Development of a Pressure Related Assessment Model of Seating Discomfort

1993 ◽  
Vol 37 (10) ◽  
pp. 831-835 ◽  
Author(s):  
Wenqi Shen ◽  
Ian A. R. Galer
Keyword(s):  
Factor Model ◽  
Pressure Ratio ◽  
Assessment Model ◽  
Maximum Pressure ◽  
Extensive Literature ◽  
Interface Pressure ◽  
Measuring Device ◽  
Seat Angle ◽  
Postural Changes ◽  
Seating Discomfort

This study consisted of the development of a factor model and a sitting interface pressure related assessment model of sitting discomfort, based on an extensive literature review. The factor model identified the force applied on the sitter's body as one of the main factors causing seating discomfort. The assessment model proposed that sitting discomfort mainly arises from feelings in the lumbar and buttock areas, and that local discomfort either depends upon or, is reflected by, the interface pressure. A pilot experiment was conducted to explore the utility of the assessment model by change of postural angles. Eleven subjects attended a 40 min sitting session. The independent variables were seat angle and seat-to-backrest angle. A pressure measuring device was used to record interface pressure between the subject and a prototype seat surface. A general comfort scale was administered after each pressure measurement. Results showed that all pressure measures were sensitive to postural changes of varied angulation, and that subjective ratings of comfort correlated with pressure measures, especially maximum pressure, average pressure ratio and maximum pressure gradient. Evidence from the pilot suggested that the model may have utility and eventually be used to assess seating discomfort.

Performance of Strongly Bowed Stators in a Four-Stage High-Speed Compressor

2004 ◽  
Vol 126 (3) ◽  
pp. 333-338 ◽  
Author(s):  
Axel Fischer ◽  
Walter Riess ◽  
Joerg R. Seume
Keyword(s):  
Mass Flow ◽  
High Speed ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Pressure Rise ◽  
Maximum Pressure ◽  
Controlled Diffusion ◽  
Stage 4 ◽  
The University

The FVV sponsored project “Bow Blading” (cf. acknowledgments) at the Turbomachinery Laboratory of the University of Hannover addresses the effect of strongly bowed stator vanes on the flow field in a four-stage high-speed axial compressor with controlled diffusion airfoil (CDA) blading. The compressor is equipped with more strongly bowed vanes than have previously been reported in the literature. The performance map of the present compressor is being investigated experimentally and numerically. The results show that the pressure ratio and the efficiency at the design point and at the choke limit are reduced by the increase in friction losses on the surface of the bowed vanes, whose surface area is greater than that of the reference (CDA) vanes. The mass flow at the choke limit decreases for the same reason. Because of the change in the radial distribution of axial velocity, pressure rise shifts from stage 3 to stage 4 between the choke limit and maximum pressure ratio. Beyond the point of maximum pressure ratio, this effect is not distinguishable from the reduction of separation by the bow of the vanes. Experimental results show that in cases of high aerodynamic loading, i.e., between maximum pressure ratio and the stall limit, separation is reduced in the bowed stator vanes so that the stagnation pressure ratio and efficiency are increased by the change to bowed stators. It is shown that the reduction of separation with bowed vanes leads to a increase of static pressure rise towards lower mass flow so that the present bow bladed compressor achieves higher static pressure ratios at the stall limit.

scholarly journals Evaluation of a 38 L Explosive Chamber for Testing Coal Dust Explosibility

2019 ◽  
Vol 2019 ◽  
pp. 1-7
Author(s):  
Robert Eades ◽  
Kyle Perry
Keyword(s):  
United States ◽  
Standardized Tests ◽  
Coal Dust ◽  
Pressure Ratio ◽  
Mining Industry ◽  
The United States ◽  
Maximum Pressure ◽  
Underground Coal Mine ◽  
Industry Research ◽  
Dust Explosions

Coal dust explosions are the deadliest disasters facing the coal mining industry. Research has been conducted globally on this topic for decades. The first explosibility tests in the United States were performed by the Bureau of Mines using a 20 L chamber. This serves as the basis for all standardized tests used for combustible dusts. The purpose of this paper is to investigate the use of a new 38 L chamber for testing coal dust explosions. The 38 L chamber features design modifications to model the unique conditions present in an underground coal mine when compared to other industries where combustible dust hazards are present. A series of explosibility tests were conducted within the explosive chamber using a sample of Pittsburgh pulverized coal dust and a five kJ Sobbe igniter. Analysis to find the maximum pressure ratio and Kst combustible dust parameter was performed for each trial. Based upon this analysis, observations are made for each concentration regarding whether the explosibility test was under-fueled or over-fueled. Based upon this analysis, a recommendation for future explosibility testing concentrations is made.

