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The surface topography of engineering rough surfaces has an enormous influence on contact mechanics of the interface and further the dynamics of the contact system. In this paper, the force-deflection characteristic and the nonlinear vibration of a rough surface interacting with a rigid flat surface are studied. A three-dimensional rough surface is constructed using a modified two-variable Weierstrass–Mandelbrot fractal function and the force-deflection is determined to be a positive power-law function. The power has the values larger than unity and increases with a rougher surface topography. Approximation of the force-deflection characteristic is also presented. Accordingly, the natural frequency is determined both exactly and approximately from the numerical calculation of the natural period and using the multiple scales method on the approximate equation, respectively. The primary resonance responses under harmonic excitation are also determined as well as the jump-up and jump-down responses. The nonlinear contact stiffness characteristics and the effect on natural frequency and the frequency responses are illustrated for different rough surface topographies. It is shown that the variation of natural frequency with amplitude and the multi-valued region of frequency responses increase with a rougher surface topography; however, the jump-up and jump-down frequencies both decrease, as well as the peak amplitude.

PE and PPE are two large families of proteins typical of mycobacteria whose structural genes in the Mycobacterium tuberculosis complex (MTBC) occupy about 7% of the total genome. The most ancestral PE and PPE proteins are expressed by genes that belong to the same operon and in most cases are found inserted in the esx clusters, encoding a type VII secretion system. Duplication and expansion of pe and ppe genes, coupled with intragenomic and intergenomic recombination events, led to the emergence of the polymorphic pe_pgrs and ppe_mptr genes in the MTBC genome. The role and function of these proteins, and particularly of the polymorphic subfamilies, remains elusive, although it is widely accepted that PE and PPE proteins may represent a specialized collection used by MTBC to interact with the complex host immune system of mammals. In this chapter, we summarize what has been discovered since the identification of these genes in 1998, focusing on M. tuberculosis genetic variability, host-pathogen interaction and TB pathogenesis.

Jeffrey A Gudin,1 Michael J Brennan,2 E Dennis Harris,3 Peter L Hurwitz,3 Derek T Dietze,4 James D Strader5 1Pain Medicine and Palliative Care, Englewood Hospital and Medical Center, Englewood, NJ, 2The Pain Center of Fairfield, Fairfield, CT, 3Clarity Science, Austin, TX, 4Metrics for Learning, LLC, Queen Creek, AZ, 5Safe Harbor Compliance and Clinical Services, LLC, Austin, TX, USA Background: Opioids and other controlled substances prescribed for chronic pain are associated with abuse, addiction, and death, prompting national initiatives to identify safe and effective pain management strategies including topical analgesics.Methods: This prospective, observational study evaluated changes from baseline in overall mean severity and interference scores on the Brief Pain Inventory scale and the use of concurrent pain medications at 3- and 6-month follow-up assessments in chronic pain patients treated with topical analgesics. Changes in pain severity and interference and medication usage were compared between treated patients and unmatched and matched controls.Results: The unmatched intervention group (unmatched-IG) included 631 patients who completed baseline and 3-month follow-up surveys (3-month unmatched-IG) and 158 who completed baseline and 6-month follow-up assessments (6-month unmatched-IG). Baseline and 3-month follow-up data were provided by 76 unmatched controls and 76 matched controls (3-month unmatched-CG and matched-CG), and 51 unmatched and 36 matched patients completed baseline and 6-month follow-up surveys (6-month unmatched-CG and matched-CG). Baseline demographic characteristics and mean pain severity and interference scores were similar between groups. There were statistically significant decreases from baseline in mean pain severity and interference scores within the 3- and 6-month unmatched-IG (all P

There is good evidence that Mycobacterium tuberculosis evolved with Homo sapiens and, like our ancestors, migrated throughout the rest of the world from Africa some 70,000 years ago ([1][1]). Since M. tuberculosis, which is now a familiar human pathogen, coexisted with other mycobacteria within

Single-degree-of-freedom (SDOF) mechanical oscillators have been the most common type of generators used to harvest energy from mechanical vibrations. When the excitation is harmonic, optimal performance is achieved when the device is tuned so that its natural frequency coincides with the excitation frequency. In such a situation, the harvested energy is inversely proportional to the damping in the system, which is sought to be very low. However, very low damping means that there is a relatively long transient in the harvester response, both at the beginning and at the end of the excitation, which can have a considerable effect on the harvesting performance. This paper presents an investigation into the mechanical design of a linear resonant harvester to scavenge energy from time-limited harmonic excitations to determine an upper bound on the energy that can be harvested. It is shown that when the product of the number of excitation cycles and the harvester damping ratio is greater (less) than about 0.19, then more (less) energy can be harvested from the forced phase of vibration than from the free phase of vibration at the end of the period of excitation. The analytical expressions developed are validated numerically on a simple example and on a more practical example involving the harvesting of energy from trackside vibrations due to the passage of a train.

