bluuebunny/crossref_metadata_2025 huggingface dataset:
NECK FRAGMENTATION IN FISSION AND QUASIFISSION OF HEAVY AND SUPERHEAVY NUCLEI
Authors: RUBCHENYA V. A. , TRZASKA W. H. , VARDACI E.
Published: May 2009

The generalized approach is proposed for the ternary fission and the neck fragmentation of the dinuclear system formed in the heavy ion quasifission reactions. The light-charged-particles accompanied the fission and quasifission are the valuable probes for studies of the dynamics of the hyperdeformed nuclear configurations with neck. The developed model describes well the light-charged-particle emission probabilities and their mass distributions in the ternary fission of actinide nuclei. The model is also applied to analyze the double differential distributions of the protons and α-particles accompanied fragmentation in the reaction 86 Kr + 206 Pb at E Kr = 500 and 600 MeV. It was found that the near scission emission multiplicities of α-particles are [Formula: see text] and 0.070 ± 0.005 at lower and higher energies, respectively. The neck emission of the protons was not detected.
COMPARISON OF THE FUSION-FISSION AND QUASIFISSION MECHANISMS IN HEAVY-ION COLLISIONS
Authors: NASIROV AVAZBEK , FAZIO GIOVANNI , GIARDINA GIORGIO , MANDAGLIO GIUSEPPE , MANGANARO MARINA , HANAPPE FRANCIS , MUMINOV AKHTAM , SCHEID WERNER
Published: May 2009

The decrease of the evaporation residue yields in reactions with massive nuclei is explained by an increase of the competition between quasifission and complete fusion processes and by the decrease of the survival probability of the heated and rotating nuclei against fission along the de-excitation cascade of the compound nucleus. The experimental data on the yields of evaporation residue, fusion-fission and quasifission fragments in the 48 Ca + 154 Sm reaction are analyzed in the framework of the combined theoretical method based on the dinuclear system concept and advanced statistical model. The measured yields of evaporation residues of the 48 Ca + 154 Sm reaction have been well reproduced and yields of fission fragments were analyzed using the partial fusion and quasifission cross sections calculated in the dinuclear system model. Such a way of calculation is used to find optimal conditions for the synthesis of the new element Z = 120 (A = 302) by studying the excitation functions of evaporation residues of the 54 Cr + 248 Cm , 58 Fe + 244 Pu , and 64 Ni + 238 U reactions. Our estimations show that the 54 Cr + 248 Cm reaction is preferable in comparison with the two others.
ABOUT THE INCONSISTENCY BETWEEN BOHR-WHEELER'S TRANSITION-STATE METHOD AND KRAMERS' ESCAPE RATE IN NUCLEAR FISSION
Authors: SCHMIDT KARL-HEINZ
Published: May 2009

The problem of an apparent inconsistency between the fission rates derived on the basis of Bohr-Wheeler's transition-state method and Kramers' dynamical model of nuclear fission, first pointed out by Strutinsky in 1973, is revisited. The study is based on studying the features of individual trajectories on the fission path.
PAIRING CORRELATIONS AND FISSION BARRIER HEIGHTS
Authors: POMORSKI KRZYSZTOF , IVANYUK FEDIR
Published: May 2009

The influence of a pairing strength proportional to the surface of the deformed nucleus, on the fission barrier heights evaluated within the macroscopic-microscopic model which does not contain the average pairing energy in its macroscopic part is investigated. The calculations were carried out with the Lublin-Strasbourg drop model and the folded-Yukawa single-particle potential.
FISSION POTENTIAL ENERGY SURFACES IN TEN-DIMENSIONAL DEFORMATION SPACE
Authors: PASHKEVICH V. , PYATKOV Y. , UNZHAKOVA A.
Published: May 2009

Various fission processes are described in terms of high-dimensional potential energy surface in the frame of the Strutinsky shell correction method for actinide region. The complete deformation space is necessary to study the potential energy minima responsible for the cluster radioactivity, cold fission and cold multi-fragmentation valleys. The nuclear shape families for the different fission configurations are obtained without any specific change of the parameters. The coordinate system based on the Cassini ovaloids makes it possible to increase the number of independent deformation parameters without divergence. The higher orders of the deformation are shown to play an important role in the description of the potential energy surface structure.
DEFORMED NUCLEI USING THE BARCELONA-CATANIA-PARIS ENERGY DENSITY FUNCTIONAL
Authors: VIÑAS X. , ROBLEDO L. M. , BALDO M. , SCHUCK P.
Published: May 2009

We have recently presented a new non-relativistic nuclear energy density functional which is constructed, not as usual, from an effective density dependent nucleon-nucleon force but directly introducing in the functional results from microscopic nuclear and neutron matter Bruckner G -matrix calculations at various densities. We add a purely phenomenological finite range part to account for surface properties. We take from the literature a density dependent zero range force to describe the pairing correlations. We find that only four to five adjustable parameters, spin-orbit included, suffice to reproduce nuclear binding energies and radii to the same accuracy as those obtained with some of the best effective forces for both spherical and deformed nuclei. The deformation properties of this new functional are in excellent agreement with the results computed using the Gogny D1S force.
ISOSPIN MIXING IN THE HIGHER TAMM-DANCOFF APPROXIMATION
Authors: BONNEAU LUDOVIC , LE BLOAS JULIEN , QUENTIN PHILIPPE , BARTEL JOHANN , STROTTMAN DANIEL
Published: May 2009

