"Ladder" structure in tonal noise generated by laminar flow around an airfoil

The presence of a “ladder” structure in the airfoil tonal noise was discovered in the 1970s, but its mechanism hitherto remains a subject of continual investigation in the research community. Based on the measured noise results and some numerical analysis presented in this letter, the variations of four types of airfoil tonal noise frequencies with the flow velocity were analyzed individually. The ladder structure is proposed to be caused by the acoustic/hydrodynamic frequency lag between the scattering of the boundary layer instability noise and the discrete noise produced by an aeroacoustic feedback loop

Modular assembly with postponement to improve health, safety & productivity in construction

This paper presents the outcome of an engineering study as part of the design and development of a lean and agile construction system and in particular its supply chain component. This combines modular assembly with a postponement function to be tested on a case study project (not reported here), the objective of which is to improve health, safety and productivity for the company sponsoring the research. The contribution to research is the combination of countermeasures described in this paper that have been developed and incorporated into a wider construction system, in the same way that manufacturing has used this strategy with great success. Also, a further output is the development and use of an innovative method for assembling, transporting and installing mechanical and electrical modules, whereby modularization can be achieved with or without offsite manufacturing capability. The research forecasts a reduction of onsite labor of 35% compared to using traditional methods of construction, with less onsite operatives at risk of injury carrying out simpler assembly tasks within ergonomic mobile work cells. Further research is proposed to measure the benefits of the construction system following its implementation on a case study project

On the birational section conjecture with local conditions

A birationally liftable Galois section s of a hyperbolic curve X/k over a number field k yields an adelic point x(s) in the smooth completion of X. We show that x(s) is X-integral outside a set of places of Dirichlet density 0, or s is cuspidal. The proof relies on $GL_2(F_\ell)$-quotients of $\pi_1(U)$ for some open U of X. If k is totally real or imaginary quadratic, we prove that all birationally adelic, non-cuspidal Galois sections come from rational points as predicted by the section conjecture of anabelian geometry. As an aside we also obtain a strong approximation result for rational points on hyperbolic curves over Q or imaginary quadratic fields.Comment: Theorem C (and Section 7) of the original version have been deleted due to a gap in the proof. This is the journal versio

Numerical modelling of heat generated by electroosmotic flows in micro-channels

This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications.In this paper, numerical modeling of Joule heating in electroosmotic flows is described in some detail. The finite element method is used for the spatial discretization along with the characteristic based split (CBS) time discretization. A new non-dimensional scaling is also introduced. In addition to standard problems of micro channel flows, flow and heat generation in a T-mixer are also discussed in this paper

Poro-Serrated trailing edge devices for airfoil self-noise reduction

This paper represents the continuation of the works previously published in Chong et al. (“Self-Noise Produced by an Airfoil with Nonflat Plate Trailing-Edge Serrations,” AIAA Journal, Vol. 51, No. 11, 2013, pp. 2665–2677), who used several nonflat plate serrated trailing edges for the reduction of airfoil self-noise. The poro-serrated concept developed in the current work improves substantially the overall noise performance of the nonflat plate trailing-edge serration type. The use of porous metal, synthetic foams, or thin brush bundles to fill the gaps between adjacent members of the sawtooth can completely suppress the bluntness-induced vortex shedding tonal noise. Most important, up to 7 dB turbulent boundary layer–trailing-edge broadband noise reduction can simultaneously be achieved without compromising the aerodynamic performances in lift and drag. The poro-serrated trailing edges do not cause any noise increase throughout the frequency range investigated here. The reduction of the turbulent broadband noise is primarily caused by the serration effect, but under a condition that the sawtooth surface must be solid and nonporous. The primary role of the porous metal foams in a poro-serrated trailing edge is to suppress the vortex shedding tonal noise. However, an optimum selection of the porous material is also found to be able to further reduce the broadband noise level. The new serrated trailing-edge concept developed here has the potential to improve the industrial worthiness of the serration technology in achieving low noise radiation in fan and turbine blades.The EPSRC Doctoral Training Grants in the United Kingdo

Asymptotic boundary forms for tight Gabor frames and lattice localization domains

We consider Gabor localization operators $G_{\phi,\Omega}$ defined by two parameters, the generating function $\phi$ of a tight Gabor frame $\{\phi_\lambda\}_{\lambda \in \Lambda}$, parametrized by the elements of a given lattice $\Lambda \subset \Bbb{R}^2$, i.e. a discrete cocompact subgroup of $\Bbb{R}^2$, and a lattice localization domain $\Omega \subset \Bbb{R}^2$ with its boundary consisting of line segments connecting points of $\Lambda$. We find an explicit formula for the boundary form $BF(\phi,\Omega)=\text{A}_\Lambda \lim_{R\rightarrow \infty}\frac{PF(G_{\phi,R\Omega})}{R}$, the normalized limit of the projection functional $PF(G_{\phi,\Omega})=\sum_{i=0}^{\infty}\lambda_i(G_{\phi,\Omega})(1-\lambda_i(G_{\phi,\Omega}))$, where $\lambda_i(G_{\phi,\Omega})$ are the eigenvalues of the localization operators $G_{\phi,\Omega}$ applied to dilated domains $R\Omega$, $R$ is an integer and $\text{A}_\Lambda$ is the area of the fundamental domain of the lattice $\Lambda$.Comment: 35 page

Application of EFT at Thermal Energies

We have been evaluated some observables of n-d systems by using pionless Effective Field Theory(\EFTNoPion) and insertion of the three-body force up to next-to-next to leading order(N$^2$LO). The evaluated data has been compared with experimental and the three-nucleon calculation of the total cross section with modern realistic two- and three-nucleon forces AV18/UrbIX potential models calculations.Comment: 3 pages, 1 figure and 1 table. Talk given at 20th European Conference on Few-Body Problems in Physics (EFB 20), Pisa, Italy, 10-14 Sep 200

The Benefits of Peer Review and a Multisemester Capstone Writing Series on Inquiry and Analysis Skills in an Undergraduate Thesis.

This study examines the relationship between the introduction of a four-course writing-intensive capstone series and improvement in inquiry and analysis skills of biology senior undergraduates. To measure the impact of the multicourse write-to-learn and peer-review pedagogy on student performance, we used a modified Valid Assessment of Learning in Undergraduate Education rubric for Inquiry and Analysis and Written Communication to score senior research theses from 2006 to 2008 (pretreatment) and 2009 to 2013 (intervention). A Fisher-Freeman-Halton test and a two-sample Student's t test were used to evaluate individual rubric dimensions and composite rubric scores, respectively, and a randomized complete block design analysis of variance was carried out on composite scores to examine the impact of the intervention across ethnicity, legacy (e.g., first-generation status), and research laboratory. The results show an increase in student performance in rubric scoring categories most closely associated with science literacy and critical-thinking skills, in addition to gains in students' writing abilities