Made available in DSpace on 2018-12-11T16:48:02Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-07-01 A new design method for selecting the physical parameters of a free piston Stirling engine (FPSE) is presented. The dynamics of FPSE are described in the form of a transfer function including the inherent feedback mechanism. The simplified Nyquist stability criterion is used to derive the operation condition, where the indices of the magnitude amplification factor (MAF) and the operation limit factor (OLF) are introduced in terms of the physical parameters. Further, a measure for the efficiency of the engine is defined as the damping ratio of the power piston system (DRP). Parametric studies of these quantities are carried out as well as benchmarking against the design values of the standard RE-1000 engine. A design method is presented that defines the physical parameters of an FPSE which is working at a given operation frequency. School of Mechanical Engineering Hoseo University Department of Mechanical Engineering UNESP Alstom Switzerland Ltd. Small and Medium Enterprises Support Center Korea Institute Science and Technology Department of Mechanical Engineering UNESP

Made available in DSpace on 2018-12-11T17:09:46Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-06-01 A simple loop shaping technique is applied to design an optimal, robust feedback controller to reduce the interior noise of an acoustic cavity. It is a data-based technique that uses the measured plant response to tune the parameters of a fixed-structure controller in a graphical way. The two cases studied are narrowband noise control in a small cavity and broadband noise control in a long duct. Each control system consists of a microphone, a loudspeaker, and a controller connecting the two transducers that are further collocated. The fixed-structure of each controller should be chosen ahead of loop shaping and is determined in this paper solely based on the Nyquist plot of each plant measured. It turns out that a single band (high) pass filter of second order is suitable for the narrowband (broadband) noise control case considered. It is finally demonstrated with experiments that the technique is practical and a second order filter can be effectively used for active control of cavity noise in a single narrow or broad frequency band. Department of Mechanical Engineering UNESP—Sao Paulo State University, Ilha Solteira 15385-000 Department of Mechanical Engineering UNESP—Sao Paulo State University, Ilha Solteira 15385-000

The genome of Mycobacterium tuberculosis , the bacterium responsible for the disease tuberculosis, contains an unusual family of abundant antigens (PE/PPEs). To date, certain members of this multigene family occur only in mycobacteria that cause disease. It is possible that the numerous proteins encoded by these mycobacterial genes dictate the immune pathogenesis of this bacterial pathogen. There is also evidence that some of these antigens are present at the cell surface and that they affect the pathology and immunology of the organism in many ways. Also, they elicit both antibodies and T cells, they may be involved in antigenic variation, and they may be good candidates for vaccines and drugs. However, since they are plentiful and extremely homologous, these PE/PPEs are very challenging to study, and it is difficult to be certain what role(s) they have in the pathogenesis of tuberculosis. Consequently, how to develop treatments like vaccines using these antigens as candidates is complex.

The effects of nonlinearity, particularly stiffness nonlinearity, has been of concern to structural engineers for many years. Primarily this has been because this type of nonlinearity can cause unpredictable dynamics, and considerable effort is necessary to analyze nonlinear structures. Due to the constant drive to improve the performance and efficiency of structures and mechanical devices, engineers have recently started to investigate whether nonlinearity can be incorporated into structures to provide some benefit. This chapter discusses some of the problems that stiffness nonlinearity can cause, and gives three examples where this type of nonlinearity can be put to good use. The examples are in vibration isolators, vibration absorbers and energy harvesters. If the nonlinearity is introduced in an appropriate way then it should not have an adverse impact on probabilistic prognostics and health management of energy systems.

The development of new, safe, and effective tuberculosis (TB) vaccines to prevent TB across all age groups and countries in an affordable and sustainable manner is critical for the eventual control of TB worldwide. Several new TB vaccines are currently being investigated in human clinical trials, mostly in Africa, including new live recombinant, protein-adjuvanted subunit, and virally vectored products. Since it is unclear at this time whether they will be effective, research on new types of TB vaccines containing novel antigens and unique modes of delivery continues to be important, as does research on the immunological basis of the disease. Likewise, a better understanding of the various manifestations of the disease, including latent infection, remains a critical goal for making better vaccines. Clinical studies of new vaccines and new delivery approaches in emerging countries throughout the world will be required in order to identify vaccines that will have a meaningful impact on global TB.

Gears are the components in many mechanical systems that are likely to develop faults due to their dynamic characteristics, such as the cyclic loading applied to the meshing teeth. The main faults in gears are pitting and scuffing, where the tooth profile (involute) is heavily affected, and hence, signal processing techniques have been developed to aid in the detection of gear faults in their early stages. It is already known that the dynamic behaviour of a mechanical system changes when its characteristics are affected (such as in the presence of a fault), and as a result, the vibration of such a system can be used to detect a fault in its early stage. To investigate and develop techniques based on vibration analysis, a physical understanding of the system involving meshing gears is required. In this chapter, a model is introduced that can be used for simulating vibration data of toothed meshing gears. The data generated by the simulations is then used to investigate some classic techniques used in gear fault detection problems.

