| 1. |
- Brus, Elisabet, et al.
(författare)
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Bed agglomeration characteristics of biomass fuels using blast-furnace slag as bed material
- 2004
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Ingår i: Energy & Fuels. - Washington, D.C. : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 18:4, s. 1187-1193
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Tidskriftsartikel (refereegranskat)abstract
- Agglomeration of bed material may cause severe operating problems during fluidized bed combustion. The attack or coating layers that are formed on the bed particles during combustion play an important role in the agglomeration process. To reduce bed agglomeration tendencies, alternative bed materials may be used. In this paper, bed agglomeration characteristics during the combustion of biomass fuels using a relatively new bed material (iron blast-furnace slag) as well as ordinary quartz sand were determined. Controlled agglomeration tests lasting 40 h, using five representative biomass fuels (bark, olive residue, peat, straw, and reed canary grass) were conducted in a bench-scale fluidized bed. The bed materials and agglomerates were analyzed using SEM/EDS and X-ray diffraction. Chemical equilibrium calculations were performed to interpret the experimental findings. The results showed that blast-furnace slag had a lower tendency to agglomerate than quartz sand for most of the fuels. The quartz particles showed an inner attack layer more often than did the blast-furnace slag. The blast-furnace slag had a lower tendency to react with elements from the fuel. The outer coating layer had similar characteristics and thickness for both bed materials when the same fuel was combusted. However, the inner attack layer thickness was larger for quartz particles. SEM/EDS analyses of the agglomerates showed that the inner Ca-K-silicate-rich attack layer was responsible for the agglomeration of quartz sand. The composition of blast-furnace slag agglomerate was similar to the outer coating layer. Chemical equilibrium calculations showed that the original composition of the blast-furnace slag was close to the equilibrium composition, and hence there was no major driving force for reactions between that bed material and K and Ca from the fuel. The homogeneous silica-rich attack layer (with a low melting temperature) was not formed to the same extent for blast-furnace slag, thus explaining the lower bed agglomeration tendency.
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| 2. |
- Schmidt, Peter, 1965-
(författare)
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Analysis of adhesively bonded joints : an asymptotic approach
- 2001
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Simulations using the Finite Element Method (FEM) play an increasingly important role in the design process of joints and fasteners in the aerospace industry. In order to utilize the potential of using adhesive bonding, there is an increasing need for effective and accurate computational methods. The geometry and the nature of an adhesive joint is, however, not so simple to describe effectively using regular FEM-codes. The main reason is that the very thin and soft adhesive layer must be modelled by a large number of FEM-elements in the thickness direction to achieve sufficiently accurate calculations. To overcome this difficulty, special FEM-elements can be developed that provides a material surface treatment of the adhesive and the joined parts. In order to create a model that reflects the above features one may introduce proper scalings on the geometry and on the material properties in terms of a perturbation parameter. Within the framework of three-dimensional elasticity, together with an asymptotic expansion method, a material surface model is obtained through a systematic procedure of derivation. In such derivation no a priori assumptions on the displacements or stress fields are needed. The final result is a variational equation posed over a single reference surface, which forms the basis of a structural element for the compound joint.
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| 3. |
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| 4. |
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| 5. |
- Berbyuk, Viktor, 1953, et al.
(författare)
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Energy-optimal control of bipedal locomtion systems
- 2002
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Ingår i: J. Stability and Control: Theory and Application, (SACTA).. - 1563-3276. ; 4:2, s. 74-89
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Tidskriftsartikel (refereegranskat)abstract
- The mathematical statement of the problem of energy-optimal control for a bipedal locomotion system is given. The proposed statement of the problem is characterized by broad utilization of experimental data of normal human locomotion. It is done mainly by means of the mathematical formulation of the constraints imposed both on the phase coordinates and on the controlling stimuli of a system. A numerical method for the solution of optimal control problems for highly nonlinear and complex bipedal locomotion systems is proposed. The method is based on a special procedure of converting the initial optimal control problem into a standard nonlinear programming problem. This is made by an approximation of the independent variable functions using smoothing cubic splines and by the solution of inverse dynamics problem. The key features of the method are its high numerical effectiveness and the possibility to satisfy a lot of restrictions imposed on the phase coordinates of the system automatically and accurately. The proposed method is illustrated by computer simulation of the energy-optimal anthropomorphic motion of the bipedal walking robot over a horizontal surface.
