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A secondary flow system with a dominant passage vortex pattern has been observed in many gas turbine vane passage studies in which there is no upstream coolant injection or only near-passage endwall coolant injection (no combustor cooling). However, it was shown in recent studies that combustor coolant introduced upstream of the vane passage changes secondary flow patterns in the passage. This results in a different secondary flow vortex system, called the ‘impingement vortex’ system. It was discussed in recent literature having combustor coolant injection. Until now, there has been no study on how increases in combustor coolant momentum effect transition from the passage vortex system to the impingement vortex system. Such a study is presented in the present paper. Velocity component measurements are taken using a five-hole probe at three axial locations in the vane passage to document secondary flow development throughout the passage. Four combustor coolant flowrate cases are considered along with a comparison case having no coolant injection. It is shown that as the combustor coolant flowrate increases, the passage vortex system weakens and, at a sufficiently high combustor coolant flowrate, the impingement vortex system appears. Knowing the detailed flow physics of this transition between the two secondary flow systems is helpful for turbine thermal designers who wish to understand how secondary flows transport coolant within the turbine vane passage.

The great majority of metallic materials in use are not single crystals but disordered. We model such a material specimen as being composed of nanoclusters, each cluster being a small mutually interacting cluster of atoms. In this modeling, a material specimen is then treated as a mixture of nanocrystalline and glassy-state atoms. If we define the degree of crystallinity of the object by the probability that an atom is a member of a crystallite existing within the specimen, the probability would be smaller than unity. Structural disorder in such metallic alloys affects thermophysical properties of the alloy specimen in myriad ways. Transport properties in turn impact material utilization in significant ways to the extent that the specimen could behave as possessing completely different alloy properties. This approach to changing alloy properties can serve useful purposes. We show how one might approach such modification of alloy properties without changing alloy composition with a sample of copper-nickel alloy.

Due to the proximity of the first stage gas turbine vanes to the combustor, coolant introduced to the combustor walls interacts with the endwall film coolant and changes the vane passage flow physics. Recent results show that combustor coolant contributes significantly to cooling the endwall and vane surfaces. In this paper, the traditional combustor-turbine interface was modified to improve overall cooling performance. The performance of this new injection cooling scheme on passage fluid dynamics and surface cooling is assessed. The first of this two-part paper reports detailed experimental tests that document secondary flows and coolant transport throughout the vane passage for four combustor coolant flowrates. The experimental facility imitates combustor coolant injection and engine-level turbulence and has a modified transition duct design, called the ‘close-coupled combustor-turbine interface.’ The ‘impingement vortex’ seen in previous studies with combustor cooling appears as the dominant secondary flow. It is observed in the present study over a wide range of flowrates, confirming its tie to the combustor coolant flowrate and not the combustor-turbine interface geometry. It was found, however, that the location and size of the impingement vortex are affected by coolant flowrate. The second of this two-part paper discusses the impact of the observed secondary flows on cooling vane passage surfaces.

Flow over gas turbine endwalls is complex and highly three-dimensional. As boundaries for modern engine designs are pushed, this already-complex flow is affected by aggressive application of film cooling flows that actively interact. This two-part study describes, experimentally, the aero-thermal interaction of cooling flows near the endwall of a first-stage nozzle guide vane passage (NGV). The approach flow conditions represent flow exiting a low-NOx combustor. The test section includes geometric and cooling details of a combustor-turbine interface in addition to endwall film cooling flows injected upstream of the passage. The first part of this study describes in detail, the passage aerodynamics as affected by injection of cooling flows. It reveals a system of secondary flows, including the newly discovered Impingement Vortex, which redefines our understanding of the aerodynamics of flow in a modern, film-cooled, first-stage vane row. The second part investigates, through thermal measurements, the distribution, mixing, and disruption of cooling flows over the endwall. Measurements are made with and without active endwall film cooling. Descriptions are made through adiabatic surface effectiveness measurements and correlations with in-passage velocity (presented in part one) and thermal fields. Results show that the newly discovered impingement vortex has a positive effect on coolant distribution through passage vortex suppression and by carrying the coolant to hard-to-cool regions in the passage, including the pressure surface near the endwall.

The first-stage turbine of a modern gas turbine is subjected to high thermal loads which lead to a need for aggressive cooling schemes to protect its components from melting. Endwalls are particularly challenging to cool due to the complex system of secondary flows near them that wash the protective film coolants into the mainstream. This paper shows that without including combustor cooling, the complex secondary flow physics is not representative of modern engines. Aggressive injection of all cooling flows upstream of the passage is expected to interact and change passage aerodynamics and, subsequently, mixing and transport of coolants. This study describes, experimentally, the aero-thermal interaction of cooling flows near the endwall of a first-stage nozzle guide vane passage. The test section involves an engine-representative combustor–turbine interface geometry, combustor coolant flow, and endwall film cooling flow injected upstream of a linear cascade. The approach flow conditions represent flow exiting a cooled, low-NOx combustor. This first part of this two-part study aims to understand the complex aerodynamics near the endwall through detailed measurements of passage three-dimensional velocity fields with and without endwall film cooling. The aerodynamic measurements reveal a dominant vortex in the passage, named here as the Impingement Vortex, that opposes the passage vortex formed at the airfoil leading edge plane. This Impingement Vortex completely changes our description of flow over a modern film cooled endwall.

