Vertical Feeding Research Articles

Effect of pressure and supply configuration on mixing efficiency through Venturi effect for co2/h2- ch4/h2 mixtures in Power-To-Gas process: CFD analysis

Introduction: The present article is one of the outcomes of the project “Desarrollo de un sistema “power to gas” (PTG) en el contexto de las fuentes de energía renovables y convencionales disponible en la Guajira” This project was carried out by the University of Antioquia and the University of La Guajira during the period 2019-2023. Problem: Efficiency and uniformity in gas mixing for Power-to-Gas applications are influenced by pressure varia- tions and supply configurations. Objective: To assess the impact of pressure variations and supply configurations on the efficiency of the Venturi mixing process, utilizing indicators such as the Z-factor and the coefficient of variation (CoV). Methodology: Numerical simulations were conducted for four mixer configurations. For CO2/H2 mixtures, pressures of 1 bar (case i) and 4 bars (case ii) were considered; for CH4/H2 mixtures, pressures of 3 bars (case i) and 35 bars (case ii) were studied. Results: As the inlet gas pressure increases, uniformity decreases for both mixtures. Horizontal H2 feeding improves CO2/H2 uniformity, while vertical feeding benefits CH4/H2 mixing. The mixer reduces CoV by an average of 80% for CO2/H2. For CH4/H2 mixtures at 3 bars, there is a 60% reduction, but at 35 bars, coefficients increase by 56%. Conclusion: Pressure and supply configuration significantly influence the mixing process, underscoring the impor- tance of considering these factors in Power-to-Gas applications. Originality: The study explores the Venturi mixing process in specific gas mixtures for Power-to-Gas applications. Limitations: The studied conditions and configurations may not encompass all possible scenarios in Power-to-Gas applications.

Engineering Designs of Dual-Polarized Antennas With Reduced Profile and Mutual Coupling for 5G Microcell Application

In this letter, a miniaturized, low profile and low mutual coupling antenna array with stable radiation pattern for fifth-generation microcell is presented. The antenna element contains three parts, folded dipole radiator, vertical feeding baluns, and reflector. Four striplines with end connections and stepped slots etched on the main radiator are adopted to enhance the impedance bandwidth and miniaturized the antenna's aperture in the low-profile configuration. While folded stripline structure is applied to reduce the mutual coupling in dual-polarized antenna. The height of proposed antenna is only 0.1 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the free-space wavelength referring to the center operation frequency) and the antenna's aperture is only 0.4 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.4 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> . Measured results show that the antenna array has good performances, exhibiting low voltage standing-wave ratio (VSWR < 1.5), high isolation (> 30 dB), and wide bandwidth (3.2–3.9 GHz, 20%). Stable radiation patterns are measured across the operating bandwidth.

Multi‐resonance dual‐polarised symmetrically cross‐slotted square patch antenna for 5G millimetre‐wave broadband applications

AbstractA dual‐polarised symmetrically cross‐slotted square patch (SCSSP) antenna with multimode resonance is proposed for 5G millimetre‐wave broadband applications. A symmetrical cross‐slot is etched on the square patch surface to change the original E‐field distribution where a whole square patch is cut into four disconnected equal parts. For both polarisations, this etching also tunes the resonance frequencies of the two modes to be sufficiently close to each other. Therefore, the antenna can realize good impedance performance within the wide designated bandwidth. Dual‐polarised radiation of the SCSSP is vertically excited by three bow‐tie‐shaped slots and fed by two orthogonal substrate integrated coaxial lines. Simulated and measured results show that the fabricated prototype achieves a broad overlapped impedance bandwidth of 50.0% (24–40 GHz), isolation higher than 30 dB between the two input ports, stable radiation pattern, and low cross‐polarisation over the operating band. Moreover, the proposed SCSSP antenna with compact size, planar shape, and simple vertical feeding is very well‐suited for two‐dimensional array design.

