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Статті в журналах з теми "Méthode Effective Internal Variable"
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Kersan-Skabic, Ines. "Is internal devaluation policy in the EU effective?" Ekonomski anali 61, no. 211 (2016): 29–46. http://dx.doi.org/10.2298/eka1611029k.
Повний текст джерелаАнотація:
This research provides indepth analysis of the causes and outcomes of internal devaluation policy in EU. It is conducted using statistical and econometric tools on a sample of three groups of EU member states: EU new member states, PIIGS, and the rest of the EU (EU-core). The analysis points to the key drivers of economic growth in the whole of the EU as being productivity and investment (and consumption in EU new member states and EU core members). Unit labour costs are relevant for GDP growth in PIIGS but with a positive sign, while for the rest of the EU it is not a significant variable. The policy of internal devaluation is unsuitable for application in any EU member states, due to individual specificities. The solution is stronger EU governance that takes the heterogeneity of EU member states into consideration in the process of creating policies and finding solutions.
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Johanes, Johanes, and Susanto Soekiman. "ANALISIS FAKTOR-FAKTOR INTERNAL PERUSAHAAN YANG MEMPENGARUHI KEPUASAN KERJA KARYAWAN PT. PETRO CENTRAL GRESIK." EKUITAS (Jurnal Ekonomi dan Keuangan) 9, no. 4 (January 1, 2007): 585. http://dx.doi.org/10.24034/j25485024.y2005.v9.i4.2394.
Повний текст джерелаАнотація:
Human as source, as generally and their live looking for happiness while constitute of equation from live satisfaction. Every individual has satisfaction level while different – appropriate with value – has been valid in their self. More many aspects in the job while equation with those individual desire so more lower of satisfaction level that he feels. Satisfaction work according Herzberg (1957:107) configured to be 2 category that is: satisfaction or motivator and dissatisfies or hygiene factor. Satisfies is factors as source of satisfied work configure: opportunity achievement, confession, responsibility, work while more challenge and dissatisfies configure: work condition, salary/ fee, supervision/ leadership style while constitute of dissatisfies work. To increase productivity and effective work of employ the researcher adopt problem satisfied work of employ PT. Petro Central Gresik. Research while writer has been done with used analyst factor from program SPSS. Result finding variable while dominan affect work satisfied employ is salary variable/ fee (X2) with loading 0,86. Beside that influenced by six other variable that is in a series: variable of leadership style with loading 0,8; variable of work condition with loading 0,78; variable working while more challenge with loading 0,77; and variable confession with loading 0,74.Based on that finding, the researcher suggest for PT. Petro Central Gresik to increase satisfaction work of employ, where more give attention is: the leader of company should cooperate to increase satisfaction work of employ as whole, this very important to maximize result, because higher of work satisfaction employ could be increase productivity and effective work of employ, so leader of company holding on 2 core factor and 7 variable, with stress of core factor also variable while dominant influenced about work satisfaction, so can increase that productivity and effective work.
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Soekiman, Johanes F. X. Susanto. "ANALISIS FAKTOR-FAKTOR INTERNAL PERUSAHAAN YANG MEMPENGARUHI KEPUASAN KERJA KARYAWAN PT. PETRO CENTRAL GRESIK." EKUITAS (Jurnal Ekonomi dan Keuangan) 9, no. 4 (September 17, 2018): 585–605. http://dx.doi.org/10.24034/j25485024.y2005.v9.i4.312.
Повний текст джерелаАнотація:
Human as source, as generally and their live looking for happiness while constitute of equation from live satisfaction. Every individual has satisfaction level while different – appropriate with value – has been valid in their self. More many aspects in the job while equation with those individual desire so more lower of satisfaction level that he feels. Satisfaction work according Herzberg (1957:107) configured to be 2 category that is: satisfaction or motivator and dissatisfies or hygiene factor. Satisfies is factors as source of satisfied work configure: opportunity achievement, confession, responsibility, work while more challenge and dissatisfies configure: work condition, salary/ fee, supervision/ leadership style while constitute of dissatisfies work. To increase productivity and effective work of employ the researcher adopt problem satisfied work of employ PT. Petro Central Gresik. Research while writer has been done with used analyst factor from program SPSS. Result finding variable while dominan affect work satisfied employ is salary variable/ fee (X2) with loading 0,86. Beside that influenced by six other variable that is in a series: variable of leadership style with loading 0,8; variable of work condition with loading 0,78; variable working while more challenge with loading 0,77; and variable confession with loading 0,74.Based on that finding, the researcher suggest for PT. Petro Central Gresik to increase satisfaction work of employ, where more give attention is: the leader of company should cooperate to increase satisfaction work of employ as whole, this very important to maximize result, because higher of work satisfaction employ could be increase productivity and effective work of employ, so leader of company holding on 2 core factor and 7 variable, with stress of core factor also variable while dominant influenced about work satisfaction, so can increase that productivity and effective work.
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Pan, Jiaying, Lin Chen, Haiqiao Wei, Dengquan Feng, Sili Deng, and Gequn Shu. "On autoignition mode under variable thermodynamic state of internal combustion engines." International Journal of Engine Research 21, no. 5 (September 4, 2018): 856–65. http://dx.doi.org/10.1177/1468087418796617.
Повний текст джерелаАнотація:
Autoignition modes under premixed combustion conditions are usually studied in constant-volume configurations. However, the autoignition events related to knocking combustion in spark-ignition engines do experience variable volumes in combustion chamber and ever-changing thermodynamic states caused by reciprocating piston motion and main flame front compression. Such combustion situations may lead to different autoignition modes from constant-volume scenarios. Using one-dimensional direct numerical simulations with detailed chemistry and transport of H2/air mixture, the autoignition modes during knocking combustion were studied under different engine combustion boundary conditions. It was the first to identify important influence of variable thermodynamic states on the development of autoignition modes through changing critical temperature gradients. Four autoignition modes—thermal explosion, supersonic deflagration, detonation, and subsonic deflagration—were observed, which, however, were quantitatively different from the constant-volume configurations in regime boundaries. Meanwhile, on comparison with intake temperature and equivalence ratio, intake pressure shows greater impact on detonation formation, characterized by a regime extension under high intake pressures. To classify the autoignition modes responsible for various knocking events with different intensities in a straightforward manner, a regime diagram was proposed based on the temperature gradients and the effective energy density used for universally quantifying various intake conditions. This diagram was found useful to determine the distributions of different autoignition modes (especially for detonation) and the potential approaches for achieving maximum thermal efficiency while suppressing engine knock. In addition, detonation mode was prevailing under high effective energy density conditions, and the underlying reasons were ascribed to the significant reduction of excitation time and pre-flame temperature increases by pressure wave.
