Nakhoon Baek

A Z-map update method for linearly moving tools

In numerically controlled (NC) machining simulation, a Z-map has been frequently used for representing the workpiece. Since the Z-map is usually represented by a set of z-axis aligned vectors, the machining process can be simulated through calculating the intersection points between the vectors and the surface swept by a machining tool. In this paper, we present an efficient method to calculate those intersection points when automatically programmed tool-type tools move along a linear tool path. Each of the intersection points can be expressed as the solution of a system of non-linear equations. We transform this system of equations into a single-variable equation, and calculate the candidate interval in which the unique solution exists. We prove the existence of a solution and its uniqueness in this candidate interval. Based on these properties, we can effectively apply numerical methods to finally calculate the solution of the non-linear equations within a given precision. The whole process of NC simulation is achieved by updating the Z-map properly. Our method can improve accuracy greatly while increasing processing time negligibly in comparison with previous Z-map update methods, making it possible to verify the tool path more accurately and reliably.

Vehicle Color Classification Based on the Support Vector Machine Method

We present a vehicle color classification method from outdoor vehicle images. Although the vehicle color recognition is important especially for the newest applications including ITS (intelligent transportation system), we have no significant previous results at least to our knowledge. In this paper, we started from converting the vehicle image into an HSV(hue-saturation-value) color model-based image, to eliminate distortions due to the intensity changes. Then, we construct the feature vector, which is a two-dimensional histogram for the hue and saturation pairs. We use the SVM(support vector machine) method to classify these feature vectors into five vehicle color classes: black, white, red, yellow and blue. Our implementation result shows 94.92% of success rate for 500 outdoor vehicle images.

Implementing OpenGL ES on OpenGL

We present an OpenGL ES implementation which utilizes the existing OpenGL library, aiming to support various embedded systems in current consumer markets. Nowadays OpenGL ES becomes an improved version of OpenGL for embedded systems through introducing new features including the fixed-point numeric type. We optimized arithmetic operations on its specific data types such as fixed-point numbers, and achieved totally new optimized implementations of newly introduced features. Efficient ways of parameter conversions between our OpenGL ES implementation and underlying OpenGL are also accomplished even with strictly obeying the standard specifications. Our final implementation result of OpenGL ES 1.1 library completely provides more than 200 API functions in the standard specification and satisfies all the conformance tests. From the efficiency point of view, we compared execution speeds of real world applications to existing commercial implementations to finally show at most 33.147 times speed-ups, which is fastest among the same category implementations.

AlexVG: An OpenVG implementation with SVG-Tiny support

Embedded systems and web browsers have started to provide two-dimensional vector graphics features, to finally support scalability of graphics outputs, while traditional graphics systems have focused on the raster and bitmap operations. Nowadays, SVG and Flash are actively used and OpenVG from Khronos group plays the role of a de facto low-level API standard to support them. In this paper, we represent the design and implementation process and the final results of the first commercial OpenVG implementation, AlexVG. From its design stage, our implementation aims at the cooperation with SVG-Tiny, another de facto standard for embedded systems. Currently, our overall system provides not only the OpenVG core features but also a variety of OpenVG application programs and SVG-Tiny media file playing capabilities. For the conformance with the standard specifications, our system completely passed the whole OpenVG conformance test suites and the graphics output portions of the SVG-Tiny conformance test suites. From the performance point of view, we focused on the efficiency and effectiveness especially on the mobile phones and embedded devices with limited resources. As the result, it showed impressive benchmarks on the small-scale CPUs such as ARMs, even without neither any other libraries nor acceleration hardware. We had started commercial services of our AlexVG products since September 2005, and successfully entered the retail market with a good deal of mobile phones up to the present time.

