Toughest question ever asked in any interview

I- Interviewer, C- Candidate

I: There is a circular race-track of diameter 1 km. Two cars A and B are standing on the track diametrically opposite to each other. They are both facing in the clockwise direction. At t=0, both cars start moving at a constant acceleration of 0.1 m/s/s (initial velocity zero). Since both of them are moving at same speed and acceleration and clockwise direction, they will always remain diametrically opposite to each other throughout their motion.

At the center of the race-track there is a bug. At t=0, the bug starts to fly towards car A. When it reaches car A, it turn around and starts moving towards car B. When it reaches B, it again turns back and starts moving towards car A. It keeps repeating the entire cycle. The speed of the bug is 1 m/s throughout.

After 1 hour, all 3 bodies stop moving. What is the total distance traveled by the bug?

How would you, the reader, approach this problem?

First of all here is a graphic to help you visualize initial condition.

Now, let’s try to visualize the path of the bug. The question states that it will always be moving towards one of the cars. But the cars themselves are moving. So, bug’s path would not be a straight line. It would be a complicated spiral like path. Plus, the cars are not moving at constant velocity. They are accelerating, this will further complicate the spiral path.

So, the approach is clear. We need to find mathematical equation corresponding to bug’s path for one cycle. Then we can simply calculate the distance from this equation and a little integral calculus. Then multiply the answer with the number of cycles.

But how to calculate the equation of the complicated spiral path?

At this point my friend simply gave up.

The interviewer encouraged him to at least tell his approach. My friend explained above approach.

At this interviewer replied - “Are you ready to hear my solution?”

My friend was more than eager.

The interviewer said - “Bug is traveling at a constant speed of 1 m/s throughout it’s motion. At this constant speed, he travels for 1 hour. So distance = speed x time = 1 m/s x 3600s = 3.6 km.”

Sea Water for Mixing Concrete

It is advisable, as stated above, to use clean water fit for drinking purposes for making cement concrete. However, at places where sea water is available in abundance and potable water is costly, the sea water can be used for making cement concrete. The problem of using sea water for mixing concrete has to be studied from the following two aspects:

(1) Strength 
(2) Corrosion of reinforcement.

(1) Strength:

Below table shows the analysis of average sea water. It contains about 3.50 per cent of dissolved salts. The approximate percentages of various salts are 78 per cent of sodium chloride, 15 per cent of magnesium chloride and magnesium sulphate and the rest 7 per cent of calcium sulphate, potassium sulphate, etc.

Now all chlorides tend to accelerate the setting of cement and to improve the strength of concrete in early stages. On the other hand, the sulphates tend to retard the setting of cement and to discourage the strength of concrete in early stages.

It is found that the net effect of these two contradictory actions is the fall in strength of concrete to the tune of about 8 to 20 per cent. Hence the sea water can be used for mixing cement concrete for structures where such fall in strength is permissible or where it is possible to correct the same by adjusting water- cement ratio, cement content in concrete, etc.

The sea water tends to develop dampness and efflorescence. Hence it can be adopted for concrete structures where finishing characteristics are not important or where persistent dampness of the surface is permissible.

(2) Corrosion of reinforcement:

It is found that the sea water does not lead to the corrosion of reinforcement, provided the concrete is dense and there is enough cover to the reinforcement.

The minimum cement content for concrete permanently under sea water should be 3 kN per m³and the minimum cover over the reinforcement should be 75 mm. However it is not advisable to take the risk of corrosion of reinforcement for prestressed concrete and hence the sea water should not be used for making prestressed concrete.

Concrete Segregation – Segregation of Concrete

It is the separating of the coarse aggregate from the rest of the mix or the separating of the cement-water paste from the aggregate. Segregation generally indicates poor aggregate grading or mix design. Segregation may occur in mixes which are too wet or too dry, and most frequently in under-sanded mixes.

Segregation can generally be reduced by altering the water or sand content or by using a finer sand. Even with a mix of satisfactory design, segregation may be caused by mishandling during transport, faulty placing or over-compaction. Segregation leads to lack of uniformity causing honey-combing which reduces the strength and durability of the structure.

