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To respond to the need for preventing offshore and coastal accidents, damage and flooding, a state-of-the-art coastal wave forecast system for the East Coast of Korea waters is being developed. Given that the quality of the input wind has been identified as the main factor influencing the quality of the wave results, the effectiveness of adjusting the wind fields by means of data assimilation using the ensemble Kalman filter technique has been explored. In this article the model setup, the data assimilation parameters and the validation of the predictions during stormy periods is described. The validation shows that the model is able to provide predictions of coastal waves fulfilling available benchmarks; especially, the data assimilation analysis and forecast predictions are judged to be of high quality.

A semi-parametric method based on the theory of max-stable processes is proposed that can be used to determine the time- and space-evolving wind fields associated with a given return value of wind speed at a specified reference location. The method uses wind velocity time series over a grid of locations and their location-specific extreme value distributions in order to ‘lift’ observed extreme events (storms) into yet unobserved and even more extreme events. Because the lifted fields are needed to force hydrodynamic models used in the determination of extreme hydraulic conditions, they need to be continuous in time and space and to extend over a few days before the peak of the storm in order to allow the spin up of the hydrodynamic models. Thus, even if the original values of the wind fields are not above the threshold used to determine the location-specific extreme value distributions at a given location and instant (outside the validity of the method) they still need to be lifted. This can be achieved by augmenting the location-specific extreme value distributio\ns by the empirical distributions of the observations and lifting using the same method also the values below the thresholds. Mainly as a consequence of this procedure, the resulting lifted wind fields show low temporal and spatial wind speed gradients away from the peak of the storm. These gradients have raised concerns about the validity of the fields and it has been suggested that the lifting by means of a simple scaling factor may be preferable. To address these concerns, a thorough validation of the lifted fields has been carried out by 1) assessing the characteristics of the lifted fields and 2) assessing the ability of the lifted fields to reproduce extreme hydraulic conditions. The main recommendation of this study is that the proposed method be considered further for the determination of temporally and spatially evolving hydraulic conditions.

Injury rates are a thing of the past: building better performance measures for better conversations to provoke change.The Oil & Gas industry has measured safety performance using Injury frequency rates for the last 40 years. Industry thinking is based on the premise that: if we do not have injuries then we are safe, andif we have injuries we are not safe.This paper examines the fallacy of that premise, and the use of injury rates, as a key performance indicator. It argues that, as a key performance indicator, injury frequency rate is no longer a valid measure. Indeed, in many cases its use creates unhelpful discussions in leadership teams and therefore prevents the culture of many organisations from changing.The paper reviews the current state of knowledge in accident causation, in part based on the ground-breaking research from the 1980s through to the early 2010s. It demonstrates how, through the use of Jim Reason's Swiss Cheese Model, Reason and Rasmussen's Generic Error Model (GEMS) and Willem Albert Wagenaar's Tripod model of accident causation, key performance indicators can be developed that will enable leadership teams to transform the culture of the organisation by changing what they believe to be important.Cultures change through the behaviours of both formal and informal leaders. Those leaders create and react to the environment they are placed in. By maintaining injury rates as the industry's key performance indicator we are inhibiting that change and disfranchising our workforce.The paper gives examples of how different indicators both in terms occupational and process safety created different conversations and behaviours in both leaders and the workforce - some appeared extremely positive and others extremely negative. It will then provide examples of how to create better indicators more suitable for your organisation.

For the design, assessment and flood control of water defences, hydraulic loads in terms of water levels and wave conditions are required and often obtained from numerical models. For these hydraulic loads to be reliable, accurate atmospheric forcing is required. Waves and surges are typically forced by surface stress. However, in most cases, the input for these models consists of 10-m wind velocities that are internally converted to surface stress by applying a particular drag relation. This procedure generally leads to inconsistencies, since the hydrodynamic, wave and atmospheric models often apply different drag relations. By means of a case study, we explored the consequences of this inconsistency in the drag formulation for a North Sea storm wave and surge hindcast. This was done by forcing the hydrodynamic and wave models using both the 10-m wind velocity and the surface stress fields computed by the atmospheric model. Our study results show significant differences between the wave parameter values and water levels computed with surface stress input and 10-m wind velocity input. Our goal is not to assess different drag parameterizations but to raise awareness for this issue and to plea for the use of a consistent drag relation in meteorological and hydrodynamic/wave models. The consistent use of one drag formulation facilitates the identification of problems and the eventual improvement of the drag formulation. Furthermore, we suggest using the so-called pseudo-wind, which is a translation of the surface stress to the 10-m wind speed using a reference drag relation.

