Pressure Levels Research Articles

Noise Analysis and Structural Optimization of Automobile Scroll Compressor Air Valve

The air conditioning compressor is a critical component in automobile heating, ventilation and air conditioning systems. However, compressor noise has long been a problem for automobile manufacturers. In recent years, the development and application of automobile air conditioning scroll compressors has increased significantly due to their low mechanical vibration and noise. However, their limitations in terms of airflow pulse and noise cannot be ignored, especially in low speed and high load conditions where the noise generated has a negative impact on driving and passenger experience. Noise and airflow pulses are important considerations that cannot be ignored. This study innovatively modifies the end cap structure of the scroll compressor, using the principles of expansion muffler and insertion tube structure, with the aim of improving the acoustic quality of the scroll compressor. The results show that the novel valve construction can significantly reduce the sound pressure level of the scroll compressor noise to a maximum of 75.20 dBA. The results of this study provide a theoretical basis and practical technical applications for future research and development in the automobile industry.

Role of Hyperbaric Oxygen Therapy in Traumatic Brain Injury: A Systematic Review of Randomized Controlled Trials

Abstract Background Traumatic brain injury (TBI) is a significant public health concern. Standard care involves conservative management and pharmacological and surgical interventions. Hyperbaric oxygen therapy (HBOT) has emerged as a potential treatment for TBI, with varied findings in the literature. Our systematic review aims to comprehensively assess the efficacy and safety of HBOT in TBI management, addressing existing knowledge gaps and providing insights for clinical practice and future research. Methods A systematic literature search was performed in PubMed, SCOPUS, Central Cochrane Registry of Controlled Trials (The Cochrane Library), and ScienceDirect databases for the role of HBOT in TBI. We included studies involving randomized controlled trials (RCTs). Quasi-randomized controlled studies, prospective, retrospective observational studies, case series, case reports, letters, editorials, comments, animal studies, and studies from non-English literature were excluded. Results After identifying 306 articles, we narrowed it to 8 for qualitative synthesis. The studies were categorized into subgroups: those on patients with an acute history of cerebral injury and those with a history of mild TBI. The combined RCTs involved 651 patients (326 in the first subgroup, 325 in the second). Despite a uniform HBOT session duration of 60 minutes, variations in compression, decompression phases, and pressure used (1.5ATA to 2.5ATA) hindered meta-analysis comparability. Outcome measures differed, complicating comparisons. Overall, HBOT appears beneficial in the first group and less so in the second. Complications are primarily pulmonary, which include dyspnea, cyanosis, hyperoxic pneumonia, and increased fraction of inspired oxygen requirement. Conclusion Our study encountered challenges in reaching definitive conclusions due to outcome variability among the included studies. Despite mixed results, HBOT shows potential benefits for acute TBI patients. Conversely, our findings suggest the limited efficacy of HBOT for chronic traumatic brain injury patients. Further research is crucial, particularly exploring diverse HBOT treatment protocols to establish optimal pressure levels and the required number of sessions for effective outcomes

Remyelination-oriented clemastine treatment attenuates neuropathies of optic nerve and retina in glaucoma.

As one of the top causes of blindness worldwide, glaucoma leads to diverse optic neuropathies such as degeneration of retinal ganglion cells (RGCs). It is widely accepted that the level of intraocular pressure (IOP) is a major risk factor in human glaucoma, and reduction of IOP level is the principally most well-known method to prevent cell death of RGCs. However, clinical studies show that lowering IOP fails to prevent RGC degeneration in the progression of glaucoma. Thus, a comprehensive understanding of glaucoma pathological process is required for developing new therapeutic strategies. In this study, we provide functional and histological evidence showing that optic nerve defects occurred before retina damage in an ocular hypertension glaucoma mouse model, in which oligodendroglial lineage cells were responsible for the subsequent neuropathology. By treatment with clemastine, an Food and Drug Administration (FDA)-approved first-generation antihistamine medicine, we demonstrate that the optic nerve and retina damages were attenuated via promoting oligodendrocyte precursor cell (OPC) differentiation and enhancing remyelination. Taken together, our results reveal the timeline of the optic neuropathies in glaucoma and highlight the potential role of oligodendroglial lineage cells playing in its treatment. Clemastine may be used in future clinical applications for demyelination-associated glaucoma.

