Dnyandeep - Personal Blogsite of Dr. S. V. Ranade: September 2013

Friday, September 20, 2013

पर्यावरण

Index of Blogs on Education

शालेय शिक्षणासाठी वेबसाईट, शिक्षणासाठी संगणक, शिक्षणाचे माध्यम - मराठी का इंग्रजी, किती वाजले?, ज्ञानदीप मंडळ
सर्वांसाठी मोफत शिक्षण, शिक्षण व उद्योग यांची सांगड घालणारे हॉर्वर्ड विद्य..., अभ्यास कसा करावा?, संगणक प्रशिक्षण - सरकारी खाक्या, नागरिकशास्त्र - एक महत्वाचा पण दुर्लक्षित विषय
Free Education? Why not?, In defense of Marathi medium schools,
Retired People– Untapped Resource of Knowledge
e-Bussiness through website, Role of e-Architect for future education system
India's Vision - Education to All, Adobe and Google moving towards Global Virtual Uni...
Extravagant Infrastructure for Educational Institu..., Treat Education as Serious and Healthy Business
Web modules for educational institutes
Internet Service Forum, Yes, you also can be a good writer.
Writing blog in English, Some thoughts on drawing pictures,
Science quizzes for kids -1, Science quizzes -2, -3, -4, - 5, -6

वेबटेक्नॉलॉजी

Saturday, September 14, 2013

Search Engine Optimisation Part-1

In my earlier article on professional website design, I have illustrated importance of look and feel of the website. The visitor should be pleased to browse through the pages and should get impressed by the high quality status of the company. However, the first requirement is to attract visitor to your site. Unless it is found by him through internet search, it is rare that he would visit your site, even if, you have the thing that he is in search of. It is therefore, far more important to pay attention to design of the site for high ranking by search engines. This is called as search engine optimization.

Website owners feel that their website should be visited by maximum number of people and mainly those who are in need of the product or services they are offering. However, most of the times website name does not convey the information about the contents in the site and the name also is not known to many except those related to the organization. Naturally people in need of products or services search the suppliers on the internet by using popular search engines like yahoo, google, bing or rediff.

As soon as they write the name of product or type of service in address bar, the search engines give a list of thousands of websites having contents similar to the request text. This list is segregated in number of pages. Generally, the websites listed in the first few pages only get visited by the users. As the search encompasses the entire worldwide websites, it becomes very difficult to have a place for our website in the first few pages of search results.

Special techniques are required to be implemented write from web design stage to its continuous maintenance for making the site search engine friendly so that chances of its ranking in the first few pages can be assured. As almost every serious company employees these techniques, there remains a stiff global competition in this effort.

We cannot comprehend how the search engine displays long list of websites in few seconds. Lot of preparatory work is being done continuously by search engines to speedup the search process. In order to design a search engine optimized website, it is necessary to understand the mechanism and procedure of search engines in ranking the websites based on content relevance. Google search provides lot of information about the working of search engines.

Every search engine does this work in three steps

The crawler (or spider)- This is self actuating program ( robot) which crawls (or works like spider) and records contents in all websites at regular time intervals and creates a raw data for search operation. It visits every old or new website and makes changes in archived data if the contents are changed or adds data of new sites. It should to be remembered here that it is a computer program, who blindly goes through the page source and collects information. For example, it cannot see or recognize images, unless you specify description of image by alt tag. It however takes note of meta tags, links, header tags.

The Indexer – Indexer program classifies the gata gathered by the crawler and fills it in appropriate database tables.

The Ranker – This is most important part of search engine. This program reads the request information filled by the user in address bar and based on preferences and relevance, sorts the web pages, gives rank numbers and displays the entire list in page wise format to the user.

Thursday, September 12, 2013

Reverse Osmosis

Rainwater, though purest form of natural water, cannot be harvested before it falls on the ground. Once it falls on the soil, it gets polluted due to mixing of soil, organic matter and mineral salts. Therefore, water from surface water sources like rivers and nallas is turbid and needs to be filtered before use. The groundwater looks clean and colorless but it contains dissolved mineral salts. The conventional water treatment plants are designed to remove colloidal and suspended impurities but cannot remove dissolved salts. If water is brackish or salty ( Like sea water)) it cannot be used for drinking purpose.

Saline water – Seawater contains about 35000 mg/l of total dissolved solids ( TDS). Out of total salts, 30,000 mg/l is common salt ( sodium chloride). Drinking water should have less than 500mg/l of total dissolved solids and less than 300mg/l of chlorides. Hence, the seawater cannot be used for drinking unless the salts are removed. The groundwater in wells near sea coast, contains 5000 to 10000 mg/l of dissolved solids and is not potable. Use of excess water and chemical fertilizers on land for irrigation increases salt content in wells and it is found to be in the range of 2000 to 5000mg/l, which is not suitable for drinking and even for irrigation.

Conversion of saline water into fresh potable water is very complex and costly process. 2/3^rd part of earth’s surface is covered with sea and contains huge quantity of water, but due to it’s excess salt contents it is not potable. Hence people travelling in ship may find water everywhere but not a drop to drink . One can get potable water by distillation of seawater, but it requires energy and costly equipment. Now this can be achieved by a new technology developed for conversion salt water to potable water. This technology is called as Reverse Osmosis.

