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International audience; The ground-state magnetic dipole moment of the neutron-rich O21 isotope has been measured via β-ray-detected nuclear magnetic resonance (β-NMR) spectroscopy by using a spin-polarized secondary beam of O21 produced from the Ne22 primary beam. From the present measurement, the g factor |gexp(Og.s.21)|=0.6036(14) has been determined. Based on the comparison of this value with Schmidt values, we unambiguously confirm the νd5/2 configuration with spin and parity assignments Iπ=5/2+ for the O21 ground state, suggested by previously reported studies. Consequently, the magnetic moment has been determined as μexp(Og.s.21)=(−)1.5090(35)μN. The obtained experimental magnetic moment is in good agreement with the predictions of the shell-model calculations using the USD, YSOX, and SDPF-M interactions as well as random phase approximation (RPA) calculations. This observation indicates that the O21 nucleus in its ground state does not manifest any anomalous structure and is not influenced by the proximity of the drip line.

The gyromagnetic factor of the low-lying E=251.96(9) keV isomeric state of the nucleus ^{99}Zr was measured using the time-dependent perturbed angular distribution technique. This level is assigned a spin and parity of J^{π}=7/2^{+}, with a half-life of T_{1/2}=336(5) ns. The isomer was produced and spin aligned via the abrasion-fission of a ^{238}U primary beam at RIKEN RIBF. A magnetic moment |μ|=2.31(14)μ_{N} was deduced showing that this isomer is not single particle in nature. A comparison of the experimental values with interacting boson-fermion model IBFM-1 results shows that this state is strongly mixed with a main νd_{5/2} composition. Furthermore, it was found that monopole single-particle evolution changes significantly with the appearance of collective modes, likely due to type-II shell evolution.

Exotic nuclei are characterized by a number of neutrons (or protons) in excess relative to stable nuclei. Their shell structure, which represents single-particle motion in a nucleus, may vary due to nuclear force and excess neutrons, in a phenomenon called shell evolution. This effect could be counterbalanced by collective modes causing deformations of the nuclear surface. Here, we study the interplay between shell evolution and shape deformation by focusing on the magnetic moment of an isomeric state of the neutron-rich nucleus 75Cu. We measure the magnetic moment using highly spin-controlled rare-isotope beams and achieving large spin alignment via a two-step reaction scheme that incorporates an angular-momentum-selecting nucleon removal. By combining our experiments with numerical simulations of many-fermion correlations, we find that the low-lying states in 75Cu are, to a large extent, of single-particle nature on top of a correlated 74Ni core. We elucidate the crucial role of shell evolution even in the presence of the collective mode, and within the same framework, we consider whether and how the double magicity of the 78Ni nucleus is restored, which is also of keen interest from the perspective of nucleosynthesis in explosive stellar processes., 10 pages, 4 figures

We report on a new in situ laser spectroscopy technique using superfluid helium and a highly energetic ion beam. In taking advantage of superfluid helium as a host matrix for laser spectroscopy, we were able to develop an extremely low background detection system. The first demonstration using Rb-85(31+) ion beam (66 MeV/nucleon) accelerated at the RIKEN accelerator facility shows improvement of detection limit by two orders of magnitude. A quantitative evaluation of Rb atoms in the observation region enables an analysis of their optical absorption cross-section in superfluid helium from the fluorescence intensity dependence on ion-beam intensity and applied laser power. (C) 2018 The Japan Society of Applied Physics

Traditional “magic numbers” were once regarded as immutable throughout the nuclear chart. However, unexpected changes were found for unstable nuclei around N = 20. With both proton and neutron numbers around the magic number of 20, the neutron-rich 39Cl isotope provides a good test case for the study of the quantum-state evolution across the major shell. In the present work, the negative parity states in 39Cl are investigated through the β decay spectroscopy of 39S. Newly observed γ transitions together with a new state are assigned into the level scheme of 39Cl. The spin parity of 5/2− for the lowest negative parity state in 39Cl is reconfirmed using the combined γ transition information. These systematic observations of the negative parity states in 39Cl allow a comprehensive comparison with the theoretical descriptions. The lowest 5/2− state in 39Cl remains exotic in terms of comparisons with existing theoretical calculations and with the neighboring isotopes having similar single-particle configurations. Further experimental and theoretical investigations are suggested.

