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Igor Boiko 《Journal of The Franklin Institute》2017,354(12):4826-4837
A criterion of orbital stability of a limit cycle in a Lure system is formulated using the dynamic harmonic balance (DHB) principle and the describing function (DF) method. It is demonstrated that a more precise formulation of orbital stability than that provided by the Loeb's criterion can be produced. This enhancement is achieved through elimination of the assumption that is used in Loeb's criterion derivation. It is demonstrated in the paper that this assumption does not hold. An example of analysis is given. 相似文献
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Object‐oriented analysis, design, and programming is a software development technology which has attracted universal attention in the past few years. We do not think that object‐oriented technology is a completely new approach to software construction; it is merely the consequent continuation of software engineering principles which have evolved since 1968, the year of the birth of software engineering. This article describes a course on software engineering with objects which track the evolution of this discipline. We work through the history of these concepts using a single application domain, demonstrating how the relevant analysis and design methods evolved over time, culminating in object‐oriented techniques. 相似文献
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Igor Yegorov 《Research Policy》2009,38(4):600-609
In the late 1980s, the Soviet Union was among the foremost leaders of world science, thanks in large part to its heavy involvement in military programmes. The USSR developed a large research infrastructure but it lacked effective mechanisms for the commercialization of research results. The main aim of the transformation of R&D systems in the post-Soviet states in the 1990s and early 2000s was the re-orientation of scientific activities away from military and towards civilian goals. Analysis of statistical data at the macro-level suggests that this attempt was not particularly successful. Indeed, most newly independent states could not even preserve a ‘critical mass’ of scientific activities in order to remain among the list of significant producers of research results. In the post-Soviet countries (and in this paper we focus on Russia and Ukraine as the largest states of the region), inputs from the R&D system have failed to generate wealth-creating outputs because of a systemic inability to use the resources for generating commercially viable results effectively. All post-Soviet countries, including Russia and Ukraine, urgently need not only a major transformation within the R&D system, but also important changes in the wider ‘environment’. It is important to stress that, in recent years, changes in R&D have been determined not only by the general economic situation itself but also by the general policy of the post-Soviet states. While Russia has expressed ambitions to regain its former influence as a great power and to use S&T to achieve this goal, Ukraine has no clearly determined objectives for the development of its national science system. However, both countries face certain common problems. The development of relevant institutes and the stimulation of demand for R&D results from the side of industry, broader involvement in the international division of scientific work, and the introduction of adequate legal protection for intellectual property rights are all of critical importance for S&T institutes and other research organizations in Russia and Ukraine. This paper shows that the reforms in the R&D sector have been relatively modest and rather unsystematic over the last one and a half decades. The key challenges, which relate to the inertia and the negative aspects of the previous period (for example, a extremely low level of replacement of aging manpower, largely outdated scientific equipment in research laboratories, and institutional mechanisms that are not relevant to the market economy), pose serious problems for the transformation of the R&D systems in both countries, despite new possibilities and a willingness to increase financial support for R&D. 相似文献
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Luciano Rossi Rafael J.P. Damaceno Igor L. Freire Etelvino J.H. Bechara Jesús P. Mena-Chalco 《Journal of Informetrics》2018,12(4):1042-1058
Academic genealogy aims to structure and analyze the mentoring relationships between advisor and advisee. The representation of this structure results in academic genealogy graphs. For the analysis and characterization of these graphs, we present a set of metrics and their corresponding mirror metrics that capture the characteristics of its topological structure and represent them as quantitative attributes. The metrics of fecundity, fertility, descendants, cousins, generations, and relationships consider the descendants of the academics represented in the graph. The mirror metric of these topological metrics considers the ascendancy of academics. Individually, the metrics have strong semantic intuition and define characteristics regarding the performance in the mentoring of an academic. Together, the metrics are useful for the identification, characterization, and classification of communities and their members. The genealogical data available through the platforms of the Mathematics Genealogy Project and the Academic Family Tree were used as case studies. Two hundred thirteen thousand and 675,000 academic records were obtained for each project. We analyze the capacity of characterization of the metrics using the structuring of a similarity graph and through the distribution of the nodes in principal components. We observed that the set of metrics is capable of capturing the configuration pattern existing in genealogy graphs independently of its scale. 相似文献
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Amador García-Ramos Igor Stirn Vojko Strojnik Paulino Padial Blanca De la Fuente Javier Argüelles-Cienfuegos 《Sports biomechanics / International Society of Biomechanics in Sports》2016,15(3):329-341
