| 1. |
- Salama, Amgad, et al.
(författare)
-
Flow and transport in tight and shale formations : A review
- 2017
-
Ingår i: Geofluids. - : Hindawi Publishing Corporation. - 1468-8115 .- 1468-8123. ; , s. 1-21
-
Forskningsöversikt (refereegranskat)abstract
- A review on the recent advances of the flow and transport phenomena in tight and shale formations is presented in this work. Exploration of oil and gas in resources that were once considered inaccessible opened the door to highlight interesting phenomena that require attention and understanding. The length scales associated with transport phenomena in tight and shale formations are rich. From nanoscale phenomena to field-scale applications, a unified frame that is able to encounter the varieties of phenomena associated with each scale may not be possible. Each scale has its own tools and limitations that may not, probably, be suitable at other scales. Multiscale algorithms that effectively couple simulations among various scales of porous media are therefore important. In this article, a review of the different length scales and the tools associated with each scale is introduced. Highlights on the different phenomena pertinent to each scale are summarized. Furthermore, the governing equations describing flow and transport phenomena at different scales are investigated. In addition, methods to solve these equations using numerical techniques are introduced. Cross-scale analysis and derivation of linear and nonlinear Darcy's scale laws from pore-scale governing equations are described. Phenomena occurring at molecular scales and their thermodynamics are discussed. Flow slippage at the nanosize pores and its upscaling to Darcy's scale are highlighted. Pore network models are discussed as a viable tool to estimate macroscopic parameters that are otherwise difficult to measure. Then, the environmental aspects associated with the different technologies used in stimulating the gas stored in tight and shale formations are briefly discussed.
|
|
| 2. |
- Birgisson, Björn, et al.
(författare)
-
Influence of Mixture Properties on Fracture Mechanisms in Asphalt Mixtures
- 2010
-
Ingår i: International Journal on Road Materials and Pavement Design. - : Informa UK Limited. - 1468-0629 .- 2164-7402. ; 11, s. 61-88
-
Tidskriftsartikel (refereegranskat)abstract
- This paper reports a research study aimed at providing insight into key mechanisms and mixture properties that influence fracture in asphalt concrete. The experimental analysis was based on the Hot Mix Asphalt (HMA) Fracture Mechanics visco-elastic crack growth law. HMA cracking mechanism was investigated using multiple laboratory test configurations on both unmodified and polymer modified mixtures. A Digital Image Correlation (DIC) was employed to more accurately capture localized or non-uniform stress distributions in asphalt mixtures and as a tool for detecting first fracture. Crack initiation and crack growth were predicted effectively using a Displacement Discontinuity (DD) boundary element method.
|
|
| 3. |
- Laurell Lyne, Åsa, et al.
(författare)
-
Interaction forces between mineral aggregates and bitumen Calculated using the Hamaker constant
- 2010
-
Ingår i: International Journal on Road Materials and Pavement Design. - : Informa UK Limited. - 1468-0629 .- 2164-7402. ; 11, s. 305-323
-
Tidskriftsartikel (refereegranskat)abstract
- Moisture damages to bituminous pavements leads to costly repairs. The most serious outcome of the influence of water is the loss of adhesion between binders and aggregates. This is often described as stripping. Adhesion is the ability at a molecular level of materials to stick steadfastly to one another. An alternative way of explaining the adhesion of bitumen to aggregates is presented in this paper using the Hamaker constant, a measure of the van der Waals attraction forces between two materials. The Hamaker constant is significantly lower for water as the intervening medium than for air. For the aggregates and minerals studied, the Lifshitz-van der Waals interactions contribute 65-78 percent of the 'work of adhesion' calculated by the acid-base method. The performance of the aggregates and minerals correlates well to A(total) where resistance to stripping data is available.
|
|
| 4. |
- Montepara, Antonio, et al.