If segregation occurs the larger particles of aggregate tend to move to the bottom and this causes undesirable variation of strength through the thickness of the slab

Concrete Bleeding – Bleeding of Concrete

Concrete bleeding is the appearance of a watery scum (also called laitance) on the surface of a concrete after compaction. It is- an indication that there is too much water or deficiency of fine material in the mix, or that too much tamping, floating or troweling has been done. The result is a porous, dusty and weak surface. This scum should be removed. Bleeding makes weak joints between successive lifts in structural work. Concrete bleeding can be reduced by using less water, a finer sand, or by adding a finely ground inert material (stone dust).

The aggregate commonly used are seldom found in a perfectly dry state in the field. Moreover, aggregates have to be washed very often for removing impurities which further add to the moisture content. The moisture content varies considerably from time to time with the changing weather conditions, and this is especially so in the case of sand. The aggregate when dry will absorb water from the concrete and when wet at the surface the mixture will, have excess of water. Therefore, while computing the quantity of water due consideration must be given to the surface conditions of the aggregate that would exist at the time of preparing the mix.

Small size of aggregate need more water than big size and angular aggregate need more than rounded aggregate. In other words, a concrete containing a finely graded aggregate will require more water for a given workability than one containing an aggregate with a coarser grading. Consequently, the more finely graded aggregate, or that containing a larger proportion of fine aggregate and similarly a concrete with angular aggregate will produce a weaker concrete.

Concrete Shrinkage – Shrinkage of Concrete

Concrete shrinks during setting and drying due to hydration of cement and produces shrinkage cracks. The drying shrinkage increases with an increase in cement content or an increase in water content. Shrinkage is greater with richer mixes (more of cement) and also with aluminious cements. Other things being equal, shrinkage of concrete is almost directly proportional to the amount of-:water in the mix. The type of aggregate used does not generally affect the shrinkage seriously though it has an indirect effect due to the difference of water/cement ratio depending on the type of the aggregate ; with large size of aggregate shrinkage is low. Where shrinkage may give rise to high tensile stresses such as in road slabs, lean dry mixes are desirable. Rich mixtures are uneconomical and are used only for impermeable constructions to ensure water-tightness.

Types of Piles – Deep Foundations

Depending upon their function, the different types of piles are,

• Bearing piles
• Friction piles
• Sheet piles
• Anchor piles
• Batter piles
• Fender piles
• Compaction piles

Combination of Types of Piles

(i) Bearing piles: Bearing piles are those which are driven into the ground until a hard stratum is reached. Such piles act as pillars supporting the super-structure and transmitting the load down to the level at which it can be safely borne by the ground. Thus bearing piles, by themselves do not support the load, rather they act as a medium to transmit the load from the foundation to the resisting sub-stratum.

Bearing Piles

(ii) Friction piles:  When piles are required to b driven at a site where the soil is weak or soft to a considerable depth, the load carried by a pile is borne by the friction developed between the sides of the pile and the surrounding ground (skin friction). In such cases the pile is named as friction or floating pile. Thus friction piles are driven in the type of soil whose strength does not increase with depth or, where rate of increase in strength with depth is very slow.

Friction Piles

(iii) Sheet piles: Sheet piles differ from bearing or friction piles in that they are rarely used to furnish vertical support but are used to function as retaining wall. Sheet piles are used for retaining soil that is liable to escape laterally when subjected to pressure or to enclose the area required for some foundation and protect it from the action of running water or leakage.

(iv) Anchor piles: When piles are used to provide anchorage against horizontal pull from sheet piling walls or other pulling forces, they are termed as anchor piles.

(v) Batter piles: When piles are driven at inclination to resist large horizontal or inclined forces,, the piles are termed as batter piles.

(vi) Fender piles:  When the piles are used to protect concrete deck or other water front structures from the abrasion or impact that may be caused from the ships or barges (when they are tied up at the deck) they are called fender piles. The fender piles are ordinarily made up of timber.

(vii) Compaction piles: When piles are driven in granular soil with the aim of increasing the bearing capacity of the soil, the piles are termed as compaction piles.

Where Does Our Electricity Come From in US ?

Where Does Our Electricity Come From in US?

