Middle Channel Research Articles

Geomorphologic changes around a mid-river bar system at a meandering reach in the lower Yangtze River, China: Impacts of the three Gorges dam (TGD) and human activities

Mid-river bars are important agents that impact the flow and sediment dynamics of rivers and are commonly used for the development of human society. This study focused on the geomorphologic change (riverbed and bar morphology) around a large-scale river bar system in the lower Yangtze River (namely, Heishazhou) that was possibly impacted by the Three Gorges Dam (TGD) and other river engineering works. Relevant data sources including field surveys, hydrological station records, satellite images and historical practice reports were gathered for the investigation. The Heishazhou bar system previously consisted of two major subbars and recently merged as an entirety. Rapid bar growth occurred after the construction and operation of the TGD, leading to the closure of the Middle Channel and the South Channel dominating water conveyance at the reach. With the examination of another three bar systems in the lower Yangtze River, the lower-reach bar systems generally grew due to sediment deposition around bars, which differred from those in the middle reach that generally shrunk. The underlying cause may be that the middle-reach riverbed still supplies sediment to the lower reach. The riverbed at the Heishazhou reach, however, experienced apparent erosion after the construction of the TGD. Combining historical investigations and satellite images, a conceptual description was created to understand the geomorphologic cycle of river bar systems at a meandering reach and found that the formation of an inner-bank bar shall be a major force driving the geomorphologic cycle. Sediment deficits caused by the TGD and human activities such as dikes, bank revetments and riverbed dredging are highly likely to cause a slow-down of the geomorphologic cycle of these river bar systems with distinct mechanisms.

A flexible on-fiber H2O2 microfluidic fuel cell with high power density

To promote the simplification and integration of membraneless microfluidic fuel cell (MMFC) system and combine with flexible portable devices, a flexible on-fiber MMFC exploiting H2O2 as sole reactant is presented, eliminating the separation requirement of fuel and oxidant. Nickel (Ni) nano-particles and Prussian blue with multiwalled carbon nanotube (PB-MWCNT) are coated on hydrophilic braided carbon fibers (BCFs) to serve as the anode and cathode, respectively. The three-dimensional (3D) flow-through anode and cathode with a wealth of exposed electroactive sites improve reactant mass transfer. The anode and cathode are respectively wound on both sides of the middle cotton thread-based flow channel for separation. Under the combination of capillary force and gravity, reactants flow continuously through the fiber-based microchannels without external pumps. Importantly, the H2O2 MMFC achieves the highest maximum power density (MPD) of 14.41 mW cm−2 so far in one-chamber or single-stream H2O2 fuel cells. Besides, no serious deterioration in the power-generation performance is observed in complex practical operating conditions including bending with various angles, repeated folding and dropping. Three presented flexible MMFCs are connected to power a handheld calculator, indicating the tremendous potential of developing micro power supplies based on abundant flexible materials as well as green and sustainable energy.

Modular, Fabrication Free, Three-Dimensional Micro-Electrode Based Electrochemical Platform