A High-Efficiency Microstrip Antenna Pair with Similar Pi-Shaped Decoupling Structure for 3.5 GHz 5G Ultrathin Smartphones

In this paper, a low profile and high-efficiency decoupling antenna pair for multiunit smartphones is proposed using a similar π-shaped feed structure that can excite the dipole radiation mode of microstrip antenna. Ordinarily, symmetrical single-port T-shaped microstrip antennas can only excite monopole modes of bilateral radiation. This paper changes the vertical feeding microstrip structure into two oblique, similar π-shaped feeding structures. This oblique feeding structure can excite the dipole mode of unilateral radiation of the microstrip antenna. Using this method, the antenna design can be simplified, and the low-coupling independent radiation on both sides of the microstrip antenna can be freely controlled without the need for additional structures. Considering the ultra-thin characteristics of 5G smartphone devices, the parameters of the antenna are further optimized: the optimized antenna profile is only 3.7 mm. The measured results show that the 2 × 2 microstrip antenna pairs can effectively cover the 3.5 GHz band (3.4–3.6 GHz), with a coupling that varies from −16.14 dB to −11.01 dB and an efficiency that varies from 80% to 94.1%. The 8 × 8 MIMO smartphone antenna results show that the coupling varies from −20.1 dB to −12.17 dB, the efficiency varies from 79.72% to 93.7%, and the envelope correlation coefficient (ECC) is lower than 0.05. The microstrip antenna decoupling pair with a similar π-shaped feed structure proposed in this paper has high efficiency and low-profile characteristics have important application value in the decoupling design of 3.5 GHz 5G ultra-thin smartphone antennas.

Численный анализ процесса электронно-лучевой аддитивной наплавки с вертикальной подачей проволочного материала

Introduction. At present, additive technologies are actively developing all over the world and are becoming more and more widely used in industrial production. The use of electron beams in additive processes of directed energy input, the so-called Directed Energy Deposition (DED) technologies, has several advantages, the main ones being the flexibility of controlling the spatial and energy characteristics of the thermal source and the presence of a vacuum protective environment. The standard scheme for additive electron beam deposition is melting of a wire filler material fed from the side into the electron beam affected area, but this additive electron beam deposition pattern does not provide a uniform thermal impact in the deposited area. The most effective method for electron-beam deposition is vertical wire feeding, which provides the most stable formation of the liquid metal bath and, consequently, the deposited beads. At the same time, so far there are no results of numerical analysis of this process in order to determine its main regularities. The aim of the work is to carry out numerical experiments for qualitative analysis and determination of the regularities of formation of deposited beads and transfer of filler material, the dependence of the geometric characteristics of the obtained beads on the influence of vapor pressure forces, direction and value of the azimuthal angle of heat sources. The research methods were a series of numerical experiments, which analyzed variants of the electron-beam surfacing process at the location of the surfacing rate vector in the action plane of electron beams and perpendicular to this plane to determine the basic regularities of deposited beads formation and transfer of filler material, dependence of geometric characteristics of obtained beads on the influence of vapor pressure forces, direction of heat sources and the azimuth angle of heat sources. Results and discussion. It is found that the geometric characteristics of the deposited beads significantly depend on the relative position of the deposition velocity vector with respect to the plane of the electron beams, and consideration of the vapor pressure has a significant influence on the results of numerical simulation of the weld pool formation and the hydrodynamic processes occurring in it. In this case, the location of the deposition velocity vector perpendicular to the action plane of the electron beams, there is a more uniform geometry of the deposited metal beads, and increasing the azimuthal angle of the heat sources increases the probability of spitting to the periphery of the deposited bead, which is associated with limitation of the melt motion in the longitudinal direction by the vapor pressure forces.

