Middle Channels Research Articles

Effects of microchannel width on fluid flow and temperature uniformity

Compact, lightweight and efficient microchannel radiator technology has become an effective way to solve the heat dissipation of microelectronic devices. This article is oriented to the heat dissipation requirements of electronic chips. The heat transfer performance and pressure drop characteristic for microchannel heat exchangers with various widths are investigated in this article to obtain an optimal width design. Results show that for the microchannel with the same width, the mass flow rate in the middle channels is larger than that on both sides. The heat transfer can be enhanced and the uniformity of the temperature distribution is improved by increasing the channel width gradually from the central position. A width distribution expression for an optimal reduction percentage of the channel width is formulated using the performance evaluation criterion for non-uniform channels developed in this article. A wave form microchannel was used to validate the formula for optimal structure design, which shows that the formula is suitable for a different type of microchannel.

Two-phase flow evolution and bubble transport characteristics in flow field of proton exchange membrane water electrolyzer based on volume of fluid-coupled electrochemical method

Proton exchange membrane water electrolyzer (PEMWE) holds great promise as a hydrogen production technology powered by renewable energy sources. In this study, a novel volume of fluid (VOF)-coupled electrochemical method was developed to investigate the two-phase flow evolution and bubble transport characteristics in flow field of PEMWE. The results show the bubbles in each sub-channel undergo processes of growth, coalescence, separation, and wall adhesion. Besides the liquid water flow velocity and the adhesion of the wall to the bubble, the accumulation of bubbles in the outlet manifold also affects the bubble removal rate, and cause bubble backflow. Hydrophilic anode porous transport layer (APTL) results in higher slug flow proportion in middle channels of flow field, causing lower bubble removal rates. Film and wavy flow formation in hydrophobic APTL significantly delays bubbles reaching the outlet manifold. Moreover, a larger APTL contact angle increases liquid water transport resistance and parasitic power in PEMWE. A 10°–130° APTL contact angle change results in 89.02%, 598.79%, and 37.68% increments in average dimensionless bubble diameter, bubble coverage on the bottom wall, and pressure drop of all channels, respectively. Moreover, uniform APTL contact angle arrangement better enhances mass transport capacity in PEMWE than gradient arrangement. These findings provide valuable insights into the mass transport mechanism of PEMWE.

Transfer Learning Dehazing Network by Gaussian Process Mapping

Haze seriously interferes with the high-quality imaging process, resulting in a significant difference from a haze-free scene to a hazy status. This phenomenon makes dehazing challenging. To make real data dehazing effective, we propose a novel Transfer Learning Dehazing Network (TLDN) with Gaussian Process Mapping (GPM) for the single image dehazing in this paper. Under our observation, we believe there is a correlation between hazy and haze-free scenes in the middle hidden channels. Therefore, we suppose a transfer functional relationship in some latent features encoded by two kinds of networks and embedded into a latent vector space. The two encoder–decoder networks are introduced to learn the corresponding high-dimensional feature representation between pairs of hazy and haze-free images. These features would be employed to build a mapping relationship under the Gaussian process regression. Finally, experimental results on synthetic data and real-world samples demonstrate the effectiveness of our proposed method.

Channel Processes Disconnectivity in Rivers Hydromorphology

The present paper deals with five main structural levels of channel processes and channel patterns due to disconnectivity of fluvial processes. River braiding is related to existence of point, bar, channel (island), anabranching and large distributary channels (located in the deltas of large and largest rivers). Meandering is related to sinuosity of the flow and formation of complex loop and large meanders, the dimensions of which are larger than those corresponding to the water content of the river, and the meanders of the meandering belts. Due to the instability of the straight flow, the structural levels of the straight single channel are distinguished by their size: pool hollows on the riffles, reaches between adjacent bends and segments of braided channel, sections between single branches and stretched stretch areas along the bedrock banks or in the incised channel. Each structural level is related to the previous one forming scaling sequence (middle and side channels are the basis for the formation of branches and bends, etc.), representing genetic series, although in some cases they may have a different origin (intra-floodplain intercepts, relics of delta branches, etc.). The meandering process happens over various scales in both braided and straight channels. The formation of structural levels is governed by river size, geology, effective discharges and local drivers.

