Secondary Channel Research Articles

A Hybrid Spatial Adaptive Modulation and Frequency Stochastic Approach for MU-MIMO-OFDM Systems in the Context of Underlay Cognitive Radios

In this paper, low complexity rate and power optimization schemes operating in the spatial and frequency domains are proposed in a cognitive radio (CR) setting involving multi-user multiple-input-multiple-output-orthogonal frequency division multiplexing (MU-MIMO-OFDM). Under the assumption of a perfect secondary channel state information (CSI) at the receiver, the presented architectures encompass two main stages. In the first one, spatial power waterfilling-like method is performed per each MIMO subchannel pertaining to each subcarrier of each secondary user (SU). The resulting allocated power per each eigen-channel is considered as the power budget in the second stage. In this latter, stochastic algorithm-based approach wherein the transmit parameters per each subcarrier of each SU are adapted such that to maximize the achievable sum-rate capacity of the SUs. Three different schemes are introduced in this work. First, the derivation of the continuous rate MU-MIMO-OFDM-CR version, referred to as C-MU-MIMO-OFDM-CR is presented. Obviously, this proposition is theoretical and is taken as a benchmark for the two remaining counterparts. The second proposition we called discrete-rate MU-MIMO-OFDM-CR, and briefly designated as D-MU-MIMO-OFDM-CR which is to round the provided allocated rate. Finally, the third modified solution, denoted as P-D-MU-MIMO-OFDM-CR proceeds in a similar way as the D-MU-MIMO-OFDM-CR alternative, but superimposes the non/over-used amount of power to the power budget in next iteration. The simulation results show that, compared to the discrete rate D-MU-MIMO-OFDM-CR solution, the P-D-MU-MIMO-OFDM-CR approach exhibits an approximate power gain of 1 dB when the SNR level is low, and of 5 dB at high SNR range.

A critical review on single-phase thermo-hydraulic enhancement in geometrically modified microchannel devices

The usage of liquid-cooled microchannel heat dissipation devices is gaining importance in thermal management of electronic components owing to miniaturization. The development of such devices requires a deeper knowledge of the flow characteristics within geometrically modified microchannels. This article critically examines the research on modifications in geometry of channels for thermo-hydraulic performance enhancement. The article aims to determine the best channel configuration with optimal parameters that can maximize the overall performance of the device. For this purpose, collected research have been scrutinized in ascending order of the complexity in channel design. This article explores various designs and their influencing parameters, starting with linear and non-linear microchannel shapes, followed by bifurcated and connected secondary channels and, in the end, configurations with structured roughness such as cavities, ribs and cavity-rib combinations in it. Finally, conclusions of the examined research are presented with an analysis of their implications as well as gaps and potential recommendations for future research.

Floating rooted hydrophytes and flow and sediment dynamics: Field study in secondary channels of the Paraná River

Worldwide, aquatic vegetation is a key component in many river systems due to its diverse interactions as well as the environmental services it provides. In the Paraná fluvial system, large mats of floating rooted hydrophytes are present in channels with different water conditions whose interaction with flow and sediment dynamics is currently unknown. This work aimed to evaluate the temporal coverage variation of floating rooted hydrophytic mats as well as the alteration of flow dynamic and sediment deposition associated with their presence in natural conditions. Four different secondary channels were analyzed for two different and consecutive water stages: mean and high-water levels. Hydrophytic coverage ranged from 5% to 67% and from about 3% to 14% of the total discharge drained throughout the vegetated areas of the channels, being the lowest values recorded during the high-water stage. The specific discharge distribution and flow velocities at the vegetated cross-sections were altered when compared to non-vegetated sections. Mean velocities and depths were markedly lower inside vegetation mats. Additionally, fine sediments (silt and clay) dominated the bed samples below the hydrophytic mats of the vegetated sections in all the channels and water level stages under study. Nonetheless, the highest wash load was mainly recorded outside the hydrophytic mats during mean waters, while it was registered within the mats during high waters. Grain size of bed material below the hydrophytic mats as well as flow velocities inside them indicated sedimentation promoted by the hydrophytic mats. Understanding how flow and sediment deposition can be altered by hydrophytic mats is of great relevance not only in terms of the role they play in the Paraná fluvial dynamics, but also for their appropriate inclusion in hydraulic field measurements and hydrodynamic models widely used to predict such dynamics.

