Incremental Adjustment Research Articles

Realizing the Potential of Micro-Phase Separated Block Copolymer Electrolytes: Ion Domain Connectivity Plays a Prominent Role in Ion Conduction

Single ion conducting polymer electrolyte membranes (PEMs) are found at the heart of many electrochemical devices (e.g., fuel cells, flow batteries, electrolyzers, electrodialysis, etc.).(1) The key requirements for such materials include high ionic conductivity, electron insulation, mechanical resilience, selectivity (i.e., high transference #), and chemical, thermal, and mechanical stability.(2, 3) Ionic conductivity is particularly important because it strongly influences the ohmic overpotential in the said electrochemical devices affecting device efficiency.(1, 4) Block copolymer electrolytes represent an attractive set of PEM materials because their micro-phase architecture yields greater ion conduction over their random copolymer counterparts.(5-7) Furthermore, the block copolymer charateristic gives rise to a variety of morphological architectures, while engineering of the block copolymer’s self-assembly influences domain alignment.(8-12) However, there is lack of systematic studies correlating molecular level structural design to bulk material properties like ion transport. In this work, a model lamellae-forming diblock copolymer electrolyte system was manipulated to examine the extent of ion domain connectivity on ion conduction.(13, 14) Careful control of the model system’s volume fraction gave diblock copolymer structures with slightly rich electrolyte domains or slightly rich hydrophobic domains. The slightly rich electrolyte domains had greater contiguous area fraction while simultaneously demonstrating fewer terminal defects. Having a contiguous area fraction from 0.95 to 1.0 resulted in a 2x improvement in ionic conductivity over a non-micro-phase separated block copolymer electrolyte or a micro-phase separated block copolymer electrolyte with poor connectivity. Incremental adjustment in the extent of connectivity revealed an exponential growth curve for ion conductivity as a function of contiguous area fraction. Furthermore, the benefits that a micro-phase separated block copolymer electrolyte affords in terms of ion conductivity were not realized when the block copolymer electrolyte had poor connectivity. The results of this work have far reaching implication into the rationale design of PEM materials based upon block copolymer designs. This talk will emphasize the importance of maximizing ion domain connectivity while taking great strides to minimize terminal defects to boost ion transport in PEM materials. This talk will close with future directions on how molecular level engineering of block copolymer electrolytes offer the potential to reveal how other structural features (e.g., tortuosity(15), grain boundaries(5), and counterion condensation) alter ion transport in PEM materials(16, 17). 1. H. Strathmann et al., Ion-Exchange Membranes in the Chemical Process Industry. Industrial & Engineering Chemistry Research 52, 10364-10379 (2013). 2. H. Strathmann, Ion-Exchange Membrane Separation Processes, Volume 9. Membrane Science and Technology (Elsevier Science, Amsterdam, The Netherlands, 2004), vol. 9. 3. T. Sata, Ion Exchange Membranes: Preparation, Characterization, Modification and Application. (Royal Society of Chemistry, Cambridge, UK, 2004). 4. A. Z. Weber, J. Newman, Modeling Transport in Polymer-Electrolyte Fuel Cells. Chemical Reviews 104, 4679-4726 (2004). 5. Y. A. Elabd, M. A. Hickner, Block Copolymers for Fuel Cells. Macromolecules 44, 1-11 (2011). 6. N. Li, M. D. Guiver, Ion Transport by Nanochannels in Ion-Containing Aromatic Copolymers. Macromolecules 47, 2175-2198 (2014). 7. Y. Schneider et al., Ionic Conduction in Nanostructured Membranes Based on Polymerized Protic Ionic Liquids. Macromolecules 46, 1543-1548 (2013). 8. H. Hu, M. Gopinadhan, C. O. Osuji, Directed self-assembly of block copolymers: a tutorial review of strategies for enabling nanotechnology with soft matter. Soft Matter 10, 3867-3889 (2014). 9. M. Luo, T. H. Epps, III, Directed Block Copolymer Thin Film Self-Assembly: Emerging Trends in Nanopattern Fabrication. Macromolecules 46, 7567-7579 (2013). 10. S. Ji, L. Wan, C.-C. Liu, P. F. Nealey, Directed self-assembly of block copolymers on chemical patterns: A platform for nanofabrication. Progress in Polymer Science, 54-55, 76-127 (2016). 11. S.-J. Jeong et al., Directed self-assembly of block copolymers for next generation nanolithography. Materials Today 16, 468-476 (2013). 12. M. P. Stoykovich, P. F. Nealey, Block copolymers and conventional lithography. Materials Today 9, 20-29 (2006). 13. I. P. Campbell, G. J. Lau, J. L. Feaver, M. P. Stoykovich, Network Connectivity and Long-Range Continuity of Lamellar Morphologies in Block Copolymer Thin Films. Macromolecules 45, 1587-1594 (2012). 14. C. G. Arges, Y. Kambe, H. S. Suh, L. E. Ocola, P. F. Nealey, Perpendicularly Aligned, Anion Conducting Nanochannels in Block Copolymer Electrolyte Films. Chemistry of Materials 28, 1377-1389 (2016). 15. X. Feng et al., Scalable Fabrication of Polymer Membranes with Vertically Aligned 1 nm Pores by Magnetic Field Directed Self-Assembly. ACS Nano 8, 11977-11986 (2014). 16. K. M. Beers, D. T. Hallinan, X. Wang, J. A. Pople, N. P. Balsara, Counterion Condensation in Nafion. Macromolecules 44, 8866-8870 (2011). 17. K. M. Beers, N. P. Balsara, Design of Cluster-free Polymer Electrolyte Membranes and Implications on Proton Conductivity. ACS Macro Letters 1, 1155-1160 (2012). Figure 1

