Machine workshop area project development for manufacturing banking-liner VMPR 000.002.001 to improve the methods of effective selection processes of manufacturing helical spirals of energy blanks

Спроектовано дільницю механічної обробки Вал-втулки ВМПР 000.002.001. Розроблено технологію виготовлення деталі та спеціальні верстатні пристрої для її реалізації. Прийняті в дипломній роботі інженерні рішення дали змогу підвищ.ити якість виготовлення деталі і зменшити підготовчо-заключний час на операціях, забезпечили концентрацію операцій, мобільність виробництва а також скорочення затрат на виготовлення деталі. Для забезпечення безпечних умов роботи персоналу розроблено питання охорони праці і безпеки у надзвичайних ситуаціях. Досліджено та розроблено прогресивні ресурсоощадні технологічні процеси формоутворення нових типів заготовок для деталей з гвинтовими елементами, що вирізняються хорошими технологічними характеристиками і розширеними функціональними можливостями. Правильність прийнятих рішень підтверджено обґрунтуванням економічної ефективності.Shop area for machining of the banking-liner VMPR 000.002.001 has been designed. The technology for manufacturing a part and special machine-tool devices for its realization has been developed. Engineering solutions made in diploma paper provided the possibility to increase part manufacturing quality and minimize operation setting-up time, ensured operations concentration, manufacturing mobility and reduction in manufacturing prime cost. To secure staff working environment the comprehensive operational health and safety issues for emergencies have been developed. Researched and developed advanced resource-saving technological processes of formation of new types of blanks for parts with screw elements include good technological features and enhanced functionality. The accuracy of solutions made has been proved by economic feasibilit

Critical current anisotropy in Nd-1111 single crystals and the infuence of neutron irradiation

We report on angle-resolved magnetization measurements on NdFeAsO$_{0.65}$F$_{0.35}$ (Nd-1111) single crystals. The field dependence of the critical current density, $J_c$, is non-monotonous in these crystals at all orientations and temperatures due to the fishtail effect, which strongly influences the angular dependence of $J_c$. The currents decrease as the field is tilted from the crystallographic c-axis at low fields, but increase at high fields. A peak occurs in the angular dependence of $J_c$ at intermediate fields. The critical currents are significantly enhanced after irradiation with fast neutrons and the fishtail disappears. The different current anisotropies at low and high fields, however, persist. We discuss the data in the framework of the anisotropic scaling approach and propose a transition from dominant pinning by large defects of low density at low fields to pinning by small defects of high density at high fields in the pristine crystal. Strong pinning dominates at all fields after the irradiation, and the angular dependence of $J_c$ can be described by anisotropic scaling only after an appropriate extension to this pinning regime

Magnetotransport studies of Superconducting Pr4_4Fe2_2As2_2Te1−x_{1-x}O4_4

We report a detailed study of the electrical transport properties of single crystals of Pr$_4$Fe$_2$As$_2$Te$_{1-x}$O$_4$, a recently discovered iron-based superconductor. Resistivity, Hall effect and magnetoresistance are measured in a broad temperature range revealing the role of electrons as dominant charge carriers. The significant temperature dependence of the Hall coefficient and the violation of Kohler's law indicate multiband effects in this compound. The upper critical field and the magnetic anisotropy are investigated in fields up to 16 T, applied parallel and perpendicular to the crystallographic c-axis. Hydrostatic pressure up to 2 GPa linearly increases the critical temperature and the resistivity residual ratio. A simple two-band model is used to describe the transport and magnetic properties of Pr$_4$Fe$_2$As$_2$Te$_{1-x}$O$_4$. The model can successfully explain the strongly temperature dependent negative Hall coefficient and the high magnetic anisotropy assuming that the mobility of electrons is higher than that of holes

MgB2 single crystals substituted with Li and with Li-C: Structural and superconducting properties

The effect of Li substitution for Mg and of Li-C co-substitution on the superconducting properties and crystal structure of MgB2 single crystals has been investigated. It has been found that hole doping with Li decreases the superconducting transition temperature Tc, but at a slower rate than electron doping with C or Al. Tc of MgB2 crystals with simultaneously substituted Li for Mg and C for B decreases more than in the case where C is substituted alone. This means that holes introduced by Li cannot counterbalance the effect of decrease of Tc caused by introduction of electrons coming from C. The possible reason of it can be that holes coming from Li occupy the pi band while electrons coming from C fill the sigma band. The temperature dependences of the upper critical field Hc2 for Al and Li substituted crystals with the same Tc show a similar dHc2/dT slope at Tc and a similar Hc2(T) behavior, despite of much different substitution level. This indicates that the mechanism controlling Hc2 and Tc is similar in both hole and electron doped crystals. Electrical transport measurements show an increase of resistivity both in Li substituted crystals and in Li and C co-substituted crystals. This indicates enhanced scattering due to defects introduced by substitutions including distortion of the lattice. The observed behavior can be explained as a result of two effects, influencing both Tc and Hc2. The first one is doping related to the changes in the carrier concentration, which may lead to the decrease or to the increase of Tc. The second one is related to the introduction of new scattering centers leading to the modification of the interband and/or intraband scattering and therefore, to changes in the superconducting gaps and to the reduction of Tc.Comment: 22 pages, 17 figures, submitted to PR

Local quasiparticle density of states of superconducting SmFeAsO1−x1-xFxx single crystals: Evidence for spin-mediated pairing

We probe the local quasiparticles density-of-states in micron-sized SmFeAsO$_{1-x}$F$_{x}$ single-crystals by means of Scanning Tunnelling Spectroscopy. Spectral features resemble those of cuprates, particularly a dip-hump-like structure developed at energies larger than the gap that can be ascribed to the coupling of quasiparticles to a collective mode, quite likely a resonant spin mode. The energy of the collective mode revealed in our study decreases when the pairing strength increases. Our findings support spin-fluctuation-mediated pairing in pnictides.Comment: 11 pages, 4 figure