The earliest food producers in Africa were mobile pastoralists who left limited archaeological traces. As a result archaeologists studying the spread of food production in the region have difficulty distinguishing early pastoralists from hunter-gatherers with whom they interacted. This geo-ethnoarchaeological study contributes to the resolution of the problem through identification of sediments...

A kind of noise is dominated by broadband noise with low frequency tonal components. To achieve noise control on whole frequency band, it is necessary to implement hybrid control technique combining passive control and active control. There are three methods to combine passive control and active control, including active control in passive enclosures, active control outside passive enclosure an...

background: the adverse effects of noise are well known and noise problems due to industrialization of communities are increasing over the time. oil industries due to the process and nature of production; contain many noise sources such as compressors, turbines, and pumps, which cause excessive noise exposure. the objective of this study was to evaluate the noise characteristics of compressors ...

in this paper, free convection in an inclined stepped chamber has been studied. one wall of this enclosure is kept cold and the opposite wall equipped with constant heat source. the remaining walls are maintained adiabatic. there is one adiabatic step on the bottom wall. the aim of the present study is to forecast the effect of raleigh number, slope of enclosure, step dimension, and heat source...

a numerical investigation of laminar mixed convection heat transfer in a shallow two-sided lid driven rectangular enclosure of aspect ratio 5, (ar=5) is executed. the natural convection effect is sustained by subjecting the bottom wall to a higher temperature than its top counterpart. in addition, the two horizontal walls of the enclosure are moving in different directions and the two vertical ...

the concept of  -semihyperring is a generalization of semiring, a generalization of semihyperring and a generalization of      -semiring. since the theory of ideals plays an important role in the theory of  - semihyperring, in this paper, we will make an intensive study of the notions of noetherian, artinian, simple and   regular      -semihyperrings. the bulk of this paper...

While there has been some research on the parliamentary enclosure of upland waste in England and Wales during the eighteenth and nineteenth centuries, this topic still receives little attention in some recent accounts of parliamentary enclosure. Many aspects of the processes involved, and their impact on the landscape, are also poorly understood. Much research has proceeded either at a very gen...

Lithocarpus dahuoaiensis Ngoc & L. V. Dung, a new species from the Central highland of Vietnam, is described and illustrated. The new species is morphologically similar to Lithocarpus macphailii (M. R. Hend.) Barnett or Lithocarpus encleisocarpus (Korth.) A. Camus in having completely entire leaf margin, solitary cupule, long stalks of fruits, deeply cup-shaped or turbinate cupules, with a numb...

Engaging middle school youth in STEM curricula resulting in desired conceptual changes is challenging. Furthermore, social media are identified as platforms where youth naturally congregate for sustained interaction. Studio STEM was designed as an after school programme to engage learners (ages 11–15) in design-based science inquiry within a studio environment, enhanced by social media and digi...

Active control of sound can be employed globally to reduce noise levels in an entire enclosure, or locally around a listener‘s head. Recently, spherical loudspeaker arrays have been studied as multiple-channel sound sources capable of generating sound fields with high complexity. In this paper, several aspects of using a spherical loudspeaker array for local active control of sound are investig...