Direct Analysis Method Research Articles

Development of a decentralized nonlinear controller for a class of uncertain polynomial interconnected systems: Application for a large scale power system

This paper presents a new robust decentralized control of nonlinear interconnected systems, which is applied and validated on a large scale power system. Our work is performed in three steps. Firstly, we have developed the polynomial description of the nonlinear uncertain and interconnected system using odd Kronecker power of state vectors, which is an easy-manipulation model for such complex systems. Then we applied Lyapunov’s direct method of stability analysis, associated with a quadratic function, in order to determine a sufficient condition for global asymptotic stability by applying a nonlinear, decentralized and optimal polynomial control. Finally, we carried out a simulation study on a nonlinear uncertain power system with three interconnected machines. We considered different cases of perturbations on its state variables as well as different cases of fault locations. We prove via advanced simulations, the effectiveness of the proposed control technique which is able to mitigate the successive amplitudes of the oscillations, to limit the control actions and to enhance the power system transient stability.

Depletion chain optimization of lattice code STREAM for LWR fuel assembly burnup analysis

A depletion chain simplification method is applied to UNIST lattice code STREAM (Steady state and Transient REactor Analysis code with Method of Characteristics) in this paper to alleviate the computational burden of depletion calculation associated with a large depletion matrix. A simplified burnup matrix (burnup chain) of 464 nuclides and 10,638 transitions is thus created from a large detailed burnup matrix containing 3,837 nuclides and 43,416 transitions from ENDF/B-VII.0 nuclear decay data. The simplified burnup matrix is optimized for the purpose of calculating effective neutron multiplication factors (keff) and power distributions with reduced computation time and memory usage. The nuclide selection method relies on the Generalized Perturbation Theory (GPT): by exploiting the adjoint function of nuclide number densities as derived with GPT, a set of nuclides which must be included in the simplified chain (nuclides with important contribution to reactivity) is determined. Numerical verification of the simplified burnup chain is conducted using the deterministic neutron transport analysis code STREAM, developed to perform whole light water reactor (LWR) core calculations with the direct transport analysis method and the two-step method. The simplified burnup chain is tested on the 16 LWR fuel assembly depletion problems from the Virtual Environment for Reactor Application (VERA) benchmarks, including burnable poison (BP) pin cells commonly used in nuclear reactor design such as gadolinia, Pyrex, AIC, B4C and IFBA, and one OPR-1000 fuel assembly with gadolinium bearing fuel depletion problem. For burnup up to 80 MWd/kg and 235U enrichment ranging from 2.1 w/o to 4.6 w/o, the calculations with the simplified burnup chain predict the keff variations within 10 pcm and identical power distributions, with a speed-up factor from 20 to 40 in depletion calculation and a reduction factor by 3–4 of the total simulation time compared to the ones with the detailed burnup chain.

Notch pathway connections in primary leukaemia samples of limited size

BackgroundThe Notch pathway combined with other signalling molecules acts specifically for the development of each blood cell type and differentiation stage. A causative role of Notch dysfunction in leukaemia development has been found in many studies so, initially only for T- acute lymphoblastic leukaemia (T-ALL) but more recently also for B cell and myeloid leukaemia. The aim of our study is to introduce a method for multiple direct analysis of the Notch pathway partners in a population of only 500 or fewer cells. The notion of this method consists in gaining insight into gene expression at the level of the malignant clone population. A small number of cells is a significant limitation when working on primary cells either when freshly isolated or when analysed after several days in cocultures.MethodsThe primers were designed to avoid genomic amplification through the selection of 3′ and 5′ primers that hybridise with different exons. Cell lines and primary cells were collected and multiplex quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) performed on a descending number of cells, ranging from 2,500 cells up to 50 cells per sample, for the Notch pathway genes and other transcription factors important for cell differentiation. ImageJ program, STATISTICA 13.1 software package and Student’s t-test were used for statistical evaluation. We checked protein expression by western blot.ResultsWe characterised the gene expression levels of Notch, Ikaros and Parp genes in leukaemia cell lines of B and T origin and in primary leukaemia samples of limited size. We further compared our results to the cDNA analysis obtained by total RNA isolation from a large number of cells as routinely performed in clinical laboratories, and finally tested the method described on primary cells from leukaemia patients.ConclusionsThis rapid multiple gene expression analysis of a small population of cells provides efficient cell classification determining malignant changes as an important additional information for clinical leukaemia diagnostics as well as for in vitro studies of primary cells.