Magnetically launched flyer plate technique for probing electrical conductivity of compressed copper

The electrical conductivity of materials under extremes of temperature and pressure is of crucial importance for a wide variety of phenomena, including planetary modeling, inertial confinement fusion, and pulsed power based dynamic materials experiments. There is a dearth of experimental techniques and data for highly compressed materials, even at known states such as along the principal isentrope and Hugoniot, where many pulsed power experiments occur. We present a method for developing, calibrating, and validating material conductivity models as used in magnetohydrodynamic (MHD) simulations. The difficulty in calibrating a conductivity model is in knowing where the model should be modified. Our method isolates those regions that will have an impact. It also quantitatively prioritizes which regions will have the most beneficial impact. Finally, it tracks the quantitative improvements to the conductivity model during each incremental adjustment. In this paper, we use an experiment on Sandia National Laboratories Z-machine to isentropically launch multiple flyer plates and, with the MHD code ALEGRA and the optimization code DAKOTA, calibrated the conductivity such that we matched an experimental figure of merit to +/−1%.

University Leadership and Public Policy in the Twenty-First Century: A President's Perspective, by Peter MacKinnon

University Leadership and Public Policy in the Twenty-First Century: A President's Perspective, by Peter MacKinnon. Toronto, University of Toronto Press, 2014. ix, 190 pp. $65.00 Cdn (cloth), $24.95 Cdn (paper). Peter MacKinnon, former law dean (1988-98) and president (1999-2012) of the University of Saskatchewan, states that he wrote this book to illuminate features of the present condition of Canadian universities and to point to ways of improving them. He has done this. He states that his book is about and is neither memoir nor local history, though it contains elements of both (p. viii). Unfortunately, insofar as the book is memoir and history (and a significant part is) it suffers from being written by a lawyer since the author provides only the evidence that supports his case. In the interest of objectivity I should note that I was a faculty member of the University of Saskatchewan (U of S) from 1966 to 2001 and have followed its ups and downs since. 1 have known Peter MacKinnon from the time he arrived in Saskatoon in 1975. We have discussed and agreed on many things, especially before 2002, and have disagreed on others, especially after that date. The first two chapters are basically a history of the recent past of the U of S seen through the eyes of an author who favours change that attempts to alter a path, rather than incremental adjustment. The six chapters that follow discuss policies that he believes are of interest to everyone concerned with Canadian universities. In the first two chapters MacKinnon advocates strongly that the U of S should commit to meeting the highest standards of medical-doctoral universities and concentrate on selected areas in which it could become pre-eminent, while affirming its sense of place. In fact, during his presidency he pushed the university to become research intensive, to attract international students and to emphasize graduate education. In the process of advocacy MacKinnon tends to denigrate those who disagreed with his vision of what the U of S should become, while often misrepresenting their ideas. He also ignores how his operating policies differed from those he advocated while campaigning for the presidency. In the six policy chapters MacKinnon occasionally engages in lawyerlike selection of evidence, for example by ignoring the role academic administrators have played in creating conditions that led to faculty unionization from the U of S twenty-five years ago to Simon Fraser University this year. The policies he chooses to discuss are central to the life of any university. These include tuition levels, relations with governments, academic freedom, university autonomy, philanthropy, university-industry partnerships, corporatization of universities, the tensions created by methods of labour relations, university governance and collegial management, the role of universities in advancing Canada's scientific capacity, the changing nature of Canadian university presidency and the effects of the global search for talent. …

