Geophysical Modelling Essay Example | Topics and Well Written Essays - 1750 words

Geophysical Modelling - Essay Example Firstly, we may declare the thermal conductivity of the soil layers as constant value (2nd assumption). Indeed, if heat transfer is plane and steady, and if is not large (in our case ), one can make a reasonably accurate approximation using a constant average value of (Lienhard &Lienhard 2003, p. 51). Then, we may declare the density and the specific heat of the soil layers as constants and (3rd assumption). It is necessary to note that such assumption is somewhat groundless, especially for the cases of strictly inhomogeneous soils. However, only after this we may introduce a constant diffusion coefficient () of the soil (Bird et al. 2002, p. 268). Finally, we may declare that the rate of internal energy conversion is negligibly small (4th assumption). In fact, such assumption is declaration of absence of the heat generation or consumption within the soil. Again we note that this assumption can be groundless for the inhomogeneous soils with stone inclusions, fluid- or air-filled interstices with internal convective flows. Moreover, the heat transfer in such porous and composite media is very difficult to analyze (Bird et al. 2002, p. 281-283). for the steady boundary conditions and ; is the thickness of the soil upon the rock background. Solution (5) is easy to derive analytically (Haberman 1983, p. 13-14), so we will use it for checking our numerical model by approximation at . Heat transfer model parameters The simplified problem (4) is stated by following values: m, m2s-1. Boundary conditions are: , (1st case), and (2nd case). Initial values are stated by equation . Model discretization is stated by number of soil layers , their thicknesses m, and the timestep (in seconds) which we can modify (240s, or 550s). Model geometry is shown at the figure 1. In our model zero-level () is located at the surface of the rock background because the soil thickness is rather unstable parameter. Indeed, thickness of the real soil cover is a function and for the small areas only. Therefore, we will use more "stable" rock surface to count out -values of the soil layers. Model dynamics (i.e. heat conduction process) is described by (4) which is transformed in a form of difference equation ; (6) here, denotes ; , ; , . The work equation (6) is derived from (4) by FTCS scheme, when forward differentiation was used for and centered differentiation was used for (Boyce & DiPrima 2001, p. 419f). Figure 1 - Model geometry Solutions 1. Let us transform the FTCS scheme (6) into an explicit form: . (7) For the bottom soil layer () we have (8) because of . For the layer near the soil surface () we have (9) because of . 2. To create a Matlab script for solving equation (4) in the explicit FTCS form (7), we can use both initial script and examples of (Mathews & Fink 1999, p. 526-536). Work model code is in

Human Evolution Article Example | Topics and Well Written Essays - 1000 words

Human Evolution - Article Example In this case, relating human evaluation with how humans connect to animals is a new idea altogether. This is because in most cases and with most scientists, human evolution is generally considered as a physical change. The author believes that most developments in the evolution of human beings are contributed by the care shown by humans towards other animals. For example, about 2.6 million years ago, when hunting was the main activity among humans, after hunters were attacked by tigers and lions, they developed weapons and advanced tools for defense. Connecting with other animals compel humans to learn more about them, as well as, having a better understanding of one self. This is because, caring for other animals humans is an ecological transition that no other living thing has made. In addition, by doing these, humans are in a position to learn what other living things do, where they are, their way of communication, as well as, the way they move. There are a number of development o bserved as a result of human connection with animals. The first one is development of symbols and language. The author indicates that human beings developed symbols to alert or warn their fellow humans upon a threat by either predators or dangerous animals. The second one is domestication of animals. Roughly 40,000 years ago, human being started rearing animals not only to get food but also with the motive of getting other resources such as clothing and security, therefore, these prompted them start selectively breed certain animals with specific traits. Lastly, evolution in the means of transport where animals are used as an aid in transporting goods. For example, in the arid areas hardly animals such as camels were used in transporting cargo across the deserts. From the article it is clear that the connection of human to animals has led to human evolution. However, the article does not illustrate how human connection to animals influence physical change. Also not all people like o r are close to animals as such. Therefore, how did such people evolve? The second article is driven by the desire to find out the truth claims advanced by some scholars that human beings are still evolving. This article provides an analysis of the research done by a leading scientist Stephen Stearn who believe that human beings are still evolving. This article ascertains that human beings are evolving gradually and over the years an average human being will be 2cm shorter and 1kg heavier. The study was carried out in great caution to eliminate the chances of cultural and social influences. The study also suggests that natural selection in today’s environment is not based on survival but on the fertility levels of women. It asserts that women with high fertility levels are likely to pass on certain traits on to their children and grandchildren. In addition, the physical characteristics of mothers had a direct correlation with the number of children that she gave birth to. The other thing that has emerged from the article is that evolution is a gradual process that is difficult to notice. The author asserts that cultural factors tend to play a larger role in influencing evolution of human beings than natural selection. This makes persons to neglect the idea of evolution, Genetic evidence also proves this assertion by indicating that about 1800 variant genes have spread faster due to their modern day evolution benefits. In addition, it was realized that mutations