scholarly journals Investigating Composting as a Mitigation Strategy for Climate Change Using a Modelling Approach

2021 ◽  
Vol 10 (4) ◽  
pp. 97
Author(s):  
Preeya Vijayalakshmee Ramasamy Coolen ◽  
Toshima Makoondlall-Chadee ◽  
Chandradeo Bokhoree ◽  
Ravi Foogooa
Keyword(s):  
Waste Management ◽  
Lumped Parameter Model ◽  
Kitchen Waste ◽  
Management Scenarios ◽  
Yard Waste ◽  
Lumped Parameter ◽  
The Impact ◽  
Optimal Set ◽  
Home Composting ◽  
Modelling Approach

The waste management sector accounts for 19% of greenhouse gases produced by the island of Mauritius, and is second to the energy sector which contributes about 77% of total emissions. Significant mitigating measures are being sought to reduce the impact of the waste sector. The main greenhouse gas produced from waste in Mauritius is methane from landfill disposal. Among the different alternate waste management scenarios proposed, home composting is one strategy to achieve carbon reductions in the sector.  However, this target can only be achieved if the composting process is properly controlled.  Objectively, a lumped parameter model was used to analyse the set of variation parameters to achieve greatest reduction in methane through optimal composting.   The composting matrix was modelled as a point source. Mass balance equations were coupled with heat transport equations and reaction kinetics equations to determine the optimal set of parameters for efficient composting of yard waste and kitchen waste.  The simulations demonstrated that bulking of vegetable waste prior to composting is required to prevent production of methane.

A Simple Dynamic Modeling of Head Slap in Hard Disk Drive

2001 ◽  
Author(s):  
Seong-Hun Lee ◽  
Jeong-Hak Lee ◽  
Kwang-Joon Kim
Keyword(s):  
Hard Disk Drive ◽  
Dynamic Modeling ◽  
Structural Design ◽  
Continuous System ◽  
Disk Drive ◽  
Lumped Parameter Model ◽  
Test Results ◽  
Lumped Parameter ◽  
Shock Resistance ◽  
The Impact

Abstract In order to understand mechanism of the impact between head and disk of a HDD subject to a shock and to improve the shock resistance effectively, it is essential to develop a dynamic model which can represent well the head slap. Although motion of the head and disk subject to a shock requires modeling by a continuous system to be rigorous, in this study, a simplified lumped parameter model is developed to understand basic dynamics of the head slap and to determine crucial parameters for the improvement of the structural design. In addition, drop test results of the HDD are presented to back to up the derived model.

scholarly journals Nutrient Analysis of Food Waste from Ships’ Greywater in the Baltic Sea

Water ◽  
2021 ◽  
Vol 13 (17) ◽  
pp. 2421
Author(s):  
Renate Kalnina ◽  
Ieva Demjanenko ◽  
Dzesika Gorbacenko ◽  
Valdis Priednieks ◽  
Janis Baronins
Keyword(s):  
Waste Management ◽  
Baltic Sea ◽  
Food Waste ◽  
Potential Risk ◽  
Nutrient Content ◽  
The Baltic Sea ◽  
Management Scenarios ◽  
Nutrient Analysis ◽  
The Baltic ◽  
The Impact

This case study presents the results of assessments of the potential risk of pollution by food waste in different applied shipping scenarios. A four-step model was used to analyse the applied procedures. The first step of the study involved the identification of possible strategies for on-board food waste management. In the second step, physicochemical tests of visually selected greywater detected high contents of nutrients (NTotal ≤ 238 mg·L−1 and PTotal ≤ 71 mg·L−1). Daily nutrient content (DNC) calculations of different food waste management scenarios allowed us to estimate the highest emission value from the discharge of greywater mixed with shredded food waste in the third step. In the final stage of the study, the results obtained made it possible to qualitatively assess the impact of DNC load on food waste management methods in the Baltic Sea environment. This study highlights the potential risk of polluting the Baltic Sea with nutrients and other contaminants in various scenarios, which will impact the marine recovery process. The presented research helps to outline waste management approaches for the reduction of these risks.

