Дисертації з теми "Minimal replacement"
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1
CLERICI, ALBERTO. "Development of a novel technology platform for thoracoscopic aortic valve replacement." Doctoral thesis, Politecnico di Torino, 2019. http://hdl.handle.net/11583/2745352.
Повний текст джерела
2
Parsa, Maryam. "Optimum Decision Policy for Gradual Replacement of Conventional Power Sources by Clean Power Sources." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24015.
Повний текст джерелаАнотація:
With the increase of world population and industrial growth of developing countries, demand for energy, in particular electric power, has gone up at an unprecedented rate over the last decades. To meet the demand, electric power generation by use of fossil fuel has increased enormously thereby producing increased quantity of greenhouse gases. This contributes more and more to atmospheric pollution, which climate scientists believe can adversly affect the global climate, as well as health and the welfare of the world population. In view of these issues, there is global awareness to look for alternate sources of energy such as natural gas, hydropower, wind, solar, geothermal and biomass. It is recognized that this requires replacement of existing infrastructure with new systems, which cannot be achieved overnight.
Optimal control theory has been widely used in diverse areas of physical sciences, medicine, engineering and economics. The main motivation of this thesis is to use this theory to find the optimum strategy for integration of all currently available renewable energy sources with the existing electric power generating systems. The ultimate goal is to eliminate fossil fuels. Eight main energy sources namely, Coal, Petroleum, Natural Gas, Conventional Hydro, Wind, Solar, Geothermal and Biomass are considered in a dynamic model. The state of the dynamic model represents the level of energy generation from each of the sources.
Different objective functions are proposed in this thesis. These range from meeting the desired target level of power generation from each of the available sources at the end of a given plan period, to reducing the implementation and investment costs; from minimizing the production from polluted energy sources to meeting the electricity demand during a whole plan period. Official released data from the U.S. Energy Information Administration have been used as a case study. Based on real life data and the mathematics of optimal control theory, we present an optimal policy for integration of renewable energy sources to the national power grid.
3
Alkhalil, Ahmad. "Outcomes Of Early Versus Late Discharge In Transfemoral Transcatheter Aortic Valve Replacement Via Minimally Invasive Strategy: A Propensity-Matched Analysis." Case Western Reserve University School of Graduate Studies / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=case1465592493.
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4
Sell, Andres. "Determining the minimum local anaesthetic requirements for hip replacement surgery under spinal anaesthesis : a study employing a spinal catheter /." Online version, 2005. http://dspace.utlib.ee/dspace/bitstream/10062/1081/5/sell.pdf.
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Shehada, Sharaf-Eldin Ibrahim Hassan [Verfasser], Bernhard J. [Akademischer Betreuer] Voss, and Rüdiger [Akademischer Betreuer] Lange. "Propensity Score Analysis of Outcomes following Minimally Invasive versus Conventional Aortic Valve Replacement / Sharaf-Eldin Ibrahim Hassan Shehada. Gutachter: Bernhard J. Voss ; Rüdiger Lange. Betreuer: Bernhard J. Voss." München : Universitätsbibliothek der TU München, 2015. http://d-nb.info/1069621714/34.
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6
Lok, Peter Yin Cheung. "Development of a novel minimally invasive scaffold system for spinal disc repair." Thesis, The University of Sydney, 2014. http://hdl.handle.net/2123/12583.