THE PECULIARITIES IN THE FORMATION OF GUNSHOT WOUNDS CHANNELS CAUSED BY 7.62 MM EXPANSIVE «HPBT» AND «SP» TYPE BULLETS

The aim of the study – to study the peculiarities of wound channel formation, causedby 7.62 mm «HPBT» and «SP» bullets, by means of experimental methods of forensicballistics with the use of human biological tissue simulators.Materials and methods. Experimental investigations were carried out under conditionsof the ballistic route of the National Scientific Center «Hon. Prof. M. S. Bokarius ForensicScience Institute». To determine the velocities of the fired bullets, the optoelectronicmeasuring complexes IBX-731.4 were used. Ballistic plasticine «Beschussmasse,6287156» was used as a simulator of human body tissues. The experimental shooting wascarried out with a TS.M308 model .308 «Winchester» sniper rifle. For the experimentalshooting 7.62 × 51 mm (.308 «Winchester») cartridges were used, which were filled with«SP» and «HPBT» bullets.Results. In the course of experimental shooting, the peculiarities of the formation ofdamage channels caused by 7.62 mm «SP» and «HPBT» bullets were determined. Basedon the results of experimental studies, it has been found that the bullets of these types ofthe same caliber and practically the same mass are able to cause different amounts ofbodily injury, which is primarily due to the peculiarities of the design of the bullets. SPtype bullets with a bare core cause more severe bodily injuries, they are less subject tofragmentation and in most cases retain a relatively heavy bottom part. As a consequence,such bullets are able to cause longer wound channels than other types of expansivebullets. HPBT-type bullets can also cause sufficiently large amounts of bodily injury,but because of their design, they are more prone to fragmentation when hitting thehuman body. In the course of the research it has been established that there are severalperipheral (secondary) channels in the area of the main wound channel. They are formeddue to destruction of the bullet and movement of its separate fragments away from themain direction, which leads to complication of diagnostics and further treatment of suchgunshot wounds.Conclusions. The use of 7.62 × 51 mm (.308 «Winchester») expansive «SP» and «HPBT»type bullets in the course of combat operations for firing modern sniper systems resultsto severe bodily injuries. Wounds caused by such bullets are characterized by significantin volume zones of direct traumatic necrosis (contusion), which significantly extend deepinto the tissues and structures of the human body and form even larger in size zonesof conditional necrosis (contusion) and morpho- functional changes. The formationnature of both the main wound channel and the peripheral wound channels, caused byfragments of bullet structural elements, depends on the velocity, design features andposition (projection) of the bullet at the moment of impact. Changes in biological tissuesin the area of wounds caused by these types of expansive bullets have rather complexarchitectonics, which significantly complicates the issue of clear delimitation of gunshotwound zones and adequate surgical intervention. The used investigation methods of thestriking properties of expansive bullets are suitable for predicting the severity and volumeof the caused injuries, as well as for determining the individual characteristic complex ofgunshot wounds signs caused by such bullets.

The pre-Jurassic Meng-Shaan paleochannel and its control on the accumulation model of Yan 10 reservoir in Central Ordos Basin

