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Messages - skarul.eee

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EEE / Power Supply Voltage
« on: April 22, 2017, 11:07:17 PM »
What exactly is the difference between a 110v and a 220v labeled power outlet. As far as i can see, the outlet is just a piece of plastic with some metal connecting to the power cables? Does it pose a problem to mount a 110v power outlet on a 220v power cable? Both types of outlets seem to be identically build. To clarify, the plugged in devices are using 220v as the power system provides, the question is really just about the power outlet itself.

EEE / How to Treat Electrical Burns
« on: April 22, 2017, 11:03:27 PM »
1. Do not touch the person if he or she is still in contact with the electrical current. Unplug the appliance or turn off the main power source to the house to stop the electrical flow to the victim first.[1]
If it is not immediately possible to shut off the power, stand on a dry surface—such as a rubber doormat or a pile of papers or books—and use a dry wooden object—such as a broom handle—to push the person away from the electrical source.[2] Do not use anything wet or made of metal.

EEE / How to Treat Electrical Burns
« on: April 22, 2017, 11:00:43 PM »
Electrical burns occur when a person contacts an electrical source, such as grounded appliances, and the electricity passes through the person's body. The severity can vary from first- to third-degree burns depending on the amount of time the victim was in contact with the current, the strength and type of current, and what direction the current passed through the body. If second- and third-degree burns are incurred, the burns may be very deep and may also cause numbness. Electrical burns can lead to additional complications because they can affect internal organs in addition to simply the contacted flesh. With a little bit of preparation, you can know exactly how to react in the event that you or someone nearby receives an electrical burn.

A new device the size of a coffee mug can generate drinkable water from desert air using nothing but sunlight.

“With this device, you can harvest the equivalent of a Coke can’s worth of water in an hour,” says cocreator Omar Yaghi, a chemist at the University of California, Berkeley. “That’s about how much water a person needs to survive in the desert.”

Though that may not sound like much, its designers say the current device is just a prototype. But the technology could be scaled up to supply fresh water to some of the most parched and remote regions of the globe, such as the Middle East and North Africa, they say.

Previous attempts at low-energy water collection struggled to function below 50 percent relative humidity (roughly the average afternoon humidity of Augusta, Ga.). Thanks to a special material, the new device pulled water from air with as low as 20 percent relative humidity, Yaghi and colleagues report online April 13 in Science. That’s like conjuring water in Las Vegas, where the average afternoon relative humidity is 21 percent.

Drinking water supplies can’t keep up with the rising demands of a growing human population, and shifts in rainfall caused by climate change are expected to exacerbate the problem. Already, two-thirds of the world’s population is experiencing water shortages (SN: 8/20/16, p. 22). One largely untapped water source is the atmosphere, which contains more than 5 billion Olympic-sized pools’ worth of moisture in the form of vapor and droplets.

Getting that moisture out is easy when the air is saturated with water. But humid regions aren’t where the water-shortage problem is, and drawing water from the drier air in parched areas is a greater challenge. Spongy materials such as silica gels can extract moisture from the air even at low relative humidity. Those materials, however, either amass water too slowly or require lots of energy to extract the collected water from the material.

The new device uses a material that avoids both problems. MIT mechanical engineer Evelyn Wang, Yaghi and colleagues repurposed an existing material composed of electrically charged metal atoms linked by organic molecules. This metal-organic framework, christened MOF-801, creates a network of microscopic, spongelike pores that can trap such gases as water vapor. At room temperature, water vapor collects in the pores. As temperatures rise, the water escapes.

The team’s prototype includes a layer of MOF-801 mixed with copper foam. Left in the shade, this layer collects water vapor from the air. When moved into direct sunlight, the layer heats up and the water vapor escapes into an underlying chamber. A condenser in the chamber cools the vapor, converting it into a potable liquid. This entire process takes around two hours.

Laboratory tests of the device harvested 2.8 liters of water per day for every kilogram of MOF-801 used. As it is now, the device could be used as a personal water source in dry regions without water-producing infrastructure, Yaghi says, or the system could be scaled up to produce enough water for a whole community.

