Overlay Structures Research Articles

The Effect of Interpass Temperature on the Mechanical Properties and Microstructure of Components Made by the WAAM Method from Inconel 718 Alloy

The following study examines the impact of temperature on the deposition of components using Cold Metal Transfer–Wire Arc Additive Manufacturing technology. In the experiment, two overlay weld wall structures were created by applying an interpass temperature of 100 °C and without additional cooling. Subsequently, the microstructural and mechanical properties were observed. No changes in the microstructure due to the application of the interpass temperature were confirmed, and the microstructure of the manufactured components, in both cases, consisted of columnar dendrites. It was found that applying an interpass temperature reduced the average ultimate tensile strength by nearly 65 MPa and the average offset yield strength by 82 MPa. The influence of the cooling strategy on the resulting microstructure was not confirmed. Transmission electron microscopy analysis confirmed the presence of strengthening phases γ′/γ″ in both components; however, a larger amount of the strengthening phase γ″ was found in the component manufactured without the application of an interpass temperature.

Application of an overlay for spurious suppression of multi-layered surface acoustic wave resonators with double busbar configuration

Abstract This paper discusses the suppression of a spurious resonance called the gap mode which appears when the double busbar configuration is applied to multi-layered surface acoustic wave resonators. Two kinds of overlay structures are proposed for the gap mode mitigation. First, the use of lossy ones is studied. The results indicate that the lossy overlay can effectively mitigate the gap mode response when the viscosity is adequate. The layer thickness has a negligible impact on the mitigation. Then, the discussion is extended to the application of high-acoustic-velocity materials as the overlay. The resonance frequency of the gap mode can be moved to the upper-frequency side without affecting the main resonance by simply depositing a high-velocity overlay to the gap region. Finally, the comparison and choice of overlay materials are also studied. The results point out that Si3N4 is the optimum choice for industrial use.

Assessment of Asphalt Mixture Disk-Shaped Compact Tension Test Indexes for Reflective Cracking Performance

Abstract Disk-shaped compact tension (DCT) testing is a commonly used low-temperature fracture test to determine the cracking resistance of asphalt mixtures. The current testing specification only considers the fracture energy (Gf) from load-crack mouth opening displacement test data. However, Gf does not directly take into consideration the behavior of the post peak region of the curve, which may indicate the mixture’s ability to resist crack propagation and provide insight into fracture processes (e.g., crack growth velocity). It is possible to have two DCT specimens with similar Gf values but dramatically different load-displacement responses. The main focus of this paper is to make a comparative evaluation of various performance indexes developed for DCT fracture testing with respect to field reflective cracking performance of 10 full-scale asphalt concrete overlay test sections. This study evaluates Gf in addition to three other indexes: fracture strain tolerance (FST), rate-dependent cracking index (RDCI) and a proposed DCTIndex from Minnesota Department of Transportation that considers the post peak load-displacement behavior. An equivalent performance index approach is adopted to make comparisons of test sections with varying overlay structures in terms of thickness and material properties. Results from this study showed there was relatively good agreement between all equivalent laboratory performance indexes in identifying the best and worst performing overlay sections, according to normalized field performance indexes after approximately three years of service. In general, the equivalent FST and RDCI laboratory indexes rank test sections similarly, while equivalent Gf and DCTIndex have comparable ranking.

Structure- and Ligand-Based in silico Studies towards the Repurposing of Marine Bioactive Compounds to Target SARS-CoV-2

This work was a structured virtual screening for marine bioactive compounds with reported antiviral activities which were subjected to structure-based studies against SARS-CoV-2 co-crystallized proteins. The molecular docking of marine bioactive compounds against the main protease (Mpro, PDB ID: 6lu7 and 6y2f), the spike glycoprotein (PDB ID: 6vsb), and the RNA polymerase (PDB ID: 6m71) of SARS-CoV-2 was performed. Ligand-based approach with the inclusion of rapid overlay chemical structures (ROCS) was also addressed in order to examine the probability of these marine compounds sharing relevance and druggability with the reported drugs. Among the examined marine library, the highest scores in different virtual screening aspects were displayed by compounds with flavonoids core, acyl indole, and pyrrole carboxamide alkaloids. Moreover, a complete overlay with the co-crystallized ligands of Mpro was revealed by sceptrin and debromo-sceptrin. Thalassoilin (A-B) which was found in the Red Sea exhibited the highest binding and similarity outcomes among all target proteins. These data highlight the importance of marine natural metabolites in regard to further studies for discovering new drugs to combat the COVID-19 pandemic.

