Nonlinear aeroelasticity of rotating and flapping wings - a review

The interaction between large deflections, rotation effects and unsteady aerodynamics makes the dynamic analysis of rotating and flapping wing a nonlinear aeroelastic problem. This problem is governed by nonlinear periodic partial differential equations whose solution is needed to calculate the response and loads acting on vehicles using rotary or flapping wings for lift generation. We look at three important problems in this paper. The first problem shows the effect of nonlinear phenomenon coming from piezoelectric actuators used for helicopter vibration control. The second problem looks at the propagation on material uncertainty on the nonlinear response, vibration and aeroelastic stability of a composite helicopter rotor. The third problem considers the use of piezoelectric actuators for generating large motions in a dragonfly inspired flapping wing. These problems provide interesting insights into nonlinear aeroelasticity and show the likelihood of surprising phenomenon which needs to be considered during the design of rotary and flapping wing vehicle

Nonlinear vibration analysis of composite laminated and sandwich plates with random material properties

Nonlinear vibration analysis is performed using a C-0 assumed strain interpolated finite element plate model based on Reddy's third order theory. An earlier model is modified to include the effect of transverse shear variation along the plate thickness and Von-Karman nonlinear strain terms. Monte Carlo Simulation with Latin Hypercube Sampling technique is used to obtain the variance of linear and nonlinear natural frequencies of the plate due to randomness in its material properties. Numerical results are obtained for composite plates with different aspect ratio, stacking sequence and oscillation amplitude ratio. The numerical results are validated with the available literature. It is found that the nonlinear frequencies show increasing non-Gaussian probability density function with increasing amplitude of vibration and show dual peaks at high amplitude ratios. This chaotic nature of the dispersion of nonlinear eigenvalues is also r

Structures of apo and GTP-bound molybdenum cofactor biosynthesis protein MoaC from Thermus thermophilus HB8

The first step in the molybdenum cofactor (Moco) biosynthesis pathway involves the conversion of guanosine triphosphate (GTP) to precursor Z by two proteins (MoaA and MoaC). MoaA belongs to the S-adenosylmethioninedependent radical enzyme superfamily and is believed to generate protein and/or substrate radicals by reductive cleavage of S-adenosylmethionine using an Fe-S cluster. MoaC has been suggested to catalyze the release of pyrophosphate and the formation of the cyclic phosphate of precursor Z. However, structural evidence showing the binding of a substrate-like molecule to MoaC is not available. Here, apo and GTP-bound crystal structures of MoaC from Thermus thermophilus HB8 are reported. Furthermore, isothermal titration calorimetry experiments have been carried out in order to obtain thermodynamic parameters for the protein-ligand interactions. In addition, molecular-dynamics (MD) simulations have been carried out on the protein-ligand complex of known structure and on models of relevant complexes for which X-ray structures are not available. The biophysical, structural and MD results reveal the residues that are involved in substrate binding and help in speculating upon a possible mechanism.

Ways of Explaining Workplace Bullying: A Review of Enabling, Motivating, and Precipitating Structures and Processes in the Work Environment

This paper summarizes literature explaining workplace bullying and focuses on organisational antecedents of bullying. In order to better understand the logic behind bullying, a model discussing different types of explanations is put forward. Thus, explanations for and factors associated with bullying are classified into three groups, i.e. enabling structures or necessary antecedents (e.g. perceived power imbalances, low perceived costs, and dissatisfaction and frustration), motivating structures or incentives (e.g. internal competition, reward systems, and expected benefits), and precipitating processes or triggering circumstances (e.g. downsizing and restructuring, organisational changes, changes in the composition of the workgroup). The paper concludes that bullying is often an interaction between structures and processes from all three groupings.

Excited-state structures of molecules with nearby electronic states

Vibronic coupling among the nearby excited electronic states via the in-plane and the out-of-plane nuclear motions is examined in benzene, pyrazine, formaldehyde and thioformaldehyde. Results reveal that in benzene the structure distorts via the most active nuclear bending (planar) motion while in the other molecules the structures distort through an out-of-plane bending motion in their respective lowest excited states.

