The effects induced by the presence of incoming wakes on the boundary layer developing over a high-lift low-pressure turbine profile have been investigated in a linear cascade at mid-span.The tested Reynolds number is...The effects induced by the presence of incoming wakes on the boundary layer developing over a high-lift low-pressure turbine profile have been investigated in a linear cascade at mid-span.The tested Reynolds number is 70000,typical of the cruise operating condition.The results of the investigations performed under steady and unsteady inflow conditions are analyzed.The unsteady investigations have been performed at the reduced frequency of f+=0.62,representative of the real engine operating condition.Profile aerodynamic loadings as well as boundary layer velocity profiles have been measured to survey the separation and transition processes.Spectral analysis has been also performed to better understand the phenomena associated with the transition process under steady inflow.For the unsteady case,a phase-locked ensemble averaging technique has been employed to reconstruct the time-resolved boundary layer velocity distributions from the hot-wire instantaneous signal output.The ensemble-averaging technique allowed a detailed analysis of the effects induced by incoming wakes-boundary layer interaction in separation suppression.Time-resolved results are presented in terms of mean velocity and unresolved unsteadiness time-space plots.展开更多
This article discusses a practical, evidence-based approach to the diagnosis and management of liver cirrhosis by focusing on etiology, severity, presence of complications, and potential home-managed treatments. Relev...This article discusses a practical, evidence-based approach to the diagnosis and management of liver cirrhosis by focusing on etiology, severity, presence of complications, and potential home-managed treatments. Relevant literature from 1985 to 2010 (PubMed) was reviewed. The search criteria were peer-reviewed full papers published in English using the following MESH headings alone or in combination: "ascites", "liver fibrosis", "cirrhosis", "chronic hepatitis", "chronic liver disease", "decompensated cirrhosis", "hepatic encephalopathy", "hypertransaminasemia", "liver transplantation" and "portal hypertension". Forty-nine papers were selected based on the highest quality of evidence for each section and type (original, randomized controlled trial, guideline, and review article), with respect to specialist setting (Gastroenterology, Hepatology, and Internal Medicine) and primary care. Liver cirrhosis from any cause represents an emerging health issue due to the increasing prevalence of the disease and its complications worldwide. Primary care physicians play a key role in early identification of risk factors, in the management of patients for improving quality and length of life, and for preventing complications. Specialists, by contrast, should guide specific treatments, especially in the case of complications and for selecting patient candidates for liver transplantation. An integrated approach between specialists and primary care physicians is essential for providing better outcomes and appropriate home care for patients with liver cirrhosis.展开更多
The aerodynamic flow field downstream of a Low-Pressure High-Lift(HL)turbine cascade has been experimentally investigated for different Reynolds numbers under both steady and unsteady inflows,in order to analyse the c...The aerodynamic flow field downstream of a Low-Pressure High-Lift(HL)turbine cascade has been experimentally investigated for different Reynolds numbers under both steady and unsteady inflows,in order to analyse the cascade performance under real engine operating conditions.The Reynolds number has been varied in the range 100000<Re<300000,where lower and upper limits are typical of cruise and take-off/landing conditions,respectively.The effects induced by the incoming wakes at the reduced frequency f+=0.62 on both profile and secondary flow losses have been investigated.Total pressure,velocity and secondary kinetic energy distributions at the downstream tangential plane have been measured by means of a miniaturized 5-hole probe.These quantities provide information on both blade wake and secondary flow structures(passage and horse-shoe vortices).The analysis of the results allows the evaluation of the aerodynamic performance of the HL front-loaded blade in terms of both profile and secondary losses.展开更多
The present paper reports the results of a detailed experimental study aimed at investigating the dynamics of a laminar separation bubble, from the origin of separation up to the breakdown to turbulence of the large s...The present paper reports the results of a detailed experimental study aimed at investigating the dynamics of a laminar separation bubble, from the origin of separation up to the breakdown to turbulence of the large scale co- herent structures generated as a consequence of the Kelvin-Helmholtz instability process. Measurements have been performed along a fiat plate installed within a double contoured test section, designed to produce an adverse pressure gradient typical of Ultra-High-Lift turbine blade profiles, which induces the formation of a laminar separation bubble at low Reynolds number condition. Measurements have been carried