Chip-based electrochemical platforms typically use planar interdigitated microelectrode ("P-IDμE"). However, P-IDμE suffers from a limited electric field penetration, limiting its sensitivity and selectivity for sensor usage. Hence researchers have devised novel methods to increase the field penetration for P-IDμE, including (i) inclusion of nanomaterials to increase the active electrode surface area or (ii) design elaborated device structure. A simple yet elegant method to fabricate a microfluidic electrochemical sensor based on the P-IDμE architecture for ultrasensitive detection remains a challenge.Our lab has devised a novel three-dimensional (3D) electrode architecture, as shown in Figure 1. Our method to fabricate this 3D electrode is simple and convenient. Our 3D electrode architecture consists of three layers: the top and bottom glass layers decorated with platinum (Pt) or gold (Au) μEs, and a middle microfluidic channel layer of double-sided polypropylene tape. The tape layer with desired channel pattern is sandwiched by nonplanar interdigitated microelectrodes ("NP-IDμE"). The use of polypropylene tape allows NP-IDμE to have a 3D electrode structure without extensive and costly fabrication steps. Further, the polypropylene middle layer provides the advantages of (i) A reasonably wide operating temperature window (−40°C to 120°C). (ii) Fast and easy electrode assembly. (iii) Excellent reagent-resist properties.Interestingly the 3D electrode architecture of NP-IDμE leads to some sustained electrochemical advantages over conventional P-IDμE besides the improved electric field penetration. A finite element analysis (FEA) simulation using COMSOL Multiphysics was undertaken to observe the enhanced field penetration in NP-IDμE, as demonstrated in Figure 1. Further, in P-IDμE’s, the electrode process is predominated by radial diffusion process, while in NP-IDμE, the diffusion is linear semi-infinite process. This change in the diffusion allows NP-IDμE to extract more significant insight into the analyte's electron transfer mechanism.Moreover, as the μE arrays are nonplanar, it allows us to observe the effect of the inderdigitization of the electrodes. It is observed experimentally that only when the electrodes in NP-IDμE are interdigitated, one observes a well-defined cyclic voltammetry (CV) and differential pulse voltammetry (DPV) profiles. We attribute this to the weakening of the electromigration term from the increased separation between the μE pairs. This was validated by electrochemical impedance spectroscopy (EIS). In EIS, we see a substantial increase in the charge transfer resistance as the μE arrays are further and further apart. As the electrodes are not modified, and the electrolyte conductivity is unchanged, this phenomenon is driven by the decrease in the electromigration term between the electrodes.NP-IDμE was further evolved to make a quasi 4D electrode. Room temperature, operator-independent, instrumentation less fabrication protocol for NP-IDμE allows us to pack NP-IDμE with different dielectric materials like metal organic framework (MOF) materials or conducting materials like carbon nanotubes (CNTs). This allows us to change the electrode response of NP-IDμE substantially. One example of such response is from packing MOFs in the channel. Nanoporous MOFs are loaded into the fluid channel and sandwiched between μE layers. This MOFs-based-NP-IDμE configuration adapted in this work provides the following sensor advantages. (i) Shear force enhanced: For our flow-based NP-IDμE microfluidic device, the introduction of nanoporous MOFs allows us to tremendously increase the shear force in the device, improving the selectivity and hence reducing false positives. (ii) Convective transport: The packing of the channel leads to a substantial increase in the convective transport in the NP-IDμE device. This enhances mixing, allowing more collisions between the capture sites in the MOF and the target analyte, leading to increased sensitivity. Further, the convective transport removes any diffusional limitations, which pushes the double layer relaxation time to high frequency. This allows us to measure the charge transfer resistance at high frequency, allowing for increased signal to noise and high sensitivity, thus lowering false negatives. Figure 1

A study of cold roll forming technology and peak strain behavior of asymmetric corrugated channels

The peak strain (PS) of sheet metal highly affects the process design and the quality of roll formed product. Different from the traditional roll forming technology (RFT) that all the cross section contours of the product are rolled simultaneously, a symmetric RFT is developed with respect to the corrugated channels to avoid defects like tearing, twist, and redundant deformations. The behaviors of their peak strains are subsequently simulated with finite element (FE), and the effects of three factors of the rolling speed, friction coefficient, and the bending angle of roll are analyzed, respectively. Finally, both the rationality of RFT and the accuracy of final rolled product are verified by experiments. Results show that the maximum peak strains are also distinguished for their different channel width, with respect to two symmetrical channels forming simultaneously even under the same bending angle and the pressure of roll. The maximum PS of the narrow channel is significantly larger than that of the wide, and the closer to the middle channel, the greater the PS of the narrow channel, which is on the right of bending angle of the trough. Moreover, the maximum PS is mainly influenced by the friction coefficient and bending angle of the first forming pass. This can provide a reference for other design of RFT and rolled forming quality improvement of the corrugated channels.

