On the synchronizing band of a rational harmonic injection locking

 Compared with the harmonic injection locking(HIL),a rationai harmonic injection locking (RHIL)can make the circuit even simpler and more flexible.A common formula for the synchro- nizing band ⊿ω(s_m)max of the RHIL is derived and analysed in this paper.The result shows that the formula given by Schmideg(1971)is only its special case.A method for extending the RHIL\'s synchronizing band with full-pass network is presented.Using the method,a 2/3 injection locking VHF divider consisting of the FZ1C,a type of IC,is developed,with a stability factor n=⊿f_((3/2)max)/ ⊿f_((-40-+85℃))≥4;while for the original circuit,n≈0.6.Thus,the RHIL may be of more practical value in applications.     

Spatial Link Scheduling for SCDMA Multihop Cellular Networks: A Cross Layer Framework

Probability of error based Spatial Code Division Multiple Access scheduling algorithm is presented in this paper to systematically reuse the orthogonal CDMA codes in a given cell for Multihop Cellular Network. We assign and reuse the CDMA codes to peer-to-peer links such that the probability of error in all scheduled links are below certain threshold. The proposed scheduling algorithm PoE-LinkSchedule involves two phases. In the first phase we present a scheduling metric “Probability of Error (PoE)” as a function of first and second order statistics of wireless channel coefficients between nodes. The second phase presents a graph theoretical as well as PoE based centralized scheduling algorithm. For a graph of network with n number of nodes, U number of links and θ thickness, the proposed scheduling algorithm has computational complexity of O(Unlogn + Unθ) as opposed to O(U ^U ) in the case of exhaustive search algorithm. The performance of the proposed algorithm is evaluated in terms of spatial reuse and end-to-end throughput. We show that the proposed algorithm has considerably higher end-to-end throughput and higher spatial reuse compared to existing link scheduling algorithms.     

On minimizing the total power of <Emphasis Type="Italic">k</Emphasis>-strongly connected wireless networks

Given a wireless network, we want to assign each node a transmission power, which will enable transmission between any two nodes (via other nodes). Moreover, due to possible faults, we want to have at least k vertex-disjoint paths from any node to any other, where k is some fixed integer, depending on the reliability of the nodes. The goal is to achieve this directed k-strong connectivity with a minimal overall power assignment. The problem is NP-Hard for any k ≥ 1 already for planar networks. Here we first present an optimal power assignment for uniformly spaced nodes on a line for any k ≥ 1. We also prove a number of useful properties of power assignment which are also of independent interest. Based on it, we design an approximation algorithm for linear radio networks with factor min{2,(\frac \Updelta d)^a },\hbox{min}\left\{2,\left(\frac {\Updelta} {\delta}\right)^\alpha \right\}, where Δ and δ are the maximal and minimal distances between adjacent nodes respectively and parameter α ≥ 1 being the distance-power gradient. We then extend it to the weighted version. Finally, we develop an approximation algorithm with factor O(k ²), for planar case, which is, to the best of our knowledge, the first non-trivial result for this problem.     

Spaser operation in the presence of external optical field

The operation of surface plasmon amplifier by stimulated emission of radiation (spaser) in the presence of external optical field is analyzed. The range of external field amplitude E and mismatch Δ of the external field frequency and the spaser generation frequency (Arnold tongue) E > E _synchr(Δ) in which the spaser works at the external field frequency is determined. The analytical and numerical calculations at the given mismatch Δ yield three ranges: E < E _synchr(Δ) (the spaser exhibits stochastic regime and point (Δ, E) is outside the Arnold tongue), E _synchr(Δ) < E < E _L (Δ) (transient range where the spaser polarization weakly depends on the field amplitude and is mainly determined by the pump level), and E > E _L (the spaser generation is suppressed and the spaser polarization is equal to the polarization of nanoparticle in the presence of external field).     