Response of nonlinear systems to narrow-band excitation

The hardening cubic spring oscillator is studied under narrow-band gaussian excitation. Equivalent linearization leads to multiple steady states. The realizability of the solution is discussed through stochastic stability analysis. Theoretical results are supported by numerical simulation.

Electronic structures of electron donor-acceptor complexes: results from ultraviolet photoelectron spectroscopy and molecular orbital calculations

HeI photoelectron spectra of 1:1 electron donor-acceptor complexes are discussed in the light of molecular orbital calculations. The complexes discussed include those formed by BH3, BF3 and SO2. Some systematics have been found in the ionization energy shifts of the complexes compared to the free components and these are related to the strength of the donor-acceptor bond. Hel spectra of hydrogen bonded complexes are discussed in comparison with results from MO calculations. Limitations of such studies as well as scope for further investigations are indicated.

Performance analysis of a suprathreshold, stochastic resonance based nonlinear detector

In this paper we introduce a nonlinear detector based on the phenomenon of suprathreshold stochastic resonance (SSR). We first present a model (an array of 1-bit quantizers) that demonstrates the SSR phenomenon. We then use this as a pre-processor to the conventional matched filter. We employ the Neyman-Pearson(NP) detection strategy and compare the performances of the matched filter, the SSR-based detector and the optimal detector. Although the proposed detector is non-optimal, for non-Gaussian noises with heavy tails (leptokurtic) it shows better performance than the matched filter. In situations where the noise is known to be leptokurtic without the availability of the exact knowledge of its distribution, the proposed detector turns out to be a better choice than the matched filter.

An Empirical Comparison of Linear and Nonlinear Volatility Models for Nordic Stock Returns

This paper examines how volatility in financial markets can preferable be modeled. The examination investigates how good the models for the volatility, both linear and nonlinear, are in absorbing skewness and kurtosis. The examination is done on the Nordic stock markets, including Finland, Sweden, Norway and Denmark. Different linear and nonlinear models are applied, and the results indicates that a linear model can almost always be used for modeling the series under investigation, even though nonlinear models performs slightly better in some cases. These results indicate that the markets under study are exposed to asymmetric patterns only to a certain degree. Negative shocks generally have a more prominent effect on the markets, but these effects are not really strong. However, in terms of absorbing skewness and kurtosis, nonlinear models outperform linear ones.

Effective treatment of infectious diseases: A nonlinear adaptive control theoretic approach

A nonlinear adaptive system theoretic approach is presented in this paper for effective treatment of infectious diseases that affect various organs of the human body. The generic model used does not represent any specific disease. However, it mimics the generic immunological dynamics of the human body under pathological attack, including the response to external drugs. From a system theoretic point of view, drugs can be interpreted as control inputs. Assuming a set of nominal parameters in the mathematical model, first a nonlinear controller is designed based on the principle of dynamic inversion. This treatment strategy was found to be effective in completely curing "nominal patients". However, in some cases it is ineffective in curing "realistic patients". This leads to serious (sometimes fatal) damage to the affected organ. To make the drug dosage design more effective, a model-following neuro-adaptive control design is carried out using neural networks, which are trained (adapted) online. From simulation studies, this adaptive controller is found to be effective in killing the invading microbes and healing the damaged organ even in the presence of parameter uncertainties and continuing pathogen attack.