السمات الجيومورفولوجية والمورفومترية للأودية الموسمية في منطقة السبلوقة - شمال الخرطوم السودان

Research done on Sabaloka area (latitudes 160 12/, and 160 24/ N., and longitudes 330 and 330 36/ E) focused more on its geology rather than on its geomorphology, and particularly the seasonal wadis in the area. The authors consider that, understanding the geomorphological and morphometrical characteristics of these seasonal wadis is important for better understanding of its geomorphology, the influence of paleoclimate and for future utilization. The objective of this research is to identify the geomorphological and morphometrical characteristics of the seasonal wadis of Sabaloka area and to discuss the influence of major physical factors, particularly paleoclimate, on determining the nature and origin of these wadis. Methods of data collection included field works during 1996 and 1997, field trips between 2010 and 2014, and analysis of satellite images for the years 1983 and 2014, to determine the in particular the morphometric and topographic characteristics.. اًاThe main analysis revealed that seasonal wadis of the study area can be divided geographically into eastern wadis and western wadis based on the area’s topography, water divides and slope towards the River Nile. The Eastern wadis exhibit differences in depth, type,, shape, and size of deposits whereas in the western wadis,differences are confined to the shape and size of the deposits.In general, all these wadis have contributed to the formation of the flood plain of the Nile because they usually transport clayey, sandy and gravelly deposits. The main channels of the seasonal wadis reveal parallel and dendritic patterns of drainage which are characteristic in the upper reaches of Abu Gadad valley and the middle channel of Abu Gaduiem valley, and the radial pattern in Musa, Shuluk, and Sada wadis which drain the volcanic plateau . Morphometrical analysis of Abu Gaidoum and Abu Gadad wadis revealed that Abu Gaidoum is more developed than Abu Gadad, and morphometrical differences between these two wadis could be attributed to area factor. The research arrived at the conclusion that seasonal wadis of Sabaloka area could be considered as part of the paleo drainage systems of the River Nile, the Sahara and Red Sea Hills, and that paleoclimate and geological structure have significantly determined the geomorphological and morphometrical characteristics of these wadis and the differences between them.

Simultaneous and consecutive charging and discharging of a PCM-based domestic air heater with metal foam

• Study simultaneous and consecutive charging and discharging of storage heater. • Study a composite phase change material/metal heat exchanger cooled by air. • Study different modes of system operation for the purpose of domestic space heating. • Lower output air temperature for a higher air flow with a higher discharging rate. • 6.5 h for charging 15.32 kg phase change material with 90% porosity aluminum foam. Numerical investigations of the melting/solidification in a metal foam saturated with phase change material (PCM) were performed for simultaneous and consecutive operational modes. The composite is embedded in a rectangular compound cooled by passing air in a middle channel which is then employed to heat the room as a space heater. The composite is heated by two-rod heating elements to store thermal energy for peak-shaving purposes. The study covered the evaluation of the system in different operational modes for charging and discharging rate, the impacts of the metal foam and the influence of coolant flow rate on the solidification performance. The presence of PCM on one hand due to having almost constant temperature during the phase change process and the use of metal foam on the other hand due to proving high heat transfer rate from the PCM to the coolant, help in providing a uniform output temperature from the system which is a key factor for highly efficient space heaters. Moreover, evaluation of the operational modes can help to understand the behavior of the system in real scenarios when there is a need to charge the storage system and heat the room (discharging) simultaneously. The results show that the melting process is fully achieved due to the faster-charging process rate in modes I (8-hour charging and 8-hour discharging separately) and III (2-hour charging and 14-hour simultaneous charging-discharging), compared with mode II (2-hour charging and 2-hour discharging separately, repeated for 16 h). The temperature distribution in Mode III was more constant, which produced uniform heat exchanged between the PCM and the cooling fluid. The porosity is inversely proportional to the liquid development rate. The PCM melts entirely within 6.5 h for 90% porosity while 78% of the PCM melts in 8 h for the 95% porosity case. The final mean PCM temperature changed from 69.9 °C to 66.4 °C, when the air flow rate increases from 0.01 kg/s to 0.03 kg/s.

