We consider Hurwitz stability region in the parameter space of monic polynomials. Firstly, a multilinear map from the positive first octant of the cartesian coordinate system to the stability region ...is defined. Based on this map a necessary and sufficient condition for stability is obtained. Starting from stable points, polytopes with infinite edge lengths are defined. Stability of the edges of these polytopes is equivalent to the stability of the convex combinations of third and fourth order factor polynomials. If all edges of polytope are stable then by the edge theorem the polytope is robust stable. The obtained result is important for understanding the geometry of stability domain, and can be used for generation of convex subsets of stable polynomials and for stabilization by fixed order controllers and other related problems.
On polytopes in Hurwitz region Dzhafarov, Vakif; Esen, Özlem; Büyükköroğlu, Taner
Systems & control letters,
July 2020, 2020-07-00, Letnik:
141
Journal Article
Recenzirano
We consider the stability region of monic polynomials in the coefficient space. Starting from specially chosen stable points we define polytopes, whose edges are either stable or belong to the ...stability boundary. Therefore by the Edge Theorem the interiors are stable. Stable polytopes, in the reverse directions which are directed to infinity have been studied in the work (Dzhafarov et al., 2019). Some applications of the obtained results to the synthesis of fixed-order stabilizing controllers are given.
PurposeThis study explores tourists' virtual reality experiences during the transition to the Metaverse.Design/methodology/approachQualitative approach was employed to capture tourists' virtual ...reality experiences and knowledge of the Metaverse at two five-star hotels in Kusadasi (Republic of Turkey). The data were collected from Kusadasi using a purposive sampling technique. The research design focused on data collection with the structured interview technique. The interview form consisted of 7 questions in total, and a voice recorder was used to record the answers of the participants. After the first 4 questions were asked, the participants were presented a virtual reality experience with the virtual reality (VR) glasses. The interview was held face-to-face with thirty-five participants consisting of domestic and foreign tourists in two five-star hotels in the summer season of 2022. The collected data were analyzed with the content analysis technique and themes were created.FindingsThis study's findings enhance the conceptual capital in this emerging field and provide insights into many of the participants who have and have never experienced virtual reality applications and who are familiar and unfamiliar with the Metaverse as a concept.Research limitations/implicationsThis study generates empirical data that informs contemporary debates about virtual reality and the Metaverse.Practical implicationsThe findings show that most participants have never experienced a virtual reality application. Hotels and travel agencies should be aware of this new futuristic technology before the Metaverse transition. Metaverse is for generation Y and Z instead of Baby Boomers and generation X.Originality/valueThis study is unique in terms of depth and fills the gap as it provides useful insights regarding the evaluation of tourists' virtual reality experiences in the transition process to the Metaverse.
Decolorization of Reactive Black 5 (RB5) was investigated by heterogeneous photocatalysis using N-doped TiO2. N-doped TiO2 photocatalysts were synthesized by means of a sol-gel process. X-ray ...diffraction performed the characterization of synthesized samples, scanning electron microscopy and X-ray photoelectron spectroscopy measurements. Photocatalytic activity of N-doped TiO2 samples was assessed by following decolorization and degradation efficiency of RB5. N-TiO2(3) sample yielded the highest decolorization efficiency. The apparent first-order rate constants for decolorization of RB5 with N-TiO2(X) samples followed the order of N-TiO2(3) > N-TiO2(2) > N-TiO2(4) > N-TiO2(1). Improvement of decolorization efficiency of TiO2 was observed doping with nitrogen. The effect of actual sunlight on decolorization efficiency was also investigated. 96% and 49% of decolorization efficiency levels were attained within 60 minutes of reaction time with outdoor sunlight and fluorescent daylight lamps, respectively.
