Interface concrete

In this paper we have introduced the LARES formalism for the specification of dependability models of reconfigurable systems. The formalism follows a structured hierarchical approach and includes features that allow the user to describe arbitrarily complex dynamic behavior. The paper described the textual user interface, concretized by two examples from the literature. Next steps will include the definition of a formal semantics for LARES. Based on this semantics, we will develop model transformations in order to automatically convert different application-specific modeling formalisms to the LARES formalism, and implement interfaces to existing analysis engines, which will be used to perform the quantitative analysis of the specified models. 

Four mechanisms contribute to the shear resistance at the interface concrete-to-concrete adhesion, concrete-to-concrete friction (Fig. 4a), the connecting action from either steel bars placed across the interface between the old and the new concrete (Fig. 4b), and bent-down bars welded between the bars of the old and the new crmcrete (Fig. 4c Dritsos 2007). These four mechanisms can be subdivided into the two groups of unreinforced and reinforced interfaces, depending on whether or not additional steel is placed across the interface or welded between the bars of the old and the new concrete (Dritsos 2007). 

Fig. 5, also an A-scan, shows the possibility of the echo-technique for concrete. The interface and backwall-echo of a 20 cm thick concrete specimen are displayed (RF-display). A HILL-SCAN 3041NF board and a broadband transducer (40mm element 0) are used which enable optimal pulse parameters in a range of 50 to 150 kHz. Remarkable for concrete inspections is the high signal-to-noise ratio of about 18 dB. 

Fig. 5 Echo-technique for concrete inspections with HILL-SCAN 304INF interface- and backwall echo of a 20 cm thick concrete specimen, 0.1 V/div. and 20ps/div.

Cement coatings are usually applied as linings for water pipes and water tanks, but occasionally also for external protection of pipelines [7]. Cement is not impervious to water, so electrochemical reactions can take place on the surface of the object to be protected. Because of the similar processes occurring at the interface of cement and object and reinforcing steel and concrete, data on the system iron/ cement mortar are dealt with in this chapter taking into account the action of electrolytes with and without electrochemical polarization. To ensure corrosion protection, certain requirements must be met (see Section 5.3 and Chapter 19). 

A WBL can also be formed within the silicone phase but near the surface and caused by insufficiently crosslinked adhesive. This may result from an interference of the cure chemistry by species on the surface of substrate. An example where incompatibility between the substrate and the cure system can exist is the moisture cure condensation system. Acetic acid is released during the cure, and for substrates like concrete, the acid may form water-soluble salts at the interface. These salts create a weak boundary layer that will induce failure on exposure to rain. The CDT of polyolefins illustrates the direct effect of surface pretreatment and subsequent formation of a WBL by degradation of the polymer surface [72,73]. 

Another aspect of epoxy resin mortar floorings which needs careful attention is that their coefficients of thermal expansion are approximately three times that of concrete. This, coupled with the relative low thermal conductivity of epoxy mortar, can cause stresses to be induced at the resin mortar/concrete interface under conditions of thermal shock (e.g. thermal cleaning), resulting in break-up of the flooring due to initial failure in the concrete. Two approaches have been tried to overcome this problem ... 

Polyester resin floor toppings, similar in performance to the epoxy toppings, have been used but, as indicated earlier, polyester systems tend to shrink and, without careful formulation and laying, shrinkage stresses with polyester resin systems can develop at the interface between the topping and the concrete substrate. Coupled with the additional stresses due to the differences in their coefficients to thermal expansion, this can cause failure at the surface of the concrete substrate." ... 

The coating composition is iridium-rich to favour oxygen rather than chlorine evolution, and to assist in reducing the formation of acidic conditions at the anode-concrete interface. 

One can further elaborate a model to have a concrete form of /(ft), depending on which aspect of the adsorption one wants to describe more precisely, e.g., a more rigorous treatment of intermolecular interactions between adsorbed species, the activity instead of the concentration of adsorbates, the competitive adsorption of multiple species, or the difference in the size of the molecule between the solvent and the adsorbate. An extension that may be particularly pertinent to liquid interfaces has been made by Markin and Volkov, who allowed for the replacement of solvent molecules and adsorbate molecules based on the surface solution model [33,34]. Their isotherm, the amphiphilic isotherm takes the form... 

