John Aasted Sørensen

Reduction of broad-band noise in speech by truncated QSVD

We consider an algorithm for reduction of broadband noise in speech based on signal subspaces. The algorithm is formulated by means of the quotient singular value decomposition (QSVD). With this formulation, a prewhitening operation becomes an integral part of the algorithm. We demonstrate that this is essential in connection with updating issues in real-time recursive applications. We also illustrate by examples that we are able to achieve a satisfactory quality of the reconstructed signal.

Marginal and internal fits of fixed dental prostheses zirconia retainers

OBJECTIVESnCAM (computer-aided manufacturing) and CAD (computer-aided design)/CAM systems facilitate the use of zirconia substructure materials for all-ceramic fixed partial dentures. This in vitro study compared the precision of fit of frameworks milled from semi-sintered zirconia blocks that were designed and machined with two CAD/CAM and one CAM system.nnnMETHODSnThree-unit posterior fixed dental prostheses (FDP) (n=10) were fabricated for standardized dies by: a milling center CAD/CAM system (Etkon), a laboratory CAD/CAM system (Cerec InLab), and a laboratory CAM system (Cercon). After adaptation by a dental technician, the FDP were cemented on definitive dies, embedded and sectioned. The marginal and internal fits were measured under an optical microscope at 50x magnification. A one-way analysis of variance (ANOVA) was used to compare data (alpha=0.05).nnnRESULTSnThe mean (S.D.) for the marginal fit and internal fit adaptation were: 29.1 microm (14.0) and 62.7 microm (18.9) for the milling center system, 56.6 microm (19.6) and 73.5 microm (20.6) for the laboratory CAD/CAM system, and 81.4 microm (20.3) and 119.2 microm (37.5) for the laboratory CAM system. One-way ANOVA showed significant differences between systems for marginal fit (P<0.001) and internal fit (P<0.001).nnnSIGNIFICANCEnAll systems showed marginal gaps below 120 microm and were therefore considered clinically acceptable. The CAD/CAM systems were more precise than the CAM system.

Three-year clinical prospective evaluation of zirconia-based posterior fixed dental prostheses (FDPs)

This clinical study evaluated posterior three-unit fixed dental prostheses (FDPs) made of zirconia substructures veneered with pressable glass–ceramic. Nineteen patients received 21 FDPs replacing either the second premolar, first molar, or second molar. The FDPs were cemented with glass ionomer. Recall examinations were performed every 12xa0months. The mean service time of the FDP was 40xa0months. At 30xa0months, one maxillary FDP exhibited zirconia framework fracture at a thinned occlusal area of the abutment. Loss of retention led to the removal of one FDP after 38xa0months. The Kaplan–Meier survival probability was 90.5% after 40xa0months for all types of failures and 95.2% concerning framework fractures. The overpressing technique appears to be reliable in terms of the veneering material. However, one framework fracture was observed in this study.

Precision of fit: zirconia three-unit fixed dental prostheses

The purpose of this in vitro study was to compare the precision of fit of substructures milled from semi-sintered zirconia blocks fabricated with two different computer-assisted design (CAD)/computer-assisted manufacturing (CAM) systems. Three-unit posterior fixed dental prostheses (FDP) were fabricated for standardized dies (nu2009=u200910) with the Lava CAD/CAM system (Lava) and the Procera-bridge-zirconia CAD/CAM system (Procera). After cementation to the dies, the FDP were embedded and sectioned. Four cross-sections were made of each abutment tooth, and marginal and internal fit were evaluated under an optical microscope. A one-way analysis of variance was used to compare data (αu2009=u20090.05). Mean gap dimensions at the marginal opening for Lava and Procera were 15 (±7)xa0μm and 9 (±5)xa0μm, respectively. Mean marginal openings (Pu2009=u20090.012) and internal adaptation at two out of three measurement locations were significantly different. Within the limitations of this study, the results suggest that the accuracy of both investigated systems is satisfactory for clinical use.

Load-bearing capacity of all-ceramic three-unit fixed partial dentures with different computer-aided design (CAD)/computer-aided manufacturing (CAM) fabricated framework materials

The purpose of this in vitro study was to compare the load-bearing capacity of posterior three-unit fixed dental prostheses (FDP) produced with three different all-ceramic framework materials: glass-infiltrated alumina (ICA), glass-infiltrated alumina strengthened with zirconia (ICZ), and yttria-stabilized polycrystalline zirconia (YZ). Additionally, the influence on aging of mechanical cyclic fatigue loading and thermal cycling in water were evaluated. A total of 20 frameworks each were fabricated from ICA, ICZ, and YZ by a computer-aided design (CAD)/computer-aided manufacturing (CAM) system. The framework designs were identical for all specimens. All frameworks were veneered with porcelain and cemented with glass-ionomer. Prior to fracture testing, 10 FDP of each experimental group were subjected to thermal and mechanical cycling. Additionally, fractographic analysis was performed. Statistical analysis showed that FDP made from YZ had significantly higher load to failure, whereas no difference was found between the other two materials. Aging did not have a significant effect on the fracture load.

