Experimental analysis of heat recoveries with heat pipes operating in low inclination angle

Heat recovery devices are important in the optimization of thermal systems, since they can be used to reduce thermal losses to the environment. The use of heat pipes in these types of equipment can provide heat recoveries of higher efficiency, since both fluid flows are external and there are less contamination risks between the hot and cold fluids. The objective of this work is to study a heat recovery unit constructed with heat pipes and mainly, to analyze the influence of the inclination of the heat pipes on the performance of the equipment. For this analysis, a heat recovery unit was constructed which possesses 48 finned heat pipes in triangular geometry, the evaporator and condenser being of the same length. This unit was tested in an air-air system simulating a heat recovery process in which heat was supplied to the hot fluid by electrical resistances. The results have shown that there exists an inclination at which the system has a better performance, but for higher inclinations there is no significant increase of the efficiency of the system. This paper also presents the influence of inclination of heat pipes on effectiveness and NTU parameters which are important in heat exchanger design.

Influence of pile inclination angle on the dynamic properties and seismic response of piled structures.

[EN] This paper aims to contribute to clarify whether the use of battered piles has a positive or negative influence on the dynamic response of deep foundations and superstructures. For this purpose, the dynamic response of slender and non-slender structures supported on several configurations of 2X2 and 3X3 pile groups including battered elements is obtained through a procedure based on a substructuring model whick takes soil-structure interaction into account.

Effect of tibial tray inclination on the femoro-tibial contact pattern of a mobile total knee arthroplasty

Introduction: The posterior inclination of the tibial component is an important factor that can affect the success of total knee arthroplasty. It can reduce the posterior impingement and thus increase the range of flexion, but it may also induce instability in flexion, anterior impingement between the polyethylene of postero-stabilizing knee prosthesis, and anterior conflict with the cortical bone and the stem. Although the problem is identified, there is still a debate on the ideal inclination angle and the surgical technique to avoid an excessive posterior inclination. The aim of this study was to predict the effect of a posterior inclination of the tibial component on the contact pattern on the tibial insert, using a numerical musculoskeletal model of the knee joint. Methods: A 3D finite element model of the knee joint was developed to simulate an active and loaded squat movement after total knee arthroplasty. Flexion was actively controlled by the quadriceps muscle and muscle activations were estimated from EMG data and were synchronized by a feedback algorithm. Two inclinations of the tibial tray were considered: a posterior inclination of 0° or 10°. During the entire range of flexion, the following quantities were calculated: the tibiofemoral and patello-femoral contact force, and the contact pattern on polyethylene insert. The antero-posterior displacement of the contact pattern was also measured. Abaqus 6.7 was used for all analyses. Results: The tibio-femoral and patello-femoral contact forces increased during flexion and reached respectively 4 and 7 BW (bodyweight) at 90° of flexion. They were slightly affected by the inclination of the tibial tray. Without posterior inclination, the contact pattern on the tibial insert remained centered. The contact pressure was lower than 5 MPa below 60° of flexion, but exceeded 20 MPa at 90° of flexion. The posterior inclination displaced the contact point posteriorly by 2 to 4 mm. Conclusion: The inclination of the tibial tray displaced the contactpattern towards the posterior border of the tibial insert. However, even for 10° of inclination, the contact center remained far from the posterior border (12 mm). There was no instability predicted for this movement.

Maxillary sinus floor extension and posterior tooth inclination in adolescent patients with Class II Division 1 malocclusion treated with maxillary first molar extractions

INTRODUCTION Our objective was to investigate potential associations between maxillary sinus floor extension and inclination of maxillary second premolars and second molars in patients with Class II Division 1 malocclusion whose orthodontic treatment included maxillary first molar extractions. METHODS The records of 37 patients (18 boys, 19 girls; mean age, 13.2 years; SD, 1.62 years) treated between 1998 and 2004 by 1 orthodontist with full Begg appliances were used in this study. Inclusion criteria were white patients with Class II Division 1 malocclusion, sagittal overjet of ≥4 mm, treatment plan including extraction of the maxillary first permanent molars, no missing teeth, and no agenesis. Maxillary posterior tooth inclination and lower maxillary sinus area in relation to the palatal plane were measured on lateral cephalograms at 3 time points: at the start and end of treatment, and on average 2.5 years posttreatment. Data were analyzed for the second premolar and second molar inclinations by using mixed linear models. RESULTS The analysis showed that the second molar inclination angle decreased by 7° after orthodontic treatment, compared with pretreatment values, and by 11.5° at the latest follow-up, compared with pretreatment. There was evidence that maxillary sinus volume was negatively correlated with second molar inclination angle; the greater the volume, the smaller the inclination angle. For premolars, inclination increased by 15.4° after orthodontic treatment compared with pretreatment, and by 8.1° at the latest follow-up compared with baseline. The volume of the maxillary sinus was not associated with premolar inclination. CONCLUSIONS We found evidence of an association between maxillary second molar inclination and surface area of the lower sinus in patients treated with maxillary first molar extractions. Clinicians who undertake such an extraction scheme in Class II patients should be aware of this potential association and consider appropriate biomechanics to control root uprighting.

