Concurrent validity of accelerations measured using a tri-axial inertial measurement unit while walking on firm, compliant and uneven surfaces

Although accelerometers are extensively used for assessing gait, limited research has evaluated the concurrent validity of these devices on less predictable walking surfaces or the comparability of different methods used for gravitational acceleration compensation. This study evaluated the concurrent validity of trunk accelerations derived from a tri-axial inertial measurement unit while walking on firm, compliant and uneven surfaces and contrasted two methods used to remove gravitational accelerations: i) subtraction of the best linear fit from the data (detrending), and; ii) use of orientation information (quaternions) from the inertial measurement unit. Twelve older and twelve younger adults walked at their preferred speed along firm, compliant and uneven walkways. Accelerations were evaluated for the thoracic spine (T12) using a tri-axial inertial measurement unit and an eleven-camera Vicon system. The findings demonstrated excellent agreement between accelerations derived from the inertial measurement unit and motion analysis system, including while walking on uneven surfaces that better approximate a real-world setting (all differences <0.16 m.s−2). Detrending produced slightly better agreement between the inertial measurement unit and Vicon system on firm surfaces (delta range: −0.05 to 0.06 vs. 0.00 to 0.14 m.s−2), whereas the quaternion method performed better when walking on compliant and uneven walkways (delta range: −0.16 to −0.02 vs. −0.07 to 0.07 m.s−2). The technique used to compensate for gravitational accelerations requires consideration in future research, particularly when walking on compliant and uneven surfaces. These findings demonstrate trunk accelerations can be accurately measured using a wireless inertial measurement unit and are appropriate for research that evaluates healthy populations in complex environments.

Objective measurement of physical activity in youth : current issues, future directions

Second-generation activity monitors have revolutionized the way in which we measure youth physical activity. Use of the monitors avoids the problems associated with self-report methods and allows for the estimation of physical activity patterns over time. This article examines important methodological issues related to the use of activity monitors in children and adolescents.

Validation of accelerometry for physical activity measurement in ambulant adolescents with cerebral palsy

Background Promoting participation physical activity (PA) is an important means of promoting healthy growth and development in children with cerebral palsy (CP). The ActiGraph is a uniaxial accelerometer that provides a realtime measure of PA intensity, duration and frequency. Its small, light weight design makes it a promising measure of activity in children with CP. To date no study has validated the use of accelerometry as a measure of PA in ambulant adolescents with CP. Objectives To evaluate the validity of the ActiGraph accelerometer for measuring PA intensity in adolescents with CP, using oxygen consumption (VO2), measured using portable indirect calorimetry (Cosmed K4b2), as the criterion measure. Design Validation Study Participants/Setting: Ambulant adolescents with CP aged 10–16 years, GMFCS rating of I-III. The recruitment target is 30 (10 in each GMFCS level). Materials/Methods Participants wore the ActiGraph (counts/min) and a Cosmed K4b2 indirect calorimeter (mL/kg/min) during six activity trials: quiet sitting (QS), comfortable paced walking (CPW), brisk paced walking (BPW), fast paced walking (FPW), a ball-kicking protocol (KP) and a ball-throwing protocol (TP). MET levels (multiples of resting metabolism) for each activity were predicted from ActiGraph counts using the Freedson age-specific equation (Freedson et al. 2005) and compared with actual MET levels measured by the Cosmed. Predicted and measured METs for each activity trial were classified as light (> 1.5 METs and <4.6 METs) or moderate to vigorous intensity (≥ 4.6 METs). Results To date 36 bouts of activity have been completed (6 participants x 6 activities). Mean VO2 increased linearly as the intensity of the walking activity increased (CPW=9.47±2.16, BPW=14.06±4.38, FPW=19.21±5.68 ml/kg/min) and ActiGraph counts reflected this pattern (CPW=1099±574, BPW=2233±797 FPW=4707±1013 counts/min). The throwing protocol recording the lowest VO2 (TP=7.50±3.86 ml/kg/min) and lowest overall counts/min (TP=31±27 counts/min). When each of the 36 bouts were classified as either light or moderate to vigorous intensity using measured VO2 as the criterion measure, the Freedson equation correctly classified 28 from 36 bouts (78%). Conclusion/Clinical Implications These preliminary findings suggest that there is a relationship between the intensity of PA and direct measure of oxygen consumption and that therefore the ActiGraph may be a promising tool for accurately measuring free living PA in the community. Further data collection of the complete sample will enable secondary analysis of the relationship between PA and severity of CP (GMFCS level).

