Computer-aided Design Procedure Research Articles

In vitro comparison of the accuracy (trueness and precision) of six extraoral dental scanners with different scanning technologies

Statement of problemThe fabrication of prosthetic restorations using computer-aided design and computer-aided manufacturing (CAD-CAM) procedures depends on scanning surfaces. However, limited information is available regarding the effect of extraoral scanning systems on the accuracy of the fabrication process. PurposeThe purpose of this in vitro study was to evaluate and compare the accuracy (trueness and precision) and resolution of 6 CAD-CAM extraoral scanners by comparing features and scan technology. Material and methodsA master die was fabricated to simulate a dental preparation. The die was measured with a coordinate measuring machine (CMM) to obtain an accurate digital CAD reference model (CRM). The master die was then scanned 10 times with 3 structured light scanners, 2 laser scanners, and 1 contact scanner. The resulting laboratory scan data (LSD) were converted to a stereolithography (STL) format. The discrepancies between measurements were compared 3-dimensionally and at 3 selected areas of a virtual sagittal cut using CAD software. The Kruskal–Wallis 1-way analysis of variance was first performed to compare scanners and then to group data according to scanner type. The Spearman rank correlation coefficient was used to test the association between resolution and all other variables (α=.05). ResultsFor all 6 scanners, the mean resolution value was 133.9 (SD 93.9) points/mm2. The value for trueness was 38.8 (SD 6.2) μm and for precision 45.5 (SD 4.8) μm. Trueness values were 20.3 μm (SD 32.7) at the axial surfaces, 46.6 μm (SD 25.9) at the margin of the preparation, and 55.8 μm (SD 29.3) at the center of the occlusal groove. The ZENO Scan was the most accurate and precise of the 6 scanners for most of the variables measured. ConclusionsThe reliability of CAD-CAM scanners is not affected by a specific technology (light, laser, or contact) but by definite parameters. In addition, the entire scanning procedure is more accurate if the scanned surfaces are smooth and regular.

Design Procedure of a Permanent Magnet D.C. Commutator Motor

Electrical machine with electro magnet as excitation system many problems out of which, less efficiency is a major one. Self excited dc machine has to sacrifice some power for excitation system as a result, power available for useful work become less. This problem can be solved to some extent whatever may be the amount , by using permanent magnet for the excitation system of dc machine and there by contributing towards the conservation of conventional energy sources which are alarmingly decrease day by day . Using of permanent magnet in the electrical machine helps in burning of less conventional fossil fuel and contributes indirectly in conservation of air-pollution free environment. With permanent magnet dc motor, the efficiency of the machine also rise up considerably. This paper is an effort to give a computer aided design procedure of permanent magnet dc motor.

Comparison of chairside and laboratory CAD/CAM to conventional produced all-ceramic crowns regarding morphology, occlusion, and aesthetics.

There are many ways to produce all-ceramic crowns. Computer-aided design and computer-aided manufacturing (CAD/CAM) procedures compete against conventional fabricated restorations. As different methods of production may produce variable results, this study aims to compare chairside and laboratory-based CAD/CAM systems to conventional crowns regarding their similarity to original tooth morphology, number of occlusal contacts, occlusal adjustment time, and subjective aesthetic perception. Impressions of caries-free jaws were taken, and the resulting gypsum casts were scanned with a laboratory scanner. Preparations for all-ceramic full crowns were performed on first molars, and three different restorations were made: CEREC restorations (CER), laboratory-produced CAD/CAM crowns (LABCAD), and conventional waxed-up/pressed ceramic crowns (CONV). Time for occlusal adaptation and the number of occlusal contacts were noted. Two dentists performed aesthetic gradings of restorations. Statistical analysis included one-way ANOVA with least significant difference (LSD) post hoc test, t test, and Kruskal-Wallis test. Metrical deviations of the re-scanned crowns to the original, unprepared tooth surface were 220.55 ± 54.31μm for CER, 265.94 ± 61.39 for LABCAD, and 252.44 ± 68.77μm for CONV group. One-way ANOVA showed significant lower deviations for the CER group. LABCAD crowns showed significantly more occlusal contacts, whereas CONV crowns required the least time for occlusal adaptation andshowed excellent aesthetic gradings. All three methods had pros and cons regarding different parameters. Further improvements of CAD/CAM software shall lead to restorations comparable to conventional restorations in all aspects, especially in aesthetics. All tested methods of production for all-ceramic crowns produced clinically acceptable results. Thus, in an individual case, the method chosen can be determined by the dentist's preference.

