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The “taper tantrum” of 2013 represents one of the largest monetary policy shocks since the 1980s. During this episode, long-term interest rates spiked 100 basis points—a move unintentionally induced by policymakers. However, this had no observable negative effect on the overall U.S. economy. Output, employment, and other important variables, all performed either in line with or better than consensus forecasts, often improving considerably relative to their earlier trends. We conclude that, from low levels, a 100 basis point increase in long-term interest rates is probably too small to affect overall economic activity and discuss the implications for monetary policy.

We propose a hexagonal 16QAM modulator based on compact microring resonators and validated through simulation and theoretical analysis. We have also analyzed the constellation points and calculated the mathematical equation for each of the constellation points. Equidistant symbols of hexagonal architecture have the advantage of a higher symbol detection margin compared to the classical 16QAM modulation format. A bit error rate (BER) of 10−3 is achieved at 16.5 dB optical signal to noise ratio (OSNR).

Adhesion and friction of soft solids on hard surfaces are the important properties for a variety of practical applications. In the present study, Coulomb's law of friction is used for characterizing adhesive friction as well as normal stress-dependent dynamic friction of a gelatin hydrogel on a fixed glass surface. The experimental data, concerning normal stress-dependent dynamic friction of different shear velocity, are obtained from literature. It is observed that both components of friction increase with shear velocity. More importantly, the scaling law shows that adhesive stress varies almost linearly with corresponding coefficient of friction of the hydrogel. A dynamic friction model is also used to analyze the same experimental data to predict a negative normal stress at which dynamic friction reduces to zero, and this result matches closely with the experimental value.

We have proposed an 8PSK modulator based on three microring modulators (MRM). The design consists of three MRMs, each with a radius of 11.1μm. Of these three, two MRMs are connected in parallel and they together generate a QPSK (Quadrature phase shift keying) signal. While at the output port of the QPSK, a third MRM is connected in series works as an angle modulator, which is basically a 45o phase shift modulator; i.e., the output of the MRM varies by 45o depending on the bit pattern fed to it, ’0’or ’1’ respectively. In the result section, we have simulated and shown the performance of the proposed 2.5 GBaud 8PSK modulator after transmitting the modulated signal through various lengths of optical fiber. The bit error rate (BER) vs. optical signal to noise ratio (OSNR) curve shows that, 10−3BER has been achieved at 13.5dB OSNR.

The present experimental study investigates the frictional properties of gelatin based soft lubricants between two smooth glass surfaces. Slide-hold-slide (SHS) experiments in direct shear mode show that the frictional behaviour of the thin layer of the lubricant is very similar to the soft solids. It is observed that static, dynamic and residual stresses increase with both shear velocity and concentration of gelatin in the lubricant. Coulomb’s law of friction is used for determining adhesive stress and coefficient of friction of the sliding interface. Both components of friction increase with gelatin concentrations. The scaling laws, in terms of lubricant concentration, reveal that their exponent follows the trend as static>dynamic>residual stress. Further, although exponent of the adhesive stress is larger than the coefficient of friction in the case of static friction, the same is opposite in the case of dynamic and residual stresses. These observations are explained in view of the relative competition between normal stress and molecular chains controlled friction mechanisms at the sliding interface of the gelatin based soft lubricants.

High-dimensional modulation schemes have become the preferred choice for high data rate transmission. Compared to the conventional square 16QAM, hexagonal 16QAM configuration is less vulnerable to noise. This paper presents a theoretical error performance of uncoded hexagonal 16QAM using a lower computational complex approach.

In this paper, we experimentally demonstrate an integrable and wavelength preserving dual-modulation format for the simultaneous generation of quadrature phase-shift keying(QPSK) signal over the on–off keying (OOK) signal. We have demonstrated the successful operation of dual modulation by using three microring modulators in two different configurations. The OOK and QPSK signals are fed with different bitrates. The performance of the modulator in the presence of amplified spontaneous emission (ASE) noise and phase noise has also been investigated.

A better understanding of the nucleation process of an earthquake is of practical importance for early warning and hazard assessment. In present chapter, chaotic nucleation of an earthquake is investigated numerically using spring-mass slider with the rate- and state-dependent friction (RSF) law. The main focus during the numerical simulations is to identify the onset of chaotic motion showing irregular changes in frictional stress as well as slip velocity. It is observed that the chaotic tendency of the sliding system increases with number of state variables in the RSF model. Moreover, the stiffness at which chaos occurs also increases with number of the state variables. Thus, the present study justifies that the RSF laws could also be useful to study the multiscale nature of friction of hard surfaces such as metals and rocks.