Hypomagnesemia and Mortality in Incident Hemodialysis Patients

In the general population, low serum magnesium levels are associated with poor outcomes and death. While limited data suggest that low baseline magnesium levels may be associated with higher mortality in hemodialysis (HD) patients, the impact of changes in magnesium levels over time is unknown. We examined the association of time-varying serum magnesium levels with all-cause mortality using multivariable time-varying survival models adjusted for clinical characteristics and other time-varying laboratory measures. 9,359 maintenance HD patients treated in a large dialysis organization between 2007 and2011. Time-varying serum magnesium levels across 5 magnesium increments (<1.8, 1.8-<2.0, 2.0-<2.2, 2.2-<2.4, and≥2.4mg/dL). All-cause mortality. 2,636 individuals died over 5 years. Time-varying serum magnesium levels< 2.0mg/dL were associated with higher mortality after adjustment for demographics and comorbid conditions, including hypertension, diabetes, and malignancies (reference: magnesium, 2.2-<2.4mg/dL): adjusted HRs for serum magnesium level< 1.8 and 1.8 to<2.0mg/dL were 1.39 (95% CI, 1.23-1.58; P<0.001) and 1.20 (95% CI, 1.06-1.36; P=0.004), respectively. Some associations were attenuated to the null after incremental adjustment for laboratory test results, particularly serum albumin. However, among patients with serum albumin measurements, low albumin level (<3.5g/dL) and magnesium level< 2.0mg/dL were associated with an additional death risk (adjusted HR, 1.17; 95% CI, 1.05-1.31; P=0.004), whereas patients with high serum albumin levels (≥3.5g/dL) exhibited low death risk (adjusted HRs of 0.53 and 0.53 [P≤0.001] for magnesium< 2.0 and≥2.0mg/dL, respectively; reference: albumin< 3.5g/dL and magnesium≥ 2.0mg/dL). Causality cannot be determined, and residual confounding cannot be excluded given the observational study design. Lower serum magnesium levels are associated with higher mortality in HD patients, including those with hypoalbuminemia. Interventional studies are warranted to examine whether correction of hypomagnesemia ameliorates adverse outcomes in this population.

Determinants of Chinese equity financing behaviours: traditional model and the alternatives

AbstractThis paper studies the capital structure of Chinese SEO issuers, from the perspective of equity. The traditional model is subject to several problems including spurious correlation, cumulative measure and endogeneity. System GMM (generalised method of moments) is superior to the traditional model. Corporate governance is positively correlated to firm equity level; however, it does not affect incremental managerial adjustments to equity. In addition, state control positively influences equity level but has a negative effect on incremental managerial adjustment. Mixed evidence is found for the established capital structure theories in the Chinese context.

Incremental light bundle adjustment for structure from motion and robotics

Bundle adjustment (BA) is essential in many robotics and structure-from-motion applications. In robotics, often a bundle adjustment solution is desired to be available incrementally as new poses and 3D points are observed. Similarly in batch structure from motion, cameras are typically added incrementally to allow good initializations. Current incremental BA methods quickly become computationally expensive as more camera poses and 3D points are added into the optimization. In this paper we introduce incremental light bundle adjustment (iLBA), an efficient optimization framework that substantially reduces computational complexity compared to incremental bundle adjustment. First, the number of variables in the optimization is reduced by algebraic elimination of observed 3D points, leading to a structureless BA. The resulting cost function is formulated in terms of three-view constraints instead of re-projection errors and only the camera poses are optimized. Second, the optimization problem is represented using graphical models and incremental inference is applied, updating the solution using adaptive partial calculations each time a new camera is incorporated into the optimization. Typically, only a small fraction of the camera poses are recalculated in each optimization step. The 3D points, although not explicitly optimized, can be reconstructed based on the optimized camera poses at any time. We study probabilistic and computational aspects of iLBA and compare its accuracy against incremental BA and another recent structureless method using real–imagery and synthetic datasets. Results indicate iLBA is 2–10 times faster than incremental BA, depending on number of image observations per frame.

