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Depth Measurements (depth + measurement)
Selected AbstractsComparability of three-dimensional optic disc imaging with different techniquesACTA OPHTHALMOLOGICA, Issue 1 2000A study with confocal scanning laser tomography, raster tomography ABSTRACT. Purpose: We wanted to compare optic nerve head topography measurements and discrimination between normal and glaucomatous eyes with two entirely different three-dimensional optic disc imaging techniques, confocal scanning laser tomography (Heidelberg Retina Tomograph, Heidelberg Engineering) and raster tomography (Glaucoma-Scope, Ophthalmic Imaging Systems). Methods: Both eyes of 225 normal subjects and 229 eyes of 166 patients with glaucoma at different stages were imaged with the Heidelberg Retina Tomograph and the Glaucoma-Scope. Optics discs were analysed in 15° sectors around the circumference. Depth measurements were calibrated on objects with known dimensions. Results: We observed no significant differences in absolute measurements of maximum cup depth and cup area between the two instruments. We observed small differences in absolute measurements of disc anti rim area between the two instruments. Discrimination between normal and glaucomatous eyes was close to identical for the two instruments. Both instruments had the same ability to distinguish glaucomatous regional alterations of optic nerve head topography from normal disc configuration. Conclusion: Both instruments while using entirely different principles for three-dimensional optic disc imaging gave very similar results. This correspondence of results implies that the same optic disc parameters can be analysed, and the results interpreted similarly for both methods, and probably with other three-dimensional imaging instruments. It may also indicate that results of studies with one of the instruments have general validity. [source] Estimating the mean speed of laminar overland flow using dye injection-uncertainty on rough surfacesEARTH SURFACE PROCESSES AND LANDFORMS, Issue 4 2001David Dunkerley Abstract A common method for estimating mean flow speeds in studies of surface runoff is to time the travel of a dye cloud across a measured flow path. Motion of the dye front reflects the surface flow speed, and a correction must be employed to derive a value for the profile mean speed, which is always lower. Whilst laminar flow conditions are widespread in the interrill zone, few data are available with which to establish the relationship linking surface and profile mean speeds, and there are virtually none for the flow range 100,<,Re,<,500 (Re,=,Reynolds number) which is studied here. In laboratory experiments on a glued sand board, mean flow speeds were estimated from both dye speeds and the volumetric flow relation v,=,Q/wd with d measured using a computer-controlled needle gauge at 64 points. In order to simulate conditions applicable to many dryland soils, the board was also roughened with plant litter and with ceramic tiles (to simulate surface stone cover). Results demonstrate that in the range 100,<,Re,<,500, there is no consistent relation between surface flow speeds and the profile mean. The mean relationship is v,=,0·56 vsurf, which departs significantly from the theoretical smooth-surface relation v,=,0·67 vsurf, and exhibits a considerable scatter of values that show a dependence on flow depth. Given the inapplicability of any fixed conversion factor, and the dependence on flow depth, it is suggested that the use of dye timing as a method for estimating v be abandoned in favour of precision depth measurement and the use of the relation v,=,Q/wd, at least within the laminar flow range tested. Copyright © 2001 John Wiley & Sons, Ltd. [source] Comparison of LiDAR waveform processing methods for very shallow water bathymetry using Raman, near-infrared and green signalsEARTH SURFACE PROCESSES AND LANDFORMS, Issue 6 2010Tristan Allouis Abstract Airborne light detection and ranging (LiDAR) bathymetry appears to be a useful technology for bed topography mapping of non-navigable areas, offering high data density and a high acquisition rate. However, few studies have focused on continental waters, in particular, on very shallow waters (<2,m) where it is difficult to extract the surface and bottom positions that are typically mixed in the green LiDAR signal. This paper proposes two new processing methods for depth extraction based on the use