Influência da idade no comportamento da frequência cardíaca na transição repouso-exercício: uma análise por deltas e regressão linear

BACKGROUND: Changes in heart rate during rest-exercise transition can be characterized by the application of mathematical calculations, such as deltas 0-10 and 0-30 seconds to infer on the parasympathetic nervous system and linear regression and delta applied to data range from 60 to 240 seconds to infer on the sympathetic nervous system. The objective of this study was to test the hypothesis that young and middle-aged subjects have different heart rate responses in exercise of moderate and intense intensity, with different mathematical calculations. METHODS: Seven middle-aged men and ten young men apparently healthy were subject to constant load tests (intense and moderate) in cycle ergometer. The heart rate data were submitted to analysis of deltas (0-10, 0-30 and 60-240 seconds) and simple linear regression (60-240 seconds). The parameters obtained from simple linear regression analysis were: intercept and slope angle. We used the Shapiro-Wilk test to check the distribution of data and the t test for unpaired comparisons between groups. The level of statistical significance was 5%. RESULTS: The value of the intercept and delta 0-10 seconds was lower in middle age in two loads tested and the inclination angle was lower in moderate exercise in middle age. CONCLUSION: The young subjects present greater magnitude of vagal withdrawal in the initial stage of the HR response during constant load exercise and higher speed of adjustment of sympathetic response in moderate exercise.

Trapezoidal cross-sectional influence on FinFET threshold voltage and corner effects

Fin field effect transistors (FinFETS) are silicon-on-insulator (SOI) transistors with three-dimensional structures. As a result of some fabrication-process limitations (as nonideal anisotropic overetch) some FinFETs have inclined surfaces, which results in trapezoidal cross sections instead of rectangular sections, as expected. This geometric alteration results in some device issues, like carrier profile, threshold voltage, and corner effects. This work analyzes these consequences based on three-dimensional numeric simulation of several dual-gate and triple-gate FinFETs. The simulation results show that the threshold voltage depends on the sidewall inclination angle and that this dependence varies according to the body doping level. The corner effects also depend on the inclination angle and doping level. (C) 2008 The Electrochemical Society.

BONA FIDE, STRONG-VARIABLE GALACTIC LUMINOUS BLUE VARIABLE STARS ARE FAST ROTATORS: DETECTION OF A HIGH ROTATIONAL VELOCITY IN HR CARINAE

We report optical observations of the luminous blue variable (LBV) HR Carinae which show that the star has reached a visual minimum phase in 2009. More importantly, we detected absorptions due to Si lambda lambda 4088-4116. To match their observed line profiles from 2009 May, a high rotational velocity of nu(rot) similar or equal to 150 +/- 20 km s(-1) is needed (assuming an inclination angle of 30 degrees), implying that HR Car rotates at similar or equal to 0.88 +/- 0.2 of its critical velocity for breakup (nu(crit)). Our results suggest that fast rotation is typical in all strong-variable, bona fide galactic LBVs, which present S-Dor-type variability. Strong-variable LBVs are located in a well-defined region of the HR diagram during visual minimum (the ""LBV minimum instability strip""). We suggest this region corresponds to where nu(crit) is reached. To the left of this strip, a forbidden zone with nu(rot)/nu(crit) > 1 is present, explaining why no LBVs are detected in this zone. Since dormant/ex LBVs like P Cygni and HD 168625 have low nu(rot), we propose that LBVs can be separated into two groups: fast-rotating, strong-variable stars showing S-Dor cycles (such as AG Car and HR Car) and slow-rotating stars with much less variability (such as P Cygni and HD 168625). We speculate that supernova (SN) progenitors which had S-Dor cycles before exploding (such as in SN 2001ig, SN 2003bg, and SN 2005gj) could have been fast rotators. We suggest that the potential difficulty of fast-rotating Galactic LBVs to lose angular momentum is additional evidence that such stars could explode during the LBV phase.

