Automatic segmentation and approximation of digitized data for reverse engineering

Reverse engineering is the process of developing a computer-aided design (CAD) model and a manufacturing database for an existing object. This process is used in CAD modelling of part prototypes, in designing moulds and in automated inspection of parts with a complex surface. This paper reports on the automatic segmentation and approximation of three-dimensional digitized points for reverse engineering. Based on an innovation that uses the properties of a non-uniform rational B-spline (NURBS) or B-spline and makes ordered digitized points be control points directly to construct a NURBS or B-spline surface, which takes less computation time than traditional algorithms in calculating surface normals and curvatures at digitized points, an algorithm was developed for automatic segmentation and NURBS surfaces fitting for digitized points.     

A Primal Simplex Specialization for the Equal Flow Problem

This paper presents a primal simplex specialization for the equal flow problem. This approach is motivated by a desire to exploit the special structure of the side constraints and to maintain as much of the characteristics of pure network problems as possible. The simplex computations are discussed and a starting solution based on the subgradient optimization technique is presented. Our implementation is tested on problems with up to 1500 nodes, 6600 arcs and 600 equal flow pairs. These problems are also solved using MPSX and another specialized code for the equal flow problem. We present Computational experience which indicates that our approach is well suited for problems with up to 150 side constraints. As the number of pairs increased, MPSX with an advanced start procedure, performed better than our specialized code.     

Design model generation for reverse engineering using multi-sensors

Reverse engineering is the process of creating a design model and a manufacturing database for an existing part or prototype. The applications of reverse engineering are in redesigning of existing partstools or prototype parts where the CAD model of the part is not available. Reverse engineering, for the most part, is performed as an interactive process where the designer identifies the surface features from digitized data and then models the surfaces accordingly. This paper presents the algorithms and implementation results for a reverse engineering system which is intended to automatically create CAD representations of part prototypes. An integrated sensory system combining contact and non-contact sensors has been developed to digitize parts surfaces. The sensory system fuses data from machine vision and a coordinate measuring machine (CMM) in order to automatically digitize the part surface. Machine vision is used to capture the orthographic views of the part. The images of these orthographic views are processed and vectorized to create five views of the part in the form of an engineering drawing. The system utilizes the generated orthographic projections to automatically drive the CMM to capture a grid of point coordinates from the part surface. The CMM digitization process is guided by the segmentation provided from the orthographic views. The segmented data from the part surface is input to the surface modeling module of the system where parametric surfaces are fitted through the digitized points. The surfaces are then extended and intersected using the Hermite approximation method to develop the 3-D CAD model of the part. Accuracy and automation is achieved by combining global shape information obtained from part images with the accurate point data acquired by a CMM. Algorithms for surface segmentation, part digitization, surface extension, and surface intersection modeling are described in this paper.     

Synthesis, Photophysical and Photovoltaic Properties of New [60]Fullerene Pyrrolidine Derivatives

Two new [60]fullerene pyrrolidine derivatives 2 and 3 were synthesized and characterized by ¹H NMR, ¹³C NMR and MS. Their photophysical processes have been investigated by using laser flash photolysis. The experiments show quenching of oligomer singlet excited state and the evidence of the fullerene singlet excited emission. And the intramolecular of electron transfer and also energy transfer of 2 and 3 occurred and the triplet excited state of fullerene moiety in 2 and 3 have different lifetime due to their different structures. A photovoltaic device using compound 2 as the only photoactive material has also been investigated which showed the energy conversion efficiency is 0.011%.     

Degradation products of mycophenolate mofetil in aqueous solution

The thermal and peroxide-catalyzed degradation products of mycophenolate mofetil (1) were studied in aqueous solution at pH 2.0, 3.5, 6.0, and 8.2. The major thermal degradation product observed was mycophenolic acid (2). At pH 6.0 and 8.2, 2 was the only product observed in the absence of peroxide, while at pH 2.0 and 3.5, the lactone analogue of mycophenolic acid (5), a hydroxylactone due to oxygenation of the double bond (6), and an unidentified product were formed. Compound 6 degraded to 4-hydroxy-6-methoxy-7-methyl-3-oxo-1,3-dihydro-isobenzofuran-5-carbaldehyde (9) on prolonged storage and was present in the sample stressed at pH 2. Mycophenolic acid (2), the N-oxide of mycophenolate mofetil (3), the hydroxylactone of mycophenolic acid (6), and the erythro form of 4-methoxy-5-methyl- 2-(2-methyl-5-oxo-tetrahydro-furan-2-yl)-3,6-dihydro-2H-1,7-dioxa-as-indacen-8- one (8) were observed in the presence of hydrogen peroxide at pH 3.5, 6.0, and 8.2. In addition, at pH 8.2, 4-hydroxy-4-(4-methoxy-5-methyl-8-oxo-2,3,6,8-tetrahydro-1,7-dioxa-as-indacen-2-yl)-pentanoic acid (7) was seen. Peroxide-stressed samples at pH 2.0 gave no major degradation peaks, but a small amount of the hydroxylactone of mycophenolic acid (6) was formed.     