We have developed a neural network technique for retrieving accurate 12.5-km resolution wind speeds from Ku-band scatterometer measurements in tropical cyclone conditions including typical rain events in such storms. The method was shown to retrieve accurate wind speeds up to 40 m/s when compared with aircraft reconnaissance data, including GPS dropwindsondes and Stepped-Frequency Microwave Radiometer surface wind speed measurements, and when compared to global best track maximum wind speeds. Wind directions were unchanged from the current (version 3) Jet Propulsion Laboratory (JPL) global wind vector product. The technique removes positive biases with respect to best track winds in the developing phase of tropical cyclones that occurred in the nominal (version 2) JPL QuikSCAT product. The new technique also reduces negative biases with respect to best track wind speeds that occurred in the nominal product (both versions 2 and 3) during the most extreme period of the lifetime of intense storms. The wind regime with the most notable improvement is 20–40 m/s (40–80 kn), with more modest improvement for higher winds and the improvement at lower winds comparable to that achieved previously by the version 3 JPL global rain-corrected product. The net effect of all the wind speed improvements is a much better measurement of storm intensity over time in the new product than what has been previously available. When compared with speed data from aircraft flights in Atlantic hurricanes, the new product exhibited a 1–2-m/s positive overall bias and a 3-m/s mean absolute error. The random error and systematic positive bias in the new scatterometer wind product is similar to that of the Hurricane Research Division H*WIND analyses when aircraft data are available for assimilation. This similarity may be explained by the fact that H*WIND data are used as ground truth to fit the coefficients used by the new technique to map radar measurements to wind speed. The fact that H*WIND was designed to match maximum winds while preserving radial symmetry may explain the overall positive biases that we observe in both H*WIND and the new scatterometer wind product which compared to aircraft reconnaissance data. The new scatterometer product could also be inheriting systematic biases in the presence of rain from H*WIND. Under the most extreme rain conditions, the radar signal from the surface can be lost. In such cases, the technique makes use of measurements in the 87.5-km region comprising the 7 $\times$ 7 neighboring cells around the target 12.5-km wind vector cell. In so doing, we sacrifice resolution in cases where the highest resolution region has no useful measurements. Even so, the most extreme rain conditions can result in reduced accuracy. The new technique has been used to retrieve wind fields for every tropical cyclone of tropical storm force or above that has been observed by QuikSCAT during the period of time from October 1999 to November 2009. The resulting data set has been made available online for use by the tropical cyclone research community.

The vibration isolation characteristics of a high-static-low-dynamic-stiffness (HSLDS) isolator, which has geometrically nonlinear stiffness, have been well established both theoretically and experimentally in the recent literature. However, the shock isolation characteristics of such an isolator subject to base excitation are not currently known. In this paper, these characteristics are determined for two illustrative inputs, which are a rounded step and a versed sine displacement, using a simple model of the isolator comprising a vertical spring coupled to two horizontal springs. The isolator is configured to reduce the dynamic stiffness of the isolator and hence increase the frequency range of isolation. The shock responses of the isolator are determined analytically for low levels of excitation, and numerically for high levels of excitation. It is found that when the shock amplitude is small, the nonlinearity is beneficial, and that the quasi-zero stiffness isolator has the best shock performance in terms of the smallest displacement and acceleration of the suspended mass.

A mass–spring–damper system is at the core of both a vibration absorber and a harvester of energy from ambient vibrations. If such a device is attached to a structure that has a high impedance, then it will have very little effect on the vibrations of the structure, but it can be used to convert mechanical vibrations into electrical energy (act as an energy harvester). However, if the same device is attached to a structure that has a relatively low impedance, then the device may attenuate the vibrations as it may act as both a vibration absorber and an energy harvester simultaneously. In this paper such a device is discussed. Two situations are considered; the first is when the structure is excited with broadband random excitation and the second is when the structure is excited by a single frequency. The optimum parameters of the device for both energy harvesting and vibration attenuation are discussed for these two cases. For random excitation it is found that if the device is optimized for vibration suppression, then this is also adequate for maximizing the energy absorbed (harvested), and thus a single device can effectively suppress vibration and harvest energy at the same time. For single frequency excitation this is found not to be the case. To maximize the energy harvested, the natural frequency of the system (host structure and absorber) has to coincide with the forcing frequency, but to minimize vibration of the host structure, the natural frequency of the absorber has to coincide with the forcing frequency. In this case, therefore, a single resonator cannot effectively suppress vibration and harvest energy at the same time.

A new and improved vaccine against tuberculosis (TB) would provide a powerful tool to conquer one of the most insidious infectious diseases of mankind. Protection afforded by bacillus Calmette-Guérin (BCG) has been shown to be limited and inconsistent, especially in adults that are known to transmit TB disease. In the last two decades, several new vaccines have been developed and tested with the aim to elicit robust and long-lived T-cell responses against Mycobacterium tuberculosis antigens. Although much progress has been made in the TB vaccine field, there is an urgent need to address critical research questions about TB immunity with a special focus on designing vaccines aimed at preventing infection and transmission of TB. Here, we discuss the rationale behind the current immunization strategies being implemented for TB vaccines and provide some suggestions for hypothesis driven research to encourage the development of novel TB vaccines.

A common way to detect and locate leaks in buried water pipes is to use leak noise correlators. Vibration or acoustic signals are measured on or in the pipe using sensors placed either side of the leak, and the difference in the leak noise arrival times (time delay) at the sensors is estimated from the peak in the cross-correlation function of these signals. Over many years, much effort has been spent on improving the quality of the leak noise signals with the aim of improving the time delay estimate. In this paper it is shown that even if the signals suffer from severe amplitude distortion through either clipping or quantization, then an accurate time delay estimate can be obtained provided that the zero crossings in the noise data are preserved. This is demonstrated by using polarity co-incidence correlation on simulated and measured data. The use of random telegraph theory is also used as an approximation to allow the derivation of approximate analytical solutions for the cross-correlation function and cross spectral density of clipped noise to facilitate further insight into the effects of severe clipping.