Adjoint Attenuation Tomography of Sichuan–Yunnan Region

AbstractWe use seismic waveform adjoint tomography to constrain the shear-wave attenuation models of the crust and upper mantle in Sichuan–Yunnan region of China. On the base of 3D velocity model with high accuracy by the previous work, we use the adjoint approach to efficiently construct the anelastic structures. Spectral element method with graphic processing unit acceleration is implemented in our work. We use an envelope-based misfit function and develop a mini-batch gradient descent algorithm for model update. We have applied the adjoint tomography algorithms to 41 seismic events, including 1911 high-quality three-component displacement seismic records from 2009 and 2017 in Sichuan–Yunnan region. Synthetic tests show that the attenuation model is well resolved. The generated shear-wave attenuation model reveals detailed structural characteristics of the upper mantle in Sichuan–Yunnan region. Some notable features are observed, such as an obvious strong-attenuation zone in northern Yunnan, which provides evidence for the existence of high-attenuation middle and lower crustal channels.

Study on the Plugging Limit and Combination of CO2 Displacement Flow Control System Based on Nuclear Magnetic Resonance (NMR)

CO2 displacement is an important technology to reduce emissions and improve crude oil recovery, as well as prevent CO2 escape. Effective storage is key to the successful implementation of this technology, especially for medium and high permeability reservoirs. The current flow control systems that are applied to seal gas escape are mainly gas/water alternation, CO2 foam, and CO2 foam gel, but there is no clear understanding of the plugging limits of various flow control systems and the mechanism of their combined use of residual oil. Therefore, in this paper, a series of core replacement experiments are conducted for different flow control systems and their combinations. The quantitative characterization of the core pore size distribution before and after the replacement is carried out using the NMR technique to try and determine the plugging limits of different plugging systems, and to investigate the residual oil utilization patterns of self-designed flow control system combinations and common flow control system combinations under two reservoir conditions with and without large pores. The results show that the plugging limits of water/gas alternation, CO2 foam, and CO2 foam gel systems are 0.86–21.35 μm, 0.07–28.23 μm, and 7–100 μm, respectively, as inferred from the T2 (lateral relaxation time) distribution and pore size distribution. When different combinations of flow control systems are used for repelling, for reservoirs without large pore channels, the combination of flow control systems using higher strength CO2 foam first can effectively improve the degree of crude oil mobilization in small pore throats, compared to using gas/water alternation directly. For reservoirs containing large pore channels, using high-strength CO2 foam gel first to seal the large pore channels increases the degree of utilization of the large pore channels; using water/gas alternation first causes damage to the middle pore channels; High-strength CO2 foam gel seals the large pore channels when the plugging strength is not enough; and using water/gas alternation can effectively improve the degree of utilization of small and medium pore channels. The results of this paper can provide theoretical guidance for the multi-stage flow control of CO2 displacement in the field.

Moving Risk of Crowds in the Entrance Confluence Area in the Presence of Channelizing Facilities

In recent years, the measures to interfere the crowds movement with physical facilities (such as channelizing, separation railing) have become more and more common, but how they affect the crowd movement and what moving risks exist in the entrance confluence area have not been fully revealed. Therefore, this paper analyzes the moving risk of the crowds before the bottleneck entrance area, in the presence of the channelizing barriers by controllable laboratory experiments. The visual color cloud charts of the local density, speed and confusion degree of moving directions within the entrance confluence area are analyzed in the presence of different gaps (1.05m and 0.7m) channelizing barriers, to further quantify the motion risk of the crowds. The study finds that the narrower gaps of the channelizing railings, the larger area of high-risk zones, and they have clear ‘lane formation’ effect in shaping the risk zones. The both ends of the channelizing barriers are higher moving risk zones for multi-entry sides conditions, but the area before the middle channels also needs to be closely concerned when the participants entering from two opposite entering sides. The study will provide theoretical basis for evaluating the safety of the setting conditions of the channelizing barriers and conducting scientific crowd management decisions.