General Hydrography of the Beagle Channel, a Subantarctic Interoceanic Passage at the Southern Tip of South America

The Beagle Channel (BC) is a long and narrow interoceanic passage (∼270 km long and 1–12 km wide) with west-east orientation and complex bathymetry connecting the Pacific and Atlantic oceans at latitude 55°S. This study is the first integrated assessment of the main oceanographic features of the BC, using recent oceanographic observations from cruises, moored instruments and historical observations. The waters transported into the BC are supplied mainly by the Cape Horn Current, which carries Subantarctic Water (SAAW) at depth (100 m below surface) along the Pacific Patagonian continental shelf break. SAAW enters the continental shelf via a submarine canyon at the western entrance of the BC. The SAAW is diluted by fresh, nutrient depleted (nitrate, phosphate and silicic acid) Estuarine Water (EW) from Cordillera Darwin Ice Field (CDIF) forming modified SAAW (mSAAW). Freshwater inputs from the CDIF generate a two-layer system with a sharp pycnocline which delimits the vertical distribution of phytoplankton fluorescence (PF). Two shallow sills (<70 m) along the BC contribute to EW and mSAAW mixing and the homogenization of the entire water column east of the sills, coherent with Bernoulli aspiration. The central section of the BC, extending ∼100 km toward the east, is filled by a salty (31–32) variety of EW. In winter, this central section is nearly vertically homogeneous with low nutrient concentrations (0.9–1.1 μM PO4 and 7.5–10 μM NO3) and PF. The temporal variability of seawater temperature from 50 to 195 m in the central section of the BC was found to be mostly dominated by the annual and semiannual cycles and influenced by tidal forcing. The middle section of the BC was less influenced by oceanic inputs and its basin-like structure most likely favors retention, which was observed from the weakly stratified water column at the mooring site. Toward the east, the central section bathymetry is disrupted at Mackinlay Strait where another shallow sill separates the middle channel from the shallow eastern entrance that connects to the Atlantic Ocean. In this section, a weakly stratified two-layer system is formed when the eastward surface outflow (salty-EW) flows over a deeper, denser tongue of oceanic mSAAW.

The Stegodon Bonebed of the Middle Pleistocene Archaeological Site Mata Menge (Flores, Indonesia): Taphonomic Agents in Site Formation

The Middle Pleistocene fluvial channel site of the Upper Fossil-bearing Interval at Mata Menge in the So’a Basin, Flores, Indonesia, has yielded the earliest fossil evidence for Homo floresiensis in association with stone artefacts and fossils of highly endemic insular fauna, including Stegodon, giant rats, crocodiles, Komodo dragons, and various birds. A preliminary taphonomic review of the fossil material here aimed to provide additional context for the hominin remains in this bonebed. Analysis was performed on two subsets of material from the same fluvial sandstone layer. Subset 1 comprised all material from two adjacent one-metre square quadrants (n = 91), and Subset 2 all Stegodon long limb bones excavated from the same layer (n = 17). Key analytical parameters included species and skeletal element identification; fossil size measurements and fragmentation; weathering stages; bone fracture characteristics; and other biological and geological bone surface modifications. Analysis of Subset 1 material identified a highly fragmented assemblage with a significant bias towards Stegodon. A large portion of these bones were likely fractured by trampling prior to entering the fluvial channel and were transported away from the death-site, undergoing surface modification causing rounding. Subset 2 material was less likely to have been transported far based on its limited susceptibility to fluvial transport. There was no significant difference in weathering for the long limb bones and fragments, with the highest portion exhibiting Stage 2 weathering, indicating that prior to final burial, all material was exposed to prolonged periods of surface exposure. Approximately 10% of all material have characteristics of fracturing on fresh bone, contributing to the taphonomic context for this bonebed; however insufficient evidence was found for anthropogenic modification.

