Source Conditions Research Articles

Comparison of the protein composition of isolated extracellular vesicles from mouse brain and dissociated brain cell culture medium.

Extracellular vesicles (EVs) play a crucial role in intercellular communication. Characterizing EV protein composition is essential to understand EV function(s). Isolating EVs from cell culture medium is a common approach to study EVs, but it remains unclear whether EVs isolated from in vitro conditions accurately reflect physiological conditions of the same source in vivo tissues. Here, we analyzed the protein composition of EVs isolated from freshly dissected mouse forebrain and primary dissociated mouse forebrain culture medium. In total, 3,204 and 3,583 proteins were identified in EVs isolated in vivo and in vitro, respectively. Among the proteins identified from both EV sources, there was substantial overlap (~86%). While the overall proteome compositions were very similar, in vitro EVs were relatively enriched with transmembrane/GPI-anchored membrane and cytosolic proteins (MISEV2023 category 1 and 2) typically associated with EVs. Conversely, while both in vivo and in vitro EVs express likely non-EV proteins (MISEV2023 category 3), the in vivo samples were significantly more enriched with these probable contaminants, specifically ribosomal proteins. Our findings highlight that in vitro EVs may be representative of in vivo EVs when isolated from the same source tissue using similar methodology; however, each population of EVs have differences in both total and, primarily, relative protein expression likely due to differing levels of co-eluting contaminants. Therefore, these points must be considered when interpreting results of EV studies further suggesting that improved methods of isolation to reduce non-EV contaminants should be further investigated.

Roadmap for Power Generation of Industrial Hot Extruded Bi2Te3-Based Thermoelectric Device in Real-World Heat Sources.

Recovering waste heat through thermoelectric (TE) technology is critical for enhancing energy efficiency. However, commercial devices often require n- and p-type thermoelectric units to have similar cross-sectional areas and conductivities, complicating optimization of their figure of merit (ZT). Moreover, real-world heat sources are not constant temperature sources, and only heat flux can be measured. Given these constraints, selecting appropriate parameters for TE devices to maximize their output power for specific heat sources is of significant scientific and practical importance. In this work, we studied a series of n- and p-type Bi2Te3-based TE materials, prepared using commercial hot extrusion techniques, with average conductivities of approximately 650 S cm-1, 820 S cm-1, 1050 S cm-1, and 1300 S cm-1 over the temperature range of 50-250 °C. These materials were assembled into four different thermoelectric devices (HE1, HE2, HE3, and HE4). Finite element simulations for devices HE1, HE2, HE3, and HE4 (TE leg: 1.4 mm × 1.4 mm × 1.6 mm, device area: 40 mm × 40 mm) showed maximum power densities of 3953.5 W m-2 and 1300.8 W m-2 at 67,000 W m-2 and 33,500 W m-2 heat fluxes, respectively. The fabricated devices achieved maximum power densities of 2907.1, 3014.0, 2910.9, and 2525.4 W m-2 at 67,000 W m-2 heat flux, with discrepancies attributed to interface thermal resistance. Based on these findings, we have plotted output performance roadmaps for TE devices with different average electrical conductivities under various heat flux densities (67,000 W m-2 and 33,500 W m-2) as functions of external load and TE leg height. These roadmaps enable rapid design of TE devices tailored to specific external heat source conditions and cost requirements, thereby maximizing waste heat recovery. This study's use of electrical conductivity as a performance indicator for final device output power density offers direct guidance for practical waste heat recovery applications.

Research on the Current Situation and Sustainable Development Measures for Urban–Rural Water Supply Integration in Yunnan Province, China

Urban–Rural Water supply integration is one of the effective ways to address rural drinking water safety issues. With the rapid economic development and urbanization, the gap between urban and rural water supply has become increasingly evident, and rural areas face severe challenges such as insufficient water sources and substandard water quality. Yunnan Province, due to its unique topography and natural environment, encounters numerous difficulties in promoting the construction and development of urban–rural water supply integration, and there is a severe lack of research specifically focused on sustainable development measures for urban–rural water supply integration in Yunnan Province. In light of this, this paper first reviews the current research status on urban–rural water supply integration both domestically and internationally, pointing out that existing studies mainly focus on optimizing urban water supply systems, addressing rural drinking water safety issues, and exploring water supply management models. It then analyzes the challenges faced by Yunnan Province in advancing urban–rural water supply integration, including limitations in engineering construction, inadequate operation and maintenance, complex and variable water source conditions, and insufficient public awareness of water conservation. In response to these issues, a series of sustainable development measures are proposed, including revitalizing existing assets, enhancing construction planning and quality, promoting water pricing reforms, upgrading the technical system for drinking water safety assurance, and advancing the information technology construction of urban–rural water supply integration, with the aim of providing references and insights for the sustainable development of urban–rural water supply integration in Yunnan Province and other regions.