Comparative In Vitro evaluation of cumulative release of the urinary antiseptics Nalidixic acid, Pipemidic acid, Cinoxacin, and norfloxacin from white beeswax Microspheres

The in vitro diffusion of nalidixic acid (1), pipemidic acid (2), cinoxacin (3), and norfloxacin (4) was studied. The transfer rate constants (k_d) from simulated gastro-intestinal juices to simulated plasma, throughout artificial wall lipid membranes, were defined. The k_d values suggested that the four drugs are absorbed both in gastric and intestinal environments in similar amounts. To obtain lack of gastric unwanted effects white beeswax microspheres containing 1, 2, 3, and 4 were investigated as a vehicle for the drug intestinal release; they were prepared by the meltable dispersion process using wetting agents. Discrete, reproducible free flowing microspheres were obtained. The drug content increased when the particle size growed; it ranged from 4% to 18%. More than 95% of the isolated microspheres were of particle size range 100-500 μm. The drug release was evaluated in vitro. Dissolution of entrapped active ingredients was greatly retarded allowing absorption only in the intestinal tract as result of microsphere formation.     

Design of an i.v. formulation of an unstable prodrug candidate for prostate cancer treatment: solution chemistry of N-(glutaryl-hyp-ala-ser-cyclohexylglycyl-gln-ser-leu)-doxorubicin

The chemical degradation of N-(glutaryl-hyp-ala-ser-cyclohexylglycyl-gln-ser-leu)-doxorubicin (henceforth referred to as doxorubicin peptide conjugate 1) was studied in buffered aqueous solution. The pH-rate profile of degradation shows that the doxorubicin conjugate is most stable between pH 5 and 6. The dependence of log k_obsd on pH in acidic medium is characteristic of specific acid-catalysis of the sugar hemiaminal of 1 (as in the case of doxorubicin). Isolation of degradates and structural determination shows that the degradation at lower pH values yields the water-insoluble aglycone doxorubicinone, supporting the mechanism of acid-catalyzed loss of the amino sugar. At pH higher than 5, a more complicated degradation pattern is observed, including the loss of the amino sugar and the aromatization of the saturated ring to give 7,8-dehydro-9,10-desacetyldoxorubicinone as one of the major products. Around the pH of maximum stability in solution, the rate of degradation of 1 is significantly greater than that for doxorubicin, which rules out the formulation of a room temperature solution product with a sufficiently long shelflife for market use. Design of a stable lyophilized formulation for sterile reconstitution based on the physicochemical properties of 1 is described.     

Ketoprofen 1-alkylazacycloalkan-2-one esters as dermal prodrugs: in vivo and in vitro evaluations

Six new 1-alkylazacycloalkan-2-one esters of ketoprofen (1-6) were synthesized and evaluated as potential dermal prodrugs of ketoprofen. Their lipophilicity by both experimental lipophilicity indices (log k') and calculated ClogP was also determined. In vitro experiments were carried out to evaluate the chemical and enzymatic stability and permeation through excised human skin of these new ketoprofen derivatives. Furthermore, we investigated the in vivo topical anti-inflammatory activity of ester 5, which showed the best in vitro profile, evaluating the ability of this compound to inhibit methyl nicotinate-induced skin erythema on healthy human volunteers. Esters 1-6 showed increased lipophilicity compared with the parent drug (ketoprofen), good stability in phosphate buffer pH 7.4, and were readily hydrolyzed by porcine esterase. Results from in vitro percutaneous absorption studies showed that, among all esters synthesized, only for esters 1 and 5 did a higher cumulative amount of drug penetrate through the skin, compared with that obtained after topical application of ketoprofen. In vivo results showed an interesting delayed and sustained activity of ester 5, compared with the parent drugs.     

