An interative learning control scheme using the weighted least-squares method

An iterative learning control scheme is described for linear discrete-time systems. A weighted least-squares criterion of learning error is optimized to obtain a unique control gain for a case when the number of sampling is relatively small. It is then shown that algorithmic convergence can be readily guaranteed, because the present learning rule consists of a steady-state Kalman filter. By paying attention to the sparse system structure for the system's impulse response model, we further derive a suboptimal iterative learning control for a practical case when the number of sampling is large.     

Viewer,converter and preprocessor for smart machining process using an industrial robot

In this paper, viewer and converter softwares are presented for smart machining process using an industrial robot. The viewers for NC, CLS, DXF and STL files illustrate their surface representation with normal direction vectors. For example, the DXF is a data format developed by Autodesk to realize data interoperability among different makers’ CAD systems. The STL means Stereolithography which is a file format proposed by 3D Systems and recently is supported by many design tools and CAD/CAM softwares. In addition, the converters for DXF and STL files generate the corresponding CLS files with normal direction vectors for machining. Further, the proposed preprocessor allows the developed machining robot to work based on information included in STL files. The convenience and user-friendliness of the proposed integrated system are confirmed through experiments of viewing, converting and machining.     

Biodegradable polymers based on renewable resources. VI. Synthesis and biodegradability of poly(ester carbonate)s containing 1,4:3,6‐dianhydro‐D‐glucitol and sebacic acid units

Poly(ester carbonate)s with different compositions were synthesized by bulk polycondensation of 1,4:3,6‐dianhydro‐D ‐glucitol with diphenyl sebacate and diphenyl carbonate in the presence of zinc acetate as a catalyst. Most of the poly(ester carbonate)s as well as the corresponding polycarbonate were amorphous, except the poly(ester carbonate) with a small carbonate content and the corresponding polyester, which are semicrystalline. All these poly(ester carbonate)s are soluble in chloroform, pyridine, dimethylformamide, dimethyl sulfoxide, and N,N‐dimethylacetamide. Soil burial degradation tests, biochemical oxygen demand (BOD) measurements in an activated sludge, and enzymatic degradation tests indicated that these poly(ester carbonate)s are potentially biodegradable. The biodegradability was found to be maximum for the poly(ester carbonate)s with carbonate contents of 10–20 mol % and to decrease markedly for the poly(ester carbonate)s with the carbonate content above 50 mol %. The biodegradability of the poly(ester carbonate)s is discussed in terms of the crystallinity, glass transition temperature, and surface hydrophobicity of the polymer films. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 872–880, 2002     

A discontinuous exponential stabilization law for an underactuated X4-AUV

In this paper, stabilization of a class of second-order nonholonomic systems for an underactuated X4-AUV is investigated. We present a model of the underactuated X4-AUV with six degrees of freedom (DOF) and four control inputs. Then, the system is written in a control-affine form by applying a partial linearization technique, and a dynamic controller based on Astolfi’s discontinuous control is derived to stabilize all states of the system to the desired equilibrium point exponentially. The present approach does not necessitate the conversion of the system model into a “chained form”, and thus does not rely on any special transformation techniques to obtain a canonical form. A simulation is conducted to demonstrate the effectiveness of the proposed controller.     

Time‐harmonic electromagnetic field analysis in multisphere model by Gumerov's method of two scalar potentials

Time‐harmonic electromagnetic fields in multisphere models were calculated by the method of two scalar potentials proposed by Gumerov. The analyzed models were an eccentric two‐sphere model and a ten‐sphere model including the brain core and a pair of eyeballs. The applied fields were a plane wave and a dipole magnetic field, and the frequency was 1.8 or 2.0 GHz. The truncation degree p of the multipole and local expansion had values of up to 170 to 200. The peak power density on the x–y plane and the absorbed power in each tissue almost monotonically converged as p increased. These results demonstrate the usefulness of Gumerov's method. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 178(2): 1–10, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002–eej.21224     

Fabrication of Monodispersed Barium Titanate Nanoparticles with Narrow Size Distribution