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| 6. |
- Berbyuk, Viktor, 1953, et al.
(författare)
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Modeling an design of robotic systems having spring-damper actuators
- 2000
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Ingår i: Proceedings of the 7th Mechatronics Forum International Conference, 6-8 September 2000, Atlanta, Georgia, USA, PERGAMON, 2000.. - 0080437036
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The role of inherent dynamics for the improvement of control strategies of robotic systems is studied. A mathematical formulation of the optimal control problem that is suitable for this investigation is proposed. In solving this problem closed-form expressions have been obtained for the optimal control strategies for n degrees-of-freedom robotic systems with passive (unpowered) drives and no restrictions upon their controlling stimuli, and with non-linear viscoelastic spring-damper actuators. The obtained results can be used in designing optimal spring-damper-like passive drives for robotic systems.
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| 7. |
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| 8. |
- Berbyuk, Viktor, 1953, et al.
(författare)
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Optimization problems of controlled multibody systems having spring-damper actuators
- 2001
-
Ingår i: International Applied Mechanics. ; 37:7, s. 935-940
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Tidskriftsartikel (refereegranskat)abstract
- The optimal control of the motion of mechanical systems is studied. A characteristic feature of these systems is the presence of passive actuators (springs, dampers, etc.). Energy-optimal control laws and structural parameters of nonlinear springdamper actuators are determined analytically, which is necessary to impart arbitrary motion to a controllable mechanical system with n degrees of freedom. As an example, a numerical solution is presented for the problem of designing an energy-optimal spring actuator for a robot manipulator of closed kinematic structure.
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| 9. |
- Berbyuk, Viktor, 1953, et al.
(författare)
-
Optimization problems of controlled multibody systems having spring-damper actuators
- 2000
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- To incorporate spring-damper actuators into the structure of multibody systems and to design optimally their parameters can give several advantages. In this paper, we tackle optimal control problems for multibody systems having spring-damper actuators. We study a fundamental question about optimal interaction between controlling stimuli generated by external drives and proportional-differential forces described by linear and angular stiffness and damping parameters. A range of questions are also addressed about the role of inherent dynamics, and how much multibody system should be governed by external drives and how much by the system's inherent dynamics. We are in particular investigating semi-passively actuated manipulator robots and bipedal walking mechanisms having spring-damper actuators. Results obtained can help to design simpler control systems of manipulator robots and legged autonomous mechanisms having less weight and energy consumption.
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| 10. |
- Boman, Christoffer, et al.
(författare)
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Characterization of inorganic particulate matter from residential combustion of pelletized biomass fuels
- 2004
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 18:2, s. 338-348
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Tidskriftsartikel (refereegranskat)abstract
- The increased focus on potential adverse health effects associated with exposure to ambient particulate matter (PM) motivates a careful characterization of particle emissions from different sources. Combustion is a major anthropogenic source of fine PM, and, in urban areas, traditional residential wood combustion can be a major contributor. New and upgraded biomass fuels have become more common, and fuel pellets are especially well-suited for the residential market. The objective of the present work was to determine the mass size distributions, elemental distributions, and inorganic-phase distributions of PM from different residential combustion appliances and pelletized biomass fuels. In addition, chemical equilibrium model calculations of the combustion process were used to interpret the experimental findings. Six different typical pellet fuels were combusted in three different commercial pellet burners (10-15 kW). The experiments were performed in a newly designed experimental setup that enables constant-volume sampling. Total-PM mass concentrations were measured using conventional filters, and the fractions of products of incomplete combustion and inorganic material were thermally determined. Particle mass size distributions were determined using a 13-step low-pressure cascade impactor with a precyclone. The PM was analyzed for morphology (using environmental scanning electron microscopy, ESEM), elemental composition (using energy-dispersive spectroscopy, EDS), and crystalline phases (using X-ray diffractometry, XRD). For complementary chemical structural characterization, time-of-flight secondary ion mass spectrometry (TOF-SIMS), X-ray photoelectron spectroscopy XPS and X-ray absorption fine structure (XAFS) spectroscopy were also used. The emitted particles were mainly found in the fine ( less than or equal 1 μm) mode with mass median aerodynamic diameters of 0.20 - 0.39 μm and an average PM1 of 89.5% ± 7.4% of total PM. Minor coarse-mode fractions (>1 μm) were present primarily in the experiments with bark and logging residues. Relatively large and varying amounts (28%-92%) were determined to be products of incomplete combustion. The inorganic elemental compositions of the fine particles were dominated by potassium, chlorine, and sulfur, with minor amounts of sodium and zinc. The dominating alkali phase was KCl, with minor but varying amounts of K3Na(SO4)2 and, in some cases, also K2SO4. The results showed that zinc is almost fully volatilized, subsequently and presumably forming a more complex solid phase than that previously suggested (ZnO). However, the formation mechanism and exact phase identification remain to be elucidated. With some constrains, the results also showed that the amounts and speciation of the inorganic PM seemed to be quite similar to that predicted by chemical equilibrium calculations.