Phylogeography of Baryancistrus xanthellus (Siluriformes: Loricariidae), a rheophilic catfish endemic to the Xingu River basin in eastern Amazonia

Baryancistrus xanthellus (Loricariidae) is an endemic fish species from the Xingu River basin with its life history in the shallow rapid waters flowing over bedrock substrates. In order to investigate the genetic diversity and demographic history of B. xanthellus we analyzed sequence data for one mitochondrial gene (Cyt b) and introns 1 and 5 of nuclear genes Prolactin (Prl) and Ribosomal Protein L3 (RPL3). The analyses contain 358 specimens of B. xanthellus from 39 localities distributed throughout its range. The number of genetically diverged groups was estimated using Bayesian inference on Cyt b haplotypes. Haplotype networks, AMOVA and pairwise fixation index was used to evaluate population structure and gene flow. Historical demography was inferred through neutrality tests and the Extended Bayesian Skyline Plot (EBSP) method. Five longitudinally distributed Cyt b haplogroups for B. xanthellus were identified in the Xingu River and its major tributaries, the Bacajá and Iriri. The demographic analysis suggests that rapids habitats have expanded in the Iriri and Lower Xingu rivers since 200 ka (thousand years) ago. This expansion is possibly related to an increase in water discharge as a consequence of higher rainfall across eastern Amazonia. Conversely, this climate shift also would have promoted zones of sediment trapping and reduction of rocky habitats in the Xingu River channel upstream of the Iriri River mouth. Populations of B. xanthellus showed strong genetic structure along the free-flowing river channels of the Xingu and its major tributaries, the Bacajá and Iriri. The recent impoundment of the Middle Xingu channel for the Belo Monte hydroelectric dam may isolate populations at the downstream limit of the species distribution. Therefore, future conservation plans must consider the genetic diversity of B. xanthellus throughout its range.

Water Level Fluctuation Patterns in Restricted Intermediate Navigable Channels with Different Lock Emptying Processes

The fluctuation of water level caused by the unsteady flow of lock discharge, where the key problem is the relationships between the hydraulic factors in the restricted middle navigable channel and the transformation of unsteady flow and the corresponding scales are investigated. Based on the restricted middle navigable channel of the Baise navigation project, the relationship between the unsteady flow discharge process of lock and the water surface fluctuation process in the restricted middle channel is studied through systematic experiments, and the conclusion is drawn as follows. The main reason caused the flow fluctuation is attributed to the insufficient energy dissipation and rapid increase of discharge during the lock discharge process. And the sectional discharge method which reduces the peak value of the discharge process can reduce the fluctuation of upstream and downstream water level effectively. By reducing the peak value of the time-discharge curve, the energy dissipation along with restricted middle navigable channel increases, with the fluctuation amplitude of upstream and downstream flow reduces, and the attenuation rate of the energy dissipation increases. Furthermore, a fixed phase lag is formed between the reflection wave formed by the downstream ship lift gate and the discharge wave formed by the upstream ship lock discharge, which has little relationship with the discharge curve.

Parametric study of multichannel desalination battery for low-energy electrochemical deionization of brackish water

Multichannel desalination batteries (MC-DBs) have been utilized to enhance the performance of battery electrodes by decoupling the electrodes (side channels) and target brackish water (middle feed channel), enabling independent control of the channels. Nevertheless, the technological level of MC-DB is at an infancy, and further understanding of the role of operating conditions is required for its practical application. In this study, a parametric investigation of the applied current, cutoff voltage, and solution concentration fed to the feed and side channels was performed to improve the electrochemical deionization of MC-DB to achieve low-energy brackish water desalination. With presence of 20 times concentration difference between the feed and side channels, the MC-DB retained approximately 76% of the initial desalination capacity even upon a ten-fold increase in the current density (5–50 A·m−2). Moreover, MC-DB exhibiting a salinity gradient minimized the resistance penalty resulting from the low-salinity of brackish water. A high battery-utilization ratio (>80%) was achieved at various feed water concentrations. Up to 73% of the energy consumed for desalination was recovered through modification of the current and cutoff voltage. Consequently, under the optimized conditions, the MC-DB system could desalinate low-salinity brackish water with a substantially reduced energy consumption of 5.5 kJ·mol−1.