Noradrenaline-induced changes in cerebral blood flow in health, traumatic brain injury and critical illness: a systematic review with meta-analysis.

Noradrenaline is a standard treatment for hypotension in acute care. The precise effects of noradrenaline on cerebral blood flow in health and disease remain unclear. We systematically reviewed and synthesised data from studies examining changes in cerebral blood flow in healthy participants and patients with traumatic brain injury and critical illness. Twenty-eight eligible studies were included. In healthy subjects and patients without critical illness or traumatic brain injury, noradrenaline did not significantly change cerebral blood flow velocity (-1.7%, 95%CI -4.7-1.3%) despite a 24.1% (95%CI 19.4-28.7%) increase in mean arterial pressure. In patients with traumatic brain injury, noradrenaline significantly increased cerebral blood flow velocity (21.5%, 95%CI 11.0-32.0%), along with a 33.8% (95%CI 14.7-52.9%) increase in mean arterial pressure. In patients who were critically ill, noradrenaline significantly increased cerebral blood flow velocity (20.0%, 95%CI 9.7-30.3%), along with a 32.4% (95%CI 25.0-39.9%) increase in mean arterial pressure. Our analyses suggest intact cerebral autoregulation in healthy subjects and patients without critical illness or traumatic brain injury., and impaired cerebral autoregulation in patients with traumatic brain injury and who were critically ill. The extent of mean arterial pressure changes and the pre-treatment blood pressure levels may affect the magnitude of cerebral blood flow changes. Studies assessing cerebral blood flow using non-transcranial Doppler methods were inadequate and heterogeneous in enabling meaningful meta-analysis. Noradrenaline significantly increases cerebral blood flow in humans with impaired, not intact, cerebral autoregulation, with the extent of changes related to the severity of functional impairment, the extent of mean arterial pressure changes and pre-treatment blood pressure levels.

Time-series variation in the locomotor behavior and vocal traits of Japanese medaka (Oryzias latipes) acutely exposed to organophosphorus pesticide chlorpyrifos

Organophosphorus pesticides (OPs), such as chlorpyrifos (CPF), are the most commonly used pesticides worldwide. Considering that OPs will eventually enter aquatic ecosystems due to runoff from agricultural lands, accidental leakage, and other unforeseen emergencies, monitoring water pollution of those substances is crucial for environmental protection and public health. In this study, Japanese medaka (Oryzias latipes) were exposed to CPF (0.03, 0.06, and 0.12 mg/L) for 6 h, and the time-series variations in their locomotor behavior and vocal traits were investigated. Compared with that measured before exposure, significantly changed locomotor behavior and vocal traits in Japanese medaka exposed to CPF could be observed at 4 h after exposure and thereafter, and the pattern of behavioral changes depends on the CPF concentrations. Exposure to CPF also changed the frequency-sound pressure level curve of Japanese medaka at 6 h after exposure, especially at 0.12 mg/L. Moreover, CPF exposure could significantly inhibit the acetylcholinesterase (AChE) activity in the brains and eyes of medaka, which exhibited significant correlations with the variation of locomotor behavioral and vocal traits. Considering that inhibiting the AChE activity is the primary mechanism underlying the neurobehavioral toxicity of all OPs, our finding suggested that simultaneously monitoring changes in the locomotor behavioral and vocal traits has a high potential to reflect the pollution of organophosphorus substances.

Design and Scalable Fast Fabrication of Biaxial Fabric Pouch Motors for Soft Robotic Artificial Muscle Applications

Soft pouch motors, engineered to mimic the natural movements of skeletal muscles, play a crucial role in advancing robotics and exoskeleton development. However, the fabrication techniques often involve multistage processes; they lack soft sensing capabilities and are sensitive to cutting and damage. This work introduces a new textile‐based pouch motors with the capacity for biaxial actuation and capacitive sensory functions, achieved through the application of computerized knitting technology using ultrahigh molecular weight polyethylene yarn (Spectra) and conductive silver yarns. This method enables the rapid and scalable mass fabrication of robust pouch motors. The resulting pouch motors exhibit maximum lifting capacity of 10 kg, maximum contraction of 53.3% along the y‐axis, and transverse extension of 41.18% along the x‐axis at 50 kPa pressure. Finite element analysis closely matches the experimental data. The capacitance signals in relation to contraction motion are well suited for detecting air pressure levels and hold promise for applications requiring robotic control. Notably, it effectively elevates an ankle joint simulator at a 20° angle, highlighting its potential for applications such assisting individuals with foot drop. This study presents a practical demonstration of the soft ankle exosuit designed to provide lifting support for individuals facing this mobility challenge.

