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Stratified sampling technique

Posted by on 22/ 11/ 15

The stratified sampling technique is a well-established area in statistical sam­pling (Cochran, 1966). Variance reduction by the stratified sampling technique is achieved by taking more samples in important subregions. Consider a prob­lem in which the expectation of a function g (X) is sought, where X is a random variable with a PDF fx(x), x є E. Referring to Fig. 6.13, the domain E for the random variable X is divided into M disjoint subregions Em, m = 1, 2,…, M. That is,

m

S = U Sm 0 = Sm Fl Sm! m = m

m=1

Stratified sampling technique

Let pm be the probability that random variable X will fall within the sub­region Em, that is, f fx(x)dx = pm. Therefore, it is true that Lmpm = 1.

The expectation of g (X) can be computed as

m.. M

G = g(x) fx(x) dx =^2 / g(x) fx(x) dx =^2 Gm (6.86)

m=1J Em m=1

where Gm = fw g...

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BATHING UNITS

Posted by on 22/ 11/ 15

Bathing units for handicap use are required to be equipped with grab bars.

Bathtubs and showers for handicap use are often different in size and equip­ment from what you would find in a standard fixture (Fig. 10.10, Fig. 10.11).

The minimum clear space in front of a bathing unit is 30 inches from the edge of the enclosure away from the unit and 48 inches wide. If a situation exists where a bathing unit is not accessible from the side, the clear space in front of the unit must be increased to a minimum of 48 inches. Faucets for showers and bathtubs must be equipped with a hand-held shower. The hose for these showers must be a minimum of 60 inches in length. The faucets must be able to be opened and closed with a maximum force of five pounds.

Grab bars are required in handicap bathing units...

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Boundary Conditions

Posted by on 22/ 11/ 15

In the preceding section, differential equations were given for three types of prob­lems. In order to solve these equations, we need to define boundary and initial con­ditions. Classical boundary conditions may be considered: imposed displacements or forces for solid mechanics problems and imposed fluid pressures, temperatures, concentrations or fluxes for diffusion and advection-diffusion problems.

However, it may be useful to consider much more complex boundary conditions. For example, in solid mechanics, unilateral contact with friction or interface be­haviour is often to be considered.

When coupling phenomena, the question of boundary conditions increases in complexity and has to be discussed.

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INSTALLING FIBERGLASS BATTS

Posted by on 22/ 11/ 15

All batts are installed in basically the same way, so the following tips for installing fiberglass batts also hold true for cotton and mineral-wool batts, unless otherwise noted.

Getting started. Carefully seal air leaks before insulating; air currents can dramatically reduce
an installation’s R-value. Then suit up with the appropriate safety gear to keep fiberglass off your skin and out of your lungs. Wear a respirator mask, eye protection, long-sleeved shirt, long pants tucked into your socks, and work gloves.

To determine how much insulation to buy, measure the square footage of walls, ceilings, and floors and then divide by the number of square feet in an insulation package. Also printed on the packaging is the insulation’s R-value and the width of the batts...

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Material Selection

Posted by on 22/ 11/ 15

Material selection is a concern for green framing. The following are six ways in which material selection is considered green.

1. Use of Forest Stewardship Council (FSC) and Sustainable Forest Initiative (SFI) certified lumber. This is lumber that is harvested following environmentally

Forest Stewardship Council Label

friendly guidelines for sustainable practices. This lumber is tracked through the chain of custody from the forest to the end user. It is labeled for identification.

2. Use of salvaged or reused material. reusing lumber minimizes the need for new lumber.

3. Use of regional material. This is material that is harvested typically within 500 miles of the end use. The value gained is from the transportation energy savings.

4. Use of rapidly renewable material...

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Dry wall and Painting

Posted by on 22/ 11/ 15

I’M NOT SURE WHEN DRYWALL—also known as gypsum board, wallboard, and Sheetrock®— was first used in construction. I have seen drywall on pre-WWII houses, but we defi­nitely didn’t have drywall in my old prairie home. It wasn’t until the late ’50s in California, where I was working, that drywall became the preferred wall covering in residential housing. “Knock on the Wall! Demand Genuine Lath and Plaster!” was the rallying cry of the once-mighty plaster industry, as they struggled against the newcomer—drywall.

