Structural Style

FIGURE 3.8 Photograph of near vertical, irregular, clay-filled fault in sedimentary siltstone and sandstone strata. 

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Lowell, James D.(1985) Structural Styles in Petroleum Exploration, 460p, OGGI Publications... 

Gabrielse, H. 1991. Structural Styles. In Gabrielse, H. Yorat, C.J. (ed.). Geology of the Cordilleran Orogen in Canada. Geological Survey of Canada, Ottawa, ON, 81-98. 

The UART top-level model glues all these blocks together using module instantiations. The microprocessor entity, MP, is described in the structural style, that is, using module instances. The remaining three are described using the behavioral style. In this chapter, only the behavioral blocks are described. 

Watts, N.L., 1987. Theoretical aspects of cap-rock and fault seals for single- and two-phase hydrocarbon columns. Marine and Petroleum Geology, Vol. 4, November 1987, pp. 274-307 Weber, K.J., 1982. Influence of common sedimentary structures on fluid flow in reservoir models. Journal of Petroleum Technology, March 1982, pp. 665-672 Weber, K.J., 1987. Hydrocarbon distribution patterns in Nigerian growth fault structures controlled by structural style and stratigraphy. Journal of Petroleum Science and Engineering, 1, pp. 91-104... 

Even in Pennsylvania, where Professor H.D. Rogers indicated that several of the successful new wells were located on anticlines less than a year after the drilling of Drake s well, such information was ignored. Of course, it is always easy to ridicule this primitive approach. However, undoubtedly many geological advisors were quite unreliable. Moreover, if the structural style is not too complicated, empirical rules often work. Trends of rivers frequently played a part in predictions and these are often parallel to the structural strike. Another characteristic of early exploration efforts was the technical difficulty of drilling to any considerable depth and the poor recording of stratigraphic detail, which both hamper the subsurface analysis. 

Weber, K.J. 1987. Hydrocarbon distribution patterns in Nigerian growth fault structures controlled by structural style and stratigraphy. J. Pet. Sci. Eng., 1 91-104. 

The structural style of the Heidrun area is the result of episodes of stretching and of salt tectonics. The patterns of sedimentation in the area generally reflect the simultaneous operation of these two processes. Based on seismic, well, structural and sedi-mentological data, the structural history of the Greater Heidrun study area is summarised by Bukoviks et al. (1984), Schmidt (1992), Knott et al. 

Tankard, A.J. Welsink, H.J. (1988) Extensional tectonics, structural styles and stratigraphy of the Mesozoic Grand Banks of Newfoundland. In Triassic-Jurassic Rifting Continental Breakup and the Origin of the Atlantic Ocean and Passive Margins, Part A (Ed. Manspeizer, W.). Devel. Geotectonics 22, 129-165. Elsevier, Amsterdam. 

Rowan, M. G. 1995. Structural styles and evolution of allochthonous salt, central Louisiana outer shelf and upper slope. In Jackson, M. P. A., Roberts, D. G. Snelson, S. (eds) Salt Tectonics A Global Perspective. American Association of Petroleum Geologists Memoir, 65, 199-228. 

Jackson, J. S. Hastings, D. S. 1986. The role of salt movement in the tectonic history of Haltenbanken and Traenabanken and its relationship to structural style. In Spencer, A. M. (ed.) Habitat of Hydrocarbons in the Norwegian Continental Shelf. Graham Trotman, 241-257. 

Chen Haiyun, Yu Jianguo, Shu Liangshu, et al. The structural styles and their relation with petroleum-gas resources of the Jiyang Depression. Geological Journal of China Universities, 2005 11(4) 622-632. 

Bradshaw JD, Laird MG, Wodzicki A (1982) Structural style and tectonic history in northern Victoria Land. In Craddock C (ed) Antarctic geoscience. University Wisconsin Press, Madison, WI, pp 809-816... 

Structural style The design is expressed as a netlist of basic Mocks and can be generally synthesized with no proMems. The quality d the produced results depend on the quality of the input description. 

In an ideal world, the structure, style and content of a safety case would be enough to convince an approving body of the credibility of the developing organization. However, in reality credibility needs to be explicit and this could be achieved by including some or all of the evidence mentioned above. This is not widely understood and so situations can arise where a company may refuse to give any evidence of individual competence (or even the names of individuals who had been involved in the project). In worst-case scenarios, these types of problems may lead to projects failing to deliver. 

