Academic literature on the topic 'Single Replacement Design'
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Journal articles on the topic "Single Replacement Design"
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Ashraf, Yasir, Hafiz Javaid Iqbal, Shanaka Senevirathana, and Tanweer Ashraf. "Has the modern design of Attune total knee replacement improved outcome in patients with isolated patellofemoral arthritis?" Journal of Orthopaedic Surgery 28, no. 3 (May 1, 2020): 230949902097555. http://dx.doi.org/10.1177/2309499020975553.
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Introduction and Aim: Modern knee replacements aim to improve patient function in arthritis affecting different compartments of the knee. This study evaluates the Patient Reported Outcome Measure (PROM) and functional outcome of a modern total knee replacement (Attune, DePuy) in patients with isolated patellofemoral arthritis. Methods: A total of 50 consecutive patients with isolated unilateral patellofemoral arthritis having had Attune total knee replacements at a single institution between 2010 and 2016 were prospectively studied. Five patients who developed symptoms on the opposite side during the study and two patients lost to follow-up were excluded. One patient needed early revision for loosening, leaving a total of 42 patients to be followed up over a period of 4 years. The Oxford Knee score (OKS) and Knee Injury and Osteoarthritis Outcome Score (KOOS) recorded pre-operatively and at follow-up was compared. A Functional assessment at around 8 months after operation was undertaken. Results: At average follow-up of 24 months the mean OKS score improved by 15 points and the KOOS score improved by 20 points. Final KOOS sub-score for Pain was 80, Symptom 80, and ADL 82, Sports & Recreation 32 and QOL 60. Functional assessment at mean 8 months showed that a significant number of patients were able to Kneel (50%); Sit cross legged (23%); sit on their heel (23%) and were able do a single leg dip test (86%). Conclusion: This unique study of a modern design total knee replacement (Attune) in patients with isolated unilateral patellofemoral arthritis shows good PROM scores at 2 years and good functional assessment results at 8 months. The PROM scores are marginally better than the published results with Attune’s predecessor, in a similar cohort of patients, but falls short of the published results of patellofemoral replacement implants. Large randomised comparative studies between traditional and the modern implant design is recommended to answer the question if design modification has influenced clinical outcome in patients with patellofemoral arthritis.
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Mushtaq, Nadeem, David Isaac, Katherine Dillow, Paul Gill, and Alexander Liddle. "Patient-Reported Outcomes following Single- and Multiple-Radius Total Knee Replacement: A Randomized, Controlled Trial." Journal of Knee Surgery 31, no. 01 (May 5, 2017): 087–91. http://dx.doi.org/10.1055/s-0037-1602132.
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AbstractAlthough single-radius (SR) designs of total knee replacement (TKR) have theoretical benefits, the clinical advantage conferred by such designs is unknown. The aim of this randomized, controlled study was to compare the short-term clinical outcomes of the two design rationales. A total of 105 knees were randomized to receive either a single radius (Scorpio, Stryker; SR Group) or multiple radius (AGC, Zimmer Biomet; MR group) TKR. Patient-reported outcomes (Oxford Knee Score [OKS] and Knee Society Score [KSS]) were collected at 6 weeks, 6 months, and 1 year following surgery. No knees were revised. There was no difference in primary outcomes: OKS was 39.5 (95% confidence interval [CI]: 36.9–42.1) in the SR group and 38.1 (95% CI: 36.0–40.3) in the MR group (p = 0.40). KSS was 168.4 (95% CI: 159.8–177.0) in the SR group; 159.5 (95% CI 150.5–168.5) in the MR group (p = 0.16). There was a small but statistically significant difference in the degree of change of the objective subscale of the KSS, favoring the SR design (p = 0.04), but this is of uncertain clinical relevance. The reported benefits of SR designs do not provide demonstrable functional advantages in the short term.
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Murali, R., and Dr R. Rajappan. "Design and Analysis of Interpretation for Orthopedic Plate with Titanium Alloy." International Journal for Research in Applied Science and Engineering Technology 10, no. 7 (July 31, 2022): 4127–33. http://dx.doi.org/10.22214/ijraset.2022.45955.
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Abstract: The bone is considered as a linear-elastic, isotropic, and homogeneous materials. Trauma is a major cause of death and disability in both developed and developing nations. The mainly consider interpretation of accident after healing orthopaedic surgery plate replacement material design, evaluation, machining and optimization can be consider in this project. In this project setup is simply replacement method for three models of healing plate of single hole, four holes and six holes plate design in Solid Works. Evaluation process used in 3D finite element methods for a fractured bone with three models of titanium alloy plates is analysed using ANSYS workbench.
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Hanipah, Mohd Razali, Shahin Mansor, M. R. M. Akramin, and Akhtar Razul Razali. "Design and parametric characterization of flexure bearing as automotive valve spring replacement." Journal of Mechanical Engineering and Sciences 13, no. 1 (March 28, 2019): 4704–17. http://dx.doi.org/10.15282/jmes.13.1.2019.25.0395.
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Automotive valve springs occupy substantial space in the cylinder head of an internal combustion engine. In this paper, the design and analyses of a flat spring concept, known as flexure bearing are presented. Further, design approach, characteristics and parametric characterizations of a single-piece flexure bearing concept are outlined. Finite element analysis was used in examining the flexure bearing strength for different designs, materials and thicknesses. The results show that the maximum stress values are independent of the material types when the number of arm is three and above. The strain values are limited to less than 1% for all materials when the thickness is more than 1mm. The results have provided characteristics for future selection of the flexure bearing in relation to the intended axial displacement.
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Clarke, Henry D., Timothy A. Damron, Robert T. Trousdale, Franklin H. Sim, and Dirk R. Larson. "Head and Neck Replacement Prostheses in Revision Hip Arthroplasty: Experience With a Single Modern Design." Orthopedics 22, no. 3 (March 1999): 313–18. http://dx.doi.org/10.3928/0147-7447-19990301-07.
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Tu, Tsung-Hsi, Jau-Ching Wu, Li-Yu Fay, Chin-Chu Ko, Wen-Cheng Huang, and Henrich Cheng. "Vertebral body split fracture after a single-level cervical total disc replacement." Journal of Neurosurgery: Spine 16, no. 3 (March 2012): 231–35. http://dx.doi.org/10.3171/2011.11.spine11210.
