Maple Toolbox for Switched Stabilizing Controller

This paper is celebrating the increment of interest in the application of  computer algebra in control system analysis. A Maple toolbox for stabilizing state feedback controllers for a class of switched system is presented. The attention is focused on finding the existence of common Lyapunov function  (CLFs), as this ensures stability for arbitrary switching sequences between several subsystems. The system considered here are restricted to second order linear  systems. In order to find the common Lyapunov function and the ability of the Maple software, the toolbox is proved to be less computational demanding compared to a lot of methods that has been solved by Linear Matrix Inequalities (LMI)

Case-Fatality Ratio of Blood Culture-Confirmed Typhoid Fever in Dhaka, Bangladesh.

With impending rollout of new conjugate typhoid vaccines, better estimates of typhoid case-fatality ratio are needed for countries to set priorities for public health programs. We enrolled 1425 patients of all ages with blood culture-confirmed Salmonella Typhi from laboratory networks serving inpatients and outpatients in Dhaka, Bangladesh. Participants were asked about symptoms and complications including death experienced over a median 3-month period following blood culture diagnosis. Four fatal cases were identified (case-fatality ratio of 0.3% [95% confidence interval, .05%-.55%]). Applying this case-fatality ratio to global typhoid burden estimates would reduce deaths by 70%

A study of the effect of carbon nanodots on TNF-a induced human aortic endothelial inflammation

Atherosclerosis, a prevalent contributor to cardiovascular disease (CVD) on a global scale, is primarily triggered by inflammation, which plays a critical role in initiating the disease process. This inflammatory response leads to endothelial cell dysfunction or damage, ultimately resulting in the formation of plaque buildup within the inner walls of arteries. The emerging nanomaterials provide new prospects to lower the economic and healthcare costs associated with CVD. Carbon nanodots (CNDs), a type of nanoparticle, are particularly attractive due to their biocompatibility, fluorescent capabilities, and potential antioxidant properties. While much research has been conducted on the use of CNDs as bioimaging and drug-delivery tools, their potential anti-inflammatory effects, particularly in the cardiovascular system, have yet to receive much attention. The aorta is particularly vulnerable to atherosclerosis, being the largest affected area. In this study, HAEC (human aortic endothelial cells) were chosen as the cell line due to their capability to express endothelial cell surface biomarkers, and their common use in vascular research has provided a comprehensive understanding of cell lines. However, the impact of CNDs on HAEC has not been investigated yet. In this study, the impact of CNDs on TNF-a induced inflammation in HAEC was studied. Our results demonstrate CNDs inhibited the production of inflammatory genes, such as IL-8, E-Selectin, and CCL2, in vitro in response to TNF-a. With concentrations of up to 0.6 mg/mL used, CNDs did not show any cytotoxic capabilities in our results in HAEC. Fluorescence microscopy data indicated that HAEC were able to uptake CNDs at the concentrations used. The NF-?B Luciferase Reporter Cell assay results showed that CNDs have the ability to reduce TNF-a-mediated increase in NF-kB activity. The results of the Nrf2 pathways also indicated that CNDs can activate Nrf2 transcription, thus leading to an increase in Nrf2-mediated upregulation of various antioxidant genes, including HO-1, GCLC, NQO-1, and GR. Through these results, it can be suggested that the anti-inflammatory effects of CNDs can be related to the downregulation of the NF-?B pathway and the up-regulation of the Nrf2 pathway signaling. This is the first study to examine the effects of CNDs on human aorta endothelial inflammation. [This abstract may have been edited to remove characters that will not display in this system. Please see the PDF for the full abstract.]]]> 2023 English http://libres.uncg.edu/ir/uncg/f/Amin_uncg_0154M_13858.pdf oai:libres.uncg.edu/39109 2023-07-11T15:48:04Z UNCG Gait variability, cognitive control, and brain BOLD signal variability in healthy, young adults Angelino, Shena A. NC DOCKS at The University of North Carolina at Greensboro <![CDATA[Gait variability has been studied in various diseases and in aging, however variability is observed even in young, healthy adults. Variability in stride time can be characterized in terms of short-term, or step-by-step variability, and long-term variability. It is plausible that these temporal parameters in gait have similar neural origins to the dual modes of cognitive control since both require goal-oriented, higher-order processing. A handful of frontoparietal areas have been widely observed to be important for the dynamic nature of these abilities. The purpose of this study is to test the hypothesis that the adaptability of this frontoparietal network, as defined by the variability of the blood oxygen level-dependent (BOLD) signal, underlies a relationship between cognitive control strategies and stride time variability. We recruited twenty healthy young adults between 18 and 35 years old (10 females; average age = 23.6 ± 3.9 years old) to measure performance on a stepping-in-place task, cognitive control, and BOLD signal variability using resting-state functional MRI. A Pearson correlation wase used to determine the association between proactive and reactive cognitive control strategies and long and short-term gait variability, and a partial least squares correlation was used to determine if there is a pattern of BOLD signal variability in a set of frontoparietal regions that jointly explains these cognitive-gait relationships. There was no relationship between cognitive control strategy and long- or short-term variability, however there was a pattern of BOLD variability, primarily in control and salience/ventral attention network regions, that was associated with both short-term gait variability, and to a lesser extent, long-term gait variability (Permutation p = 0.0323). These findings provide evidence of gait variability as a marker of brain variability in healthy, young adults and may open the door to understanding its role as a biomarker of brain health

