Number of scales per octave: Compare each point to its 8 neighbors at the same level, 9 neighbors in the level above, and 9 neighbors in the level below i. In following figure, represent 3 scale space, In such situation every descriptor is surrounded from nearest descriptor 26 descriptors. These descriptors are generated from the SIFT method.
The goal of the present dynamic characteristics study is to increase the sensitivity of the measurement system while simultaneously reducing its variability.
A time- and cost-efficient finite element analysis method is utilized to investigate the effects of the deposited mass upon the resonant frequency output of the SAW biosensor. The results show that the proposed methodology not only reduces the design cost but also promotes the performance of the sensors.
Introduction Owing to its many advantages of high sensitivity, simplicity, low cost and ability to perform rapid measurements, the piezoelectric quartz crystal resonator has been widely used as a mass sensitive detector in electrochemical experiments recently.
The application of an alternating electrical field perpendicular to the surface of the piezoelectric quartz crystal PQC induces a mechanical vibration of the piezoelectric surface, whose frequency is changed by loading effects generated when a small mass is deposited on the resonator surface [ 1 — 3 ].
Previous studies have shown that surface acoustic wave SAW sensors provide a superior resolution than quartz crystal microbalance QCM devices due to their higher operating frequencies of to MHz.
The output response of the SAW device varies as a linear function with the input signal, which corresponds to the deposited mass, and some researchers have successfully optimized their mass sensitivity by considering the calibration curve of device response versus mass concentration [ 6 — 8 ].
SAW sensors consist of a thin ST-cut quartz disk sandwiched between metal electrodes and then coated with sensitive membranes. Traditionally, the design and development of these devices has relied heavily upon an experimental approach.
However, the effects of operative error, or of faulty apparatus, are virtually impossible to eliminate in such a case. Consequently, discrepancies frequently exist between the design specification and the experimental results.
Modern computer-aided design finite element method FEM techniques provide powerful simulation tools for the task of designing piezoelectric systems [ 9 — 10 ].
These techniques facilitate coupled-field finite element analysis and are capable of generating excellent results. The Taguchi robust design method enables the main effects of certain designated design parameters to be evaluated.
This method ensures the reproducibility of the experimental results and enables the optimum combination of design parameters i. Taguchi parameter design can be divided into static and dynamic cases, in which the former case has no signal factor, while the latter has signal factors for the output optimization goals.
Generally speaking, the accuracy of a measurement system is influenced by dynamic characteristics such as time-varying input signals or by the presence of noise [ 13 ].
However, this study ignored the sensitivity considerations relating to mass effects i. Hence, the robustness of the measuring system was not assured.
Dynamic methods enable the measuring system to be optimized with an enhanced sensitivity over a range of output values, and therefore yield a more robust solution. This study integrates computer-aided simulation experiments with the Taguchi dynamic method to generate a robust SAW gas sensor design.
The main objective of the proposed methodology is to reduce design and development costs and to enhance the robustness of the biosensor measuring performance. Basic Piezoelectric Theory 2.
SAW Mass Effect Surface acoustic wave sensors are highly sensitive to mass changes on their surfaces. Even the deposition of a small mass on the surface of ST-cut quartz crystal in air causes a reduction of its original resonant frequency as shown in Figure 1.
This frequency shift is proportional to the deposited mass per unit area of the sensing film. Ignoring oscillation circuit stability considerations, the higher the resonant frequency of the device leads to the smaller the mass variation is capable of detecting.
SAW delay-line type devices are used in many mass-sensing applications. The Rayleigh wave type can be excited using an interdigital transducer IDT. In this technique, the spatially periodic field of the IDT produces a periodic mechanical strain pattern [ 16 ] which causes acoustic waves to propagate away from either side of the IDT in a direction essentially perpendicular to the interdigital alignment of the transducer electrodes.
As shown in Figure 2the delay-line device consists of two IDTs with a constant electrode overlap, w, and a separation distance, L, implemented on an ST-cut quartz piezoelectric substrate. The resonant frequency shift of a SAW sensor is directly proportional to the deposited mass per unit area, and hence provides an indication of the mass sensitivity of the device.
A device that develops a higher value of R or a greater frequency shift than other devices for the same deposited mass possesses a superior sensitivity.
The response R for an uncoated substrate is defined as [ 16 ]:Constructing Orthogonal Arrays Robust System Design MIT. Standard Orthogonal Arrays Orthogonal Array Number of Rows Maximum Number of Factors • What is the smallest standard array that will work? Robust System Design MIT.
Choosing an Array -- Example 2. Chapter Taguchi Designs. Introduction. Taguchi experimental designs, often called orthogonal arrays (OA’s), consist of a set of fractional factorial designs which ignore interaction and concentrate on main effect estimation.
This procedure generates the most design is perhaps the most popular. An orthogonal array and analysis of variance (ANOVA) are employed to investigate the factors: material, module and gear width on the safety coefficient for surface durability.
Orthogonal array testing is a black box testing technique that is a systematic, statistical way of software testing.   It is used when the number of inputs to the system is relatively small, but too large to allow for exhaustive testing of every possible input to the systems.
. Another major disadvantage of one-parameter-at-a-time approach is that it fails to consider any possible interaction between the parameters  Orthogonal Arrays The Taguchi Robust Design method uses a mathematical tool called Orthogonal Arrays (OAs) to study a large number of process variables with a small number of experiments [ it is.
The number of experiments is reduced to minimize the cost and time using an orthogonal array (OA).
a confirmation experiment was performed to verify the optimum process parameters acquired from the parameter design The Taguchi design method is suitable for determining optimal cutting parameters.