Using a stair horizontal-vertical illusion to increase foot clearance over an inconsistently taller stair-riser

Introduction Stair falls can be caused by inconsistent stair dimensions. During ascent, inconsistently taller stair risers lead to reduced foot clearances as the inconsistency goes unnoticed. A stair horizontal-vertical illusion increases perceived riser heights and foot clearance and could offset reduced foot clearances over inconsistently taller risers, though this might impact other stair safety measures. Method Twelve participants (age: 22 (3) years) ascended a seven-step staircase under three conditions: i) all steps consistent in riser height (consistent), ii) a 1cm increase in step 5 riser height (inconsistent) and iii) a 1cm increase in step 5 riser height, superimposed with a stair horizontal-vertical illusion (illusion). Vertical foot clearance, foot overhang, and margins of stability were assessed over step 4, 5 and 6. Perceived riser height due to the illusion was determined through a computer perception test. A One-Way Repeated Measures ANOVA compared biomechanical variables between conditions. A One Sample t test compared perceived riser height to the true height. Results Over the inconsistent step 5, foot clearance reduced by 0.8cm compared to consistent. Illusion increased foot clearance by 1.1cm and decreased foot overhang by 4% compared to inconsistent. On step 4 the illusion led to more anterior instability compared to inconsistent. Illusion and inconsistent led to more mediolateral stability compared to consistent. The illusion increased perceived riser height by 12%. Discussion Foot clearance reductions over inconsistently taller risers can be offset by a stair horizontal-vertical illusion. Additional benefits included a safer foot overhang and unaffected stability over the inconsistent riser. Changes to step 4 stability might have resulted from leaning forward to look at the step 5 illusion. The stair horizontal-vertical illusion could be a practical solution for inconsistently taller stair risers, where a rebuild is usually the only solution.

Mathematical modeling and numerical investigation of density wave instability of supercritical natural circulation loop

In present paper, a mathematical model based on the one dimensional nonlinear mass, momentum and energy conservation equations has been developed to study the density wave instability (DWI) in horizontal heater and horizontal cooler supercritical water natural circulation loop (HHHC-SCWNCL). The one dimensional nonlinear mass, momentum and energy conservation equations are discretized by using finite difference method (FDM). The numerical model is validated with the benchmark results (NOLSTA model). Numerical simulations are performed to find the threshold stability zone (TSZ) and draw the stability map for natural circulation loop. Further, effect of change in diameter and riser height on the density wave instability of SCWNCL has been investigated.

Impact pressure on an orifice plate by a rising water column driven by an air pocket in a vertical riser

Occurrences of storm geyser events have attracted significant attention in recent years. Previous studies suggest that using an orifice plate can reduce the intensity of a geyser event but may induce a water-hammer type of pressure on the orifice plate. This study was conducted to explore the factors that influence the pressure transients when an orifice plate was installed in a vertical riser. A novel model was developed to simulated the movement of a rising water column driven by an air pocket in a vertical riser with an orifice plate on the top. Water-hammer type of pressure occurs when the water column reaches the orifice plate. The current model accurately simulates the dynamics of the water column considering its mass loss due to the flow along the wall of the riser (film flow) and the existence of the orifice plate. It was found that the initial water column length and the driving pressure, as well as the riser material, have a strong relationship with the peak pressure. The riser diameter and riser height have minor effect on the peak pressure. The water-hammer induced peak pressure reaches the maximum when the orifice opening is around 0.2 times the diameter of the vertical riser.

Hydrodynamic and combustion behavior of low grade coals in the riser of a circulating fluidized bed combustor

This study is conducted for understanding the fluidization behavior in a CFB combustor for low ranked coals. A lab-scale cold CFB test rig was built at the NFCIET Multan for understanding the fluidization behaviour. Influence of fluidizing air on the fluidization behavior was observed. It was found that voidage along the riser height is affected by riser geometry. The combustion behavior of low grade coals from Thar coal was also explored in a CFB Combustor. The influence of the fluidizing air on the combustion erformance was examined and their effect on emissions was established. The temperature in the riser of the CFB rose quickly to around 900°C. This rise in temperature has caused an increase in the amount of exhaust gasses which has their influence on the suspension density. From this study, a firsthand experience of combustion behavior of low grade Pakistani coals was documented.