Validation of a method for analysis of glyphosate and AMPA in drinking water using ion chromatography

A análise de resíduos de agrotóxicos em água é um dos requisitos da legislação de potabilidade ligadas à saúde humana. A análise de cromatografia iônica (CI) é uma alternativa técnica que vem contribuir para quantificação do herbicida glifosato e seu metabólito ácido amino metil fosfônico (AMPA) em água de consumo humano por ser rápida de preparo (filtrar e injetar), alta seletividade, boa precisão e exatidão. Esta pesquisa tem como objetivo desenvolver e validar este método para análise direta destes agrotóxicos, sem etapa de tratamento da amostra ou derivatização. Na validação proposta foram considerados os parâmetros de seletividade, exatidão e precisão, limites de detecção e quantificação, linearidade e estimativa de incerteza de medição. Os resultados obtidos indicaram que esta técnica é adequada e apresenta boa sensibilidade para a quantificação destes analitos na matriz água, sendo os resultados da validação apropriados frente aos limites máximos de concentração estipulados na Portaria 2914/11 do Ministério da Saúde.

A New Voltage Sensitivity Analysis Method for Medium-Voltage Distribution Systems Incorporating Power Losses Impact

—In this paper, a novel voltage sensitivity analysis method is proposed. It presents a complementary formulation of the direct sensitivity analysis approach which has been previously developed based on the topological structure of the network. The proposed method named improved direct sensitivity analysis (IDSA) incorporates variations of power losses in the system branches due to the nodal power changes and their eventual impacts on the node voltages. Effectiveness of the IDSA in voltage estimation is investigated and compared with the voltage results obtained by the direct, Jacobian-based, as well as the perturb-and-observe sensitivity analysis methods. To this end, firstly, the introduced sensitivity analysis methods are tested when active or reactive power is changed at the selected nodes of the studied test systems. Accuracy of voltage responses obtained by each of the considered sensitivity analysis methods is evaluated with respect to the exact voltage value obtained from the load flow study. Moreover, performance of the introduced sensitivity analysis methods is examined when they are separately embedded in a multi-step voltage control algorithm which manages active and reactive powers of distributed generation units in order to keep the system voltages within the permitted voltage limits. Simulation results confirm that when the power losses impact is considerable, the IDSA outperforms the direct, perturb-and-observe, and Jacobian-based sensitivity analysis methods in terms of accuracy of the voltage estimation.

Ultimate Load Capacity Analysis of Steel Scaffoldings Using Direct-Analysis Method

For ensuring the safe load capacity of steel scaffoldings, the ultimate load capacity analysis is performed including an experimental test and numerical modeling. The test is relatively costly; therefore, it is used specifically for small configurations. Then, the parametric methods based on the calibrated numerical modeling are used. The ultimate strength analysis of steel structure requires a sophisticated nonlinear inelastic computer analysis and cumbersome procedure. As an alternative, elastic second-order computer analysis and the direct analysis method (DAM) are tried. The loading is given incrementally, and at each stage the available strengths and required strengths are evaluated. The ultimate limit load is considered achieved when the available capacity in the critical member equals that required. It has been proven that the calibrated DAM can be used to trace the ultimate load well. It can even be used to evaluate the effectiveness of bracing or lateral support placements. It is important especially for multistory steel scaffoldings that belong to sway frames because their strengths are significantly influenced by the stability issues.

