Recoverable Definition

Yield stress may be regarded most simply as the minimum stress at which permanent strain is produced when the stress is subsequently removed. Although this deformation is satisfactory for metals, where there is a clear distinction between elastic recoverable definition and plastic irrecoverable deformation, in polymers the distinction is not so straightforward. In many cases, such as the tensile tests discussed above, yield coincides with the observation of a maximum load in the load-elongation curve. The yield stress then can be defined as the true stress at the maximum observed load (Figure 11.8(a)). Because this stress is achieved at a comparatively low elongation of the sample, it is often adequate to use the engineering definition of the yield stress as the maximum observed load divided by the initial cross-sectional area. 

Estimates of the amount of natural gas available are made within the context of definitions and are subject to revision as definitions change, as additional information becomes available, as resources are consumed, or as undedyiag assumptions are altered. These definitions iaclude proved reserves where the resource is expected to be recoverable and marketable usiag known technology and prices probable reserves where a resource has been identified but not completely characterized and possible or potential gas where estimates are based on the available geological iaformation, historical trends, and previous successes. There are variations ia these definitions throughout the world. 

Debate continues over just how much natural gas remains in North America. Part of this debate centers on the definition of gas reserves—the amount of gas in a given area that is recoverable and gas resource, the total amount of gas in the ground. Gas production to date, as might be expected, has most commonly been from easy-to-produce conventional... 

The definitions above are an abbreviated version of those used in a veiy complex and financially significant exercise with the ultimate goal of estimating resei ves and generating production forecasts in the petroleum industry. Deterministic estimates are derived largely from pore volume calculations to determine volumes of either oil nr gas in-place (OIP, GIP). This volume when multiplied by a recovery factor gives a recoverable quantity of oil or natural gas liquids—commonly oil in standard barrels or natural gas in standard cubic feet at surface conditions. Many prefer to use barrels of oil equivalency (BOE) or total hydrocarbons tor the sum of natural gas, natural gas liquids (NGL), and oil. For comparison purposes 6,000 cubic feet of gas is considered to be equivalent to one standard barrel on a British thermal unit (Btu) basis (42 U.S. gallons). 

Note 5 Creep is sometimes described in terms of non-linear viscoelastic behaviour, leading, for example, to evaluation of recoverable shear and steady-state recoverable shear compliance. The definitions of such terms are outside the scope of this document. 

A good operational definition of rubber-like elasticity is high deformability with essentially complete recoverability.81 84 The high deformability can be remarkably high, with some rubbery materials extending up to 15 times their original lengths. 

Keeping in mind the problems stated in the introduction, we have up to this point not made use of any procedures that would risk a physical formulation that would incorporate any loss of information and/or memory. It is true that the definition of an unstable state proceeds via the redefinition of appropriate domains and ranges. However, this is recoverable information within the realm of the time-independent formulation. What about the state of affairs in the time-dependent situation Formally it looks straightforward to write the causal evolution operator as... 

Workable definitions of EOR and lOR are necessary not just for improved communication, but also to recoverable reserves booking, contract negotiations, government incentives, taxation, and regulatory authorities when looking at fiscal issues (Stosur et al., 2003). The following sections summarize the existing definitions used in the petroleum industry and then propose this book s definitions of EOR and lOR. 

For IR-based methods, TPH is defined as any compound extractable by a solvent (Freon 113 or tetrachloroethylene), which is not removed by silica gel or florisil clean-up and which can be measured at a specified wavelength. This definition is similar to that of mineral oil discussed previously. The method most referred to is the EPA Method 418.1 which is used for recoverable petroleum hydrocarbons. This method often suffers from poor accuracy and precision, especially for heterogeneous soil samples. This method gives neither the information on petroleum type nor the presence or absence of toxic materials, and is thus of little use in risk estimation. 

Once a recovery process has been fixed, based on a definitive feedstock sample, it is important to make clear to the feedstock producers that they are responsible for informing the recoverer of any significant changes in the feedstock s composition, including accidental contamination while under their control. 

Resources are defined as reserves plus all other mineral deposits that may eventually become arailable - either known deposits that are not economically or technologically recoverable at present, or unknown deposits, rich or lean, that may be inferred to exist but have not yet been discovered" [54]. Use of e term "resources implies that the extent and quality of a phosphate deposit cannot be definitively estimated because of insufficient information. The term resources also implies that the deposit cannot be economically exploited under current conditions. 

Storage/archiving Definition of location and type of the archive. Ensuring long-term archiving and recoverability for the planned retention period... 

This explanation implies the importance of die geometry, flow rate and a characteristic pol)mier time. More detailed explanations are needed to arrive at a quantitative definition for die swell. In this respect, the recoverable strain and the first normal stress difference are critical rheological variables. 

The theoretical stored energy is that whieh is determined only on the basis of the aetive material. Due to its definition, stored energy does not depend on the discharge current amplitude. Given that not all the active material is fully delithiable or electrically accessible (poor conductivity of certain materials such as lithium iron phosphate, LFP), this theoretical stored energy is not fully recoverable. 

The recoverable compliance, therefore, increases with dilution. The effect of dilution on J° is best understood physically from its definition in Eq. (3.9) in terms of the recovery phase after steady-state creep. Dilution reduces the concentration of strands in the entanglement network that support the stress. Thus, for a given stress, the coils are more deformed because the stress per strand is higher, so the recoverable strain and hence J° are larger in the diluted system. 

There is a single dimensionless group, XVjL, which is known as the Weissenberg number, denoted by various authors as We or Wi. (We is more common, but it can lead to confusion with the Weber number, so Wi will be used here.) The shear rate in any viscometric flow is equal to a constant multiplied by V/L, so it readily follows that the ratio of the first normal stress difference to the shear stress is equal to twice that constant multiphed by Wi. Hence, Wi can be interpreted as the relative magnitude of elastic (normal) stresses to shear stresses in a viscometric flow. The ratio of the shear stress to the shear modulus, G, is sometimes known as the recoverable shear and is denoted Sr. Sr differs from Wi for a Maxwell fluid only by the constant that multiplies F jL to form the shear rate for a given flow. In fact, many authors define Wi as the product of the relaxation time and the shear rate, in which case Wi = Sr. It is important to keep the various definitions of Wi in mind when comparing results from different authors. 

Rheology is the study of flow by definition, and polymer melt riieology is basically concerned with the description of the deformation of polymer melts under the influence of applied stresses. Molten thermc lastics are viscoelastic materials in the sense that their response to deformation lies in varying extent between that of viscous liquids and elastic solids. In purely viscous liquids, the mechanical energy is di pated into the systmns in the form of beat and cannot be recovered by releasing the stresses. Ideal solids, on the other hand, deform elastically such that the deformation is reversible and the energy of deformation is fully recoverable when the stresses are released. 

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