Time-averaged second-order pressure and velocity measurements in a pressurized oscillating flow prime mover

Nonlinear phenomena in oscillating flow devices cause the appearance of a relatively minor secondary flow known as acoustic streaming, which is superimposed on the primary oscillating flow. Knowledge of control parameters, such as the time-averaged second-order velocity and pressure, would elucidate the non-linear phenomena responsible for this part of the decrease in the system’s energetic efficiency. This paper focuses on the characterization of a travelling wave oscillating flow engine by measuring the time-averaged secondorder pressure and velocity. Laser Doppler velocimetry technique was used to measure the time-averaged second-order velocity. As streaming is a second-order phenomenon, its measurement requires specific settings especially in a pressurized device. Difficulties in obtaining the proper settings are highlighted in this study. The experiments were performed for mean pressures varying from 10 bars to 22 bars. Non-linear effect does not constantly increase with pressure

Caractérisation des écoulements redressés dans les moteurs thermoacoustiques à ondes progressives

Un intérêt croissant est porté par les laboratoires de recherche aux machines de conversion d'énergie ayant des performances énergétiques et environnementales élevées. Les systèmes thermoacoustiques utilisant des fluides non-polluants sont parmi les machines les plus convoitées. Leur efficacité énergétique, principal frein à leur développement, est désormais au centre des préoccupations actuelles. Les travaux présentés dans ce papier fournissent un modèle permettant de quantifier le transfert énergétique qui a lieu de l'écoulement oscillant vers l'écoulement secondaire

Experimental investigation of an actively controlled automotive cooling fan using steady air injection in the leakage gap

ne pas mettre sur hal c'est déjà faitIn an axial fan, a leakage flow driven by a pressure gradient between the pressure side and the suction side occurs in the gap between the shroud and the casing. This leakage flow is in the opposite direction to the main flow and is responsible for significant energy dissipation. Therefore, many authors have worked to understand this phenomenon in order to reduce these inherent energy losses. Up to now, most of the studies reported in the literature have been passive solutions. In this paper, an experimental controlling strategy is suggested to reduce the leakage flow rate. To this end, a fan with hollow blades and a specific drive system were designed and built for air injection. Air is injected in the leakage gap at the fan periphery. The experiment was performed for three rotation speeds, five injection rates and two configurations: 16 and 32 injection holes on the fan's circumference. The experimental results of this investigation are presented in this articl

Active control of the leakage flow by air injection into the rotational shroud or the fixed carter of an axial fan composed of hollow blades

In axial fan, the static pressure difference between the suction and the pressure side of the impeller produces a leakage flow through the blade and the casing. This secondary flow occurs in the opposite direction of the working flow and has a negative impact on the overall performances. It tends to reduce the pressure coefficient, the efficiency and the fan operating range while increasing the noise level. That is why many studies dealt with ways to reduce this leakage flow. In this paper, the study focusses on the control of the secondary flow by air injection. Two ways to control this flow are compared. In a first case, the air is ejected from the fixed casing and in a second case the air exit from the rotating shrouds. In both configurations, the ejected air has a direction to counter the leakage flow. To realize the second configuration, a new method to build fan with hollow blades was developed. This new kind of fan allows having internal flows which could exit by any area of the fan. The results obtained by the active controls on the fan characteristic and the efficiency are presented in this article

Conventional rotational molding process and aerodynamic characteristics of an axial-flow hollow blades rotor

n this work, the rotational molding process is developed to manufacture in one piece an axial-flow turbomachine rotor with hollow blades. Giving to our knowledge, this process has never been employed in the making of these turbomachine components. Indeed, the blades of these rotors are typically solid blades and are making by injection molding, machining, or thermoforming. The effects of three relevant factors of the rotational molding process are studied here: oven temperature, time of heating, and cooling rate. The cooling of the moving mold is managed by simple convection-of-air, or by convection-of-air charged with water particles. For the oven temperature of 285 °C, hollow-blades rotors of good quality are gotten in 12 min per cycle. In addition, aerodynamic characteristics of one rotational molded rotor are compared to those of another part machined in aluminum piece. Characteristics of this aluminum rigid-rotor are assumed as reference

The Gene expression Grade Index: a potential predictor of relapse for endocrine-treated breast cancer patients in the BIG 1–98 trial

