Switching Controller Design for a Class of Markovian Jump Nonlinear Systems Using Stochastic Small-Gain Theorem

Switching controller design for a class of Markovian jump nonlinear systems with unmodeled dynamics is considered in this paper. Based on the differential equation and infinitesimal generator of jump systems, the concept of Jump Input-to-State practical Stability (JISpS) in probability and stochastic Lyapunov stability criterion are put forward. By using backsetpping technology and stochastic small-gain theorem, a switching controller is proposed which ensures JISpS in probability for the jump nonlinear system. A simulation example illustrates the validity of this design

Simultaneous determination of position and mass in the cantilever sensor using transfer function method

We present the simultaneous measurement of mass and position of micro-beads attached to the cantilever-based mass sensors using the transfer function method. 10 ??m diameter micro-beads were placed on micro-cantilevers and the cantilevers were excited by lead-zirconate-titanate through low-pass filtered random voltages. The cantilever vibration was measured via a laser Doppler vibrometer before and after applying the beads. From the measured transfer function, the bead position was identified using its influence on the cantilever kinetic energy. The bead mass was then obtained by analyzing the wave propagation near the beads. The predicted position and mass agreed well with actual values.open0

Gas Metal Arc Welding with Undermatched Filler Wire for hot-press-formed steel of 2.0 GPa strength: Influence of filler wire strength and bead geometry

Commercial welding filler wires have less strength than hot-press-forming (HPF) steels. As the 2.0 GPa-HPF steel sheets have been released, their lap welding characteristics were investigated using gas metal arc welding in this study. The base metal was 1.1 mm-thick 2.0 GPa-HPF steel sheets, and three filler metal wires considered in this study (W540, W920, and W980) had tensile strengths of 540, 920, and 980 MPa, respectively. Gas metal arc welding was performed under a controlled short-circuit mode, and the wire feed speed (WFS) was selected as a process parameter. Tensile-shear test and microscopy were performed to evaluate the joint strength and metallurgical characteristics. The joint strength increased when WFS increased. When the WFS was 6 m/min or higher and high strength filler wires were applied to it, a heat affected zone (HAZ) fracture was observed in the tensile-shear test, with a tensile strength of approximately 1150 MPa. The fracture location was the boundary of the sub-critical HAZ (comprising tempered martensite) and intercritical HAZ (comprising polygonal ferrite and martensite). The weld metal (WM) hardness for W540 welds was 270 HV, and that for W920 and W980 was 414–419 HV, while the joint strength for the WM fracture was proportional to the throat thickness. For low WFS (when the heat input per unit length and welding current were low), high strength filler metals enhanced the joint strength, while high welding currents and deep penetration welding modes were recommended for W540. This study provided the filler wire and bead geometry design for the lap welds of 2.0 GPa HPF steel sheets

Determination of Fluid Density and Viscosity by Analyzing Flexural Wave Propagations on the Vibrating Micro-cantilever

The determination of fluid density and viscosity using most cantilever-based sensors is based on changes in resonant frequency and peak width. Here, we present a wave propagation analysis using piezoelectrically excited micro-cantilevers under distributed fluid loading. The standing wave shapes of microscale-thickness cantilevers partially immersed in liquids (water, 25% glycerol, and acetone), and nanoscale-thickness microfabricated cantilevers fully immersed in gases (air at three different pressures, carbon dioxide, and nitrogen) were investigated to identify the effects of fluid-structure interactions to thus determine the fluid properties. This measurement method was validated by comparing with the known fluid properties, which agreed well with the measurements. The relative differences for the liquids were less than 4.8% for the densities and 3.1% for the viscosities, and those for the gases were less than 6.7% for the densities and 7.3% for the viscosities, showing better agreements in liquids than in gases

Simultaneous position and mass determination of a nanoscale-thickness cantilever sensor in viscous fluids