Mathematical model of porous solid impregnation based on multichannel representation of the pore system

In this work, based on the development of previously constructed concepts of modeling the process of impregnation of porous media with an unknown pore structure, a mathematical model was developed for calculation the change in water absorption of a body immersed in a liquid. The model is based on considering a porous structure in the form of a system of unconnected channels of three different radii. Using a theoretical model and experimental data approximations, the corresponding curves characterizing the truncated radial distribution of porous channels were obtained. Satisfactory agreement with experimental data was obtained for various porous materials. The presented calculations showed that, despite the roughness of the assumptions in the theory of fluid motion through pore channels and the pore system itself, the idea of multichannel is quite justified. It is possible that the variety of channels and their sizes determine mainly the fractal properties of the impregnated samples. The accepted scheme of pore channels shows somewhat underestimated values of the diameters of the middle channels. This indicates the need to include in the structure at least one more parameter, for example, tortuosity, in order to approximate the real characteristics of porous materials.

Application scheme and performance analysis of free space optical communication technology in INMARSAT

Abstract In this study, we propose an application scheme of free space optical communication technology in INMARSAT, and propose a 1.12 Tbit/s coherent free-space optical (FSO) communication system based on wavelength division multiplexing (WDM) and polarization-multiplexing quadrature phase shift keying (PM-QPSK) modulation technology. Based on optisystem software platform, the spectrum, bit error rate (BER), received power, error vector magnitude (EVM), and receiver sensitivity of the edge and middle channels of the system are analyzed. The simulation results show that the transmission rate and channel capacity of INMARSAT communication system are greatly improved by selecting the channel spacing and transmission environment reasonably.

Characteristics and origins of middle Miocene mounds and channels in the northern South China Sea

Numerous elongated mounds and channels were found at the top of the middle Miocene strata using 2D/3D seismic data in the Liwan Sag of Zhujiang River Mouth Basin (ZRMB) and the Beijiao Sag of Qiongdongnan Basin (QDNB). They occur at intervals and are rarely revealed by drilling wells in the deepwater areas. Origins of the mounds and channels are controversial and poorly understood. Based on an integrated analysis of the seismic attribute, palaeotectonics and palaeogeography, and drilling well encountering a mound, research results show that these mounds are dominantly distributed on the depression centres and/or slopes of the Liwan and Beijiao sags and developed in a bathyal sedimentary environment. In the Liwan and Beijiao sags, the mounds between channels (sub) parallel to one another are 1.0–1.5 km and 1.5–2.0 km wide, 150–300 m and 150–200 m high, and extend straightly from west to east for 5–15 km and 8–20 km, respectively. Mounds and channels in the Liwan Sag are parallel with the regional slope. Mounds and channels in the Beijiao Sag, however, are at a small angle to the regional slope. According to internal geometry, texture and external morphology of mounds, the mounds in Beijiao Sag are divided into weak amplitude parallel reflections (mound type I), blank or chaotic reflections (mound type II), and internal mounded reflections (mound type III). The mounds in Liwan Sag, however, have the sole type, i.e., mound type I. Mound type I originates from the incision of bottom currents and/or gravity flows. Mound type II results from gravity-driven sediments such as turbidite. Mound type III is a result of deposition and incision of bottom currents simultaneously. The channels with high amplitude between mounds in the Beijiao and Liwan sags are a result of gravity-flow sediments and it is suggested they are filled by sandstone. Whereas channels with low-mediate amplitudes are filled by bottom-current sediments only in the Beijiao Sag, where they are dominantly composed of mudstone. This study provides new insights into the origins of the mounds and channels worldwide.

RETRACTED: Accurate diagnosis of early lung cancer based on the convolutional neural network model of the embedded medical system

Early detection of infections can help reduce mortality. The malignant growth of the lungs is an irreversible disease whenever it is isolated in its early stages. Procedures are widely used in the clinical space for image enhancement in early detection. In this proposed approach, Computed Tomography (CT) -Image pre-processing techniques will be used as a channel for commotion exclusion, used for picture division. Then the extraction will give the questionable area of ​​interest of cancer affectless. This method and describes characterization methods for detecting cellular breakdown in the lungs. The lung images and their database in the basic three stages of pre-processing, division and highlight extraction stage to achieve greater quality and accuracy at the site of the cellular breakdown in the lungs. The Convolutional Neural Network providing precise order applications and strategy for detecting cellular breakdown in lung lungs using channels and division methods is proposed. Computed CT-Image images captured from cellular fragmentation in patients with computer hemorrhage are dissociated by creating a digital image-making strategy. The results obtained are similar to the standard features obtained from the ongoing investigation. Therefore settlement counting techniques can detect the cellular breakdown in the lungs with the middle channels and assembly of medical equipment and assist clinical specialists in detecting the cellular breakdown in the lungs.