Effective coolant schemes are required for providing cooling to the first-stage stator vanes of gas turbines. To correctly predict coolant performance on the endwall and vane surfaces, these coolant schemes should also consider the effects of coolant streams introduced upstream in the combustor section of a gas turbine engine. This two-part paper presents measurements taken on a first-stage nozzle guide vane cascade that includes combustor coolant injection. The first part of this paper explains how coolant transport and coolant-mainstream interaction in the vane passage is affected by changing the combustor coolant and endwall film coolant flowrates. This paper explains how those flows affect the coolant effectiveness on the endwall and vane surfaces. Part one showed that a significant amount of coolant injected upstream of the endwall is present along the pressure surface of the vanes as well as over the endwall. Part two shows effectiveness measurement results taken in this study on the endwall and pressure and suction surfaces of the vanes. Sustained endwall coolant effectiveness is observed along the whole passage for all cases. It is uniform in the pitch-wise direction. Combustor coolant flow significantly affects cooling performance even near the trailing edge. The modified flowfield results in the pressure surface being cooled more effectively than the suction surface. While the effectiveness distribution on the pressure surface varies with combustor and film coolant flowrates, the distribution along the suction surface remains largely unchanged.

The stators of the first stage of a gas turbine are exposed to severe temperatures. The coolant streams introduced to prevent the stators from thermal damage further complicate the highly three-dimensional vane passage flow. Recent results have shown that the coolant streams injected for cooling the combustor also influence the flow physics and the cooling effectiveness in the first-stage stator vanes passage. However, the effects of changing the mass flowrate of these combustor coolant streams on the passage flowfield have not been studied. As understanding the coolant transport is necessary for analyzing changes in cooling effectiveness in the vane passage, detailed aerodynamic and thermal measurements along the whole vane passage are required. This two-part paper presents such measurements taken for a variety of combustor coolant and endwall film coolant flowrates. The experiments were conducted in a low-Mach number facility with engine-representative Reynolds numbers and large-scale high-level turbulence. The objective of the first part is to describe the flow that influences endwall and vane surface cooling effectiveness distributions, which are presented in the second part. The measurements show changes in the passage flowfield due to changes in both combustor coolant and endwall film coolant flowrates. Overall, the flow physics remains largely unaffected by changes in coolant flowrates except in the endwall-vane surfaces region where the combustor coolant flowrate dominates changes in coolant transport. This is shown to have a high impact on endwall and vane surface cooling.

Modern gas turbines are subjected to very high thermal loading. This leads to a need for aggressive cooling to protect components from damage. Endwalls are particularly challenging to cool due to a complex system of secondary flows near them that wash and disrupt the protective coolant films. This highly three-dimensional flow not only affects but is also affected by the momentum of film cooling flows, whether injected just upstream of the passage to intentionally cool the endwall or as combustor cooling flows injected further upstream in the engine. This complex interaction between the different cooling flows and passage aerodynamics has been recently studied in a first stage nozzle guide vane. The present paper presents a detailed study on the sensitivity of aero-thermal interactions to endwall film cooling mass flow to mainstream flow ratio. The test section represents a first stage nozzle guide vane with a contoured endwall and endwall film cooling injected just upstream of it. The test section also includes an engine-representative combustor–turbine interface geometry with combustor cooling flows injected at a constant rate. The approach flow conditions represent flow exiting a low-NOx combustor. Adiabatic surface thermal measurements and in-passage velocity and thermal field measurements are presented and discussed. The results show the dynamics of passage vortex suppression and the increase of impingement vortex strength as MFR changes. The effects of these changes of secondary flows on coolant distribution are presented.

Effective coolant schemes are required for providing cooling to the first stage stator vanes of gas turbines. To correctly predict coolant performance on the endwall and vane surfaces, these coolant schemes should also consider the effects of coolant streams introduced upstream in the combustor section of a gas turbine engine. This two-part paper presents measurements taken on a first-stage nozzle guide vane cascade that includes combustor coolant injection. The first part of this paper explains how coolant transport and coolant-mainstream interaction in the vane passage is affected by changing the combustor coolant and endwall film coolant flow rates. This paper explains how those flows affect the coolant effectiveness on the endwall. Part one showed that a significant amount of coolant injected upstream of the endwall is present along the pressure surface of the vanes as well as over the endwall. Part two shows effectiveness measurement results taken in this study on the endwall and pressure and suction surfaces of the vanes. Sustained endwall coolant effectiveness is observed along the whole passage for all cases. It is uniform in the pitch-wise direction. Combustor coolant flow significantly affects cooling performance even near the trailing edge. The modified flow field results in the pressure surface being cooled more effectively than the suction surface. While the effectiveness distribution on the pressure surface varies with combustor and film coolant flow rates, the suction surface remains largely unchanged.

Flow over gas turbine endwalls is complex and highly three-dimensional. As boundaries for modern engine designs are pushed, this already-complex flow is affected by aggressive application of film cooling flows that actively interact. This two-part study describes, experimentally, the aero-thermal interaction of cooling flows near the endwall of a first stage nozzle guide vane passage. The approach flow conditions represent flow exiting a low-NOx combustor. The test section includes geometric and cooling details of a combustor-turbine interface in addition to endwall film cooling flows injected upstream of the passage. The first part of this study describes in detail, the passage aerodynamics as affected by injection of cooling flows. It reveals a system of secondary flows, including the newly-discovered Impingement Vortex, which redefines our understanding of the aerodynamics of flow in a modern, film-cooled, first-stage vane row. The second part investigates, through thermal measurements, the distribution, mixing and disruption of cooling flows over the endwall. Measurements are made with and without active endwall film cooling. Descriptions are made through adiabatic surface effectiveness measurements and correlations with in-passage velocity (presented in part one) and thermal fields. Results show that the newly-discovered impingement vortex has a positive effect on coolant distribution through passage vortex suppression and by carrying the coolant to hard-to-cool regions in the passage, including the pressure surface near the endwall.