Повний текст джерелаАнотація:
Debilitating chronic back pain caused by severe spinal disc degeneration leads to loss of mobility, affecting quality of life, a significant loss of productivity for the employee and the employer. Currently available surgical intervention options, such as spinal fusion and total disc replacement, seeking only to alleviate pain, are not only invasive, but fail to address the underlying biological causes of spinal disc degeneration, or restore normal physiological spinal motion. Recently proposed tissue engineering approaches focus on stopping and reversing the degenerative cascade, which has a promising regenerative effect, though not without significant challenges before a clinical application is made available, including tumourigenesis risks and proof of efficacy. A minimally invasive nucleus pulposus replacement option, which preserves the competent annulus fibrosis, while replacing the removed degenerated nucleus tissue with a prosthesis, provides an alternative for early disc degeneration, though most commercially available types are at clinical trial stages. There is an opportunity for developing a minimally invasive nucleus pulposus replacement type spinal implant system that restores disc biomechanics and addresses biological degenerative causes. This body of work details the design, development, fabrication, prototyping, verification and validation of this novel implant system. The implant system consisted of a configuration of scaffold and hydrogel interpenetrating polymer network composite delivered minimally invasively via a cannula system, after the nucleus pulposus is removed in a nucleotomy with a set of specialised tools. Implantation of the novel prosthesis was shown to be successful in various spinal disc models, in meeting identified design and functional requirements, including biomechanical loading, resistance to expulsion and radiopacity.
7
Vicente, José Ricardo Negreiros. "Estudo comparativo entre a via de acesso minimamente invasiva posterior e a via de acesso lateral direta nas artroplastias totais do quadril não cimentadas." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/5/5140/tde-13022008-080950/.
Повний текст джерелаАнотація:
Um estudo terapêutico comparativo prospectivo é realizado para avaliar o acesso posterior minimamente invasivo em artroplastia total do quadril comparado com o acesso lateral direto tradicional. O estudo inclui 76 pacientes submetidos à artroplastia total do quadril primárias não cimentadas por diagnóstico de osteoartrose primária e secundária. Não são incluídos, pacientes com qualquer tipo de coagulopatia, em uso de anticoagulantes ou antiagregante plaquetário, pacientes hipertensos sem controle medicamentoso, pacientes submetidos à qualquer cirurgia prévia do quadril, e pacientes com seqüela de displasia do desenvolvimento do quadril que tenham a cabeça femoral ectópica. O objetivo principal deste estudo é avaliar a perda volêmica que ocorre nestes pacientes. Há diferença de média de idade (p=0,017) no acesso minimamente invasivo (50,1 anos) em relação ao grupo controle (56,8 anos), porém não observamos diferenças entre os grupos quanto ao índice de massa corpórea, lado operado e diagnóstico inicial. Observa-se um sangramento menor (p<0,001) no período intra-operatório (745,6 ml contra 1282,8 ml), assim como, menor sangramento total (p<0,001) no acesso minimamente invasivo posterior (1083,5 ml contra 1682,3 ml). Relatamos diferença entre os grupos quanto à necessidade de transfusão alogênica, favorável aos pacientes do grupo minimamente invasivo (p=0,02), com 8,8% dos pacientes sendo transfundidos em relação a 28,6% dos pacientes do grupo controle. Nossa estimativa de sangramento no acesso minimamente invasivo posterior é significativamente maior que a literatura, porém a quantidade de unidades de concentrados de hemáceas transfundidas,assim como, a proporção de pacientes transfundidos são menores em relação aos outros autores. Concluímos que os pacientes submetidos ao acesso minimamente invasivo posterior apresentam menor sangramento, melhor resultado clínico precoce e posicionamento adequado dos componentes da prótese.A therapeutic, comparative, prospective study was carried out to evaluate the minimally invasive posterior approach to total hip arthroplasty in relation to the traditional direct lateral approach. The study included 76 cases of primary total hip arthroplasty due to a diagnosis of primary or secondary osteoarthrosis. Patients were excluded from the study if they presented any type of coagulopathy and were using anticoagulants or platelet antiagregants; hypertension without medicinal control; any previous hip surgery; and sequelae of hip developmental dysplasia that might have led to an ectopic femoral head. The objective of our study was to evaluate the blood loss among patients for whom the minimally invasive posterior access is used. Regarding our patients\' ages, we observed a significant difference between the two groups: the mean age of the mini-incision group (50,1 years) was lower than the mean of the control group (56,8 years), p= 0.01. Lower total estimated bleeding was found in the mini-incision group (means of 1083,5 ml versus 1682,3 ml; p < 0.001) and lower intraoperative bleeding (means of 745,6 ml versus 1282,8 ml; p <0.001). There was difference in the need of allogenic transfusion between the two groups (8,8% versus 28,6%,p = 0.13). Our volumes of bleeding from the minimally invasive posterior approach were significantly higher than in the literature, but the mean quantity of transfused red cells and the proportion of transfused patients were both significantly lower than in the literature. Our final impression of the minimally invasive approach is positive with regard to lower blood loss, better clinical results after six months and a satisfactory alignment of the acetabular and femoral components.