We present a formalism to study the isospin content of a nuclear state in the framework of the Higher Tamm-Dancoff Approximation. This formalism is then applied to the description of even-even N = Z nuclei. Finally a schematic two-level model provides some insight into the isospin-mixing mechanism at work and the impact of the pairing correlations on the isospin-mixing parameter.
QUANTUM PHASE TRANSITIONS AND NUCLEAR STRUCTURE
Authors: CEJNAR P. , STRÁNSKÝ P. , MACEK M.
Published: May 2009

We report on recent progress in the description of shape transitions in atomic nuclei. The main experimental signatures are mentioned along with basic theoretical models describing the critical character of the nuclear shape evolution. We then discuss some new theoretical results obtained within the framework of the interacting boson model and related approaches. It is argued that these models can be used to probe some fundamental aspects of quantum phase transitions.
SKYRME-RANDOM-PHASE-APPROXIMATION DESCRIPTION OF E1 STRENGTH IN 92–100Mo
Authors: KVASIL J. , VESELY P. , NESTERENKO V. O. , KLEINIG W. , REINHARD P.-G. , FRAUENDORF S.
Published: May 2009

The isovector dipole E1 strength in 92,94,96,98,100 Mo is analyzed within the self-consistent separable random-phase approximation (SRPA) model with Skyrme forces SkT6, SkM*, SLy6, and SkI3. The special attention is paid to the low-energy region near the particle thresholds (4-12 MeV), which is important for understanding of astrophysical processes. We show that, due to a compensation effect, the influence of nuclear deformation on E1 strength below 10-12 MeV is quite modest. At the same time, in agreement with previous predictions, the deformation increases the strength at higher energy. At 4-8 MeV the strength is mainly determined by the tail of E1 giant resonance. The four Skyrme forces differ in description of the whole giant resonance but give rather similar results below 12 MeV.
ISOMERIC DECAY STUDIES IN NEUTRON-RICH N ≈ 126 NUCLEI
Authors: STEER S. J. , PODOLYÁK ZS. , PIETRI S. , GÓRSKA M. , FARRELLY G. F. , REGAN P. H. , RUDOLPH D. , GARNSWORTHY A. B. , HOISCHEN R. , GERL J. , WOLLERSHEIM H. J. , GRAWE H. , MAIER K. H. , BECKER F. , BEDNARCZYK P. , CÁCERES L. , DOORNENBAL P. , GEISSEL H. , GRȨBOSZ J. , KELIC A. , KOJOUHAROV I. , KURZ N. , MONTES F. , PROKOPOWICZ W. , SAITO T. , SCHAFFNER H. , TASHENOV S. , HEINZ A. , KURTUKIAN-NIETO T. , BENZONI G. , PFÜTZNER M. , JUNGCLAUS A. , BALABANSKI D. L. , BRANDAU C. , BROWN A. , BRUCE A. M. , CATFORD W. N. , CULLEN I. J. , DOMBRÁDI ZS. , ESTEVEZ M. E. , GELLETLY W. , ILIE G. , JOLIE J. , JONES G. A. , KMIECIK M. , KONDEV F. G. , KRÜCKEN R. , LALKOVSKI S. , LIU Z. , MAJ A. , MYALSKI S. , SCHWERTEL S. , SHIZUMA T. , WALKER P. M. , WERNER-MALENTO E. , WIELAND O.
Published: May 2009

Heavy neutron-rich nuclei were populated via relativistic energy fragmentation of a E / A = 1 GeV 208 Pb beam. The nuclei of interest were selected and identified by a fragment separator and then implanted in a passive plastic stopper. Delayed γ rays following internal isomeric decays were detected by the RISING array. Experimental information was obtained on a number of nuclei with Z = 73-80 ( Ta - Hg ), providing new information both on the prolate-oblate transitional region as well as on the N = 126 closed shell nuclei.
THE SYMMETRY ENERGY AND OTHER OPEN QUESTIONS CONCERNING EFFECTIVE FUNCTIONALS
Authors: COLÒ G.
Published: May 2009

The nuclear structure community is striving to determine a nuclear energy functional which is as universal and as accurate as possible. When a functional is determined by fitting free parameters, the constraints on these parameters coming from excited states (like the well-known giant resonances) are not, as a rule, imposed. This work shows that at least three constraints could be imposed on Skyrme functionals, by explaining the physical background and discussing their relevance.
COLLECTIVE HAMILTONIANS WITH TETRAHEDRAL SYMMETRY: FORMALISM AND GENERAL FEATURES
Authors: GÓŹDŹ A. , MIŚKIEWICZ M. , DUDEK J. , DOBROWOLSKI A.
Published: May 2009

