Wide Range Of Source Research Articles

Investigating the mineralogical and geochemical composition of fluvial sediments of Watari river system, Kano, Nigeria

A key objective of this research is to conduct a mineralogical and geochemical screening of the fluvial sediments in Watari river. Data collected from this study can be used to further enhance scientific understanding of the fluvial processes in the Watari basin as well as the larger Hadejia-Jama' are basin. The geological data can also be used as input information for the prediction of sedimentation rates in the Watari dam, Kano. An intensive field was conducted to explore thebedforms (sand bars, ripples, and sand filled channel or dunes) of the proximal channel environments, platform geometry and sinuosity.X-ray diffraction (XRD) and X-ray fluorescence (XRF) analyses were used to study the mineralogy and chemical composition of the collected samples, respectively. The Watari river can be considered as braided due to the presence of smaller multi-threaded channels, braid or channel bars. The lithology of exposures observed at the river bank show a series of depositional cycles that comprise mudrocks (light and dark), sandstone, conglomerate and a basal quartzitic gravel deposit. The wacke and sub-litheranite rocks were sourced from mafic and intermediate igneous rocks. The relatively high La and Ce in the mudrocks can be attributed mainly to the adsorption of Ce onto Fe-oxides which are abundant in the fluvial sediments eroded from lateritic soils. From the bivariate plot of Al2O3/SiO2 against Fe2O3+MgO, the sandstone facies fall under the passive continental margin, while the quartzite and conglomerate facies are grouped under the foreland basin, and the light mudrock facies is classified under the continental island arc. In addition, the plot of Al2O3/(CaO + Na2O) against Fe2O3+MgO shows the sandstone and quartzite facies fall under the foreland basin. The relatively high concentration of feldspar and muscovite mica in the siliciclastic facies is indicative of close proximity to parent material, and low degree of weathering and diagenesis. The variability in the mineral composition points toward different cycles of fluvial sedimentation, diverse provenance, and wide range of source materials.The geochemical data further buttresses the variability in provenance, wider geographic area of the sediments or re-deposition and reworking by fluvial actions.

Review of Single-Phase Bidirectional Inverter Topologies for Renewable Energy Systems with DC Distribution

Recent developments in renewable energy installations in buildings have highlighted the potential improvement in energy efficiency provided by direct current (DC) distribution over traditional alternating current (AC) distribution. This is explained by the increase in DC load types and energy storage systems such as batteries, while renewable energy sources such as photovoltaics (PVs) produce electricity in DC form. In order to connect a DC distribution system to the alternating current grid (e.g., for backup, delivering energy storage to the grid) there is a need for a bidirectional inverter, which needs to operate over a wide range of source and load conditions and is therefore critical to the overall system performance. However, DC distribution in buildings is relatively new, with much of the research focused on the control of the DC bus connection between sources and loads, rather than on the grid connection. Therefore, this review aims to explore recent developments in bidirectional inverter technologies and the associated challenges imposed on grid-connected DC distribution systems. The focus is on small-scale building applications powered by photovoltaic (PV) installations, which may include energy storage in the form of batteries. An evaluation of existing inverter topologies is presented, focusing on semiconductor technologies, control techniques, and efficiency under variable source and load conditions. Challenges are identified, as are optimal solutions based on available technologies. The work provides a basis for future developments to address current shortcomings so that the full benefits of DC distribution can be achieved.