A Correction to the Barotropic Model of Gaseous Cavitation in Choked Converging-Diverging Nozzle Flows

2020 ◽  
Author(s):  
Michael Waldrop ◽  
Flint Thomas
Keyword(s):  
Static Pressure ◽  
Pressure Ratio ◽  
Normal Shock ◽  
Inlet Pressure ◽  
Maximum Pressure ◽  
Prediction Errors ◽  
Cavitation Model ◽  
Static Pressure Distribution ◽  
Shock Solution ◽  
Nozzle Inlet

Abstract The Barotropic Cavitation Model describes the behavior of a homogeneous mixture of liquid and gas bubbles (gaseous cavitation) as it traverses a converging-diverging (CD) nozzle. Its normal shock formulation makes reliable and accurate predictions of streamwise static pressure distribution from the nozzle inlet to just downstream of the throat and in the diverging section as the flow approaches the nozzle outlet. It fails in the intermediate portion of the divergence with maximum pressure prediction errors (as a fraction of nozzle inlet pressure) roughly equivalent to the back pressure ratio (as high as 0.46). A correction to the streamwise static pressure distributions predicted by the normal shock solution of the Barotropic Cavitation Model is proposed, applied and compared to experiments with aerated and non-aerated cavitation in several fluids. When used to simulate aerated cavitation of dodecane in a CD nozzle it predicts the location of first disagreement between the normal shock solution and experimental static pressure measurements within 4% of nozzle length. A polynomial curve fit between this predicted point (xcorr) and the normal shock location (xshock) then reduces maximum prediction error for static pressure in the correction region to no more than 0.11 (as a fraction of inlet pressure) for the aerated dodecane cases examined. For non-aerated gaseous cavitation in dodecane, water or JP8 jet fuel this error ratio does not exceed 0.13 and typical values are less than 0.07.

An analytic network process (ANP) model to examine LEED-certified buildings’ operational performance

2017 ◽  
Vol 7 (4) ◽  
pp. 366-376 ◽  
Author(s):  
Gulbin Ozcan Deniz
Keyword(s):  
Life Cycle ◽  
Analytic Network Process ◽  
Economic Life ◽  
The Body ◽  
Assessment Model ◽  
Operational Performance ◽  
Building Performance ◽  
Extensive Literature ◽  
Content Type ◽  
Network Process

Purpose The purpose of this paper is to create and present a Leadership in Energy and Environmental Design New Construction (LEED NC) building performance assessment model that will identify and prioritize external parameters affecting a LEED-certified building’s operational performance. Design/methodology/approach The uncertainty associated with external parameters affecting a LEED-certified building’s operational performance is examined through the use of analytic network process (ANP). An ANP model is created based on the extensive literature research and experiences of professionals in the green building industry. Eight case studies are analyzed, and data collected through interviews with experts are utilized in prioritizing external parameters affecting buildings’ operational performance. Findings The findings show that the most important external parameters affecting a LEED-certified building’s operational performance are lack of enhanced commissioning, lack of life cycle assessment/life cycle costing analysis, lack of energy modeling, and lack of knowledge in green technology. The results demonstrate that both asset value and profit, as well as the economic life of the facility, are mostly affected by the energy efficiency of the building, and consequently LEED NC energy and atmosphere category. Originality/value This research contributes to the body of knowledge on green architecture by defining and prioritizing external parameters and their relationships to operational building performance in LEED NC projects. The proposed model can be used by construction managers and facility managers to operate LEED-certified buildings better and reduce environmental impacts throughout the functional life cycle of the building.

Lean and Straight Nozzle Vanes in a Variable Geometry Turbine: A Steady and Pulsating Flow Investigation

2008 ◽  
Author(s):  
Srithar Rajoo ◽  
R. F. Martinez-Botas
Keyword(s):  
Pressure Ratio ◽  
Velocity Ratio ◽  
Pulsating Flow ◽  
Maximum Pressure ◽  
Variable Geometry ◽  
Flow Investigation ◽  
Variable Geometry Turbine ◽  
The Difference ◽  
Vane Angle ◽  
Ratio Range

Variable Geometry Turbines (VGT) are widely used to improve engine-turbocharger matching and currently common in diesel engines. VGT has proven to provide air boost for wide engine speed range as well as reduce turbo-lag. This paper presents the design and experimental evaluation of a variable geometry mixed flow turbocharger turbine. The tests have been carried out with a permanent magnet eddy current dynamometer within a velocity ratio range of 0.47 to 1.09. The peak efficiency of the variable geometry turbine corresponds to vane angle settings between 60° and 65°, for both the lean and straight vanes in the region of 80%. The variable geometry turbine was tested under pulsating flow with straight and lean nozzle vanes for different vane angle settings, 40Hz and 60Hz flow. In general, the range of mass flow parameter is higher in the straight nozzle vanes with an average of 66.4% and 69.7% for 40Hz and 60Hz flow respectively. The straight nozzle vanes also shows increasing pressure ratio range compared to the lean nozzle vanes, which is more apparent in the maximum pressure ratio experienced by the turbine in an unsteady cycle. In overall, the cycle averaged efficiency in the straight vane configuration is marginally higher than the lean vane. Furthermore, the difference to the equivalent quasi-steady is better in the straight vane configuration compared to the lean vane.

