Polygonal Technique Research Articles

Integration of gauge and radar rainfall to enable best simulation of hydrological parameters

ABSTRACTThis study is about use of spatially distributed rain in physically based hydrological models. In recent years, spatially distributed radar rainfall data have become available. The distributed radar rain is used to precisely model hydrologic processes and it is more realistic than the past practice of distribution methods like Thiessen polygons. Radar provides a highly accurate spatial distribution of rainfall and greatly improves the basin average rainfall estimates. However, quantification of the exact amount of rainfall from radar observation is relatively difficult. Thus, the fundamental idea of this study is to apply hourly gauge and radar rainfall data in a distributed hydrological model to simulate hydrological parameters. Hence the comparison is made between the outcomes of the WetSpa model from radar rainfall distribution and gauge rainfall distributed by the Thiessen polygon technique. The comparative plots of the hydrograph and the results of hydrological components such as evapotranspiration, surface runoff, soil moisture, recharge and interflow, reflect the spatially distributed radar input performing well for model outflow simulation.EDITOR D. KoutsoyiannisASSOCIATE EDITOR F. Pappenberger

An enhanced algorithm for estimation of a digitized curve length using B-splines

Abstract A digitized curve length estimation is a hot topic of research. All the methods tend to estimate the length of the original curve from which the digitized curve is obtained. When comparing different methods of estimation, the main performance criterium is the accuracy of this estimation. In this paper a novel approach is presented. It shows a significant improvement compared to all the other methods, regardless of the resolution and the type of curve. The method is based on B-splines. The initial number of control points and their location is determined by the reverse polygonization, which is one of the polygonal approximation techniques. The method then iteratively updates the location of the control points of the B-spline based on the specified cost function. Due to the fact that it shows the same level of accuracy for different B-spline orders it is also much more convenient to use than the other methods because it doesn’t require the selection of appropriate parameter(s). Beside that it doesn’t require nonlinear optimization techniques. The performance of the method is verified on various test curves including the ones with multiple paths within pixel at different grid resolutions.

Subdivision exterior calculus for geometry processing

This paper introduces a new computational method to solve differential equations on subdivision surfaces. Our approach adapts the numerical framework of Discrete Exterior Calculus (DEC) from the polygonal to the subdivision setting by exploiting the refin-ability of subdivision basis functions. The resulting Subdivision Exterior Calculus (SEC) provides significant improvements in accuracy compared to existing polygonal techniques, while offering exact finite-dimensional analogs of continuum structural identities such as Stokes' theorem and Helmholtz-Hodge decomposition. We demonstrate the versatility and efficiency of SEC on common geometry processing tasks including parameterization, geodesic distance computation, and vector field design.

The Historical Significance of the Geometric Designs in the Northeast Dome Chamber of the Friday Mosque at Isfahan

Surviving architectural monuments provide the primary source for understanding the historical development of Islamic geometric design. The early Islamic architecture of Khurasan and eastern Persia establishes the Samanids, Qarakhanids, Ghaznavids, Ghurids and Seljuks as principle contributors in the maturation of the geometric ornamental tradition. The collective architectural legacy of these cultures reveals the significance of their contribution to our knowledge of Islamic geometric design. However, no individual monument surpasses the historical importance of the northeast dome chamber of the Friday Mosque at Isfahan. New research indicates that many of the geometric designs employed within this chamber are the earliest examples of their ornamental variety. What is more, these patterns represent a methodological breakthrough in the application of the polygonal technique of pattern generation, thereby facilitating ever-greater stylistic and geometric innovation.

Asymptotics of orbits of a Kolmogorov type planar vector field with a fixed Newton polygon

Using the Newton polygon technique we show that the orbits of a Kolmogorov type planar vector field, consisting of a finite sum of power terms, have power asymptotics while tending to the equilibria on the axes and on the boundary of the Poincaré sphere.

