Extensions of LDA by PCA mixture model and class-wise features

Linear discriminant analysis (LDA) is a data discrimination technique that seeks transformation to maximize the ratio of the between-class scatter and the within-class scatter. While it has been successfully applied to several applications, it has two limitations, both concerning the underfitting problem. First, it fails to discriminate data with complex distributions since all data in each class are assumed to be distributed in the Gaussian manner. Second, it can lose class-wise information, since it produces only one transformation over the entire range of classes. We propose three extensions of LDA to overcome the above problems. The first extension overcomes the first problem by modelling the within-class scatter using a PCA mixture model that can represent more complex distribution. The second extension overcomes the second problem by taking different transformation for each class in order to provide class-wise features. The third extension combines these two modifications by representing each class in terms of the PCA mixture model and taking different transformation for each mixture component. It is shown that all our proposed extensions of LDA outperform LDA concerning classification errors for synthetic data classification, hand-written digit recognition, and alphabet recognition.     

Incomplete two-manifold mesh-based tool path generation

This paper presents a new paradigm for three-axis tool path generation based on an incomplete two-manifold mesh model; namely, an inexact polyhedron. When geometric data is transferred from one system to another system and tessellated for tool path generation, the model does not have any topological data between meshes and facets. In contrast to the existing polyhedral machining approach, the proposed method generates tool paths from an incomplete two-manifold mesh model. In order to generate gouge-free tool paths, cutter-location meshes (CL-meshes) are generated by offsetting boundary edges, boundary vertices, and facets. The CL-meshes are sliced by machining planes and the calculated intersections are sorted, trimmed, and linked. The grid method is used to reduce the computing time when range searching problems arise. The method is fully implemented and verified by machining an incomplete two-manifold mesh model.     

Robust segment-based object tracking using generalized hyperplane approximation

Tracking based on gradient descent algorithm using image gradient is one of the popular object tracking method. However, it easily fails to track when illumination changes. Although several illumination invariant features have been proposed, applying the invariant feature to the gradient descent method is not easy because the invariant feature is represented as a non-linear function of image pixel values and its Jacobian cannot be calculated in a closed-form. To make it possible, we introduce the generalized hyperplane approximation technique and apply it to histogram of oriented gradient (HOG) feature, one of the well-known illumination invariant feature. In addition, we achieve partial occlusion invariance using image segments. The hyperplanes are calculated from training segment images obtained by perturbing the motion parameter around the target region. Then, it is used to map the difference in non-linear feature of image onto the increment of alignment parameters. This process is mathematically same to the gradient descent method. The information from each segment is integrated by a simple weighted linear combination with confidence weights of segments. Compared to the previous tracking algorithms, our method shows very fast and stable tracking results in experiments on several practical image sequences.     

Experimental investigation of mortars using activated Hwangtoh

Hwangtoh (loess) is a Korean traditional building material that is environment-friendly. It is a natural pozzolanic material with many advantages as a substitute for cement-based materials. It has a high heat-storing capability along with purifying, deodorizing and antibiotic properties. Moreover, the emission of infrared radiation from Hwangtoh is beneficial to the human body. However, because of several practical disadvantages, such as shrinkage cracking and low strength development of concrete incorporating Hwangtoh, the application of Hwangtoh as a mineral admixture has not been quite successful. This study attempts to utilize the advantages of Hwangtoh in the field of modern construction, and suggests potential application of Hwangtoh as a substitute for cement-based material. For this purpose, Hwangtoh is activated in the furnace to investigate the optimal activation conditions and the physical properties of mortar incorporating Hwangtoh are investigated. It is found from the results that Hwangtoh shows changes in phase composition and the least amount of voids when activated in the range of 800–850 °C. The slump flow decreases as fineness and replacement ratio increases. The mortar incorporating Hwangtoh still has problems in flow behavior and drying shrinkage, but, at least, our findings lead us to conclude that the activated Hwangtoh can be used as pozzolanic mineral admixtures.     

