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

We propose an alternate method to sense inertial rotation using semiconductor ring laser gyroscope (SRLG). We show that inertial rotation causes change in the magnitude of voltage across the terminals of semiconductor gain medium which can be measured externally to determine angular rotation velocity. The resonant oscillating frequency of the counter-traveling waves are not involved in the measurement which leads to elimination of lock-in in the gyro. The mathematical analysis and simulation results of the proposed method are also shown.

A novel method of rotation sensing by semiconductor ring laser gyroscope

A nuclear radiation monitoring system with a transmission range of 10 km is developed and validated. The designed system can be used for remote monitoring of nuclear radiation and collecting the data at ground stations located far apart from active site. It can be used to interface any wireless nuclear radiation sensor and has 10 years of operating lifetime. The transceiver is implemented using novel Low Power Wide Area Network (LPWAN) technology which is specially designed for applications requiring long range transmissions at low data rate. The experimental testing of designed system shows that dose rate information can be transmitted upto 10 km in rural and 7 km in urban environment. Moreover, there is possibility of creating a network where number of different sensors located geographically apart can transmit to the same base station, thus providing simultaneous data analysis.

Long Range Nuclear Radiation Monitoring System using LPWAN Technology

Radiation hard flexible resistive random access memory (ReRAM) devices with the ultrathin HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> active layer deposited by atomic layer deposition (ALD) are demonstrated. Effect of gamma radiation is investigated on switching characteristics to observe the radiation hardness. Fabricated ReRAM devices show excellent switching characteristics with good data retention and multiple cycle operation, which is retained even after the <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">60</sup> Co gamma radiation with a dose of 1 kGy. Effect of extreme gamma radiation of 5 kGy on device behavior was also examined, however, a degradation in performance was observed at these high doses. For dose of 1 kGy, the SET voltage slightly changed from 1.0 V to 1.1 V after irradiation, whereas the RESET changed slightly from -1.48 V to -1.5 V for the first cycle. These values were also compared for mean and median of 125 cycles of resistive switching. With repeatability of more than 125 cycles, excellent retention time of 5000 s was observed. Additionally, by bending the irradiated devices at 12.5 mm radius and then at 7 mm radius, the electro-mechanical stability was examined. Our results show these flexible ReRAM devices can be utilized in gamma radiation environments. 

Radiation Hardened ReRAM Devices for Flexible Electronics

In this paper, a programmable current source based simple, compact and low cost MOSFET dosimetry system is developed and characterized for the measurement of cumulative gamma radiation doses. The proposed readout system is microcontroller based which can be used to set-up different zero temperature coefficient currents ( I ZTC ) (range: 200 μ A – 400 μ A ) using digital rheostat and subsequently measuring changes in the threshold voltages of irradiated sensors. The proposed current source characterized by interfacing with six indigenously developed MOSFET sensors under gamma environments up to 1000 cGy with an average sensitivity of 5 mV/cGy and its performance is compared with commercially available Keithley’s source measurement unit, albeit at much lower cost and size. The comparison shows that the threshold voltage measured from both the systems differ less than 1%.

Design of programmable current source for MOSFET based gamma dosimetry system

Resolution of POF based pressure sensor was improved by suppressing voltage fluctuation in LED-fiber-Photodiode setup using time windowing technique. This reduced the standard deviation by 98%, thereby showing significant improvement in gait analysis images.

Arpit Khandelwal

Papers

A novel method of rotation sensing by semiconductor ring laser gyroscope

Long Range Nuclear Radiation Monitoring System using LPWAN Technology

Radiation Hardened ReRAM Devices for Flexible Electronics

Design of programmable current source for MOSFET based gamma dosimetry system

Novel Contrast Enhancing Technique For Gait Analysis Images