We report simultaneous determination of the mass and position of micro-beads attached to a nanoscale-thickness cantilever sensor by analyzing wave propagations along the cantilever while taking into account viscous and inertial loading due to a surrounding fluid. The fluid-structure interaction was identified by measuring the change in the wavenumber under different fluid conditions. The predicted positions and masses agreed with actual measurements. Even at large mass ratios (6%-21%) of the beads to the cantilever, this wave approach enabled accurate determination of the mass and position, demonstrating the potential for highly accurate cantilever sensing of particle-based bio-analytes such as bacteria. © 2015 AIP Publishing LLCopen0

The state of the Martian climate

60°N was +2.0°C, relative to the 1981–2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Best-value in Korean public building construction

Although the low-bid system has played a major role in public building construction sector for a long time, this system has arguably delivered work of low quality, an continued and rising number of claims within the industry. With these challenges in mind, the Korean government has sought to examine and possibly adopt best-value procurement as an alternative approach to delivering public building construction projects within Korea. The reality however is that although delivering arguably a number of advantages, best-value does present the government with its own peculiar challenges because of a lack of a precise understanding of what ‘best-value’ means. Hence, in this study, the author seeks to examine the concept of best-value and its application to Korean public building construction. To achieve the stated objectives, the author draws upon extant literature in ‘value’ procurement to critically examine the impact of ‘best-value’ concepts in Korean public building procurement. Data is obtained from a survey of 180 managers involved in the procurement and management of public buildings in Korea. Utilising ‘best-value’ criteria drawn from literature, the author employs Analytic Hierarchy Process (AHP) to weight ‘best-value’ criteria identified through the survey. Based on the results of the AHP exercise, the following are found; (i) value depends on the state of each individual building which can be defined from a ‘need’ perspective, (ii) the primary criteria for ‘best-value’ in Korea public construction projects were ‘serviceability’, ‘safety’, ‘comfort’, ‘environmental friendliness’, ‘economical feasibility’, and ‘artistry’ and finally that (?) the importance of each primary criteria was dependent on the building type

Special Feature Vibration-Based Structural Health Monitoring

Structural health monitoring by vibration requires the understanding of multidisciplinary fields of engineering sciences [...

Effects of mechanical properties of sealing systems on aerodynamic noise generation inside vehicles

One dominant “wind noise” generating mechanism in road vehicles is the interaction between turbulent flows and flexible structures: specifically door seals and side glass windows. In this study, the effects of seal mechanical properties on interior aerodynamic noise were investigated. The sound transmission characteristics of seals were first investigated. The vibration response together with the radiated sound power was computed using FE-analysis. Experimental data obtained for several seal specimens using reverberation room test methods was used in the validation of numerical models. The developed tools were used to compare sound transmission characteristics of seals made of EPDM and TPE. The validated numerical model was then utilized to investigate the influence of various design parameters on the sound transmission characteristics of seals. It was found that any unconstrained structural coupling between seal walls should be avoided to minimize sound transmission. The sound radiated by a seal-supported, rectangular plate excited by turbulent flows was then investigated. The primary goal was to assess the influence of support properties on the noise generated from the plate. The flow-induced vibration of the plate was calculated using the Corcos model for the surface pressure loading and an assumed-modes method. The results showed that support tuning can yield significant reduction in vibration amplitudes for a fixed excitation amplitude. Two different methods to calculate the optimal support stiffness were developed. The first model, based on a one-dimensional transverse wave assumption, yielded a good first cut approximation of the optimal properties. The second model, based on the assumed-modes method, yielded more accurate estimations. The optimal support stiffnesses calculated from the two different methods were in close agreement. Finally, experimental techniques to measure viscoelastic properties of foamed elastomers at high frequencies were developed and applied to measure mechanical properties of seal materials. The measurements were performed for foams with various void fractions, from which the relationship between the void fraction and the dynamic moduli was measured. The measurement results were compared to the predictions from several different micromechanics models. The results can be used to determine optimal seal mechanical properties that minimize the aerodynamic noise