Vertical displacement measurement using fibre Bragg grating (FBG) sensors for structural health monitoring of bridges

This thesis developed a practical, cost effective, easy-to-use method for measuring the vertical displacements of bridges using fiber Bragg grating (FBG) sensors, which includes the curvature and inclination approaches. These approaches were validated by the numerical simulation tests on a full scale bridge and the laboratory-based tests. In doing so, a novel frictionless FBG inclination sensor with extremely high sensitivity and resolution has also been developed and validated.

Interchangeability of infrared and conductive devices for the measurement of human skin temperature

This thesis is a comparative investigation of the methodology applied to human skin temperature measurement. The findings of this thesis suggest that clinical and significant differences exist between conductive and infrared devices which are commonly employed in the assessment of human skin temperature. These significant differences could potentially influence the interpretation of results, diagnosis and therefore treatment outcomes for health, clinical and exercise science applications.

Demonstration of nonlinear absorption in Au semi-continuous film by electrical measurement

We have demonstrated the nonlinear absorption at 532 nm wavelength in an Au semi-continuous film (SF) resulting from smearing of the Fermi distribution and diffusion of conduction electrons into the substrate. The Au SF was irradiated by a pulsed laser with 8 ns pulse width at 532 nm in near resonance with the interband transition of the Au. We determined the temperature increase in the SF for different intensities by electrical measurement. We calculated the temperature increase by using a 1D heat transport equation; comparing the results of the calculation with measured values for the temperature increase, revealed the nonlinear absorption in the Au SF. We employed this deviation from linear behaviour to determine the nonlinear absorption coefficient.

Firm-customer mobile digital connectedness : conceptualization, measurement and implications

Firm-customer digital connectedness for effective sensing and responding is a strategic imperative for contemporary competitive firms. This research-in-progress paper conceptualizes and operationalizes the firm-customer mobile digital connectedness of a smart-mobile customer. The empirical investigation focuses on mobile app users and the impact of mobile apps on customer expectations. Based on pilot data collected from 127 customers, we tested hypotheses pertaining to firm-customer mobile digital connectedness and customer expectations. Our test analysis using linear and non-linear postulations reveals those customers raise their expectations as they increase their digital interactions with a firm.

Measurement of small ions near a busy motorway

Combustion sources are well-known sources of electrical ions (Howard, J.B. et al. 1973). Motor vehicles emissions are one of the main sources of ions in urban environments. The presence of charged particles in motor vehicle emissions has been known for many years (Kittelson, 1986; Yu et al, 2004; Jung and Kittelson, 2005). Although these particles are probably charged by the attachment of air ions, there is very little information on the nature, sign and magnitude of the small ions (diameter < 1.6 nm) emitted by motor vehicles and/or present by the sides of roads.

Determinants and measurement of lean body mass in Indian adults

Indians tend to have lower lean body mass than other ethnic groups which increases the risk of chronic diseases. Three complementary studies included in this thesis advanced knowledge on determinants of lean body mass in Indians and the techniques to measure it. The first study examined the determinants of lean body mass in young Indian adults and highlighted the importance of diet and physical activity for development of lean body mass. This study has important implications for policy on prevention of chronic diseases in India. The other two studies helped refinement of the techniques of lean body mass measurement and are expected to facilitate future research in this area. The thesis is presented in the form of publications in high ranking journals.

Measurement studies on Superhydrophobic materials

Superhydrophobicity is directly related to the wettability of the surfaces. Cassie-Baxter state relating to geometrical configuration of solid surfaces is vital to achieving the Superhydrophobicity and to achieve Cassie-Baxter state the following two criteria need to be met: 1) Contact line forces overcome body forces of unsupported droplet weight and 2) The microstructures are tall enough to prevent the liquid that bridges microstructures from touching the base of the microstructures [1]. In this paper we discuss different measurements used to characterise/determine the superhydrophobic surfaces.