ANALYSIS OF LUBRICANT OIL DEGRADATION AND SOUND PRESSURE LEVEL FOR CI ENGINE USING BLEND FUELS

Long-term engine running has been the subject of extensive research on the deterioration of engine oil. In contrast, it is not fully clear what effect synthetic and biofuels will have. Modern engines, traditional fuels and lubricants should be used to provide a research basis for characterizing novel fuel-related phenomena in engines. This study makes an effort to characterize how lubricating engine oil behaves over the course of its service life using data on friction and wear. Every 20 hours, oil samples from the engine were obtained to evaluate its chemical makeup. On a reciprocating test rig, friction and wear measurements were taken. Kinematic viscosity, density, and wear metals such as cadmium (Cd), cobalt (Co), and lead (Pb) were measured for the lubricant oil analysis. In general, n-pentanol aids in the reduction of engine wear debris, contamination, and lubricating oil oxidation. According to the findings of this study, a D60WCO20Pe15 ternary combination can be used in a diesel engine without any alteration. The sound pressure level (SPL) increased by 7.8 dB at engine speed of 1300 RPM in the case of the DF95WCO5. However, when compared to base line, the average SPL of D60WCO20Pe15 ternary blend was 4.3 dB lower.

Airflow and Pressure Design Review of Modular Negative Pressure Wards

In the aftermath of the COVID-19 pandemic, the urgent need for the rapid deployment of healthcare facilities propelled the rise of modular construction using an infill approach. In these modular, negative-pressure wards, the design of indoor airflow and pressure plays a crucial role in meeting the ventilation strategies required for isolation facilities. Accordingly, this paper focuses on modular negative-pressure wards employing an infill construction method and proposes an appropriate spatial pressure distribution to address the problem of air tightness degradation due to leakage. This study analyzed the indoor airflow and pressure distribution of a unit module corresponding to an infill. It aimed to examine whether the pressure difference with the adjacent room is maintained and to assess its effectiveness in isolating contaminated air. First, the airflow rate of the heating, ventilation, and air conditioning system in the unit module was calculated to ensure that it would meet the performance criteria of the negative-pressure ward. Afterward, based on the calculated rate, the study assessed the airflow and room-specific pressure within a typical floor, encompassing both the unit module and associated nursing support facilities. Here, the airflow in the external corridor of the typical floor was divided into two cases according to the pressure distribution: negative pressure and atmospheric pressure. The calculation results were compared using a computational fluid dynamics tool. The analysis results confirm that the air isolation performance is adequate as the pressure difference between adjacent rooms in the unit module and the typical floor was maintained at 2.5 Pa. Additionally, the indoor airflow in the negative-pressure isolation room formed a stable flow at a slow speed of 0.1–0.2 m/s, minimizing the possibility of air contamination from outside the isolation room. In particular, Case B of the typical floor design proposes a method to optimize the pressure distribution in the modular negative-pressure ward by designing the ventilation flow rate at atmospheric pressure level. Thus, this study emphasizes that atmospheric pressure design is appropriate when designing pressure in areas where negative-pressure control is difficult and can contribute to the design and improvement of similar medical facilities in the future.