The electricity that powers American homes and businesses comes from a variety of sources. Coal, nuclear, and natural gas account for about 86% of the electricity generated each year. Renewable energy is becoming much more important, but currently only meets about 13% of U.S. demand. Hydroelectric power and wind energy are the largest renewable resources, accounting for 87% of all renewable electricity.

New Book on Electricity Sector Sustainability Features EPRI and Industry Expertise

The Electric Power Research Institute (EPRI) announced today the publication of a first-of-its-kind book titled Sustainable Electricity: Case Studies from Electric Power Companies in North America. The book is a compilation of company-authored case studies describing how power companies are working toward sustainable electricity in North America as the industry experiences rapidly changing energy system operations and business models.

EPRI senior program manager, Jessica Fox, is the book's editor. The book was developed under the guidance of EPRI's sustainability research program. The program is the largest collaboration in the electric power industry around sustainability. The focus is to help electric power companies address sustainability challenges and opportunities in the electric industry through collaboration, technical research, and opportunities to interact with key sustainability experts.

"Power companies seeking to understand the process for implementing meaningful sustainability projects in their organizations will greatly benefit from the insights shared in this volume," said Fox. "This book will initiate broader societal discussion about what 'sustainable electricity' means and how to move forward when the win-win outcomes are elusive."

Chapters discuss some of the most hotly debated energy and electricity challenges of today: renewable energy, water use, species impacts, employee engagement, stakeholder communication, climate change resiliency and adaptation, distributed energy, energy efficiency, demand-side management, greenhouse gas emissions, consumer preferences, and business vitality. Each chapter shares topic-focused case studies regarding the challenges, key issues, and reality of implementing sustainable electricity in North America.

Anda Ray, EPRI's chief sustainability officer and senior vice president for energy, environment, and external relations, added, "Often competing demands among electric power company stakeholders, shareholders, regulators, and customers, make sustainable electricity a highly complex and challenging proposition for this industry. But just like EPRI's collaborative business model, we can learn from others and use those lessons for the benefit of the public; that is just what this book is about. The case studies brought forth in the book demonstrate the challenges, but more importantly, call attention to the choices companies make as they strive for real world solutions and successes."

Each chapter is authored by leading sustainability experts representing 12 electric power companies including American Electric Power, BC Hydro, Consolidated Edison Company of New York, CPS Energy, DTE Energy, Duke Energy, Entergy, Exelon Corporation, Hoosier Energy Rural Electric Cooperative, Los Angeles Department of Water and Power, Southern California Edison, and Tennessee Valley Authority.

"Sustainable Electricity tackles the thorny issues of what sustainability means in practice, how to reconcile demands from competing stakeholders—consumers, investors, regulators, environmentalists, and others—and how to turn sustainability into a business opportunity," said Janet Ranganathan, vice president for science and research, World Resources Institute and author of the book's foreword. "It cuts to the chase, compiling practical industry-told case studies of how electric power companies are already moving toward more sustainable electricity."

More information about Sustainable Electricity is available here. Information on EPRI's sustainability research is available at www.epri.com/sustainability.

About EPRI:

The Electric Power Research Institute, Inc. (EPRI, www.epri.com) conducts research and development relating to the generation, delivery and use of electricity for the benefit of the public. An independent, nonprofit organization, EPRI brings together its scientists and engineers as well as experts from academia and industry to help address challenges in electricity, including reliability, efficiency, affordability, health, safety and the environment. EPRI's members represent approximately 90 percent of the electricity generated and delivered in the United States, and international participation extends to more than 30 countries. EPRI's principal offices and laboratories are located in Palo Alto, Calif.; Charlotte, NC; Knoxville, Tenn.; and Lenox, Mass. 

- See more at: http://www.epri.com/Press-Releases/Pages/New-Book-on-Electricity-Sector-Sustainability-Features-EPRI-and-Industry-Expertise.aspx#sthash.0ge6qDXU.dpuf

UPSC 2015 topper - Tina Dabi

Story Of Tina Dabi The Youngest To Pass Out UPSC Exam

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​Source : Dontgiveupworld 

Meet Tina Dabi A 22-year-old woman from Delhi topped the 2015 civil services examination on her first attempt . she is so young age of 22 years.