The device’s ability to produce water at low relative humidity is a breakthrough, says Krista Walton, a chemical engineer at Georgia Tech in Atlanta. “No one else is using MOFs like this today,” she says.

As for the cost of scaling up, the ingredients used in the device’s metal-organic framework “aren’t exotic,” Walton says. Producing large amounts of the material “would definitely be possible if the demand were there".

Faculty Sections / Re: Proper use of Forum
« on: April 20, 2017, 11:49:30 PM »
Good one

Md. Askarul Haque
Dept. of EEE
Daffodil International University

Faculty Sections / Leopard, Where Fools May Follow
« on: April 20, 2017, 11:47:02 PM »
This story entails a Leopard attack on humans. It entails violence and blood, and thus reader discretion is advised. Not suitable for children.

Where Fools May Follow

Before man was born to this world, Mother Nature ruled with a rhythmic beat that
engraved the lyrics of life onto the earth’s soils. With man’s great mind knowing no boundaries and accepting every challenge presented to him, he soon came to think of himself as the ruler of all. We are graciously reminded from time to time, that this is not necessarily the truth.

January, 1961

This story was told to me by a 60-year old Ju/hoansi bushman and begins in the Nhoma maramba, a place referred to by the local inhabitants as the Khaudum. In 1989, the Khaudum was declared a Game Reserve by the Namibian Government, and in 1998, it was promoted to National Park status. Prior to 1989, local people were still allowed to move through the Khaudum and hunt on a sustainable basis.

The Nhoma maramba (dry river bed) crawls from Botswana into Namibia’s North Eastern corner and gradually dies a sandy death somewhere near the middle of this great country. With its importance long ago determined by Mother Nature, this maramba acts as a vein of life with migratory trails leading from close to the Okavango Delta into Namibia. Its rich vegetation provides a nutritional haven for her many inhabitants.

Where the Nhoma maramba takes a gradual turn southwards, a little village sprang up during the early 1950’s. The place was called Soncana and even today it is known by that name. A powerful and seemingly non-exhaustible watering hole drew wildlife and people to its edges, giving life to one and all.

The Soncana village was home to about twelve families of the Gciriku tribe (Kavango), and two or three families were of the Ju/hoansi tribe (Bushman). Despite their cultural differences, the villagers understood each other well and harmony existed among them.
This is also where Af-oor (an Afrikaans name meaning “one ear” or “off ear”) shot an Eland with his bow and arrow. According to the Bushman tradition, he was then allowed to choose any woman to be his wife, even if she was already married. He chose a young woman whose husband at that time was working in the Gold mines of South Africa. Today, he is employed by the Ministry of Environment and Tourism and lives with his “Eland wife” in Tsumkwe, the biggest village in Eastern Bushmanland.

The Kavango people at Soncana quickly mastered the art of tracking and hunting, as they had been taught by their neighbors who had lived off the land since the beginning of time. From the time Soncana was occupied, there was never a meat shortage in the little village. Nature provided all. Respect for Her was the village phrase. Elephants regularly moved through the village in search of fresh pumpkins which the villagers grew with ease. The huge herds with abundance of young ones encouraged the villagers to be always thankful for what they had, and never to underestimate nature’s power and mercy. They believed that if Mother Nature was not duly respected, She would take avenge on them.

Muhako and his brother were all that was left of their specific blood line (family). They took pride in their language, traditions and swore an oath to stay together until their days on earth would end. The elder of the two was married to a beautiful young woman and together their love brought forth a strong and healthy son. Years passed with ease and their commitment to each other grew with each passing day. They were privileged to witness the boy growing in strength, mind and character, and felt assured that he would one day be an honest and respectable person. At age 15, he had already learned much about hunting and the importance of respect for nature. His parents were as proud of him as he was of them.

