Discrete optimization by optimal control methods. II. The static traveling salesman problem

The static minisum traveling salesman problem is formulated as an optimal control problem. Two-sided algorithms based on the sufficient conditions for global optimality for solving this problem and a new algorithm for approximating the quality criterion from above to its optimal value are designed.     

Synthesis and characterization of ZnO nanowires for nanosensor applications

In this paper we report the synthesis of ZnO nanowires via chemical vapor deposition (CVD) at 650 °C. It will be shown that these nanowires are suitable for sensing applications. ZnO nanowires were grown with diameters ranging from 50 to 200 nm depending on the substrate position in a CVD synthesis reactor and the growth regimes. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), and Raman spectroscopy (RS) have been used to characterize the ZnO nanowires. To investigate the suitability of the CVD synthesized ZnO nanowires for gas sensing applications, a single ZnO nanowire device (50 nm in diameter) was fabricated using a focused ion beam (FIB). The response to H₂ of a gas nanosensor based on an individual ZnO nanowire is also reported.     

Unfolding study of native bacteriorhodopsin under acidic condition

In this study, we measured the structural properties of “blue membrane”, which is specific formation of a purple membrane (PM) upon acid titration or removal of cations, by the force curve measurement mode of an atomic force microscopy. The PM fragments were immobilized on a glass substrate and force curve measurements were carried out on the fragments under neutral (pH 7.2) and acidic (pH 2.4) condition. The results revealed that peak positions of the unfolding spectra obtained under acidic condition were shifted to the shorter extension region than those at neutral pH and that the relative position of only the first peak was changed by about 5 nm. These results suggest the possibility that the specific secondary structure is formed at the site from its C-terminus to helices F in acidified PM.     

Experience from design and application of the top-level system of the process control system of nuclear power-plant

Consideration was given to the design of the top-level system of the nuclear power-plant process control system with regard for the impact on its safety. This system is aimed at centralizing process instrumentation and control. The top-level system is a sophisticated hardware complex supported by the computer-aided design and adjustment system and intended for integrating all subsystems of the process control system. The top-level system executes the informational, control, service, and auxiliary functions of the nuclear power-plant process control system. Consideration was given to the structure of the top-level system, the structure of its software, and the principles of design providing high performance of the top-level system.     

The three-dimensional assignment and partition problems. New lower bounds

For the three-dimensional assignment problem, new sharp lower bounds are derived from its relationship with the partition problem. The new sharp lower bounds derived for the partition problem from optimal control theory are of great value not only for the three-dimensional assignment problem, but also for the partition problem itself.     

Structural and optical properties of single-crystalline ultraviolet-emitting needle-shaped ZnO nanowires

Well-crystallized with excellent optical properties, needle-shaped ZnO nanowires have been synthesized on silicon substrate in a high density via the thermal evaporation of metallic zinc powder without the use of catalysts or additives. Extensive structural analysis showed that the grown nanowires are highly crystalline with the wurtzite hexagonal phase, grown along the [0001] in the c-axis direction. The presence of an optical-phonon E₂ mode in Raman spectrum at 437 cm^{− 1} and sharp and strong UV emission at 379 nm with no green emission in the room-temperature photoluminescence (PL) spectrum confirms good crystallinity with the excellent optical properties for the deposited nanowires.     

Comparisons to establish a force-balanced piston gauge and a spinning rotor gauge as the new measurement standards of MIKES

Centre for Metrology and Accreditation (MIKES) has worked towards expanding its calibration capabilities in the absolute pressure range downwards from 0.2 Pa and lowering measurement uncertainties in the range <10 kPa using a force-balanced piston gauge (FPG) and a spinning rotor gauge (SRG).MIKES was the first national pressure laboratory to purchase a novel type of piston manometer, FPG, developed by DH Instruments Inc., USA. The effective area of the FPG was at first determined at MIKES by a comparison with a conventional pressure balance. The result was confirmed in comparisons in the same pressure range with two other laboratories, Swedish National Testing and Research Institute (SP), Sweden and Institute for Metrology and Technology—Van Swinden Laboratorium (NMi-VSL), Netherlands. Next a direct comparison with the mercury column manometer of Physikalisch-Technische Bundesanstalt (PTB), Germany in the absolute pressure range from 1 to 15 kPa was carried out. Use of the FPG for calibration of capacitance diaphragm gauges (CDGs) is also presented.MIKES now uses two SRGs as reference standards, manufactured by MKS Instruments, Inc., USA. A comparison of SRGs in the range from 0.1 to 5 Pa between MIKES, SP and Vaisala Oyj accredited laboratory was performed in 2001-2002.     

Two-level orientation control system of flexible spacecraft with active stabilization of structural elastic oscillations

Active stabilization of the elastic oscillations of the flexible objects belonging to the class of flexible spacecraft (FSC) was shown to be required for stable orientation control in addition to the main goal of control. An algorithm of Kalman estimation of the FSC coordinates and parameters was constructed, and a principle was proposed for two-level orientation control based on realtime estimates of the controlled coordinates. At that, the first level of control orients the FSC by the estimated “rigid” component of the total motion, and the second level stabilizes its structural elastic oscillations using the estimated elastic modes as controls. A number of algorithms was proposed to actively damp the elastic oscillations, and the methods of mathematical modeling were used to prove that in the case of two-level control the combined FSC motion is a stable manifold closed in a bounded domain where the requirements on the desired dynamics of FSC orientation processes are satisfied.     

Non-smooth guiding potentials in problems on forced oscillations

New classes of non-smooth guiding potentials are determined. The introduced concepts are used for solving the problem on periodic oscillations of controlled objects described by the system of differential equations and by the system of differential inclusions.     

The phase diagram YF3-GdF3

The binary phase diagram YF₃-GdF₃ was studied by differential scanning calorimetry (DSC). Yttrium fluoride and gadolinium fluoride show complete miscibility in all three phases (orthorhombic room temperature phase, trigonal or hexagonal high temperature phase, liquid). The transformations between room temperature and high temperature phases are of first order and occur at 1338.6 K (YF₃) or 1174.8 K (GdF₃). Melting points are 1403.1 K (YF₃) or 1525.7 K (GdF₃), respectively. The c_p(T) curve of GdF₃ shows a λ shaped local maximum at 1333 K that might be related to a further solid phase transformation of second order.