Amino acid isotopes in functional assemblages of Collembola reveal the influence of vertical resource heterogeneity and root energy supply on trophic interactions in soil food webs

The vertical heterogeneity of trophic interactions in soil food webs in temperate forest systems and its response to deprivation of root energy supply are poorly understood. In the present study, community-level trophic niches of Collembola functional groups (epedaphic, hemiedaphic and euedaphic) were analyzed using compound specific isotope analysis (CSIA) of carbon (C) and nitrogen (N) in amino acids (AAs) in a root-trenching experiment. The δ15N values of phenylalanine, serving as proxy for N resources, were higher in euedaphic Collembola than in ep-/hemiedaphic Collembola, suggesting that euedaphic Collembola mainly utilized N from processed organic substrate in deeper soil, while leaf litter was the dominant N source for ep-/hemiedaphic Collembola. The trophic position calculated from CSIA (TPCSIA) of euedaphic Collembola was higher than that of epedaphic Collembola in most of the studied forest sites, reflecting a higher number of trophic transfers in the soil than in the litter layer. For the first time, we found evidence that the deprivation of root energy supply can decrease the TPCSIA of soil omnivores, suggesting that root-derived C may increase the number of trophic transfers and food chain length in soil food webs. However, effects varied among functional groups of Collembola in different forest stands, indicating that the association between root energy supply and trophic interactions is only partially in line with the ‘productivity hypothesis’ and strongly mediated by vertical resource heterogeneity, regional conditions and feeding strategies of consumers. Finally, our results are in line with recent studies, suggesting that saprotrophic microorganisms, especially saprotrophic fungi, are the predominant resources for Collembola, whereas the contribution of mycorrhizal fungi and plants is subordinate. Overall, by using CSIA of AAs our study provides novel information on trophic niches of microarthropods in forest soils, extending our understanding of the influences of vertical resource heterogeneity and root energy supply on trophic interactions in soil food webs.

Corrigendum: A trait‐based carbon export model for mesopelagic fishes in the Gulf of Mexico with consideration of asynchronous vertical migration, flux boundaries, and feeding guilds

Corrigendum: A trait‐based carbon export model for mesopelagic fishes in the Gulf of Mexico with consideration of asynchronous vertical migration, flux boundaries, and feeding guilds

Simulation of the multi-beam electron-beam wire-feed additive manufacturing process in a vacuum

The paper considers modelling the wire deposition process with vertically fed wire by several symmetrically acting heat sources. We proposed the mathematical model to describe the above process, considering surface tension force, Marangoni force, vapor pressure force, and heat loss on evaporation. To solve the mathematical model, we use the smoothed particle hydrodynamics method. We carried out a series of numerical experiments for modelling the melting process of vertically fed wire with two symmetrically acting heat sources with different power and direction of action of heat sources. We found that vertical wire feeding provides uniform heating with the absence of shaded areas and flexible control of heat input into the metal. On the other hand, the weld bead geometry characteristics significantly depend on the heat sources’ power and direction.

A trait‐based carbon export model for mesopelagic fishes in the Gulf of Mexico with consideration of asynchronous vertical migration, flux boundaries, and feeding guilds

AbstractFish‐mediated carbon export provides a significant proportion of the biological carbon pump in oligotrophic regions. Bioenergetic models estimate this carbon transport, but many lack species‐specific traits and no carbon export model has been developed in the mesopelagic Gulf of Mexico. Intensive mesopelagic sampling efforts in the northern and eastern Gulf of Mexico have provided high‐resolution information regarding community composition, species' vertical migratory characteristics, diel depth occupancies, and diets. A stochastic, individual‐based model was developed for deep‐pelagic fishes in the northern Gulf of Mexico to estimate bioenergetic rates and carbon export fluxes. Fishes that ate gelatinous zooplankton consumed more mass per body weight per day than predators of cephalopods and fishes, ostensibly to increase the throughput of prey with less carbon (gelata) or more refractory materials (Crustacea). A dynamic energy budget submodel indicated that during 81% of occurrences, asynchronous vertically migrating fishes rested for 1 d before migrating again, but migrations on successive days were possible. In terms of carbon export, myctophids and stomiids contributed greater than 53% and 12% of the active carbon flux for the entire assemblage in all scenarios. The assemblage‐wide carbon export rate driven by vertically migrating fishes was 0.14–0.72 mg C m−2 d−1, 61% of the ingested carbon by the assemblage. Incorporating species‐specific traits and individual variability in bioenergetic models allows for more complex research questions (e.g., the effect of feeding guilds and asynchronous migration on carbon export) compared to the carbon export models that otherwise assume all fishes within a functional group are equivalent.