With the seasonal rains painting the land into a kaleidoscope of greens, the young man (boy) one day decided to go for a walk around the village. As was taught by his father, he took along his spear and a catapult. The spear was of typical Kavango design with a three foot raisin bush stick fitted with a sharpened steel blade, which was more than enough to kill even a lion, but only at very close range. The catapult was ideal for knocking down birds with a simple little rounded stone. On this day, he was specifically looking for Double- Banded Sand Grouse, a very tasty bird with plenty of meat to feed a person. These birds rely mostly on their extreme camouflage and stillness for defense. Movement always gives away your position in such surroundings. Survival of the fittest determines and shapes adaptation; hence camouflage was given to the not so strong and slower species.

Thoughts of adulthood filled the boy’s mind as he aimlessly walked towards a nearby pan. The Sand Grouse song suddenly pulled the boy’s eyes towards the sky. A flock of at least 50 birds came drifting in with the wind, wings stretched out as they landed with precision a mere 100 meters in front of the boy, running like fat geese towards the pan’s edge where the crystal blue water lay. He crouched with eyes fixed on the birds, a little stone ready to be launched at his command. Ever so slowly, he crept towards them, closer and closer, until he was finally within range to make the vital shot. As he gently pulled back his firing arm and strained the catapult’s rubber launchers, a movement caught his eye. He was already committed to the shot and could not be distracted by averting his eyes. The release of the hand and the hissing of the stone as it split the air in two, coincided with a sudden thump to the boy’s upper body and face. As he stood up from his firing position, he wondered why he had actually fallen down. Thinking that he had lost his balance as he had fired the shot, he stared at the little pan in front of him, hoping to see a flutter of wings and a dead grouse. A drop of sweat fell onto his hand. Instinctively, he wiped his forehead.

The bright red color of blood covered his hand. One drop after the other dripped from his face. A sudden pain rushed through him. His heart surfed on a giant wave of adrenaline. Gently he felt the gush above his left eye with his fingers, trying to judge the severity of the wound using touch. It was not a deep cut, but a vein had definitely been severed, hence the blood flow which was increasing with every passing second. Amazed at what had just happened, the boy looked around. Had he slipped on a rock whilst he fired his catapult? Keeping his hand on the wound, he turned around to head home.

By now the boy’s left eye was totally covered in blood and with half vision and a growing sense of dizziness due to blood loss, he struggled to find the path home. A soft growl drew his attention to a dense yellow-wood bush about three meters to his right. With devastation sliding into the boy like a thousand shining knives, he realized he was staring a huge Leopard in the eyes. It is a common belief that if a Leopard is encountered in the bush, one should never stare it in the eyes, as the predator will feel threatened that its camouflage has been given away. Attack is then imminent so as to spare its own life.

For a second, which felt like an eternity, the boy was fixated upon the most dangerous cat that ruled the undergrowth of the bush. Knowing full well that the leopard is capable of taking down any large antelope, the boy knew that he was in very serious trouble. The leopard would surely now spring from the bush onto him and shred his frail body into strips of lean meat.

After walking a kilometer, he took his first breath. His mind was blank with fear and his body exhausted from the lack of air. Only then could he realize what had transpired in the last few minutes. He had simply turned around and walked away from the Leopard! Amazingly the predator did not follow and showed no intent of acting in defense toward this threat that the boy posed. The tears came flowing and mixed with the blood that by now had covered almost his entire shirt.

His mother was busy cooking lunch over an open fire when her blood-covered son appeared from the bush, crying like a young child. Frantic screams from the woman shook the village into a state of alert. She cried as she ran towards her son, embracing him as if she had not seen him for many years.

The wound was cleaned and dressed with a local medicinal ointment, made from cooked antelope fat mixed with dried “Rain-tree” roots. The villager’s were well aware that the events that had transpired that day could have resulted in the boy’s tragic and brutal death. They all knew that today they had been greatly blessed.

By that time, the father of the injured boy and his brother returned home from working the local crop fields. The terrible encounter was told to them in high pitched voices.

Immediately the men started to talk among each other; of how they would have surely slain the leopard had THEY been there. These affirmations of manhood have been responsible for many men’s fate being sealed with the dark stamp of death. The boy’s mother, still very upset by her son’s near-death experience, simply started cursing the father and his brother. She vehemently explained to them that they could never be as brave as her son had just proven to be. -- That they did not have the courage to even go and kill this beast that had driven its dirty claws into her child. The humiliation that followed, in front of all the other villagers, was devastating. Silence fell like dark rain-carrying clouds onto the men, crushing their egos and fueling their desire to prove her wrong.