Collective octupole variables invariant under tetrahedral point group transformations are used to construct tetrahedrally invariant collective Hamiltonians. The so-called intrinsic groups are considered as a tool for symmetry analysis of such Hamiltonians in intrinsic frames of a nuclei.
NEW EXPERIMENTAL APPROACH FOR HEAVY AND SUPERHEAVY ELEMENT PRODUCTION
Authors: BARBUI M. , MATERNA T. , SAHU P. , WIELOCH A. , BECCHETTI F. D. , CHUBARYAN G. , CINAUSERO M. , O'DONNELL T. W. , FABRIS D. , GRIFFIN H. , HAGEL K. , KOWALSKI S. , LUNARDON M. , MAJKA Z. , MORETTO S. , MURTHY R. , NATOWITZ J. B. , NEBBIA G. , PESENTE S. , PRETE G. , QIN L. , RIZZI V. , SOSIN Z. , SOULIOTIS G. , VIESTI G. , WADA R. , WANG J.
Published: May 2009

In this article we present a new experimental approach for production of heavy and superheavy elements (HE, SHE). Nuclear reactions at low incident energies induced by heavy ion (HI) projectiles on fissile target nuclei are investigated. Dedicated detection setup is presented and the preliminary results for the reaction 197Au(7.5 MeV /u) + 232Th, studied at the Cyclotron Institute of Texas A&M University, are given.
ADIABATIC MASS PARAMETERS FOR SPONTANEUS FISSION
Authors: BARAN A. , SHEIKH J. A. , NAZAREWICZ W.
Published: May 2009

The collective mass tensor derived from the adiabatic time-dependent Hartree-Fock-Bogoliubov theory, perturbative cranking approximation, and the Gaussian overlap approximation to the generator coordinate method is discussed. Illustrative calculations are carried out for 252 Fm using the nuclear density functional theory with Skyrme interaction SkM* and seniority pairing.
PERES LATTICES IN NUCLEAR STRUCTURE
Authors: MACEK MICHAL , STRÁNSKÝ PAVEL , CEJNAR PAVEL
Published: May 2009

A method by Peres is used to represent spectra of the interacting boson model as lattices in the plane of energy versus an arbitrary observable average (or variance). Ordered (disordered) lattices are signatures of regularity (chaos) in both quantum and classical dynamics. The method is also apt to disclose exact or approximate dynamical symmetry.
CONFIGURATIONS OF EXTREMAL EVEN UNIMODULAR LATTICES
Authors: KOMINERS SCOTT DUKE
Published: May 2009

We extend the results of Ozeki on the configurations of extremal even unimodular lattices. Specifically, we show that if L is such a lattice of rank 56, 72, or 96, then L is generated by its minimal-norm vectors.
POISSON SPACING STATISTICS FOR VALUE SETS OF POLYNOMIALS
Authors: KURLBERG PÄR
Published: May 2009

If f is a non-constant polynomial with integer coefficients and q is an integer, we may regard f as a map from Z/qZ to Z/qZ. We show that the distribution of the (normalized) spacings between consecutive elements in the image of these maps becomes Poissonian as q tends to infinity along any sequence of square free integers such that the mean spacing modulo q tends to infinity.
A METHOD OF ESTIMATING THE p-ADIC SIZES OF COMMON ZEROS OF PARTIAL DERIVATIVE POLYNOMIALS ASSOCIATED WITH A QUINTIC FORM
Authors: SAPAR S. H. , ATAN K. A. MOHD.
Published: May 2009

It is known that the value of the exponential sum [Formula: see text] can be derived from the estimate of the cardinality |V|, the number of elements contained in the set [Formula: see text] where [Formula: see text] is the partial derivatives of [Formula: see text] with respect to [Formula: see text]. The cardinality of V in turn can be derived from the p-adic sizes of common zeros of the partial derivatives [Formula: see text]. This paper presents a method of determining the p-adic sizes of the components of (ξ,η) a common root of partial derivative polynomials of f(x,y) in Zp[x,y] of degree five based on the p-adic Newton polyhedron technique associated with the polynomial. The degree five polynomial is of the form f(x,y) = ax5 + bx4y + cx3y2 + sx + ty + k. The estimate obtained is in terms of the p-adic sizes of the coefficients of the dominant terms in f.
A SIMULATION STUDY ON DYNAMIC-SAMPLING-MODE FOR FLUORESCENCE MOLECULAR TOMOGRAPHY
Authors: XU ZHUN , BAI JING
Published: May 2009

Fluorescence tomography can obtain a sufficient dataset and optimal three-dimensional images when projections are captured over 360° by CCD camera. Herein a non-stop dynamic sampling mode for fluorescence tomography is proposed in an attempt to improve the optical measurement speed of the traditional imaging system and stability of the object to be imaged. A series of simulations are carried out to evaluate the accuracy of dataset acquired from the dynamic sampling mode. Reconstruction with the corresponding data obtained in the dynamic-mode process is also performed with the phantom. The results demonstrate the feasibility of such an imaging mode when the angular velocity is set to the appropriate value, thus laying the foundation for real experiments to verify the superiority in performance of this new imaging mode over the traditional one.
RADIATIVE TRANSPORT IN THE DELTA-P1 APPROXIMATION FOR LAMINAR OPTICAL TOMOGRAPHY
Authors: YUAN BAOHONG
Published: May 2009