Effect of joint spacing and pavement thickness on concrete overlay performance

Concrete overlays provide cost-effective maintenance and rehabilitation strategies for pavement systems. A database has been developed in Iowa that records the historical performance of overlays based on records of International Roughness Index (IRI) and Pavement Condition Index (PCI) over a 20-year period. Based on these data concrete overlay service life has been modeled for various joint spacings. The data demonstrate that durability and service life can be improved. A review of PCI data indicates that improving construction quality to eliminate premature failure has the potential to add at least 10 years to the service life of PCC overlays. Even though concrete overlay technology is not a new concept, most of its design procedures still follow empirical methods, therefore this study applied AASHTOWare Pavement ME Design (Version 2.3.1) software to identify the effects of design para ms on concrete overlay service life. The theoretical insights provided by Pavement ME Design were compared with historical performance data and used to provide recommendations with respect to optimized joint spacing in overlay pavement structures. Comparison of the historical performance-related data with Pavement ME Design software results indicates that the Pavement ME Design software is conservative in predicting concrete overlay service life.

Analysis of the Fatigue Crack Propagation Process of the Stress-Absorption Layer of Composite Pavement Based on Reliability

The stress-absorption layer in cement concrete pavement delays the development of reflection cracks and is good at fatigue resistance. Laboratory investigations of the anti-crack performance of the high viscous asphalt sand stress-absorption layer (HVASAL) and rubber asphalt stress-absorption layer (RASAL) were carried out by force-controlled fatigue crack propagation tests, for which three types of overlay structures with three types of pre-crack (i.e., the middle crack, the side crack, and the 45° inclined crack) were designed. A probability model was established to describe the propagation of the fatigue cracks. The fatigue crack propagation, the fatigue life, the crack propagation rate, and the crack propagation mechanism of the three types of overlay structure were compared and analyzed. The results show that the stress-absorption layers have good anti-crack fatigue performance, and that the RASAL is better than the HVASAL. The crack propagation patterns of the three types of overlay structure were found. In the double logarithmic coordinate, the curves of the three types of cracks are straight lines with different intercepts and slopes. The probability model quantifies the relationship between the crack propagation rate and ∆K. The influences of the three types of crack on the fatigue properties of the asphalt overlays are different.

Fusion Imaging for EVAR with Mobile C-arm

Fusion imaging is a technique that facilitates endovascular navigation but is only available in hybrid rooms. The goal of this study was to evaluate the feasibility of fusion imaging with a mobile C-arm in a conventional operating room through the use of an angionavigation station. From May 2016 to June 2017, the study included all patients who underwent an aortic stent graft procedure in a conventional operating room with a mobile flat-panel detector (Cios Alpha, Siemens) connected to an angionavigation station (EndoNaut, Therenva). The intention was to perform preoperative 3D computerized tomography/perioperative 2D fluoroscopy fusion imaging using an automatic registration process. Registration was considered successful when the software was able to correctly overlay preoperative 3D vascular structures onto the fluoroscopy image. For EVAR, contrast dose, operation time, and fluoroscopy time (FT) were compared with those of a control group drawn from the department's database who underwent a procedure with a C-arm image intensifier. The study included 54 patients, and the procedures performed were 49 EVAR, 2 TEVAR, 2 IBD, and 1 FEVAR. Of the 178 registrations that were initialized, it was possible to use the fusion imaging in 170 cases, that is, a 95.5% success rate. In the EVAR comparison, there were no difference with the control group (n=103) for FT (21.9±12 vs. 19.5±13min; P=0.27), but less contrast agent was used in the group undergoing a procedure with the angionavigation station (42.3±22mL vs. 81.2±48mL; P<0.001), and operation time was shorter (114±44 vs. 140.8±38min; P<0.0001). Fusion imaging is feasible with a mobile C-arm in a conventional operating room and thus represents an alternative to hybrid rooms. Its clinical benefits should be evaluated in a randomized series, but our study already suggests that EVAR procedures might be facilitated with an angionavigation system.

