Blog Archives

SMALL REPAIRS

Posted by on 22/ 11/ 15

Small cracks or holes in plaster can be filled with patching plaster or a setting-type joint compound such as Durabond 90, which sets in 90 minutes. Because joint compound is softer, sands easily, and sets slower than patching plaster, it’s easier to work with. Setting-type joint compounds (also known as hot mud) are also better for patching than drying-type joint compounds, which just aren’t as strong. Note: To ensure a good bond, strip paint from the surfaces you’re patching and sand the adjacent areas lightly before applying compound.

Small cracks in plaster are repaired by stripping surface paint, cleaning loose plaster, and under­cutting the cracks slightly with a knife or a small, sharp-pointed lever-type can opener (also called a "church key”) Undercutting allows the patching materi...

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Texturing Drywall and Plaster

Posted by on 22/ 11/ 15

Joint compound is a marvelous medium for texturing a drywall patch or matching the texture of existing plaster. All that’s needed is a little ingenuity.

► For a stippled plaster look, place joint compound in a paint tray, thin it with water till it is the consistency of thick whipping cream, and roll it onto the wall or ceiling using a stippled roller. Don’t over-roll the compound, or you’ll flatten the stipples.

► Create an irregular "splatter" texture by thinning the compound to a heavy-cream consistency, sucking it into a turkey baster and squirting it onto the wall.

► For an open-pore, orange-peel look, use a stiff-bristle brush or whisk broom to jab compound that is just starting to dry. Jab lightly and keep the bristles clean.

► To achieve the flat but hand-tooled look of real plaste...

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Physical Aspects: Various Terms of Coupling

Posted by on 22/ 11/ 15

A large number of different phenomena may be coupled. It is impossible to discuss here all potential terms of coupling, and we will restrict ourselves to some basic cases often implied in environmental geomaterial mechanics. In the following para­graphs, some fundamental aspects of potential coupling are briefly described.

11.3.2.1 Hydro-Mechanical Coupling

In the case of hydro-mechanical coupling, the number of d. o.f. per node will be 3 (2 displacements +1 pore pressure) for 2D analysis and 4 (3 displacements +1 pore pressure) for 3D analysis.

Coupling mechanical deformation of soils or rock mass and water flow in pores is a frequent problem in geomechanics...

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Pedestrian Conflict Area Classifications

Posted by on 22/ 11/ 15

The above classifications appropriately describe general conditions of vehicular traffic conflict in urban areas. A second type of conflict is vehicle/pedestrian interaction. The magnitude is mostly determined by the land use of the abutting properties. Three clas­sifications of pedestrian night activity levels and types of land use with which they are typically associated are used in the lighting criteria tables:

High. Areas with significant numbers of pedestrians expected to be on the side­walks or crossing the streets during darkness. Examples are downtown retail areas and areas near theaters, concert halls, stadiums, and transit terminals.

Medium. Areas where lesser numbers of pedestrians utilize the streets at night...

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Coupling Various Problems

Posted by on 22/ 11/ 15

11.3.1 Finite Element Modelling: Monolithical Approach

Modelling the coupling between different phenomena should imply the need to model each of them and, simultaneously, all the interactions between them. A first approach consists in developing new finite element and constitutive laws especially dedicated to the physical coupled problem to be modelled. This approach allows taking accurately all the coupling terms into account. However there are some draw­backs that will be discussed in Section 11.3.4. Constitutive equations for coupled phenomena will be discussed in the following sections.

The number of basic unknowns and, consequently, the number of degrees of freedom – d. o.f. – per node are increased...

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FACILITY AND AREA CLASSIFICATIONS

Posted by on 22/ 11/ 15

The following descriptions of facility types and area classifications are used to describe the warranting conditions and design needs of roadway lighting.

7.15.1 Roadway, Pedestrian Walkway, and Bikeway Classifications [3, 6]

• Freeway. A divided major roadway with full control of access (no crossings at grade). This definition applies to toll as well as nontoll roads.

• Freeway A: Roadways with greater visual complexity and high traffic volumes. Usually this type of freeway will be found in major metropolitan areas in or near the central core and will operate through some of the early evening hours of darkness at or near design capacity.

• Freeway B: All other divided roadways with full control of access.

• Expressway...

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Advection Diffusion Processes

Posted by on 22/ 11/ 15

Let us first consider a purely advective process. In this case, the transport is gov­erned by the advection Eq. 11.11 and by the balance Eq. 11.6. Associating these two equations, one obtains:

(VTC). ffluld + C = 0 (11.45)

diff v ‘

which is a hyperbolic differential equation. It cannot be solved by the finite element or finite difference problem, but by characteristic methods. The idea is to follow the movement of a pollutant particle by simply integrating step by step the fluid velocity field. This integration has to be accurate enough, as errors are cumulated from one step to the next.

On the other hand, if advection is very small compared to diffusion, then the finite element and finite difference methods are really efficient.

For most practical cases, an intermediate situation holds...

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Windmills

Posted by on 22/ 11/ 15

The origin of the windmill is controversial. In a manuscript on Pneumatics, Heron of Alexandria includes the description of a wheel driven by the wind and driving the pis­ton of an organ. But the authenticity of this passage has not been resolved – it could have been added during the Islamic period. In any case, even if this passage is authentic, the link between this invention and the appearance of the true windmill in central Asia seems to be very weak.

The backdrop of Heron’s apparent reference to a windmill is the ubiquitous presence of water mills on all of the rivers. On the Tigris at Baghdad, on the Seguro at Murcia, on the Ebre at Saragossa, there are even boat-mounted water mills. Mills are the indis­pensable tools of an agricultural economy...

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TAPING AND FINISHING

Posted by on 22/ 11/ 15

To finish drywall, seal the panel joints with tape or cornerbead, then cover them with joint com­pound. Typically, three coats of compound are applied in successively wider coats and sanded after each application. The first coat, usually a high-strength taping compound, embeds the tape. The second coat should be a thin layer of topping compound or all-purpose compound that you feather out to hide the joints. With the third coat, you feather out the compound farther, creating a smooth, finished surface. (See "Joint Compounds,” on p. 358, for more about these materials.)

First coat. Fill nail holes or screw dimples in an X pattern: One diagonal knife stroke applies the compound, and the other stroke removes the excess.

If you use paper tape on the joints, apply a swath of taping compound ...

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The norias

Posted by on 22/ 11/ 15

The hydraulic noria, sometimes called the current noria, first appeared in the period of the Roman Empire. Herein we simply call this the noria. The very first evidence is found in the description of Vitruvius (around 25 BC) as we have cited in Chapter 6. Vitruvius describes the machine very clearly, but says nothing about the location of the particular device. Moreover we are not aware of any other mention of the noria by Roman writers. The second piece of evidence is found in the very heart of the land that will become the location of the largest norias: it is in a mosaic discovered at Apamea, a Hellenistic and Roman city located some fifty kilometers to the north of Hama oppo­site the depression of Gharb where the Orontes flows...

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