Discussions on localization capabilities of MSL and MER rovers

The National Aeronautics and Space Administration (NASA) of the United States has launched several rover missions for Martian surface exploration. The two most recent ones include the Mars Exploration Rover (MER) mission in 2003 and the Mars Science Laboratory (MSL) mission in 2011. Both of these missions require highly accurate rover localization and navigation techniques to obtain precise rover traverse information in order to develop long-term science planning and execute daily operations. This paper discusses several localization and navigation techniques for the MER and MSL rovers by using satellites and the instruments on board the rovers, and compares their advantages and disadvantages. The techniques discussed include wheel odometry, visual odometry, incremental bundle adjustment, identifying rovers directly from high-resolution satellite images, and matching ground features between rover images and satellite images.

Adaptation and transformation

Transformation as an adaptive response to climate change opens a range of novel policy options. Used to describe responses that produce non-linear changes in systems or their host social and ecological environments, transformation also raises distinct ethical and procedural questions for decision-makers. Expanding adaptation to include transformation foregrounds questions of power and preference that have so far been underdeveloped in adaptation theory and practice. We build on David Harvey’s notion of activity space to derive a framework and research agenda for climate change adaptation seen as a political decision-point and as an opportunity for transformation, incremental adjustment or resistance to change in development pathway. Decision-making is unpacked through the notion of the activity space into seven coevolving sites: the individual, technology, livelihoods, discourse, behaviour, the environment and institutions. The framework is tested against practitioner priorities to define an agenda that can make coherent advances in research and practice on climate change adaptation.

Positioning resilience for 2015: the role of resistance, incremental adjustment and transformation in disaster risk management policy.

Resilience is a ubiquitous term in disaster risk management and is an increasingly prominent concept in early discussions focused on elaborating the post-2015 international policy landscape. Riddled with competing meanings and diverse policy implications, however, it is a concept caught between the abstract and operational. This paper provides a review of the rise to prominence of the concept of resilience and advances an elaboration of the related concepts of resistance, incremental adjustment and transformation. We argue that these concepts can contribute to decision-making by offering three distinct options for risk management policy. In order to deliberately and effectively choose among these options, we suggest that critical reflexivity is a prerequisite, necessitating improved decision-making capacity if varied perspectives (including those of the most vulnerable) are to be involved in the selection of the best approach to risk management.

Long-Term Air Pollution Exposure and Diabetes in a Population-Based Swiss Cohort

Air pollution is an important risk factor for global burden of disease. There has been recent interest in its possible role in the etiology of diabetes mellitus. Experimental evidence is suggestive, but epidemiological evidence is limited and mixed. We therefore explored the association between air pollution and prevalent diabetes, in a population-based Swiss cohort. We did cross-sectional analyses of 6392 participants of the Swiss Cohort Study on Air Pollution and Lung and Heart Diseases in Adults [SAPALDIA], aged between 29 and 73 years. We used estimates of average individual home outdoor PM10 [particulate matter <10μm in diameter] and NO2 [nitrogen dioxide] exposure over the 10 years preceding the survey. Their association with diabetes was modeled using mixed logistic regression models, including participants' study area as random effect, with incremental adjustment for confounders. There were 315 cases of diabetes (prevalence: 5.5% [95% confidence interval (CI): 2.8, 7.2%]). Both PM10 and NO2 were associated with prevalent diabetes with respective odds ratios of 1.40 [95% CI: 1.17, 1.67] and 1.19 [95% CI: 1.03, 1.38] per 10μg/m(3) increase in the average home outdoor level. Associations with PM10 were generally stronger than with NO2, even in the two-pollutant model. There was some indication that beta blockers mitigated the effect of PM10. The associations remained stable across different sensitivity analyses. Our study adds to the evidence that long term air pollution exposure is associated with diabetes mellitus. PM10 appears to be a useful marker of aspects of air pollution relevant for diabetes. This association can be observed at concentrations below air quality guidelines.

