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The quality of latex solution harvested from a para rubber tree is determined by the amount of dry rubber content (DRC). In this work, we propose the use of an ultrasonic pulse for quantifying the DRC in latex solution. Fresh latex solutions are acquired locally from different regions in the south of Thailand. The DRC of the solutions is evaluated for calibration purposes by the standard technique as recommended in ISO126:2005. Along with the calibration experiment, the ultrasonic pulse experiment is performed on the same set of the solutions in cylindrical tubes of different lengths. The ultrasonic pulse transverse longitudinally through the tubes which are fully contained with the latex solutions. Ultrasonic speeds and spatial attenuations for different dry rubber contents can then be obtained. Our results reveal that the ultrasonic speed and spatial attenuation are linearly proportional to the amount of dry rubber content in latex solution. Using the empirical relationship between the spatial attenuation and the DRC, we can predict the DRC with the accuracy comparable to that of the microwave-drying technique. Given the size of the tube, our setup is relatively small and can be portable

We propose the use of the image analysis technique to determine the surface tension of water and the attenuation coefficients of surface water waves in terms of frequency. Tap water from two different locations is used in our experiments. Water waves are continuously generated at various frequencies in a ripple tank by a plastic blade driven by a function generator. Images of the water waves are then captured by a digital camera and analyzed by using Tracker. As a result, we obtain the surface tension of water at 25°C from both locations that are in good agreement with those resulting from the capillary rise technique. In addition, a linear relationship between the attenuation coefficient of the water waves and driven frequencies, ranging from 40 to 90 Hz, can be observed. Our results indicate that the greater the surface tension the longer distance the water wave takes before its amplitude decreases to 1/e of its original value. This work brings forward a relatively simple technique that can be applied to determine the surface tension and attenuation coefficients of surface water waves in a ripple tank with notable results. PACS Nos.: 47.80.-J, 92.40.Qk, 68.03.Cd. Resume : Nous proposons une technique d'analyse d'image pour determiner la tension superficielle de l'eau et le coefficient d'attenuation des vaguelettes de surface en fonction de la frequence. Nous utilisons ici de l'eau du robinet provenant de deux lieux differents. Les ondes sont generees continuellement a differentes frequences dans un reservoir d'ondulation a l'aide d'une bande de plastique actionnee par un generateur de fonction. Des images des vaguelettes sont captees par une camera numerique et analysees par le logiciel Tracker. Nous en tirons des valeurs de tension superficielle a 25°C pour les deux echantillons d'eau, qui sont en bon accord avec les resultats obtenus de la technique de l'effet capillaire. Nous observons aussi une relation lineaire pour le coefficient d'attenuation en fonction de la frequence entre 40 et 90 Hz. Nos resultats indiquent que plus la tension superficielle est elevee, plus loin voyagent les vaguelettes, avant que leur amplitude soit reduite a 1/e de leur valeur initiale. Ce travail propose une technique relativement simple, utilisable pour obtenir de bonnes valeurs de tension superficielle et du coefficient d'attenuation des vaguelettes. [Traduit par la Redaction], 1. Introduction Surface water waves are possibly the most common example for imparting the physical concepts of waves to students because they can be visually perceived. In general, the demonstration [...]

The Old Historical Wall, located in Bo Yang, Songkhla Province, Thailand, is an archaeological icon believed to have been constructed during the reign of Rama III, as indicated in the royal archives, around 1837-1840 CE. However, the recorded age is the result of unofficial documentation. The establishment was based on speculation from circumstantial evidence and local stories. The wall is made of bricks that underwent a heating process before being used for the construction. We therefore propose the use of the thermoluminescence technique for dating the wall. The samples include brick rubble from three excavation sites next to the wall. To determine the age, we estimate the radiation dose rate and the accumulated dose for each sample. The dose rate of the sample is determined using gamma spectroscopy with a high-purity germanium detector. For the accumulated dose, we employ the additive dose method using Co-60 with a dose range of 0-100 Gy. Glow curves are then deconvoluted using the general-order kinetics model. The results yield three superposition glow peaks at three different temperature ranges. Plateau tests are also carried out to find a proper temperature for dating purposes. Comparing the plateau test and the result of deconvolution, we find that the glow curve temperature suitable for dating was within 200-310 °C. The accumulated doses are then evaluated using the area under the curve of the peak temperature. The date is then determined as the ratio between the accumulated dose and the dose rate. The results indicate that the age is approximately 174-192 years, so that the wall was built around 1827-1841 CE, with one standard deviation interval. The duration is in agreement with the recorded age of the wall inscribed in the country's historical archives., Competing Interests: The authors declare no conflict of interest., (© 2021 Published by Elsevier Ltd.)