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Huijiao, Duan. "Internal Control, Manager ability and Enterprise performance – Empirical Analysis Based on DEA data Envelopment Model." E3S Web of Conferences 292 (2021): 02027. http://dx.doi.org/10.1051/e3sconf/202129202027.
Повний текст джерелаАнотація:
Internal control has become an important part of corporate governance. This paper selects all Chinese A-share listed companies from 2015 to 2019 as samples to study the relationship between internal control and corporate performance, and to investigate the effect of managers’ ability on the process of internal control affecting corporate performance. It is found that there is a significant negative correlation between internal control defects and enterprise performance, which indicates that there are significant internal control defects, which will restrain the enterprise’s financial performance; the effectiveness of internal control operation is significantly positively correlated with enterprise performance, which shows that the operation of effective internal control helps to promote the financial performance of enterprises. When we introduce management competence as a moderating variable, we find that competent managers can improve financial performance in an effective internal control environment.
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Kidron, Aviv, Yuval Ofek, and Herztel Cohen. "New perspective on the black box of internal auditing and organisational change." Managerial Auditing Journal 31, no. 8/9 (September 5, 2016): 804–20. http://dx.doi.org/10.1108/maj-07-2015-1220.
Повний текст джерелаАнотація:
Purpose The shift from the traditional audit towards performance audit implies that internal auditors in the public sector function as change agents who underpin the fundamental change process. This paper aims to propose a model that identifies the determinants of organisational change in the public sector that result from internal auditing and the way internal auditors facilitate it. Design/methodology/approach The conceptual discussion of this paper is based on a review of relevant literature, both practical and academic. Findings This paper develops an innovative model that describes the factors leading to auditees’ change readiness after undergoing internal audit processes. The independent variable is audit information quality and the dependent variable, organisational change. Auditees’ perceptions is the mediator variable, and accessibility to audit information is the moderator variable. Practical implications The proposed model suggests the advantages that can be gained by audit-related services, which in turn will add value to the organisation. The relationships between the variables inform practitioners on how to support effective audits as a means of increasing performance and influencing organisational change. Originality/value As the paper offers an innovative model, it may open up new research areas in internal auditing that can be studied by using both qualitative and quantitative methods.
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Binamer, Yousef, Laura Sowerby, and Therese El-Helou. "Treatment of Ulcerative Necrobiosis Lipoidica with Topical Calcineurin Inhibitor: Case Report and Literature Review." Journal of Cutaneous Medicine and Surgery 16, no. 6 (November 2012): 458–61. http://dx.doi.org/10.1177/120347541201600621.
Повний текст джерелаАнотація:
Background: Ulcerative necrobiosis lipoidica (UNL) is an uncommon disease, which is frequently recalcitrant to available therapies. It is characterized by well-defined, ulcerated plaques with indurated borders and atrophic centers. Multiple therapeutic options have been described, with variable success rates. Objective: To report the efficacy of using topical tacrolimus in treating UNL. Method: Topical tacrolimus was used in the treatment of two patients with UNL. Result: Topical tacrolimus is effective in treating UNL. Conclusion: Topical tacrolimus is a reasonably effective choice in treating UNL. Contexte: La nécrobiose lipoïdique ulcérée (NLU) est une maladie rare, qui est souvent réfractaire au traitement. Elle se caractérise par des placards ulcérés et bien définis, des bords indurés et des centres atrophiques. Différentes formes de traitement ont été utilisées et se sont soldées par des taux variables de réussite. Objectif: L'étude visait à faire état de l'efficacité du tacrolimus topique dans le traitement de la NLU. Méthode: Nous avons fait usage de tacrolimus topique dans le traitement de la NLU chez deux patients. Résultat: Le tacrolimus topique s'est montré efficace dans le traitement de la NLU. Conclusion: Le tacrolimus topique est un moyen relativement efficace de traitement de la NLU.
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Sun, Xinchao, Lianyu Zhao, and Zhenzhong Liu. "A model reference adaptive variable impedance control method for robot." MATEC Web of Conferences 336 (2021): 03005. http://dx.doi.org/10.1051/matecconf/202133603005.
Повний текст джерелаАнотація:
As a simple and effective force tracking control method, impedance control is widely used in robot contact operations. The internal control parameters of traditional impedance control are constant and cannot be corrected in real time, which will lead to instability of control system or large force tracking error. Therefore, it is difficult to be applied to the occasions requiring higher force accuracy, such as robotic medical surgery, robotic space operation and so on. To solve this problem, this paper proposes a model reference adaptive variable impedance control method, which can realize force tracking control by adjusting internal impedance control parameters in real time and generating a reference trajectory at the same time. The simulation experiment proves that compared with the traditional impedance control method, this method has faster force tracking speed and smaller force tracking error. It is a better force tracking control method.
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Mahmoud, ADAMU Mohammed, and Y. M. DAMAGUN. "Determinants of Internal Audit Effectiveness in the Nigerian Paramilitary Agencies." International Journal of Research and Innovation in Social Science VII, no. XI (2023): 1005–22. http://dx.doi.org/10.47772/ijriss.2023.7011079.
Повний текст джерелаАнотація:
The objective of this study is to examine the determinants of internal audit effectiveness in the Nigerian paramilitary agencies. The methodology of the study is qualitative using a questionnaire as a primary data source. The population and sample size comprises of three hundred and forty (340) audit staff from six (6) paramilitary agencies in Nigeria. The period of this study covers 10 years (2013-2022). Normality Test, Correlation, Regression Analysis were conducted on the collected data. The regression results revealed that internal audit quality with “β” and “sig” values of 0.125, and 0.044 respectively. Hence, internal audit quality has statistical significant impact on internal audit effectiveness of Nigerian Paramilitary services, it also shows that Independency of audit staff with “β” and “sig” values of 0.037, and 0.578 respectively. This indicates that the variable has a positive effect and it is statistically insignificant at 5% because the p-value is greater than 0.05. Hence independency of audit staff has no impact on internal audit effectiveness of Nigerian Paramilitary services, the results also revealed that Professional proficiency and competence of audit staff with “β” and “sig” values of 0.086, and 0.151 respectively. This indicates that the variable has a positive effect and it is statistically insignificant at 5% because the p-value is greater than 0.05. Hence professional proficiency and competence of audit staff has no impact on internal audit effectiveness of Nigerian Paramilitary services, also Organizational setting with “β” and “sig” values of -0.051, and 0.415 respectively. This indicates that the variable has a negative effect and it is statistically insignificant at 5% because the p-value is greater than 0.05. Hence, organizational setting has no impact on internal audit effectiveness in Nigerian Paramilitary services. The regression results revealed that internal audit quality with “β” and “sig” values of 0.189, and 0.003 respectively. This indicates that the variable has a positive effect and it is statistically significant at 5% because the p-value is less than 0.05. Hence, scope of internal audit work has impact on internal audit effectiveness of Nigerian Paramilitaries services and the results revealed that management support with “β” and “sig” values of 0.398, and 0.000 respectively. Hence, management support has statistical significance impact on internal audit effectiveness of Nigerian Paramilitary services. Therefore, we recommend that Internal audit staff should be fully independent in order to have unbiased internal audit report. Paramilitary agencies should implement policies and procedures against which organizational settings are to be gauged. The policies and procedures should be well-understood by the management staff so as to allow the setting of the organization to be effective. Finally, management of Nigerian Paramilitary agency should give support to the internal audit on widening the scope of the audit work in order to have a more reliable and effective internal audit report.
