Academic literature on the topic 'Direct pulp protection'
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Journal articles on the topic "Direct pulp protection"
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Menezes, Renato, Clóvis Monteiro Bramante, Roberto Brandão Garcia, Ariadne Letra, Vanessa Graciela Gomes Carvalho, Everdan Carneiro, Sérgio Brunini, Rodrigo Cardoso Oliveira, Giovana Calichio Canova, and Fernanda Gomes de Moraes. "Microscopic analysis of dog dental pulp after pulpotomy and pulp protection with mineral trioxide aggregate and white Portland cement." Journal of Applied Oral Science 12, no. 2 (June 2004): 104–7. http://dx.doi.org/10.1590/s1678-77572004000200004.
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Considering previous studies on the similarity between the chemical composition of the mineral trioxide aggregate and the Portland cement, the purpose of this study was to investigate the pulp response of dog's teeth after pulpotomy and direct pulp protection with MTA Angelus and white Portland cement. Thirty eight pulp remnants were protected with these materials. One hundred and twenty days after treatment, the animals were sacrificed and the specimens removed and prepared for histological analysis. Both materials demonstrated the same results when used as pulp capping materials, inducing hard tissue bridge formation and maintaining pulp vitality in all specimens. The MTA Angelus and the white Portland cement showed to be effective as pulp protection materials following pulpotomy.
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Asgary, Saeed, Masoud Parirokh, Mohammad Jafar Eghbal, Jamileh Ghoddusi, and Ali Eskandarizadeh. "SEM evaluation of neodentinal bridging after direct pulp protection with mineral trioxide aggregate." Australian Endodontic Journal 32, no. 1 (April 5, 2006): 26–30. http://dx.doi.org/10.1111/j.1747-4477.2006.00004.x.
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Arandi, Naji Ziad, and Tarek Rabi. "TheraCal LC: From Biochemical and Bioactive Properties to Clinical Applications." International Journal of Dentistry 2018 (2018): 1–6. http://dx.doi.org/10.1155/2018/3484653.
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Background. Direct pulp capping is a popular treatment modality among dentists. TheraCal LC is a calcium silicate-based material that is designed as a direct/indirect pulp capping material. The material might be very attractive for clinicians because of its ease of handling. Unlike other calcium silicate-based materials, TheraCal LC is resin-based and does not require any conditioning of the dentine surface. The material can be bonded with different types of adhesives directly after application. There has been considerable research performed on this material since its launching; however, there are no review articles that collates information and data obtained from these studies. This review discusses the various characteristics of the material with the aim of establishing a better understanding for its clinical use. Methods. A search was conducted using search engines (PubMed and Cochrane databases) in addition to reference mining of the articles that was used to locate other papers. The process of searching for the relevant studies was performed using the keywords pulp protection, pulp capping, TheraCal, and calcium silicates. Only articles in English published in peer-reviewed journals were included in the review. Conclusion. This review underlines the fact that further in vitro and in vivo studies are required before TheraCal LC can be used as a direct pulp capping material.
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Tonoli, Gustavo Henrique Denzin, Sérgio Francisco dos Santos, José Antonio Rabi, Wilson Nunes dos Santos, and Holmer Savastano Junior. "Thermal performance of sisal fiber-cement roofing tiles for rural constructions." Scientia Agricola 68, no. 1 (February 2011): 1–7. http://dx.doi.org/10.1590/s0103-90162011000100001.
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Roofing provides the main protection against direct solar radiation in animal housing. Appropriate thermal properties of roofing materials tend to improve the thermal comfort in the inner ambient. Nonasbestos fiber-cement roofing components reinforced with cellulose pulp from sisal (Agave sisalana) were produced by slurry and dewatering techniques, with an optional addition of polypropylene fibers. Nonasbestos tiles were evaluated and compared with commercially available asbestos-cement sheets and ceramic tiles (frequently chosen as roofing materials for animal housing). Thermal conductivity and thermal diffusivity of tiles were determined by the parallel hot-wire method, along with the evaluation of the downside surface temperature. Cement-based components reinforced with sisal pulp presented better thermal performance at room temperature (25ºC), while those reinforced with sisal pulp added by polypropylene fibers presented better thermal performance at 60ºC. Non-asbestos cement tiles provided more efficient protection against radiation than asbestos corrugated sheets.
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Chisini, Luiz Alexandre, Marcus Cristian Muniz Conde, Marcos Britto Correa, Raquel Venâncio Fernandes Dantas, Adriana Fernandes Silva, Fernanda Geraldes Pappen, and Flávio Fernando Demarco. "Vital Pulp Therapies in Clinical Practice: Findings from a Survey with Dentist in Southern Brazil." Brazilian Dental Journal 26, no. 6 (December 2015): 566–71. http://dx.doi.org/10.1590/0103-6440201300409.