8
Nourbakhsh, Ghavameddin. "Reliability analysis and economic equipment replacement appraisal for substation and sub-transmission systems with explicit inclusion of non-repairable failures." Thesis, Queensland University of Technology, 2011. https://eprints.qut.edu.au/40848/1/Ghavameddin_Nourbakhsh_Thesis.pdf.
Повний текст джерелаАнотація:
The modern society has come to expect the electrical energy on demand, while many of the facilities in power systems are aging beyond repair and maintenance. The risk of failure is increasing with the aging equipments and can pose serious consequences for continuity of electricity supply. As the equipments used in high voltage power networks are very expensive, economically it may not be feasible to purchase and store spares in a warehouse for extended periods of time. On the other hand, there is normally a significant time before receiving equipment once it is ordered. This situation has created a considerable interest in the evaluation and application of probability methods for aging plant and provisions of spares in bulk supply networks, and can be of particular importance for substations. Quantitative adequacy assessment of substation and sub-transmission power systems is generally done using a contingency enumeration approach which includes the evaluation of contingencies, classification of the contingencies based on selected failure criteria. The problem is very complex because of the need to include detailed modelling and operation of substation and sub-transmission equipment using network flow evaluation and to consider multiple levels of component failures. In this thesis a new model associated with aging equipment is developed to combine the standard tools of random failures, as well as specific model for aging failures. This technique is applied in this thesis to include and examine the impact of aging equipments on system reliability of bulk supply loads and consumers in distribution network for defined range of planning years. The power system risk indices depend on many factors such as the actual physical network configuration and operation, aging conditions of the equipment, and the relevant constraints. The impact and importance of equipment reliability on power system risk indices in a network with aging facilities contains valuable information for utilities to better understand network performance and the weak links in the system. In this thesis, algorithms are developed to measure the contribution of individual equipment to the power system risk indices, as part of the novel risk analysis tool. A new cost worth approach was developed in this thesis that can make an early decision in planning for replacement activities concerning non-repairable aging components, in order to maintain a system reliability performance which economically is acceptable. The concepts, techniques and procedures developed in this thesis are illustrated numerically using published test systems. It is believed that the methods and approaches presented, substantially improve the accuracy of risk predictions by explicit consideration of the effect of equipment entering a period of increased risk of a non-repairable failure.
9
Ericson, Petter. "Complexity and expressiveness for formal structures in Natural Language Processing." Licentiate thesis, Umeå universitet, Institutionen för datavetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-135014.
Повний текст джерелаАнотація:
The formalized and algorithmic study of human language within the field of Natural Language Processing (NLP) has motivated much theoretical work in the related field of formal languages, in particular the subfields of grammar and automata theory. Motivated and informed by NLP, the papers in this thesis explore the connections between expressibility – that is, the ability for a formal system to define complex sets of objects – and algorithmic complexity – that is, the varying amount of effort required to analyse and utilise such systems. Our research studies formal systems working not just on strings, but on more complex structures such as trees and graphs, in particular syntax trees and semantic graphs. The field of mildly context-sensitive languages concerns attempts to find a useful class of formal languages between the context-free and context-sensitive. We study formalisms defining two candidates for this class; tree-adjoining languages and the languages defined by linear context-free rewriting systems. For the former, we specifically investigate the tree languages, and define a subclass and tree automaton with linear parsing complexity. For the latter, we use the framework of parameterized complexity theory to investigate more deeply the related parsing problems, as well as the connections between various formalisms defining the class. The field of semantic modelling aims towards formally and accurately modelling not only the syntax of natural language statements, but also the meaning. In particular, recent work in semantic graphs motivates our study of graph grammars and graph parsing. To the best of our knowledge, the formalism presented in Paper III of this thesis is the first graph grammar where the uniform parsing problem has polynomial parsing complexity, even for input graphs of unbounded node degree.
