excel spreadsheet and modelling

                                           what is an excel spreadsheet?

Microsoft Excel is a spreadsheet program which allows one to enter numerical values or data into the rows or columns of a spreadsheet, and to use these numerical entries for such things as calculations, graphs, and statistical analysis.

Spreadsheets (like Microsoft Excel) can be very useful for student interactive activities, interactive lectures, and instructor use for developing materials for class. Example aspects of spreadsheets that are relevant to science education are:

·         Using Excel as a calculator to explore what mathematical equations can tell us about how the real world works for specific input conditions or for a range of possible values.

o    The calculator can be pre-constructed with a focus on student exploration or students can be guided to construct their own calculators and then explore. The first option saves time but the second option prepares students to use Excel for their own projects and future activities.

·         Graphically displaying equations (analytical models) and real data.

·         Obtaining numerical solutions to more mathematically complex models.

·         Graphically comparing results from a model and observations.

·         Statistical analysis including mean, standard deviation, error bars on graphs, linear and polynomial fits, multivariate analysis, etc.

·         Spectral analysis (Fast Fourier Transforms).

·         Displaying histograms of students results or student response to exams or questions.

                                     what is spreadsheet modelling?

A spreadsheet model uses a spreadsheet to explore different possible answers. These models are usually financial, mathematical or scientific. This is sometimes called “what if” modeling and shows what will happen to the results if you change some of the data within a spreadsheet. It can also be used to discover simple rules within the model. In the context of the examination, you may be asked to build a simple spreadsheet model and change data within the model, or even the model itself, to produce different results.

System life cycle

 The systems life cycle (SLC) is a methodology used to describe the process for building information systems, intended to develop information systems in a very deliberate, structured and methodical way, reiterating each stage of the life cycle.

The system life cycle in systems engineering is an examination of a system or proposed system that addresses all phases of its existence to include system conception, design and development, production and/or construction, distribution, operation, maintenance and support, retirement, phase-out and disposal.

System Analysis

In this phase, the current system is studied in detail. A person responsible for the analysis of the system is known as analyst. In system analysis, the analyst conducts the following activities.

Needs Analysis

This activity is known as requirements analysis. In this step the analyst sums up the requirements of the system from the user and the managers. The developed system should satisfy these requirements during testing phase.

Data Gathering

In this step, the system analyst collects data about the system to be developed. He uses different tools and methods, depending on situation. These are:

- Written Documents

The analyst may collect the information/data from written documents available from manual-files of an organization.

- interview is another data gathering technique.

-Questionnaires

Questionnaires are the feedback forms used to collect Information.

-Observations 

In addition to the above-mentioned three techniques to collect information, the analyst  (or his team) may collect Information through observation.

After completion of this step the collected data about the system is analyzed to ensure that the data is accurate and complete.

then the requirements collected for the system are documented in a presentable form. It means that the analysis report is prepared. It is done for review and approval of the project from the higher management.

differences between the central and the normal air conditioning systems

central conditioning systems:

It is an air conditioning system that uses ducts to distribute cooled and/or dehumidified air to more than one room, or uses pipes to distribute chilled water to heat exchangers in more than one room, and which is not plugged into a standard electrical outlet.

With a typical split system, the condenser and compressor are located in an outdoor unit; the evaporator is mounted in the air handler unit. With a package system, all components are located in a single outdoor unit that may be located on the ground or roof.

Central air conditioning performs like a regular air conditioner but has several added benefits:

    When the air handling unit turns on, room air is drawn in from various parts of the building through return-air ducts. This air is pulled through a filter where airborne particles such as dust and lint are removed. Sophisticated filters may remove microscopic pollutants as well. The filtered air is routed to air supply ductwork that carries it back to rooms. Whenever the air conditioner is running, this cycle repeats continually.

    Because the condenser unit (with its fan and the compressor) is located outside the home, it offers a lower level of indoor noise than a free-standing air conditioning unit.

 Through-the-wall air conditioners are a cooling option for buildings that do not have central air conditioning installed. The units are relatively cheap. They typically cost anywhere from two hundred to four hundred dollars, depending on the size. Most units are designed to cool only one room, though some larger units may be able to cool additional rooms as well. No matter how large the unit, the ability to cool additional rooms is limited because the vent that blows cool air is only in one room.

 A through the wall air conditioner works by sucking hot air from the room into the unit. The hot air that enters the unit is brought over the air conditioning condenser and cooled. The cooled air is pushed back into the room. The motor that runs the unit produces hot air. The air conditioner pushes the hot air from the motor out through the vents in the back of the unit so that it does not heat the room.