Phase relations in Cu- RO1.5- O (R < Ho,Er, Yb) and gibbs energy of formation of Cu2R2O5 (R < Ho,Er, Yb) between 1000 and 1325K

Phase relations in Cu-RO_1.5-O(R < Ho,Er,Yb) ternary systems at 1273K have been established by isothermal equilibration of samples containing different ratios of Cu:R(R < Ho,Er,Yb) in flowing air or high purity argon atmosphere for four days. The samples were then rapidly cooled to ambient temperature and the coexisting phases were identified by powder x-ray diffraction analysis. Only one ternary oxide, Cu₂R₂O₅(R < Ho,Er,Yb) was found to be stable. The chemical potential of oxygen for the coexistence of the three phase assemblage, Cu₂O + R₂O₃ + Cu₂R₂O₅(R < Ho,Er,Yb) has been measured by employing the solid-state galvanic cells,< (−) Pt, Cu₂O + Ho₂O₃+ Cu₂Ho₂O₅//CSZ//Air (Po₂< 2.12 × 10⁴ Pa), Pt (+) (−) Pt, Cu₂O + Er₂O₃+ Cu₂Er₂O//CSZ//Air (Po₂< 2.12 × 10⁴ Pa), Pt (+) (−) Pt, Cu₂O + Yb₂O₃ + Cu₂Yb₂O₅//CSZ//Air (Po₂ < 2.12 × 10⁴ Pa), Pt (+) in the temperature range of 1000 to 1325K. Combining the measured emf of the above cells with the chemical potential of oxygen at the reference electrode, using the Nernst relationship, gives for the reactions, 2Cu₂O(s) + 2Ho₂O₃(s) + O₂(g) → 2Cu₂Ho₂O₅(s) (1) 2Cu₂O(s) + 2Er₂O₃(s) + O₂(g) → 2Cu₂Er₂O₅(s) (2) and 2Cu₂O(s) + 2Yb₂O₃(s) + O₂(g) → 2Cu₂Yb₂O₅(s) (3) δΜo₂ = −219,741.3 + 145.671 T (±100) Jmol⁻¹ (4) δΜo₂ = −222,959.8 + 147.98 T(±100) Jmol⁻¹ (5) and δΜo₂ = −231,225.2 + 151.847 T(±100) Jmol⁻¹ (6) respectively. Combining the chemical potential of oxygen for the coexistence of Cu₂O + R₂O₃ + Cu₂R₂O₅(R− Ho,Er,Yb) obtained in this study with the oxygen potential for Cu₂O + CuO equilibrium gives for the reactions, 2 CuO(s) + Ho₂O₃(s) → Cu₂Ho₂O₅(s) (7) 2 CuO(s) + Er₂O₃(s) → Cu₂Er₂O₅(s) (8) and 2 CuO(s) + Yb₂O₃(s) → Cu₂Yb₂O₅(s) (9) δG‡ < 22,870.3 − 23.160 T (±100) Jmol⁻¹ (10) δG‡ < 21,261.1 − 22.002 T (±100) Jmol⁻¹ (11) and δG‡ < 17,128.4 - 20.072 T (±100) Jmol^-1 (12) It can be clearly seen that the formation of Cu₂R₂O₅R < Ho,Er,Yb) from the component oxides is endothermic. Further, Cu₂R₂O₅(R < Ho,Er,Yb) are an entropy stabilized phases. Based on the results obtained in this study, the oxygen potential diagram for Cu-R-O(R < Ho,Er,Yb) ternary system at 1273K has been composed.     

A depth‐first dynamic programming procedure for the extended tree knapsack problem in local access network design

The Extended Tree Knapsack Problem (ETKP) is a generalized version of the Tree Knapsack Problem where an arbitrary nonlinear traffic‐flow cost is imposed. This problem can be solved by the straight‐forward “bottom‐up” approach with a time complexity of O(nH ²), where n is the number of nodes in the tree, and H is the knapsack capacity. In this paper, we show that if the traffic‐flow cost function is the cable expansion cost, which occurs in the Local Access Telecommunication Network (LATN) expansion, this special ETKP can be solved by a depth‐first dynamic programming procedure in a time complexity of O(nδH), where δ is the largest existing cable capacity in LATN. This result indicates that the depth‐first dynamic programming algorithm can be applied for solving a general class of tree optimization problems. The computational results of our algorithm for the ETKP are also provided. This revised version was published online in June 2006 with corrections to the Cover Date.     