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| 11. |
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| 12. |
- Boström, Annika, et al.
(författare)
-
Duplex scanning as the sole preoperative imaging method for infrainguinal arterial surgery
- 2002
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Ingår i: European Journal of Vascular and Endovascular Surgery. - : Elsevier BV. - 1078-5884 .- 1532-2165. ; 23:2, s. 140-145
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: to evaluate preoperative duplex as the sole investigation prior to lower limb reconstruction. Design retrospective analysis. MATERIALS AND METHODS: between January 1995 and December 1999, 157 of 329 surgical interventions for chronic infrainguinal arterial or aneurysmal disease were performed without preoperative angiography. RESULTS: in patients undergoing femoral artery endarterectomy, the extent of the stenosis and the status of the distal deep femoral artery were correctly diagnosed with duplex scanning in all but one patient. Duplex scan findings in patients undergoing infrainguinal bypass procedures were in agreement with the findings obtained from on-table angiography in regard to the selection of optimal outflow anastomotic sites in 123 (98%). Duplex scanning correctly evaluated the status of runoff in 113 (90%). There were no significant differences in 30-day occlusion rate and patency at 12 months between reconstructions performed with and without preoperative angiography. CONCLUSION: in patients with conclusive duplex scan findings there is no need to perform angiography prior to lower limb reconstruction.
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| 13. |
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| 14. |
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| 15. |
- Boström, Anders E, 1951
(författare)
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On wave equations for elastic rods
- 2000
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Ingår i: Zeitschrift für Angewandte Mathematik und Mechanik. ; 80, s. 245-251
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Tidskriftsartikel (refereegranskat)abstract
- The derivation of one-dimensional wave equtions for axially symmetric waves in elastic rods is discussed. By series expansions in the radial coordinate a hierarchy of wave equations are derived. As the lowest reasonable approximation the usual simple wave equation for the rod is recovered. At the next level a fourth order wave equation is obtained. The dispersion relation and the displacements for these approximations and for Love's equation are compared with the lowest branch of the exact Pochhammer-Chree equation. An excitation with a shear force is also solved and compared among the theories.
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| 16. |
- Boström, Anders E, 1951
(författare)
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Review of hypersingular integral equation method for crack scattering and application to modeling of ultrasonic nondestructive evaluation
- 2003
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Ingår i: Applied Mechanics Reviews. - : ASME International. - 1088-8535 .- 0003-6900 .- 2379-0407. ; 56:4, s. 383-405
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Tidskriftsartikel (refereegranskat)abstract
- The scattering of elastic waves by cracks in isotropic and anisotropic solids has important applications in various areas of mechanical engineering and geophysics, in particular in ultrasonic nondestructive testing and evaluation. The scattering by cracks can be investigated by integral equation methods, eg, boundary elements methods, but here we are particularly concerned with more analytically oriented hypersingular integral equation methods. In these methods, which are only applicable to very simple crack shapes, the unknown crack opening displacement in the integral equation is expanded in a set of Chebyshev functions, or the like, and the integral equation is projected onto the same set of functions. This procedure automatically takes care of the hypersingularity in the integral equation. The methods can be applied to cracks in 2D and 3D, and to isotropic or anisotropic media. The crack can be situated in an unbounded space or in a layered structure, including the case with an interface crack. Also, problems with more than one crack can be treated. We show how the crack scattering procedures can be combined with models for transmitting and receiving ultrasonic probes to yield a complete model of ultrasonic nondestructive testing. We give a few numerical examples showing typical results that can be obtained, also comparing with some experimental results. This review article cites 78 references.
