Streaming Rate Research Articles

Heavy paraffin dehydrogenation and hydrogenation of nitrobenzene to aniline: Effects of operating conditions

ABSTRACTAuto-thermal heat exchanger configurations are recognized as a novel concept in process intensification. In the current study, the influence of operating conditions in a novel coupling reactor with radial-flow pattern is investigated for heavy paraffin dehydrogenation process. Catalytic hydrogenation of nitrobenzene to aniline takes place in the exothermic side and supplies the necessary heat for the endothermic dehydrogenation of heavy paraffin reaction. The performance of the reactor is numerically investigated for various key operating variables, such as inlet molar flow rates of exothermic and endothermic streams, number of subsections, and exothermic side angle. The reactor performance is analyzed based on temperature, olefin production rate, and nitrobenzene conversion.

Meltblown Solvated Mesophase Pitch-Based Carbon Fibers: Fiber Evolution and Characteristics

Potentially low-cost continuous carbon fibers are produced from solvated mesophase pitch through a patented meltblowing process. The structural evolution and properties of the fibers are characterized by various analytical methods. The meltblown fibers are continuous fibers which are collected into a fibrous web form, and the diameter of the filaments is attenuated by the flow rate of air streams. The spun fibers can be rapidly stabilized in air due to the high melting mesogens and the removable solvent. The carbonized fibers show a high carbon yield of 75 wt % (or 86 wt % if the solvents are neglected) and a mean diameter of 8–22 μm with typical fiber diameter distribution and variation. The evolution of the fiber structure depends not only on the processing temperature but also on the fiber diameter. The processed carbon fibers retain the same form as the spun fibers and have a low packing density and reasonable mechanical properties.

Counter-propagating solitons in microresonators

Solitons occur in many physical systems when a nonlinearity compensates wave dispersion. Their recent formation in microresonators opens a new research direction for nonlinear optical physics and provides a platform for miniaturization of spectroscopy and frequency metrology systems. These microresonator solitons orbit around a closed waveguide path and produce a repetitive output pulse stream at a rate set by the round-trip time. In this work counter-propagating solitons that simultaneously orbit in an opposing sense (clockwise/counter-clockwise) are studied. Despite sharing the same spatial mode family, their round-trip times can be precisely and independently controlled. Furthermore, a state is possible in which both the relative optical phase and relative repetition rates of the distinct soliton streams are locked. This state allows a single resonator to produce dual-soliton frequency-comb streams having different repetition rates, but with high relative coherence useful in both spectroscopy and laser ranging systems.

Batch and continuous synthesis upscaling of powder and monolithic ordered mesoporous silica COK-12

COK-12 is an ordered mesoporous silica material (OMS) analogous to SBA-15, with hexagonally-packed cylindrical ordered pores of 5.5–6 nm in diameter. The synthesis of COK-12 takes place at room temperature under mild reaction conditions, and in comparison with the most widely known OMS materials syntheses, is more time efficient, inexpensive and environmentally friendly. This work encompasses investigations regarding the production of powder COK-12 in terms of upscaling of the synthesis in batch and continuous mode, as well as direct synthesis and upscaling of granular (monolithic) COK-12. Batch upscaling of the syntheses by a factor of 25 was carried out in a batch reactor at room temperature. In terms of upscaling in continuous mode, the installation and operation of a continuous powder COK-12 production unit was carried out and the influence of the flow rate of the feed streams on the properties of the material was studied. It was demonstrated that batch and continuous upscaling can be carried out, yielding up to 65 g or 330 g/run of powder COK-12, respectively. Upscaling of the direct synthesis of monolithic COK-12 granules was also carried out, yielding up to 60 g of material.

Home-Made Micro Valve for Determining Malachite Green Dye by Flow Injection Analysis

The research is included studying and designing micro flow injection system which is characterized with rapidity, simplicity, and low cost for the determination of green malachite dye. The study of flow rate of carrier stream, repeatability, dispersion coefficient, and calibration graph are conducted. It is found that the optimum conditions for the determination of mentioned dye are flow rate 4.200 mL/min, sampling rate 102 sample/h, limit of detection 0.05 ppm, linear range (0.05-18.00) ppm with linearity (R 2 =0.9700), RSD is 0.355, the repeatability for seven successive injections is studied for the two concentrations 5 ppm and 12 ppm, and the dispersion coefficient values are 1.73 and 1.28 at the two concentrations 2 ppm and 9 ppm respectively.

