Location Of Transition Research Articles

When and How Much Did the Green Line LRT Increase Single-Family Housing Values in St. Paul, Minnesota?

Studies quantifying value added of transit often cannot differentiate whether the premiums are transit effects or location effects. Limited studies have examined the timing of value added. Using before and after data, this study explores the impact of the Green Line LRT on housing sales prices. Compared to the studied period before its funding announcement, its announcement increased housing values by $9.2/sq ft and its commencement increased sales prices by $13.7/sq ft. Further analyses show that housing value appreciation actually occurred after the announcement but before the commencement. Thus, using the right timing of value added is critical for value capture programs and benefit–cost analysis.

Proper orthogonal decomposition of time-resolved LIF visualization: scalar mixing in a round jet

Time-resolved planar laser-induced fluorescence imaging of the scalar concentration field of a round jet was performed in this study, together with proper orthogonal decomposition (POD) analysis to extract the spatial pattern and spatio-temporal evolution of the dominant structures of unsteady behavior from the large image data. Particular attention was paid to ensuring quantitative representation of the dynamically varying concentration field. Three Reynolds numbers based on the nozzle diameter $$D$$ and the bulk velocity $$U_{j}$$ were compared, i.e., $$Re$$ = 2400, 3000, and 6000. The preliminary instructive view of the jet characteristics at these three Reynolds numbers was first obtained from the instantaneous and time-mean concentration field, the concentration fluctuation intensity fields, and then the cross correlation of the concentration field. In the POD analysis, five regions, each overlapping its neighbor by 50%, were carefully chosen for the close-up view of the locally unsteady behavior. The POD mode results convincingly reflected the helical mode in the jet at $$Re$$ = 2400; both the helical and the axisymmetric modes buried in the jets at $$Re$$ = 3000 and 6000 were recognized. This confirmed that the axisymmetric mode decayed rapidly beyond the $$x/D$$ = 4 station, while the helical mode dominated the far field. The POD mode captured the streamwise oscillation of the transition location at $$Re$$ = 2400 and 3000, which has relatively large energy among all the POD modes. The mode coefficients indicated a wide range of dominant frequencies in relation to the organized motions, and also the frequency decay in the downstream direction. Finally, each instance of energetic behavior superimposed in the highly unsteady jets was separately revealed through low-order reconstruction of the specified POD modes, shedding light on its global variation throughout the whole field.

Modeling and Measurements of Heat/Mass Transfer in a Linear Turbine Cascade

Measurements of the mass/heat transfer coefficients on the blade and end wall surfaces of a linear turbine cascade are compared to numerical predictions using the standard shear stress transport (SST) closure and the SST model in combination with the Reθ–γ transition model (SST-TRANS). Experiments were carried out in a wind tunnel test section composed of five large-scale turbine blades, using the naphthalene sublimation technique. Two cases were tested, with exit Reynolds number of 600,000 and inlet turbulence values of 0.2% and 4%, respectively. The main secondary flow features, consisting of the horseshoe vortex system, the passage vortex, and the corner vortices, are identified and their influence on heat/mass transfer is analyzed. Numerical simulations were carried out to match the conditions of the experiments. Results show that large improvements are obtained with the introduction of the Reθ–γ transition model. In particular, excellent agreement with the experiments is found, for the whole spanwise extension of the blade, on the pressure surface. On the suction surface, performance is very good in the highly three-dimensional region close to the end wall, but some weaknesses appear in predicting the location of transition in the two-dimensional region. On the end wall surface, the SST model in combination with the transition model produces satisfactory results, greatly improved compared to the standard SST model.