An Improved Delay-Resistant and Reliable Hybrid Overlay for Peer-to-Peer Video Streaming in Wired and Wireless Networks

Live streaming applications become hugely popular in the Internet era. However, these applications place tremendous pressure on video servers. Peer-to-Peer (P2P) communication models are a wise solution to video server pressure due to their scalability and low cost. Many P2P streaming schemes have been proposed and deployed on the Internet. These approaches are mainly based on the tree, mesh, and hybrid overlay structures. However, most overlay structures are proposed for either wired or wireless networks, and their performance was not investigated for both wired and wireless networks. We propose a reputation-based, resilient, delay-resistant hybrid overlay streaming structure called AStream. This hybrid structure aims to multicast videos to peers with the primary goal of delivering video packets before the deadline and maintaining good video quality over both wired and wireless networks. The overlay evolves from tree to a hybrid structure consists of tree and mesh clusters over a period of time. Initially, a tree is constructed using arrival time and location-based approach and is then transformed to a hybrid overlay to reduce delays in video data delivery. Video continuity during peer dynamics is guaranteed by providing multiple parents and auxiliary connections. Simulations are carried out by applying the proposed scheme in both wired and wireless networks. We also investigate the additional delays incurred when the video server is located outside the Wi-Fi network compared to those when the video server is located inside the wireless mesh network. Simulation results show that AStream outperforms the existing overlay structures and delivers faster, better video content with reduced load on the underlying physical network.

Algade 9 i Aalborg – Husenes udvikling fra vikingetid til nutid

Algade 9 i Aalborg – Husenes udvikling fra vikingetid til nutid

Evaluation of microstructure and damage evolution for asphalt pavements in an advanced repeated load permanent deformation test using X-ray computed tomography

It is significant to capture the microstructure characteristics and evolution of asphalt mixtures since it is well related to the macroscopic pavement performance. The X-ray Computed Tomography (CT) technique is a suitable candidate to gather and analyse the image information of the internal structure for materials. An advanced repeated load permanent deformation (ARLPD) test that could largely simulate the confining pressure and temperature gradient of actual pavements was conducted on several typical newly constructed and overlay pavement structures. CT and digital image processing techniques were used to characterise the evolution behaviour of microstructure and damage in asphalt layers before and after testing at high temperatures. Combining the macroscopic pavement performance with microstructure evolution, the failure mechanism for different pavements and layers was finally discussed. It is found from the ARLPD test that newly constructed hot mix asphalt pavements show much better rutting resistance than the overlay pavements. The middle asphalt layer and the overlay layer, respectively, contribute approximate half of the total rut depth for newly constructed and overlay pavements. After testing, the change of air void content varies in different layers and pavements, indicating different rutting mechanisms (densification or shear flow). In the middle asphalt layer of overlay pavements, some cracks are formed with a great increase in air void aspect ratio and a significant decrease in air void number. Using the crack density as an indicator, the correlation of permanent deformation and cracks at high temperatures is preliminarily found.

3D P2P overlay over MANETs

We study the challenging problems of the mismatch between the overlay and the physical network and the resilience of the overlay structure in peer-to-peer (P2P) protocols over a mobile ad hoc network (MANET). Existing P2P protocols have used inflexible overlay structures to arrange peers and do not consider intra-neighbor relationships of peers when assigning logical identifiers. The intra-neighbor relationships of peers are crucial to exactly interpret the physical proximity of peers in an overlay and to avoid the mismatch between the overlay and the physical network that causes extensive routing overhead, larger average file discovery delay, increased false-negative ratio, and high average path-stretch. In this paper, we present a novel P2P overlay over MANETs that exploits a 3-dimensional overlay and 3D space that takes into account the physical intra-neighbor relationship of a peer and exploits a 3D-overlay to interpret that relationship. In the proposed protocol, each peer runs a distributed algorithm that exploits a 3D-overlay to calculate a consecutive logical identifier to a peer. Moreover, the protocol utilizes the 3D-overlay to maintain multi-paths to a destination peer that provides resilience against a node/link failure. Simulation results show that the proposed 3D-overlay outperforms the existing P2P overlay protocol in terms of routing overhead, average file-discovery delay, false-negative ratio, and average path-stretch.

Providing Fast Channel Switching in P2P IPTV Systems

In spite of the increasing deployment of IPTV services, various functionalities still need to be improved. One of the main challenges is a reduction in startup delays, especially in channel switchings, a problem which is quite relevant in P2P IPTV systems due to bandwidth limitations, as well as the employment of buffers and overlay structures. This paper presents and compares four novel schemes for providing fast channel switching that reduce the occurrence of latency. The results suggest that, in general, the proposed schemes are all capable of performing 68% of all channel switchings instantaneously on average. Moreover, the Fast 2 scheme, which presented the best performance, reduces the overall stream quality received less than 19%, on average.

A survey of channel switching schemes for IPTV

In spite of the increasing deployment of IPTV services, various functionalities still need to be improved. One of the main challenges is a reduction in startup delays, especially in channel switching, a problem that is quite relevant in IPTV systems due to bandwidth limitations, as well as the employment of buffers and distribution structures. The problem is essentially more serious in P2P IPTV systems, since the dynamic nature of P2P networks requires larger buffers and the exchange of more signaling messages to establish the overlay structures. Since users expect to be able to switch channels quickly, IPTV services must reduce startup delays to just a few seconds or even milliseconds. The aim of this article is to provide a survey of existing channel switching schemes for IPTV systems.

