Microenvironment temperature prediction between body and seat interface using autoregressive data-driven model

There is a need to develop a greater understanding of temperature at the skin–seat interface during prolonged seating from the perspectives of both industrial design (comfort/discomfort) and medical care (skin ulcer formation). Here we test the concept of predicting temperature at the seat surface and skin interface during prolonged sitting (such as required from wheelchair users). As caregivers are usually busy, such a method would give them warning ahead of a problem. This paper describes a data-driven model capable of predicting thermal changes and thus having the potential to provide an early warning (15- to 25-min ahead prediction) of an impending temperature that may increase the risk for potential skin damages for those subject to enforced sitting and who have little or no sensory feedback from this area. Initially, the oscillations of the original signal are suppressed using the reconstruction strategy of empirical mode decomposition (EMD). Consequentially, the autoregressive data-driven model can be used to predict future thermal trends based on a shorter period of acquisition, which reduces the possibility of introducing human errors and artefacts associated with longer duration “enforced” sitting by volunteers. In this study, the method had a maximum predictive error of <0.4 °C when used to predict the temperature at the seat and skin interface 15 min ahead, but required 45 min data prior to give this accuracy. Although the 45 min front loading of data appears large (in proportion to the 15 min prediction), a relative strength derives from the fact that the same algorithm could be used on the other 4 sitting datasets created by the same individual, suggesting that the period of 45 min required to train the algorithm is transferable to other data from the same individual. This approach might be developed (along with incorporation of other measures such as movement and humidity) into a system that can give caregivers prior warning to help avoid exacerbating the skin disorders of patients who suffer from low body insensitivity and disability requiring them to be immobile in seats for prolonged periods

Noise removal applied to a temperature signal from body and seat contact surface based on the EMD method

People today spend longer seated resulting from changes in demand on the workforce. As a result there is a need for a greater understanding of factors affecting pressure sore formation and comfort in general. In order to monitor the body-cushion interface temperature, we have developed a portable five-channel temperature measuring system which can be powered by a laptop. An Empirical Mode Decomposition (EMD) was used to remove noise of thermal data between body and seat contact surface. The performance of this data driven filter was compared with three other filters (medium filter, adaptive filter and wavelet filter) with the help of the goodness of fitness statistics as judgment criteria. Results showed the EMD-based filter worked better than traditional de-noising algorithms with the lowest RMSE (root-mean-square-error) and the highest R2 values

The Physics of the B Factories

This work is on the Physics of the B Factories. Part A of this book contains a brief description of the SLAC and KEK B Factories as well as their detectors, BaBar and Belle, and data taking related issues. Part B discusses tools and methods used by the experiments in order to obtain results. The results themselves can be found in Part C

Design and development of a thermal imaging system based on a temperature sensor array for temperature measurements of enclosed surfaces and its use at the body-seat interface

We describe a mapping system based on 64 evenly spaced digital sensors (thermal in this example) and interpolation algorithms. Current pressure mapping systems are suspect to noise, signal drift (creep), hysteresis and drop out of pixels, requiring frequent recalibration all of which impact on accuracy and experimental protocols. The system described here uses a one-wire-based protocol for easy configuration and reliable measurement without requiring frequent recalibration and can continuously measure temperature over a surface (seat or mattress) for hours. Additionally, in this example, the system can be used to overcome inherent drawbacks of traditional temperature (or humidity) assessment, being capable of mapping entire regions simultaneously. It greatly outperforms visual imaging (i.e. infrared) techniques at enclosed surfaces. The system, as shown here, could prove invaluable in future development of monitoring systems as it allows for more accurate parameter modelling at enclosed surfaces such as the body-seat interface. This will be useful when creating more realistic understanding of the changes occurring and how to moderate them effectively in order to reduce problems associated with prolonged wheelchair use

Does prolonged sitting with limited legroom affect the flexibility of a healthy subject and their perception of discomfort?

This study examined for differences in subjective ratings of discomfort and comfort (Numerical Rating Scale) and objective measures of hamstring (Sit-Reach test), lumbar (Schöber's test) and neck (Cervical Range of Motion) flexibility in healthy young subjects (n = 24) following 4 h of sitting on stacking chairs with or without limited legroom.When comparing the limited and unlimited legroom groups for differences in subjective and objective measures over 4 h, no significant findings were seen at the 5% level of confidence. However, differences in buttock, neck, shoulder and average discomfort were significantly negatively correlated to differences between post-warm up Sit-Reach scores (Correlation Co-efficients: -763, -434, -408, and -445; p values of .004, .034, .048, and .029, respectively). The difference in buttock discomfort was significantly negatively correlated to the difference between pre-warm up Sit-Reach scores (Correlation Coefficient: -750; p = 0.005), post-sitting/pre-warm up and pre-sitting/post-warm up Sit-Reach scores (Correlation Coefficient: -756; p = 0.004), and Schöber's tests (Correlation Coefficient: -578; p = 0.049).Although the above results suggest a relationship between a loss in flexibility and an increase in discomfort, the mechanism influencing this relationship is not clear from this study. What does appear clear is that the limiting of legroom to the parameters used in this study does not seem to exacerbate change in flexibility and discomfort which are a consequence of prolonged sitting. Relevance to industry: Many forms of public transport provide limited legroom for their passengers, which may have an adverse affect on the user's flexibility or experience of discomfort. Determining which objectively measurable parameters are associated with the subjective level of discomfort during sitting should allow for a greater appreciation of the changes that underpin such subjective perceptions