To provide a computational efficient forward model with moderate accuracy for rapid 3D optical tomography in small volumes, radiative transport in the delta-P1 approximation combined with the approximation of the reciprocity was examined. Perturbations of optical signals caused by absorption and fluorescence heterogeneities submerged in a resin-based liquid phantom with background parameters close to rat brain tissues were measured using a recently constructed laminar optical tomography system. These measured perturbations were used to examine the theoretically calculated fluence perturbations based on the delta-P1 approximation and the reciprocity approximation. Results show that the errors between the predicted and measured data are acceptable, especially for fluorescence perturbations.
DETECTION OFCa2+-DEPENDENT NEURONAL ACTIVITY SIMULTANEOUSLY WITH DYNAMIC CHANGES IN CEREBRAL BLOOD VOLUME AND TISSUE OXYGENATION FROM THE LIVE RAT BRAIN
Authors: DU CONGWU , LUO ZHONGCHI , YU MEI , BENVENISTE HELENE , TULLY MELISSA , PAN RUBING , CHANCE BRITTON
Published: May 2009

We present a catheter-based optical diffusion and fluorescence (ODF) probe to study the functional changes of the brain in vivo. This ODF probe enables the simultaneous detection of the multi-wavelength absorbance and fluorescence emission from the living rat brain. Our previous studies, including a transient stroke experiment of the rat brain as well as the brain response to cocaine, have established the feasibility of simultaneously determining changes in cerebral blood volume (CBV), tissue oxygenation ( StO2) and intracellular calcium ([ Ca2+]i, using the fluorescence indicator Rhod2). Here, we present our preliminary results of somatosensory response to electrical forepaw stimulation obtained from the rat cortical brain by using the ODF probe, which indicate that the probe could track brain activation by directly detecting [ Ca2+]ialong with separately distinguishing CBV and StO2in real time. The changes of CBV, StO2and [ Ca2+]iare comparable with the blood-oxygen-level-dependent (BOLD) response to the stimulation obtained using functional magnetic resonance imaging (fMRI). However, the high temporal resolution of the optical methodology is advanced, thus providing a new modality for brain functional studies to understand the hemodynamic changes that underlie the neuronal activity.
Clusters, language models, and ad hoc information retrieval
Authors: Kurland Oren , Lee Lillian
Published: May 2009

The language-modeling approach to information retrieval provides an effective statistical framework for tackling various problems and often achieves impressive empirical performance. However, most previous work on language models for information retrieval focused on document-specific characteristics, and therefore did not take into account the structure of the surrounding corpus, a potentially rich source of additional information. We propose a novel algorithmic framework in which information provided by document-based language models is enhanced by the incorporation of information drawn from
clusters
of similar documents. Using this framework, we develop a suite of new algorithms. Even the simplest typically outperforms the standard language-modeling approach in terms of mean average precision (MAP) and recall, and our new
interpolation
algorithm posts statistically significant performance improvements for both metrics over all six corpora tested. An important aspect of our work is the way we model corpus structure. In contrast to most previous work on cluster-based retrieval that partitions the corpus, we demonstrate the effectiveness of a simple strategy based on a nearest-neighbors approach that produces overlapping clusters.
Universally Composable RFID Identification and Authentication Protocols
Authors: Burmester Mike , Van Le Tri , De Medeiros Breno , Tsudik Gene
Published: May 2009

As the number of RFID applications grows, concerns about their security and privacy become greatly amplified. At the same time, the acutely restricted and cost-sensitive nature of RFID tags rules out simple reuse of traditional security/privacy solutions and calls for a new generation of extremely lightweight identification and authentication protocols.

This article describes a universally composable security framework designed especially for RFID applications. We adopt RFID-specific setup, communication, and concurrency assumptions in a model that guarantees strong security, privacy, and availability properties. In particular, the framework supports modular deployment, which is most appropriate for ubiquitous applications. We also describe a set of simple, efficient, secure, and anonymous (untraceable) RFID identification and authentication protocols that instantiate the proposed framework. These protocols involve minimal interaction between tags and readers and place only a small computational load on the tag, and a light computational burden on the back-end server. We show that our protocols are provably secure within the proposed framework.
ACM-W celebrates women in computing
Authors: Weyuker Elaine
Published: May 2009

Computer science is no longer the hot, high-enrollment field it once was.
Hard-disk drives
Authors: Elerath Jon
Published: May 2009

New drive technologies and increased capacities create new categories of failure modes that will influence system designs.
Whither sockets?
Authors: Neville-Neil George V.
Published: May 2009

High bandwidth, low latency, and multihoming challenge the sockets API.
Securing frame communication in browsers
Authors: Barth Adam , Jackson Collin , Mitchell John C.
Published: May 2009

Many Web sites embed third-party content in frames, relying on the browser's security policy to protect against malicious content. However, frames provide insufficient isolation in browsers that let framed content navigate other frames. We evaluate existing frame navigation policies and advocate a stricter policy, which we deploy in the open-source browsers. In addition to preventing undesirable interactions, the browser's strict isolation policy also affects communication between cooperating frames. We therefore analyze two techniques for interframe communication between isolated frames. The first method, fragment identifier messaging, initially provides confidentiality without authentication, which we repair using concepts from a well-known network protocol. The second method, postMessage, initially provides authentication, but we discover an attack that breaches confidentiality. We propose improvements in the postMessage API to provide confidentiality; our proposal has been standardized and adopted in browser implementations.
PuzzledSolutions and sources
Authors: Winkler Peter
Published: May 2009