For facilities susceptible to the contamination of nitroglycerin liquids and vapors, basic construction materials of wood framing, reinforced concrete, fiberglass reinforced plastic, and sandwich panels were chosen for development of architectural details incorporating lead conductive floor lining, equipment doors, personnel escape chutes and doors, ceiling and wall interfaces, interior finishes, joint sealing, door and wall louvers, wall vents, wall penetrations, and fixed windows. 

The function f(it) can be given in a concrete expression as "S"-shape nonlinear function, schematically shown on the left in Figure 8A. For the convenience of analysis we take the approximation to express the "S"-shape characteristics with the combination of two straight lines as shown on the right in Figure 8A. The third term of Equation 2-2 means the increment of [D] with compression at the air/water interface. To simplify the analysis, we further assume kj k i. This assumption is consistent with the observed stability of the bilayers formed at the zero surface pressure point. The kinetics of [D] can be then expressed as... 

Documentation of a framework—a set of abstract and concrete classes and types that must be extended by the client before using it—should also explicitly include the super-class/subclass interface and describe what is expected of anyone extending and overriding methods in the framework. 

Concrete classes typically inherit from the default implementation, but they could also independently implement the required interface. 

The framework approach to code reuse provides a concrete, yet incomplete, implementation of the architecture The rules and policies about how application objects interact are codified and enforced by the framework itself. Frameworks can be both white-box—a template method in the superclass must be overriden by a subclass after understanding the calls made in the superclass implementation—and black-box, in which interfaces for the plug-in calls are explicitly specified and implemented according to the spec. 

The starting point for describing an architecture is to define the kinds of elements that constitute it. At the simplest level, interfaces and implementations are the elements of architecture. Beyond that, concrete implemented elements—specific kinds of buffers, synchronization primitives, coordinators, kits of parts to be assembled—can be specified as types or interfaces more-abstract ones—design patterns, patterns of connectors and components—can be described using model frameworks. It is even possible for certain architectural qualities to be quantified, in a parameterized form, on the framework level. After these elements have been defined, the architecture itself can be described using these as primitives. ... 

Figures 10.9S(a,b) show isopleths calculated between (a) corium and siliceous concrete and (b) corium and limestone concrete. Comparison between experimental (Roche et al. 1993) and calculated values for the solidus are in reasonable agreement, but two of the calculated liquidus values are substantially different. However, as the solidus temperature is more critical in the process, the calculations can clearly provide quite good-quality data for use in subsequent process simulations. Solidus values are critical factors in controlling the extent of crust formation between the melt-concrete and melt-atmosphere interface, which can lead to thermal insulation and so produce higher melt temperatures. Also the solidus, and proportions of liquid and solid as a function of temperature, are important input parameters into other software codes which model thermal hydraulic progression and viscosity of the melt (Cole et al. 1984).

In addition, further oxidation and cathodic reactions lead to the production of oxides and oxyhydroxides of Fe (III), which produces a low-permeability, passive film that slows down the corrosion rate considerably. Where corrosion can continue (by depassivation), the expansion of corrosion products at the cement-steel interface and the subsequent spalling of cover concrete can occur. Many examples of this can be seen in concrete structures. 

Aligizaki, K. du Rooij, M.R. Macdonald, D.D. (2000) Analysis of iron oxides accumulating at the interface between aggregates and cement paste. Cement Concrete Res. 30 1941-1948... 

The stability of the concrete mix can be considered in terms of its cohesion , which is a subjective term used to describe its ability to maintain a homogeneous appearance when subjected to applied stress. Lack of cohesion leads to segregation of the mix components into layers relevant to their densities. A further term associated with mix stability is that of bleeding , which is the movement of water to the surface of the fresh concrete. This phenomenon can occur either in isolation or as a manifestation of segregation. Bleeding in excess is normally considered to be undesirable because of the dangers of water runs at the shutter/concrete interface and cracking due to plastic settlements, and there is also the possibility of adverse effect on the concrete-reinforcement bond due to the collection of water beneath the steel. 

