Nach oben pdf Structural defence for plunge pool scour

Structural defence for plunge pool scour

Structural defence for plunge pool scour

(permeability) of the employed structures has a significant effect on the scour mechanism. Tests in which a S type structure was employed show that the presence of this structure typology generally causes an increase of the scour depth compared to the reference test which is carried out in the same hydraulic conditions, whereas in presence of a SG10 type structure the scour depth is generally less. The effect of the tailwater is to reduce the jet impact energy on stilling basin. It means that an increase of the tailwater causes a reduction of the scour depth and transported bed material volume. In presence of an upstream channel discharge, with all the other parameters constant, the scour depth increases because of the removal of a certain quantity of bed material from scour hole and ridge. The maximum reduction of the scour depth and of material volume removed by jet energy was observed in presence of a SG10 type structure located at
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Rock Plunge Pools: A Design Approach for Limiting Scour Extent

Rock Plunge Pools: A Design Approach for Limiting Scour Extent

When plotting the dimensionless maximum fissure pressure ( P max_ pool / H where H = kinetic energy head of the jet) as a function of dimensionless plunge pool depth ( Y D / ) it is found that the maximum pressure occurs at a depth of approximately eight times the jet dimension. This does not mean that the maximum plunge pool is at approximately eight times the jet dimension, but this relationship can be used to assess the maximum scour depth by considering the brittle fracture and fatigue characteristics of the rock (Bollaert 2002). This is done by calculating the stress intensity in a fissure and comparing it with its fracture toughness. The complete procedure for doing this is quite involved and, due to space limitations, is not repeated here. It is useful to note that the maximum pressure decreases to minimal values at dimensionless depths of 15 or more. Obviously, the absolute value of the maximum pressure will be a function of whether the jet is intact or broken and can be determined using approaches referred to in the previous section.
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Kariba Dam Plunge Pool Scour

Kariba Dam Plunge Pool Scour

Two methods are used to predict the amount of scour likely to occur for a given discharge. These are Annandale’s EIM [4,5] and Bollaert’s CFM and DI models [1]. In general, the EIM is used to determine a total scour depth, while the CFM and DI model are used to give insight to the type of failure (i.e., brittle fracture, fatigue, or dynamic impulsion) occurring over that total depth, in addition to providing a total scour depth. For Kariba Dam, the scour depths predicted by the EIM as well as the CFM (namely fatigue failure) are of most importance.
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Three Dimensional Scour

Three Dimensional Scour

= 0.8) and is a characteristic length scale. The size of bow thrusters and the engine power installed in ships have increased continuously over the past years. If u b,m is 2 m/s, thus U e is about 6 m/s and assuming that U u = u b,m , r 0 = 0.2, U c = 0.5 m/s, = 0.8 and = z p = 2 m, the scour depth reaches a depth of 2 cm after 1 minute and 14 cm after 10 minutes. Verheij (1983) investigated bed stability and scour caused by propellers in harbours. Figure 4 shows the time-dependent scour process for some experiments in which various hydraulic parameters were varied (d 50 = 0.0056 m, 0.14 m < h < 0.37 m, 0.6 m/s < u m,b < 1.0 m/s, 1.5 m/s < U e < 1.65 m/s and 0.06 m < z p < 0.16 m). Although the modelling shows a tendency to agree with the experimental results, it is recom- mended prototype tests be used to validate Eq. 9.
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Do Couples Pool Their Income?

Do Couples Pool Their Income?

There is a class of papers that uses structural household consumption models to test the hypothesis with micro data. Browning et al. (1994) reject the unitary household model with Canadian survey data in a structural framework and identify a household sharing rule of resources. They find that personal expenditures is significantly affected by the share of income a spouse contributes to total household income. Browning and Chiappori (1998) test a series of theoretical assumptions within a structural demand system and find evidence for a collective household model for couples instead of the unitary one. Phipps and Burton (1998) test the pooling hypothesis in a demand system also with Canadian data and find mixed results for different expenditure data. Income pooling cannot be rejected e.g. for housing but on the other side, wives are more likely to spend their income on child care than husbands. The study of Lundberg et al. (1997) belongs to a class of papers that uses a policy change as natural experiment. A child allowance was transferred to wives in the UK starting in 1977. The authors find strong evidence of a shift toward greater expenditures on women’s and children’s clothing due to the reform which is not in line with the pooling hypothesis. A more recent reform of child and working tax credits in 2003 in the UK was used by Fisher (2016) to analyze the effects on spending patterns. He finds significant positive effects on expenditures related to children. Ward-Batts (2008) combines a structural model with the exogenous variation of the UK reform in 1977 and confirms the findings of Lundberg et al. (1997). Another line in the literature uses survey questions that are directly related to pooling in the household. Bonke and Uldall-Poulsen (2007) exploit Danish survey data and find that most couples fully or partly pool their income. They also show that the probability of income pooling depends on several household characteristics as e.g. the duration of marriage and the existence of children in the household. Bonke and Browning (2009) use the same data and report that two-thirds of couple households answers that they pool their resources. However, a small part of them indicates inconsistency if other answers are taken into account.
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Starting over: for a Franco-German initiative in European defence