Gravitational effects on ocular pressure and perfusion pressure

2021 ◽  
Author(s):  
Lonnie G. Petersen ◽  
Richard Stuart Whittle ◽  
Justin Hyunwoo Lee ◽  
Jeremy Sieker ◽  
Joseph Carlson ◽  
...  
Keyword(s):  
Supine Position ◽  
Perfusion Pressure ◽  
Lumped Parameter Model ◽  
Lumped Parameter ◽  
Postural Changes ◽  
Gravitational Stress ◽  
Gravitational Vector ◽  
Head Up Tilt ◽  
The Impact ◽  
Ocular Hemodynamics

Changes in the gravitational vector by postural changes or weightlessness induce fluid shifts impacting ocular hemodynamics and regional pressures. This investigation explores the impact of changes in direction of the gravitational vector on intraocular pressure (IOP), mean arterial pressure at eyelevel (MAPeye), and ocular perfusion pressure (OPP), which is critical for ocular health. Thirteen subjects underwent 360° of tilt (including both prone and supine positions) at 15º increments. At each angle, steady-state IOP and MAPeye were measured and OPP calculated as MAPeye-IOP. Experimental data were compared to a 6-compartment lumped parameter model of the eye. Mean IOP, MAPeye, and OPP significantly increased from 0º supine to 90º head down tilt (HDT) by 20.7±1.7 mmHg (ᵅD; < 0.001), 38.5±4.1 mmHg (ᵅD; < 0.001), and 17.4±3.2 mmHg (ᵅD; <0.001), respectively. Head up tilt (HUT) significantly decreased OPP by 16.5±2.5 mmHg (ᵅD; < 0.001). IOP was significantly higher in prone vs. supine position for much of the tilt range. Our study indicates that OPP is highly gravitationally dependent. Specifically, data show that MAPeye is more gravitationally dependent than IOP, thus causing OPP to increase during HDT and to decrease during HUT. Additionally, IOP was elevated in prone position compared to supine position due to the additional hydrostatic column between the base of the rostral globe to the mid-caudal plane, supporting the notion that hydrostatic forces play an important role in ocular hemodynamics. Changes in OPP as a function of changes in gravitational stress and/or weightlessness may play a role in the pathogenesis of spaceflight-associated neuro-ocular syndrome.

Can high rates of passive volcanic gas emissions induce reservoir depressurization at Ambrym volcano (Vanuatu)?

2021 ◽  
Author(s):  
Tara Shreve ◽  
Raphaël Grandin ◽  
Marie Boichu
Keyword(s):  
Ground Deformation ◽  
Lumped Parameter Model ◽  
Magma Ascent ◽  
Large Reservoir ◽  
Gas Emissions ◽  
Volcanic System ◽  
Lumped Parameter ◽  
Gas Geochemistry ◽  
The Impact

&lt;p&gt;Satellite-based UV spectrometers can constrain sulphur dioxide (SO&lt;sub&gt;2&lt;/sub&gt;) fluxes at passively degassing volcanoes over decadal time scales. From 2005 to 2015, more than 15 volcanoes had mean passive SO&lt;sub&gt;2 &lt;/sub&gt;fluxes greater than 1 kiloton per day. Although the processes responsible for such high emission rates are not clearly established, this study aims to investigate the impact of strong degassing on the pressurization state of volcanic systems and the resulting ground deformation. One possible result of high degassing rates is the depressurization of the region where the melt releasing gas is stored, which may result in subsidence at the Earth&amp;#8217;s surface. Passive degassing may depressurize pathways between deep and shallow magma storage regions, resulting in magma ascent and possibly eruption.&lt;/p&gt;&lt;p&gt;A lumped-parameter model developed by Girona et al., 2014 couples the mass loss by passive degassing with reservoir depressurization in an open volcanic system. However, this model has yet to be tested using real measurements of gas emissions and ground deformation. In our study, we focus on Ambrym volcano, the past decade&amp;#8217;s top passive emitter of volcanic SO&lt;sub&gt;2&lt;/sub&gt;, which exhibits intriguing long-term subsidence patterns and no obvious pressurization preceding eruptive periods. We compare subsidence rates measured by InSAR to the system&amp;#8217;s average daily SO&lt;sub&gt;2&lt;/sub&gt; flux, focusing on a subsidence episode spanning 2015 to 2017 that is not clearly linked to magma removal from the system. Using realistic input parameters for Ambrym&amp;#8217;s system constrained by petrology and gas geochemistry, a range of reservoir volumes and conduit radii are explored. Large reservoir volumes (greater than 30 km&lt;sup&gt;3&lt;/sup&gt;) and large conduit radii (greater than 300 m) are consistent with depressurization rates obtained from geodetic modelling of InSAR measurements using the Boundary Element method. By comparing these values of reservoir volume and conduit radius with those estimated from geodesy, gas geochemistry, and seismology, we test the applicability and discuss uncertainties of the aforementioned lumped-parameter physical model to interpret the long-term subsidence at Ambrym volcano as a result of sustained passive degassing.&lt;/p&gt;

scholarly journals The total cavopulmonary connection resistance: a significant impact on single ventricle hemodynamics at rest and exercise