Tina was born in Bhopal, Madhya Pradesh. She did her schooling from Carmel Convent School there.Tina is the eldest daughter of the family. Her younger sister Ria has passed Class XII this year.

Tina’s father Jaswant is a serving IES officer.Mother Himali a former Indian Engineering Service (IES) officer, who took voluntary retirement from the job.

She Started Her Preparation when she was in 11th Standard. Her Mom told that you should go for Humanity instead of Science. Her grooming started in Class 11th and she took arts. She was the topper of Graduation  of Lady Shri Ram College , Delhi.

“My mother is my role model. She wanted me to study political science. I chose it and got through in the examination. It was one of my main subjects,” she said, crediting her mother.”

“She was the topper of her school , She was the topper of her College and We were expecting that she will clear Civil service Examinations.

But She will do Top , It is just a big surprise for us.She has made us proud. She was very dedicated towards her UPSC Examinations and all the strategy of studies was well planned.

He also added that he supported her a lot in every expect of her studies. we played the good role of parents in her complete preparation of UPSC.”her father told.

She used to study 8 hours a day.When asked why in every Competitive exam only girls top the exam, she said: ” There’s nothing like the only female can top, it’s who work hard will succeed.

“Women empowerment is very important. I have seen how my mother has brought up me. It is because of her guidance and support that I could get top position in the test,” she said in interview.

Citing less number of working women in Haryana, Civil Services exam topper Tina Dabi today said she wants to work in the neighbouring state to contribute in empowerment of fairer sex there.

“I always wanted to work in a challenging state. That is why I chose Haryana. We all know the sex ratio of girl and boy child is quiet less and that is why I would like to contribute my efforts for the empowerment of women there,” she said.

Elaborating more on her choice of Haryana as preferred state to work in, she said women should be given more chance to work in administration.

Message from IAS Tina Dabi to Future UPSC Aspirants

“Hard work is the key to success,” the 22-year-old said when asked about her success mantra.

She was Expecting that she will be selected in UPSC exam but Getting the rank AIR 1 in unbelievable for her.For the Preparation of IAS UPSC exam she has given lots of efforts but as she got the All India Rank 1, It is fruitful for her. All her efforts are converted into productivity.

The Journey Towards Civil Service Examination is over and He has devoted her days and Night at very Young age.

India Launches First Indigenous Space Shuttle RLV-TD

The Indian space agency undertook the maiden launch of its very own fully 'Made in India’ reusable space shuttle, on the lines of SpaceX's Falcon 9 and Falcon Heavy and earlier than them!

The only operational space shuttles were made by America and Russia, all of which are now out of service, but ISRO scientists are now using this concept to considerably reduce the cost of launching satellites into orbit, and thus turning the rocket recycled or usable. France and Japan had made some experimental flights, but the shuttles never went into operation.

• The vehicle, almost the weight and size of an SUV, hurled into lower earth orbit and brought back to the surface has been named the Reusable Launch Vehicle-Technology Demonstrator (RLV-TD).
• It was developed by Vikram Sarabhai Space Centre (VSSC). RLV-TD is considered to be a giant leap in the history of ISRO.
• Very similar in its looks to the American space shuttle, the RLV-TD being experimented is a scale model which is almost 6 times smaller than the final version.
• Spaceships like the RLV-TD can bring down operation costs during a space mission to 10 percent the actual revenue!
• Astronaut Kalpana Chawla's death was a result of failure of the thermal coating on the American space shuttle Columbia. As a result, scientists at VSSC have developed very lightweight heat resistant silica tiles that are plastered on the underbelly of this space shuttle and can withstand 5000-7000 degrees Celsius temperature that the exterior of the vehicle is faced with as it comes back into the dense atmosphere after its journey in space!