out by means of comple- mentary techniques： hot-wire （HW） anemometry, Laser Doppler Velocirnetry （LDV） and Particle Image Veloci- metry （PIV）. The high accuracy 2-dimensional LDV results allow investigating reverse flow magnitude and both Reynolds normal and shear stress distributions along the separated flow region, while the high frequency response of the HW anemometer allows analyzing the amplification process of flow oscillations induced by instability mechanisms. PIV results complement the flow field analysis providing information on the generation and evolu- tion of the large scale coherent structures shed as a consequence of the separated shear layer roll-up, through in- stantaneous velocity vector maps. The simultaneous analysis of the data obtained by means of the different meas- uring techniques allows an in depth view of the instability mechanisms involved in the transition/reattachrnent processes of the separated shear layer.展开更多
Objective: To evaluate the results of a novel protocol that allows to rescue IVF unfertilized oocytes by intracytoplasmic sperm injection (ICSI).Design: Prospective clinical trial.Setting: Private reproductive medical...Objective: To evaluate the results of a novel protocol that allows to rescue IVF unfertilized oocytes by intracytoplasmic sperm injection (ICSI).Design: Prospective clinical trial.Setting: Private reproductive medical center.Patient(s): Thirty patients undergoing IVF.Intervention(s): Controlled ovarian stimulation (COS), conventional IVF, rescue ICSI, embryo culture, and embryo transfer.Main Outcome Measure(s): Identification of unfertilized IVF oocytes 6 hours after insemination and fertilization, and developmental rates of those oocytes after rescue microinjection, as well implantation and pregnancy rates (PR).Result(s): All oocytes (392) from 30 patients were inseminated with standard IVF 3 hours after ovum pick- up.Polar body (PB) status was checked at decumulation and rechecked 3 hours later.Eighty- two oocytes were fertilized after IVF alone and 184 nonactivated oocytes (failed fertilization) were rescue microinjected and 166 of them fertilized (20 patients).Cleavage stage on day 2 was significantly more advanced and embryo grade was higher after standard IVF fertilization than after rescue ICSI.Eight of the 30 embryos transferred were implanted in the IVF- only patients (27% )- and 8 of 68 embryos in the rescue ICSI patients (12% ).Conclusion(s): Rescue ICSI of unfertilized IVF oocytes 6 hours after insemination (9 hours after egg retrieval) can provide normal fertilization, embryo development, and pregnancy; however, corresponding outcome parameters tend to be impaired in comparison to the standard IVF fertilization results.展开更多
The present paper reports the results of an experimental investigation aimed at comparing aerodynamic perform- ance of three low-pressure turbine cascades for several Reynolds numbers under steady and unsteady inflows...The present paper reports the results of an experimental investigation aimed at comparing aerodynamic perform- ance of three low-pressure turbine cascades for several Reynolds numbers under steady and unsteady inflows. This study is focused on finding design criteria useful to reduce both profile and secondary losses in the aero-engine LP turbine for the different flight conditions. The baseline blade cascade, characterized by a standard aerodynamic loading （Zw=1.03）, has been compared with two Ultra-High-Lift profiles with the same Zweifel number （Zw=1.3 for both cascades）, but different velocity peak positions, leading to front and mid-loaded blade cascade configurations. The aerodynamic flow fields downstream of the cascades have been experimentally in- vestigated for Reynolds numbers in the range 70000〈Re〈300000, where lower and upper limits are typical of cruise and take-off/landing conditions, respectively. The effects induced by the incoming wakes at the reduced frequency ./＋=0.62 on both profile and secondary flow losses for the three different cascade designs have been studied. Total pressure and velocity distributions have been measured by means of a miniaturized 5-hole probe in a tangential plane downstream of the cascade for both inflow conditions. The analysis of the results allows the evaluation of the aerodynamic performance of the blade cascades in terms of profile and secondary losses and the understanding of the effects of loading distribution and Zweifel number on secondary flows. When operating un- der unsteady inflow, contrarily to the steady case, the mid-loaded cascade has been found to be characterized by the lowest profile and secondary losses, making it the most attractive solution for the design of blades working in real conditions where unsteady inflow effects are present.展开更多
