Browsing by Subject "Human-computer interaction."

Now showing 1 - 11 of 11

Open Access
Cluster based collaborative filtering with inverted indexing
(2005) Subakan, Özlem Nurcan
Collectively, a population contains vast amounts of knowledge and modern communication technologies that increase the ease of communication. However, it is not feasible for a single person to aggregate the knowledge of thousands or millions of data and extract useful information from it. Collaborative information systems are attempts to harness the knowledge of a population and to present it in a simple, fast and fair manner. Collaborative filtering has been successfully used in domains where the information content is not easily parse-able and traditional information filtering techniques are difficult to apply. Collaborative filtering works over a database of ratings for the items which are rated by users. The computational complexity of these methods grows linearly with the number of customers which can reach to several millions in typical commercial applications. To address the scalability concern, we have developed an efficient collaborative filtering technique by applying user clustering and using a specific inverted index structure (so called cluster-skipping inverted index structure) that is tailored for clustered environments. We show that the predictive accuracy of the system is comparable with the collaborative filtering algorithms without clustering, whereas the efficiency is far more improved.
Open Access
A collaborative system for providing routes between locations
(2008) Uluğ, Kerem Ali
Many systems, such as in-car GPS devices and airline company web sites, provide route information between locations. Although such systems are used widely and can provide route information successfully, users of these systems cannot contribute to the data entry process. In these systems, data is entered by the administrators and these systems cannot take advantage of the route expertise of their users. In this work, we present a collaborative system, which provides routes between locations upon user queries. The data in the system is entered by the users of the system. We present a model which is containing locations, links between locations and relationships between locations (containment, neighborhood and intersection) in order to store the data. For the route finding purpose, we present a customized version of the A* search algorithm. This customized version, named A*CD (A* for Collaborative Data), uses heuristics for estimating the cost remaining to the target location while processing the nodes. A*CD can also provide alternative routes, exclude certain link types in the searches according to user preferences and handle the problems associated with multiple stop transportation lines. As the cost models, we use duration and financial cost. We also present the intuitive connections concept. Even if a route does not exist between the selected locations, the system can provide a route with missing links. The gap(s) between the disconnected locations are filled by the help of the relationships between locations. In order to evaluate the performance of the A*CD algorithm, we present automated tests. These tests show that the costs of the routes that are provided by the A*CD algorithm are close to the actual shortest routes. In order to demonstrate the intuitive connections concept, we also present manual test queries.
Open Access
Comparing designers' cognitive behaviors in geometry-based and parametric 3D modeling environments
(2014) Tünger, Çetin
Digital design area has been constantly developed by scientific studies, but it is observed that studies in this area have mostly focused on the technical aspects of the subject (i.e. development of new tools and courses). User, tool, and process are three fundamental elements of a digital design system, so there is a need for studies on users and processes as well as tools. This study was carried out to understand and compare the cognitive behaviors of designers in conventional geometry-based and parametric 3D modeling environments within the framework mentioned above. While the geometry-based modeling tools are based on creation and the modification of the geometry, parametric modeling environments include an algorithmic structure underlying the form generation process. The study utilized Rhino as a geometric tool and Grasshopper as a parametric 3D tool. Six design students participated in the study. The data was collected by protocol analysis method and analyzed with a content-oriented coding scheme developed in this study. Results indicated that the cognitive actions of designers were significantly different in geometric and parametric modeling environments.
