Multivariate statistical analysis of Raman images of a pharmaceutical tablet

This paper describes the application of principal component analysis (PCA) and independent component analysis (ICA) to identify the reference spectra of a pharmaceutical tablet's constituent compounds from Raman spectroscopic data. The analysis shows, first with a simulated data set and then with data collected from a pharmaceutical tablet, that both PCA and ICA are able to identify most of the features present in the reference spectra of the constituent compounds. However, the results suggest that the ICA method may be more appropriate when attempting to identify unknown reference spectra from a sample. The resulting PCA and ICA models are subsequently used to estimate the relative concentrations of the constituent compounds and to produce spatial distribution images of the analyzed tablet. These images provide a visual representation of the spatial distribution of the constituent compounds throughout the tablet. Images associated with the ICA scores are found to be more informative and not as affected by measurement noise as the PCA based score images. The paper concludes with a discussion of the future work that needs to be undertaken for ICA to gain wider acceptance in the applied spectroscopy community.     

Unveiling Molecular Changes in Water by Small Luminescent Nanoparticles

Nowadays a large variety of applications are based on solid nanoparticles dispersed in liquids—so called nanofluids. The interaction between the fluid and the nanoparticles plays a decisive role in the physical properties of the nanofluid. A novel approach based on the nonradiative energy transfer between two small luminescent nanocrystals (GdVO₄:Nd³⁺ and GdVO₄:Yb³⁺) dispersed in water is used in this work to investigate how temperature affects both the processes of interaction between nanoparticles and the effect of the fluid on the nanoparticles. From a systematic analysis of the effect of temperature on the GdVO₄:Nd³⁺ → GdVO₄:Yb³⁺ interparticle energy transfer, it can be concluded that a dramatic increase in the energy transfer efficiency occurs for temperatures above 45 °C. This change is properly explained by taking into account a crossover existing in diverse water properties that occurs at about this temperature. The obtained results allow elucidation on the molecular arrangement of water molecules below and above this crossover temperature. In addition, it is observed that an energy transfer process is produced as a result of interparticle collisions that induce irreversible ion exchange between the interacting nanoparticles.     

Internal multiple-scattering hole-enhanced Raman spectroscopy: improved backscattering Fourier transform Raman sampling in pharmaceutical tablets utilizing cylindrical-conical holes

The benefits of Raman signal enhancement and improved measurement precision are demonstrated using 180° backscattering Fourier transform Raman (FT-Raman) spectroscopy from drilled cylindrical-conical holes within pharmaceutical tablet cores. Multiple scattering of the incident laser light within the holes results in an increased Raman signal due to the larger Raman sampling volume. This is important for overcoming typical sub-sampling issues encountered when employing FT-Raman backscattering of heterogeneous pharmaceutical tablets. Hole depth and diameter were found to be important experimental parameters and were optimized to yield the greatest signal enhancement. The FT-Raman spectra collected using backscattering from cylindrical-conical holes is compared to typical 180° backscattering from flat surfaces using tablet cores of Excedrin? and Vivarin?. Raman chemical images are used to establish a representative sampling area. We observe a three- to five-fold increase in the Raman intensity and a two-fold improvement in the measurement precision when sampling from cylindrical-conical holes rather than classic backscattering from flat tablet cores. Self-absorption effects on analyte band ratios are negligible in the fingerprint region but are more significant at the higher near-infrared (NIR) absorbances found in the C-H/O-H/-N-H stretching region. The sampling technique will facilitate developing quantitative FT-Raman methods for application to pharmaceutical tablets using the fingerprint spectral region.     

Advances in Switched-Mode Power Conversion Part I

A new concept in the design of switched-mode power conversion circuitry is presented. Because of its extreme simplicity, flexibility, and efficiency, it has the potential to replace some conventional electrical power processing methods currently in use. A thorough discussion of the background, development, and operation of the ?uk converter and several of its extensions is included. The coupled-inductor technique further improves efficiency and reduces size and weight. The basic converter and its extensions to two-quadrant and four-quadrant operation are attractive for many applications, i.e., solar (dc) to utility line (ac) power conversion, variable speed dc or ac motor drives, switching power supplies, uninterruptible power supplies, and many others.     

Two Algorithms for Determining the Most Reliable Path of a Network

This paper presents two algorithms for determining the most reliable paths of a communication network, taking into account both the reliabilities of nodes and links. A network is modeled by a linear graph. The first algorithm adapts a node labeling scheme; second is based on the shortest-path matrix algorithm. Both algorithms can be applied to oriented and nonoriented nonsymetric networks. The numerical examples confirm that both algorithms efficiently handle networks with hundreds of nodes and edges. The total amount of computation, expressed by the number of multiplications and comparisons, increases in the labeling procedure with the square of the number of nodes, and in the matrix method with the cube of the number of nodes.     

Development of new models for the estimation of deformation moduli in rock masses based on in situ measurements

Bulletin of Engineering Geology and the Environment - Knowledge of the deformation properties of the rock mass is essential for the stress–strain analysis of structures such as dams, tunnels,...     

A new experiments-based methodology to define the stability threshold for any vehicle exposed to flooding

A vehicle exposed to flooding, after losing stability, becomes buoyant and may be washed away with potential injuries and fatalities. Such vehicles cause additional disruption to traffic that is already affected by flooding, which may lead to substantial indirect economic impact, especially in urban areas. Therefore, the analysis of the stability of vehicles exposed to flooding is important in order to make decisions to reduce damages and hazards. In this research, based on an experimental campaign that included a range of twelve car models, a new methodology to obtain the stability threshold for any real vehicle exposed to flooding is developed. A stability coefficient (SC_mod) is derived with which the vehicles can be sorted by stability against water flows and their stability functions may be determined. The experiments were conducted with three different model scales (1:14, 1:18 and 1:24) and involved analysis of both friction and buoyancy effects, which made this the most comprehensive research study to date. This methodology enables the definition of a stable area in the flow depth-velocity domain for any real vehicle. A tool is provided that decision-makers in the field of urban flood risk management can employ and after defining a design vehicle they can obtain its corresponding stability threshold.     

Development of an independent hydrology audit methodology to support flood risk assessment in the planning process in Scotland

The recent flooding in the North–East of Scotland has highlighted issues around climate change due to significant changes in duration, severity and volume of precipitation events. The Planning (PA) and Flood Authorities (FA) often do not have the capacity or resources to review and check the accuracy and robustness of the SUD schemes nor the calculations submitted by developers. This study demonstrates the development and application of an Independent Hydrology Audit (IHA) service aimed at auditing and reviewing ‘in principle’ planning applications from the aspect of flooding risk to the wider community the development is located within. The output of this service is to establish a more accurate representation of surface water impact from developments through the use of adequate green/blue infrastructure, provide a greater assurance to the communities at risk of flooding, and help the PA and FA meet their statutory obligations at the initial stage of planning.