Big plaster fought a losing battle. It took two or three weeks to cover walls with layers of plaster, and the process left the house frame waterlogged. In the winter, it could take a month or more for a house to dry out well...

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CLEANING UP MOLD

Posted by on 22/ 11/ 15

Mold can’t grow without moisture, so first identi­fy and correct the source(s) of the excess mois­ture before you start cleaning up. Otherwise, the mold can return.

Necessary precautions. Limit your exposure to mold spores by wearing a respirator mask with N95 (or higher) filters, rubber gloves, eye protec-

I A Bathroom Fan

Подпись: Moisture can condense in bathroom-fan ducts that run through unheated areas. To reduce in-duct condensation, insulate the ducts; keep the duct runs short; and if you're venting the duct through a wall, slope the duct downward toward the wall cap so the moisture will run out if it does condense.Подпись: 1111Подпись:Подпись:image699

tion, and disposable coveralls, which you should discard at the end of each day. After assessing the mold’s extent, determine the shortest way out of the house for contaminated materials—maybe out a window—to minimize spreading mold spores to clean areas. Use sheet plastic to seal doorways and heating registers in affected areas, and turn off central HVAC systems till the reme­dial work is complete...

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In the heart of the Arab world: the splendor of the Umeyyades and the Abbassids

Posted by on 22/ 11/ 15

Byzantium, the Sassanides and the new Arab empire

Water supply systems of the Byzantine cities do not measure up to those of the Romans, either in quality or in quantity. In many Byzantine cities, such as Apamea-on-Orontes or even Constantinople itself, aqueducts are abandoned in favor of cisterns, sometimes very large and fed by runoff from rainstorms. Small rural communities located along wadis or on small rivers implement numerous hydraulic developments at their scale[317] –
such as modest derivation canals that support gravity irrigation of valley fields, with many small mills.

The Byzantines indulge in large-scale hydraulic activity in Anatolia, where they build several dams. One among them is the Dara dam, constructed under Justinian (527­565) on a tributary of the Khabur...

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Air – Conditioning: Bigger Isn’t Better

Posted by on 22/ 11/ 15

Подпись: HEATING AND COOLING■ BY CHRIS GREEN

S

itting in a green-and-white woven lawn chair, fanning away the sweat, my grandmother said, "It’s not the heat, it’s the humidity." With seven Virginia summers behind me, I suspected that the heat did have something to do with it, but I kept this thought to myself.

It turns out that each of us had it partly right. It was the combination of high heat and humidity that raised us to our exalted level of discomfort on that oppressive summer day.

Seven years later, my parents finally built a house that included central air­conditioning. Although it was better than being without, the air-conditioning system wasn’t ideal. The house had cold and hot spots, and my basement bedroom always felt cold and damp.

Unfortunately, these problems weren’t limited to my parents’ house ...

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Choose Energy-Efficient Mechanical Help

Posted by on 22/ 11/ 15

While I’m a firm advocate for passive cooling, I also believe there is a place for mechanical systems. Used in conjunction with passive-cooling techniques, the effec­tiveness of both can be enhanced, leading to lower energy use without any compromise in comfort.

Choose Energy-Efficient Mechanical HelpПодпись: Start small. Strategically placed mechanical devices, such as the fan at the top of the hallway, can enhance passive design.That said, if you are going to use both passive and mechanical systems, it’s im­portant they work together. When hiring a heating and cooling contractor, choose someone who can size a mechanical system with your passive-cooling elements in mind and who will recommend energy-efficient equipment.

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Sources

Seeking Solar Professionals

When considering passive design, you should seek the services of a qualified pro familiar with the right strategies for your home and climate. professionals accredited by the U. S...

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