Open Access
Controller design for haptic systems under delayed position and velocity feedback
(2012) Koru, Ahmet Taha
This thesis considers controller design for haptic systems under delayed position and velocity feedback. More precisely, a complete stability analysis of a haptic system, where local dynamics are described by some second-order mechanical dynamics, is presented. Characteristic equation of this system with time delays involves quasipolynomials. By a change of variables in the characteristic equation, stability conditions are obtained analytically and regions are plotted by using Matlab. Next, using two optimization techniques (H∞ and stability margin optimization) optimal choice for the controller gains is proposed. H∞ optimization minimizes tracking error between devices while avoiding large control action inputs. H∞ analysis requires high computational cost for accurate results due to its dependency to frequency domain. On the other hand, stability margin optimization defines a cost function that expresses the trade-off between system bandwidth and robustness with low computational cost. The derived results are tested on a three degree of freedom real-time experimental platform to illustrate the theoretical results. Finally robustness analysis is performed for optimal parameters to find allowable delay perturbations
Open Access
Crowdy a framework for supporting socio-technical software : ecosystems with stream-based human computation
(2014) Kalender, Mert Emin
The scale of collaboration between people and computers has expanded leading to new era of computation called crowdsourcing. A variety of problems can be solved with this new approach by employing people to complete tasks that cannot be computerized. However, the existing approaches are focused on simplicity and independency of tasks that fall short to solve complex and sophisticated problems. We present Crowdy, a general-purpose and extensible crowdsourcing platform that lets users perform computations to solve complex problems using both computers and human workers. The platform is developed based on the stream-processing paradigm in which operators execute on the continuos stream of data elements. The proposed architecture provides a standard toolkit of operators for computation and configuration support to control and coordinate resources. There is no rigid structure or requirement that could limit the problem-set, which can be solved with the stream-based approach. The streambased human-computation approach is implemented and verified over different scenarios. Results show that sophisticated problems can be easily solved without significant amount of work for implementation. Also possible improvements are discussed and identified that is a promising future work for the existing work.
Open Access
A dept perception aware pen-based 3D sketching system
(2012) Yıldız, Cansın
This thesis proposes a method that resembles a natural pen and paper interface to create curve based 3D sketches. The system is particularly useful for representing initial 3D design ideas without much effort. Users interact with the system by the help of a pressure sensitive pen tablet, and a camera. The input strokes of the users are projected onto a drawing plane, which serves as a paper that they can place anywhere in the 3D scene. The resulting 3D sketch is visualized emphasizing depth perception by implementing several monocular depth cues, including motion parallax performed by tracking user’s head position. Our evaluation involving several naive users suggest that the system is suitable for a broad range of users to easily express their ideas in 3D. We further analyze the system with the help of an architect to demonstrate the expressive capabilities of the system that a professional can benefit.
Open Access
Dual-finger 3D interaction techniques for mobile devices
(2012) Telkenaroğlu, Can
Three-dimensional capabilities on mobile devices are increasing, and interactivity is becoming a key feature of these tools. It is expected that users will actively engage with the 3D content, instead of being passive consumers. Because touchscreens provide a direct means of interaction with 3D content by directly touching and manipulating 3D graphical elements, touch-based interaction is a natural and appealing style of input for 3D applications. However, developing 3D interaction techniques for handheld devices using touch-screens is not a straightforward task. One issue is that when interacting with 3D objects, users occlude the object with their fingers. Furthermore, because the user’s finger covers a large area of the screen, the smallest size of the object users can touch is limited. In this thesis, we first inspect existing 3D interaction techniques based on their performance with handheld devices. Then, we present a set of precise Dual-Finger 3D Interaction Techniques for a small display. Then, we present the results of an experimental study, where we evaluate the usability, performance, and error rate of the proposed and existing 3D interaction techniques. Finally, we integrate the proposed methods of different user modes.
Open Access
Early diagnosis of acute coronary syndromes automatically by using features of ECG recordings = EKG kayıtlarının öznitelikleri kullanılarak akut koroner sendromların otomatik olarak erken teşhisi
(2014) Terzi, Merve Begüm
In patients with acute coronary syndrome, temporary chest pains together with changes in the ST/T sections of ECG occur shortly before the start of myocardial infarction. In order to diagnose acute coronary syndromes early, we propose a new technique which detects changes in the ST/T sections of ECG. For this purpose, by using real ECG recordings, we identify ECG features that are critical in the detection of acute coronary syndromes. By using support vector machines (SVM) operating with linear and radial basis function (RBF) kernels, we obtain classifiers that use 2 or 3 most discriminating features of the ST/T sections. To improve performance, classification results on multiple segments are fused. The obtained results over a considerable number of patients indicate that the proposed classification technique provides highly reliable detection of acute coronary syndromes. To develop a detection technique that can be used in the absence of unhealthy ECGs, we also investigate the detection of acute coronary syndromes based on ECG recordings of a patient obtained during healthy stage only. For this purpose, a Gaussian mixture model is used to represent the joint pdf of the selected features. Then, a Neyman-Pearson type of approach is developed to provide detection of outliers that would correspond to acute coronary syndromes.
