Blog Archives

Simplicity

Posted by on 18/ 11/ 15

It is ironic that simplicity is by far the most difficult of the seven principles to achieve. Simplification is a complicated process. It demands that every pro­portion and axis be painstakingly honed and that every remaining detail be absolutely essential. The more simplified a design becomes; the more any imperfection is going to stand out. Everything in a plain design must make sense, because every little thing means so much. The result of this arduous effort will look like something a child could come up with. The most refined art always looks as if it had been easy to achieve.

This sort of streamlining demands a firm understanding of what is neces­sary to a home. As stated before, there is no room in an honest dwelling for anything apart from what truly makes its occupant(s) happy...

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Water and Soil Sampling Procedures

Posted by on 18/ 11/ 15

7.4.1 Introduction

The procedure for sampling is primarily influenced by the source of the water (e. g. in a borehole, in a pipe) and by the equipment available with which to sample it. The equipment, itself, is largely controlled by the sampling location. Once collected by the sampling device, water samples must be quickly processed before changes in make-up occur due to various physical and biological processes. The following sections discuss the collection and immediate treatment of surface and sub-surface waters and of soil. They provide a general overview of the techniques and pro­cedures for application in pavements and the ground around highways...

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Insulated Glass Reduces Heat Loss

Posted by on 18/ 11/ 15

Manufacturers typically refer to glass as glazing. Using glazing as a noun is a bit pretentious, like referring to a window as a fenestration, but it does give the sense that glass assemblies in today’s windows are a far cry from the single-pane windows installed in the 1970s.

Those single-pane windows have been abandoned in most heating climates be­cause glass is a horrible insulator. A standard window today relies on an insulated glass unit (sometimes called an IG). This unit is a sealed sandwich of two or three pieces of glass with an airspace between the panes. IG units are manufactured by a few glass com­panies that supply the hundreds of window manufacturers in North America.

Подпись: What's a U-Factor?Подпись: U-factor rates a window's insulating properties by measuring the flow of nonsolar heat through the window. You can think of it as the rate of conduction; the lower the U-factor, the less heat will flow through the window. (U-factor is the reciprocal of the more familiar R-value used to rate insulation. R-value measures resistance, so higher numbers are desirable.) Although we tend to think of a window as primarily glass, the frame makes up 20% to 30% of the unit. U-factors are measured for the edge of the glass area, the center of the glass area, and the frame; but the important U-factor is for the entire window unit. Buy Insulated Glass Reduces Heat Lossing decisions should be based on this number, which appears on the NFRC label (above).

U-factors for operab...

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Size Determination for Long-Span Structures

Posted by on 18/ 11/ 15

Because culvert shapes are so numerous and new shapes are often developed, design charts showing performance curves are not available for all culvert sizes and shapes. One example is long-span corrugated-metal sectional plate structures. Although the product is available in several cross-sectional shapes, performance curves are avail­able only for circular or elliptical cross-sections (Fig. 5.17) and high – and low-profile arches (Fig. 5.18). These charts, which are for inlet control only, address four different inlet configurations ranging from mitered to beveled-edge ends. Because long-span structures are commonly used when headroom is low, they generally do not flow under head at design discharge but flow partly full.

The first step in using these charts is to obtain information on ava...

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Time-dependent resistance

Posted by on 18/ 11/ 15

For a hydraulic structure placed in a natural environment over a period of time, its operational characteristics could change over time owing to deterioration, aging, fatigue, and lack of maintenance. Consequently, the structural capacity (or resistance) would vary with respect to time. Examples of time-dependent characteristics of resistance in hydrosystems are change in flow-carrying capacity of storm sewers owing to sediment deposition and settlement, decrease in flow-carrying capacity in water distribution pipe networks owing to aging, seasonal variation in waste assimilative capacity of natural streams, etc.

Modeling time-dependent features of the resistance of a hydrosystem re­quires descriptions of the time-varying nature of statistical properties of the resistance...

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Galien of Pergamon and the beginnings of biomechanics

Posted by on 18/ 11/ 15

There is another branch of fluid mechanics that sees some early development in this peri­od: this is the knowledge of blood circulation. Whereas it was believed that the arteries contained only air prior to this period, Galien of Pergamon (129 – 200? AD)[202] is the first to describe arterial circulation and to study seriously the circulation of blood in the heart. For this he relies on an intense practice of dissection.[203] His only error is in believing that the blood passes directly from the right ventricle to the left ventricle.

The first discovery of the resistance to motion through the air

We mentioned in Chapter 4 the dominant theory of Aristotelian Greek science on the movement of objects in air...

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Critical Depth Determination

Posted by on 18/ 11/ 15
Подпись: IOO Подпись: 150 Critical Depth Determination Подпись: 350

The critical depth for various culvert cross-sections may be found from charts in HEC 5. An example is given in Fig. 5.16 for a rectangular section. In this case, the ratio of the flow Q (ft3/s) to the width B (ft) is used to find the critical depth dc (ft). Of course, dc cannot exceed the depth of the box section.

Подпись: MOTEac CANNOT EXCEED D

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Heron of Alexandria and the first expression of the volumetric discharge of a canal

Posted by on 18/ 11/ 15

Before Heron, no correct notion of the discharge of a canal, pipe, or river had been cor­rectly formulated. Indeed, the notion of velocity was essentially unknown in Greek mechanics. The quantity of water delivered by an aqueduct or canal was quantified uniquely by a measure of the flow area. It was Heron who formulated for the first time the notion that the volumetric discharge, i. e. the volume of water delivered in a unit of time, is the product of the flow area and the velocity. One finds the following in his work Dioptra:

“It is to be noted that in order to know how much water the spring supplies it does not suffice to find the area of the cross section of the flow… It is necessary also to find the speed of the flow, as the swifter the flow is, the more water the spring supplies...

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Production of SMA in a Drum-Mix Plant

Posted by on 18/ 11/ 15

There are two types of drum-mix plants: parallel-flow drum-mix plants and counter-flow drum-mix plants (conventional and double barrel). In drum-mix plants, cool aggregate is delivered from cold-feed bins to a dryer-mixer and then into a silo through a slat conveyor. The mixture gradation control is exercised
through establishing suitable proportions of individual aggregate fractions in cold-feed bins and the rate of aggregate supplied by the feeder belt. The conveyor is equipped with a weight and speed-control system that enables control over the coating plant’s throughput in tons per hour. The general categories of drum-mix plants depend on the flow direction of the aggregate relative to the hot air move­ment from the burner...

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Hurricane clips and frieze blocks

Posted by on 18/ 11/ 15

A hurricane can tear a roof completely off a house. Hurricane clips, which are designed to prevent this, are required by code in some parts of the country. After the trusses are nailed in position, hurricane clips are easy to install from inside or outside the house. Drive nails into the trusses and the top p. atesofthe wall (see the photo at left). Be sure to use the special short, strong “hanger” nails that arc sold with the clips.

In many parts of the country, frieze blocks are required between trusses. I’m in favor of these blocks, which you can cut from the plentiful supply of 2x scrap that your crew has been collecting. Installed at the top of the wall, these 2x blocks connect the bottom chords or, depending on the truss design, the rafters of adjacent trusses...

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