Extraction of xylose from rice straw and lemongrass via microwave assisted

In recent years, agricultural wastes cause serious pollution to the environment. Agricultural residues can be used to produce value-added products in order to control environmental pollution, therefore these wastes are a promising feedstock as it has many advantages such as wide range of source, low cost and renewable. Rice straw and lemongrass leaves which are the renewable sources for the production of many useful products such as xylose. The aim of this study is to compare the content of xylose produced from rice straw and lemongrass leaves, in order to obtain highest yield of xylose and to optimize the acid hydrolysis time, concentration of sulphuric acid, liquid–solid ratio and the power of the microwave towards the maximum extraction of xylose. Microwave assisted acidic hydrolysis method was used to extract xylose from rice straw and lemongrass leaves. The acid hydrolysis of both rice straw and lemongrass was performed at different time (1–5 min), acid concentration (1%–5%), liquid solid ratio (1:30, 2:30, 3:30, 4:30 and 5:30) and power (160 W, 320 W, 480 W, 640 W, 800 W). The results obtained indicate that the yield of xylose from rice straw (2.98 g/L) via the microwave assisted is slightly higher than lemongrass (2.91 g/L) with optimum conditions of 3 min of hydrolysis time, 2% of sulphuric acid concentration, 1:30 of liquid solid ratio and 320 W of microwave power. Meanwhile, the optimum conditions for lemongrass leaves are 4 min of hydrolysis time, 4% of sulphuric acid concentration, 2:30 of liquid solid ratio and 480 W of microwave power. Thus, rice straw has slightly higher capability in production of xylose compared to lemongrass.

Extraction of Xylose from Rice Straw and Lemongrass Leaf via Microwave Assisted

In recent years, agricultural wastes cause serious pollution to the environment. Agricultural residues can be used to produce value-added products in order to control environmental pollution, therefore these wastes are a promising feedstock as it has many advantages such as wide range of source, low cost and renewable. Rice straw and lemongrass leaves which are the renewable sources for the production of many useful products such as xylose. The aim of this study is to compare the content of xylose produced from rice straw and lemongrass leaves, in order to obtain highest yield of xylose and to optimize the acid hydrolysis time, concentration of sulphuric acid, liquid-solid ratio and the power of the microwave towards the maximum extraction of xylose. Microwave assisted acidic hydrolysis method was used to extract xylose from rice straw and lemongrass leaves. The acid hydrolysis of both rice straw and lemongrass was performed at different time (1-5 minutes), acid concentration (1%-5%), liquid solid ratio (1:30, 2:30, 3:30, 4:30 and 5:30) and power (160W, 320W, 480W, 640W, 800W). The results obtained indicate that the yield of xylose from rice straw (2.98g/L) via the microwave assisted is slightly higher than lemongrass (2.91 g/L) with optimum conditions of 3 minutes of hydrolysis time, 2% of sulphuric acid concentration, 1:30 of liquid solid ratio and 320W of microwave power. Meanwhile, the optimum conditions for lemongrass leaves are 4 minutes of hydrolysis time, 4% of sulphuric acid concentration, 2:30 of liquid solid ratio and 480W of microwave power. Thus, rice straw has slightly higher capability in production of xylose compared to lemongrass.

A natural polymer-based porous sponge with capillary-mimicking microchannels for rapid hemostasis

Natural polymer materials have attracted great attention in the field of hemostasis because of their wide range of source, nontoxicity, hydrophilicity, and air permeability. In the present study, two natural polymers composed of carboxymethyl chitosan (CMCS) and sodium carboxymethylcellulose (CMCNa) plus γ-(2,3-epoxypropoxy) propytrimethoxysilane (KH560) that serves as a crosslinking agent were selected to synthesize a capillary-mimicking composite hemostatic (CCK) sponge with a low density, interconnected microchannel architecture, suitable mechanical strength, high resilience, and ultrastrong liquid absorption capacity. The introduction of a large number of hydrophilic carboxymethyl functional groups and the design of capillary-mimicking structures formed by the ice segregation-induced self-assembly (ISISA) process endowed the CCK sponges with an ultrastrong liquid absorption capacity, which significantly enhanced the hemostatic ability of the materials. Both in vivo and in vitro hemostatic experiments confirmed the potential of the CCK sponges to achieve rapid hemostasis. Additionally, cytotoxicity and hemolysis assays showed that the CCK sponges exhibited good biocompatibility and hemocompatibility. The possible hemostatic mechanism was also discussed in this study. In conclusion, the capillary-mimicking hemostatic sponge exhibits a high potential to induce rapid hemostasis in prehospital emergency and clinical settings. STATEMENT OF SIGNIFICANCE: In the present study, an oriented composite hemostatic (CCK) sponge with a capillary-mimicking structure formed by the ice segregation-induced self-assembly (ISISA) process was designed and used to achieve rapid hemostasis. The unique aligned microchannel structure of the sponge exhibited an ultrastrong capillary-mimicking action and endowed the prepared CCK hemostatic sponge with a strong liquid absorption capacity. By changing the proportion of raw materials, we could modify the unique capillary-mimicking structure with aligned microchannels. Two natural polymer-based materials with abundant hydrophilic groups were chosen to prepare the CCK sponge to fully utilize the characteristics of this structure. The oriented natural polymer-based porous sponge with capillary-mimicking microchannels exhibited a strong hemostatic ability in both in vivo and in vitro tests. The results showed that the CCK sponge with the capillary-mimicking structure has a high potential to achieve rapid hemostasis.

