Physical models for numerical simulation of Si-based nanoscale FETs and sensors

To continuously improve the performance of metal-oxide-semiconductor field-effect-transistors (MOSFETs), innovative device architectures, gate stack engineering and mobility enhancement techniques are under investigation. In this framework, new physics-based models for Technology Computer-Aided-Design (TCAD) simulation tools are needed to accurately predict the performance of upcoming nanoscale devices and to provide guidelines for their optimization. In this thesis, advanced physically-based mobility models for ultrathin body (UTB) devices with either planar or vertical architectures such as single-gate silicon-on-insulator (SOI) field-effect transistors (FETs), double-gate FETs, FinFETs and silicon nanowire FETs, integrating strain technology and high-κ gate stacks are presented. The effective mobility of the two-dimensional electron/hole gas in a UTB FETs channel is calculated taking into account its tensorial nature and the quantization effects. All the scattering events relevant for thin silicon films and for high-κ dielectrics and metal gates have been addressed and modeled for UTB FETs on differently oriented substrates. The effects of mechanical stress on (100) and (110) silicon band structures have been modeled for a generic stress configuration. Performance will also derive from heterogeneity, coming from the increasing diversity of functions integrated on complementary metal-oxide-semiconductor (CMOS) platforms. For example, new architectural concepts are of interest not only to extend the FET scaling process, but also to develop innovative sensor applications. Benefiting from properties like large surface-to-volume ratio and extreme sensitivity to surface modifications, silicon-nanowire-based sensors are gaining special attention in research. In this thesis, a comprehensive analysis of the physical effects playing a role in the detection of gas molecules is carried out by TCAD simulations combined with interface characterization techniques. The complex interaction of charge transport in silicon nanowires of different dimensions with interface trap states and remote charges is addressed to correctly reproduce experimental results of recently fabricated gas nanosensors.

Combined bone and soft-tissue augmentation surgery in temporo-orbital contour reconstruction

Temporal hollowing due to temporal muscle atrophy after standard skull base surgery is common. Various techniques have been previously described to correct the disfiguring defect. Most often reconstruction is performed using freehand molded polymethylmethacrylate cement. This method and material are insufficient in terms of aesthetic results and implant characteristics. We herein propose reconstruction of such defects with a polyetheretherketone (PEEK)-based patient-specific implant (PSI) including soft-tissue augmentation to preserve normal facial topography. We describe a patient who presented with a large temporo-orbital hemangioma that had been repaired with polymethylmethacrylate 25 years earlier. Because of a toxic skin atrophy fistula, followed by infection and meningitis, this initial implant had to be removed. The large, disfiguring temporo-orbital defect was reconstructed with a PEEK-based PSI. The lateral orbital wall and the temporal muscle atrophy were augmented with computer-aided design and surface modeling techniques. The operative procedure to implant and adopt the reconstructed PEEK-based PSI was simple, and an excellent cosmetic outcome was achieved. The postoperative clinical course was uneventful over a 5-year follow-up period. Polyetheretherketone-based combined bony and soft contour remodeling is a feasible and effective method for cranioplasty including combined bone and soft-tissue reconstruction of temporo-orbital defects. Manual reconstruction of this cosmetically delicate area carries an exceptional risk of disfiguring results. Augmentation surgery in this anatomic location needs accurate PSIs to achieve satisfactory cosmetic results. The cosmetic outcome achieved in this case is superior compared with previously reported techniques.

Light curing through glass ceramics with a second- and a third-generation LED curing unit: effect of curing mode on the degree of conversion of dual-curing resin cements