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de Lavergne, Casimir, Gurvan Madec, Julien Le Sommer, A. J. George Nurser, and Alberto C. Naveira Garabato. "The Impact of a Variable Mixing Efficiency on the Abyssal Overturning." Journal of Physical Oceanography 46, no. 2 (February 2016): 663–81. http://dx.doi.org/10.1175/jpo-d-14-0259.1.
Повний текст джерелаАнотація:
AbstractIn studies of ocean mixing, it is generally assumed that small-scale turbulent overturns lose 15%–20% of their energy in eroding the background stratification. Accumulating evidence that this energy fraction, or mixing efficiency Rf, significantly varies depending on flow properties challenges this assumption, however. Here, the authors examine the implications of a varying mixing efficiency for ocean energetics and deep-water mass transformation. Combining current parameterizations of internal wave-driven mixing with a recent model expressing Rf as a function of a turbulence intensity parameter Reb = εν/νN2, the ratio of dissipation εν to stratification N2 and molecular viscosity ν, it is shown that accounting for reduced mixing efficiencies in regions of weak stratification or energetic turbulence (high Reb) strongly limits the ability of breaking internal waves to supply oceanic potential energy and drive abyssal upwelling. Moving from a fixed Rf = 1/6 to a variable efficiency Rf(Reb) causes Antarctic Bottom Water upwelling induced by locally dissipating internal tides and lee waves to fall from 9 to 4 Sverdrups (Sv; 1 Sv ≡ 106 m3 s−1) and the corresponding potential energy source to plunge from 97 to 44 GW. When adding the contribution of remotely dissipating internal tides under idealized distributions of energy dissipation, the total rate of Antarctic Bottom Water upwelling is reduced by about a factor of 2, reaching 5–15 Sv, compared to 10–33 Sv for a fixed efficiency. The results suggest that distributed mixing, overflow-related boundary processes, and geothermal heating are more effective in consuming abyssal waters than topographically enhanced mixing by breaking internal waves. These calculations also point to the importance of accurately constraining Rf(Reb) and including the effect in ocean models.
Дисертації з теми "Méthode Effective Internal Variable"
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Vernier, Patricia. "Homogenization of composite materials with fractional viscoelastic constituents." Electronic Thesis or Diss., Sorbonne université, 2023. http://www.theses.fr/2023SORUS552.
Повний текст джерелаАнотація:
Cette thèse porte sur la prédiction des propriétés mécaniques effectives de matériaux hétérogènes composés de constituants viscoélastiques fractional, au moyen d'une approche incrémentale variationnelle. Nous appliquons la méthode Effective Internal Variable (EIV) développée par Lahellec and Suquet (2007), particulièrement attrayante pour le traitement de comportements viscoélastiques (Tressou et al., 2016). Contrairement aux méthodes d'homogénéisation communément utilisées qui reposent sur le principe de correspondance et pour lesquelles les fluctuations des champs ne sont pas accessibles, cette approche incrémentale permet de calculer les propriétés effectives dans le domaine direct au moyen des méthodes variationalles de Ponte Castañeda (1991 et 2002) qui prennent en compte les seconds-moments des champs mécaniques. La méthode EIV s'inscrit dans le cadre des Matériaux Standards Généralisés (MSG), dans lequel le comportement des matériaux dissipatifs est décrit par deux potentiels thermodynamiques convexes. Nous considérons des constituants viscoélastiques fractionnaires, dont la loi constitutive est décrite par des équations différentielles linéaires avec des dérivées fractionnaires. En accord avec des observations expérimentales, ce formalisme prend en compte des effets de mémoire longue à travers la superposition de plusieurs temps caractéristiques (Caputo et Mainardi, 1971). La distribution de ces derniers est donnée explicitement par l'expression du spectre en loi puissance. Les potentiels thermodynamiques des matériaux viscoélastiques fractionnaires sont définis en cohérence avec le cadre des MSG. Cette cohérence s'appuie sur l'interprétation rhéologique de l'élément fractionnaire comme un Maxwell généralisé (Lion, 1997). Ainsi, nous tirons parti de l'extension de la méthode EIV à plusieurs variables internes développée par Tressou et al. (2023) afin d'homogénéiser des matériaux composites contenant des constituants viscoélastiques fractionnaires. De plus, les temps caractéristiques sont adéquatement choisis à partir de la discrétisation du spectre. Cette discrétisation est réalisée avec la procédure de Papoulia et al. (2010), basée sur une méthode des trapèzes améliorée. Plus précisément, nous appliquons cette méthode à la fonction de Mittag-Leffler impliquée dans la définition des spectres de relaxation. Nous abordons deux problèmes hétérogènes différents au moyen de la méthode EIV. Nous considérons d'abord un composite de type matrice-inclusions sous chargement harmonique, pour lequel nous rencontrons des difficultés numériques. Nous évaluons ensuite la méthode EIV sur un polycristal de glace soumis à un essai de fluageThis PhD thesis deals with the prediction of the mechanical effective properties of composite materials with linear fractional viscoelastic constituents by means of an incremental variational approach. We make use of the Effective Internal Variable (EIV) method developed by Lahellec and Suquet (2007), which is particularly attractive for viscoelasticity (Tressou et al., 2016). Contrary to the common homogenization methods that rely on the correspondence principle and where the fluctuations are not accessible, this incremental method evaluates the effective properties into the direct domain through the variational methods of Ponte Castañeda (1991 and 2002) that take into account the second-moments of the fields. The EIV method is based on the Generalized Standard Materials framework, in which the dissipative materials are described by means of two convex thermodynamic potentials. We consider local fractional viscoelastic constituents, of which the constitutive behaviours follow linear differential equations with fractional derivative operators. In accordance with experimental observations, this formalism takes into account long-memory effects through the superposition of several characteristic times (Caputo and Mainardi, 1971). Their distribution is provided by the explicit expression of the spectrum as a power law. The potentials of fractional viscoelastic constituents are consistently defined in the GSM framework through the rheological interpretation of the fractional damping element as a generalized Maxwell model (Lion, 1997). Therefore, we take advantage of the extension of the EIV method to several internal variables, developed by Tressou et al. (2023) for the homogenization of composites with local fractional viscoelastic behaviours. Besides, the characteristic times are appropriately chosen by discretizing the spectrum. This is done using the midpoint-based procedure developed by Papoulia et al. (2010). More specifically, we apply their method to the Mittag-Leffler function involved in the definition of the relaxation spectrum. We use the EIV method to tackle two different heterogeneous problems. We consider a matrix-inclusion composite under harmonic loading, for which we come accros numerical issues. We then evaluate the EIV method for a polycrystal subject to a monotonous creep loading
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Faye, Mactar. "Structure interne et propriétés thermiques macroscopiques, application aux matériaux de construction." Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30032/document.