A Hierarchical Procedure for Synthesis of a Base Case Solid Oxide Fuel Cell System in Aspen HYSYS

Presented is a computer-aided process design and analysis procedure for use in creating Aspen HYSYS-based base-case design simulations for a Solid Oxide Fuel Cell. This procedure is based on the work of Douglas. This approach provides a step by step method to system design that permits preliminary assessments of the economic viability, which allows for expeditious creation of realistic and economic design simulations. Each step presents heuristics designed to aid in the specific design element addressed in that step. An example design of a Solid Oxide Fuel Cell from the Department of Energy's Fuel Cell Handbook is used to illustrate the design process. This example answers the questions presented by Douglas, and culminates in an energy balance and a capital cost table for the process. The example illustrated has an expected return on investment of 15% and serves as a guide for teaching the use of a hierarchical procedure for the synthesis of a modern chemical process.

Experimental Study on Forging Process of Micro Stepped Gear

This paper proposes an integrated computer-aided design and computer-aided manufacturing procedure to produce the forging die for experiment, and the forging formability of micro stepped gear was explored. In the forging process, this paper proposes a novel hybrid forging method with a single die set which would execute two forging stages including the first stage of Upsetting and the second stage of Clamping type Gear forging. In the case study, the materials were fully filled into tooth cavity of small gear of module 0.12mm. On the other hand, the estimated unfilled rate of bigger gear is less 8 to 12%, showing this method is exactly feasible.

Effects of H2 Addition to Compressed Natural Gas Blends on Cycle-to-Cycle and Cylinder-to-Cylinder Combustion Variation in a Spark-Ignition Engine

An experimental investigation and a burning-rate analysis have been performed on a production 1.4 liter compressed natural gas (CNG) engine fueled with methane-hydrogen blends. The engine features a pent-roof combustion chamber, four valves per cylinder, and a centrally located spark plug. The experimental tests have been carried out in order to quantify the cycle-to-cycle and the cylinder-to-cylinder combustion variation. Therefore, the engine has been equipped with four dedicated piezoelectric pressure transducers placed on each cylinder and located by the spark plug. At each test point, in-cylinder pressure, fuel consumption, induced air mass flow rate, pressure, and temperature at different locations on the engine intake and exhaust systems as well as “engine-out” pollutant emissions have been measured. The signals related to engine operation have been acquired by means of a National Instruments PXI-DAQ system and software developed in house. The acquired data have then been processed through a combustion diagnostic tool resulting from the integration of an original multizone thermodynamic model with a computer-aided design (CAD) procedure for the evaluation of the burned-gas front geometry. The diagnostic tool allows the burning velocities to be computed. The tests have been performed over a wide range of engine speeds, loads, and relative air-fuel ratios (up to the lean operation limit (LOL)). For stoichiometric operation, the addition of hydrogen to CNG has produced a brake-specific fuel combustion (bsfc) reduction ranging between 2% and 7% and a brake-specific total unburned hydrocarbons (bsTHCs) decrease up to 40%. These benefits have appeared to be even higher for lean mixtures. Hydrogen has shown to significantly enhance the combustion process, thus leading to a sensibly lower cycle-to-cycle variability. Hydrogen addition has generally resulted in extended operation up to relative air-to-fuel ratio (RAFR) = 1.8. Still, the LOL consistently varies depending on the considered cylinder.