2008 ◽  
Vol 295 (6) ◽  
pp. H2427-H2435 ◽  
Author(s):  
Kartik S. Sundareswaran ◽  
Kerem Pekkan ◽  
Lakshmi P. Dasi ◽  
Kevin Whitehead ◽  
Shiva Sharma ◽  
...  
Keyword(s):  
Heart Rate ◽  
Single Ventricle ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Lumped Parameter Model ◽  
Total Cavopulmonary Connection ◽  
Dynamic Simulations ◽  
Lumped Parameter ◽  
The Impact ◽  
Cavopulmonary Connection

Little is known about the impact of the total cavopulmonary connection (TCPC) on resting and exercise hemodynamics in a single ventricle (SV) circulation. The aim of this study was to elucidate this mechanism using a lumped parameter model of the SV circulation. Pulmonary vascular resistance (1.96 ± 0.80 WU) and systemic vascular resistances (18.4 ± 7.2 WU) were obtained from catheterization data on 40 patients with a TCPC. TCPC resistances (0.39 ± 0.26 WU) were established using computational fluid dynamic simulations conducted on anatomically accurate three-dimensional models reconstructed from MRI ( n = 16). These parameters were used in a lumped parameter model of the SV circulation to investigate the impact of TCPC resistance on SV hemodynamics under resting and exercise conditions. A biventricular model was used for comparison. For a biventricular circulation, the cardiac output (CO) dependence on TCPC resistance was negligible (sensitivity = −0.064 l·min−1·WU−1) but not for the SV circulation (sensitivity = −0.88 l·min−1·WU−1). The capacity to increase CO with heart rate was also severely reduced for the SV. At a simulated heart rate of 150 beats/min, the SV patient with the highest resistance (1.08 WU) had a significantly lower increase in CO (20.5%) compared with the SV patient with the lowest resistance (50%) and normal circulation (119%). This was due to the increased afterload (+35%) and decreased preload (−12%) associated with the SV circulation. In conclusion, TCPC resistance has a significant impact on resting hemodynamics and the exercise capacity of patients with a SV physiology.

scholarly journals Optimal Occupant Kinematics and Crash Pulse for Automobile Frontal Impact

2009 ◽  
Vol 16 (1) ◽  
pp. 61-73 ◽  
Author(s):  
Zhiqing Cheng ◽  
Joseph A. Pellettiere ◽  
Jeff R. Crandall ◽  
Walter D. Pilkey
Keyword(s):  
Lumped Parameter Model ◽  
Frontal Impact ◽  
Vehicle Interior ◽  
Impact Speed ◽  
Vehicle System ◽  
Lumped Parameter ◽  
Passive Restraint ◽  
System Optimal ◽  
Occupant Kinematics ◽  
The Impact

Based on a lumped-parameter model of the occupant-vehicle system, optimal kinematics of the occupant in frontal impact are investigated. It is found that for the minimization of the peak occupant deceleration, the optimal kinematics move the occupant at a constant deceleration. Based on this the optimal vehicle crash pulse is investigated. The optimal crash pulse for passive restraint systems is found to be: a positive impulse at the onset, an immediate plunge followed by a gradual rebound, and finally a positive level period. The relation of the peak occupant deceleration to the impact speed, crash deformation, and vehicle interior rattlespace is established. The optimal crash pulse for active and pre-acting restraint systems is discussed.

scholarly journals Multiphase CFD Simulation of Solid Propellant Combustion in a Small Gun Chamber

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Ahmed Bougamra ◽  
Huilin Lu
Keyword(s):  
Cfd Simulation ◽  
Numerical Study ◽  
Lumped Parameter Model ◽  
Charge Weight ◽  
Maximum Pressure ◽  
Multiphase Model ◽  
Velocity Increase ◽  
Muzzle Velocity ◽  
Lumped Parameter ◽  
The Impact

The interior ballistics simulations in 9 mm small gun chamber were conducted by implementing the process into the mixture multiphase model of Fluent V6.3 platform. The pressure of the combustion chamber, the velocity, and the travel of the projectile were investigated. The performance of the process, namely, the maximum pressure, the muzzle velocity, and the duration of the process was assessed. The calculation method is validated by the comparison of the numerical simulations results in the small gun with practical tests, and with lumped-parameter model results. In the current numerical study, both the characteristics and the performance of the interior ballistic process were reasonably predicted compared with the practical tests results. The impact of the weight charge on the interior ballistic performances was investigated. It has been found that the maximum pressure and the muzzle velocity increase with the increase of the charge weight.

