One of the most intriguing protein materials found in nature is bone, a material composed of assemblies of tropocollagen molecules and tiny hydroxyapatite mineral crystals that form an extremely tough, yet lightweight, adaptive and multifunctional material. Bone has evolved to provide structural support to organisms, and therefore its mechanical properties are of great physiological relevance. In this article, we review the structure and properties of bone, focusing on mechanical deformation and fracture behavior from the perspective of the multidimensional hierarchical nature of its structure. In fact, bone derives its resistance to fracture with a multitude of deformation and toughening mechanisms at many size scales ranging from the nanoscale structure of its protein molecules to the macroscopic physiological scale.

On the Mechanistic Origins of Toughness in Bone

Fiber ring interferometer

Low-cost chip-scale optoelectronic gyroscopes having a resolution ≤ 10 °/h and a good reliability also in harsh environments could have a strong impact on the medium/high performance gyro market, which is currently dominated by well-established bulk optical angular velocity sensors. The R&D activity aiming at the demonstration of those miniaturized sensors is crucial for aerospace/defense industry, and thus it is attracting an increasing research effort and notably funds. In this paper the recent technological advances on the compact optoelectronic gyroscopes with low weight and high energy saving are reviewed. Attention is paid to both the so-called gyroscope-on-a-chip, which is a novel sensor, at the infantile stage, whose optical components are monolithically integrated on a single indium phosphide chip, and to a new ultra-high Q ring resonator for gyro applications with a configuration including a 1D photonic crystal in the resonant path. The emerging field of the gyros based on passive ring cavities, which have already shown performance comparable with that of optical fiber gyros, is also discussed.

https://www.jeos.org/index.php/jeos_rp/article/download/14013/1170

Recent advances in miniaturized optical gyroscopes

We show that a certain fundamental limit applies to the accuracy of all optical rotation sensors which use laser light as a probe. We derive this fundamental rotation-rate uncertainty from the Heisenberg uncertainty relations and Glauber's minimum uncertainty states. The same relationship is obtained from a spontaneous-emission noise formulation. We present experimental data on a (nondithered) four-frequency ring laser gyroscope for which this limit is attained.

Laser gyro at quantum limit

Role of interfacial transition zone in phase field modeling of fracture in layered heterogeneous structures

Crack propagation in staggered structures of biological and biomimetic composites

We present a mathematical analysis and comparison of the performance of integrated on-chip semiconductor ring laser gyroscope (SRLG) fabricated using GaAs/AlGaAs and InP/InGaAsP technologies. The performance parameters of the gyro are modeled in terms of fundamental material, waveguide, and resonator parameters. In addition to this, influence of phenomena specific to semiconductor lasers such as nonlinear coupling, spatial hole burning, gain grating formation, and carrier induced index change on the gyro performance is also included. The analysis helps in identifying critical parameters, which must be optimized to improve the gyro performance.Best achievable performance of integrated SRLG is calculated, and design modifications are suggested to enhance it for high-performance military applications.

Performance Evaluation of Integrated Semiconductor Ring Laser Gyroscope

The sensitivity of a monolithically integrated semiconductor ring laser gyro is severely limited by the high value of the lock-in threshold. In this work, we calculate the lock-in threshold using perturbation theory and coupled mode theory analysis. It is shown that gyro sensitivity is limited to an input rotation rate of 108 deg / h due to nonlinear coupling between the countertraveling modes. This coupling arises due to the backreflection of modes from moving index gratings, induced by rotation. Lock-in threshold is directly proportional to the strength of nonlinear coupling and spatial overlap of the modes’ energy densities with periodic index perturbations.

Limits imposed by nonlinear coupling on rotation sensitivity of a semiconductor ring laser gyroscope.

The Synchronous machine angle and speed variables availability give us an exact picture of the overall condition of power system networks leading therefore to an improved situational cognizance by system operators. As the enlargement of power systems continue, the challenge of real time monitoring and its control gets bigger. All significant network parameters are measured at various points on the system and that collected data transferred to the control center, where the data is used for Estimation Process through various Energy Management System (EMS) functions. Accuracy is directly dependent upon the data collected through Phasor Measurement Unit (PMU) with their underlying high veracity and the unique ability to evaluate the voltage angles, offers an advantage in improving the overall accuracy. This paper compares the performance of four filtering approaches in estimating dynamic states of a power system network using PMU data. The five methods are extended Kalman filter (EKF), unscented Kalman filter (UKF), Particle Filter (PF), and Enhanced unscented Kalman filter. The statistical performance of each algorithm is compared using IEEE 30 and IEEE 14 bus test system. Under the statistical framework, Efficiency of Interpolation, Sensitivity of the missing data with computation time are evaluated and compared for each approach. According to the comparison, this paper makes some recommendations for the proper use of the methods.

Power system state estimation comparison of Kalman filters with a new approach

In this paper, we have mathematically modeled and analyzed the composite cavity Semiconductor Fiber Ring Laser for its use as an inertial rotation sensor or gyroscope. The rate equations of Semiconductor Optical Amplifier and the transfer function of other components in the configuration, viz. optical filter, output coupler and Y-junction coupler have been considered separately for modelling. The final output expression shows the effect of these components on the intensity of the beat signal. The frequency of the beat signal intensity is shown to be independent of the parameters of the components, which underlines the advantage of frequency-domain sensing.

Arpit Khandelwal

Papers

Crack propagation in staggered structures of biological and biomimetic composites

Performance Evaluation of Integrated Semiconductor Ring Laser Gyroscope

Limits imposed by nonlinear coupling on rotation sensitivity of a semiconductor ring laser gyroscope.

Power system state estimation comparison of Kalman filters with a new approach

Mathematical model of semiconductor fiber ring laser gyroscope