Last month (May 2009, p. 112) we posed a trio of brain teasers, including one as yet unsolved, concerning relationships among numbers.
Collision-free construction of animated feathers using implicit constraint surfaces
Authors: Weber Andrew J. , Gornowicz Galen
Published: May 2009

We present a scheme for constructing complex feather geometry suitable for feature animation. The key points of our approach include the use of a potential field derived from guide geometry and an implicit constraint surface to create nonpenetrating feather geometry. Our method is frame independent and produces visually smooth animation that is free from popping and other visual artifacts. We provide details of the implementation and examples of the technique applied to an animated character with several thousand feathers.
2D piecewise algebraic splines for implicit modeling
Authors: Li Qingde , Tian Jie
Published: May 2009

2D splines are a powerful tool for shape modeling, either parametrically or implicitly. However, compared with regular grid-based tensor-product splines, most of the high-dimensional spline techniques based on nonregular 2D polygons, such as box spline and simplex spline, are generally very expensive to evaluate. Though they have many desirable mathematical properties and have been proved theoretically to be powerful in graphics modeling, they are not a convenient graphics modeling technique in terms of practical implementation. In shape modeling practice, we still lack a simple and practical procedure in creating a set of bivariate spline basis functions from an arbitrarily specified 2D polygonal mesh. Solving this problem is of particular importance in using 2D algebraic splines for implicit modeling, as in this situation underlying implicit equations need to be solved quickly and accurately. In this article, a new type of bivariate spline function is introduced. This newly proposed type of bivariate spline function can be created from any given set of 2D polygons that partitions the 2D plane with any required degree of smoothness. In addition, the spline basis functions created with the proposed procedure are piecewise polynomials and can be described explicitly in analytical form. As a result, they can be evaluated efficiently and accurately. Furthermore, they have all the good properties of conventional 2D tensor-product-based B-spline basis functions, such as non-negativity, partition of unit, and convex-hull property. Apart from their obvious use in designing freeform parametric geometric shapes, the proposed 2D splines have been shown a powerful tool for implicit shape modeling.
Efficient reconstruction of nonrigid shape and motion from real-time 3D scanner data
Authors: Wand Michael , Adams Bart , Ovsjanikov Maksim , Berner Alexander , Bokeloh Martin , Jenke Philipp , Guibas Leonidas , Seidel Hans-Peter , Schilling Andreas
Published: May 2009

We present a new technique for reconstructing a single shape and its nonrigid motion from 3D scanning data. Our algorithm takes a set of time-varying unstructured sample points that capture partial views of a deforming object as input and reconstructs a single shape and a deformation field that fit the data. This representation yields dense correspondences for the whole sequence, as well as a completed 3D shape in every frame. In addition, the algorithm automatically removes spatial and temporal noise artifacts and outliers from the raw input data. Unlike previous methods, the algorithm does not require any shape template but computes a fitting shape automatically from the input data. Our reconstruction framework is based upon a novel topology-aware adaptive subspace deformation technique that allows handling long sequences with complex geometry efficiently. The algorithm accesses data in multiple sequential passes, so that long sequences can be streamed from hard disk, not being limited by main memory. We apply the technique to several benchmark datasets, significantly increasing the complexity of the data that can be handled efficiently in comparison to previous work.
A BSP-based algorithm for dimensionally nonhomogeneous planar implicit curves with topological guarantees
Authors: Gomes Abel J. P. , Morgado José F. M. , Pereira Edgar S.
Published: May 2009

Mathematical systems (e.g., Mathematica, Maple, Matlab, and DPGraph) easily plot planar algebraic curves implicitly defined by polynomial functions. However, these systems, and most algorithms found in the literature, cannot draw many implicit curves correctly; in particular, those with singularities (self-intersections, cusps, and isolated points). They do not detect sign-invariant components either, because they use numerical methods based on the Bolzano corollary, that is, they assume that the curve-describing function
f
flips sign somewhere in a line segment
AB
that crosses the curve, or
f
(
A
)·
f
(
B
) < 0. To solve these problems, we have generalized the False Position (FP) method to determine two types of zeros: (i) crossing zeros and (ii) extremal zeros (local minima and maxima without function sign variation). We have called this method the
Generalized False Position
(GFP) method. It allows us to sample an implicit curve against the Binary Space Partitioning (BSP), say bisection lines, of a rectangular region of R
2
. Interestingly, the GFP method can also be used to determine isolated points of the curve. The result is a general algorithm for sampling and rendering planar implicit curves with topological guarantees.
Automatic pre-tessellation culling
Authors: Hasselgren Jon , Munkberg Jacob , Akenine-Möller Tomas
Published: May 2009

Graphics processing units supporting tessellation of curved surfaces with displacement mapping exist today. Still, to our knowledge, culling only occurs
after
tessellation, that is, after the base primitives have been tessellated into triangles. We introduce an algorithm for
automatically
computing tight positional and normal bounds on the fly for a base primitive. These bounds are derived from an arbitrary vertex shader program, which may include a curved surface evaluation and different types of displacements, for example. The obtained bounds are used for backface, view frustum, and occlusion culling
before
tessellation. For highly tessellated scenes, we show that up to 80% of the vertex shader instructions can be avoided, which implies an “instruction speedup” of 5×. Our technique can also be used for offline software rendering.
Video Modeling for Training Older Adults to Use New Technologies
Authors: Struve Doreen , Wandke Hartmut
Published: May 2009