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| 17. |
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| 18. |
- Boström, Anders E, 1951, et al.
(författare)
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Scattering of elastic waves by a rectangular crack in an anisotropic half-space
- 2003
-
Ingår i: Wave Motion. - 0165-2125. ; 38, s. 91-107
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Tidskriftsartikel (refereegranskat)abstract
- The scattering of elastic waves by a rectangular crack in a half-space of arbitrary anisotropy is considered. The application in mind is ultrasonic testing of thick-walled anisotropic components where the crack is close to a planar back surface. The orientation of the crack and the back surface may be arbitrary relative the anisotropy. The scattering problem is formulated as hypersingular integral equation for the crack-opening-displacement (COD) by means of a half-spce Green's tensor. The integral equation is solved by expanding the COD in a double series of Chebyshev functions with the correct behavior along the crack's edges. Insertion inte the integral equation and projection onto the same set of functions result in a linear system of equations for the expansion coefficients appearing in the representation of the COD. The transmitting transducer is modeled by the traction beneath it on the scanning surface and the incident field may then be calculated. An electromechanical reciprocity relation is used to model the receiving transducer. Numerical examples are included which show the influence of the anisotropy and espcially the prexence of a nearby planar back surface.
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| 19. |
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| 20. |
- Boström Ardin, Annika, et al.
(författare)
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Selection of patients with infrainguinal arterial occlusive disease for percutaneous transluminal angioplasty with duplex scanning
- 2002
-
Ingår i: Acta Radiologica. - 0284-1851 .- 1600-0455. ; 43:4, s. 391-395
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Tidskriftsartikel (refereegranskat)abstract
- AIM: To evaluate the role of duplex scanning in the selection of patients with infrainguinal arterial occlusive disease for percutaneous transluminal angioplasty (PTA). MATERIAL AND METHODS: From January 1995 through May 2000, 702 patients (952 limbs), with chronic lower extremity ischemia due to infrainguinal atherosclerotic disease diagnosed by duplex scanning, were retrospectively studied. Diagnostic angiography (130 limbs) or infrainguinal PTA (108 limbs) was performed in 238 limbs. Two investigators retrospectively analyzed the duplex examinations and angiographies in a blinded manner and used similar criteria for the interpretation of lesions suitable or not suitable for PTA. RESULTS: The superficial femoral, popliteal and crural artery lesions were correctly selected for PTA in 85%, 66% and 32%, respectively. The accuracy, sensitivity, specificity, negative predictive value and positive predictive value of duplex scanning to appropriately categorize femoropopliteal lesions as suitable or unsuitable for PTA were 89%, 83%, 92%, 94% and 78%, respectively. The accuracy of duplex scanning for predicting the performance of infrainguinal PTA was 83%. CONCLUSION: Duplex scanning has an important impact on the selection of treatment modalities in limbs with infrainguinal arterial occlusive disease. Femoropopliteal lesions can be reliably selected to PTA according to duplex scan findings.
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| 21. |
- Boström Ardin, Annika, et al.
(författare)
-
Surgical reconstruction without preoperative angiography in patients with aortoiliac occlusive disease
- 2002
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Ingår i: Annals of Vascular Surgery. - : Elsevier BV. - 0890-5096 .- 1615-5947. ; 16:3, s. 273-278
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this study was to evaluate the feasibility of performing surgical reconstructions in patients with aortoiliac occlusive disease with findings obtained solely from duplex scanning. Between January 1995 through December 1999, among 112 patients who underwent surgical intervention due to aortoiliac occlusive disease, 44 were operated on with findings obtained solely from preoperative duplex scanning. Deviations from preoperatively planned surgical interventions according to duplex scan findings and the outcome were analyzed. Our results showed that surgical reconstructions for treatment of aortoiliac occlusive disease can be safely performed by using duplex scanning as the sole preoperative diagnostic modality in patients with conclusive duplex scan findings.