10
Mohlala, Tshwari Phineas. "Repair cost-limit replacement policies with minimal repairs." Thesis, 2008. http://hdl.handle.net/10539/5075.
Повний текст джерелаАнотація:
This dissertation examines a number of maintenance models that
are implemented to reduce incidences of system failures or to
return a failed system to the operating state. In particular, the
repair cost-limit (RCL) replacement models are investigated. On
failure the system is replaced by an equivalent new one if the
random repair costs C exceeds a given repair cost limit c , or at
age t by a preventive replacement if in the time interval #1;0,t #2; no
failure induced a replacement of the system. Otherwise, after
failure a minimal repair is carried out. After any replacement, the
time is returned to zero.
For instance, in everyday life, one has to make such decisions
once in a while: repair or replace a car, a television set or a
refrigerator, depending on the cost of a repair. If the cost of repair
is high, then it is more economical to replace the item by a new
one.
This dissertation considers the combination of the RCL
replacement policy with the age replacement policy. An
expression for the expected long run cost per unit time
(maintenance cost rate) is derived. The optimum values of c and
t are obtained.
11
Li, Peichu, and 林培竹. "The Optimal Replacement Policy with Minimal Repair under Free Warranty." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/99319993027762830085.
Повний текст джерелаАнотація:
碩士靜宜大學
財務與計算數學系
101
In today's society, almost all of the products will be sold with a free warranty service, or even a lifetime warranty. Therefore, in such a competitive market environment, has a good warranty service products, is absolutely necessary for manufacturers to consider the conditions. Warranty service is actually based on the product manufacturer to market demand, to give consumers a product tailored to ensure the contractual agreement. Its contents are all described in the product being sold, in the event of failure within the warranty period (or ineffectiveness), vendors will self-absorbed to provide additional repair costs to consumers free repair, or even a direct replacement new products. Main purpose of this thesis, according to Jack & Murthy,2010[11] proposed cutting type replacement warranty service model concept, design a high maintenance cost model for warranty replacement policy. By numerical examples, analysis of this new warranty service model strategies, and find out the best chance of replacement, the replacement time interval and the warranty period, making the high cost of maintenance warranty replacement policy lowest cost model. And with Jack & Murthy,2001[15] proposed a model for comparison.
12
Lin, Chen Yi, and 林貞儀. "The Impact of Free-Minimal Repair Warranty on Age- Replacement Policy." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/81385064441336545466.
Повний текст джерелаАнотація:
碩士國立臺灣科技大學
工業管理系
92
This paper investigates the effects of a free-minimal repair warranty on the age replacement policy for a repairable product. When a repairable product sold with a free-minimal repair warranty, the seller has to repair the failed item under the warranty period, but the buyer still has to pay the downtime cost. In this paper, cost models are developed for both a non-warranted and a warranted product, and the corresponding optimal ages are derived such that the expected cost per unit time is minimized. For a product with an increasing failure rate, the structural properties about the optimal age are obtained, and an algorithm is developed to derive the optimal age replacement policy. Finally, the impact of a product warranty on the optimal age replacement policy is illustrated through some numerical examples.
13
李慶強. "Periodic replacement with minimal repair at failure and general random repair cost." Thesis, 1990. http://ndltd.ncl.edu.tw/handle/01068521212965740687.
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14
曾碧卿. "A study on optimal order point and number of minimal repair before replacement." Thesis, 1990. http://ndltd.ncl.edu.tw/handle/52651881309281668736.
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15
Chen, Wei-han, and 陳暐涵. "Optimal Replacement for Repairable Products with Free Minimal Repair Warranty within a Finite Horizon." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/11582320061441252493.