We report on a new in situ laser spectroscopy technique using superfluid helium and a highly energetic ion beam. In taking advantage of superfluid helium as a host matrix for laser spectroscopy, we were able to develop an extremely low background detection system. The first demonstration using 85Rb31+ ion beam (66 MeV/nucleon) accelerated at the RIKEN accelerator facility shows improvement of detection limit by two orders of magnitude. A quantitative evaluation of Rb atoms in the observation region enables an analysis of their optical absorption cross-section in superfluid helium from the fluorescence intensity dependence on ion-beam intensity and applied laser power.

We describe the oscillatory crack propagation for small propagation velocities at the atomistic scale that was recently observed for brittle metallic glasses [G. Wang, Y.T. Wang, Y.H. Liu, M.X. Pan, D.Q. Zhao, W.H. Wang, Appl. Lett. 89 (2006) 121909; G. Wang, D.Q. Zhao, H.Y. Bai, M.X. Pan, A.L. Xia, B.S. Han, X.K. Xi, Y. Wu, W.H. Wang, Phys. Rev. Lett. 98 (2007) 235501]. Based on a simple model of crack propagation [Y. Braiman, T. Egami, Phys. Rev. E, 77 (2008) 065101(R)], we derived and analyzed expressions for the feature size, oscillation period, and maximum strain accumulated in the material.

Most of the ferroelectric and piezoelectric materials used in transducers and electronics are complex mixed-ion alloys, in which atomic disorder plays an important role in the ferroelectric properties. The extreme case is relaxor ferroelectric solids with diffuse ferroelectric transition and glass-like relaxation behavior. In this review I discuss how advanced characterization techniques, such as neutron scattering, enabled a determination of the local structure and facilitated the understanding of the ferroelectric and piezoelectric properties of these complex systems. In particular, I focus on the role of Pb2+ ions in mixed ferroelectrics and the atomistic mechanism of relaxor ferroelectrics.

The Las Vegas Valley PM10 Study was conducted during 1995 to determine the contributions to PM10 aerosol from fugitive dust, motor vehicle exhaust, residential wood combustion, and secondary aerosol sources. Twenty-four-hr PM10 samples were collected at two neighborhood-scale sites every sixth day for 13 months. Five week-long intensive studies were conducted over a middle-scale sub-region at 29 locations that contained many construction projects emitting fugitive dust. The study found that the zone of influence around individual emitters was less than 1 km. Most of the sampling sites in residential and commercial areas yielded equivalent PM10 concentrations in the neighborhood region, even though they were more distant from each other than they were from the nearby construction sources. Based on chemical mass balance (CMB) receptor modeling, fugitive dust accounted for 80-90% of the PM10, and motor vehicle exhaust accounted for 3-9% of the PM10 in the Las Vegas Valley.

A histologic study of the para-vestibular canaliculus (PVC), its contents, and its relationship to the vestibular aqueduct (VA), is presented. 20 normal human temporal bones were fixed in 10% formalin solution, embedded in celloidin, and sectioned horizontally at intervals of 20 micrometers. Every tenth section was stained with hematoxylin and eosin (HE) and studied under a light microscope. Three significant observations were made. First, in 80% of the specimens, two rather than one PVC were found in the area of the vestibular orifice of the VA. Second, in 70% of the specimens, the PVC was found to merge with the VA rather than to enter the posterior cranial fossa (PCF) separately. Third, in all the specimens examined, a vein was seen to traverse the entire length of the PVC. However, in 17 specimens, no artery could be identified within the PVC. In the 13 (65%) specimens in which arteries could be identified in the PVC, the arteries extended only half the length of the PVC, from the PCF to the VA. In no specimen examined could arteries be seen extending the full length of the PVC from the PCF to the vestibule.

A novel mechanism of atomic transport in amorphous metallic alloys, or metallic glasses, is proposed based upon the fluctuations in the local structure. The proposed mechanism is very different from those in crystalline solids and from the free volume model, and is characterized by the bond-exchange action triggered by the local topological instability of the atomic environment. The implications of this mechanism on the liquid fragility and bulk metallic glass formation are discussed.

