Study of local flow conditions over a hemispherically blunted 25 deg cone for a shallow re-entry trajectory

Local flow conditions over hemispherically blunted 25 deg cone for shallow reentry trajector

Studi Penentuan Panjang Dan Kedalaman Retak Sambungan Las Pada Konstruksi Kapal Menggunakan Pengujian Ultrasonik Dengan Variasi Frekuensi Dan Ukuran Kristal Dan Variasi Kondisi Permukaan Coating Dan Uncoating

Ketidaksempurnaan dalam pengelasan diikuti dengan pengoperasian sering kali menimbulkan retak serta cacat-cacat dalam pengelasan pada sambungan las pondasi mesin di kapal yang telah dicat, pengujian ultrasonik dilakukan untuk mendeteksi lokasi retak tersebut tanpa membuang cat yang terdapat dipermukaan konstruksi. Pada tugas akhir ini dilakukan penelitian pada sambungan tumpul las sebanyak lima buah specimen dengan ukuran 400x200x12 mm dan pada setiap spesimen diberikan beberapa variasi ketebalan cat yaitu 0 mikron, 60 mikron, 120 mikron, 250 mikron, dan 300 mikron dimana sebelum diberikan variasi ketebalan cat terlebih dahulu diberikan retak buatan pada setiap specimen di daerah toe sambungan las dengan ukuran panjang 20 mm, 30 mm, 50 mm, dan 70 mm, dengan kedalaman 2 mm, 4 mm, 6 mm dan 8 mm, pengujian ultrasonik dilakukan dengan memvariasikan ukuran transducer yaitu 8 x 9 mm (2MHz), 20 x 22 mm (2MHz), dan 8 x 9 mm (4MHz). Setelah itu dilakukan pemeriksaan dengan menggunakan metode ultrasonik untuk membandingkan retak aktual dengan retak hasil scanning untuk panjang dan kedalaman retak. Hasil penelitian memperlihatkan bahwa semakin besar variasi ketebalan cat yang diberikan pada spesimen uji maka efektivitas pembacaan ukuran retak dengan menggunakan metode ultrasonik test akan menurun. Frekuensi transducer yang lebih besar memiliki kemampuan yang lebih sensitif untuk mendeteksi retak dan ukuran kristal transducer yang lebih besarakan lebih sensitif untuk mendeteksi retak dikarenakan penyebaran berkas suara yang lebih konstan. Dari ketiga jenis transducer yang paling akurat adalah 8 x 9 mm (4MHz)

Memory, learning and language in autism spectrum disorder

Background and aims: The ‘dual-systems’ model of language acquisition has been used by Ullman and colleagues to explain patterns of strength and weakness in the language of higher-functioning people with autism spectrum disorder (ASD). Specifically, intact declarative/explicit learning is argued to compensate for a deficit in non-declarative/implicit procedural learning, constituting an example of the so-called ‘see-saw’ effect. Ullman and Pullman (2015) extended their argument concerning a see-saw effect on language in ASD to cover other perceived anomalies of behaviour, including impaired acquisition of social skills. The aim of this paper is to present a critique of Ullman and colleagues’ claims, and to propose an alternative model of links between memory systems and language in ASD. Main contribution: We argue that a 4-systems model of learning, in which intact semantic and procedural memory are used to compensate for weaknesses in episodic memory and perceptual learning, can better explain patterns of language ability across the autistic spectrum. We also argue that attempts to generalise the ‘impaired implicit learning/spared declarative learning’ theory to other behaviours in ASD are unsustainable. Conclusions: Clinically significant language impairments in ASD are under-researched, despite their impact on everyday functioning and quality of life. The relative paucity of research findings in this area lays it open to speculative interpretation which may be misleading. Implications: More research is need into links between memory/learning systems and language impairments across the spectrum. Improved understanding should inform therapeutic intervention, and contribute to investigation of the causes of language impairment in ASD with potential implications for prevention