Numerical simulation of bubble transport during steam generator tube rupture accident of Lead-cooled Fast Reactor

Steam generator tube rupture (SGTR) is a design basis accident in Lead-cooled Fast Reactor (LFR). A 1/8 centrosymmetric scale geometric model of ELSY primary system is adopted to build the computational domain. A Eulerian-Lagrangian CFD Discrete Phase Model (DPM) with an appropriate drag coefficient correlation is performed, and a base case of bubble transport study is analyzed to obtain the distribution of bubbles. Furthermore, the possibility of bubbles entrained to the core is evaluated. Results show that bubbles firstly reach the core edge channels and then to the middle channels. Meanwhile, a rupture at low and peripheral position can inject more bubbles to the core. In addition, 0.3 mm-0.6 mm and 1 mm bubbles have the largest probability to reach the core, considering the amount of bubbles with different sizes. This study is a guiding paper for bubble transport in SGTR, and it can provide useful reference for judging the impact of accident.

Texture Analysis using wavelet Transform

In this research application of wavelet based multiscale image analysis methods for texture analysis has been highlighted. These methods are based on multiresolution properties of the two-dimensional wavelet transform, which is used to extract the features needed to discriminate and differentiate various textures more accurately then existing methods, we also took into account the texture model, the noise distribution, and the inter-dependence of the texture features which further help in discriminating factor. Multiresolution approach is nothing but a modified wavelet transform called the tree-structured wavelet transform or wavelet packets for texture analysis and classification. This approach is motivated by the observation that a large class of natural textures can be modeled as quasi-periodic signals whose dominant frequencies are located in the middle frequency channels. With the transform, we are able to zoom into any desired frequency channels for further decomposition and thus we could extract more texture features as compared to other methods.

Nitrogen removal performance and bacterial community in a full-scale modified Orbal oxidation ditch with internal nitrate recycle and biocarriers

A modified Orbal oxidation ditch with biocarriers and internal nitrate recycle was used in a full-scale municipal wastewater treatment plant, and nitrogen removal performance and microbial community were investigated. The results indicated that ammonia nitrogen removal efficiency increased from 80.5% to 95.4% after increasing oxygen supply and adding biocarriers in inner channel, and biocarriers played an important role in ammonia nitrogen removal. Internal recycle could enhance total nitrogen (TN) removal in outer channel, with TN removal efficiency of modified Orbal oxidation ditch reaching 76.5 %, which was higher than that of the traditional Orbal oxidation ditch (68.7 %). The pyrosequencing results revealed that bacterial community of the activated sludge in inner, middle and outer channels were very similar, but differed to that of the biofilm. The relative abundance of Nitrospira was 15.3 % in biofilm and less than 1.5 % in activated sludge. Nitrospira was enriched in the biofilm, thereby ammonia nitrogen removal was enhanced.

Automated Microseismic Processing and Integrated Interpretation of Induced Seismicity during a Multistage Hydraulic-Fracturing Stimulation, Alberta, Canada

ABSTRACT The development of organic-rich, low-permeability formations for hydrocarbon production requires the use of unconventional techniques such as multiwell pad drilling of horizontal wells and massive multistage hydraulic-fracturing stimulations. However, proliferation of these unconventional development methods has been linked to localized cases of fault reactivation during or shortly after hydraulic fracturing. In the Duvernay formation, located in Alberta, Canada, induced seismicity from hydraulic fracturing has occurred on nearly vertical strike-slip faults that are difficult to detect with conventional seismic exploration methods. In such cases, faults may only be discernible from seismic events with precise and accurate locations, which generally requires dense seismic monitoring arrays deployed near the stimulated wells. In this study, we introduce a new, semiautomated workflow for processing passive seismic data from a dense array and then integrate it with a 3D seismic dataset to characterize seismicity clusters related to hydraulic fracturing and pre-existing faults. The reactivated faults inferred from the distribution of the microseismic events directly overlie a system of incised, middle Devonian channels below the Duvernay formation observed in time slices extracted from the 3D seismic data. The channel system exhibits a set of lateral offsets, interpreted as ancient strike-slip fault displacements, the detection of which is further enhanced by use of a similarity attribute calculated from the 3D seismic data. Taken together, integrated interpretation of induced seismicity and 3D seismic data support a model of a regional left-lateral strike-slip fault system that was active during the middle Devonian and reactivated in a reverse sense (right-lateral strike slip) during hydraulic-fracturing operations.