Monitoring and measurement analysis of key indexes for the implementation of mining, dressing, backfilling, and controlling technology in coal resources—A case study of Tangshan Mine

AbstractBased on the mining, dressing, backfilling, and X technology framework, we proposed the key operation indexes by exploring the principle, system, and integrated process of “mining, dressing, backfilling, and controlling” technology. After that, the index monitoring method was established to further analyze the change law of key indexes and implementation effects of “mining, dressing, backfilling, and controlling” technology. The mining engineering of Tangshan mine showed that the “mining, dressing, backfilling, and controlling” technology solves the problems of gangue discharge, construction protection, and safe mining of compressed coal resources. The vertical feeding capacities and filling capacities are 337,171 and 422,428 t/year, respectively. The stress change in the filling body is consistent with the dynamic roof subsidence, with a compacting ratio of 81.3%. The average filling mass ratio (1.28) is greater than the design value (1.2). The maximum ground subsidence is 49 mm, and the deformation of the structure is controlled within the range of Level I. The research result provides evidence for the deepening of the theoretical and technical researches of “mining, dressing, backfilling, and X.” It also provides a technical reference for mines with similar geological conditions and engineering problems.

Relationship between vertical stratification and feeding habits of mosquito (Diptera: Culicidae) assemblages collected in conservation units in the green belt of the city of São Paulo, Brazil

São Paulo is one of the largest cities in the world and has several characteristics that favor a diversity of urban and wild mosquitoes. Little is known about how variations in mosquito diversity and feeding preferences for different hosts in different vegetation strata can influence the risk of pathogen transmission to humans. We investigated vertical stratification of mosquitoes and its relationship with vertebrate hosts in environments with different degrees of conservation in two conservation units in the city of São Paulo. Adult mosquitoes were collected using CDC traps, aspiration and Shannon traps. After morphological identification, host blood in engorged females was analyzed by PCR with a vertebrate-specific primer set based on mitochondrial cytochrome b DNA of vertebrates commonly found in the two conservation units.Although a higher abundance of the species Anopheles cruzii and Culex nigripalpus was found in the canopy, blood not only from birds but also from humans and rodents was identified in these mosquitoes. In one of the units, Wyeomyia confusa and Limatus durhamii were found occupying mainly niches at ground level while Culex vaxus was frequently found in the canopy. Haemagogus leucocelaenus, the main vector of yellow fever, was found in low abundance at all collection points, particularly in the canopy. Species richness and composition tended to vary little between canopy and ground level in the same environment, but the abundance between canopy and ground level varied more depending on the species analyzed, the most abundant and frequent species exhibiting a predilection for the canopy. Even those mosquito species observed more frequently in the canopy did not show an association with hosts found in this stratum as most of the blood identified in these species was from humans, suggesting opportunist feeding behavior, i.e., feeding on the most readily available host in the environment. The two most common species in the study, An. cruzii and Cx. nigripalpus, may be able to act as bridge vectors for pathogens to circulate between the forest canopy and ground level.

Volume of the whale shark and their mechanism of vertical feeding

The present study provides a noninvasive method to estimate the body volume of sharks (Elasmobranchii, Selachii) using a computational geometric model. This method allows the volume of sharks to be estimated from lateral and ventral photographs assuming an elliptical body cross-sectional geometry. A comparison of the estimated and actual body volumes of several shark species showed that the estimation error was < 0.5%. The accuracy of the model decreased if photographs that were inclined to the orthogonal plane were used, although this error was on average < 2.3% if the inclination angle was 10° or less.Applying this model to captive whale sharks (Rhincodon typus) that were 8.0 and 8.8 m in total length revealed that their body volumes were 3.5 and 4.5 m3, respectively. These estimates allowed for the quantitative evaluation of our hypothesis, that the whale shark uses suctioned air for buoyancy control during vertical feeding—a behavior unique to this species among elasmobranchs. The volume estimates of the captive whale sharks, together with the density estimates from their liver proportions, revealed that the air occupying a part of oro-pharyngeal and branchial cavities can help the whale sharks to keep their body floating. This hypothesis may explain how the whale shark sometimes stays at the water surface without fin motion during vertical feeding, even though their body density is greater than that of seawater.