An experimental investigation on the near and far wake of a cascade of high-lift low-pressure turbine blades subjected to boundary layer separation over the suction side surface has been carried out, under steady and ...An experimental investigation on the near and far wake of a cascade of high-lift low-pressure turbine blades subjected to boundary layer separation over the suction side surface has been carried out, under steady and unsteady inflows. Two Reynolds number conditions, representative of take-off/landing and cruise operating conditions of the real engine, have been tested. The effect of upstream wake-boundary layer interaction on the wake shed from the profile has been investigated in a three-blade large-scale linear turbine cascade. The comparison between the wakes shed under steady and unsteady inflows has been performed through the analysis of mean velocity and Reynolds stress components measured at midspan of the central blade by means of a two-component crossed miniature hot-wire probe. The wake development has been analyzed in the region between 2% and 100% of the blade chord from the central blade trailing edge, aligned with the blade exit direction. Wake integral parameters, half-width and maximum velocity defects have been evaluated from the mean velocity distributions to quantify the modifications induced on the vane wake by the upstream wake. Moreover the thicknesses of the two wake shear layers have been considered separately in order to identify the effects of Reynolds number and incoming flow on the wake shape. The self-preserving state of the wake has been looked at, taking into account the different thicknesses of the two shear layers. The evaluation of the power density spectra of the velocity fluctuations allowed the study of the wake unsteady behavior, and the detection of the effects induced by the different operating conditions on the trailing edge vortex shedding.展开更多
Peroxisome proliferator activated receptors(PPARs)are ligand-activated transcription factors that are located in the cytoplasm.After activation by specific ligands,PPARs enter the nucleus and heterodimerize with the r...Peroxisome proliferator activated receptors(PPARs)are ligand-activated transcription factors that are located in the cytoplasm.After activation by specific ligands,PPARs enter the nucleus and heterodimerize with the retinoid x receptor.This heterodimer binds to PPAR response element in DNA to regulate the transcription of genes that are involved in different physiological processes,including insulin sensitization,inflammatory response,and neuroprotection(Kapadia et al.,2008).展开更多
In the present work the aerodynamic performances of an innovative rotor blade row have been experimentally investigated. Measurements have been carried out in a large scale low speed single stage cold flow facility at...In the present work the aerodynamic performances of an innovative rotor blade row have been experimentally investigated. Measurements have been carried out in a large scale low speed single stage cold flow facility at a Reynolds number typical of aeroengine cruise, under nominal and off-design conditions. The time-mean blade aerodynamic loadings have been measured at three radial positions along the blade height through a pressure transducer installed inside the hollow shaft, by delivering the signal to the stationary frame with a slip ring. The time mean aerodynamic flow fields upstream and downstream of the rotor have been measured by means of a five-hole probe to investigate the losses associated with the rotor. The investigations in the single stage research turbine allow the reproduction of both wake-boundary layer interaction as well as vortex-vortex interaction. The detail of the present results clearly highlights the strong dissipative effects induced by the blade tip vortex and by the momentum defect as well as the turbulence production, which is generated during the migration of the stator wake in the rotor passage. Phase-locked hot-wire investigations have been also performed to analyze the time-varying flow during the wake passing period. In particular the interaction between stator and rotor structures has been investigated also under off-design conditions to further explain the mechanisms contributing to the loss generation for the different conditions.展开更多
Objective: Partially damaged frozen and thawed embryos are currently considered to have a lower viability than intact ones. This study was undertaken to compare the performance of intact frozen and thawed embryos with...Objective: Partially damaged frozen and thawed embryos are currently considered to have a lower viability than intact ones. This study was undertaken to compare the performance of intact frozen and thawed embryos with that of partially damaged embryos after removal of the necrotic blastomeres. Design: Observational clinical series. Setting: Private hospital. Patient(s): Three hundred twenty-six infertile couples undergoing frozen embryo transfer. Intervention(s): Removal of necrotic blastomeres from frozen-thawed human embryos. Main Outcome Measure(s): Pregnancy and implantations rates. Result(s): Outcomes of frozen embryo transfer cycles in which all embryos were fully intact (group 1) were compared with those in which all embryos have lost 1-2 blastomeres (group 2) or 3-4 blastomeres (group 3). Laser-assisted hatching was performed in all embryos, and necrotic blastomeres were removed from partially damaged embryos on this occasion. Only embryos that resumed mitotic activity after thawing were transferred. Comparable clinical pregnancy rates (PR) (38.7%, 39.6%, and 29.4%), delivery rates (34.4%, 34.0%, and 29.4%), and implantation rates (21.6%, 21.4%, and 17.2%) were obtained in groups 1, 2, and 3, respectively. Conclusion(s): The developmental potential of partially damaged frozen and thawed embryos can be equivalent to fully survived embryos if the necrotic blastomeres are removed from the partially damaged embryos and only those of them that show post-thaw cleavage are selected for transfer.展开更多