Natural laminar flow shape optimization in transonic regime with competitive Nash game strategy

• NLF shape design in transonic regime is considered as a MCO problem. • A multi-level PNEAs is developed and used to solve NLF optimization efficiently. • Both wave drag and friction drag performances of a NE are greatly improved. • Performance of NE for NLF shape optimization is equivalent to that of Pareto front. The Natural Laminar Flow (NLF) airfoil/wing design optimization is an efficient method which can reduce significantly turbulence skin friction by delaying transition location at high Reynolds numbers. However, the reduction of the friction drag is competitively balanced with the increase of shock wave induced drag in transonic regime. In this paper, a distributed Nash Evolutionary Algorithms (EAs) is presented and extended to multi-level parallel computing, namely multi-level parallel Nash EAs. The proposed improved methodology is used to solve NLF airfoil shape design optimization problem. It turns out that the optimization method developed in this paper can easily capture a Nash Equilibrium (NE) between transition delaying and wave drag increasing. Results of numerical experiments demonstrate that both wave drag and friction drag performances of a NE are greatly improved. Moreover, performance of the NE is equivalent to that of cooperative Pareto-optimum solutions, but it is more efficient in terms of CPU time. The successful application validates efficiency of algorithms in solving complex aerodynamic optimization problem.

Tributary effects in rivers: interactions of spatial scale, network structure, and landscape characteristics

Landscape characteristics in combination with the physical structure of branched stream networks define the environmental conditions available for lotic biota. From simple stream network “laws” can emerge a spatially explicit understanding of habitat heterogeneity. Based on geographic information system analyses, we explore how stream networks integrate spatial heterogeneity of the landscape and form new characteristics as stream segments accumulate into progressively larger drainages and how these changes in landscape characteristics relate to confluence symmetry ratio and drainage size. Simple expectations for stream networks include the following: (i) abrupt changes in longitudinal patterns are more probable among the numerous small and diverse headwater streams than in large, rare, and characteristically similar tributaries, (ii) the many small tributaries flowing into large mainstem channels cause individually small, yet collectively gradual, changes in longitudinal patterns. Such a spatial understanding of where change is likely to occur helps to reconcile gradual river continuum and abrupt discontinuum views of patterns in rivers and predict the locations of important confluences, ecological transitions, longitudinal gradients, and patterns of biodiversity in stream networks.

New control methodology for a morphing wing demonstrator

A morphing wing can improve the aircraft aerodynamic performance by changing the wing airfoil depending on the flight conditions. In this paper, a new control methodology is presented for a morphing wing demonstrator tested in a subsonic wind tunnel in the open-loop configuration. Actuators integrated inside the wing are used to modify the flexible structure, which is an integral part of the wing. In this project, the actuators are made in-house and controlled with logic control, which is developed within the main frame of this work. The characterization of the flow (laminar or turbulent) over the wing is obtained starting from the pressure signals measured over the flexible part of the wing (upper surface). The signals are acquired by using some pressure sensors (Kulite sensors) incorporated in this flexible part of the wing upper surface. The technique used to collect Kulite pressure data and the post-processing methodology are explained. The recorded pressure data are sometimes subjected to noise, which is filtered before being processed. The standard deviation and power spectrum visualization of the pressure data approaches are used to evaluate the quality of the flow over the wing and estimate the transition point position in the area monitored by the Kulite sensors. In addition, infrared thermography visualization is implemented to observe the transition region over the entire wing upper surface, and to validate the methodology applied to the pressure data in this way. The demonstrator measures 1.5 m chordwise and 1.5 m spanwise. Four miniature actuators fixed on two actuation lines are used to morph the wing. The wing is also equipped with a rigid aileron. The experimental aerodynamic results obtained after post processing validate the numerical prediction for the transition location.

γ-ReƟ 천이 모델을 사용한 KARI-11-180 익형의 천이 유동해석

본 연구에서는 KFLOW에서 사용하고 있는 <TEX>${\gamma}-Re_{\theta}$</TEX> 천이 모델을 사용하여 KARI-11-180 익형의 공력특성을 수치적으로 예측하고 그 결과를 실험 결과 및 XFOIL과 MSES의 결과와 비교하였다. 완전 난류모델은 천이모델에 비해 마찰항력을 크게 예측하기 때문에 전체적으로 높은 항력을 예측하는 등 천이모델과 완전 난류모델간의 차이를 확인하였다. KFLOW의 <TEX>${\gamma}-Re_{\theta}$</TEX> 모델을 사용한 결과는 실험을 통해 확인된 천이 유동 실험 결과의 특성을 잘 예측하고 있었으며 XFoil이나 MSES의 결과와도 잘 일치하고 있음을 확인하였다. 본 연구를 통해 drag-bucket현상이 익형 표면의 천이점의 급격한 변화로 인해 발생함을 확인하였다. In this study, numerical simulations were performed using the <TEX>${\gamma}-Re_{\theta}$</TEX> transition model of KFLOW for the transitional flow over the KARI-11-180 airfoil. Numerical results of KFLOW were compared with experimental data and two other numerical results of XFoil and MSES. Fully turbulence model was predicted high skin friction drag than transition model because fully turbulence model could not solve the transitional flow. Numerical predictions using the <TEX>${\gamma}-Re_{\theta}$</TEX> model of KFLOW show a good agreement with experimental data and other numerical results. Present numerical results were confirmed the state of drag bucket due to dramatic changing of the transition location on the airfoil surface.