Повний текст джерелаАнотація:
L'objectif de cette thèse est d'étudier l'impact de la structure interne des matériaux isotropes granulaires sur leurs propriétés thermiques macroscopiques. Nous avons développé un code de calcul pour résoudre les transferts thermiques au sein d'un matériau hétérogène tridimensionnel. Ce code est couplé avec un algorithme de génération de structures aléatoires. Après validation expérimentale, nous avons généré des géométries granulaires dont nous avons caractérisé la structure interne, puis nous avons étudié l'impact de cette structure sur la conductivité thermique. Nous avons également développé une nouvelle méthode de mesure expérimentale de la capacité thermique surfacique d'un élément de paroi à structure interne complexe. L'originalité de cette méthode est le couplage d'un modèle analytique de la capacité thermique, indépendant des propriétés thermiques des constituants, et d'une étude expérimentaleThe objective of this thesis is to study the impact of the internal structure of isotropic granular materials on the macroscopic thermal properties. We have developed a model to solve the heat transfer problem within a heterogeneous three-dimensional material. This code is coupled with an algorithm generating random structure. After an experimental validation, we first generated granular materials and we characterized their internal structure; then we studied the impact of this structure on the thermal conductivity. We also developed a new experimental method for measuring the heat capacity area of a wall element with complex internal structure. The originality of this method is the coupling of an analytical model of heat capacity area, which is independent of the thermal properties of the constituents, and an experimental study
Частини книг з теми "Méthode Effective Internal Variable"
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Biliuk, Anatolii, and Olena Diachynska. "THE APPLIED ORIENTATION OF THE PHYSICS COURSE AS AN EFFECTIVE TOOL FOR FORMING THE PROFESSIONAL COMPETENCE MODEL OF FUTURE TECHNOLOGICAL ENGINEERS." In Modern educational technologies in the training of specialists in the agricultural sector during the crisis. Publishing House “Baltija Publishing”, 2023. http://dx.doi.org/10.30525/978-9934-26-298-2-1.
Повний текст джерелаАнотація:
Reliability of structures is the most important problem in modern meсhanical engineering. Its solution poses the task of creating materials with high stable physical, mechanical, chemical and other properties. The materials that make up the basis of structures are, as a rule, operated in variable fields of various nature (mechanical, temperature, etc.), therefore they continuously change their properties. In this regard, progress in the field of mechanical engineering cannot be achieved without full knowledge of the real structure of materials, without a deep understanding of the microprocesses that occur in the materials during their processing and operation.Therefore, the purpose of the work is to describe methods and techniques for determining damping, structural and mechanical characteristics of materials and to evaluate the nature of their changes under the influence of temperature, time and force factors.The most promising non-destructive physical research methodsinclude the method of mechanical spectroscopy (internal friction) and the microhardness method. With the help of the method of mechanical spectroscopy, it is possible to reliably determine such seemingly different properties of materials as the ability to dampen vibrations arising during the operation of machine parts, the diffusion mobility of atoms in the crystal lattice and along dislocations. Internal friction (IF), which characterizes the ability to dissipate the energy of mechanical vibrations with a large and small amplitude in the material, can often be unambiguously associated with the number and mobility of dislocations and point defects of the crystal lattice. At the same time, it allows you to assess the material's susceptibility to another consequence, creep and grain boundary relaxation. Processes such as separation and dissolution of residual phases, relaxation, rest, hardening and tempering, dispersion hardening, plastic deformation and deformation aging and return have been successfully studied for many years by the method of internal friction. IF not only makes it possible to determine damping, structural and mechanical characteristics, but also to follow the nature of their changes in the fields of various nature [1–4]. Microhardness, which characterizes the energy of the interatomic bond of the crystal, its mechanical strength or the resistance of the crystal lattice to large plastic deformations and destruction, was chosen as a controlling characteristic in the study of the results.The research results showed that thermal cycling leads not only to the for-mation of high density dislocations in alloys, but also to their redistribution into polygonal walls. This is due to the fact that the available impurities, their complexes or separate dispersed allocations significantly block the newly formed dislocations and the already formed substructure, and thus increase its thermal stability and increase the heat resistance of the material. At the same time, as the strength characteristics increase, the damping properties are not significantly lost.Value/originality. Application of thermocycling under load is possible not only for materials made of dispersion-hardening alloys, which serve as raw materials for technology and industry, but also for finished parts and technical structures made of them. This will simplify the processing technology, reduce energy consumption and allow to obtain a significant economic effect.
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Tverdokhlib, Ihor, and Yurii Polievoda. "THE INFLUENCE OF PARAMETERS OF RUNNING SYSTEMS AND THEIR SUSPENSION ON THE SAFETY OF OPERATORS OF MOBILE MACHINES AND ENERGY EQUIPMENT." In Modernization of research area: national prospects and European practices. Publishing House “Baltija Publishing”, 2022. http://dx.doi.org/10.30525/978-9934-26-221-0-13.
