Joint action

Erosion is the deterioration of a surface by the abrasive action of solid particles in a liquid or gas, gas bubbles in a liquid, liquid droplets in a gas or due to (local) high-flow velocities. This type of attack is often accompanied by corrosion (erosion-corrosion). The most significant effect of a joint action of erosion and corrosion is the constant removal of protective films from a metal s surface. This can also be caused by liquid movement at high velocities, and will be particularly prone to occur if the solution contains solid particles that have an abrasive action. 

At the junction of the adsorbed film and the liquid meniscus the chemical potential of the adsorbate must be the resultant of the joint action of the wall and the curvature of the meniscus. As Derjaguin pointed out, the conventional treatment involves the tacit assumption that the curvature falls jumpwise from 2/r to zero at the junction, whereas the change must actually be a continuous one. Derjaguin put forward a corrected Kelvin equation to take this state of affairs into account but it contains a term which is difficult to evaluate numerically, and has aroused little practical interest. 

Erosion-corrosion can be defined as the accelerated degradation of a material resulting from the joint action of erosion and corrosion when the material is exposed to a rapidly moving fluid. Metal can be removed as solid particles of corrosion product or, in the case of severe erosion-corrosion, as dissolved ions. 

Figure 4-361. Knuckle joint action to retrieve a fish in a washout. (Courtesy Bowen Tools, Inc.)...

In the case considered in this section of a joint action of concentration and activation polarization, in the polarization equation (6.10) we must take into account the concentration changes of the rectants near the electrode surface ... 

Each of the main risk analysis elements consists of three interactive studies. Exposure estimates result from the integration of pollutant dispersion patterns and human population patterns. The dispersion patterns, in turn, result from the joint action of emissions and dispersion processes. 

Ormrod, D.P., J.C. Hale, O.B. Allen, and P.J. Laffey. 1986. Joint action of particulate fall-out nickel and rooting medium nickel on soybean plants. Environ. Pollut. 41A 277-291. 

A new direction in searching for the atmospheric CO2 sink considering the joint action of carbonate dissolution, global water cycle and the photosynthetic uptake of die by aquatic organisms... 

Conclusions and Perspective We have shown an important potential C02 sink by joint action of carbonate dissolution, GWC and the photosynthetic uptake of DIC by aquatic. The sink constitutes up to 0.82 Pg C/a 0.47 Pg C/a goes to sea via continental rivers and precipitation over sea, 0.12 Pg C/a is returned to the atmosphere, and 0.23 Pg C/a is stored in the continental aquatic ecosystem. The net sink, then, could be 0.70 Pg C/a, or 9% of the total anthropogenic C02 emission and 25% of the missing C02 sink (Melnikov O Neill 2006). 

Synergistic Effect Joint action of agents that when taken together increase each other s effectiveness. 

Abstract joint actions come from Disco [Kurki-Suonio90], the OBJ tradition [Goguen90], and database transactions as well as from the general notion of the Objec-tory use case. 

Objects that have similar behaviors are members of the same type they satisfy the specification of that type. Behaviors are specified in terms of attributes that are a valid abstract model, called a type model, of many possible implementations. Each action is described in terms of its effect on the attributes of the participating objects and the outputs it produces. The most interesting aspects of a design are the interactions between objects. You can abstract away detailed interaction protocols between objects by using joint actions and collaborations and you can describe specific interactions as refinements of a more abstract description. 

The second kind of action is a joint action To describe behavior and interactions of a group of objects, we focus on the net effect of interactions between multiple objects, and we specify that effect as a higher-level action with all objects involved. A joint action is written... 

Notice that the joint action is not centered on a single distinguished object type. There are directed variations of joint actions in which a sender and a receiver are designated, but the action effect is still described in terms of all participants. 

At the business level, it takes a sequence of interactions between client and seminar company, including enquire, schedule, deliver, follow-up, and pay, to together constitute an abstract purchaseCourse action. This sequence has a net effect on both client and seminar company not only has the seminar company delivered a service and gained some revenue, but also the client has paid some fees and gained knowledge. In software, it may take a sequence of low-level operations via the user interfaces (UIs) of multiple applications and databases to complete a scheduleCourse operation. Such a joint action, also called a use case, is the subject of Chapter 4. 