A fast NC simulation method for circularly moving tools in the Z-map environment

In numerically controlled (NC) machining simulation, the Z-map is frequently used to represent the workpiece. Since the Z-map is usually represented by a set of Z-axis aligned vectors, the machining process can be simulated through updating it with the intersection points between the vectors and the tool swept surface. In our previous work (S.R. Maeng et al., 2003), we achieved a fast Z-map update method for linearly moving tools. On the other hand, typical NC simulation codes contain lots of circular tool movements especially for the free-form surface machining. This paper represents how to directly calculate the intersection points for the circularly moving tools. For fast computation, we express each of intersection points with a single-variable nonlinear function and calculate the candidate interval in which the unique intersection point exists. Then, we prove the existence of a solution and its uniqueness in this candidate interval. Based on these properties, we can effectively apply numerical methods to finally calculate the solution of the nonlinear function within a given precision. Due to space limitations, we focus on the filleted-end mills, the most general case of the APT (automatically programmed tool) tools. Since other tools such as ball-end mills and flat-end mills can be regarded as the special cases of the filleted-end mills, our result can be applied to the circular motions of any APT tools. Combining it to our previous result on the linear motion, we can cover most of NC simulation codes. Finally, our implementation and its result show that the new numerical approach is more efficient and reliable, in comparison to the previous methods.

OpenGL ES 1.1 implementation based on OpenGL

In this paper, we present an efficient way of implementing OpenGL ES 1.1 3D graphics API library for the environments with hardware-supported OpenGL facility, typically as desktop PCs. Although OpenGL ES was started from the existing OpenGL features, it rapidly became the standard 3D graphics library customized for embedded systems through introducing fixed-point arithmetic operations, buffer management with fixed-point data type supports, completely new texture mapping functions and others. Currently, it is the official 3D graphics API for Google Android, Apple iPhone, Sony PlayStation3, etc. In this paper, we achieved improvements on the arithmetic operations for the fixed-point number representation, which is the most characteristic data type for OpenGL ES 1.1. For the conversion of fixed-point data types to the floating-point number representations for the underlying OpenGL, we show the way of efficient conversion processes even with satisfying OpenGL ES standard requirements. We also introduced a specialized memory management scheme to manage the converted data from the buffer containing fixed-point numbers. In the case of texture processing, the requirements in both standards are quite different, and thus we used completely new software-implementations. Our final implementation of OpenGL ES library provides all of more than 200 functions in the standard specification and passed its conformance test, to show its compliance with the standard. From the efficiency point of view, we measured its execution times for several OpenGL ES-specific application programs and achieved remarkable improvements.

IT Convergence and Security 2017

A solution to get the problem off, have you found it? Really? What kind of solution do you resolve the problem? From what sources? Well, there are so many questions that we utter every day. No matter how you will get the solution, it will mean better. You can take the reference from some books. And the it convergence and security 2012 is one book that we really recommend you to read, to get more solutions in solving this problem.

Real-time approximation of molecular interaction interfaces based on hierarchical space decomposition

The interaction interface between two molecules can be represented as a bisector surface equidistant from the two sets of spheres of varying radii representing atoms. We recursively divide a box containing both sphere-sets into uniform pairs of sub-boxes. The distance from each new box to each sphere-set is conservatively approximated by an interval, and the number of sphere-box computations is greatly reduced by pre-partitioning each sphere-set using a kd-tree. The subdivision terminates at a specified resolution, creating a box partition (BP) tree. A piecewise linear approximation of the bisector surface is then obtained by traversing the leaves of the BP tree and connecting points equidistant from the sphere-sets. In 124 experiments with up to 16,728 spheres, a bisector surface with a resolution of 1/2^4 of the original bounding box was obtained in 28.8 ms on average.

Implementation of OpenVG 1.0 using OpenGL ES

OpenVG 1.0 is a 2D vector graphics standard and its API (Application Programming Interface) was released by the Khronos Group. In this paper, we introduce our OpenVG 1.0 implementation, accelerated by OpenGL ES 1.x hardware. Our implementation is an efficient and cost-effective way of accelerating OpenVG, fully utilizing the existing hardware in current embedded systems. Conclusively, our OpenVG implementation shows dramatically outstanding performance with low power consumption.

A cost-effective OpenGL SC solution for the consumer electronics market: An emulation library approach

We present our design and implementation of the OpenGL SC (safety-critical) 3D graphics standard, as a software emulation library over the widely used OpenGL ES 1.1 hardware. It accomplished a remarkable cost-down of the OpenGL SC products, to finally provide highly reliable full 3D graphics features to the safety-critical consumer electronics devices.