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[en] We study the optimal performance of Feynman’s ratchet and pawl system operating as a heat engine (refrigerator), by optimizing the product of efficiency (coefficient of performance) and power output (cooling power), which is known as the efficient power (-criterion) in the literature. The analysis is performed by recourse to two different methods: the first employs an exact optimization over the internal energy scales of the device, and the second method is based on the use of prior information to estimate the optimal performance of the device. From the two-parameter optimization, universal features of the efficiency at maximum efficient power (EMEP) are shown. Then, an exact one-parameter optimization is carried out for the linear model of the engine in high temperature regime, by constraining one of the energy scales, and well-known forms of efficiency are obtained. Further, using the prior information approach, the obtained efficiency concurs with the EMEP of an endoreversible heat engine. An analogous analysis is carried out for the Feynman’s ratchet as a refrigerator. From the estimated behavior of the device under limited information, we are able to highlight universal features of its performance that remain robust under an inference analysis. (paper: classical statistical mechanics, equilibrium and non-equilibrium)
[en] The possibility for a collimated one-mode laser beam used as a fiducial line is considered. The technology for an “extended” laser beam formation and application for a much-extended fiducial line is proposed.
[en] A review of the archive’s documents on the main stages of the creation of the synchrocyclotron at the Hydrotechnical Laboratory (now known as the Dzhelepov Laboratory of Nuclear Problems) is presented. The review is based on minutes of the Special Committee and Scientific and Technical Council (NTS), which belongs to the First Chief Directorate (PGU) concerning the era of the Soviet atomic project (1945–1953). The analysis of these minutes has enabled us to prepare a chronicle of events that deal with the creation of the synchrocyclotron, as well as the discussion of the project and its place of construction, the research and development program, and so on. The minutes of two NTS meetings dated May 5 and 12, 1952 are devoted to discussing the results the research and development program in 1950–1951. The minutes of NTS meetings have not been published previously.
[en] In this paper, a multi-band metasurface (MS) antenna array with low radar cross section (RCS) performance is proposed and measured. Firstly, a 4 × 4 antenna array is composed of four 2 × 2 Jerusalem cross structure antenna arrays working at different frequency bands, which is aimed at enhancing the bandwidth effectively. Then, each antenna can be seen as a unit of MS in spite of adding the feeding structure. Based on phase cancellation principle, the MS is arranged into a chessboard configuration in order to realize wideband RCS reduction. Thus, excellent radiation and scattering characteristics are obtained simultaneously. Simulated and measured results indicate that this work provides a novel method to achieve bandwidth expansion as well as wideband RCS reduction of the antenna array. (paper)
[en] Multi-model frameworks are widely used to identify the appropriate model structure for the study catchment. However, most frameworks mainly consider the process complexity of the model, and few of them consider the spatial complexity. In this paper, we investigated the appropriate model structure for a karst catchment from the aspect of spatial complexity. The purpose is twofold: (1) to investigate whether the spatial complexity is needed to simulate the spring discharge of this karst catchment and (2) to investigate whether the increase of model’s spatial complexity can make up its deficiency on the process complexity. Three simple lumped models with different process complexities were chosen to gradually increase the spatial heterogeneity of their parameters to investigate the appropriate model structure for simulating the discharge of a karst spring. The results show that the performances of three lumped models highly improve when adding the routing function to them. However, further considering the spatial parameter heterogeneity, only one model shows obvious performance improvement and other two models show limited improvement. Moreover, this model with relatively complex spatial parameter heterogeneity still shows worse performance than another lumped model. This indicates an increase of models’ spatial complexity cannot always make up their process deficiencies. The final comparison results indicated that the lumped model or their semi-lumped version with flexible process complexity is enough to simulate the discharge of this karst spring and no extra spatial complexity is needed. Our studies also indicated that the increase in spatial complexity of the model cannot always fully compensate its deficiency in process complexity.
[en] Effects of strongly anisotropic turbulent mixing on the critical behavior are studied by means of the renormalization group. Existence of new nonequilibrium types of critical regimes (universality classes) is established.
[en] The primary cooling system is designed to cool the heat generated from the core of a pool type research reactor (JRTR, Jordan Research and Training Reactor). The system penetrates the pool and is connected to the reactor. The reactor and pool should be kept clean as a caution during commissioning because re-cleaning or disassembling and re-assembling will require additional time and cost. Thus, the reactor, fluid equipment, instruments and pipes should be fabricated based on the cleaning procedure in accordance with the requirements of the related code and standard. The reactor and primary cooling system should be installed using the installation procedure because the interface between the reactor assembly and the related system including the fluid system, platform, pool door, instruments, detector conduits,and pool covers inside the pool is considerably complicated. After the primary cooling system is installed in the reactor and pool, system flushing is performed to remove any dust, particles,or other foreign matter using closed and open flushing methods. After the flushing and required CATs (Construction Acceptance Test) are completed and the demineralized water is filled in the pool and system, the SPT (System Performance Test) including measuring the system flow rate and pressure loss and checking the function of the pumps, valves, and system alarms can be started. Because the control valve is not used in the safety system, the pressure loss of the system is adjusted by replacing the system orifice plates with the planned procedure to meet the system flow rate during the SPT. The PST (Pre-Service inspection Test), which is a prerequisite for developing an in-service test program can be performed after the results of SPTs satisfy the acceptance criteria of the tests. (author)