In the setting of the increasing density of exploration wells, and the decreasing scale and increasing difficulty of discovering Jurassic paleogeomorphology reservoirs, it is urgent to deepen the fine depiction of pre-Jurassic paleogeomorphology features and to analyze their controlling effect on reservoirs. Based on abundant logging data combined with indoor microscopic observation and experimental testing, the paper applies the theory of reservoir configuration analysis for the first time to the single-channel period division of the pre-Jurassic Meng-Shaan paleochannel which deposited with the braided channel sand bodies. Meanwhile, it reveals the controlling effect of hydrocarbon accumulation and the distribution characteristics of the Yan 101 reservoir as ' paleogeomorphology and sedimentary facies combination' to determine the type, 'migration channel' to determine the distributing range, and 'low-amplitude structure' to determine the trap in the study area, and also the reservoir accumulation modes in different channel ranges have established. In conclusion, the single-channel boundary of the Meng-Shaan paleochannel in different periods controls the path of oil and gas migration, thus controlling the distribution range and reservoir type of the Yan 10 reservoir. Moreover, depending on the production data we derived that it should prefer the composite trap reservoir of the Fuxian period and the Yan 102 period, as well as the structural reservoir on the periphery of the Yan 102 period single-channel for the further exploration of the Yan 10 paleogeomorphology reservoirs within the development range of the Meng-Shaan ancient river. In particular, the lithologic trap reservoirs within the Fuxian period channel and the Meng-Shaan main channel, such as the reservoirs of the 'Source' of the secondary channel type and the paleochannel type, which could as a replacement accumulation model for increasing reserves and production.

Design and thermal performance analysis of a new micro-fin liquid cooling plate based on liquid cooling channel finning and bionic limulus-like fins

As the current channel-type liquid cooling plate generally suffer from high pressure loss and low cooling efficiency, making electric vehicles have to face problems such as high battery pack temperature and short mileage. To solve the above problems with channelized liquid-cooled plate, the conventional liquid-cooled channel was first rectangularly finned, and the size of the fins was optimized by varying the longitudinal spacing ratio f/a and transverse spacing ratio w/b between adjacent fins. Results show that the liquid-cooled plate had the lowest average temperature and pressure drop and the best overall performance when the size of the fins in the corresponding directions and the size of the spacing between the corresponding directions were equal. Secondly, on the basis of the optimization, the preferred fin form was preliminarily biomimetic. CFD simulation results show that the bionic limulus-like fins (BLLF) were more effective, with pressure drop (ΔP) and average temperature (T_ave) improved to a certain extent, compared with the rectangular and oval conventional shape fins. Subsequently, the number of inlets and outlets and their layout positions were discussed. Then, in order to further improve the performance of the cold plate, according to the shape characteristics of the limulus, the scrambler fins were homogenized to form a central channel and two secondary channels were added diagonally upward, which continued to construct a new type of microfin for the bionic limulus, and a multi-objective optimization of the secondary channels was carried out with L, W, α, and β as the parameters. Compared with the original model, T_ave and ΔP of the optimal model were reduced by 1.69 °C (4.61 %) and 6.81 Pa (54.26 %). Finally, the effect of the variation of Reynolds number on the thermal performance was discussed. It can be seen that the bionic fin design approach obtained in this study will provide a reference for liquid-cooled channel finning optimization.

Asymmetric evolution of river mouth bifurcation under angled river‐tide interaction, a case study at river mouths of Lingding Bay, Pearl River estuary

AbstractA thorough understanding of the evolutionary trends of river bifurcation channels is crucial for effective estuarine management in China's Greater Bay Area due to significant morphological changes observed in river mouth channels. At this tide‐influenced river mouth, where suspended sediment transport is dominant, how river mouth bifurcated channels that have different angles to the major axis of the incoming tidal flow in the receiving basin evolve on decadal scales remains unclear. Based on a comparative analysis of historical bathymetric data and numerical experiments using a validated morphodynamic model, we developed a conceptual model to illustrate the two end members of the morphological evolution of river mouth channels: a low‐angle (<45°) main channel and a high‐angle (>45°) secondary channel relative to the major axis of tidal flow in the receiving basin. If the mouth outflow also has a low angle with the main channel, the incoming tidal discharge fluxes have first‐order control over changes in the evolutionary trend of the bifurcated channels by changing the partition of residual sediment discharges between the two bifurcated channels. For example, a high incoming tidal discharge that varies around the mean flow increases the partitioning of residual sediment discharges from the upstream channel to the low‐angle channel, facilitating tide‐induced erosion in the low‐angle channel. By contrast, a low incoming tidal discharge decreases the partitioning of residual sediment discharges from the upstream channel to the low‐angle channel, which facilitates fluvial‐induced erosion in the high‐angle channel. Thus, high tidal discharges usually coincide with the river mouth adopting a single channel, and low tidal discharges facilitate the formation of fluvial‐induced bifurcation. The historical evolution of the river mouth and modern velocity measurements corroborated results derived from model experiments. The conceptual model applies to river mouths where suspended sediment transport is dominant and influenced by angled incoming tides.