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Studies based on dentists' clinical practice possess vital relevance to understand factors leading the clinicians to choose by a specific technique over another. This study investigated which clinical conduct therapies are adopted by dentists in front of deep caries. Was evaluated how the place of work, post-graduate training and years since complete graduation influenced their decisions. A cross-sectional study was performed using a self-applied questionnaire with dentists (n=276) in Southern Brazil. Information regarding post-graduation training (specialization, master's or PhD), clinical experience (years since completing graduation) and place of work were investigated. The information regarding pulp vital therapies (materials for direct pulp capping; techniques for caries removal in deep cavities and strategies for indirect pulp capping) were collected by specific questions. Data were submitted to descriptive analysis and Exact Fischer Test. Response rate was 68% (187). The majority of dentists selected the calcium hydroxide (CH) as first material for direct (86.3%) and indirect (80.3%) pulp protection. Partial caries removal was reported by 61.9% of dentists. Less experienced clinical dentists choose partial caries removal more frequently (p=0.009), if compared with dentists graduated 10 years and up ago. The use of MTA was more common among professionals working at academic environment. Besides, MTA was not mentioned by professionals working exclusively in the public health service (p=0.003). In conclusion, the time since graduation influenced the clinical conduct related to caries removal. The choice of liner materials was influenced by dentists' workplace.
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Jeya Gopika, G., Sathyanarayanan Ramarao, Carounanidy Usha, Bindu Meera John, and N. Vezhavendhan. "Histological evaluation of human pulp capped with light-cured calcium based cements: a randomized controlled clinical trial." International Journal of Scientific Reports 3, no. 5 (April 29, 2017): 120. http://dx.doi.org/10.18203/issn.2454-2156.intjscirep20171926.
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<p><strong>Background: </strong>Calcium hydroxide has traditionally been used as the pulp capping material for pulpal exposures in permanent teeth. The tunnel defects in the barrier and the tendency for dissolution, however, fails to provide permanent protection to the pulp. Light curable resin based cements have been introduced to enable a better marginal seal and lesser dissolution. The purpose of this study was to compare and evaluate the response of human pulp following direct pulp capping with the new resin based Calcium silicate (TheraCal LC) and Calcium hydroxide with hydroxyapatite (Septocal LC) cements compared with calcium hydroxide (Dycal). <strong></strong></p><p><strong>Methods: </strong>72 intact human premolars scheduled for orthodontic extractions were exposed to direct pulp capping procedures using three different pulp capping agents. Teeth were randomly divided into 3 groups, Group A: Dycal, Group B: TheraCal LC, Group C: Septocal LC. The teeth were extracted at the end of 15 and 40 days’ and were evaluated histologically. They were scored for reparative dentin formation and inflammatory response. Inferential statistics was done using Chi square test<strong>. </strong><strong></strong></p><p><strong>Results: </strong>Majority of the specimens in all three groups at the end of 15 days’ showed partial to lateral deposition of hard tissue. There was continuous deposition of hard tissue and severe inflammatory response at the end of 40 days’ in Dycal. There was partial deposition of hard tissue and reduced inflammatory response at the end of 40 days’ in TheraCal LC and Septocal LC. However, the results were not statistically significant between the three groups at two different time periods. <strong></strong></p><p><strong>Conclusions: </strong>Light cured,<strong> </strong>Calcium silicate (TheraCal LC) and Calcium hydroxide with hydroxyapatite (Septocal LC) cements were as effective as calcium hydroxide (Dycal) in inducing the formation of reparative dentin and evoking inflammatory response.</p>
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Baerle, Alexei. "MICROENCAPSULATION OF FUNCTIONAL COMPONENTS IN THE FOOD TECHNOLOGY: PARTIALLY OPTIMISTIC VIEW." Journal of Engineering Science 28, no. 3 (September 2021): 139–57. http://dx.doi.org/10.52326/jes.utm.2021.28(3).12.