Long-term air pollution exposure and diabetes in a population-based Swiss cohort

Air pollution is an important risk factor for global burden of disease. There has been recent interest in its possible role in the etiology of diabetes mellitus. Experimental evidence is suggestive, but epidemiological evidence is limited and mixed. We therefore explored the association between air pollution and prevalent diabetes, in a population-based Swiss cohort.We did cross-sectional analyses of 6392 participants of the Swiss Cohort Study on Air Pollution and Lung and Heart Diseases in Adults [SAPALDIA], aged between 29 and 73years. We used estimates of average individual home outdoor PM10 [particulate matter <10μm in diameter] and NO2 [nitrogen dioxide] exposure over the 10years preceding the survey. Their association with diabetes was modeled using mixed logistic regression models, including participants' study area as random effect, with incremental adjustment for confounders.There were 315 cases of diabetes (prevalence: 5.5% [95% confidence interval (CI): 2.8, 7.2%]). Both PM10 and NO2 were associated with prevalent diabetes with respective odds ratios of 1.40 [95% CI: 1.17, 1.67] and 1.19 [95% CI: 1.03, 1.38] per 10μg/m3 increase in the average home outdoor level. Associations with PM10 were generally stronger than with NO2, even in the two-pollutant model. There was some indication that beta blockers mitigated the effect of PM10. The associations remained stable across different sensitivity analyses.Our study adds to the evidence that long term air pollution exposure is associated with diabetes mellitus. PM10 appears to be a useful marker of aspects of air pollution relevant for diabetes. This association can be observed at concentrations below air quality guidelines.

RULES-IT: incremental transfer learning with RULES family

In today's world of excessive development in technologies, sustainability and adaptability of computer applications is a challenge, and future prediction became significant. Therefore, strong artificial intelligence (AI) became important and, thus, statistical machine learning (ML) methods were applied to serve it. These methods are very difficult to understand, and they predict the future without showing how. However, understanding of how machines make their decision is also important, especially in information system domain. Consequently, incremental covering algorithms (CA) can be used to produce simple rules to make difficult decisions. Nevertheless, even though using simple CA as the base of strong AI agent would be a novel idea but doing so with themethods available in CA is not possible. It was found that having to accurately update the discovered rules based on new information in CA is a challenge and needs extra attention. In specific, incomplete data with missing classes is inappropriately considered, whereby the speed and data size was also a concern, and future none existing classes were neglected. Consequently, this paper will introduce a novel algorithm called RULES-IT, in order to solve the problems of incremental CA and introduce it into strong AI. This algorithm is the first incremental algorithm in its family, and CA as a whole, that transfer rules of different domains to improve the performance, generalize the induction, take advantage of past experience in different domain, and make the learner more intelligent. It is also the first to introduce intelligent aspects into incremental CA, including consciousness, subjective emotions, awareness, and adjustment. Furthermore, all decisions made can be understood due to the simple representation of repository as rules. Finally, RULES-IT performance will be benchmarked with six different methods and compared with its predecessors to see the effect of transferring rules in the learning process, and to prove how RULES-IT actually solved the shortcoming of current incremental CA in addition to its improvement in the total performance.

Avoiding Complications and Technical Variability During Arthroscopically Assisted Transtibial ACL Reconstructions by Using a C-Arm With Image Intensifier.

Background:Surgical reconstruction of the anterior cruciate ligament (ACL) can be complicated by incorrect and variable tunnel placement, graft tunnel mismatch, cortical breaches, and inadequate fixation due to screw divergence. This is the first report describing the use of a C-arm with image intensifier employed for the sole purpose of eliminating those complications during transtibial ACL reconstruction.Purpose:To determine if the use of a C-arm with image intensifier during arthroscopically assisted transtibial ACL reconstruction (IIAA-TACLR) eliminated common complications associated with bone–patellar tendon–bone ACL reconstruction, including screw divergence, cortical breaches, graft-tunnel mismatch, and improper positioning of the femoral and tibial tunnels.Study Design:Case series; Level of evidence, 4.Methods:A total of 110 consecutive patients (112 reconstructed knees) underwent identical IIAA-TACLR using a bone–patellar tendon–bone autograft performed by a single surgeon. Intra- and postoperative radiographic images and operative reports were evaluated for each patient looking for evidence of cortical breeching and screw divergence. Precision of femoral tunnel placement was evaluated using a sector map modified from Bernard et al. Graft recession distance and tibial α angles were recorded.Results:There were no femoral or tibial cortical breaches noted intraoperatively or on postoperative images. There were no instances of loss of fixation screw major thread engagement. There were no instances of graft-tunnel mismatch. The positions of the femoral tunnels were accurate and precise, falling into the desired sector of our location map (sector 1). Tibial α angles and graft recession distances varied widely.Conclusion:The use of the C-arm with image intensifier enabled accurate and precise tunnel placement and completely eliminated cortical breach, graft-tunnel mismatch, and screw divergence during IIAA-TACLR by allowing incremental adjustment of the tibial tunnel and knee flexion angle. Incremental adjustment was essential to accomplish this. Importantly, a C-arm with image intensifier can be used with any ACL reconstruction that incorporates tunnels in the technique, with the expectation of increase in accuracy and precision and the elimination of common complications.Clinical Relevance:The use of an image intensifier during transtibial ACL reconstruction will substantially reduce the common complications associated with the procedure and improve both accuracy and precision of tibial and femoral tunnel placement. Use of an image intensifier unit is generalizable to an individual surgeon’s preferences for graft choices and drilling techniques and will be especially valuable when the intercondylar architecture is altered from injury, time, or prior surgery.

