Depressurization characteristics of steam-based reciprocating vacuum pump

This dissertation introduces a novel vacuum technology that leverages low-pressure saturated steam and cooling-controlled condensation, offering an efficient way to utilize low-grade thermal energy sources like waste heat, steam, or solar energy. At the heart of this technology is a unique duo-chamber vacuum pump system, featuring a reciprocating piston and a heat-conductive wall, designed to generate a vacuum through steam-condensation and cooling processes. The core of this research lies in developing and validating mechanistic models for the steam-condensation depressurization process, a complex phenomenon involving phase change and transport mechanisms. Prior to this work, these mechanisms were not sufficiently modeled or understood, limiting the potential for quantitative assessment and optimization of the technology. This study addresses this gap by establishing comprehensive models that simulate the dynamic depressurization process, incorporating factors like transient cooling and non-uniform steam condensation. Dynamic depressurization characteristics, such as chamber pressure, condensation rate, and vapor temperature, have been investigated, along with parametric effects of key operation and system parameters, including initial vapor pressure/temperature, coolant flowrate and temperature, and system geometric dimensions and material selections. Specifically, a parametric model of depressurization process is developed, which is based on a modified formulation of film condensation within an enclosed cylinder. This model, based on simplified lumped-heat capacity approximation of system components, can reasonably predict various parametric effects on the depressurization process, including the parametric effects of initial steam vapor pressure or temperature, coolant flow rate, and inlet temperature of coolant. These parametric analyses are vital to the optimized system design selections and operations. To account for the transient and nonuniformity of heat and mass transfer with coolant-flow-influenced vapor condensation in a three-dimensional system, a more complicated numerical model and associated computational fluid dynamics (CFD) simulation is conducted. The depressurization-process CFD model of the condensing vapor-liquid two-phase flow is based on a Eulerian approach with the volume of fraction (VOF) method and space condensation modeling approximation. The CFD simulation reveals some strong three-dimensional non-uniform temperature distributions of both steam vapor and coolant flow. The steam condensation is also strongly non-uniformly distributed near the cooling wall of inner cylinders. However, the transient vapor pressure is nearly uniformly distributed within the chamber at any moment. The deviation between the non-uniform vapor temperature distribution and the uniform pressure distribution clearly suggests that there exists strong thermodynamic non-equilibrium in the vapor phase during the vapor condensation process, and the depressurization is mainly due to the vapor condensation rather than the cooling of vapor. A lab-scale prototype of the vacuum pump system was constructed to provide the quantitative proof-of-concept assessment of the innovative vacuum generation technology. The experimental system is also used to provide important measurements on vacuum generation processes for the validation of the proposed parametric and CFD models. In addition, a preliminary design of the automatic operation of the dual-chamber steam-based reciprocating vacuum pump is proposed. All these results and preliminary studies not only demonstrate the practical viability of the proposed vacuum technology but also provide critical insights for its optimized design and automated operation, which also lay down some foundation for the follow-up research

Non-communicable diseases sustained high call: China's health care model should be transformed as soon as possible

Background: There is sufficient evidence that the prevalence of non-communicable diseases (NCDs) in China is increasing rapidly. Results from the Fourth China National Health Services Survey (2008) show that compared to 2003, the prevalence of chronic diseases in China increased by 5%, while results from the Fifth National Health Services Survey (2013) showed an increase of 9% since 2008. As the world's most populous country and in the face of the rapid rise of non-communicable diseases, China lacks effective measures to achieve significant results on aspects of tobacco use, unhealthy diet, lack of exercise, harmful alcohol use and other risk factors. Of more concern is that the Chinese health care model is still stuck in the "medical services" stage. The "therapy" of health care models not only cause China to experience high health costs - there is also a steady increase in adverse health outcomes, with a failure to timely and effectively respond to the challenges of NCDs. Purpose: This article aims to analyze health care inputs and outputs since Chinese health care reform, and to provide a useful reference to improve Chinese future health care policies

Antibacterial characterization of Bacillus velezensis LG37 and mining of genes related to biosynthesis of antibacterial substances

Bacillus velezensis LG37 secretes various antibacterial substances and inhibits the growth of other bacteria. Here, we analyzed the antibacterial characteristics and the screening and verification of genes related to the synthesis of the antibacterial substance of LG37 by antibacterial activities experiment, Local BLAST+, and RT-PCR. LG37 was isolated from aquaculture water and preserved in our laboratory. The phylogenetic tree was used to analyze the genetic relationship between LG37 and the bacteriostatic test indicator strain. LG37 had a more substantial inhibitory effect on closely related strains, while the inhibitory effect on the more distantly related strains was weak. Combined with the results of genome sequencing, the ribosomal peptide (RP) bacteriocin gene and non-ribosomal peptide synthetase (NRPSs) related gene clusters were screened and analyzed. A total of six gene-coding RP bacteriocins and two genes coding surfactins and fengycin A NRPSs gene cluster were screened. Local BLAST+ analysis revealed a total of 11 NRPSs gene clusters. The active expression of the NRPSs and RP encoding genes was further validated by RT-PCR. The findings revealed various genes and gene clusters encoding RP bacteriocins and NRPSs in B. velezensis LG37. The bacterium is potentially valuable in diverse applications in aquaculture