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This work deals with the use of microencapsulation of biologically active compounds (BAC) as an alternative method of protection and prolongation of their functional properties in the food products. The main methods for the formation of microcapsules (MC) are considered. Biopolymer materials, suitable for MCs production, are outlined. Some technological solutions, suitable for microencapsulation and successfully used in other industries, present interest only for laboratory researches in the food science, but are not suitable for industrial scale food production. It is discussed why the methods of simple and complex coacervation, liposomal entrapment are thermodynamically advantageous for obtaining microcapsules in comparison with others. To achieve further progresses of microencapsulation in food technologies, the direct integration of the microencapsulation into the food production technological cycle is necessary. Products should initially have a texture and consistency that allow microcapsules to be resistant to premature aggregation. MCs should not exfoliate or break down, while execute their functions of protection and targeted delivery of biologically active compounds. Only high viscous colloidal systems, as traditional fermented dairy products (kefir, yoghurts, ice cream, curd and cheese) and fruit juices with pulp, are mostly suitable for supplementation of them by BACs using microencapsulation.
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Zaki, Harith Mohammed, Shakir Ahmed Salih, and Iqbal Naeem Gorgis. "Characteristics of Paper-cement Composite." Journal of Engineering 25, no. 4 (April 1, 2019): 122–38. http://dx.doi.org/10.31026/j.eng.2019.04.09.
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This study “discusses the benefit of “addition waste paper as a “new cellulose material “in mortar mixes. A partial addition of waste paper by cement weight was achieved to produce cement composite mortar. Pulp and paper is the third major industrial dumper of air, soil and water. In recent year, paper and paperboard constitute a greater portion of many countries’ urban solid discarded generation. Beside, it increases characteristic “strength due to existence “of hydrogen links “in the microstructure of “paper. Furthermore, it consume “better thermal protection. The addition percentages “of waste paper used “in this work were (5%, 10%, 15% and 20%) by “mass of cement to measure and evaluate some “properties of the mortar produced (compressive“, direct “tensile, and flexural) strength, thermal “properties such as (thermal conductivity), and “microstructure investigation “like (scanning electron microscope “(SEM)). The results indicated that the fresh mortar “properties affected expressively with higher wastepaper percent. The mechanical properties (compression, direct tensile and flexural strength) were “reduced by increasing the content of waste paper, it reduces to (74%, 50%, and 86%) respectively, with (20%) addition of waste paper than the reference mix. Moreover, using waste “paper with different percentages “led to noticeable “decrease in thermal “conductivity, especially with increasing addition percentages.
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Oliferenko, G. L., A. N. Ivankin, A. V. Ustyugov, and A. N. Zarubina. "Issue of technological equipment corrosion at chemical wood processing enterprises (review)." FORESTRY BULLETIN 25, no. 3 (June 2021): 142–51. http://dx.doi.org/10.18698/2542-1468-2021-3-142-151.
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The review is devoted to the problem of corrosion in the chemical processing of wood. Corrosion processes of technological equipment at enterprises of the pulp and paper, hydrolysis and wood chemical industries are considered. The influence of the main chemical substances involved in the technological process or formed during the chemical processing of wood is discussed. The importance of using alloyed, corrosion-resistant steels of grades 10Kh17N13M2T, 10Kh17N13M3T, 08Kh17N15M3T in the processes of chemical transformation is shown. The information on methods of protection of structural materials from corrosion at enterprises in recent years is presented. The prospects of industrial use of the method of anodic protection, which consists in creating a passivating film on the surface of the protected structure by anodic polarization from an external source of direct current, is noted. The importance of using inhibitors in the composition of technological media is discussed, as one of the most effective ways to combat metal corrosion in aggressive media. It is noted that in addition to the well-known inhibitors of acid corrosion KI-1, PB-5, PKU-3, KhOSP-10, urotropin, KPI-3, I-1-V, BA-6, the use of green chemistry advances is promising, in particular, the use of as anticorrosive agents for waste processing of both wood itself and corrosion inhibitors based on plant extracts.
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Kim, Kyeong-Jin, and Ick-Tae Yeom. "Analysis of the contributions of pollution to industrial discharge categories in Korea using the Modified Toxic Weighting Factor." Water Science and Technology 65, no. 5 (March 1, 2012): 859–66. http://dx.doi.org/10.2166/wst.2012.883.
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In 2007, 45,163 domestic industrial direct/indirect discharge sources were registered in Korea, which have been categorized into 82 divisions based on the characteristics of their products, raw materials and wastewaters. The purpose of this study was to set priorities using a risk assessment of pollutants toxic weighting for each industrial category with respect to pollution prevention and control. This study developed the upgraded Modified Toxic Weighting Factors (MTWFs) rather than the Toxic Weighting Factors (TWFs) suggested by the United States Environmental Protection Agency (USEPA) with respect to domestic environmental regulations, and the assessment of existing databases of domestic industrial wastewater characteristics for the 82 categorized industries in Korea. Finally, priority of industrial categories and pollutants were established to determine the target industries and pollutants requiring controls. High contributing categories in order of their pollution loads were pulp, paper and paper products manufacturing, dyeing and processing facilities, etc. The top 10 industrial category loads accounted for 76.0% of the total effluent equivalent kilograms of pollution. High contributing categories, in order of their toxic level were synthetic resins and other plastics manufacturing, leather and fur processing and manufacturing.