Objectives The aim of this study was to measure the degree of conversion (DC) of five dual-curing resin cements after different curing modes with a second- and a third-generation light-emitting diode (LED) curing unit. Additionally, irradiance of both light curing units was measured at increasing distances and through discs of two glass ceramics for computer-aided design/manufacturing (CAD/CAM). Materials and methods Irradiance and spectra of the Elipar FreeLight 2 (Standard Mode (SM)) and of the VALO light curing unit (High Power Mode (HPM) and Xtra Power Mode (XPM)) were measured with a MARC radiometer. Irradiance was measured at increasing distances (control) and through discs (1.5 to 6 mm thickness) of IPS Empress CAD and IPS e.max CAD. DC of Panavia F2.0, RelyX Unicem 2 Automix, SpeedCEM, BisCem, and BeautiCem SA was measured with an attenuated total reflectance–Fourier transform infrared spectrometer when self-cured (negative control) or light cured in SM for 40 s, HPM for 32 s, or XPM for 18 s. Light curing was performed directly (positive control) or through discs of either 1.5- or 3-mm thickness of IPS Empress CAD or IPS e.max CAD. DC was analysed with Kruskal–Wallis tests followed by pairwise Wilcoxon rank sum tests (α = 0.05). Results Maximum irradiances were 1,545 mW/cm2 (SM), 2,179 mW/cm2 (HPM), and 4,156 mW/cm2 (XPM), and all irradiances decreased by >80 % through discs of 1.5 mm, ≥95 % through 3 mm, and up to >99 % through 6 mm. Generally, self-curing resulted in the lowest DC. For some cements, direct light curing did not result in higher DC compared to when light cured through ceramic discs. For other cements, light curing through ceramic discs of 3 mm generally reduced DC. Conclusions Light curing was favourable for dual-curing cements. Some cements were more susceptible to variations in curing mode than others. Clinical relevance When light curing a given cement, the higher irradiances of the third-generation LED curing unit resulted in similar DC compared to the second-generation one, though at shorter light curing times.

Surface Roughness and Microhardness of Two Recent CAD/CAM-Materials After Storage

Objectives: To investigate surface roughness and microhardness of two recent resin-ceramic materials for computer-aided design/computer-aided manufacturing (CAD/CAM) after polishing with three polishing systems. Surface roughness and microhardness were measured immediately after polishing and after six months storage including monthly artificial toothbrushing. Methods: Sixty specimens of Lava Ultimate (3M ESPE) and 60 specimens of VITA ENAMIC (VITA Zahnfabrik) were roughened in a standardized manner and polished with one of three polishing systems (n=20/group): Sof-Lex XT discs (SOFLEX; three-step (medium-superfine); 3M ESPE), VITA Polishing Set Clinical (VITA; two-step; VITA Zahnfabrik), or KENDA Unicus (KENDA; one-step; KENDA Dental). Surface roughness (Ra; μm) was measured with a profilometer and microhardness (Vickers; VHN) with a surface hardness indentation device. Ra and VHN were measured immediately after polishing and after six months storage (tap water, 37°C) including monthly artificial toothbrushing (500 cycles/month, toothpaste RDA ~70). Ra- and VHN-values were analysed with nonparametric ANOVA followed by Wilcoxon rank sum tests (α=0.05). Results: For Lava Ultimate, Ra (mean [standard deviation] before/after storage) remained the same when polished with SOFLEX (0.18 [0.09]/0.19 [0.10]; p=0.18), increased significantly with VITA (1.10 [0.44]/1.27 [0.39]; p=0.0001), and decreased significantly with KENDA (0.35 [0.07]/0.33 [0.08]; p=0.03). VHN (mean [standard deviation] before/after storage) decreased significantly regardless of polishing system (SOFLEX: 134.1 [5.6]/116.4 [3.6], VITA: 138.2 [10.5]/115.4 [5.9], KENDA: 135.1 [6.2]/116.7 [6.3]; all p<0.0001). For VITA ENAMIC, Ra (mean [standard deviation] before/after storage) increased significantly when polished with SOFLEX (0.37 [0.18]/0.41 [0.14]; p=0.01) and remained the same with VITA (1.32 [0.37]/1.31 [0.40]; p=0.58) and with KENDA (0.81 [0.35]/0.78 [0.32]; p=0.21). VHN (mean [standard deviation] before/after storage) remained the same regardless of polishing system (SOFLEX: 284.9 [24.6]/282.4 [31.8], VITA: 284.6 [28.5]/276.4 [25.8], KENDA: 292.6 [26.9]/282.9 [24.3]; p=0.42-1.00). Conclusion: Surface roughness and microhardness of Lava Ultimate was more affected by storage and artificial toothbrushing than was VITA ENAMIC.