Synthetic Control of Exciton Behavior in Colloidal Quantum Dots.

Colloidal quantum dots are promising optical and optoelectronic materials for various applications, whose performance is dominated by their excited-state properties. This article illustrates synthetic control of their excited states. Description of the excited states of quantum-dot emitters can be centered around exciton. We shall discuss that, different from conventional molecular emitters, ground-state structures of quantum dots are not necessarily correlated with their excited states. Synthetic control of exciton behavior heavily relies on convenient and affordable monitoring tools. For synthetic development of ideal optical and optoelectronic emitters, the key process is decay of band-edge excitons, which renders transient photoluminescence as important monitoring tool. On the basis of extensive synthetic developments in the past 20-30 years, synthetic control of exciton behavior implies surface engineering of quantum dots, including surface cation/anion stoichiometry, organic ligands, inorganic epitaxial shells, etc. For phosphors based on quantum dots doped with transition metal ions, concentration and location of the dopant ions within a nanocrystal lattice are found to be as important as control of the surface states in order to obtain bright dopant emission with monoexponential yet tunable photoluminescence decay dynamics.

On computing the location of laminar–turbulent transition in compressible boundary layers

Abstract Evolution equations of small disturbances aimed to compute the location of a laminar–turbulent transition in boundary layers by the e N -method taking into account the compressibility and heat transfer are described and justified for aerodynamic applications. The results of computation of N-factors and transition locations with the use of locally-parallel flow assumption for a flat plate exposed to supersonic flow at zero angle of attack are given. The results agree well with known numerical and experimental data.

Glass transition in hard-core fluids and beyond, using an effective static structure in the mode coupling theory.

The dynamical arrest in classical fluids is studied using a simple modification of the mode coupling theory (MCT) aimed at correcting its overestimation of the tendency to glass formation while preserving its overall structure. As in previous attempts, the modification is based on the idea of tempering the static pair correlations used as input. It is implemented in this work by computing the static structure at a different state point than the one used to solve the MCT equation for the intermediate scattering function, using the pure hard-sphere glass for calibration. The location of the glass transition predicted from this modification is found to agree with simulations data for a variety of systems --pure fluids and mixtures with either purely repulsive interaction potentials or ones with attractive contributions. Besides improving the predictions in the long-time limit, and so reducing the non-ergodicity domain, the same modification works as well for the time-dependent correlators.

The potential of asteroseismology for probing the core chemical stratification in white dwarf stars

Context. The details of the C/O core structure in white dwarf stars has mostly remained inaccessible to the technique of asteroseismology, despite several attempts carried out in the past. Aims. We aim to re-assess the potential of asteroseismology for probing the chemical stratification in white dwarf cores, in light of new highly efficient tools recently developed for that purpose. Methods. Using the forward modeling approach and a new parameterization for the core chemical stratification in ZZ Ceti stars, we tested several situations typical of the usually limited constraints available, such as small numbers of observed independent modes, to carry out asteroseismology of these stars. Results. We find that, even with a limited number of modes, the core chemical stratification (in particular, the location of the steep chemical transitions expected in the oxygen profile) can be determined quite precisely due to the significant sensitivity of some confined modes to partial reflexion (trapping) effects. These effects are similar to the well known trapping induced by the shallower chemical transitions at the edge of the core and at the bottom of the H-rich envelope. We also find that success to unravel the core structure depends on the information content of the available seismic data. In some cases, it may not be possible to isolate a unique, well-defined seismic solution and the problem remains degenerate. Conclusions. Our results establish that constraining the core chemical stratification in white dwarf stars based solely on asteroseismology is possible, an opportunity that we have begun to exploit.