Dissertations / Theses on the topic "Direct pulp protection"
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Machado, Ana Cláudia Poléri. "Aplicações do agregado trióxido mineral (MTA) em endodontia." Master's thesis, [s.n.], 2014. http://hdl.handle.net/10284/4466.
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Projeto de Pós-Graduação/Dissertação apresentado à Universidade Fernando Pessoa como parte dos requisitos para obtenção do grau de Mestre em Medicina DentáriaO Agregado Trióxido Mineral ( MTA) é um material que tem sido utilizado já à vários anos devido às suas boas propriedades mecânicas, físico-químicas e biológicas. Após esta descoberta vários autores têm mostrado muito interesse em desenvolver estudos no âmbito de melhorar as aplicações e propriedades do MTA em Endodontia. Este trabalho foi realizado no âmbito da disciplina “Projeto de Pós Graduação/Dissertação” para obtenção do título de mestre em Medicina Dentária. O objetivo deste trabalho foi, através de uma revisão bibliográfica sobre o Agregado Trióxido Mineral e a sua aplicação em Endodontia, analisando as suas propriedades físicas- químicas e biológicas, realizando uma interligação com as suas aplicações em atos clínicos. Foram usados alguns recursos sobre o tema, tais, como, bases de dados em linha, teses e revistas,com as palavras-chave: “MTA”, “Apicetomia”,”Pulpotomias”, “Fraturas radiculares”, Proteção pulpar direta”,“Apicoformação”,“apexogénese”, “apexificação”, “Reabsorções Internas e Externas” e “ Perfurações de Furca e Radiculares”,”Apexification”,”Mineral Trioxide Aggregate”,”Pulpotomy”. Tendo em atenção artigos disponíveis on-line, nos motores de pesquisa Pubmed, Scielo e Google Scholar. O MTA é considerado um material de eleição em alguns tratamentos Endodônticos, comparado com outros cimentos, embora possa ser utilizado em outras áreas clínicas inerentes à Endodontia. Não promove uma inflamação tecidual significativa, permitindo uma reparação do órgão pulpar. The Mineral Trioxide Aggregate ( MTA ) is a material that has already been used for several years due to its good mechanical , physical, chemical and biological properties . After this discovery, several authors have shown much interest in developing curriculum in the context of improving the applications of MTA in Endodontics . This work was performed under the discipline " Project Graduate / Master " to obtain a Master's degree in dentistry , the aim of this study was , through a literature review on the Mineral Trioxide Aggregate and its application in Endodontics , analyzing the physicochemical and biological their properties, making a connection with their applications in clinical acts . Some resources on the topic , such as , online databases , theses and journals, with key words were used : " MTA " , " Apicetomia " , " Pulpotomy " , " root fractures ," direct pulp protection " ,” Apicoformação”, " apexogénese " , " apexificação " , " Internal and External resorptions " and " furcation perforations and Root”,”Apexificaton”,”Mineral Trioxide Aggregate”, “Pulpotomy”.Taking into account articles available online, in search PubMed , SciELO and Google Scholar engines . The MTA is considered to be a material of choice in some endodontic treatment, as compared to other cements , but may be used in other clinical areas inherent in endodontics . Does not promote significant tissue inflammation, allowing for repair of pulp organ.
Book chapters on the topic "Direct pulp protection"
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Banerjee, Avijit, and Timothy F. Watson. "Principles of management of the badly broken down tooth." In Pickard's Guide to Minimally Invasive Operative Dentistry. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780198712091.003.0009.
