A simple adaptive PI controller for linear systems with constantdisturbances

It is known that an adaptive controller via high-gain output feedback can globally stabilize a class of minimum phase systems with relative degree one. However, exact output regulation is difficult for systems with disturbances. In this paper, we consider linear single-input/single-output (SISO) systems with unknown constant disturbances. We present a simple adaptive output feedback controller with an integral action and show that it can asymptotically stabilize those disturbed systems. The proposed PI type adaptive controller can also deal with the output tracking problem of a step reference     

Molecular pharmacology of voltage-dependent calcium channels

Voltage-dependent Ca2+ channels serve as the only link to transduce membrane depolarization into cellular Ca(2+)-dependent reactions. A wide variety of chemical substances that have the ability to modulate Ca2+ channels have been demonstrated both for their clinic utility and for importance in elucidating the molecular basis of various biological responses. Recently, introduction of molecular biology to pharmacology has brought a great deal of information about the molecular basis of drug action in Ca2+ channels. In this review, we attempt to overview recent progress in understanding the interactions between Ca2+ channels and their blockers, namely Ca2+ antagonists, from a molecular and structural point of view.     

Global adaptive stabilization of infinite-dimensional systems

The purpose of this paper is to show that a first-order adaptive regulator globally stabilizes a class of infinite-dimensional systems having no right half plane zeros. Knowledge of the spectrum of the model's high-frequency gain is not required.     

MOCVD Growth of Erbium Monoantimonide Thin Filmand Nanocomposites for Thermoelectrics

We report the growth of erbium monoantimonide (ErSb) thin films on indium antimonide (100) substrates by low-pressure metalorganic chemical vapor deposition. The growth rate of ErSb thin films shows strong dependency on the growth temperature and the Sb/Er precursor molar flow rate ratio. Scanning electron microscopy, energy-dispersive x-ray spectroscopy, and x-ray diffractometry (XRD) were employed to study the ErSb thin films grown under the growth conditions that gave the maximum growth rate in the range we investigated. We also report the growth of two types of nanocomposites in which ErSb nanocolumns or nanoslabs with lengths ~500 nm and diameters 20 nm to 30 nm are embedded in Zn-doped InGaSb (ErSb/InGaSb:Zn) and ErSb nanoparticles with diameters of ~30 nm are embedded in Zn-doped InSbAs (ErSb/InSbAs:Zn). These nanocomposites were intended to increase phonon scattering in a mid-to-long phonon wavelength range to reduce lattice thermal conductivity. We used time-domain thermoreflectance to measure total thermal conductivity for the two types of nanocomposites, obtaining 4.0 ± 0.6 W/mK and 6.7 ± 0.8 W/mK for the ErSb/InAsSb:Zn and ErSb/InGaSb:Zn nanocomposites, respectively, which suggests that the thermal conductivity was close to or slightly smaller than the alloy limit of the two ternary alloy hosts. The two nanocomposites were further studied by transmission electron microscopy (TEM) to reveal their microscopic features and by XRD to assess their crystalline structures.     

Growth of AgGaTe2 and AgAlTe2 Layers for Novel Photovoltaic Materials

AgGaTe₂ and AgAlTe₂ layers were grown on a-plane sapphire substrates by closed-space sublimation. These compounds replace Cd in CdTe with group I and III elements, and are, hence, expected to be ideal novel candidate materials for solar cells. The grown layers were confirmed to be stoichiometric AgGaTe₂ and AgAlTe₂ by x-ray diffraction (XRD). The AgAlTe₂ layers had strong preference for the (112) orientation. The XRD spectrum of the AgGaTe₂ layer was different from that of the AgAlTe₂ layer, and strong peaks were observed for (103) and (110) diffraction. The variation in orientations of the grown layers was analyzed in detail by use of XRD pole figures, which revealed that the AgGaTe₂ layers had an epitaxial relationship with the a-plane sapphire substrates.     

MBE growth and microstructural evaluation of Zn(S,Se)-based LEDs and diode lasers

The use of a nitrogen radio frequency plasma source together with an appropriate quantum well configuration have recently resulted in the successful realization of p-type ZnSe by molecular beam epitaxy. This has enabled a variety of pn heterojunction based devices to be built including the first semiconductor injection lasers operating in the blue/green portion of the spectrum first reported by 3M and the Brown/Purdue group. In this paper, we discuss two lattice matched multiple quantum well structures that produce laser emission in the blue and blue/green portion of the spectrum.     

InP/InGaAs double-heterojunction bipolar transistor with step-graded InGaAsP collector

An MOCVD-grown InP/InGaAs double-heterojunction bipolar transistor with a step-graded InGaAsP collector is described. This transistor allows high injection current densities over 2.9*10/sup 5/ A/cm/sup 2/, which suggests no significant current blocking related to the wide-gap InP layers. A cutoff frequency of 155 GHz and a maximum oscillation frequency of 90 GHz are obtained at the collector current density of 1.6*10/sup 5/ A/cm/sup 2/.<>     

Design of pseudo-ternary and quaternary alloys by superlattices consisting of (zn,cd)(s,se) binary ii–vi compounds

Theoretical design of pseudo-ternary and quaternary alloys by superlattice structures consisting of (Zn,Cd)(S,Se) binary II–VI compounds has been studied. For pseudo-ternary ZnCdS and ZnCdSe alloys, the superlattices with two layers in a cycle, i.e., ZnS/CdS and ZnSe/CdSe are considered, and for pseudo-quaternary ZnCdSSe alloy, the two superlattice structures with more than two layers in a cycle are considered. In order to design and evaluate these superlattices, the expression for the equilibrium in-plane lattice constant of these superlattices has been derived by minimizing the total elastic strain energy in the cycle. The combinations of layer thicknesses in a cycle and the effective bandgap of these superlattices have been calculated while the elastic strain effect was included. The usefulness of these superlattice structures has been evaluated.     

Comparison of the effect of a proteolytic enzyme dispase and a chelator for the preparation of epidermal sheet from nude mice.

Histochemical studies of epidermal Langerhans cells require well-preserved epidermal sheets. We studied the conditions for the preparation of the epidermal sheets from the skin of the ear, hind limb and trunk of nude mice. Two types of commercial dispase, and ethylenediaminetetraacetic acid (EDTA), were used at several concentrations and the effects were compared. Dermo-epidermal separation was evaluated by the preservation of ATPase activity of Langerhans cells in the epidermal sheet and by the ultrastructure of epidermal cells (Langerhans cells and keratinocytes) as well as epidermal-dermal junction. Good separation depended on the combination of the concentration of the reagent and site of the skin. The concentrations of both dispase and EDTA effective for separation of the epidermis in the nude mouse were lower than those in other mouse strains reported.     

All-active monolithic InP-based HBT VCO with tunable HEMT inductor

A novel HEMT-HBT VCO is presented; it is the first all-active analogue VCO demonstrated using InP HEMT-HBT integrated MMIC technology. The MMIC monolithically integrates an InP common-collector HBT oscillator with a tunable InP HEMT active inductor using selective MBE. The novel HEMT-HBT VCO can provide performance advantages over analogue VCOs such as the multi-vibrator, and has direct implications for high speed clock recovery circuits needed in InP based optoelectronic IC applications