Повний текст джерелаАнотація:
碩士國立臺灣科技大學
工業管理系
100
With the advancement of technology, surety bond to become one of the strategies for marketing products equipment buyers and sellers to ensure that the contract bound by mutual rights and obligations. General to ensure that the contract also contains maintenance requirements, such as product equipment to ensure the failure period, the seller (manufacturer) have to bear the maintenance responsibility;, unless the warranty period failure, the buyer (consumer) must pay for maintenance costs. The papers to the buyer (consumer) purchase of equipment, machine position to explore a serviceable machine in a finite interval, when the machine equipment in the free minor repairs to ensure production operations during the period, the seller have to bear to ensure the failure of the fault period machine costs, the buyer will be borne by the cost of crashes caused due to equipment, machine failure. The buyer point of view, the establishment of the three machine equipment to ensure the length and machine replacement time of the expected total profit mode, and deduced three modes, so expect the highest total profits of the optimal replacement time. Finally, a numerical example analysis shows that the implementation of the guarantee contract machine equipment in the finite interval, the expected total profit.
16
Csenki, Attila. "Marginal cost analysis of single-item maintenance policies with several decision variables." 2004. http://hdl.handle.net/10454/3203.
Повний текст джерелаАнотація:
NoThe marginal cost approach for the analysis of repair/replacement models was introduced by Berg in 1980 and has since been applied to many maintenance policies of various complexity. All models hitherto analysed in the literature by the marginal cost approach have one single decision variable only, this being, typically, the age of the current item at the time of ordering or replacement. This paper is concerned with the extension of the marginal cost technique to maintenance policies with several decision variables. After addressing the general framework appropriate for the multi-parameter case, we exemplify the workings of the technique by analysing a two-variable maintenance model involving replacement and minimal repair. We demonstrate that the marginal cost approach is an attractive and intuitively appealing technique also for models with several decision variables. Just as in the single-parameter situation, the approach is amenable to economic interpretation, a welcome feature for users of maintenance models with a prime interest in its economic (rather than its mathematical) aspects. As an added bonus of the marginal cost approach, in our example, some otherwise necessary tools from the theory of stochastic processes are dispensable.
17
Teng, Li-Hsiu, and 鄧立修. "Optimal periodic replacement for a deteriorating production system with inspection and general minimal repair costs." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/76389859321318697789.
Повний текст джерелаАнотація:
碩士國立中正大學
數理統計研究所
84
This article investigates a generalized inspection policy for a deteriorating production system with general random minimal repair costs. Unlike many previous efforts, the inspection times for the sequential inspection strategy are assumed to be non-negligible. Furthermore, uncertainty probabilities associated with inspections are introduced. Our objective here is to maximize the profit per unit time for a given overhaul/replacement time by using the numerical search technique. Dynamic programming is provided to derive the optimal periodic overhaul/replacement time and the corresponding optimal number of inspections and their schedule.
18
Chang, Chan-Lun, and 張展綸. "Optimal Single-Replacement for Repairable Products with Free Minimal Repair Warranty under a Finite Horizon." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/75423603562544130656.
Повний текст джерелаАнотація:
碩士國立臺灣科技大學
工業管理系
99
In this thesis, we investigate the effects of repairable products’ single-replacement on a free minimal repair warranty under a finite horizon. When a product is being sold with a free minimal repair warranty, the vendor is responsible for the reparation and the related cost, while despite the vendee is free from the repairing cost, they still need to afford for the downtime cost. The research develops four cost models which are related to product warranty period and product usage period. And derived from the model, we obtain the corresponding optimal single-replacement time so that the expected total cost is minimized. Under the case of product failure rate is increased with time, the research further obtain the characteristic about the optimal single-replacement time, and an algorithm is developed to derive the optimal single-replacement time. Finally, the impact of repairable products’ single-replacement with a free minimal repair warranty under a finite horizon is illustrated through a numerical example.
19
Lin, Tsung-Ching, and 林宗慶. "The results and effect of minimal invasive total knee replacement surgery: the discussion of kinetic analyses and functional recovery." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/17707269407943452027.