COMPARATIVE HYDRO-MORPHOLOGICAL ANALYSIS OF THE ISLANDS OF DIFFERENTLY BRANCHED UPPER OB AND MIDDLE LENA RIVER CHANNELS

This article is devoted to the formation conditions and morphometric features of the river islands. Also it considers the rate of branching of the Upper Ob and Middle Lena river channels. They are the largest rivers, but the Middle Lena River is bigger than the Upper Ob River by 6.15 times of total runoff and 2.5 times of width. However, both of them have unstable or weakly stable channels, characterized by parallel-sleeve, alternating, one-sided and single branchings, formed by numerous islands. Their comparison makes it possible to establish the dependence of the conditions of islands formation, their parameters (length - L , width - B , shape - L / B ), types and number on the indicators of stability, total runoff, branching types and location in the channel (active or peripheral part). These correlations based on hydro-morphological analysis show that the shape of islands L / B and the branching rate of the channel - n / x depend on the degree of stability. It is a common feature of all branching types and stages of island evolution (elementary, small, large islands and island massifs). Uniform dependencies of island parameters on river bed stability for both rivers, despite their large-scale distortions, were obtained by taking into account the connection of channel width ( b ) with its runoff ( Q ) by introducing a correction factor of 2.5 for the river size. Also the formation conditions of elongated islands ( L / B > 5), were determined. Their shape does not correspond to the optimal ratio L / B = 3...4. The revealed patterns give an opportunity to clarify the previously proposed classification of the islands.

Performance Study of Concentrated Circular Channels System (Orbal) for Removing Nutrients from Domestic Wastewater

A biological nutrient removal was investigated as a continuous flow (orbal) system to study the efficiency of system for removing phosphor and nitrogen compounds, and to predict the effect of internal and external recirculation rates on its performance. The pilot plant consisted of three concentric circular channels: outer, intermediate and inner in capacities of 24, 16.8 and 8.7 m3 respectively. The last sedimentation basin has sludge return system to the outer channel. Pilot plant also has an internal cycle to return the mixed liquor from the inner channel to the intermediate one. Continues Flow was used to feed the plant with raw municipal wastewater from Al-Khadraa residential quarter at an average flow rate of 66.7 m3/day. The plant was equipped with a modified surface aeration system operating in total power equal to 0.48 kW to achieve the required dissolved oxygen concentrations in the outer, middle, and inner channels: 0.38, 1.3, and 2.4 mg /L respectively. The three-channel was operated on two levels of returned activated sludge (RAS): 60% and 80%. It has three levels of internal cycle (IR): 100%, 150% and 200%. The results showed: the total removal efficiencies of phosphorous, and ammonia were in the range of: (93.3% - 88.5%) and (93.5% - 92.4%), respectively. The results meet the Iraqi standards for wastewater disposal into rivers. This study revealed there is no significant correlation between removal efficiency of ammonia with the internal and external recirculation ratios, while the effluent phosphor concentrations significantly affected by RAS and IR ratios. This study adopted the hypothesis: the process of simultaneous nitrification and denitrification (SND) occurs in the outer channel, while the phosphorus removal by the pilot plant was performed by the mechanism of enhanced biological phosphorous removal (EBPR).

Enhancement in Desalination Performance of Battery Electrodes via Improved Mass Transport Using a Multichannel Flow System.

