As we are facing the uncertainly in supply of crude oil, as well as affluent prices, other fuel source is a happening and hot topic. An interesting option could be ethanol, now made out of plants like corn and sugar cane. Companies and universities are eagerly working to grow this process of making ethanol from many other kinds of plant substance; that might considerably augment the amount of ethanol accessible as fuel. Nanotechnology might be to assist this important effort.
Presently ethanol that is used in fuel in the United States is made out of corn especially. The starch in the corn kernels is rehabilitated to sugar using enzymes. This starch is further fermented to shape up ethanol. Any how, in order to make a necessary reduction in the United States consummation of crude oil, we require up that production by a long way. The goal prepared recently by the United States government is to make 35 billion gallons of ethanol a year within the next ten years.
Researchers at Michigan State University are trying nanotechnology in a neat trick. They are heritably engineering corn to comprise the required enzyme. The plan is to make the enzyme unmoving until activated by high temperatures. When the cellulous part of the corn, like stalk, is procedures, the high giving out temperatures might set in motion the enzyme and change the cellulous to starch. This would avoid the added cost of creation the enzyme separately.
Researchers at the University of Rochester are as well studying how bacteria select an exacting enzyme, or enzymes, to break at specific kind of plant or other bio mass. They expect to make enzymes, which could change cellulous to ethanol in one step, other than the two steps used by the accessible processes. The advantage of cars that could be filled up with either fuel or ethanol has been verified in Brazil, they use much of its sugar cane crop to make ethanol. Using nanotechnology / genetic engineering to make ethanol from cellulous has the latent to make a serious dent in our use of crude oil. However we do require keeping an eye on some safety issues.
sharmkan@gmail.com
Wednesday, April 28, 2010
Nanotechnology
The Axiomatic Approach to Design
The creative process of mapping the FRs in the functional domain to DPs in the physical domain is not unique; the solution varies with a designer’s knowledge base and creative capacity. As a consequence, solution alternatives may vary in their effectiveness to meet the customer’s needs. The axiomatic approach to design is based on the premise that there are generalizable principles that form the basis for distinguishing between good and bad designs.
Suh (1990) identi ed two design axioms by abstracting common elements from a body of good designs, including products, processes, and systems. The rst axiom is called the Independence Axiom.
It states that the independence of functional requirements (FRs) must be always maintained, where FRs are de ned as the minimum set of independent functional requirements that characterize the design goals.The second axiom is called the Information Axiom, which states that among those designs that satisfy the Independence Axiom the design that has the highest probability of success is the best design. During the mapping process (for example, mapping from FRs in the functional domain to DPs in the physical domain), the designer should make correct design decisions using the Independence Axiom. When several designs that satisfy the Independence Axiom are available, the Information Axiom can be used to select the best design.
Axioms are general principles or self-evident truths that cannot be derived or proven to be true;
however they can be refuted by counterexamples or exceptions. Through axioms such as Newton’s laws and the laws of thermodynamics, the concepts of force, energy, and entropy have been de ned. One of the main reasons for pursuing an axiomatic approach to design is the generalizability of axioms, which leads to the derivation of corollaries and theorems. These theorems and corollaries can be used as design rules that precisely prescribe the bounds of their validity because they are based on axioms. The following corollaries are presented in Suh (1990).
Corollary 1:
(Decoupling of Coupled Designs)
Decouple or separate parts or aspects of a solution if FRs are coupled or become interdependent in
the designs proposed.
Corollary 2:
(Minimization of (FRs)
Minimize the number of FRs and constraints.
Corollary 3:
(Integration of Physical Parts)
Integrate design features in a single physical part if FRs can be independently satis ed in the proposed
solution.
Corollary 4:
(Use of Standardization)
Use standardized or interchangeable parts if the use of these parts is consistent with FRs and
constraints.
Corollary 5:
(Use of Symmetry)
Use symmetrical shapes and/or components if they are consistent with the FRs and constraints.
Corollary 6:
(Largest Tolerance)
Specify the largest allowable tolerance in stating FRs.
Corollary 7:
(Uncoupled Design with Less Information)
Seek an uncoupled design that requires less information than coupled designs in satisfying a set of FRs.
The ultimate goal of axiomatic design is to establish a science base for design and improve design
activities by providing the designer with a theoretical foundation based on logical and rational thoughtprocesses and tools.
Nam P
The Energy Control Center
The following criteria govern the operation of an electric power
system:
• Safety
• Quality
• Reliability
• Economy
The first criterion is the most important consideration and aims to ensure the safety of personnel, environment, and property in every aspect of system operations. Quality is defined in terms of variables, such as frequency and voltage, that must conform to certain standards to accommodate the requirements for proper operation of all loads connected to the system.
Reliability of supply does not have to mean a constant supply of power, but it means that any break in the supply of power is one that is agreed to and tolerated by both supplier and consumer of electric power. Making the generation cost and losses at a minimum motivates the economy criterion while mitigating the adverse impact of power system operation on the environment.
Within an operating power system, the following tasks are performed in order to meet the preceding criteria:
• Maintain the balance between load and generation.