In this paper wave scattering from an asymmetrical change of cross-sectional area in a beam is numerically studied. Incident symmetric and antisymmetric Lamb waves are considered and multiple wave mode conversion due to interaction with the discontinuity are investigated up to high frequency (above the cut-off of the second symmetric Lamb wave mode, S 2). Results are presented in terms of transmission power coefficients, kinetic energy, and energy velocity. These are evaluated using the Wave Finite Element method to predict the wave modes from FE cross-sectional nodal displacements and nodal forces. It is shown that the methodology proposed can give an insight into wave scattering and multiple converted Lamb wave modes, which can be useful in Structural Health Monitoring.

Because of the threat that Hurricane Irene (2011) posed to the United States, supplemental observations were collected for assimilation into operational numerical models in the hope of improving forecasts of the storm. Synoptic surveillance aircraft equipped with dropwindsondes were deployed twice daily over a 5-day period, and supplemental rawinsondes were launched from all upper-air sites in the continental United States east of the Rocky Mountains at 0600 and 1800 UTC, marking an unprecedented magnitude of coverage of special rawinsondes at the time. The impact of assimilating the supplemental observations on National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) model track forecasts of Irene was evaluated over the period that these observations were collected. The GFS track forecasts possessed small errors even in the absence of the supplemental observations, providing little room for improvement on average. The assimilation of the combined dropwindsonde and supplemental rawinsonde data provided small but statistically significant improvements in the 42–60-h range for GFS forecasts initialized at 0600 and 1800 UTC. The primary improvement from the dropwindsonde data was also within this time range, with an average improvement of 20% for 48-h forecasts. The rawinsonde data mostly improved the forecasts beyond 3 days by modest amounts. Both sets of observations provided small, additive improvements to the average cross-track errors. Investigations of individual forecasts identified corrections to the model analyses of the Atlantic subtropical ridge and an upstream midlatitude short-wave trough over the contiguous United States due to the assimilation of the extra data.

This paper describes the application of a technique, known as synchrophasing, to the control of machinery vibration. It is applicable to machinery installations, in which several synchronous machines, such as those driven by electrical motors, are fitted to an isolated common structure known as a machinery raft. To reduce the vibration transmitted to the host structure to which the machinery raft is attached, the phase of the electrical supply to the motors is adjusted so that the net transmitted force to the host structure is minimised. It is shown that while this is relatively simple for an installation consisting of two machines, it is more complicated for installations in which there are more than two machines, because of the interaction between the forces generated by each machine. The development of a synchrophasing scheme, which has been applied to propeller aircraft, and is known as Propeller Signature Theory (PST) is discussed. It is shown both theoretically and experimentally, that this is an efficient way of controlling the phase of multiple machines. It is also shown that synchrophasing is a worthwhile vibration control technique, which has the potential to suppress vibration transmitted to the host structure by up to 20 dB at certain frequencies. Although the principle of synchronisation has been demonstrated on a one-dimensional structure, it is believed that this captures the key features of the approach. However, it should be realised that the mode-shapes of a machinery raft may be more complex than that of a one-dimensional structure and this may need to be taken into account in a real application.

To determine the location of leaks in buried water pipes, acoustic methods are often used. These have proven to be very effective in metallic pipes but have been problematic in modern plastic pipes. In this paper the reason why this is so is discussed together with some measurements that were made on a bespoke test rig built by South Staffs Water plc. It is shown that there are significant issues in obtaining an accurate estimate of the wavespeed when a leak is present in the system. A method is proposed that overcomes some of these problems, which is discussed and is demonstrated using some data from the bespoke test-rig.

Chronic pain is largely underdiagnosed, often undertreated, and expected to increase as the American population ages. Many patients with chronic pain require long-term treatment with analgesic medications, and pain management may involve use of prescription opioids for patients whose pain is inadequately controlled through other therapies. Yet because of the potential for abuse and addiction, many clinicians hesitate to treat their patients with pain with potentially beneficial agents. Finding the right opioid for the right patient is the first – often complicated – step. Ensuring that patients continue to properly use the medication while achieving therapeutic analgesic effects is the long-term goal. Combined with careful patient selection and ongoing monitoring, new formulations using extended-release technologies incorporating tamper-resistant features may help combat the growing risk of abuse or misuse, which will hopefully reduce individual suffering and the societal burden of chronic pain. The objective of this manuscript is to provide an update on extended-release opioids and to provide clinicians with a greater understanding of which patients might benefit from these new opioid formulations and how to integrate the recommended monitoring for abuse potential into clinical practice.

Leakage in buried pipes is one of the main concerns for water companies due to the scarcity of potable water sources. Older metallic pipelines have been replaced by plastic pipes in such systems, which makes it more difficult to locate leaks using acoustics and vibration. This is mainly because of the high attenuation of leak signals caused by the damping in the pipe-wall. To investigate acoustic methods in leak location in controlled conditions, a bespoke test rig was constructed in the UK. In this paper, data from this test-rig is used to discuss some issues that arise when using two contemporary correlators. Of particular interest, is the way in which a resonance in the system can have a profound effect on the estimate of the position of the leak depending on the way in which the leak noise signals are processed.