A structural style architecture describes the circuit primarily in terms of components. These may be drawn from libraries supplied by ASIC ven-... 

The architecture body specifies which components are contained in a design and how they are interconnected. The main VHDL topics associated with structural style architectures include the following ... 

The required circuit characteristics. If ikxe circuit must possess a particular gate level structure, then that must be imposed by the designer using a more structural style. If the structure is flexible and the synthesizer is allowed to select by itself how the circuit is organized, then a more flexible (behavioural) style can be used. 

Just as a Process statement identifies a behavioural style, component declarations and instantiations identify a structural style. Unlike the behavioural style, which specifies what the circuit has to do, a VHDL description in the structural style determines the operation of the circuit by the manner in which any number of functional blocks - components - are interconnected. These may contain anything from simple two-input logic gates to 16 x 16 bit multipliers. 

Three different architecture bodies have been designed in the structural style for the multiplexer example. The components in each one are as follows ... 

The second structural style architecture makes use of only two-input And gates, two-input Or gates and inverters. As a result, more component instances and so more component interconnection is required. In this ii>stance, the equation for the logic of the function is equation 4.3. 

The structural style architecture lends itself to a demonstration of the differing effects of optimizing a circuit by flattening or preserving its hierarchy. These techniques were discussed in section 2.4. The circuit statistics... 

Figure 430 Structural style circuit flattened by optimization.

Table 4.6 Logic synthesis and optimization statistics for the structural style architectures...

Section 4.2 has illustrated a number of different ways in which a simple multiplexer can be designed in VHDL. Not all of these approaches are recommended for such a circuit, but die nature of the example has allowed a number of concurrent and sequential language statements to be introduced, not least various Signal assignment statements and the Case and If statements. For structural style architectures, a number of different techniques that allow components to be used in a design have also been demonstrated. 

Finally, circuits constructed in the structural style have components and therefore an explicit hierarchy. Flattening the hierarchy during optimization resulted in a circuit that was always smaller than when the hierarchy was preserved and only the components optimized. 

This circuit contains two identical components. One drives the HI-DRIVER bus and the other the LO-DRIVER bus. The former decodes the upper 4 bits or nibble of the input and the latter the lower nibble. This suggests that a structural style would be an appropriate approach to adopt for a top-level architecture. This modular approach has the benefits of easier design and debugging, and also a simple expansion capability. Within each component, a straightforward transform is required from a 4-bit BCD to a seven-segment display bit pattern. Of the possible language constructs studied so far, it would seem that a Case statement is most appropriate for this task and therefore a behavioural style architecture is required. 

The approach that was applied to the structural style architecture examples in section 4.2 must also be used for this circuit. The component must be compiled first in the working directory followed by the entity-architecture pair, CONVERTER-STRUCTURAL This top-level circuit will generate two instances of the component. 

A structural style architecture can be used to model sequential circuits. The storage elements used in a sequential circuit are edge-triggered latches - flip flops - or level-triggered latches - transparent latches. These can be instantiated from libraries provided by the synthesis tool or technology vendor. This can limit the flexibility of an implementation as not all vendor technologies will support all types of storage elements. Elements such as flip flops with asynchronous preset and clear inputs, for example, may be omitted from a library. 

A structural style description of the 4-bit shift register can be constructed in two ways. The most straightforward approach is to instantiate storage elements with the required functionality from vendor-supplied libraries. If the required type of flip flop is not available, the designer may choose to construct a component with the required function using a behavioural description. Ultimately, this approach will still produce a circuit with storage elements extracted from a vendor s library along with some combinational... 

The Generate statement allows a section of a concurrent VHDL description to be replicated using an iterative scheme. It is frequently applied to the creation of multiple instances of the same component in a structural style architecture or used to create circuits with any regular structure. The iteration parameter is used as an index to create uiuque instances of eadt statement. 

This section looks at the components used in the structural style architectures of the shift register. These components are constructed in a behavioural style and describe D and JK-type flip flops. Both architectures, DFF and JKFF respectively, contain a synchronous reset, PC, and employ a Walt statement. 

Table 5.4 Logic synthesis and optimization statistics for the structural style architectures. Manually instantiated D-type and regular/irregular generated JK-type structures. All components are the optimized versions...

The structural style of creating an architecture allows the designer to specify explicitly ... 

One way to implement this circuit would be to use a structural style and instantiate components that implement the behaviour of the Decoder and the Enabler. It is not possible to use a function in this case as ... 

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