• Maintain the reactive power balance in order to control the voltage
profile.
• Maintain an optimum generation schedule to control the cost and
environmental impact of the power generation.
• Ensure the security of the network against credible contingencies.
This requires protecting the network against reasonable failure of equipment or outages. The fact that the state of the power network is ever changing because loads and networks configuration change, makes operating the system difficult. Moreover, the response of many power network apparatus is not instantaneous. For example, the startup of a thermal generating unit takes a few hours. This essentially makes it not possible to implement normal feed-forward control. Decisions will have to be made on the basis of predicted future states of the
system. Several trends have increased the need for computer-based operator
support in interconnected power systems. Economy energy transactions, reliance
on external sources of capacity, and competition for transmission resources have all resulted in higher loading of the transmission system. Transmission lines bring large quantities of bulk power. But increasingly, these same circuits are being used for other purposes as well: to permit sharing surplus generating capacity between adjacent utility systems, to ship large blocks of power from low-energy-cost areas to high-energy cost areas, and to provide emergency
reserves in the event of weather-related outages. Although such transfers have helped to keep electricity rates lower, they have also added greatly to the burden on transmission facilities and increased the reliance on control. Heavier loading of tie-lines which were originally built to improve reliability, and were not intended for normal use at heavy loading levels, has
increased interdependence among neighboring utilities. With greater emphasis on economy, there has been an increased use of large economic generating units. This has also affected reliability. As a result of these trends, systems are now operated much closer to security limits (thermal, voltage and stability). On some systems, transmission links are being operated at or near limits 24 hours a day. The implications are:
The trends have adversely affected system dynamic performance.
A power network stressed by heavy loading has a substantially different response to disturbances from that of a non-stressed system.
• The potential size and effect of contingencies has increased dramatically. When a power system is operated closer to the limit, a relatively small disturbance may cause a system upset. The situation is further complicated by the fact that the largest size contingency is increasing. Thus, to support operating functions many more scenarios must be anticipated and analyzed. In
addition, bigger areas of the interconnected system may be affected by a disturbance.
• Where adequate bulk power system facilities are not available, special controls are employed to maintain system integrity. Overall, systems are more complex to analyze to ensure reliability
and security.
Some scenarios encountered cannot be anticipated ahead of time. Since they cannot be analyzed off-line, operating guidelines for these conditions may not be available, and the system operator may have to “improvise” to deal with them (and often does). As a result, there is an ever increasing need for mechanisms to support dispatchers in the decision making process. Indeed, there is a risk of human operators being unable to manage certain functions
unless their awareness and understanding of the network state is enhanced.
To automate the operation of an electric power system electric utilities
rely on a highly sophisticated integrated system for monitoring and control.
Such a system has a multi-tier structure with many levels of elements. The bottom tier (level 0) is the high-reliability switchgear, which includes facilities for remote monitoring and control. This level also includes automatic equipment such as protective relays and automatic transformer tap-changers. Tier 1 consists of telecontrol cabinets mounted locally to the switchgear, and provides facilities for actuator control, interlocking, and voltage and current
measurement. At tier 2, is the data concentrators/master remote terminal unit which typically includes a man/machine interface giving the operator access to data produced by the lower tier equipment. The top tier (level 3) is the supervisory control and data acquisition (SCADA) system. The SCADA system accepts telemetered values and displays them in a meaningful way to operators, usually via a one-line mimic diagram. The other main component of a SCADA
system is an alarm management subsystem that automatically monitors all the inputs and informs the operators of abnormal conditions. Two control centers are normally implemented in an electric utility, one for the operation of the generation-transmission system, and the other for
the operation of the distribution system. We refer to the former as the energy management system (EMS), while the latter is referred to as the distribution management system (DMS). The two systems are intended to help the dispatchers in better monitoring and control of the power system. The simplest of such systems perform data acquisition and supervisory control, but many also have sophisticated power application functions available to assist the operator.
Since the early sixties, electric utilities have been monitoring and controlling their power networks via SCADA, EMS, and DMS. These systems provide the “smarts” needed for optimization, security, and accounting, and indeed are really formidable entities. Today’s EMS software captures and archives live data and records information especially during emergencies and system disturbances. An energy control center represents a large investment by the power
system ownership. Major benefits flowing from the introduction of this system include more reliable system operation and improved efficiency of usage of generation resources. In addition, power system operators are offered more in-depth information quickly. It has been suggested that at Houston Lighting & Power Co., system dispatchers’ use of network application functions (such as Power Flow, Optimal Power Flow, and Security Analysis) has resulted in considerable economic and intangible benefits. A specific example of $ 70,000 in savings achieved through avoiding field crew overtime cost, and by leaving equipment out of service overnight is reported for 1993. This is part of a total of $ 340,000 savings in addition to increased system safety, security and reliability has been achieved through regular and extensive use of just some network analysis functions
Press LLC
Iinduction and Fractional
We will then discuss motors of the fractional-horsepower class used for applications requiring low power output, small size, and reliability. Standard ratings for this class range from 2 0
1 to 1 hp. Motors 1 hp are called subfractional-horsepower motors and are rated for less than 20 rated in millihorsepower and range from 1 to 35 mhp. These small motors provide power for all types of equipment in the home, office, and commercial installations. The majority are of the induction-motor type and operate from a single-phase supply.