The transition process of the boundary layer developing over a flat plate with elevated inlet Free Stream Turbulence Intensity(FSTI)has been studied by means of Large Eddy Simulation(LES).To this purpose,four cases wi...The transition process of the boundary layer developing over a flat plate with elevated inlet Free Stream Turbulence Intensity(FSTI)has been studied by means of Large Eddy Simulation(LES).To this purpose,four cases with different inflow disturbances have been tested varying the magnitude and the length scale of turbulence.LES has been performed by using the finite-volume ANSYS Fluent code.The computational domain,which was constituted by a rectangular domain with a zero thickness plate,was based on an ERCOFTAC test case in order to provide a validation with a well-known set of data by comparing the boundary layer integral parameters and mean and fluctuating streamwise velocity profiles.The four cases were discussed within the paper by looking at classical statistical properties as well as advanced post-processing tools.It was shown that the decrease in the free stream turbulence level postpones the transition location,whereas the variation of the integral length scale has a very low influence on the distribution of the time-mean flow properties.Proper Orthogonal Decomposition(POD)has been applied to the instantaneous LES flow fields in order to provide a statistical representation of the structures responsible for transition and their response to free-stream turbulence intensity and length scale.The presence of vortical filaments parallel to the wall,typically referred as boundary layer streaks,is clearly identified;their characteristic dimensions and how they change as a function of FSTI properties were analyzed within the paper.展开更多
The suction side boundary layer evolution of a high-lift low-pressure turbine cascade has been experimentally in- vestigated at low and high free-stream turbulence intensity conditions. Measurements have been carded o...The suction side boundary layer evolution of a high-lift low-pressure turbine cascade has been experimentally in- vestigated at low and high free-stream turbulence intensity conditions. Measurements have been carded out in order to analyze the boundary layer transition and separation processes at a low Reynolds nttmber, under both steady and unsteady inflows. Static pressure distributions along the blade surfaces as well as total pressure distri- butions in a downstream tangential plane have been measured to evaluate the overall aerodynamic efficiency of the blade for the different conditions. Particle. Image Velocimetry has been adopted to analyze the time-mean and time-varying velocity fields. The flow field has been surveyed in two orthogonal planes （a blade-to-blade plane and a wall-parallel one）. These measurements allow the identification of the Kelvin-Helmholtz large scale cohe- rent structures shed as a consequence of the boundary layer laminar separation under steady inflow, as well as the investigation of the three-dimensional effects induced by the intermittent passage of low and high speed streaks. A close inspection of the time-mean velocity profiles as well as of the boundary layer integral parameters helps to characterize the suction side boundary layer state, thus justifying the influence of free-stream turbulence intensity on the blade aerodynamic losses measured under steady and unsteady inflows.展开更多
The present work is part of an extensive experimental activity carried out by the authors in recent years aimed at investigating the boundary layer transition phenomenon in turbine blades. The large scale of the casca...The present work is part of an extensive experimental activity carried out by the authors in recent years aimed at investigating the boundary layer transition phenomenon in turbine blades. The large scale of the cascade and the use of advanced LDV instrumentation and precision probe traversing mechanism resulted in high degree of spatial resolution and high accuracy of measurements. The main dissipation mechanism determining the profile losses in turbomachinery blades is the work of deformation of the mean motion within the boundary layer operated by both viscous and turbulent shear stresses. In the present paper, the local viscous and turbulent deformation works have been directly evaluated from the detailed measurements of boundary layer mean velocity and Reynolds shear stress. The results show the distributions and the relative importance of the viscous and turbulent contributions to the loss production, in relation with the boundary layer states occurring along the turbine profile.展开更多