The phase diagram of kernel interpolation in large dimensions

Abstract The generalization ability of kernel interpolation in large dimensions, i.e., 𝑛 ≍ 𝑑𝛾 for some 𝛾 > 0, might be one of the most interesting problems in the recent renaissance of kernel regression, since it may help us understand the ‘benign overfitting phenomenon’ reported in the neural networks literature. Focusing on the inner product kernel on the unit sphere, we fully characterize the exact order of both the variance and bias of large-dimensional kernel interpolation under various source conditions 𝑠 ≥ 0. Consequently, we obtain the (𝑠, 𝛾)-phase diagram of large-dimensional kernel interpolation, i.e., we determine the regions in the (𝑠, 𝛾)-plane where the kernel interpolation is minimax optimal, sub-optimal and inconsistent.

The influence of natural factors on poverty in West Halmahera

Poverty remains one of the persistent social issues faced by governments in many regions, including coastal and small island communities. The poverty experienced in these areas is driven by a combination of natural, social, and economic factors. Dynamic environmental conditions, such as seasonal changes, extreme weather, wide geographic dispersion between sea and land, isolation due to limited accessibility, and vulnerability to natural disasters, often trap coastal populations in a cycle of poverty. Data from West Halmahera Regency indicates that poverty levels have shown little improvement up until 2023. This research focuses on a sample of 390 poor residents from the region, utilizing Confirmatory Factor Analysis (CFA) and Principal Component Regression Analysis (PCRA) to examine the factors affecting poverty. The findings reveal that within the Natural Capital variable (X1), the most significant indicators are the distance from the house to a clean water source (X4), with a coefficient of 0.894, the condition of the water source near the residence (X5), with a coefficient of 0.884, and accessibility to clean water sources (X3), with a coefficient of 0.89. West Halmahera, being a coastal and mountainous region, suffers from an unequal distribution of essential infrastructure, particularly in areas far from the district capital. Clean water infrastructure remains absent in many areas, and even in mountainous regions where water piping exists, geographic challenges hinder functionality. Addressing these issues requires collaboration between local governments, the private sector, universities, and the community. Solutions may include programs that incorporate local wisdom and focus on infrastructure development, sustainable water management, and environmentally friendly practices. Such initiatives could enhance access to clean water, improve the local economy, and ultimately reduce poverty in West Halmahera.

Challenges, coping strategies, and sources of support available to South African parents with children with autism spectrum disorder during the COVID-19 lockdown: a qualitative study

Parenting a child with autism spectrum disorder (ASD) is known to be complex and challenging and likely to be exacerbated under conditions of stress and uncertainty. We aimed to explore how parents experienced parenting their child with ASD during the initial COVID-19 lockdown in 2020. We also aimed to identify the coping strategies and sources of support available to them during this time. Using an exploratory qualitative design within an interpretivist paradigm, we interviewed 23 parents of children with ASD between the ages of 6 and 12 years. Parents were recruited from an online support group for ASD in South Africa. Interviews were semi-structured and transcribed verbatim for thematic analysis, using ATLAS.ti. We identified five themes: (1) The experience of communicating lockdown rules and disease containment measures to children, (2) Consequences of disruption to routine, (3) Parenting and interpersonal relationships in conditions of confinement, (4) Help-seeking and sources of support, and (5) Finding ways to cope amid a crisis. The findings demonstrate that the initial COVID-19 lockdown placed parents of children with ASD under considerable stress. Disrupted routines and interrupted access to financial, psychological, social, and educational support during the initial lockdown period exacerbated parenting experiences. This study highlights the importance of providing parents of children with ASD strategies to communicate significant change and various forms of support to navigate the negative effects of routine disruptions during conditions of uncertainty and crisis.