D-grade residential coal is being widely used as a fuel source for heating and cooking by most of the lower-income urban communities in South Africa. Emissions from residential coal combustion have been a major cause of elevated air pollution levels in the industrialized areas of South Africa. The adverse health effects resulting from exposure to residential coal combustion emissions have been a major public concern for many years. To address this, the Department of Minerals and Energy of South Africa conducted a macro-scale experiment in the township of Qalabotjha during the winter of 1997 to assess the technical and social benefits of combusting low-smoke fuels. This paper reports the PM2.5 and PM10 chemical mass-balance (CMB) source apportionment results from Qalabotjha during a 30-day sampling period, including a 10-day period when a large proportion of low-smoke fuels was combusted. Though emission rates of D-grade coal and low-smoke fuels may vary, their chemical abundances are too similar to be separated in CMB calculations. The source apportionment study confirmed that residential coal combustion is by far the greatest source of air pollution, accounting for 62.1% of PM2.5 and 42.6% of PM10 at the three Qalabotjha sites. Biomass burning is also a major source, accounting for 13.8% of PM2.5 and 19.9% of PM10. Fugitive dust is only significant in the coarse particle fraction, accounting for 11.3% of PM10. Contributions from secondary ammonium sulfate are three–four times greater than from ammonium nitrate, accounting for 5–6% of PM mass. Minor contributions (less than 1%) were found for power plant fly ash, motor vehicle exhaust, and agricultural lime. Average PM2.5 and PM10 mass decreased by 20 and 25%, respectively, from the D-grade coal combustion period (days 1–10) to the majority of the low-smoke fuel period (days 11–20). Relative source contribution estimates (SCE) were quite similar among the three sampling periods for PM2.5, and were quite different for PM10 during the second period when 14% higher residential coal combustion and 9% lower biomass burning source contributions were found.

Non-methane organic compound (NMOC) emissions from different sorts of food preparation sites, were quantified for the first time in Mexico, in order to develop emission profiles for further application in the chemical mass balance receptor model (CMB). Restaurants using charcoal grills and LP gas stoves, “tortillerias”, food frying places and rotisseries were sampled using SUMMA ® stainless-steel canisters to analyse NMOC by high-resolution gas chromatography. The results obtained show that profiles determined from food cooking processes have similarities to those found in LP gas combustion, which is the most common fuel in Mexico used for this purpose, although there were differences in the relative composition of propane and butane in both cases. This suggests that, the rates of combustion of propane and butane are different. It has also been detected that propene, a reactive olefin is produced during the combustion process. The obtained profiles of restaurants, rotisseries and fried food show an important contribution of two carbon compounds (ethane, ethylene and acetylene) that can be attributed to the complex process of grease and meat cooking. The presence of these compounds cannot be attributed to vehicular sources since the concentrations are higher than in ambient air. These were also determined from aromatic compounds such as benzene, toluene and xylene in the combustion of vegetal charcoal. The measured concentrations indicate that NMOC emissions from cooking may become an important indoor source of NMOC under crowded conditions in closed places.

The adsorption and reaction of NO on ceria-based model catalysts was studied using a combination of temperature programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). Specific systems investigated included: CeO 2 (1 1 1), CeO 2 /α-Al 2 O 3 (0 0 0 1), CeO 2 /YSZ(1 0 0), Rh/α-Al 2 O 3 (0 0 0 1), Rh/CeO 2 /α-Al 2 O 3 (0 0 0 1), and Rh/CeO 2 /YSZ(1 0 0). The results of this study show that NO does not adsorb on fully oxidized CeO 2 surfaces, while on partially reduced CeO 2 surfaces NO adsorbs and dissociates. The reaction of NO on Rh supported on a ceria thin film was found to be similar to that for reaction on Rh/α-Al 2 O 3 (0 0 0 1) and Rh single crystals as long as the surface of the ceria film was fully oxidized. For Rh supported on partially reduced CeO 2 , adsorbed oxygen atoms, formed via dissociation of NO, migrated from the Rh to the ceria resulting in oxidation of the surface of the oxide film. The results of this study also demonstrate that interactions at the CeO 2 –YSZ(1 0 0) interface influence the extent of reduction of the ceria film, its thermal stability, and oxygen ion transport properties.