Повний текст джерелаАнотація:
The scientific work is based on the tasks of applied research on initiative topics on the topic: «Substantiation of parameters and modes of interaction of the drive wheel with the soil», state registration number 0117U006833. The authors’ research is aimed at solving current problems of vibrational vibrations on the operators of technological means. All machines and mechanisms used by man in production and in everyday life are sources of various mechanical measurements and, accordingly, hazards. Of all the types of hazards caused by mechanical influences, vibration is the most dangerous for humans. It is human physiology that contributes to the negative effects of vibration. Due to the fact that the human body consists of hard bones, soft muscles, joints, various internal organs, it can be considered as a complex oscillatory system, the mechanical reaction of which depends on the parameters of vibration. At high frequencies (less than 2 Hz), the body responds to total vibration like a hard mass. At higher frequencies, the body responds as an oscillating system with one or more degrees of freedom. This is manifested in resonance increases in the oscillations of individual organs of the body at certain frequencies. It is for the sitting body position (in which the mobile operator is most of the time) that the resonance is at a frequency of 4-6 Hz.One of the most effective ways to reduce the negative impact of vibrational vibrations on the operator is to reduce the oscillations in the source of their occurrence, as well as the path of propagation from source to operator. This can be partially achieved, including the choice of rational pressure in the wheels of the vehicle, as well as high-quality and timely diagnosis of its individual components and units. This work is devoted to these important issues, and therefore its relevance is beyond doubt.In the scientific work the question of influence of a condition of a basic surface and geometrical parameters of a wheel of a tractor on speed of its movement and frequency of vibration fluctuations which arise at it is investigated. This issue is of considerable theoretical and practical importance, because the road and wheel oscillations caused by road irregularities cause a significant deterioration in the performance of the tractor. These issues have been studied by a number of researchers, but they have varied narrowly. That is why the task was to consider more deeply the connection between the state of the wheel and the coating with the parameters of vibration oscillations that occur during movement. In theoretical studies, the relationship between the length of the wheel chords and the irregularities between the two points of contact of the wheel was established. The support surface equation was represented by a sinusoid with a variable amplitude coefficient. Depending on the ratio of the radius of the wheel and the geometric dimensions of the protrusions and depressions of the support surface, two groups of equations were obtained that describe the parameters of vibrational oscillations. The results of analytical studies were illustrated by the corresponding geometric relationships. To verify the theoretical references, experimental studies were conducted with a system for measuring the parameters of vibration oscillations of controlled axles of wheeled agricultural tractors. The study was performed on two variants of the road surface. The results of experimental research are presented graphically in the form of oscillograms of vibration acceleration of the controlled axle of the tractor, as well as in tabular form. Theoretical and experimental studies show that there is an inverse relationship between the value of the wheel radius and the parameters of vibrational oscillations. As the translational speed of the tractor increases, the parameters of vibration oscillations also increase. The aim of the work is to reduce the negative impact of vibration load on the operator of a mobile vehicle by substantiating the rational parameters of the wheel and determining the location and method of diagnosing its individual components and units. To achieve this goal you need to perform the following tasks: determine the causes of injuries in the operation of mobile vehicles; to analyze the harmful effects of vibration oscillations on the mobile operator; identify ways to reduce vehicle vibrations; to carry out mathematical formalization of the process of oscillations of the operator’s workplace; to build a mathematical model of oscillations of the system «road – vehicle – operator».In this research we used research methods to determine theoretical data based on mechanical and mathematical modeling of the interaction of elastic propulsion and curved support surface using the basic principles of theoretical mechanics and higher mathematics.
Тези доповідей конференцій з теми "Méthode Effective Internal Variable"
1
Ye, Zhengmao, Liguang Li, and Habib P. Mohamadian. "Multi-Variable Optimization on Variable Intake Valve Closing Timing System for Engine Overall Performance." In ASME 2005 Internal Combustion Engine Division Spring Technical Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/ices2005-1099.
Повний текст джерелаАнотація:
Variable valve timing (VVT) technology has a remarkable impact on engine power output, fuel economy and emission levels. To achieve a tradeoff among its potential benefits on various aspects, a novel multi-objective optimization method is proposed to complement among engine performances over entire speed-load regions. Intake valve closing (IVC) timing has been widely accepted to be the most effective means of VVT technologies. IVC timing is therefore investigated to accomplish engine overall performance optimization. The bench tests have been conducted using an introduced variable working position belt extender system. A 5-valve, double overhead cam (DOHC) spark ignition engine is selected. The sample testing data of engine power and torque outputs, fuel economy and emission levels are collected from engine bench tests, which are then interpolated with regular engine speed operating ranges via smoothing cubic spline fitting. For multi-objective control problem, principal component analysis can be conducted for the multiple-objective analysis by alternating different engine parameters, such as valve timing, sparking timing, A/F ratio, and so on. On account of the extra expense of engine experiments, a simplified optimization approach is then formulated in order to analyze the potential of IVC technology in terms of engine power output and fuel economy under constraints of emission levels at individual high speed, medium speed and low speed regions, etc. Variable IVC timing control has been shown in this research to improve engine performance throughout speed-load regions. Multi-variable optimization is also demonstrated to be feasible and effective for the optimal performance achievement on speed-load regions.
2
Malpress, Ray, and David R. Buttsworth. "A Comparison Between Two-Position Variable Compression Ratio and Continuously Variable Compression Ratio Engines Using Numerical Simulation." In ASME 2009 Internal Combustion Engine Division Fall Technical Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/icef2009-14042.
Повний текст джерелаАнотація:
Two types of variable compression ratio engine are considered: i) a continuously variable compression ratio (VCR) device that optimises engine efficiency at all loads, and ii) a VCR device that allows the engine to operate at one of two discrete compression ratios. The simulated engine configuration uses late intake valve closing (LIVC). A maximum geometric compression ratio (GCR) of 17:1 is adopted in the simulations resulting in a constant effective compression ratio of 10.2:1 in all configurations. Reduction from full load is achieved in the simulation with LIVC until the maximum GCR is reached after which lower loads are achieved through throttling. In the two-position VCR engine simulation, the full load range is achieved through throttling in combination with LIVC. At part load, in combination with LIVC, the VCR devices increase the geometric compression ratio to return the effective compression ratio to that for full load in each case. Fuel consumption for the New European Driving Cycle (NEDC) is assessed via numerical simulation for a representative vehicle. The simulations indicate that the increase in net fuel consumption over a driving cycle is effectively no different for the two-position VCR engine relative to a continuously variable CR and this justifies further research into two-position VCR technology. Net fuel consumption can also be improved by the use of a limited acceleration that maintains the engine in the reduced compression stroke configuration. An acceleration rate with a driver feedback mechanism is proposed which, in combination with a two-position VCR engine, shows potential for significant reduction in fuel consumption of greater than 15% relative to the full compression, fixed CR configuration for the NEDC.