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| 22. |
- Boström, Magnus, 1972-, et al.
(författare)
-
Den dubbelbottnade frivilligheten
- 2004
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Ingår i: <em>Den organiserade frivilligheten</em>. - Lund : Liber. - 9147074221 ; , s. 190-209
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 23. |
- Boström, Magnus, 1972-, et al.
(författare)
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Organiserad frivillighet
- 2004
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Ingår i: Den organiserade frivilligheten. - Lund : Liber. - 9147074221 ; , s. 7-21
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 24. |
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| 25. |
- Diligent, O, et al.
(författare)
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The low-frequency reflection and scattering of the S0 Lamb mode from a circular through-thickness hole in a plate: Finite Element, analytical and experimental studies
- 2002
-
Ingår i: Journal of the Acoustical Society of America. - : Acoustical Society of America (ASA). - 1520-8524 .- 0001-4966. ; 112:6, s. 2589-2601
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Tidskriftsartikel (refereegranskat)abstract
- A study of the interaction of the S0 Lamb wave with a circular through-thickness hole in a plate is presented. The study is limited to the nondispersive frequency range of this wave, in which the distributions of stress and displacement are simple. This allows a Finite Element analysis to be undertaken using a two-dimensional membrane discretization. Predictions of the direct reflection of the S0 mode and the lateral scattering of the SH0 mode are made for a range of diameters of the hole. At the same time, an analytical solution based on modal superposition is developed, and this is also used to predict the reflection and scattering coefficients. Both sets of predictions are validated by experimental measurements. It is found that the trends of the reflection coefficients for different hole diameters, frequencies and distances from the hole satisfy a simple normalization. On a detailed scale, the functions exhibit undulations which are shown to result from the interference of the direct reflection with secondary reflections which arrive slightly later.
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| 26. |
- Karacagil, Sadettin, et al.
(författare)
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Anastomotic rupture at the site of polytetrafluoroethylene (PTFE) and distal vein cuff of femoropopliteal bypass : Two case reports
- 2000
-
Ingår i: Upsala Journal of Medical Sciences. - 0300-9734 .- 2000-1967. ; 105:3, s. 245-248
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Tidskriftsartikel (refereegranskat)abstract
- Two female patients, 63 and 78 years of age, underwent femoropopliteal bypass with polytetrafluoroethylene (PTFE) graft and distal vein cuff. They developed graft occlusion due to false aneurysm at the site of vein cuff during one and eight weeks after surgery, respectively. Improper suture technique or weak vein wall might lead to suture disruption leading to false aneurysm as presented in this article.
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| 27. |
- Logason, Karl, et al.
(författare)
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Carotid artery endarterectomy solely based on duplex scan findings
- 2002
-
Ingår i: Vascular and endovascular surgery. - : SAGE Publications. - 1538-5744 .- 1938-9116. ; 36:1, s. 9-15
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to review experience with carotid artery surgery based on findings obtained solely from duplex scanning with special regard to unexpected findings during surgery and the early outcome. From January 1993 through December 1999, 271 consecutive patients underwent 287 carotid endarterectomies (CEAs), 229 (80%) of which were performed solely based on duplex scan findings. During the study period 5,932 carotid artery duplex scans were performed in 4,466 patients. Of 589 patients with internal carotid artery (ICA) stenosis 70%, 246 underwent CEA compared to 25 of 156 with 50-69% ICA stenosis. The indications for CEA were transient ischemic attack (TIA) in 88 (30.7%), amaurosis fugax in 60 (20.9%), previous stroke in 91 (31.7%) and asymptomatic disease in 48 (16.7%) cases. There were no statistically significant differences between the groups operated on with and without preoperative angiography with respect to the indications for surgery, associated risk factors, or the degree of stenosis on the contralateral side. In patients undergoing surgery without angiography, there were no unexpected findings that influenced the performance of surgery, in all except 1. There were no significant differences in perioperative morbidity and mortality in patients undergoing surgery with and without conventional angiography. The combined mortality and major stroke rates were 3.4% and 2.2%, respectively. It is concluded that CEA can safely be performed without preoperative angiography in cases with conclusive duplex scan findings.