Structural evolution of bed drainage channels under the shear effect of the whole process of tailings thickening

Cemented paste backfill (CPB) technology has the advantages of safety, environmental friendliness, economics, and efficiency. This method offers assurances for practical underground mining and tailings pond management. The bed drainage channel structure and coarse particles with diameters above 45 μm were reconstructed and quantitatively characterized in 3D by computed tomography (CT) for the whole tailings thickening process. The spherical pore diameter evolution trends, stick throat channel radius and throat channel length were analyzed with and without shear using the pore network model (PNM). The functional relationship between the average spherical pore diameter and bed pressure is given, and the boundary values between the bed’ primary and secondary drainage channels are clarified. The ratio of throat length to diameter (Tw) is proposed to measure the difficulty of throat channel structure on the water discharge in the bed. The effects of the volume and number of coarse particles with diameters above 45 μm on the bed porosity and pore connectivity were analyzed. The range of particle diameters that significantly affect the bed porosity and pore connectivity was clarified. The results show that the spherical pore diameter, throat channel radius, and throat channel length decrease with increasing bed pressure with and without shear. Moreover, the average spherical pore diameter in the bed has a power-law relationship with the bed pressure. The spherical pore diameter, throat channel radius, and throat channel length with shear were lower than without shear, and the slurry concentration was higher than without shear. The main drainage channels of the bed with and without shear consisted of large pore structures with diameters of not less than 433.3 μm and 329.8 μm, respectively. The throat channel structure parameter Tw increases with the increase of bed pressure. When Tw is higher than 8.7, the discharge of water in the bed is hindered, making it challenging to improve the slurry concentration. The porosity and pore connectivity of the bed decreases with increasing volume and number of coarse particles. Among them, coarse particles in the diameter 150–300 μm range significantly reduce the bed porosity and pore connectivity. This study guides the preparation of high-concentration paste filling slurry, which is helpful to improve the efficient mining capacity of mines and have fewer tailings ponds.

Numerical investigation of a Coandă-based fluidic thrust vectoring system for subsonic nozzles

The numerical investigation of a novel subsonic thrust concept for fluidic thrust vectoring (FTV) of jet engines is the subject of this publication. FTV possibly offers advantages over conventional mechanical thrust vector control such as decreased complexity, mass and maintenance costs. The operating principle of the FTV nozzles under investigation at the Institute of Jet Propulsion is based on the Coandă effect. The applied concept of thrust vectoring uses dedicated secondary flow channels which are mounted in parallel around the nozzle inner cone or the nozzle wall. If required, bleed air, provided by extraction from the engine compressor or from an external source, is injected at a specific nozzle pressure ratio at the nozzle throat A_8 through these secondary ducts, resulting in the redirection of the secondary jet towards the convex Coandă surface. The interaction between the primary mass flow and the secondary jet leads to a redirection of the primary exhaust mass flow of the engine and thus to a vectoring of the exhaust flow. In this paper, the influence of different nozzle geometric parameters and different operating points are investigated within an extensive parametric study applied to a convergent two-dimensional thrust vectoring nozzle using computational fluid dynamics tools. Thrust vector deflection of up to {20}^{circ } at a maximum secondary to primary mass flow ratio of 10 % is achieved. Reducing this mass flow rate to 5 % still yields vectoring angles of up to {15}^{circ } whereby similar deflection angles compared to conventional mechanical thrust vectoring systems are achievable.