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Cervical total disc replacement (TDR) is a viable option for the surgical treatment of degenerative disc disease. This 67-year-old nonsmoking male patient underwent single-level ProDisc-C cervical TDR at C5–6 without any intraoperative problem. His radicular pain improved and he had no neck pain immediately after the operation. However, on postoperative Day 3, a radiograph demonstrated a vertical split fracture of the C-5 vertebra. This fracture was managed conservatively, and 2 years postoperatively a follow-up CT scan demonstrated stable device position and fusion of the fracture. Although the linear fracture caused no neurological symptoms or device migration, the authors advocate prudence in selection and installation of keel-design prostheses, even in a single-level cervical TDR scenario.
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Jain, Nickul Saral, Ailene Nguyen, Blake Formanek, Ram Alluri, Zorica Buser, Ray Hah, and Jeffrey Chun Wang. "Cervical Disc Replacement: Trends, Costs, and Complications." Asian Spine Journal 14, no. 5 (October 31, 2020): 647–54. http://dx.doi.org/10.31616/asj.2019.0246.
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Study Design: Retrospective review of insurance database.Purpose: To investigate national trends, complications, and costs after cervical disc replacement (CDR) using an administrative insurance database representative of the United States population.Overview of Literature: As CDR continues to be used to treat patients with cervical stenosis, it is important to gain a better understanding of its use on a national level, potential complications, and cost. This information will allow for optimal patient counseling, risk stratification, and healthcare cost assessments. Several prior studies have investigated complications associated with CDR, but they have been limited by small sample size, single institution experiences, limited follow-up, and potential conflicts of interest.Methods: Patients who underwent single or multilevel CDR between 2007 and 2015 were identified using an insurance database. We collected data on annual trends, reimbursement costs, patient demographic information, hospital information, and information on complications from the time of operation to 1 year postoperative.Results: Total of 293 patients underwent either single or multilevel CDR. The number of procedures increased nonlinearly over time at an average of 17% per year, with a greater increase seen in the outpatient setting. Less than 3.7% of patients had new onset pain within 1 year after CDR. Within 1 year, 12.3% of patients reported a mechanical and/or bone-related complication. There were no patients who indicated a new nerve injury within 6 months of follow-up. Less than 3.7% of patients presented with dysphagia or dysphonia within 6 months, infection within 3 months, or a revision or reoperation within 1 year. Average reimbursement for single-level inpatient versus outpatient CDR was US $33,696.28 and US $34,675.12, respectively (p =0.29).Conclusions: This study demonstrated that the use of CDR continued to increase. The most common complication was mechanical and/or bone-related, and cost analysis demonstrated no significant difference between inpatient and outpatient CDR.
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Naumovic, Milica. "Comparative study of zero effects in pole-placement control system design via the shift and delta transforms." Facta universitatis - series: Electronics and Energetics 18, no. 3 (2005): 439–51. http://dx.doi.org/10.2298/fuee0503439n.
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This paper deals with the special replacement of the shift operator and its associated z transform by delta operator and ? transform, respectively. The aim of the paper is to clarify the role of zeros of discretized linear single input single output continuous-time systems modeled by shift and delta operators. In particular, the effect of zero dynamics on the control system design based on classical pole-zero assignment in the case of both operators is considered. The analysis is illustrated by simulation results.
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Mohapatra, Eleena, Jhansirani Jena, Devika Jena, Sanghamitra Das, and Taraprasanna Dash. "Design technique co-optimization approach to GAA FETs for inverter design at advanced technology node." Nanomaterials and Energy 12, no. 2 (June 1, 2023): 1–7. http://dx.doi.org/10.1680/jnaen.23.00029.
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Gate-all-around Nanosheet field-effect transistor (GAA-NSFET) is a potential replacement for the state-of-art FinFET devices at advanced technology nodes. In this article, the impact of process-induced variability such as gate work function variation (WFV) on NSFETs using 3D TCAD numerical device simulation is studied. The WFV of NSFETs and NWFETs using multiple stack channels are also analyzed. The fluctuation in the threshold voltage (σVTH) and on-current (σION) of NSFETs is mainly affected by the WFV of the metal gate. It is investigated that single and 3-stacked NSFET shows superior immunity to WFV compared to NWFET. Furthermore, a layout-based NSFET inverter design using the DTCO technique is followed and the advantages of the stacked NSFET in terms of delay, power dissipation and switching energy are also reported.
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Protea, Liviu-Bogdan, and Cristian-Mircea Muscai. "Design of low voltage electrical circuits for industrial receivers." Studia Universitatis Babeș-Bolyai Engineering 67, no. 1 (November 11, 2022): 216–23. http://dx.doi.org/10.24193/subbeng.2022.1.21.
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The paper presents the creation of a software for designing, verifying and analyzing voltage drops on electrical circuits, taking into account the classic design formulas and also the reactance of low-voltage electric cables. With the help of the application, it is possible to dimension and verify the existing electrical circuits as well as those of the single-wire schemes being designed as a result of the modernization or replacement of equipment in existing distribution networks. The application can be used for designing general consumers or for electrical equipment operated with direct start, star-delta or frequency converter electric motors.
Book chapters on the topic "Single Replacement Design"
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Farías, Oscar, Pablo Cornejo, Cristian Cuevas, Jorge Jimenez, Meylí Valín, Claudio Garcés, and Sebastian Gallardo. "Design of a Condensing Heat Recovery Integrated with an Electrostatic Precipitator for Wood Heaters." In Proceedings of the XV Ibero-American Congress of Mechanical Engineering, 210–16. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-38563-6_31.
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AbstractHigh emission of particulate matter from fixed sources of biomass combustion and the effects on the health of the population have driven the implementation of public policies for changes in the energy matrix and a technological replacement in Chile. Due to this, a prototype of a condensing heat exchanger is developed integrating an electrostatic precipitator, seeking to enhance the positive effects of these technologies in a single and relatively compact device. The state of the art shows similar developments, but with high levels of complexity in construction, as a shell and tube heat exchanger, that is why the concept of a thermocannon was optimized to condense the moisture present in the fumes and reduce smoke emissions through an electric field. It is expected that using an electrostatic precipitator, up to 90% of particulate matter emissions will be captured, and thermal efficiencies of an additional 9%. For its design, heat transfer and thermodynamics models were used and validated through CFD modeling.
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Ark-Yıldırım, Ceren, and Marc Smyrl. "Does Cash Transfer Promote Market Citizenship?" In Social Cash Transfer in Turkey, 143–49. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-70381-3_7.
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AbstractThe most obvious conclusion of this book is that there is no single Turkish experience. Nor can we reach definitive once-and-for-all conclusions about the impact of CT as an instrument of social assistance. Comparison among our cases highlights variables grounded in local conditions and policy design that help determine the outcome of CT projects, and whose relevance extends far beyond Turkey. Among these are human and financial resources, but also of the capacity for local knowledge. When these allow consistent and appropriate targeting, CT can provide an important step in the direction of inclusion and equality in a market context. It would be misleading, however, to believe that this instrument on its own is sufficient. At the core of market citizenship is the dignity conferred not only by paying one’s own way, but also by earning one’s own way: CT instruments work best as a complement to, not replacement for, access to the official labor market.