Technical complications and failures of zirconia-based prostheses supported by implants followed up to 7 years: a case series.

PURPOSE To evaluate technical complications and failures of zirconia-based fixed prostheses supported by implants. MATERIALS AND METHODS Consecutive patients received zirconia-based single crowns (SCs) and fixed dental prostheses (FDPs) on implants in a private clinical setting between 2005 and 2010. One dentist performed all surgical and prosthetic procedures, and one master technician performed and coordinated all laboratory procedures. One-piece computer-aided design/ computer-assisted manufacture technology was used to fabricate abutments and frameworks, which were directly connected at the implant level, where possible. All patients were involved in a recall maintenance program and were finally reviewed in 2012. Data on framework fractures, chipping of veneering ceramics, and other technical complications were recorded. The primary endpoint was failure of the prostheses, ie, the need for a complete remake. A life table analysis was calculated. RESULTS A total of 289 implants supported 193 zirconia-based prostheses (120 SCs and 73 FDPs) in 127 patients (51 men, 76 women; average age: 62.5 ± 13.4 years) who were reviewed in 2012. Twenty-five (13%) prostheses were cemented on 44 zirconia abutments and 168 (87%) prostheses were screw-retained directly at the implant level. Fracture of 3 frameworks (1 SC, 2 FDPs) was recorded, and significant chipping resulted in the remake of 3 prostheses (1 SC, 2 FDPs). The 7-year cumulative survival rate was 96.4% ± 1.99%. Minor complications comprised 5 loose screws (these were retightened), small chips associated with 3 prostheses (these were polished), and dislodgement of 3 prostheses (these were recemented). Overall, 176 prostheses remained free of technical problems. CONCLUSIONS Zirconia-based prostheses screwed directly to implants are clinically successful in the short and medium term.

Stiffness, Strength, and Failure Modes of Implant-Supported Monolithic Lithium Disilicate Crowns: Influence of Titanium and Zirconia Abutments

PURPOSE The objective of this study was to evaluate stiffness, strength, and failure modes of monolithic crowns produced using computer-aided design/computer-assisted manufacture, which are connected to diverse titanium and zirconia abutments on an implant system with tapered, internal connections. MATERIALS AND METHODS Twenty monolithic lithium disilicate (LS2) crowns were constructed and loaded on bone level-type implants in a universal testing machine under quasistatic conditions according to DIN ISO 14801. Comparative analysis included a 2 × 2 format: prefabricated titanium abutments using proprietary bonding bases (group A) vs nonproprietary bonding bases (group B), and customized zirconia abutments using proprietary Straumann CARES (group C) vs nonproprietary Astra Atlantis (group D) material. Stiffness and strength were assessed and calculated statistically with the Wilcoxon rank sum test. Cross-sections of each tested group were inspected microscopically. RESULTS Loaded LS2 crowns, implants, and abutment screws in all tested specimens (groups A, B, C, and D) did not show any visible fractures. For an analysis of titanium abutments (groups A and B), stiffness and strength showed equally high stability. In contrast, proprietary and nonproprietary customized zirconia abutments exhibited statistically significant differences with a mean strength of 366 N (Astra) and 541 N (CARES) (P < .05); as well as a mean stiffness of 884 N/mm (Astra) and 1,751 N/mm (CARES) (P < .05), respectively. Microscopic cross-sections revealed cracks in all zirconia abutments (groups C and D) below the implant shoulder. CONCLUSION Depending on the abutment design, prefabricated titanium abutment and proprietary customized zirconia implant-abutment connections in conjunction with monolithic LS2 crowns had the best results in this laboratory investigation.

