Pages

▼
Sunday, September 20, 2020

WHAT TO KNOW ABOUT POOL CHEMICAL SAFETY - Pool chlorinating products are generally safe when handled properly. The key to avoiding injury at the pool is prevention! Make sure to follow all the safety rules at the pool and follow the instructions for handling all pool chemicals. Whether it's in your backyard or at a local community center, keeping a swimming pool clean and properly maintained is important to limit people's exposure to recreational water illnesses (RWIs). According to the Centers for Disease Control and Prevention (CDC), RWIs are caused by bacteria and other germs that spread by swallowing, inhaling, or making skin contact with contaminated water. The most common RWI is diarrhea, which can be caused by organisms such as Cryptosporidium, E. coli, and norovirus. Pool owners and maintenance teams must keep the chlorine concentration within a range that is high enough to effectively kill germs yet low enough to avoid injury to swimmers. The CDC recommends keeping a free chlorine concentration of at least 1 ppm in pools and 3 ppm in hot tubs. Maintaining an optimal pH also contributes to protecting swimmers from the spread of germs in pool water. If the pH or chlorine concentration is out of the recommended range, it can sometimes cause mild irritation to the skin and eyes of swimmers.

›
...............................................................................................................................................
Friday, September 18, 2020

FUNDAMENTAL FORCES OF NATURE - A force is defined as a push or pull that changes an object's state of motion or causes the object to deform. Newton defined a force as anything that caused an object to accelerate. The force of gravity pulls you down into your seat, toward the Earth's center. You feel it as your weight. Why don't you fall through your seat? Well, another force, electromagnetism, holds the atoms of your seat together, preventing your atoms from intruding on those of your seat. Electromagnetic interactions in your computer monitor are also responsible for generating light that allows you to read the screen. Gravity and electromagnetism are just two of the four fundamental forces of nature, specifically two that you can observe every day. The remaining two forces work at the atomic level, which we never feel, despite being made of atoms. The strong force holds the nucleus together. Lastly, the weak force is responsible for radioactive decay, specifically, beta decay where a neutron within the nucleus changes into a proton and an electron, which is ejected from the nucleus. Without these fundamental forces, you and all the other matter in the universe would fall apart and float away. The first force that you ever became aware of was probably gravity. Gravity holds the moon, planets, sun, stars and galaxies together in the universe in their respective orbits. It can work over immense distances and has an infinite range. Isaac Newton envisioned gravity as a pull between any two objects that was directly related to their masses and inversely related to the square of the distance separating them.

›
  .............................................................................................................................................

SOLDIERS MARCHING IN STEP ON A BRIDGE - Why Soldiers Break Stride On A Bridge - Marching soldiers are cautioned to break stride on a bridge, lest they match the bridge's frequency of vibration. In April 1831, a brigade of soldiers marched in step across England's Broughton Suspension Bridge. The bridge broke apart beneath the soldiers, throwing dozens of men into the water. After this happened, the British Army reportedly sent new orders: Soldiers crossing a long bridge must "break stride," or not march in unison, to stop such a situation from occurring again. Structures like bridges and buildings, although they appear to be solid and immovable, have a natural frequency of vibration within them. A force that's applied to an object at the same frequency as the object's natural frequency will amplify the vibration of the object in an occurrence called mechanical resonance. Sometimes your car shakes hard when you hit a certain speed, and a girl on a swing can go higher with little effort just by swinging her legs. The same principle of mechanical resonance that makes these incidents happen also works when people walk in lockstep across a bridge. If soldiers march in unison across the structure, they apply a force at the frequency of their step. If their frequency is closely matched to the bridge's frequency, the soldiers' rhythmic marching will amplify the vibrational frequency of the bridge.

›
  .............................................................................................................................................
Thursday, September 17, 2020

BUOY MOORING - A buoy-based system must be moored to ensure that it remains stationary. The buoy is usually moored via a stainless steel mooring line, bottom chain and anchor. It is recommended to moor the buoy in the deepest part of the waterway to ensure the most inclusive measurements. This allows for multiple measurement depths and will best reflect the characteristics of the water body as a whole. Buoy-based systems are typically moored as either a single-point or two-point mooring, based on environmental and application-specific factors. Single-point moorings are not common, but they require the least amount of mooring equipment. This setup can be deployed in very calm waters with minimal instruments. A single-point mooring should only be used when all sensors and equipment are housed within an instrument cage or deployment pipe. Hanging sensors risk getting damaged or entangled with the anchor line. A cage or pipe protects the instruments from entanglement, subsurface debris, and currents without affecting sensor readings. In a single-point configuration, a mooring line connects the buoy directly to a bottom chain and anchor. The sensors are typically housed within a central deployment pipe or attached to a rigid instrument cage. The anchor, bottom chain, and mooring line are assembled and attached to the buoy prior to deploying the system.

›
  .............................................................................................................................................