Aspects of the current understanding of the supercurrent transport in (Bi,Pb)2Sr2Ca2Cu3O10 silver-sheathed Tapes—the “railway-switch” model

The “railway-switch” model describes the superconducting current transport in (Bi,Pb)₂Sr₂Ca₂Cu₃O₁₀ silver-sheathed tapes under the basic assumption that small-angle c axis tilt grain boundaries (“railway-switch”) constitute strong intergrain links for the supercurrent in the textured filament [B. Hensel, J.-C. Grivel, A. Jeremie, A. Perin, A. Pollini, and R. Flükiger,Physica C 205, 329 (1993)]. We give an overview of the model and some recent experimental results with the objective to identify the mechanisms that limit the critical current density. The measurements have been performed on monofilamentary “powderin-tube” samples [J_c(T < 77K, B < 0 T) < 20..30 kA/cm²] that were prepared in long lengths by rolling as the only tape-forming process. We conclude that the low intragrain critical current density j_c ^c along the c axis (or the even lower critical current density j_c ^t across twist boundaries or intergrowths) is the dominant limitation for the transport critical current in high-quality tapes. We discuss possible starting points for a performance improvement of the (Bi,Pb)₂Sr₂Ca₂Cu₃O₁₀ silver-sheathed tapes for applications. On leave from Consorzio INFM, Universitá di Genova, Italy.     

Correlation between the temperature dependence of the band gap and the temperature dependence of the enthalpy of semiconductor crystals

The first-principles pseudopotential method of density-functional theory is used to study electron-phonon interactions in silicon. The temperature shift of the indirect band gap, the phonon spectrum, and the enthalpy are calculated consistently within the density-functional theory. The relationship between the temperature dependence of the energy gap ΔE _g(T) and the temperature dependence of the enthalpy ΔH(T) is ΔH(T)=K|ΔE _g(T)|. The physical origin of this correlation is discussed. Fiz. Tekh. Poluprovodn. 32, 1025–1028 (September 1998)     

On the Excess Oxygen in Four-Layered Rock-Salt-Type Units of Modulated Thermoelectric Bi-Sr-(Co,Rh)-O Compounds

Excess oxygen exists in four-layered rock-salt (RS)-type units of modulated misfit-layered Bi-Sr-(Co,Rh)-O compounds, which consist of interpenetrating CdI₂-type (Co,Rh)O₂ and distorted four-layered RS-type block subsystems, which have two b-axes, i.e., b ₁ and b ₂, respectively. From carefully determined chemical contents and misfit ratios, p = b ₁/b ₂, two structural characteristics are concluded, namely, intermixing metal ions in the RS-type layers and excess oxygen δ in, or in the vicinity of, them. The chemical formulae are proposed as [(Bi_1−x (Co,Rh) _x )₂(Sr_1−y Bi _y )₂O_4+δ ] _p (Co,Rh)O₂. The valence states of␣cobalt and rhodium ions are close to 3.3+. These valence states are quite reasonable for good thermoelectric oxides, such as γ-Na_0.7CoO₂ and [Ca₂CoO₃]_0.62CoO₂. Excess oxygen would cause the undulated atomic arrangement.     

Surface morphology and electrical properties of Au/Ni/?C?/n-Ga2O3/p-GaSe?KNO3? hybrid structures fabricated on the basis of a layered semiconductor with nanoscale ferroelectric inclusions

Features of the formation of Au/Ni/〈C〉/n-Ga₂O₃ hybrid nanostructures on a Van der Waals surface (0001) of “layered semiconductor-ferroelectric” composite nanostructures (p-GaSe〈KNO₃〉) are studied using atomic-force microscopy. The room-temperature current-voltage characteristics and the dependence of the impedance spectrum of hybrid structures on a bias voltage are studied. The current-voltage characteristic includes a resonance peak and a portion with negative differential resistance. The current attains a maximum at a certain bias voltage, when electric polarization switching in nanoscale three-dimensional inclusions in the layered GaSe matrix occurs. In the high-frequency region (f > 10⁶ Hz), inductive-type impedance (a large negative capacitance of structures, ∼10⁶ F/mm²) is detected. This effect is due to spinpolarized electron transport in a series of interconnected semiconductor composite nanostructures with multiple p-GaSe〈KNO₃〉 quantum wells and a forward-biased “ferromagnetic metal-semiconductor” polarizer (Au/Ni/〈C〉/n ⁺-Ga₂O₃/n-Ga₂O₃). A shift of the maximum (current hysteresis) is detected in the current-voltage characteristics for various directions of the variations in bias voltage.     