(författare)
-
Strain Localization and Damage Distribution in SBS Polymer Modified Asphalt Mixtures
- 2010
-
Ingår i: International Journal on Road Materials and Pavement Design. - : Informa UK Limited. - 1468-0629 .- 2164-7402. ; 11:4, s. 899-915
-
Tidskriftsartikel (refereegranskat)abstract
- A laboratory investigation was conducted to estimate the macroscopic cracking response of Styrene Butadiene Styrene (SBS) polymer modified asphalt mixtures by analyzing the localized strain distribution within the material microstructure. Five asphalt mixtures composed by the same aggregate gradation but different SBS modified asphalt binders were produced in the laboratory. An in-house developed Digital Image Correlation (DIC)-based system was employed to obtain 2D full-field strain maps of the specimens during tensile loading. Strain distributions were observed from three different test configurations, namely the Indirect Tensile Test (IDT), the Semi-Circular Bending (SCB) test and the Three-Point Bending (3PB) test. The cracking performances of the mixtures were evaluated using a viscoelastic fracture mechanics-based model entitled HMA Fracture Mechanics. The results clearly show the beneficial effect of SBS polymer modifier in redistributing the stress within the mastic.
|
|
| 5. |
- Petersson, Jesper, 1974
(författare)
-
Technospatialities and telehealthcare: Unfolding new spaces of visibility
- 2016
-
Ingår i: Information, Communication & Society. - 1369-118X .- 1468-4462. ; 19:6, s. 824-842
-
Tidskriftsartikel (refereegranskat)abstract
- The umbrella term ‘telehealthcare’ denotes an array of information and communication technology-based solutions for digitally connecting citizens with healthcare services. Guided by the conviction that bodies can be translated into digital data which may serve as the basis for clinical decisions made elsewhere, these designs are widely assumed to enable a mode of healthcare delivery which is independent of space and time. Addressing the increasing use of telehealthcare for personalized health monitoring targeting the growing populations of elderly and chronic-care patients, this paper suggests that such designs invariably unfold new spaces of visibility. Based on an analysis of articles published in a leading telehealthcare journal, I argue that these new visibilities do not provide a window onto something that is already there. Instead, such visibilities are shaped by the way techno-medical practices and knowledge production processes are intertwined with a specific politico-economic agenda. The paper explores differences with respect to the positioning of older people and chronic-care patients in relation to two versions of health monitoring. While each version represents an attempt to promote individual freedom, improve health outcomes and ensure a functioning healthcare system, contrasting rationales are involved and different types of spaces are being unfolded.
|
|
| 6. |
- Aghaali, Habib, 1981-, et al.
(författare)
-
Evaluation of different heat transfer conditions on an automotive turbocharger
- 2014
-
Ingår i: International Journal of Engine Research. - : Sage Publications. - 1468-0874 .- 2041-3149. ; 16:2, s. 137-151
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a combination of theoretical and experimental investigations for determining the main heat fluxes within a turbocharger. These investigations consider several engine speeds and loads as well as different methods of conduction, convection, and radiation heat transfer on the turbocharger. A one-dimensional heat transfer model of the turbocharger has been developed in combination with simulation of a turbocharged engine that includes the heat transfer of the turbocharger. Both the heat transfer model and the simulation were validated against experimental measurements. Various methods were compared for calculating heat transfer from the external surfaces of the turbocharger, and one new method was suggested.The effects of different heat transfer conditions were studied on the heat fluxes of the turbocharger using experimental techniques. The different heat transfer conditions on the turbocharger created dissimilar temperature gradients across the turbocharger. The results show that changing the convection heat transfer condition around the turbocharger affects the heat fluxes more noticeably than changing the radiation and conduction heat transfer conditions. Moreover, the internal heat transfers from the turbine to the bearing housing and from the bearing housing to the compressor are significant, but there is an order of magnitude difference between these heat transfer rates.
|
|
| 7. |
- Grahn, Markus, 1978, et al.
(författare)
-
Data-driven emission model structures for diesel engine management system development
- 2014
-
Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 15:8, s. 906-917
-
Tidskriftsartikel (refereegranskat)abstract
- This article discusses some specific data-driven model structures suitable for prediction of NOx and soot emissions from a diesel engine. The model structures can be described as local linear regression models where the regression parameters are defined by two-dimensional lookup tables. It is highlighted that this structure can be interpreted as a B-spline function. Using the model structure, models are derived from measured engine data. The smoothness of the derived models is controlled by using an additional regularization term, and the globally optimal model parameters can be found by solving a linear least squares problem. Experimental data from a five-cylinder Volvo passenger car diesel engine is used to derive NOx and soot models, using a leave-one-out cross-validation strategy to determine the optimal degree of regularization. The model for NOx emissions predicts the NOx mass flow with an average relative error of 5.1% and the model for soot emissions predicts the soot mass flow with an average relative error of 29% for the mea- surement data used in this study. The behavior of the models for different engine management system settings regarding boost pressure, amount of exhaust gas recirculation, and injection timing has been studied. The models react to the dif- ferent engine management system settings in an expected way, making them suitable for optimization of engine manage- ment system settings. Finally, the model performance dependence on the selected model complexity and on the number of measurement data points used to derive the models has been studied.
|
|
| 8. |
- Liu, Yang, et al.
