Christopher Kumar Anand

An empirical evaluation of user interfaces for a mobile video game

Abstract In this paper we empirically test the effectiveness and enjoyability of three user interfaces used to play an iPod Touch scroll shooter video game. Mobile devices are currently undergoing a surge in market penetration both in business and with consumers. These devices allow for user interface options such as touch screens and accelerometers, which are novel to mobile platforms and to large portions of the general public. To explore the effectiveness and enjoyability of these user interface options, the game was implemented with an accelerometer based interface, a touch screen based interface involving simulated buttons and a touch screen based interface involving finger gestures. The game has been formally tested with 36 human subjects each playing the game with each of the three interfaces. We present statistically significant results that the accelerometer based interface was the preferred interface and the interface in which participants performed best. We hope manufacturers will consider using the approach used in this paper to test user interfaces in-house before releasing them, since, as we show, it is inexpensive to obtain statistically significant results. We propose heuristics for mobile user interface design based on an analysis of the results and suggest an avenue for future work.

Gamification and serious game approaches for adult literacy tablet software

Abstract In this paper, we overview the design of tablet apps we designed and built to teach literacy to adults, and present the results and conclusions derived from experiments performed with target users. Low adult literacy is a significant problem with a high economic cost both for the individuals and for society. Programs created to address low adult literacy face access and engagement barriers that tablet software may be able to help overcome. We designed three tablet apps, using two contrasting approaches of incorporating game-design elements to engage the users. We tested the apps with participants from the Brant Skills Centre, a non-profit organization that offers adult literacy programs in Brantford, Ontario. Though participants were divided on whether they preferred the apps to more traditional instruction, most participants preferred using the apps in addition to more traditional instruction. Based on this we conclude that gamification and serious game design approaches were effective at increasing learner engagement, and we propose a direction for future research.

Exact solution to the Bloch equations and application to the Hahn echo

The exact symbolic solution of the Bloch equations is given in the Lagrange form and illustrated with R2 experiments using a Hahn echo. Two different methods are also applied to approximately solve the Bloch equations, we find that splittings with effective-field interpretations are very substantially better than other approximations by comparing the errors. Estimates of transverse relaxation, R2, from Hahn echos are effected by frequency offset and field inhomogeneity. We use exact solutions of the Bloch equations and simulations to quantify both effects, and find that even in the presence of expected B0 inhomogeneity, off-resonance effects can be removed from R2 measurements, when∥ω∥⩽0.5γB1, by fitting the exact solutions of the Bloch equations. Further, the experiments and simulations show that the fitting models with the exact solutions of the Bloch equations do not depend on the sampling density and delay times.

Problems, artifacts and solutions in the INADEQUATE NMR experiment.

The INADEQUATE experiment can provide unequalled, detailed information about the carbon skeleton of an organic molecule. However, it also has the reputation of requiring unreasonable amounts of sample. Modern spectrometers and probes have mitigated this problem, and it is now possible to get good structural data on a few milligrams of a typical organic small molecule. In this paper, we analyze the experiment step by step in some detail, to show how each part of the sequence can both contribute to maximum overall sensitivity and can lead to artifacts. We illustrate these methods on three molecules: 1‐octanol, the steroid 17α‐ethynylestradiol and the isoquinoline alkaloid β‐hydrastine. In particular, we show that not only is the standard experiment powerful, but also a version tuned to small couplings can contribute vital structural information on long‐range connectivities. If the delay in the spin echo is long, pairs of carbons with small couplings can create significant double‐quantum coherence and show correlations in the spectrum. These are two‐ and three‐bond correlations in a carbon chain or through a heteroatom in the molecule. All these mean that INADEQUATE can play a viable and important role in routine organic structure determination. Copyright

Designing optimal universal pulses using second-order, large-scale, non-linear optimization.

Recently, RF pulse design using first-order and quasi-second-order pulses has been actively investigated. We present a full second-order design method capable of incorporating relaxation, inhomogeneity in B(0) and B(1). Our model is formulated as a generic optimization problem making it easy to incorporate diverse pulse sequence features. To tame the computational cost, we present a method of calculating second derivatives in at most a constant multiple of the first derivative calculation time, this is further accelerated by using symbolic solutions of the Bloch equations. We illustrate the relative merits and performance of quasi-Newton and full second-order optimization with a series of examples, showing that even a pulse already optimized using other methods can be visibly improved. To be useful in CPMG experiments, a universal refocusing pulse should be independent of the delay time and insensitive of the relaxation time and RF inhomogeneity. We design such a pulse and show that, using it, we can obtain reliable R(2) measurements for offsets within ±γB(1). Finally, we compare our optimal refocusing pulse with other published refocusing pulses by doing CPMG experiments.