Modern gas turbines are subjected to very high thermal loading. This leads to a need for aggressive cooling to protect components from damage. Endwalls are particularly challenging to cool due to a complex system of secondary flows near them that wash and disrupt the protective coolant films. This highly three-dimensional flow not only affects but is also affected by the momentum of film cooling flows, whether injected just upstream of the passage to intentionally cool the endwall, or as combustor cooling flows injected further upstream in the engine. This complex interaction between the different cooling flows and passage aerodynamics has been recently studied in a first stage nozzle guide vane. The present paper presents a detailed study on the sensitivity of aero-thermal interactions to endwall film cooling MFR (cooling mass flow to mainstream flow ratio). The test section represents a first stage nozzle guide vane with a contoured endwall and endwall film cooling injected just upstream of it. The test section also includes an engine-representative combustor-turbine interface geometry with combustor cooling flows injected at a constant rate. The approach flow conditions represent flow exiting a low-NOx combustor. Adiabatic surface thermal measurements and in-passage velocity and thermal field measurements are presented and discussed. The results show the dynamics of passage vortex suppression and the increase of impingement vortex strength as MFR changes. The effects of these changes of secondary flows on coolant distribution are presented.

The first stage turbine of a modern gas turbine is subjected to high thermal loads which lead to a need for aggressive cooling schemes to protect its components from melting. Endwalls are particularly challenging to cool due to the complex system of secondary flows near them that wash the protective film coolants into the mainstream. This paper shows that without including combustor cooling, the complex secondary flow physics are not representative of modern engines. Aggressive injection of all cooling flows upstream of the passage is expected to interact and change passage aerodynamics and, subsequently, mixing and transport of coolants. This study describes, experimentally, the aero-thermal interaction of cooling flows near the endwall of a first stage nozzle guide vane passage. The test section involves an engine-representative combustor-turbine interface geometry, combustor coolant flow and endwall film cooling flow injected upstream of a linear cascade. The approach flow conditions represent flow exiting a cooled, low-NOx combustor. This first part of this two-part study aims to understand the complex aerodynamics near the endwall through detailed measurements of passage three-dimensional velocity fields with and without endwall film cooling. The aerodynamic measurements reveal a dominant vortex in the passage, named here as the Impingement Vortex, that opposes the passage vortex formed at the airfoil leading edge plane. This Impingement Vortex completely changes our description of flow over a modern film cooled endwall.

During the lifetime of a turbine stage, some of the blade tips may undergo changes due to mechanical rubbing with casing surface and also due to thermal oxidation. Understanding the effect these damaged blades have over the undamaged blades is essential to estimate the performance of the turbine stage in the operable tip clearance range. In this paper, the passage to passage aerodynamic interaction in a turbine stage is studied by modifying the tip gap of selected turbine blades and analyzing their effect on the neighboring blade passage flows. The experiments in this study are carried out in a single-stage low-speed axial turbine facility. All measurements are taken in the stationary frame of reference using a time-accurate differential dynamic pressure transducer mounted in a Kiel probe head. The experimental results from this study show that even with a significant increase on a selected blade’s tip clearance, its effect on the AFTRF turbine flow is only confined to its neighboring blade passage. The disturbances due to the altered tip clearance of one passage are not measurably propagated to its neighboring turbine passages. The changes made in one of the blades in a turbine stage do not significantly alter the aerodynamic performance of other blades. This result is particularly important for large-scale turbine research rigs such as AFTRF where the unsteady total pressure field is mapped in a time-efficient and phase-locked manner.

Both steady and unsteady Reynolds Averaged Navier-Stokes (RANS) techniques coupled with the k - e and k - ω ( SST ) turbulence models are utilized to study the flow characteristics and hot gas ingestion through rim seal in a subscale 1.5-stage axial gas turbine. A scalar transport equation is solved for a tracer gas to represent the coolant flow interaction with the main stream flow. To validate the numerical methodology, radial pressure and sealing effectiveness distributions are compared with the experimental data. The k - ω ( SST ) turbulence model has the capability to predict secondary flow characteristics, reattachment and separation, thus leading to better agreement with the experimental data. Both radial and circumferential pressure distributions are analyzed to get deeper insight into rotationally and externally induced ingress mechanisms. The circumferential pressure peak-to-trough amplitude is significantly attenuated in the cavity region compared to annulus region. Finally, different purge flow rates and rotational speeds are examined. Results indicate that as purge flow rate increases, the static pressure in the disk cavity region raises remarkably and consequently the sealing effectiveness improves. Averaged sealing effectiveness in the rim cavity decreases linearly with the rotational speed. To visualize different mechanisms of ingestion, streamline and flow field are shown.

Entropy production (EP) is a fundamental quantity useful for understanding irreversible process. In stochastic thermodynamics, EP is more evident in probability density functions of trajectories of a particle in the state space. Here, inspired by a previous result that complex networks can serve as state spaces, we consider a data packet transport problem on complex networks. EP is generated owing to the complexity of pathways as the packet travels back and forth between two nodes along the same pathway. The total EPs are exactly enumerated along all possible shortest paths between every pair of nodes, and the functional form of the EP distribution is proposed based on our numerical results. We confirm that the EP distribution satisfies the detailed and integral fluctuation theorems. Our results should be pedagogically helpful for understanding trajectory-dependent EP in stochastic processes and exploring nonequilibrium fluctuations associated with the entanglement of dividing and merging among the shortest pathways in complex networks.

Endwalls impose a challenge to cool because of the complex system of secondary flows and separation lines disrupting surface film coolant coverage. The interaction of film cooling flows with secondary flow structures is coupled. The momentum exchange of the film coolant with the mainstream affect the formation the secondary flows, which in turn affect the coolant coverage. Therefore, to develop better endwall cooling schemes, a good understanding of passage aerodynamics as affected by interactions with coolant flows is required. This study presents experimental and computational results for cascade representing the first stage nozzle guide vane of a high-pressure gas turbine. The cascade is subsonic, linear, and stationary with an axisymmetrically-contoured endwall. Two cooling flows are simulated; upstream combustor liner coolant-in the form of an aero-thermal profile simulated in the approach flow and endwall slot film cooling, which is injected immediately upstream of the passage inlet. The experiment is run with engine representative combustor exit flow turbulence intensity and integral length scales, with high turbine passage exit Reynolds number of 1.61 × 106. Measurements are performed with various slot film cooling mass flow rate to mainstream flow rate ratios (MFR). Aerodynamic effects are documented with five-hole probe measurements at the exit plane. Varying the slot film cooling MFR results in minimal effects on total pressure loss for the range tested. Vorticity distributions show a very thin, yet intense, cross-pitch flow on the contoured endwall side. Coolant distribution fields that were previously presented for the same cascade are discussed in context of the aerodynamic measurements. A coolant vorticity parameter presenting the advective mixing of the coolant due to secondary flow vorticity is introduced. This parameter gives developers a new prospective on aerodynamic-thermal performance associated with cooled turbine endwall. The numerical study is conducted for the same test section geometry and is run under the same conditions. The applicability of using RANS turbulence closure models for simulating this type of flow is discussed. The effects of including the combustor coolant in the approach flow is also briefly discussed in context of the numerical results.