Ciclo biológico de Caligo Idomeneus (Nymphalidae) bajo condiciones controladas con jardines verticales en Tarapoto

El trabajo fue ejecutado en el mariposario de la UNSM-T, Morales, desarrollando una metodología para la cría de Caligo idomeneus (Lepidoptera: Nymphalidae) bajo condiciones de mariposario, con jardines verticales y sustrato de alimentación con heliconia y plátano. Los huevos tuvieron una duración de 7 días, la larva pasó por 5 estadíos, el primer instar tuvo una duración de 2 a 3 días, no tuvo presencia de cuernos, el promedio de ancho de cápsula cefálica fue de 0,38 mm y una longitud de 1,9 mm; en el segundo instar se pudo apreciar la aparición de dos pequeños cuernos en la parte anterior de la cabeza de 0,36 mm en promedio, tuvo un promedio de ancho de cápsula cefálica de 0,56 mm y duración de 2,2 días y una longitud de 4,12 mm; el tercer instar tuvo una duración de 3 días, con un ancho de cápsula cefálica de 1,04 mm, longitud de cuernos de 5,74 mm y una longitud de 10,40 mm; el cuarto instar tuvo una duración de 4,4 días y 4,27 mm en promedio de ancho de cápsula cefálica, con una longitud de cuernos de 8,02 mm y una longitud de 18,07 mm; el quinto instar tuvo 6,26 mm de ancho de cápsula cefálica y tuvo una duración de 8,86 días, con longitud de cuernos de 14,93 mm y 36,33 mm de longitud; el promedio de pupa fue de 17,46 días. La duración del ciclo, desde huevo a adulto fue de 66,90 días en promedio.

Design and Optimization of Feeding Device for Sterile Seed Long Fiber Extractor

The feeding status of feeding device is an important factor that affects the performance of the main machine and even the process line. Taking the assembly layout of the feeding device and the structure of key parts as the research object, we conducted research design and analysis of the feed roller and cotton-feeding roller structure and their configurations. The results show that vertical feeding is conducive to the continuous and uniform feeding of materials; the combined use of cotton-plucking feed roller with roller is superior to the combination of multiple rollers; the progressive differential feeding mode makes for gradually thinning the material bed, improving the long fiber extraction rate, reducing the impurity rate, reducing the unattached fiber and greatly improving the machine performance; Φ58×1200mm cotton-feeding roller with a hexagonal spindle structure has higher deformation resistance than simple hollow structure. The research can be a reference for the optimization and design of sterile cottonseed extraction machine and equipment.

Change in agrochemical and biochemical parameters during the laboratory vermicomposting of spent mushroom substrate after cultivation of Pleurotus ostreatus

Pleurotus ostreatus is one of the most cultivated mushrooms in the Czech Republic. The production of 1 kg of mushrooms generates about 5 kg of spent mushroom substrate. A gentle and fast method for using this substrate is vermicomposting. Vermicomposting of spent mushroom substrate using Eisenia andrei was conducted for seven months. For control purposes, a treatment without earthworms was also prepared. The vermicomposting process used vertical continuous feeding vermicomposters. The agrochemical and biological parameters were analysed. Values of electrical conductivity were very high in both vermicomposters (higher than 2000 μS/cm). During the vermicomposting process the C/N ratio decreased. The number and biomass of earthworms decreased with the age of the layers. The values of total P, K and Mg were higher in the vermicomposter without earthworms. There were also lower microbial phospholipid fatty acids content - than in the vermicomposter with earthworms. However, the fungal phospholipid fatty acids content were two times higher in the vermicomposter without earthworms. The highest hydrolytic enzyme activity was found in lipase, acid phosphatase and β-D-glucosidase. Most hydrolytic enzymes were more active in the vermicomposter without earthworms, with the exception of arylsulphatase. Mn-peroxidase activity was higher in the vermicomposter without earthworms and laccase activity was below the detection limit.

Dual-frequency dual orthogonal polarization wave multiplexing using decoupled pixels based on Holographic technique.