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Kelly, Ashley Scott, and Xiaoxuan Lu. "Western Alternative Development and Chinese Development." In Critical Landscape Planning during the Belt and Road Initiative, 127–58. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-4067-4_6.
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AbstractThis chapter, Western alternative development and Chinese development, presents two strategic planning proposals that are generated from frictions between rural development as construed by western aid agencies and forms of Chinese aid, especially regarding the speed of development and their cache of neoliberal ideologies. These programs dominated northern Laos in the 1990s and 2000s and have resulted in a patchwork landscape of development assistance and foreign investment. One featured strategic planning proposal references these earlier programs in Laos’s Muang Sing valley to help guide a strategy for basin-scale agricultural pollution remediation and increased water security, while the other proposal traces the legacies of opium’s replacement, primarily via Chinese investment, with rubber in northern Laos and the how the resultant patchwork of rubber, subsistence and cash crops, and ethnic diversity might deal with increasing rural–urban migration and significant associated strain on the rural agricultural labor force. These proposals exhibit the difficult balancing act between participating in the language and valuation metrics of development but with design concepts and approaches that actively resist easy constitution or reduction. The emphasis of alternative development on livelihood security, environmental sustainability and social development may be commendable, but the building of social capital takes time.
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Hankin, David G., Michael S. Mohr, and Ken B. Newman. "Sampling through time." In Sampling Theory, 268–94. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198815792.003.0013.
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Many ecological research and resource monitoring programs must deliver good estimates of both current resource status and long-term trend. The simple two-occasion context frames the trade-offs in design of surveys to achieve these objectives. If the objective is to estimate change in status (trend), then most precise estimation is achieved by full retention of a random sample selected at time 1. If the objective is to estimate average status, then most precise estimation is achieved by selecting independent random samples. If a survey has both objectives, then a compromise design, involving partial retention and partial replacement of the initial sample, is optimal (i.e., will have intermediate performance for status and trend). Sampling designs for long-term monitoring (and before/after assessment monitoring) have two distinct components: a membership design which specifies selection of groups of units to be designated as sample panels, and a revisit design that specifies when these panels of units should be visited (revisited). For example, some randomly selected panels might be visited in years one to three, then dropped out of rotation for three years and then revisited in years–seven to nine, and so on. One panel might be revisited every year, and other panels might be visited only a single time. Design-based estimates of measures of status and trend are derived for some simple membership and revisit designs. The theory of dual frame sampling is applied to estimation of the number of active bald eagle nests on a wildlife refuge.
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Cookson, Richard, James Love-Koh, Colin Angus, and James Lomas. "Introduction to the training exercises." In Distributional Cost-Effectiveness Analysis, edited by Richard Cookson, Susan Griffin, Ole F. Norheim, and Anthony J. Culyer, 92–102. Oxford University Press, 2020. http://dx.doi.org/10.1093/med/9780198838197.003.0005.
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This chapter introduces the handbook spreadsheet training exercises, which are designed to provide hands-on experience in using the methods of distributional cost-effectiveness analysis (DCEA). Seven of the exercises form a cumulative step-by-step sequence relating to nicotine replacement therapy (NRT) in England, which is a classic example of a preventive healthcare programme designed to improve health and reduce health inequality. This allows us to illustrate all the main steps involved in conducting a DCEA using a single common example. There are also two stand-alone exercises relating to other topics in other countries.
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Andersen, Torben M. "The Danish Pension System in an International Comparison." In The Danish Pension System, 8–40. Oxford University PressOxford, 2022. http://dx.doi.org/10.1093/oso/9780198867425.003.0002.
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Abstract The Danish pension system is attracting international attention for its structure and outcomes. Notably it involves a transition towards a more funded pension system, it delivers high replacement rates, and it is financially robust. The main characteristics of the Danish pension system are presented with outset in the theoretical literature on pension system design and how to address the three main objectives of a pension system: coverage (distribution), adequacy (consumption smoothing), and insurance. This calls for a multipillar pension scheme, which in the Danish case is based on defined benefit public pensions and defined contribution funded occupational pensions. The key elements of this system are presented, and the outcomes in terms of poverty alleviation, replacement rates, and macroeconomic consequences are discussed. The Danish pension system is compared in terms of structure and outcomes to those of the other Nordic countries; a comparison which is interesting since these countries share similar welfare models and yet have adopted very different pension systems. Finally, the robustness of the system in relation to changing demographics and market returns is discussed.
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Swayne, Richard W. "Repair/Replacement Activities for Nuclear Power Plant Items." In Companion Guide to the ASME Boiler & Pressure Vessel Codes, Volume 2, Sixth Edition, 28–1. ASME Press, 2023. http://dx.doi.org/10.1115/1.886526_ch28.
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Abstract This chapter addresses the requirements of IWA-4000 for repair/replacement (R/R) activities for nuclear power plant items. It examines the background of these R/R activities, notes some of the changes in R/R activity requirements since the original 1970 Edition, and reviews in detail the requirements in IWA-4000 in the 2015 Edition of Section XI of the ASME Boiler and Pressure Vessel Code. The discussion of the scope and applicability of Section XI R/R activities is informative to both new and longtime users. The chapter discusses the alternative requirements for small items, which is described in IWA-4131.1 and covers the requirements for items that are rotated from stock and for those involving mechanical clamping devices. It describes the responsibilities of two organizations, identified in IWA-4000, that may perform R/R activities: the Owner and the R/R Organization. The chapter explains the content of the R/R program and the R/R plan and discusses three additional general requirements included in IWA-4000: verification of acceptability, inspection by an Authorized Inspection Agency, and documentation. The new provisions that have been added in IWA-4200, such as provisions for addition of new systems, and improved and expanded provisions for reconciliation of Construction Codes and Owner’s Requirements, are also described. The chapter includes numerous Code Interpretations and Code Cases to help clarify and implement R/R activities. It looks at the design provisions that were added in the new Subarticle IWA-4300. The chapter details the changes and addenda made to IWA-4400 in the area of welding, brazing, metal removal/defect removal, fabrication, and installation and explains the specific requirements of IWA-4400. It discusses the examination and pressure testing requirements provided by IWA-4500 as part of the R/R activity. The chapter also provides a general overview of the alternative, specialized welding methods mentioned in IWA-4600. History Richard E. Gimple was the original author of this chapter for the first, second and third editions. Richard W. Swayne updated this chapter for the fourth, fifth and sixth editions.