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This textbook has covered the common causes of broken down teeth: dental caries, tooth wear, and trauma. In addition, long-term failure of parts, or all, of the existing tooth–restoration complex can be significant and may require further operative intervention for its successful management (see Chapter 9). Many intra-coronal defects can be repaired with direct adhesive restorations, as discussed in Chapters 5 and 9. However, the situation can be complicated by the loss of significant portions of existing restoration or tooth structure (e.g. cusps, buccal/lingual walls), which influence the restorative procedures used in an attempt to maintain the tooth longevity, as well as pulp viability, for as long as possible. For direct restorations to succeed clinically, they require healthy dental tissues to aid support, retention, and ideally provide an element of protection from excessive occlusal loads. With diminishing amounts of tooth structure to work with, greater thought and care are required to manage and prepare the remaining viable hard tissues to support and retain the larger restoration. The core restoration describes the often large direct plastic restoration used to build up the clinically broken down crown. It is retained and supported by remaining tooth structure wherever possible (sometimes including the pulp chamber and posts in root canals of endodontically treated teeth). These large restorations often benefit from further overlying protection to secure their clinical longevity, by means of indirect onlays, and partial or full coverage crowns. Before carrying out a detailed clinical examination of the individual tooth and the related oral cavity, it is always important to justify your clinical decisions, for both operative and non-operative preventive interventions. The five key reasons for minimally invasive (MI) operative intervention are:… • to repair hard tissue damage/cavitation caused by the active, progressing caries/tooth-wear process (where non-operative prevention has failed repeatedly) • to remove plaque stagnation areas within cavities/defects which will increase the risk of caries activity due to the lack of effective plaque removal by the patient • to help to manage acute pulpitic pain caused by active caries by removing the bacterial biomass and sealing the defect, thereby protecting the pulp • to restore the tooth to maintain structure and function in the dental arch • aesthetics.
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Goldfinger, Eliot. "Individual Muscles Attachments, Action, & Structure." In Animal Anatomy for Artists. Oxford University Press, 2004. http://dx.doi.org/10.1093/oso/9780195142143.003.0010.
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The muscles of the head consist of the chewing muscles (temporalis, masseter, and digastric) and the facial muscles (zygomaticus, orbicularis oris, etc.). The chewing muscles are thick and volumetric, and they originate and insert on bone. They open and close the lower jaw, with the action taking place at the jaw joint (temporomandibular joint). The facial muscles are thin. They originate either from the skull or from the surface of other muscles, and they generally insert into other facial muscles or into the skin. When they contract, they move the features of the face (eyes, nose, mouth, ears). As they pull the facial features, they often gather the skin into folds and wrinkles that lie perpendicular to the direction of their muscular fibers (perpendicular to the direction of pull). The mouth region receives the most muscles; therefore, it is the most mobile part of the face. Some facial muscles are so thin that they do not create any direct form on the surface (caninus, malaris, orbicularis oculi), whereas other facial muscles or their tendons may create surface form directly (buccinator, levator labii maxillaris, zygomaticus, and depressor labii mandibularis). Facial muscles are generally more visible on the surface in the horse and the ox than in the dog and feline. The facial muscles, as they move the eyes, nose, mouth, and ears, generate whatever facial expressions animals are capable of producing. . . . • Attachment: A short ligament at the inner corner of the eye, whose inner end attaches to the skull. . . . . . . • Action: Eyelid portion: closes eyelids (blinking), primarily by depressing the upper eyelid. Outer portion: tightens and compresses the skin surrounding the eye, protecting the eyeball. . . . . . . • Structure: The orbicularis oculi is a flat, elliptical muscle consisting of two portions. The eyelid portion lies in the upper and lower eyelids, and the outer portion surrounds the eye and lies on the skull. . . .
Conference papers on the topic "Direct pulp protection"
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Ramirez, Oscar, and Ting Yu. "Variable Frequency Drive Applications and Their Electrical Protection Scheme for Liquids Pipelines." In 2012 9th International Pipeline Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/ipc2012-90339.
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Motor and pump units can start either directly across the line (utility) or through a VFD. If the power system is weak (high impedance and relatively low available MVA), the result will be limitations on the maximum size of motor that may be started directly across the line. Currently some available power systems are not capable of starting large motors across the line and therefore VFD systems are required. A VFD can be used for starting purposes or to operate a motor/pump unit (unit) continuously. Liquids pipelines have been using VFDs for unit starting purposes and for pressure control while either one of the units connected to the VFD or while there is a dedicated VFD per unit. One VFD can be used to operate all the units. The VFD starts the motor, ramps it up, and synchronizes it with the utility to switch the motor from VFD operation to utility operation. The VFD follows the same sequence with the next unit. The VFD also switches the motor from utility operation to VFD operation. With pumps in series, one unit can remain connected to the VFD for pressure control in liquids pipelines. Each unit can also be controlled by a dedicated VFD, allowing independent control of each unit for start-up and speed control. Both single VFD or dedicated VFD per unit offer advantages. Benefits of using a single VFD for all units are cost savings for some applications, a backup start across the line when allowed by the power system, and station pressure control. The benefits of a dedicated VFD per unit application include more flexibility in flow and pressure control, ease of expansion without interrupting existing operations for an extended period, energy efficiency, and redundancy. Motor protection schemes for the above two VFD applications are discussed and compared in this paper. In order to maintain a safe and reliable pipeline system, comprehensive motor protection functions are provided to the pump unit. Although the principles are the same, there are some differences between the two motor protection applications. For a dedicated VFD per unit application, the VFD protection/control circuitry normally provides motor protection because the motor is always connected to the VFD. RTDs over-temperature protection is not typically a standard feature of VFDs, however, it can be provided by proper PLC programming or the VFD incoming feeder protection relay.