The Gas Generation Process and Modeling of the Source Rock from the Yacheng Formation in the Yanan Depression, South China Sea

The research on deepwater oil and gas exploration areas is relatively limited, and sample collection is difficult. A drilled coal sample from Yanan Depression was used to investigate the hydrocarbon generation process, and the potential, by a gold tube thermal simulation experiment. The results show that the total gas yield was much higher than the oil yield. According to an analysis of the gas pyrolysis data, as represented by ln(C1/C2) and ln(C2/C3), the gas generation process consisted of two forms, namely, primary gas with ~1.33% Ro and secondary gas that occurred at levels greater than 1.33% Ro. The primary gas from kerogen was generated at ~1.33% Ro, which coincided with the %Ro value of the maximum oil yield. The activation energy distribution of the C1–C5 generation processes ranged from 54 to 72 kcal/mol, with a frequency factor of 6.686 × 1014 s−1 for the coal sample. We constructed the history of gas generation on the basis of the process and kinetic parameters, combined with data on the sedimentary burial and thermal history. The extrapolation of the gas history revealed that the gas has been generated from 5 Ma to the present, with a maximum yield of 178.5 mg/gTOC. This history suggests that the coal has good primary gas generation potential and provides favorable gas source conditions for the formation of gas fields. This study provides a favorable basis for expanding the effective source rock areas.

Solidification cracking susceptibility of alloy 718 during additive manufacturing and evaluating method

Although hot cracks frequently occur during metal additive manufacturing (AM), there are very few fundamental studies on the cracking behaviour and susceptibility. In this study, a horizontal tensile-type hot cracking test was investigated for evaluating the solidification cracking susceptibility of alloy 718 quantitatively during AM, particularly in laser powder bed fusion. The factors influencing the cracking susceptibility were also examined. The solidification cracking was reproduced by the melting of the AMed specimen with a tensile load under conditions of heat source simulating the AM process. The critical initial tensile stress for solidification crack initiation could apply as an evaluation index for cracking susceptibility. The critical initial stress decreased with increasing the laser power. A similar tendency was observed during the melting of the powders set on tiny groove for simulating AM process. The critical strain rate for solidification cracking (CST) was derived by a thermal elastic–plastic analysis using the critical initial stress measured experimentally. The CST at the laser power of 1125 W was higher than that of 1000 W for no crack condition. Therefore, high CST corresponding to penetration shape with high laser power induce to deteriorate the solidification cracking susceptibility.

Regulation strategies and optimizations of the expander and pump in organic Rankine cycle under off-design conditions

For the present investigations of the off-design performance of organic Rankine cycle systems, which are mainly based on indirect parameters such as temperature and pressure, it is difficult to provide direct theoretical guidance for the actual operation of the system. Therefore, this paper introduces a novel, directly regulated coupling model based on a quasi-two-stage single screw expander and a multistage centrifugal pump. In addition, to enhance the matching between the expander and the pump during the regulation, the coupled model is optimized using the particle swarm optimization algorithm. The results reveal that the net efficiency initially increases and then decreases when exploring regulation strategies for the expander and the pump, suggesting the existence of optimal operating points. Specifically, after applying the particle swarm algorithm, the net efficiency reached 13.23 % at an expander speed of 5076 RPM and a pump frequency of 46.8 Hz, reflecting a better match between the pump and expander regulation with the heat source conditions. For instance, at a heat source temperature of 200 °C, the net efficiency increased by up to 1.45 % compared to the original results.

Numerical Simulation of the Effects of Compartment Height, Fire Source Location, and Vent Location on Compartment Fire Phenomena with a Ceiling Vent

In this study, the numerical simulations of the effects of compartment height, fire source location, and vent location on the compartment fire phenomena with a ceiling vent were performed. Under the same fire source and vent location conditions, the compartment height of 5.5 m showed a higher mass flow rate across the vent than that of 11 m. For the fire source at the center, the vent on the left showed a lower mass flow rate than that at the center for both compartment heights. For the fire source on the left, the vents on the right and left exhibited the lowest mass flow rates at the compartment heights of 5.5 m and 11 m, respectively. Moreover, for the fire source on the left, a macroscopic rotational flow in the clockwise direction was observed at the compartment height of 5.5 m, whereas at the compartment height of 11 m, macroscopic rotational flows in the clockwise and counterclockwise directions appeared at its lower and upper portions, respectively. It was confirmed that these macroscopic rotational flows were closely related to the change in the mass flow rate across the vent with the vent location. The compartment height of 11 m had a lower average temperature inside the compartment than that of 5.5 m, which was because of the increase in the surrounding wall area. In addition, under each compartment height condition, the changes in the average temperature inside the compartment with the fire source and vent locations were minor.

Combined Transcriptome and Metabolome Analysis Reveals That Carbon Catabolite Repression Governs Growth and Pathogenicity in Verticillium dahliae.