The increasing permeation of technology in our society leads to the challenge that everybody needs to interact with technology systems. Older adults often meet difficulties while trying to interact with complex, demanding systems in their daily life. One approach to enable older adults to use new technologies in a safe and efficient way is the provision of training programs. In this article we report about a promising training strategy using video modeling in conjunction with other instructional methods to enhance learning. Cognitive as well as socio-motivational aspects will be addressed. We assessed if guided error training in video modeling will improve learning outcomes for a Ticket Vending Machine (TVM). To investigate if the training method might be beneficial for younger adults as well, we compared 40 younger and 40 older adult learners in a guided error training course with error-free training. Younger and older participants made fewer mistakes in guided error training, but no differences occurred in task completion times. Moreover, self-efficacy increased with training for both age groups, but no significant differences were found for the training condition. Analysis of knowledge gains showed a significant benefit of guided error training in structural knowledge. Overall, the results showed that guided error training may enhance learning for younger and older adults who are learning to use technology.
Developing authentic problem solving skills in introductory computing classes
Authors: Falkner Katrina , Palmer Edward
Published: May 2009

The ability to solve problems is the key to developing software, and it is an ability that can be difficult to learn. Introductory Computer Science students are often taught syntax and semantics, along with simple problems designed to develop logical, structured thinking, but authentic problem-solving skills are rarely developed at these early stages.

In this paper we describe an approach to introductory computer science education that addresses student engagement through integrating cooperative learning techniques and authentic problem solving processes throughout each aspect of the curriculum.

Over a period of 4 years, the introductory computer science course at the University of Adelaide has been modified to support a cooperative learning style. A three-stage methodology has been implemented in place of traditional lectures to achieve this. The process focuses on observing the application of programming techniques, observing problem solving techniques and then applying cooperative problem solving exercises in the classroom. The results from this change in teaching methodology have been an increase in attendance rates at lectures and practical sessions as well as improved learning outcomes as measured by exam results. Student experience surveys show students have greater motivation for learning and believe they have a better understanding of concepts since the changes have occurred.
Using collaborative, modified peer led team learning to improve student success and retention in intro cs
Authors: Biggers Maureen , Yilmaz Tuba , Sweat Monica
Published: May 2009

It is common knowledge that enrollments in computer science have plummeted and educators are challenged to find ways to engage and promote success and retention of students while maintaining standards in introductory computer science courses. This study focuses on the implementation of a collaborative, modified peer-led team learning (PLTL) instructional approach in a large sized introductory computer science course. The site is a major southeastern university in the United States where all students are required to take one of three introductory computer science classes. The course version selected for this study specifically targets computer science majors and the study spans three years of data, and involves 591 students. Students who experienced the student-centered instruction and worked in small groups facilitated by a peer leader (treatment) in years 2006-07 and 2007-08 were compared with students who experienced a traditional recitation lecture section (control) in 2005-06. The content and the course owner was the same for all three years. Quantitative data analysis show marked and statistically significant improvements in student performance, for both male and female students. These findings suggest that using undergraduate leaders to implement a peer-led team learning model can be as effective in promoting achievement and retention in computer science education as it has shown to be in math and science classes over the past several years.
CS1 students speak
Authors: Hanks Brian , Murphy Laurie , Simon Beth , McCauley Renée , Zander Carol
Published: May 2009

We collected advice on how to succeed at learning to program from 164 CS1 students at 3 institutions during a "saying is believing" intervention designed to encourage a growth mindset. More students gave general advice (63%) than programming-specific (23%) or attitudinal advice (34%), despite being prompted to encourage future students to develop a growth mindset toward programming. Advice categories and quotes offer educators insights into student beliefs and practices and suggest a framework for considering how best to advise students. We discuss the implications of students offering advice to other students and provide a handout of representative advice intended for distribution to students in introductory programming courses.
Successful and unsuccessful problem solving approaches of novice programmers
Authors: Hanks Brian , Brandt Matt
Published: May 2009

Learning to program continues to be challenging for many students. This paper reports on problem-solving approaches undertaken by pair programming students. We examine reasons why some approaches lead to success while others lead to failure. We also identify some aspects of the Java language that appear to lead to student misconceptions. Finally, we provide suggestions for educators interested in helping students learn successful approaches and avoid unsuccessful ones.
Do students differentiate between computing disciplines?
Authors: Courte Jill , Bishop-Clark Cathy
Published: May 2009

We are in a time where computing programs are seeking to differentiate themselves. The ACM suggests that there are five distinct computing disciplines -- Computer Science (CS), Information Technology (IT), Information Systems (IS), Computer Engineering (CE), and Software Engineering (SE). In practice, it seems that there can be extensive overlap between these disciplines. For example, IS is defined by the ACM as computing in an
organization context, typically in business
while IT is defined as focusing on
computing infrastructure and needs of individual users
. If each of the different types of programs wishes to identify and attract interested students, it is important to understand if students perceive differences between them.

