A comparison between different optimization criteria for tuned mass dampers design

Tuned mass sampers (TMDs) are widely used strategies for vibration control in many engineering applications, so that many TMD optimization criteria have been proposed till now. However, they normally consider only TMD stiffness and damping as design variables and assume that the tuned mass is a pre-selected value. In this work a more complete approach is proposed and then also TMD mass ratio is optimized. A standard single degree of freedom system is investigated to evaluate TMD protection efficiency in case of excitation at the support. More precisely, this model is used to develop two different optimizations criteria which minimize the main system displacement or the inertial acceleration. Different environmental conditions described by various char- acterizations of the input, here modelled by a stationary filtered stochastic process, are considered. Results show that all solutions obtained considering also the mass of the TMD as design variable are more efficient if compared with those obtained without it. However, in many cases these solutions are inappropriate because the optimal TMD mass is greater than real admissible values in practical technical applications for civil and mechanical engineering. Anyway, one can deduce that there are some interesting indications for applications in some actual contexts. In fact, the results show that there are some ranges of environmental parameters ranges where results attained by the displacement criterion are compatible with real applications requiring some percent of main system mass. Finally, the present research gives promising indications for complete TMD optimization application in emerging technical contexts, as micro- mechanical devices and nano resonant beam

Eulerian and Lagrangian time scales of the turbulence above staggered arrays of cubical obstacles

We present results from water-channel experiments on neutrally-stable turbulent flows over staggered arrays of cubical obstacles modelling idealised urban canopies. Attention is concentrated on the vertical profiles of the Eulerian (TE) and Lagrangian (TL) time scales of the turbulence above three canopies with different plan area fractions (λP = 0.1, 0.25 and 0.4). The results show that both the streamwise and vertical components of TL increase approximately linearly with height above the obstacles, supporting Raupach’s linear law. The comparisons with the Lagrangian time scales over canyon-type canopies in the skimming flow and wake interference regimes show that the staggered configuration of cubical obstacles increases the streamwise TL, while decreasing its vertical counterpart. A good agreement has also been found between the eddy viscosities (KT) estimated by applying Taylor’s theory and the classical first order closure relating the momentum flux to the velocity gradient. The results show that KT obeys Prandtl’s theory, particularly for λP = 0.25 and 0.4

Transferencia de operación de manufactura de EE. UU. a México. Estudio de caso

Companies are continuously looking for resources and skills which lead them to a higher performance. Companies should manage not only the resource access, but a collaborative strategy as well, which maximizes the benefits of a healthy and constructive interaction expected between customer and provider. This paper analyzes the case of a company accustomed to operate with a traditional business model, and the paradigm shift that was necessary as a result of its exposure to the new customer’s requirements and demands for total openness, cooperation and transparency.Las empresas están permanentemente en búsqueda de recursos y capacidades que las habiliten hacia un nivel superior de desempeño. Es necesario que la empresa administre la estrategia colaborativa que maximice los beneficios de esa interacción sana y constructiva que se espera entre cliente y proveedor. En este documento se analiza el caso de una empresa acostumbrada a operar con un modelo de negocios tradicional, y el cambio de paradigma que fue necesario adoptar, como resultado de su exposición a los nuevos requerimientos y exigencias del cliente, que demanda apertura, colaboración, y transparencia

As formigas são atraídas por folhas herbivoradas de Caryocar brasiliense Camb. (Caryocaraceae)?

Different profiles of secondary compounds are released by plants after herbivore attack. Many of these compounds are used by predators and parasitoids to locate herbivores that are damaging leaves. Such an induced indirect defense was tested with the Caryocar brasiliense-ant system in the dry season, when C. brasiliense has old leaves, and in the rainy season, when C. brasiliense has new leaves. A total of 20 plants were analyzed per season. Two opposite leaves of the same branch were selected for each plant. Approximately 40% of the area of one leaf was removed (treatment leaf) while the other leaf remained intact (control). The number of ants that visited each leaf was counted simultaneously for a period of 15 minutes and the mean difference in ant number was tested by paired t-test. The mean number of ants differed significantly between treatment and control only in the rainy season (t = 3.004, df = 19, p = 0.007). This finding suggests the presence of induced defense in this system only when the leaves are young. The study supports the Optimal Defense Theory since young leaves of C. brasiliense with artificial damage attracted significantly more ants than leaves without damage and represents the first evidence of an induced defense mechanism in the C. brasiliense-ant system.Diferentes compostos químicos são liberados pelas plantas após o ataque dos herbívoros. Muitos desses compostos são usados por predadores e parasitoides para localizar os herbívoros que estão injuriando as plantas. Esse tipo de defesa induzida indireta foi testada no sistema Caryocar brasiliense e formigas em duas estações: seca (quando C. brasiliense está com folhas maduras) e chuvosa (quando C. brasiliense está com folhas jovens). Nós analisamos 20 plantas por estação do ano. Em cada planta nós selecionamos duas folhas opostas de um mesmo ramo. Nós removemos cerca de 40% da área de uma das folhas, deixando a outra folha intacta. Nós mensuramos simultaneamente o número de formigas que visitaram cada tipo de folha por 15 min e analisamos a diferença entre o número de formigas em cada tipo de folha através de teste t pareado. Nós observamos diferença significativa no número de formigas que patrulham as folhas tratamento (com herbivoria artificial) e controle (sem hervivoria artificial) apenas na estação chuvosa (t = 3,004, df = 19, p = 0,007). Isso sugere que existe defesa induzida nesse sistema somente quando as folhas são jovens. Nosso estudo corrobora a Teoria de Defesa Ótima já que apenas as folhas jovens de C. brasiliense com dano artificial atraíram significativamente mais formigas do que as folhas sem danos. Esta é a primeira vez que mecanismos de defesa induzida são observados no sistema C. brasiliense-formigas

