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Hydraulic Power Regulation
Published in Qin Zhang, Basics of Hydraulic Systems, 2019
These four basic equations provide the needed theoretical basis to design hydraulic shock absorbers. In practice, absorber performance is analyzed by using some device-specific empirical equations, formulated based on experimental data. The shock-absorbing time and the piston displacement equations are among the most commonly used absorber performance empirical equations. The following empirical equations are examples of shock-absorbing time and the piston displacement equations applicable to simple orifice type shock absorbers as illustrated in Figure 5.4(a). The shock-absorbing time is normally defined as the time interval in which the piston speed decreases from its initial velocity to 10% of the initial value, and it is expressed as follows: ta=m−vaC2vaC1
Absorbers
Published in Trevor J. Cox, Peter D'Antonio, Acoustic Absorbers and Diffusers, 2016
Trevor J. Cox, Peter D'Antonio
Traffic is a major cause of noise problems, and although modern cars are quieter than their older ancestors, the increase in traffic levels has meant that average noise levels have not changed very much in recent decades. One partial solution is to use porous asphalt to reduce noise, the properties of which are discussed in Chapter 6. Another possibility is to use barriers to reduce noise propagation from roads to neighbouring houses and other buildings. Double reflections from high-sided vehicles enable some of the noise to bypass barriers, however, as shown in Figure 2.15a. Even more important, reflections from barriers on one side of the road can pass over barriers on the other side, as shown in Figure 2.15b. These additional reflections typically change sound levels by between 2 and 6 dB(A).15 One solution is to apply absorption as shown in Figure 2.15c. The problem with absorption is that it tends to wear badly under the harsh conditions of high winds, salt, and water, which are common next to busy roads. Consequently, absorber performance is likely to decrease over time unless specialized and expensive durable absorbers are used.
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Published in Charles E. Baukal, Industrial Combustion Pollution and Control, 2003
One type of FGD is the lime process which is a wet, nonregenerable S02 absorption process. An alkaline slurry is recirculated through a scrubber/absorber tower. Calcium sulfite and sulfate are formed by the reaction, which are then separated in settlers or clarifiers and filters. A sludge is produced that can be inerted and then landfilled. The systems generally have four major operations: scrubbing or absorption to capture the gaseous S02, flue-gas handling including ductwork and fans, lime handling and preparation, and sludge processing. The scrubber/absorber may be a tray absorber, a packed scrubber, a mobile bed scrubber, a venturi scrubber, or a spray tower. The limestone process is very similar to the lime process except that the feed preparation equipment is different. Limestone is less reactive than lime so some of the process parameters are different. The so-called double alkali process is basically an indirect lime/limestone process where some of the plugging and scaling associated with lime/limestone processes can be avoided. Many of these systems are large, capital intensive, have significant operating costs, and produce a sludge that needs to be disposed of properly. They may only be economically feasible for larger SO* emission sources.
Thermal performance enhancement in parabolic trough solar collectors by using an absorber tube with spherical pins
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2022
Belkacem Agagna, Omar Behar, Arezki Smaili
An important noteworthy outcome from Ref. (Shahzad Nazir et al. 2021) is that the combination of different ideas, including the use of many geometrical modifications as well as using nano fluid as a working fluid, can lead to higher performances. However, these techniques are associated with higher manufacturing costs and have an influence on the life of the absorber. Also, they induce more control during plant operation. This is why further studies with manufacturers and deep technical-economic analysis are needed. Finally, the present geometry compromises by proposing a simplified structure with encouraging improvement, which proves its good position among the others cited above.
Noise control material using jute (Corchorus olitorius): effect of bulk density and thickness
Published in The Journal of The Textile Institute, 2021
Surajit Sengupta, Gautam Basu, Mallika Datta, Sayandeep Debnath, Devarun Nath
Indoor public places such as auditoriums, classrooms, halls, working places induce scarcity in speech intelligibility during day to day communication due to the imperfection of acoustic design. In addition, prolonged exposure to unwanted noise in absence of proper noise treatment of those places may adversely affect human health, as well as create annoyance which may cause sleep disturbance, hearing loss, decrease in productivity, learning ability and scholastic performance and increase in stress-related hormones and blood pressure (Stansfeld & Matheson, 2003). Use of sound absorbers to create indoor acoustical ambiance is a well-known practice since the late nineteenth century (Sabine & Egan, 1994). Absorbers are mainly of three types viz. porous absorber, panel, and resonators. However, none of the types can provide effective absorbency over the entire range of audible frequencies. Fibrous absorbers are suitable for tackling mid to high-frequency waves, starting from 2000 Hz and above as reported (Seddeq, 2009) . Whereas, Panel based absorbers are effective for controlling lower frequencies of the noise spectrum (Maa, 1998). If we can combine the absorptive attributes of, at least, fibrous and panel absorbers; it is possible to provide noise control over a wider range of frequencies than any of the individual type would perform. Conventionally, manmade fibrous materials such as glass wool, rock wool, polyester, polypropylene, polyurethane foams are widely used as fibrous absorbers (Arenas & Crocker, 2010; Lou et al., 2005; Wang & Torng, 2001). But, high carbon footprint, health hazards and non-recyclability associated with the manufacturing of these materials in addition to non-biodegradability alarms the need for their abandoned use (Joshi et al., 2004). To replace these existing materials, researchers across the globe are looking forward to use a post-harvest natural fibres (Bansod et al., 2016; Fatima & Mohanty, 2011; Fouladi et al., 2011; Koizumi et al., 2002; Zulkifli et al., 2008) for acoustic treatments because of their biodegradability, sustainability and renewability (Oldham et al., 2011). Properly designed textile materials may be considered as noise control elements in a wide range of applications, including wall claddings, acoustic barriers and acoustic ceilings (Shoshani & Yakubov, 2000). Zheng et al. (2015) suggested using kapok fibre as sound absorbing material.