The Use of Trace Eyeblink Classical Conditioning to Assess Hippocampal Dysfunction in a Rat Model of Fetal Alcohol Spectrum Disorders

Neonatal rats were administered a relatively high concentration of ethyl alcohol (11.9% v/v) during postnatal days 4-9, a time when the fetal brain undergoes rapid organizational change and is similar to accelerated brain changes that occur during the third trimester in humans. This model of fetal alcohol spectrum disorders (FASDs) produces severe brain damage, mimicking the amount and pattern of binge-drinking that occurs in some pregnant alcoholic mothers. We describe the use of trace eyeblink classical conditioning (ECC), a higher-order variant of associative learning, to assess long-term hippocampal dysfunction that is typically seen in alcohol-exposed adult offspring. At 90 days of age, rodents were surgically prepared with recording and stimulating electrodes, which measured electromyographic (EMG) blink activity from the left eyelid muscle and delivered mild shock posterior to the left eye, respectively. After a 5 day recovery period, they underwent 6 sessions of trace ECC to determine associative learning differences between alcohol-exposed and control rats. Trace ECC is one of many possible ECC procedures that can be easily modified using the same equipment and software, so that different neural systems can be assessed. ECC procedures in general, can be used as diagnostic tools for detecting neural pathology in different brain systems and different conditions that insult the brain

Thermo-Hydraulic Performance of Heated Tube with Twisted Delta Winglet Swirler Insert: A Numerical Simulation

Among the various methods for enhancing heat transfer in a heat exchanger, a passive method of inserting a continuous swirler inside a heated tube provides a secondary flow along the fluid that reduces the thickness of the thermal boundary layer, thus increasing the efficiency of convection heat transfer performance. The research’s primary goal is to conserve energy, materials, and money by operating efficient heat exchanger equipment. However, the continuous swirler along the fluid flow creates a persistent obstruction, which amplifies the friction factor and increases the working fluid’s energy loss. As a result, this research presented the twisted delta winglet swirler (TDWS), a new design of a decaying swirler that uses delta winglets twisted to 180° to produce a swirling flow along the tube. The swirler comprises four twisted delta winglets arranged in a circle with a diameter 6% smaller than the tube and a length of L/D=2.2. It was placed at the entrance to a heated tube test section with a diameter of 0.016 m and a length of L/D=93.75. The Reynolds Stress Model was used to simulate the flow domain with a water-ethylene glycol mixture was chosen as the working fluid. TDWS transformed the uniform inlet flow from potential energy to high kinetic energy, resulting in a high intensity of swirling flow downstream of the circular tube up to L/D=46.88 before decaying and reaching a steady state. Compared to other decaying swirlers, TDWS obtained one of the lowest relative friction factors, 1.36, with this flow. The maximum global relative Nusselt number increased by only 11% because this value considered the area where the flow reached a steady state. Since the TDWS is a decaying swirler, the thermal-hydraulic performance reached unity along the tube. However, the optimal performance of TDWS in the plain tube with a length of L/D=93.75 can be found if the dimension or geometric configuration of the TDWS is modified, or two or more TDWS may be placed in an array orientation