This paper discusses a method for predicting hot gas migration into turbine disk cavities using two incompressible orifices for ingress and egress flows at the main flow path-to-rim seal interface. The method employs a flow network system that involves axisymmetric disk cavity flow solver elements to model inflows and outflows that exist in a turbine disk cavity subject to a simulated main gas path pressure field. A modified lumped-parameter two-orifice model in which ingress/egress discharge coefficients and the corresponding orifice physical areas are explicitly defined is demonstrated for predicting sealing effectiveness as part of a flow network system. This model has been calibrated against CO2 concentration measurements results previously reported for a 1.5-stage disk cavity research rig at Arizona State University. The boundary pressures for the entire flow network system were defined to be the peak and trough pressures measured. Two fractional variables are introduced in defining the ingress orifice physical area and driving pressure difference between the main gas flow path and the rim cavity. An exponential curve-fit model for the ingress area fraction was developed to compute orifice egress discharge coefficients for a pre-determined ingress discharge coefficient. Excellent agreement with sealing effectiveness data was observed for a radial-gap rim seal geometry for the tested ranges of rotational Reynolds number and non-dimensional purge flow rate. Assumptions employed in developing the model were supported by a 90 degree sector RANS CFD result for the same disk cavity geometry and flow conditions.

Disordered binary alloys are modeled as a randomly close-packed assembly of nanocrystallites intermixed with randomly positioned atoms, i.e., glassy-state matter. The nanocrystallite size distribution is measured in a simulated macroscopic medium in two dimensions. We have also defined, and measured, the degree of crystallinity as the probability of a particle being a member of nanocrystallites. Both the distribution function and the degree of crystallinity are found to be determined by alloy composition. When heated, the nanocrystallites become smaller in size due to increasing thermal fluctuation. We have modeled this phenomenon as a case of thermal dissociation by means of the law of mass action. The crystallite size distribution function is computed for AuCu $$_{3}$$ as a function of temperature by solving some 12 000 coupled algebraic equations for the alloy. The results show that linear thermal expansion of the specimen has contributions from the temperature dependence of the degree of crystallinity, in addition to respective thermal expansions of the nanocrystallites and glassy-state matter.

It has been well established that thermal forcing of disordered multielement metallic alloys results in permanent modification of their thermal transport properties. The mechanism depends on the detail of heating and its duration, and entails rearrangement of the spatial distribution of constituent atoms within the material proper. It presents a serious complication in developing a body of properties data as a function of temperature because establishment of a thermal state for a specimen is often cast into question. A new general technique is presented for simultaneous multiple-temperature measurements of thermal diffusivity and local composition for a single specimen. The specimen is heated steeply into a state of temperature nonuniformity. The measurement is carried out by time-resolved spectroscopy of single-shot laser-produced plasma (LPP) plume emissions; analysis is made of the emissions as a function of position within the laser focal area. The procedure for analysis is presented together with the results for 80 mass% Ni-20 mass% Cr Nichrome specimens.

Thermophysical properties of amorphous alloys represent the features of a given material specimen, and, as such, they are dependent, in general, on their elemental composition. Some properties are measured at surfaces, and others are measured for the bulk as a whole. Complications arise when the elemental composition varies as a function of position within the material specimen, as demonstrated by simultaneous measurements of thermal diffusivity and elemental composition by time-resolved spectroscopy of laser-produced plasma (LPP) plume emissions. To further understand the source of a rather common near-surface elemental composition anomaly, the evolution of the surface composition of Wood’s alloy under the influence of thermal cycling with, and without, a temperature gradient over the specimen has been investigated. Surface composition modifications have been found to take place by accumulation of irregularly spaced gray patches of an inhomogeneous composition on the surface in the presence of a temperature gradient. Determination of elemental composition by LPP spectroscopy shows the three-dimensional structure of the patches.

Thermophysical properties are collective measures of a material to transport dynamical quantities of physical nature on its surface or through the bulk. As such, the exact nature of couplings between particles in a many-body assembly of building block atoms or molecules sensitively determines their values. The couplings between nearest neighbors are the product of the local elemental composition and the material phase. In this study, thermal cycling of a four-element Wood’s alloy specimen brings out cadmium-rich patches to the top surface of the specimen. An assembly of such patches leads to depth-dependent deviations of elemental composition from that of the bulk. Surface-layer atoms are driven to form a high temperature laser-produced plasma (LPP), and time-resolved spectroscopy of their emissions show the variability of elemental composition over surface positions as well as over depth from the surface. These thermal history-driven composition anomalies contribute to significant variability in the measured values of spectral emissivity and thermal diffusivity.

Thermophysical data in the literature for metallic alloys, including single-element specimens, exhibit a high degree of variability. Of interest is if the reasons are intrinsic. That there exists as a rule a surface layer whose elemental composition differs from that of the bulk has been demonstrated. Such a near-surface composition anomaly can, in principle, account for the significant part of the variability. The method of time-resolved spectroscopy of emissions from laser-produced plasma (LPP) plumes has been the key in this new development because both the elemental composition and thermal diffusivity can be measured simultaneously. Multiple application of LPP analysis leads to depth-resolved measurements. A variety of alloy specimens have been subjected to different scenarios of thermal cycling to find that thermal cycling modifies the near-surface composition profile of a given specimen. A new study has been carried out with Wood’s alloy as a model system by forcing the specimen into melting at increasing temperature. This investigation has revealed that the near-surface composition undergoes sharp irreversible changes when the highest elemental melting point has been exceeded before the specimen is cooled to resolidification. A possible mechanism is suggested.