Carbon catabolite repression (CCR) is a common transcriptional regulatory mechanism that microorganisms use to efficiently utilize carbon nutrients, which is critical for the fitness of microorganisms and for pathogenic species to cause infection. Here, we characterized two CCR genes, VdCreA and VdCreC, in Verticillium dahliae that cause cotton Verticillium wilt disease. The VdCreA and VdCreC knockout mutants displayed slow growth with decreased conidiation and microsclerotium production and reduced virulence to cotton, suggesting that VdCreA and VdCreC are involved in growth and pathogenicity in V. dahliae. We further generated 36 highly reliable and stable ΔVdCreA and ΔVdCreC libraries to comprehensively explore the dynamic expression of genes and metabolites when grown under different carbon sources and CCR conditions. Based on the weighted gene co-expression network analysis (WGCNA) and correlation networks, VdCreA is co-expressed with a multitude of downregulated genes. These gene networks span multiple functional pathways, among which seven genes, including PYCR (pyrroline-5-carboxylate reductase), are potential target genes of VdCreA. Different carbon source conditions triggered entirely distinct gene regulatory networks, yet they exhibited similar changes in metabolic pathways. Six genes, including 6-phosphogluconolactonase and 2-ODGH (2-oxoglutarate dehydrogenase E1), may serve as hub genes in this process. Both VdCreA and VdCreC could comprehensively influence the expression of plant cell wall-degrading enzyme (PCWDE) genes, suggesting that they have a role in pathogenicity in V. dahliae. The integrated expression profiles of the genes and metabolites involved in the glycolysis/gluconeogenesis and pentose phosphate pathways showed that the two major sugar metabolism-related pathways were completely changed, and GADP (glyceraldehyde-3-phosphate) may be a pivotal factor for CCR under different carbon sources. All these results provide a more comprehensive perspective for further analyzing the role of Cre in CCR.

Phase equilibrium constraints on the pre-eruptive conditions of alkaline basalts of the Main Ethiopian Rift and their bearing on the production of peralkaline rhyolites

Abstract Bimodal magmatism is characteristic of the geodynamic evolution of the Main Ethiopian Rift (MER), which is a reference area for the study of the processes leading to continental break-up before seafloor spreading. There are abundant emissions of basalts and rhyolites, which are in possible parent-daugther relationships. However, the P-T-H2O conditions of production and storage of the basaltic end member remain unclear. Crystallization experiments have been conducted on an alkali basalt from the MER to define its pre-eruptive conditions and shed light on the compositional evolution of derivative liquids and source conditions. The experiments were performed at 100-200 MPa, 975-1080°C, varying H2O/CO2 ratios, corresponding to melt water contents of 1-5 wt%, at fO2 slightly lower than the Fayalite-Magnetite-Quartz (FMQ) solid buffer. Comparison between the petrological attributes of the starting rock and the experiments shows that the basaltic magma was stored at 150-200 MPa, 1050 ± 10°C, with 1-2 wt% H2O in melt, with fO2 near FMQ prior to eruption. Geochemical modelling shows that the corresponding mantle source contained about 0.1 wt% H2O, reflecting a metasomatized source. Extensive crystallization of such basalts produces SiO2-rich liquids, which are not yet peralkaline, however. This underscores that extreme fractionation (>90 wt%) is required in order to produce peralkaline derivatives from mildly alkaline basalts. This extreme fractionation and the water-rich nature of the starting basalt readily explain the H2O-rich condition of peralkaline rhyolites that have fueled caldera forming eruptions in the Rift.

Convergence Rates for Identification of Robin Coefficient from Terminal Observations

This paper deals with the problem of identification of a Robin coefficient (also known as impedance coefficient) in a parabolic PDE from terminal observations of the temperature distributions. The problem is ill-posed in the sense that small perturbation in the observation may lead to a large deviation in the solution. Thus, in order to obtain stable approximations, we employ the Tikhonov-regularization. We propose a weak source condition motivated by the work of Engl and Zou (2000) and obtain a convergence rate of O(δ12)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$O(\\delta ^\\frac{1}{2})$$\\end{document}, where δ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\delta $$\\end{document} is the noise level of the observed data. The obtained rate is better than some of the previous known rates. Moreover, the advantage of the proposed source condition is that the above mentioned convergence rate is obtained without the need for characterizing the range space of modelling operator and its Fréchet derivative, which is in contrast to the general convergence theory of Tikhonov-regularization for non linear operators.

