Open-Circuit Fault-Tolerant Strategy for Interleaved Boost Converters via Filippov Method

Interleaved converters use an increased number of power electronics switches; this may subsequently affect their reliability. However, this is an opportunity to develop fault-tolerant strategies to improve their reliability and to ensure continuity of service. This is why we herein propose, for the first time, a mathematical function to simultaneously model the healthy and faulty conditions of each switch, thus enabling a unique model of the system. This model is then used in an original fault-tolerant strategy based upon the peak current control with slope compensation. This method not only extends the stable range of the load variation but also ensures the stability in faulty conditions. Finally, the simulation results validate its effectiveness and confirm the theoretical analysis.

ABELIAN CYCLES IN THE HOMOLOGY OF THE TORELLI GROUP

In the early 1980s, Johnson defined a homomorphism $\mathcal {I}_{g}^1\to \bigwedge ^3 H_1\left (S_{g},\mathbb {Z}\right )$ , where $\mathcal {I}_{g}^1$ is the Torelli group of a closed, connected, and oriented surface of genus g with a boundary component and $S_g$ is the corresponding surface without a boundary component. This is known as the Johnson homomorphism. We study the map induced by the Johnson homomorphism on rational homology groups and apply it to abelian cycles determined by disjoint bounding-pair maps, in order to compute a large quotient of $H_n\left (\mathcal {I}_{g}^1,\mathbb {Q}\right )$ in the stable range. This also implies an analogous result for the stable rational homology of the Torelli group $\mathcal {I}_{g,1}$ of a surface with a marked point instead of a boundary component. Further, we investigate how much of the image of this map is generated by images of such cycles and use this to prove that in the pointed case, they generate a proper subrepresentation of $H_n\left (\mathcal {I}_{g,1}\right )$ for $n\ge 2$ and g large enough.

Duo property for rings by the quasinilpotent perspective

In this paper, we focus on the duo ring property via quasinilpotent elements, which gives a new kind of generalizations of commutativity. We call this kind of rings qnil-duo. Firstly, some properties of quasinilpotents in a ring are provided. Then the set of quasinilpotents is applied to the duo property of rings, in this perspective, we introduce and study right (resp., left) qnil-duo rings. We show that this concept is not left-right symmetric. Among others, it is proved that if the Hurwitz series ring $H(R; \alpha)$ is right qnil-duo, then $R$ is right qnil-duo. Every right qnil-duo ring is abelian. A right qnil-duo exchange ring has stable range 1.

Effect of small heat release and viscosity on thermal-diffusive instability

The linear stability of a thermal reaction front has been investigated based on the thermal-diffusive model proposed by Zel’dovich and Frank-Kamenetskii, which is called ZFK model. In the framework of ZFK model, heat-conduction and mass-diffusion equations are treated without the effect of hydrodynamic flow. Then, two types of instability appear: cellular and oscillatory instabilities. The cellular instability has only positive real part of growth rate, while the oscillatory instability is accompanied with non-zero imaginary part. In this study, the effect of heat release and viscosity on both instabilities is investigated asymptotically and numerically. This is achieved by coupling mass-conservation and Navier–Stokes equations with the ZFK model for small heat release. Then, the stable range of Lewis number, where the real part of growth rate is negative, is widened by non-zero values of heat release for any wavenumber. The increase of Prandtl number also brings the stabilization effect on the oscillatory instability. However, as for the cellular instability, the viscosity leads to the destabilization effect for small wavenumbers, opposed to its stabilization effect for moderate values of wavenumber. Under the limit of small wavenumber, the property of viscosity becomes clear in view of cut-off wavenumber, which makes the real part of growth rate zero.

Dynamic Tourism in ASEAN Countries: Do Institutional Indicators Matter?

Tourism is one of the fastest-growing industries. Tourism is able to move the economy forward at the micro-level such as encouraging the informal sector and local potential while at the macro level it can increase currency transactions. In various countries, the tourism sector is able to increase domestic and foreign demands as well as to encourage transportation, hospitality, and manufacturing industries. This study examines the effect of institutional indicators on tourism in ASEAN countries during 2000-2018 under dynamic panel estimation. The number of observations was about 180, namely: time series from 2000-2018 and cross-section of 10 countries. ASEAN as one of the destinations in the world requires an increase in institutional quality to be able to compete and provide world-class tourism services. The six institutional indicators were employed such as voice and accountability, political stability and absence of violence, government effectiveness, regulatory quality, rule of law, and control of corruption. Moreover, the dynamic panel estimation was expressed by Pooled OLS and REM estimations. Interestingly, the findings show that political stability compromises the number of tourist arrivals while government effectiveness can stimulate tourist arrivals. Similarly, GDP per capita can hinder the number of tourist arrivals, while the exchange rate leads increasing of tourism arrivals. Thus, the governments in ASEAN countries can promote and cooperate together to develop tourism in the regional level. The GDP per capita of ASEAN countries should be increased, and the level of exchange rate can be maintained at a stable range. Besides, the governments should also improve the quality of institutions.

