| 31. |
- Berg, Miguel
(författare)
-
Maintaining high Capacity for Centralized DCA with Limited Measurements and Signaling
- 1999
-
Ingår i: Proceedings of the 1999 10th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC '99, Osaka, Japan, Sept 12 - 15, 1999. - New York : IEEE.
-
Konferensbidrag (refereegranskat)abstract
- Centralized dynamic channel allocation strategies can, in theory, achieve very high capacity in terms of achievable load at a certain quality level. Unfortunately, these strategies have often been considered non-feasible in practice due to the massive amount of measurements and signaling typically required. In this paper we evaluate some methods to maintain high performance while drastically reducing the measurement and signaling requirements. Our DCA algorithm is based on measurements of the link gain matrix. We show that for a microcellular Manhattan environment, only the gains from the three strongest beacons have to be measured and signaled by each mobile in order to achieve almost the same capacity as an ideal system where all beacons can be measured.
|
|
| 32. |
- Berg, Miguel
(författare)
-
Performance of Mobile Station Location Methods in a Manhattan Microcellular Envoronment
- 2001
-
Ingår i: 3GW 2001, San Fransisco, June 2001.
-
Konferensbidrag (refereegranskat)abstract
- Positioning of users in cellular systems is an area attracting large interest and the number of applications for the location information is growing rapidly. Large-scale deployment of such applications will require methods for positioning that are simple enough to be used in mobile phones. In this paper, we evaluate the location accuracy for some different algorithms in a microcellular environment. We propose some simple but quite accurate methods and compare them with commonly known methods. Our results show that in the studied environment, all our proposed algorithms can at least manage the US E911 phase II requirements of positioning emergency calls within 125 m, 67 percent of the time.
|
|
| 33. |
- Berglund, P., et al.
(författare)
-
Alcohols as enantioselective inhibitors in a lipase catalysed esterification of a chiral acyl donor
- 1995
-
Ingår i: Biotechnology Letters. - 0141-5492. ; 17:1, s. 55-60
-
Tidskriftsartikel (refereegranskat)abstract
- Increased reaction rates and increased enantioselectivities were observed with decreased concentrations of n-alkanols when resolving 2-methyldecanoic acid by esterification catalysed by immobilised lipase from Candida rugosa at controlled water activities in cyclohexane. The enantioselectivity was found to be independent of the water activity in the reaction medium at the n-heptanol concentrations investigated. However, when n-decanol was used as the acyl acceptor, not only the alcohol concentration but also the water activity in the reaction medium, influenced the enantioselectivity. The results obtained showed that the low enantioselectivity seen at a high alcohol concentration could be explained by the alcohol influencing the apparent V(max)(S) and V(max)(R) differently.
|
|
| 34. |
- Berglund, Per, et al.
(författare)
-
Enantiorecognition of Chiral Acids by Candida rugosa Lipase : Two Substrate Binding Modes Evidenced in an Organic Medium
- 2001
-
Ingår i: Applied Biocatalysis in Speciality Chemicals and Pharmaceuticals. - : American Chemical Society (ACS). - 0841236798 ; 776, s. 263-273
-
Konferensbidrag (refereegranskat)abstract
- We have identified the existence of different modes of binding the enantiomers of 2-methyl-branched carboxylic acids to a lipase active site by rational substrate engineering. Similar to hydrolysis, previously investigated, we have now evidence for differential binding modes in the Candida rugosa lipase-catalyzed esterifications in cyclohexane. The relevance of considering two different binding modes to understand lipase enantiorecognition is demonstrated by introducing bulky substituents on a chiral carboxylic acid which impose a different orientation of the substrate acyl chain in the active site of Candida rugosa lipase. With this substrate engineering approach based on molecular modeling it is thus possible to markedly alter the enantioselectivity of the lipase. Examples from hydrolysis and new results from esterifications in an organic solvent are presented and discussed.
|
|
| 35. |
|
|
| 36. |
|
|
| 37. |
- Bertilsson, Kent, et al.
(författare)
-
Calculation of lattice heating in SiC RF power devices
- 2004
-
Ingår i: Solid-State Electronics. - : Elsevier BV. - 0038-1101 .- 1879-2405. ; 48:12, s. 1721-1725
-
Tidskriftsartikel (refereegranskat)abstract
- Silicon carbide MESFET devices are suitable for high-speed and high-power applications. In this paper we are studying thermal effects in 4H-SiC RF power devices. The simulations are based on a combination of 2D device simulations for the electrical transport, and 3D thermal simulations for the lattice heating. We show that the method gives good accuracy, efficiency, flexibility and capacity dealing with tasks, where a 2D coupled electrical-thermal simulation is not sufficient. We also present an improvement of Roschke and Schwierz mobility model, based on Monte Carlo simulations for the temperature dependencies of the mobility parameters beta and v(sat).
|
|
| 38. |
- Bertilsson, Kent, et al.
(författare)
-
Monte Carlo simulation of vertical MESFETs in 2H, 4H and 6H-SiC
- 2001
-
Ingår i: Diamond and related materials. - 0925-9635 .- 1879-0062. ; 10:3-7, s. 1283-1286
-
Tidskriftsartikel (refereegranskat)abstract
- The 4H-SiC static induction transistor (SIT) is a very competitive device for high frequency and high power applications (3-6 GHz range). The large breakdown voltage and the high thermal conductivity of 4H-SiC allow transistors with extremely high current density at high voltages. The SIT transistor shows better output power capabilities but the unity current-gain frequency is lower compared to a MESFET device. In this work we show, using a very accurate numerical model, that a compromise between the features given by the SIT structure and the ordinary MESFET structure can be obtained using the vertical MESFET structure. The device dimension has been selected very aggressively to demonstrate the performance of an optimized technology. We also present results from drift-diffusion simulations of devices, using transport parameters obtained from the Monte Carlo simulation. The simulations indicate that 2H-SiC is superior to both 4H and 6H-SiC for vertical devices. For lateral devices, 2H-SiC is slightly faster compared to an identical 4H-SiC device
|
|
| 39. |
- Bertilsson, Kent, et al.
(författare)
-
Simulation of a low atmospheric-noise modified four-quadrant position sensitive detector
- 2001
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - 0168-9002 .- 1872-9576. ; 466:1, s. 183-187
-
Tidskriftsartikel (refereegranskat)abstract
- A modified four-quadrant position sensitive detector (PSD) is developed. This structure is less sensitive to atmospheric turbulence that is a major drawback with the traditional four-quadrant detector. The inter-electrode resistance is as high as for the four-quadrant detector, which is an advantage compared to the lateral effect PSD. The linearity for the modified four-quadrant detector is good in the whole active range of sensing. The structures are limited to small sensing areas with well focused beams and are suitable for use in detectors up to 1 mm in size.
|
|
| 40. |
- Bertilsson, Kent, et al.
(författare)
-
The Effect of Different Transport Models in Simulation of High Frequency 4H-SiC and 6H-SiC Vertical MESFETs
- 2001
-
Ingår i: Solid-State Electronics. - 0038-1101 .- 1879-2405. ; 45:5, s. 645-653
-
Tidskriftsartikel (refereegranskat)abstract
- A full band Monte Carlo (MC) study of the high frequency performance of a 4H-SiC Short channel vertical MESFET is presented. The MC model used is based on data from a full potential band structure calculation using the local density approximation to the density functional theory. The MC results have been compared with simulations using state of the art drift-diffusion and hydrodynamic transport models. Transport parameters such as mobility, saturation velocity and energy relaxation time are extracted from MC simulations
|
|