Template Synthesis of Carbon Nanofibers Containing Linear Mesocage Arrays

Carbon nanofibers containing linear mesocage arrays were prepared via evaporation induced self-assembly method within AAO template with an average channel diameter of about 25 nm. The TEM results show that the mesocages have an elongated shape in the transversal direction. The results of N2 adsorption–desorption analysis indicate that the sample possesses a cage-like mesoporous structure and the average mesopore size of the sample is about 18 nm

Prevalence and Characterization of Staphylococcus aureus Isolated From Women and Children in Guangzhou, China

The prevalent Staphylococcus aureus clones and antibiotic susceptibility profiles are known to change dynamically and geographically; however, recent S. aureus strains causing infections in women and children in China have not been characterized. In this study, we analyzed the molecular epidemiology and antimicrobial resistance of S. aureus isolated from patients in four centers for women and children in Guangzhou, China. In total, 131 S. aureus isolates (100 from children and 31 from women) were analyzed by spa typing, multi-locus sequence typing, virulence gene and antimicrobial resistance profiling, staphylococcal chromosomal cassette mec typing, and mutation analyses of rpoB. A total of 58 spa types, 27 sequence types (STs), and 10 clonal complexes (CCs) were identified. While CC59 (ST59-IV, 48.8%; ST338-III, 35.7%) and CC45 (ST45-IV, 100%) were the major clones (84.4%) among MRSA isolates, CC5 (ST188, 24.3%; ST1, 21.6%) and CC398 (ST398, 70%) were the major ones (70.1%) among MSSA isolates. ST338-MRSA-III mostly found in pus but hardly in respiratory tract samples while ST45-MRSA-IV was on the opposite, even though they both found in blood and cerebrospinal fluid sample frequently. Staphylococcal enterotoxin genes seb-seq-sek were strongly associated with ST59 and ST338, while sec was associated with ST45, ST121, ST22, and ST30. All ST338, ST1232, and SCCmec III isolates carried lukF/S-PV genes. A total of 80% of ST338 isolates were resistant to erythromycin, clindamycin, and tetracycline. All ST45 isolates exhibited intermediate or complete resistance to rifampicin. In total, 481 HIS/ASN mutations in rpoB were found in rifampicin-resistant or intermediate-resistant isolates. ST338-III and ST45-IV emerged as two of three major clones in MRSA isolates from women and children in Guangzhou, China, though ST59-MRSA-IV remained the most prevalent MRSA clone. Clonal distribution of S. aureus varied, depending on the specimen source. Virulence genes and antibiograms were closely associated with the clonal lineage. These results clarified the molecular epidemiology of S. aureus from women and children in Guangzhou, China, and provide critical information for the control and treatment of S. aureus infections

EVALITA Evaluation of NLP and Speech Tools for Italian - December 17th, 2020

Welcome to EVALITA 2020! EVALITA is the evaluation campaign of Natural Language Processing and Speech Tools for Italian. EVALITA is an initiative of the Italian Association for Computational Linguistics (AILC, http://www.ai-lc.it) and it is endorsed by the Italian Association for Artificial Intelligence (AIxIA, http://www.aixia.it) and the Italian Association for Speech Sciences (AISV, http://www.aisv.it)

Superimposition of Contractional Structures in Models and Nature

Superimposition of contractional structures is widely observed in different scales in the world. Superimposed structures form due to different processes: change in strain accommodation from one type of structure to another during a single progressive shortening; successive coaxial shortening phases separated by an unconformity; superimposition of different non-coaxial shortening phases. Using results of a series of systematic analogue models and detailed field structural mapping, this thesis focuses on the geometry and kinematics of such superimposed structures that are formed by these three processes. During a single progressive folding, thrusts develop within a fold to accommodate stain variations in different regime of the fold. Limited displacement along these thrusts does not significantly modify the geometry of the fold. However, during multiple shortening phases (coaxial or non-coaxial), early formed structures are modified by the later phase ones. The later thrusts can cut and displace the pre-existing structures. The early folds are tightened or interfered by the later folding phase. Pre-existing thrusts may be reactivated either in dip direction and/or along strike during the later shortening. The pre-existing structures in turn influence development of the later structures, which results in change in structure spacing. An angular unconformity between two shortening phases clearly truncates the early phase structures and separates structures of different levels. Unlike in the post-erosional layers, in the layers below the unconformity, complicated superimposed structures are visible. This thesis shows that geometry and sequence of structures formed during one progressive shortening or multiple shortening phases strongly depend on the mode of the superimposition (coaxial, orthogonal or oblique) and the orientation of pre-existing structures