For the assessment of the safety of the Dutch flood defences extreme open-water winds need to be computed. There are, however, no sufficiently long and reliable in-situ data available. On the other hand, there is a rich dataset of decades of measurements at certain coastal and relatively close by inland stations. A commonly used two-layer model for neutral atmospheres was thought to provide reasonably accurate open-water winds from the available data, given that the model assumptions seemed plausible for the extreme winds of interest. However, the model results were deemed inaccurate and not usable. Given that this was unexpected, many of the model assumptions were analysed and, with the gained further insight, their validity and contribution to the invalidity of the deemed simple model approach assessed. Our conclusion is that the quality of the model results is significantly affected by at least two aspects: the assumption of neutral stability in the model, and – equally important – the assumption of independence between the surface roughness and the wind speed.

This paper is the product of the wave modelling community and it tries to make a picture of the present situation in this branch of science, exploring the previous and the most recent results and looking ahead towards the solution of the problems we presently face. Both theory and applications are considered. The many faces of the subject imply separate discussions. This is reflected into the single sections, seven of them, each dealing with a specific topic, the whole providing a broad and solid overview of the present state of the art. After an introduction framing the problem and the approach we followed, we deal in sequence with the following subjects: (Section) 2, generation by wind; 3, nonlinear interactions in deep water; 4, white-capping dissipation; 5, nonlinear interactions in shallow water; 6, dissipation at the sea bottom; 7, wave propagation; 8, numerics. The two final sections, 9 and 10, summarize the present situation from a general point of view and try to look at the future developments.

The Guyana coastal system is characterized by very thick deposits of Amazon mud and high mud concentrations in its coastal waters. The mud deposits can be quite soft and may liquefy under incoming waves. Subsequently, the liquefied mud damps the incoming waves effectively. This paper presents a simple model to predict wave attenuation over soft (fluid) mud beds. This model is based on the two-layer approach by Gade [Gade, H.G., 1958, Effects of a non-rigid, impermeable bottom on plane surface waves in shallow water, Journal of Marine Research, 16 (2) 61–82.] which is implemented in the standard version of the state-of-the-art wave-prediction model SWAN. Input to the mud wave damping module consists of the extension, thickness, density and viscosity of the liquefied (fluid) mud layer. The model is validated against small-scale wave attenuation measurements carried out in a laboratory wave flume. The model predictions agree favourably with the experimental data. Next, the model is applied to predict wave height and wave attenuation in the Guyana coastal system. Extension and thickness of the liquefiable layer could be assessed from dual-frequency echo soundings. In the absence of field data, the density of the liquefied mud layer is obtained from literature, whereas the value of the mud's viscosity had to be established by trial and error — the selected value, though, is in the range of literature values. The model predicts significant wave attenuation. The computed changes in wave energy spectrum agree qualitatively with measurements in Surinam, whereas the decrease in significant wave height agrees more or less with historic observations along the Guyana coast.

The phase-averaged wave model Simulating WAves Nearshore (SWAN) is often used for the design of dikes and harbors. However, various hindcast studies have shown that SWAN underpredicts the wave energy when waves are penetrating into bathymetries with shallow areas traversed by channels, such as tidal inlets or harbor entrances. The underprediction of these waves could lead to dike failure or shipping downtime as a consequence of incorrect hydraulic loads. This paper presents an explanation for the underprediction of this wave penetration. By comparing a series of SWAN computations with laboratory measurements and computations with the Boussinesq-type wave model TRITON, it is demonstrated that the absence of various subharmonic and superharmonic interactions in SWAN causes an unrealistic amount of energy to be trapped on the channel slopes owing to wave refraction. The two-dimensional nonlinear interactions, which appear to be present in the measurements and TRITON results, broaden the directional r...