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| 28. |
- Löfberg, Anne-Marie, et al.
(författare)
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Percutaneous transluminal angioplasty of the femoropopliteal arteries in limbs with chronic critical lower limb ischemia
- 2001
-
Ingår i: Journal of vascular surgery. - : Elsevier BV. - 0741-5214. ; 34:1, s. 114-121
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: The aim of the study was to evaluate the results of percutaneous transluminal angioplasty (PTA) of femoropopliteal arteries in patients with subcritical or critical lower limb ischemia. Materials and Methods: Ninety-two patients underwent 121 PTA procedures, 68 were of the superficial femoral artery (SFA), 13 of the popliteal and 40 of both arteries. Fifty-seven procedures were performed for treatment of occlusions. Eighty-four patients (94 procedures) were monitored with duplex scanning. RESULTS: Technical success rate was 88%. Primary success rates at 12 and 60 months in the whole series were 40% and 27%, respectively. The primary success rate in limbs with SFA occlusion of longer than 5 cm was only 12% after 5 years compared with 32% if the occlusion was CONCLUSION: The results of femoropopliteal PTA performed for treatment of subcritical or critical lower limb ischemia seemed to be inferior to the results of infrainguinal bypass grafting reported in literature. However, because the PTA procedure does not preclude the performance of bypass grafting, it might be an alternative to surgical intervention in limbs with stenotic femoropopliteal lesions. PTA might also be considered in patients with high surgical risk and limited life expectancy, having short occlusive lesions (< 5 cm).
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| 29. |
- Löfberg, Anne-Marie, et al.
(författare)
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The role of duplex scanning in the selection of patients with critical lower-limb ischemia for infrainguinal percutaneous transluminal angioplasty
- 2001
-
Ingår i: Cardiovascular and Interventional Radiology. - : Springer Science and Business Media LLC. - 0174-1551 .- 1432-086X. ; 24:4, s. 229-232
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To investigate the role of duplex scanning in the selection of patients with critical lower-limb ischemia (CLI) for infrainguinal percutaneous transluminal angioplasty (PTA). METHODS: One hundred and sixty-two limbs with CLI (150 patients) that underwent duplex scanning within 3 months prior to conventional diagnostic angiography (n = 88) or infrainguinal PTA (n = 74) were retrospectively studied. The findings obtained from duplex scanning and angiography were analyzed in a masked fashion by two different investigators. RESULTS: The accuracy, sensitivity, specificity, and negative and positive predictive values of duplex scanning in the selection of patients for infrainguinal PTA were 86%, 84%, 89%, 86%, and 87% respectively. Forty-two procedures (57%) were performed at multiple arterial segments. The accuracy of duplex scanning in the selection of femoropopliteal and crural lesions for PTA was over 85%. However, the sensitivity of duplex scanning in the selection of popliteal and crural lesions for PTA was 49% and 38% respectively, compared with 80% for superior femoral artery lesions. In 39% of patients who were correctly selected for PTA, duplex scanning misdiagnosed one of the multiple lesions treated by PTA. CONCLUSION: Duplex scanning can safely be used for the selection of patients for infrainguinal PTA. The sensitivity of duplex scanning in the selection of lesions for PTA was less satisfactory in the popliteal and crural arteries compared with the femoropopliteal arteries.
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| 30. |
- Palm, Anders, et al.
(författare)
-
Kontext
- 2000
-
Ingår i: Tolv begrepp inom de estetiska vetenskaperna. - 9172039175
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 31. |
- Råberg, Mathias, et al.
