Assessing blood flow control through a bootstrap method

In order to assess blood flow control, the relationship between blood pressure and blood flow can be modeled by linear filters. We present a bootstrap method, which allows the statistical analysis of an index of blood flow control that is obtained from constrained system identification using an established set of pre-defined filters.     

Analysis of non-adiabatic heat-recirculating combustors

A simple first-principles model of counter current heat-recirculating combustors is developed, including the effects of heat transfer from the product gas stream to the reactant stream, heat loss to ambient, and heat conduction in the streamwise direction through the dividing wall (and heat transfer surface) between the reactant and product streams. It is shown that streamwise conduction through the wall has a major effect on the operating limits of the combustor, especially at small dimensionless mass fluxes (M) or Reynolds numbers that would be characteristic of microscale devices. In particular, if this conduction is neglected, there is no small-M extinction limit because smaller M leads to larger heat recirculation and longer residence times that overcome heat loss if M is sufficiently small. In contrast, even a small effect of conduction along this surface leads to significantly higher minimum M. Comparison is made with an alternative configuration of a flame stabilized at the exit of a tube, where heat recirculation occurs via conduction through tube wall; it is found that the counter-current exchanger configuration provides superior performance under similar operating conditions. Implications for microscale combustion are discussed.     

Some remarks on the engineering application of the fatigue crack growth approach under nonzero mean loads

The well-known fatigue crack growth (FCG) curves are two-parameter dependents. The range of the stress intensity factor ?K and the load ratio R are the parameters normally used for describing these curves. For engineering purposes, the mathematical representation of these curves should be integrated between the initial and final crack sizes in order to obtain the safety factors for stresses and life. First of all, it is necessary to reduce the dependence of the FCG curves to only one parameter. ?K is almost always selected and, in these conditions, considered as the crack driving force. Using experimental data from literature, the present paper shows how to perform multiple regression analyses using the traditional Walker approach and the more recent unified approach. The correlations so obtained are graphically analyzed in three dimensions. Numerical examples of crack growth analysis for cracks growing under nominal stresses of constant amplitude in smooth and notched geometries are performed, assuming an identical material component as that of the available experimental data. The resulting curves of crack size versus number of cycles (a vs. N) are then compared. The two models give approximately the same (a vs. N) curves in both geometries. Differences between the behaviors of the (a vs. N) curves in smooth and notched geometries are highlighted, and the reasons for these particular behaviors are discussed.     

Amine-modified silica surface applied as adsorbent in the phenol adsorption assisted by ultrasound

Abstract

Phenolic compounds are toxic pollutants that are harmful to the human body and aquatic environments, with carcinogenic potential and frequently found in industrial effluents at high levels. Adsorption processes are often employed for the removal of these compounds. Mesoporous materials based on modified silica with amine have been used as adsorbents and can be considered promising for this job due to its high selectivity and better adsorption capacity when compared to materials without any modifications. In addition, adsorption studies can be performed using ultrasound as a mixing mechanism, improving mass transfer through cavitation and acoustic current. In this context, the goal of this study is to modify the surface of mesoporous silica with 3-aminopropyltriethoxysilane (APTES) and to evaluate its efficiency in the adsorption of phenol in an ultrasonic bath. In the phenol adsorption experiments, the Si-APTES showed higher adsorption capacity (12?mg g^?1) than the SiO₂ (2?mg g^?1). The kinetic models of pseudo second-order have shown to be good fits to the experimental data. The adsorption equilibrium data of the phenol on the materials studied were best described in the Langmuir isotherm.     

Modified Fourier transform method for interferogram fringe pattern analysis

A modified Fourier transform method for interferogram fringe pattern analysis is proposed. While it retains most of the advantages of the Fourier transform method, the new method overcomes some drawbacks of the previous method. It eliminates the assumptions of slowly varying phase variation in the test section and the constant spatial carrier frequency. It also extends the frequency bandwidth and avoids phase distortion caused by discreteness of the sampling frequency. Both numerical simulation and experimental examination are performed to evaluate the performance of the method.     

Energy-ecological efficiency of the fuel cell electric vehicle powered by different biofuels

Clean Technologies and Environmental Policy - This paper examines the net environmental impact for the Fuel Cell Electric Vehicle, in special the Solid Oxide Fuel Cell Electric Vehicle (SOFCEV), by...     

Association of coronary artery calcium score and vascular dysfunction in long‐term hemodialysis patients

Long‐term hemodialysis patients are prone to an exceptionally high burden of cardiovascular disease and mortality. The novel temperature‐based technology of digital thermal monitoring (DTM) of vascular reactivity appears associated with the severity of coronary artery disease in asymptomatic population. We hypothesized that in hemodialysis patients, the DTM and coronary artery calcium (CAC) score have a gradient association that follows that of subjects without kidney disease. We examined the cross‐sectional DTM‐CAC associations in a group of long‐term hemodialysis patients, and their 1:1 matched normal counterpart. Area under the curve for temperature (TMP‐AUC), the surrogate of the DTM index of vascular function, was assessed after a 5‐minute arm‐cuff reactive hyperemia test. Coronary calcium score was measured via electron beam computed tomography or multidetector computed tomography scan. We studied 105 randomly recruited hemodialysis patients (age: 58 ± 13 years, 47% men) and 105 age‐ and gender‐matched controls. In hemodialysis patients vs. controls, TMP‐AUC was significantly worse (114 ± 72 vs. 143 ± 80, P = 0.001) and CAC score was higher (525 ± 425 vs. 240 ± 332, P < 0.001). Hemodialysis patients were 14 times more likely to have CAC score >1000 as compared with controls. After adjustment for known confounders, the relative risk for case vs. control for each standard deviation decrease in TMP‐AUC was 1.46 (95% confidence interval: 1.12–1.93, P = 0.007). Vascular reactivity measured via the novel DTM technology is incrementally worse across CAC scores in hemodialysis patients, in whom both measures are even worse than their age‐ and gender‐matched controls. The DTM technology may offer a convenient and radiation‐free approach to risk‐stratify hemodialysis patients.     

Fields of knowledge in higher education institutions,and innovative start‐ups: An empirical investigation

We investigate the role played by different fields of academic knowledge and various types of higher education institutions in the emergence of innovative start‐ups in a region. We show that education and research in the applied and natural sciences have the strongest effect on the emergence of new businesses in innovative industries. Distinguishing between different indicators for these types of knowledge, the strongest effects are found for the number of professors, the number of students and the amount of external funds attracted.     

Spectral Analysis of Electrical Impedance Measurements on the Lower Limbs

Electrical impedance signals from the lower limbs of normal individuals and patients with atherosclerosis have been studied in the frequency domain. A current of 1 mA at 40 kHz was introduced with strip electrodes around the ankles, and voltage differences were measured with electrodes above the knee and above the current electrode of the same limb. The impedance signal AZ and the ECG were recorded on magnetic tape and transferred to a digital computer. The first derivative of the impedance signal, dZ/dt, was calculated by numerical methods from the coherent average of at least 20 AZ signals, and the spectra were obtained by an FFT algorithm. For young normal individuals, only 1 percent of the dZ/dt signal energy lies above 12 Hz. Patients with arterial obstructions present a greater attenuation in the lower harmonics, stretching the 99 percent energy bandwidth to 32 Hz. Although the amplitude of some spectral components can be used for noninvasive evaluation of arterial disease with a precision of up to 90 percent, it was found that the phase spectra are very little influenced by atherosclerosis.