Tissue thromboplastin may contaminate the first tube sample due to the trauma of the venipuncture, and therefore, affect the accuracy of coagulation testing. This practice was stopped by Clinical and ...Laboratory Standards Institute after several studies. However, most of the studies have verified these conclusions and refuted the need for a discard tube when drawing samples for coagulation tests in healthy groups. The purpose of our study was to evaluate the clinical importance of discarding a tube for prothrombin time (PT) determinations on large samples with international normalized ratio (INR) values between and over targeted therapeutic range. Patients receiving oral anticoagulation therapy (OAT) managed by our cardiology service were selected for this study. Tube 1 was always treated as the discard tube. Tube 2 was allocated to be analyzed along with the tube 1 for coagulation tests. Individual values were grouped into four cohorts according to the INR range. The ranges were as follows: less than 2.0, 2.1-3.0, 3.1-4.5 and more. Three hundred and seventy-six samples were drawn for PT/INR and activated partial thromboplastin time testing. We found statistically significant differences between tube 1 and tube 2 (P < 0.05), and satisfactory correlation coefficients were obtained by linear regression analysis (0.86 or greater in all cases). This study consisted of a high number of samples. Our data suggest that drawing a discard tube is still necessary for coagulation testing. Consideration should be given to revising the international guidelines related to the necessity of a discard tube for repeated evaluation of coagulation tests especially receiving long-term OAT.
In this work we consider the problem of existence and determination of a common positive definite solution (common quadratic Lyapunov function) to a set of Lyapunov matrix inequalities. We ...investigate a parameterized matrix family and a compact (in particular finite) set of 2 × 2 matrices.
Rural tourism is one of the tourism types, which contributes region's improvement significantly and promotes natural and the cultural resources as well. It is one of the tourism types that is ...catching more attention increasingly in Turkey and in the World. It becomes popular thanks to its uniqueness and as it can be done in the four seasons of the year, in addition to that, it is an alternate tourism type, that is not consisted of sea-sand-sun trio. Tourism industry a bridge between tourists and civilizations in terms of social and cultural exchange. Tourism is not only an economic income source, but also it is a bridge that provides social and cultural exchange between the tourists and societies. These festivals, which are organized to provide social and cultural exchange, are important attractive reasons for the tourists to prefer the region. Aim of the study is to manifest the festivals' contribution to the Caferli's image, where is connected to Aydın province and Kuşadası district. Semi-structured interview technique, which is among the qualitative research technique, is used in this study. With this aim, interviews have been done with local business owners. Significance of this study is that, it will be a guide for the local business owners who are living in the region and for the other stakeholders by evaluating festivals' effects on rural tourism and contributes to the destination image. Results of this study present information about negative and positive effects on the destination image of festivals in rural tourism. Being as a rural tourism area, in Caferli, flower festival and fall- environment festivals are held twice in a year, which contributed to the Caferli’s development by attracting tourists, is reached as a result.
TiO
2
nanotubes were synthesized by hydrothermal reaction using commercially available TiO
2
powder at 150 °C for 24 h. The transmission electron microscopy, X-ray diffraction, nitrogen ...adsorption-desorption isotherms and Fourier Transform-Infrared spectroscopy were used to characterize the nanotubes. Anatase phase was not transformed into rutile phase in the range of calcination temperature studied. Increase in calcination temperature result in enhancement of crystallinity and reduction in BET surface area. Photocatalytic removal of Reactive Red 239 (RR239) was investigated using prepared TiO
2
nanotubes. Effects of pH, TiO
2
nanotube dosage, initial RR239 concentration and calcination temperature were studied. 99%, 97% and 55% of removal efficiency values were attained at pH = 3, 5 and 7, respectively within 60 min or reaction time. With an increase in dosage of TiO
2
nanotube in the range of 0.25-0.75 g dm
−3
, removal rate increased by a steeper slope. Complete removal of RR239 was observed at 20 mg dm
−3
RR239 concentrations within 30 min but longer time was required for complete removal at higher concentrations. Langmuir-Hinshelwood kinetic expression was proposed based on nonlinear regression analysis. The removal efficiency of nanotubes calcined at 300 − 450 °C significantly increased but further increase in calcination temperature caused to decrease the efficiency.100% and 85% removal efficiency values were observed using actual solar light within 120 min of reaction time in July and January, respectively. Experiments conducted with scavengers showed that holes and adsorbed hydroxyl radicals were the major species involved in removal of RR239. A pathway for degradation of RR239 was suggested according to detected intermediate compounds.
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