Osmosis – If we put raisin in water, in a short time it’s size and volume increases. This happens due to entry of water in raisin. However, if we drop a grape in sugar syrup, it contracts. In one case water moves in raisin, whereas water from grape moves out leading to it’s contraction. You may have a doubt as to what determines the direction of water flow. Osmosis is the answer to this question. It depends on concentration level of water in and out of raisin or grape. Water flows through the skin of grape or raisin from high concentration side to low concentration side. The action is similar to flow of water from high level to low level. The structure of grape or raisin skin is responsible for such action. Plant roots also have similar structure. The cells inside root skin contain high salt concentration ( low water concentration) hence water from soil ( high concentration) gets absorbed in the root. This process is called as osmosis.

Salts can easily pass through root or grape skin, hence salts can be absorbed by plants but sugar molecules being larger in size cannot pass the skin and water concentration governs the process. As saline water contains salts hence to prevent flow of salt, a special semi permeable membrane is used in reverse osmosis.

Reverse Osmosis – The process of getting potable water from saline water is based on above osmosis

principle. If we keep saltwater and potable water in two compartments separated by a salt flow preventing membrane, the water from potable ( less salt) side will flow to saltwater ( high conc. of salt) side.

Thus as shown in Fig. 1, if the side contains salt water, the water level on that side will increase due to osmotic pressure. The osmotic pressure will be indicated by the difference in water levels. If however, external pressure is applied on salt water side which is greater than osmotic pressure( Fig.2), the water from salt water side will flow to potable (less salt conc.) water side against osmotic pressure. This is reverse osmosis. As the salts cannot pass through the membrane, the potable water will be generated in the process and salt concentration on salt water side will go on increasing. Such high concentrated salt water will have to be drained and replaced by saline water. In this way, can use reverse osmosis process for converting saline water to potable water.

Microfilter membranes with micron size holes can be used to separate fine particles and large molecules from water. But membranes used in reverese osmosis are different than such microfilters and are called semipermeable membranes as they allow only flow of water from one side to another.

Research – In 1950, scientists Reid & Braton from Florida University in USA proved that cellulose acetate effectively prevents flow of salt through the membrane . Later technocrats Loeb and Sorairajan developed such membrane technology and showed that potable water can be generated by such membrane at rate of 500 to 1000 liter per square meter area under the gauge pressure of 40 to 50 bar. It was observed that 90 % salts are retained by such membrane.

India is fortunate tio have a vast sea coast. There is acute scarcity of potable water in these coastal areas. Central Salt and Marine Institute is established at Bhavnagar in Gujarath. Research on reverse osmosis technology is being conducted in this institute . As of now, the institute has become successful in converting brackish water from wells to potable quality water by using reverse osmosis system developed in the institute. This will greatly help in solving drinking water problem in rural area having groundwater with high salinity. NEERI, Nagpur has also developed such technology of producing cellulose membranes.

The osmotic pressure of salt water in sea is 20 bar i.e. 20 times that of air pressure. During reverse osmosis, the salt concentration of water goes on increasing leading to corresponding increase in osmotic pressure. Hence reverse osmosis process needs to operated at 60 to 70 bar pressure. For desalination of well water, a pressure of 15 to 30 bar is sufficient.

Membranes -

The membrane used for reverse osmosis is very delicate and to prevent its rupture, it is supported by plastic screen sheet. As the flow is very small, large surface has to be used to get required water quantity. Hence various types of membranes are used.

Micro fibers – These fabrics are smaller in size than human hair and tubular in nature. Salt water is outside of such fibers and good quality water is inside the tube. These membranes are prepared from cellulose acetate, polyvinyl alcohol and polyamide.
Plain sheet or rolled sheet- Alternative layers composed of membrane and supporting plastic screen are used for preparing plain sheet or wound type sheets for reverse osmosis. The pipes for carrying salt water and good quality water are provided in the system.
Tubular type – The membranes are in the form of 12mm to 25 mm dia tubes. This type of system is suitable for turbid water as these tubes can be cleaned by passing water through the tubes. Of course, as these tubes provide very small area of membrane, the potable water generation is also in small quantity.

Pre Treatment – In order to design reverse osmosis system, good knowledge of chemistry, microbiology is required to control accumulation of salt layers on the surface of membranes and possibility of decomposition of membranes due to microbial action. Moreover, water quality information as regards, turbidity, dissolved gases, temperature, pH, chlorine, salt concentration and filtration capacity of membrane should be known. This information is useful to decide the type of tretreatment necessary before reverse osmosis process. Water filtration, aeration, passing through specific resin columns may be necessary to have effective functioning of reverse osmosis and protection of membranes from damage.In order to prevent formation of calcium carbonate layer on the membrane surface, acid and phosphates may have to be added to water to be treated. Water subjected to reverse osmosis process should have following quality

Iron – Less than 0.1mg/l

Manganese – Less than 0.05 mg/l

Clorine – Less than 0.1 mg/l.

Turbidity – nil

Large scale reverse osmosis plants have been erected in middle east countries as potable water sources are less. These plants are used for converting sea water to potable quality water. Considering the potential of reverse osmosis technology in future, many foreign companies are investing in research and development of this technology. India also should take a leading role in this aspect.

Other uses – Now reverse osmosis is being used in various fields. As this technology can effectively remove pollutants from industrial wastes, the waste water can be recycled back in the process , avoiding environmental pollution. Use of reverse osmosis process is increasing in pharmaceutical industries, canning industry, distillery,, milk and food processing industry. Thus reverse osmosis process has become a boon to society.

Friday, September 20, 2013

Index of Blogs on Accounting

Index of Blogs on Social Topics

Index of Translated Poems

Index of Blogs on Management

Index of Blogs on Environment