Optimal Taxes Without Commitment.

In the problem of optimal taxation in an economy with two productive factors, labor and capital, the optimal solution when the government can commit to a sequence of tax rates, has the tax on capital tending to zero in the limit, with all the tax burden on labour. It is well known, however, that this solution is time inconsistent; so if the commitment power is not perfect, this second best tax plan will not be suitable. We model explicitly the tradeoff between the cost of revising the tax plan, and the benefit of the revision.FISCAL POLICY;CAPITAL;TAXES;TAXATION

η\eta collective mode as A1g_{1g} Raman resonance in cuprate superconductors

We discuss the possible existence a spin singlet excitation with charge $\pm2$ ($\eta$-mode) originating the $A_{1g}$ Raman resonance in cuprate superconductors. This $\eta$-mode relates the $d$-wave superconducting singlet pairing channel to a $d$-wave charge channel. We show that the $\eta$ boson forms a particle-particle bound state below the $2\Delta$ threshold of the particle-hole continuum where $\Delta$ is the maximum $d$-wave gap. Within a generalized random phase approximation and Bethe-Salpether approximation study, we find that this mode has energies similar to the resonance observed by Inelastic Neutron Scattering (INS) below the superconducting (SC) coherent peak at $2\Delta$ in various SC cuprates compounds. We show that it is a very good candidate for the resonance observed in Raman scattering below the $2\Delta$ peak in the $A_{1g}$ symmetry. Since the $\eta$-mode sits in the $S=0$ channel, it may be observable via Raman, X -ray or Electron Energy Loss Spectroscopy probes

Performance improvement of shunt active power filter based on indirect control with a new robust phase-locked loop

Introduction. Since the development of the first active power filter (APF) in 1976, many efforts have been focused on improving the performances of the APF control as the number of different nonlinear loads has continued to increase. These nonlinear loads have led to the generation of different types of current harmonics, which requires more advanced controls, including robustness, to get an admissible total harmonic distortion (THD) in the power system. Purpose. The purpose of this paper is to develop a robust phase-locked loop (PLL) based on particle swarm optimization-reference signal tracking (PSO-RST) controller for a three phase three wires shunt active power filter control. Methodology. A robust PLL based on PSO-RST controller insert into the indirect d-q control of a shunt active power filter was developed. Results. Simulation results performed under the MATLAB/SimPowerSystem environment show a higher filtering quality and a better robustness compared to the classical d-q controls. Originality. Conventional PLLs have difficulty determining the phase angle of the utility voltage sources when grid voltage is distorted. If this phase angle is incorrectly determined, this leads to a malfunction of the complete control of the active power filters. This implies a bad compensation of the current harmonics generated by the nonlinear loads. To solve this problem we propose a robust and simple PLL based on PSO-RST controller to eliminate the influence of the voltage harmonics. Practical value. The proposed solution can be used to improve the functioning of the shunt active power filter and to reduce the amount of memory implementation.Вступ. З моменту розробки першого фільтра активної потужності (ФАП) у 1976 р. багато зусиль було спрямовано на покращення характеристик управління ФАП, оскільки кількість різних нелінійних навантажень продовжувала зростати. Ці нелінійні навантаження призвели до генерації різних типів гармонік струму, що потребує більш досконалих засобів управління, у тому числі стійких, для отримання допустимого повного гармонічного спотворення (THD) в енергосистемі. Мета. Метою даної статті є розробка надійного контуру фазового автопідстроювання частоти (ФАПЧ) на основі контролера відстеження еталонного сигналу оптимізації рою частинок (ВЕС ОРЧ) для трифазного трипровідного шунтуючого фільтра активної потужності. Методологія. Розроблено надійну систему ФАПЧ на основі контролера ВЕС ОРЧ, вбудованого в непрямий d-q контроль шунтуючого фільтра активної потужності. Результати. Результати моделювання, виконаного в середовищі MATLAB/SimPowerSystem, демонструють високу якість фільтрації та більшу надійність у порівнянні з класичним d-q керуванням. Оригінальність. Звичайні ФАПЧ мають труднощі з визначенням фазового кута джерел напруги, коли напруга мережі спотворена. Неправильне визначення цього фазового кута призводить до порушення повного керування фільтрами активної потужності. Це означає погану компенсацію гармонік струму, створюваних нелінійними навантаженнями. Для вирішення цієї проблеми ми пропонуємо стійкий та простий ФАПЧ на основі контролера ВЕС ОРЧ для усунення впливу гармонік напруги. Практична цінність. Запропоноване рішення може бути використане для поліпшення роботи шунтуючого фільтра активної потужності і зменшення обсягу потрібної пам'яті.

Three energy scales in the superconducting state of hole-doped cuprates detected by electronic Raman scattering

We explored by electronic Raman scattering the superconducting state of Bi-2212 single crystal by performing a fine tuned doping study. We found three distinct energy scales in A1g, B1g and B2g symmetries which show three distinct doping dependencies. Above p=0.22 the three energies merge, below p=0.12, the A1g scale is no more detectable while the B1g and B2g scales become constant in energy. In between, the A1g and B1g scales increase monotonically with under-doping while the B2g one exhibits a maximum at p=0.16. The three superconducting energy scales appear to be an universal feature of hole-doped cuprates. We propose that the non trivial doping dependence of the three scales originates from Fermi surface topology changes and reveals competing orders inside the superconducting dome.Comment: 6 pages, 5 figure

Follow the Leader: On Growth and Diffusion

economic growth ; game theory

A comparative analysis of cultural value orientations of Polish and Turkish employees:implications for international human resource management

This study empirically compares and contrasts the cultural value orientations of employees from Poland and Turkey by testing the compatibility of their values in three stages through seven cultural dimensions. The first phase of the study deals with the assessment of inter-country cultural value differences; the second phase investigates the intra-country cultural dynamics between selected demographic groups; and the third phase examines the inter-country cultural differences among the selected demographic groups of employees. The research has been conducted adopting the Maznevski, DiStephano, and Nason's (1995) version of cultural perspectives questionnaire with a sample of 744 (548 Polish and 196 Turkish) respondents. The results show significant cultural differences between Poland and Turkey, a presence of cultural dynamics among certain demographic groups within the country, and a mixture of convergence and divergence in the value systems of certain demographic groups both within and between the two nation(s). The research findings convey important messages to international human resource strategists in order for them to employ an effective and rational employment policy and business negotiation approach(es) to effectively operate in these countries. It also highlights that diversity of cultural values not only requires viewing each of them through cultural dimensions at a macro-level with a cross-country reference, but also requires monitoring their dynamics at the micro-level with reference to controlled demographic groups