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Balla, Vamsi Krishna, Mitun Das, Someswar Datta, and Biswanath Kundu. "Articulating Biomaterials." In Biomedical Engineering, 859–910. IGI Global, 2018. http://dx.doi.org/10.4018/978-1-5225-3158-6.ch038.
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This chapter examines the importance of surface characteristics such as microstructure, composition, crystallographic texture, and surface free energy in achieving desired biocompatibility and tribological properties thereby improving in vivo life of artificial articulating implants. Current implants often fail prematurely due to inadequate mechanical, tribological, biocompatibility, and osseointegration properties, apart from issues related to design and surgical procedures. For long-term in vivo stability, artificial implants intended for articulating joint replacement must exhibit long-term stable articulation surface without stimulating undesirable in vivo effects. Since the implant's surface plays a vital and decisive role in their response to biological environment, and vice versa, surface modification of implants assumes a significant importance. Therefore, overview on important surface modification techniques, their capabilities, properties of modified surfaces/implants are presented in the chapter. The clinical performance of surface modified implants and new surfaces for potential next-generation articulating implant applications are discussed at the end.
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Balla, Vamsi Krishna, Mitun Das, Someswar Datta, and Biswanath Kundu. "Articulating Biomaterials." In Processing Techniques and Tribological Behavior of Composite Materials, 218–67. IGI Global, 2015. http://dx.doi.org/10.4018/978-1-4666-7530-8.ch009.
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This chapter examines the importance of surface characteristics such as microstructure, composition, crystallographic texture, and surface free energy in achieving desired biocompatibility and tribological properties thereby improving in vivo life of artificial articulating implants. Current implants often fail prematurely due to inadequate mechanical, tribological, biocompatibility, and osseointegration properties, apart from issues related to design and surgical procedures. For long-term in vivo stability, artificial implants intended for articulating joint replacement must exhibit long-term stable articulation surface without stimulating undesirable in vivo effects. Since the implant's surface plays a vital and decisive role in their response to biological environment, and vice versa, surface modification of implants assumes a significant importance. Therefore, overview on important surface modification techniques, their capabilities, properties of modified surfaces/implants are presented in the chapter. The clinical performance of surface modified implants and new surfaces for potential next-generation articulating implant applications are discussed at the end.
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BADILLO-ÁNGELES, Sergio, Zaira Betzabeth TREJO-TORRES, and Karla María VELÁZQUEZ-LUCHO. "Diseño y construcción de módulos de block no estructural incorporando el reciclaje de taparroscas." In Arquitectura y Sustentabilidad Handbook T-I, 35–45. ECORFAN-Mexico, S.C., 2021. http://dx.doi.org/10.35429/h.2021.14.1.35.45.
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The present research aims to report the design and construction of non-structural concrete blocks incorporating caps from polyethylene terephthalate (PET) bottles as a replacement material for granzón, since these caps can be incorporated if they are crushed or crushed into particles. smaller (approximately 1 cm), which will improve the block, giving it a different texture. Thanks to the properties of plastic, this alternative block may be lighter than the traditional block, considering it as a non-structural block, which can be implemented as dividing walls in the various constructions within the field of architecture. Given that it has a wide variety of applications, this would lead to reducing its production costs. On the other hand, it is very important to characterize the block and for this it is necessary to carry out thermal, acoustic and resistance tests. Regarding the latter, the compressive strength of the ecological block is one of the most important goals of the prototype since it must abide by the regulations stipulated by the MNX-C-441-ONNCCE-2013. In addition, plastic generates good thermal insulation, and its degradation time is estimated between 200 and 300 years, which guarantees a highly durable home over time.
Conference papers on the topic "Single Replacement Design"
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Fan, Rong, Christopher M. Hobson, Ahmed Bayoumi, John E. Mayer, William R. Wagner, and Michael S. Sacks. "Design of Tissue-Engineered Leaflet Shape for the Ovine Pulmonary Valve Single Leaflet Replacement Surgery." In ASME 2011 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2011. http://dx.doi.org/10.1115/sbc2011-53949.
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Pulmonary valve (PV) replacement surgery is a treatment option for patients with a congenitally defective pulmonary outflow track. A tissue engineered pulmonary valve (TEPV) is a potential approach to serve as a replacement pediatric heart valve that has the potential for somatic growth. The single leaflet replacement surgical model can assist in assessing candidate biomaterials responses to in-vivo function. However, an empirically determined unloaded leaflet shape may result in abnormal valve function due to incomplete coaptation of leaflets and asymmetric stress distributions. Thus, to determine the final deformed shape of an engineered scaffold replacement PV leaflet under transvalvular pressure the following key factors must be determined: the scaffold anisotropic mechanical properties, optimal thickness, and the exact initial leaflet shape. We have used electrospun poly (ester urethane) ureas (ES-PEUU) scaffolds since they exhibit mechanical properties very similar to the native PV [1]. In this work we present a design framework of the optimal leaflet shape determination utilizing a single sheet of ES-PEUU for single leaflet replacement surgery via finite element (FE) simulation. The mechanical properties of ES-PEUU scaffold for leaflet replacement were obtained from biaxial in-plane tension and three-point bending flexural deformation experiments. Generalized Fung-type hyperelastic constitutive model [2] was implemented into a commercial FE software package to simulate the mechanical behavior of ES-PEUU scaffolds. By perturbing the initial shape of leaflet and simulating its quasi-static deformation under PV diastolic loading, the optimal shape of unloaded leaflet can be determined by comparing the deformed shape of leaflet obtained from FE simulation of TEPV with the one from microCT scan of a native ovine PV.
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Dharia, Mehul A., Jeff E. Bischoff, Duane Gillard, Fred Wentorf, and Matt Mroczkowski. "Impact of Articulation Geometry on Contact Mechanics in Total Ankle Replacement Design." In ASME 2011 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2011. http://dx.doi.org/10.1115/sbc2011-53107.
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Total ankle replacement designs have evolved since their introduction in the mid 1970s. While the first-generation total ankle replacement (TAR) designs had unacceptably high failure rates, recent designs have demonstrated improved outcomes [1]. Two philosophies are commonly used in TAR design: mobile-bearing and fixed-bearing. Unlike mobile-bearing designs which have two articulating surfaces, fixed-bearing designs have only one articulating surface. While fixed-bearing designs have lower risk of dislocation than mobile-bearing designs, the single articulation feature can produce higher contact stress on the articulating surface, increasing the potential for polyethylene wear [1, 2].
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Berglund, Michael D., Spencer P. Magleby, and Larry L. Howell. "Design Rules for Selecting and Designing Compliant Mechanisms for Rigid-Body Replacement Synthesis." In ASME 2000 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/detc2000/dac-14225.