The impact of hip-spine relations on the results of total hip arthroplasty (literature review)

Spine balance can alter THA outcomes, but the exact mechanism is not yet well recognized. We aimed at bridging the gap between hip and spine surgeons with an up-to-date analysis of the best available literature review concerning to data as for total hip arthroplasty results of those patient with concomitant spine disorders. In total hip arthroplasty accurate acetabular cup placement is essential for impingement free and stable range of motion. For decades, hip surgeons have relied on traditional safe acetabular zones to reduce prosthetic instability. Nevertheless, hip dislocation is one of the most common complications following total hip arthroplasty. Numerous studies have shown that patients with abnormal spinopelvic mobility due to degene­rative spinal diseases and after spinal fusion surgery had an increased rate of dislocations after THA. In our review we described the main spine-pelvic parameters, such as pelvic tilt, sacral slope, pelvic incidence, lumbar lordosis etc. and spino-pelvic motions and how they can change in standing and sitting postures. Measurements of these parameters are necessary for presurgical planning before hip arthroplasty especially those patients who had previously made spine fusion. A review of lite­rature shows that sagittal pelvic kinematics, but not the pelvic incidence, influences the risk of prosthetic impingement or dislocation. Pelvic position is dynamic during gait and other daily living activities. Variations in anteroposterior pelvic tilt affects the resulting spatial orientation of the acetabulum. Recommendations for cup positioning are switching from a classic Lewinneck safe zone to a patient-specific approach, with the standing cup orientation giving way to a new parameter of interest: the functional orientation of the cup. Thus, functional cup anterversion should be taken into consideration. Abnormal spinopelvic mobility is a risk factor for THA dislocation. Thus patients with combined spine and hip pathology are at higher risk for further complications and they should be identified and screened more carefully. Key words. Spine-pelvic relations, sagittal alingement, hip arthroplasty, dislocation

Effects of a diuretic regimen on body weight and echocardiographic parameters of the tricuspid valve in patients scheduled for transcatheter tricuspid annuloplasty

Background Echocardiographic severity of tricuspid regurgitation is known to be highly variable and strongly related to the volume status of the individual patient. Interventional therapies for tricuspid valve repair or replacement are dependent on reliable measurements in order to select the appropriate device size. Purpose In patients scheduled for transcatheter tricuspid valve annuloplasty, we sought to evaluate the effects of a diuretic regimen started at the screening visit on body weight and tricuspid valve dimensions at the time point of transcatheter intervention. Methods After successful screening for transcatheter tricuspid annuloplasty, an individualized intensified diuretic regimen was initiated in 15 patients. At baseline and at the timepoint of the intervention, body weight and 3D echocardiographic dimensions of the tricuspid valve were documented and compared. Results The cohort comprised 6 males and 9 females (mean age 77±7 years) with severe or higher degree functional tricuspid regurgitation. In all patients not more than mild pulmonary artery hypertension was present (PaP mean 29±5 mmHg). The interval between the screening visit and the timepoint of the procedure was 64±50 days. At baseline mean body weight was 72±12 kg. In 11 patients a reduction of the body weight could be achieved, with a median weight reduction of 2.2 kg (min/max 1.2/6.4 kg). Overall, the average relative reduction of the tricuspid annulur perimeter was 13% (p<0,001), of the tricuspid valve area 2.7% (n.s.), the anterseptal diameter 3.3% (n.s.), while the bicommissural diameter remained almost unchanged (0.4%; n.s.). The average predicted required band length changed by only 1.5% (n.s.). The strongest correlations were found between the absolute change in body weight and the change of the tricuspid valve area (r=0.48), relative change in body weight and relative change of tricuspid valve area (r=0.52), absolute change in body weight and absolute change in predicted band length (r=0.48), and relative changes of the respective variables (r=0.52). More importantly, in 13 out of 15 patients the band size which would have been selected was identical between the screening and the annuloplasty procedure. Only in two patients a smaller device was implanted than predicted at the screening visit. Conclusion Instituting a diuretic therapy in candidates for transcatheter tricuspid annuloplasty prior to the procedure helps to keep tricuspid valve dimensions in a stable range. Changes in body weight in patients with functional tricuspid regurgitation are correlated to changes of tricuspid valve dimensions. FUNDunding Acknowledgement Type of funding sources: None.

