Blog Archives

Egypt under the Lagide rulers: maritime commerce

Posted by on 17/ 11/ 15

In Chapter 3, devoted to Egypt of the pharaohs, we mentioned several projects that rep­resented completion or termination of efforts that the Ptolemites had begun earlier. In their development of commerce with distant partners in Arabia, and even as far as India according to Strabo, the Ptolemites needed to develop the infrastructure to access the Red Sea and to launch a fleet for this purpose. Necho’s canal, linking the pelusiac branch of the Nile with the Gulf of Suez, passing through Lake Timsah and the Bitter Lakes, is maintained or brought back into service. As we have seen in Chapter 3, a device (a single gate?) making it possible to accommodate water-level changes in the Gulf of Suez is installed. A new city, Arisone,[181] named for the sister-spouse of Ptolemy II Philadelph, is ...

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Culverts and Storm Drains

Posted by on 17/ 11/ 15

The open-end conduits used to convey water from one side of the roadway through the embankment to the other side are typically referred to as culverts. A network or system of conduits to carry storm water intercepted by inlets is referred to as a storm drain system. Conduits for culverts and storm drains are available in many different shapes, sizes, and materials, as discussed subsequently. Available shapes include circular, elliptical (horizontal or vertical), pipe-arch, arch, and box shapes. Factors that affect the shape at a particular site include the fill height, construction costs, and potential for clogging by debris. Where the cover over the conduit is limited, pipe-arch, arch, elliptical (horizontal), or box shapes may be more applicable...

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PRACTICAL CONSIDERATIONS OF THE SMA PRODUCTION PROCESS

Posted by on 17/ 11/ 15

By and large, the production of an SMA in contemporary asphalt plants does not present particular problems. The following are a few general tips about the production of SMA:

• SMA requires some production consistency with no breaks, stoppages, or similar “jerking” of the production process. Any alterations to the type of mixture being produced require adjustments of the batching device con­trols, the weight of mixture constituents for the mixer, and so on. Potentially more troublesome, any stoppages necessitate restarting the machine and beginning the production again.

• The moisture content of the aggregate leaving the dryer should not be higher than 0.5%, optimally less than 0.2% (USACE Handbook, 2000).

• When initial batching (cold feeders) limits the machine’s output, an addi­...

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STEP 5 ADD DRYWALL BACKING

Posted by on 17/ 11/ 15

At this point, you need to add backing (some­times called deadwood) to walls that run paral­lel to the joist chords. The backing provides a nailing base for ceiling drywall (see the illustra­tion on p. 127). It’s easier to put the backing in now rather than after the roof is complete and hampered by sheathing. This is a good place to use knotty, crooked 2x stock. Nail the stock, one 16d nail every 16 in., to the double top plate of parallel walls so that the 2x backing overhangs the double top plate by at least 1 in. on both sides. Some builders use drywall clips instead of solid backing, but I like to fasten nails

Doing carpentry on the ground is easier than doing carpentry on top of the house. You really have to watch your step.

We handle the trusses carefully.

Plenty of bracing is...

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Pathways and Targets

Posted by on 17/ 11/ 15

Once having entered the road area, pollutants may start their transport to other ecosystem compartments. Any ecosystem compartment that may be affected by a pollutant can be considered a target. The pollutants will not be permanently trapped at these destinations but may stay there for a prolonged period of time.

Pollutants in the solid and in the liquid form are transported to the environment in various ways (see Fig. 6.5):

• infiltration into the road structure and further transport to the groundwater;

• pavement runoff;

• splashing to the road shoulders and ditches;

• spray.

The relationship between different sources of pollution and different targets will be a function of

• the “strength” of the source (i. e. the rate of the emission);

• the pollutant pathway from the sou...

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Chainsaw Mills

Posted by on 17/ 11/ 15

There is an alternative timber procurement strategy for those with their own stand of large straight trees, and that is to make the timbers yourself with a chainsaw mill, essentially an attachment for a chainsaw. There are several different styles and qualities and costs vary a great deal. Here are some choices, with contact information for all of them found in Appendix C:

• The Beam Machine. First, you nail a two-by-four to the log that you want to make into a beam. The Beam Machine is an inexpensive ($40) bar attachment that slides along the two-by-four. Their ad says the “dog-tooth pivoting action takes most of the strain out of sawing because it supports the weight of the saw and provides you with a smooth, leveraged sawing motion.” See Sidebar, on pages 54-55. [4]

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The Production of SMA

Posted by on 17/ 11/ 15

Having designed and checked the SMA mixture, the time has come to produce it according to the job mix formula (JMF). In this chapter we shall deal with

• Requirements for the organization of an asphalt plant

• Assumptions and control over the SMA production process

• Production of the SMA mixture in a batch plant or in a drum-mix plant

• Storage of manufactured SMA in a silo

9.1 REQUIREMENTS FOR THE ORGANIZATION OF AN ASPHALT MIXING PLANT

The organizational requirements of an asphalt mixing plant and its surround­ings are much the same for the production of SMA as for other asphalt mixtures. Some special issues may arise, however, when dealing with SMA, such as the following:

• Storage of aggregates

• Stockpiled aggregate should not be mixed with underlying-soil material.

• Co...

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Biological Processes

Posted by on 17/ 11/ 15

Usually, roadside soils are or become covered by vegetation. Especially where the plant cover is large or the vegetation dense, the vegetation as a physical body influ­ences the air-borne transport of pollutants from the road and traffic to the surrounding environment. Usually, however, the vegetationis kept low by mowing andbushcutting. To some extent, pollutants deposited on leafy surfaces enter the interior of the plant.

Under good growing conditions, plants will produce a more or less dense root system. Their root mass will greatly influence the movement not only of water but also of pollutants in the soil. Root uptake can withdraw large quantities of water from percolation. Root uptake also forms an important pathway of pollutants into the plant...

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HOMES WITH 1 TO 11/2 BATHROOMS

Posted by on 17/ 11/ 15

We will start our sizing exercises with homes where less than two bath­rooms are present. You will see tables for gas-fired, electric, and oil-fired water heaters. The number of bedrooms in our sample homes can range from one to three. You will have to use the chart to size a water heater for the examples given. Let’s start with a gas-fired water heater. The house we will size it for will have two bedrooms and one bathroom. What size water heater is needed (Fig. 7.1)?

All you have to do is scan the table for the answer to sizing question. Look under the heading for two bedrooms and run down to the column that lists storage. You will see that a 30-gallon water heater is the minimum size recommended for the application...

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Formation of Aqueous Complexes (“Particle”[14] Exchange)

Posted by on 17/ 11/ 15

Complexes are chemical compounds consisting of a central atom (metal) and ligands (consisting of a group, molecule or ion) tied to the central atom with at least one co-ordination bond. A chelate is a special form of complex where the ligand is attached to the central atom by at least two bonds. The most common ligand in water solutions is the water molecule itself but anions such as hydroxide, carbonate, hydrocarbonate, sulphate and organic acids also form ligands. The formation of a complex from a metal and a ligand is a balanced reaction characterized by a constant (Kc) that is often pH dependent. Some complexations can be considered as “surface complexation” reactions (e. g. of a metal with an iron oxide) as opposed to “aqueous complexation” reactions.

Organic and inorganic com...

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