Search

Using the vortex-resolving RANS/ILES method, the flow in a paired model supersonic air intake (SAI) of mixed compression with a boundary layer (BL) bleed system is investigated. The influence of the type of BL bleed system and throttling of each of the SAI on the flow characteristics, the level and spectra of pressure pulsations in the neighboring SAIs is analyzed. Cases with the same and different throttling in each of the SAIs, as well as a common and individual bleed system for neighboring SAIs, are considered. A brief description of the calculation method and boundary conditions is given. The levels of OASPL in the SAI are presented depending on the degree of throttling. The influence of throttling of one of the SAIs on the flow and features of the 1/3-octave spectra of pressure pulsations in the neighboring SAI is revealed. [ABSTRACT FROM AUTHOR]

This paper examines how entrepreneurial opportunities co-evolve within a sustainable entrepreneurship ecosystem (SEE). Most of the literature on entrepreneurial ecosystems falls short on integrating the entrepreneurial process in empirical research. To analyze data collected from pre-start-up teams within a nascent SEE on high-tech cellulose-based materials over 3 years, we apply a design science approach that helps understand actors' collaborative sensemaking in designing and structuring ecosystem features and relationships. Our findings show that the SEE can be seen as a design artifact which evolves by ecosystem actors collectively engaging in new venture ideation and developing opportunity confidence. Furthermore, the paper presents a novel SEE framework, which elaborates on phases and enablers of the opportunity co-evolution process within an emerging ecosystem. We contribute to the literature on sustainable as well as general entrepreneurial ecosystems and offer a new theoretical foundation for a process view on ecosystems. [ABSTRACT FROM AUTHOR]

The Reynolds-averaged Navier–Stokes (RANS)/Implicit Large Eddy Simulation (ILES) method is applied to analyze the effect of variable heat capacity on the flow characteristics and pressure pulsation spectra for various operation modes of a model high-speed air intake. The dependence of the heat capacity on temperature is described by a fourth-degree polynomial. The calculation method and the technique for calculating the high-order heat capacity on the faces of the computational cells consistent with the technique for calculating flow parameters are briefly outlined. The calculations are performed under the incoming flow temperature corresponding to real flight conditions. [ABSTRACT FROM AUTHOR]

The paper is devoted to the RANS/ILES high-resolution method application for studying the influence of a nonuniformity of the inflow temperature field on the throttle characteristics of a supersonic mixed compression inlet, and the intensity and spectral characteristics of pressure pulsations in the inlet duct. Five cases of inflow parameters are investigated, three of which have a nonuniform temperature field. The sound pressure level distributions in the inlet duct and the pressure pulsation spectra at points on the inlet walls are obtained. [ABSTRACT FROM AUTHOR]

We address the problem of progressively deploying a set of robots to a formation defined as a point cloud, in a decentralized manner. To achieve this, we present an algorithm that transforms a given point cloud into an acyclic directed graph. This graph is used by the control law to allow a swarm of robots to progressively form the target shape based only on local decisions. This means that free robots (i.e., not yet part of the formation) find their location based on the perceived location of the robots already in the formation. We prove that for a 2D shape it is sufficient for a free robot to compute its distance from two robots in the formation to achieve this objective. We validate our method using physics-based simulations and robotic experiments, showing consistent convergence and minimal formation placement error. [ABSTRACT FROM AUTHOR]

“Buzz” during the period leading up to commercial release is commonly cited as a critical success factor for new products. But what exactly is buzz? Based on an extensive literature review and findings from a theories-in-use study (consumer depth interviews and focus groups), the authors argue that pre-release consumer buzz (PRCB) is not just a catchword or a synonym for “word of mouth” but is a distinct construct for which a precise, shared conceptual understanding is notably absent. The authors define PRCB as the aggregation of observable expressions of anticipation by consumers for a forthcoming new product; they conceptualize the construct as being manifested in three distinct types of behaviors (communication, search, and participation in experiential activities) along two dimensions (amount and pervasiveness). PRCB is unique because prior to, versus after, a product’s release, (1) differing information is available, (2) differing mental processes occur, and (3) consumers’ behaviors have differing effects on other consumers, affecting diffusion differently. A quantitative study using secondary data for 254 new products illustrates the performance of the theory-based conceptualization. [ABSTRACT FROM AUTHOR]