There are nearly ten million new cases and 1.4 million deaths from tuberculosis (TB) each year, and the 90-year old bacille calmette-guérin (BCG) vaccine in widespread use appears to have minimal impact on the worldwide incidence, despite demonstrating reasonable efficacy against complications of infant TB and death. Novel vaccine development has accelerated in the past ten years, with at least 16 candidates entering human trials, and a few vaccines have entered into Phase 2b efficacy studies. However, different vaccines may be needed due to the varying disease states (naïve, latently infected, or active), the ages affected (infants, adolescents and young adults, the elderly), and patient health status (HIV and immunocompromised patients especially). Modeling has shown that mass vaccination of latently infected populations, especially adolescents and young adults, will likely have the largest impact on new infection rates. At present, research and development of TB vaccines is hampered by the lack of validated animal models, the absence of correlates of immunity and a human challenge model, as well as by the size and cost of Proof-of-Concept clinical trials. Nonetheless, ongoing research and clinical studies should remove many of these barriers over the next five years, and lead to an increased understanding of the pathogenicity of Mycobacterium tuberculosis and what may constitute protective immunity during various stages of infection and disease.

In this paper, an exact series solution for the vibration analysis of circular cylindrical shells with arbitrary boundary conditions is obtained, using the elastic equations based on Flugge’s theory. Each of the three displacements is represented by a Fourier series and auxiliary functions and sought in a strong form by letting the solution exactly satisfy both the governing differential equations and the boundary conditions on a point-wise basis. Since the series solution has to be truncated for numerical implementation, the term “exactly satisfying” should be understood as a satisfaction with arbitrary precision. One of the important advantages of this approach is that it can be universally applied to shells with a variety of different boundary conditions, without the need of making any corresponding modifications to the solution algorithms and implementation procedures as typically required in other techniques. Furthermore, the current method can be easily used to deal with more complicated boundary conditions such as point supports, partial supports, and non-uniform elastic restraints. Numerical examples are presented regarding the modal parameters of shells with various boundary conditions. The capacity and reliability of this solution method are demonstrated through these examples.

This paper investigates the most desirable configuration of a two-stage nonlinear vibration isolation system, in which the isolators contain hardening geometric stiffness nonlinearity and linear viscous damping. The force transmissibility of the system is used as the measure of the effectiveness of the isolation system. The hardening nonlinearity is achieved by placing horizontal springs onto the suspended and intermediate masses, which are supported by vertical springs. It is found that nonlinearity in the upper stage has very little effect and thus serves little purpose. The nonlinearity in the lower stage, however, has a profound effect, and can significantly improve the effectiveness of the isolation system. Further, it is found that it is desirable to have high damping in the upper stage and very low damping in the lower stage.

This paper analyzes the Amihud (2002) measure of illiquidity and its role in asset pricing. It is shown first that the effect of illiquidity on asset pricing is clarified by using the turnover version of the Amihud measure and including firm size as a separate variable. When we decompose the Amihud measure into elements that correspond to positive (up) and negative (down) return days, we find that in general, only the down-day element commands a return premium. Further analysis of the up- and down-day elements using order flows shows that a sidedness variable, which captures the tendency for orders to cluster on the sell side on down days, is associated with a more significant return premium than the other components of the Amihud measure.

A novel design of a two-stage nonlinear vibration isolation system, with each stage having a high-static-low-dynamic stiffness (HSLDS), is studied experimentally in this paper. The positive stiffness in each stage is realized by a metallic plate, and the corresponding negative stiffness is realized by a bistable carbon fiber–metal (CF) composite plate. An analytical model is developed as an aid to design a bistable composite plate with the required negative stiffness, and a static test of the plate is conducted to measure the actual stiffness of the plate. Dynamic tests of the two-stage isolator are carried out to determine the effectiveness of the isolator. Two tests are conducted, one with the bistable composite plates removed so that the isolator behaves as a linear device and one with the bistable composite plates fitted. An improvement in the isolator transmissibility of about 13 dB at frequencies greater than about 100 Hz is achieved when the bistable composite plates are added.

We decompose PIN, the probability of informed trading, into good-news (PIN_G) and bad-news (PIN_B) components, which we estimate at a quarterly frequency. We first assess the validity of PIN as a measure of informed trading by calculating its association with measures of the adverse-selection component of the cost of trading. We then provide new evidence that PIN_G and PIN_B capture informed trading around earnings announcements by showing that they predict positive and negative earnings surprises, respectively. Conjecturing that investors who take long positions will be more concerned about informed selling than about informed buying since the former depresses the sale price whereas the latter raises it, we then investigate asymmetry in the pricing of private information. We find strong evidence of such asymmetry in that the effect of PIN_B on the cost of equity capital is large and highly significant, whereas the effect of PIN_G is small and statistically insignificant. Data, as supplemental material, are available at http://dx.doi.org/10.1287/mnsc.2015.2250 . This paper was accepted by Neng Wang, finance.