Species Trees from Highly Incongruent Gene Trees in Rice

Several methods have recently been developed to infer multilocus phylogenies by incorporating information from topological incongruence of the individual genes. In this study, we investigate 2 such methods, Bayesian concordance analysis and Bayesian estimation of species trees. Our test data are a collection of genes from cultivated rice (genus Oryza) and the most closely related wild species, generated using a high-throughput sequencing protocol and bioinformatics pipeline. Trees inferred from independent genes display levels of topological incongruence that far exceed that seen in previous data sets analyzed with these species tree methods. We identify differences in phylogenetic results between inference methods that incorporate gene tree incongruence. Finally, we discuss the challenges of scaling these analyses for data sets with thousands of gene trees and extensive levels of missing data

Seeing other perspectives: Evaluating the use of virtual and augmented reality to simulate visual impairments (OpenVisSim)

Simulations of visual impairment are often used to educate and inform the public. However, evidence regarding their accuracy remains lacking. Here we evaluated the effectiveness of modern digital technologies to simulate the everyday difficulties caused by glaucoma. Twenty5 three normally-sighted adults performed two everyday tasks that glaucoma patients often report difficulties with: a visual search task in which they attempted to locate a mobile phone in virtual domestic environments (Virtual Reality; VR), and a visual mobility task in which impairments were overlaid onto a real-world environment using Augmented Reality (AR). On some trials, a gaze-contingent simulated scotoma --- generated using perimetric data from a patient with advanced glaucoma --- was presented in either the superior or inferior hemifield. The main outcome measure was task completion time. Eye and head movements were also tracked and used to assess individual differences in looking behaviors. The results showed that the simulated impairments substantial impaired performance in both the VR (visual search) and AR (visual mobility) tasks (both P < 0.001). Furthermore, and in line with previous patient data: impairments were greatest when the simulated VFL was inferior versus superior (P < 0.001), participants made more eye and head movements in the inferior VFL condition (P < 0.001), and participants rated the inferior VFL condition as more difficult (P < 0.001). Notably, the difference in performance between the inferior and superior conditions was almost as great as the difference between a superior VFL and no impairment at all (VR: 71%; AR: 70%). We conclude that modern digital simulators are able to replicate and objectively quantify some of the key everyday difficulties associated with visual impairments. Advantages, limitations and possible applications of current technologies are discussed. Instructions are also given for how to freely obtain the software described (OpenVisSim)

Interesting magnetic properties of Fe1−x_{1-x}Cox_xSi alloys

Solid solution between nonmagnetic narrow gap semiconductor FeSi and diamagnetic semi-metal CoSi gives rise to interesting metallic alloys with long-range helical magnetic ordering, for a wide range of intermediate concentration. We report various interesting magnetic properties of these alloys, including low temperature re-entrant spin-glass like behaviour and a novel inverted magnetic hysteresis loop. Role of Dzyaloshinski-Moriya interaction in the magnetic response of these non-centrosymmetric alloys is discussed.Comment: 11 pages and 3 figure

Fine Structure of Rydberg States. V. n=5 and 6F and G States of He4

We have made 17 new high-precision measurements of the nF-nG intervals (n=5,6) of neutral He4 using the microwave-optical method. The rms one-standard-deviation experimental uncertainty for the transitions reported here is 188 kHz (14 ppm). The new measurements agree with the predictions of a least-squares fit to previous experimental data, and are up to 40 times more precise. The nF-nG manifold is now known experimentally to better than 1 MHz for all values of the quantum numbers. The precision of the experimental measurement exceeds that of the best currently available theory by approximately three orders of magnitude

Numerical evidence for the spin-Peierls state in the frustrated quantum antiferromagnet