Thermal conductivity and dynamic viscosity of mono and hybrid organic- and synthetic-based nanofluids: A critical review

Thermal conductivity and dynamic viscosity are two critical properties of nanofluids that indicate their heat transfer performance and flow. Nanofluids are prepared by dispersing mono or several organic or synthetic nanoparticles in selected base fluids to form mono or hybrid nanofluids. The qualitative and quantitative stability measurement of nanofluids will then be addressed, followed by a detailed discussion on how the dispersion of nanoparticles in water (W), ethylene glycol (EG), and themixture of W:EG 60:40%by volume affects the thermal conductivity and dynamic viscosity ratio. The data comparison demonstrated that the thermal conductivity ratio increases with increasing normalized concentrations, the bulk temperature of nanofluids, and the smaller nanoparticle size. The dynamic viscosity ratio is multiplied by the normalized concentration increase. Nevertheless, as the bulk temperature climbed from 0 to 80°C, the dynamic viscosity ratio was scattered, and the dynamic viscosity ratio trend dropped with increasing particle size. While the majority of nanofluids enhanced thermal conductivity ratio by 20%, adding carbon-based nanoparticles to synthetic nanofluid increased it by less than 10%. The disadvantage of nanofluids is that they multiply the dynamic viscosity ratio of all nanofluids, which increase power consumption and reduces the efficiency of any mechanical system

Effect of diameter, twist angle, and blade count on the thermal-hydraulic performance of a decaying twisted swirler

Inserting a decaying swirler into a heat exchanger has been shown to improve heat transfer with minimal effect on the friction factor. The study analyses the effect of diameter, twist angle, and blade count on the thermal-hydraulic performance of a Decaying Twisted Swirler (DTS) in a horizontally heated tube. The diameter, twist angle, and DTS's blade count are examined for 13.5 mm–15.5 mm with a 0.5 mm interval, 0°–360° with a 60° gap, and 2 to 6 blades, respectively. The Nusselt number, friction factor, and thermal-hydraulic performance are examined for Reynolds numbers between 4583 and 35000. The relative Nusselt number and friction factor increase as DTS diameter and twist angle increase, reaching a maximum value at Re = 4583. Despite this, the relative Nusselt number dispersed as the blade count increased. The relative friction factor increases as the blade count increases. Maximum relative Nusselt number and friction factor reached 1.64 and 3.25, respectively with DTS's 15.5 mm diameter, 360° angle, and 4 blades. Nonetheless, the thermal-hydraulic performance is greatest when the DTS has a diameter of 15.5 mm, a twist angle of 180°, and 2 blades with 1.17

Numerical Simulation of Heat Transfer Performance of Water: Ethylene Glycol Mixture (W:EG) Through Turbine-Like Decaying Flow Swirler

The propeller-type swirler has been mentioned several times in the literature as one of the decaying flow swirlers designed to improve heat transfer performance while maintaining a low friction factor. However, the distance travelled by swirling flow varies according to the swirler’s design configuration. As a result, the purpose of this paper is to investigate the heat transfer performance and friction factor of a new turbine-like decaying flow swirler (TDS). The distance traversed and decays downstream the tube by the created swirling flow will then be determined. The TDS is a rigid turbine or compressor consist of four twisted blades at 172.2° set at the entrance of a fully developed 1.5 m tube with a dimensionless length (L/D) of 93.75. A 60:40% water and ethylene glycol mixture was employed as a working fluid for the turbulent flow with Reynolds numbers ranging from 4583 to 35,000. The results indicate that the maximum relative heat transfer is 1.16 and the highest relative friction factor is 1.47 at the lowest Reynolds number tested. For Reynolds numbers less than and equal to 10,136, the thermal hydraulic performance achieved unity. The obtained relative heat transfer is deemed to be poor in comparison to several publications. The swirl flow finally entirely decays after L/D = 70.32 after being visualised through the vortex core and cross-sectional plane of the tube, contributing to a reduced heat transfer performance. In conclusion, TDS performance can be optimised for a lower dimensionless length using the same design configuration, or the design configuration should be modified to increase the generated swirl flow intensity