Desalination technologies have heavily been investigated to utilize the abundant salt water on Earth due to the global freshwater shortage. During recent years, the desalination battery (DB) has attracted attention for its low-cost, eco-friendly, and energy-efficient characteristics. However, the current DB system is subject to inevitable performance degradation because of the mass-transfer limitation at the electrode-electrolyte interface, particularly when the system is used to treat brackish water. Here, we present a novel strategy to overcome the intrinsic mass-transfer limitation of DB in brackish water using an effective cell design based on a multichannel flow system. Compared to the conventional DB that consists of one feed channel, the multichannel desalination battery (MC-DB) is configured using two side channels introducing a highly concentrated solution to the electrodes and one middle feed channel for water desalination. The MC-DB showed a desalination capacity of 52.9 mg g-1 and a maximum salt removal rate of 0.0576 mg g-1 s-1 (production rate of 42.3 g m-2 h-1) when a salinity gradient between the feed streams in the middle (10 mM NaCl) and side (1000 mM NaCl) channels was present, which were 3-fold higher than those in the case with no salinity gradient. In addition, the high concentration solution in the side channel significantly enhanced the rate capability of MC-DB, allowing the system to operate under a high current density of 40 A m-2 with a desalination capacity of 34.1 mg g-1. Considering the effect of electrolyte concentration on the battery electrode performance through electrochemical characterization, the highly saline medium at the side channel in the MC-DB creates an optimal environment for the battery electrode to fully capitalize the high desalination capacity, salt removal rate, and capacity retention of the battery electrodes.

PENGARUH VEGETASI TERHADAP TAHANAN ALIRAN PADA SALURAN IRIGASI

Irrigation channel in D.I. Timbang Deli, Deli Serdang district Sumut province has a total area of 520 Ha and a 5000 meter long secondary channel. Irrigation channel in D.I. Timbang Deli overgrown vegetation at the base and wall of the channel so it is expected to affect roughness. The objective of the study was the flow resistance with the variation of vegetation volume to the variation of the discharge. The method used in this study is field observation by measuring flow velocity, flow depth and vegetation volume (VT) on trapezoidal tract width of 3.75 m and height of 0.90 m along 154 m. Measurements were performed on 3 points of upstream, middle and downstream channels and 5 transverse dots X1 through X5 4 times with D1 debit variation of 1.32 m³/s and D2 of 0.98 m³/s. The dominant vegetation channels are rigid. Measurement velocity using current meter while for vegetation volume (VT) using grid method. The results showed that vegetation volume VT0 (0,00 m³/0,00%), VT1 (52,417 m³/21,14%), VT2 (70,7921 m³/24,51%) and VT3 (83,053 m³/30,42%). It is seen that the increase in vegetation volume can affect the flow resistance. The result of measurement increased the resistance of flow to VT0 0,052, VT1 equal to 0,062 with percentage 16,13%, VT2 equal to 0,108 with percentage 51,85% and VT3 equal to 0,122 with percentage 57,37% atD1. Meanwhile, at D2 there is an increase of flow resistance to VT0 by 0,044, VT1 is 0,052 with percentage 15,38%, VT2 equal to 0,058 with percentage 24,14% and VT3 equal to 0,070 with percentage 37,14%. This shows that the flow resistance VT0 is smaller than the flow resistance VT1, VT2 and VT3. From the above results are expected to conduct O and P channels by surrounding communities and related government.

Experimental and numerical research on heat transfer and flow characteristics in two-turn ribbed serpentine channel with lateral outflow

This paper experimentally and numerically investigates the heat transfer and flow characteristics of a two-turn ribbed serpentine channel with lateral outflow. The heat transfer coefficient was measured by a transient liquid crystal technique. Experiments were carried out at Reynolds numbers between 5,000 and 20,000 and rotation numbers of 0 and 0.03. The results indicate that with increasing inlet Reynolds number, the high-Nusselt number regions of the middle and lateral outflow channels gradually move to upstream ribs. The inlet channel shows the highest increase rate of the Nusselt number; whereas, the rate is lowest at downstream turning area. The rotation increases the trailing surface Nusselt number of the inlet and lateral outflow channels, and the increase rate is more prominent for higher values of the Reynolds number. However, the rotation has negative effects on the averaged area Nusselt number of the middle channel in cases of Re ≤ 17,000. The pressure coefficients decrease the in inlet and middle channels along the flow direction; whereas, they slightly increase in the lateral outflow channel. There is a long low-velocity vortex formed in the lateral outflow channel, and the vortex size is considerably reduced by the rotation. Accordingly, the rotation has the most positive effects on the pressure coefficient of the lateral outflow channel.