Dynamics, bifurcations and chaos in coupled lasers

Experiments and numerical modelling on two different class B lasers that are subjected to external optical light injection are presented. This presentation includes ways of measuring the changes in the laser output, how to numerically describe the systems and how to construct diagrams of the dynamical states in the plane frequency detuning between lasers and injection strength. The scenarios for the semiconductor laser include an area of frequency locking and islands of chaotic behaviour embedded in and mixed with periodic doubling regimes. Using a rate equation model, the largest Lyapunov exponent is calculated as a measure of the stability of equilibriums and the amount of chaos in chaotic regimes. In the solid-state laser case, different dynamical regions were clearly observed. The found boundaries were identified experimentally, using an identification method, and numerically, from bifurcation analysis, as Hopf, saddle-node, period-doubling and torus bifurcations.     

Scalability of a Metropolitan Bidirectional Multifiber WDM-Ring Network

We analyze the scalability of a metropolitan bidirectional multifiber wavelength-division-multiplexed (WDM) ring network. The analysis is carried out by using a bidirectional transmission model for optical networks and by building an experimental network. The model includes major limiting factors in WDM-ring networks such as relative intensity noise (RIN) due to multiple Rayleigh backscattering, amplified spontaneous emission (ASE) accumulation in a cascade of bidirectional erbium-doped fiber amplifiers (EDFA), tilting of the EDFA gain spectrum and input saturation power of the EDFA. We found that in metropolitan areas the scalability of a WDM-ring network using bidirectional transmission is not mainly limited by the RIN arising from the Rayleigh backscattering. The result was verified experimentally. The maximum size of the demonstrated network is 33–43 nodes with a spacing of 5–10 km between nodes. With this spacing, which is typical in metropolitan areas, the scalability of the network is mainly limited by the gain tilt and the input saturation power of the EDFA.     

POD analysis of oscillating grid turbulence in water and shear thinning polymer solution

Oscillating grids are frequently used with water and Newtonian fluids to generate controlled turbulence and mixing. Yet, their use with shear thinning fluids still requires experimental characterization. Proper orthogonal decomposition (POD) is applied to PIV measurements of the flow generated by an oscillating grid in water and a shear thinning dilute polymer solution (DPS) of xanthan gum. The aims are to investigate the ability of POD to isolate periodic flow structures, and to use it to describe the effects of the shear thinning property. A dominance of the low order POD modes is evidenced in DPS. The methods applied in blade stirred tanks to identify oscillatory motion fail here. However, a strong mode coupling in the grid swept region is observed, determined by the working fluid and by an underlying chaotic nature of the flow. Possibilities of reconstructing turbulence properties using high order modes are discussed.     

Fan pressure-based testing,adjusting, and balancing of a ventilation system

Ventilation systems are responsible for the thermal comfort and air quality of indoor spaces. The adjustment of ventilation systems is a time-consuming task that may need multiple iterations. Incorrect adjustments of a ventilation system can reduce the quality of working and living conditions and degrade the energy efficiency of the ventilation. In this paper, a testing, adjusting, and balancing method for a ventilation system is presented that uses only the knowledge of the fan total flow rate and pressure. The method does not need additional instrumentation for the ventilation adjustment as the fan operating point can be estimated with the variable-speed drive. The method is noniterative, thereby saving time, and the ventilation system is adjusted to its minimum energy consumption setting without compromise in system operation. The proposed method is assessed with a laboratory test setup to verify the correct operation of the method in practice.     

A new class of algorithms for classical plasticity extended to finite strains. Application to geomaterials

A recently proposed methodology for computational plasticity at finite strains is re-examined within the context of geomechanical applications and cast in the general format of multi-surface plasticity. This approach provides an extension to finite strains of any infinitesimal model of classical plasticity that retains both the form of the yield criterion and the hyperelastic character of the stress-strain relations. Remarkably, the actual algorithmic implementation reduces to a reformulation of the standard return maps in principal axis with algorithmic elastoplastic moduli identical to those of the infinitesimal theory. New results in the area of geomechanics included a fully implicit return map for the modified Cam-Clay model, extended here to the finite deformation regime, and a new semi-explicit scheme that restores symmetry of the algorithmic moduli while retaining the unconditional stability property. In addition, a new phenomenological plasticity model for soils is presented which includes a number of widely used models as special cases. The general applicability of the proposed methodology is illustrated in several geomechanical examples that exhibit localization and finite deformations.Partial support provided by the Max Kade Foundation under Grant No. 2-DJA-616 and with Stanford University, and the Naval Civil Engineering Laboratory at Port Huaneme     

Paediatric pyogenic granuloma presenting as a unilateral nasal polyp

The 42/43-residue amyloid beta-peptide (Abeta) is widely believed to play a major role in Alzheimer's disease. The present study shows that the rat brain contains a carboxypeptidase that efficiently deletes three amino acids from Abeta1-43. The carboxypeptidase activity in the brain was completely inhibited by 1 mM phenylmethylsulfonyl fluoride, suggesting the protease is a serine carboxypeptidase. The carboxy-terminal truncation of Abeta1-43 was moderately inhibited by carbobenzoxy-Leu-leucinal, carbobenzoxy-Leu-Leu-leucinal, and carbobenzoxy-Leu-Leu-norvalinal, and weakly by antipain. The present data suggest that the serine carboxypeptidase contributes to the generation of short-tailed Abeta peptides and is important in the intracellular clearance of Abeta1-42/43 in brains.     

Acidity reduction in northern region berry juices by the malolactic bacterium Oenococcus oeni

Acidity of juices from northern berries was reduced by inoculating with a malolactic microorganism, Oenococcus oeni. The berries were white and black currant, bilberry, lingonberry, and, for comparison, an apple cultivar. Malic acid was first converted to lactic acid in all fermentations, while soluble sugars and citric acid remained unattacked. Upon exhaustion of malic acid, sugar and citric acid degradations were initiated simultaneously. Sequential utilization of substrates by O. oeni offers a basis for multitude compositional changes in acidic juices. Elimination of malic acid alone led to a noticeable reduction of acidic taste in these berry juices.     

考虑异方差效应的风电不确定性建模及其在调度中的应用

随着风电在电力系统中渗透率的不断提升,其不确定性为电网的安全经济运行带来了重大挑战。为获得精准的风电不确定性模型,帮助运行人员实现系统的安全经济运行,文中提出了考虑异方差效应的风电预测误差条件概率分布建模方法。首先,分析了风电预测误差与各类因素的相依性水平,并基于分析结果与动态Copula理论,建立了风电波动性与风电预测误差的动态相依性模型;之后,针对边缘分布所显示出的时域特征,结合差分整合移动平均自回归(ARIMA)模型与广义自回归条件异方差(GARCH)模型,考虑异方差效应,建立了时变边缘分布模型;最后,将两模型相结合,给出了不同波动水平下的风电条件预测误差分布情况,并在不确定性机组组合模型中进行验证,证明了模型的有效性。