Measurement of contact voltage drop and resistance in organic solar cells

Bulk heterojunction organic solar cells based on poly[4,7-bis(3- dodecylthiophene-2-yl) benzothiadiazole-co-benzothiadiazole] and [6,6]-phenyl C71-butyric acid methyl ester are investigated. A prominent kink is observed in the fourth quadrant of the current density-voltage (J-V) response. Annealing the active layer prior to cathode deposition eliminates the kink. The kink is attributed to an extraction barrier. The J-V response in these devices is well described by a power law. This behavior is attributed to an imbalance in charge carrier mobility. An expected photocurrent for the device displaying a kink in the J-V response is determined by fitting to a power law. The difference between the expected and measured photocurrent allows for the determination of a voltage drop within the device. Under simulated 1 sun irradiance, the peak voltage drop and contact resistance at short circuit are 0.14 V and 90 Ω, respectively. © 2012 American Institute of Physics.

The technical efficiency of the Japanese banks : non-radial directional performance measurement with undesirable output

The paper analyses technical efficiency of the Japanese banks from 2000 to 2007. The estimation technique is based on the Russell directional distance function that takes into consideration not only desirable outputs but also an undesirable output that is represented by non-performing loans (NPLs). The results indicate that NPLs remain a significant burden as for banks' performance. We show that banks' inputs have to be utilised more efficiently, particularly labour and premises. We also argue that a further restructuring process is needed in the segment of Regional Banks. We conclude that the Japanese banking system is still far away from being fully consolidated and restructured.

Service quality and performance measurement : evidence from the Indian Water Sector

The conventional measures of benchmarking focus mainly on the water produced or water delivered, and ignore the service quality, and as a result the 'low-cost and low-quality' utilities are rated as efficient units. Benchmarking must credit utilities for improvements in service delivery. This study measures the performance of 20 urban water utilities using data from an Asian Development Bank survey of Indian water utilities in 2005. It applies data envelopment analysis to measure the performance of utilities. The results reveal that incorporation of a quality dimension into the analysis significantly increases the average performance of utilities. The difference between conventional quantity-based measures and quality-adjusted estimates implies that there are significant opportunity costs of maintaining the quality of services in water delivery.

Simulation study for analysis of online dielectric measurement problems on transformer insulation system

Determining the condition as well as the remaining life of an insulation system is essential for the reliable operation of large oil-filled power transformers. Frequency-domain spectroscopy (FDS) is one of the diagnostic techniques used to identify the dielectric status of a transformer. Currently, this technique can only be implemented on a de-energized transformer. This paper presents an initial investigation into a novel online monitoring method based on FDS dielectric measurements for transformers. The proposed technique specifically aims to address the real operational constraints of online testing. This is achieved by designing an online testing model extending the basic “extended Debye” linear dielectric model and taking unique noise issues only experienced during online measurements into account via simulations. Approaches to signal denoising and potential problems expected to be encountered during online measurements will also be discussed. Using fixed-frequency sinusoidal excitation waveforms will result in a long measurement times. The use of alternatives such as a chirp has been investigated using simulations. The results presented in the paper predict that reliable measurements should be possible during online testing.

Performance Measurement in Perspective: An exploratory study of Australian foundations’ approaches to performance measurement

Performance measurement in Australian philanthropic foundations is a hot topic. Foundation staff and board members are concerned with striking the right balance between their need for information with which to assess the effectiveness of their grant-making programs, and the costs in both time and money for grantees. Influenced by normative pressures, the increasing size and professionalism of the Australian philanthropic sector, and trends from the U.S.A and the U.K, foundations are talking amongst themselves, seeking expert advice and training, consulting with grantees and trying different approaches. Many resources examine methods of data collection, measurement or analysis. Our study instead treads into less charted but important territory: the motivations and values that are shaping the debate about performance measurement. In a series of 40 interviews with foundations from Queensland, New South Wales, Victoria and South Australia, we asked whether they felt under pressure to measure performance and if so, why. We queried whether everyone in the foundation shared the same views on the purposes of performance measurement; and the ways in which the act of performance measurement changed their grant-making, their attitude to risk, their relationship with grantees and their collaborations with other funders. Unsurprisingly, a very diverse set of approaches to performance measurement were revealed.