Starting over: for a Franco-German initiative in European defence

The Common Concept not only helped to allay the earlier irritations, it also offered a road map for further bilateral co-operation on military and armament issues, possibly leading to a common European effort at a later stage. Regrettably, both countries were to neglect this potential, except perhaps in some institutional aspects. The Nuremberg meeting came up with a series of Franco-German proposals for the Intergovernmental Con- ference (IGC) preceding the EU Amsterdam summit, many of which found their way into the new Amsterdam Treaty: the creation of the post of a High Representative of the EU for foreign and security policy with his own planning and early warning unit; the introduction of a “constructive abstention” in the EU’s Common Foreign and Security Policy (CFSP) to facilitate agreement in otherwise unanimous decisions, the reform of the ‘troika’ for the Union’s external representation, and the integration of the Petersberg missions into the Union treaty. Their most important proposal, the gradual fusion of WEU into the EU framework, did not, however, gain the necessary support, blocked as it was by a coalition of Britain and Den- mark, the more “Atlanticist” members, with the former neutrals, Ireland, Finland, Sweden, and Austria.
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Propeller Induced Scour

Propeller Induced Scour

Immediately after the propeller was turned on, the sand close to the surface was eroded quickly. The flow was very turbulent and the scour at this stage was vigorous. Most of the eroded particles were transported as suspended load. After a short time, a definite shape of the eroded bed could be seen and further erosion occurred as time progresses. At the crest of the ridge, sand was impelled into suspension and settled down some distance away. After a few hours, the rate of erosion decreased considerably. The scour reached an equilibrium stage asymptotically when the change in maximum depth over time is less than 0.05cm/h.
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Building a 2nd line of defence for safer rail

Building a 2nd line of defence for safer rail

It is common knowledge that despite significant invest- ments in railway safety technology, the amount of collisions of trains with trains, cars or other obstacles still remains high today, both in Europe and worldwide. The cause of train collisions is frequently attributed to a "chain of unfortunate circumstances" or "human error", in some cases also to exceptional operational conditions – all factors which prevented a first line of defence to avoid the risky situation. And this is exactly the crux of the matter: serious accidents often have a highly complex pattern of faults. Simple cause-effect scenarios are covered by infrastructural or operative measures. They guarantee to a large extent that dangerous situations are identified and avoided. However it is impossible to entirely avoid situations that nobody has ever thought of, but which could turn into catastrophes. And humans continue to be the greatest element of uncertainty.
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The great plunge in oil prices: Causes, consequences, and policy responses

The great plunge in oil prices: Causes, consequences, and policy responses

Abstract: Following  four  years  of  relative  stability  at  around  $105  per  barrel,  oil  prices  have  declined sharply since June 2014. This paper presents a comprehensive analysis of the sources of  the recent decline in prices, and examines its macroeconomic, financial and policy implications.  The  recent  drop  in  prices  is  a  significant,  but  not  an  unprecedented  event  as  it  has  some  significant parallels with the price collapse in 1985‐86. The recent decline has been driven by a  number of factors: several years of upward surprises in the production of unconventional oil;  weakening global demand; a significant shift in OPEC policy; unwinding of some geopolitical risks;  and an appreciation of the U.S. dollar. Although the relative importance of each factor is difficult  to  pin  down,  OPEC’s  renouncement  of  price  support  and  rapid  expansion  of  oil  supply  from  unconventional sources appear to have played a crucial role since mid‐2014. The oil price drop  will lead to substantial income shifts from oil exporters to oil importers resulting in a net positive  effect for global activity over the medium term. Although  several factors could counteract its  impact on global growth and inflation, the drop in oil prices will pose significant challenges for  monetary, fiscal, and structural policies. 
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View of Taking the plunge. Repositories and Research pooling in Scotland

View of Taking the plunge. Repositories and Research pooling in Scotland

The project must also work with the pools in order to assist them in making best use of their aggregated content, particularly in order for them to meet their reporting needs, but also to help with the development of systems to manage knowledge transfer, expertise management and to facilitate collaborative activities both nationally and internationally.