Quantization of magnetic induction in a 2D system under conditions of the quantum Hall effect

In this paper we show that in a 2D system situated in an external transverse magnetic field H the magnetic induction B can under certain conditions, as a result of the de Haas-van Alfvén effect, take only certain discrete values, i.e., it is “quantized.” In this case the dependence B(H) consists of jumps and a plateau. At the plateau B(H)=const. As a consequence of quantization of the magnetic induction B(H), quantization of the Hall resistivity ρ _xy(H) is possible. Fiz. Tekh. Poluprovodn. 33, 1144–1147 (September 1999)     

Determination of the si-conducting polymer interfacial properties using A-C impedance techniques

A study was made of the interfacial properties of Poly(pyrrole) (PP) deposited electrochemically onto single crystal p-Si surfaces. The interfacial properties are dependent upon the counterions. The formation of “Quasi-Ohmic” and “non-Ohmic” contacts, respectively, of PP(C1O₄) and PP films doped with other counterions (BF₄ and para-toluene sulfonate) with p-Si, are explained in-terms of the conductivity of these films and the flat band potential,V _fb, of PP relative to that ofp-Si. The PP film seems to passivate or block intrinsic surface states present on thep-Si surface. The differences in the impedance behavior of para-toluene sulfonate doped and C1O₄ doped PP are compared.     

Superconducting Properties of (M x /YBa2Cu3O7−δy )N Multilayer Films with Variable Layer Thickness x

The superconducting properties of (M _x /YBa₂Cu₃O_7−δy )_N multilayer films were studied for varying layer thickness x. Different M phases were examined including green-phase Y₂BaCuO₅ (211), Y₂O₃, BaZrO₃, CeO₂, SmBa₂Cu₃O_7−δ (Sm123), brown-phase La₂BaCuO₅ (La211), and MgO. Multilayer (M _x /YBa₂ Cu₃O_7−δy )_N structures were grown by pulsed laser deposition onto SrTiO₃ or LaAlO₃ single-crystal substrates by alternate ablation of separate YBa₂Cu₃O_7−δ (123) and M targets, at temperatures of 750°C to 790°C. The x layer thickness was varied from 0.1 nm to 4.5 nm, and the y 123 layer thickness was kept constant within a given range of 10 to 25 nm. Different M phase and x layer thicknesses caused large variations of the microstructural and superconducting properties, including superconducting transition (T _c), critical current density as a function of applied magnetic field J _c(H), self-field J _c(77 K), and nanoparticle layer coverage. Strong flux-pinning enhancement up to 1 to 3x was observed to occur for M additions of 211 and BaZrO₃ at 65 to 77 K, Y₂O₃ at 65 K, and CeO₂ for H < 0.5 T. BaZrO₃ had a noticeably different epitaxy forming smaller size nanoparticles ∼8 nm with 3 to 4x higher areal surface particle densities than other M phases, reaching 5 × 10¹¹ nanoparticles cm⁻². To optimize flux pinning and J _c (65 to 77 K, H = 2 to 3 T), the M layer thickness had to be reduced below a critical value that correlated with a nanoparticle surface coverage <15% by area. Unusual effects were observed for poor pinning materials including Sm123 and La211, where properties such as self-field J _c unexpectedly increased with increasing x layer thickness.     

OS-CFAR and CMLD threshold optimization in distributed systems using evolutionary strategies

This paper proposes an improvement of the threshold optimization in distributed ordered statistics constant false alarm rate and censored mean level detector using Evolutionary Strategies (ESs). The target is assumed to be Rayleigh distributed and the observations are independent from sensor to sensor. Two fusion rules; “AND” and “OR” were considered. An ES was tested and a comparison with a genetic algorithm improved by a tournament selection was also analyzed. Among a variety of evolution strategies, the most popular proposed in the literature are the strategy (μ, λ) and the strategy (μ + λ). We proposed an (μ + λ) evolution strategy, by which a self-adaptation mutation is used. The results showed that, although the ES is more difficult to implement and is in a certain manner slower than the GA, it improves the performance of the system.     