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Liu, Lanbin, Lin Fu, and Shigang Zhang. "A Study of the Design and Analysis of Two Exhaust Heat Recovery Systems for Public Shower Facilities." In ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-39635.
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For large-scale public shower facilities which open up at a specified time, (such as those in schools, barracks, and natatoriums), a great deal of heat is wasted. If this exhaust heat can be recovered and recycled, it will have significant impact in saving energy and environmental protection, with significant economic benefits. In this paper, two different kinds of heat pumps, an electric and an absorption heat pump, used in heat recovery systems are proposed. Specifically, the used shower water is drained through a pipe and first collected in a gray water pool. After a period of time, as the wastewater accumulates volume, the heat pump system can begin heat recovery and recycling. The wastewater is filtered through a filter and piped to a heat exchanger to heat the tap water. Therefore, the tap water temperature can be heated from 12°C to 25°C, and the wastewater temperature will drop from 30°C to 17 °C. Afterwards, the wastewater is piped to the heat pump evaporator and the tap water piped to the condenser for additional heating. At the same time, according to the different characteristics of the electric heat pump and absorption heat pump, different heat recovery system processes and control are detailed. On this basis, the paper analyses the economic and environmental benefit of three schemes for retrofitting based on a practical example: “exhaust heat recovery using electric heat pump”, “exhaust heat recovery using electric heat pump + gas boiler” and “exhaust heat recovery using direct-fired heat pump”, then finds that direct-fired absorption heat pump heat recovery have lower energy consumption, less pollution, lower operating costs, payback period is shorter and has a promising practical application.
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Baron, Barbara R., and Robert J. Lutz. "Insights Into Operating a Low Pressure Feed Pump for Loss of All AC and DC Power." In 16th International Conference on Nuclear Engineering. ASMEDC, 2008. http://dx.doi.org/10.1115/icone16-48901.
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Generic guidance for Pressurized Water Reactors (PWRs) has been developed to address the beyond design basis event of coincident loss of all Alternating Current (AC) and Direct Current (DC) power. The generic guidance included a strategy to use a low pressure feed pump to provide adequate secondary side heat removal via the Steam Generators (SGs) to delay or prevent core uncovery following loss of all AC power with battery depletion, loss of all DC power, seismic initiated events, and/or terrorist initiated events. The purpose of the project was to use thermal hydraulic analyses, operating experience, and other engineering analyses to identify and evaluate technical issues associated with the implementation of the low pressure feed pump strategy at Westinghouse and Combustion Engineering (CE) designed plants. The technical issues that were evaluated are those issues typically addressed in the development of a plant’s Emergency Operating Procedures (EOPs) and Off-Normal Operating Procedures (ONOPs). The thermal hydraulic analyses were performed using the computer code MAAP 4.0.5 and a plant model of a 4-loop Westinghouse designed PWR. The results of the analyses are also applicable to 2-Loop and 3-Loop Westinghouse and CE designed PWRs. The results of the evaluation indicated that the key technical issue potentially impacting the prevention of core uncovery for the implementation of the low pressure feed pump strategy is the potential and consequences of injecting nitrogen into the Reactor Coolant System (RCS) from the cold leg accumulators/Safety Injection Tanks (SITs). The results of the evaluation were used to develop sample instructions for implementing the low pressure feed pump strategy for Westinghouse and CE designed PWRs. The sample instructions were developed for two categories of low pressure feed pumps: (1) low pressure feed pumps with shutoff heads greater than the pressure that nitrogen injects into the RCS and (2) low pressure feed pumps with shutoff heads less than the pressure that nitrogen injects into the RCS. The usefulness of the sample instructions is maximized when the low pressure feed pump has local flow indication, throttling capabilities, deadhead protection, and local SG pressure indication is available. The results demonstrated that the design characteristics of the low pressure feed pump are important to prolonging/preventing the time of core uncovery.
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Xiao, Chenzhang, Omid Jahanian, Alyssa Schnorenberg, Brooke Slavens, and Elizabeth Hsiao-Wecksler. "Design and Biomechanical Evaluation Methodology of Pneumatic Ergonomic Crutch." In 2017 Design of Medical Devices Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/dmd2017-3512.
