Large eddy simulation of round jets with mild temperature difference

Understanding the behaviour of hot jets is crucial for various engineering and environmental applications. The present work studies the influence of heat transfer on the dynamics of horizontal round hot jets through Large Eddy Simulations (LES). Our focus lies on trajectory development, large-scale coherent structures, and turbulent kinetic budget analysis in the near-field and intermediate-field regions. LES of two horizontal round hot jets with Reynolds numbers (3934 and 5100) and corresponding Froude numbers (32.98 and 17.07) were carried out using buoyantPimpleFoam solver in OpenFOAM, and the simulation on an isothermal jet was also performed as a baseline for comparison. The results reveal that the jet core temperature decays faster in the streamwise direction but more slowly in the radial direction, indicating a wider temperature spread than velocity, and the maximum difference between the temperature and velocity spread is about 0.5D. Moreover, the energy associated with the large-scale coherent structure decreases with increasing initial jet temperature. The energy of the first two modes of snapshot Proper Orthogonal Decomposition (POD) and extended POD dropped by 12% and 14%, respectively. The coherent motion with the greatest correlation between the temperature and velocity fluctuations is identified as four pairs of Q1 and Q3 events, which are Reynolds shear stress dominant events. Furthermore, compared with the isothermal jet, the turbulent kinetic energy budgets of the hot jets indicate that the diffusion and generation terms are both reduced by approximately 50%, suggesting a transfer of more kinetic energy into potential energy rather than turbulence. The finding highlights the potential of heightened temperatures to mitigate instabilities associated with large-scale motions in hot jets. This study fills the gap on a comprehensive analysis of heat transfer effects on jet dynamics, and quantitative insights into the large-scale coherent structures are provided, contributing to a better understanding of hot jet behaviour

Proactive caching placement for arbitrary topology with multi-hop forwarding in ICN

With the rapid growth of network traffic and the enhancement of the quality of experiences of users, Information-Centric Networking (ICN), which is a content-centric network architecture with named data caching and routing, is proposed to improve the multimedia content distribution efficiency. In arbitrary topology, cache nodes and users are randomly distributed and connected, hence it is challenging to achieve an optimal caching placement under this situation. In this paper, we propose a caching placement algorithm for arbitrary topology in ICN. We formulate an optimization problem of proactive caching placement for arbitrary topology combined with multi-hop forwarding, with an objective to optimize the user delay and the load balancing level of the nodes simultaneously. Since the original problem is NP-hard, we solve the formulated caching placement problem in two sub-problems, content replica allocation subproblem and content replica placement sub-problem. First, in the content replica allocation sub-problem, the replica number of each content is obtained by utilizing the auction theory. Second, the replica number of each content is used as a constraint for the content replica placement sub-problem, which is solved by matching theory. The caching placement algorithm combined with multi-hop NRR forwarding maximizes the utilization of cache resources in order to achieve better caching performance. The numerical results show that significant hop count savings and load balancing level improvement are attainable via the proposed algorithm

Influence Mechanism of Urban Staggered Shared Parking Policy on Behavioral Intentions of Users and Providers Based on Extended Planned Behavior Theory

Shared parking has been widely accepted as an effective way to deal with the mismatch between parking demand and supply. Especially for adjacent construction areas with mixed residential and commercial land, staggered shared parking has broad application prospects. From the previous practice, the public welfare from the government, the commercial interests of parking enterprises, and the individual income of residents will be the key elements to promote a staggered parking policy in adjacent construction areas. However, the current research on shared parking mainly focused on the commercial factors to improve the operating efficiency and operating benefit for parking enterprises; there is a lack of research on the implementation process of staggered parking policies which will solve residential areas’ parking problem with the interests of residents as the core. Here, this paper focuses on exploring residents’ and businesses’ intention to participate in the process of a staggered shared parking policy, where businesses have certain location and condition qualifications. Firstly, this study used two extended theoretical models of planned behavior to explore the behavioral intentions of users and providers in this staggered shared parking event, respectively. Secondly, the research hypothesis was examined using a structural equation approach, and a questionnaire was designed to survey 323 residents and 282 enterprises in the core urban area of Beijing. Ultimately, the study indicated that, for residents, perceptual behavior control has the greatest impact on the perceived intention, while the perceived ease of use and perceived usefulness play a crucial influential role in the willingness to use staggered shared parking. For companies, attitude has the strongest impact on the perceived intention. Our findings reveal the intrinsic impact mechanism of the policies in the decision-making process, contributing to the precise policy implementation to alleviate the problem of difficult parking for residents, thus improving the city’s parking management