Numerical Simulation of 3D Flow in Turbomolecular Pump by Direct Simulation Monte Carlo Method

2005 ◽  
Author(s):  
S. Wang ◽  
H. Ninokata
Keyword(s):  
Monte Carlo ◽  
Stokes Equations ◽  
Pressure Ratio ◽  
Direct Simulation Monte Carlo ◽  
Speed Ratio ◽  
Maximum Pressure ◽  
3D Analysis ◽  
Direct Simulation ◽  
Turbomolecular Pump ◽  
Simulation Monte Carlo

A Turbomolecular pump (TMP) is one of the key apparatus to produce high and ultrahigh vacuum. It works mainly in the conditions of free molecular and transitional regimes, where the Navier-Stokes equations of continuum gas dynamics can not be correctly applied. In this study, the flow field in single blade row of one stage TMP is investigated by direct simulation Monte Carlo (DSMC) method with a 3D analysis in a rotating reference frame. Considering the Coriolis and centrifugal accelerations, the equations about the molecular velocities and position are deduced on this frame. The VSS model and NTC collision schemes are used to calculate the intermolecular collisions. The diffuse reflection is employed on the molecular reflection from the surfaces of boundary. The transmission probabilities are calculated and applied to analyze the relationship between the outlet pressure and the maximum pressure ratio. The pumping performances between H2 and N2 on the same blade speed and same blade speed ratio are compared and analyzed carefully. The maximum pumping efficiencies on the different blade angles are also calculated. Numerical results show good quantitative agreement with existing experiment data.

scholarly journals An evaluation of force attenuation, comfort properties and density of materials for hip protective pads

2019 ◽  
Vol 14 ◽  
pp. 155892501985395 ◽  
Author(s):  
Wiah Wardiningsih ◽  
Olga Troynikov
Keyword(s):  
Elderly Women ◽  
Interface Pressure ◽  
Plate Interface ◽  
Evaporative Resistance ◽  
Measuring Device ◽  
Nonwoven Fabrics ◽  
Wear Comfort ◽  
Materials Used ◽  
Spacer Fabrics ◽  
Dry Thermal Resistance

We evaluated 15 materials for their effectiveness as hip protective pads for elderly women, including several materials used in commercially available pads and novel materials. The materials’ densities were measured, and they were tested for force attenuation (relevant to protection), permeability index (relevant to thermophysiological wear comfort) and interface pressure delivery (relevant to pressure comfort). Force attenuation values were obtained in drop impact tests. Permeability data were obtained from the dry thermal resistance and evaporative resistance of the pads tested using a sweating guarded hot plate. Interface pressure delivery values were acquired using a Salzmann pressure-measuring device MST MK IV. Experimental pads were graded, rated and ranked on their overall performance using weights applied to the four parameters. Vertically lapped nonwoven fabrics and treated knitted spacer fabrics were highly ranked and could be used as material for hip protective pads.

Telemetric Intracranial Pressure Recording via a Shunt System Integrated Sensor: A Safety and Feasibility Study

2017 ◽  
Vol 78 (06) ◽  
pp. 572-575 ◽  
Author(s):  
Elvis Hermann ◽  
Hans Heissler ◽  
Joachim Krauss ◽  
Philipp Ertl
Keyword(s):  
Intracranial Pressure ◽  
Normal Pressure Hydrocephalus ◽  
Sampling Rate ◽  
Normal Pressure ◽  
Shunt Surgery ◽  
Shunt System ◽  
Measuring Device ◽  
Handheld Device ◽  
Additional Surgery ◽  
Postural Changes

