Othman Sidek

An In-depth Review: Structural Health Monitoring using Fiber Optic Sensor

Abstract Fiber optic sensors (FOSs) are being extensively developed and utilized in various fields due to their exclusive properties compared with conventional sensing technologies, such as their complete immunity to electromagnetic interference, capability of functioning in hostile surroundings, elevated sensitivity, and user-friendliness. The deterioration of concrete structures over time is one of the major growing problems worldwide. The characteristics of FOSs can provide more accurate and precise detection of crack damage in these structures. In this paper, the latest research and progress activities regarding crack detection in concrete structures have been investigated and discussed. This paper also provides a comprehensive critical review and comparison study of various approaches used in detecting crack damage using FOSs. A separate section is devoted to highlight the areas where further improvements are required. The compatibility and sustainability of the latest FOSs in detecting damage have also been studied and evaluated in this paper.

Effect of heater geometry on the high temperature distribution on a MEMS micro-hotplate

Temperature uniformity on a micro-hotplate is important for gas sensor sensitivity, linearity, and resolution. There are several ways to create a uniform temperature distribution on a micro-hotplate. In this paper, the modification of microheater geometry is the method used. Four different heater geometries are simulated using ConvetorWare software to determine which geometry can give the most uniform temperature distribution. The simulations show that the heater geometry which combines parallel and meander shapes results in the most uniform heat distribution. The electrical potential and current distributions of the four different micro-heater geometries are also evaluated.

Fiber optic sensor-based concrete structural health monitoring

Fiber optic sensors are being extensively developed and utilized in various fields, compared to conventional sensing technologies, due to their exclusive properties, such as complete immunity to electromagnetic interference, capability of functioning in hostile surroundings, elevated sensitivity and user-friendliness. The unique characteristics of fiber optic sensors can provide more accurate and precise detection of crack damage in concrete structures, the deterioration of which is one of the major growing problems worldwide. This paper provides a comprehensive critical review and comparison of various approaches used in detecting crack damage using fiber optic sensors. A separate section is devoted to highlight the areas where further improvements are required. The compatibility and sustainability of the latest fiber optic sensors in detecting concrete damage are also studied and evaluated in this paper.

Compact Modeling of Mechanical STI y-Stress Effect

In this paper, we proposed two new MOS compact model parameters (synuO and sypuO) to be added to the mobility parameter uO to model the mechanical shallow trench isolation (STI) y-stress. By using a layout experiment, we show that the STI y-stress causes the hook shaped Idsat versus width curve. We demonstrate that by introducing these new model parameters, we are able to fit the actual data more accurately. The STI y-stress effect is modeled by using the synuO parameter (for NMOS) and sypuO parameter (for PMOS) to control the fit to the hook shaped Idsat curve

CMOS shallow trench isolation x-stress effect on channel width for 0.18/spl mu/m technology

We have investigated the effect of shallow trench isolation (STI) induced mechanical x-stress (in the direction of channel length) effect on transistor channel width. STI x-stress has less effect on narrow width NMOS transistor for both threshold voltage (Vt) and drain current (Id). For narrow width PMOS transistor, STI x-stress has higher effect on Id. PMOS Vt is not affected by STI x-stress.

Shape Optimization of Cantilever-based MEMS Piezoelectric Energy Harvester for Low Frequency Applications

The ambient vibration-based micro electromechanical systems (MEMS) piezoelectric harvester has become an important subject in most research publications. Providing a green and virtually infinite alternative power source to traditional energy sources, this harvester will significantly expand the applications of wireless sensor networks and other technologies. Using piezoelectric materials to harvest the ambient vibrations that surround a system is one method that has seen a dramatic rise in the power-harvesting applications. The simplicity associated with piezoelectric micro-generators makes them very attractive for MEMS applications in which ambient vibrations are harvested and converted into electric energy. These micro-generators can become an alternative to the battery-based solutions in the future, especially for remote systems. In this paper, we propose a model and present the simulation of a MEMS-based energy harvester under ambient vibration excitation using the COVENTORWARE2010 approaches. This E-shaped cantilever-based MEMS energy harvester that operates under ambient excitation in frequencies of 12.8, 17.1, and 21.3 Hz within a base acceleration of 1 m/s2 produces an output power of 1.0 W at 2kO load.

A novel tunable water-based RF MEMS solenoid inductor

This paper proposed a novel tunable MEMS solenoid inductor. This tunable solenoid inductor benefits from a liquid-injected core which varies the permeability of the core corresponding to the level of injection of the liquid; hence, the change in permeability of the core causes the change in the inductance. In this work, HFSS is used for 3D EM simulation. The proposed Solenoid inductor is simulated in Silicon substrate with Copper metal as the coil and injected salted water (CaCl2 solved in water) as the solenoid core. The similar previous works for tunable MEMS inductor employing ferromagnetic cores and liquid-based spiral inductors could not exceed an operating frequency of 2 GHz and a Q factor of 12. Here, a maximum Q factor of 18 and tuning range of 60% were achieved at 18 GHz. Also, the implementation procedure of the proposed variable solenoid inductor is simpler and more cost-effective than the other works.

Application of carbon nanotube in wireless sensor network to monitor carbon dioxide

Carbon nanotubes (CNTs) are allotropes of carbon with a cylindrical nanostructure. Over the years, new discoveries have led to new applications, often taking advantage of their unique electrical properties, extraordinary strength and efficiency in heat conduction. Since industrialisation, human activities have resulted in steadily increasing concentrations of the greenhouse gases. Excess amount of carbon dioxide (CO2) in living environment is toxic and unsuitable for human consumption. Thus, a need exists for accurate, inexpensive, long-term monitoring of environmental contaminants using sensors that can be operated on site. Over the past decade, many wireless sensor network (WSN)-based monitoring applications have been proposed. This article reviews the developments of sensing elements to monitor CO2 in the environment. The cylindrical carbon molecules have novel properties that make them potentially useful in many applications in nanotechnology, electronics, optics and other fields of materials science, as well as potential sensing element in wireless sensor technology. They exhibit extraordinary strength and unique electrical properties, and are efficient thermal conductors. The unique properties of CNT makes it a potential sensing element in the WSN technology.

Physical-Based SPICE Model of CMOS STI y-Stress Effect

In this paper, we proposed a new physical-based equation to model the CMOS transistor STI y-stress (in the direction of channel width). It can be used in any SPICE MOS model and it has been verified on 0.13 um CMOS transistors. The physical characteristics of the compressive STI y-stress effect on saturation drain current, Idsat are captured by using a new proposed transistor layout method. The equation that is able to describe the physical characteristics of the STI y-stress effect is incorporated into the electron and hole mobility, uO of the SPICE model to capture the y-stress effect on Idsat. With the combination of the new y-stress parameters and the default delta width parameters in the SPICE model, we are able to fit the simulation curve to the hook shaped Idsat curve from the actual silicon data.

Layout dependence effect on high speed CMOS transistor leakage current

We investigated the layout dependence effect that is caused by different active space, Sa, on 130 nm CMOS transistors leakage current, Ioff. This layout dependence phenomenon is known as STI stress effect. The results show that when Sa changes from 5 /spl mu/m to 0.34 /spl mu/m, the NMOS Ioff decreases and the PMOS Ioff increases. The decrease of NMOS Ioff and increase of PMOS Ioff under compressive stress is similar to the trend of saturation current, Idsat but opposite the trend of linear threshold voltage, Vtlin. The layout dependence (or STI stress effect) not only affects the Vtlin and Idsat but also the Ioff of the 130 nm CMOS transistors.