Made available in DSpace on 2018-12-11T16:41:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-08-01 This work concerns the application of certain non-linear phenomena - jump frequencies in a base-excited Duffing oscillator - to the estimation of the parameters of the system. First, approximate analytical expressions are derived for the relationships between the jump-up and jump-down frequencies, the damping ratio and the cubic stiffness coefficient. Then, experimental results, together with the results of numerical simulations, are presented to show how knowledge of these frequencies can be exploited. Centre for Advanced Research on Energy and Automotive (CARE) Faculty of Mechanical Engineering Universiti Teknikal Malaysia Melaka Department of Mechanical Engineering UNESP Centre of Excellence for Vibro-Acoustic Systems and Signal Processing Faculty of Technical Sciences University of Novi Sad Department of Mechanical Engineering University of Auckland Department of Aerospace Engineering University of Bristol Department of Mechanical Engineering UNESP

Made available in DSpace on 2018-12-11T16:58:55Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-01-15 Acoustic correlators have been used for many years to locate and detect leaks in buried water distribution pipes. Currently, the only way to compare different correlators directly is in the field. This can be problematic as it may be difficult to present exactly the same conditions to each correlator. In recent years, the way in which leak noise propagates in buried water pipes has been determined, and this has enabled the development of a virtual pipe whose behaviour can be simulated in the computer. By coupling the filtering properties of the pipe with electrodynamic shakers, a proof-of-concept virtual pipe test-rig has been developed that will allow different correlators to be compared directly in laboratory conditions. Different situations, such as pipe material and size, and measurement positions, as well as leak strength can be simulated. The theoretical basis of the test-rig and details of the proof-of-concept system are discussed in this paper. It is shown that careful consideration of the dynamics of the shakers is vital if the system is to faithfully model situations that are found in the field. Department of Mechanical Engineering, UNESP, Ilha Solteira Department of Biosystem Engineering, UNESP, Tupã Institute of Sound and Vibration Research, University of Southampton Department of Mechanical Engineering, UNESP, Ilha Solteira Department of Biosystem Engineering, UNESP, Tupã

Describing the dynamic behaviour of structures in terms of waves is particularly useful when high frequency vibration is of interest. This is the case in active and passive vibration control, and in structural health monitoring. In this chapter, the concept of wave motion is introduced and different types of waves are discussed, namely waves in a string, a rod and a beam. Using the wavenumber, the phenomenon of dispersion is introduced as is phase and group velocity, and cut-off. The emphasis is on the physical concepts rather than mathematics, and to this end, the majority of the chapter concentrates on one-dimensional uniform structures.

In order to secure the structural integrity of aeronautic structures, several structural health monitoring techniques have been studied throughout history. One of the most recent technologies developed involves the use of continuous sensors, made of thin films of nanocomposite material. Previous works proved that the ITO/PMMA nanocomposite sensor (ITO—indium tin oxide) nanobelts inserted in a matrix of PMMA (poly(methyl methacrylate)) was capable of detecting a certain damage by comparing the values of resistances between two points before and after the damage occurrence, however some uncertainties were found. Two problems were found during the development of the sensors: first of them was the difficulty to obtain uniformity of the coating material through its monitored area and; the second one was the influence of environmental changes on the measurements. The uniformity problem was solved by enhancing the nanocomposite synthetizing method, which resulted in more constant readings of resistances, although there were still variations on measurements taken on different days. To verify the cause of this oscillation, several tests were performed in an environmental chamber, in which the temperature and the humidity were controlled during the measurements, making it possible to find out which parameter would cause more changes on the readings.

Universidad Autonoma de Nuevo Leon Facultad de Ingenieria Mecanica y Electrica San Nicolas de Los Garza

The development of an experimental switching stiffness device for shock isolation is presented. The system uses magnetic forces to exert a restoring force, which results in an effective stiffness that is used to isolate a payload. When the magnetic force is turned on and off, a switchable stiffness is obtained. Characterization of the physical properties of the device is presented. They are estimated in terms of the percentage stiffness change and effective damping ratio when switched between two constant stiffness states. Additionally, the setup is used to implement a control strategy to reduce the shock response and minimize residual vibration. The system was found to be very effective for shock isolation. The response is reduced by around 50 percent compared with passive isolation showing good correlation with theoretical predictions, and the effective damping ratio in the system following the shock was increased from about 4.5 percent to 13 percent.

In this paper a new method for choosing the parameters of a Two degree-of-freedom (dof) tuned vibration absorber (TVA) with translational and rotational degrees of freedom is described. The dynamic stiffness approach is used to model the device, which is constrained to move in the translational direction and to rotate. The choice of the parameters involves a procedure similar to that proposed by Den Hartog in the optimization of a single dof TVA, in which the invariant (fixed) points of the frequency response function of the TVA and the host structure are used to determine the stiffness of the TVA for a given mass. In this paper the approach is extended and applied to the design of a 2dof TVA, and a numerical procedure is used to determine the optimum amount of damping. The method is simple and easy to implement. A numerical example is presented to compare the performance of the 2dof TVA designed using the method described here with the optimal 2dof TVA. It is shown that the performances of the TVAs are similar, validating the new approach.

We estimate buy- and sell-order illiquidity measures (lambdas) for a comprehensive sample of NYSE stocks. We show that sell-order liquidity is priced more strongly than buy-order liquidity in the cross-section of equity returns. Indeed, our analysis indicates that the liquidity premium in equities emanates predominantly from the sell-order side. We also find that the average difference between sell and buy lambdas is generally positive throughout our sample period. Both buy and sell lambdas are significantly positively correlated with measures of funding liquidity such as the TED spread as well option implied volatility.