Arrangement of Nondestructive Tests for Technical Inspection Process of Electrofusion Weld in Gas Polyethylene Pipe

Due to the reduction of operational costs, Non-corrosiveness, and ease of implementation, polyethylene pipes are a suitable replacement for steel pipes in gas distribution networks. Considering the irreversible events of gas leakage, effective and feasible non-destructive testing of electrofusion welding is an essential factor to avoid the hazards of gas leakage. To control the quality of welds, the nature of the electrofusion structure leads us to manufacture vacuum boxes, internal pressure devices, and Tapping Saddle Connector for testing polyethylene joint leakages. This article focuses on the sequence of these non-destructive tests to monitor the health of polyethylene electrofusion joint structures under gas network project implementation conditions. To examine the testing chain and the proposed sequence of non-destructive tests, the data gathering process was performed, and with respect to the sensitivity of the electrofusion weld to the operator's skill, welding process, and the condition of the pipe and fittings, in each case the influential factors to find the key parameters were evaluated. The results of laboratory tests in cases of short tests and long-life tests using artificial defects such as slow crack growth with defective samples of on-site joints and defects reported in projects were compared. To validate leak detection, leak location, and leak measurement, weld simulation with finite element and CFD software analysis conforming to real conditions was considered. The test sequence, acceptance criteria, and calibration method of the tools according to EN 1555 standard were argued for performing the final inspection steps. In this perspective, for each leak testing technique, the average type, pressure level, test duration, and finally the acceptance criteria were proposed. The main outcome is the technical specifications for electrofusion weld assessment and baseline risk- based inspection scheme in gas supply projects. In this regard, a database software based on the proposed ITP (Inspection and Testing Plan) has been developed, which is fundamental for monitoring the whole project from the first stage of polyethylene granule control, pipe and fitting manufacture, and gas injection to the final stage in network and commissioning. Operations to determine failure causes and suitability for performance assessment. Another proposed idea is standardizing the recent technical specifications internationally. This idea will be implemented when management realizes that non-destructive testing can lead to cost savings, protection of humans and the environment, and when codes and standards encompass such requirements.

Analysis of mechanical stresses in silicone rubber joint tubes using a hyper-elastic model

A 2D model of a silicone rubber joint tube is proposed to calculate mechanical pressure. An analysis of radial and circumferential stresses within a joint tube based on a hyper-elastic model, employing finite element method is presented. This paper shows that assuming a constant elastic modulus for rubber leads to miscalculation of stresses within the joint tube. In addition, restricting the expansion ratio without considering the material’s elasticity could elevate the possibility of introducing high circumferential stress. Depending on the elastic modulus and expansion ratio, these circumferential stresses may approach 50% of the material’s tensile strength however, none of the simulated materials showed any critical values. A rigid semiconducting deflector could potentially generate significant circumferential stress, especially at the deflector-joint insulation interface, posing an increased risk if the material is relatively weak. Achieving the required pressure with stiffer materials necessitates a lower expansion ratio, while softer materials demand higher expansion ratios to accomplish the necessary pressure levels.

An improved creep model for unsaturated reticulated red clay

Establishment of a creep model is an important method to analyze the relationship between soil creep deformation and time, and the element model is widely used for studying soil creep. However, the element creep model is employed for fitting saturated soil, and the mechanical element model is generally linear, which cannot well fit the nonlinear deformation of the soil with time in practice. The creep process of the soil is not only time-dependent, but also related to the deviatoric stress level. Therefore, the fractional calculus theory and a parameter n reflecting the effect of deviatoric stress level on the creep properties of the soil were introduced into the element model, and the fractional qBurgers creep model was established by using the fractional Koeller dashpot and Caputo fractional calculus. The proposed model was used to fit the triaxial test data of reticulated red clay under different net confining pressures and matric suctions by unsaturated triaxial apparatus. The proposed model can well describe the nonlinearity of unsaturated reticulated red clay, has memory and global correlation to the creep development process of unsaturated reticulated red clay, and has clear physical meaning. The functional relationships of the model parameters with the matric suction, net confining pressure and deviatoric stress level were deduced, so that the creep curves of unsaturated reticulated red clay can be obtained for any conditions, which is of great value for the study of unsaturated soils.