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Lofstrand, or forearm, crutch users experience a concerning amount of force in their wrists that can approach 30% of body weight during swing-through gait, along with hyperextension of the wrist [1]. Such repetitive large loads and poor wrist posture could cause joint pain, injury and carpal tunnel syndrome in long-term crutch users [2]. To address these issues in Lofstrand crutch users, we previously reported two different designs. The first involved attaching a passive orthosis to the grip handle and shaft that directly supported the wrist [3]. The second proposed a soft pneumatic sleeve attached to the forearm cuff of the crutch along with a concept to harvest pneumatic energy during walking via a piston pump at the crutch tip, i.e., the Pneumatic Ergonomic Crutch (PEC) [4]. This paper first describes the full system design of the PEC, which contains an improved pneumatic sleeve orthosis, an energy-harvesting shock-absorbing crutch tip, and a control system with three modes of operation and safety protection. We also present pilot data from one healthy control subject performing a proposed biomechanical evaluation of the pneumatic sleeve orthosis. More tests will be conducted with a group of able-bodied subjects to evaluate the overall effectiveness of the PEC.
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Jagani, Jakin, Elizabeth Mack, Jihyeon Gong, and Alexandrina Untaroiu. "Effect of Stent Design Parameters on Hemodynamics and Blood Damage in a Percutaneous Cavopulmonary Assist Device." In ASME 2018 5th Joint US-European Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/fedsm2018-83210.
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Hypoplastic Right Heart Syndrome is a type of congenital heart defect where the right ventricle is underdeveloped in an infant to pump blood from the body to the lungs. The three-staged surgical Fontan procedure provides a temporary treatment; however, in most of the cases, a heart transplantation is required due to postoperative complications. Currently, there are no devices commercially available in the market to provide a therapeutic assistance to these patients until a donor heart is available. Thus, a novel dual propeller pump concept is developed to provide cavopulmonary assistance to these patients. The designed blood pump would be percutaneously inserted via the Femoral vein and deployed at the center of the Total Cavopulmonary Connection (TCPC). The two propellers, each placed in the Superior Vena Cava (SVC) and the Inferior Vena Cava (IVC) are connected by a single shaft and rotating at same speed. The device is supported with the help of a self-expanding stent whose outer walls are anchored to the inner walls of the IVC and the SVC. Each of the IVC and the SVC propeller without the stent provides a modest pressure augmentation of 5–6 mm Hg. To expand on this, the current study focusses on studying the effect of the introduction of stent around the propeller on the hemodynamic performance of the pump. Five different stent design parameters, viz. the strut thickness, width, number, the stent length and number of strut columns were selected for a range of values. Each of the design parameters was varied by keeping all others constant and equal to the base stent design. All the stent models were analysed to see their effect on pressure rise, flow pattern and blood damage using 3D CFD analysis. The blood damage potential for different studied designs was predicted using a non-linear mathematical power law model along with Lagrangian particle tracking to predict the blood flow path. The introduction of stent resulted in pressure reduction of around 0.4 and 0.2 mm Hg around the IVC and SVC propeller with an increase in blood damage index (BDI) by almost 2 times for the final dual propeller pump assembly. It was observed that the blood damage potential was directly related to the amount of pressure rise where the stent length, stent column number, strut width, and strut thickness had a converse effect showing a reduction in pressure rise and blood damage with their increment. While the number of struts gave a desirable effect of increasing pressure rise and reducing blood damage with its increment. The study also demonstrated that the introduction of stent around a circulatory pump increases the Wall Shear Stress (WSS) value at the stent-artery wall interface thereby preventing the occurrence of restenosis and thrombosis initiating due to very low WSS (< 0.5 Pa). Thus, this study acts as an initial step to design a protective stent support around a percutaneous assist device by analysing the sensitivity of stent design parameters on the hemodynamic performance of the pump.
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Lele, H. G., A. Srivastava, B. Chatterjee, A. J. Gaikwad, Rajesh Kumar, and S. K. Gupta. "Transient Analysis for the Case of Changes in Coolant Inventory for Advanced Heavy Water Reactor." In 12th International Conference on Nuclear Engineering. ASMEDC, 2004. http://dx.doi.org/10.1115/icone12-49148.