This paper concerns an investigation into the use of cubic nonlinearity in a vibration neutralizer to improve its effectiveness. It is assumed that the frequency of the harmonic excitation is well above the resonance frequency of the machine to which the neutralizer is attached, and that the machine acts as a simple mass. It is also assumed that the response of the system is predominantly at the harmonic excitation frequency of the machine. The harmonic balance method is used to analyze the system. It is shown how the nonlinearity has the effect of shifting the resonant peak to a higher frequency away from the tuned frequency of the neutralizer so that the device is robust to mistune. In a linear neutralizer this can only be achieved by adding mass to the neutralizer, so the nonlinearity has a similar effect to that of adding mass. Some characteristic features are highlighted, and the effects of the system parameters on the performance are discussed. It is shown that, for a particular combination of the system parameters, the effect of the nonlinearity is also to increase the bandwidth of the device compared to the linear neutralizer with similar mass and damping. Some approximate expressions are derived, which facilitate insight into the parameters which influence the dynamics of the system. The results are validated by some experimental work.

The research trend for harvesting energy from the ambient vibration sources has moved from using a linear resonant generator to a non-linear generator in order to improve on the performance of a linear generator; for example, the relatively small bandwidth, intolerance to mistune and the suitability of the device for low-frequency applications. This article presents experimental results to illustrate the dynamic behaviour of a dual-mode non-linear energy-harvesting device operating in hardening and bi-stable modes under harmonic excitation. The device is able to change from one mode to another by altering the negative magnetic stiffness by adjusting the separation gap between the magnets and the iron core. Results for the device operating in both modes are presented. They show that there is a larger bandwidth for the device operating in the hardening mode compared to the equivalent linear device. However, the maximum power transfer theory is less applicable for the hardening mode due to occurrence of the maximum power at different frequencies, which depends on the non-linearity and the damping in the system. The results for the bi-stable mode show that the device is insensitive to a range of excitation frequencies depending upon the input level, damping and non-linearity.

Automotive turbochargers, which operate at very high speeds, exceeding 180,000 r/min, exhibit two strong sub-harmonic modes of vibrations due to oil-whirl instability. These are a conical mode and an in-phase whirl mode. The gyroscopic effects can be very important in such a rotor system. This article presents a theoretical investigation into these effects on the conical whirl instability of a turbocharger induced by the angular (tilting) motion of a rigid rotor. A simplified linear model is used to analyse the rotor-bearing system by investigating the effects of the gyroscopic moment on the internal moments. A gyroscopic coefficient, defined by the geometry of the rotor, is shown to govern the stability of the conical whirl motion. A threshold value of ½ is determined for this coefficient to suppress the conical whirl. This value remains unaffected if the rotor is asymmetric and is supported by floating ring bearings, which is the case in a practical turbocharger.

The chromosome of Mycobacterium tuberculosis encodes five type VII secretion systems (ESX-1-ESX-5). While the role of the ESX-1 and ESX-3 systems in M. tuberculosis has been elucidated, predictions for the function of the ESX-5 system came from data obtained in Mycobacterium marinum, where it transports PPE and PE_PGRS proteins and modulates innate immune responses. To define the role of the ESX-5 system in M. tuberculosis, in this study, we have constructed five M. tuberculosis H37Rv ESX-5 knockout/deletion mutants, inactivating eccA(5), eccD(5), rv1794 and esxM genes or the ppe25-pe19 region. Whereas the Mtbrv1794ko displayed no obvious phenotype, the other four mutants showed defects in secretion of the ESX-5-encoded EsxN and PPE41, a representative member of the large PPE protein family. Strikingly, the MtbeccD(5) ko mutant also showed enhanced sensitivity to detergents and hydrophilic antibiotics. When the virulence of the five mutants was evaluated, the MtbeccD(5) ko and MtbΔppe25-pe19 mutants were found attenuated both in macrophages and in the severe combined immune-deficient mouse infection model. Altogether these findings indicate an essential role of ESX-5 for transport of PPE proteins, cell wall integrity and full virulence of M. tuberculosis, thereby opening interesting new perspectives for the study of this human pathogen.

Uncertainty information from ensemble prediction systems can enhance and extend the suite of tropical cyclone (TC) forecast products. This article will review progress in ensemble prediction of TCs and the scientific issues in ensemble system development for TCs. Additionally, it will discuss the needs of forecasters and other users for TC uncertainty information and describe some ensemble-based products that may be able to be disseminated in the near future. We hope these proposals will jump-start a community-wide discussion of how to leverage ensemble-based uncertainty information for TC prediction. A supplement to this article is available online (10.1175/2011BAMS3106.2)

Engineers often face the challenge of reducing the level of vibrations experienced by a given payload or those transmitted to the support structure to which a vibrating source is attached. In order to increase the range over which vibrations are isolated, soft mounts are often used in practice. The drawback of this approach is the static displacement may be too large for reasons of available space for example. Ideally, a vibration isolator should have a high-static stiffness, to withstand static loads without too large a displacement, and at the same time, a low dynamic stiffness so that the natural frequency of the system is as low as possible which will result in an increased isolation region. These two effects are mutually exclusive in linear isolators but can be overcome if properly configured nonlinear isolators are used. This paper is concerned with the characterisation of such a nonlinear isolator comprising three springs, two of which are configured to reduce the dynamic stiffness of the isolator. The dynamic behaviour of the isolator supporting a lumped mass is investigated using force and displacement transmissibility, which are derived by modelling the dynamic system as a single-degree-of-freedom system. This results in the system dynamics being approximately described by the Duffing equation. For a linear isolator, the dynamics of the system are the same regardless if the source of the excitation is a harmonic force acting on the payload (force transmissibility) or a harmonic motion of the base (displacement transmissibility) on which the payload is mounted. In this paper these two expressions are compared for the nonlinear isolator and it is shown that they differ. A particular feature of the displacement transmissibility is that the response is unbounded at the nonlinear resonance frequency unless the damping in the isolator is greater than some threshold value, which is not the case for force transmissibility. An explanation for this is offered in the paper.