(författare)
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Improvement of the binary phase diagram Na2CO3 -Na2S
- 2003
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Ingår i: Energy & Fuels. - : American Chemistry Society. - 0887-0624 .- 1520-5029. ; 17:6, s. 1591-1594
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Tidskriftsartikel (refereegranskat)abstract
- Gasification of black liquor is an attractive alternative to the traditional recovery boiler. However, in process modeling of gasification, thermodynamic data for the key components are quite uncertain, which will reduce the reliability of the modeling of the chemical processes in a gasifier. The objective of this work was to experimentally re-determine and improve data on the binary phase diagram Na2CO3−Na2S, especially on the Na2CO3 side of the system, which is the region of interest concerning black liquor combustion and gasification, and also the region with the most significant uncertainties. Measurements were carried out in a dry inert atmosphere at temperatures from 25 to 1200 °C, using high-temperature microscopy (HTM) and high-temperature X-ray powder diffraction (HT-XRD). To examine the influence of pure CO2 atmosphere on the melting behavior, HTM experiments in the same temperature interval were made. This paper presents new data complementary to earlier published data on the binary phase diagram Na2CO3−Na2S. These include re-determination of liquidus curves, in the Na2CO3-rich area, melting points of the pure components, as well as determination of the extent of the solid solution, Na2CO3(ss), area.
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| 32. |
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| 33. |
- Svensson, Mats, 1960, et al.
(författare)
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Neck injuries in car collisions--a review covering a possible injury mechanism and the development of a new rear-impact dummy
- 2000
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Ingår i: Accident Analysis and Prevention. - 0001-4575. ; 32:2, s. 167-75
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Tidskriftsartikel (refereegranskat)abstract
- A review of a few Swedish research projects on soft tissue neck injuries in car collisions is presented together with some new results. Efforts to determine neck injury mechanisms was based on a hypothesis stating that injuries to the nerve root region in the cervical spine are a result of transient pressure gradients in the spinal canal during rapid neck bending. In experimental neck trauma research on animals, pressure gradients were observed and indications of nerve cell membrane dysfunction were found in the cervical spinal ganglia. The experiments covered neck extension, flexion and lateral bending. A theoretical model in which fluid flow was predicted to cause the transient pressure gradients was developed and a neck injury criterion based on Navier-Stokes Equations was applied on the flow model. The theory behind the Neck Injury Criterion indicates that the neck injury occurs early on in the rearward motion of the head relative to the torso in a rear-end collision. Thus the relative horizontal acceleration and velocity between the head and the torso should be restricted during the early head-neck motion to avoid neck injury. A Bio-fidelic Rear Impact Dummy (BioRID) was developed in several steps and validated against volunteer test results. The new dummy was partly based on the Hybrid III dummy. It had a new articulated spine with curvature and range of motion resembling that of a human being. A new crash dummy and a neck injury criterion will be very important components in a future rear-impact crash test procedure.
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| 34. |
- Timby, Niklas, et al.
(författare)
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Gamma-hydroxybutyrate associated deaths.
- 2000
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Ingår i: American Journal of Medicine. - 0002-9343. ; 108:6, s. 518-9
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 35. |
- Zhang, Bixing, 1963, et al.
(författare)
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Antiplane shear waves from a piezoelectric strip actuator: exact versus effective boundary condition solutions
- 2004
-
Ingår i: Smart Materials and Structures. - 0964-1726 .- 1361-665X. ; 13, s. 161-168
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Tidskriftsartikel (refereegranskat)abstract
- A piezoelectric strip of finite width and thickness is placed on top of an isotropic half-space. It operates in actuator mode and a time harmonic voltage is thus applied across it. The piezoelectric material is of type 6mm oriented so that a 2D antiplane (scalar) problem results. By Fourier series expansions the problem is solved exactly and this result is compared to the case when the piezoelectric strip is replaced by an effective boundary condition, which is derived by series expansions in the thickness coordinate in the piezoelectric strip. At low frequencies the results agree very well and this corresponds to the situation usually found in practice. In general the effective boundary condition should be easier to apply and it is in particular noted that this is the case when using a FEM program where the option of a piezoelectric material is usually not available.
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| 36. |
- Öhman, Marcus, et al.