This paper presents the results of a survey to determine if students differentiate between these five disciplines. Computing majors and non-majors were presented with several task descriptions commonly associated with each discipline and asked to identify them as belonging to one of the five disciplines. Data was collected from over 300 students at several different institutions and from a variety of different majors and computing disciplines. The results of the survey are presented along with comparisons of the perceptions of majors and non-majors.
An activity-based sensor networks course for undergraduates with sun spot devices
Authors: Tyman Damon , Bulusu Nirupama , Mache Jens
Published: May 2009

Wireless sensor networks are revolutionizing the instrumentation of the physical world, across scientific, industrial and military applications. In this paper, we describe our efforts developing and classroom-testing hands-on materials for use in undergraduate-accessible courses on sensor networks. In Winter 2008 at Portland State University, we introduced an in-class laboratory component to a sensor networks course that had previously been entirely lecture-based. For the laboratory exercises, we utilized Sun's Java-programmable Sun SPOT [7] sensor network technology. We found the Sun SPOT based laboratory activities to be quite powerful as a teaching and excitement-fostering tool.
Breadth-last technical electives
Authors: White William W. , Weinberg Jerry B.
Published: May 2009

In this paper, we introduce the concept of
breadth-last
technical elective courses, which are designed to assist undergraduate CS students in integrating their entire core curriculum into a coherent whole at the end of their degree programs. Specific breadth-last courses in intelligent mobile robotics and computer game development have been implemented and are presented here to demonstrate the pedagogical concepts being discussed.
Renaissance computing
Authors: Soh Leen-Kiat , Samal Ashok , Scott Stephen , Ramsay Stephen , Moriyama Etsuko , Meyer George , Moore Brian , Thomas William G. , Shell Duane F.
Published: May 2009

We report on a recently funded project called Renaissance Computing, an initiative for promoting student participation in computing. We propose a radical re-thinking not only of our core curriculum in CS, but of the role of CS at the university level. In our conception, ''computational thinking'' is neither easily separated from other endeavors nor easily balkanized into a single department. We thus imagine a CS curriculum that is inextricably linked to other domains. Our proposed initiative covers introductory, depth, and capstone courses, targeting both CS majors and minors. It is also aimed to develop interdisciplinary CS courses in sciences, engineering, arts, and humanities. Furthermore, the framework embraces collaborative learning to help improve learning.
Rediscovering the passion, beauty, joy, and awe
Authors: Garcia Daniel D. , Cutler Robb , Dodds Zachary , Roberts Eric , Young Alison
Published: May 2009

At the SIGCSE Symposium in 2007, the ACM Education Board organized a well-attended special session exploring the crisis in computing education and its underlying causes. The idea behind the session was to provide a forum at which a larger and more broadly representative subset of the education community could engage in direct dialogue with the members of the ACM Education Board and Education Council, who are charged with developing educational policy for the ACM as a whole. Last year, we extended that dialogue and explored concrete strategies for emphasizing the "passion, beauty, joy, and awe" (PBJA) of computing about which Grady Booch spoke so eloquently in his 2007 keynote address. The extremely positive feedback we received served as motivation to continue the discussion this year, to allow us to hear from new voices and receive updates on the current state of the crisis. It is increasingly clear that students today find less joy in the process of creating software than their predecessors did a generation ago. At the same time, these skills have become increasingly important, forcing companies to cast an ever widening net in their search for people with the necessary skills and training. Continued progress in the computing disciplines--and indeed the economic health of a society that relies increasingly on computing technology--can continue only if we can encourage an even larger number of students to pursue the many opportunities that careers in computing provide.
Experiences with just-in-time teaching in systems and design courses
Authors: Davis Janet
Published: May 2009

I report on my experiences with Just-in-Time Teaching (JiTT) in two systems courses and two design courses as a new instructor at a small liberal arts college. My purposes are threefold: to further raise awareness of JiTT in the computer science education community, to show instructors can achieve JiTT's goals with simple technology and preparation on the fly, and to consider strengths and limitations of the approach, particularly for new faculty. My experience has been very positive: classes have been fun, engaging, and conversational. Students have reported that they come to class better prepared and appreciate the opportunity to ask and discuss questions before class. Where others have warned of the high workload with this approach, my experience is that the workload is reasonable compared to preparing a new course from scratch; the approach discourages some types of overpreparation. For these reasons, I would recommend the approach for other new instructors.
Representation of women in CS
Authors: Richards Brad
Published: May 2009

This paper presents an analysis of the data on representation of women in US liberal arts computer science departments, using 10 years' worth of IPEDS data. What began as a search for departments with exemplary representation ended with the conclusion that the representation data is too unstable to be a useful measure of success: The correlation between average representation values in consecutive five-year periods is small, only r=0.156, and not significantly different from zero (p=0.143, t=1.477) for this set of institutions. Other metrics and sample populations are considered with similar results. This result has important implications for studies assessing the impact of departmental interventions on the representation of women, as well as research on the factors that influence representation.
Hadoop at home
Authors: Brown Richard A.
Published: May 2009