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A parsimonious fundamental model for wholesale electricity markets: Analysis of the plunge in German futures prices

A parsimonious fundamental model for wholesale electricity markets: Analysis of the plunge in German futures prices

Contrarily to previous works, (e. g. [2] or [3]), who focus solely on the integration of RES, our results indicate that while RES play an important role, they are not the largest driver of falling electricity prices in German. The model results show that emission prices are quantita- tively the most important driver of the futures electricity price in Germany between 2007 and 2013. This can be explained by the fact that emission prices impact the production costs of most conventional power plants, which results in changes of the supply stack’s shape in most intervals. Recently [24] quantified the impact on electricity prices in Germany between 2006 and 2010 if no emission trading system or renewable energy support schemes were in place. The authors rather focus on the quantity reduction of emissions then on price effects and found a positive interaction effect for the German electricity market between higher RES in- jection and lower CO2 Emissions. A valid question in this context is whether the measurable impact of emission prices on electricity prices (as found in the present work) may interact with RES additions, as investigated by, e. g.[1], [25] or [26]. Their analysis into the interac- tions between RES support and emission trading supports the argument that additional RES feed-in substitutes electricity from fossil fuels and thus reduces the demand for emission cer- tificates, which in turn leads to decreasing emission prices. Bases on a scenario analysis in an simulation model [25] state a likely significant effects from RES deployment an Allowance prices for the EU 12 Member states. The authors found a maximum reduction of emission
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View of Taking the plunge. Repositories and Research pooling in Scotland

View of Taking the plunge. Repositories and Research pooling in Scotland

• Facilitate knowledge/expertise management based on information gained through examining research outputs. • Identify the impact of capital investment in resources (other than h[r]

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Manufacturing and characterisation of photoresponsive composites for defence applications

Manufacturing and characterisation of photoresponsive composites for defence applications

18 Figure 2.1.4: Reaction scheme for free radical polymerisation In a wide range of studies conventional free radical polymerisation has been preferred method for the synthesis of azobenzene- based polymers to be studied in this project, 11,12,19, 34, 35 since this method is simple and cost effective. For example, it can be conducted by mixing and heating an appropriate amount of monomer, initiator and solvent (not necessarily). Then the polymerisation process is continued under a specific time and temperature, depending on the kinetics of the reaction. Finally, the polymer should be isolated from the solvent by a more appropriate technique like crystallisation, precipitation or evaporation of solvent. Common organic solvents used for polymerisation are, for example, tetrahydrofuran (THF), chloroform (CHCl3), and dimethylformamide (DMF). The free radical polymerisation technique is often used for preparation of polymeric films containing azobenzene molecules by photopolymerisation. 36-39 Photopolymerisation involves the use of UV and visible light that produces free radicals leading to the formation of a polymer or its network. The reaction rates can be controlled and increased by turning the light on and off and by changing the light intensity, respectively. Photopolymerisation can be fast and conducted at room temperatures and thus offers cost-effectiveness and environmental benefits. 40
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Proposing A New Portable Device For Bridge Scour Inspection

Proposing A New Portable Device For Bridge Scour Inspection

This paper presents a new portable monitoring device developed to inspect bridge scour and foundations. This device consists of three parts: installation deck, automatic operating equipment and measuring devices. The installation deck enables to mount the device on the shoulder of bridge and to be easily movable to other locations along the shoulder. The underwater camera is equipped to photograph and identify the condition of bridge foundations without divers. The ultrasonic acoustic sensor is also equipped to measure scour depths around piers. They are mounted on the end of the arm of the automatic operating equipment that is allowed to rotate and move to all the directions. All the devices are easily driven using the buttons of the control box placed on the installation deck. Through the field test accomplished at Daehwa Bridge, the performance of the new portable scour monitoring device was verified. The scour monitoring device is proposed to practical use of the bridge scour and foundation inspection as a meaningful and cost- effective method.
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Confederation Bridge- New Scour Design Methodology for Complex Materials

Confederation Bridge- New Scour Design Methodology for Complex Materials

requirements/costs, Baird again recommended that a systematic reassessment of the scour assessment and design methodologies be undertaken. SCBL has initiated this process, with detailed multi-beam sonar (MBS) seabed surveys being undertaken around 14 piers (including all nine AA piers) in the summer of 2001. The remaining piers are to be surveyed using MBS in the summer of 2002. The MBS survey data provide an accurate description of the existing seabed surface, and have be overlain on the pre-construction/ as-built seabed surveys to allow an estimate of changes in the seabed elevation between the two surveys. A sample result, showing the change in seabed elevation around a West approach pier between 1997 (as-built) and 2001 (four years later), is presented in Figure 14.
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Design of Scour Protection for Sutong Bridge, P.R. China