Effects of watershed subdivision level on semi-distributed hydrological simulations: case study of the SLURP model applied to the Xiangxi River watershed, China

This study investigates the impacts of watershed subdivision on hydrological simulations. The SLURP (Semi-distributed Land Use-based Runoff Processes) model was employed in the Xiangxi River watershed, China, with eight watershed subdivision schemes. Under each scheme, the SLURP model was calibrated using both manual and automatic methods to simulate watershed hydrological processes over the period 1991–1998. The results indicate that model performance could be enhanced by increasing the degree of subdivision. However, there is a threshold level, beyond which no significant improvements can be obtained. The simulated water balance components and runoff contributions from different land types were found to vary among subdivision levels. Differences were slight when the watershed was divided into more than 73 sub-watersheds. These results were partly caused by the altitude-based precipitation correction, where the reduced generalization of terrain characteristics could lead to increasing consideration of small watersheds in the weighted Thiessen polygon technique; thus, the elevation-correction adjustments in deriving distributed meteorological inputs were increased. Parameter sensitivity analysis revealed that increasing the subdivision level was likely to enhance model efficiency. However, the difference became negligible among fine subdivisions. Although a threshold was identified in this study, determination of an appropriate subdivision level should also be based on the modelling objective, the quality of model inputs, the complexity of the watershed system and the resulting uncertainty.Editor D. Koutsoyiannis; Associate editor I. NalbantisCitation Han, J.-C., Huang, G.-H., Zhang, H., Li, Z., and Li, Y.-P., 2013. Effects of watershed subdivision level on semi-distributed hydrological simulations: case study of the SLURP model applied to the Xiangxi River watershed, China. Hydrological Sciences Journal, 59 (1), 108–125.

Locating the Eigenvalues of Matrix Polynomials

Some known results for locating the roots of polynomials are extended to the case of matrix polynomials. In particular, a theorem by Pellet [Bull. Sci. Math. (2), 5 (1881), pp. 393--395], some results from Bini [Numer. Algorithms, 13 (1996), pp. 179--200] based on the Newton polygon technique, and recent results from Gaubert and Sharify (see, in particular, [Tropical scaling of polynomial matrices, Lecture Notes in Control and Inform. Sci. 389, Springer, Berlin, 2009, pp. 291--303] and [Sharify, Scaling Algorithms and Tropical Methods in Numerical Matrix Analysis: Application to the Optimal Assignment Problem and to the Accurate Computation of Eigenvalues, Ph.D. thesis, Ecole Polytechnique, Paris, 2011]). These extensions are applied to determine effective initial approximations for the numerical computation of the eigenvalues of matrix polynomials by means of simultaneous iterations, like the Ehrlich--Aberth method. Numerical experiments that show the computational advantage of these results are presented.

Assessing the combined performance of texture and morphological parameters in distinguishing breast tumors in ultrasound images

This work aims to investigate the combination of morphological and texture parameters in distinguishing between malignant and benign breast tumors in ultrasound images. Linear discriminant analysis was applied to sets of up to five parameters, and then the performances were assessed using the area A(z) (± standard error) under the receiver operator characteristic curve, accuracy (Ac), sensitivity (Se), specificity (Sp), positive predictive value, and negative predictive value. The most relevant individual parameter was the normalized residual value (nrv), calculated from the convex polygon technique. The best performance among all studied combinations was achieved by two morphological and three texture parameters (nrv, con, std, R, and asm(i)), which correctly distinguished nearly 85% of the breast tumors. This result indicates that the combination of morphological and texture parameters may be useful to assist physicians in the diagnostic process, especially if it is associated with an automatic classification tool.

Measuring Historical Coastal Change using GIS and the Change Polygon Approach

AbstractThis study compares two automated approaches, the transect‐from‐baseline technique and a new change polygon method, for quantifying historical coastal change over time. The study shows that the transect‐from‐baseline technique is complicated by choice of a proper baseline as well as generating transects that intersect with each other rather than with the nearest shoreline. The change polygon method captures the full spatial difference between the positions of the two shorelines and average coastal change is the defined as the ratio of the net area divided by the shoreline length. Although then change polygon method is sensitive to the definition and measurement of shoreline length, the results are more invariant to parameter changes than the transect‐from‐baseline method, suggesting that the change polygon technique may be a more robust coastal change method.

