scholarly journals Two-dimensional analysis of ice ridging in the Beaufort Sea using aerial photography

1994 ◽  
Vol 19 ◽  
pp. 25-32
Author(s):  
J. E. Lewis ◽  
P. Budkewitsch ◽  
G. Newton ◽  
M. Sayed ◽  
R. M. W. Frederking
Keyword(s):  
Aerial Photography ◽  
Principal Direction ◽  
Extraction Procedure ◽  
Beaufort Sea ◽  
Digital Data ◽  
Computer Algorithms ◽  
Direction Parallel ◽  
Edge Linking ◽  
Minimum Number ◽  
Two Parameters

Aerial photography was obtained for the Beaufort Sea north of Tuktoyaktuk. The flight path covered two distinct ice zones over a 15.5 km transect extending perpendicular to the coast, yielding fifty-nine photographs at a scale of 1 : 2000. The process of ridge extraction was automated using a series of computer algorithms for image filtering, edge detection and edge linking. Examples from two different sections along the transect are chosen for presentation: (a) a heavily ridged area, and (b) an area with one dominant linear ridge feature that separates ice cover of different age. Two parameters used in the automated process, a minimum edge gradient and minimum number of connected pixels said to form a continuous ridge segment, influence the number, length and spatial pattern of extracted ridges. Direct one-to-one correlations between manually interpreted ridges from photographs and the algorithm extracted ridges from digital data are not always possible. However, results indicate that the automated ridge extraction procedure reliably characterizes the overall direction and density of the ice ridges. The distribution of the ice-ridge directions is estimated from circular (angular) histograms constructed directly from the digital data. Analysis of the Beaufort Sea transect reveals that the ice ridging is strongly anisotropic, with a principal direction parallel to the local coastline.

scholarly journals Two-dimensional analysis of ice ridging in the Beaufort Sea using aerial photography

1994 ◽  
Vol 19 ◽  
pp. 25-32
Author(s):  
J. E. Lewis ◽  
P. Budkewitsch ◽  
G. Newton ◽  
M. Sayed ◽  
R. M. W. Frederking
Keyword(s):  
Aerial Photography ◽  
Principal Direction ◽  
Extraction Procedure ◽  
Beaufort Sea ◽  
Digital Data ◽  
Computer Algorithms ◽  
Direction Parallel ◽  
Edge Linking ◽  
Minimum Number ◽  
Two Parameters

Aerial photography was obtained for the Beaufort Sea north of Tuktoyaktuk. The flight path covered two distinct ice zones over a 15.5 km transect extending perpendicular to the coast, yielding fifty-nine photographs at a scale of 1 : 2000. The process of ridge extraction was automated using a series of computer algorithms for image filtering, edge detection and edge linking. Examples from two different sections along the transect are chosen for presentation: (a) a heavily ridged area, and (b) an area with one dominant linear ridge feature that separates ice cover of different age. Two parameters used in the automated process, a minimum edge gradient and minimum number of connected pixels said to form a continuous ridge segment, influence the number, length and spatial pattern of extracted ridges. Direct one-to-one correlations between manually interpreted ridges from photographs and the algorithm extracted ridges from digital data are not always possible. However, results indicate that the automated ridge extraction procedure reliably characterizes the overall direction and density of the ice ridges. The distribution of the ice-ridge directions is estimated from circular (angular) histograms constructed directly from the digital data. Analysis of the Beaufort Sea transect reveals that the ice ridging is strongly anisotropic, with a principal direction parallel to the local coastline.

On identifiability and order of continuous-time aggregated Markov chains, Markov-modulated Poisson processes, and phase-type distributions

1996 ◽  
Vol 33 (3) ◽  
pp. 640-653 ◽  
Author(s):  
Tobias Rydén
Keyword(s):  
Markov Chain ◽  
Markov Chains ◽  
Continuous Time ◽  
Poisson Processes ◽  
Hitting Times ◽  
Phase Type ◽  
Phase Type Distributions ◽  
Minimum Number ◽  
Markov Modulated ◽  
Two Parameters

An aggregated Markov chain is a Markov chain for which some states cannot be distinguished from each other by the observer. In this paper we consider the identifiability problem for such processes in continuous time, i.e. the problem of determining whether two parameters induce identical laws for the observable process or not. We also study the order of a continuous-time aggregated Markov chain, which is the minimum number of states needed to represent it. In particular, we give a lower bound on the order. As a by-product, we obtain results of this kind also for Markov-modulated Poisson processes, i.e. doubly stochastic Poisson processes whose intensities are directed by continuous-time Markov chains, and phase-type distributions, which are hitting times in finite-state Markov chains.