Design of Scour Protection for Sutong Bridge, P.R. China

This paper presents the results of scour assessment and conceptual design of scour protection structures for the Sutong Bridge, P.R. China. The SuTong Bridge, to date the Worlds Largest Cable-Stayed Bridge, is presently being constructed in the Yangtze River near the city of Nantong, P.R. China. The main pylons and approach piers are founded in the river and as a result they are susceptible to scouring of the erodible river bed. State-of-the-art methods have been used in the assessment and the design of scour protection for the SuTong Bridge. The designed scour protection primarily consists of quarry stones and is separated into three areas, Central Area, Outer Area and Falling Apron Area. During construction, extensive surveys using Multi-beam echo sounder were made in order to control and verify the amount of materials dumped. When finished, the scour protection is still a flexible structure that will be subject to some displacement of material. Therefore a detailed monitoring programme was prepared.
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Scaling Issues for Laboratory Modeling of Bridge Pier Scour

Scaling Issues for Laboratory Modeling of Bridge Pier Scour

The laboratory scaling issue is partly attributable to the choice of model sediment size. Scaling the sediment size according to the geometric scale based on Shields’ criterion for fully rough turbulent flow leads to very fine model sediment sizes exhibiting interparticle forces that are not present in sand bed rivers. This state of affairs has led to the practice of reproducing the flow intensity factor (ratio of approach velocity to critical velocity of the model sediment) which can violate Froude number similarity because of the larger critical velocities associated with model sediment sizes that are necessarily too large. An additional model distortion occurs with respect to the ratio of the pier diameter to sediment size due to the constrained choice of model sediment size. These issues are currently being explored by conducting physical model studies of several bridges in Georgia as part of a larger effort to improve the reliability of scour prediction formulas based on field studies and CFD modeling as well. This paper focuses on the laboratory scaling problem using as an example one of the bridges that was modeled in the laboratory at Georgia Tech.
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Designing a WAAM based manufacturing system for defence applications

Designing a WAAM based manufacturing system for defence applications

The following phase consists in developing the deposition parameters perform setup activities, which generally takes up to 1.5 hour and manufacture jigs and substrate. Substrate manufacturing is a standardized process as is based on cutting and de-burring standard metal sheets with different thickness. Jigs manufactures require a high level of customization and therefore needs to be manufactured tailor made. Lead times of both activities are difficult to estimate as they are not standard. In order to guide the robot to perform the designed path, a robot code needs to be generated and in parallel the wire needs to be loaded on the machine. Afterwards the robot code has to be simulated with the design of the substrate to check if conflicts occur. Moreover a dry run with actual substrate and jigs is considered necessary to perform a second check for conflicts. During the deposition, conflicts might compromise the entire build, the substrate and damages to the torch may occur.
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Study on cooperative missile guidance for area air defence

Study on cooperative missile guidance for area air defence

Applications In this chapter, for the application of the proposed algorithms, we will first address several practical issues and propose some algorithms to resolve these issues. In order to implement any guidance laws, it is required to estimate the motion information of the target. Since the update from the ground station can be lost and the target acceleration profile is hard to be predicted, the estimation and prediction of the target state is one of main implementation issues. Successful estimation and prediction lie in the quality of extracting useful information about the target’s state based on observations and suitable set of hypotheses. This information is greatly enhanced if one uses a suitable model, i.e. one that exploits the knowledge available on the target motion. Classical approach computes the interception control (missile acceleration) using minimum covariance and unbiased estimates of the target state. The determination of the guidance law and its optimality relies on the certainty equivalence principle and a set of assumptions on the final aim of the target (Neslin & Zarchan, 1981; Lin, 1998). However, the performance of the resulting law is tightly linked with the adequacy of these hypotheses and the quality of estimation. In this study, the set estimation is used to resolve this issue. The set estimation algorithm used in this study is designed by Dr Hélène Piet-Lahanier as a part of our joint work for the UK MoD and French DGA MCM-ITP (Materials and Components for Missile - Innovation and Technology Partnership) programme.
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Comparsion of General Scour Prediction Equations for River Crossings

Comparsion of General Scour Prediction Equations for River Crossings

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