Повний текст джерелаАнотація:
碩士國立臺灣師範大學
運動科學研究所
99
Purpose: To investigate the kinetic parameters of lower limb and nature course of functional recovery of the patient who underwent the minimal invasive total knee replacement surgery and determine the change of maximal torque in knee flexors and knee extensors at different muscle strength testing condition. Methods: In this prospective study, twenty-two participants underwent the unilateral minimal invasive total knee replacement surgery, and the knee extensors, knee flexors muscle strength were evaluated at five different times: before surgery, post surgery 1th, 2th, 6th and 12th month. Isometric, isokinetic muscle strength, range of motion(ROM), joint sense and rate of force development(RFD) were analyzed. Results: There is significant difference in isokinetic muscle strength of knee extensor and ROM between both sides before surgery. On post surgery 1st and 2nd month, the maximal torquethe of knee extensor in the operative side were significant smaller than the non-operative side at isometric testing in 60°, and isokinetic test at 60°, and 180° angular velocity. There is no significant difference between post surgery 2nd month and pre surgery in operative side.Only isokinetic 180° the maximal torque of knee extensors in non-operation side was greater than the operation side. 0-150ms RFD of operative leg is significant smaller than non-operative leg duing post surgery 1th, 2th, 6th and 12th month.Conclusion: This study concluded that there was a significant decreased maximal torque of operative leg at one month after surgery compare with the value before surgery; The muscle strength of operative leg can recover to the level before surgery at post surgery 2nd month;There is still lower muscle strength of fast msucle in operative leg than non-operative leg at post surgery 6th month.The values of RFD in operative leg is always lower than non-operative leg during post surgery 1 year.This conclusion could be the reference for the exercise scientists or other exercise experts to design the exercise equipment and exercise prescription.
20
Kumar, Sanjeev. "Space-Time Gauge Theories for Continuum Modelling of Viscoplasticity, Damage And Electro-Magneto-Mechanical Phenomena in Solids." Thesis, 2022. https://etd.iisc.ac.in/handle/2005/6048.
Повний текст джерелаАнотація:
Over the years, sustained research efforts have aimed to understand the material behaviour
under a broad range of response regimes, especially from micromechanical or phenomenological
perspectives — via both continuum modeling and experiments conducted at different
scales. However, a review of the relevant literature has revealed that physics-based models
that can replicate experimental results are very few, and models depicting consistent coupling
phenomena observed in solids beyond elasticity are elusive. Symmetry-driven approaches to
continuum mechanics of solids typically have a unifying nature, combining the prediction
of diverse observed phenomena under a single umbrella. This thesis attempts to derive a
unified field theory for various physical phenomena in solids by exploring local symmetry,
which offers a framework to consistently arrive at the relations among polarization vector,
temperature, scalar potential, vector potential, and the electric and magnetic field for multiphysics
phenomena. Furthermore, this approach enables a consistent and robust coupling
among flow stress, strain rate, and other variables describing the kinematics of plasticity and
damage.
This thesis draws upon continuous and local symmetry-based principles of gauge theory
to arrive at continuum models for various electro-magneto-mechanical coupling phenomena
and inelastic responses involving plasticity and damage in solids. The specific local symmetries
we exploit in the process are conformal (scaling) and translational in space-time.
The work presented may thus be classed in two parts – one focusing on a unified continuum
description of multi-physics phenomena such as piezoelectricity, piezo-magnetism, coupled
thermoelasticity and flexoelectricity and the other on dissipative phenomena such as plasticity
and damage.
Under an inhomogeneous (local) action of the symmetry (gauge) group, invariance of the
energy density is lost. Minimal replacement is used to restore gauge invariance of the energy
density; this requires the definition of a gauge covariant operator in place of the ordinary
partial derivative. Minimal replacement introduces a non-trivial gauge compensating 1-form
field. The 1-form field is decomposed into an anti-exact part and the exact differential of a
scalar-valued function. The other essential ingredient of gauge theory is minimal coupling
21
Bruns, Peter. "Optimale Strategien fuer spezielle Reparatursysteme." Doctoral thesis, 2000. https://repositorium.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-2000090838.