Bioinspired perovskite quantum dots microfibers from microfluidics

As perovskite quantum dots (PeQDs) are performing their outstanding characteristics, incremental efforts have been devoted to such materials. Here, inspired by the spider spinning process, we present novel PeQDs microfibers with tailorable morphologies and functions from a multi-injection microfluidic approach. The microfibers were generated by introducing PeQDs precursors into each barrel of the inner capillary array and mixing them in the spindle middle channel, where the poly(vinylidene fluoride) (PVDF) dissolved in N,N-dimethyl formamide (DMF) was also injected as their sheath fluid. During this process, the PeQDs were in situ synthesized with the connection of precursor cations and anions in the core fluid; while the PVDF formed solidified microfibers to encapsulate PeQDs with the fast dispersion of DMF into the outer aqueous solution. Thus, the good encapsulation of PeQDs was achieved in PVDF microfibers, which effectively protected them from different hostile environments. Because of the highly tunable spinning processes, the microfibers exhibited controllable diameters and helical geometric structures, and the encapsulated PeQDs could yield adjustable emission peaks. Based on the PeQDs microfibers, we have explored their potential as luminescent materials in barcodes and as flexible photodetectors, which make such microfibers highly versatile for different areas.

Experimental investigation on thermal performance of a pumped two‐phase battery cooling system using mini‐channel cold plate

This study presents an experimental investigation on a pumped two-phase battery cooling system using R1233zd(E) as the refrigerant. The thermodynamic cycle of the system, together with the heat transfer and pressure drop characteristics of the mini-channel cold plate, were analyzed under different conditions. Results showed that the pressure rise of the pump was increased under higher heat flux and mass flux, and the overall system pressure was elevated when the coolant bath temperature was raised. The effects of the mass flux on the overall heat transfer coefficient of the cold plate were different under various heat fluxes, while pressure loss of the cold plate showed a dramatic rise after the heat flux was over 2 W·cm−2. The average temperature of the cold plate was generally decreased with the increasing mass flux, while the maximum temperature difference was nearly constant when the heat transfer was dominated by single-phase forced convection. However, the maximum temperature difference could be lowered after flow boiling became dominant. In addition, the local heat transfer characteristics for different channels and the temperature uniformity in the cold plate were investigated. It was found that the local temperature was increased and then stabilized along the flow direction, while the local heat transfer coefficient was increased monotonously. Meanwhile, lower local temperature and higher heat transfer coefficient were found in the upper channel for the intensive boiling with lower mass flux which compared to the middle channel. Novelty Statement This study investigated the performance of a pumped two-phase battery cooling system using mini-channel plate under higher heat flux and discussed the reasons for wall temperature variation and temperature uniformity under different heat transfer mechanisms.

Tidal stream energy resource characterization in the Salish Sea

The Salish Sea, a large estuary on the Pacific Northwest coast, represents a great tidal stream resource because of its strong tidal currents in many tidal channels. However, the tidal energy resource in the Salish Sea has not been systematically characterized. This paper presents a modeling study conducted to characterize the tidal energy resource in the Salish Sea based on a high-resolution tidal hydrodynamic model, which was validated using data derived from 10 tide gauges and 132 current stations. A total of 16 tidal channels with strong currents were identified as hotspots for potential tidal energy development in the Salish Sea. Probability distributions and exceedance of the cross-channel average velocity were calculated at all 16 channels based on international standards for tidal energy resource characterization. The tidal energy resource at the 16 hotspots was also characterized using power density distributions and kinetic energy fluxes. The ranking of the kinetic energy fluxes suggested that Admiralty Inlet, Rosario Strait, and Middle Channel are the top three tidal energy hotspots in the Salish Sea. The study demonstrated the need of a high-resolution modeling framework for accurate simulation of tidal currents in large complex estuarine systems, in the context of tidal resource characterization and assessment.