Wet Etching of Silicon in Planar Nanochannels

Silicon (Si) alkaline etching constitutes a fundamental process in the semiconductor industry. Although its etching kinetics on plain substrates have been thoroughly investigated, the kinetics of Si wet etching in nanoconfinements have yet to be fully explored despite its practical importance in three-dimensional (3-D) semiconductor manufacturing. Herein, we report the systematic study of potassium hydroxide (KOH) wet etching kinetics of amorphous silicon (a-Si)-filled two-dimensional (2-D) planar nanochannels. Our findings reveal that the etching rate would increase with the increase in nanochannel height before reaching a plateau, indicating a strong nonlinear confinement effect. Through investigation using etching solutions with different ionic strengths and/or different temperatures, we further find that both electrostatic interactions and the hydration layer inside the nanoconfinement contribute to the confinement-dependent etching kinetics. Our results offer fresh perspectives into the kinetic study of reactions in nanoconfinements and will shed light on the optimization of etching processes in the semiconductor industry

Protection of endothelial cells against Ang II-induced impairment: Involvement of both PPARα and PPARγ via PI3K/Akt pathway

<p>The aim of our study is to explore the involvement of PPARα and PPARγ in Ang II-induced endothelial injury. We found that Ang II significantly elevated the oxidative stress in HUVECs, causing apoptosis and cellular impairment in a time-dependent pattern. Activation of either PPARα by docosahexaenoic acid (DHA) or PPARγ by rosiglitazone protected the endothelial cells. Interestingly, a more significant effect was observed when DHA and rosiglitazone were administrated together. Moreover, we found that this protection was mediated through the PI3K/Akt pathway. Our study may help to understand the mechanism of endothelial dysfunction, contributing to the treatment of hypertension and other endothelial-related diseases.</p

Rewritable printing of ionic liquid nanofilm utilizing focused ion beam induced film wetting

Abstract Manipulating liquid flow over open solid substrate at nanoscale is important for printing, sensing, and energy devices. The predominant methods of liquid maneuvering usually involve complicated surface fabrications, while recent attempts employing external stimuli face difficulties in attaining nanoscale flow control. Here we report a largely unexplored ion beam induced film wetting (IBFW) technology for open surface nanofluidics. Local electrostatic forces, which are generated by the unique charging effect of Helium focused ion beam (HFIB), induce precursor film of ionic liquid and the disjoining pressure propels and stabilizes the nanofilm with desired patterns. The IBFW technique eliminates the complicated surface fabrication procedures to achieve nanoscale flow in a controllable and rewritable manner. By combining with electrochemical deposition, various solid materials with desired patterns can be produced

Identification of 4,5-Dihydro-4-hydroxygeldanamycins As Shunt Products of Geldanamycin Biosynthesis

Two new geldanamycin (GDM) analogues, (4<i>S</i>)-4,5-dihydro-4-hydroxygeldanamycin (<b>1</b>) and (4<i>R</i>)-4,5-dihydro-4-hydroxygeldanamycin (<b>2</b>), were identified from <i>Streptomyces hygroscopicus</i> 17997. Compounds <b>1</b> and <b>2</b> were not normal intermediates of GDM biosynthesis but shunt products of C-4,5 oxidation catalyzed by GdmP, a cytochrome P450 oxidase acting as a desaturase in GDM biosynthesis. Preliminary assays implied that, compared with GDM, <b>1</b> and <b>2</b> exhibited decreased cytotoxicity