The holographic technique is a promising way to manipulate light distribution and wave-front in the optical regime. In recent years, many researchers have extended this concept to microwave regime to manipulate phase, amplitude, and polarization of waves in a convenient way revealing diverse intriguing applications. Unlike the previous studies with optimization-based schemes, in this paper, we propose a simple route to design dual frequency dual-polarization holographic metasurfaces with negligible interference between the operating (lower and upper) frequencies. For this purpose, a Jerusalem-shape unit-cell is used to realize two distinct impedance distributions which yield two decoupled field profiles over the aperture of the metasurface at each frequency band. Consequently, the proposed metasurface radiator can operate in two frequency bands, independently. Each set of horizontal (vertical) cross-bars of the Jerusalem-shape unit-cell is illuminated by a vertical (horizontal) feeding network from one side of the metasurface. Side feeding has a null-free advantage, this undesired null emerges in central feeding metasurfaces and leads to an undesirable rabbit's ears phenomenon. As the proof-of-concept, a prototype of the metasurface radiator for operating at 11.5 GHz and 14 GHz is fabricated and measured. The experimental results depict a good agreement with the full-wave simulations.

Development of a High Pressure Dry Coal Feed System for a 100 kWt Oxy-Coal Reactor

Abstract A design concept to feed dry coal from a hopper to a 100 kWt pressurized oxy-coal (POC) reactor using CO2 at 2 MPa was developed using transient computational fluid dynamics (CFD) simulations and bench-scale measurements. The feed system was required to maintain a steady flow of gas and solids at a coal flowrate of approximately 3.8 g/s and a CO2-to-coal mass ratio in the range 1–2. A 5.08-cm diameter vertical coal hopper feeding into a 0.635-cm diameter horizontal pipe was used to represent key elements of the feed system. A fluidized bed concept was found capable of providing the desired coal flowrate and CO2-to-coal flow ratio. Use of separate fluidization and dilution flows allowed the coal flowrate and CO2-to-coal flow ratio to be controlled independently. The amount of coal transported from the hopper was dependent on the net CO2 flow in the hopper but independent of the CO2 dilution flow. Pipe exit coal flowrates were found to fluctuate at levels acceptable for steady burner operation. Tests from a bench-scale apparatus using Pittsburgh 8 coal with a median particle diameter of 50 µm and moisture content of 6% confirmed the feasibility of the fluidization design. However, for a given CO2 fluidization flowrate, experimental coal flowrates were lower than predicted coal flow, in part due to simplifying assumptions of dry, spherical coal particles and smooth piping in the simulations.

Fine-scale horizontal distributions of multiple species of larval tuna off the Nansei Islands, Japan

To quantitatively evaluate the distribution of tuna larvae relative to oceanographic conditions, we conducted investigations off the Nansei Islands in the western North Pacific in June from 2015 to 2017. Five species, namely Pacific bluefin tuna Thunnus orientalis (PBF), yellowfin tuna T. albacares (YFT), skipjack tuna Katsuwonus pelamis (SKJ), frigate tuna Auxis thazard, and bullet tuna A. rochei (BT), were collected in each year. The most dominant species was BT throughout the 3 yr period, followed by SKJ in 2015 and YFT in 2016 and 2017. The horizontal larval distributions of the 5 species were largely influenced by the Kuroshio Current: larvae of the 2 Auxis species were distributed in the Kuroshio and the Kuroshio inshore waters, whereas those of the other species were found in the Kuroshio offshore waters. These differences are consistent with the differences in spawner distributions among the tunas. Generalized additive models (GAMs) indicated that the larval densities were affected by the sea surface height anomaly and that the larvae were not always amassed by horizontal transport. Sea surface temperature (SST) and salinity possibly influenced the larval physiology and survival, thereby determining their densities. In the GAMs, PBF and YFT showed similar responses to SST, and YFT and SKJ similarly responded to salinity. To avoid overlapping their ecological niches, the larvae of 3 species (PBF, YFT, and SKJ) are expected to differ in other ways, including their vertical distributions and feeding habits.