Infertility affects 10%–15%of couples worldwide.Of all infertility cases,20%–70%are due to male factors.In the past,men with severe male factor(SMF)were considered sterile.Nevertheless,the development of intracytopl...Infertility affects 10%–15%of couples worldwide.Of all infertility cases,20%–70%are due to male factors.In the past,men with severe male factor(SMF)were considered sterile.Nevertheless,the development of intracytoplasmic sperm injection(ICSI)drastically modified this scenario.The advances in assisted reproductive technology(ART),specifically regarding surgical sperm retrieval procedures,allowed the efficacious treatment of these conditions.Yet,before undergoing ICSI,male factor infertility requires careful evaluation of clinical and lifestyle behavior together with medical treatment.Epidemiologically speaking,women whose male partner is azoospermic tend to be younger and with a better ovarian reserve.These couples,in fact,are proposed ART earlier in their life,and for this reason,their ovarian response after stimulation is generally good.Furthermore,in younger couples,azoospermia can be partially compensated by the efficient ovarian response,resulting in an acceptable fertility rate following in vitro fertilization(IVF)techniques.Conversely,when azoospermia is associated with a reduced ovarian reserve and/or advanced maternal age,the treatment becomes more challenging,with a consequent reduction in IVF outcomes.Nonetheless,azoospermia seems to impair neither the euploidy rate at the blastocyst stage nor the implantation of euploid blastocysts.Based on the current knowledge,the assessment of male infertility factors should involve:(1)evaluation–to diagnose and quantify seminologic alterations;(2)potentiality–to determine the real possibilities to improve sperm parameters and/or retrieve spermatozoa;(3)time–to consider the available“treatment window”,based on maternal age and ovarian reserve.This review represents an update of the definition,prevalence,causes,and treatment of SMF in a modern ART clinic.展开更多
文摘The effects induced by the presence of incoming wakes on the boundary layer developing over a high-lift low-pressure turbine profile have been investigated in a linear cascade at mid-span.The tested Reynolds number is 70000,typical of the cruise operating condition.The results of the investigations performed under steady and unsteady inflow conditions are analyzed.The unsteady investigations have been performed at the reduced frequency of f+=0.62,representative of the real engine operating condition.Profile aerodynamic loadings as well as boundary layer velocity profiles have been measured to survey the separation and transition processes.Spectral analysis has been also performed to better understand the phenomena associated with the transition process under steady inflow.For the unsteady case,a phase-locked ensemble averaging technique has been employed to reconstruct the time-resolved boundary layer velocity distributions from the hot-wire instantaneous signal output.The ensemble-averaging technique allowed a detailed analysis of the effects induced by incoming wakes-boundary layer interaction in separation suppression.Time-resolved results are presented in terms of mean velocity and unresolved unsteadiness time-space plots.
文摘This article discusses a practical, evidence-based approach to the diagnosis and management of liver cirrhosis by focusing on etiology, severity, presence of complications, and potential home-managed treatments. Relevant literature from 1985 to 2010 (PubMed) was reviewed. The search criteria were peer-reviewed full papers published in English using the following MESH headings alone or in combination: "ascites", "liver fibrosis", "cirrhosis", "chronic hepatitis", "chronic liver disease", "decompensated cirrhosis", "hepatic encephalopathy", "hypertransaminasemia", "liver transplantation" and "portal hypertension". Forty-nine papers were selected based on the highest quality of evidence for each section and type (original, randomized controlled trial, guideline, and review article), with respect to specialist setting (Gastroenterology, Hepatology, and Internal Medicine) and primary care. Liver cirrhosis from any cause represents an emerging health issue due to the increasing prevalence of the disease and its complications worldwide. Primary care physicians play a key role in early identification of risk factors, in the management of patients for improving quality and length of life, and for preventing complications. Specialists, by contrast, should guide specific treatments, especially in the case of complications and for selecting patient candidates for liver transplantation. An integrated approach between specialists and primary care physicians is essential for providing better outcomes and appropriate home care for patients with liver cirrhosis.
文摘The aerodynamic flow field downstream of a Low-Pressure High-Lift(HL)turbine cascade has been experimentally investigated for different Reynolds numbers under both steady and unsteady inflows,in order to analyse the cascade performance under real engine operating conditions.The Reynolds number has been varied in the range 100000<Re<300000,where lower and upper limits are typical of cruise and take-off/landing conditions,respectively.The effects induced by the incoming wakes at the reduced frequency f+=0.62 on both profile and secondary flow losses have been investigated.Total pressure,velocity and secondary kinetic energy distributions at the downstream tangential plane have been measured by means of a miniaturized 5-hole probe.These quantities provide information on both blade wake and secondary flow structures(passage and horse-shoe vortices).The analysis of the results allows the evaluation of the aerodynamic performance of the HL front-loaded blade in terms of both profile and secondary losses.