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Abstract There exists a need for methodologies on designing mechanical devices with flexible elements (compliant mechanisms). Many engineers currently have little direction in their designing efforts and have difficulty improving the performance of devices with flexible members. This paper presents a step towards a process and a set of rules for designing compliant mechanisms which aid engineers in selecting the best design concept among a set of alternatives. The approach is a more rational method for selecting and improving designs than the existing intuitive approach engineers now take. The general design rules aid the engineer in identifying good and bad design features and practices for devices containing flexible elements. The design rules help engineers avoid oversights and/or overlooked factors in design problems. Since many equivalent compliant mechanisms can be made from a single rigid-body solution, the rules can help engineers select between the compliant alternative designs.
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McFadden, Matthew, Douglas Raby, Konstantinos Kris Mermigas, and Brian Utigard. "Design of Integral Abutment Bridges for a Lateral Slide Replacement." In IABSE Congress, New York, New York 2019: The Evolving Metropolis. Zurich, Switzerland: International Association for Bridge and Structural Engineering (IABSE), 2019. http://dx.doi.org/10.2749/newyork.2019.2337.
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<p>Jacobs is completing the preliminary and detailed design of two bridge replacements on County Road 17 in Ontario, Canada using an accelerated bridge construction technique known as lateral slide (also known as slide-in-bridge or jack-and-slide) for the Ontario Ministry of Transportation. The Hawkesbury Creek & CNR Overhead is a multi-span slab-on-girder structure spanning a creek and locomotive tracks. The Highway 34 Overpass is a single-span rigid frame structure spanning over the main road leading to the Town of Hawkesbury. The existing structures are approaching the end of their useful service life and rehabilitation is no longer a viable option. The new superstructures will be built on temporary supports located north of the existing structures. The new foundations consist of non-standard integral abutment details supported by composite caissons drilled through the existing roadway using temporary lane closures along County Road 17. This is an alternative to conventional integral abutment design which typically consists of a single row of steel H-piles. County Road 17 will be closed for up to four weeks to permit rapid demolition of the existing structures followed by the lateral slide. This is the first integral abutment lateral slide in the Province of Ontario. New design concepts, non-standard details and construction sequencing have been developed to achieve an economical, practical and robust design solution.</p>
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Patel, Dhiren, Gurprit Singh T. Virdi, and A. D. Dhass. "Modeling and Analysis of Gear Tooth Replacement System Against Breaking of Single Tooth." In ASME 2021 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/imece2021-73316.
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Abstract A gear is a mechanical machine part that transmits motion by successfully engaging teeth and gives the impression of positive action by coordinating and interlocking precise effort to achieve the desired result. Gear design necessitates a thorough investigation, and the loads, as well as the gear parameters, were determined by trial and error. When a single tooth on any gear breaks, the transfer of power is halted, resulting in material, time, and cost waste. The design and development of spur gear with teeth portability is the subject of this research paper. ANSYS is used to perform gear design analysis. To ensure precision, a wire cut electric discharge machine is used to cut each tooth, which is then assembled into gear using a gear blank, cover plate, nut, and bolt. The results of the analysis performed in the program Ansys 15.0 show that the proposed portable tooth spur gear can withstand maximum principal stress of 1.1886 × 108 Pa and total deformation that will occur at this stress 5.7897 × 10(−6) m. If the portable tooth spur gear is used, the cost of replacing all 65 teeth would be about 3000 Rupees. Keeping this in mind, replacing all 65 teeth twice a year would cost about 11500 Rupees, which is less than the total cost of the traditional gear design. In comparison to the conventional gear design, the proposed design reduces long-term maintenance costs.
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Yan, Yan, and Gregory S. Chirikjian. "Molecular Replacement for Multi-Domain Structures Using Packing Models." In ASME 2011 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/detc2011-48583.
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Molecular replacement (MR) is frequently used to obtain phase information for a unit cell packed with a macromolecule of unknown structure. The goal of MR searches is to place a homologous/similar molecule in the unit cell so as to maximize the correlation with x-ray diffraction data. MR software packages typically perform rotation and translation searches separately. This works quite well for single-domain proteins. However, for multi-domain structures and complexes, computational requirements can become prohibitive and the desired peaks can become hidden in a noisy landscape. The main contribution of our approach is that computationally expensive MR searches in continuous configuration space are replaced by a search on a relatively small discrete set of candidate packing arrangements of a multi-rigid-body model. These candidate arrangements are generated by collision detections on a coarse grid in the configuration space first. The list of feasible arrangements is short because packing constraints together with unit cell symmetry and geometry impose strong constraints. After computing Patterson correlations of the collision-free arrangements, an even shorter list can be obtained using the 10 candidates with highest correlations. In numerical trials, we found that a candidate from the feasible set is usually similar to the arrangement of the target structure within the unit cell. To further improve the accuracy, a Rapidly-exploring Random Tree (RRT) can be applied in the neighborhood of this packing arrangement. Our approach is demonstrated with multi-domain models in silico for 3D, with ellipsoids representing both the domains of the model and target structures. Configurations are defined by sets of angles between the ellipsoids. Our results show that an approximate configuration can be found with mean absolute error (MAE) less than 5 degrees.
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Fan, Rong, Michael S. Sacks, Ahmed Bayoumi, John E. Mayer, Christopher M. Hobson, and William R. Wagner. "Optimization of Engineered Ovine Pulmonary Heart Valve Leaflet Tissue Shape for Single Leaflet Replacement." In ASME 2012 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/sbc2012-80824.
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Pulmonary valve (PV) replacement surgery is a treatment option for patients with a congenitally defective pulmonary outflow track. While a tissue engineered approach offers many potential advantages, develop of such a valve involves a complex process of optimization. As an intermediate step, we have used a single leaflet replacement surgical model to further our understanding of the in-vivo remodeling process. A critical step is to determine the deformed shape of the replacement PV leaflet under transvalvular pressure. Key factors in this process are: the scaffold anisotropic mechanical properties, optimal thickness, and the exact initial leaflet shape. We have used electrospun poly (ester urethane) ureas (ES-PEUU) scaffolds since they exhibit mechanical properties very similar to the native PV. In this work we present a design framework of the optimal leaflet shape determination utilizing a single sheet of ES-PEUU for single leaflet replacement surgery via finite element (FE) simulation. The mechanical properties of ES-PEUU scaffold for leaflet replacement were obtained from biaxial in-plane tension experiments. Generalized Fung-type hyperelastic constitutive model [1] was implemented into a commercial FE software package to simulate the deformation of ES-PEUU scaffolds under pressure. By perturbing the initial shape of leaflet and simulating its quasi-static deformation under PV diastolic loading, the optimal shape of unloaded leaflet was determined by comparing the deformed shape of leaflet obtained from FE simulation of TEPV with the one from microCT scan of a native ovine PV. In-vitro test of PV after single leaflet replacement was also conducted to validate the developed method.