The induction motor is characterized by simplicity, reliability, and low cost, combined with reasonable overload capacity, minimal service requirements, and good efficiency. An induction motor utilizes alternating current supplied to the stator directly. The rotor receives power by induction effects. The stator windings of an induction motor are similar to those of the synchronous machine. The rotor may be one of two types. In the wound rotor motor, windings similar to those of the stator are employed with terminals connected to insulated slip rings mounted on the shaft. The rotor terminals are made available through carbon brushes bearing on the slip rings. The second type is called the squirrel-cage rotor, where the windings are simply conducting bars embedded in the rotor and short-circuited at each end by conducting end
rings.
LLC Press
Heat Radiation
Here we are concerned with the type of radiation which is principally dependent on the temperature of the body, known as thermal radiation and belonging mostly to the infrared and to a small extent to the visible portion of the electromagnetic radiation spectrum. The heat transferred into or out of an object by thermal radiation is a function of several components. These include its surface re ectivity, emissivity, surface area, temper-
ature and geometric orientation with respect to other thermally participating objects.
In turn, an object’s surface re ectivity and emissivity is a function of its surface conditions (roughness, nish, etc.) and composition.
To account for a body’s outgoing radiation (or its emissive power, de ned as the heat ux per unit time), one makes a comparison to a perfect body, which absorbs the entire amount of heat radiation falling on its surface as well as emits the maximum possible thermal radiation at any given temperature. Such an object is known as a black body. The concept of black body is important in understanding the radiation of heat. According to Stefan–Boltzmann’s law, heat emitted by a black body at any given temperature, qb (W m 2 ), is expressed as follows for a unit area in a unit time:
qb ¼ sT4
where qb is the heat ow through radiation from the surface of a black body, T the temperature, and s a constant known as the Stefan–Boltzmann constant, with a theoretical value of 5.67 10 8 Wm 2 K 4 . Because no material ideally ful lls the properties of absorption and emission of the theoretically de ned black body, for practical purposes a new constant of emissivity, e, is de ned for real surfaces as
¼ q
qbq being the radiant heat from a real surface
Detail...
Heat Convection
Free or natural convection refers to the free motion of a uid and is solely due to differences in the densities of the heated and cold particles of a uid. The origin and intensity of free convection are solely determined by the thermal conditions of the process and depend on the kind of uid, temperature, potential and volume of the space in which the process takes place. Forced convection occurs under the in uence of some external force. Flow of water in hot springs and heat transport due to volcanic eruptions are examples of forced convection (advection). Forced convection depends on the physical properties of the uid, its temperature, ow velocity, shape
and size of the passage in which forced convection of uid occurs. Genera lly speaking, forced convection may be accompanied by free convection, and the relative in uence of the latter increases with the difference in the temperatures of individual particles of the uid and decreases with the velocity of the forced ow. The in uence of na tural convection is negligible at high- ow velocity.
In problems dealing with the transmission of heat through the process of convection, the uid under consideration is usually bounded on one or more sides by a solid. Let at any given time, Ts be the temperature of the solid at its boundary with the uid and TN the uid temperature at a far-off yet unspeci ed point. In accordance with Newton’s law of cooling, the amount of heat owing would be proportional to the temperature difference and could be expressed as
q ¼ hðTs T1 Þ
where h is the heat transfer coef cient. The heat is transferred by convection and consequently the heat transfer coef cient depends, in general, upon the thermal boundary condition at the solid– uid boundary. However, under many situations, hcan be estimated satisfactorily when the uid dynamics of the ow system is known.
Detail...
Heat Conduction
Inside the Earth, however, conduction of heat takes place mainly through poorly conducting solid rocks constituting the crust and the mantle, which are comprised of minerals having a very few conduction electrons. Another type of conduction, called lattice or phonon conduction, caused by lattice vibrations in the rocks, is primarily responsible for heat transfer in such cases. Detailed treatment of heat conduction is provided in several textbooks (e.g., Carslaw and Jaeger, 1959; Jacob, 1964); applications of heat conduction to problems in geothermics have been dealt by Kappelmeyer and Haenel (1974), Lachenbruch and Sass (1977), Haenel et al. (1988) and others. In this section we shall discuss some basic concepts, which are useful in understanding the heat ow and temperature distribution inside the Earth.
Fourier’s Equation of Heat Conduction
When a temperature gradient exists within a body, heat energy will ow from the region of high temperature to the region of low temperature. This phenomenon is known as conductive heat transfer, and is described by Fourier’s equation, ~q ¼ k ~rT
ð3:6Þ
where ~q is the ow of heat per unit area per unit time (called as heat ow), k the thermal conductivity of the body (assumed isotropic) and ~ rT is the temperature gradient. The negative sign appears because heat ows in the direction of decreasingtemperature.
Detail...