of different LiDAR signals [green, near-infrared (NIR), Raman] of the SHOALS-1000T sensor. They have been tested on a very shallow coastal area (Golfe du Morbihan, France) as an analogy to very shallow rivers. The first method is based on a combination of mathematical and heuristic methods using the green and the NIR LiDAR signals to cross validate the information delivered by each signal. The second method extracts water depths from the Raman signal using statistical methods such as principal components analysis (PCA) and classification and regression tree (CART) analysis. The obtained results are then compared to the reference depths, and the performances of the different methods, as well as their advantages/disadvantages are evaluated. The green/NIR method supplies 42% more points compared to the operator process, with an equivalent mean error (,4·2,cm verusu ,4·5,cm) and a smaller standard deviation (25·3,cm verusu 33·5,cm). The Raman processing method provides very scattered results (standard deviation of 40·3,cm) with the lowest mean error (,3·1,cm) and 40% more points. The minimum detectable depth is also improved by the two presented methods, being around 1,m for the green/NIR approach and 0·5,m for the statistical approach, compared to 1·5,m for the data processed by the operator. Despite its ability to measure other parameters like water temperature, the Raman method needed a large amount of reference data to provide reliable depth measurements, as opposed to the green/NIR method. Copyright © 2010 John Wiley & Sons, Ltd. [source] Modelling ductile fracture behaviour from deformation parameters in HSLA steelsFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 10 2004S. SIVAPRASAD ABSTRACT In this work, an attempt is made to model the ductile fracture behaviour of two Cu-strengthened high strength low alloy (HSLA) steels through the understanding of their deformation behaviour. The variations in deformation behaviour are imparted by prior deformation of steels to various predetermined strains. The variations in parameters such as yield strength and true uniform elongation with prior deformation is studied and was found to be analogous to that of initiation fracture toughness determined by independent method. A unique method is used to measure the crack tip deformation characterized by stretch zone depth that also depicted a similar trend. Fracture toughness values derived from the stretch zone depth measurements were found to vary in the same fashion as the experimental values. A semiempirical relationship for obtaining ductile fracture toughness from basic deformation parameters is derived and model is demonstrated to estimate initiation ductile fracture toughness accurately. [source] Measurement sampling and scaling for deep montane snow depth dataHYDROLOGICAL PROCESSES, Issue 4 2006S. R. Fassnacht Abstract The resolution of snow depth measurements was scaled from a nominal horizontal resolution of approximately 1·5 m to 3, 5, 10, 20, and 30 m using averaging (AVG) and resampling with a uniform random stratified sampling (RSS) scheme. The raw snow depth values were computed from airborne light detection and ranging data by differencing summer elevation measurements from winter snow surface elevations. Three montane study sites from the NASA Cold Lands Processes Experiment, each covering an 1100 m × 1100 m area, were used. To examine scaling, log,log semi-variograms with 50 log-width bins were created for both of the different subsetting methods, i.e. RSS and AVG. From the raw data, a scale break, going from a structured to a nearly spatially random system, was observed in each of the log,log variograms. For each site, the scale break was still detectable at slightly greater than the resampling resolution for the RSS scheme, but at approximately twice the subsetting resolution for the AVG scheme. The resolution required to identify the scale break was still from 5 to 10 m, depending upon the location and sampling method. Copyright © 2006 John Wiley & Sons, Ltd. [source] Simulation of ice phenology on Great Slave Lake, Northwest Territories, CanadaHYDROLOGICAL PROCESSES, Issue 18 2002Patrick Ménard Abstract A one-dimensional thermodynamic lake ice model (Canadian Lake Ice Model or CLIMo) is used to simulate ice phenology on Great Slave Lake (GSL) in the Mackenzie River basin, Northwest Territories, Canada. Model simulations are validated against freeze-up and break-up dates, as well