This article presents results from the particulate monitoringcampaign conducted at Qalabotjha in South Africa during the winter of 1997. Combustion of D-grade domestic coal and low-smoke fuels were compared in a residential neighborhood to evaluate the extent of air quality improvement by switchinghousehold cooking and heating fuels.Comparisons are drawn between the gravimetric results from the two types of filter substrates (Teflon-membrane and quartz-fiber) as well as between the integrated and continuous samplers. It is demonstrated that the quartz-fiber filters reported 5 to 10% greater particulate mass than the Teflon-membrane filters, mainly due to the adsorption of organic gases onto the quartz-fiber filters. Due to heating of sampling stream to 50 °C in the TEOM continuous sampler and the high volatile content of the samples, approximately 15% of the particulate mass was lost during sampling.The USEPA 24-hr PM2.5 and PM10 National Ambient Air Quality Standards (NAAQS) of 65 μg m-3 and 150 μg m-3, respectively, were exceeded on several occasions during the 30-day field campaign. Average PMconcentrations are highest when D-grade domestic coal was used, and lowest between day 11 and day 20 of the experiment when a majority of the low-smoke fuels were phased in. Source impacts from residential coal combustion are also found to be influenced by changes in meteorology, especially wind velocity.PM2.5 and PM10 mass, elements, water-soluble cations (sodium, potassium, and ammonium), anions (chloride, nitrate, and sulfate), as well as organic and elemental carbonwere measured on 15 selected days during the field campaign. PM2.5 constituted more than 85% of PM10 at three Qalabotjha residential sites, and more than 70% of PM10 at the gradient site in the adjacent community of Villiers. Carbonaceous aerosol is by far the most abundant component, accounting for more than half of PM mass at the three Qalabotjha sites, and for more than a third of PM mass at the gradient site. Secondary aerosols such as sulfate, nitrate,and ammonium are also significant, constituting 8 to 12% of PM mass at the three Qalabotjha sites and 15 to 20% at the Villiers gradient site.

The reaction of CO and ethylene on oxide-supported Rh particles was studied using temperature programmed desorption. The model systems investigated consisted of Rh particles on the following oxide supports: α-Al2O3(0001), yttria-stabilized zirconia (100) [YSZ(100)], CeO2 thin film on α-Al2O3(0001) and CeO2 thin film on YSZ(100). The results of this study demonstrate that both the ceria and YSZ supports are able to donate oxygen for reaction with carbon species adsorbed on the supported Rh particles. The reducibility of the ceria thin films was found to be influenced by the underlying oxide supports. Ceria films supported on YSZ(100) underwent reduction upon heating to 900 K, while those on α-Al2O3(0001) did not.

D-grade (i.e. poor quality) coal is widely used for household cooking and heating purposes by lower-income urban communities in South Africa. The smoke from the combustion of coal has had a severe impact on the health of society in the townships and cities. To alleviate this escalating problem, the Department of Minerals and Energy of South Africa evaluated low-smoke fuels as an alternative source of energy. The technical and social implications of such fuels were investigated in the course of the Qalabotjha Low-Smoke Fuels Macro-Scale Experiment. Three low-smoke fuels (Chartech, African Fine Carbon [AFC], and Flame Africa) were tested in Qalabotjha during the winter of 1997. This paper examines diurnal variations of PM 10 (particles with aerodynamic diameters less than 10 μm) concentrations at the clinic site in Qalabotjha. Both the fuel type and the wind were found to have an effect on the air particulate concentrations. This paper demonstrates how continuous PM 10 data together with wind measurements can be modelled. Pronounced dual-peak diurnal variations of PM 10 concentrations were found in winter’s stable atmosphere with 30-min PM 10 levels often exceeding 1000 μg/m 3 around 07:00–08:00 h in the morning and around 18:00 h in the evening. PM 10 diurnal variations coincided with surface radiation inversions and residential cooking activity, suggesting that human exposure is confined to a very localized environment. On windy days, very low PM 10 concentrations with very little to no diurnal variations were found. Much of the locally generated cooking emissions may have been diluted by dispersion and transport. An exponential model that allowed for all measured particulate concentrations to be re-calculated to ‘zero wind’ values was created to estimate the impact of D-grade coal combustion. From analysis of variance (ANOVA) calculations on the ‘zero wind’ concentrations, it is concluded that the combustion of low-smoke fuels would make a significant improvement to the air quality in Qalabotjha.