To identify the genes involved in cervical carcinogenesis, we applied the mRNA differential display method and identified a candidate tumor suppressor gene, HCCS-1, which was present in normal cervical tissue but absent in cervical cancer, metastatic lymph node and CUMC-6 cervical cancer cell line. HCCS-1 transcripts were expressed in many normal tissues including leukocyte, lung, spleen, liver, heart and uterine cervix. Its expression was absent in 8 human cancer cell lines. HCCS-1-transfected HeLa cells exhibited growth inhibition by about 50%. This inhibitory effect of HCCS-1 on cervical cancer cells was associated with apoptotic process including DNA fragmentation. HCCS-1-transfected HeLa cells were shown to release cytochrome c from mitochondria, which activates caspase-9 and -3 and finally results in cleavage of poly(ADP-ribose) polymerase. Apoptosis formation was detected by propidium-iodide/annexin V. HCCS-1-transfected HeLa cells were more sensitive to adriamycin or UVC ray triggered apoptosis. These results suggest that HCCS-1 is downregulated in multiple human tumor types and may serve as a candidate tumor suppressor gene through apoptotic pathway against human cervical cancer. © 2001 Wiley-Liss, Inc.

The transport properties of condensed phase materials are, in principle, dependent on the local structure and composition of the specimen. This is particularly evident near the free surface of a solid alloy specimen where the morphology, composition, and thermal diffusivity exhibit significant depth dependence, as demonstrated in an earlier study of the depth-resolved thermal diffusivity of a galvanized steel specimen. A new non-contact method was used, based on time-resolved, spectroscopic measurement of the total mass removed from the specimen surface representatively in elemental composition by a high-power laser pulse. A new study of a titanium thin film of varying thickness deposited on a copper substrate is presented. The titanium thin film is first fabricated in a vacuum and then immediately analyzed for composition and thermophysical properties in situ, both by the method of representative laser-produced plasmas (LPP). Successive ablation layers of the thin film, as exposed by LPP ablation, have revealed the dependence of the thermophysical properties on film thickness as well as on depth. The existence of a characteristic length over which the substrate influences the dynamics of thermal transport in the titanium thin film has also been observed.

In a series of recent experiments, utilizing the method of time resolved spectroscopy of laser-produced plasma (LPP) plumes from specimen surfaces, the near-surface elemental composition profiles were observed to be nonuniform and significantly different from the respective bulk composition. A new study of three alloy systems is reported, with a view toward establishing the causal relationship between the near-surface elemental composition profile of a specimen and its thermophysical properties in general and thermal diffusivity in particular. The systems in question are as follows: two-element Nichrome ribbon; four-element magnetic Mumetal foil; and four-element Wood's alloy. The method of LPP plume spectroscopy has been used throughout to successively expose new surface layers and measure the composition and thermal diffusivity. With two of the systems, modification of the near-surface elemental composition profiles has been forced. Sustained electrical heating of a Nichrome ribbon specimenrevealed preferential diffusion of chromium to the surface, affecting the spectral emissivity and thermal diffusivity as well as depth-dependent local heating rates. In the case of Wood's alloy a sample is melted and re-solidified under a protocol that highlights gravitational forcing. The noncontact spectroscopic method has been used to discover that the top and bottom surfaces acquire two different composition profiles and exhibit commensurate disparity in the measured thermal diffusivity profiles.

A new all-spectroscopic method for depth-resolved thermal diffusivity measurement of metallic specimens has been demonstrated. The method entails measurement of the mass entrained into a laser-produced plasma (LPP) plume in such a manner that the plume is representative of the specimen in elemental composition. Both the abundance of matter and its elemental composition are measured by time-resolved spectroscopy for each LPP plume. In order to delineate the morphology versus composition basis of the depth dependence, a new study on a Nichrome ribbon specimen heated by ohmic heating in a vacuum is presented. A set of depth-resolved thermal diffusivity measurements is carried out, while noting the attendant changes in the spectral emissivity and elemental composition at succeeding ablation layers. Additional measurements are carried out after the specimen has been treated under varying heating conditions. Preferential diffusion of chromium at high temperatures has been found to contribute to the dynamics of surface thermophysical properties at high temperatures. Representative LPP ablation is well suited for removal of surface impurities prior to thermophysical property measurements by the pulse heating technique.

Swirling flows for combustion stabilization, flame confinement, and proper fuel mixing and recirculation are prevalent in gas turbine combustor applications. Modern gas turbines use swirlers to induce strong rotating vortices and recirculation of the combustion gases to enhance combustion efficiency and stability. This study presents an experimental investigation of the flow field and wall heat transfer characteristics inside a model annular combustor equipped with radial swirlers. 2D Particle Image Velocimetry (2D-PIV) was used to characterize the flow field inside the combustor model. PIV measurements were taken for a single Reynolds number of 70000. To study the recirculation zone, data along the axial direction of the combustor were captured. The data show a slightly asymmetric flow, with the recirculation zone extending up to , where D is the hydraulic diameter of the entire annulus ( m). To study the evolution of the rotating vortex and the flow velocity close to the liner walls, PIV data was also captured at six cross-sections of the annular combustor. The vortex center was observed to be below the center of the swirler, consistent with the asymmetry observed in the axial measurements. Infrared (IR) thermography was used to measure the steady state heat transfer coefficients along the outer and inner liner walls for Reynolds numbers of , , and . The comparison between the heat transfer results for the different Reynolds numbers reveals a relatively constant position for the peak heat transfer at from the swirler exit for both walls. Computational Fluid Dynamics (CFD) calculations were also performed to better understand the characteristics of the flow inside the model combustor. The CFD model reproduces the experimental setup with a mesh of 25 million cells. A ReynoldsAveraged Navier-Stokes (RANS) model was used in the simulation, qualitatively reproducing the overall characteristics observed in the experiment.