HARMONY: a server for the assessment of protein structures

Protein structure validation is an important step in computational modeling and structure determination. Stereochemical assessment of protein structures examine internal parameters such as bond lengths and Ramachandran (phi, psi) angles. Gross structure prediction methods such as inverse folding procedure and structure determination especially at low resolution can sometimes give rise to models that are incorrect due to assignment of misfolds or mistracing of electron density maps. Such errors are not reflected as strain in internal parameters. HARMONY is a procedure that examines the compatibility between the sequence and the structure of a protein by assigning scores to individual residues and their amino acid exchange patterns after considering their local environments. Local environments are described by the backbone conformation, solvent accessibility and hydrogen bonding patterns. We are now providing HARMONY through a web server such that users can submit their protein structure files and, if required, the alignment of homologous sequences. Scores are mapped on the structure for subsequent examination that is useful to also recognize regions of possible local errors in protein structures. HARMONY server is located at http://caps.ncbs.res.in/harmony/

Crystal structures and photocatalysis of the triclinic polymorphs of BiNbO4 and BiTaO4

The high-temperature polymorphs of two photocatalytic materials, BiNbO4 and BiTaO4 were synthesized by the ceramic method. The crystal structures of these materials were determined by single-crystal X-ray diffraction. BiNbO4 and BiTaO4 crystallize into the triclinic system P (1) over bar (No. 2), with a = 5.5376(4) angstrom, b = 7.6184(3) angstrom, c = 7.9324(36) angstrom, alpha = 102.565(3)degrees, beta = 90.143(2)degrees, gamma = 92.788 (4)degrees, V = 326.21 (5) angstrom(3). Z = 4 and a = 5.931(1) angstrom, b = 7.672(2) angstrom, c = 7.786(2) angstrom, alpha = 102.94 (3)degrees, beta = 90.04(3)degrees gamma = 93.53(3)degrees, V = 344.59(1) angstrom(3) and Z = 4, respectively. The structures along the c-axis, consist of layers of [Bi2O2] units separated by puckered sheets of (Nb/Ta)O-6 octahedra. Photocatalytic studies on the degradation of dyes indicate selectivity of BiNbO4 towards aromatics containing quinonic and azo functional groups

Topology design of three-dimensional structures using hybrid finite elements

Conventional three-dimensional isoparametric elements are susceptible to problems of locking when used to model plate/shell geometries or when the meshes are distorted etc. Hybrid elements that are based on a two-field variational formulation are immune to most of these problems, and hence can be used to efficiently model both "chunky" three-dimensional and plate/shell type structures. Thus, only one type of element can be used to model "all" types of structures, and also allows us to use a standard dual algorithm for carrying out the topology optimization of the structure. We also address the issue of manufacturability of the designs.

Managers Talk about Gender: What Managers in Large Transnational Corporations Say about Gender Policies, Structures and Practices

Mainstream research on management generally continues to ignore gender relations. Even so, over recent years there has been a major growth of international research on gender relations in organizations. Yet, most of this has focused on gender relations in lower or middle levels rather than at the apex of the organization. This book draws on research on gender policies, structures and practices of management in large Finnish corporations. It builds on earlier survey work of gender policies in the 100 largest corporations in Finland, to examine, through qualitative interviews, more detailed gendered processes in seven selected corporations. These represent corporations that are ‘relatively active’, ‘moderately active’, and ‘not active’ in relation to gender equality. Key issues include contrasts between formal policies and organizational practices; different corporate contexts and individual managers’ views; definition and scope of gender policy; and the relation of gender policies and diversity policy. This focus on gender policies is understood and located within organizational structures, most obviously gendered corporate hierarchies. Important structures include national context in relation to transnationalization, relations of headquarters and subsidiaries, and interrelations of management, policy development and policy implementation. Gender relations in practice and gender practices are considered in more detail. These women and men managers operate at the intersections of gendered transnational managerial work, careers and family-type relations, including marriage and children, or lack thereof. Women and men managers may be part of the same management levels or management teams, but have totally different family-type situations and gendered experiences. Interconnections of management, domestic life and transnationalizations are intensely gendered matters. The debate on the public/private continues to be important for both gender relations and organizational relations, but complicated through transnationalizations. The modern transnational corporation is considered in terms of gender divisions and gender power, with particular reference to top management. The concluding discussion notes implications for research and policy.