Where Cartographies Collide

2017 ◽  
Author(s):  
Jess Bier
Keyword(s):  
Aerial Photography ◽  
Digital Data ◽  
The Internet ◽  
Production Of Knowledge ◽  
Unique Position ◽  
Parallel Lives ◽  
Traveling Theory ◽  
Practice Of Science ◽  
Israeli Occupation

Chapter 1, “Where Cartographies Collide”, analyzes the unique position of maps in Palestine and Israel. Maps are everywhere in the region, but many of them are not used for getting around. This is because of the difficulties updating maps due to the restrictions on mobility under the Israeli occupation. The chapter introduces the notion of the geographic production of knowledge, which draws attention to the materialities and spatialities of technoscience. It also analyzes three main themes that run throughout the book: internationalism, landscape, and symmetry. In the process, it tells the story of the parallel lives of two pivotal cartographers of the mid-20th century: Sami Hadawi and David Amiran. Through a comparison of these major figures, it explores how politics shape the practice of science and technology. It also delineates how, despite the use of aerial photography and digital data transmitted via the internet, maps continue to be shaped by where and how they are made—as well as who is making them. Lastly, it draws on Edward Said’s notion of traveling theory to present an argument for a reflexive method of traveling ethnography.

Airborne Video Digital Data for Resource Analysis and Management in the Northeast

1988 ◽  
Vol 5 (2) ◽  
pp. 117-120
Author(s):  
Roger H. Greene
Keyword(s):  
Information System ◽  
Spatial Data ◽  
Aerial Photography ◽  
Value Of Information ◽  
Video Data ◽  
Digital Data ◽  
Forest Types ◽  
Digital Form ◽  
Resource Analysis ◽  
Data Bases

Abstract Airborne video data in digital form provides an inexpensive alternative to aerial photography to provide up-to-date information on the size, kinds, and distribution of forest types. Its capability to be incorporated into a geographic information system can augment the value of information produced during analysis. In Maine, Landmark Applied Technologies has developed and is using a system which includes acquiring the video imagery, extracting scenes in digital form, analyzing these data, and incorporating them into an Intergraph GIS to provide a mechanism for rapid updating of spatial data bases. North. J. Appl. For. 5:117-120, June 1988.

On Computing Component (Edge) Connectivities of Balanced Hypercubes

2019 ◽  
Vol 63 (9) ◽  
pp. 1311-1320 ◽  
Author(s):  
Mei-Mei Gu ◽  
Jou-Ming Chang ◽  
Rong-Xia Hao
Keyword(s):  
Upper Bound ◽  
Edge Connectivity ◽  
Combinatorial Properties ◽  
Minimum Number ◽  
Two Parameters ◽  
Disconnected Graph

Abstract For an integer $\ell \geqslant 2$, the $\ell $-component connectivity (resp. $\ell $-component edge connectivity) of a graph $G$, denoted by $\kappa _{\ell }(G)$ (resp. $\lambda _{\ell }(G)$), is the minimum number of vertices (resp. edges) whose removal from $G$ results in a disconnected graph with at least $\ell $ components. The two parameters naturally generalize the classical connectivity and edge connectivity of graphs defined in term of the minimum vertex-cut and the minimum edge-cut, respectively. The two kinds of connectivities can help us to measure the robustness of the graph corresponding to a network. In this paper, by exploring algebraic and combinatorial properties of $n$-dimensional balanced hypercubes $BH_n$, we obtain the $\ell $-component (edge) connectivity $\kappa _{\ell }(BH_n)$ ($\lambda _{\ell }(BH_n)$). For $\ell $-component connectivity, we prove that $\kappa _2(BH_n)=\kappa _3(BH_n)=2n$ for $n\geq 2$, $\kappa _4(BH_n)=\kappa _5(BH_n)=4n-2$ for $n\geq 4$, $\kappa _6(BH_n)=\kappa _7(BH_n)=6n-6$ for $n\geq 5$. For $\ell $-component edge connectivity, we prove that $\lambda _3(BH_n)=4n-1$, $\lambda _4(BH_n)=6n-2$ for $n\geq 2$ and $\lambda _5(BH_n)=8n-4$ for $n\geq 3$. Moreover, we also prove $\lambda _\ell (BH_n)\leq 2n(\ell -1)-2\ell +6$ for $4\leq \ell \leq 2n+3$ and the upper bound of $\lambda _\ell (BH_n)$ we obtained is tight for $\ell =4,5$.