(författare)
-
Competitiveness development of Chinese manufacturing enterprises in global context for crisis management
- 2010
-
Ingår i: International Journal of Management and Enterprise Development. - : InderScience Publishers. - 1468-4330 .- 1741-8127. ; 9:1, s. 87-115
-
Tidskriftsartikel (refereegranskat)abstract
- This paper connects previous research in global competitiveness analysis, taking the impact of global financial crisis into account, to evaluate how manufacturing companies are able to manage crisis by adjusting their manufacturing strategy and transformational leadership together with technology level to improve operational competitiveness performance. It develops a theoretical approach of integrating the core factors which influence the operational competitiveness performance, i.e. manufacturing strategy, and transformational leadership with technology level, into conceptual analytical models to evaluate overall competitiveness. The empirical studies are focused to case companies in the most dynamic market - China, especially large- and medium-sized manufacturing enterprises, and compare their operational performances in global context. The overall competitiveness of multiple cases are studied using the proposed analytical models to conclude the experience of crisis management, which can become a model for crisis management studies of companies globally as well as foreign companies in China.
|
|
| 9. |
- Pasternak, M., et al.
(författare)
-
Diesel engine performance mapping using a parametrized mixing time model
- 2018
-
Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 19:2, s. 202-213
-
Tidskriftsartikel (refereegranskat)abstract
- A numerical platform is presented for diesel engine performance mapping. The platform employs a zero-dimensional stochastic reactor model for the simulation of engine in-cylinder processes. n-Heptane is used as diesel surrogate for the modeling of fuel oxidation and emission formation. The overall simulation process is carried out in an automated manner using a genetic algorithm. The probability density function formulation of the stochastic reactor model enables an insight into the locality of turbulence–chemistry interactions that characterize the combustion process in diesel engines. The interactions are accounted for by the modeling of representative mixing time. The mixing time is parametrized with known engine operating parameters such as load, speed and fuel injection strategy. The detailed chemistry consideration and mixing time parametrization enable the extrapolation of engine performance parameters beyond the operating points used for model training. The results show that the model responds correctly to the changes of engine control parameters such as fuel injection timing and exhaust gas recirculation rate. It is demonstrated that the method developed can be applied to the prediction of engine load–speed maps for exhaust NO x , indicated mean effective pressure and fuel consumption. The maps can be derived from the limited experimental data available for model calibration. Significant speedup of the simulations process can be achieved using tabulated chemistry. Overall, the method presented can be considered as a bridge between the experimental works and the development of mean value engine models for engine control applications.
|
|
| 10. |
- Ahmed, Abubeker W., 1981-, et al.
(författare)
-
Evaluation of a permanent deformation model for asphalt concrete mixtures using extra-large wheel-tracking and heavy vehicle simulator tests
- 2015
-
Ingår i: International Journal on Road Materials and Pavement Design. - : Informa UK Limited. - 1468-0629 .- 2164-7402. ; 16:1, s. 154-171
-
Tidskriftsartikel (refereegranskat)abstract
- This paper evaluates a mechanistic–empirical permanent strain model for asphalt concrete mixtures. The evaluation was carried out based on two different types of tests: an extra-large wheel-tracking (ELWT) test and a full-scale accelerated pavement test using a heavy vehicle simulator (HVS). Asphalt slabs from three different types of asphalt mixtures were prepared for the ELWT test and tested at several pavement temperatures and tyre inflation pressures. Lateral wandering was also incorporated.The measured permanent deformations in the asphalt slabs were thereafter modelled using the permanent strain model from the US Mechanistic-Empirical Pavement Design Guide and model parameters were estimated for the three types of mixes. For validation, data from an HVS tested pavement structure consisting of the same asphalt mixtures as those tested using the ELWT were used. A set of calibration factors for the three mixtures were therefore obtained between the two tests. In all cases, the calibration factors were within ±20% from unity. Differences in geometry, scale, wheel loading configuration as well as the speed of loading between the two test devices could be the possible reasons for the differences in observed calibration factors.
|
|