Computer-aided molecular design of solvents for accelerated reaction kinetics

Solvents can significantly alter the rates and selectivity of liquid-phase organic reactions, often hindering the development of new synthetic routes or, if chosen wisely, facilitating routes by improving rates and selectivities. To address this challenge, a systematic methodology is proposed that quickly identifies improved reaction solvents by combining quantum mechanical computations of the reaction rate constant in a few solvents with a computer-aided molecular design (CAMD) procedure. The approach allows the identification of a high-performance solvent within a very large set of possible molecules. The validity of our CAMD approach is demonstrated through application to a classical nucleophilic substitution reaction for the study of solvent effects, the Menschutkin reaction. The results were validated successfully by in situ kinetic experiments. A space of 1,341 solvents was explored in silico, but required quantum-mechanical calculations of the rate constant in only nine solvents, and uncovered a solvent that increases the rate constant by 40%.

Research on the Procedure for Computer-Aided Pattern Design of Uygur's Flowered Hats

Xinjiang Uygur’s flowered hats is famous all over the world, it leads the world of headwear of variou nationalities within China by the variety of styles, the various ways of how to emroider pattern design and exquisite manufacture. It is unusual even in national costumes art of the world. The poupose of this study is to analyze Uygur's headwear, study the rules of Uygur's headwear pattern, analyze the characteristic of the basic pattern, research on the procedure for computer-aided pattern design of Uygur's flowered hat, explore the application of computer-aided design in traditional costume's pattern design and to realize application exploration of computer- aided design in designing of costume and dress adornment.

Systematic and efficient side chain optimization for molecular docking using a cheapest‐path procedure

Molecular docking of small-molecules is an important procedure for computer-aided drug design. Modeling receptor side chain flexibility is often important or even crucial, as it allows the receptor to adopt new conformations as induced by ligand binding. However, the accurate and efficient incorporation of receptor side chain flexibility has proven to be a challenge due to the huge computational complexity required to adequately address this problem. Here we describe a new docking approach with a very fast, graph-based optimization algorithm for assignment of the near-optimal set of residue rotamers. We extensively validate our approach using the 40 DUD target benchmarks commonly used to assess virtual screening performance and demonstrate a large improvement using the developed side chain optimization over rigid receptor docking (average ROC AUC of 0.693 vs. 0.623). Compared to numerous benchmarks, the overall performance is better than nearly all other commonly used procedures. Furthermore, we provide a detailed analysis of the level of receptor flexibility observed in docking results for different classes of residues and elucidate potential avenues for further improvement.

Genetic Algorithm Approach for Improved Design of a Variable Speed Axial-Flux Permanent-Magnet Synchronous Generator

Optimal design for an axial-flux permanent magnet synchronous generator (AFPMSG) using genetic algorithm (GA) is presented, and the condition for minimum active material cost is deduced. A computer-aided design procedure based on the results of the GA is proposed. In the design procedure the practical and performance characteristics are taken into account as some restrictions for the object function used in the optimization algorithm. A 30-kW AFPMSG with two parallel connected stators and rotor-surface PMs is designed using the developed program, and then 3-D finite-element analyses are carried out to validate the design procedure.

A Systematic Computer-Aided Product Design and Development Procedure: Case of Disinfectant Formulations

Product formulation design involves selecting a few ingredients from a large set through screening based on several criteria, and using the optimal proportion in the formulation. The limitation in the traditional strategy for chemical product formulation design is to carry out a large number of trials, which in most practical cases, is either economically infeasible or a very slow process. Furthermore, the presence of constraints, sometimes contradictory to some extent, further complicates the formulation design process. Such traditional trial-and-error and one-factor-at-a-time methodologies can be very cumbersome. They can also lead to a slow and high-cost process. The outcome of following such techniques does not usually lead to optimal designs. In this work, a methodology that deals with the complexity of product formulation design problem with contradictory constraints is presented and illustrated in a real case study. This methodology starts with defining needs for a new product and generating ideas. It then screens the candidate ingredients, using design of experiment techniques, and develops a model for each response. It then inverts the models using a nonlinear optimization technique, and obtains an optimal design for the product based on the desired properties. This methodology is proven to be more effective, faster, and less expensive in the development of new products or improvements on the existing ones. Furthermore, the final product is an optimal formulation, with respect to a preset performance measure and desired properties. The procedure is illustrated and tested on the case of disinfectant formulations. The optimized formulation was prepared, tested, and compared to an existing formulation. The optimized formulation faired significantly better than the existing product, in terms of technical and economic preference.