The potential benefits of data-intensive scalable computing (DISC) in CS education are considered in the context of a small college with an active student-operated Beowulf cluster initiative. The map-reduce computational model, of great importance in industry, is reviewed, and the
Hadoop
implementation of that model is connected to specific courses throughout the undergraduate CS curriculum. Concerns when running a local
Hadoop
-capable cluster at a small college are identified.
Seattle
Authors: Cappos Justin , Beschastnikh Ivan , Krishnamurthy Arvind , Anderson Tom
Published: May 2009

Cloud computing is rapidly increasing in popularity. Companies such as RedHat, Microsoft, Amazon, Google, and IBM are increasingly funding cloud computing infrastructure and research, making it important for students to gain the necessary skills to work with cloud-based resources. This paper presents a free, educational research platform called Seattle that is community-driven, a common denominator for diverse platform types, and is broadly deployed.

Seattle is community-driven -- universities donate available compute resources on multi-user machines to the platform. These donations can come from systems with a wide variety of operating systems and architectures, removing the need for a dedicated infrastructure.

Seattle is also surprisingly flexible and supports a variety of pedagogical uses because as a platform it represents a common denominator for cloud computing, grid computing, peer-to-peer networking, distributed systems, and networking. Seattle programs are portable. Students' code can run across different operating systems and architectures without change, while the Seattle programming language is expressive enough for experimentation at a fine-grained level. Our current deployment of Seattle consists of about one thousand computers that are distributed around the world. We invite the computer science education community to employ Seattle in their courses.
Has the paradigm shift in CS1 a harmful effect on data structures courses
Authors: Gal-Ezer Judith , Vilner Tamar , Zur Ela
Published: May 2009

The ongoing debate among Computer Science educators about the advantages and disadvantages of the shift from the procedural to the Object-Oriented paradigm usually relates to the introductory course. Indeed, we were also concerned when in our institute we decided to implement this shift in our introductory course and started to teach Java, instead of a procedural paradigm. In our previous study we saw that the effect of the shift did not lower the achievements of students taking the CS1 course. Furthermore, we wanted to be equally sure that this was the case when students take Data Structures courses. This is the focus of the study presented in this paper. The results show that there is no significant difference in the achievements of students who came from different paradigm backgrounds. This encouraging result probably relates to the fact that our CS1 course focuses on the fundamentals of introductory Computer Science and does not only emphasize the language aspects.
Using open source software to engage students in computer science education
Authors: Hislop Gregory W. , Ellis Heidi J.C. , Tucker Allen B. , Dexter Scott
Published: May 2009

This panel will discuss issues and methods for incorporating free and open source software (FOSS) in computer science education. The panelists are investigating approaches to student participation in FOSS that produce results that are contributed to the FOSS community and actually used by others.
Sexism
Authors: Cohoon J. McGrath , Wu Zhen , Chao Jie
Published: May 2009

Using longitudinal survey data from women in the CRA-W Graduate Cohort program, we measured the prevalence of observed or experienced sexism and its impact on departure from Computer Science and Computer Engineering (CSE) doctoral programs. Our data suggest that sexist behavior is perceived less often by these women than it is by women in general. In addition, few of the women who observe sexism are motivated by it to think of leaving their CSE doctoral programs. Nevertheless, when their reason for thinking of leaving is due to sexism they observed or experienced, the odds of women actually departing are at least 21 times greater than if they thought of leaving for any other reason.
Using
ink
to expose students' thought processes in CS2/CS7
Authors: Pargas Roy P. , Bryfczynski Samuel
Published: May 2009

This paper presents and discusses a web-based software tool called
GraphPad
designed to facilitate interactivity in a CS2 or CS7 (data structures) course in which Tablet PCs or WACOM tablets are available. We describe how
GraphPad
enables an instructor to: establish a temporary network with the instructor's Tablet as server and the students' Tablets as clients, broadcast instructions and collect student
Ink
responses, evaluate student submissions and distribute evaluations with a single button-click, use student submissions as examples to guide lecture, and save student submissions in a database. The saved submissions may then be reviewed individually, tagged for errors, and analyzed statistically. An immediate goal is to use
GraphPad
to deliver CS2/CS7 course content more effectively. A long term goal is to use data collected by
GraphPad
to help understand the thought process of the CS2/CS7 student for the purpose of identifying students at risk early in order to provide intervention assistance.
Teaching computational thinking through bioinformatics to biology students
Authors: Qin Hong
Published: May 2009

Modern biology has transformed from an insular entity into an interdisciplinary science, which in turn demands interdisciplinary and cross-disciplinary training for future work force in biology and life sciences. Computational thinking is a way of thinking that uses concepts and methodologies of computing to address questions in a broad range of subjects, and as such, computational thinking offers an important skill set in modern sciences. Despite its importance, the concept of computational thinking has generally been side-stepped in undergraduate biology education. Many students in life sciences are often weak in quantitative/computing skills and tend to avoid computing-orient courses. To address these issues, we incorporated computational thinking into a bioinformatics course for undergraduate life science majors. We developed comprehensive computer laboratory exercises that offer hands-on learning experience for the targeted student pool, and employed peer-assisted collaborative learning environment. Preliminary results of these explorative efforts will be helpful for others to teach computational thinking to biology students.