3
Miller, Tyler, Joel Duncan, William Hensley, John Beard, Jeremy Worm, and Jeffrey Naber. "Design, Actuation, Experimental Setup and Testing of a 4-Cylinder Gasoline Spark Ignited Variable Compression Ratio Engine." In ASME 2020 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/icef2020-2960.
Повний текст джерелаАнотація:
Abstract The thermal efficiency of an Otto cycle engine is directly related to the compression ratio (CR). However, in a spark-ignited engine, the CR is often restricted by full load knock, thus limiting part load efficiency. A proof of concept design and experimental study has been conducted on a 4-cylinder naturally aspirated spark-ignited (SI) engine whereby a four-bar linkage mechanism has been implemented to vary the CR. The base engine selected was a production 2.0L GM-LNF SI 4-cylinder engine with a stock CR of 9.2:1 and with a bore and stroke of 86mm and 86mm, respectively. The engine was modified to allow the centerline axis of rotation of the crankshaft to translate in an arc about a fixed point. With the use of the four-bar mechanism, and larger dome volume pistons, a range of 8:1 to 11.5:1 CR was achieved. The prototype VCR engine was tested and analyzed at three different CR’s at a fixed load of 600 kPa net indicated mean effective pressure gross (IMEPGROSS) at an engine speed of 1000 revolutions per minute (RPM). At this condition, a sweep of combustion phasing was conducted. with a stoichiometric air to fuel mixture for each case. The CR’s selected for engine testing were 8.7:1, 10.2:1, and 11.1:1. The processed data includes averaged cycle analysis of each of the test conditions including combustion phasing, combustion duration, and cycle variation. The combustion data was also analyzed to determine overall heat release, indicated gross, net, pumping mean effective pressures, and indicated fuel conversion efficiency for each of the CR’s. The studies show an indicated fuel conversion efficiency of 31.2% for the 8.7:1 CR. As the CR was increased to 10.2:1 and 11.1:1 the relative increase in efficiency was 7.1% and 9.7% respectively at MBT combustion phasing.
4
Carpenter, Andrew L., Troy L. Beechner, Brian E. Tews, and Paul E. Yelvington. "Hybrid-Electric Turbocharger and High-Speed SiC Variable-Frequency Drive Using Sensorless Control Algorithm." In ASME 2017 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/icef2017-3521.
Повний текст джерелаАнотація:
Electrically-assisted engine boosting systems lend themselves to better throttle response, wider effective operating ranges, and can provide the ability to extract excess energy during deceleration and high-load events (and store it in a vehicle’s onboard batteries). This can lead to better overall vehicle performance, emissions, and efficiency while allowing for further engine downsizing and increased power density. In this research effort, a hybrid-electric turbocharger, variable-frequency drive (VFD), and novel sensorless control algorithm were developed. An 11kW permanent-magnet machine was coupled to a commercial turbocharger via an in-line, bolt-on housing attached to the compressor inlet. A high-efficiency, high-temperature variable-frequency drive, consisting of custom control and power electronics, was also developed. The variable-frequency drive uses SiC MOSFETS to achieve high-switching frequency and can be cooled using an existing engine coolant loop operating at up to 105 °C at an efficiency greater than 98%. A digital sliding mode-observer (DSMO) sensorless speed control algorithm was created to command and regulate speed and achieved ramp rates of over 68,000 rpm/sec. A two-machine benchtop motor/generator test stand was constructed for initial testing and tuning of the VFD and sensorless control algorithm. A gas blow-down test stand was constructed to test the mechanical operation of the hybrid-electric turbocharger and speed control using the VFD. In addition, a liquid-pump cart was assembled for high-temperature testing of the VFD. Initial on-engine testing is planned for later this year. This paper intends to present a design overview of the in-line, hybrid-electric device, VFD, and performance characterization of the electronics and sensorless control algorithm.
5
Rajput, Oudumbar, Youngchul Ra, Kyoung-Pyo Ha, and You-sang Son. "Numerical Analysis of a Six-Stroke Gasoline Compression Ignition (GCI) Engine Combustion With Continuously Variable Valve Duration (CVVD) Control." In ASME 2018 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/icef2018-9590.
Повний текст джерелаАнотація:
Engine performance and emissions of a six-stroke Gasoline Compression Ignition (GCI) engine with wide range of Continuously Variable Valve Duration (CVVD) control were numerically investigated at low engine load conditions. For the simulations, an in-house 3-D CFD code with high fidelity physical sub-models was used and the combustion and emissions kinetics were computed using a reduced kinetics mechanism for a 14-component gasoline surrogate fuel. Double injections were employed to effectively form the local fuel/air mixtures with optimal reactivity. Several valve timing and duration variations through the CVVD control were considered under both positive valve overlap (PVO) and negative valve overlap (NVO) conditions. Effects of intake-valve re-breathing between the first expansion and the second compression strokes were also investigated. Close attention was paid to understand the effects of two additional strokes of the engine cycle on the thermal and chemical conditions of charge mixtures that alter ignition, combustion and energy recovery processes. Double injections were found to be necessary to effectively utilize the additional two strokes for the combustion of overly mixed lean charge mixtures during the second power stroke (PS2). It was found that combustion phasing in both power strokes is effectively controlled by the intake valve closure (IVC) timing since it affects the effective compression ratio. Engine operation under NVO condition with fixed exhaust valve opening (EVO) and IVC timings tends to advance the ignition timing of the first power stroke (PS1) but has minimal effect on the ignition timing of PS2. Re-breathing was found to be an effective way to control the ignition timing in PS2 at a slight expense of the combustion efficiency. The operation of a six-stroke GCI engine could be successfully simulated and the operability range of the engine could be substantially extended by employing the CVVD technique. In addition, the control of valve timings could successfully control the thermodynamic and compositional conditions of in-cylinder mixtures that enable to control the combustion phasing.
6
Burk, Reinhard, Frederic Jacquelin, and Russell Wakeman. "Using Co-Simulation Methods to Establish Variable Valve Actuation Hardware Specifications and Control Strategies." In ASME 2001 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/2001-ice-427.