We have developed a novel diagnostic technique for weakly nonideal laser-produced plasma (LPP) plumes, based entirely on the continuum, and present the result for aluminum plasma. Due to significant self-absorption, the analysis is carried out in close coupling with plasma equilibrium calculations. We first invoke scaling relations linking the time- and position-resolved specific continuum intensity I, integrated over the spectral range of a streak camera, to the local temperature T and pressure p: T=STIα and p=SpIα+β. Inversion of the two-dimensional luminosity profile into the specific continuum intensity profile (three-dimensional) is carried out self-consistently, subject to the 16 independent measurements: target mass loss, energy deposited into the LPP plume and laser beam attenuation at fundamental and its harmonic frequencies, all at four different laser energies. An agreement to within 6.1% of the measurements overall has been achieved with α=0.45±0.03, β=1.0±0.03, ST=0.190±0.003 and Sp=340±5.

A single laser pulse is used to produce weakly nonideal plasma from a metallic aluminum target immersed in a dense neutral gas. The attendant increase in plasma density due to neutral gas confinement precipitates interfacial instability when the gas density exceeds a threshold value. This is accompanied by large fluctuations in the total attenuation of the laser beam by the laser-produced plasma plume. We have developed a new diagnostic method utilizing two mutually orthogonal side-view streak photographs of plasma continuum luminosity at a fixed distance from the target surface. The lack of axial symmetry is overcome by using a front-view luminosity image of the plasma at time zero as a two-dimensional weighting factor. The resulting profile at one time is used as the weighting factor for the next time segment. The time-resolved reconstructed plasma profiles clearly exhibit the near-threshold behavior of Rayleigh–Taylor type instability.

A new laser-based method for real-time in situ measurement of thermophysical properties of materials has been developed. It entails production by a high-power laser pulse of a plasma plume from the surface of a condensed-phase specimen and simultaneous measurement of a material's response to the excitation. The specimen may be a solid or in a molten state at high temperatures. It has been shown that the thermal diffusivity can be determined, for instance, from the mass loss due to laser excitation. In one implementation the mass loss is determined from the impulse imparted on the surface by the ablated matter which is measured by an impulse transducer. In this paper, we present a new spectroscopic method for measurement of the mass loss, facilitating in situ non-contact measurement of the thermal diffusivity for the first time. An implementation of this method is described, whereby the thermal diffusivity of a complex layered surface is determined as a function of depth with resolutions as small as 13 nm.

This work concerns the spontaneous gas bubble nucleation after rapid decompression in organic solution initially saturated with dissolved gas and the subsequent bubble growth to macroscopic size. The decompression limit for gas bubble formation was obtained from the stability condition of the critical cluster of dissolved gas molecules. This work also clarifies how the critical cluster grows to the critical size bubble, the first object which is separated from liquid molecules by interface. Further growing of this critical size bubble by diffusion process was treated by an integral method for the concentration boundary layer thickness. The calculation values of the amount of decompression for the homogeneous gas bubble formation in organic solutions and the time required for the birth of macroscopic bubble size are in reasonable agreement with experimental results.

Objectives/Hypothesis Caudal septal deviation interrupts normal nasal breathing, due to the narrowing of the external valve area and nasal valve angle. In this study, we found a different approach for correction of caudal septal deviation with no associated deformity of the external nose. Study Design Individual case–control study. Methods The 39 patients completed questionnaires by interviews postoperatively for assessment of nasal obstruction. In addition, patients assessed the severity of their nasal symptoms (i.e., mouth breathing, mouth dryness, hyposmia, rhinorrhea, epistaxis, snoring, postnasal drip, and headache) preoperatively and postoperatively using a visual analog scale (VAS). Improvement in the treatment of nasal obstruction using a VAS and a questionnaire for subjective satisfaction were evaluated 3 months after septoplasty. To evaluate outcomes objectively, endoscopic photographs of the nasal cavity and acoustic rhinometry before and after surgery were evaluated. For comparison between preoperative and postoperative status, the Wilcoxon signed ranks test was used. Results Patients reported a significant decrease in the VAS severity of all nasal symptoms. The minimal cross-sectional area (MCA1) of the convex side after vascular constriction using acoustic rhinometry showed significant widening. Patients were divided into a turbinoplasty group and a nonturbinoplasty group, and the turbinoplasty group showed a significant increase in both the convex side and concave side in MCA1 and in the convex side in the anterior portion of the inferior turbinate. Conclusions Endonasal septoplasty using bony batten grafting for caudal septal deviation resulted in an improvement of nasal obstruction symptoms and acoustic rhinometry components. Level of Evidence 3b Laryngoscope, 124:1771–1776, 2014

A high-power pulsed laser excitation of a material surface generates a well-separated sequence of plasma, fluid flow, and acoustic events. When the movement of the surface due to evaporation by laser heating is kept in pace with the thermal diffusion front, the ablative mass loss from a solid surface becomes strongly correlated with the thermal diffusivity of the target matter. The other thermophysiocal properties which figure in this correlation are the mass density, heat of formation, and molecular weight. The functional relationship, which is given in this text for the first time, can be exploited to measure the thertnophysical properties. We have now extended such an approach to measurement of the thermal diffusivity of molten specimens by developing a new instrumentation for determining the ablative mass loss due to a single laser pulse. This has been accomplished by combining a facility for controlled generation of a molten specimen and a novel transducer for real-time measurement of the impulse imparted to the molten target by a laser-produced plasma plume, The transducer design, calibration, signal recovery, and method of extracting the mass loss per laser excitation are detailed by comparing the results for metallic specimens in the solid and molten state.