​Sources:

ISRO To Launch Its First Reusable Space Shuttle In 2016

RLV: India’s first reusable space shuttle

The Electric Car in 2050

Is electric transportation a reality, or is it plugged into science fiction? Today a mere 300,000 of the 250 million automobiles on U.S. highways can be plugged into a charger and propelled by electricity. The internal combustion engine dominates. But history reveals that a future dominated by electric vehicles is entirely possible. The marriage of transportation and electricity predates Henry Ford and the rise of gasoline-powered automobiles. As early as the 1890s, Indiana power generators helped streetcars replace the horse and buggy for local transportation, and within a few decades electric railways known as interurbans connected cities and towns in the Hoosier State. Public Service Indiana, the predecessor of Duke Energy Indiana, owes its beginning in part to the need to transport passengers to and from places such as New Albany, Kokomo, and Indianapolis. “The original business model of some electric utilities in the United States was based on providing electricity to the electrified railroads that existed 100 years ago,” said Mike Rowand, director of technology development at Duke Energy. Only later did their core business expand to delivering power to homes and businesses. With that in mind, there’s evidence today that transportation is moving back to an electrified future. Dan Bowermaster, EPRI’s electric transportation program manager, points out that plug-in hybrid vehicles are selling at more than double the rate that non-plug-in hybrids did a decade ago. 

Electric Renaissance on Wheels?
 As electric transportation enters what appears to be a renaissance, EPRI Journal examines its prospects in 2050. Through more than a dozen interviews with utilities, automakers, and EPRI experts, we gathered insights on how electric vehicles could affect emissions, the grid, utility business models, the driver experience, and more. Two common themes emerged in these perspectives: Many electric vehicles are on their way, and thank goodness they are. “I think there will be some huge changes in the transportation sector, all for the better,” said Bowermaster. For one, the prevalence of electric vehicles will drastically reduce or eliminate trips to gas stations. “For most drivers of the future, 70% to 90% of fueling will be done at home or work,” said Bowermaster. Mid-century car owners will be able to drive inexpensively. Even though gasoline prices are currently low, few expect that to last for decades. Indeed, the economics of fueling electric vehicles have long been superior to gas fueling and likely will become more so. Michael Tinskey, global director of electrification and infrastructure at the Ford Motor Company, points out that the gallon-of-gasoline equivalent for electricity prices has been cheaper since the middle of the 20th century. “Where electricity used to be eight times more expensive than gas, now it’s one quarter the cost or less. We believe that trend will continue,” said Tinskey. Among those interviewed, broad agreement emerged that electrification will be standard by mid-century. “I could see every vehicle having a battery that does some or all the work,” said Britta Gross, director of advanced vehicle commercialization policy at General Motors. Though questions remain on what the future of electrified transportation will look like, we know this: It’s going to be an interesting ride. Key EPRI Technical Experts

Electricity Generation

Electricity generation and distribution has been described as the most important technology development in human history. Electricity is an essential part of today's society and culture and plays a role in almost every human activity and advancement.

The technologies used to generate electricity today derive their energy from three groups of resources – fossil fuels, such as coal, natural gas and oil; nuclear materials; and renewable sources, including solar, wind, hydropower, geothermal and biomass energy.

Fossil fuels have been an integral component of the power generation portfolio since commercial electricity's inception in the late nineteenth century. Today, fossil fuel plants account for more than 60 percent of the world's electricity production and are a reliable source of power with low operating costs. Research and development efforts can help utilities reduce emissions from current assets and build new and increasingly efficient and operationally flexible generating units with advanced emissions control technologies.

The commercial use of nuclear energy to generate electricity began in the 1950s and currently accounts for about 14% of the world's electricity production. More than 400 nuclear reactors operate around the world in 30 countries, and several more countries are pursuing nuclear power. Nuclear power plants are reliable generation sources, often operating for 18-24 months without shutting down. Further, because the energy is derived from the fission of a nucleus and not from chemical combustion, emissions are minimal. Research and technology can help address the key challenges of high capital costs, management of radioactive waste, and the aging of plant components and materials.

Evolving energy policies, changes in power markets and rapid technology improvements make it ever more important for electricity generators to include and expand renewable generation resources in their asset mix. As these renewable resources become increasingly integrated with the grid, environmental impacts relative to land use, vegetation management, species and ecosystem interaction and human health and safety must be considered. EPRI is assessing the status, performance, and cost of renewable generating technologies and providing a variety of critical information for the comparison, selection, operation and maintenance of these resources.

-Source:  more at: http://www.epri.com