The oxygen-storage properties of ceria in three-way automotive catalysts are promoted and stabilized by mixing with zirconia. In the present study, this promotion was investigated using model catalysts in which ceria films were vapor deposited onto α-Al2O3, polycrystalline ZrO2, polycrystalline Y2O3-stabilized ZrO2 (YSZ), and YSZ(1 0 0), (1 1 1), and (1 1 0) single crystals. Following deposition of Pd, both TPD of CO and steady-state CO-oxidation kinetics suggest that the ceria films on the zirconia-based substrates were much more easily reduced than films on α-Al2O3. Polycrystalline zirconia and YSZ and the YSZ single crystals were equally effective in promoting ceria reducibility. Structural studies of ceria on YSZ(1 0 0), using both TEM and EDSXD (energy-dispersive, surface X-ray diffraction), demonstrate that ceria forms ordered overlayers on YSZ(1 0 0), oriented with respect to the YSZ surface. The lattice parameter for ceria is decreased by only 0.6% compared to bulk CeO2, but the coherence length suggests that the overlayer may have a high defect density. It is suggested that the structure-directing properties of zirconia are responsible for the enhanced properties of ceria–zirconia mixed oxides.

The reaction of ethylene on a model automotive emissions control catalyst consisting of Rh particles on an epitaxial ceria film grown on the (100) surface of an yttria‐stabilized zirconia single crystal was studied using TPD. The TPD results showed that ethylene undergoes dehydrogenation on the model catalyst at temperatures below 500 K depositing carbon on the Rh particles. Surface carbon formed in this manner was oxidized to CO upon heating to above 550 K using oxygen supplied by the ceria lattice. Heating to 900 K was found to induce reduction of the ceria film resulting in a marked decrease in oxidation activity.

The atomic structure of lead zirconate, PbZrO3 (PZ), was studied using Rietveld refinement and atomic pair distribution function analysis of pulsed neutron powder diffraction data for the antiferroelectric, intermediate and paraelectric phases. The symmetry of PZ at T = 20 K in the antiferroelectric phase was determined to be Pbam. The structure was characterized by distortions of the ZrO6 octahedra which are smaller than in previous studies. Locally correlated displacements of Pb in the c direction develop with increasing temperature. The average magnitude was 0.06 Å at room temperature, 0.14 Å at T = 473 K and 0.20 Å in the intermediate phase at T = 508 K. The intermediate phase was characterized by in-plane antiferroelectric Pb displacements which produce 1\over 2{110} superlattice diffraction peaks. Above 473 K the local structure of PZ remains largely unchanged, in spite of the transitions in the long-range order from the antiferroelectric to the intermediate and to the paraelectric phases.

SJVAQS/AUSPEX acquired PM2.5, PM10, and gas samples at ten sites in central California during five ozone episodes over a period of 14 intensive sampling days. Four sample sets per day were collected for 5-and 7-hour durations during this period and analyzed for particulate mass, elements, ions, and organic and elemental carbon (OC and EC). Gaseous ammonia, nitric acid, and sulfur dioxide were collected with absorbing filters. Ozone (O3), nitrogen oxides (NOx), and peroxyacetyl nitrate (PAN) were measured continuously. Concentrations varied by sampling site, time of the day, and ozone episode. The highest concentrations of most chemical species were found at sites in the southern San Joaquin Valley. Nitrate occurred mainly in the gas phase during the daytime when temperatures exceeded 25°C, and in the particulate phase during the nighttime when temperatures decreased to less than 10°C. Significant amounts of nitrate volatilized from particles collected on quartz-fiber filters. Diurnal patterns of ozone, nitrogen oxides, PAN, nitric acid, and total particle nitrate were similar at most of the sites, which were separated by hundreds of kilometers, showing evidence of both photochemical conversion and transport of polluted air masses.

Experimental studies of local structure by pulsed neutron PDF analysis on manganites and cuprates suggest that these oxides are locally distorted due to a strong electron-lattice interaction, and charge carriers organize themselves most likely into a tweed-like state. Measurements by inelastic neutron scattering as well as calculations on the Hubbard model show that the electron-lattice interaction is strongest at the zone boundaries, enhanced by phonon-induced spin-correlations. Such a strong electron-lattice interaction must be the origin of these local distortions, and may form the basis for the microscopic mechanism of superconductivity.