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Ma, Zining, Honglan Jiang, Hongpeng Li, Yong Wu, Chenchen Deng, and Leibo Liu. "Design of DMS-RRIP replacement algorithm for L1-cache of RISC-V-based single-core embedded processor." In International Conference on Electronic Information Technology (EIT 2023), edited by Wendong Xiao and Lu Leng. SPIE, 2023. http://dx.doi.org/10.1117/12.2685759.
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Schraeder, Robert, and Josh Mattheis. "Gerald Desmond Bridge Replacement Project Industry Innovations." In IABSE Congress, New York, New York 2019: The Evolving Metropolis. Zurich, Switzerland: International Association for Bridge and Structural Engineering (IABSE), 2019. http://dx.doi.org/10.2749/newyork.2019.0284.
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<p>The design and construction of the Gerald Desmond Bridge Replacement brings many firsts and innovations to California’s infrastructure landscape. Preliminary engineering studies carried out for this design-build project resulted in a 305-meter cable-stayed main span bridge, 157-meter tall mono-pole towers, and single and double-celled box girder approaches built on a moveable scaffolding system.</p><p>This paper reviews some of the innovations of the winning proposal design: approach viaduct optimization, viaduct frame dynamic response balancing and tower geometry conception. The focus of the review is interaction between design and construction teams in project innovation.</p><p>The review concludes that while project innovation is best served by healthy communication between design and construction teams at the preliminary engineering phase, the most challenging innovations benefit from healthy communication maintained through execution. This way mutual constraints and objectives are conceptually recognized by the innovation, while unknown obstacles associated with executing a new idea may be addressed expediently with the collective design and construction skill set.</p>
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McGowan, Patrick, and Guangbo Hao. "Design of a Single-Input Morphing Compliant Mechanism With Separate Gripping and Retraction Modes." In ASME 2022 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/detc2022-90939.
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Abstract A key aspect of robotics and automation is continuous repetition of predefined travel and actions. One such example is a robotic gripper, gripping an object and displacing it linearly. Compliant mechanisms are designed to replicate the motion of rigid mechanisms through the use of flexible beam elements that take advantage of the elastic deformation properties of a material. Arrangements of compliant beams can be used to successfully transmit or transform purposeful motion and force. In this paper a compliant gripper is proposed that grips an object (X displacement) and retracts it linearly (Y displacement) based on a single actuation. The design is comprehensively analyzed through finite element analysis (FEA) method and is optimized using the design exploration tools. The mechanism is firstly designed by the Rigid Body Replacement method and is based on the double slider mechanism. Morphing is successfully achieved through the use of contact aided features and a pseudo spring beam to decouple the X and Y displacements. The design is refined and optimized using commercial finite element analysis software to closely match an ideal X and Y displacement path and displacement activated transition from X displacement to Y displacement whilst minimizing the input actuation force. Experimental tests are to be conducted to validate the design.
Reports on the topic "Single Replacement Design"
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Wilson, Thomas E., Avraham A. Levy, and Tzvi Tzfira. Controlling Early Stages of DNA Repair for Gene-targeting Enhancement in Plants. United States Department of Agriculture, March 2012. http://dx.doi.org/10.32747/2012.7697124.bard.
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Gene targeting (GT) is a much needed technology as a tool for plant research and for the precise engineering of crop species. Recent advances in this field have shown that the presence of a DNA double-strand break (DSB) in a genomic locus is critical for the integration of an exogenous DNA molecule introduced into this locus. This integration can occur via either non-homologous end joining (NHEJ) into the break or homologous recombination (HR) between the broken genomic DNA and the introduced vector. A bottleneck for DNA integration via HR is the machinery responsible for homology search and strand invasion. Important proteins in this pathway are Rad51, Rad52 and Rad54. We proposed to combine our respective expertise: on the US side, in the design of zincfinger nucleases (ZFNs) for the induction of DNA DSBs at any desired genomic locus and in the integration of DNA molecules via NHEJ; and on the Israeli side in the HR events, downstream of the DSB, that lead to homology search and strand invasion. We sought to test three major pathways of targeted DNA integration: (i) integration by NHEJ into DSBs induced at desired sites by specially designed ZFNs; (ii) integration into DSBs induced at desired sites combined with the use of Rad51, Rad52 and Rad54 proteins to maximize the chances for efficient and precise HR-mediated vector insertion; (iii) stimulation of HR by Rad51, Rad52 and Rad54 in the absence of DSB induction. We also proposed to study the formation of dsT-DNA molecules during the transformation of plant cells. dsT-DNA molecules are an important substrate for HR and NHEJ-mediatedGT, yet the mode of their formation from single stranded T-DNA molecules is still obscure. In addition we sought to develop a system for assembly of multi-transgene binary vectors by using ZFNs. The latter may facilitate the production of binary vectors that may be ready for genome editing in transgenic plants. ZFNs were proposed for the induction of DSBs in genomic targets, namely, the FtsH2 gene whose loss of function can easily be identified in somatic tissues as white sectors, and the Cruciferin locus whose targeting by a GFP or RFP reporter vectors can give rise to fluorescent seeds. ZFNs were also proposed for the induction of DSBs in artificial targets and for assembly of multi-gene vectors. We finally sought to address two important cell types in terms of relevance to plant transformation, namely GT of germinal (egg) cells by floral dipping, and GT in somatic cells by root and leave transformation. To be successful, we made use of novel optimized expression cassettes that enable coexpression of all of the genes of interest (ZFNs and Rad genes) in the right tissues (egg or root cells) at the right time, namely when the GT vector is delivered into the cells. Methods were proposed for investigating the complementation of T-strands to dsDNA molecules in living plant cells. During the course of this research, we (i) designed, assembled and tested, in vitro, a pair of new ZFNs capable of targeting the Cruciferin gene, (ii) produced transgenic plants which expresses for ZFN monomers for targeting of the FtsH2 gene. Expression of these enzymes is controlled by constitutive or heat shock induced promoters, (iii) produced a large population of transgenic Arabidopsis lines in which mutated mGUS gene was incorporated into different genomic locations, (iv) designed a system for egg-cell-specific expression of ZFNs and RAD genes and initiate GT experiments, (v) demonstrated that we can achieve NHEJ-mediated gene replacement in plant cells (vi) developed a system for ZFN and homing endonuclease-mediated assembly of multigene plant transformation vectors and (vii) explored the mechanism of dsTDNA formation in plant cells. This work has substantially advanced our understanding of the mechanisms of DNA integration into plants and furthered the development of important new tools for GT in plants.