Spirostomum teres: A Long Term Study of an Anoxic-Hypolimnion Population Feeding upon Photosynthesizing Microorganisms

The pelagic / anoxic hypolimnion population of Spirostomum teres was investigated as a part of the long-term ciliates’ monitoring (2003–2016) in an oligo- to mesotrophic monomictic hyposaline crater lake Alchichica (Puebla / Veracruz, Mexico), including an analysis of picoplankton (both heterotrophic, HPP and autotrophic, APP) and inorganic compounds of nitrogen (ammonium, nitrite, nitrate), phosphorus (dissolved reactive phosphorus, DRP) and silicon. Additionally, detailed studies of the ciliate vertical distribution and feeding activity measured upon fluorescently labelled APP (picocyanobacteria) were carried out. The results were compared with those from a neighbour freshwater crater lake La Preciosa and with a meromictic karstic lake La Cruz (Cuenca, Spain). The ciliate vertical distribution within the water column was very well defined: During the first decade, the benthic population was frequently found throughout a developing stratification of the lake. The established stratification of the lake turned the conditions favourable for the formation of an oxycline / hypolimnion population, typically, several meters below the deep chlorophyll maximum (formed basically by diatoms); the population preferred the layers without detectable dissolved oxygen. However, an observed gradient of light (PAR) could support both oxygenic and anoxygenic photosynthesis. Late stratification after deepening of the thermocline reduced the layers with S. teres population to a minimum apparently due to the drastic change in physicochemical conditions within a metalimnion, coupled with an oxycline, and limited to 1 to 2 meters; microstratification was found. Last years, the very bottom population disappeared or it was reduced and the late stratification S. teres peaks were smaller or did not appeared. Generally, S. teres oxycline / anoxic hypolimnion population was observed from June through November. Optimum picoplankton numbers in conditions that supported the ciliate growth were found: The ciliate was peaking at APP of 0.6 to 1 × 105 cells mL–1; the optimum of HPP was observed round 1.4 × 106 cells mL–1. S. teres was efficiently feeding upon picocyanobacteria in numbers of 105 cells mL–1 reaching the clearance rate of 2000 nL cell–1h–1, which represented in average 130 to 210 cells cell–1h–1 ingested. Feeding upon purple sulphur bacteria was observed but only during the end of the lake stable stratification when the ciliate population was already dropping. On the other hand, the volume specific clearance of S. teres upon picocyanobacteria (103 h–1) did not support the hypothesis that they could serve as a sole prey. Feeding upon eukaryote phytoplankton (chlorophytes Monoraphidium minutum, diatoms Cyclotella choc tawhatcheeana) could be of higher importance that previously supposed. Additionally, a use of ingested and retained photosynthetic prokaryotes is hypothesized.

The role of vapor venting and liquid feeding on the dryout limit of two-layer evaporator wicks

Vapor chambers developed for high-heat-flux operation require advanced evaporator wick designs that can sustain capillary flow when boiling occurs over the heater region. A two-layer evaporator wick integrates a thin base wick layer that is supplied with liquid from a thick cap layer through an array of vertical feeding posts distributed over the heated area. This design allows boiling to occur within the thin base layer, while separating the incoming liquid feeding and outgoing vapor venting pathways. In our prior work, boiling in two-layer wicks was experimentally demonstrated to provide high-heat-flux dissipation over larger heater areas and at low thermal resistance. The current study experimentally explores the effect of two-layer wick design parameters, specifically the dimensions that alter the area available for liquid feeding and vapor venting, on the thermal performance and dryout limit of the wick, using water as the working fluid. Four different two-layer wick designs are fabricated over a 1 cm2 evaporator area by sintering 180–212 μm copper particles. Increasing the vapor-venting area from 7% to 16% of the total evaporator area yielded a significant increase in the dryout limit, from 315 W/cm2 to 405 W/cm2. Increasing the liquid-feeding area using wider posts increased the dryout limit further. Finally, a parametrically optimized design with fewer but larger posts and vents resulted in better performance compared to a design with denser features. With this two-layer wick design, we demonstrate an extremely high dryout limit of 512 W/cm2 over the large 1 cm2 heated area at a thermal resistance of 0.08 K/W.