New Biotechnological Microencapsulating Methodology Utilizing Individualized Gradient-Screened Jet Laminar Flow Techniques for Pancreatic β-Cell Delivery: Bile Acids Support Cell Energy-Generating Mechanisms.

In previous studies, we developed a new technique (ionic gelation vibrational jet flow; IGVJF) in order to encapsulate pancreatic β-cells, for insulin in vivo delivery, and diabetes treatment. The fabricated microcapsules showed good morphology but limited cell functions. Thus, this study aimed to optimize the IGVJF technique, by utilizing integrated electrode tension, coupled with high internal vibration, jet-flow polymer stream rate, ionic bath-gelation concentrations, and gelation time stay. The study also utilized double inner/outer nozzle segmented-ingredient flow of microencapsulating dispersion, in order to form β-cell microcapsules. Furthermore, a microcapsule-stabilizing bile acid was added, and microcapsule's stability and cell functions measured. Buchi-based built-in system utilizing IGVJF technology was screened to produce best microcapsule-containing β-cells with or without a stabilizing-enhancing bile acid. Formed microcapsules were examined, for physical characteristics, and encapsulated cells were examined for survival, insulin release, and inflammatory profiles. Optimized microencapsulating parameters, using IGJVF, were: 1000 V voltage, 2500 Hz frequency, 1 mL/min flow rate, 3% w/v ionic-bath gelation concentration, and 20 min gelation time. Microcapsules showed good morphology and stability, and the encapsulated cells showed good survival, and insulin secretion, which was optimized by the bile acid. Deployed IGVJF-based microencapsulating parameters utilizing stability-enhancing bile acid produced best microcapsules with best pancreatic β-cells functions and survival rate, which, suggests potential application in cell transplantation.

Designing the optimal geometry of a membrane reactor for hydrogen production from a pre-reformed gas mixture based on the extent of the reaction boundary layer

A typical hydrogen-production system consisting of a pre-reformer catalytic reactor and a membrane reactor is considered: if equilibrium conditions are achieved in the pre-reformer, the reaction in the membrane reactor can only proceed once the hydrogen partial pressure has been reduced by effect of its permeation. An accurate transport-reaction-permeation model of methane steam reforming in catalytic membrane reactors suggests that, in these conditions, only a fraction of the catalyst volume is effectively active towards the advancement of the reaction and hydrogen production is confined to a reaction boundary layer (RBL) located in the near-membrane zone, whose extent is relatively insensitive to the thickness of the catalytic bed. Based on this observation, we developed a detailed study of the structure of the RBL in a wide range of operating parameters for different reactor geometries and showed that, for an assigned value of the total mass flow rate of the process stream, the optimal reactor performance is obtained whenever the thickness of the catalyst bed is comparable to that of the RBL.

Thermal regimes of Rocky Mountain lakes warm with climate change.

Anthropogenic climate change is causing a wide range of stresses in aquatic ecosystems, primarily through warming thermal conditions. Lakes, in response to these changes, are experiencing increases in both summer temperatures and ice-free days. We used continuous records of lake surface temperature and air temperature to create statistical models of daily mean lake surface temperature to assess thermal changes in mountain lakes. These models were combined with downscaled climate projections to predict future thermal conditions for 27 high-elevation lakes in the southern Rocky Mountains. The models predict a 0.25°C·decade-1 increase in mean annual lake surface temperature through the 2080s, which is greater than warming rates of streams in this region. Most striking is that on average, ice-free days are predicted to increase by 5.9 days ·decade-1, and summer mean lake surface temperature is predicted to increase by 0.47°C·decade-1. Both could profoundly alter the length of the growing season and potentially change the structure and function of mountain lake ecosystems. These results highlight the changes expected of mountain lakes and stress the importance of incorporating climate-related adaptive strategies in the development of resource management plans.

