Extraction of chemical information of suspensions using radiative transfer theory to remove multiple scattering effects : application to a model two-component system

An approach for removing multiple light scattering effects using the radiative transfer theory (RTE) in order to improve the performance of multivariate calibration models is proposed. This approach is then applied to the problem of building calibration models for predicting the concentration of a scattering (particulate) component. Application of this approach to a simulated four component system showed that it will lead to calibration models which perform appreciably better than when empirically scatter corrected measurements of diffuse transmittance (Td) or reflectance (Rd) are used. The validity of the method was also tested experimentally using a two-component (Polystyrene-water) system. While the proposed method led to a model that performed better than that built using Rd, its performance was worse compared to when Td measurements were used. Analysis indicates that this is because the model built using Td benefits from the strong secondary correlation between particle concentration and pathlength travelled by the photons which occurs due to the system containing only two components. On the other hand, the model arising from the proposed methodology uses essentially only the chemical (polystyrene) signal. Thus this approach can be expected to work better in multi-component systems where the pathlength correlation would not exist

Understanding Learning Style Variations among Undergraduate Students

A study was conducted in Vellore district of Tamil Nadu state to understand the learning styles of students. The term learning style refers to the way or method or approach by which a student learns. The study explored the possible learning style variations among agricultural, horticultural, engineering and arts & science students and their association with academic achievement. One hundred and twelve students were randomly selected from the four streams and their learning styles were analyzed. In the agricultural and horticultural streams, a majority of the students were auditory learners. They were also found to be predominantly unimodal learners. Overall, it was found that majority of the students were visual learners followed by auditory and kinesthetic style. The highest percentage of kinesthetic learners was found among engineering students. Trimodal learners scored the highest mean percentage of marks. The influence of learning styles on the academic achievements of the students did not show a significant relationship

Full correction of scattering effects by using the radiative transfer theory for improved quantitative analysis of absorbing species in suspensions

Sample-to-sample photon path length variations that arise due to multiple scattering can be removed by decoupling absorption and scattering effects by using the radiative transfer theory, with a suitable set of measurements. For samples where particles both scatter and absorb light, the extracted bulk absorption spectrum is not completely free from nonlinear particle effects, since it is related to the absorption cross-section of particles that changes nonlinearly with particle size and shape. For the quantitative analysis of absorbing-only (i.e., nonscattering) species present in a matrix that contains a particulate species that absorbs and scatters light, a method to eliminate particle effects completely is proposed here, which utilizes the particle size information contained in the bulk scattering coefficient extracted by using the Mie theory to carry out an additional correction step to remove particle effects from bulk absorption spectra. This should result in spectra that are equivalent to spectra collected with only the liquid species in the mixture. Such an approach has the potential to significantly reduce the number of calibration samples as well as improve calibration performance. The proposed method was tested with both simulated and experimental data from a four-component model system

Implementation of a MSP430-based ultrasonic distance measurement module

This application report describes a distance-measuring system based on ultrasonic sound utilizing the MSP430F413 ultralow-power microcontroller. The system transmits a burst of ultrasonic sound waves towards the subject and then receives the corresponding echo. The MSP430 integrated analog comparator Comparator_A is used to detect the arrival of the echo to the system. The time taken for the ultrasonic burst to travel the distance from the system to the subject and back to the system is accurately measured by the MSP430. Assuming the speed of sound in air at room temperature to be 1100 ft/s, the MSP430 computes the distance between the system and the subject and displays it using a two-digit static LCD driven by its integrated LCD driver. The distance is displayed in inches with an accuracy of ±1 inch. The minimum distance that this system can measure is eight inches and is limited by the transmitter’s transducer settling-time. The maximum distance that can be measured is ninetynine inches. The amplitude of the echo depends on the reflecting material, shape, and size. Sound-absorbing targets such as carpets and reflecting surfaces less than two square feet in area reflect poorly. The maximum measurable range is lower for such subjects. If the amplitude of the echo received by the system is so low that it is not detectable by the Comparator_A, the system goes out of range. This is indicated by displaying the error message E

Thermodynamic properties of Pb determined from pressure-dependent critical-field measurements

We have carried out extensive low-temperature (1.5 to 10 K) measurements of the critical field, $H_c$, for the element Pb up to a pressure of $P=1.2$ GPa. From this data the electronic entropy, specific heat, thermal expansion coefficient and compressibility is calculated as a function of temperature, pressure and magnetic field. The zero-field data is consistent with direct thermodynamic measurements and the $P$-dependence of $T_c$ and specific heat coefficient, $\gamma(T,P)$ allows the determination of the $P$-dependence of the pairing interaction.Comment: 5 pages, 6 figures, in press Phys. Rev.