PROPAGATION OF CARGO SHIP WAKE INTO SECONDARY CHANNELS

Cargo ship wake can be a strong and frequent source of energy along shorelines in the vicinity of commercial shipping channels. Large vessels in narrow channels produce low-frequency wake that consists of a positive front wave at the bow of the vessel, a depression (drawdown) spanning the length of the vessel, and an upwards surge produced by the stern wave at the stern. This low-frequency wake is followed by high-frequency wedge-shaped Kelvin wake, as well as continued low-frequency oscillations that may persist in the channel more than 30 minutes after a vessel passage. Low-frequency cargo ship wake with wave heights up to 2.8 meters was identified as the dominant source of erosion at Bird/Long Islands in the Savannah River, Georgia, USA based on the analysis of one month of Aquadopp measurements that captured over 300 large vessel wake events. The islands divide the river into the Main Channel, which contains the shipping channel, and the South Channel, a shallow, sheltered secondary channel trafficked only by small craft. Cargo ship wake was the primary energy source in both channels. The dominance of cargo ship wake energy in the sheltered South Channel demonstrated that the effects of wake extend beyond the shipping channel shorelines. This finding motivated three follow-up studies to quantify the extent and significance of cargo ship wake in the far-field, secondary channels connected directly or indirectly to the shipping channel.

Examining Safety & Security, Reliability and Punctuality of Public Transportation Quality Services: Cases of Kuala Lumpur, Malaysia

Urban public transportation in Kuala Lumpur rely heavily on land-based transportation such as taxis, grab, and buses as well as rail-based transportation, namely commuter trains, light rapid transit (LRT), and mass rapid transit (MRT). The metropolitan town of Kuala Lumpur, Malaysia's capital city with approximately 10 million people, has boosted the transportation demand. Thus, this paper examines the public transportation service quality issue of safety and security, reliability, and punctuality. Several points and actions would serve as foundations for service providers in improving public transportation services. This secondary study employs relevant information through secondary channels: journal papers, the internet, newspaper, magazines, and books. It offers an understanding of public transportation issues in Kuala Lumpur. Interestingly, findings indicated that safety & security, reliability, and punctuality are prominent in influencing the quality of public transportation quality service. Suggestions for future research were given to enhance the study further.

Pre- and postsettlement depositional processes and environments of the 3rd- to 5th-order White Clay Creek watershed, Piedmont Province, Pennsylvania and Delaware, USA

We extend two hypotheses based on studies of 1st- to 3rd-order Piedmont watersheds of southeastern Pennsylvania, USA, by collecting data in a larger 3rd- to 5th-order watershed nearby. One hypothesis posits that presettlement river corridors were dominated by wetlands, and the other suggests that river valleys were filled by millpond sedimentation following European settlement. Both hypotheses support new river restoration practices, so their generality is important to assess. Ten lithofacies indicate depositional environments, while pedostratigraphic criteria and 14C dating define presettlement and postsettlement stratigraphic units. Basal gravels similar to modern stream bed sediments represent presettlement channels with active bedload transport. Wedge-shaped gravel deposits resembling modern bars further document presettlement bedload transport by channelized flows. Extensive presettlement and postsettlement units of massive, organic-poor, fine-grained sediment formed when overbank flows inundated floodplains. Peat deposits, exposed at a single site (but absent elsewhere), represent a presettlement wetland. Decimeter-thick, discontinuous, massive carbonaceous fine-grained sediments occasionally overlie basal gravels; these may represent localized wetlands adjacent to presettlement channels or hydraulic backwater environments. Laminated sand and mud accumulated behind one 3-m-high mill dam, but these millpond deposits are absent at other sites. Instead of being dominated by wetlands, presettlement river corridors are better described as a complex mosaic of riparian environments including older colluvial landforms, floodplains (some of which may have been seasonally inundated wetlands), primary (and possibly secondary) channels, and depending on geomorphic setting, either localized or valley-spanning wetlands. After European settlement, millponds were important locally, but their deposits represent a minor component of the stratigraphic record.