Повний текст джерелаАнотація:
The thesis contains 3 repairable systems and 2 replacement systems: First a repairable system is considered with Markovian deterioration and imperfect repair, carried out at fixed times. We look for optimal strategies under certain conditions. Two optimality criteria are considered: expected discounted cost and long-run average cost. Conditions are found under which the optimal policy is a control-limit policy as used by Derman or Ross. We explicitly explain how to derive this optimal policy; numerical examples are given, too. The special case of unbounded cost is also studied. With the first model the state space is numerable but with the second it is not. With the fourth model the system occurs a shock process and is only inspected after such a shock. Models 3 and 5 are replacement systems with Morkovian deterioration and finite state space {0,...,N}. A system in state N is considered to be in a very serious situation. Hence there is the condition, e.g. stipulated by law, that the percentage of all replaced machines in state N in the group of all replaced machines may not be larger than 100 epsilon for a fixed epsilon in [0,1]. We prove that a generalized control limit policy maximizes the expected running time of a machine and we explain explicitly how to derive this optimal policy. Illustrated numerical examples are given.
22
Lin, Cheng-Kai, and 林晟楷. "Comparisons of In Vivo Three-Dimensional Kinematics of Minimally-Invasive and Patient-Specific Instrument Total Knee Replacements During Functional Activities." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/42265921916245020968.
Повний текст джерелаАнотація:
碩士國立臺灣大學
醫學工程學研究所
104
Total knee replacements (TKR) have been the main choice of treatment for alleviating pain and restoring physical function in advanced degenerative osteoarthritis (OA) of the knee. In recent years, interests in minimally invasive surgery TKR (MIS-TKR) have increased substantially in industry and between orthopedic surgeons and patients. Moreover, patient-specific instrumentation (PSI) was designed to replace the previous surgical instrumentations without the needs for the computer navigation system. PSI-TKR was a newly developed surgical technique, aiming to more accurately restore the knee axis of the TKR than previous approaches, and was conducted with the minimally invasive surgical approaches in general. Therefore, the purposes of the project were to measure the 3D kinematics of the TKR in vivo. The kinematic data of the knee for the patients with MIS-TKR and PSI-TKR after surgery six-monthly have been calculated during functional tasks , i.e. active knee extension, flexion and sit-to-stand. According to the results, The performances of MIS-TKR and PSI-TKR patients are regarded to be equal on the translation except on the M/L direction. However, the differences on the M/L direction were too slight to affect the movement clinically. To be mentioned, MIS-TKR didn’t externally rotate to represent the screw home mechanism as a normal knee. It could induce abnormal articular contact pattern to the plastic insert which might shorten the life cycle of the TKR. It is suggested that the anatomical pose of the TKR in the minimally invasive surgery should be dealt with much more care to avoid consistent lateral contact broken.
23
Gofus, Ján. "Vliv miniinvazivního přístupu na respirační funkce u pacientů po aortální náhradě." Doctoral thesis, 2021. http://www.nusl.cz/ntk/nusl-438373.
Повний текст джерелаАнотація:
of the dissertation Impact of minimally invasive approach on pulmonary function in patients undergoing aortic valve replacement MUDr. Ján Gofus The most common minimally invasive approach to aortic valve replacement is upper hemisternotomy, which has been implemented at our department, as well. Preserving the lower half of thoracic cage could lead to lower postoperative drop of pulmonary function, apart from other benefits. Nevertheless, publications on this topic are insufficient and controversial. Our aim was to perform a prospective randomized trial comparing upper hemisternotomy with standard (median) sternotomy in terms of pulmonary function changes perioperatively. We also added a novel exercise tolerance test, one-minute sit-to-stand test, and a quality of life evaluation to the study. We included patients indicated for elective isolated aortic valve replacement with bioprosthesis who were older than 65 years, signed informed consent, and in which both surgical approaches were technically feasible. Exclusion criteria were re-do surgery and concomitant cardiac surgery. Patients were randomized to minimally invasive and standard group in 1:1 ratio. On the day of admission, on the 7th postoperative day and 3 months postoperatively, the patients underwent pulmonary function testing and one-minute...