Barriers to accessing adequate maternal care in Georgia: a qualitative study

BackgroundThe maternal health outcomes in Georgia are linked to shortcomings in healthcare such as inequities in access to adequate maternal care. Due to the macro-level, quantitative approach applied in most previous studies, little is known about the underlying reasons that influence maternal care and care-seeking behaviour of pregnant women.MethodsThis qualitative study explores the stakeholders’ perspectives on access to adequate maternal care in Georgia. Focus-group discussions are conducted with mothers who gave birth within in the past four years and in-depth interviews are conducted with decision-makers and health professionals in the field. Five access-related aspects are studied: availability, appropriateness, affordability, approachability and acceptability of maternal care. The method of direct content analysis is applied.ResultsResults indicate problems with maternal care standards, inequalities across population groups and drawbacks in maternal care financing. This includes gaps in clinical quality and staff skills, as well as poor communication between women and health professionals. Geographical barriers to adequate maternal care exist in rural and mountainous areas due to the weak infrastructure (poor roads and weak transportation), in addition to financial hardships. Despite improvements in the coverage of maternal care, affordability remains an access barrier. Poorer population groups are financially unprotected from the high out-of-pocket payments for maternal care services.ConclusionThese findings imply that micro-level indicators, such as disrespectful behaviour of health professionals and affordability of care, should be taken into account when assessing maternal care provision in Georgia. It should complement the existing macro-level indicators for a comprehensive evaluation of maternal care.

Numerical investigation of the design of single‐span steel portal frames using the effective length and direct analysis methods

AbstractThe era of globalization enables the design, fabrication and erection of steel structures to take place in different locations far away from each other. Therefore, a widely acceptable steel design standard is required, and designers should be familiar with alternative specifications that may be considerably different from one another. This study deals with single‐span unbraced steel portal frames and makes a comparison between the design methodologies adopted by the Australian and American design provisions, in particular, the effective length method (ELM) and direct analysis method (DAM). A brief discussion on the main features of both standards is also presented. Furthermore, the results of the parametric study are portrayed, highlighting the differences between these two design standards regarding stress interaction. Finally, of the two aforementioned methods, the most applicable optimization method for the design and development of cost‐effective industrial portal frame buildings is proposed with respect to the structure geometry.

Study of Direct Finite Element Method of Analysing Soil–Structure Interaction in a Simply Supported Railway Bridge Subjected to Resonance

This paper presents the dynamic soil–bridge interaction under high-speed railway lines, under different soil stiffness conditions. Starting from the analysis of a simply supported Euler–Bernoulli beam model subjected to moving loads, a three-dimensional multi-body (soil–abutment–bridge–ballast–sleeper–rail) model formulated in the time domain to study the vibrations induced due to the passage of moving concentrated loads was analysed using the direct finite element method of soil–structure interaction analysis. The high-speed train was considered to be a set of concentrated loads, the rail was modelled as a Euler–Bernoulli beam (frame element), and the sleepers, ballast, bridge, abutments and soil were modelled using eight-node solid (brick) elements. Layered soil stratum’s effects on the dynamic response of the bridge deck and variation of stresses were studied. From this study, it was observed that the direct method of FE analysis can be an effective tool to solve the complex dynamic soil–structure interaction problems.

Direct differentiation method for sensitivity analysis based on transfer matrix method for multibody systems

SummaryOn one hand, the new version of transfer matrix method for multibody systems (NV‐MSTMM), has been proposed by formulating transfer equations of elements in acceleration level instead of position level as in the original discrete time transfer matrix method of multibody systems to study multibody system dynamics. This new formulation avoids local linearization and allows using any integration algorithms. On the other hand, sensitivity analysis is an important way to improve the optimization efficiency of multibody system dynamics. In this paper, a totally novel direct differentiation method based on NV‐MSTMM for sensitivity analysis of multibody systems is developed. Based on direct differentiation method, sensitivity analysis matrix for each kind of element is established. By assembling transfer matrices and sensitivity analysis matrices based on differentiation law of multiplication, the sensitivity analysis equation of overall transfer equation is deduced. The computing procedure of the proposed method is also presented. All these improvements as well as three numerical examples show that the direct differentiation method based on NV‐MSTMM is suitable for optimizing the dynamic sensitivity in multi–rigid‐body systems.