Open Access
Human face detection and eye location in video using wavelets
(2006) Türkan, Mehmet
Human face detection and eye localization problems have received significant attention during the past several years because of wide range of commercial and law enforcement applications. In this thesis, wavelet domain based human face detection and eye localization algorithms are developed. After determining all possible face candidate regions using color information in a given still image or video frame, each region is filtered by a high-pass filter of a wavelet transform. In this way, edge-highlighted caricature-like representations of candidate regions are obtained. Horizontal, vertical and filter-like edge projections of the candidate regions are used as feature signals for classification with dynamic programming (DP) and support vector machines (SVMs). It turns out that the proposed feature extraction method provides good detection rates with SVM based classifiers. Furthermore, the positions of eyes can be localized successfully using horizontal projections and profiles of horizontal- and vertical-crop edge image regions. After an approximate horizontal level detection, each eye is first localized horizontally using horizontal projections of associated edge regions. Horizontal edge profiles are then calculated on the estimated horizontal levels. After determining eye candidate points by pairing up the local maximum point locations in the horizontal profiles with the associated horizontal levels, the verification is also carried out by an SVM based classifier. The localization results show that the proposed algorithm is not affected by both illumination and scale changes.
Open Access
The sense of direction in virtual environments
(2005) Kutlu, Z. Gözde
Improvements in the computer technology lead people to investigate the potential of the virtual environments. The spatial factors, that are significant for spatial navigation in real- world environments, are important also in virtual environments. Performances of people during navigation through a virtual environment may be influenced by the individual differences as well as the learning method of the layout. In this experiment, sense of direction as an important spatial ability has been investigated considering the influence of gender and learning methodology in the virtual environments (VEs). The analysis of the experiment showed that sense of direction has a positive effect on the performances of the independent viewpoint participants in misaligned questions. Apart from this, contrary to the earlier bias, no significant difference was found related to gender and sense of direction ability as well as the learning performances of the participants in the VE.
Open Access
Virtual sculpting with advanced gestural interface
(2013) Kılıboz, Nurettin Çağrı
In this study, we propose a virtual reality application that can be utilized to design preliminary/conceptual models similar to real world clay sculpting. The proposed system makes use of the innovative gestural interface that enhances the experience of the human-computer interaction. The gestural interface employs advanced motion capture hardware namely data gloves and six-degrees-of-freedom position tracker instead of classical input devices like keyboard or mouse. The design process takes place in the virtual environment that contains volumetric deformable model, design tools and a virtual hand that is driven by the data glove and the tracker. The users manipulate the design tools and the deformable model via the virtual hand. The deformation on the model is done by stuffing or carving material (voxels) in or out of the model with the help of the tools or directly by the virtual hand. The virtual sculpting system also includes volumetric force feedback indicator that provides visual aid. We also offer a mouse like interaction approach in which the users can still interact with conventional graphical user interface items such as buttons with the data glove and tracker. The users can also control the application with gestural commands thanks to our real time trajectory based dynamic gesture recognition algorithm. The gesture recognition technique exploits a fast learning mechanism that does not require extensive training data to teach gestures to the system. For recognition, gestures are represented as an ordered sequence of directional movements in 2D. In the learning phase, sample gesture data is filtered and processed to create gesture recognizers, which are basically finite-state machine sequence recognizers. We achieve real time gesture recognition by these recognizers without needing to specify gesture start and end points. The results of the conducted user study show that the proposed method is very promising in terms of gesture detection and recognition performance (73% accuracy) in a stream of motion. Additionally, the assessment of the user attitude survey denotes that the gestural interface is very useful and satisfactory. One of the novel parts of the proposed approach is that it gives users the freedom to create gesture commands according to their preferences for selected tasks. Thus, the presented gesture recognition approach makes the human-computer interaction process more intuitive and user specific.