The impact of HIV and its treatment on the effects of alcohol remain unclear. Blood alcohol concentrations have been noted to be higher in HIV infected individuals prior to antiretroviral initiation. Our goal was to compare number of drinks to “feel a buzz or high” among HIV infected and uninfected men, stratified by viral load (VL) suppression. Data includes 1478 HIV infected and 1170 uninfected men in the veterans aging cohort study who endorsed current drinking. Mean (SD) number of drinks to feel a buzz was 3.1 (1.7) overall. In multivariable analyses, HIV infected men reported a lower mean number of drinks to feel a buzz compared to uninfected men (coef = −14 for VL < 500; −34 for VL ≥ 500; p ≤ .05). Men with HIV, especially those with a detectable VL, reported fewer drinks to feel a buzz. Future research on the relationship between alcohol and HIV should consider the role of VL suppression. [ABSTRACT FROM AUTHOR]

Turbulent flow in a mixed compression intake is investigated. The unsteady compressible Navier-Stokes equations are solved using a stabilized finite element method with 6-noded triangular element. The Spalart-Allmaras model is used for turbulence closure. For comparison, the laminar flow is studied as well. A bleed of 6 % is utilized to overcome the start-up problem of the intake. The effect of back pressure on the performance of the intake is studied via the total pressure recovery and distortion index. Total pressure recovery is relatively lower while distortion index is higher for turbulent flow compared to laminar flow. The critical back pressure ratio, for unstart of the intake, for turbulent flow is higher compared to laminar flow. The effect of bleed on the performance of the intake is studied. [ABSTRACT FROM AUTHOR]

An extensive wind tunnel tests were conducted on an axisymmetric supersonic inlet at Mach numbers from 1.8 to 2.2 and at different values of mass flow rates. Frequencies of the buzz were achieved from the pressure data as well as the high speed shadowgraph pictures. For each Mach number, two main frequencies for the buzz were obtained. The inlet at its design condition was stable, but when the mass flow rate was reduced, at first the shock wave started to oscillate with a small amplitude which is matched the Ferri criterion (little buzz). In this situation, both high- and low-frequency oscillations occurred; however, the high frequency one was dominant, but the oscillations seemed to be irregular. By further decreasing the inlet mass flow, the shock oscillations got a single low frequency and high amplitude, which in agreement with the Dailey criterion (big buzz). At a free stream Mach number of 2.2, the frequencies of these two kinds of instabilities are about 554 and 137 Hz, respectively. At this Mach number for moderate mass flow, an oscillation with high frequency/large amplitude and constant period was observed. The oscillation has the combined characteristics of the little buzz and the big buzz, which is named 'added buzz' here. It is shown that at fairly constant mass flow, the frequency of the buzz is independent of the Mach number. It is further found that the buzz instability affects the external flow as well as the internal one with the same frequency. [ABSTRACT FROM AUTHOR]

The approach phase of landing vespertilionid bats ends with a group of calls, which either consists of buzz I alone or buzz I and buzz II. To understand the possible role of buzz II, we trained Myotis myotis to land on a vertical grid, and compared the flight and echolocation behavior during approach in trials with and without buzz II. During the approach, we did not find any differences in the echolocation behavior until the end of buzz I which indicated whether buzz II was emitted or not. However, bats flying from the periphery of the flight channel, such that they had to make a small turn at the very last moment, finished the sequence with a buzz II. Bats flying on a rather stereotyped trajectory near the center of the flight channel without last instant corrections emitted buzz I alone. Our results indicate that buzz II occurred only on trajectories that implied a higher risk to fail at landing. The information delivered by buzz II reaches the bat too late to be used for landing. Therefore, we hypothesize that buzz II may help the bats to evaluate unsuccessful attempts and to eventually react adequately. [ABSTRACT FROM AUTHOR]