A real time virtual desired signal design method for the control system which has already designed is proposed in this paper. The virtual desired signal is introduced to improve the tracking performance for the real desired signal. Points of the proposed design method are real time design and consideration on the designed control characteristics. Those are realized by feedback of the state variables of the control system which has already been designed and by feedforward from the real desired signal. In addition to the basic method, the design method with consideration on the preview action is proposed. An optimal control system with this real time virtual desired signal is designed and it is applied to an air slide linear dc brushless motor. Some experimental studies are carried out for confirming the effectiveness.

Domain nucleation and growth kinetics were investigated in sputter-deposited amorphous thin films of Tb 20.2 Fe 67.8 Co 12.0 . After magnetically saturating the films, a reverse external field was applied and the specimens were pulse-heated by an excimer laser. During this heat treatment the reversal of the magnetization was observed in-situ using the magneto-optical Kerr effect. In addition the domain nucleation was studied using a polarizing microscope. Combining the nucleation and magnetization reversal measurements the domain wall velocity was determined as a function of temperature at three different applied external fields. The results are discussed with reference to existing models for domain wall motion.

The atomic structure of CeO2 overlayers on the (001) surface of cubic Yttrium stabilized zirconia was studied by energy-dispersive surface X-ray diffraction. It is shown that the CeO2 layers form epitaxial islands with 5–15 monolayers in thickness with a nearly relaxed lattice constant. The results demonstrate that the energy-dispersive surface X-ray scattering is a powerful tool in certain cases of surface structural studies.

We have obtained a model of short and intermediate range atomic structure in the relaxor ferroelectric Pb(Mg1/3,Nb2/3)O3 (PMN) by pair-density function (PDF) analysis of pulsed neutron and synchrotron x-ray powder diffraction data. All atomic species are found to be displaced from their ideal cubic perovskite lattice sites in a manner consistent with an eight site crystallographic disorder model. Use of the pair-density function in analyzing the structure of PMN has allowed short and intermediate range displacement correlations to be explored. Our structural model shows strong local displacement correlations resulting in two structurally distinct regions. Here we show that this model is in agreement with observed electron diffraction patterns and high resolution transmission electron microscopy images, and examine how it may be used in interpreting them. Differences in the local structure of the two regions may be important in explaining the relaxor behavior.

A laboratory resuspension chamber is described that segregates dried and sieved geological material into size fractions less than 0, 1.0, 2.5, 10 and ∼30 gmm aerodynamic diameters onto filter media suitable for chemical analysis. Eight impactor inlets located in a rectangular array within a 0.4 m 3 chamber provide the size segregation. Tests show that mass concentrations across the array vary by no more than ± 10%. Filter samples are normally submitted to gravimetric, X-ray fluorescence, ion chromatography, automated colorimetric, atomic absorption spectrophotometric, and thermal/optical reflection analysis for ∼ 50 chemical species. Chemical profiles and size distribution have been measured on more than 200 dust samples throughout the world.

Relaxor ferroelectrics are a particularly interesting and technologically important subset of the perovskite family of ferroelectrics. Ferroelectric relaxors undergo a diffuse paraelectric-ferroelectric phase transition, the origin of which is not well understood. An understanding of the microscopic origin of this behavior may lead to a more systematic approach to the development of materials with applications-tailored properties and may provide important insight into the phenomenon of ferroelectricity in general. Recently we reported a model of local atomic structure in the relaxor ferroelectric Pb(Mg1/3, Nb2/3)O3 1. Here we present refinements to that model, and simulated electron diffraction images based upon this model.

We report inelastic x-ray scattering measurements of the temperature dependence of phonon dispersion in the prototypical charge-density-wave (CDW) compound 2H-NbSe2. Surprisingly, acoustic phonons soften to zero frequency and become overdamped over an extended region around the CDW wave vector. This extended phonon collapse is dramatically different from the sharp cusp in the phonon dispersion expected from Fermi surface nesting. Instead, our experiments, combined with ab initio calculations, show that it is the wave vector dependence of the electron-phonon coupling that drives the CDW formation in 2H-NbSe2 and determines its periodicity. This mechanism explains the so far enigmatic behavior of CDW in 2H-NbSe2 and may provide a new approach to other strongly correlated systems where electron-phonon coupling is important.