Metal–Organic Frameworks for Water Desalination

AbstractRapid industrialization and ever‐increasing global population culminate in continuous upsurge in freshwater crisis worldwide. The most reliable and promising solution to this crisis is utilizing sea‐water as the freshwater source, and desalination technologies pave the way for efficient production of freshwater from sea‐water. In this regard, membrane‐based desalination method comes forth owing to its' efficient separation, operational ease, and low‐energy consumption. Metal–organic frameworks (MOFs), the most explored crystalline porous materials, show tremendous promise as membrane‐materials for desalination owing to their structural diversity, tunability, and porous voids which provide secondary water channels. Given significant advances are made in MOF‐materials for desalination in the past few years, it is crucial to systematically summarize the recent progress and development of this field. In this review, a brief overview of various saline water systems and prerequisites for desalination are first presented. Then, advanced fabrication strategies MOF‐membranes followed by the recent progress in MOF‐materials for various desalination processes such as reverse osmosis and forward osmosis are systematically summarized. Finally, the authors’ perspectives on the unsolved scientific and technical challenges and opportunities for MOF‐integrated membranes toward real‐world implementation are proposed. With further systematic development, MOF‐materials promise to provide an ideal platform for next‐generation desalination technology.

Priority Handling of Teurebeh Irrigation Assets, Aceh Besar District, Aceh Province

Teurebeh Irrigation scheme is one of the promising irrigation areas in Aceh Besar District, Aceh Province. It is also one of the buffers in the agricultural sector, covering 750 hectares of agricultural area. However, the construction has shrunk over time, and the evaluation at the end of 2020 classified it as "Poor Performance and Requiring Attention." This study aims to determine the handling priority for the irrigation networks at the Teurebeh Irrigation scheme. Data on irrigation network inventory was used as input. The determination of handling priority was conducted using the Mann-Whitney method. The ranking for determining the importance of irrigation assets is based on the condition and function of the irrigation assets. ArcGIS and Google Earth software were used to determine the condition and handling of all assets. The results show that the handling priority levels are between the primary and secondary channels. The tapping structure of BDT.8, BDT.6, BDT.4, BDT.1, and BDT.7 are ranked 1 to 5, meaning they must be fixed immediately as the conditions are severe to moderately damaged and not functioning to functioning poorly. BDT.1 to BDT.3 is in the Primary Channel, while BDT.4 to BDT.8 is in the Secondary Channel. The handling priority for irrigation construction in the primary channel (BDT.1, BDT.1a, and BDT.1c) and the secondary channel (BDT.8, BDT.6, and BDT.7a) are within priority 1 to 3. The Mann-Whitney test on the proposed hypothesis comparing the urgency level between the two channels is insignificant, indicating no significant difference between the handling of primary and secondary channels, as both have similar conditions and functions. The results are expected to contribute to decision-making at the Irrigation Department in designing proposals for renovating irrigation networks.

Coupling Relationships between Sedimentary Microfacies, Sand Bodies, and Tectonic Fracture Characteristics in Braided River Deltas: A Case Study of the Bashijiqike Formation in the Keshen 2 Area

Fractures are crucial as main natural gas transport channels in tight sandstone reservoirs. In order to reveal the correlation between the combination of fractures in Block Keshen 2 and sandstone, we have collected drilling core data, logging curve data, imaging logging data, and rock thin-section data from the Bashjiqike Formation in the Keshen 2 area, and by classifying and statistically analyzing the different influencing factors of fractures, we have established a correlation between the development of fractures and sandstone thickness, lithology, and sedimentary microfacies. The results reveal the following: (1) frequent vertical superposition and lateral migration occur in the sedimentary sand bodies of the Bashijiqike Formation. Three types of patterns of sand bodies have been identified according to the changes in microfacies. Type I refers to the patterns of sand bodies developed in main subaqueous distributary channels, type II refers to the patterns of sand bodies developed in secondary subaqueous distributary channels or mouth bars, and type III refers to the patterns of sand bodies developed in isolated subaqueous distributary channels; (2) three types of fracture patterns have been described in the various sand bodies of the Bashijiqike Formation in the Keshen area, including high–medium-angle branch-like fracture patterns, medium-angle reticular fracture patterns, and isolated fractures; (3) the coupling relationship among sedimentary microfacies, sand body patterns, and fracture patterns has been established. The high–medium-angle branch-like fracture patterns mainly develop in the main underwater distributary channel and the type I sand body patterns. The medium-angle reticular fracture patterns mainly develop in the secondary underwater distributary channel and mouth bars, as well as the type II sand body patterns. Isolated fractures can occur in all sedimentary microfacies but are sporadically distributed within the three types of sand body patterns. The research results present the regularity of fracture development in fractured reservoirs, which can be applied to oil and gas fields with the same background, providing certain geological evidence for exploration and development.