The aim of this study was to improve the antifungal activity of the volatile Litsea cubeba essential oil and its main components (citral and limonene) on brown rice snack bars by applying He-Ne laser treatment. Different volumes (50-200 μL) of L. cubeba, citral or limonene were absorbed into a filter paper and placed inside an oven (18 L). Ten brown rice snack bars (2 cm wide × 4 cm long × 0.5 cm deep) were put in an oven and heated at 180 °C for 20 min. The shelf-life of the treated snack bars at 30 °C was assessed and sensory testing was carried out to investigate their consumer acceptability. A count of total phenolic content (TPC) and Fourier transform infrared spectroscopy (FTIR) on the properties of essential oil, citral, and limonene before and after the laser treatment was studied for possible modes of action. It was found that the laser treatment improved the antifungal activity of the examined volatile L. cubeba and citral with Aspergillus flavus inhibition by 80% in comparison with those of the control not treated with the laser. L. cubeba vapor at 100 μL with the laser treatment was found to completely inhibit the growth of natural molds on the snack bars for at least 25 days; however, without essential oil vapor and laser treatment, naturally contaminating mold was observed in 3 days. Results from the sensory tests showed that the panelists were unable to detect flavor and aroma differences between essential oil treatment and the control. Laser treatment caused an increase in TPC of citral oil whereas the TPC in limonene showed a decrease after the laser treatment. These situations could result from the changing peak of the aliphatic hydrocarbons that was revealed by the FTIR spectra., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Thermal diffusion, also known as the Ludwig-Soret effect, refers to the separation of mixtures in a temperature gradient. For a binary mixture the time dependence of the change in concentration of each species is governed by a nonlinear partial differential equation in space and time. Here, an exact solution of the Ludwig-Soret equation without mass diffusion for a sinusoidal temperature field is given. The solution shows that counterpropagating shock waves are produced which slow and eventually come to a halt. Expressions are found for the shock time for two limiting values of the starting density fraction. The effects of diffusion on the development of the concentration profile in time and space are found by numerical integration of the nonlinear differential equation.

The Ludwig-Soret effect or thermal diffusion, which refers to the separation of liquid mixtures in a temperature gradient, is governed by a nonlinear, partial differential equation in space and time. It is shown here that the solution to the nonlinear differential equation for a binary mixture predicts the existence of shock waves completely analogous to fluid shocks and obeys an expression for the shock velocity that is an exact analogue of the Rankine-Hugoniot relations. Direct measurements of the time dependent, spatial absorption profile of a suspension of nanometer sized particles subjected to a sinusoidal temperature field generated by a pair of continuous laser beams, as well as self-diffraction experiments, show motion of the particles in agreement with the predictions of nonlinear theory.

Separation of liquid mixtures in a thermal gradient, known as the Ludwig-Soret effect or thermal diffusion, is governed by a nonlinear, partial differential equation. It is shown here that the nonlinear differential equation for a binary mixture can be reduced to a Hamiltonian system of equations and that a solution can be obtained for the linear problem. The calculation gives a closed form expression for the space and time dependence of the concentration profile of the mixture, valid at short times.

The quantum-cascade laser can be used as an infrared source for a small portable photoacoustic trace gas detector. The device that we describe uses a quantum-cascade laser without collimating optics mounted inside an acoustic resonator. The laser is positioned in the center of a longitudinal resonator at a pressure antinode and emits radiation along the length of the resonator exciting an axially symmetric longitudinal acoustic mode of an open-ended cylindrical resonator. Experiments are reported with an 8-microm, quasi-cw-modulated, room-temperature laser used to detect N2O.