Microstructure and physico-chemical transformation of some common woods from Cameroon during drying

Journal of Thermal Analysis and Calorimetry - The influence of drying on the microstructure, physical and chemical properties of some tropical wood species has been investigated using...     

Equivalent level of railroad noise with and without barrier

This paper presents models for predicting the equivalent level, $\text{L}{}_{\mathrm{<mtext>eq</mtext>}}$ of railroad noise. For open terrain two cases are considered: with and without ground effects (second section). On the assumption that, at a given point, $\text{L}{}_{\mathrm{<mtext>eq</mtext>}}\text{= L}{}_{\mathrm{<mtext>eq</mtext>}}{}^{\mathrm{*}}$ is required, the problems of barrier length, height and position are discussed (third section). Examples of the application of presented theories are given.     

Prognosis for urban noise in the United States—The present to 1990

A forecast of $\text{L}{}_{\mathrm{dn}}$ changes within the residential areas of constant population density is made in terms of external noise levels ($\text{L}{}_1\text{L}{}_2$) and ‘vehicle travels’ ($\text{N}{}_1\text{N}{}_2$) for cars, trucks and buses. Anticipated increases of $\text{N}{}_1$ and $\text{N}{}_2$ have been estimated by the use of trend line analysis (Figs. 3 and 4). A few hypotheses of $\text{L}{}_1$ and $\text{L}{}_2$ decrease have been considered. Increase of $\text{L}{}_{\mathrm{dn}}$ by more than 3 dB may be expected until 1993.     

Estimation of the long term average sound level from hourly average sound levels

It is shown how to estimate the long-term average sound level, L_AeqLT (for free flowing road traffic) from measurements of the hourly A-weighted equivalent sound level, L_Aeq1h. To estimate the parameters of the model which describe noise emission and attenuation, concurrent measurements of L_Aeq1h at two distances from the considered road are needed. A semi-empirical formula is derived for L_AeqLT approximation. Also the uncertainty of this approximation is given as a function the distance from the road and receiver height.     

The annual average sound level of road traffic noise estimated from the speed-flow diagram

The speed-flow diagram correlates traffic speed and traffic flow on a road. The presented method enables estimation of the annual average sound level of the road traffic noise when the characteristics of the diagram are available: traffic flow capacity, free traffic speed, and traffic capacity speed (Fig. 1). Bunches of vehicles decrease the traffic speed and traffic noise.     

Road traffic noise prediction based on speed-flow diagram

The method enables calculation of the annual average sound level of the road traffic noise, when the characteristics of the speed-flow diagram are available: the average speed of freely cruising vehicles, capacity of the traffic flow, traffic speed at the traffic flow capacity, and the slope of the decreasing traffic speed versus traffic flow. Under any conditions, traffic congestion reduces the annual average sound level. The final conclusion is that strong traffic congestion cannot be ignored in noise prediction.     

Predicted effects of a speed bump on light vehicle noise

A speed bump reduces traffic noise levels during the deceleration phase and increases them during the acceleration phase. The net effect of a speed bump on noise from a light vehicle is assessed by means of the concept of noise energy density, S. This is a function of the instantaneous distance between the vehicle and the bump, S(x). To determine the function S(x) explicitly, five measurements of the sound exposure level, for each vehicle, are needed. It is assumed that the noise from each vehicle is generated by a single non-directional point source and propagates without vertical-surface reflections. An example prediction is presented based on measurements of sound exposure levels due to passenger cars.     

Is a wind turbine a point source? (L)

Measurements show that practically all noise of wind turbine noise is produced by turbine blades, sometimes a few tens of meters long, despite that the model of a point source located at the hub height is commonly used. The plane of rotating blades is the critical location of the receiver because the distances to the blades are the shortest. It is shown that such location requires certain condition to be met. The model is valid far away from the wind turbine as well.     

Prediction of noise changes due to traffic speed control

The effects of vehicle speed variation on road traffic noise are analyzed. The steady speed motion is replaced by deceleration, cruise, and acceleration. Because of a relatively loud acceleration noise, such a speed variation results not only in the noise decrease zones, but in the noise increase zones as well. The location of these zones depends slightly upon the ground covering (grass, concrete, etc.). Conversely, their boundaries change dramatically with the parameters describing noise emission during deceleration, cruise, and acceleration. For example, the Japanese and Polish models of noise emission have been applied. The critical length L(*) of the cruise segment of the road is introduced: for L>L(*) the sound energy decline (due to speed reduction) compensates the sound energy growth (due to acceleration). The results obtained could be useful for road administrators.     

Antiproliferative and cytotoxic secondary metabolites from fruits of Leplaea mayombensis

Two new seco-lanostane-type triterpenes, named mayomlactones A (1) and B (2) were isolated from the fruits of Leplaea mayombensis together with 10 known compounds (3–12). Structures of the new compounds were elucidated by extensive spectroscopic studies. Except compounds 11 and 12, all the other chemical compounds are newly reported from Leplaea genus. From the results of this investigation, compounds 1–10 were examined for antiproliferative activity against HeLa cells as well as cytotoxicity against 3T3 cell line. Compounds 3 and 4 showed moderate antiproliferative activity with IC₅₀ values of 10.4 ± 0.1 and 18.6 ± 0.2 μM, respectively. On the other hand, compounds 1, 4 and 9 showed weak cytotoxicity with IC₅₀ values 44.1 ± 0.5, 55.8 ± 0.7 and 55.1 ± 0.5 μM. Overall, none of the tested compounds showed good selectivity (SI ranging from 0.51 to 3.06) but high toxicity against the 3T3 cell line.