Influence of recycle streams of C5/C6 and C4 hydrocarbon cuts on the performance of methanol to propylene (PVM) reactors

Conversion of methanol to propylene combined with cracking of C5/C6 and C4 hydrocarbon cuts was studied on a commercial Süd-Chemie Germany ZSM-5 catalyst. The C5/C6 hydrocarbon cut consisted of hydrocarbons with 5 and 6 carbons in their structure (27.74% i-pentene, 43.14% i-hexene, 3.70% i-pentane and 7.37% i-hexane). The C4 hydrocarbon cut consisted of both olefinic and paraffinic molecules. A fraction of the feed hydrocarbon mixture was converted to other hydrocarbons while the conversion of methanol was remained close to 100%. It was observed that co feeding of the hydrocarbons mixture with methanol considerably increase propylene selectivity. Propylene selectivity up to 61% was gained in the propylene via methanol (PVM) process by co feeding of C5/C6 hydrocarbon cuts. For the C4 hydrocarbon cut, propylene selectivity up to 65% was obtained. However, these values do not represent the actual selectivity at actual flow rates of recycle streams. Based on third order polynomials, effects of steady state recycle streams of these cuts are also predicted in this paper. At the best conditions of a steady state recycle stream, 47.7% selectivity was obtained for propylene in the PVM reactors.

Real-time WebRTC-based design for a telepresence wheelchair.

This paper presents a novel approach to the telepresence wheelchair system which is capable of real-time video communication and remote interaction. The investigation of this emerging technology aims at providing a low-cost and efficient way for assisted-living of people with disabilities. The proposed system has been designed and developed by deploying the JavaScript with Hyper Text Markup Language 5 (HTML5) and Web Real-time Communication (WebRTC) in which the adaptive rate control algorithm for video transmission is invoked. We conducted experiments in real-world environments, and the wheelchair was controlled from a distance using the Internet browser to compare with existing methods. The results show that the adaptively encoded video streaming rate matches the available bandwidth. The video streaming is high-quality with approximately 30 frames per second (fps) and round trip time less than 20 milliseconds (ms). These performance results confirm that the WebRTC approach is a potential method for developing a telepresence wheelchair system.

Context-aware obstacle detection for navigation by visually impaired

This paper presents a context-aware smartphone-based based visual obstacle detection approach to aid visually impaired people in navigating indoor environments. The approach is based on processing two consecutive frames (images), computing optical flow, and tracking certain points to detect obstacles. The frame rate of the video stream is determined using a context-aware data fusion technique for the sensors on smartphones. Through an efficient and novel algorithm, a point dataset on each consecutive frames is designed and evaluated to check whether the points belong to an obstacle. In addition to determining the points based on the texture in each frame, our algorithm also considers the heading of user movement to find critical areas on the image plane. We validated the algorithm through experiments by comparing it against two comparable algorithms. The experiments were conducted in different indoor settings and the results based on precision, recall, accuracy, and f-measure were compared and analyzed. The results show that, in comparison to the other two widely used algorithms for this process, our algorithm is more precise. We also considered time-to-contact parameter for clustering the points and presented the improvement of the performance of clustering by using this parameter.

Water and sediment yields from two catchments with different land cover areas

Land cover and human activities affect water yield and soil erosion-sedimentation in a catchment. Therefore, a study to obtain information of water and sediment yields from two catchments covered by different land cover areas has been conducted in Tanjung and Bakar catchments. The catchments are located in Tanah Laut Regency, South Kalimantan Province. The area of secondary forest inTanjung and Bakar catchments are 31 and 10%. The water yield was obtained by measuring Stream Water Level (SWL) and converted the data into stream water discharge using a stream water discharge rating curve. Sediment samples were taken for every increament of SWL. The sediment concentration in water samples were converted to sediment discharge (kg/second) using a sediment discharge rating curve. The results showed that water and sediment yields in 2016 of Tanjung cacthment were higher than Bakar catchment. The water and sediment yields of Tanjung were 2994 mm and 15.7 t/ha. Bakar catchment produces water yield 2750 mm and sediment yield 7.4 t/ha. Based on the study, it shows that the suspended sediment in stream water is not only affected by the percentage of forest cover, but it is also influenced by the activities within the catchment such as traditional mining.