An Approach Based on Finite Element Method for CAD of Printed Antennas

A novel computer-aided design (CAD) procedure for microstrip antennas is proposed in this letter. It is based on a previously developed analysis methodology that combines the finite element method (FEM), domain decomposition, and a technique called multipurpose admittance matrix. This method is reformulated in order to allow continuous geometry variations of conducting surfaces, making a 2D-FEM optimization process possible. Measured and numerical results for a practical broadband microstrip antenna design demonstrate its robustness and versatility.

Integration of non-linear, radiation, and propagation CAD techniques for MIMO link design

The paper outlines an exhaustive computer-aided design (CAD) procedure for the circuit-level simulation of entire multi-input multi-output (MIMO) links. The multiple transmitting and receiving antennas are treated as multiport radiating systems characterized by electromagnetic (EM) analysis. The effects of mutual couplings in terms of the frequency-dependent near-field and far-field performance of each element are accounted for in a straightforward and rigorous way. The set of transmitters is treated as a unique non-linear system loaded by the multiport antenna, and is analyzed by non-linear circuit techniques. The same is done for the set of receivers. In order to establish the connection between transmitters and receivers, the radiated far-field is evaluated by EM analysis, and the field incident on each receiver antenna is computed by extending to the MIMO case an available ray tracing technique. EM theory is then used to describe the receiving array as a linear active multiport network. This technique allows analysis of several MIMO systems, exploiting different array element spatial locations and frequencies of operation in a straightforward and automatic way. Bit error rate (BER) computation and minimization are demonstrated at the circuit level.

Improved centrifugal compressor impeller optimization with a radial basis function network and principle component analysis

The development of a fast and reliable computer-aided design and optimization procedure for centrifugal compressors has attracted a great deal of attention both in the industry and in academia. Artificial neural networks (ANNs) have been widely used to create an approximate performance map to substitute the direct application of flow solvers in the optimization procedure. Although ANNs greatly decrease the computational time for the optimization, their accuracies still limit their applications. Furthermore, ANNs also bring errors to the final results. In this study, principal component analysis (PCA) or independent component analysis (ICA) is applied to transform the training database and make a radial basis function network (RBFN), a type of ANN, trained in a new coordinate system. The present study compares the accuracies of three different trained ANNs: RBFN, RBFN with PCA, and RBFN with ICA. Furthermore, the total performances of the centrifugal compressor impeller optimization procedures using these three different trained ANNs are compared. Genetic algorithm (GA) is used as an optimization method in the optimization procedure and influences of GA parameters on the optimization procedure performances are also studied. All results demonstrate that the application of PCA significantly increases the accuracy of trained ANN as well as the total performance of the centrifugal compressor impeller optimization procedure.

CAD-CAM construction of a provisional nasal prosthesis after ablative tumour surgery of the nose: a pilot case report

The computer-aided design of a nasal prosthesis based on pre-operative virtual laser scanning of the affected site was virtually adapted to the post-operative laser-scanned surface. The designed volume of the nose was rapidly prototyped and used to fabricate a provisional prosthesis and a computed tomography diagnostic template to check the available premaxilla bone for implants. The mould for the nasal prosthesis was prototyped using a computer-aided design and manufacturing (CAD-CAM) procedure. In addition, the mesiostructure of an eyeglasses-supported provisional prosthesis was also designed and prototyped using CAD-CAM procedures.

FE Analysis and Computer-Aided Design of a Sandwiched Axial-Flux Permanent Magnet Brushless DC Motor

In this paper, a comprehensive computer-aided design (CAD) procedure for an axial-flux permanent magnet brushless dc (PM BLDC) motor having a stator sandwiched between two permanent magnet rotors is presented. The basic output equations are derived and used for the design algorithm. The developed CAD program gives the design data and the calculated performances of the motor. The optimized ratio of outer diameter to the inner diameter is used to derive the sizing equation. The design variables such as airgap flux density, slot electric loading, winding factor, stacking factor, stator current density, slot space factor, magnet fraction, slot fraction, flux density in the stator back iron, etc., are assumed. Three different motors or rating 70 W, 2.2 kW, and 20 kW are designed using the developed program, and then three dimensional finite-element analyses are carried out to validate the designs

