419 research outputs found
RESEARCH AND APPLICATION OF TECHNOLOGY FOR DRY WET BIOGAS FERMENTATION
No full textGreat differences exist between the rural situations of North China and South
China. It is difficult to adopt only one kind of biogas fermentation process to
suit these different conditions. After the success of studies on dry fermentation
with agricultural wastes, we studied the technology of combining dry and
conventional, or wet, biogas fermentations. Dry fermentation was used to
treat stalks and herbs, wet fermentation to treat human and animal excreta.
Separating the treatment of stalks from excreta in dry fermentation can avoid
the formation of crusts which lead to loss of gas-producing materials, and
other faults of conventional, wet, biogas digesters treating stalks and excreta
together
A Connection Between the Monogenicity of Certain Power-Compositional Trinomials and -Wall-Sun-Sun Primes
No full textWe say that a monic polynomial of degree is
monogenic if is irreducible over and
is a basis for the ring of
integers of , where .
Let be a positive integer, and let be the Lucas sequence
of the first kind defined by U_0=0,\quad U_1=1\quad
\mbox{and} \quad U_n=kU_{n-1}+U_{n-2} \quad \mbox{ for $n\ge 2$}. A
-Wall-Sun-Sun prime is a prime such that where is the length of the period of modulo .
Let if , and if . Suppose that
and is squarefree, and let denote the class number of
. Let be an integer such that, for
every odd prime divisor of , is not a square modulo
and . In this article, we prove that
is monogenic for all integers if and only if
no prime divisor of is a -Wall-Sun-Sun prime
A comprehensive uncertainty analysis of model-estimated longitudinal and lateral dispersion coefficients in open channels
No full textAbstractThe complexity of pollutant-mixing mechanism in open channels generates large uncertainty in estimation of longitudinal and lateral dispersion coefficients (Kx and Ky). Therefore, Kx and Ky estimation in rivers should be accompanied by an uncertainty analysis, a subject mainly ignored in previous studies. We introduce a method based on thorough analysis of different calibration datasets, resampled from a global database of tracer studies, to determine the uncertainty associated with five applicable intelligent models for estimation of Kx and Ky (model tree, evolutionary polynomial regression (EPR), gene-expression programming, multivariate adaptive regression splines (MARS), and support vector machine (SVM)). Our findings suggest that SVM gives least uncertainty in both Kx and Ky estimation, while EPR and MARS generate most uncertainty in Kx and Ky estimation, respectively. By considering significant uncertainty in the model estimations, we suggest that the methodology we introduce here for uncertainty determination of the models be incorporated in empirical studies on estimation of Kx and Ky in rivers.Abstract
The complexity of pollutant-mixing mechanism in open channels generates large uncertainty in estimation of longitudinal and lateral dispersion coefficients (Kx and Ky). Therefore, Kx and Ky estimation in rivers should be accompanied by an uncertainty analysis, a subject mainly ignored in previous studies. We introduce a method based on thorough analysis of different calibration datasets, resampled from a global database of tracer studies, to determine the uncertainty associated with five applicable intelligent models for estimation of Kx and Ky (model tree, evolutionary polynomial regression (EPR), gene-expression programming, multivariate adaptive regression splines (MARS), and support vector machine (SVM)). Our findings suggest that SVM gives least uncertainty in both Kx and Ky estimation, while EPR and MARS generate most uncertainty in Kx and Ky estimation, respectively. By considering significant uncertainty in the model estimations, we suggest that the methodology we introduce here for uncertainty determination of the models be incorporated in empirical studies on estimation of Kx and Ky in rivers
Dynamic shell buckling behavior of multi-walled carbon nanotubes embedded in an elastic medium
No full textThis paper studies the dynamic shell buckling behavior of multi-walled carbon nanotubes (MWNTs) embedded in an elastic medium under step axial load based on continuum mechanics model. It is shown that, for occurrence of dynamic shell buckling of MWNTs or MWNTs embedded in an elastic medium, the buckling stress is higher than the critical buckling stress of the corresponding static shell buckling under otherwise identical conditions. Detailed results are demonstrated for dynamic shell buckling of individual double-walled carbon nanotubes (DWNTs) or DWNTs embedded in an elastic medium. A phenomenon is shown that DWNTs or embedded DWNTs in dynamic shell buckling are prone to axisymmetric buckling rather than non-axisymmetric buckling. Numerical results also indicate that the axial buckling form shifts from the lower buckling mode to the higher buckling mode with increasing buckling stress, but the buckling mode is invariable for a certain domain of buckling stress. Further, an approximate analytic formula is presented for the buckling stress and the associated buckling wavelength for dynamic axisymmetric buckling of embedded DWNTs. The effect of radii is also examined
Sensitivity analysis for the number of incident HIV cases (KX) and the number of prevalent HIV cases (Y<sub>1–4</sub>).
