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May 23, 2012
Tony Pugh: More private colleges offering tuition discounts
Mary Beth Franklin: How to Choose the Right Annuity for You
Tina Susman: The wig wasn't enough: Man gets 13 years for posing as his dead mom
The Kosher Gourmet by Emma Christensen:A simple way to do fish right
May 22, 2012
Warren Richey: Can US group challenge overseas surveillance act? Supreme Court to decide
Thomas M. Anderson: Walking Away From a Mortgage
The Kosher Gourmet by Megan Gordon: Enjoy a celebration of the most rich and layered flavors: Black bean, sweet potato and quinoa chili
May 21, 2012
Mark Clayton: Cybersecurity: How US utilities passed up chance to protect their networks
Howard LaFranchi: NATO summit: Who will foot the bill for long-term Afghanistan security?
Chris Farrell : Earn Dividends in Emerging Markets with This WisdomTree ETF
Stephen Whiteside, Ph.D. : Mayo Clinic Medical Edge: Social anxiety disorder --- or just shy?
Guy Jackson : Victim's father regrets death of Lockerbie bomber
The Kosher Gourmet by Mario Batali: Famed chef's veal shoulder farsumagru: A festive meat course for late spring
May 18, 2012
Rabbi Berel Wein: Striving: The People of the Book's Book for (All of) the People
Steven Goldberg: 5 Great Stock Picks and the Exchange-Traded Fund that Owns Them
Mary Pickett, M.D.: Ask the Harvard Experts: Don't be forced into gluten-free lifestyle based merely on a doctor's false-positive test
The Kosher Gourmet by Carolyn Malcoun: DIY healthy lunchbox treats: HOMEMADE FRUIT BARS for kids and brown-bagging adults alike
May 17, 2012
Warren Richey: Teacher fired for being unwed and pregnant can sue religious school, court rules
Josh Mitnick: Netanyahu's 'centrist' coalition is already proving it's anything but
Steven Goldberg: Earn Dividends in Emerging Markets with This WisdomTree ETF
Amina Khan: Research links coffee to lower death rates
The Kosher Gourmet by Faith Duran : Cheesy Potato Breakfast Casserole with Cheddar and Sun-Dried Tomatoes
May 16, 2012
Carmen Terzic, M.D., Ph.D. : Mayo Clinic Medical Edge: A variety of exercises can help improve balance
Melissa Healy: National strategy on Alzheimer's disease aims to halt it by 2025
The Kosher Gourmet by Joyce White : GOODNESS GRACIOUS: GREENS! 4 winning recipes that are no longer just for down-home folks (Includes expert tips & techniques)
May 15, 2012
Kristen Chick: Obama administration resumes arms sales to Bahrain despite serious unresolved human rights issues. Activists feel abandoned
Pat Mertz Esswein: Homes are now affordable again and mortgage rates are low. What you need to know before you buy
Kathy Kristof: Our Practical Investor Fights Inflation with These 6 Investments
Sue Hubbard, M.D.: The Kid's Doctor: Lactose intolerant young child? Check again
The Kosher Gourmet by Kathy Hunt: Spread a Little Excitement with EXOTIC CONDIMENTS (4 RECIPES)
May 14, 2012
Lisa Gerstner: How to Protect Your Identity, Finances If You Lose Your Phone
Harvard Health Letters: Heart disease and dementia
The Kosher Gourmet by Megan Gordon: MANGO COCONUT OAT MORNING MUFFINS are a bright but hearty delight
May 11, 2012
Jessica L. Anderson: Get the Best Deal on a Used Car
Jett Stone: Forget face-lifts and fake knees. Scientists have seen the fountain of youth --- and it's broccoli
The Kosher Gourmet by Chef Mario Batali: The famed chef's vegetable dish that tastes true to the season: FAVAS AND SUGAR SNAP PEAS WITH POTATOES AND TARRAGON
May 10, 2012
Sergei L. Loiko: Putin sends warning to U.S., NATO in Victory Day speech at Red Square
Mary Rourke: How being a 'mentch' got Vidal Sasoon his start and fighting in Israel's War of Independence provided him with confidence and a strong sense of his own identity
Jeff Bertolucci: Get Home Phone Service for Less Than $10 a Month
The Kosher Gourmet by Betty Rosbottom: Gleaming with its golden, crimson, and snowy white hues, this silken smooth and creamy STRAWBERRY ORANGE TRIFLE looks impressive, but is easy to prepare
May 9, 2012
Sharon Palmer, R.D. How you can reduce your risk -- or delay -- chronic diseases associated with aging
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Jewish World Review
How submarines work
By
Marshall Brain
http://www.JewishWorldReview.com | (MCT)
Submarines have been a little mysterious since they were invented more than two centuries ago. That's because most submarines have been owned by the military. But recently, subs have started to get friendlier. There is a growing market for personal subs, and many coastal resort areas now have tourist subs that let visitors see underwater reefs and wrecks in air conditioned comfort. Let's take a look at how these different kinds of subs work.