Thermodynamic analysis of high-temperature pumped thermal energy storage systems: Refrigerant selection, performance and limitations

One of the bottlenecks for a wider implementation of renewable energies is the development of efficient energy storage systems which can compensate for the intermittency of renewable energy sources. Pumped thermal energy storage (PTES) is a very recent technology that can be a promising site-independent alternative to pumped hydro energy storage or compressed air energy storage, without the corresponding geological and environmental restrictions. Accordingly, this paper presents a full thermodynamic analysis of a PTES system consisting of a high-temperature heat pump (HTHP), which drives an organic Rankine cycle (ORC) by means of an intermediate high-temperature thermal energy storage system (HT-TES). The latter combines both latent and sensible heat thermal energy storage sub-systems to maximize the advantage of the refrigerant subcooling. After validating the proposed model, several parametric studies have been carried out to assess the system performance using different refrigerants and configurations, under a wide range of source and sink temperatures. The results show that for a system that employs the same refrigerant in both the HTHP and ORC, and for a latent heat thermal energy storage system at 133ºC, R-1233zd(E) and R-1234ze(Z) present the best performance. Among all the cases studied with a latent heat thermal energy storage system at 133°C, the best system performance, also considering the impact on the environment, has been achieved employing R-1233zd(E) in the HTHP and Butene in the ORC. Such a system can theoretically reach a power ratio of 1.34 under HTHP source and ORC sink temperatures of 100 and 25°C, respectively.

Spherical multifocusing method for irregular topography

Moveout correction for irregular topography has been a longstanding challenge in processing seismic exploration data. Irregular topography usually results in large moveout among traces, a low signal-to-noise ratio (S/N), and difficulty in modeling near-surface velocities. Conventional normal moveout (NMO) corrections and elevation static methods are imprecise and tend to introduce significant errors for large offsets. Over the past two decades, several multiparameter time corrections and stacking techniques to reduce noise and improve resolution have been proposed in place of the classic NMO and common-midpoint stack. These include the common-reflection-surface (CRS), common-offset CRS, nonhyperbolic CRS, implicit CRS, multifocusing (MF), irregular surface MF (IS-MF), spherical MF (SMF), and common-offset MF methods. Various CRS-type operators that consider the top-surface topography have been proposed. For MF-type operators, only IS-MF can be applied directly to the irregular topography with no elevation statics required. In this study, we have developed a new MF formulation, modifying the SMF method to consider nonzero elevations of sources and receivers and we corrected moveout of nonplanar data directly without prior elevation static corrections. The proposed extension combines the sensitivity to spherical reflectors of SMF with the applicability of the IS-MF method to irregular topography. We investigated the behavior of the new operator using a physical model data set and compared the results with those from the conventional IS-MF method. The results revealed that the new operator is more robust over a wide range of source and receiver elevations and has advantages on strongly curved interfaces. We also confirmed the potential of the proposed approach by comparing stacking results for a real-land data set with a low S/N.