Each occurrence of such a joint action is shown as a horizontal bar with ellipses in a sequence diagram, whereas the finer-grained operations were depicted as simple arrows. Note that each action occurrence could be realized by many different finer-grained interactions, eventually reducing to a sequence of operations. 

However, there is nothing to stop you from using a type in a model even though the type happens to have an implementation somewhere. In fact, good implementations of domain objects will often have their specs reused in this way. The more important design decision hinges on how the types in an implementation will be used, and those decisions involve joint actions recorded in collaboration diagrams. 

A joint action represents a change in the state of some number of participant objects without stating how it happens and without yet attributing the responsibility for it to any... 

Let s look at some differences between joint actions and localized actions. First, localized actions are invoked. A localized action represents an interaction in which the receiver (the object taking responsibility) is requested to achieve the postcondition. It should do so if the precondition is met. 

Joint actions represent possibilities A joint action represents a specification of something that may occur. It can be referred to in other specifications (e.g., To achieve restocking, one or more sales must occuf ) but can t be invoked directly from the program code. To do that, you must have an implementation (such as one of the sequences in Figure 4.1), which will tell you one of the ways to start. 

Localized actions provide preconditions. When a localized action is invoked, if the precondition is fine we are assured that the postcondition will be achieved. Joint actions represent descriptions of history Looking at the history of the world, wherever this and that has happened, we call that a sale. Wherever something else happened that started the same way but ended up differently, we call it something else, such as a theft. 

We sometimes find it convenient to write preconditions on joint actions, but they are really only clauses that should be wrapped up in a big (,..) pre and conjoined with the rest of the postcondition.)... 

A directed joint action encompasses any way one object may stimulate another to do something. 

In a joint action, some of the parameters may be distinguished as participants and drawn linked to the use case pictorially, whereas other parameters are written in text style. For example, in Figure 4.5, buyer and vendor are participants, whereas item is a parameter. In business analysis, the difference is a matter of convenience and is analogous to the equivalence of the associations and attributes of object types. In a software design, the participants can be used to represent objects that we know will definitely exist in the final code and that will, between them, take responsibility for executing the action. The list of parameters, on the other hand, represents information transferred between them whose implementation is yet to be determined. 

This represents a joint action with three participants, with no distinguished initiator or receiver. The effect refers to all participants, parameters, and their attributes. 

A joint action, this time initiated by the retailer. It is now meaningful to mark some parameters as inputs—determined by the initiator by means unspecified in the effects clause—and others as outputs—determined by other participants, used by the initiator in ways not fully specified in the effects clause. 

A directed joint action initiated by an object and received by the agent. Nothing is known about the type of the initiator or its role in this action hence, initiator is declared to be of unknown type Object. 

A localized operation is a degenerate case of a joint action with a distinct receiver, in which nothing is known or stated about the initiator s identity or attributes. All relevant aspects of the initiator are abstracted into the input and output parameters of the operation. The following is a fully localized operation that cannot refer to the initiator at all. 

The concept of inputs and outputs is meaningful only for directed requests either fully localized operations or joint actions with initiators and receivers, in which the invoker of an operation somehow provides the inputs and uses the outputs. In the case of joint actions that have no distinguished initiators or receivers, the effect is expressed in terms of, and on, all participants, and there is no need to explicitly list inputs or outputs. 

The input parameters in a directed action are simply attributes of the initiator in a corresponding undirected joint action they represent state information known to the initiator when it provides the inputs to a directed request. Similarly, the outputs of a directed action are state changes in attributes of the sender in the joint action. When parameters are used in a joint action, the parameter list represents information exchanged that is not fully determined by attributes in the participants that is, they provide a degree of nondeterminism. 

We have seen how an entire sequence of interactions between objects can be abstracted and described as a single joint action. We will next see how even in program code, an operation invocation itself has two sides the sender and the receiver. By using input and output parameters, a localized operation specification decouples the effect on the receiver from any information about the initiator. 

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