Axial acoustic signature of dual detonation tubes

The axial acoustic characteristics of detonation sound waves generated by single and dual detonation tubes, utilizing methane as fuel and oxygen as oxidizers, are experimentally investigated. Various acoustic parameters are analyzed, including the effective sound pressure level, A duration, and energy characteristics. By the A duration, we mean the time when the sound pressure ascends to a significant maximum and then swiftly descends to the ambient pressure. Experimental results reveal that the decay rate of the effective sound pressure level gradually decreases with increasing distance, with ground reflection prolonging the A duration. The energy of the detonation sound wave is primarily concentrated in the low frequency, and the proportion of low-frequency energy increases with distance. For the dual detonation tubes, the detonation sound wave exhibits a higher effective sound pressure level and A duration compared to the single detonation tube. Although the energy proportion and wave structures of detonation sound waves generated by the dual detonation tubes are similar to those of the single detonation tube, the high-frequency energy experiences greater gain. The effective sound pressure level of the dual detonation tubes increases with the separation distance. Altering the ignition interval can transfer energy to lower frequencies, albeit slightly reducing the effective sound pressure level. These findings highlight the significant impact of the spacing between dual detonation tubes on the effective sound pressure level, and the potential for changing the ignition interval to modify the energy characteristics of the detonation sound wave.

Two-dimensional sound pressure distribution: Visualization and calibration-free quantification via optical wave microphone CT scanning

In recent years, the optical wave microphone has emerged as an innovative technique, employing Fraunhofer diffraction of a laser beam, and shows promising applications in various acoustic domains where high electric and/or magnetic fields preclude the use of traditional microphones. This study utilized an optical wave microphone computed tomography (CT) scan and calibration-free quantification to ascertain sound pressure levels at multiple distances from the ultrasonic oscillator. The cornerstone of this study, which is different from the author’s previous studies, is the quantification of sound pressure distribution via a theoretical model that encompasses all physical parameters pertinent to the optical wave microphone’s experimental arrangement. This method has proven effective in visualizing and quantifying the two-dimensional sound pressure distribution emitted by an ultrasonic oscillator (40 kHz) without the necessity for calibration. The results demonstrate that the sound pressure distribution determined using the calibration-free optical wave microphone CT scan is in good agreement with the measurements obtained through a condenser microphone.

Loss model of low pressure compressor for mechanical vapor recompression system

Abstract Low pressure compressor (LPC) serves the role of enhancing pressure levels of secondary steam at nominal pressure ratios (1.5), procured from the evaporator as a primary thermal energy source. A loss model has been proficiently proposed to rapidly predict the performance of the LPC. Instead of conventional lump sum loss equations, the model adopts well-established one-dimensional (1D) loss formulations scattered across scholarly publications. Given an explicit configuration of the LPC, the environmental conditions, rotational velocity, and capacity, static and total temperatures, static and total pressures, pressure reductions, polytropic head, and efficiencies of each individual segment of the compressor can be calculated. Validation of this model was done using computational fluid dynamics (CFD) analysis. This model renders it feasible to conduct a parametric examination of the impact of each loss apparatus on the LPC’s capability, thereby aiding designers in substantiating design choices that minimize these losses and consequently positively influencing the comprehensive efficiency.

A nutrition intervention study’s effect to hematology profiles on elderly group in social retirement home

The increase in the elderly brings consequences, including a higher risk of disease. Inappropriate nutritional intake is also known as one of the risk factors related to the elderly's non-communicable diseases, and nutritional intervention is essential to improve the elderly nutritional status and quality of life. It was an interventional study with a before-after one-group approach. The study was conducted for three months (October-December 2021) in three social retirement homes. The intervention given was supplementation with additional protein sources and snacks each day. The biochemistry profiles were taken 2 times: before and after three months of intervention, comprised of HbA1c, lipid, transferrin, creatinine, and blood pressure level. The data will be analyzed for its normality before being processed with paired t-test or Wilcoxon signed rank based on the normality results. The analysis results show that there are significantly lower transferrin levels (p=0.040), an increase in cholesterol level (p=0.000), and low-density lipoprotein (LDL) level increased from 114.05±32.03 to 125.94±31.41 (p=0.000). There is also a remarkable decrease in hemoglobin (p=0.005) and high-density lipoprotein (HDL) levels. Conversely, there are an increase in HbA1C (p=0.007) and triglyceride level (p=0.005). There is no significant difference in creatinine level. We conclude that nutrition interventions have a significant effect on elderly blood profiles. However, to achieve an improvement, the study should consider physical activity and other variables that might be altering the results.