Numerical Simulation of the Motion of a Large Scale Unmanned Surface Vessel in High Sea State Waves

The motion stability of the Unmanned Surface Vessel (USV) is threatened by the action of waves under a rough sea state. In the present paper, the motion of a large-scale USV is numerically simulated under high sea state of level 5 and 7. The overset grid method and Reynolds Averaged Navier–Stokes (RANS) approach are employed to solve Navier–Stokes (N-S) equations. For the case of wave incident angle 0° and 30°, the heave, pitch and roll motion response of a large scale USV are investigated by using the six Degrees of Freedom (6-DOF) numerical model. The effects of different sea states, as well as different wave directions, on the motion of USV are compared. The comparative results indicate that the response of this USV in waves is the periodic free-motion according to the corresponding amplitude, which does not exceed the stable range, and there are no overturning and other situations that may affect the safety, in the case of level 5 and 7 sea states. The corresponding pressure at the bottom of this USV meets the range of material strength, and no structural damage or injury to the hull occurs, although the pressure varies at different wave periods. For the case of different wave directions, the analysis of the boundary layer thickness shows that the wave direction is of great importance to the boundary layer thickness distribution, both in the level 5 and level 7 sea states.

ІННОВАЦІЙНІ ТЕХНОЛОГІЇ МОДУЛЬНОГО ПРОЄКТУВАННЯ КОНСТРУКТИВНО- УНІФІКОВАНИХ РЯДІВ СТАБІЛЬНОГО АСОРТИМЕНТУ

The Objective of this research is to identify the logistics of the coordination of the modular design processes of constructively-unifi ed rows of competitive garments. The methodology of the modern researches is a combination of analytical methods used in situational modeling of within the sets of models of stable assortment. The nomenclature of structural modules is determined by the method of generating the structural elements of the design of men's jacket design. The method of combinatorial synthesis of composite elements determines the route of modifi cation techniques in the process of developing a design documentation. Results. As a result of research of logistic coordination of sequence of cyclist of working out of a constructively-unifi ed number of models expediency of modifi cation of par ameters of a constructive prototype is revealed. The key areas of innovative technology of a modular design of a stable range are identifi ed as follows:- the objectivity of the assessment of the functionality of the product (the competitiveness of the range increases);- drawing attention to the gradation of structural states of the design object (the algorithm of design solutions is simplifi ed);- unifi cation of structural elements of constructive modifi cation (expands the possibilities of smart technologies by the search function «yes-no»);- coordination of synergetic connections in the game space of the morphological structure of the object (provides minimization of information arrays in updating the models of the industrial collection);- operational planning of stages of design and technological preparation of production (determines the vector of the models selection of an industrial series for start in technological process).Practical value. The obtained results are recommended for the implementation in the production and marketing activities of enterprises in order to increase the effi cie ncy of project documentation and, as a result, improve the competitiveness of products. Provided expansion of smart technologies in business, the logistics of accelerating the design and technological preparation of production has high prospects in application.

Increasing temporal variance leads to stable species range limits

What prevents populations of a species from adapting to the novel environments outside the species' geographic distribution? Previous models highlighted how gene flow across spatial environmental gradients determines species expansion vs. extinction and the location of species range limits. However, space is only one of two axes of environmental variation — environments also vary in time, and we know temporal environmental variation has important consequences for population demography and evolution. We used an individual based evolutionary model to explore how temporal stochasticity in environmental conditions influences the spread of populations across a spatial environmental gradient. We find that temporal stochasticity greatly alters our predictions for range dynamics compared to temporally static environments. When temporal variance is equal across the landscape, the fate of species (expansion vs. extinction) is determined by the interaction between the degree of temporal autocorrelation in environmental fluctuations and the steepness of the spatial environmental gradient. When the magnitude of temporal variance changes across the landscape, stable range limits form where this variance becomes large enough to prevent local population adaptation and persistence. These results illustrate the pivotal influence of temporal stochasticity on the likelihood of populations colonizing novel habitats and the location of species range limits.