Removing Speckle Noise in Synthetic Aperture Radar Images using Combined Intensity Coherence Vector & Hybrid Filtering

Noise will be unavoidable in image securing practice and denoising is a fundamental advance to recoup the image quality. The image of Synthetic Aperture Radar (SAR) is intrinsically misrepresented in dot noise that happens because of coherent nature of the dispersing wonders. Denoising SAR images target eliminating dot while safeguarding image highlights, for example, surface, edges, and point targets. The blend of nonlocal gathering and changed area filtering has coordinated the cutting edge denoising methods. Notwithstanding, this methodology makes an intense suspicion that image fix itself gives a brilliant guess on the genuine boundary, which prompts predisposition issue transcendently under genuine dot noise. Another impediment is that the for the most part utilized fix pre-determination techniques can't productively avoid the exceptions and harm the edges. The SAR image is infused with spot noise, and afterward edge based marker controlled watershed division is applied to recognize the homogeneous locales in SAR image. For every locale, the local pixels are distinguished by utilizing Intensity Coherence Vector (ICV) and are denoised autonomously by utilizing a half and half filtering, which contains the improved forms of ice, middle and mean channel. The exploratory outcomes show that the proposed strategy outflanks different techniques, for example, fix based filtering, non-nearby methods, wavelets and old style dot channels in wording higher wavelets signal-to-noise and edge conservation proportions relatively.

Anal ultrasonography in monitoring and postoperative evaluation of anorectal malformations

Objectives: We aimed to describe anal ultrasound for monitoring anorectal malformations. Methods: A descriptive and retrospective study of patients diagnosed and/or intervened with anorectal malformations rated by anal ultrasonography, between 2016-2017, was performed. We employed a transducer of 10 megahertz to identify the anatomy of the anal channel. Results: Eight patients, 5 men and 3 women were included, with a mean of 8.37 years old (range, 3-11). Three patients had a diagnosis of an anterior anus (not operated). Surgery was performed in 5 patients: 2 had a rectourethral fistula, 1 had a rectovesical fistula, and 1 had a rectovestibular and a perineal fistula. The most significant ultrasound findings were partial absence of the anterior part of the external sphincter, internal sphincter hypertrophy in the middle channel, and absence of internal sphincter in the median and high channel plus the absence of external sphincter in the anterior region. These results belonged to a patient with clinical incontinence and to 2 patients that were previously diagnosed with an anterior anus. Conclusions: Anal ultrasonography is a non-invasive method, economic, and feasible to be performed without anesthesia. It offers useful anatomical information to establish the best therapeutic option. Its main limitation is the unfeasibility of carrying it out on patients under 3 years old.

Performance Evaluation of a Virtual Impactor with an Additional Pretreatment Structure for Particle Separation

ABSTRACT In this paper, a proposed method based on a microfluidic chip that can arrange the collected particles in radial positions according to their sizes before virtual impactor separation was introduced. The main objective of this paper was to design a novel micro-separator structure composed of two major parts: a virtual impactor, and a pretreatment that consists of a sheath flow and a backward-facing step flow configuration. In the separation process, the particles firstly were aggregated on the middle channel by the sheath flow, then ordered in radial position of backward-facing step flow, and finally separated in virtual impactor. To determine the effects of the pretreatment, both simulations and experiments were conducted. A parameter optimization was performed on the micro-separator where the cut-off size of the virtual impactor was 2.5 µm. The results demonstrated that when the flow ratio between inlet flow rate and the total flow rate was set to 50% and the expansion ratio (Er) was 2. The cut-off size of the micro-separator was reduced by 20.77% from 2.436 µm to 1.93 µm, and the wall loss (WL) was acceptable compared with the result only using PM2.5 virtual impactor. The effect of pretreatment on PM1 and PM5 virtual impactor also saw an improvement of collection efficiency even when the additional pretreatment had varying Reynold numbers and nozzle sizes. Accordingly, the stk50 value was reduced by 44.39% from 0.669 to 0.372 by adding pretreatment before the virtual impactor.