Diels-Alder Reaction of [60]Fullerene with Dienes Having an Ester Substituent at 1-Position

Treatment of [60]fullerene with ethyl trans, trans-hexa-2,4-dienoate (1) and methyl trans, trans-octa-2,4-dienoate (2) at 70 ∼ 100 °C afforded products 3 and 4, respectively, which are resulted from Diels-Alder addition of the dienoates to a 6/6 ring junction of [60]fullerene.     

Terrain analysis from curvature profiles

This paper describes a new algorithm which uses Gaussian and mean curvature values of the terrain surface to extract feature points. These points are then used for recognition of particular subregions of the terrain and in estimating relative positions of these subregions in the terrain. The Gaussian and mean curvatures are chosen because they are invariant under rotation and translation. In the Gaussian and mean curvature images, the points of maximum and minimum curvatures are extracted and used for matching. The stability of the position of these points in the presence of noise and with resampling is investigated. The input for this algorithm is 3D digital terrain data. Curvature values are calculated from the data by fitting a quadratic surface over a square window and calculating directional derivatives of this surface. A method of surface fitting that is invariant to sensor-centered coordinate system transformation is suggested and implemented. Real terrain data are used in our experiments. The algorithm is tested with and without the presence of noise, and its performance is described.     

Diels-Alder Reactions of the [60]Fullerene: From Regularly Functionalized Carbon Spheres to Cyclophanes

Diels-Alder reactions allow the regioselective preparation of various derivatives of the [60]fullerene (1) with exohedral functionalization. A symmetric sixfold [2+4]-cycloaddition of 1,3-dienes to 1 opens direct synthetic access to hydrocarbons with a novel cyclophane structure.     

Improved neural network model for reverse engineering

While conventional engineering transforms engineering concepts into real parts, in reverse engineering real parts are transformed into engineering models. The construction of a surface from three-dimensional (3D) measuring data points is an important problem in reverse engineering. This paper presents a reconstruction method for the sculptured surfaces from the 3D measuring data points. The surface reconstruction scheme is presented based on a neural network. The reconstruction of the existing surfaces is realized by training the network. A series of measuring points from existing sculptured surfaces is used as a training set. Once the neural network has been trained, it serves as a geometric model to generate all the points that are needed. However, the learning rate for the neural network is relatively slow, and the learning accuracy is often unacceptably low. In this paper, to improve the performance of the neural network, a pre-processor is proposed before the input layer. The pre-processor maps the input into the larger space by generating a set of linearly independent values. The effect of the pre-processor is to increase modelling accuracy, and reduce learning time. Based on this method, experimental results are given to show that the reconstructed surfaces are faithful to the original data points. The proposed scheme is useful for regular or irregular digitized data.     

Thermal Transformation of Ring-Opened [2 2] C60 Dimer into a Wide-Bridged C120 Isomer. A Computational Evaluation of Fulvalene-Naphthalene Rearrangements

As a continuation of the studies on thermal transformation of the [2+2] C₆₀ dimer (1), the consequence of the pyracylene-rearrangement-like valence isomerization of the fulvalene partial structure at the bridge of the ring-opened product from 1, namely 2, was searched by dynamic reaction coordinate /AM1 semiempirical MO calculations. It is predicted that the fulvalene bridge of 2 rearranges into naphthalene partial structure by the concerted 'in-plane' mechanism to give a wide-bridged C₁₂₀ intermediate having twenty five-membered rings and two ten-membered rings (3). The computed energy of activation (145 kcal/mol) is 40 kcal/mol lower than those computed for pyracylene rearrangements. In contrast, the recently reported analogous rearrangement of indigo (13) to dibenzonaphthyridindione (14) is computed to occur by the stepwise 'sp³' mechanism.     

Negative zooplankton do not exist—a response to 'On the stability of some equilibrium points in a plankton population model'

Simple models of the plankton ecosystem have been usefully analysed and understood using dynamical-systems techniques. These techniques have addressed important ecological questions and have provided insight into how models should be constructed. Edwards and Brindley [1996, Oscillatory behaviour in a three-component plankton population model. Dynamics and Stability of Systems, 11, 347-370] used such methods to investigate the dynamics of a model that represented the concentrations of nutrients, phytoplankton and zooplankton. Halanay [2003, On the stability of some equilibrium points in a plankton population model. Dynamical Systems, 18, 227-229] asserted that Edwards and Brindley incorrectly determined the stability of one of the model's steady states. However, Halanay's assertion requires the consideration of negative zooplankton concentrations, and so is not relevant to the biological meaning of the model.     