Thermal Performance Optimization of Integrated Microchannel Cooling Plate for IGBT Power Module.

In high-integration electronic components, the insulated-gate bipolar transistor (IGBT) power module has a high working temperature, which requires reasonable thermal analysis and a cooling process to improve the reliability of the IGBT module. This paper presents an investigation into the heat dissipation of the integrated microchannel cooling plate in the silicon carbide IGBT power module and reports the impact of the BL series micropump on the efficiency of the cooling plate. The IGBT power module was first simplified as an equivalent-mass block with a mass of 62.64 g, a volume of 15.27 cm3, a density of 4.10 g/cm3, and a specific heat capacity of 512.53 J/(kg·K), through an equivalent method. Then, the thermal performance of the microchannel cooling plate with a main channel and a secondary channel was analyzed and the design of experiment (DOE) method was used to provide three factors and three levels of orthogonal simulation experiments. The three factors included microchannel width, number of secondary inlets, and inlet diameter. The results show that the microchannel cooling plate significantly reduces the temperature of IGBT chips and, as the microchannel width, number of secondary inlets, and inlet diameter increase, the junction temperature of chips gradually decreases. The optimal structure of the cooling plate is a microchannel width of 0.58 mm, 13 secondary inlets, and an inlet diameter of 3.8 mm, and the chip-junction temperature of this structure is decreased from 677 °C to 77.7 °C. In addition, the BL series micropump was connected to the inlet of the cooling plate and the thermal performance of the microchannel cooling plate with a micropump was analyzed. The micropump increases the frictional resistance of fluid flow, resulting in an increase in chip-junction temperature to 110 °C. This work demonstrates the impact of micropumps on the heat dissipation of cooling plates and provides a foundation for the design of cooling plates for IGBT power modules.

Stringent Response Factor DksA Contributes to Fatty Acid Degradation Function to Influence Cell Membrane Stability and Polymyxin B Resistance of Yersinia enterocolitica.

DksA is a proteobacterial regulator that binds directly to the secondary channel of RNA polymerase with (p)ppGpp and is responsible for various bacterial physiological activities. While (p)ppGpp is known to be involved in the regulation and response of fatty acid metabolism pathways in many foodborne pathogens, the role of DksA in this process has yet to be clarified. This study aimed to characterize the function of DksA on fatty acid metabolism and cell membrane structure in Yersinia enterocolitica. Therefore, comparison analysis of gene expression, growth conditions, and membrane permeabilization among the wide-type (WT), DksA-deficient mutant (YEND), and the complemented strain was carried out. It confirmed that deletion of DksA led to a more than four-fold decrease in the expression of fatty acid degradation genes, including fadADEIJ. Additionally, YEND exhibited a smaller growth gap compared to the WT strain at low temperatures, indicating that DksA is not required for the growth of Y. enterocolitica in cold environments. Given that polymyxin B is a cationic antimicrobial peptide that targets the cell membrane, the roles of DksA under polymyxin B exposure were also characterized. It was found that DksA positively regulates the integrity of the inner and outer membranes of Y. enterocolitica under polymyxin B, preventing the leakage of intracellular nucleic acids and proteins and ultimately reducing the sensitivity of Y. enterocolitica to polymyxin B. Taken together, this study provides insights into the functions of DksA and paves the way for novel fungicide development.