A NEW APPROACH FOR AN INCREMENTAL ORIENTATION OF MICRO-UAV IMAGE SEQUENCES

Abstract. Civil applications for small size unmanned aerial vehicles (UAV) have become quite important in recent years and so have accurate orientation and navigation of these devices in unknown terrain. In this work we focus on on-line compatible positioning in facade observation based on monocular low resolution still images acquired by a camera mounted on a UAV. Also, a 3D point cloud of the facade is generated. This allows further processing steps, e.g. navigation assistance, collision avoidance or the evaluation of the point cloud density, verifying completeness of the data. To be able to deal with the increasing amount of observations and unknown parameters we implement an incremental bundle adjustment based on automatically determined tie points and sliding image triplets. The tripletwise orientation allows for an efficient double cross-check of the detected feature points and hence guarantees reliable initial values for the nonlinear bundle adjustment. The initial values are estimated within a convex formulation delivering a sound basis for the incremental adjustment. Our algorithm is evaluated by means of imagery we took of the facade of the Welfenschloss in Hannover, captured from a manually flown Microdrones md4-200 micro-UAV.We compare the orientation results of our approach with an approach in which initial values for the unknown object coordinates are computed algebraically.

A marker-free automatic alignment method based on scale-invariant features

In electron tomography, alignment accuracy is critical for high-resolution reconstruction. However, the automatic alignment of a tilt series without fiducial markers remains a challenge. Here, we propose a new alignment method based on Scale-Invariant Feature Transform (SIFT) for marker-free alignment. The method covers the detection and localization of interest points (features), feature matching, feature tracking and optimization of projection parameters. The proposed method implements a highly reliable matching strategy and tracking model to detect a huge number of feature tracks. Furthermore, an incremental bundle adjustment method is devised to tolerate noise data and ensure the accurate estimation of projection parameters. Our method was evaluated with a number of experimental data, and the results exhibit an improved alignment accuracy comparable with current fiducial marker alignment and subsequent higher resolution of tomography.

SfM with MRFs: Discrete-Continuous Optimization for Large-Scale Structure from Motion

Recent work in structure from motion (SfM) has built 3D models from large collections of images downloaded from the Internet. Many approaches to this problem use incremental algorithms that solve progressively larger bundle adjustment problems. These incremental techniques scale poorly as the image collection grows, and can suffer from drift or local minima. We present an alternative framework for SfM based on finding a coarse initial solution using hybrid discrete-continuous optimization and then improving that solution using bundle adjustment. The initial optimization step uses a discrete Markov random field (MRF) formulation, coupled with a continuous Levenberg-Marquardt refinement. The formulation naturally incorporates various sources of information about both the cameras and points, including noisy geotags and vanishing point (VP) estimates. We test our method on several large-scale photo collections, including one with measured camera positions, and show that it produces models that are similar to or better than those produced by incremental bundle adjustment, but more robustly and in a fraction of the time.

