Convergence acceleration of continuous adjoint solvers using a reduced‐order model

A novel acceleration technique using a reduced‐order model is presented to speed up convergence of continuous adjoint solvers. The acceleration is achieved by projecting to an improved solution within an iterative process solely using early solution results. This is achieved by forming basis vectors from early iteration adjoint solutions to perform model order reduction of the adjoint equations. The reduced‐order model of the adjoint equations is then substituted into the full‐order discretized governing equations to determine weighting coefficients for each basis vector. With these coefficients, a linear combination of the basis vectors is used to project to an improved solution. The method is applied to 3 inviscid quasi‐1D nozzle flow cases including fully subsonic flow, subsonic inlet to supersonic outlet flow, and transonic flow with a shock. Significant cost reductions are achieved for a single application as well as repeated applications of the convergence acceleration technique.     

Identification of biologically active PDE11-selective inhibitors using a yeast-based high-throughput screen

The biological roles of cyclic nucleotide phosphodiesterase 11 (PDE11) enzymes are poorly understood, in part due to the lack of selective inhibitors. To address the need for such compounds, we completed an ~200,000 compound high-throughput screen (HTS) for PDE11 inhibitors using a yeast-based growth assay, and identified 4 potent and selective PDE11 inhibitors. One compound, along with two structural analogs, elevates cAMP and cortisol levels in human adrenocortical cells, consistent with gene association studies that link PDE11 activity to adrenal function. As such, these compounds can immediately serve as chemical tools to study PDE11 function in cell culture, and as leads to develop therapeutics for the treatment of adrenal insufficiencies. Our results further validate this yeast-based HTS platform for the discovery of potent, selective, and biologically active PDE inhibitors.     

Speech intelligibility of English,Polish, Arabic and Mandarin under different room acoustic conditions

This paper examines the impact of room acoustic conditions on the speech intelligibility of four languages (English, Polish, Arabic and Mandarin). Listening test scores (diagnostic rhyme tests, phonemically balanced word tests and phonemically balanced sentence tests) of the four languages were compared under four room acoustic conditions defined by their speech transmission index (STI = 0.2, 0.4, 0.6 and 0.8). The results obtained indicated that there was a statistically significant difference between the word intelligibility scores of languages under all room acoustic conditions, apart from the STI = 0.8 condition. English was the most intelligible language under all conditions, and differences with other languages were larger when conditions were poor (maximum difference of 29% at STI = 0.2, 33% at STI = 0.4 and 14% at STI = 0.6). Results also showed that Arabic and Polish were particularly sensitive to background noise, and that Mandarin was significantly more intelligible than those languages at STI = 0.4. Consonant-to-vowel ratios and languages’ distinctive features and acoustical properties explained some of the scores obtained. Sentence intelligibility scores confirmed variations between languages, but these variations were statistically significant only at the STI = 0.4 condition (sentence tests being less sensitive to very good and very poor room acoustic conditions). Overall, the results indicate that large variations between the speech intelligibility of different languages can occur, especially for spaces that are expected to be challenging in terms of room acoustic conditions. Recommendations solely based on room acoustic parameters (e.g. STI) might then prove to be insufficient for designing a multilingual environment.     

Synthesis, photochemical, and electrochemical properties of naphthalene-1,4,5,8-tetracarboxylic acid-bis-(N,N′-bis-(2,2,4(2,4,4)-trimethylhexylpolyimide)) and poly(N,N′-bis-(2,2,4(2,4,4)-trimethyl-6-aminohexyl) 3,4,9,10-perylenetetracarboxdiimide)

Two new soluble polymers (naphthalene containing: TH-NPI, perylene containing: TH-PPI) have been synthesized via incorporation of branched chain substituent unit into their backbones. Because of existence of branched alkyl spacer, the polymers showed good solubility in common solvents such as chloroform without sacrificing their stability and caused a red shifted excimer-like emission. Their monomers (TH-NDI and TH-PDI) have been synthesized for comparison. The compounds are characterized by UV-vis, IR, MS, DSC, TGA, CV, GPC and viscosity measurements. Polymers TH-NPI and TH-PPI with inherent viscosities of 0.50 and 0.30 dL/g were obtained corresponding to their molecular weights 40,000 and 17,000 respectively. Thermogravimetric analysis (TGA) showed that TH-NDI, TH-NPI, TH-PDI and TH-PPI are thermally stable up to 380, 445, 512 and 515 °C respectively. The LUMO energy levels of these compounds are calculated as −3.66, −3.71, −3.62 and −3.61 eV respectively. The red-shifted (TH-NPI: 400-650 nm, TH-PPI: 535-800) excimer-like fluorescence in chloroform is attributed to the formation of ground state complexes probably due to intermolecular and intramolecular π-stackings of the polymers in solution. The fluorescence lifetimes, quantum yields and singlet-state energies are presented.     

Resolution of Gibbs phenomenon using a modified pseudo-spectral operator in harmonic balance CFD solvers*

A new pseudo-spectral operator is developed for time-spectral harmonic balance solutions of periodic unsteady flows. The method utilises a mechanism similar to sigma-approximation technique with Lanczos filtering function that alters the inverse of the discrete Fourier transformation matrix, leading to a modified pseudo-spectral operator. The modified operator is then used instead of the original operator that mimics the time-derivative term of the unsteady governing equations. The modified operator is capable of damping high-frequency nonlinearities in the harmonic balance solution, thus alleviating the effects of high-frequency oscillations that result in Gibbs-type phenomena. The effectiveness and robustness of the technique are demonstrated through various test cases.