Morphological effects of leading-edge sawtooth on the vortex evolution and acoustic characteristic of an ultra-thin centrifugal fan

Serrations on the owl wings' leading edge (LE) are considered one of the critical characteristics leading to their silent flight. Inspired by this, LE sawtooth was innovatively induced on ultra-thin centrifugal fan blades, and the morphological effects of these teeth on the vortex evolution and aeroacoustic characteristics of the fan were studied using large eddy simulation and the Ffowcs Williams–Hawkings analogy. A single-passage model was adopted to finely simulate the flow mechanism between blades with an acceptable scale. Five sawtooth schemes with relative tooth width λ/b from 7.96% to 29.84%, as well as the prototype, were calculated and analyzed. It is found that the optimal λ/b ranges from 8% to 17.05%, which reduces the overall sound pressure level (SPL) by over 1 dB without impacting the blade pressure and efficiency. These sawteeth inhibited the LE separation, shattered the leading-edge vortex (LEV) into small vortices, and consequently weakened the pressure fluctuations on the blades. However, more prominent teeth (λ/b > 23.8%) intensify the interactions between LEV and other passage vortices, changing the dominant pressure pulsations to high frequency, in turn raising the overall SPL. Too small sawteeth are challenging to process on such ultra-thin blades, so the largest sawtooth among the suggested range was considered the optimal scheme (λ/b = 17.05%) and was manufactured to measure. The results show that the SPL of the fan with LE sawtooth is 0.24–0.57 dB lower than that of the prototype under the same flow rates, even though its rotational speed is increased.

Повышение акустической безопасности производственного помещения

Sound-emitting production and technological as well as engineering equipment located within the enclosed space of industrial premises can form paired interacting sound fields with similar values of expressed dominant emission frequencies in the spectra, ultimately causing the formation of a physical process of sound vibration beats. The process manifests in negative psychoacoustic impacts on a human characterized by pulsating sound pressure levels over time with a pulsation frequency equal to the difference between similar frequency values of discrete components of interacting sound fields. The article provides the results of experimental studies to determine the required value of frequency mismatch of sound fields for individual sources of noise emissions mounted in industrial premises. The industrial premises have been presented as a rectangular parallelepiped with rigid sound-reflective fences. Simulation experiments have been carried out using an electroacoustic sound-emitting system represented as two autonomous sound-emitters — electroacoustic loudspeakers. The loudspeakers have simulated noise-generating engineering units with the specified passport steady-state speed operating modes ns and accompanied by the respective established physical processes of sound energy emission whose spectral composition contains specific discrete values of operating dominant functional sound frequencies fs. The technical result of the study is achieved by the implementation of a sufficient degree of frequency mismatch of expressed discrete components of sound emissions of individual autonomous sources of noise preventing the formation of the physical process of generation of intense sound vibration beats. The suggested technical method aiming to increase the acoustic safety of industrial premises assumes that the discrete values of operating dominant functional sound frequencies fs differ from each other by a limiting value Δf exceeding the value of 5 Hz.

Response of selected peanut commercial cultivars to leaf spot diseases as influenced by fungicide inputs

Early leaf spot (caused by Passalora arachidicola) and late leaf spot (caused by Nothopassalora personata) are the most widespread, damaging foliar diseases of peanuts in the southeastern United States. When left nontreated, both diseases can prematurely defoliate peanuts and reduce peanut yields by up to 70%. Leaf spot diseases are primarily managed through a combination of fungicide applications and cultivar selection. In this study, six field experiments were conducted from 2021 to 2022 in Brewton, Headland, and Tallassee, Alabama, to evaluate the response of ten selected commercial peanut cultivars to various levels of leaf spot pressure as influenced by low- and high-input fungicide programs when compared to nontreated controls. The low input fungicide program included seven applications of chlorothalonil, whereas the high input fungicide program comprised of fluxapyroxad, pyraclostrobin, mefentrifluconazole, flutolanil, bixafen, flutriafol, tebuconazole, and/or chlorothalonil. Effects on leaf spot and pod yields were assessed. Leaf spot severity was higher for TUFRunner™ ‘297’, Georgia-16HO, and FloRun ‘331’, but was lower for AU-NPL 17, Georgia-06G, Georgia-12Y, and Georgia-14N. In terms of yield, leaf spot tolerant varieties showcased superior performance in high disease pressure, whereas susceptible varieties excelled in low disease pressure. Fungicides significantly enhanced the performance of susceptible cultivars under high leaf spot pressure, with marginal impact in low leaf spot pressure. These results highlight the importance of selecting cultivars and fungicide spray programs based on disease pressure to maximize profits.