A Comparative Study of Fatigue Performance to Resist Reflective Cracking among three Different Stress-Absorbing Materials

Through full-scale fatigue test, a comparative study of the ability to resist temperature fatigue and load fatigue was performed among high elasticity rubber mastic stress-absorbing band, fiberglass-polyester paving mat and SAMPAVE stress-absorbing layer, which were technologies to prevent reflection cracking. And they were verified by engineering. The results suggest that the overlay structures with the old cement concrete pavement partially treated with high elasticity rubber mastic stress-absorbing band are of the best fatigue performance to prevent reflection crack caused by load, and its temperature fatigue performance is equivalent to the overlay including SAMPAVE stress-absorbing layer. At the same time, Rubber Mastic Stress-absorbing Band is the most economical way.

WE-E-BRB-11: Riview a Web-Based Viewer for Radiotherapy.

Collaborations involving radiotherapy data collection, such as the recently proposed international radiogenomics consortium, require robust, web-based tools to facilitate reviewing treatment planning information. We present the architecture and prototype characteristics for a web-based radiotherapy viewer. The web-based environment developed in this work consists of the following components: 1) Import of DICOM/RTOG data: CERR was leveraged to import DICOM/RTOG data and to convert to database friendly RT objects. 2) Extraction and Storage of RT objects: The scan and dose distributions were stored as .png files per slice and view plane. The file locations were written to the MySQL database. Structure contours and DVH curves were written to the database as numeric data. 3) Web interfaces to query, retrieve and visualize the RT objects: The Web application was developed using HTML 5 and Ruby on Rails (RoR) technology following the MVC philosophy. The open source ImageMagick library was utilized to overlay scan, dose and structures. The application allows users to (i) QA the treatment plans associated with a study, (ii) Query and Retrieve patients matching anonymized ID and study, (iii) Review up to 4 plans simultaneously in 4 window panes (iv) Plot DVH curves for the selected structures and dose distributions. A subset of data for lung cancer patients was used to prototype the system. Five user accounts were created to have access to this study. The scans, doses, structures and DVHs for 10 patients were made available via the web application. A web-based system to facilitate QA, and support Query, Retrieve and the Visualization of RT data was prototyped. The RIVIEW system was developed using open source and free technology like MySQL and RoR. We plan to extend the RIVIEW system further to be useful in clinical trial data collection, outcomes research, cohort plan review and evaluation.

SU‐E‐J‐52: Validation of 3D Structure Projection Onto 2D DRR in Commercial Treatment Planning Systems

The use of structure overlay on setup DRRs can aid the image alignment procedure for daily image-guided setup procedures. However, the accuracy of a 3D region-of-interest (ROI) projected on a 2D digitally reconstructed radiograph (DRR) has rarely been evaluated quantitatively. The goal of this study is to test the accuracy of two commercial treatment planning systems (TPS) in producing overlay structures on setup DRRs. We designed a novel method to identify landmarks which were on the boundary of the projected ROI on a DRR. The 3D ROIvolume is composed of a stack of 2D curves. We first mathematically project each 2D curve onto a beams-eye-view (BEV) plane. Next, we detectthe boundary points of the projected curves. Those boundary points serve aslandmarks. Finally, we project the binary mask of the 3D ROI volume using ray tracing method onto the BEV plane. This projected binary mask is used to exclude the false landmarks. Once those landmarks are detected, wecompute the distance between the landmarks and ROI outlines from the TPS. We applied our validation method to 13 ROIs from a lung patient and 4 simulated ROIs on 2 BEV DRRs for two different TPS (Eclipse and Pinnacle). Average distance between the landmarks and ROIoutlines was 0.5mm for both Eclipse and Pinnacle approaches, which is close to the pixel resolution of the DRR. The maximum distance andaverage maximum distance was 2mm and 1 mm, respectively, for both TPS.The maximum distance occurred at points where the ROI curve has a sharpchange between slices. The accuracy of Eclipse and Pinnacle ROI projection method seems to be acceptable to within 1mm althoughprojection error can be as large as 2mm when structure shape has a sharp variation from one slice to the next.