Measurements in a laboratory flume have shown unexpected wave-induced changes in the vertical profile of the mean horizontal velocity. Two theoretical explanations for these changes have been proposed so far. One is based on a local force balance in the longitudinal direction and the other relies on secondary circulations in the cross-sectional plane. In this study, a two-dimensional (2DV lateral) model based on the so-called generalized Lagrangian mean (GLM) formulation has been developed to investigate the three-dimensional effect of waves on the steady current and in particular to investigate the validity of the two fundamentally different explanations. Formulations for the three-dimensional wave-induced driving force have been implemented in an existing 2DV non-hydrostatic numerical flow model. Computations for regular waves following and opposing a turbulent current over a horizontal bed have been carried out and the results are compared with both experimental results and results from an existing numerical model. The results clearly indicate predominance of the longitudinal component of the wave-induced driving force over the cross-sectional components. Although the 2DV model has only been applied to and verified with measurements in wave–current systems in a laboratory flume, the approach followed here is relevant for a wider class of problems of wave–current interactions.

The generalized Lagrangian mean (GLM) formulation is used to describe the interaction of waves and currents. In contrast to the more conventional Eulerian formulation the GLM description enables splitting of the mean and oscillating motion over the whole depth in an unambiguous and unique way, also in the region between wave crest and trough. The present paper deals with non-breaking long-crested regular waves on a current using the GLM formulation coupled with a WKBJ-type perturbation-series approach. The waves propagate under an arbitrary angle with the current direction. The primary interest concerns nonlinear changes in the vertical distribution of the mean velocity due to the presence of the waves, but modifications of the orbital velocity profiles, due to the presence of a current, are considered as well. The special case of no initial current, where waves induce a so-called drift velocity or mass-transport velocity, is also studied.

Martin (1999a) proposes that present-day society differs from mankind's evolutionary past by a change from immediate returns, when living as hunter-gatherers, to a delayed-return system with the onset of agriculture and urban living. He assumes that a delayed-return system lacks frequent feedback necessary for goal orientation and perceived control, which may lead to various social psychological thinking errors, cognitive distortions and an external locus of control. This study was aimed at examining whether Martin's I-D compensation theory could be applied in a sample of incarcerated juvenile delinquents in The Netherlands who frequently lack adequate feedback and control. Using questionnaires (N = 144) and semi-structured interviews (N = 40) with adolescents in secure institutional facilities, the results showed that feedback in the form of responsiveness of group workers was positively related to behavioural competence and subsequently to fewer criminal cognitions and self-serving cognitive distortions. In addition, self-serving cognitive distortions were positively associated with an external locus of control. These results provide insight into antecedents of criminal behaviour, and can be used to develop efficacious institutional treatment for juvenile delinquents.

This paper deals with the implementation of a domain decomposition method for the three-dimensional shallow water equations. The domain decomposition method belongs to the class of generalized additive Schwarz methods. It is based on a local coupling mechanism that allows for a flexible formulation of subdomain interfaces. For a real-life application in the Netherlands numerical results are presented. The experiments are carried out on a HP workstation and on a CRAY C90.

The performance of the spectral wind wave model SWAN in tidal inlet seas was assessed on the basis of extensive wave measurements conducted in the Amelander Zeegat tidal inlet and the Dutch Eastern Wadden Sea, as well as relevant data from other inlets, lakes, estuaries and beaches. We found that the 2006 default SWAN model (version 40.51), the starting point of the investigation, performed reasonably well for measured storm conditions, but three aspects required further attention. First, over the near-horizontal tidal flats, the computed ratio of integral wave height over water depth showed an apparent upper limit using the default depth-limited wave breaking formulation and breaker parameter, resulting in an underprediction of wave heights. This problem has been largely solved using a new breaker formulation. The second aspect concerns wave-current interaction, specifically the wave age effect on waves generated in ambient current, and a proposed enhanced dissipation in negative current gradients. Third, the variance density of lower-frequency wind waves from the North Sea penetrating through the inlets into the Wadden Sea was underpredicted. This was improved by reducing the bottom friction dissipation relative to that of the default model. After a combined calibration, these improvements have resulted in a relative bias reduction in Hm0 from -3% to -1%, in Tm-1,0 from -7% to -3%, and in Tm01 from -6% to -2%, and consistent reductions in scatter, compared to the 2006 default model.