The protection of steel reinforcements. Concrete produces a layer of passivity at the steel/concrete interface and any breakdown of this can increase the chance of reinforcement corrosion. In addition, it is important that concrete be maintained in a state of low permeability to minimize the passage of moisture and air to the steel. 

The action of an admixture in relation to attack on reinforcement can be considered either in direct chemical reaction with the steel or, alternatively, a breakdown of the passive layer imparted by concrete which normally prevents corrosion at the cement/steel interface. In this respect, any accelerating water-reducing admixtures containing calcium chloride can be considered hazardous as far as raising susceptibility of steel reinforcement to corrosion is concerned. It is particularly so at calcium chloride contents in the concrete at or above 1.5% by weight of cement as discussed in the section on accelerators. The use of such materials has been controlled by relevant codes of practice where embedded metal is present in the concrete. 

The formation of the passive layer at the concrete/reinforcement interface referred to earlier (Section 1.4) is due to the alkaline nature of the concrete. The alkalinity is due to calcium, sodium and potassium hydroxides which, over a period of time, react with atmospheric carbon dioxide to form carbonates. This reduction in alkalinity in reflected in a diminished protective capacity towards the steel reinforcement. 

There are no recorded data to indicate that materials of this type would alter the stiffness of the concrete into which they are incorporated. However, the fact that these materials are associated with the matrix/air interface, and not the cement hydrates themselves, would suggest that the physical properties of the bonding constituents of the hardened cement would remain unchanged. 

The presence of calcium chloride at concentrations greater than about 1.5% by weight of cement can lead to breakdown of the passive layer of Fe203 normally present at the steel/concrete interface, rendering the... 

Monteiro, P. J. M. Mehta, P. K. 1985. Ettringite formation on the aggregate-cement paste interface. Cement and Concrete Research, 15, 378-380. 

A recently developed technology takes a different approach to solving the stress problem (14). Rather than chemically plasticizing the sulphur, non-reactive additives are used to holistically plasticize the sulphur concrete mix. In essence these additives are lubricants which operate at the sulphur/aggregate interface to allow slippage and stress relief without disruption and cracking. The apparent permanency of this plasticization approach has been demonstrated by extensive testing over a four year period. 

In discussing this modification, it is helpful to consider a concrete example. Suppose that the electron-transfer reaction at the interface under study is... 

It is naive because the getCompounds method of CompoundLibrary class returns a concrete data type—ArrayList—instead of an abstraction. If for some reason the developer of CompoundLibrary class decides to switch compoundList to a Vector, or a LinkedList, or some other customized List implementation, the clients of CompoundLibrary class all need to change because none of these implementations are interchangeable. This kind of coupling between the internal data structure of a class and its clients is not desirable and can be avoided by using better abstractions to hide CompoundLibrary s implementation details with their interfaces. 

Now the method getCompounds returns an interface—List, which is a super type of all possible concrete List classes. No matter what kind of list CompoundLibrary uses to hold its compounds, its clients do not need to care any more because what they get is the common abstraction List. Another way to achieve this is to have getCompounds to return an iterator. Please note the iterator() method in Java Collection Framework creates a new iterator object every time it is called and therefore is an expensive operation and should be used with discretion. 

Note Whether the member variable compoundList of CompoundLibrary should be declared as an interface—List or a concrete type—ArrayList should be determined on a case-by-case basis. If the concrete class has methods that are not defined in the interface or the abstract class, you are better off defining the variable as the concrete type. Otherwise, you need to explicitly cast the variable to the concrete type every time you use those methods. Either way, the clients of CompoundList are no longer affected by the decision made by the developer of CompoundLibrary with regard to the data type of compoundList variable, which is what abstraction or encapsulation is all about. 

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