FE analysis and CAD of radial-flux surface mounted permanent magnet brushless DC motors

In this paper, a comprehensive computer-aided design (CAD) procedure for a radial-flux surface mounted permanent magnet brushless dc motor is presented. The design variables such as airgap flux density, slot electric loading, winding factor, stacking factor, stator current density, slot space factor, magnet fraction, slot fraction, flux density in the stator back iron, etc., are assumed. The basic output equations are derived and used for the design algorithm. The developed CAD program gives the design data and the calculated performances of the motor. Three different motors of rating 70 W, 2.2, and 20 kW are designed using the developed program and then finite-element analyses are carried out to validate the designs.

Computer aided design of multi-phase switched reluctance motor

In this paper, a comprehensive computer-aided design (CAD) procedure of multiphase switched reluctance motor (SRM) is presented. Better approach for calculation of the outer dimensions, phase inductance, flux linkage and losses, and also a different concept for calculating the average torque of the motor are incorporated in the CAD program. The average torque is calculated based on the most effective 15° (for 8∕6 SRM) of the static torque profile of the motor. A sample design of a 5hp SRM is presented in detail and the design is validated by conducting a two-dimensional finite element analysis of the motor.

Orthoses for Mild Scoliosis: A Prospective Study Comparing Traditional Plaster Mold Manufacturing With Fast, Noncontact, 3-Dimensional Acquisition

A prospective comparison of 2 different methods to make orthoses in mild scoliosis. To evaluate the therapeutic efficiency of orthoses made by a computer-aided design procedure. It is now possible to make orthoses by a computer-aided design procedure. In order to evaluate this new method, we carried out a comparative study between the traditional and computer-aided design-manufactured orthoses. In this prospective study, we compared the 2 methods by studying the cases of 30 adolescents with mild scoliosis. For each patient requiring orthopaedic treatment, we made 2 ortheses: 1 using the traditional method and 1 using the computer-aided design method. There were 26 girls and 4 boys whose average age was 13 years and 3 months. Each body jacket was successively used in random order following the same protocol. Neither the prescriber nor the patient knew the origin of the orthosis used. The final choice of the orthosis was made using 3 criteria: first, improvement of the scoliotic curves on the frontal and lateral radiologic planes, and second, the patient's impression of comfort. For the 30 cases, 13 traditional and 16 computer-aided design body jackets were chosen. In 1 case, no significant difference allowed us to chose one body jacket rather than the other. For the frontal radiologic correction, the better results were obtained 3 times with the computer-aided design body jacket, 5 times with the traditional one, and in 22 cases, the results were equivalent. For the lateral radiologic correction, the better results were obtained 11 times with the computer-aided design body jacket, 3 times with the traditional one, and in 16 cases, the results were equivalent. For the comfort of the 2 body jackets for each patient, the better results were obtained 12 times with the computer-aided design body jacket, 8 times with the traditional one, and in 10 cases, the results were equivalent. Based on our results, we believe that the computer-aided design procedure is equally efficient to traditional method for mild scoliotic curves.

Annealing Algorithm Applied in Optimum Design of 2.4 GHz and 5.2 GHz Dual-Wideband Microstrip Line Filters

This paper presents a computer-aided design procedure of simulated annealing algorithm to optimize dual-wideband microstrip line filters with symmetrical at least 500MHz bandwidths respectively. This method demonstrates the superiority of designing microstrip line dual-band filters. The value of characteristic impedances and electrical lengths of transmission lines synthesizing 2.4 GHz and 5.2 GHz dualband filters with a single input and a single output are adjusted to the annealing process by the optimization algorithm. The fabricated dual-wideband spectral transmittance and reflectance curves of these filters applying this method all effectively achieved desired high performances and resulted in a lower cost dual-band filters and open the way to commercial mass production. The method is applicable not only in 2.4 GHz and 5.2 GHz, but can be applied to any other multi-frequency bands.