A preliminary design of a phonetic vocoder based on a diphone model

We report on the initial development of a phonetic vocoder operating at 100 b/s. With each phoneme, the vocoder transmits the duration and a single pitch value. The synthesizer uses a large inventory of diphone templates to synthesize a desired phoneme string. To determine a phoneme string from input speech, the analyzer takes into account the synthesis model by using the same inventory of diphone templates, augmented by additional diphone templates to account for alternate pronunciations. The phoneme string is chosen to minimize the difference between the diphone templates and the input speech according to a distance measure.

Antioxidant properties of green tea extract protect reduced fat soft cheese against oxidation induced by light exposure.

The effect of two different antioxidants, EDTA and green tea extract (GTE), used individually or in combination, on the light-induced oxidation of reduced fat soft cheeses (0.2 and 6% fat) was investigated. In samples with 0.2% fat, lipid hydroperoxides as primary lipid oxidation products were not detected, but their interference was suggested from the formation of secondary lipid oxidation products such as hexanal and heptanal. The occurrence of these oxidation markers was inhibited by spiking with 50 ppm EDTA or 750 ppm GTE, or a combination of the two prior to irradiation. In contrast, addition of 50 ppm EDTA to samples with 6% fat was ineffective, but 750 ppm GTE (alone or in combination with EDTA) strongly reduced levels of hexanal and heptanal. Accumulation of primary lipid hydroperoxides was not affected by GTE, hence antioxidative activity was ascribed to scavenging of hexanal and heptanal precursors. These radical intermediates result from hydroperoxide disintegration, and subsequent scavenging by GTE, which acts as a radical sink, corroborates the intense signal observed by electron paramagnetic resonance (EPR) spectroscopy.

Cholesterol oxidation in feta cheese produced from high-temperature bleached and from non-bleached butteroil from bovine milk

During chill storage, cholesterol oxidation in feta cheese produced from bovine butteroil bleached at high temperature was compared with cholesterol oxidation in feta cheese produced from non-bleached butteroil. The bleaching was performed at two different temperatures, 265 and 280 °C, and the oil was bleached for 2.4, 3.8 or 4.3 min; a reference feta cheese was produced without bleaching. All cheeses were stored in brine at 4 °C, and cholesterol oxidation was measured during a storage period of 5 months. For the first 11 weeks of storage, the concentration of cholesterol oxides was comparable for the bleached feta cheeses, but on longer storage the concentration of oxysterols was highest in feta cheeses produced from the butteroil bleached at 280 °C. The bleaching temperature rather than the bleaching time affected cholesterol oxidation, which was minimal in the non-bleached reference cheese throughout the storage period compared with the bleached feta cheeses. 7-Ketocholesterol was found to be the dominant oxysterol in the feta cheeses at the end of the storages comprising ∼50% of the total cholesterol oxides. In feta cheeses based on butteroil bleached at 265 °C, the concentration of 7-ketocholesterol ranged from 3.7 to 4.9 μg/g lipid at the end of the storage period, and in feta cheese based on butteroil bleached at 280 °C the concentration was 10.4-13.1 μg/g lipid. In the reference feta cheese the concentration of 7-ketocholesterol was 1.2 μg/g lipid. There was no difference in yellowness, measured by tristimulus colorimetry as the Hunter b characteristic, of the feta cheeses bleached at 265 and 280 °C, and a small scale bleaching experiment with butteroil showed that it was possible to secure complete bleaching at temperatures down to 220 °C. We suggest that bleaching of butteroil for feta production should be performed at temperatures as low as possible in order to prevent cholesterol oxidation.

Experimental comparison of signal subspace based noise reduction methods

The signal subspace approach for non-parametric speech enhancement is considered. Several algorithms have been proposed in the literature but only partly analyzed. Here, the different algorithms are compared, and the emphasis is put onto the limiting factors and practical behavior of the estimators. Experimental results show that the signal subspace approach may lead to a significant enhancement of the signal to noise ratio of the output signal.

Multimodal Wireless Networks: Communication and Surveillance on the Same Infrastructure

In this paper, we propose a new family of wireless networks-the multimodal wireless networks. These networks offer multiple functionalities realized on the same infrastructure. A multimodal wireless network has two modes of operation: 1) the communication mode, when the network is used as a traditional wireless communication network, and 2) the surveillance mode, when the network is used as a distributed sensor network that can detect illegal intrusion. The surveillance functionality is realized by analyzing the properties of the received signals, and the change of the propagation environment caused by the intruder serves as the basis for intrusion detection. We derive maximum likelihood estimators and detectors based on the generalized likelihood ratio test that detects changes in the propagation environment: the single-cycle detector, which makes decisions at the end of each scanning cycle, and the multicycle detector, which combines information from multiple scanning cycles prior to detection. We also analyze the performance of these detectors by deriving the Cramer-Rao lower bound on the variance of the parameter estimators and determining the distribution of the log-likelihood ratio under both detection hypotheses. This will allow us to compare the theoretical performance of the single-cycle and the multicycle detectors and obtain analytical results to determine the decision threshold for a given probability of false alarm. To prevent performance degradation due to slowly drifting parameter values, we propose different strategies to track and update the parameter estimates. The experimental results obtained from an implemented prototype surveillance system show very promising detection capabilities. For example, the state of a door (open or closed) could be detected with a probability of 0.99 at a probability of false alarm 10-5.