EFFECT OF SURFACE LAYER ON ELECTROMECHANICAL STABILITY OF TWEEZERS AND CANTILEVERS FABRICATED FROM CONDUCTIVE CYLINDRICAL NANOWIRES

2016 ◽  
Vol 23 (02) ◽  
pp. 1550101 ◽  
Author(s):  
MARYAM KEIVANI ◽  
ALI KOOCHI ◽  
HAMID M. SEDIGHI ◽  
MOHAMADREZA ABADYAN ◽  
AMIN FARROKHABADI ◽  
...  
Keyword(s):  
Surface Layer ◽  
Homotopy Perturbation Method ◽  
Differential Quadrature Method ◽  
Surface Elasticity ◽  
Lumped Parameter Model ◽  
Governing Equations ◽  
Lumped Parameter ◽  
The Stability ◽  
The Impact ◽  
Effect Of Surface

Herein, the impact of surface layer on the stability of nanoscale tweezers and cantilevers fabricated from nanowires with cylindrical cross section is studied. A modified continuum based on the Gurtin–Murdoch surface elasticity is applied for incorporating the presence of surface layer. Considering the cylindrical geometry of the nanowire, the presence of the Coulomb attraction and dispersion forces are incorporated in the derived formulations. Three different approaches, i.e. numerical differential quadrature method (DQM), an approximated homotopy perturbation method (HPM) and developing lumped parameter model (LPM) have been employed to solve the governing equations. The impact of surface layer on the instability of the system is demonstrated.

3D shape optimization of loudspeakers

2021 ◽  
Vol 263 (6) ◽  
pp. 954-964
Author(s):  
Peter Risby Andersen ◽  
Vicente Cutanda Henríquez ◽  
Niels Aage ◽  
Junghwan Kook
Keyword(s):  
Numerical Simulations ◽  
Large Scale ◽  
Lumped Parameter Model ◽  
Free Form ◽  
Adjoint Sensitivity ◽  
Design Changes ◽  
Lumped Parameter ◽  
Complex Engineering ◽  
Directivity Patterns ◽  
Modelling Approach

Improving the performance of loudspeaker units and cabinet designs traditionally relies on a combination of trial and error, sometimes based on a lumped parameter modelling approach. During the last decades, however, large-scale numerical simulations are playing a growing role as a means of improving performance of complex engineering devices such as loudspeakers. However, a numerical model still relies on the experience of the operating engineer to make the appropriate design changes. This can be a difficult task. The use of numerical simulations combined with optimization has a huge potential for further guiding the design process of advanced industrial products where intuition alone is not sufficient. Nevertheless, broadband acoustic simulations are still very time consuming. In this work, we explore the efficiency of a newly proposed semi-analytical adjoint sensitivity approach based on the boundary element method in combination with a lumped parameter model. The sensitivity analysis is used to shape optimize the cabinet of a loudspeaker using free form deformation. The objective of the optimization is to improve frequency responses and directivity patterns.

Lumped Parameter Model for Computing the Minimum Pressure During Mechanical Heart Valve Closure

2005 ◽  
Vol 127 (4) ◽  
pp. 648-655 ◽  
Author(s):  
Brant H. Maines ◽  
Christopher E. Brennen
Keyword(s):  
Scaling Laws ◽  
Mechanical Heart Valve ◽  
Lumped Parameter Model ◽  
System Component ◽  
Valve Closure ◽  
Current Form ◽  
Cavitation Inception ◽  
Minimum Pressure ◽  
Lumped Parameter ◽  
The Impact

The cavitation inception threshold of mechanical heart valves has been shown to be highly variable. This is in part due to the random distribution of the initial and final conditions that characterize leaflet closure. While numerous hypotheses exist explaining the mechanisms of inception, no consistent scaling laws have been developed to describe this phenomenon due to the complex nature of these dynamic conditions. Thus in order to isolate and assess the impact of these varied conditions and mechanisms on inception, a system of ordinary differential equations is developed to describe each system component and solved numerically to predict the minimum pressure generated during valve closure. In addition, an experiment was conducted in a mock circulatory loop using an optically transparent size 29 bileaflet valve over a range of conditions to calibrate and validate this model under physiological conditions. High-speed video and high-response pressure measurements were obtained simultaneously to characterize the relationship between the valve motion, fluid motion, and negative pressure transients during closure. The simulation model was calibrated using data from a single closure cycle and then compared to other experimental flow conditions and to results found in the literature. The simulation showed good agreement with the closing dynamics and with the minimum pressure trends in the current experiment. Additionally, the simulation suggests that the variability observed experimentally (when using dP∕dt alone as the primary measure of cavitation inception) is predictable. Overall, results from the current form of this lumped parameter model indicate that it is a good engineering assessment tool.

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