as ice thickness and on-ice snow depth measurements made in situ at three sites on GSL (Back Bay near Yellowknife, 1960,91; Hay River, 1965,91; Charlton Bay near Fort Reliance, 1977,90). Freeze-up and break-up dates from the lake ice model are also compared with those derived from SSM/I 85 GHz passive microwave imagery over the entire lake surface (1988,99). Results show a very good agreement between observed and simulated ice thickness and freeze-up/break-up dates over the 30,40 years of observations, particularly for the Back Bay and Hay River sites. CLIMo simulates the ice thickness and annual freeze-up/break-dates with a mean error of 7 cm and 4 days respectively. However, some limitations have been identified regarding the rather simplistic approach used to characterize the temporal evolution of snow cover on ice. Future model improvements will therefore focus on this particular aspect, through linkage or coupling to a snow model. Copyright © 2002 John Wiley & Sons, Ltd. [source] High-resolution, monotone solution of the adjoint shallow-water equationsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 2 2002Brett F. Sanders Abstract A monotone, second-order accurate numerical scheme is presented for solving the differential form of the adjoint shallow-water equations in generalized two-dimensional coordinates. Fluctuation-splitting is utilized to achieve a high-resolution solution of the equations in primitive form. One-step and two-step schemes are presented and shown to achieve solutions of similarly high accuracy in one dimension. However, the two-step method is shown to yield more accurate solutions to problems in which unsteady wave speeds are present. In two dimensions, the two-step scheme is tested in the context of two parameter identification problems, and it is shown to accurately transmit the information needed to identify unknown forcing parameters based on measurements of the system response. The first problem involves the identification of an upstream flood hydrograph based on downstream depth measurements. The second problem involves the identification of a long wave state in the far-field based on near-field depth measurements. Copyright © 2002 John Wiley & Sons, Ltd. [source] Meta-analysis of the effect of scaling and root planing, surgical treatment and antibiotic therapies on periodontal probing depth and attachment lossJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 11 2002Hsin-Chia Hung Abstract Objective: This paper reports a meta-analysis of studies that have investigated the effect of scaling and root planing on periodontal probing depth and attachment loss. Material and methods: The criteria used for inclusion of studies were as follows: root planing and scaling alone was one of the primary treatment arms; patients or quadrants of each patient were randomly assigned to study groups; 80% of patients enrolled were included in first year follow-up examinations; periodontal probing depth and attachment loss were reported in mm; the sample size of each study and substudy was reported. Sample size was used to weight the relative contribution of each study since standard errors were not reported by many studies and sample size is highly correlated with standard error and therefore statistically able to explain a substantial portion of the standard error on studies that use similar measures. Results: The meta-analysis results show that periodontal probing depth and gain of attachment level do not improve significantly following root planing and scaling for patients with shallow initial periodontal probing depths. However, there was about a 1-mm reduction for medium initial periodontal probing depths and a 2-mm reduction for deep initial periodontal probing depths. Similarly, there was about a 0.50-mm gain in attachment for medium initial periodontal probing depth measurements and slightly more than a l-mm gain in attachment for deep initial periodontal probing depth measurements. Surgical therapy for patients with deep initial probing depths showed better results than scaling and root planing in reducing probing depths. When patients were followed up over 3 years or more, these differences were reduced to less than 0.4 mm. Antibiotic therapy showed similar results to scaling and root planing. However, a consistent improvement in periodontal probing depth and gain of attachment is demonstrated when local antibiotic therapy is combined with root planing and