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Visual Programming Language for Thymio II Robot
Get PDFABSTRACT This paper introduces a visual programming language (vpl) for Thymio II, an educational robot. Our vpl is intended for children in primary school and aims at making robotics programming approachable for young children by creating a close correspondence between the icons of the programming language and the design of the robot. Its two modes of operation -basic and advanced -allow children to learn programming at a level suitable for their current skill. Moreover, our vpl provides a live generation of textual code that eases the transition to textual programming for more advanced children. This paper describes the goals and the guiding principles behind the design of our vpl and demonstrates how an iterative development process with evaluations with children resulted in an improved vpl
A trigonally charge-compensated Y2+ ion in CaF,: a Jahn-Teller system
Get PDFAbstract. We show that CaF,: Y crystals that have been X-irradiated at low temperatures contain Y2-ions associated with a trigonally located interstitial F-ion. Experimental results are presented that support this identification and that show that a trigonal Jahn-Teller effect (with warping) is involved. An estimate for the Jahn-Teller energy of E,, = 490 cm-' is obtained. The yttrium ion introduced as an impurity into calcium fluoride has a non-typical behaviour as compared with that of the Sc and La ions in this same host. These latter ions enter the cation site of the otherwise locally unperturbed CaFz lattice substitutionally [l-31. They can be converted readily into the divalent state which exhibits a weak-to-intermediate cubic Eg@ e,-type Jahn-Teller effect [ 1-31. In contrast, yttriumdoped but otherwise very pure CaF2 crystals present, after additive colouration or roomtemperature radiolysis, many optical absorption bands of variable composition, thermal and photochemical stability. Among these the four Smakula bands have been associated with yttrium Studies (e.g. [6]) of the dielectric properties as a function of temperature of CaF: Y crystals indicate that a proportion of the ytrrium ions are associated with interstitial F ions and form Y-F dipoles. Two neighbouring positions of the F ion are possible (with respect to the substitutional cation site): a tetragonal one (NN) and a trigonal one (NNN). According to several lattice dynamics calculations [ 7 , 81 the trivalent RE ions (including yttrium) associated with an interstitial F ion have lower energy than the non-associated one. The calculations further predict [8] that the energy of the (NN) site is much lower than that of the (NNN) site, indicating that this latter configuration is unlikely. This paper reports for the first time an unambiguously identified Y2+ centre in CaF:. It is observed on radiolysed CaF2: Y samples (irradiated at 78 K, typically for 36 h, at 40 kV and 35 mA). The crystals used in the experiments had all been grown under very thoroughly controlled conditions in our laboratory. In particular, they were oxygen-free within the limits of the sensitivity of our X-band EPR spectrometer (-10" spins G-l). Using EPR we found that the irradiated crystals produce, at 4.2 K, the spectra shown in figures 1 , 2 when H is oriented along a C4, C3 or C2 crystal axis. Complex superhyperfine (SHF) structure is observed and shows its best resolution when H 11 C4. EPR experiment
Influence of Additives and Hot-Press Sintering on Mechanical and Lipophilic Properties of Silicon Nitride Ceramics *
No full textFe 3 O 4 and Mo and were added to hot-press sintered Si 3 N 4 ceramics to improve their lipophilic and mechanical properties. The bending strength, relative density, hardness and fracture toughness of Si 3 N 4 ceramics with added Fe 3 O 4 and Mo were improved by hot-press sintering compared with samples prepared with the pressureless process. In particular, the bending strength and relative density were improved by about 200 and 104%, respectively. Both the macro-and micro-lipophilicity of Fe 3 O 4 -and Mo-added ceramics were improved when prepared with the hot-press process, compared with those prepared with the pressureless process. This can be attributed to the addition of Fe 3 O 4 , and the formation of MoO 3 and Si 2 N 2 O during hot-press sintering. The lower friction coefficient and high wear resistance of Fe 3 O 4 -and Mo-added ceramics have been achieved by applying the hot press process. The high wear resistance is considered to be due to the improvement of hardness and fracture toughness, which decreased the loss of particles during the wear test
7 Multifaceted Role of Angiotensin II in Vascular Inflammation and Aortic Aneurysmal Disease
No full textQuantitative explanation of satellite ionograms taken within the F 2-layer maximum
No full textAbstract. A quantitative explanation of ionograms taken within the F 2-layer maximum is presented. An assumption is made that there exist sharp horizontal irregularities of the electron density. There are ray trajectories which return back to the satellite after a deviation of the ionosonde signals by these irregularities
Present Ecological Status and Diversity of Zeuxine Lindl. a Botanically Less Known Orchid of Dibrugarh District of Assam, North East India
No full textAbstract Assam is the second largest state of North-East India and treasure trove of Indian orchids. Dibrugarh District is in the located in the eastern part of the state with rich native orchid species. This report is the outcome of our intensive field studies carried out during 2006 -2011. We have chosen opportunistic method to cover all representative areas of different habitat. We have surveyed the area covering all the seasons of the year. For microhabitat structure randomly selected quadrat of 5mx5m were laid in the field and noted down all the features. In this study a total of 114 Orchid species under 54 genera have been recorded from the district. The study revealed 29 species as terrestrial and the rest 85 species are epiphytic. Among the terrestrial genus Zeuxine is found as ecologically and taxonomically co mplex group of Orch idaceae. During this field study, 6 species of the genus Zeuxine were recorded viz. Z. clandestine; Z. glandulosa; Z. goodyeroides; Z. longilabris; Z. nervosa and Z. Strateumatica. The present study envisages the threat and status of these species with conservation recommendation. Moreover, this is the first attempt to establish the taxonomic identificat ion to workout currently accepted botanical names of the genus with its ecological status, voucher specimen numbers, habitat, phenology and distribution in this district
DISTRIBUTION AND HABITAT ASSOCIATIONS OF THE MOUNTAIN PLOVER (Chmckiusmontanus) IN CALIFORNIA
No full textABSra4CT: The mountain plover (Charadnus montanus) breeds in disturbed short-grass prairie or shrub semidesert habitats in the western Great Plains and winters in the southwest and western United States and Mexico. The number and distribution of wintering birds in California has decreased markedly since the 1800's. Loss of habitat in many states, and loss of habitat and changes in agricultural practices in California, have been implicated in population declines of over 60% from historic levels. The California Department of Fish and Game initiated a census of wintering mountain plovers in California employing skilled volunteers using standardized survey methods throughout the species historic California range. The 1998 survey resulted in detection of 2,663 birds at 3 1 sites in 1 1 California counties. The 1999 survey, which was less rigorous, resulted in detections of 1,372 birds at 10 sites in 3 counties. A similar one-day volunteer survey of historic mountain plover locations organized by the National Audubon Society in 1994 resulted in detection of an estimated 3,346 birds at 25 sites in 9 California counties. Mountain plovers selected barren, recently b e d or grazed sites for foraging and roosting