Full textAbstract:
Safety of nuclear reactor needs to be assessed against different categories of Postulated initiating events. Advanced Heavy Water Reactor is natural circulation light water cooled and heavy water moderated pressure tube type of reactor. Inventory of the system is important parameter in determination of flow characteristics of this natural circulation reactor. In view of this, various events that cause changes in PHT system inventory are analysed in this paper. One of the reason for decrease in coolant inventory is hypothetical Loss of coolant accident (LOCA) This event is of very low probability but important from designing engineered safeguard system of a reactor. Loss of coolant accident in a nuclear reactor can cause voiding of the reactor core due to expulsion of primary coolant from break. In such, a situation the reactor core experiences very low heat removal rate from the nuclear fuel though the decay heat generation continues even after tripping of the reactor. Heat generation in the reactor core is due to various sources such as decay heat, stored heat etc, can lead to heating of fuel elements. However, Emergency core cooling systems of the reactor are actuated and prevent undesirable temperature rise. These events are called design basis events and focus is on adequacy of Emergency Core Cooling System (ECCS) and fuel integrity. The scenarios, phenomena encountered and consequences depend upon size and location of break, system characteristics, and actuation and capability of different protection and engineered safeguard systems of the reactor system. Moreover, this reactor has several passive features to ensure safety of this reactor. which are considered in analyzing these events. Events under category of decrease in coolant inventory includes loss of coolant accidents due to break at different locations of different sizes. Various locations considered in this paper are steam line, inlet header, inlet feeder, ECCS header, downcomer, pressure tube, Isolation condenser inlet header, instrument line break at inlet header and steam drum. The paper also considers scenario emerging due to malfunctions like relief valve stuck open. Causes for events under category of increase in coolant inventory are Increase in Drum level controller set point, Inadvertent valving in of Accumulators and Inadvertent valving in of Gravity driven water pool (GDWP). Last two events are not analysed as they are not possible. The analysis for the above events is complex due to various complex and wide ranges of phenomena involved during different pies under this category. It involves single and two phase natural circulation at different power levels, inventories and pressures, two-phase natural circulation under depleted inventory conditions. Coupled neutronics and thermal hydraulics behaviour, Phenomena under LOCA, phenomena during ECCS injection, direct injection into fuel rod, advanced accumulator injection., vapour pull through and coupled controller and thermal hydraulics. Modelling of these phenomena for each event is discussed in this paper. In this paper summary of analyses for representive event is presented.
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Hansen, Rasmus. "Theoretical Framework for Axial Thermal Gradients and Interface Slip in Pressure Sheath Layers of Flexible Pipes." In ASME 2017 36th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/omae2017-61923.
Full textAbstract:
Axial thermal gradients in flexible pipes is a relatively novel area of research. New studies are putting focus on how the structural integrity of flexible pipes can be challenged by axial thermal gradients [1]. Significant axial thermal gradients occur, in particular, during start-up (heating) and shut-down (cooling) of the pipe in the vicinity of transition zones from pipe directly exposed to the surrounding environment, i.e. water or air, to thermally insulating parts, e.g. external anti-wear and fire protection layers, bend restrictors, bend stiffeners, and buoyancy modules. Along with differences in thermal expansion coefficients of the different pipe layers, the axial thermal gradients can cause significant shear stress in the interfaces between pipe layers. Thereby, axial thermal gradients may potentially cause relative axial displacement, or a slip displacement, between e.g. the pressure sheath and the pressure armor layers. In this way, axial loads in the pipe layers may not be properly transferred to, and thereby supported by, the tensile armor layer. A primary concern is the risk of e.g. pressure sheath pull-out of the end-fitting or carcass tearing failures. The present paper partially builds upon, and extends, the results presented earlier [1], primarily concerned with interface shear loads and slip displacements between the inner pipe layers, i.e. carcass, pressure sheath, and pressure armor, and extends that study in several ways. 1) Reconsiderations of the thermomechanical coupling between the radial and the axial spatial direction, and a detailed scale analysis, leads to a more rigorous derivation of the shear stress in the carcass / pressure sheath and pressure sheath / pressure armor interfaces in response to axial thermal gradients. These results deviate from the earlier published result only in terms of Poisson’s ratio dependent numerical pre-factors. 2) The established theoretical framework includes a thorough coupling between the interface shear stresses, and the radial, axial, and azimuthal normal stresses. This allows for an exhaustive evaluation of the mechanical state of the pipe in both pre-slip and post-slip conditions, including residual states. 3) The results are generalized to transient thermo-viscoelastic analysis, which is critical for conservatism due to the viscoelastic stress relaxation of the polymeric pressure sheath material during heating, cooling, and thermal cycling. Possible failure modes due to axial thermal gradients are currently not covered explicitly by design codes and conventional qualification testing. The model presented in this article can form basis for risk evaluations related to axial thermal gradients, input to formulations of design codes, and engineering design tools. The model contains the mechanisms that govern criticality in relation to axial thermal gradients, and its implications on interface shear stress, potential interface slip, and forces in the pipe, thereby also providing insights into possible mitigation actions for related failure modes.