The electroencephalogram, as a probe of scalp-recorded electrical activity arising from the human cortex, provides useful information because of its temporal and spatial organization. Recent developments in nonlinear dynamics suggest that an object can be constructed in an n-dimensional space out of a temporal sequence of data such as an EEG signal and that its organization is characterized by the dimensionality of the object (in this case, human brain activity). We have carried out an analysis of a set of alpha coma EEG patterns in comparison to the awake alpha EEG patterns of normal volunteers and patients. Alpha coma recorded from a single channel is visually indistinguishable from normal resting alpha due to its similar frequency spectrum (a broad-band spectrum with 1/f characteristics). Our results show that alpha coma dimensionality, however, differs from that of normal alpha in that it has a greater variability over different temporal segments of EEG. Single channel recordings in 7 patients with alpha coma were differentiable from those of 10 subjects with "normal" EEGs. Through dynamic analysis of the EEG, novel methods of signal extraction from EEG may become evident and applicable to clinical practice.

A method is developed for structure reconstruction of an arbitrary plasma from two luminosity streaks and a front-view snapshot as a weighting function (WF). Two scaling relations link the pressure and temperature to the local specific emission intensity. A trial plasma structure is proposed in terms of specific intensity, and the luminosity streaks are calculated according to the Saha equilibrium. Plasma absorption is included. Error signals between the calculated and measured luminosity are allocated according to the WF to find corrections to local specific intensities. Minimization of the errors completes the reconstruction at a given time, which in turn updates the WF for the next time step. Summing over the full plasma over time facilitates calculation of the total plasma mass, energy and beam attenuation through the plasma. When agreement with their measured counterparts is maximized, the scaling relations are calibrated.

The test facility, experimental methods, and summary results are presented from a study modeling turbine disk cooling with multiple impinging jets, such as employed on the Space Shuttle Main Engine oxygen turbopump. The study was designed to provide a comparison of detailed local convection heat transfer information obtained with a single center-supply of disk coolant, as opposed to the present flight configuration where disk coolant is supplied through an array of 19 radially outboard jets. Specially constructed turbine disk models were used in a program to evaluate possible benefits and tradeoffs of employing an alternate disk cooling scheme. The study involved the design, construction, and testing of two full-scale rotating model disks, one plane and smooth for baseline testing and the second contoured to the present flight configuration, together with the corresponding plane and contoured stators. Local heat transfer rates are determined from the color display of encapsulated liquid crystals coated on the disk in conjunction with use of a computer vision system. The test program was composed of a wide variety of disk speeds, flow rates, and geometrical configurations, including testing for the effects of bolt heads and hot gas entrainment into the disk cavity.

Burst suppression electroencephalograms from 9 comatose patients have been studied using nonlinear dynamic techniques. These EEG records show many dynamical features characteristic of nonlinear systems, including sensitive dependence on initial conditions, self-organization, similarity across scales, and intermittency. Histograms of burst durations showed an asymmetric distribution with a decreasing tail of increasing duration. Interpreting the histograms from the standpoint of intermittency classifications of iterated dynamical maps, the absence of any conspicuous maximal cut-off duration suggests a type III intermittency. The power-law exponent of the decreasing tail is − 3 2 for type III intermittency in the large scale sample size limit, and we have found the EEGs to be consistent with type III intermittency behavior. We have also developed a nonlinear algorithm which models burst suppression pattern based on a low dimensional return map. Burst suppression pattern appears to be the constrained activity of a nonlinear dynamical system at the transition to chaos.

Excitation by a high-power laser pulse of a material surface generates a sequence of plasma, fluid flow, and acoustic events. These are well separated in time, and their detection and analysis can lead to determination of material properties of the condensed phase target. We have developed a new methodology for real-time determination of molten metal composition by time-resolved spectroscopy of laser-produced plasmas (LPP). If the laser pulse is shaped in such a way that the movement of the bulk surface due to evaporation is kept in pace with the thermal diffusion front advancing into the interior of the target, the LPP plume becomes representative of the bulk in elemental composition. In addition, the mass loss due to LPP ablation is very well correlated with the thermal diffusivity of the target matter. For several elemental solid specimens, we show that the product of the ablation thickness and heat of formation is proportional to the thermal diffusivity per unit molecular weight. Such measurements can be extended to molten metal specimens if the mass loss by ablation, density, heat of formation, and molecular weight can be determined simultaneously. The results from the solid specimen study and the progress with a levitation-assisted molten metal experiment are presented.

X-pinch plasmas have been actively studied in the recent years. Numerical simulation of the ramp-up of metallic vapor emissions from wire specimens shows that under impulsive Ohmic heating the wire core invariably reaches a supercritical state before explosion. The heating rate depends sensitively on the local wire resistance, leading to highly variable vapor emission flux along the wire. To examine the vapor emission process, we have visualized nickel wire explosions by means of shock formation in air. In a single explosion as captured by shadowgraphy, there usually appear several shocks with spherical or cylindrical wave front originating from different parts of the wire. Growth of various shock fronts in time is well characterized by a power-law scaling in one form or another. Continuum emission spectra are obtained and calibrated to measure temperature near the explosion threshold. Shock front structures and vapor plume temperature are examined.

Background Cell transdifferentiation is characterized by loss of some phenotypes along with acquisition of new phenotypes in differentiated cells. The differentiated state of a given cell is not irreversible. It depends on the up- and downregulation exerted by specific molecules. Results We report here that HCCR-1, previously shown to play an oncogenic role in human cancers, induces epithelial-to-mesenchymal transition (EMT) and mesenchymal-to-epithelial transition (MET) in human and mouse, respectively. The stem cell factor receptor CD117/c-Kit was induced in this transdifferentiated (EMT) sarcoma tissues. This MET occurring in HCCR-1 transfected cells is reminiscent of the transdifferentiation process during nephrogenesis. Indeed, expression of HCCR-1 was observed during the embryonic development of the kidney. This suggests that HCCR-1 might be involved in the transdifferentiation process of cancer stem cell. Conclusions Therefore, we propose that HCCR-1 may be a regulatory factor that stimulates morphogenesis of epithelia or mesenchyme during neoplastic transformation.