A New Methodology for the Multilayer Tight Oil Reservoir Water Injection Efficiency Evaluation and Real-Time Optimization

It is important to determine the reasonable injection and production rates in the development of multilayer tight oil reservoir with water flooding treatment. Based on the INSIM (interconnection-based numeric simulation model), a connected network model, a new method is designed to evaluate the water injection efficiency of different layers in water flooding reservoirs and to optimize the injection-production system to produce more oil. Based on the types of sedimentary facies and corresponding injection-production data, the interwell connections are divided into four major categories (middle channel, channel edge, middle channel bar, and channel bar edge) and twelve subclasses. This classification standard of interwell connections could help to significantly improve the accuracy of judging the dominant flow path without constructing a complicated geological model. The interaction of interwells such as injection-production correlation and water injection efficiency could be revealed by simulating the production performance and computing the layer dividing coefficient and well dividing coefficient. A numerical example is used to validate this method by comparing results from FrontSim and this method, and the computational efficiency of this method is several dozen times faster than that of the traditional numerical simulation. This method is applied to quickly optimize the production schedule of a tight oil reservoir with the water flooding treatment, that is, the water injection rate of multilayer reservoirs could be optimized subtly by the injection efficiency of different layers, and the target of producing more oil with lower water cut could be achieved.

Non-equilibrium phase transition in the heterogenous TASEPs with binding and unbinding processes among the adjacent subsystems

Abstract Non-equilibrium phase transition is always one of the most important issue for complexity science, since it can reveal physical mechanisms of abundant physical phenomena. Exploring applications of non-equilibrium phase transitions in basic paradigm models of complexity science is vital for better comprehending essences of real physical processes. Among these processes, totally asymmetric simple exclusion process (TASEP) stands out owing to important theoretical significances and practical value, whose importance is regarded as being equivalent to Ising model. In this paper, a heterogeneous interacting particle system constituted by three-lane TASEPs with binding and unbinding processes affected by interacting energies among adjacent subsystems is proposed. Nonlinear equations about all particle configuration states of boundaries and bulk are established. We find and analyze numerical local densities and currents by performing simple and cluster mean-field analyses. Nine species of phases including homogeneous phases and mixed ones are discovered. Specifically, as for mixed phases, densities of middle channel are much larger and smaller than those of neighboring ones when specific interacting energy is positive and negative, respectively. All triple points are found to move to upper left corner of phase space with increasing interacting energy. Current phase diagrams mapped into density phase ones are explored, which reveal currents in homogenous phases rely on just one critical governing parameter (namely, injecting rate or escaping one) while those in mixed phases are controlled by the coupling effects of these two critical governing rates. Theoretical results from mean-field analyses are confirmed by simulations, which yield to fine coincidences. This work will improve understanding of non-equilibrium phase transition mechanisms in such basic paradigm models and stochastic dynamics in corresponding critical phenomena to a certain extent, especially cluster effects and related dynamic processes of self-driven particles in such systems in the area of complex system science and statistical physics at mesoscopic scale.

A direct formate microfluidic fuel cell with cotton thread-based electrodes

A direct formate microfluidic fuel cell with cotton thread-based electrodes is proposed. The palladium catalyst is directly coated on cotton threads by repeated dipping method to prepare electrodes, which integrates the flow channel and electrode together and provides exposed active sites for enhancing the mass transfer on the anode and cathode. The aqueous anolyte and catholyte transport through cotton threads by capillary force with aid of gravity, eliminating the use of any external pump and facilitating the integration and miniaturization of the whole system. In the experiment, a three-flow channel structure is employed. The fuel is sodium formate and the oxidant is hydrogen peroxide. 1 M Na2SO4 solution is introduced into the middle channel formed by cotton threads with no catalyst to alleviate the reactant crossover. Performance is evaluated under various catalyst loadings, fuel concentrations and differences in height between the inlet and outlet. Results show that the fuel cell produces an open circuit voltage (OCV) of 1.41 V. The maximum current density of 74.56 mA cm−2 and the peak power density of 24.75 mW cm−2 are yielded when the palladium loading is 1 mg cm−1 and the difference in height between the inlet and outlet is 7 cm, using 4 M HCOONa as fuel. Furthermore, the performance of the fuel cell increases first and then decreases with increasing the palladium loading. The same variation is observed with increasing the fuel concentration. However, the performance gradually increases with increasing the difference in height from 3 cm to 7 cm. The proposed microfluidic fuel cell with cotton thread-based electrodes shows enormous potential as a micro power source for portable devices.