Beyond neutrality: disentangling the effects of species sorting and spurious correlations in community analysis

The methods of direct gradient analysis and variation partitioning are the most widely used frameworks to evaluate the contributions of species sorting to metacommunity structure. In many cases, however, species are also driven by spatial processes that are independent of environmental heterogeneity (e.g., neutral dynamics). As such, spatial autocorrelation can occur independently in both species (due to limited dispersal) and the environmental data, leading to spurious correlations between species distributions and the spatialized (i.e., spatially autocorrelated) environment. In these cases, the method of variation partitioning may present high Type I error rates (i.e., reject the null hypothesis more often than the pre-established critical level) and inflated estimates regarding the environmental component that is used to estimate the importance of species sorting. In this paper, we (1) demonstrate that metacommunities driven by neutral dynamics (via limited dispersal) alone or in combination with species sorting leads to inflated estimates and Type I error rates when testing for the importance of species sorting; and (2) propose a general and flexible new variation partitioning procedure to adjust for spurious contributions due to spatial autocorrelation from the environmental fraction. We used simulated metacommunity data driven by pure neutral, pure species sorting, and mixed (i.e., neutral+species sorting dynamics) processes to evaluate the performances of our new methodological framework. We also demonstrate the utility of the proposed framework with an empirical plant dataset in which we show that half of the variation initially due to the environment by the standard variation partitioning framework was due to spurious correlations.

Comparative Screening Analytic Methods for Elderly of Blood Methylmercury Concentration between Two Analytical Institutions

Methylmercury is widely known to be a toxic substance in the human, especially a nervous system. However, it is difficult to accurately measure the amount of methylmercury in blood, and the form of methylmercury is variously presented. The purpose of study was to compare the total mercury and methylmercury measurements techniques and detection levels between analytical institutions in two countries using the same elderly human blood samples. Total mercury using gold amalgamation direct mercury analysis method (both) and methylmercury using the dithizone extraction and gas chromatography-electron capture detector (GC-ECD) method (N Lab in Japan) and the cold vapor atomic fluorescence spectrophotometer (CVAFS) method (D Lab in Korea) were measured in 47 subjects who agreed to participate in this study. Total mercury concentrations in both analytical laboratories were observed at similar levels (9.4 versus 9.5 ug/kg, p=0.898) and the distribution was highly correlated. However, the concentration of methylmercury showed some difference between two laboratories (9.1 versus 8.6 ug/kg, p<0.001). Due to different recovery rates by different analytical methods, it is assumed that the methyl/total mercury ratio in N lab in Japan was higher than D lab in Korea (96.8 versus 90.4%, p<0.001). The GC-ECD was more sensitive method than CVAFS in methylmercury analytic techniques.

Individual identification using a gait dynamics graph

In this paper, we propose a new gait representation—gait dynamics graph (GDG) for individual identification. For each gait sequence, lower limbs joint angles are extracted as gait parameters, and gait system dynamics underlying time-varying gait parameter trajectories is captured by using deterministic learning algorithm. Gait dynamics graph (GDG) is then generated by plotting the extracted dynamics information into three-dimensional graphic. Unlike other gait representations, which are not embedded with dynamics information, GDG demonstrates nonlinear gait dynamics in a new, visually intuitive manner using three-dimensional graphic representation. Both direct matching method and nonlinear dynamics analysis method can be used for GDG recognition independently. The performance of the proposed representation is evaluated and compared with the other representations experimentally on five large benchmark gait databases. This kind of gait representation is embedded with more distinctive information and preserves temporal dynamics information of human walking, which does not rely on shape or silhouettes information. Experimental results show that the GDG representation can further improve recognition rates and avoid the great drop of recognition rate when the training and test sets are under different walking conditions.

Qualitative and quantitative analysis of Teucrium polium essential oil components by GC-MS coupled with MCR and PARAFAC methods.

Teucrium polium is a herbal plant which has curative potential and pharmacological characteristics. Therefore, establishment of accurate analytical methods for characterising its active components is of prime importance. Because of the complex nature of essential oil samples, some results of direct gas chromatography-mass spectrometry (GC-MS) analysis maybe unreliable. Therefore, GC-MS is coupled with chemometric methods to resolve experimental information taken from chromatographic peaks, and assign compounds to them more correctly. Essential oil of T. Polium of Koohbanan suburb (Kerman, Iran) was extracted by hydro-distillation. Then the T. polium essential oil was qualitatively analysed using GC-MS coupled with multivariate curve resolution (MCR), to resolve experimental information taken from chromatographic peaks, and assign compounds to them more correctly. After that, the method of parallel factor analysis (PARAFAC) was implemented to quantify the concentrations of five major components of the T. polium essential oil. The number of identified components increases from 74 using the direct method of analysis to 106 using the MCR method. It is shown that α-pinene (8.93μg/L), cis-verbenol (3.98μg/L) and myrtenal (1.02μg/L) are the most abundant components in the T. polium essential oil. By coupling GC-MS and chemometric resolution methods such as MCR-alternating least squares (ALS) and PARAFAC more information with higher precision and accuracy can be obtained from raw experimental data. Also, it is shown that by implementing the PARAFAC method on the GC-MS data, it is possible to measure the concentration of the constituents of co-eluted, overlapped or embedded chromatographic peaks.