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El, Yamani Nidal. "Interventions innovantes dans le traitement des maladies valvulaires mitrales et aortiques : options de traitement actuelles et perspectives futures." Thesis, 2020. http://hdl.handle.net/1866/25185.
Повний текст джерелаАнотація:
Les maladies valvulaires constituent une cause importante de morbidité et de mortalité.
Dans les pays industrialisés, l’insuffisance mitrale et la sténose aortique sont les pathologies
valvulaires les plus fréquentes et leur prévalence augmentent avec l’âge. Étant donné
l’augmentation de l’espérance de vie dans ces pays, la prévalence des valvulopathies
dégénératives deviendra plus importante et aura un impact non négligeable sur la santé publique.
Les avancées en chirurgie cardiaque ainsi que les nouvelles percées en cardiologie
interventionnelle ont modifié considérablement la prise en charge des patients avec des
valvulopathies en offrant des approches minimalement invasives, surtout pour les patients à haut
risque chirurgical.
Dans le cadre de ce mémoire, deux études rétrospectives de cohorte ont été réalisées. La
première consiste à comparer les résultats postopératoires et sur trois ans de la chirurgie
conventionnelle par rapport à la procédure transcathéter MitraClip chez 259 patients avec une
insuffisance mitrale ischémique sévère. La deuxième étude compare les résultats postopératoires
de trois approches de remplacement de la valve aortique, soit la sternotomie, la ministernotomie
et la minithoracotomie.
La première étude permet de conclure que la procédure MitraClip a un taux de mortalité
postopératoire et sur 3 ans inférieur à celui de la chirurgie mais qu’elle est associée à un plus
haut taux de récurrence de l’insuffisance mitrale après 3 ans. La deuxième étude démontre que
les deux approches minimalement invasives, la ministernotomie et la mini-thoracotomie, ont un
taux équivalent de mortalité intra-hospitalier à la sternotomie. La mini-thoracotomie est associée
à moins de saignement périopératoire et moins de douleur au repos que la sternotomie.
En conclusion, les approches minimalement invasives offrent une excellente alternative à
la chirurgie conventionnelle dans le traitement de la maladie valvulaire. Les bénéfices cliniques
sont d’autant plus évidents lorsque les patients sont adéquatement sélectionnés; d’où
l’importance d’une ‘Heart Team’ qui collabore pour une meilleure prise en charge des patients.Valvular heart disease is an important cause of morbidity and mortality. In western countries, mitral regurgitation and aortic stenosis are the most frequent valvular pathologies and their prevalence increases with age. With the increase in life expectancy in these countries, the prevalence of degenerative valve disease will increase with a significant burden on healthcare systems. Advances in cardiac surgery as well as new breakthroughs in interventional cardiology have considerably modified the management of patients with valvular disease, by offering minimally invasive approaches, especially for patients at high surgical risk. In this thesis, two retrospective cohort studies were carried out. The first compares the postoperative and 3 years outcomes of mitral valve surgery vs MitraClip, a transcatheter procedure, in 259 patients with severe ischemic mitral regurgitation. The second study compares the postoperative results of two minimally invasive techniques (ministernotomy and minithoracotomy) for aortic valve replacement to conventional sternotomy. In the first study, MitraClip procedure had lower postoperative and 3-year mortality rate than surgery, but it was associated with higher recurrence rate of mitral regurgitation after 3 years. The second study showed that the two minimally invasive approaches had similar intrahospital mortality rate to sternotomy. Minithoracotomy was associated with less perioperative bleeding and less pain at rest than sternotomy. In conclusion, minimally invasive approaches offer an excellent alternative to conventional surgery in the treatment of valvular disease. The clinical benefits are more highlighted when patients are properly selected; hence the importance of a "Heart Team" that collaborates for better patient care.