Specific criteria have been described and accepted worldwide for diagnosing patients with complex regional pain syndrome (CRPS). Nevertheless, a clear-cut diagnosis cannot be confirmed in a number of cases.The objective of this study was to investigate the effectiveness of the described diagnostic criteria used by several clinical disciplines.We included 195 patients who were referred to our pain clinic within a period of 1 year. Data were collected on patient characteristics, signs, symptoms, disease-related medication, and the background of the referring clinicians.The Harden and Bruehl criteria were confirmed in 95 patients (49%). These patients used a higher than average number of analgesics, opiates, and anti-oxidants, and frequently received prescriptions for benzodiazepines instead of anti-depressants. The mean disease duration was 29 +/- 4.6 months and the mean visual analogue score for pain was 8.1 +/- 0.19. A subgroup of patients had a colder temperature in the affected extremity compared with the unaffected extremity. This subgroup showed a longer disease duration and higher visual analogue scale pain.The diagnostic criteria used to determine CRPS should be further improved. A large number of referred patients experienced substantial pain, without receiving adequate medication. Disease-related medication is unrelated to CRPS-specific disease activity. Knowledge of underlying mechanisms is warranted before an adequate pharmaceutical intervention can be considered.

It is not the total but the (bio)accessible concentration of veterinary medicines that determines their toxicity in the environment. We elucidate the changes in (bio)accessibility of manure-applied sulfadiazine (SDZ) with increasing contact time in soil. Fattening pigs were medicated with 14C-labeled SDZ, and the contaminated manure (fresh and aged) was amended to 2 soil types (Cambisol, Luvisol) and incubated for 218 days at 10 degrees C in the dark. Antibiotic residues of different bioaccessibility were approached by sequential extractions with 0.01 M CaCl2 (CaCl2 fraction), methanol (MeOH fraction), and finally acetonitrile/water (residual fraction, microwave extraction at 150 degrees C). In each fraction, total radioactivity, SDZ, and its major metabolites were quantified. The results showed that both SDZ and,to a lesser extent 4-hydroxysulfadiazine (4-OH-SDZ) were rapidly reformed from N-acetylsulfadiazine (N-ac-SDZ) during the first 2-4 weeks after fresh manure application, i.e., the N-acetylated metabolite does not sequester in soil to a significant extent Yet, the water and methanol extractable SDZ and 4-OH-SDZ also dissipated rapidly (DT50 = 6.0-32 days) for the fresh manure treatment with similar rate constants for both soil types. In the residual fractions, however, the concentrations of both compounds increased with time. We conclude that the residual fraction comprises the sequestered pool of SDZ and its hydroxylated metabolite. There they are entrapped and may persist in soil for several years. Including the residual fraction into fate studies thus yields dissipation half-lives of SDZ which exceed those previously reported for sulfonamides by a factor of about 100.

Abstract This paper will discuss the role of human error in accident causation. It will propose a way of rigorously and scientifically identifying the hidden systemic failures as well as identifying how management behaviours and leadership style contribute to accidents. Human error, which manifests in unsafe behaviours, is an important contributing cause in all accidents. That statement is made in the context that humans create everything in the industrial arena from the design of processes and hardware, to the operating systems and procedures, to the Business and Risk management systems. Consequently the identification of systemic failures and the elimination of human error at all levels of an organisation should be the twin targets of any accident prevention program. Tripod allows an organisation to identify the hidden systemic failures that cause accidents and categorize them in self explaining Basic Risk Factors. Tripod identifies the way in which management decisions can create the conditions likely to encourage unsafe acts in the work place. Our analyses suggest that, the climate - how people feel about working at a company - can count for 20 to 30% of business performance: getting the best out of people pays off in hard results. If climate drives business results, what drives climate? Research shows that the level of control an organization has over its Basic Risk Factors is related to the climate: the well-being, happiness, health and productivity of employees. But it is not only hidden systemic failures and management's decisions that contribute to accidents; also management's behaviours and leadership style contribute. Roughly 50 to 70% of how employees perceive their organisation's climate can be traced to one person: the leader. This paper will describe how to identify hidden systemic failures, as well as it will give a direct experience of how leadership style can affect the business performance in accident prevention or in any other facet of business. Introduction Since the publication of Human Error in 19901 a consistent trend in the interest in the contribution of human error to industrial accidents can be noticed. The common factor in this trend is the theory that prevention of human error is most effectively gained by controlling the working environment instead of focusing at the individual who ‘failed’.2,3 Safety does not, as many experts believe, depend on the number of sprinklers and hydrants installed, but a high proportion of accidents and catastrophes are the obvious result of management error.4 According to Rasmussen5 accidents are the result of lack of control: ‘A closer look at major accidents indicates that the observed coincidence of multiple errors cannot be explained by a stochastic coincidence of independent events. Accidents are more likely caused by a systematic migration toward accidents by an organization operating in an aggressive, competitive environment. [..] Safety is a control problem.’ To prevent human error a range of techniques are available, some more effective than others. Initiatives like Unsafe Act Auditing, Qualitative Risk Assessment and Technical Safety Auditing are in many companies applied to increase safety. These techniques may be necessary but are not yet sufficient to further decrease the number of accidents.