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Wu, Yingjie, Selim Gunay, and Khalid Mosalam. Hybrid Simulations for the Seismic Evaluation of Resilient Highway Bridge Systems. Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, November 2020. http://dx.doi.org/10.55461/ytgv8834.
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Bridges often serve as key links in local and national transportation networks. Bridge closures can result in severe costs, not only in the form of repair or replacement, but also in the form of economic losses related to medium- and long-term interruption of businesses and disruption to surrounding communities. In addition, continuous functionality of bridges is very important after any seismic event for emergency response and recovery purposes. Considering the importance of these structures, the associated structural design philosophy is shifting from collapse prevention to maintaining functionality in the aftermath of moderate to strong earthquakes, referred to as “resiliency” in earthquake engineering research. Moreover, the associated construction philosophy is being modernized with the utilization of accelerated bridge construction (ABC) techniques, which strive to reduce the impact of construction on traffic, society, economy and on-site safety. This report presents two bridge systems that target the aforementioned issues. A study that combined numerical and experimental research was undertaken to characterize the seismic performance of these bridge systems. The first part of the study focuses on the structural system-level response of highway bridges that incorporate a class of innovative connecting devices called the “V-connector,”, which can be used to connect two components in a structural system, e.g., the column and the bridge deck, or the column and its foundation. This device, designed by ACII, Inc., results in an isolation surface at the connection plane via a connector rod placed in a V-shaped tube that is embedded into the concrete. Energy dissipation is provided by friction between a special washer located around the V-shaped tube and a top plate. Because of the period elongation due to the isolation layer and the limited amount of force transferred by the relatively flexible connector rod, bridge columns are protected from experiencing damage, thus leading to improved seismic behavior. The V-connector system also facilitates the ABC by allowing on-site assembly of prefabricated structural parts including those of the V-connector. A single-column, two-span highway bridge located in Northern California was used for the proof-of-concept of the proposed V-connector protective system. The V-connector was designed to result in an elastic bridge response based on nonlinear dynamic analyses of the bridge model with the V-connector. Accordingly, a one-third scale V-connector was fabricated based on a set of selected design parameters. A quasi-static cyclic test was first conducted to characterize the force-displacement relationship of the V-connector, followed by a hybrid simulation (HS) test in the longitudinal direction of the bridge to verify the intended linear elastic response of the bridge system. In the HS test, all bridge components were analytically modeled except for the V-connector, which was simulated as the experimental substructure in a specially designed and constructed test setup. Linear elastic bridge response was confirmed according to the HS results. The response of the bridge with the V-connector was compared against that of the as-built bridge without the V-connector, which experienced significant column damage. These results justified the effectiveness of this innovative device. The second part of the study presents the HS test conducted on a one-third scale two-column bridge bent with self-centering columns (broadly defined as “resilient columns” in this study) to reduce (or ultimately eliminate) any residual drifts. The comparison of the HS test with a previously conducted shaking table test on an identical bridge bent is one of the highlights of this study. The concept of resiliency was incorporated in the design of the bridge bent columns characterized by a well-balanced combination of self-centering, rocking, and energy-dissipating mechanisms. This combination is expected to lead to minimum damage and low levels of residual drifts. The ABC is achieved by utilizing precast columns and end members (cap beam and foundation) through an innovative socket connection. In order to conduct the HS test, a new hybrid simulation system (HSS) was developed, utilizing commonly available software and hardware components in most structural laboratories including: a computational platform using Matlab/Simulink [MathWorks 2015], an interface hardware/software platform dSPACE [2017], and MTS controllers and data acquisition (DAQ) system for the utilized actuators and sensors. Proper operation of the HSS was verified using a trial run without the test specimen before the actual HS test. In the conducted HS test, the two-column bridge bent was simulated as the experimental substructure while modeling the horizontal and vertical inertia masses and corresponding mass proportional damping in the computer. The same ground motions from the shaking table test, consisting of one horizontal component and the vertical component, were applied as input excitations to the equations of motion in the HS. Good matching was obtained between the shaking table and the HS test results, demonstrating the appropriateness of the defined governing equations of motion and the employed damping model, in addition to the reliability of the developed HSS with minimum simulation errors. The small residual drifts and the minimum level of structural damage at large peak drift levels demonstrated the superior seismic response of the innovative design of the bridge bent with self-centering columns. The reliability of the developed HS approach motivated performing a follow-up HS study focusing on the transverse direction of the bridge, where the entire two-span bridge deck and its abutments represented the computational substructure, while the two-column bridge bent was the physical substructure. This investigation was effective in shedding light on the system-level performance of the entire bridge system that incorporated innovative bridge bent design beyond what can be achieved via shaking table tests, which are usually limited by large-scale bridge system testing capacities.
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Welch, David, and Gregory Deierlein. Technical Background Report for Structural Analysis and Performance Assessment (PEER-CEA Project). Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, November 2020. http://dx.doi.org/10.55461/yyqh3072.