(författare)
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Ash transformations during combustion of meat-, bonemeal, and RDF in a (bench-scale) fluidized bed combustor
- 2003
-
Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 17:5, s. 1153-1159
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Tidskriftsartikel (refereegranskat)abstract
- Following the recent Bovine spongiform encephalopathy (BSE) experiences, thermal treatment of meat- and bonemeal (MBM) in existing fluidized bed combustion (FBC) plants for refuse-derived fuels (RDFs) has evolved as an interesting disposal and disintegration method. However, only a limited number of studies have previously been performed for combustion of MBM in fluidized beds. The objectives of the present work were, therefore, to determine the bed agglomeration tendencies of these materials during combustion in fluidized beds and to evaluate the effects of dolomite and kaolin addition to the fuel mix, as well as to elucidate the overall ash transformation mechanisms governing the potential bed agglomeration and fouling processes. By controlled agglomeration experiments in a 5 kW bench-scale fluidized bed reactor, the fuel-specific critical agglomeration temperatures in normal quartz bed material were determined for the different fuel/additive mixtures. All collected samples of bed materials, final bed agglomerates, and cyclone ashes were analyzed using SEM/EDS and XRD. The results indicated that the MBM fuels could be expected to be problematic concerning bed agglomeration in normal quartz beds, while kaolin and possibly dolomite addition could be used to reduce this risk to moderate levels. A significant elemental fractionation between the bed material and the cyclone ash was obtained. Apatite (Ca5(PO4)3(OH) or potentially some other calcium phosphates are elutriated from the bed and enriched in the fly ash, while sodium and potassium are enriched in the bed material. The characteristics and the corresponding melting behavior estimations of the necks formed between agglomerated bed particles suggest that silicate melts are responsible for the bed agglomeration. Results from XRD analysis of the fly ash formed from the fuels used in the present study indicated that the risk for melt-related fly ash problems seem relatively small.
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| 37. |
- Öhman, Marcus, et al.
(författare)
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Effect of kaolin and limestone addition on slag formation during combustion of wood fuels
- 2004
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Ingår i: Energy & Fuels. - Washington, D.C. : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 18:5, s. 1370-1376
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Tidskriftsartikel (refereegranskat)abstract
- Ash-related problems have more than occasionally been observed in wood-fuel-fired boilers and also recently in wood-pellet burners. These problems can lead to reduced accessibility of the combustion systems as well as bad publicity for the market. The objectives of the present work were, therefore, to determine the effects of kaolin and limestone addition on the slagging propensities of problematic and problem-free wood fuels during combustion in residential pellet appliances (burners), thus contributing to the understanding of the role of kaolin and limestone in preventing slagging on furnace grates. Pellets with additive-to-fuel ratios between 0 and 0.7 wt %d.s. were combusted in three different types of burner constructions (10 kW): over-, horizontal-, and under-feeding of the fuel. The collected slag deposits from the under-fed burner as well as the corresponding deposited fly ash in the boiler were characterized with X-ray diffraction (XRD) and inductively coupled plasma atomic emission spectroscopy (ICP-AES). The initial sintering temperatures of the formed slags were also determined. By adding limestone with an additive-to-fuel ratio of 0.5 wt %d.s. to the problematic stemwood raw material (Si-enriched probably because of contamination of sand/soil), the severe slagging of the fuel could totally be eliminated. Adding kaolin to the problematic raw material gave a minor decrease in slagging tendency of the problematic raw material and a major increase in slagging tendency of the problem-free stemwood raw material. When adding limestone to the problematic raw material, the composition of the formed slag was changed from relatively low temperature melting silicates to high temperature melting silicates and oxides. On the other hand, kaolin addition to the problematic raw material changed the content of the slag from mainly Ca-Mg silicates to be dominated by K-Al silicates which have relatively low melting points. When introducing kaolin to the problem-free raw material, the high temperature melting Ca-Mg oxides react to form lower temperature melting Ca-Al-K silicates. Chemical equilibrium model calculations were used to interpret the experimental findings, and generally good qualitative agreements between modeling and experimental results were obtained. © 2004 American Chemical Society.
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| 38. |
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