Analysis of Video Quality Losses in Homogeneous HEVC Video Transcoding

This paper presents a detailed, quantitative analysis of video quality losses in a homogeneous HEVC video transcoder together with the analysis of the origin of those quality losses and the influence of quantization step alignment on transcoding. With the use of HM15.0 reference software and a set of test video sequences, the cascaded pixel domain video transcoder (CPDT) concept has been used to gather all the necessary data needed for the analysis. This experiment was performed for a wide range of source and target bitrates. The essential result of the work is an extensive evaluation of CPDT, commonly used as a reference in works on effective video transcoding. So far, no such extensively performed study has been made available. The quality degradation between a transcoded video and a video that would be the result of direct compression of the original video at the same bitrate as the transcoded one has been reported. The dependences between quality degradation caused by transcoding and bitrate changes of the transcoded data stream are clearly presented in graphs.

Investigation on Type-4 and Type-11 Mixed Topology of LLC Resonant Converter

LLC resonant converter can adjust the output for a wide range of source and load with a small fluctuation of switching frequency, so it is used widely. This paper introduces all arrangements of LLC topological group, then proposes a new topology which is consist of Type-4 and Type-11 that used widely,in this paper we also give its calculate method of resonant frequency. Lastly we get gain characteristics of the topologies in the PSpice simulation environment and analyse the influence factors on adjustment ability in certain load range .

Experiment and Research on the Waste Tire Rubber in the Whole Sugarcane Harvester

Stripping leaves system is the core system of small whole stalk sugarcane harvester, and the leaf -peeling element is a key part of the stripping leaves system. At present a lot of problems such as large amount of use and short service life exists in the leaf –peeling brush of the sugarcane harvester in China. As a result of waste tire’s wide range of source, lower price, the experiment shows that waste tire rubber processed could be used as leaf –peeling brush, which has a good effect on stripping leaves and top broken.

Strategic options for sustainable water management at new developments: the application of a simulation model to explore potential water savings

Research on appropriate technologies and infrastructures to support water reuse has progressed rapidly over recent decades and there are now a wide range of source--treatment--reuse options for planners to choose from. Although the economics of water reuse schemes favours application to new developments rather than retrofit projects, there are few studies which have sought to address strategic option selection issues for large developments. The potential advantages of using treatment and reuse systems in new developments require an understanding of the relationships between a wide variety of social, environmental, technological, and operational factors. The operational effectiveness and economic efficiency of specific technology choices will vary as a function of network configuration, wastewater characteristics, how different technologies respond to dynamic loading (variability of feed strength and flow) and potential spiking, as well as equipment reliability, climate and household behaviour. Using a commercially available software package, the study reports the design and implementation of a low resolution simulation tool to explore sustainable water management options for a live case study site in the south of England (a peri-urban development of 4,500 new homes) with particular reference to opportunities for rainwater harvesting, and water reuse.

3D description and inversion of reflection moveout of PS-waves in anisotropic media