A novel automatic method for the urban canyon parametrization needed by turbulence numerical simulations for wind energy potential assessment

The energy transition to more sustainable forms is currently ongoing worldwide, because of the environmental impacts produced by the non-renewable energy sources employed in the last decades. Among the main alternatives, wind plays a key role and, nowadays, innovative instruments, such as small-scale turbines allow for installation of wind turbines in urban areas. Their energy potential assessment requires high-accuracy simulations of the turbulent flows in the urban canopy layer, which, in turn, require detailed information about the geometrical properties of the basic element to classify urban surfaces, i.e., the urban canyon, often not available. In this work, we propose a novel automatic method, based on Voronoi graph, to univocally identify urban canyons and to extract their geometrical parameters from online available GIS (Geographic Information System) data, and test it on four European cities that differ in size, story and location. Results show the capability of the method to identify the single urban canyon and to properly extract its geometrical parameters, which tend to assume similar values for the largest cities. Moreover, we first attempt to propose and test some curves to generally describe the data probability distribution, which may be useful for turbulence simulations for urban wind energy assessment and planning. The best results are found for the canyon aspect ratio

A street graph-based morphometric characterization of two large urban areas

Urban microclimate modelling, both numerical and in the laboratory, has strong implications in many relevant health and life-style management issues e.g., in studies for assessment and forecast of air quality (for both outdoor and, as boundary conditions, indoor investigations), for thermometric trend analysis in urban zones, in cultural heritage preservation, etc. Moreover, the study of urban microclimate modelling is largely promoted and encouraged by international institutions for its implication in human health protection. In the present work, we propose and discuss an adaptive street graph-based method aimed at automatically computing the geometrical parameters adopted in atmospheric turbulent flow modelling. This method has been applied to two real cases, the Italian cities of Rome and Cagliari, and its results has been compared with the ones from traditional methods based on regular grids. Results show that the proposed method leads to a more accurate determination of the urban canyon parameters (Canyon Aspect Ratio and Building Aspect Ratio) and morphometric parameters (Planar Area Index and Frontal Area Index) compared to traditional regular grid-based methods, at least for the tested cases. Further investigations on a larger number of different urban contexts are planned to thoroughly test and validate the proposed algorithm

Surrogate-Assisted Artificial Immune Systems for Expensive Optimization Problems

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Novel tau filament fold in chronic traumatic encephalopathy encloses hydrophobic molecules

Chronic traumatic encephalopathy (CTE) is a neurodegenerative tauopathy that is associated with repetitive head impacts or exposure to blast waves. First described as punch-drunk syndrome and dementia pugilistica in retired boxers1-3, CTE has since been identified in former participants of other contact sports, ex-military personnel and after physical abuse4-7. No disease-modifying therapies currently exist, and diagnosis requires an autopsy. CTE is defined by an abundance of hyperphosphorylated tau protein in neurons, astrocytes and cell processes around blood vessels8,9. This, together with the accumulation of tau inclusions in cortical layers II and III, distinguishes CTE from Alzheimer's disease and other tauopathies10,11. However, the morphologies of tau filaments in CTE and the mechanisms by which brain trauma can lead to their formation are unknown. Here we determine the structures of tau filaments from the brains of three individuals with CTE at resolutions down to 2.3 Å, using cryo-electron microscopy. We show that filament structures are identical in the three cases but are distinct from those of Alzheimer's and Pick's diseases, and from those formed in vitro12-15. Similar to Alzheimer's disease12,14,16-18, all six brain tau isoforms assemble into filaments in CTE, and residues K274-R379 of three-repeat tau and S305-R379 of four-repeat tau form the ordered core of two identical C-shaped protofilaments. However, a different conformation of the β-helix region creates a hydrophobic cavity that is absent in tau filaments from the brains of patients with Alzheimer's disease. This cavity encloses an additional density that is not connected to tau, which suggests that the incorporation of cofactors may have a role in tau aggregation in CTE. Moreover, filaments in CTE have distinct protofilament interfaces to those of Alzheimer's disease. Our structures provide a unifying neuropathological criterion for CTE, and support the hypothesis that the formation and propagation of distinct conformers of assembled tau underlie different neurodegenerative diseases

Abnormal iron metabolism in fibroblasts from a patient with the neurodegenerative disease hereditary ferritinopathy

<p>Abstract</p> <p>Background</p> <p>Nucleotide duplications in exon 4 of the ferritin light polypeptide (FTL) gene cause the autosomal dominant neurodegenerative disease neuroferritinopathy or hereditary ferritinopathy (HF). Pathologic examination of patients with HF has shown abnormal ferritin and iron accumulation in neurons and glia in the central nervous system (CNS) as well as in cells of other organ systems, including skin fibroblasts. To gain some understanding on the molecular basis of HF, we characterized iron metabolism in primary cultures of human skin fibroblasts from an individual with the <it>FTL c.497_498dupTC </it>mutation.</p> <p>Results</p> <p>Compared to normal controls, HF fibroblasts showed abnormal iron metabolism consisting of increased levels of ferritin polypeptides, divalent metal transporter 1, basal iron content and reactive oxygen species, and decreased levels of transferrin receptor-1 and IRE-IRP binding activity.</p> <p>Conclusions</p> <p>Our data indicates that HF fibroblasts replicate the abnormal iron metabolism observed in the CNS of patients with HF. We propose that HF fibroblasts are a unique cellular model in which to study the role of abnormal iron metabolism in the pathogenesis of HF without artifacts derived from over-expression or lack of endogenous translational regulatory elements.</p