Cork Boards Research Articles

Ten years of classroom acoustical design

Bradley found [J. Acoust. Soc. Am. 80, 837–845] with word score tests that S/N and room reverberation time (RT) affect speech intelligibility, and that computed U50 [J. Acoust. Soc. Am. 80, 846–854] was maximum for rooms having RT<0.6 sec and quieter than 35 dBA. This was applied to teleconferencing rooms [J. Acoust. Soc. Am. 111, 2411(A)], and classrooms for distance learning [J. Acoust. Soc. Am. 107, 2861(A)]. Economic strategies to reduce classroom RT and HVAC noise were developed. RT from 0.5 to 0.7 s and NC less than 30 are economically achieved: Absorption is provided by acoustical ceiling tiles of NRC>0.6. Carpets help. Chalk and cork boards provide some wall absorption, while in-use posters and book storage add more later. Central air handling systems promote NC-25 HVAC design. Noisy supply (VAV) air boxes are placed in the corridor ceiling. The transmitting manifold is lined. A flexible duct link to diffusers provides more noise attenuation at no added cost. Larger supply air diffusers satisfy NC-25. Common ceiling return air plenums compromise noise isolation between classrooms. High CAC ceiling tiles and return air openings near the room center provide NIC>40 versus recommended NIC50. Sketches and some cost estimates are provided.

Densification of black agglomerate cork boards and study of densified agglomerates

This work is related to a study about the densification of black agglomerate cork boards, through the development of a densification process and changing of different operational parameters. The densification allows a diversification of the fields of application for this material, shown by the densified products characteristics. The densification process is easy to use by the existing industries, and shows up and downstream advantages and a competing utilisation. This process gave rise to a patent application.

皮膚／木質材料界面における熱挙動のシミュレーション

This paper deals with the simulation of thermal behavior at a boundary between skin and woody materials when the woody materials laid over a cement mortar block are in contact with a man's palm. Plywoods, MDF (medium density fiberboards), and cork boards with different thickness were used as the overlays. Changes in temperature at the skin-overlay-underlayment interfaces were measured with thermo-couples at 10 to 30sec intervals. Furthermore, a thermal transfer model based on a numerical method with finite differences was proposed to analyze the changes in temperature and rate of heat transfer at the interfaces. Thermal constants for the model were obtained by fitting them with the experimental values. Then the changes in temperature and rate of heat transfer were simulated by this model for various overlay materials having different thickness. Not only the model is able to obtain the thermal behavior at the interfaces in good agreement with the experimental results on the samples of various woody materials, but also it is valuable to estimate the sensory warmth felt by man's palm in contact with the surface of the overlays, since both the temperature at the skin surface and the heat transfer across the boundary are highly related with the sensory warmth.

Growth stresses and strains in cork

A detailed study of the growth stresses and strains in the cork shell of the cork-oak was undertaken based on experimentally determined constitutive relations for cork in tension and compression. The stresses depend on the thicknesses of the cork shell and of the back layer around the cork shell, on the radius of the trunk and on its increase due to growth. The circumferential stresses in the cork shell and back layer are tensile and increase with increasing distance to the tree axis. The radial stresses are compressive and decrease with increasing distance to the tree axis. The strains due to growth are not recovered when the cork boards are removed, unless the boards are heated, for example, by immersion in boiling water. Other consequences of the growth stresses are analysed, such as the occurrence of corrugations in the lateral cell walls of cork, the variation of width of the successive growth rings and the occurrence of cracks in the back layer and outer cork layers.

液態空氣を利用する低温用恒温凾と低温用引張並に硬度試驗器

An increasing demand of making use of sub-zero temperatures in the scientific as well as in the industrial field has brought an growing activity to the study of the properties of metals and alloys at low temperatures, especially, of their mechanical properties. Here is described the construction of a cryostat-box whose wall is made of carbonized cork boards. The interior of this box can be cooled, by the aid of liquid nitrogen, down to -130°, and preserve it with the accuracy, a few tenth -of one degree. In this cryostatat-box is placed a portable type tensometer, i.e. a small size testing machine, the construction and the manipulation of which are also explained here.