# Introduction  (Page 3/5)

 Page 3 / 5

## Curves, surfaces, and volumes

We will be dealing with regions of space, V , having volume that may be bound by surfaces, S, having area. Regions of the surface may be bound by a closed curve, C , having length.

Surfaces are defined by one relationship between the spatial coordinates.

${x}^{3}=f\left({x}^{1},{x}^{2}\right),\phantom{\rule{0.277778em}{0ex}}or\phantom{\rule{0.277778em}{0ex}}F\left({x}^{1},{x}^{2},{x}^{3}\right)=0,\phantom{\rule{0.277778em}{0ex}}or\phantom{\rule{0.277778em}{0ex}}F\left(x\right)=0$

Alternatively, a pair of surface coordinates, ${u}^{1}$ , ${u}^{2}$ can define a surface.

${x}^{i}={x}^{i}\left({u}^{1},{u}^{2}\right),\phantom{\rule{0.277778em}{0ex}}i=1,2,3\phantom{\rule{0.277778em}{0ex}}or\phantom{\rule{0.277778em}{0ex}}\mathbf{x}=\mathbf{x}\left({u}^{1},{u}^{2}\right)$

Each point on the surface that has continuous first derivatives has associated with it the normal vector, n , a unit vector that is perpendicular or normal to the surface and is outwardly directed if it is a closed surface. Fluid-fluid interfaces need to also be characterized by the mean curvature, H, at each point on the surface to describe the normal component of the momentum balance across the interface. The flux of a vector, f , across a differential element of the surface is denoted as follows, i.e. the normal component of the flux vector multiplied by the differential area.

$\mathbf{f}\mathbf{·}\mathbf{n}\phantom{\rule{0.277778em}{0ex}}da$

Curves are defined by two relationships between the spatial coordinates or by the intersection of two surfaces.

${f}_{1}\left({x}^{1},{x}^{2},{x}^{3}\right)=0\phantom{\rule{0.277778em}{0ex}}and\phantom{\rule{0.277778em}{0ex}}{f}_{2}\left({x}^{1},{x}^{2},{x}^{3}\right)=0,\phantom{\rule{0.277778em}{0ex}}or\phantom{\rule{0.277778em}{0ex}}{f}_{1}\left(x\right)=0\phantom{\rule{0.277778em}{0ex}}and\phantom{\rule{0.277778em}{0ex}}{f}_{2}\left(x\right)=0$

Alternatively, a curve in space can be parameterized by a single parameter, such as the distance along the curve, s or time, t .

$\mathbf{x}=\mathbf{x}\left(s\right)$

The tangent vector is a unit vector that is tangent to each point on the curve.

$\mathbf{\tau }=d\mathbf{x}\left(s\right)/ds$

The component of a vector, f , tangent to a differential element of a curve is denoted as follows.

$\mathbf{f}·\mathbf{\tau }\phantom{\rule{0.277778em}{0ex}}ds$

If the parameter along the curve is time, the differential of position with respect to time is the velocity vector and the differential of velocity is acceleration.

$\begin{array}{l}\mathbf{v}=\frac{d\mathbf{x}}{dt}\\ \mathbf{a}=\frac{d\mathbf{v}}{dt}\end{array}$

## Coordinate systems

Scalars, vectors, and tensors are physical entities that are independent of the choice of coordinate systems. However, the components of vectors and tensors depend on the choice of coordinate systems. The algebra and calculus of vectors and tensors will be illustrated here with Cartesian coordinate systems but these operations are valid with any coordinate system. The student is suggested to read Aris to learn about curvilinear coordinate systems. Bird, Stewart, and Lightfoot express the components of the relevant vector and tensor equations in Cartesian, cylindrical polar, and spherical polar coordinate systems.

Cartesian coordinates have coordinate axes that have the same direction in the entire space and the coordinate values have the units of length. Curvilinear coordinates, in general, may have coordinate axis that are in different directions at different locations in space and have coordinate values that may not have the units of length, e.g., θ in the cylindrical polar system. If ( ${y}^{1}$ , ${y}^{2}$ , ${y}^{3}$ ) are Cartesian coordinates and ( ${x}^{1}$ , ${x}^{2}$ , ${x}^{3}$ ) are curvilinear coordinates, a differential length is related to the differential of the coordinates by the following relations.

$\begin{array}{c}d{s}^{2}=\sum _{k=1}^{3}d{y}^{k}d{y}^{k}\hfill \\ d{y}^{k}=\frac{\partial {y}^{k}}{\partial {x}^{i}}d{x}^{i}\equiv \frac{\partial {y}^{k}}{\partial {x}^{1}}d{x}^{1}+\frac{\partial {y}^{k}}{\partial {x}^{2}}d{x}^{2}+\frac{\partial {y}^{k}}{\partial {x}^{3}}d{x}^{3}\hfill \\ d{s}^{2}=\sum _{k=1}^{3}\left(\frac{\partial {y}^{k}}{\partial {x}^{i}}d{x}^{i}\right)\left(\frac{\partial {y}^{k}}{\partial {x}^{j}}d{x}^{j}\right)\hfill \\ ={g}_{ij}d{x}_{i}d{x}_{j}\\ {g}_{ij}=\sum _{k=1}^{3}\left(\frac{\partial {y}^{k}}{\partial {x}^{i}}\right)\left(\frac{\partial {y}^{k}}{\partial {x}^{j}}\right)\hfill \end{array}$

where g ij are components of the metric tensor which transforms differential of the coordinates to differential of length. Summation is understood for repeated indices. Calculus in a curvilinear coordinate system will require the metric tensor.

are nano particles real
yeah
Joseph
Hello, if I study Physics teacher in bachelor, can I study Nanotechnology in master?
no can't
Lohitha
where we get a research paper on Nano chemistry....?
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
Ali
what are the products of Nano chemistry?
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
hey
Giriraj
Preparation and Applications of Nanomaterial for Drug Delivery
revolt
da
Application of nanotechnology in medicine
has a lot of application modern world
Kamaluddeen
yes
narayan
what is variations in raman spectra for nanomaterials
ya I also want to know the raman spectra
Bhagvanji
I only see partial conversation and what's the question here!
what about nanotechnology for water purification
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
what king of growth are you checking .?
Renato
how did you get the value of 2000N.What calculations are needed to arrive at it
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