Повний текст джерелаАнотація:
Abstract With the increasing recognition that variable valve actuation (VVA) in its various forms is a powerful tool for optimizing the performance of internal combustion engines, more and more production systems are being designed and implemented throughout the industry. However, as these control systems become more capable of altering lift, timing, duration, and even the number of valve events, the complexity of designing algorithms and calibrating them becomes enormous. In addition, without prior knowledge of an engine’s response to these algorithms, designing a cost-effective mechanism which provides adequate but not over-reaching capability is difficult. Ricardo has developed methodology for timestep coupled simulations which enables the use of one-dimensional (1-D) gas dynamics simulation of engine performance (WAVE™) coupled to a simulation of the valve actuation mechanism constructed in MATLAB® and AMESim®. This arrangement allows valve motion input to the 1-D code to be controlled either manually or by a VVA controller simulation, allowing such engine parameters as torque, fuel consumption, NVH, and EGR rates to be monitored as a function of valve timing strategy. This method allows the examination of such engine development concerns as tolerances, valve velocities and accelerations, and interactions with other engine controls to be studied without the costs, leadtimes, or hardware reliability problems that are associated with prototyping a VVA system. In addition, the interfacing of the valve control/engine performance simulation combination with the Design of Experiments optimization software iSIGHT allows the control system space to be explored automatically, without the brute force numerical search required to examine all permutations of the control strategies. The output of this procedure is an array of requirements which can be quickly translated into a specification document which will guide hardware and controls design efforts.
7
Zhang, Yu, Praveen Kumar, Meng Tang, Yuanjiang Pei, Brock Merritt, Michael Traver, and Sriram Popuri. "Impact of Geometric Compression Ratio and Variable Valve Actuation on Gasoline Compression Ignition in a Heavy-Duty Diesel Engine." In ASME 2020 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/icef2020-3035.
Повний текст джерелаАнотація:
Abstract Gasoline compression ignition (GCI) is a promising powertrain solution to simultaneously address the increasingly stringent regulation of oxides of nitrogen (NOx) and a new focus on greenhouse gases. GCI combustion benefits from extended mixing times due to the low reactivity of gasoline, but only when held beneath the threshold of the high temperature combustion regime. The geometric compression ratio (GCR) of an engine is often chosen to balance the desire for low NOx emissions while maintaining high efficiency. This work explores the relationship between GCR, variable valve actuation (VVA) and emissions when using GCI combustion strategies. The test article was a Cummins ISX15 heavy-duty diesel engine with an unmodified production air and fuel system. The test fuel was an ethanol-free gasoline with a market-representative research octane number (RON) of 91.4–93.2. In the experimental investigation at 1375 rpm/10 bar BMEP, three engine GCRs were studied, including 15.7, 17.3, and 18.9. Across the three GCRs, GCI exhibited a two-stage combustion process enabled through a split injection strategy. When keeping both NOx and CA50 constant, varying GCR from 15.7 to 18.9 showed only a moderate impact on engine brake thermal efficiency (BTE), while its influence on smoke was pronounced. At a lower GCR, a larger fraction of fuel could be introduced during the first injection event due to lower charge reactivity, thereby promoting partially-premixed combustion and reducing smoke. Although increasing GCR increased gross indicated thermal efficiency (ITEg), it was also found to cause higher energy losses in friction and pumping. In contrast, GCI performance showed stronger sensitivity towards EGR rate variation, suggesting that air-handling system development is critical for enabling efficient and clean low NOx GCI combustion. To better utilize gasoline’s lower reactivity, an analysis-led variable valve actuation investigation was performed at 15.7 GCR and 1375 rpm/10 bar BMEP. The analysis was focused on using an early intake valve closing (EIVC) approach by carrying out closed-cycle, 3-D CFD combustion simulations coupled with 1-D engine cycle analysis. EIVC was shown to be an effective means to lengthen ignition delay and promote partially-premixed combustion by lowering the engine effective compression ratio (ECR). By combining EIVC with a tailored fuel injection strategy and properly developed thermal boundary conditions, simulation predicted a 2.3% improvement in ISFC and 47% soot reduction over the baseline IVC case while keeping NOx below the baseline level.
8
Fu, Chiayu, I. Charles Ume, and David L. McDowell. "Thermomechanical Stress Analyses of Plated-Through Holes in PWB Using Internal State Variable Constitutive Models." In ASME 1996 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/imece1996-0891.
Повний текст джерелаАнотація:
Abstract In application of multiaxial fatigue theories, extrapolation of concepts developed from uniaxial fatigue research must be used with caution. Previous related research on plated-through hole (PTH) fatigue investigations has been based on so-called effective stress/strain methods, which did not account for the fact that fatigue crack nucleation and growth is observed to occur on specifically oriented planes. Moreover, previous related thermal stress/strain analyses on PTH has been based on so-called bilinear constitutive relations for modeling copper plating with a linear kinematic hardening assumption, and this cannot capture many aspects of cyclic stress/strain behavior during thermal excursions. In this paper, thermal stress analyses using thermodynamics-based constitutive models of metallic consituents of PTHs are conducted by finite element package ABAQUS (1995) for multiaxial fatigue studies. Two types of PTHs (via) are investigated: ordinary empty PTH and PTH with solder filler. Two thermal profiles which simulate temperature fields in service are applied, with one experiencing the glass transition temperature of FR4. Residual stresses generated from previous process temperature history are considered. From the stress analyses, critical plane orientations for tensile type and shear type fatigue cracks are located.
9
Hareendranath, Dilunath, Nilesh Gajarlawar, Murali Manickam, and Ghodke Pundlik. "Low End Performance Improvement by Effective Use of Multiple Injection Strategy in Common Rail Diesel Engine." In ASME 2009 Internal Combustion Engine Division Spring Technical Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/ices2009-76039.
Повний текст джерелаАнотація:
Main advantages of diesel engine are low fuel consumption coupled with high specific power output. However, benchmark Noise, Vibration and Harshness (NVH) of its counterpart (Gasoline), future stringent emission norms and overall system cost poses tough challenges. In a growing market like India, these benefits of diesel attract the buyer over its counterpart. Diesel engines are known for its heavy visible black smoke. The black smoke formation is more prominent in lower engine speed. This is due to lower injection pressure and the system limitation in conventional injection system and less air availability. Introduction of the common rail injection technology overcomes this difficulty by allowing the injection pressure to build irrespective of the engine speed. However, improving the air flow is a challenge. Generally waste gate turbo chargers are optimized for higher engine speed to match the rated engine performance, but compromising the lower engine speed performance. The use of Variable Geometry turbo charging (VGT), increase in number of valves per cylinder, two stage turbo charging are some of the solutions to this problem but it involves additional cost and fundamental design changes. Hence, it was a challenge to come up with a strategy to overcome this problem without any cost impact. Multiple injection strategy is one of the tools which improve the engine torque without the penalty of smoke. In this paper, a Multi Utility Vehicle (MUV) powered by a 2.5Ldiesel common rail engine, low end performance was effectively improved by this strategy. Current engine has BOSCH 2nd generation common rail system with waste gate Turbocharger. Torque at full load in lower engine speed was improved by introducing the early pilot with relatively higher quantity. However, in the part load, this pilot quantity was split into two successive pilot injections. Selection of pilot separation was optimized in such a way that Noise and Smoke levels are maintained or improved. In part load, improvement in smoke and BSFC was achieved without sacrificing noise level. Engine level trials were conducted with cylinder pressure and Noise Measurement with AVL Indicom. The Concept of Design of experiment (DOE) was used to minimize the number of iteration and for analysis of results. The vehicle performance, pass by noise were found to be improved.