文摘The present paper reports the results of a detailed experimental study aimed at investigating the dynamics of a laminar separation bubble, from the origin of separation up to the breakdown to turbulence of the large scale co- herent structures generated as a consequence of the Kelvin-Helmholtz instability process. Measurements have been performed along a fiat plate installed within a double contoured test section, designed to produce an adverse pressure gradient typical of Ultra-High-Lift turbine blade profiles, which induces the formation of a laminar separation bubble at low Reynolds number condition. Measurements have been carried out by means of comple- mentary techniques： hot-wire （HW） anemometry, Laser Doppler Velocirnetry （LDV） and Particle Image Veloci- metry （PIV）. The high accuracy 2-dimensional LDV results allow investigating reverse flow magnitude and both Reynolds normal and shear stress distributions along the separated flow region, while the high frequency response of the HW anemometer allows analyzing the amplification process of flow oscillations induced by instability mechanisms. PIV results complement the flow field analysis providing information on the generation and evolu- tion of the large scale coherent structures shed as a consequence of the separated shear layer roll-up, through in- stantaneous velocity vector maps. The simultaneous analysis of the data obtained by means of the different meas- uring techniques allows an in depth view of the instability mechanisms involved in the transition/reattachrnent processes of the separated shear layer.
文摘Objective: To evaluate the results of a novel protocol that allows to rescue IVF unfertilized oocytes by intracytoplasmic sperm injection (ICSI).Design: Prospective clinical trial.Setting: Private reproductive medical center.Patient(s): Thirty patients undergoing IVF.Intervention(s): Controlled ovarian stimulation (COS), conventional IVF, rescue ICSI, embryo culture, and embryo transfer.Main Outcome Measure(s): Identification of unfertilized IVF oocytes 6 hours after insemination and fertilization, and developmental rates of those oocytes after rescue microinjection, as well implantation and pregnancy rates (PR).Result(s): All oocytes (392) from 30 patients were inseminated with standard IVF 3 hours after ovum pick- up.Polar body (PB) status was checked at decumulation and rechecked 3 hours later.Eighty- two oocytes were fertilized after IVF alone and 184 nonactivated oocytes (failed fertilization) were rescue microinjected and 166 of them fertilized (20 patients).Cleavage stage on day 2 was significantly more advanced and embryo grade was higher after standard IVF fertilization than after rescue ICSI.Eight of the 30 embryos transferred were implanted in the IVF- only patients (27% )- and 8 of 68 embryos in the rescue ICSI patients (12% ).Conclusion(s): Rescue ICSI of unfertilized IVF oocytes 6 hours after insemination (9 hours after egg retrieval) can provide normal fertilization, embryo development, and pregnancy; however, corresponding outcome parameters tend to be impaired in comparison to the standard IVF fertilization results.
文摘The present paper reports the results of an experimental investigation aimed at comparing aerodynamic perform- ance of three low-pressure turbine cascades for several Reynolds numbers under steady and unsteady inflows. This study is focused on finding design criteria useful to reduce both profile and secondary losses in the aero-engine LP turbine for the different flight conditions. The baseline blade cascade, characterized by a standard aerodynamic loading （Zw=1.03）, has been compared with two Ultra-High-Lift profiles with the same Zweifel number （Zw=1.3 for both cascades）, but different velocity peak positions, leading to front and mid-loaded blade cascade configurations. The aerodynamic flow fields downstream of the cascades have been experimentally in- vestigated for Reynolds numbers in the range 70000〈Re〈300000, where lower and upper limits are typical of cruise and take-off/landing conditions, respectively. The effects induced by the incoming wakes at the reduced frequency ./＋=0.62 on both profile and secondary flow losses for the three different cascade designs have been studied. Total pressure and velocity distributions have been measured by means of a miniaturized 5-hole probe in a tangential plane downstream of the cascade for both inflow conditions. The analysis of the results allows the evaluation of the aerodynamic performance of the blade cascades in terms of profile and secondary losses and the understanding of the effects of loading distribution and Zweifel number on secondary flows. When operating un- der unsteady inflow, contrarily to the steady case, the mid-loaded cascade has been found to be characterized by the lowest profile and secondary losses, making it the most attractive solution for the design of blades working in real conditions where unsteady inflow effects are present.