No full text<p>A-1. Averaged sensitivities in magnitudes of the number of incident HIV cases (KX) per year to each parameter. A-2. Sensitivities of the number of incident HIV cases (KX) per year to each parameter at 10 year. B-1. Averaged sensitivities in magnitudes of the number of prevalent HIV cases (Y<sub>1–4</sub>) per year to each parameter. B-2. Sensitivities of the number of prevalent HIV cases (Y<sub>1–4</sub>) per year to each parameter at 10 year. NOTE: The elasticity of KX with respect to a parameter is defined as: . The X-axis of Figures A and B represents the elasticity of incident (KX) and prevalent (Y<sub>1–4</sub>) HIV cases, respectively. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0090080#pone-0090080-t001" target="_blank">table 1</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0090080#pone.0090080.s002" target="_blank">S1</a> for referring the meaning of each abbreviations within Y-axis. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0090080#pone-0090080-g004" target="_blank">Figures 4A</a>-1 and 4B-1 show the average elasticities of outcomes over 40 years and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0090080#pone-0090080-g004" target="_blank">Figures 4A</a>-2 and 4B-2 show the elasticities of outcomes at the time point of 10 years. The boxplot contains the median value (horizontal red line), and extends from the first to the third quartile when simple random sampling with uniform distributions between ±10% of baseline of all parameters are used. Whisker bars are extended to minimum and maximum.</p
Reliability of functional forms for calculation of longitudinal dispersion coefficient in rivers
No full textAbstractAlthough dimensional analysis suggests sound functional forms (FFs) to calculate longitudinal dispersion coefficient (Kx), no attempt has been made to quantify both reliability of the estimated Kx value and its sensitivity to variation of the FFs’ parameters. This paper introduces a new index named bandwidths similarity factor (bws–factor) to quantify the reliability of FFs based on a rigorous analysis of distinct calibration datasets to tune the FFs. We modified the bootstrap approach to ensure that each resampled calibration dataset is representative of available datapoints in a rich, global database of tracer studies. The dimensionless Kx values were calculated by 200 FFs tuned with the generalized reduced gradient algorithm. Correlation coefficients for the tuned FFs varied from 0.60 to 0.98. The bws–factor ranged from 0.11 to 1.00, indicating poor reliability of FFs for Kx calculation, mainly due to different sources of error in the Kx calculation process. The calculated exponent of the river’s aspect ratio varied over a wider range (i.e., −0.76 to 1.50) compared to that computed for the river’s friction term (i.e., −0.56 to 0.87). Since Kx is used in combination with one-dimensional numerical models in water quality studies, poor reliability in its estimation can result in unrealistic concentrations being simulated by the models downstream of pollutant release into rivers.Abstract
Although dimensional analysis suggests sound functional forms (FFs) to calculate longitudinal dispersion coefficient (Kx), no attempt has been made to quantify both reliability of the estimated Kx value and its sensitivity to variation of the FFs’ parameters. This paper introduces a new index named bandwidths similarity factor (bws–factor) to quantify the reliability of FFs based on a rigorous analysis of distinct calibration datasets to tune the FFs. We modified the bootstrap approach to ensure that each resampled calibration dataset is representative of available datapoints in a rich, global database of tracer studies. The dimensionless Kx values were calculated by 200 FFs tuned with the generalized reduced gradient algorithm. Correlation coefficients for the tuned FFs varied from 0.60 to 0.98. The bws–factor ranged from 0.11 to 1.00, indicating poor reliability of FFs for Kx calculation, mainly due to different sources of error in the Kx calculation process. The calculated exponent of the river’s aspect ratio varied over a wider range (i.e., −0.76 to 1.50) compared to that computed for the river’s friction term (i.e., −0.56 to 0.87). Since Kx is used in combination with one-dimensional numerical models in water quality studies, poor reliability in its estimation can result in unrealistic concentrations being simulated by the models downstream of pollutant release into rivers
Dispersion in the Ayeyarwady: A description of the mixing of tracers in the area of the Ayeyarwady River- Chindwin River confluence
No full textThe Ayeyarwady River (also called Irrawaddy River) is the most important river of Myanmar and due to the country’s rapid development it is expected to become even more important. The river flows roughly from north to south through Myanmar and is very dynamic and mostly unregulated. With a length of 2170 km and an over the year average (highly seasonally varying) discharge of 13’000 m3/s into the Andaman Sea (Bhardwaj, Owen, & Leinbach, 2012), the Ayeyarwady is one of the bigger rivers in Asia. To more than before take into account the interests of different stakeholders, as well as ecological aspects, sustainable management of the river is needed. Understanding the key aspects of the river flow can be a first step to sustainable river management (Richter et al., 2003). Pollution due to a large variety of activities of different nature make that water quality monitoring is of high importance (Thanda Thatoe Nwe Win, Bogaard, & Van de Giesen, 2015). For monitoring and modelling the water quality, information about the mixing of tracers trough the river is needed, which can be quantified with the use of dispersion coefficients. Little research has been done about the Ayeyarwady River in general considered its size and importance. Very limited data about the mixing of tracers and the parameters needed to estimate the mixing of tracers was available. This research focuses on the situation around the Ayeyarwady-Chindwin confluence in the first week of February 2017 (dry season). Hence, there is a very different situation during for example wet season. For the water quality, mainly the mixing in the longitudinal direction (direction of the main river flow) is of interest, which can be quantified by a longitudinal dispersion coefficient (Kx). First