Canopies

This paper describes the construction and use of a diffusion tube for sampling NO2 from the atmosphere. Examples of its use include the determination of NO2 concentrations at various heights above ground level in an urban environment and through a tree s leaf canopy. 

Arcraft canopies Arcraft engines Arcraft fittings Arcraft fuels Arcraft sealants... 

Windows in airplanes, trains, and schools commonly use polycarbonate. Exotic appHcations include military use, for example in high speed aircraft canopies, where tests have shown polycarbonate to withstand impact with fowl at Mach 2. Polycarbonate is also used for security appHcations as laminates with glass or other materials. Polycarbonate offers unsurpassed projectile-stopping capabiHty, as the material softens upon impact with a bullet, absorbing the projectile s energy. 

Chemical treatment of diseases is not common, because of legislative controls and costs caused by the difficulty of appHcation through the leaf canopy. Breeding of resistant varieties is the main weapon for disease control. Some diseases, chiefly ratoon stunting disease, are controlled by hot water treatment of cane (6,8). 

Figure 10 Canopy resistanees for NO, and O, deposition at the Halvergate site on 15 September 1989.

NH3 Canopy compensation point, ambient NH3 concentration, surface water (SOj concentration) For limited areas V... 

The emissions of NO from soil may be oxidized readily within plant canopies to NOj, which may then be absorbed by stomata within the canopy or emitted from the canopy to the atmosphere. These processes, described by Pilegaard et... 

Figure 12 Interactions of soil emissions of NO with O3 in plant canopies and NO, uptake by vegetation in determining the net exchange of NO between soil-plant and the atmosphere.

That till the covers and canopies are fitted in their correct locations. 

In outdoor type switchgear or controlgear assemblies the normal practice is to provide a double door in the front to house the front panel and protect the door knobs, meters, lights, pushbuttons, reset knobs or other accessories mounted on the door and thus prevent water or dust leaking through joints, knockouts and fitments etc. It is also recommended to have a canopy on the top of the enclosure to protect the panel from direct rain. Figures 13.6 and 13.28 illustrate this type of construction. 

In such conditions, it is important that adequate care is taken to construct the bus enclosure lo weather the outdoor conditions such as by providing a canopy on the top and special paint treatment on the outdoor part. It is also recommended to seal off the indoor from the outdoor part to prevent the eflecl of rainwater, dust and temperature and other weather conditions on the indoor part. This can be achieved by providing seal-off bushings, one on... 

In fact, it is the solar effect that is causing the maximum heat. The factors considered for the solar effect are also highly conservative. Nevertheless, a canopy over the outdoor part is advisable in the above case. This will ensure the same size of enclosure for the outdoor as well as the indoor parts and also eliminate the requirement for a thicker enclosure or a forced cooling arrangement. Now there will be no direct solar radiation over the bus system and the total solar effect can be eliminated, except for substituting the indoor ambient temperature of 48 C with the maximum outdoor temperature for the outdoor part of the bus system. 

When a forest system is subjected to acid deposition, the foliar canopy can initially provide some neutralizing capacity. If the quantity of acid components is too high, this limited neutralizing capacity is overcome. As the acid components reach the forest floor, the soil composition determines their impact. The soil composition may have sufficient buffering capacity to neutralize the acid components. However, alteration of soil pH can result in mobilization or leaching of important minerals in the soil. In some instances, trace metals such as Ca or Mg may be removed from the soil, altering the A1 tolerance for trees. 

If one is studying the transport of material through the tree canopy of a forest, it is most desirable to disturb the natural environment as little as possible in making a wind measurement in the canopy. An extremely sensitive wind system is necessary because one would expect the winds to be extremely light. Also, it may be necessary to make supporting measurements both above and below the canopy, so that a wind speed profile is obtained. 

Fire standing panel framework including a weather protection canopy (against rain and sun). 

Fixed systems are those where movement of the hood or other changes to the system, except perhaps opening and closing of lids and doors, is not possible. One example is the hood with a sliding door surrounding a drilling or a milling machine another is the laboratory fume hood and another is the canopy hood above or the enclosure around a paper machine. 

The exterior hoods described here are divided into basic openings, rim exhausts, low-volume high-velocity (LVHV) hoods, receptor hoods (canopy hoods), and downdraft ventilation tables. Many varieties of these types of hoods exist. Some of these have been described and investigated more thoroughly than others because they are used more often or they are of more general use and applicability than the more specialized hoods. 

Receptor hoods, also called canopy hoods, are designed to capture contaminants given off by heated processes. They take advantage of the thermal updraft caused by such processes by placing the hood in the path of the updraft, they receive the exhaust and capture the contaminants. 

Heated sources can cause strong updrafts that carry contaminants upward. Receptor hoods take advantage of this updraft, as shown in Fig. 10.31. The process shown to the left in Fig. 10.31 is at room temperature, while the process to the right in Fig. 10,31 is operating at elevated temperature. A canopy... 

FIGURE 10.31 Canopy hoods over a cold process (left) and a hot process (right). 

FIGURE 10.3 2 Canopy hood with an airflow rate less than the thermal updraft airflow from a hot process. 

FIGURE 10.33 Canopy hoods according to Hemeon left, low hood, right, high hood. 

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