Common-midpoint moveout of converted waves is generally asymmetric with respect to zero offset and cannot be described by the traveltime series t2(x2) conventionally used for pure modes. Here, we present concise parametric expressions for both common-midpoint (CMP) and common-conversion-point (CCP) gathers of PS-waves for arbitrary anisotropic, horizontally layered media above a plane dipping reflector. This analytic representation can be used to model 3D (multi-azimuth) CMP gathers without time-consuming two-point ray tracing and to compute attributes of PS moveout such as the slope of the traveltime surface at zero offset and the coordinates of the moveout minimum. In addition to providing an efficient tool for forward modelling, our formalism helps to carry out joint inversion of P and PS data for transverse isotropy with a vertical symmetry axis (VTI media). If the medium above the reflector is laterally homogeneous, P-wave reflection moveout cannot constrain the depth scale of the model needed for depth migration. Extending our previous results for a single VTI layer, we show that the interval vertical velocities of the P- and S-waves (VP0 and VS0) and the Thomsen parameters e and δ can be found from surface data alone by combining P-wave moveout with the traveltimes of the converted PS(PSV)-wave. If the data are acquired only on the dip line (i.e. in 2D), stable parameter estimation requires including the moveout of P- and PS-waves from both a horizontal and a dipping interface. At the first stage of the velocity-analysis procedure, we build an initial anisotropic model by applying a layer-stripping algorithm to CMP moveout of P- and PS-waves. To overcome the distorting influence of conversion-point dispersal on CMP gathers, the interval VTI parameters are refined by collecting the PS data into CCP gathers and repeating the inversion. For 3D surveys with a sufficiently wide range of source–receiver azimuths, it is possible to estimate all four relevant parameters (VP0, VS0, e and δ) using reflections from a single mildly dipping interface. In this case, the P-wave NMO ellipse determined by 3D (azimuthal) velocity analysis is combined with azimuthally dependent traveltimes of the PS-wave. On the whole, the joint inversion of P and PS data yields a VTI model suitable for depth migration of P-waves, as well as processing (e.g. transformation to zero offset) of converted waves.

A comparison of select trigger algorithms for automated global seismic phase and event detection

AbstractDigital algorithms for robust detection of phase arrivals in the presence of stationary and nonstationary noise have a long history in seismology and have been exploited primarily to reduce the amount of data recorded by data logging systems to manageable levels. In the present era of inexpensive digital storage, however, such algorithms are increasingly being used to flag signal segments in continuously recorded digital data streams for subsequent processing by automatic and/or expert interpretation systems. In the course of our development of an automated, near-real-time, waveform correlation event-detection and location system (WCEDS), we have surveyed the abilities of such algorithms to enhance seismic phase arrivals in teleseismic data streams. Specifically, we have considered envelopes generated by energy transient (STA/LTA), Z-statistic, frequency transient, and polarization algorithms. The WCEDS system requires a set of input data streams that have a smooth, low-amplitude response to background noise and seismic coda and that contain peaks at times corresponding to phase arrivals. The algorithm used to generate these input streams from raw seismograms must perform well under a wide range of source, path, receiver, and noise scenarios. Present computational capabilities allow the application of considerably more robust algorithms than have been historically used in real time. However, highly complex calculations can still be computationally prohibitive for current workstations when the number of data streams become large. While no algorithm was clearly optimal under all source, receiver, path, and noise conditions tested, an STA/LTA algorithm incorporating adaptive window lengths controlled by nonstationary seismogram spectral characteristics was found to provide an output that best met the requirements of a global correlation-based event-detection and location system.

Non-linear propagation of broadband noise signals

Measurements of aircraft flyover noise have strongly suggested that non-linear propagation effects can significantly modify the noise spectrum. The data show that over ranges of 500 to 1000 m the attenuation in the range 5 to 10 kHz may fall considerably short of that predicted on the basis of linear propagation, if the noise is sufficiently intense. Such distances are comparable to those used in aircraft noise certification measurements, and the frequencies involved have an important influence on the perceived noise level. Therefore a scheme is required for predicting the finite amplitude propagation of random signals over a wide range of source and atmospheric conditions. Taylor series solutions to a generalized Burgers' equation are generated for stationary noise signals. The expansions are in powers of the range variable, and any frequency dependence of attenuation and dispersion is allowed. The limitations of such an approach are discussed, and it is found that the number of terms needed increases rapidly with range. For propagation over a long range, when non-linear effects are important, it is recommended that one of the differential equations derived for the power spectrum be used, together with a closure hypothesis. Individual terms in the series may be treated separately as local spectrum evolution equations, valid at all points along the propagation path. With appropriate modelling of the non-linear terms, such an equation can form a basis for aircraft noise prediction schemes.