Any sub, from smallest to largest, has to solve three basic problems. First, it has to be able to move through the water. Second, it has to be able to sink down below the surface of the water and then rise back again. And third, it has to provide an environment that keeps the humans on board the sub alive.
Moving through the water is probably the simplest part, because most submarines use a propeller just like a boat would. The interesting difference between a sub and a boat is the lack of air. A boat's motor, being above the water, can use air freely in a gasoline or diesel engine. Since a sub is underwater, it loses access to free air. Subs have two ways to solve this problem.
The more common approach uses a large bank of batteries and an electric motor to spin the propeller. That is all that's needed for a tourist sub. When the sub returns to dock, it can plug in to recharge the batteries. But a military sub might need to stay out for a month or more. Therefore, military subs that use the battery approach have a diesel engine and a generator. The sub surfaces, runs the diesel engine long enough so that the generator can recharge the batteries, and then can dive again.
The most advanced military subs are gigantic - so big that they can house a small nuclear power plant on board. Since a nuclear reactor needs no oxygen to generate electricity, these subs can stay underwater for months at a time. The only real limitation is the need to resupply food for the crew members. A nuclear sub can run for years before it needs to refuel.
Getting the sub to sink and rise is straightforward. A sub has tanks known as ballast tanks that allow the sub to float when they are full of air. By letting the air out of the ballast tanks and filling them with water, the sub gains enough weight to sink. When the sub wants to surface, high pressure air can force out the water in the tanks, allowing the sub to rise again.
Keeping the air inside the sub safe for humans to breath is the third challenge, and may be the most complex. The air we breathe on earth is made up of three important gases: Nitrogen (about 80 percent), oxygen (about 20 percent) and carbon dioxide (0.04 percent or so). Plus there is almost always some amount of water vapor in the air.
When we breathe in air, our bodies consume its oxygen and convert it to carbon dioxide. Exhaled air contains about 5 percent carbon dioxide. Our bodies do not do anything with nitrogen. We breathe it in and out without changing it.
A submarine is a sealed container that contains people and a limited supply of air. There are three things that must happen in order to keep air in a submarine breathable. First, the oxygen has to be replenished as it is consumed. If the percentage of oxygen in the air falls too low, a person suffocates. Next, carbon dioxide must be removed from the air. If the concentration of carbon dioxide rises, it quickly becomes a toxin that will kill everyone on board. Then the moisture that we exhale in our breath must be removed or the humidity will get so high that water starts condensing on the walls.
Fresh oxygen can come either from pressurized oxygen tanks, an oxygen generator (which can form oxygen from the electrolysis of water) or some sort of "oxygen canister" or "oxygen candle" that releases oxygen through a chemical reaction. Oxygen is either released continuously by a computerized system, or it is released in batches through the day.
Carbon dioxide can be removed from the air chemically using soda lime (sodium hydroxide and calcium hydroxide). The carbon dioxide gets trapped in the soda lime by a chemical reaction.
The moisture gets removed by a dehumidifier or chemically.
By combining ballast tanks, a motor and propeller and an air handling system in a water tight tube, you have a submarine.
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Previously:
How miles work
How octane works
How food preservation works
How beer works
How holding your breath works
How smoke detectors work
How heat pumps work
How your night vision works
How concentrating solar collectors work
How your key fob works
How the common cold works
How the Large Hadron Collider Works
How making a TV show works
How dry cleaning works
How exoskeletons work
How an oil refinery works
How landfills work
How the Orion spacecraft works
The cutting edge in HDTV
Redefining the CD
How the HDMI cable scam works
How glow-in-the-dark toys work
How the subprime mortgage crisis works
How gift cards work
How Tasers work
How giant TV screens work
How foreclosure works
How Air Force One works
How wildfire fighting works
How vitamins work
How ejection seats work
How reattaching limbs works
How hot air balloons work
How paparazzi work
How counterfeiting works
How CDs work
How the Edsel worked
How Stinger missiles work
How hybrid cars work
How sharks work
How mosquitoes work
How diesel engines work
How water towers work
How the Dawn mission works
How Kassam rockets work
How the North American Eagle works
Why aren't we flying to work?
How tofu and soy milk work
How Colony Collapse Disorder works
How airbags work
How the U.S. income tax works
How gum works
How caffeine works
How Daylight Saving Time works
How a cruise missile works
How snow making works
© 2007, How Stuff Works Inc. Distributed by McClatchy-Tribune Information Services.
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