For the calculations of the Hydraulic Boundary Conditions in the framework of the Dutch Legal Flood Safety Assessment (WTI), wave statistics obtained at deeper water buoys need to be transformed to the toe of the dike using the wave action model SWAN. This transformation is particularly challenging in complex tidal inlet systems such as the Wadden Sea and the Western Scheldt in the Netherlands. Although various model improvements have been made in SWAN, particularly in the propagation and bottom friction dissipation, one of the unresolved issues is that the penetration of North Sea swell waves into the tidal inlets is still underestimated by SWAN. The goal of this study is to verify the hypothesis that nonlinear interactions, in particular the sub-harmonic triad interactions, play a major role in the transmission of energy from flats into the channel, and that this process can explain SWAN’s under-prediction of wave energy penetration. Since SWAN or any other wave-action equation type models lacks the relevant physics to study this problem, the Boussinesq-type TRITON model is used as well to verify the hypothesis. The conceptual idea, raised by Toledo (2013), is that sub-harmonic wave interactions between second harmonic and basic components generate a wave component of the same frequency as the primary component but at a wider angle of approach. As a consequence, the energy density spectra become directionally broader. From a series of idealized cases with monochromatic and bi-chromatic waves propagating up and down a slope we conclude that the TRITON model results confirm the conceptual idea of 2D nonlinear interactions. Both sub-harmonic wave interactions (to lower frequencies) and super-harmonic wave interactions (to higher frequencies) prove to be important. These insights can be applied to the situation with waves propagating on a tidal flat towards a channel. In case the basic components approach the channel under a sharp angle, such that they will not be able to enter the channel due to refraction, the sub-harmonic components could approach the channel under a less sharp angle and enter the channel. In our study a clear difference between the TRITON and SWAN energy density spectra in and across the channel is observed, as the 2D nonlinear interactions cannot be modeled with the co-linear 1D approach in SWAN. The hypothesis that nonlinear interactions play a major role in the transmission of energy from flats into the channel is confirmed, at least for the cases considered in this study. Additional investigations are still required in order to quantify and generalize the effect of nonlinear interactions on this transmission of energy. In addition, it is recommended to extend the presently implemented three-wave interaction formulation in SWAN to account for directional super- and sub-harmonic interactions.

There are numerous ways to derive a system of 2D Boussinesq-type wave equations from the 3D potential flow equation with free-surface boundary conditions. This freedom in design is exploited here to derive a Boussinesq-type model that has a number of unique properties. It describes the depth-integrated transport of mass and momentum in strictly conservative form. Its compact formulation is independent of the vertical reference level and allows for an efficient implementation. The model is complemented with absorbing boundary conditions that dynamically take into account the average celerity and direction of both the incoming and the outgoing wave. The model is validated by means of a number of standard test cases.

Human error is an important contributing cause in many accidents. Consequently the elimination of human error should be a most promising target for accident prevention. Tripod concentrates upon systemic factors and the way in which management decisions can propagate into substandard conditions at the work place. It attempts to help the organization to control the business process and not to focus primarily on the individual worker or the negative consequences like accidents, environmental spills and health problems. Optimal control of the controllable environmental conditions that cause human error makes an organization maximally intrinsically sound. This paper illustrates how these conditions are managed in an industrial environment.

