Development of a wide-range soft sensor for predicting wastewater BOD5 using an eXtreme gradient boosting (XGBoost) machine.

In wastewater monitoring, detecting extremely high pollutant concentrations is necessary to properly calibrate the treatment process. However, existing hardware sensors have a limited linear range which may fail to measure extremely high levels of pollutants; and likewise, the conventional "soft" model sensors are not suitable for the highly-skewed data distributions either. This study developed a new soft sensor by using eXtreme Gradient Boosting (XGBoost) machine learning to 'measure' the wastewater organics (in terms of 5-day biochemical oxygen demand (BOD5)). The soft sensor was tested on influent and effluent BOD5 of two different wastewater treatment plants to validate the results. The model results showed that XGBoost can detect these extreme values better than conventional soft sensors. This new soft sensor can function using a sparse input matrix via XGBoost's sparsity awareness algorithm - which can address the limitation of the conventional soft sensor with the fallibility of supporting hardware sensors even.

Toward orthogonal non-individualised head-related transfer functions for forward and backward directional sound: cluster analysis and an experimental study.

Individualised head-related transfer functions (HRTFs) have been shown to accurately simulate forward and backward directional sounds. This study explores directional simulation for non-individualised HRTFs by determining orthogonal HRTFs for listeners to choose between. Using spectral features previously shown to aid forward-backward differentiation, 196 non-individualised HRTFs were clustered into six orthogonal groups and the centre HRTF of each group was selected as representative. An experiment with 15 listeners was conducted to evaluate the benefits of choosing between six centre-front and six centre-back directional sounds rather than the single front/back sounds produced by MIT-KEMAR HRTFs. Sound localisation error was significantly reduced by 22% and 65% of listeners reduced their front-back confusion rates. The significant reduction was maintained when the number of HRTFs was reduced from six to five. This represents a preliminary success in bridging the gap between individual and non-individual HRTFs for applications such as spatial surround sound systems. STATEMENT OF RELEVANCE: Due to different pinna shapes, directional sound stimuli generated by non-individualised HRTFs suffer from serious front-back confusion. The reported work demonstrates a way to reduce front-back confusion for centre-back sounds generated from non-individualised HRTFs.

A low cost, non-individualized surround sound system based upon head related transfer functions: an ergonomics study and prototype development.

This paper reports on the types and magnitudes of localization errors of simulated binaural direction cues generated using non-individualized, head-related transfer functions (HRTFs) with different levels of complexity. Four levels of complexity, as represented by the number of non-zero coefficients of the associated HRTF filters (128, 64, 32, 18 non-zero coefficients), were studied. Experiment 1 collected 1728 data runs that were exhaustive combinations of the four levels of complexity, nine simulated directions of sound (no direction (i.e., diotical-mono), 0 degrees , 45 degrees , 90 degrees , 135 degrees , 180 degrees , 225 degrees , 270 degrees , and 315 degrees azimuth angles at 0 degrees elevation), two repetitions, and 24 participants). Binaural cues generated from HRTFs of reduced complexity (from 128 to 18 non-zero coefficients) produced significantly higher localization errors for the directions of 45 degrees , 135 degrees , 225 degrees , and 315 degrees azimuth angles (p<0.01). From the directions of 0 degrees , 90 degrees , and 270 degrees azimuth angles, the cues produced by HRTFs with reduced complexity did not affect the localization error (p>0.2). Surprisingly, cues produced by HRTFs of 128 non-zero coefficients did not have the lowest number of errors. From 45 degrees , 135 degrees , 225 degrees , and 315 degrees , the lowest numbers of errors were obtained from cues produced by HRTFs of 64, 32, 32, and 64 non-zero coefficients, respectively. Based on these findings, a prototype virtual headphone-based surround-sound (VHSS) system was developed. A double-blind usability experiment with 32 participants indicated that the prototype VHSS system received significantly better surround-sound ratings than did a Dolby stereo system (p<0.02). This paper reports results from an original ergonomics study and the application of these results to the design of a consumer product.

Factors affecting the appreciation generated through applying human factors/ergonomics (HFE) principles to systems of work.

This retrospective study examined the levels of appreciation (applause) given by clients to Human Factors/Ergonomic (HFE) specialists after they have modified the systems of work. Thirteen non-academic projects were chosen because the HFE interventions involved changed the way workers work at their workplaces. Companies involved range from multi-national corporations and military organizations with thousands of employees to small trading companies with less than 10 employees. In 5 cases the HFE recommendations were fully adopted and well appreciated. In 4 they were largely ignored and not appreciated, with partial adoption and some appreciation in the other 4 cases. Three factors that predict appreciation were identified: (i) alignment between the benefits HFE can provide and the project's key performance indices; (ii) awareness of HFE among the client's senior management; and (iii) a team organization appropriate for applying HFE recommendations. Having an HFE specialist on the client's side can greatly increase levels of appreciation, but lack of such a specialist will not affect levels of appreciation. A clear contractual requirement for HFE intervention does not promote appreciation significantly, but its absence can greatly reduce levels of appreciation. These relationships are discussed using the Kano's model of quality. Means to generate greater appreciation of the benefits of HFE are discussed.

Combined and interacting effects of hand and head movement delays on discrete manual performance in a virtual environment.

Transmission delays occur when a virtual environment responds to the hand and head movements of an operator. The effects of hand and head-related delays on discrete manual performance was investigated experimentally and compared. Imposed hand and head-related pure delays equal to or greater than 110 ms and 220 ms, respectively, significantly increased hand Movement Time (MT). The effect of hand-related delays was greater than that of head-related delays of the same magnitude. A regression model describing the combined effects of both delays on MT is reported (R(2) = 0.95). Analyses of the interactions among delays, target width, and distances have shown the need to adopt the traditional classification of delays into (1) control delay, and (2) display delay. The use of this taxonomy and the regression analyses to describe and explain the effects of individual and combined effects of delays on discrete target-reaching task performance in virtual environments are discussed.