<p>Abstract</p> <p>Background</p> <p>We have previously shown that the Gene expression Grade Index (GGI) was able to identify two subtypes of estrogen receptor (ER)-positive tumors that were associated with statistically distinct clinical outcomes in both untreated and tamoxifen-treated patients. Here, we aim to investigate the ability of the GGI to predict relapses in postmenopausal women who were treated with tamoxifen (T) or letrozole (L) within the BIG 1–98 trial.</p> <p>Methods</p> <p>We generated gene expression profiles (Affymetrix) and computed the GGI for a matched, case-control sample of patients enrolled in the BIG 1–98 trial from the two hospitals where frozen samples were available. All relapses (cases) were identified from patients randomized to receive monotherapy or from the switching treatment arms for whom relapse occurred before the switch. Each case was randomly matched with four controls based upon nodal status and treatment (T or L). The prognostic value of GGI was assessed as a continuous predictor and divided at the median. Predictive accuracy of GGI was estimated using time-dependent area under the curve (AUC) of the ROC curves.</p> <p>Results</p> <p>Frozen samples were analyzable for 48 patients (10 cases and 38 controls). Seven of the 10 cases had been assigned to receive L. Cases and controls were comparable with respect to menopausal and nodal status, local and chemotherapy, and HER2 positivity. Cases were slightly older than controls and had a larger proportion of large, poorly differentiated ER+/PgR- tumors. The GGI was significantly and linearly related to risk of relapse: each 10-unit increase in GGI resulted in an increase of approximately 11% in the hazard rate (p = 0.02). Within the subgroups of patients with node-positive disease or who were treated with L, the hazard of relapse was significantly greater for patients with GGI at or above the median. AUC reached a maximum of 78% at 27 months.</p> <p>Conclusion</p> <p>This analysis supports the GGI as a good predictor of relapse for ER-positive patients, even among patients who receive L. Validation of these results, in a larger series from BIG 1–98, is planned using the simplified GGI represented by a smaller set of genes and tested by qRT-PCR on paraffin-embedded tissues.</p

Downregulation of histone H2A and H2B pathways is associated with anthracycline sensitivity in breast cancer

Abstract Background Drug resistance in breast cancer is the major obstacle to effective treatment with chemotherapy. While upregulation of multidrug resistance genes is an important component of drug resistance mechanisms in vitro, their clinical relevance remains to be determined. Therefore, identifying pathways that could be targeted in the clinic to eliminate anthracycline-resistant breast cancer remains a major challenge. Methods We generated paired native and epirubicin-resistant MDA-MB-231, MCF7, SKBR3 and ZR-75-1 epirubicin-resistant breast cancer cell lines to identify pathways contributing to anthracycline resistance. Native cell lines were exposed to increasing concentrations of epirubicin until resistant cells were generated. To identify mechanisms driving epirubicin resistance, we used a complementary approach including gene expression analyses to identify molecular pathways involved in resistance, and small-molecule inhibitors to reverse resistance. In addition, we tested its clinical relevance in a BR9601 adjuvant clinical trial. Results Characterisation of epirubicin-resistant cells revealed that they were cross-resistant to doxorubicin and SN-38 and had alterations in apoptosis and cell-cycle profiles. Gene expression analysis identified deregulation of histone H2A and H2B genes in all four cell lines. Histone deacetylase small-molecule inhibitors reversed resistance and were cytotoxic for epirubicin-resistant cell lines, confirming that histone pathways are associated with epirubicin resistance. Gene expression of a novel 18-gene histone pathway module analysis of the BR9601 adjuvant clinical trial revealed that patients with low expression of the 18-gene histone module benefited from anthracycline treatment more than those with high expression (hazard ratio 0.35, 95 % confidence interval 0.13–0.96, p = 0.042). Conclusions This study revealed a key pathway that contributes to anthracycline resistance and established model systems for investigating drug resistance in all four major breast cancer subtypes. As the histone modification can be targeted with small-molecule inhibitors, it represents a possible means of reversing clinical anthracycline resistance. Trial registration ClinicalTrials.gov identifier NCT00003012 . Registered on 1 November 1999

Assessment of the jet pump impact on thermoacoustic prime mover operation

International audienceDuring recent decades, research institutions and industries showed an important interest to systems that perform energy conversion with high environmental and energetic performances. Thermoacoustic devices can reciprocally convert thermal energy into acoustic energy and use non-polluting fluids, nitrogen, helium or air. Due to their high environmental performances, they can potentially answer to this challenge. These machines can easily reach a coefficient of performance of about 20 % of the Carnot coefficient and few devices have achieved 40%. The results of the research proposed to the Icom18 conference deals with the study of the energy losses that occur in systems using oscillating flow under high mean pressure. The phenomenon of acoustic streaming has been identified as one of the major source of energy dissipation in thermoacoustic devices. This secondary flow which is superimposed to the first-order oscillating flow is generated by the nonlinear propagation of the high-amplitude waves occurring in thermoacoustic system. From energy consideration and despite its low level, this second-order phenomenon involves undesirable loss mechanisms. The experimental investigations on acoustic streaming, firstly qualitative became more quantitative with the development of laser measurement techniques such as Particle Image Velocimetry (PIV) and Laser Doppler Velocimetry (LDV). Theoretical linear model will be presented and experimental results of acoustic pressure and velocity will enable the validation of the different assumptions