This paper proposes a disturbance suppression control with preview action for brushless & coreless type linear DC motor (LDM). Brushless & coreless type linear DC motor is coggingless and has long life. It is suitable for high speed and precise positioning control. Parameter variation and load change are regarded as equivalent disturbance signal and the compensation action is applied by utilizing the estimated value of the equivalent disturbance in the inner loop. Next, optimal preview control system is synthesized including the disturbance suppression control system mentioned above. Disturbance suppression, improving of phase delay and lowing of input peak value are attained in this control system for LDM. Experimental studies applied to LDM and linear X-Y table made by LDM are shown and these effects are also confirmed.

This paper shows that optimal preview control system approaches to a decoupled preview control system as weighting (actors for control input variables in quadratic performance index tends to zero. By this property, relation between design parameters and response of optimal preview control system becomes clear. The decoupled preview control method is applied to vector control system for induction motor drive. By this application, trade off between conditions of vector control and the magnitude of input variables becomes easy.

This paper deals with vibration control of a wheeled vehicle running over an irregular terrain. The following four control metheds mainly utilizing future terrain information are considered. (1) Whole preview control methed utilizing present and future terrain information; (2) Partial preview control method utilizing present (all wheel's) and future (only rear wheel's) terrain information; (3) Feedforward compensation control methed utilizing only present terrain information; (4) Feedback control methed utilizing no future terrain information. In the simulation studies, it is shown that position control and vibration control are much improved by utilizing future terrain information.

The authors present central force many-body potentials for the Cu-Ti system which were constructed so as to reproduce a number of properties of the CuTi2 compound (tetragonal structure). The authors fitted the potentials not only to the available experimental data (equilibrium lattice parameters and enthalpy of mixing) but employed an ab initio method to determine additional data, in particular the bulk modulus. It is shown that these potentials ensure the stability of the CuTi2 crystal structure against alternate structures and changes in the c/a ratio and closely reproduce the melting temperature of CuTi2. The authors then employ these potentials in simulations of the glass transition and amorphization by irradiation and use the concept of atomic level stresses to interpret the results.

Spinor and twistor formulations of tensionless bosonic strings in 4-dimensional Minkowski space are constructed. We begin with a first-order action that is equivalent to the Nambu-Goto action in the tensionful case and that leads to a spinorial action in the tensionless case. From this spinorial action, we find an alternative spinorial action useful for constructing a simple twistor formulation of tensionless strings. The twistor formulation is steadily constructed in accordance with a fundamental concept of twistor theory. We investigate local internal symmetries inherent in the twistorial action for a tensionless string and carry out some classical analyses of the tensionless string expressed in a twistorial form., Comment: 30 pages, no figures, minor corrections, a footnote added, published version

High molecular weight poly (ethylene oxide) (PEO) ( MW = 5 × 10 6 ) based NiBr 2 electrolytes of compositions, NiBr 2 (PEO) n , n = 2, 4, 8, 16, 32, 100, where n is the number of oxygen per Ni(II) ion, were prepared by solution casting. An unusually high oxygen/metal ratio of 2 could be achieved with NiBr 2 salt. X-ray powder diffraction study and pair distribution function (PDF) analysis indicate that no crystalline PEO-salt complex phase exists until n ≤16. At low salt concentration ( n > 16), the electrolyte consists of two components: amorphous PEO containing dissolved salt and crystalline PEO in which salt ions may exist as imperfections. The interchain correlation of PEO is virtually unaffected by dilute concentrations of salt. With increasing salt concentration, a new PEO-salt crystalline complex starts to form and the interchain correlation of PEO is drastically increased. These results are consistent with those obtained from differential scanning calorimetry (DSC) analysis and show a possible correlation between changes in local atomic structure and ionic conductivity.

The significance of a structural instability against ferroelectric or antiferroelectric polarization for the high temperature superconductivity in cuprates and bismuthates has long been recognized. Such polarizations on the local scale have indeed been suggested in a number of oxide superconductors by pulsed neutron scattering. We discuss the possible roles these local polarizations could play in producing the high temperature superconductivity in these oxides.

A neutron-powder-diffraction real-space structural refinement method is applied to study the local intermolecular correlations in bulk C{sub 60} solid at 10 K. We found that the orientation of the C{sub 60} molecules often deviates locally from the long-range average structure, and a significant number (30--40 %) of molecules have the sixfold face oriented toward adjacent molecules.