We have designed and constructed a spectroscopic interferometer, and test run its operation with a pulsed discharge plasma. The plasma is produced by capacitor discharge across a gap filled with neutral argon at selected pressures. Ablation of iron from the cathode adds to argon to form equilibrium plasma of an argon-iron mixture. The ablative mass addition is measured and incorporated into the system of Saha equations. The calculated plasma energy is compared to independently measured total energy injected into the plasma to determine the peak plasma temperature. The measured coherence length of an argon emission line shows a dependence on the direction of the line of sight and a scaling with collision time within the plasma.

Pressure-side discharge is commonly employed in turbine blades and nozzle guide vanes to keep the trailing edge metal temperatures within an allowable limit while minimizing aerodynamic penalties. Despite its widespread use, film-cooling data of the discharge slot are scarce in open literature. The objectives of the present experimental study were to measure detailed local heat transfer and film-cooling effectiveness from a 10x scale trailing-edge model of an industrial gas turbine airfoil in a low speed wind tunnel. To simulate the mainstream flow acceleration in vane and blade row passages, a linear velocity gradient was imposed using an adjustable top wall. The present work employed the composite slab quasi-steady liquid crystal method that allows measurements of local heat transfer coefficients and film-cooling effectiveness from two related tests. With this technique, the heat transfer measurement can be performed in a cold wind tunnel. The coolant-to-mainstream blowing ratio was varied between 0.25 and 1.0. The slot hydraulic diameter based Reynolds number ranged from 4,760 to 19,550. The coolant-to-mainstream density ratio was fixed at 0.95. Slot discharge coefficients were also measured with mainstream acceleration. Both local heat transfer coefficients and film-cooling effectiveness displayed a strong dependency on blowing ratio and mainstream acceleration. However, the discharge coefficients showed little dependency on the mainstream acceleration.Copyright © 2005 by ASME

Summary: Currently, most carotid artery pathologic abnormalities resulting in pseudoaneurysm formation or stenosis are repaired by surgical intervention. Because surgical intervention requires proximal and distal control of the artery, pseudoaneurysms near the skull base may be very difficult to repair and pose greater risk to the patient. As a result, endovascular techniques have evolved in an effort to reduce morbidity associated with surgical techniques. Parent vessel occlusion and coil placement are the most frequently used endovascular techniques for carotid artery repair of pseudoaneurysms. Intimal hyperplasia is generally treated with balloon angioplasty, often in conjunction with uncovered stent placement. Parent vessel occlusion may be impractical if the patient is unable to tolerate occlusion of that artery. We report our experience in treating three patients with carotid artery stent grafts.

Tumor cells characteristically exhibit an increased rate of glycolysis. A higher level of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA was found in human uterine cervical cancers. This study was designed using GAPDH antisense oligodeoxynucleotide (ODN) phosphorothioate (PS) to evaluate how alterations of GAPDH expression in human cervical carcinoma could influence growth inhibition and induction of apoptosis. Northern blot analyses revealed that the levels of GAPDH gene expression were strongly elevated in three cervical carcinoma cell lines (HeLa, CUMC-3, and CUMC-6) compared with normal cervical tissue. Reverse transcription-polymerase chain reaction (RT-PCR) showed that expression of the GAPDH gene was inhibited by 10 microM of GAPDH antisense ODN in all three cell lines. Western blot analysis showed that the levels of GAPDH protein were decreased or absent after GAPDH antisense ODN treatment for 12 days in cultured cervical carcinoma cell lines. Cervical carcinoma cell lines exposed to GAPDH antisense ODN showed reduced cellular proliferation, which was accompanied by reduced colony-forming efficiency. This effect of GAPDH antisense ODN on cultured carcinoma cells was associated with the apoptotic process, including increased DNA fragmentation. These results suggest that future gene therapy using antisense ODN directed against cervical cancer-specific GAPDH mRNA might be another therapeutic tool against human uterine cervical carcinomas.

An experimental investigation of film cooling on rough surfaces has been accomplished at a Reynolds number and dimensionless boundary layer momentum thickness found in current high performance first stage turbine vanes. A transient experimental method using thermochromic liquid crystals is employed to determine both local heat transfer coefficients and film cooling effectiveness values on planar rough surfaces. Two surface roughness configurations are investigated with a single row of cooling holes spaced three diameters apart and inclined 30° to the mainstream flow. The mainstream turbulence level at the point of film injection is 8.5% and the density ratio considered is approximately 1.0. The influence of roughness on the centerline film cooling effectiveness, laterally averaged film cooling effectiveness, laterally averaged heat transfer coefficients, as well as area averaged values are presented. It is found that the presence of roughness causes a decrease in the film cooling effectiveness over that of the smooth surface for the range of experimental parameters considered in this study. In addition, significant lateral smoothing in film cooling effectiveness distribution is observed for the rougher surfaces. Measured heat transfer coefficients on rough surfaces show a trend of monotonic increase with blowing ratio. However, such increase is not as great as that for the case of smooth surface.Copyright © 1995 by ASME

A new shock tube facility has been constructed in order to help clarify: (i) the exact nature of Mach reflections in density stratified media and (ii) the growth rate of the interfacial instability under forcing by a shock wave. The shock tube is diaphragmless and has two fast-action valves at each end of the driven section, one to create a well defined interface between two dissimilar gases and the other to produce a shock propagating into the interface. Actuation of the two valves is pneumatically synchronized. The shock tube operates in the Mach number range of 1.01 to 5 with an exceptionally high degree of reproducibility and rapid turn-around time. The design, construction and performance studies of the shock tube are presented.