Time-Efficiency Analysis Comparing Digital and Conventional Workflows for Implant Crowns: A Prospective Clinical Crossover Trial

PURPOSE To compare time-efficiency in the production of implant crowns using a digital workflow versus the conventional pathway. MATERIALS AND METHODS This prospective clinical study used a crossover design that included 20 study participants receiving single-tooth replacements in posterior sites. Each patient received a customized titanium abutment plus a computer-aided design/computer-assisted manufacture (CAD/CAM) zirconia suprastructure (for those in the test group, using digital workflow) and a standardized titanium abutment plus a porcelain-fused-to-metal crown (for those in the control group, using a conventional pathway). The start of the implant prosthetic treatment was established as the baseline. Time-efficiency analysis was defined as the primary outcome, and was measured for every single clinical and laboratory work step in minutes. Statistical analysis was calculated with the Wilcoxon rank sum test. RESULTS All crowns could be provided within two clinical appointments, independent of the manufacturing process. The mean total production time, as the sum of clinical plus laboratory work steps, was significantly different. The mean ± standard deviation (SD) time was 185.4 ± 17.9 minutes for the digital workflow process and 223.0 ± 26.2 minutes for the conventional pathway (P = .0001). Therefore, digital processing for overall treatment was 16% faster. Detailed analysis for the clinical treatment revealed a significantly reduced mean ± SD chair time of 27.3 ± 3.4 minutes for the test group compared with 33.2 ± 4.9 minutes for the control group (P = .0001). Similar results were found for the mean laboratory work time, with a significant decrease of 158.1 ± 17.2 minutes for the test group vs 189.8 ± 25.3 minutes for the control group (P = .0001). CONCLUSION Only a few studies have investigated efficiency parameters of digital workflows compared with conventional pathways in implant dental medicine. This investigation shows that the digital workflow seems to be more time-efficient than the established conventional production pathway for fixed implant-supported crowns. Both clinical chair time and laboratory manufacturing steps could be effectively shortened with the digital process of intraoral scanning plus CAD/CAM technology.

Programmed design of ship forms

This paper describes a new category of CAD applications devoted to the definition and parameterization of hull forms, called programmed design. Programmed design relies on two prerequisites. The first one is a product model with a variety of types large enough to face the modeling of any type of ship. The second one is a design language dedicated to create the product model. The main purpose of the language is to publish the modeling algorithms of the application in the designer knowledge domain to let the designer create parametric model scripts. The programmed design is an evolution of the parametric design but it is not just parametric design. It is a tool to create parametric design tools. It provides a methodology to extract the design knowledge by abstracting a design experience in order to store and reuse it. Programmed design is related with the organizational and architectural aspects of the CAD applications but not with the development of modeling algorithms. It is built on top and relies on existing algorithms provided by a comprehensive product model. Programmed design can be useful to develop new applications, to support the evolution of existing applications or even to integrate different types of application in a single one. A three-level software architecture is proposed to make the implementation of the programmed design easier. These levels are the conceptual level based on the design language, the mathematical level based on the geometric formulation of the product model and the visual level based on the polyhedral representation of the model as required by the graphic card. Finally, some scenarios of the use of programmed design are discussed. For instance, the development of specialized parametric hull form generators for a ship type or a family of ships or the creation of palettes of hull form components to be used as parametric design patterns. Also two new processes of reverse engineering which can considerably improve the application have been detected: the creation of the mathematical level from the visual level and the creation of the conceptual level from the mathematical level. © 2012 Elsevier Ltd. All rights reserved. 1. Introduction

Geometric documentation of the flour factory "El Puente Colgante" in Aranjuez (Madrid).

The goal of this communication is to offer, through computer-aided design tools, a methodology to recover and virtually reconstruct disappeared buildings of our industrial historical heritage. It will be applied to the case of the flour factory "El Puente Colgante" (The Suspended Bridge) in Aranjuez, which was demolished in 2001. The process is as follows: After a historical analysis of the evolution in time of the flour factory, a field work provides data allowing an info graphic reconstruction of the factory. Once this information has been processed, a lifting of the current state is made with AutoCAD, and a three-dimensional model is built with the Rhinoceros application. Then images of the ensemble are obtained with the applications Rhinoceros and V-Ray, ending with a postproduction with Photoshop. The proposed methodology has permitted to obtain a three-dimensional model of the flour factory ?El Puente Colgante? in Aranjuez, with an accurate virtual reconstruction of its original state prior to demolition. The procedure exposed is susceptible to be generalized for any other example of industrial architecture.

Conceptual plan for an interactive highway safety design model. Final report.

Federal Highway Administration, Office of Safety and Traffic Operations Research and Development, McLean Va.

Experimental and formal language design applied to control constructs for interactive computing /

Vita.