Transition to bluff-body dynamics in the wake of vertical-axis wind turbines

We present experimental data to demonstrate that the far wake of a vertical-axis wind turbine (VAWT) exhibits features that are quantitatively similar to that of a circular cylinder with the same aspect ratio. For a fixed Reynolds number ($Re\approx 0.8\times 10^{5}$) and variable tip-speed ratio, two-dimensional particle image velocimetry (PIV) is used to measure the velocity field in the wake of four different laboratory-scale models: a 2-bladed, 3-bladed and 5-bladed VAWT, as well as a circular cylinder. With these measurements, we use spectral analysis and proper orthogonal decomposition (POD) to evaluate statistics of the velocity field and investigate the large-scale coherent motions of the wake. In all cases, we observe three distinct regions in the VAWT wake: (i) the near wake, where periodic blade vortex shedding dominates; (ii) a transition region, where growth of a shear-layer instability occurs; (iii) the far wake, where bluff-body wake oscillations dominate. We define a dynamic solidity parameter, $\unicode[STIX]{x1D70E}_{D}$, that relates the characteristic scales of the flow to the streamwise transition location in the wake. In general, we find that increasing $\unicode[STIX]{x1D70E}_{D}$ leads to an earlier transition, a greater initial velocity deficit and a faster rate of recovery in the wake. We propose a coordinate transformation using $\unicode[STIX]{x1D70E}_{D}$ in which the minimum velocity recovery profiles of the VAWT wake closely match that of the cylinder wake. The results have implications for manipulating VAWT wake recovery within a wind farm.

Location of the adsorption transition for lattice polymers

We consider various lattice models of polymers: lattice trees, lattice animals, and self-avoiding walks. The polymer interacts with a surface (hyperplane), receiving an energy reward of β for each site in the surface. It is known that there is an adsorption transition at a critical value of β. We present a new proof of the result of Hammersley et al (1982 J. Phys. A: Math. Gen. 15 539–71) that the transition occurs at a strictly positive value of β when the surface is impenetrable, i.e. when the polymer is restricted to a half-space. In contrast, for a penetrable surface, it is an open problem to prove that the transition occurs at . We reduce this problem to proving that the fraction of N-site polymers whose span is less than is not too small.

Determining the core stratification in white dwarfs with asteroseismology

Using the forward modeling approach and a new parameterization for the core chemical stratification in ZZ Ceti stars, we test several situations typical of the usually limited constraints available, such as small numbers of observed independent modes, to carry out asteroseismology of these stars. We find that, even with a limited number of modes, the core chemical stratification (in particular, the location of the steep chemical transitions expected in the oxygen profile) can be determined quite precisely due to the significant sensitivity of some confined modes to partial reflexion (trapping) effects. These effects are similar to the well known trapping induced by the shallower chemical transitions at the edge of the core and at the bottom of the H-rich envelope. We also find that success to unravel the core structure depends on the information content of the available seismic data. In some cases, it may not be possible to isolate a unique, well-defined seismic solution and the problem remains degenerate. Our results establish that constraining the core chemical stratification in white dwarf stars based solely on asteroseismology is possible, an opportunity that we have started to exploit.

Optimization of regular offshore wind-power plants using a non-discrete evolutionary algorithm

Offshore wind farms (OWFs) often present a regular configuration mainly due to aesthetical considerations. This paper presents a new evolutionary algorithm that optimizes the location, configuration and orientation of a rhomboid-shape OWF. Existing optimization algorithms were based on dividing the available space into a mess of cells and forcing the turbines to be located in the centre of a cell. However, the presented algorithm searches for the optimum within a continuous range of the eight parameters that define the OWF, which allows including a gradient-based local search operator to improve the optimization process. The study starts from a review of the economic data available in the bibliography relative to the most significant issues influencing the profitability of the investment in terms of the Internal Rate of Return (IRR). In order to address the distinctive characteristics of OWFs, specific issues arise which have been solved. The most important ones are: interpretation of nautical charts, utilization of the seabed map with different load-bearing capacities, and location of the shoreline transition.