relevant parameters for estimating Kx were identified based on the theory. This appeared to be the discharge, roughness and bathymetry. Besides, Kx has to be calibrated by floater experiments. To get better insight into the magnitude of these parameters, flow velocity and depth measurements (needed for estimating the discharge, roughness and bathymetry) and floater experiments have been done during a week of fieldwork in the area. Due to loss, theft and destruction of floaters, less data was collected than planed. To get further insight in the mixing of tracers, a numerical model was made in the software Delft3D based on data collected during the fieldwork. Based on the combined results of the theory, measurements done during the fieldwork and the Delft3D model, it is expected that the magnitude of Kx in the Ayeyarwady River is somewhere in between 50-500 m2/s (best estimate: Kx~300 m2/s), although this has to be confirmed by further research. When the found value is compared with values found for other bigger rivers this value for Kx appears to be somewhat on the low side. From the Delft3D model runs follows that the longitudinal dispersion coefficient in the Chindwin River is higher than in the Ayeyarwady, possibly even a factor 10. Besides, insight in the effect of the different parameters on the dispersion was obtained, contributing to a better understanding of processes causing the mixing of tracers in the Ayeyarwady and Chindwin rivers. Estimating the highly sensitive longitudinal dispersion coefficient (Kx) appeared to be challenging, mostly due to the remote and highly dynamic character of the area. To make a better estimate of Kx, the uncertainty in the parameters needed (discharge, roughness, bathymetry and spreading of floaters for calibration) has to be reduced. Although some modelling options in Delft3D could be tried to narrow the range of these parameters, the best option to reduce this uncertainty is collecting more (high quality) data in the field
High Resolution Optical Characterization of Graphene Functionalization
No full textThe past decades have witnessed the exponential growth of studies utilizing optical techniques to characterize graphene functionalization. The promise and potential application of graphene and related materials are substantially expanded through chemical functionalization. However, due to the fact that graphene is a single layer of carbon atoms, it is difficult to study the in situ dynamics of graphene chemistry. Moreover, the inertness of the graphene basal plane has notably limited its viable chemical modification pathways. This dissertation describes efforts by the author and colleagues to overcome these limitations. Part I of this dissertation demonstrates the direct optical visualization of in situ dynamics of graphene chemistry through interference reflection microscopy. Specifically, we uncover the unique dynamics of the redox reaction, diazonium reaction and solution-enclosing blister generation process of substrate-supported graphene at high spatiotemporal resolution. Part II of this dissertation reports facile approaches to the chemical modifications of the inert graphene basal plane under ambient conditions. Optical characterizations techniques including interference reflection microscopy, transmission microscopy, fluorescence microscopy, and Raman spectroscopy are utilized here to help establish the successful modifications of graphene through our facile approaches. These approaches include direct azidation and chlorination of the graphene basal plane through the electrochemical oxidation of an aqueous sodium azide and sodium chloride solution as well as a photocatalytic approach for the facile azidation and chemical patterning of graphene surface
Assessing the scientific integrity of the collected work of one author or author group
No full textObjectives: No published methods for research integrity review include both statistical techniques applied to groups of randomized trials and individual assessment of papers. We propose a method based on practical experience of investigating data integrity across the collected papers of an author or author group. Study Design and Setting: We report our approach to investigating the collected papers of an author or author group suspected of academic misconduct. Results: In the investigation of the work of an author or author group, we recommend a systematic search for the work of the involved authors in PubMed, Google Scholar, and the Retraction Watch database, as well as a search of trial registries for unpublished clinical trials. Summary information from studies should be tabulated to assess consistency between study registration, execution, and publication. Each paper should be investigated for unfeasible features of the governance, methodology, execution, results, and reporting of the study. Pairwise comparison of baseline and outcome tables between papers may reveal data duplication or unfeasibly large differences between baseline characteristics in similar studies. Assessment of baseline characteristics from multiple randomized trials using Carlisle's method can determine whether the data are consistent with a properly executed randomization process, as can checking whether reported baseline characteristics follow expected patterns for random variables such as Benford's law. If serious concerns are raised, a more thorough investigation should be performed by journals, publishers, and institutions. Conclusion: These methods provide a systematic and reproducible way to assess the collected work of an author or group of authors. Plain Language Summary: It is increasingly accepted that papers reporting on clinical studies may contain fraudulent or falsified data, often multiple papers by a single author or author group. Based on our experience assessing the research integrity of collections of papers by one author or author group, we present an approach to these investigations that combines published statistical methods with pragmatic assessment of study feasibility. This will help journals and publishers better identify groups of potentially untrustworthy studies
A 1,100-year palaeoenvironmental record inferred from stable isotope and trace element compositions of ostracode and plant caryopses in sediments of Cattle Pond, Dongdao Island, South China Sea
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