DOA Estimation Method for Vector Hydrophones Based on Sparse Bayesian Learning.

Through extensive literature review, it has been found that sparse Bayesian learning (SBL) is mainly applied to traditional scalar hydrophones and is rarely applied to vector hydrophones. This article proposes a direction of arrival (DOA) estimation method for vector hydrophones based on SBL (Vector-SBL). Firstly, vector hydrophones capture both sound pressure and particle velocity, enabling the acquisition of multidimensional sound field information. Secondly, SBL accurately reconstructs the received vector signal, addressing challenges like low signal-to-noise ratio (SNR), limited snapshots, and coherent sources. Finally, precise DOA estimation is achieved for multiple sources without prior knowledge of their number. Simulation experiments have shown that compared with the OMP, MUSIC, and CBF algorithms, the proposed method exhibits higher DOA estimation accuracy under conditions of low SNR, small snapshots, multiple sources, and coherent sources. Furthermore, it demonstrates superior resolution when dealing with closely spaced signal sources.

Comparison of emotional responses between young and elderly individuals under different sound source conditions

In the paper, four types of sound sources were selected, including animal sounds, human behavior sounds, natural sounds, and machine sounds. Each type of sound source contains eight types of sound sources. Six discrete emotions with anger, happiness, sadness, disgust, surprise, and fear are evaluated by young and elderly people through listening and questionnaire surveys under these sound source conditions. The results showed that machine sounds are more likely to cause emotions of anger and disgust, Natural sounds are more likely to trigger feelings of joy, sadness, surprise, or fear. Most of the six basic emotions are correlated with each other. In terms of the difference in evaluation between young and elderly people, most emotional response trends and degrees to various sound sources between young and elderly people are similar basically, but there are some sound sources that are obviously more likely to trigger related emotional reactions in young people, and less likely to trigger emotional reactions in elderly people. It provides a certain experimental reference basis for the sound environment design of urban public spaces.

An OSL-dated, stacked Holocene dust mass accumulation rate record on the Chinese Loess Plateau and its implications for Northern Hemisphere dust activity

Accurate reconstruction of geological dust activity is crucial for understanding past climate change and its interaction with dust cycle. Loess on the Chinese Loess Plateau (CLP) is an ideal and sensitive material for revisiting past dust activity. Previously, the changes in the dust mass accumulation rate (MAR) over various time scales were widely established on the CLP. However, few absolutely dated dust records have been obtained and synthesized for the Holocene. This study addresses this gap by compiling 23 optically stimulated luminescence-dated Holocene loess sections across the CLP. We developed a high-quality chronology via Bayesian age-depth modeling and derived a MAR record for each section. Then, we obtained a mean MAR record for the CLP by stacking individual records. We propose that, in contrast to site-specific MARs, stacked MARs represent the mean dust accumulation conditions for the entire CLP and can be used to track relatively large-scale dust activity and climate change. The stacked MAR record suggests a moderate weakening trend of dust accumulation from ∼11.5 to 7.5 thousand years ago (ka BP), followed by a pronounced strengthening trend from ∼7.5 to 3.0 ka BP. A comparison with other regional dust records reveals a shift in dust activity at ∼8–6 ka BP in northern China and western Mongolia. We argue that the East Asian winter and summer monsoons jointly contributed to Holocene mean dust MAR variations on the CLP by changing dust transport wind energy and dust source aridity, respectively. A comparison of Holocene dust records in Asia with those in the northwestern Pacific Ocean and Greenland suggests asynchronous variations in dust activity between proximal and distal Asia-sourced dust deposition. This is because, unlike proximal deposition, distal deposition can be controlled not only by the dust source conditions but also by the intensity and the position of the Westerlies.

Impact of cold source temperature on transcritical CO2 power cycle: Design point optimization and off-design performance analysis

The transcritical CO2 (T-CO2) power cycle is regarded as one of the most promising alternatives to the steam power cycle in nuclear power plants. However, these plants often operate with transient cold source conditions, leading to deviations from the optimal design point and performance degradation. Therefore, this study examines a double recompression T-CO2 power cycle to optimize the design point pump inlet temperature and investigate part-load performance under cold source fluctuations. Results indicate that the lowest design point pump inlet temperature is optimal for low temperature cold sources and high load conditions to maximize thermal efficiency. When the system operates at 80% load with a cold source temperature of 5oC, the thermal efficiencies at the design point pump inlet temperature of 15oC and 25oC are 58% and 56.93%, respectively. In contrast, a moderate design point pump inlet temperature is better suited for accommodating wide fluctuations in operating conditions. A lower cold source temperature helps mitigate the reduction in thermal efficiency caused by load decreases. Furthermore, reducing the split ratio of low-temperature compressor can enhance thermal efficiency as the cold source temperature increases. These findings provide an effective approach to minimizing performance degradation in the T-CO2 power cycle under off-design conditions.

