscosity, carbon residue and CCAI) was a primary driver for BC emissions. Of the two residual fuels, RMB-30 with the lower sulfur content, lower viscosity and lower residual carbon, had the highest BC emission factors. BC emission factors determined with the different instruments showed a good correlation with the PAS values with correlation coefficients R2 >0.95. A key finding of this research is the relative BC measured values were mostly independent of load and fuel, except for some instruments in certain fuel and load combinations. [ABSTRACT FROM AUTHOR]

The concentrations of Cd, Ni, Cu, Pb and Fe were determined in sediments and water samples of two aquatic systems after mineralization with HNO3, HCl and HClO4 and analyzed using Atomic Absorption Spectrophotometer model 507KL. The mean concentration obtained in sediments of Ipo stream were as follows Cd (1.2 - 1.7) mg/Kg, Ni (3.0 - 3.5) mg/Kg, Cu (14.62 - 25.22) mg/Kg, Pb (20.05 - 24.6) mg/Kg, Fe (18.20 - 24.82), while in water, in mg/L was Cd (1.09 - 1.65), Ni (3.09 - 3.72), Cu (14.14 - 24.10), Pb (20.00 - 24.20), and Fe (711 - 907). In Sombreior sediment, the following concentration in mg/Kg were obtained Cd (0.10 - 0.12), Ni (102 - 70.34), Cu (34.02 - 84.20) Pb (18.22 - 23.05), and Fe (11780 - 15642.2). However, in water the heavy metals occurred in the range Cd (<0.001 - 0.02), Ni (64.21 - 82.01), Cu (30.41 - 3961), Pb (8.02 - 16.38), and Fe (712 - 872.0) mg/L. The results showed that Ipo stream contained more heavy metals than Sombriero river and significant difference occurred in the mean concentration of heavy metals in Ipo stream and Sombreior river at p<0.05. The results showed that the major source of pollution of the study area is anthropogenic activities. [ABSTRACT FROM AUTHOR]

The purpose of the present study is to review the state-of-the-art in research and development of offshore wind turbines in order to address the latest findings and trends in structural design and response analysis. This could enhance a development of sophisticated offshore wind turbines. To complete such a task, a detailed review of offshore wind renewable energy potential, wind, wave and sea current loading as well as structural analysis and design procedures and experimental work are presented. [ABSTRACT FROM AUTHOR]

In this work, large eddy simulation data is analysed to investigate a new stochastic modeling approach for the wake of a wind turbine. The data is generated by the large eddy simulation (LES) model PALM combined with an actuator disk with rotation representing the turbine. After applying a proper orthogonal decomposition (POD), three different stochastic models for the weighting coefficients of the POD modes are deduced resulting in three different wake models. Their performance is investigated mainly on the basis of aeroelastic simulations of a wind turbine in the wake. Three different load cases and their statistical characteristics are compared for the original LES, truncated PODs and the stochastic wake models including different numbers of POD modes. It is shown that approximately six POD modes are enough to capture the load dynamics on large temporal scales. Modeling the weighting coefficients as independent stochastic processes leads to similar load characteristics as in the case of the truncated POD. To complete this simplified wake description, we show evidence that the small-scale dynamics can be captured by adding to our model a homogeneous turbulent field. In this way, we present a procedure to derive stochastic wake models from costly computational fluid dynamics (CFD) calculations or elaborated experimental investigations. These numerically efficient models provide the added value of possible long-term studies. Depending on the aspects of interest, different minimalized models may be obtained. [ABSTRACT FROM AUTHOR]

Heavy metal behavior in soil and water requires modeling for a better understanding of the potential adverse impacts on the ecosystem as well as on humans. A heavy metal transport and transformation module is combined with the well-established SWAT (Soil and Water Assessment Tool) model for the purpose of simulating the fate and transport of metals at the watershed scale. The heavy metal module accounts for sorption, complexation and slow reactions among metal species; the heavy metals in the upland are allowed to transport vertically through percolation and evaporation-induced water rising as well as horizontally through soil erosion and surface/subsurface runoff; the heavy metals in the water body, in contrast, are modeled to undergo settling, resuspension, diffusion and burial processes. As a demonstration, the SWAT-laden heavy metal module (SWAT-HM) was calibrated to simulate zinc (Zn) and cadmium (Cd) dynamics in an upstream watershed of the Liuyang River in China, which has been impacted by mining activities for decades. The model simulations were found to agree reasonably well with the monitored results. In particular, the elevation of metal loads in channels with precipitation events was well represented, demonstrating that a considerable amount of Zn and Cd in the waste rock dumps and contaminated soil was released into rivers through rainfall. After a simulation of 6 years (2009–2014), the simulated Zn and Cd concentrations were used as a surrogate for the Predicted Environmental Concentration (PEC), whereby an ecological risk assessment was conducted for the demonstrative mining area. This initiative toward developing a heavy metal module combined with SWAT has high potential for application in environmental risk analysis and pollution control. [ABSTRACT FROM AUTHOR]

The reliability analysis of a spar-supported floating offshore 5-MW wind turbine is the subject of this study. Environmental data from a selected site are employed in the numerical studies. Using time-domain simulations, the dynamic behavior of a coupled platform-turbine system is studied; statistics of tower and rotor loads as well as platform motions are estimated and critical combinations of wind speed and wave height identified. Long-term loads associated with a 50-year return period are estimated using statistical extrapolation based on loads derived from simulations. Inverse reliability procedures that seek appropriate fractile levels for underlying variables consistent with the target load return period are employed; these include use of (1) two-dimensional inverse first-order reliability method where extreme loads, conditional on wind speed and wave height random variables, are selected at median levels and (2) three-dimensional inverse first-order reliability method where variability in the environmental and load random variables is fully represented. [ABSTRACT FROM AUTHOR]

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• Numerical and analytical models are developed to predict the ultimate loads and deflections of RC beams strengthened in flexure using FRP material. • The numerical model is developed based on the finite element method using Cast3M software. • The analytical model is developed based on the moment-area theorem and the equilibrium of internal forces. • The developed models have an excellent performance in predicting the ultimate behavior of strengthened RC beams. • The numerical comparative study shows the effectiveness of NSM system. The present paper investigates the ultimate flexural behavior of strengthened reinforced concrete (RC) beams with Externally Bonded (EB) or Near-Surface Mounted (NSM) Fiber-Reinforced Polymers (FRP) reinforcement. For the purpose of predicting the ultimate loads and deflections of strengthened RC beams, numerical and analytical models were developed. Both models were developed for strengthened RC beams that fail in flexure by FRP rupture. First, an analytical model was developed based on the moment-area theorem and the equilibrium of internal forces. Second, based on the finite element (FE) method, an 3D numerical model was developed using Cast3M software, version 21. The reliability of the numerical model was tested against the analytical and experimental results collected from previous research. The selected RC beams were made with Normal-Strength (NS) and High-Strength Concrete (HSC). The comparison showed that the numerical model has an excellent performance in predicting the load–deflection response until failure. Moreover, the beam damage obtained from the numerical modeling agreed with the experimental results. Finally, a numerical comparative study between EB and NSM systems was conducted. The comparison showed the effectiveness of the NSM system in terms of strength and ductility. Further, the analysis of stress and strain showed that NSM system reduces the stresses and strains in concrete and steel reinforcement and prevents cracks propagation. [ABSTRACT FROM AUTHOR]