3-dimensional environmental contours based on a direct sampling method for structural reliability analysis of ships and offshore structures

ABSTRACTThis paper derives a simple way of calculating 3-dimensional environmental contours for structural reliability assessment and design of ships and offshore structures. The 3-dimensional contours are based on Monte Carlo sampling from the joint distribution of the input parameters for response calculations and are an extension of previously proposed 2-dimensional contours. The 3-dimensional contours offers a practical way of identifying multivariate joint extremes of relevant input variables in order to provide for analyses of extreme structural responses. The contour estimation method is applied to some simple example cases and is demonstrated to work well and give reasonable results. Hence, the 3-dimensional contours represent a practical tool for anyone involved in probabilistic structural reliability analysis and design of ships and offshore structures.

Direct analysis of textile dyes from trace fibers by automated microfluidics extraction system coupled with Q-TOF mass spectrometer for forensic applications

Textile fiber is a common form of transferable trace evidence at the crime scene. Different techniques such as microscopy or spectroscopy are currently being used for trace fiber analysis. Dye characterization in trace fiber adds an important molecular specificity during the analysis. In this study, we performed a direct trace fiber analysis method via dye characterization by a novel automated microfluidics device (MFD) dye extraction system coupled with a quadrupole-time-of-flight (Q-TOF) mass spectrometer (MS). The MFD system used an in-house made automated procedure which requires only 10μL of organic solvent for the extraction. The total extraction and identification time by the system is under 12min. A variety of sulfonated azo and anthraquinone dyes were analyzed from ∼1mm length nylon fiber samples. This methodology successfully characterized multiple dyes (≥3 dyes) from a single fiber thread. Additionally, it was possible to do dye characterization from single fibers with a diameter of ∼10μm. The MFD-MS system was used for elemental composition and isotopic distribution analysis where MFD-MS/MS was used for structural characterization of dyes on fibers.

Determination of aromatic amines in the urine of smokers using a porous organic framework (JUC-Z2)-coated solid-phase microextraction fiber

A solid-phase microextraction (SPME) fiber coated with a two-dimensional porous organic framework (POF), JUC-Z2, was synthesized by a sol-gel process. The JUC-Z2-coated SPME fiber was combined with gas chromatography-mass spectrometry/mass spectrometry (GC–MS/MS), and a direct analysis method without any derivatization step was developed for the determination of two major harmful aromatic amines (1-naphthylamine, 1-NA; 2-naphthylamine, 2-NA) in the urine of amokers. The new method exhibited satisfactory linearity in the wide range of 0.05–100 μg L−1 with correlation coefficients (R) of 0.9999. The limits of detection are 0.010 and 0.012 ng L−1. The relative standard deviations for repeated extraction (n = 6) with one fiber are less than 7.7%. The JUC-Z2-coated fiber demonstrates obviously superior extraction efficiencies for the two aromatic amines over the commercial fibers (CW/PEG, PA, PDMS/DVB, PDMS, CAR/PDMS, DVB/CAR PDMS). The structure-activity relationship was deeply investigated by the extraction comparison experiment with another similar POF material (PAF-48) and theoretical simulations. The extraction efficiencies of JUC-Z2 for 1-NA and 2-NA are 9.6 and 16.2 times higher than those of PAF-48, and JUC-Z2 has higher binding energies with the aromatic amines than PAF-48. The results indicate that the N atom on the JUZ-Z2 framework played a crucial role for adsorbing aromatic amines. Finally, the novel fiber has been successfully used to detect 1-NA and 2-NA in the urine of smokers.

Reflectance Spectrometry as a Screening Tool for Prediction of Lutein Content in Diverse Wheat Species (Triticum spp.)