scaling. Zusammenfassung Metaanalyse des Effekts von Scaling und Wurzelglätten, chirurgischer Behandlung und Antibiotikatherapien auf parodontale Sondiertiefe und Attachment-Verlust Zielsetzung: Der vorliegende Artikel beschreibt eine Metaanalyse von Studien, in denen die Wirkung von Scaling und Wurzelglätten auf parodontale Sondiertiefe und Attachment-Verlust untersucht wurden. Material und Methodik: Die Kriterien für die Aufnahme in die Studie waren wie folgt: 1) Wurzelglätten und Scaling allein war einer der primären Behandlungsverfahren; 2) Patienten oder Quadranten einzelner Patienten wurden auf Studiengruppen zufallsverteilt; 3) 80% der aufgenommenen Patienten waren in den Follow-up-Untersuchungen nach einem Jahr eingeschlossen; 4) parodontale Sondiertiefe und Attachment-Verlust wurden in mm berichtet; und 5) der Probenumfang jeder einzelnen Studie und Unterstudie wurde berichtet. Der Probenumfang wurde zur Gewichtung des relativen Beitrages jeder einzelnen Studie herangezogen, da von vielen Studien keine Standardabweichungen berichtet wurden und der Probenumfang mit der Standardabweichung stark korreliert ist. Daher lässt sich auf dem Weg über den Probenumfang ein wesentlicher Teil der Standardabweichung bei Studien mit ähnlichen Messparametern statistisch erklären. Ergebnisse: Die Ergebnisse der Metaanalyse zeigten, dass die parodontale Sondiertiefe und die Zunahme des Attachment-Niveaus nach Scaling und Wurzelglätten bei Patienten mit ursprünglich geringen Sondiertiefen keine signifikanten Verbesserungen liefern. Bei ursprünglich mittleren parodontalen Sondiertiefen konnte jedoch eine Reduktion von 1 mm, bei ursprünglich tiefen parodontalen Sondiertiefen eine Reduktion von 2 mm beobachtet werden. Dementsprechend wurde eine Zunahme des Attachment-Niveaus bei ursprünglich mittleren parodontalen Sondiertiefen von 0,5 mm eine sowie eine Zunahme von etwas mehr als 1 mm bei ursprünglich tiefen parodontalen Sondiertiefen verzeichnet. Die chirurgische Behandlung bei Patienten mit ursprünglich beträchtlicher Sondiertiefe lieferte bei der Reduktion der Sondiertiefe bessere Ergebnisse als Scaling und Wurzelglätten. Wenn sich Patienten über 3 Jahre oder länger einem Follow-up unterzogen, liessen sich diese Differenzen auf unter 0,4 mm reduzieren. Darüber hinaus kann jedoch eine konsistente Verbesserung der parodontalen Sondiertiefe und Zunahme des Attachment-Niveaus erreicht werden, wenn eine lokale Antibiotikatherapie mit Scaling und Wurzelglätten kombiniert wird. Résumé Méta-analyse de l'influence du détartrage et du surfaçage radiculaire, du traitement chirurgical et des traitements antibiotiques sur la profondeur de poche au sondage et la perte d'attache But: Ce rapport présente une méta-analyse des études qui ont porté sur l'influence du détartrage et du surfaçage radiculaire sur la profondeur de poche au sondage et la perte d'attache. Matériaux et méthodes: Les critères d'inclusion dans les études étaient les suivants: 1) le détartrage et le surfaçage radiculaire constituaient l'un des premiers moyens de traitement utilisés; 2) les patients ou les quadrants de chaque patient ont été répartis dans les groupes d'étude de façon aléatoire; 3) 80% des patients enrôlés ont fait l'objet d'examens de suivi durant un an; 4) la profondeur de poche au sondage et la perte d'attache ont été mesurés en mm; 5) la taille de l'échantillon a été relevée pour chaque étude et sous-étude. La taille de l'échantillon a été utilisée pour évaluer la contribution relative de chaque étude. En effet, de nombreuses études ne mentionnaient pas les erreurs standard, alors qu'il existe une corrélation étroite entre la taille de l'échantillon et l'erreur standard et qu'elle permet donc d'expliquer statistiquement une part substantielle de l'erreur standard dans les études qui se basent sur des mesures similaires. Résultats: Les résultats de la méta-analyse montrent que la profondeur de poche au sondage et le gain d'attache ne s'améliorent pas de façon significative suite au détartrage et surfaçage radiculaire chez les patients dont les profondeurs de poche au sondage initiales étaient faibles. Il y avait toutefois une réduction d'environ 1 mm des profondeurs de poche au sondage initiales moyennes, et une réduction de 2 mm des profondeurs de poche au sondage initiales élevées. De façon similaire, on a observé un gain d'attache d'environ 0,50 mm pour les mesures des profondeurs de poche au sondage initiales moyennes et un gain d'attache