Heuristic Procedures for Multi-Item Inventory Planning with Limited Storage

The determination of replenishment quantities for multiple products with dynamic demand, subject to storage constraints, is addressed. A lower bound is obtained by solving the dual problem. Both subgradient optimization of the Lagrangean relaxation and LP relaxation of the convexified solution space are considered. Dantzig-Wolfe decomposition is used to solve the LP relaxation. A heuristic is proposed for the generation of feasible solutions obtained by modifying solutions created at each step of either subgradient optimization or Dantzig-Wolfe decomposition. An experimental investigation of 428 test problems indicates that the heuristic coupled with sub-gradient optimization gives consistently good solutions.     

Effect of functional groups on the crystallization of ferric oxides/oxyhydroxides in suspension environment

This paper investigated the effects of five kinds of Au surfaces terminated with and without functional groups on the crystallization of ferric oxides/oxyhydroxides in the suspension condition. Self-assembled monolayers (SAMs) were used to create hydroxyl (--OH), carboxyl (--COOH), amine (--NH₂) and methyl (--CH₃) functionalized surfaces, which proved to be of the same surface density. The immersion time of substrates in the Fe(OH)₃ suspension was divided into two time portions. During the first period of 2 h, few ferric oxide/oxyhydroxide was deposited except that ?-Fe₂O₃ was detected on--NH₂ surface. Crystallization for 10 h evidenced more kinds of iron compounds on the functional surfaces. Goethite and maghemite were noticed on four functional surfaces, and maghemite also grew on Au surface. Deposition of ?-Fe₂O₃ was found on--OH surface, while the growth of orthorhombic and hexagon FeOOH were indicated on--NH₂ surface. Considering the wide existence of iron compounds in nature, our investigation is a precedent work to the study of iron biomineralization in the suspension area.     

Estimation of electromagnetic scattering patterns from sinusoidalsurfaces using FFT

The scattering of electromagnetic waves from perfectly conducting sinusoidal surfaces as prototypes of periodic rough surfaces is studied. Physical optics and Fourier methods are used to calculate the scattered far field at a function of the observation angle. The patterns for several surface parameters are evaluated and plotted. The size of the illuminated surface area is varied. Homogeneous and Gaussian field amplitude perturbation of a laser beam in TEM₀₀-mode is considered. The results are compared with other methods and show a rather good agreement. Therefore, the method may be used for far-field computation if several criteria for the validity of the Kirchhoff approximation are not violated     

Holomorphic Anosov systems, foliations and fibring complex manifolds

We study possible versions of Tischler's fibration theorem (Tischler, Topology, 9: 153-154, 1970) for the complex case. Holomorphic Anosov flows are studied as well, under the hypothesis that they preserve a codimension one holomorphic foliation.     

Applying Production Standards and Feedback to Improve Worker Productivity and Satisfaction in a Repetitive Production Task

An experimental research was conducted to determine the specific standard and feedback that would maximize worker productivity and satisfaction in a repetitive production task. The research was conducted in a university machine shop on 56 college students. They were trained individually for one hour in the task performance and performed the same task for another hour under a specific condition. The operators were assigned various levels of assigned and participative standards with feedback. A progressive increase in the assigned standards with feedback improved worker productivity significantly up to the provision of an assigned standard of 140% of normal and feedback. The increases were 14% in quantity and 10% in quality output, compared to the control group. No further improvement in worker productivity resulted as a consequence of an assigned 150% standard and feedback. The provision of a participative standard with feedback was significantly inferior to an assigned 130% standard and feedback. The provision of assigned and participative standards with feedback improved worker satisfaction significantly. No significant difference was found among the standards and feedback conditions. Monetary incentive, when provided with the 140% standard and feedback, added no incremental performance or satisfaction gain.     

On the stability of some equilibrium points in a plankton population model

It is proved that the equilibrium point (N₀, 0, 0) for the plankton population model given in Edwards and Brindley, (1996, Dynamics and Stability of Systems, 11(4): 347-370) is unstable in the case of two negative and one zero eigenvalues, thus correcting an assertion on its stability in the above quoted paper.