On Node Stability and Organization in Peer-to-Peer Video Streaming Systems

Recently, peer-to-peer video streaming technology has been widely suggested to support broadcasting videos over the Internet. Given that the application-layer nodes (peers) are autonomous and may join or leave at will. Dealing with node dynamics (known as churn) under the bandwidth and timing constraints for video streaming thus becomes a necessary yet challenging task. One conventional argument is that the stable nodes are too small a group to be effectively utilized. While we agree this argument from a whole session's point-of-view, in this paper, we argue that the significantly longer lifespans of the stable nodes allow each of them to appear in much more snapshots of the overlay than transient nodes and, as a result, they constitute a significant portion in every snapshot of the overlay, substantially affecting the performance of the overall system. Such observation has been verified by our trace analysis on PPLive, a large-scale peer-to-peer live streaming system, as well as analytical modeling based on node behaviors. Motivated by this, we further propose a tiered overlay design, with stable nodes being organized into a tier-1 backbone for serving tier-2 nodes. It offers a highly cost-effective and deployable alternative to proxy assisted designs. We develop a comprehensive set of algorithms for stable node identification and organization. Specifically, we present a novel structure, labeled tree (or LBTree in short), for the tier-1 overlay, which, leveraging stable peers, simultaneously achieves low overhead and high transmission reliability. Our tiered framework flexibly accommodates diverse existing overlay structures in the second tier. Through extensive simulations, we demonstrate that the customized optimization using selected stable nodes can greatly boost the streaming quality and also effectively reduce the control overhead.

Selfish Overlay Network Creation and Maintenance

A foundational issue underlying many overlay network applications ranging from routing to peer-to-peer file sharing is that of the network formation, i.e., folding new arrivals into an existing overlay, and rewiring to cope with changing network conditions. Previous work has considered the problem from two perspectives: devising practical heuristics for the case of cooperative peers and performing game-theoretic analysis for the case of selfish peers. In this paper, we unify the aforementioned thrusts by defining and studying the selfish neighbor selection (SNS) game and its application to overlay routing. At the heart of SNS stands the restriction that peers are allowed up to a certain number of neighbors. This makes SNS substantially different from existing network formation games that impose no bounds on peer degrees. Having bounded degrees has important practical consequences as it permits the creation of overlay structures that require O(n) instead of O(n2) link monitoring overhead. We show that a node's “best response” wiring strategy amounts to solving a k -median problem on asymmetric distance. Best-response wirings have substantial practical utility as they permit selfish nodes to reap substantial performance benefits when connecting to overlays of nonselfish nodes. A more intricate consequence is that even nonselfish nodes can benefit from the existence of some selfish nodes since the latter, via their local optimizations, create a highly optimized backbone, upon which even simple heuristic wirings yield good performance. To capitalize on the above properties, we design, build, and deploy EGOIST, an SNS-inspired prototype overlay routing system for PlanetLab. We demonstrate that EGOIST outperforms existing heuristic overlays on a variety of performance metrics, including delay, available bandwidth, and node utilization, while it remains competitive with an optimal but unscalable full-mesh overlay.

How the Shift to Individualize Supports Gets Stuck and The First Step Out of Gridlock

Many mature and successful service providers continue to find their identity in the heritage of moving people with developmental disabilities out of public institutions. Significant achievements such as providing residential alternatives to large facilities do not immune providers from criticism emerging from a growing demand for individualized supports. The Individualized Supports Think Tank, a group of self-advocates, parents, and service providers convened by the Self-Advocacy Association of New York State (2007) expressed this demand: We define individualized supports as an array of supports, services and resources that are person-centered, based on the unique interests and needs of the person, afford the person as

Overlay measurements by Mueller polarimetry in back focal plane

Angle resolved Mueller polarimetry implemented as polarimetric imaging of a back focal plane of a high NA microscope objective has already demonstrated a good potential for CD metrology. Here we present the experimental and numerical results indicating that this technique may also be competitive for the measurements of overlay error δ. A series of samples of superimposed gratings with well controlled overlay errors have been manufactured and measured with the angle resolved Mueller polarimeter. The overlay targets were 20-μm wide. When the overlay error is δ is equal to 0, absolute values of elements of real 4×4 Mueller matrix M are invariant by matrix transposition. Otherwise this symmetry breaks down. Consequently, we define the following overlay estimator matrix as E = |M| − |M|t. The simulations show that matrix element E14 is the most sensitive to the overlay error. The scalar estimator of E14 was calculated by averaging the pixel values over a specifically chosen mask. This estimator is found to vary linearly with δ for overlay values up to 50 nm. Our technique allows entering small overlay marks (down to 5-μm wide). Only one target measurement is needed for each overlay direction. The actual overlay value can be determined without detailed simulation of the structure provided two calibrated overlay structures are available for each direction.