ON-LINE COMPATIBLE ORIENTATION OF A MICRO-UAV BASED ON IMAGE TRIPLETS

Abstract. In this paper we present a robust orientation approach for an imaging sensor flown on a micro-UAV based on image triplets. Our aim is to have the orientation available online, i.e. during image acquisition. The resulting point cloud and sensor orientations can then for instance be evaluated for navigation purposes of the UAV or to analyse the completeness of the point cloud. We use low quality imagery extracted from the downlink of an onboard PAL-camera. Trilinear constraints and cross-checked matches allow for a high robustness of the sensor orientation and the sparse 3D point cloud. In order to reach the goal of on-line processing given the large number of observations and unknowns, we make use of an incremental bundle adjustment. Estimated parameters are incrementally improved without explicitly considering previous observations. Our approach combines linear projective geometry for obtaining initial values using the trifocal tensor with non-linear perspective geometry for the estimation of the unknowns. This combination allows for a high precision of the estimation, while eliminating the need for initial values. We evaluate the performance of our approach by means of imagery we acquired of the facade of theWelfenschloss in Hannover, collected with a Microdrones md4-200 micro-UAV. The results are the orientation parameters of the images and a sparse 3D point cloud representing the object. They are compared to those from a commercial bundle adjustment software and analysed in terms of geometric precision.

INCREMENTAL REAL-TIME BUNDLE ADJUSTMENT FOR MULTI-CAMERA SYSTEMS WITH POINTS AT INFINITY

Abstract. This paper presents a concept and first experiments on a keyframe-based incremental bundle adjustment for real-time structure and motion estimation in an unknown scene. In order to avoid periodic batch steps, we use the software iSAM2 for sparse nonlinear incremental optimization, which is highly efficient through incremental variable reordering and fluid relinearization. We adapted the software to allow for (1) multi-view cameras by taking the rigid transformation between the cameras into account, (2) omnidirectional cameras as it can handle arbitrary bundles of rays and (3) scene points at infinity, which improve the estimation of the camera orientation as points at the horizon can be observed over long periods of time. The real-time bundle adjustment refers to sets of keyframes, consisting of frames, one per camera, taken in a synchronized way, that are initiated if a minimal geometric distance to the last keyframe set is exceeded. It uses interest points in the keyframes as observations, which are tracked in the synchronized video streams of the individual cameras and matched across the cameras, if possible. First experiments show the potential of the incremental bundle adjustment w.r.t. time requirements. Our experiments are based on a multi-camera system with four fisheye cameras, which are mounted on a UAV as two stereo pairs, one looking ahead and one looking backwards, providing a large field of view.

The effectiveness of adaptive difficulty adjustments on students' motivation and learning in an educational computer game

Computer games that adaptively adjust difficulty are used to continuously challenge players according to their abilities. The adjustment of difficulty occurs automatically in response to a game's ongoing assessment of a player's performance. This approach to difficulty adjustment is likely to be of value in educational computer games as a means of scaffolding learning for students. However, there is limited research evaluating the effectiveness of educational computer games with adaptive difficulty adjustment when compared to non-adaptive difficulty adjustment. To expand on this research a quasi-experimental study was designed to isolate the impact of the difficulty adjustment game element on motivation and learning. A total of 234 secondary school students were allocated to one of three activities involving learning about Spanish cognates: an adaptive difficulty adjustment game, an incremental difficulty adjustment game that was non-adaptive, and a written activity. The three learning activities were designed following the same learning and motivation theories. The two games were identical apart from the difficulty adjustment mechanism. The results for motivation indicated that all students experienced high levels and there was no significant difference between the three learning activities. The pre- and post-tests results for learning indicated that significantly higher learning outcomes were achieved by students who played the adaptive game. Analysis of a game log recording the correctness of students' responses indicated that the adaptive difficulty adjustment game, in contrast to the non-adaptive incremental difficulty adjustment game, provided a scaffolding structure to enhance student learning.

Farmers’ climate change beliefs and adaptation strategies for a water scarce future in Australia

Climate change is likely to require irrigators in Australia's Murray-Darling Basin to cope with less water, which will require ongoing farm adjustment. Possible incremental adjustment strategies include expansive and accommodating responses, such as irrigators buying land and water, increasing their irrigated area, changing crop mix and adopting efficient infrastructure. Contractive strategies include selling land and water, and decreasing their irrigated area. Using historical surveys we provide a comparison of irrigators’ planned and actual strategies over the past fifteen years, thereby offering a strong foundation to support analysing future adaptation strategies. We explore influences associated with farm adjustment strategies, and in particular the role that climate change beliefs play. Farmers convinced that climate change is occurring are more likely to plan accommodating, but not expansive, strategies. The relationship between climate change belief and adopting various adaptive strategies was found to be often endogenous, especially for accommodating strategies. Such results suggest the need for irrigation farming policies to be targeted at improving irrigators’ adaptability to manage water variability, and its link with farm future viability.