The Relationship Between Extra Connectivity and t/k-Diagnosability of Regular Networks

2020 ◽  
Vol 20 (01) ◽  
pp. 2050003
Author(s):  
WENJUN LIU
Keyword(s):  
Fault Tolerant ◽  
Cayley Graphs ◽  
General Relationship ◽  
Multiprocessor System ◽  
Diagnostic Model ◽  
Star Network ◽  
Minimum Number ◽  
Two Parameters ◽  
Regular Networks ◽  
The Relationship

The g-extra connectivity of a multiprocessor system modeled by a graph G, denoted by [Formula: see text] (G), is the minimum number of removed vertices such that the network is disconnected and each residual component has no less than g + 1 vertices. The t/k-diagnosis strategy can detect up to t faulty processors which might include at most k misdiagnosed processors. These two parameters are important to measure the fault tolerant ability of a multiprocessor system. The extra connectivity and t/k-diagnosability of many well-known networks have been investigated extensively and independently. However, the general relationship between the extra connectivity and the t/k-diagnosability of general regular networks has not been established. In this paper, we explore the relationship between the k-extra connectivity and t/k-diagnosability for regular networks under the classic PMC diagnostic model. More specifically, we derive the relationship between 1-extra connectivity and pessimistic diagnosability for regular networks. Furthermore, the t/k-diagnosability and pessimistic diagnosability of some networks, including star network, BC networks, Cayley graphs generated by transposition trees etc., are determined.

The Separation of Membrane and Bending Shears in Shell With Two Birefringent Coatings

1971 ◽  
Vol 38 (1) ◽  
pp. 217-226 ◽  
Author(s):  
W. Schumann ◽  
C. Mylonas ◽  
R. Bucci
Keyword(s):  
Principal Direction ◽  
Polarized Light ◽  
Direct Determination ◽  
Inverse Solution ◽  
Bending Stress ◽  
Direction Parallel ◽  
Large Rotation ◽  
Stress Rotation ◽  
Effects Of Rotation

The determination of magnitude and principal direction of membrane and bending stress differences in plates or thin shells requires four independent items of information, such as the photoelastic retardations and principal directions in two birefringent coatings, one on each face. However, the superposition of a constant membrane and a linearly varying bending stress in general result in a change of direction of the total principal stress through the finite coating thickness. Such rotation of stress introduces considerable difficulties even in the direct determination of the photoelastic effect in known stress fields, and makes the inverse solution of stress distribution from birefringence impossible without additional techniques and data. This paper presents an explicit approximate inverse solution based on simple photoelastic observations in the two coatings, with only partial consideration of the effects of rotation. In its double, reversing path through a coating, polarized light is assumed to suffer the same changes as in a field of linearly varying stress of constant direction parallel to that at incidence and exit. The validity of the direct and inverse solutions was checked experimentally in square plates containing residual membrane stress and subjected to anticlastic bending of various magnitudes and directions. Agreement was very good, especially at the higher loads, even when large stress rotation occurred. Criteria for recognizing potentially inaccurate states with large rotation are also suggested. The proposed method should prove useful in the experimental study of shells.

scholarly journals Mechanical Characterization of Sheet Moulding Composites for the Automotive Industry