Exact solution of the CPMG pulse sequence with phase variation down the echo train: Application to R2 measurements

An implicit exact algebraic solution of CPMG experiments is presented and applied to fit experiments. Approximate solutions are also employed to explore oscillations and effective decay rates of CPMG experiments. The simplest algebraic approximate solution has illustrated that measured intensities will oscillate in the conventional CPMG experiments and that using even echoes can suppress errors of measurements of R₂ due to the imperfection of high-power pulses. To deal with low-power pulses with finite width, we adapt the effective field to calculate oscillations. An optimization model with the effective field approximation and dimensionless variables is proposed to quantify oscillations of measured intensities of CPMG experiments of different phases of the π pulses. We show, as was known using other methods, that repeating one group of four pulses with different phases in CPMG experiments, which we call phase variation, but others call phase alternation or phase cycling, can significantly smooth the dependence of measured intensities on frequency offset in the range of ±½γB₁. In this paper, a second-order expression with respect to the ratio of frequency offset to π-pulse amplitude is developed to describe the effective R₂ of CPMG experiments when using a group phase variation scheme. Experiments demonstrate that (1) the exact calculation of CPMG experiments can remarkably eliminate systematic errors in measured R₂s due to the effects of frequency offset, even in the absence of phase variation; (2) CPMG experiments with group phase variation can substantially remove oscillations and effects of the field inhomogeneity; (3) the second-order expression of the effective decay rate with phase variation is able to provide reliable estimates of R₂ when offsets are roughly within ±½γB₁; and, most significantly, (4) the more sophisticated optimization model using an exact solution of the discretized CPMG experiment extends, to ±γB₁, the range of offsets for which reliable estimates of R₂ can be obtained when using the preferred phase variation scheme.

Control-Flow semantics for assembly-level data-flow graphs

As part of a larger project, we have built a declarative assembly language that enables us to specify multiple code paths to compute particular quantities, giving the instruction scheduler more flexibility in balancing execution resources for superscalar execution. Since the key design points for this language are to only describe data flow, have built-in facilities for redundancies, and still have code that looks like assembler, by virtue of consisting mainly of assembly instructions, we are basing the theoretical foundations on data-flow graph theory, and have to accommodate also relational aspects. Using functorial semantics into a Kleene category of “hyper-paths”, we formally capture the data-flow-with-choice aspects of this language and its implementation, providing also the framework for the necessary correctness proofs.

Gamification and serious game approaches for introductory computer science tablet software

In this paper, we overview the design of tablet apps built to teach introductory computer science concepts, and present the results and conclusions from a study conducted during a first year computer science course at McMaster University. Game design elements were incorporated into the apps we designed to teach introductory computer science concepts, with the primary aim of increasing student satisfaction and engagement. We tested these apps with students enrolled in the course during their regular lab sessions and collected data on both the usability of the apps and the students understanding of the concepts. Though overall we found students preferred instruction with the apps compared to more traditional academic instruction, we found that students also recommended combined instruction using both traditional methods and the apps in the future. Based on this we conclude that gamification and serious game design approaches are effective at increasing student satisfaction, and make several recommendations regarding the usage and design of educational software incorporating game design elements.

Durga: A heuristically-optimized data collection strategy for volumetric magnetic resonance imaging

A heuristic design method for rapid volumetric magnetic resonance imaging data acquisition trajectories is presented, using a series of second-order cone optimization subproblems. Other researchers have considered non-raster data collection trajectories and under-sampled data patterns. This work demonstrates that much higher rates of under-sampling are possible with an asymmetric set of trajectories, with very little loss in resolution, but the addition of noise-like artefacts. The proposed data collection trajectory, Durga, further minimizes collection time by incorporating short un-refocused excitation pulses, resulting in above 98% collection efficiency for balanced steady state free precession imaging. The optimization subproblems are novel, in that they incorporate all requirements, including data collection (coverage), physicality (device limits), and signal generation (zeroth- and higher- moment properties) in a single convex problem, which allows the resulting trajectories to exhibit a higher collection efficiency than any existing trajectory design.

Unified Tables for Exponential and Logarithm Families

Accurate table methods allow for very accurate and efficient evaluation of elementary functions. We present new single-table approaches to logarithm and exponential evaluation, by which we mean that a single table of values works for both log(<i>x</i>) and log(1 + <i>x</i>), and a single table for <i>e</i><i>x</i> and <i>e</i><i>x</i> − 1. This approach eliminates special cases normally required to evaluate log(1 + <i>x</i>) and <i>e</i><i>x</i> − 1 accurately near zero, which will significantly improve performance on architectures which use SIMD parallelism, or on which data-dependent branching is expensive. We have implemented it on the Cell/B.E. SPU (SIMD compute engine) and found the resulting functions to be up to twice as fast as the conventional implementations distributed in the IBM Mathematical Acceleration Subsystem (MASS). We include the literate code used to generate all the variants of exponential and log functions in the article, and discuss relevant language and hardware features.