Performance Assessment of a Humidity Measurement System and Its Use to Evaluate Moisture Characteristics of Wheelchair Cushions at the User–Seat Interface

Little is known about the changes in moisture that occur at the body–seat interface during sitting. However, as increased moisture can add to the risk of skin damage, we have developed an array of MEMS (Micro-Electro-Mechanical System) humidity sensors to measure at this interface. Sensors were first evaluated against traceable standards, followed by use in a cross-over field test (n = 11; 20 min duration) using different wheelchair cushions (foam and gel). Relative humidity (RH) was measured at the left mid-thigh, right mid-thigh and coccyx. Sensors were shown to be unaffected by loading and showed highly reliable responses to measured changes in humidity, varying little from the traceable standard (<5%). Field-test data, smoothed through a moving average filter, revealed significant differences between the three chosen locations and between the gel and foam cushions. Maximum RH was attained in less than five minutes regardless of cushion material (foam or gel). Importantly, RH does not appear to distribute uniformly over the body–seat interface; suggesting multiple sensor positions would appear essential for effectively monitoring moisture in this interface. Material properties of the cushions appear to have a significant effect on RH characteristics (profile) at the body–seat interface, but not necessarily the time to peak moisture

Studying thermal characteristics of seating materials by recording temperature from 3 positions at the seat-subject interface

Aim of the study: To determine whether 3 fixed positions of seat-subject interface temperature measurement offer more information than a single point of measurement. Materials and methods: Temperature data was simultaneously acquired (sampling frequency 1 Hz/sensor) from each of three sensor positions (right & left mid-thigh and coccyx), from the subject-seat interface. The data was acquired whilst subjects (6 males, 5 females: 21-40 yrs: BMI 19.3-26.4) sat for 20 min on each of three types of seat material (foam, gel mould and solid wood). Data collection was performed at the same time of day for each subject: ambient temperature between 21.1 and 21.2 °C, ambient relative humidity 50.9%. Results: Analysis of data from the sensors, post mathematical smoothing, for each subject (n = 11; ANOVA, followed by post-hoc t-tests) revealed each of the measurement positions to have a significantly different recorded temperature (p 0.99) between subjects, a consistent finding across all 11 subjects regardless of seat material selected. Conclusion: Use of 3 positions of measurement (3 sensors) appears necessary when performing detailed studies of temperature change at the seat-subject interface. The high level of comparability of results between subjects supports potential of this method to resolve quantitative components of qualitative measurements, e.g., thermal comfort

Settling down time following initial sitting and its relationship with comfort and discomfort

This study examined the subjective rating of wheelchair comfort and discomfort (numerical rating scale questionnaire) and the duration of objective in-chair movement reduction "settling down time" following initial contact with the seating surface. Healthy young subjects (n = 22) sat for 5 min on contoured foam or wood cushion surfaces fitted to otherwise identical wheelchairs. Force sensing resistors attached to each quadrant of the sitting interface measured the relative movements of the subjects over time. A significant correlation was found between settling down time (SDT) and reported leg/feet discomfort (p = 0.003; correlation co-efficient = 0.44); and a significant negative correlation was found between SDT and overall comfort (p = 0.015; correlation co-efficient = -0.36). When comparing cushion surfaces: SDT was significantly longer (p < 0.0001) for subjects sitting on wood (5.8 s) compared to contoured foam (3.9 s); Leg/feet discomfort was significant higher (p = 0.007) for subjects sitting on wood (1.1 out of 10) compared to contoured foam (0.3 out of 10); Overall discomfort was significant higher (p = 0.009) for subjects sitting on wood (1.3 out of 10) compared to contoured foam (0.5 out of 10); Comfort was significantly lower (p = 0.001) for subjects sitting on wood (6.5 out of 10) compared to contoured foam (8.3 out of 10); Support was significantly lower (p = 0.001) for subjects sitting on wood (6.4 out of 10) compared to contoured foam (8 out of 10). The results of this study suggest that the shape and firmness of the surface at the buttock-wheelchair interface can affect a subject's SDT following initial contact with the seat as well as their perception of comfort and discomfort. In addition, there appears to be a relationship between longer SDT's and increased discomfort ratings, and shorter SDT's and increased comfort ratings. Therefore, testing for SDT's may be useful in the indirect objective assessment of wheelchair cushions and possibly other types of seating surfaces with design differences that aim to improve comfort and minimize discomfort