Laserscanning e 3D Modelling nell’archeologia urbana: lo scavo della chiesa di Sant’Agata al Carcere a Catania (Italia)

<p>Urban archaeology undoubtedly represents the most problematic branch of archaeological research, due to the many problems of conservation and promotion of the evidence. A significant example is presented by the excavations carried out by the Superintendency for Cultural Goods of Catania in the church of “Sant’Agata al Carcere”, located in the heart of down town Catania. The most important discovery of the archaeological campaign was part of a ruined archaic wall in polygonal technique, located in the western side of the sacristy of the “Sant’Agata al Carcere” church. Furthermore, a late hellenistic votive deposit located within a pit, contained two small jars and a lidded stamnos, was discovered between the stones of the fallen wall. The excavations were performed during the restoration of the church. After the restoration, due to the special function of the building, it was necessary to quickly re-open the churches, thereby hiding the archaeological monuments from public view. In this perspective, a virtual museum project was implemented by an equipe of archaeologists and information technologists of the Archeomatica Project of Catania University, in order to display the important discoveries from the sacristy, which were covered up by the re-location of the floor in situ, applying both laser-scanner and 3D modelling techniques.</p>

Assessing the performance of morphological parameters in distinguishing breast tumors on ultrasound images

This work aims at investigating seven morphological parameters in distinguishing malignant and benign breast tumors on ultrasound images. Linear discriminant analysis was applied to sets of up to five parameters and then the performances were assessed using the area Az (± standard error) under the ROC curve, accuracy ( Ac), sensitivity ( Se), specificity ( Sp), positive predictive value and negative predictive value. The most relevant individual parameters were the normalized residual value ( nrv) and overlap ratio ( RS), both calculated from the convex polygon technique, and the circularity ( C). When nrv and C were taken together with roughness ( R), calculated from normalized radial length ( NRL), a performance slightly over 83% in distinguishing malignant and benign breast tumors was achieved.

EXTRAÇÃO AUTOMÁTICA DE CONTORNOS DE TELHADOS USANDO DADOS DE VARREDURA A LASER E CAMPOS RANDÔMICOS DE MARKOV

This paper proposes a methodology for automatic extraction of building roof contours from a Digital Elevation Model (DEM), which is generated through the regularization of an available laser point cloud. The methodology is based on two steps. First, in order to detect high objects (buildings, trees etc.), the DEM is segmented through a recursive splitting technique and a Bayesian merging technique. The recursive splitting technique uses the quadtree structure for subdividing the DEM into homogeneous regions. In order to minimize the fragmentation, which is commonly observed in the results of the recursive splitting segmentation, a region merging technique based on the Bayesian framework is applied to the previously segmented data. The high object polygons are extracted by using vectorization and polygonization techniques. Second, the building roof contours are identified among all high objects extracted previously. Taking into account some roof properties and some feature measurements (e. g., area, rectangularity, and angles between principal axes of the roofs), an energy function was developed based on the Markov Random Field (MRF) model. The solution of this function is a polygon set corresponding to building roof contours and is found by using a minimization technique, like the Simulated Annealing (SA) algorithm. Experiments carried out with laser scanning DEM´s showed that the methodology works properly, as it delivered roof contours with approximately 90% shape accuracy and no false positive was verified.

CiteWiz: A Tool for the Visualization of Scientific Citation Networks

We present CiteWiz, an extensible framework for visualization of scientific citation networks. The system is based on a taxonomy of citation database usage for researchers, and provides a timeline visualization for overviews and an influence visualization for detailed views. The timeline displays the general chronology and importance of authors and articles in a citation database, whereas the influence visualization is implemented using the Growing Polygons technique, suitably modified to the context of browsing citation data. Using the latter technique, hierarchies of articles with potentially very long citation chains can be graphically represented. The visualization is augmented with mechanisms for parent–child visualization and suitable interaction techniques for interacting with the view hierarchy and the individual articles in the dataset. We also provide an interactive concept map for keywords and co-authorship using a basic force-directed graph layout scheme. A formal user study indicates that CiteWiz is significantly more efficient than traditional database interfaces for high-level analysis tasks relating to influence and overviews, and equally efficient for low-level tasks such as finding a paper and correlating bibliographical data.