Trapezoidal SOI FinFET analog parameters` dependence on cross-section shape

The trapezium is often a better approximation for the FinFET cross-section shape, rather than the design-intended rectangle. The frequent width variations along the vertical direction, caused by the etching process that is used for fin definition, may imply in inclined sidewalls and the inclination angles can vary in a significant range. These geometric variations may cause some important changes in the device electrical characteristics. This work analyzes the influence of the FinFET sidewall inclination angle on some relevant parameters for analog design, such as threshold voltage, output conductance, transconductance, intrinsic voltage gain (A V), gate capacitance and unit-gain frequency, through 3D numeric simulation. The intrinsic gain is affected by alterations in transconductance and output conductance. The results show that both parameters depend on the shape, but in different ways. Transconductance depends mainly on the sidewall inclination angle and the fixed average fin width, whereas the output conductance depends mainly on the average fin width and is weakly dependent on the sidewall inclination angle. The simulation results also show that higher voltage gains are obtained for smaller average fin widths with inclination angles that correspond to inverted trapeziums, i.e. for shapes where the channel width is larger at the top than at the transistor base because of the higher attained transconductance. When the channel top is thinner than the base, the transconductance degradation affects the intrinsic voltage gain. The total gate capacitances also present behavior dependent on the sidewall angle, with higher values for inverted trapezium shapes and, as a consequence, lower unit-gain frequencies.

Dynamics of driven three-dimensional thin films: from hdrophilic to superhydrophobic substrates

We study the forced displacement of a thin film of fluid in contact with vertical and inclined substrates of different wetting properties, that range from hydrophilic to hydrophobic, using the lattice-Boltzmann method. We study the stability and pattern formation of the contact line in the hydrophilic and superhydrophobic regimes, which correspond to wedge-shaped and nose-shaped fronts, respectively. We find that contact lines are considerably more stable for hydrophilic substrates and small inclination angles. The qualitative behavior of the front in the linear regime remains independent of the wetting properties of the substrate as a single dispersion relation describes the stability of both wedges and noses. Nonlinear patterns show a clear dependence on wetting properties and substrate inclination angle. The effect is quantified in terms of the pattern growth rate, which vanishes for the sawtooth pattern and is finite for the finger pattern. Sawtooth shaped patterns are observed for hydrophilic substrates and low inclination angles, while finger-shaped patterns arise for hydrophobic substrates and large inclination angles. Finger dynamics show a transient in which neighboring fingers interact, followed by a steady state where each finger grows independently.

Dynamics of driven three-dimensional thin films: from hdrophilic to superhydrophobic substrates

We study the forced displacement of a thin film of fluid in contact with vertical and inclined substrates of different wetting properties, that range from hydrophilic to hydrophobic, using the lattice-Boltzmann method. We study the stability and pattern formation of the contact line in the hydrophilic and superhydrophobic regimes, which correspond to wedge-shaped and nose-shaped fronts, respectively. We find that contact lines are considerably more stable for hydrophilic substrates and small inclination angles. The qualitative behavior of the front in the linear regime remains independent of the wetting properties of the substrate as a single dispersion relation describes the stability of both wedges and noses. Nonlinear patterns show a clear dependence on wetting properties and substrate inclination angle. The effect is quantified in terms of the pattern growth rate, which vanishes for the sawtooth pattern and is finite for the finger pattern. Sawtooth shaped patterns are observed for hydrophilic substrates and low inclination angles, while finger-shaped patterns arise for hydrophobic substrates and large inclination angles. Finger dynamics show a transient in which neighboring fingers interact, followed by a steady state where each finger grows independently.

A Be-type star with a black-hole companion

Stellar-mass black holes have all been discovered through X-ray emission, which arises from the accretion of gas from their binary companions (this gas is either stripped from low-mass stars or supplied as winds from massive ones). Binary evolution models also predict the existence of black holes accreting from the equatorial envelope of rapidly spinning Be-type stars (stars of the Be type are hot blue irregular variables showing characteristic spectral emission lines of hydrogen). Of the ~80 Be X-ray binaries known in the Galaxy, however, only pulsating neutron stars have been found as companions. A black hole was formally allowed as a solution for the companion to the Be star MWC 656 (also known as HD 215227), although that was based on a single radial velocity curve of the Be star, a mistaken spectral classification and rough estimates of the inclination angle. Here we report observations of an accretion disk line mirroring the orbit of the Be star. This, together with an improved radial velocity curve of the Be star through fitting sharp Fe II profiles from the equatorial disk, and a refined Be classification (to that of a B1.5-B2 III star), reveals a black hole of 3.8 to 6.9 solar masses orbiting MWC 656, the candidate counterpart of the gamma-ray source AGL J2241+4454. The black hole is X-ray quiescent and fed by a radiatively inefficient accretion flow giving a luminosity less than 1.6 x 10-7 times the Eddington luminosity. This implies that Be binaries with black-hole companions are difficult to detect by conventional X-ray surveys.