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This report outlines the development of earthquake damage functions and comparative loss metrics for single-family wood-frame buildings with and without seismic retrofit of vulnerable cripple wall and stem wall conditions. The underlying goal of the study is to quantify the benefits of the seismic retrofit in terms of reduced earthquake damage and repair or reconstruction costs. The earthquake damage and economic losses are evaluated based on the FEMA P-58 methodology, which incorporates detailed building information and analyses to characterize the seismic hazard, structural response, earthquake damage, and repair/reconstruction costs. The analyses are informed by and include information from other working groups of the Project to: (1) summarize past research on performance of wood-frame houses; (2) identify construction features to characterize alternative variants of wood-frame houses; (3) characterize earthquake hazard and ground motions in California; (4) conduct laboratory tests of cripple wall panels, wood-frame wall subassemblies and sill anchorages; and (5) validate the component loss models with data from insurance claims adjustors. Damage functions are developed for a set of wood-frame building variants that are distinguished by the number of stories (one- versus two-story), era (age) of construction, interior wall and ceiling materials, exterior cladding material, and height of the cripple walls. The variant houses are evaluated using seismic hazard information and ground motions for several California locations, which were chosen to represent the range seismicity conditions and retrofit design classifications outlined in the FEMA P-1100 guidelines for seismic retrofit. The resulting loss models for the Index Building variants are expressed in terms of three outputs: Mean Loss Curves (damage functions), relating expected loss (repair cost) to ground-motion shaking intensity, Expected Annual Loss, describing the expected (mean) loss at a specific building location due to the risk of earthquake damage, calculated on an annualized basis, and Expected RC250 Loss, which is the cost of repairing damage due to earthquake ground shaking with a return period of 250 years (20% chance of exceedance in 50 years). The loss curves demonstrate the effect of seismic retrofit by comparing losses in the existing (unretrofitted) and retrofitted condition across a range of seismic intensities. The general findings and observations demonstrate: (1) cripple walls in houses with exterior wood siding are more vulnerable than ones with stucco siding to collapse and damage; (2) older pre-1945 houses with plaster on wood lath interior walls are more susceptible to damage and losses than more recent houses with gypsum wallboard interiors; (3) two-story houses are more vulnerable than one-story houses; (4) taller (e.g., 6-ft-tall) cripple walls are generally less vulnerable to damage and collapse than shorter (e.g., 2-ft-tall) cripple walls; (5) houses with deficient stem wall connections are generally observed to be less vulnerable to earthquake damage than equivalent unretrofitted cripple walls with the same superstructure; and (6) the overall risk of losses and the benefits of cripple wall retrofit are larger for sites with higher seismicity. As summarized in the report, seismic retrofit of unbraced cripple walls can significantly reduce the risk of earthquake damage and repair costs, with reductions in Expected RC250 Loss risk of up to 50% of the house replacement value for an older house with wood-frame siding at locations of high seismicity. In addition to the reduction in repair cost risk, the seismic retrofit has an important additional benefit to reduce the risk of major damage that can displace residents from their house for many months.
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Ohad, Itzhak, and Himadri Pakrasi. Role of Cytochrome B559 in Photoinhibition. United States Department of Agriculture, December 1995. http://dx.doi.org/10.32747/1995.7613031.bard.
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The aim of this research project was to obtain information on the role of the cytochrome b559 in the function of Photosystem-II (PSII) with special emphasis on the light induced photo inactivation of PSII and turnover of the photochemical reaction center II protein subunit RCII-D1. The major goals of this project were: 1) Isolation and sequencing of the Chlamydomonas chloroplast psbE and psbF genes encoding the cytochrome b559 a and b subunits respectively; 2) Generation of site directed mutants and testing the effect of such mutation on the function of PSII under various light conditions; 3) To obtain further information on the mechanism of the light induced degradation and replacement of the PSII core proteins. This information shall serve as a basis for the understanding of the role of the cytochrome b559 in the process of photoinhibition and recovery of photosynthetic activity as well as during low light induced turnover of the D1 protein. Unlike in other organisms in which the psbE and psbF genes encoding the a and b subunits of cytochrome b559, are part of an operon which also includes the psbL and psbJ genes, in Chlamydomonas these genes are transcribed from different regions of the chloroplast chromosome. The charge distribution of the derived amino-acid sequences of psbE and psbF gene products differs from that of the corresponding genes in other organisms as far as the rule of "positive charge in" is concerned relative to the process of the polypeptide insertion in the thylakoid membrane. However, the sum of the charges of both subunits corresponds to the above rule possibly indicating co-insertion of both subunits in the process of cytochrome b559 assembly. A plasmid designed for the introduction of site-specific mutations into the psbF gene of C. reinhardtii. was constructed. The vector consists of a DNA fragment from the chromosome of C. reinhardtii which spans the region of the psbF gene, upstream of which the spectinomycin-resistance-conferring aadA cassette was inserted. This vector was successfully used to transform wild type C. reinhardtii cells. The spectinomycin resistant strain thus obtained can grow autotrophically and does not show significant changes as compared to the wild-type strain in PSII activity. The following mutations have been introduced in the psbF gene: H23M; H23Y; W19L and W19. The replacement of H23 involved in the heme binding to M and Y was meant to permit heme binding but eventually alter some or all of the electron transport properties of the mutated cytochrome. Tryptophane W19, a strictly conserved residue, is proximal to the heme and may interact with the tetrapyrole ring. Therefore its replacement may effect the heme properties. A change to tyrosine may have a lesser affect on the potential or electron transfer rate while a replacement of W19 by leucine is meant to introduce a more prominent disturbance in these parameters. Two of the mutants, FW19L and FH23M have segregated already and are homoplasmic. The rest are still grown under selection conditions until complete segregation will be obtained. All mutants contain assembled and functional PSII exhibiting an increased sensitivity of PSII to the light. Work is still in progress for the detailed characterization of the mutants PSII properties. A tobacco mutant, S6, obtained by Maliga and coworkers harboring the F26S mutation in the b subunit was made available to us and was characterized. Measurements of PSII charge separation and recombination, polypeptide content and electron flow indicates that this mutation indeed results in light sensitivity. Presently further work is in progress in the detailed characterization of the properties of all the above mutants. Information was obtained demonstrating that photoinactivation of PSII in vivo initiates a series of progressive changes in the properties of RCII which result in an irreversible modification of the RCII-D1 protein leading to its degradation and replacement. The cleavage process of the modified RCII-D1 protein is regulated by the occupancy of the QB site of RCII by plastoquinone. Newly synthesized D1 protein is not accumulated in a stable form unless integrated in reassembled RCII. Thus the degradation of the irreversibly modified RCII-D1 protein is essential for the recovery process. The light induced degradation of the RCII-D1 protein is rapid in mutants lacking the pD1 processing protease such as in the LF-1 mutant of the unicellular alga Scenedesmus obliquus. In this case the Mn binding site of PSII is abolished, the water oxidation process is inhibited and harmful cation radicals are formed following light induced electron flow in PSII. In such mutants photo-inactivation of PSII is rapid, it is not protected by ligands binding at the QB site and the degradation of the inactivated RCII-D1 occurs rapidly also in the dark. Furthermore the degraded D1 protein can be replaced in the dark in absence of light driven redox controlled reactions. The replacement of the RCII-D1 protein involves the de novo synthesis of the precursor protein, pD1, and its processing at the C-terminus end by an unknown processing protease. In the frame of this work, a gene previously isolated and sequenced by Dr. Pakrasi's group has been identified as encoding the RCII-pD1 C-terminus processing protease in the cyanobacterium Synechocystis sp. PCC 6803. The deduced sequence of the ctpA protein shows significant similarity to the bovine, human and insect interphotoreceptor retinoid-binding proteins. Results obtained using C. reinhardtii cells exposes to low light or series of single turnover light flashes have been also obtained indicating that the process of RCII-D1 protein turnover under non-photoinactivating conditions (low light) may be related to charge recombination in RCII due to back electron flow from the semiquinone QB- to the oxidised S2,3 states of the Mn cluster involved in the water oxidation process.