文摘An experimental investigation on the near and far wake of a cascade of high-lift low-pressure turbine blades subjected to boundary layer separation over the suction side surface has been carried out, under steady and unsteady inflows. Two Reynolds number conditions, representative of take-off/landing and cruise operating conditions of the real engine, have been tested. The effect of upstream wake-boundary layer interaction on the wake shed from the profile has been investigated in a three-blade large-scale linear turbine cascade. The comparison between the wakes shed under steady and unsteady inflows has been performed through the analysis of mean velocity and Reynolds stress components measured at midspan of the central blade by means of a two-component crossed miniature hot-wire probe. The wake development has been analyzed in the region between 2% and 100% of the blade chord from the central blade trailing edge, aligned with the blade exit direction. Wake integral parameters, half-width and maximum velocity defects have been evaluated from the mean velocity distributions to quantify the modifications induced on the vane wake by the upstream wake. Moreover the thicknesses of the two wake shear layers have been considered separately in order to identify the effects of Reynolds number and incoming flow on the wake shape. The self-preserving state of the wake has been looked at, taking into account the different thicknesses of the two shear layers. The evaluation of the power density spectra of the velocity fluctuations allowed the study of the wake unsteady behavior, and the detection of the effects induced by the different operating conditions on the trailing edge vortex shedding.
文摘Peroxisome proliferator activated receptors(PPARs)are ligand-activated transcription factors that are located in the cytoplasm.After activation by specific ligands,PPARs enter the nucleus and heterodimerize with the retinoid x receptor.This heterodimer binds to PPAR response element in DNA to regulate the transcription of genes that are involved in different physiological processes,including insulin sensitization,inflammatory response,and neuroprotection(Kapadia et al.,2008).
基金funded by the European Community’s Seventh Framework Programme(FP7/2007-2013)for the Clean Sky Joint Technology Initiative under grant agreement n°[323301]
文摘In the present work the aerodynamic performances of an innovative rotor blade row have been experimentally investigated. Measurements have been carried out in a large scale low speed single stage cold flow facility at a Reynolds number typical of aeroengine cruise, under nominal and off-design conditions. The time-mean blade aerodynamic loadings have been measured at three radial positions along the blade height through a pressure transducer installed inside the hollow shaft, by delivering the signal to the stationary frame with a slip ring. The time mean aerodynamic flow fields upstream and downstream of the rotor have been measured by means of a five-hole probe to investigate the losses associated with the rotor. The investigations in the single stage research turbine allow the reproduction of both wake-boundary layer interaction as well as vortex-vortex interaction. The detail of the present results clearly highlights the strong dissipative effects induced by the blade tip vortex and by the momentum defect as well as the turbulence production, which is generated during the migration of the stator wake in the rotor passage. Phase-locked hot-wire investigations have been also performed to analyze the time-varying flow during the wake passing period. In particular the interaction between stator and rotor structures has been investigated also under off-design conditions to further explain the mechanisms contributing to the loss generation for the different conditions.
文摘Objective: Partially damaged frozen and thawed embryos are currently considered to have a lower viability than intact ones. This study was undertaken to compare the performance of intact frozen and thawed embryos with that of partially damaged embryos after removal of the necrotic blastomeres. Design: Observational clinical series. Setting: Private hospital. Patient(s): Three hundred twenty-six infertile couples undergoing frozen embryo transfer. Intervention(s): Removal of necrotic blastomeres from frozen-thawed human embryos. Main Outcome Measure(s): Pregnancy and implantations rates. Result(s): Outcomes of frozen embryo transfer cycles in which all embryos were fully intact (group 1) were compared with those in which all embryos have lost 1-2 blastomeres (group 2) or 3-4 blastomeres (group 3). Laser-assisted hatching was performed in all embryos, and necrotic blastomeres were removed from partially damaged embryos on this occasion. Only embryos that resumed mitotic activity after thawing were transferred. Comparable clinical pregnancy rates (PR) (38.7%, 39.6%, and 29.4%), delivery rates (34.4%, 34.0%, and 29.4%), and implantation rates (21.6%, 21.4%, and 17.2%) were obtained in groups 1, 2, and 3, respectively. Conclusion(s): The developmental potential of partially damaged frozen and thawed embryos can be equivalent to fully survived embryos if the necrotic blastomeres are removed from the partially damaged embryos and only those of them that show post-thaw cleavage are selected for transfer.