Effect of cleaving environment on the growth of ZnSe on the GaAs (1 1 0) surface by molecular beam epitaxy

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

Heteroepitaxial growth of Zn1−xCdxSe on cleavage-induced GaAs (110) surface in ultra high vacuum

Zn_1−xCd_xSe epitaxial growth by molecular beam epitaxy (MBE) on the GaAs (110) surface cleaved in ultra high vacuum (UHV) was investigated. The growth mode of Zn_1−x Cd_xSe on GaAs (110) was not a simple Stranski–Krastanow type. At initial growth stage, growth mode was two-dimensional type. However, as the growth proceeds three-dimensional island growth and two-dimensional growth modes compete. As a result, two kinds of structures were spontaneously formed on the surface, pyramidal-shaped islands and ridge structures aligned to the [1 0] direction. Anisotropic in-plane strain relaxation on (110) is suggested as the formation mechanism of such structures.     

A 60-W Multicarrier WCDMA Power Amplifier Using an RF Predistorter

In this brief, we present a 60-W power amplifier that is linearized using an RF predistorter for multicarrier wideband code-division multiple-access (WCDMA) applications. The proposed RF predistorter is fully composed of RF or analog circuits, and it has a moderate memory effect compensation capability using a delayed third-order intermodulation (IM3) component path. It also includes the IM5 generation circuits and a compact IM3 generator that is capable of autocanceling for the fundamental component. The proposed RF predistorter was implemented and applied to a 60-W high-power WCDMA amplifier. For a four-carrier downlink WCDMA signal, the RF predistorter improved the adjacent channel leakage power ratio at a 5-MHz offset by 6.19 dB at an average output power of 48 dBm. The total efficiency of the system is as high as 13.6% at the same output power level. At an output power level of 60 W, the linearized power amplifier complies with the linearity specification of the WCDMA system.     

An optimized contour parallel tool path for 2D milling with flat endmill

Although the conventional contour parallel tool path obtained from geometric information has been successful in making desirable shapes, it seldom considers the physical process concerns like cutting forces and chatters. In this paper, an optimized contour parallel path, which maintains constant MRR (material removal rates) at all times, is introduced and the results are verified. The optimized tool path is based on a conventional contour parallel tool path. Additional tool path segments are appended to the basic tool path in order to achieve constant cutting forces and to avoid chatter vibrations in the entire machining area. The algorithm has been implemented for two dimensional contiguous end milling operations with flat end mills, and cutting tests were conducted to verify the significance of the proposed method.     

A new offset algorithm for closed 2D lines with Islands

In this paper, a new offset algorithm for closed 2D lines with islands is introduced and the result is illustrated. The main point of the proposed algorithm is that every point is set to be an offset using bisectors, and then invalid offset lines, which are not to be participated in offsets, are detected in advance and handled with an invalid offset edge handling algorithm in order to generate raw offset lines without local invalid loops. As a result, the proposed offset method is proved to be robust and simple, moreover, has a near O(n) time complexity, where n denotes the number of input lines. The proposed algorithm has been implemented and tested with 2D lines of various shapes.     

Characterization of natural organic matter in conventional water treatment processes for selection of treatment processes focused on DBPs control

Natural organic matter (NOM) from raw and process waters at a conventional water treatment plant was isolated into hydrophobic and hydrophilic fractions by physicochemical fractionation methods to investigate its characteristics. Formation potential of trihalomethanes (THMs) was highly influenced by the hydrophobic fraction, whereas haloacetic acids formation potential (HAAFP) depended more on the hydrophilic fraction. However the hydrophobic fraction was removed more than the hydrophilic fraction through conventional water treatment. Therefore residual hydrophilic NOM after conventional treatment needs to be removed to reduce HAAFP. Feasible additional processes are required to be evaluated by comparing preferential removal efficiency of hydrophilic NOM through pilot tests. The structural and chemical characteristics of hydrophobic NOM (i.e., humic substances (HS)) were further investigated to know how they are influenced by conventional treatment. The phenolic fraction in the hydrophobic NOM was mainly removed compared to the carboxylic fraction through water treatment, and a higher formation potential of THMs resulted from NOM with a higher phenolic content. The Fourier-transform infrared (FT-IR) and proton nuclear magnetic resonance ((1)H-NMR) employed for characterization of NOM through water treatment were insightful revealing that their results were quite close to each other. Decreases of ratio of UV absorbance at 253 and 203 nm, respectively (A(253)/A(203) ratio) and trihalomethane formation potential/dissolved organic carbon (THMFP/DOC) showed consistent trends; therefore, the A(253)/A(203) ratio may be a good indicator of tendency for the formation potential of disinfection by-products (DBPs).