In this article, we have studied experimentally the frictional behavior of dry multiwall carbon nanotubes (MWCNTs) nanoparticles between the metal–metal interface as function of areal concentration of the MWCNTs and normal load. The results show that critical velocity, at which stick–slip disappears, decreases with increase in areal concentrations of the nanoparticles. However, steady dynamic friction remains almost constant with the areal concentrations. These observations are explained on the basis of rolling and sliding motion the cylindrical carbon nanotubes. Future implications of the present study are also highlighted.

In this article, we study numerically the dynamic stability of the rate, state, temperature, and pore pressure friction (RSTPF) model at a rock interface using standard spring-mass sliding system. This particular friction model is a basically modified form of the previously studied friction model namely the rate, state, and temperature friction (RSTF). The RSTPF takes into account the role of thermal pressurization including dilatancy and permeability of the pore fluid due to shear heating at the slip interface. The linear stability analysis shows that the critical stiffness, at which the sliding becomes stable to unstable or vice versa, increases with the coefficient of thermal pressurization. Critical stiffness, on the other hand, remains constant for small values of either dilatancy factor or hydraulic diffusivity, but the same decreases as their values are increased further from dilatancy factor $$(\sim \;10^{ - 4} )$$ and hydraulic diffusivity $$(\sim \;10^{ - 9} \;{\text{m}}^{2} \;{\text{s}}^{ - 1} )$$. Moreover, steady-state friction is independent of the coefficient of thermal pressurization, hydraulic diffusivity, and dilatancy factor. The proposed model is also used for predicting time of failure of a creeping interface of a rock slope under the constant gravitational force. It is observed that time of failure decreases with increase in coefficient of thermal pressurization and hydraulic diffusivity, but the dilatancy factor delays the failure of the rock fault under the condition of heat accumulation at the creeping interface. Moreover, stiffness of the rock-mass also stabilizes the failure process of the interface as the strain energy due to the gravitational force accumulates in the rock-mass before it transfers to the sliding interface. Practical implications of the present study are also discussed.

In this article, stick–slip behavior of a metal–metal interface is investigated in presence of a lubricant mixed with multiwalled carbon nanotubes (MWCNTs). The friction experiments are carried out to determine the critical pulling velocity at which stick–slip motion disappears and steady sliding follows thereafter. The sliding experiments show that the critical velocity decreases with increase in concentration of MWCNTs in the lubricant up to 1.6% (wt./vol.), but further addition of the nanoparticles in the lubricant leads to increase in the critical velocity. Also, the critical velocity is found to be nearly independent of normal stress at the optimal concentration of the nanoparticles. Moreover, amplitude of stick–slip motion decreases with increase in concentration of MWCNTs up to the optimal value at a fixed velocity but the same begin to increase after the optimal concentration. The results are explained in light of the rolling-sliding mechanism of the spherical or cylindrical nanoparticles reported in literature. The present study reveals that the stick–slip instability can also be eliminated by using an optimal concentration of the nanoparticles in the lubricant.

In this chapter, we study numerically friction-induced wellbore instability due to frictional interaction between drill string and rock materials using torsional pendulum system. The classical Amontons–Coulomb (AC) friction laws are widely used for explaining the variety of sliding- and rotation-related phenomena, yet the AC laws fail to explain stiffness dependence of stick-slip motion. In recent times, the rate and state friction (RSF) model has found widespread applications for understanding the phenomena related to sliding of rock surfaces. The RSF model, which is basically modified form of the aforementioned AC laws, has not yet got any attention for studying the friction-induced wellbore instability. The RSF laws state that friction of hard surfaces such as rocks and metals at high (~MPa) normal stress depends on current slip velocity as well as nature of the sliding surfaces. The literature review reveals that rotation of drill string causes stick-slip vibration, thus potential initiation of the failure process in surrounding medium. We use linear and nonlinear stability results to discuss a critical stiffness above stick-slip behaviour of the rotating system disappears. It is also demonstrated in the numerical simulations that stick-slip motion could also be eliminated by increasing rotational velocity of the drill string.

Stick-slip vibration is an important mode of failure in many structural and mechanical systems and that generally seen in the form of jerking, chattering, squeaking, etc. It is shown experimentally that similar to friction, adhesion is also dynamic in nature and that depends on slip velocity and relaxation or hold time. Fracture mechanics analysis of a soft and hard solid interface in the direct shear sliding reveals that energy release rate (ERR) varies periodically during stick-slip motion. However, in the steady sliding regime, ERR first increases to a maximum value at static strength, becomes constant during dynamic sliding and finally, the ERR reaches at the residual strength to a constant value known as work of adhesion. It is also observed during stick-slip motion that a crack always nucleates from the rear end of the block and traverses the entire interface before the slip and is followed by healing of the same interface begins from the front edge of the block. The present study establishes that a relative competition between the crack growth rate and interface healing rate basically controls the frictional behavior of sliding surfaces.