Pulsed laser ablation (PLA) was used to prepare nanoparticles of barium titanate (BaTiO₃). PLA using a titanium-rich Ba–Ti–O ceramic target in oxygen ambience at 400 Pa and following online annealing at 1073 K enabled the production of BaTiO₃ nanoparticles (BTNPs) with a perovskite structure having nearly stoichiometric composition. These nanoparticles were directly introduced into a differential mobility analyzer for size classification, leading to the production of monodispersed and nonagglomerated BTNPs with an average particle size of 13.5 nm. The size distribution of the size-classified BTNPs was found to be reasonably narrow with a geometric standard deviation of 1.07.     

High-performance object tracking and fixation with an online neural estimator.

Vision-based target tracking and fixation to keep objects that move in three dimensions in view is important for many tasks in several fields including intelligent transportation systems and robotics. Much of the visual control literature has focused on the kinematics of visual control and ignored a number of significant dynamic control issues that limit performance. In line with this, this paper presents a neural network (NN)-based binocular tracking scheme for high-performance target tracking and fixation with minimum sensory information. The procedure allows the designer to take into account the physical (Lagrangian dynamics) properties of the vision system in the control law. The design objective is to synthesize a binocular tracking controller that explicitly takes the systems dynamics into account, yet needs no knowledge of dynamic nonlinearities and joint velocity sensory information. The combined neurocontroller-observer scheme can guarantee the uniform ultimate bounds of the tracking, observer, and NN weight estimation errors under fairly general conditions on the controller-observer gains. The controller is tested and verified via simulation tests in the presence of severe target motion changes.     

Enhancing Thermopower and Nernst Signal of High-Mobility Dirac Carriers by Fermi Level Tuning in the Layered Magnet EuMnBi2

Dirac/Weyl semimetals hosting linearly dispersing bands have received recent attention for potential thermoelectric applications, since their ultrahigh-mobility carriers could generate large thermoelectric and Nernst power factors. To optimize these efficiencies, the Fermi energy needs to be chemically controlled in a wide range, which is generally difficult in bulk materials because of disorder effects from the substituted ions. Here it is shown that the Fermi energy is tunable across the Dirac point for layered magnet EuMnBi₂ by partially substituting Gd³⁺ for Eu²⁺ in the insulating block layer, which dopes electrons into the Dirac fermion layer without degrading the mobility. Clear quantum oscillation observed even in the doped samples allows to quantitatively estimate the Fermi energy shift and optimize the power factor (exceeding 100 µ W K⁻² cm⁻¹ at low temperatures) in combination with the first-principles calculation. Furthermore, it is shown that Nernst signal steeply increases with decreasing carrier density beyond a simple theoretical prediction, which likely originates from the field-induced gap reduction of the Dirac band due to the exchange interaction with the Eu moments. Thus, the magnetic block layer provides high controllability for the Dirac fermions in EuMnBi₂, which would make this series of materials an appealing platform for novel transport phenomena.     

Deciphering cellular functions of protein phosphatases by comparison of gene expression profiles in Saccharomyces cerevisiae

Expression profiles of protein phosphatase (PPase) disruptants were analyzed by use of Pearson's correlation coefficient to find profiles that correlated with those of 316 Reference Gene (RG) disruptants harboring deletions in genes with known functions. Twenty-six Δppase disruptants exhibited either a positive or negative correlation with 94 RG disruptants when the p value for Pearson's correlation coefficient was > 0.2. Some of the predictions that arose from this analysis were tested experimentally and several new Δppase phenotypes were found. Notably, Δsit4 and Δsiw14 disruptants exhibited hygromycin B sensitivity, Δsit4 and Δptc1 disruptants grew slowly on glycerol medium, the Δptc1 disruptant was found to be sensitive to calcofluor white and congo red, while the Δppg1 disruptant was found to be sensitive to congo red. Because on-going analysis of expression profiles of Saccharomyces cerevisiae disruptants is rapidly generating new data, we suggest that the approach used in the present study to explore PPase function is also applicable to other genes.