Enhancing subsonic ejector performance by incorporating a fluidic oscillator as the primary nozzle: a numerical investigation

Primary flow structures affect ejector performance by impacting momentum transfer to the secondary flow and pressure reduction in the suction chamber. This study investigated the potential benefits of oscillating the primary flow in ejectors to enhance the shear-turbulence mixing and momentum exchange between the primary and secondary flows and improve the entrainment ratio. A vortex-based fluidic oscillator was scaled down and designed to serve as the primary nozzle in a two-dimensional subsonic ejector, embedded between the secondary channels. Prior to installation, optimal values for the nozzle exit position and mixing chamber height were obtained through a parametric study and used in the ejector with the oscillator. To evaluate the impact of the fluidic oscillator on the ejector entrainment ratio, unsteady Reynolds-averaged Navier–Stokes equations were solved using the k–ε standard and k–ω shear-stress transport turbulence models in the Fluent 2022 R2 software. The results indicated that a harmonically oscillating primary flow was generated, increasing the mixing entrainment and momentum transfer while reducing the pressure in the suction and mixing chambers. The oscillator improved the ejector's entrainment ratio by 38.3% compared to the baseline, and 11.6% compared to the parametrically optimized ejector. It also expanded the ejector's performance range.

Experimental and theoretical study on the photoionization of styrene.

This study employed a vacuum ultraviolet synchrotron radiation source and reflectron time-of-flight mass spectrometry (TOF-MS) to investigate the photoionization and dissociation of styrene. By analyzing the photoionization mass spectrum and efficiency curve alongside G3B3 theoretical calculations, we determined the ionization energy of the molecular ion, appearance energy of fragment ions, and relevant dissociation pathways. The major ion peaks observed in the photoionization mass spectra of styrene correspond to C8 H8 + , C8 H7 + and C6 H6 + . The ionization energy of styrene is measured as 8.46 ± 0.03 eV, whereas the appearance energies of C8 H7 + and C6 H6 + are found to be 12.42 ± 0.03 and 12.22 ± 0.03 eV, respectively, in agreement with theoretical values. The main channel for the photodissociation of styrene molecular ions is the formation of benzene ions, whereas the dissociation channel that loses hydrogen atoms is the secondary channel. Based on the experimental results and empirical formulas, the required dissociation energies (Ed ) of C8 H7 + , C8 H6 + and C6 H6 + are calculated to be (3.96 ± 0.06), (4.00 ± 0.06) and (3.76 ± 0.06) eV, respectively. Combined with related thermochemical parameters, the standard enthalpies of formations of C8 H8 + , C8 H7 + , C8 H6 + and C6 H6 + are determined to be 964.2, 1346.3, 1350.2 and 1327.0kJ/mol, respectively. Based on the theoretical study, the kinetic factors controlling the styrene dissociation reaction process are determined by using the Rice-Ramsperger-Kassel-Marcus (RRKM) theory. This provides a reference for further research on the atmospheric photooxidation reaction mechanism of styrene in atmospheric and interstellar environments.

Hydraulic Performance and Energy Dissipation Mechanism Analysis of the Tesla-Shaped Emitter

In this paper, a tesla-shaped emitter is proposed based on the structure of the “tesla valve” as the source of inspiration, so that the water flow in the channel would produce a variety of energy dissipation phenomena, such as diversion, hedging, and mixing, to explore the hydraulic performance and energy dissipation mechanism of the tesla-shaped emitter. The channel structure parameters were taken as factors, and 16 groups of orthogonal tests were arranged. Based on CFD technology, the pressure–flow relationship curve slope, flow ratio between the main channel and secondary channel, flow field, and head loss of the emitter were calculated and analyzed for different combinations of structural parameters. Based on a significance level α = 0.05 test, the main channel inlet section length (L3) had a significant impact on the curve slope, and the secondary channel length (L1) and main channel inlet section length (L3) had a significant impact on the flow. The multiple linear regression mathematical models between the channel structure parameters and the curve slope and the flow were constructed. The larger the ratio between the main channel and the secondary channel flow, the better the hydraulic performance of the emitter. The channel unit loss coefficient increased linearly with the increase of the emitter inlet pressure, and its value ranged from 4.5769 to 8.1716, with an excellent energy dissipation effect. The hedge mixing of the water flow was the core of the energy dissipation of the tesla-shaped emitter. By appropriately increasing the inlet size of the main channel and other elements to increase the main channel flow and optimize the flow ratio between the main channel and the secondary channel, the mixing was improved, which consequently improved the hydraulic performance of the emitter.