Influência dos Modelos Digitais de Elevação na Susceptibilidade a Escorregamento com Modelo de Regressão Logística

This paper focuses on the influence of Digital Elevation Models on the landslides susceptibility assessment in agricultural terraces, using Logistic Regression statistical model. This study was performed in a watershed located at Carvalhas Estate in Douro Valley, using an inventory of 109 landslides. To analyse the influence of the digital elevation model (DEM) resolution we used three DEMs, (A), (B) and (C). The DEMs (A) and (B) were directly obtained by processing aerial images and extracting different resolutions, 1 and 5 meters, respectively. The DEM (C), with 5m resolution, was processed with Topo to Raster interpolation method, using as input data contour lines of 10 m interval, elevation points and hydrography. The Logistic Regression was performed using two models which are distinguished by the independent variables alteration. At model 1 was used the slope, curvature, raiser slope, riser height, contributing areas and topographic wetness index. In scenario 2 we decide remove the independent variables related with the terrace geometry, riser slope and riser height. The results seems to indicate that there is no significant influence of different resolutions of Digital Elevation Models in susceptibility modelling at this small scale and using statistical methods. The independent variables riser slope and riser height provide information of the terraces geometry and the construction techniques that enter the modelling process with more detailed information.

Prediction of wind drift and evaporation losses of a sprinkler irrigation system using principal component analysis and artificial neural network technique

Principal component analysis was merged with the artificial neural network (ANN) technique to predict wind drift and evaporation losses (WDEL) from a sprinkler irrigation system. For this purpose, field experiments were conducted to determine WDEL under different conditions. Data from field experiments and previous studies were used as sample data to train the ANN model. Three models were developed to predict WDEL. In the first model (ANN1), 9 neurons (riser height, main nozzle diameter, auxiliary nozzle diameter, discharge rate of the main nozzle, discharge rate of the auxiliary nozzle, operating pressure, wind speed, air temperature and relative humidity) were used as the input layer. In the second model (ANN2), 7 neurons (riser height, operating pressure, wind speed, air temperature and relative humidity, diameter ratio and discharge ratio) were used as the input layer. The third model (ANN3) used a multivariate technique (PC1, PC2, and PC3). Results revealed that the ANN3 model had the highest coefficient of determination (R2 = 0.8349). The R2 values for the ANN1 and ANN2 models were 0.7792 and 0.4807, respectively. It can be concluded that the ANN3 model has the highest predictive capacity.

Evaluating the Effect of Operating Pressure and Riser Height on Irrigation Water Application under Different Wind Conditions in Ethiopia

Efficient and effective use of water resource is crucial to increase crop production. This can be achieved through uniform application of water and by reducing application losses. A field experiment was conducted at Wonji/Shoa Sugarcane Plantation (Ethiopia) to study the effect of sprinkler operating pressure and riser height on water distribution uniformity under different wind conditions. Three levels of operating pressure and two levels of sprinkler riser height, under three different wind conditions, were examined during the experiment. From the research evaporation and drift losses ranging from 11.2% to 16.4% were determined. Potential application efficiency (PAE) of 47.7% to 91.3% and actual application efficiency of low-quarter (AELQ) of 32.9% to 38.6% were achieved under various test combinations. Christiansen’s coefficient of uniformity (CU) of 71.7% to 81.7% and distribution uniformity (DU) of 56% to 75.7% were obtained under different test combinations. The results indicated that increase riser height leads to increase in sprinkler water uniformity. Higher sprinkler water uniformity and low application water loss have been encountered during low wind speed condition.