Biofilm‐induced bioclogging produces sharp interfaces in hyporheic flow, redox conditions, and microbial community structure

AbstractRiverbed sediments host important biogeochemical processes that play a key role in nutrient dynamics. Sedimentary nutrient transformations are mediated by bacteria in the form of attached biofilms. The influence of microbial metabolic activity on the hydrochemical conditions within the hyporheic zone is poorly understood. We present a hydrobiogeochemical model to assess how the growth of heterotrophic and autotrophic biomass affects the transport and transformation of dissolved nitrogen compounds in bed form‐induced hyporheic zones. Coupling between hyporheic exchange, nitrogen metabolism, and biomass growth leads to an equilibrium between permeability reduction and microbial metabolism that yields shallow hyporheic flows in a region with low permeability and high rates of microbial metabolism near the stream‐sediment interface. The results show that the bioclogging caused by microbial growth can constrain rates and patterns of hyporheic fluxes and microbial transformation rate in many streams.

Continuous synthesis of PVP stabilized biocompatible gold nanoparticles with a controlled size using a 3D glass capillary microfluidic device

A reliable glass capillary microfluidic method was developed for a continuous production of well-controlled gold nanoparticles (AuNPs) capped with polyvinylpyrrolidone (PVP) of different molecular weights (PVP K15, PVP K30 and PVP K90). A two-phase co-flow glass capillary microfluidic device with an injection orifice diameter ranging between 100 and 240µm was used to synthesise 100–240µm was used to synthesise AuNPs via the chemical reduction between tetrachloroaurate trihydrate (HAuCl4·3H2O) and ascorbic acid. AuNPs with an average diameter between 48 and 135nm were synthesised, as determined by DLS measurements. Decreasing the injection orifice diameter, increasing the flow rate of ascorbic acid stream and its pH resulted in smaller AuNPs. The polydispersity index (PDI) was found to be independent on the injection orifice diameter or the molecular weight of PVP, but increased with the increase of flow rate and the pH of ascorbic acid stream. The stability study over 6-week period confirmed that PVP K30 with an average Mw of 40000g/mol was the best capping agent to synthesize and stabilise smaller AuNPs. The reactor fouling due to deposition of AuNPs on reactor walls and orifices was mitigated by hydrophobization of reactor/capillary walls with octadecyltrimethoxisilane and the use of ascorbic acid solution of higher pH.

Exergy and thermoeconomic analyses of 500 MWe sub critical thermal power plant with solar aided feed water heating

In this paper, an attempt has been made to integrate solar aided feed water heating with a 500MWe sub critical coal fired thermal power plant. Complete bleed steam substitution in high pressure heaters (HPH) has been attained by placing a feed water heat exchanger (FWHE) in parallel to the HPH group for solar aided feed water heating. Exergy and thermo economic analyses have been performed on both reference 500MWe and conceptual solar aided 500MWe thermal power plants. The exergy analysis has revealed that the solar field followed by boiler have the maximum exergy destruction ratios of 78.90% and 56.52% respectively. The corresponding second law efficiencies of solar field and boiler are 21.10% and 43.48% respectively. Thermoeconomic analysis has been performed on both the plants by developing physical and productive structures for them. A set of linear equations have been developed and solved for finding the cost rates of different product streams.