文摘The transition process of the boundary layer developing over a flat plate with elevated inlet Free Stream Turbulence Intensity(FSTI)has been studied by means of Large Eddy Simulation(LES).To this purpose,four cases with different inflow disturbances have been tested varying the magnitude and the length scale of turbulence.LES has been performed by using the finite-volume ANSYS Fluent code.The computational domain,which was constituted by a rectangular domain with a zero thickness plate,was based on an ERCOFTAC test case in order to provide a validation with a well-known set of data by comparing the boundary layer integral parameters and mean and fluctuating streamwise velocity profiles.The four cases were discussed within the paper by looking at classical statistical properties as well as advanced post-processing tools.It was shown that the decrease in the free stream turbulence level postpones the transition location,whereas the variation of the integral length scale has a very low influence on the distribution of the time-mean flow properties.Proper Orthogonal Decomposition(POD)has been applied to the instantaneous LES flow fields in order to provide a statistical representation of the structures responsible for transition and their response to free-stream turbulence intensity and length scale.The presence of vortical filaments parallel to the wall,typically referred as boundary layer streaks,is clearly identified;their characteristic dimensions and how they change as a function of FSTI properties were analyzed within the paper.
文摘The suction side boundary layer evolution of a high-lift low-pressure turbine cascade has been experimentally in- vestigated at low and high free-stream turbulence intensity conditions. Measurements have been carded out in order to analyze the boundary layer transition and separation processes at a low Reynolds nttmber, under both steady and unsteady inflows. Static pressure distributions along the blade surfaces as well as total pressure distri- butions in a downstream tangential plane have been measured to evaluate the overall aerodynamic efficiency of the blade for the different conditions. Particle. Image Velocimetry has been adopted to analyze the time-mean and time-varying velocity fields. The flow field has been surveyed in two orthogonal planes （a blade-to-blade plane and a wall-parallel one）. These measurements allow the identification of the Kelvin-Helmholtz large scale cohe- rent structures shed as a consequence of the boundary layer laminar separation under steady inflow, as well as the investigation of the three-dimensional effects induced by the intermittent passage of low and high speed streaks. A close inspection of the time-mean velocity profiles as well as of the boundary layer integral parameters helps to characterize the suction side boundary layer state, thus justifying the influence of free-stream turbulence intensity on the blade aerodynamic losses measured under steady and unsteady inflows.
文摘The present work is part of an extensive experimental activity carried out by the authors in recent years aimed at investigating the boundary layer transition phenomenon in turbine blades. The large scale of the cascade and the use of advanced LDV instrumentation and precision probe traversing mechanism resulted in high degree of spatial resolution and high accuracy of measurements. The main dissipation mechanism determining the profile losses in turbomachinery blades is the work of deformation of the mean motion within the boundary layer operated by both viscous and turbulent shear stresses. In the present paper, the local viscous and turbulent deformation works have been directly evaluated from the detailed measurements of boundary layer mean velocity and Reynolds shear stress. The results show the distributions and the relative importance of the viscous and turbulent contributions to the loss production, in relation with the boundary layer states occurring along the turbine profile.
文摘Infertility affects 10%–15%of couples worldwide.Of all infertility cases,20%–70%are due to male factors.In the past,men with severe male factor(SMF)were considered sterile.Nevertheless,the development of intracytoplasmic sperm injection(ICSI)drastically modified this scenario.The advances in assisted reproductive technology(ART),specifically regarding surgical sperm retrieval procedures,allowed the efficacious treatment of these conditions.Yet,before undergoing ICSI,male factor infertility requires careful evaluation of clinical and lifestyle behavior together with medical treatment.Epidemiologically speaking,women whose male partner is azoospermic tend to be younger and with a better ovarian reserve.These couples,in fact,are proposed ART earlier in their life,and for this reason,their ovarian response after stimulation is generally good.Furthermore,in younger couples,azoospermia can be partially compensated by the efficient ovarian response,resulting in an acceptable fertility rate following in vitro fertilization(IVF)techniques.Conversely,when azoospermia is associated with a reduced ovarian reserve and/or advanced maternal age,the treatment becomes more challenging,with a consequent reduction in IVF outcomes.Nonetheless,azoospermia seems to impair neither the euploidy rate at the blastocyst stage nor the implantation of euploid blastocysts.Based on the current knowledge,the assessment of male infertility factors should involve:(1)evaluation–to diagnose and quantify seminologic alterations;(2)potentiality–to determine the real possibilities to improve sperm parameters and/or retrieve spermatozoa;(3)time–to consider the available“treatment window”,based on maternal age and ovarian reserve.This review represents an update of the definition,prevalence,causes,and treatment of SMF in a modern ART clinic.