The Logics of Transit: The Anticipation of Onward Mobility and its Consequences for Social and Economic Relations in Istanbul

This article departs from Istanbul as a transit location experiencing a constant inflow and outflow of (African) migrants, and the strong narrative among African migrants that Istanbul has nothing to offer and should be transited as fast as possible. As a consequence of this, the article identifies migrants' constant anticipation of each other's potential leaving - the logic of transit - as a useful concept to understand social and economic migrant relations in a situation of transit. Thus it offers an analysis of how this logic permeates the formation and maintenance of social networks and, consequently, impacts on trajectories of mobility. Developed through in-depth analysis of the migrants' lived experiences, it offers a new angle on transit movements and the condition of transit in general.

Economies of transit: exploiting migrants and refugees in Indonesia and Libya

Increasingly restrictive border protection measures cause more asylum seekers, refugees and labour migrants to attempt to reach their destinations by unauthorised means and enable illicit markets that facilitate irregular migration to form and expand. Smuggling networks, funds for journeys, and access to sites where passages can be negotiated allow irregular migration to flourish. The micro-economies that form at transit sites because of the irregular presence of migrants and refugees are a less recognised aspect of transit. This article compares transit sites in Indonesia and Libya - key transit locations on routes to Australia and Italy - and investigates the exploitation of transit migrants in both countries. It illustrates that those crossing borders are exploited not only in illicit spaces but also when under government control or management by international organisations. It argues that these economies of transit encourage informal networks that prey on transit migrants and extend their exploitation.

Multi-objective optimisation in scientific workflow

Engineering design is typically a complex process that involves finding a set of designs satisfying various performance criteria. As a result, optimisation algorithms dealing with only single-objective are not sufficient to deal with many real-life problems. Meanwhile, scientific workflows have been shown to be an effective technology for automating and encapsulating scientific processes. While optimisation algorithms have been integrated into workflow tools, they are generally single-objective. This paper first presents our latest development to incorporate multi-objective optimisation algorithms into scientific workflows. We demonstrate the efficacy of these capabilities with the formulation of a three-objective aerodynamics optimisation problem. We target to improve the aerodynamic characteristics of a typical 2D airfoil profile considering also the laminar-turbulent transition location for more accurate estimation of the total drag. We deploy two different heuristic optimisation algorithms and compare the preliminary results.

Economies of transit: exploiting migrants and refugees in Indonesia and Libya

Increasingly restrictive border protection measures cause more asylum seekers, refugees and labour migrants to attempt to reach their destinations by unauthorised means and enable illicit markets that facilitate irregular migration to form and expand. Smuggling networks, funds for journeys, and access to sites where passages can be negotiated allow irregular migration to flourish. The micro-economies that form at transit sites because of the irregular presence of migrants and refugees are a less recognised aspect of transit. This article compares transit sites in Indonesia and Libya - key transit locations on routes to Australia and Italy - and investigates the exploitation of transit migrants in both countries. It illustrates that those crossing borders are exploited not only in illicit spaces but also when under government control or management by international organisations. It argues that these economies of transit encourage informal networks that prey on transit migrants and extend their exploitation.

Flow pattern transition during condensation of R134a and R1234ze(E) in microchannel arrays

Two-phase flow pattern transition during the condensation of R134a and R1234ze(E) was experimentally investigated in a microchannel array made of borosilicate glass cooled symmetrically on the top and bottom by forced convection of water. The microchannel array consisted of 50 channels with the aspect ratio of 2.46, the hydraulic diameter of 301.6μm and the length of 50mm. Saturation temperatures are 20–25°C with mass fluxes varying from 6 to 50kg/m2/s. Observed patterns are annular flow, steady injection flow, quasi-symmetric wave flow and slug/bubbly flow. In addition, three flow pattern transition modes including steady injection, wave-coalescence injection, and liquid bridging were observed and mapped in terms of liquid Webb number versus condensation number. The steady injection transition was more studied in detail by measuring the bubble length variation and the moving velocity of bubbles and slugs with different mass fluxes of R134a and R1234ze(E). The transition mechanism of injection flow was identified by analyzing the force balance based on the experimental results. The flow pattern transition locations and frequencies were measured and compared with the prediction correlations in the previous investigations.