In this paper, the behavior of a single degree-of-freedom (SDOF) passive vibration isolation system with geometrically nonlinear damping is investigated, and its displacement and force transmissibilities are compared with that of a linear system. The nonlinear system is composed of a linear spring and a linear viscous damper which are connected to a mass so that the damper is perpendicular to the spring. The system is excited by a harmonic force applied to the mass or a displacement of the base in the direction of the spring. The transmissibilities of the nonlinear isolation system are calculated using analytical expressions for small amplitudes of excitation and by using numerical simulations for high amplitude of excitation. When excited with a harmonic force, the forces transmitted through the spring and the damper are analyzed separately by decomposing the forces in terms of their harmonics. This enables the effects of these elements to be studied and to determine how they contribute individually to the nonlinear behavior of the system as a whole. For single frequency excitation, it is shown that the nonlinear damper causes distortion of the velocity of the suspended mass by generating higher harmonic components, and this combines with the time-varying nature of the damping in the system to severely distort the force transmitted though the damper. The distortion of the force transmitted through the spring is much smaller than that through the damper.

Three methods are used to determine the natural frequency of undamped free vibration of a mass interacting with a Hertzian contact stiffness. The exact value is determined using the first integral of motion. The harmonic balance method is used on a transformed equation for an approximate solution, and the multiple scales method is used on an approximate equation. The maximum initial displacement avoiding contact loss is also determined, and the corresponding exact natural frequency is also obtained analytically. The methods are evaluated by studying the free vibration of an elastic sphere on a flat rigid surface.

In this paper, the dynamic behaviour of the "click" mechanism is analysed. A more accurate model is used than in the past, in which the limits of movement due to the geometry of the flight mechanism are imposed. Moreover, the effects of different damping models are investigated. In previous work, the damping model was assumed to be of the linear viscous type for simplicity, but it is likely that the damping due to drag forces is nonlinear. Accordingly, a model of damping in which the damping force is proportional to the square of the velocity is used, and the results are compared with the simpler model of linear viscous damping. Because of the complexity of the model an analytical approach is not possible so the problem has been cast in terms of non-dimensional variables and solved numerically. The peak kinetic energy of the wing root per energy input in one cycle is chosen to study the effectiveness of the "click" mechanism compared with a linear resonant mechanism. It is shown that, the "click" mechanism has distinct advantages when it is driven below its resonant frequency. When the damping is quadratic, there are some further advantages compared to when the damping is linear and viscous, provided that the amplitude of the excitation force is large enough to avoid the erratic behaviour of the mechanism that occurs for small forces.

‘Mapping the Underworld’ is a UK-based project, which aims to create a multi-sensor device that combines complementary technologies for remote buried utility service detection and location. One of the technologies to be incorporated in the device is low-frequency vibro-acoustics, and techniques for detecting buried infrastructure, in particular plastic water pipes, are being investigated. One of the proposed techniques involves excitation of the pipe at some known location with concurrent vibrational mapping of the ground surface in order to infer the location of the remainder of the pipe. In this paper, measurements made on a dedicated pipe rig are reported. Frequency response measurements relating vibrational velocity on the ground to the input excitation were acquired. Contour plots of the unwrapped phase revealed the location of the pipe to within 0.1–0.2 m. Magnitude contour plots revealed the excitation point and also the location of the pipe end. By examining the unwrapped phase gradients along a line above the pipe, it was possible to identify the wave-type within the pipe responsible for the ground surface vibration. Furthermore, changes in the ground surface phase speed computed using this method enabled the location of the end of the pipe to be confirmed.

This paper discusses the dynamic behaviour of a nonlinear two degree-of-freedom system consisting of a harmonically excited linear oscillator weakly connected to a nonlinear attachment having linear and cubic restoring forces. The effects of the system parameters on the shape of the frequency-response curve are investigated, in particular those yielding the appearance and disappearance of outer and inner detached resonance curves. In contrast to the case when the linear stiffness of the attachment is zero, it is found that multivaluedness occurs at low frequencies as the resonant peak bends to the right. It is also found that as the coefficient of the linear term increases, the range of parameters yielding detached curves reduces. Compared to the case when the attached system has no linear stiffness term, this range of parameters corresponds to smaller values of the damping and nonlinear coefficients. Approximate analytical expressions for the jump-up and jump-down frequencies of the system under investigation are also derived.

This paper investigates the feasibility of using an energy harvesting device tuned such that its natural frequency coincides with higher harmonics of the input to capture energy from walking or running human motion more efficiently. The paper starts by reviewing the concept of a linear resonant generator for a tonal frequency input and then derives an expression for the power harvested for an input with several harmonics. The amount of power harvested is estimated numerically using measured data from human subjects. Assuming that the input is periodic, the signal is reconstructed using a Fourier series before being used in the simulation. It is found that although the power output depends on the input frequency, the choice of tuning the natural frequency of the device to coincide with a particular higher harmonic is restricted by the amount of damping that is needed to maximize the amount of power harvested, as well as to comply with the size limit of the device. It is also found that it is not feasible to tune the device to match the first few harmonics when the size of the device is small, because a large amount of damping is required to limit the motion of the mass.