We propose a silicon microring modulator based two-circular quadrature amplitude modulation (16QAM). We have numerically analyzed the error performance using Voronoi diagram and compared it with the simulation results under back-to-back condition using optical band-pass filter (OBPF) before the receiver having 3-dB bandwidth of 30%, 40%, and 50% of symbol rate, respectively. The result shows 1 dB difference between each case of OBPF bandwidth and 0.5 dB difference between theoretical and simulated value.

We apply textual analysis tools to measure the degree of optimism versus pessimism of the text that describes Federal Reserve Board forecasts published in the Greenbook. The resulting measure of Greenbook text sentiment, “Tonality,” is found to be strongly correlated, in the intuitive direction, with the Greenbook point forecast for key economic variables such as unemployment and inflation. We then examine whether Tonality has incremental power for predicting unemployment, GDP growth, and inflation up to four quarters ahead. We find it to have significant and substantive predictive power for both GDP growth and unemployment, particularly since 1991: higher (more optimistic) Tonality presages higher GDP growth and lower unemployment, relative to the Greenbook point forecasts. We then test whether Tonality helps predict monetary policy and stock returns. Higher Tonality has some power to predict tighter than forecasted monetary policy, while it has substantial power for predicting higher 3-month, 6-month, and 12-month stock market returns.

A fundamental understanding of frictional sliding at rock surfaces is of practical importance for nucleation and propagation of earthquakes and rock slope stability. We investigate numerically the effect of different physical parameters such as inertia, viscous damping, temperature and normal stress on the chaotic behaviour of the two state variables rate and state friction (2sRSF) model. In general, a slight variation in any of inertia, viscous damping, temperature and effective normal stress reduces the chaotic behaviour of the sliding system. However, the present study has shown the appearance of chaos for the specific values of normal stress before it disappears again as the normal stress varies further. It is also observed that magnitude of system stiffness at which chaotic motion occurs, is less than the corresponding value of critical stiffness determined by using the linear stability analysis. These results explain the practical observation why chaotic nucleation of an earthquake is a rare phenomenon as reported in literature.

In this classical article, we study natural frequencies of the multiple pendulum systems (MPSs) in a plane under the free condition. The systems of governing differential equations for the MPSs such as triple pendulum (TP) and double pendulum (DP) are derived using the Euler–Lagrangian equation of second kind to validate the Braun’s generalized expressions (Arch Appl Mech 72:899–910, 2003) for natural frequencies of multiple pendulum systems. The governing equations of the TP and DP systems are also derived in terms of angular momentum and angular displacement to confirm the basic results obtained using the aforementioned approach. The eigenvalue analysis of the pendulum systems ranging from single pendulum to quintuple indicates that natural frequency increases with degree of freedom for equal mass and length of each pendulum in a MPS. The results show that the natural frequency of a distributed pendulum system is larger than the corresponding to the point mass pendulum system. Moreover, the natural frequency of the bottom pendulum is the most sensitive to change in length or mass of either pendulum of a MPS. However, unlike mass-dependent natural frequency, the natural frequency of all pendulums of a multiple pendulum always decreases with increasing length of a pendulum in MPS. These results are, in turn, validated with Braun’s formula for natural frequency of a MPS.

This paper investigates the steady sliding behavior of multiwalled carbon nanotubes (MWCNTs) mixed lubricants at the metal–metal interface in direct shear tests. Slide-free-slide (SFS) experiments were performed to understand dynamic frictional stress of the sliding surfaces above the critical velocity. The experimental observations show that the dynamic stress decreases with increase in sliding velocity, but the same increases with normal stress. Further, in the case of change in concentration of the MWCNTs in the lubricant, the dynamic stress increases initially and then decreases to a minimum value and then further increases with addition of more nanoparticles in the lubricant. Dynamic stress and corresponding critical velocity are found to be minimum about 1.6% (wt./vol.) of MWCNTs concentration. Magnitude of cohesion as well as the coefficient of friction were also determined experimentally with the Coulomb friction law. The friction results are discussed in terms of the scaling laws in three regimes, namely viscous, rolling and sliding. These laws are justified on the basis of the mixed lubrication regime of Stribeck curve. Surface morphology of the test specimens before and after the experiment was also examined using SEM and EDS tests. No evidence of surface damage owing to motion of the nanoparticles was observed.