Background The dynamics of intracranial pressure (ICP) after shunt surgery in patients with normal pressure hydrocephalus (NPH) are poorly known. Temporarily implanted parenchymal pressure probes are reliable for accurate ICP monitoring; however, a disadvantage of this method is that the ICP probe has to be explanted after a period of time, requiring additional surgery. We present two patients with NPH with an integrated ICP measuring device in the shunt system that allows for long-term postoperative telemetric monitoring of ICP. Methods Two patients (one man, 66 years old, and one woman, 78 years old) with normal pressure hydrocephalus underwent shunt surgery using the Aesculap-Miethke Sensor Reservoir (Potsdam) as an ICP measuring device integrated in the shunt system. On the first postoperative day and during follow-up examination 3 months later, several measurements of ICP were performed using a handheld device to read the Sensor Reservoir data. Postural changes such as lying down, sitting, and standing with different head postures were assessed according to an experimental protocol in a randomized order during which the ICP was measured. Results There were clear ICP responses due to postural changes, in line with physiologically expected values. Because the highest sampling rate of the Aesculap-Miethke Sensor Reservoir is 1 Hz for continuous measurement of ICP, however, the collected data have to be considered an approximation for actual ICP dynamics. Conclusion The Aesculap-Miethke Sensor Reservoir is an easy-to-use tool to measure ICP changes reliably in patients with a shunt system. The sampling rate and handling of data acquisition may eventually be developed further.

scholarly journals Predicting Compression Pressure of Knitted Fabric Using a Modified Laplace’s Law

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4461
Author(s):  
Yetanawork Teyeme ◽  
Benny Malengier ◽  
Tamrat Tesfaye ◽  
Simona Vasile ◽  
Wolelaw Endalew ◽  
...  
Keyword(s):  
Physical Parameters ◽  
Interface Pressure ◽  
Compression Pressure ◽  
Engineering Strain ◽  
Measuring Device ◽  
Laplace’S Law ◽  
The Difference ◽  
Experimental Pressure ◽  
Laplace's Law

The aim of this study is to develop a mathematical model for the prediction of compression pressure based on fabric parameters, such as engineering stress, engineering strain and engineering modulus of elasticity. Four knitted compression fabrics with different fibrous compositions and knit structures were used. Rectangular-cut strips were employed for the force–elongation characterization of the fabrics. The experimental pressure values between the fabric and rigid cylinder were assessed using a Picopress pressure measuring device. The mechanical and physical parameters of the fabric that influence the interface pressure, such as strain, elasticity modulus/stress and thickness, were determined and integrated into Laplace’s law. A good correlation was observed between the experimental and calculated pressure values for all combinations of fabrics, mounted with variable tension on the cylinder. Over the considered range of pressures, the difference between the two datasets was generally less than 0.5 mmHg. The effect of washing after five, ten and fifteen washing cycles on the fabric–cylinder interface pressure was found to be significant.

A case study on interface pressure pattern of two garment orthoses on a child with cerebral palsy

2020 ◽  
Vol 234 (8) ◽  
pp. 884-894
Author(s):  
Ida Hasni Shaari ◽  
Noor Azuan Abu Osman ◽  
Hanie Nadia Shasmin
Keyword(s):  
Cerebral Palsy ◽  
Maximum Pressure ◽  
Spastic Diplegia ◽  
Test Duration ◽  
Sitting Position ◽  
Interface Pressure ◽  
Truncal Ataxia ◽  
Sit To Stand ◽  
Different Levels

Many studies have shown that medical compression products produce different levels of interface pressure during the usage of the products. However, limited studies have explored the pattern of interface pressure exerted by orthotic garments. This case study aimed to investigate the pattern of interface pressure exerted by two types of orthotic garments on a child with cerebral palsy. A 13-year-old child diagnosed with ataxic spastic diplegia cerebral palsy has difficulty to perform sit-to-stand motion even with a walking frame due to his truncal ataxia. A TheraTogsTM orthosis and a Dynamic Lycra® Fabric Orthosis (DLFO) were prepared for the child. The child’s sit-to-stand ability without and with the usage of orthoses was recorded using five sit-to-stand tests. The garments’ interface pressure was measured using F-scan (9811E) and F-scan 6.5.1 version software. The pressure was recorded when the child was in sitting position and performing sit-to-stand-to-sit motion. Overall, the child completed the five sit-to-stand test duration within 2.53 ± 0.04 s and 2.51 ± 0.09 s with the usage of TheraTogsTM orthosis and DLFO, respectively. Higher pressure was exerted by Dynamic Lycra Fabric Orthosis (axillary = 122 mmHg) in contrast to TheraTogsTM orthosis (77 mmHg) when the child was in a sitting position. Lower pressure was exerted by DLFO (7 mmHg), over xiphoid level and for TheraTogsTM orthosis is 1.2 mmHg over axillary level when the child was performing sit-to-stand motion. The largest range of pressure was exerted by TheraTogsTM orthosis with a minimum pressure of 5 mmHg and a maximum pressure of 155 mmHg during sit-to-stand motion. Overall, the DLFO exerted higher mean interface pressure on the child in comparison to TheraTogsTM orthosis when the child’s body was in a sitting position wearing both upper garment and pants. Both TheraTogsTM orthosis and DLFO presented a different range of interface pressure over different body segments and activities.

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