We study the spin-$1\over2$ Heisenberg antiferromagnet with an antiferromagnetic $J_3$ (third nearest neighbor) interaction on a square lattice. We numerically diagonalize this ``$J_1$-$J_3$'' model on clusters up to 32-sites and search for novel ground state properties as the frustration parameter $J_3/J_1$ changes. For ``larger'' $J_3/J_1$ we find enhancement of incommensurate spin order, in agreement with spin-wave, large-$N$ expansions, and other predictions. But for intermediate $J_3/J_1$, the low lying excitation energy spectrum suggests that this incommensurate order is short-range. In the same region, the first excited state has the symmetries of the columnar dimer (spin-Peierls) state. The columnar dimer order parameter suggests the presence of long-range columnar dimer order. Hence, this spin-Peierls state is the best candidate for the ground state of the $J_1$-$J_3$ model in an intermediate $J_3/J_1$ region.Comment: RevTeX file with five postscript figures uuencode

Generation of atom-light entanglement in an optical cavity for quantum enhanced atom interferometry

We theoretically investigate the generation of atom-light entanglement via Raman superradiance in an optical cavity, and show how this can be used to enhance the sensitivity of atom interferometry. We model a realistic optical cavity, and show that by careful temporal shaping of the optical local oscillator used to measure the light emitted from the cavity, information in the optical mode can be combined with the signal from the atom interferometer to reduce the quantum noise, and thus increase the sensitivity. It was found in Phys. Rev. Lett. 110, 053002 (2013) that an atomic “seed” was required in order to reduce spontaneous emission and allow for single mode behavior of the device. In this paper we find that the optical cavity reduces the need for an atomic seed, which allows for stronger atom-light correlations and a greater level of quantum enhancement

Stand Characteristics and Leaf Litter Composition of a Dry Forest Hectare in Santa Rosa National Park, Costa Rica

One hectare of tropical dry forest in Guanacaste Conservation Area, Costa Rica was mapped and all trees larger than 10 cm diameter at breast height (DBH) identified. The same hectare was sampled for leaf litter and the two data sets, forest and litter, were compared. Dominant and subdominant species of the forest are represented in the leaf litter, whereas rare tree species are highly variable in their representation in the leaf litter. Relative abundance of dominant and subdominant tree species is represented well by the litter although absolute rank-order is nor identical between source forest basal area and leaf litter mass. The litter adds a significant component to the source forest data owing to the presence of vines and lianas, and more rarely small trees or shrubs. This indicates that litter studies may be able to add depth to forest diversity surveys. The source forest also was used to test foliar physiognomic reconstructions of climate that have been proposed recently by paleobotanists as an alternative to taxonomic affinities methods. The observed climate of the area does not conform to the climatic values that were predicted by application of these new methods. RESUMEN Una hectÁrea de bosque seco tropical en el Area de ConservaciÓn de Guanacaste, Costa Rica fue mapeada, y todos los Árboles mayores de 10 cm de dap fueron identificados. En la misma hectÁrea, se tomaron muestras de hojarasca y los dos colecciones de datos. bosque y hojarasca, fueron comparadas. Se encontrÓ que las especies dominantes y subdominantes del bosque estaban representadas en las muestras de hojarasca, mientras que la presencia de especias arbÓreas raras en las muestras de mojarasca fue muy variable. La abundancia relativa de especies arbÓreas dominantesestÁ bien representada en la hojarasca aunque el Área basal del bosque de origen y la masa de hojarasca no heron idÉnticos en rangos absolutos. La hojarasca aÑade un componente significativo a los datos del bosque de origen debido a la presencia de bejucos y lianas en la hojarasca, y mÁs raramente Árboles pequeÑos y arbustos. Estos datos indican que los estudios de hojarasca pueden incrementar la precisiÓn de las estimaciones de la diversidad de los bosques. El bosque de origen fue usado tarnbien para examinar reconstrucciones del clima basados en la fisiognomia foliar recientemenre propuesras por paleobotÁnicas como una alternativa a mÉtodos de afinidad raxonÓmicas. El clima observado en el Área no corresponde con los valores climÁticos que fueron predecidos por la aplicaciÓn de estos nuevos mÉtodos.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73234/1/j.1744-7429.1997.tb00034.x.pd