Performance assessment and multi-objective optimization of a novel transcritical CO2 Rankine cycle for engine waste heat recovery

In this study, a novel self-condensing transcritical CO2 Rankine cycle, which integrates the three-stage expansion process with an ejector cycle, is proposed to recover engine waste heat deeply and overcome the condensation issue caused by the relatively low critical temperature of CO2. Thermodynamic and economic mathematical models are developed, and the detailed parametric analysis is carried out to investigate the effect of main parameters on both thermodynamic and economic performances of the system. Thereafter, a multi-objective optimization is conducted to trade off the two different performances. Results show that the proposed system could operate under higher temperature cold source conditions with desirable performance. The increases of turbine1 inlet pressure and LT gas heater outlet temperature, the decreases of LT gas heater outlet pressure and turbine3 back pressure are beneficial to achieve better thermodynamic and economic performances. On the basis of multi-objective optimization, the maximum net power output is 70.04 kW, which is a 10.20 % improvement compared to the reference cycle. Meanwhile, the engine power output could be increased by 7.03 % through adopting the novel system. Furthermore, the optimal exergy efficiency and unit net power cost are 37.02 % and 0.1567$/kWh, respectively.

Characterisation of Pseudomonas mosselii H6 for aerobic denitrification: stoichiometry and reaction kinetics

The application of aerobic denitrifying bacteria in biological nitrogen removal has been of great interest. However, the mechanism of nitrogen conversion by aerobic denitrifying bacteria is unclear due to the lack of stoichiometry and kinetic studies. Therefore, this study aimed to investigate the stoichiometry and kinetics of aerobic denitrification using Pseudomonas mosselii H6 as a model strain. The results showed that the stoichiometric equations of strain H6 under different nitrogen source conditions were obtained by nitrogen balance analysis; the concentrations of different limiting substrates were set and combined with the multi-substrate Monod kinetic equation to fit the half-saturation constants of COD, ammonia, nitrate and nitrite nitrogen for strain H6, which were 230.1008, 25.3435, 4.1009 and 23.4601 mg/L, respectively; based on the model of “two-step denitrification”, the numerical simulation of the growth and aerobic denitrification of strain H6 under different limiting substrate concentrations was carried out by using AQUASIM software to test the validity of stoichiometric coefficients and kinetic constants and perfect fitting results were obtained. These parameters will help to simulate the growth and denitrification performance of aerobic denitrifying bacteria and provide an experimental basis for further quantitatively elucidating the mechanism of action in the aerobic denitrification process.

Visualization experimental study on the boiling characteristics of vapor chamber evaporator surface with different heat sources

The effective functioning of vapor chambers depends on the phase change of the working fluid at the wick surface. Given the prevalent role of vapor chambers in thermal management in the electronics industry, it is critical to study the boiling characteristics and thermal performance of vapor chambers, as well as the effect of heat source conditions. In this work, to observe phase change at the wick surface, the visualization confined chamber with wick (VCCW) is proposed and fabricated, which features a side window and a 2 mm thick wick sintered with aluminum powders. The working fluid used is acetone. The heat source is designed in three different sizes to heat the VCCW in either the middle or right position. The experimental results show that the boiling curve is divided into four stages. In the stage Ⅰ, the boiling curve is linear, and the visualization results reveal that the phase change phenomenon on the wick surface is evaporation. The Ⅱ stage is defined as ONB (Onset of Nucleate Boiling) for the vapor chamber evaporator surface. The boiling curve shows a turning, and bubbles were observed to appear and spread by visualization. In the Ⅲ and Ⅳ stages, the boiling curve remains linear. The stable nucleate boiling and intermittent local dryout is observed before and after the DNB (Departure from Nucleate Boiling). The slope of the boiling curve increases as the size of the heat source enlarges, which contributes to greater superheat and evaporation of the working fluid at smaller heat fluxes. Moreover, the position and size of the heat sources affect the ONB and DNB due to heat diffusion and capillary-driven supply of fluid.