This study aimed to correlate, compare, and determine the reliability of force, velocity, and power values collected with a force plate (FP) and a linear transducer during loaded jumps. Twenty-three swimmers performed an incremental loading test at 25, 50, 75, and 100% of their own body weight on a FP. A linear velocity transducer (LVT) was attached to the bar to assess the peak and the mean values of force, velocity, and power. Both the peak variables (r = 0.94 – 0.99 for peak force, r = 0.83 – 0.91 for peak velocity, and r = 0.90–0.94 for peak power; p < 0.001) and the mean variables (r = 0.96–0.99 for mean force, r = 0.87–0.89 for mean velocity, and r = 0.93–0.96 for mean power; p < 0.001) were strongly correlated between both measurement tools. Differences in the shape of the force-, velocity-, and power-time curves were observed. The LVT data showed a steeper increase in these variables at the beginning of the movement, while the FP recorded larger values in the latter part. Peak values were more reliable than mean values. These results suggest that the LVT is a valid tool for the assessment of loaded squat jump. 相似文献
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Karla de Jesus Kelly de Jesus J. Arturo Abraldes Alexandre Igor Araripe Medeiros Ricardo J. Fernandes João Paulo Vilas-Boas 《Journal of sports sciences》2016,34(9):871-877
We aimed to analyse the handgrip positioning and the wedge effects on the backstroke start performance and technique. Ten swimmers completed randomly eight 15 m backstroke starts (four with hands on highest horizontal and four on vertical handgrip) performed with and without wedge. One surface and one underwater camera recorded kinematic data. Standardised mean difference (SMD) and 95% confidence intervals (CI) were used. Handgrip positioning did not affect kinematics with and without wedge use. Handgrips horizontally positioned and feet over wedge displayed greater knee angular velocity than without it (SMD = ?0.82; 95% CI: ?1.56, ?0.08). Hands vertically positioned and feet over wedge presented greater take-off angle (SMD = ?0.81; 95% CI: ?1.55, ?0.07), centre of mass (CM) vertical positioning at first water contact (SMD = ?0.97; 95% CI: ?1.87, ?0.07) and CM vertical velocity at CM immersion (SMD = 1.03; 95% CI: 0.08, 1.98) when comparing without wedge use. Swimmers extended the hip previous to the knee and ankle joints, except for the variant with hands vertically positioned without wedge (SMD = 0.75; 95% CI: ?0.03, 1.53). Swimmers should preserve biomechanical advantages achieved during flight with variant with hands vertically positioned and wedge throughout entry and underwater phase. 相似文献
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Nedjeljka Ruljancic Ana Bakliza Sandra Vuk Pisk Natko Geres Katarina Matic Ena Ivezic Vladimir Grosic Igor Filipcic 《Biochemia medica : ?asopis Hrvatskoga dru?tva medicinskih biokemi?ara / HDMB》2021,31(1)
IntroductionHigh prolactin (PRL) concentrations are found in laboratory test results of patients on majority of antipsychotic drugs. Prevalence rates and degrees of severity of hyperprolactinemia (HPRL) based on PRL concentration may depend on the presence of macroprolactin in the serum. The aim of the study was to investigate the difference between PRL concentrations before and after precipitation of macroprolactin and to examine if there were any changes in the categorization of HPRL between samples prior and after precipitation.Materials and methodsTotal of 98 female patients (median age 33; range 19-47 years) diagnosed with a psychotic disorder, proscribed antipsychotic drugs, and with HPRL were included. Total PRL concentration and PRL concentration after macroprolactin precipitation with polyethylene glycol (postPEG-PRL) were determined by the chemiluminometric method on the Beckman Coulter Access2 analyser.ResultsTotal PRL concentrations (median 1471; IQC: 1064-2016 mlU/L) and postPEG-PRL concentrations (median 1453; IQC: 979-1955 mlU/L) were significantly correlated using intraclass correlation coefficient for single measurements (mean estimation 0.96; 95%CI 0.93-0.97) and average measurement (mean estimation 0.98; 95%CI 0.96-0.99), and all investigated female patient had HPRL according to PRL and postPEG-PRL concentration. The median PRL recovery following PEG precipitation was 95; IQC: 90-100%. There was substantial agreement (kappa test = 0.859, 95% CI: 0.764-0.953) between the categories of HPRL severity based on total PRL concentrations and postPEG-PRL concentrations.ConclusionThe study demonstrated that HPRL was present in all subjects using the reference interval for total PRL concentration and postPEG-PRL concentration with no significant impact of macroprolactin presence in the serum on the categorization of patients according to severity of HPRL. 相似文献
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Kyle R. Lynch Han C. G. Kemper Bruna Turi-Lynch Ricardo R. Agostinete Igor H. Ito Rafael Luiz-De-Marco 《Journal of sports sciences》2017,35(24):2421-2426
The objective of the present study was to investigate the effects of different sports on stress fractures among adolescents during a 9-month follow-up period. The sample was composed of 184 adolescents divided into three groups (impact sports [n = 102]; swimming [n = 35]; non-sports [n = 47]). The occurrence of stress fracture was reported by participants and coaches. As potential confounders we considered age, sex, resistance training, body composition variables and age at peak of height velocity. There were 13 adolescents who reported fractures during the 9-month period. Bone mineral density values were higher in adolescents engaged in impact sports (P-value = 0.002). Independently of confounders, the risk of stress fracture was lower in adolescents engaged in impact sports than in non-active adolescents (hazard ratio [HR] = 0.23 [95% confidence interval (CI) = 0.05 to 0.98]), while swimming practice was not associated to lower risk of fracture (HR = 0.49 [95% CI = 0.09 to 2.55]). In conclusion, the findings from this study indicate the importance of sports participation among adolescents in the reduction of stress fracture risk, especially with impact sports. More importantly, these results could be relevant for recognising adolescents in danger of not reaching their potential for peak bone mass and later an increased risk of fractures. 相似文献