Direct analytical methods assessing lutein content (e.g., high-performance liquid chromatography [HPLC]) are expensive and time-consuming. Their utilization in broad mapping of genetic resources or selecting among hundreds of breeding lines is limited. Therefore, the development of reliable predictive models based on reflectance spectrometry for assessing lutein content would be very useful. This study aims at finding a rapid and accurate lutein quantification method for wheat breeding purposes. Reference samples were represented by hexaploid, tetraploid, and diploid wheat species (119 accessions) cultivated in 2 years. The species Triticum aestivum L. predominated, with 81 accessions. Two near-infrared (NIR) spectroscopy devices were used to collect visible (VIS) and/or NIR spectra: the model FOSS 6500 with dispersive element and wavelength range 400–2500 nm and the Nicolet Antaris II Fourier transform spectrophotometer with wavelength range 1000–2500 nm. HPLC was used as the reference method for assessing lutein content in wheat grain. Sample grinding and proper NIR and VIS spectral combinations were essential for obtaining sufficient predictive parameters in calibration models. The FOSS 6500 calibration models were the most promising (standard error of prediction 0.46–0.78; ratio of performance to deviation 2.36–2.83 mg/kg). NIR spectral instability of ground samples during 12 days in storage was detected and evoked a significant relative increase in lutein content of about 35% using the FOSS 6500 calibration model. After excluding five time-instable spectral regions, prediction differences of lutein content were markedly eliminated and did not exceed 7% in relative terms during 12 days of storage.

Motivational support from digital game-based learning environments (DGBLEs) for scientific topics designed by novice end users

ABSTRACTThe integration of digital game-based learning environment (DGBLE) enhanced by technology in recent years has been hampered by its complexity and difficulty in realistically addressing teachers’ instructional needs. The pedagogical gap between what teachers think a DGBLE can deliver and what DGBLE can actually offer remains substantial. To preliminarily address the gap, this present qualitative study adopted an end-user-development lens to understand how K-12 teachers as novice end users interpret and design game features in their DGBLEs. The design ideas, situated in teaching scientific subjects, were collected from 19 pre-service teachers in a public university in the United States by semi-structured interviews based on game features identified in the literature. The data analysis, grounded in the ARCS (attention, relevance, confidence, satisfaction) motivational design model, employed the direct content analysis method and revealed the distribution of motivational support among participants’ DGBLEs design ideas. The finding suggested that participants were more likely to incorporate intrinsic motivational support than extrinsic support in their design. This trend could compromise the motivational support of DGBLEs when students need additional extrinsic motives toward the end of learning processes. Further, the study illuminates the importance of incorporating end users’ perspectives early on in the DGBLE design process.

Simple Sample Preparation Method for Direct Microbial Identification and Susceptibility Testing From Positive Blood Cultures.

Rapid identification and determination of the antibiotic susceptibility profiles of the infectious agents in patients with bloodstream infections are critical steps in choosing an effective targeted antibiotic for treatment. However, there has been minimal effort focused on developing combined methods for the simultaneous direct identification and antibiotic susceptibility determination of bacteria in positive blood cultures. In this study, we constructed a lysis-centrifugation-wash procedure to prepare a bacterial pellet from positive blood cultures, which can be used directly for identification by matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS) and antibiotic susceptibility testing by the Vitek 2 system. The method was evaluated using a total of 129 clinical bacteria-positive blood cultures. The whole sample preparation process could be completed in <15 min. The correct rate of direct MALDI-TOF MS identification was 96.49% for gram-negative bacteria and 97.22% for gram-positive bacteria. Vitek 2 antimicrobial susceptibility testing of gram-negative bacteria showed an agreement rate of antimicrobial categories of 96.89% with a minor error, major error, and very major error rate of 2.63, 0.24, and 0.24%, respectively. Category agreement of antimicrobials against gram-positive bacteria was 92.81%, with a minor error, major error, and very major error rate of 4.51, 1.22, and 1.46%, respectively. These results indicated that our direct antibiotic susceptibility analysis method worked well compared to the conventional culture-dependent laboratory method. Overall, this fast, easy, and accurate method can facilitate the direct identification and antibiotic susceptibility testing of bacteria in positive blood cultures.