2014 ◽  
Vol 8 (1) ◽  
pp. 108-113 ◽  
Author(s):  
G. Lamanna ◽  
A. Ceparano
Keyword(s):  
Automotive Industry ◽  
Experimental Tests ◽  
Fatigue Tests ◽  
Model Parameters ◽  
Glass Fiber Reinforced ◽  
Plane Anisotropy ◽  
Minimum Number ◽  
The Mean ◽  
Two Parameters

The mechanical properties of Sheet Moulding Composite (SMC) have been analyzed by means of static and fatigue tests in tension. SMCs show a substantial in-plane anisotropy either in terms of stiffness or strength. Fatigue data were modeled adopting a fatigue model with two parameters, represented by the cyclic number and the mean stress. The statistical implementation of such model was based on the hypothesis that the monotonic tensile strength follows a twoparameter Weibull distribution. The model has the potential to be predictive indicating that the fatigue characterization of a given laminate can be achieved with a minimum number of experimental tests. The reliability of such procedure and its applicability limits are discussed in the light of the model parameters obtained for different glass fiber reinforced composites.

Aerial photography for assessing vegetation change: a review of applications and the relevance of findings for Australian vegetation history

2002 ◽  
Vol 50 (4) ◽  
pp. 415 ◽  
Author(s):  
R. J. Fensham ◽  
R. J. Fairfax
Keyword(s):  
Aerial Photography ◽  
Vegetation Change ◽  
Vegetation History ◽  
Fire Regimes ◽  
Digital Processing ◽  
Digital Data ◽  
Great Promise ◽  
Individual Tree ◽  
Tree Crowns ◽  
Deforestation Rates

Studies attempting to calibrate vegetation attributes from aerial photography with field data are reviewed in detail. It is concluded that aerial photography has considerable advantages over satellite-based data because of its capacity to assess the vertical dimension of vegetation and the longer time period the record spans. Limitations of using the aerial photo record as digital data include standardising image contrast and rectification. Some of these problems can be circumvented by manual techniques, but problems of crown exaggeration that varies with photo scale and variation in contrast between the textures of tree crowns and the ground remain. Applications of aerial photography for assessing vegetation change are also reviewed and include deforestation, reforestation, changes in vegetation boundaries, tree density, community composition and crown dieback. These changes have been assessed at scales ranging from individual tree crowns to regional landscapes. In Australia, aerial photography has provided a clear demonstration of deforestation rates and the expansion and contraction of forest and woodland, which is generally attributed to changes in grazing and fire regimes. It is suggested that manual techniques with point-based sampling, digital processing of data for complete spatial coverages and the application of photogrammetric measurements with stereo-plotters are all techniques with great promise for utilising this underrated medium for assessment of vegetation dynamics.

scholarly journals 3D LASER SCANNING SURVEY FOR CULTURAL HERITAGE. A FLEXIBLE METHODOLOGY TO OPTIMIZE DATA COLLECTION

2020 ◽  
Vol XLIII-B2-2020 ◽  
pp. 821-828
Author(s):  
C. Costantino ◽  
D. Prati ◽  
G. Predari ◽  
C. Bartolomei
Keyword(s):  
Data Collection ◽  
Laser Scanning ◽  
Urban Centers ◽  
Standard Data ◽  
A Value ◽  
Ideal Situation ◽  
Data Collection Process ◽  
Minimum Number ◽  
Two Parameters ◽  
The University

Abstract. The paper describes an operational working methodology to be applied for surveys with phase-shift laser scanning, which allows defining a guidelines system to optimize in-field data collection. While reducing the number of scan positions still using the same quality, it is possible to obtain smaller files, in order to limit the computational requirements during editing and post-production. Nonetheless, this methodology guarantees results that are qualitatively comparable to the standard data collection process. Consequently, the angle ranges have been analyzed to find a value that guarantees for the survey a point cloud lighter and more manageable and, at the same time, that maintains a reasonable accuracy. Subsequently, two parameters were defined, “redundancy” and “closeness”, to find an operational process that allows to schematize what is usually achieved with the help of experience in the field: to evaluate the minimum number of scan points that can ensure the necessary overlap for optimal coverage of the entire building surveyed. After defining the study of the ideal situation, the model is applied in a case study, situated in a densely built context, typical of European historical urban centers: the main façade of the G. Ciamician Institute of Chemistry of the University of Bologna (Italy).

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