Over the last five years a research program has been carried out to assess the performance of the spectral wave model SWAN in the Wadden Sea so that it may be used for the transformation of offshore wave conditions to wave boundary conditions near the sea defenses (dikes and dunes). The assessment was done on the basis of extensive wave measurements conducted in Ameland inlet and the Dutch Eastern Wadden Sea, as well as relevant data from lakes and estuaries. After a first round of assessment, we found that SWAN performed reasonably well for storm conditions but three aspects required further attention. Firstly, focusing on the main channel, SWAN formulations needed to be modified in order to eliminate overprediction of the significant wave height in opposing currents. Secondly, the primary spectral peak of North Sea waves penetrating into the inlet was underpredicted. Best results were obtained when the refraction of low-frequency waves was limited and the bottom friction coefficient was set at a lower value than the current default for wind seas. Thirdly, over the tidal flats the computed ratio of integral wave height over water depth showed an apparent upper limit using the conventional Battjes and Janssen (1978) depth-limited wave breaking formulation, because the wave growth over finite depth is hampered by the present formulation of depth-induced wave breaking. The problem has been solved using a new breaker formulation. All these improvements have lead to a wave transformation model with which reliable wave conditions in the Wadden Sea and related complex areas can be determined.

For the safe maintenance of microalgae and rotifers in mass culture, it is necessary to know the exact threshold concentration of ammonia for rotifers. In order to determine this threshold concentration, the continuous culture technique was used as a sensitive method to determine the influence of ammonia on the reproduction rate of the rotifer Brachionus rubens. As expected, only unionized (free) ammonia affected the population growth. Up to a concentration of 3 mg NH 3 -N l the reproduction of Brachionus was unaffected. In the range of 3–5 mg NH 3 -N l the reproduction rate decreased, although no animals were killed. This decrease was reversible and could be overcome by lowering the NH3-N concentration. At concentrations over 5 mg NH 3 -N l the rotifers died within 2 days.

The culture tube described consists of a Jena glass tube with tapering bottom and a glass head, which are held together by means of an autoclavable screw-connector. This tube has already been successfully used in extended axenic turbidostat or chemostat experiments.

Oxygen for the aerobic treatment of wastewater in High Rate Algal Pond (HRAP) systems arises from biogenic production by microalgae during photosynthesis and from absorption of atmospheric oxygen through the air/water interphase. The total quantity of available oxygen per m 2 and day determines the permissible BOD loading rate of a HRAP. The quantity of biogenic oxygen production, has for the first time been measured in a closed bioreactor and open chemostatic cultures. Good agreement was obtained between the two methods where more than 1.92 g O 2 g(dry wt) was produced by the microalgae. This was significantly higher than oxygen yields calculated from a generalized compositional formula of algal biomass. In combination with a predictive mathematical model, it was possible to calculate the potential biogenic oxygen production per season for any latitude. This may serve as the basis of feasibility studies on application of HRAP systems.

Q-switched laser use as light source for photographing droplets in spray containing fluorescent dye excited by second harmonic of ruby light

In this study two statistical methods for computing time- and space-evolving extreme events are implemented and assessed. The implementation and application of the methods are carried out with a view towards the safety assessment of water defences. With this type of application in mind, the methods are used to produce time- and space-varying extreme wind fields, which are needed to force wave and hydrodynamic models. Furthermore, the results of the two methods are compared and effects of the choice of distribution, threshold and reference location on the resulting wind fields are assessed. Although the wind fields produced by the methods show more erratic spatial variations, due to the associated uncertainties, than those of the observed wind fields, they seem realistic and can in principle be used to drive wave and hydrodynamic models. However, an assessment of the results of these statistical methods in terms of the underlying physics still needs to be carried out and is part of future work.

Past and future changes in the North Sea extreme waves are investigated in this article. Estimates obtained from non-stationary extreme value analyses, expressing the extreme value distribution parameters as functions of time and wind speed related covariates, are given. The results show that there is a significant trend of about 9 mm/yr in the current climate extremes of significant wave height and a trend of 1 mm/yr in the projections from 2001 to 2100. The characteristics of the extremes of wave period depend on whether swell or wind-sea events are considered. If both types of events are considered, the extremes are dominated by swell events and no present or future changes are identified. Considering wind-sea events only, a trend of less than 0.01s/yr in the present climate wave periods and a trend an order of magnitude smaller in the projections from 2001 to 2001 were detected.