Geographical range size and host specificity in ectoparasites: a case study withAmphipsyllafleas and rodent hosts

AbstractAim To identify the factors that determine the geographical range sizes of ectoparasites with different degrees of host specificity.Location The study used data on the distributions of fleas of the genusAmphipsyllaand their rodent hosts across the Holarctic.Methods All known points of occurrence of 32 flea species and 51 species of their rodent hosts were mapped. The shape and size of the geographical range of each species were estimated using a combination of the minimal convex polygon technique and modelling with thegarpalgorithm. Factors determining the geographical range sizes of the fleas were identified using stepwise multiple regression analysis.Results The geographical range size of fleas that are strongly host‐specific across their entire ranges correlated positively with the geographical range size of the fleas’ principal hosts, and negatively with the geographical range size of the fleas’ potential competitors. The geographical range sizes of both (1) fleas that are locally host‐specific but that shift their host preferences geographically, and (2) host‐opportunistic fleas were positively correlated only with the area of the geographical ranges of their principal hosts. Strongly host‐specific fleas occupied 0.2–80.0% of the geographical range of their principal hosts, whereas this figure was 0.9–83.7% in locally host‐specific fleas and 16.6–63.7% in host‐opportunistic fleas.Main conclusions The main determinant of the geographical range size of a flea species is the size of the geographical range of its hosts. The role of potential competitors in determining the geographical range size is stronger in host‐specific than in host‐opportunistic fleas. Cases in which the geographical range of a parasite is smaller than the geographical range(s) of its host(s) owing to narrower parasite environmental tolerances are much more frequent in host‐opportunistic than in host‐specific fleas.

The impact of water resources development projects on water vapor pressure trends in a semi-arid region, Turkey

The aim of this study was to investigate long-term seasonal trends and decadal change patterns of monthly mean water vapor pressure (WVP) observation series at 16 meteorological stations scattered point-wisely over the Southeastern Anatolian Project (GAP) area in Turkey, where large-scale soil and water development projects have been put into practice since the 1970s. The record length of WVP observation series of each station varied between 31- and 41-years between 1962 and 2002. The monthly mean WVP observation series of each station was rearranged on seasonal basis. Sequential Mann–Kendall trend test, Sen’s slope estimator, and Spearman’s rank–order correlation tests were employed for detection of likely trends, and Kruskall–Wallis test was used to detect decadal variations in WVP series of each observation station. A possible area of representation for each meteorological station was determined by using the Thiessen polygons technique in a geographical information systems media. It was found that 15 seasonal WVP series have a positive trend covering 97% of the GAP area in the summer season; although one WVP series has a negative trend direction. However, in the spring season, 33% of the area had a positive trend, and a negative trend did not appear in any stations. WVP records in the winter season showed an increasing trend over 19% of the GAP area, whereas a decreasing trend prevailed in 9% of the area. The study results led us to conclude that the substantial increase of WVP observations in summer season could be attributed to both the shift from rain-fed agriculture to irrigated agriculture being made increasingly spacious year by year and building large water reservoirs in the GAP located in a semi-arid region. The results also indirectly suggested that the historical trends in the WVP parameters might be related to global climate change phenomenon.

Polygonal space carving with geometric anti-aliasing

This paper proposes an algorithm that solves the shape recovery problem from N arbitrary images. By introducing a polygonal carving technique, the proposed algorithm can reconstruct the image-consistent polygonal shape that is patched by input images. This algorithm eliminates the invalid vertices and polygons from the initial polygonal grid space according to the color variance that represents their image consistency. The carved shape is refined by moving the outlier vertices on the boundary of each image. The final reconstructed shape faithfully accounts for the input images, and its textured appearance reflects the similar color property of the target object.