Modelling the composition of the gas obtained by steam reforming of glycerine

In this work, we studied the influence of the variables temperature (T), water/glycerine ratio (R), and flow rate of the feeding water/glycerine solution (V̇W+G) on the non-catalysed steam reforming of glycerine. The experiments were carried out on a bench-scale equipment and the margins of the processing variables R, T, and V̇W+G were 0.7–3.3wtwt−1, 682–1018°C, and 8.5–35.5mLmin−1, respectively. The implementation of a Design of Experiment-Response Surface Methodology approach (DoE/RSM) allowed us to analyse the importance of each variable, as well as their interactions, in both the composition and the energetic features of the dry gas stream obtained. The temperature and the water/glycerine ratio played the principal role in determining the concentration of the main components (H2, CO, CH4, and CO2) and the low heating value of the resulting dry gas stream. The effect of both variables was likely related with their influence on the thermodynamic equilibrium of the different reactions taking place (reforming, water-gas shift, and methanation reactions). Two variables were defined in order to evaluate the efficiency of the glycerine gasification: the steam-reforming efficiency (SRE) and the carbon gasification efficiency (CGE). On the other hand, the rate at which the energy can be supplied by the installation (LHV̇) was strongly affected by all the three processing variables and was mainly related with the volumetric flow rate of the dry gas stream, while the LHV played a secondary role. The predicted ranges of H2, LHV, and LHV̇ were 25.8–60.7%, 9.03–14.40MJNm−3, and 0.47–5.26kW, respectively. In all cases, high interactions between the processing variables were detected, putting in evidence the usefulness of the DoE/RSM approach.

Tidal disruptions by rotating black holes: relativistic hydrodynamics with Newtonian codes

We propose an approximate approach for studying the relativistic regime of stellar tidal disruptions by rotating massive black holes. It combines an exact relativistic description of the hydrodynamical evolution of a test fluid in a fixed curved spacetime with a Newtonian treatment of the fluid's self-gravity. Explicit expressions for the equations of motion are derived for Kerr spacetime using two different coordinate systems. We implement the new methodology within an existing Newtonian Smoothed Particle Hydrodynamics code and show that including the additional physics involves very little extra computational cost. We carefully explore the validity of the novel approach by first testing its ability to recover geodesic motion, and then by comparing the outcome of tidal disruption simulations against previous relativistic studies. We further compare simulations in Boyer--Lindquist and Kerr--Schild coordinates and conclude that our approach allows accurate simulation even of tidal disruption events where the star penetrates deeply inside the tidal radius of a rotating black hole. Finally, we use the new method to study the effect of the black hole spin on the morphology and fallback rate of the debris streams resulting from tidal disruptions, finding that while the spin has little effect on the fallback rate, it does imprint heavily on the stream morphology, and can even be a determining factor in the survival or disruption of the star itself. Our methodology is discussed in detail as a reference for future astrophysical applications.

Identification of Encrypted Data Stream Based on Sparse Randomness Features and GMM

It is important to identify encrypted data stream on the network. The accurate identification of encrypted data stream not only helps insight into the operation of the entire network, but also accurately controls user behavior for specific requirements. In this paper, we proposed Gaussian mixture model using sparse feature selection of randomness to solve the identification of encrypted data stream. Experimental results show that the average identification rate of encrypted data stream is over 90%.

Continuous Top-k Monitoring on Document Streams

The efficient processing of document streams plays an important role in many information filtering systems. Emerging applications, such as news update filtering and social network notifications, demand presenting end-users with the most relevant content to their preferences. In this work, user preferences are indicated by a set of keywords. A central server monitors the document stream and continuously reports to each user the top- $k$ documents that are most relevant to her keywords. Our objective is to support large numbers of users and high stream rates, while refreshing the top- $k$ results almost instantaneously. Our solution abandons the traditional frequency-ordered indexing approach. Instead, it follows an identifier-ordering paradigm that suits better the nature of the problem. When complemented with a novel, locally adaptive technique, our method offers (i) proven optimality w.r.t. the number of considered queries per stream event, and (ii) an order of magnitude shorter response time (i.e., time to refresh the query results) than the current state-of-the-art.

A new method for calibrating hygrometers.

In this study, a new method was proposed for calibrating hygrometers. The moisture permeation cylinder, which was used to measure the water vapor permeability of fabrics, was used to generate various levels of relative humidity. A dry nitrogen stream was employed to sweep the water vapor away. It was deduced that the relative humidity of the outgoing nitrogen stream was negatively correlated to the volumetric flow rate of nitrogen stream, i.e., the lower the volumetric flow rate, the higher the relative humidity. The hygrometer HMT 333 was chosen to measure the relative humidity of the outgoing nitrogen stream at five levels. The test data indicated that good agreement was observed between the measured humidity and the observed humidity from the Vaisala, Inc. Moreover, this method offers high sensitivity and fast response. Therefore, the relative humidity of the outgoing nitrogen stream can be used as a secondary humidity reference.