Performance analyses on the air cooling battery thermal management based on artificial neural networks

Air cooling thermal management technology is a lightweight and cost-effective approach for managing heat in power battery packs for electric ships. However, it suffers from significant drawbacks such as poor temperature control and excessive noise generation. To address these challenges, this study proposes a method that combines fluid dynamics and artificial neural networks (ANNs) to optimize the thermal management and aeroacoustic performance of the air cooling battery thermal management system (BTMS) for marine power batteries. Initially, a thermal-flow coupled model and an acoustic model for the BTMS were developed to investigate the impact of system structural parameters (battery spacing d, and main channel inclination angle θ) and operating parameter (system inlet velocity v) on the thermal management performance indicators (maximum temperature Tmax, and maximum temperature difference ΔTmax) as well as the aeroacoustic performance indicator (overall sound pressure level, OSPL). Subsequently, a relationship between the system structural and operating parameters and performance indicators was established using the 50-layer Residual Network (ResNet-50) model, enabling accurate and rapid prediction of the system thermal management and aeroacoustic performance. Furthermore, by combining ResNet-50 with the evaluation method of Technique for Order Preference by Similarity to Ideal Solution (TOPSIS), this study successfully obtained the optimal system structure and operating parameters. The research indicates that keeping the remaining parameters constant, increasing the battery spacing results in higher maximum temperature and maximum temperature difference, while decreasing the overall system sound pressure level. Conversely, increasing the main channel inclination angle results in lower maximum temperature and maximum temperature difference, but higher overall system sound pressure level. In addition, increasing the inlet velocity will result in higher maximum temperature and maximum temperature difference, as well as higher overall system sound pressure level. The optimal case were found to be a main channel inclination angle θ = 3°, battery spacing d = 2 mm, and inlet velocity v = 10 m⋅s−1. Compared to the base case, the optimal case shows a maximum temperature reduction of 10.63 K, a maximum temperature difference reduction of 9.41 K, and an overall sound pressure level reduction of 4.6 dB. The prediction errors for these values are 0.08 %, 2.64 %, and 1.36 % respectively. This research demonstrates an effective and rapid approach based on fluid dynamics and ANNs in the design and optimization of BTMS.

Association between blood pressure levels and premature atrial contractions in patients with hypertension

BackgroundHigh blood pressure (BP) induces left atrial structural and functional remodeling that increases susceptibility to atrial arrhythmia. We hypothesized that lower systolic BP (SBP) levels are associated with a lower prevalence of premature atrial contractions (PACs) in patients with hypertension. MethodsThis analysis included 4,697 participants (mean age 62±13.1 years, 50% women, 25.6% blacks) with hypertension from the Third National Health and Nutrition Examination Survey who did not have a prior history of cardiovascular disease (CVD). Multivariable logistic regression was used to examine the cross-sectional association between SBP and prevalence of PACs ascertained from 12-lead resting electrocardiograms. Multivariable Cox proportional hazard analysis was used to examine the association between baseline PACs and CVD mortality. ResultsApproximately 1.6% (n=74) of participants had baseline PACs. Patients with SBP ≤140 mmHg had a lower prevalence of PACs than those with SBP ≥140 mmHg (1.1% vs. 1.9%, p-value=0.01). In a multivariable logistic regression model, each 10 mmHg decrease in SBP was associated with a 12% lower odds of PACs (OR (95%CI): 0.88 (0.77-0.99)). During 14 years of follow-up, 645 CVD deaths occurred. In a multivariable-adjusted Cox model, presence of PACs was associated with a 78% increased risk of CVD mortality (HR (95%CI): 1.78 (1.23-2.60)). ConclusionsIn patients with hypertension, lower SBP levels are associated with a lower prevalence of PACs, and presence of PACs is associated with a higher risk of CVD mortality risk. These findings highlight the potential role of BP lowering in the management of cardiac arrhythmias.