OLBA BÖLGESİ ve BÖLGEDE KULLANILAN POLYGONAL DUVAR TEKNİĞİ

The first tendencies of epigraphy and art in Greek manner appear during the Hellenistic period vvithin the Olbian priesterly dynasty in eastern Rough Cilicia. Furthermore a Greacization has taken place in the culture of the region. The effects of this time period which can be defincd as acculturation can be observed best on religious platforms. As a result of syncretizm, gods of Luwian origin werc Gracesized and the effects of the changes left important traces, not only in epigraphy or artifacts but also in cultural and social sphercs. For example the Olbian symbols which are the products of this period are the attributes of Greek gods and can be presented as one of the best cvidences of this influencc. It is also obvious that during this period the architectural characteristics of the Olba region changed radically. In the region vvhere no monumental architectural existed until the 3rd century B.C., a construction period started through the middle of the 3rd century B.C. and flourished in the 2nd century B.C. These dates coincide with the important changes observed in epigraphical, social and cultural sphercs as well as in art. The most chracteristic feature of this construction period is that the technique of polygonal vvalls found its way to Olba and started to be used dominantly. Especially the development considering epigraphy, art as well as social and cultural activities which appeared as a result of Graecization makc us think that also the architectural development followed the same way. This situation must be the product of a power, vvilling to settle the Greek culture in Olba and of a systematical planning. This povver was one of the most important kingdoms of the Hellenistic period, namely the Selcucids and the system they applied was the policy of acculturation. Thcre is a historical parallelity between the frequency of epigraphic and architectural material in this region and the event of 188 B.C. as the vvestern bordcr of the Seleucids was defined as Seleucia. It is obvious that there is a combination between these facts and that the acculturation policy of the Seleucids in Olba gained power during this period. The introduction of the polygonal wall technique and its application on civil and military architecture must be considered as a part of this policy. The settlements vvhich are not far from each other are small but posess strong fortification vvalls and the walls of these constructions within these settlements are built in polygonal technique. Duc to the diffcrent topographical features these settlements have various plans but considered as a vvhole it appears that they are part of an organised settlement and defense system. Constructions of various aims show local characteristics. Hellenistic tombs, temples and towers, built closc to the settlements, reflect the architectural character of the region. Other struetures such as fortification vvalls, their towers, bastions and houses are the buildings mostly attested within the settlements. It is a common feature that they are ali built in the polygonal technique. The defense system consists of independent towers and settlements with grandiose defense vvalls. This system is set on the shore and continued in north-south direetion along vallics and roads so that ali the region is taken under safety. The polygonal vvalls are divided into two main groups according to their contours and surfaces. There are also subgroups and these are categorized due to constructions and settlements vvhich are mostly part of the defence system. But the survcys have shown that a certain type of polygonal wall did not represent a certain architectural class (military, rcligious, civil architectural examples or graves) and that in each architectural class more than one type of contour or surface working was applied. It is also obvious that there is no chronological development between the types of polygonal walls which differ in themselves. Furthermore the polygonal walls vvhich can be dated to the Hcllenistic period do not have a Standard quality and the quality differs due to the economic, geographic, strategic or hierarchic instances. Until new discoveries are made, it is possible to suggest that the defense system with its tonibs, civil and religious architecture is to be dated to the begining of the 2nd century B.C. and that it continued until the last quartcr of the 2nd century B.C. or the last quarter of the 2nd ccntury. Actually the construction of polygonal technique continued after the Hellenistic period but with a continious decline in its quality. Independent from the improvement and settled politics of the Hellenistic period, the polygonal tcchnique even continued during the period of Early Christianity but vvithout any systcmatic and it is usually represented by single examples.

