Ivaylo Ilinkin

A Decomposition-Based Approach to Layered Manufacturing

Layered Manufacturing allows physical prototypes of 3D parts to be built directly from their computer models, as a stack of 2D layers. This paper proposes a new approach, which decomposes the model into a small number of pieces, builds each separately, and glues them together to generate the prototype. This allows large models to be built in parallel and also reduces the need for so-called support structures. Decomposition algorithms that minimize support requirements are given for convex and non-convex polyhedra. Experiments, on convex polyhedra, show that the approach can reduce support requirements substantially.

Opportunities for android projects in a CS1 course

Mobile devices have become ubiquitous in our daily lives and are replacing the desktop for email, social networking, daily planner, and so on. A typical mobile device now integrates a wide range of accessories, such as camera, GPS receiver, accelerometer, and offers a touch-screen with gesture-based interaction. This makes mobile devices an exciting platform for software development and programming projects for mobile devices have great potential to provide engaging experiences for computer science majors. This paper describes a pedagogical tool for introducing Android in a traditional CS1 course. The goal is not to teach Android programming, but to create a framework that integrates seamlessly with the CS1 course structure and supports the introduction of the fundamental computer science concepts by creating an engaging learning environment. The framework enables the students to port their CS1 projects to an Android device with minimal effort.

Evaluation of text entry methods for Korean mobile phones, a user study

This paper reports the results of a user study designed to evaluate text entry methods for mobile phones used in Korea. At present the keypad layout for Korean mobile phones has not been standardized and different manufacturers produce phones with different layouts. Included in the evaluation are three of the dominant text entry methods: Chon-ji-in, EZ-Hangul, and SKY. The metrics used in the analysis are key strokes per character, words per minute, and total error rate. The results suggest that SKY offers a good balance between speed, effort, and accuracy. The paper also introduces a phrase set that has high correlation with the Korean language and could be used in other experiments on Korean text entry methods.

Evaluation of Korean Text Entry Methods for Smartwatches

This paper presents results from a user study designed to evaluate the effectiveness of Korean text entry methods for smartwatches. Specifically, the study compares the four popular text entry methods for smartphones in the context of smartwatch use (three multi-tap 3x4 keypad methods and a QWERTY-like method). A distinctive feature of text entry in Korea is that traditionally different manufacturers have developed their own text entry methods starting with particular physical layouts on feature phones that are now available as soft keypads on smartphones. This research considers the next step in this progression by studying the viability of adopting these text entry methods on smartwatches. The results from the user study indicate that existing methods can be effective for text entry on smartwatches; analysis of the data offers suggestions for improving the effectiveness of the methods.

Design and evaluation of korean text entry methods for mobile phones

This paper presents a new keypad layout for Korean mobile phones and provides a preliminary evaluation of the feasibility of the design. At present the keypad layout for Korean mobile phones has not been standardized and different manufacturers produce phones with different layouts. The proposed layout is inspired by the structure of the Korean script and is designed to promote faster learning curve and ease of use.

Heuristics for estimating contact area of supports in layered manufacturing

Layered manufacturing is a technology that allows physical prototypes of three-dimensional(3D) models to be built directly from their digital representation, as a stack of two-dimensional(2D) layers. A key design problem here is the choice of a suitable direction in which the digital model should be oriented and built so as to minimize the area of contact between the prototype and temporary support structures that are generated during the build. Devising an efficient algorithm for computing such a direction has remained a difficult problem for quite some time. In this paper, a suite of efficient and practical heuristics is presented for estimating the minimum contact area. Also given is a technique for evaluating the quality of the estimate provided by any heuristic, which does not require knowledge of the (unknown and hard-to-compute) optimal solution; instead, it provides an indirect upper bound on the quality of the estimate via two relatively easy-to-compute quantities. The algorithms are based on various techniques from computational geometry, such as ray-shooting, convex hulls, boolean operations on polygons, and spherical arrangements, and have been implemented and tested. Experimental results on a wide range of real-world models show that the heuristics perform quite well in practice.

Multiple structure alignment and consensus identification for proteins

An algorithm is presented to compute a multiple structure alignment for a set of proteins and to generate a consensus structure which captures common substructures present in the given proteins. The algorithm is a heuristic in that it computes an approximation to the optimal alignment that minimizes the sum of the pairwise distances between the consensus and the transformed proteins. A distinguishing feature of the algorithm is that it works directly with the coordinate representation in three dimensions with no loss of spatial information, unlike some other multiple structure alignment algorithms that operate on sets of backbone vectors translated to the origin; hence, the algorithm is able to generate true alignments. Experimental studies on several protein datasets show that the algorithm is quite competitive with a well-known algorithm called CE-MC. A web-based tool has also been developed to facilitate remote access to the algorithm over the Internet.

Visualization of Floater and Gotsman's Morphing Algorithm

This video provides a visualization of an algorithm proposed by Floater and Gotsman for morphing two polygonal tilings. The algorithm represents the interior vertices of the tilings as convex combinations of their neighbors. At each time step the convex coefficients are linearly interpolated and the interior vertices of the intermediate tilings are found as the solutions to a system of linear equations.

Parametric search visualization

This video provides a visualization of parametric search using as the underlying application an algorithm for computing a tangent to a level in arrangement proposed by Matoušek [2]. The visualization is based on the framework of van~Oostrum and Veltkamp [6], which simplifies considerably the implementation of parametric search algorithms.

Terrain Polygon Decomposition, with Application to Layered Manufacturing

Efficient algorithms are given for decomposing a simple polygon into two special polygons, each with the property that every boundary and interior point can be connected to a single edge by a perpendicular line segment interior to the polygon. This allows efficient construction of certain classes of 3D parts via Layered Manufacturing.