légèrement supérieur à 1 mm pour les mesures des profondeurs de poche au sondage initiales élevées. Chez les patients à profondeur de poche au sondage initiale élevée, le traitement par chirurgie s'est avéré plus efficace que le détartrage et le surfaçage radiculaire pour réduire la profondeur au sondage. Lorsque les patients faisaient l'objet d'un suivi durant trois ans ou plus, ces différences s'abaissaient jusqu'à moins de 0,4 mm. Le traitement antibiotique a donné des résultats similaires à ceux obtenus par détartrage et surfaçage radiculaire. Une amélioration régulière de la profondeur de poche au sondage et du gain d'attache a toutefois été observée lorsque le traitement antibiotique local est combiné au détartrage et surfaçage radiculaire. [source] Facial Soft Tissue Depths in Craniofacial Identification (Part II): An Analytical Review of the Published Sub-Adult Data,JOURNAL OF FORENSIC SCIENCES, Issue 6 2008Carl N. Stephan Ph.D. Abstract:, Prior research indicates that while statistically significant differences exist between subcategories of the adult soft tissue depth data, magnitudes of difference are small and possess little practical meaning when measurement errors and variations between measurement methods are considered. These findings raise questions as to what variables may or may not hold meaning for the sub-adult data. Of primary interest is the effect of age, as these differences have the potential to surpass the magnitude of measurement error. Data from the five studies in the literature on sub-adults which describe values for single integer age groups were pooled and differences across the ages examined. From 1 to 18 years, most soft tissue depth measurements increased by less than 3 mm. These results suggest that dividing the data for children into more than two age groups is unlikely to hold many advantages. Data were therefore split into two groups with the division point corresponding to the mid-point of the observed trends and main data density (0,11 and 12,18 years; division point = 11.5 years). Published sub-adult data for seven further studies which reported broader age groups were pooled with the data above to produce the final tallied soft tissue depth tables. These tables hold the advantages of increased sample sizes (pogonion has greater than 1770 individuals for either age group) and increased levels of certainty (as random and opposing systematic errors specific to each independent study should average out when the data are combined). [source] Comparison of anterior chamber depth measurements taken with the Pentacam, Orbscan IIz and IOLMaster in myopic and emmetropic eyesACTA OPHTHALMOLOGICA, Issue 4 2009Canan Asli Utine Abstract. Purpose:, This study determined to assess the degree of agreement between anterior chamber depth (ACD) measurements obtained using three different devices and to analyse the relationship between ACD and spherical equivalent (SE) refraction. Methods:, In this cross-sectional study, 42 eyes of 42 patients with a mean SE of , 4.69 ± 4.61 D (range 0.00 D to , 14.88 D) were analysed. Measurements of ACD between the corneal epithelium and the anterior surface of the crystalline lens, obtained using the Pentacam, Orbscan IIz and IOLMaster, were compared. The relationships between SE and ACD measurements obtained with different devices were also investigated. The results were analysed using Bland,Altman analyses, single-sample t -test and Pearson's correlation test. Results:, Orbscan ACD measurements were an average of 0.05 mm less than Pentacam measurements (p = 0.01). IOLMaster measurements were an average of 0.06 mm less than Orbscan measurements (p < 0.001). None of the ACD values measured by any of the devices were correlated with increasing SE (p > 0.05 for all). There was a weak positive correlation between SE and the difference in ACD measurements with Pentacam and Orbscan (p = 0.04); however, the differences between Pentacam and IOLMaster ACD measurements and Orbscan and IOLMaster ACD measurements seemed to be independent of SE (p = 0.17 and p = 0.54, respectively). Conclusions:, The ACD in clinically normal eyes is measured differently by various non-ultrasonic devices. However, the observed mean error between these modalities is too small to create any noticeable difference in refractive outcome. No significant relationship was found between SE and ACD measurements obtained by Pentacam, Orbscan or IOLMaster. [source] | |||||||||||||