Revolving-field polygon technique for performance prediction of single-phase induction motors

This paper presents a new analytical technique for improving the performance prediction of single-phase induction motors, especially capacitor motors. The technique uses the split-phase motor electrical equivalent circuit analysis together with electrical and magnetic parameters whose variation is computed from the equivalent balanced polyphase motor, so that the same magnetic circuit analysis can be used for both. (The term split-phase is used to cover motors operating from a single-phase supply but with the phase windings split into two orthogonal windings, one of which may have a capacitor in series with it during running or starting.) The technique accounts for the elliptical envelope of the magnetizing field vector and results in improved precision, since the three-phase electromagnetic model is considered to be more precise than the normal split-phase motor analysis. An important result is the computation of vector polygons of flux density for each section of the magnetic circuit, providing a better basis for core loss prediction. The double-frequency torque ripple is also obtained from the stator magnetomotive force and flux-density polygons. Three different electrical equivalent circuit methods for the split-phase motor (based respectively on the cross-field theory, forward- and backward-revolving fields, and symmetrical components) are evaluated to determine the method best suited for incorporating the variation of the circuit parameters from the polyphase magnetic circuit analysis, and it is discussed how the core losses can be included in these circuits to obtain the best overall performance prediction.

The effect of establishing native woodland on habitat selection and ranging of moorland mountain hares (Lepus timidus), a flexible forager

Mountain hares Lepus timidus L. typify species that occupy a broad geographic range and have flexible foraging and nutritional strategies. Such species may show a range of responses to habitat modification. This study aimed to provide a basis for prediction of the impact of mountain hares on woodland establishment, and of woodland establishment on mountain hare distribution. The selection of and the extent of incorporation of new woodland into the home range of mountain hares was investigated in an area where Scots pine Pinus sylvestris L. woodland was establishing within their usual habitat in Britain, upland heather moorland. Seasonal home, day and night‐range sizes of radio‐tracked mountain hares were determined using the multinuclear probability polygon technique and analysed using residual maximum likelihood (REML). Habitat selection was analysed using compositional analysis. Three main habitat types were available to hares: heather moorland with trees, heather moorland and grassland‐mire. Mean home‐range size of mountain hares in summer was 10.3 ha and in winter 9.6 ha. There were no significant seasonal or sex differences in home‐range size. Females selected grassland‐mire habitat in summer and showed no strong selection for any habitat in winter. Males selected heather moorland in both summer and winter. Heather moorland with trees was not selected preferentially by mountain hares of either sex in summer or winter. The absence of selection for areas of newly establishing‐Scots pine woodland suggests that any browsing damage to trees by hares is most likely to be a function of the local abundance of mountain hares, rather than a result of active preference of hares for the modified habitat.

Abundance, use of space, and activity patterns of white-faced sakis (Pithecia pithecia) in French Guiana.

White-faced sakis (Pithecia pithecia) are among the least studied neotropical primates. The combination of shy and quiet behavior, their ability to move silently, and the extreme difficulty of capturing them may explain why very few field studies have been undertaken in undisturbed habitats. During the course of a wildlife rescue in French Guiana, six individuals were captured and translocated to a safe area of primary rainforest. In this area, based on the observation of 35 groups, the average group size was 2.3 animals (SD = 1.2) and a density of 0.28 group/km(2) (0.64 individuals/km(2)) was estimated from transect censuses. Our study focused successively on three radio-collared animals (two males and one female) over a 287-day period, starting from release to the loss of the animal. From the study start, the triangulation method was used prior to habitutation to human presence, followed thereafter by 1,327 hr of visual monitoring. The translocated animals settled down, and two of them had a stable and compact home range. Two of them merged in association with members of the resident population. A resident group had a much larger home range than previously reported: 148 and 287 ha, using grid cells and 100% minimum convex polygon techniques, respectively. A group composed of two translocated individuals (one male and one female) had a home range of 68 and 135 ha using the same techniques. Additionally, two solitary animals used 152 and 162 1-ha quadrats. We observed animals (translocated and residents) moving quickly in one direction up to 11.5 km. The mean daily path length of resident animals was 1,880 m. Sakis used the lower strata of the forest more when in group, and the intermediate strata more when solitary. Allogrooming is fairly common in social groups. On average, the activity period ranged from 7:17 to 15:59 hr.