10
Petrea, Renato Gabriel, Sergiu Cătălin Bîrgovan, Marin Chirazi, and Pia Simona Făgăraș. "Internal Communication and Management by Obiectives in Sports Profile Institutions." In 80th International Scientific Conference of the University of Latvia. University of Latvia Press, 2022. http://dx.doi.org/10.22364/htqe.2022.79.
Повний текст джерелаАнотація:
Effective communication is required not only in interpersonal/human relationships but also in a successful management. In the real world, there is no organization without good communication. Since the acceptance of “management” as a separate body of knowledge over a half century ago, no management tool has had such a pervasive impact on organizations as the management by objectives. In this article, a cross-sectional study was conducted using the survey method based on a questionnaire with 24 items (10 items for the variable internal communication; 10 items for the variable management by obiectives and 4 items for demographic data: gender, age, city and work institutions). The main objective of this study is to show what kind of connection there is between the variable internal communication and the variable management by objectives among teachers from high schools with sports program and the teachers from faculties of physical education and sports in the Eastern side of Romania (Moldova Region). We also wanted to see if there is a difference between internal communication among high school teachers compared to university teachers. The same aspect of the difference was analyzed in the case of the management by obiectives variable. The study has 127 validated questionnaires that were completed by 80 teachers working in eight high schools with sports program and 47 teachers working in four faculties of physical education and sports in the Eastern side of Romania.
Звіти організацій з теми "Méthode Effective Internal Variable"
1
Rahman, Shahedur, Rodrigo Salgado, Monica Prezzi, and Peter J. Becker. Improvement of Stiffness and Strength of Backfill Soils Through Optimization of Compaction Procedures and Specifications. Purdue University, 2020. http://dx.doi.org/10.5703/1288284317134.
Повний текст джерелаАнотація:
Vibration compaction is the most effective way of compacting coarse-grained materials. The effects of vibration frequency and amplitude on the compaction density of different backfill materials commonly used by INDOT (No. 4 natural sand, No. 24 stone sand, and No. 5, No. 8, No. 43 aggregates) were studied in this research. The test materials were characterized based on the particle sizes and morphology parameters using digital image analysis technique. Small-scale laboratory compaction tests were carried out with variable frequency and amplitude of vibrations using vibratory hammer and vibratory table. The results show an increase in density with the increase in amplitude and frequency of vibration. However, the increase in density with the increase in amplitude of vibration is more pronounced for the coarse aggregates than for the sands. A comparison of the maximum dry densities of different test materials shows that the dry densities obtained after compaction using the vibratory hammer are greater than those obtained after compaction using the vibratory table when both tools were used at the highest amplitude and frequency of vibration available. Large-scale vibratory roller compaction tests were performed in the field for No. 30 backfill soil to observe the effect of vibration frequency and number of passes on the compaction density. Accelerometer sensors were attached to the roller drum (Caterpillar, model CS56B) to measure the frequency of vibration for the two different vibration settings available to the roller. For this roller and soil tested, the results show that the higher vibration setting is more effective. Direct shear tests and direct interface shear tests were performed to study the impact of particle characteristics of the coarse-grained backfill materials on interface shear resistance. The more angular the particles, the greater the shear resistance measured in the direct shear tests. A unique relationship was found between the normalized surface roughness and the ratio of critical-state interface friction angle between sand-gravel mixture with steel to the internal critical-state friction angle of the sand-gravel mixture.
2
Liu and Nixon. L52305 Probabilistic Analysis of Pipeline Uplift Resistance. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), June 2010. http://dx.doi.org/10.55274/r0000002.
Повний текст джерелаАнотація:
To investigate the feasibility of probabilistic analyses of the peak uplift resistance in frozen soils by varying parameters that are known to be important for the development of the uplift resistance under the upward movement of a pipe. A buried pipeline will be subjected to a variety of forces, both internal and external, including the interaction of the pipe with the surrounding soil. The soil-pipe interaction in permafrost regions have to account for the behavior of frozen and unfrozen soil, and transitions between the two as the pipeline traverses in a discontinuous permafrost zone. The variations in the properties and behavior of frozen soils are expected to be substantial in three dimensions of the Right-of-Way (ROW) and with time (seasonal fluctuations and changes with the history of pipeline operation). Given the uncertainties with frozen soil properties and the changes in behavior with time and location, a large variation in soil-pipe interaction characteristics can exist. The uplift resistance of a pipeline is one of these soil-pipe interactions that can be impacted by a variation in soil condition and state. A need was identified to outline the use of a probabilistic analysis of pipe uplift resistance in an attempt to capture the magnitude of these variations and uncertainties of frozen soil and the impact on the soil-pipe interaction. The probabilistic analysis allows the designer of a pipeline to consider a range of uplift resistance to a certain confidence level that would represent the likely values that a pipe may be subjected to. The work presented in this report is more focused on the methodology of the probabilistic approach, rather than the analysis itself for a specific design case, even though an example is provided for illustration purposes. A series of numerical simulations using Fast Lagrangian Analysis of Continua (FLAC) were completed varying one parameter with each run to develop a library of peak uplift resistances for a variety of different temperatures, soil properties and pipe parameters. The FLAC model was previously developed for PRC, a summary of this report is provided here to outline important parameters that were used to complete this analysis. The simulations were used to develop a correlation of peak uplift resistance as a function of soil tensile strain limit, modulus of deformation, and creep of frozen soils. Each of these parameters is dependent of the pipeline conditions such as temperature, displacement rate, and effective frozen cover depth. It is noted that the scope of the work was to develop a probabilistic method of estimating peak uplift resistance in frozen soils. Even though some sensitivity analysis were carried out, as outlined later in this report, to assess the impacts of the variable, detailed uncertainty analysis or risk assessment were not performed.