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Macroscopic Quantum Coherence and Dissipation
Published in Andrei D. Zaikin, Dmitry S. Golubev, Dissipative Quantum Mechanics of Nanostructures, 2019
Andrei D. Zaikin, Dmitry S. Golubev
One can also consider a somewhat different situation of a SQUID, i.e., of a Josephson junction embedded in a superconducting ring of inductance L (see Fig. 5.2). In this case, the potential energy U(φ) consists of two terms: the Josepson energy −EJ cos φ and the magnetic energy of a ring (Φ−Φx)2/2L, where Φ is the magnetic flux inside the ring produced by circulating current I = IC sin φ and Φx is an external flux. The magnetic energy obviously violates periodicity of the Josephson potential, and one arrives at the potential profile depicted in Fig. 5.1b. By properly choosing the system parameters, one can adjust U(φ) in a way to make the energies of the two lowest potential wells very close to each other and the energies of all other wells considerably higher. In this case, we obtain an effective realization of a double-well potential in a SQUID. Such systems are of fundamental importance since they can be conveniently used in order to experimentally verify the idea of macroscopic quantum coherence (MQC) [263], e.g., by observing coherent oscillations of the magnetic flux inside the SQUID loop, as well as to study the effect of dissipation on quantum coherence in or close to the ground state. In addition, the possibility to further reduce the ring behavior to that of a two-level system opens unique opportunities for practical implementation of superconducting qubits, so-called Josephson flux qubits [291]. The issue of dephasing due to interaction with an external (dissipative) environment is absolutely crucial for such structures.
Circuit Protection, Vacuum Circuit Breakers, and Reclosers
Published in Paul G. Slade, The Vacuum Interrupter, 2020
The current counterpulse scheme has been successfully employed for switching the dc current in the Ohmic-heating coil for fusion experiments in the U.S.A. [264,274,275], Europe [273,276], and Japan [277]. The design of a successful “Ohmic-heating interrupter” that my team at Westinghouse helped develop [273] is shown in Figure 6.111. Typical parameters for this interrupter are given in Table 6.25. A dc current of 24kA initially flows through the Ohmic-heating coil (OH) and the closed vacuum interrupters. The plasma striking voltage is created by opening the two vacuum switches and by discharging the counterpulse current from the parallel capacitor. This diverts the current to the energy dissipation resistor R. The insertion of this resistor results in a rapid rate of decay of the current, which produces the striking voltage [263,274,275]. The current and voltage characteristics are shown in Figure 6.112. A current (io) is established in the Ohmic-heating coils. The vacuum interrupters are then opened to their designed contact gap and a high current, diffuse vacuum arc is established. The AMF is supplied by the circuit current opening through field coils external to the vacuum interrupters. The counter pulse from the charged capacitors is only initiated once the high current vacuum arc is in the fully diffuse mode. As the counter pulse timing has to be operated at a very precise time, an ignitron initiated the counter pulse current. During the counter pulse and interruption period, the current in the vacuum interrupters is forced to zero with a high rate of current decrease (di/dtm = 0.15 kA/μs). The inductance of the series saturable reactor shown between the vacuum interrupters becomes large at low currents and the (di/dt0 = 0.03 kA/μs) through the vacuum interrupters slows down just before the current zero. The slower rate of current decrease gives cathode spots from the diffuse vacuum arc a longer time to extinguish. This assists the recovery of the vacuum interrupters when the TRV is imposed across the open contacts once the current goes to zero. At current zero, when the vacuum arc extinguishes, a part of the pre-charge voltage remains as a residual voltage on the counterpulse capacitor C. After interruption, it is discharged in the OH coil. The vacuum interrupters see this voltage as the small negative voltage pulse (Uo). Later, C is charged by the stored energy in the OH coil and this is the TRV (dUR/dt to UR(peak)) seen across the open contacts of the vacuum interrupters.
A guanylurea ligand and its Cu(II), Ni(II) and Zn(II) complexes: antibacterial activities and DNA binding properties
Published in Inorganic and Nano-Metal Chemistry, 2020
Ozge Gungor, Seda Nur Kertmen Kurtar, Feridun Koçer, Muhammet Kose
A single absorption band was observed in the ligand, whereas two absorption bands were observed in the complexes. The complexes [Cu(L)2]·(ClO4)2 and [Ni(L)2]·(ClO4)2 and [Zn(L)Cl2] exhibit absorption bands in the UV region at 252, 263 and 270 nm, respectively. By the addition of increasing amounts of FSds-DNA to the complex solutions, a sharp hyperchromic effect in the absorption bands with a moderate red shift of 5, 3 and 10 nm, respectively is observed. Hyperchromic effect reflects the corresponding changes of DNA in its conformation and structure after the complex–DNA interaction has occurred. The binding constants of the complexes were calculated as 4.7 × 104, 6.2 × 104 and 2.3 × 105, respectively. Binding constants of ligands and complexes are given in Table 3.
Nitrogen centered inverse coordination complexes. A survey of molecular topologies
Published in Journal of Coordination Chemistry, 2018
Structures based upon “head-on/head-on” connectivity are known for titanium [199–217], zirconium [215, 218–220], hafnium [221], vanadium [222–225], niobium [225–228], tantalum [225, 229–231], chromium [232, 233], molybdenum [212, 234–252], tungsten [212, 253–261], manganese [215, 262, 263], technetium [264], rhenium [265], iron [80, 215, 263, 266–283], ruthenium [284–295], osmium [296, 297], cobalt [298, 299], rhodium [300–302], iridium [303–308], and nickel [309–315]. A small sample of examples (46-53) selected from a large number of known structures are shown in Scheme 18 to illustrate the variety of bonding modes. The bonding in [(µ2-N2){M(η5-C5H5)2}2] inverse coordination complexes was theoretically analyzed with the aid of DFT method [316].
Effect of cerium oxide nanoadditive on Annona Methyl Ester in a thermally coated direct injection diesel engine
Published in International Journal of Ambient Energy, 2022
Vadivel Ayyakkannu, Periyasamy Sivanandi
Figure 10 displays the variance of EGT with load for diesel, AMEB20, and AMEB20 + CeO2 50 in uncoated and coated conditions. It is an indicator of the heating potential of the fuel. One-third of the heat is exhausted from the engine through exhaust gas. The burning efficiency of the engine was assessed by the exhaust gas temperature. The combustion was carried out steps by steps such as ignition lag, unrestricted combustion, controlled combustion, and post-combustion. For all test fuels, an increase of EGT was observed while increasing the load applied to the engine from a low level to a high level. At peak load condition, the EGT was observed as 215°C, 221°C and 235°C for diesel, AMEB20 and AMEB20 + CeO2 50 in the uncoated engine and 220°C, 240°C and 263°C for diesel, AMEB20 and AMEB20 + CeO2 50 in coated engine respectively. For coated engine, the EGT value is higher than the conventional engine for all test fuels due to the effect of TBC applied to the combustion chamber parts. Further, the EGT value is higher for AMEB20 + CeO2 50 as compared to diesel and AMEB20. This may be due to the active combustion is taking place with the excess oxygen content of biodiesel in presence of nanoadditive and TBC mode contribute to the effective combustion which in turn raises the temperature of the exhaust gas. Similar findings were obtained by Kumar, Dinesha, and Bran (2017) with Pongamia biodiesel blends with ferrofluid as the additive in the coated engine. By adding the nanoparticles with fuel, the cetane number (CN) of the fuel increases whereas ignition delay (ID) will be reduced, and hence major part of the combustion completes before the top dead centre (bTDC).