The two men had no other choice at this point. To spare the last ounce of dignity they had left, they had to go and kill the king of the undergrowth.

Encouraging each other as they walked out of the village, the two men “reminded” each other that they did not fear the leopard. Of course it was only fear that kept them walking without falling down due to the sudden weakness they felt in their legs. Each armed with a spear; they started following the boy’s footprints.

Swearing at themselves for uttering the “pride-breaking” words, the two men were convinced that the leopard had already moved on and that their hunt would be unsuccessful. They walked very close to each other at a snail’s pace, scanning every bush in front of them, searching for that bright yellow coat that most likely won’t be seen until it’s ripping out your throat and disemboweling you with its rear feet.

Eventually they reached the spot where the boy had dropped his catapult. They realized that they were at the exact spot where the boy had met the leopard in surprise. Gripping their spears with such force that their knuckles turned white, the one brother looked to the left, whilst the other looked to the right, standing back to back, expecting a fight that would last to the end. After a few minutes of heavy breathing and thundering hearts that could be heard all over the African plains, the two men decided to call it the quits. The leopard had moved on, and they knew better than to follow into its’ domain of camouflage. They turned around and started walking back to the village with much lighter hearts, and at least a little regained pride as they had also collected the catapult, even if only to prove that they had actually reached the spot of the attack.

It was not even two steps from where the boy had been attacked, that the father of the child suddenly felt a numbness creeping onto his upper body and face as he dropped with great force to the ground. As had happened with his son, he wondered what had caused his fall. Slowly he rose to his feet again, making a joke to his brother so as to hide his clumsiness. His brother looked at him in amazement. Suddenly blood started to pump from a gush above his eyes. He tried to wipe the blood from his face, but only succeeded in spreading it all over his eyes, rendering him nearly blind.

They now realized that the leopard was in a thick yellow-wood bush in front of them. The battle between life and death was upon them. Their bravery was to be put to the test. Years of hunting experience suddenly vanished as quickly as their rival did. And so did their bravery. They wanted to run, but could not. They were frozen in time.

Again the boy’s father was struck by the leopard, with lightning speed and accuracy. They had no chance against this master warrior of the bush. The leopard’s claws shredded the man’s forehead into threads of the red skin. With both eyes covered in blood, the man’s vision faded with his hopes of ever seeing his family again.

A sudden yellowish glaze sped past the injured man. He could not clearly identify the shape due to the blood in his eyes, but he was convinced that it was indeed the leopard which they pursued. With all the power in his body and adrenaline pumping wildly through his veins, he threw his spear in the direction of the movement. Almost instantaneously, he heard the familiar slicing sound as his spear found its mark, thrusting deep into flesh. The only weapon he now held was his hunting knife which he drew quickly with a firm grip and waited for the avenge that was to follow from the wounded. Blinded with blood and disoriented, he stood his ground.

Minutes passed and nothing happened. Eventually the pain of his wounds came to life and he moaned like a sick child, constantly trying to stop the bleeding and clearing his eyes. Then he heard another moan. It was that of his brother. Feeling around with his hands and using the absolute minimal sight available to him, he found his brother three steps from him, lying on the ground. In his upper thigh, the spear he had thrown was driven deep into his brother’s muscle, rendering him temporarily paralyzed.

One fearless hunter blinded, the other crippled by his own brother’s spear, the two clung together using the crippled man’s vision and the blinded man’s good legs, and hobbled their way home to Soncana. Needless to say, humiliation was bestowed upon them by every single villager.

Both men recovered from their physical wounds, but the story is still told around many campfires here in Bushmanland and how man’s fool-heartedness can be lethal. The two men indeed gained a greater respect for the almighty leopard and his mother, Nature. The tale of “the fools that followed” will forever remind us of our humble place in her world.

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