Electrical and Thermal Properties of the Ca3?xGdxCo4O9+δ System

The effects of Gd substitution on the thermoelectric (TE) properties of Ca₃Co₄O_9+δ have been systematically investigated from 25 K to 335 K. Partial substitution of Gd in Ca₃Co₄O_9+δ results in an increase of thermopower and resistivity, and a decrease of thermal conductivity. A maximum dimensionless figure of merit (ZT) of 0.028 was achieved at 335 K for Ca_2.4Gd_0.6Co₄O_9+δ , which is about one order of magnitude larger than that for Ca₃Co₄O_9+δ . The investigation demonstrates that the TE performance of the Ca₃Co₄O_9+δ system can be improved through Gd doping.     

Preparation and gas-sensing properties of α-Fe2O3 thin films

Haematite (α-Fe₂O₃) thin films are prepared by two different chemical vapor deposition (CVD) processes: the atmospheric pressure CVD (APCVD) and the plasma enhanced CVD (PECVD). The films are analyzed by x-ray diffraction and scanning electron microscopy; their gas-sensing properties are also investigated. Experimental results show that APCVD α-Fe₂O₃ films are highly sensitive and selective to smoke while PECVD films are highly sensitive and selective to alcohol. A certain amount of quadrivalent metal in the films has an effect on their sensitivity and selectivity to gases. It is found that the films will “break down” under certain conditions.     

Amorphous hydrogenated silicon films exhibiting enhanced photosensitivity

Amorphous hydrogenated silicon (a-Si:H) films with photoconductivities as high as 10⁶, i.e., exceeding the photoconductivity of “standard” a-Si:H by two orders of magnitude, are investigated. The dark conductivity (σ _d ) of the films has an activation energy ΔE=0.85–1.1 eV. The photoconductivity σ _ph is measured at a photocarrier generation rate of 10¹⁹ cm⁻³ · s⁻¹ and photon energy ɛ=2 eV. Several distinctive characteristics are ascertained in the behavior of σ ^ph and σ _d as functions of ΔE and also in the spectral curve and decay kinetics of σ _ph during prolonged illumination. It is concluded that the investigated material holds major promise for photovoltaic device applications. Fiz. Tekh. Poluprovodn. 33, 110–113 (January 1999)     

Thermoelectric Properties of the One-Dimensional Cobalt Oxide CaCo<Subscript>2</Subscript>O<Subscript>4</Subscript>

In this work we studied the crystal structure and physical properties of the new one-dimensional cobalt oxide CaCo₂O_4+δ . The CaCo₂O_4+δ phase crystallizes as a calcium-ferrite-type structure, which consists of a corner- and edge-shared CoO₆ octahedron network including one-dimensional double chains. The specific-heat Sommerfeld constant γ was found to be 4.48(7) mJ/mol K². This result suggests that the CaCo₂O_4+δ phase has a finite density of states at the Fermi level. Metallic temperature dependence of the Seebeck coefficient S with a large thermoelectric power (S = 151 μV/K at 387 K) was observed. The origin of the large thermoelectric power may be attributed to the quasi one-dimensional character of the energy band near the valence band maximum in CaCo₂O_4+δ .     

Defect centroid,patial distribution,and areal density in process-induced radiation-damaged IGFETs with gate insulators grown at 1000 and 800° C

IGFET devices were fabricated with “dry” gate oxides grown at 1000 and 800° C in the thickness range 5–50 nm. They were then exposed in an electrically unbiased state to Al K_α x-ray (1.49 keV) radiation to simulate process-induced ionizing radiation exposure. Gate oxide defects were measured before and after irradiation using optically assisted electron injection. Following irradiation and injection, the measured voltage shifts indicate that radiation-induced “extrinsic” defects are localized near, but not exactly at, the Si/SiO₂ interface.ΔV _T is found to be linear int _ox for oxide thicknesses where the top electrode resides above the defect region, and quadratic int _ox for thicknesses where the top electrode encroaches upon the defect region. For very thin oxides,ΔV _T is observed to approach zero. Application of a defect distribution model based on this behavior reveals that the oxidation temperature does not influence the distribution of radiation-induced defects, but does influence their concentration; with the 800° C oxides always containing more defects than the 1000° C oxides. A gate oxide thickness regime of less than 5-6 nm is identified in which radiation-induced threshold voltage shifts are observed to approach zero.     

An Efficient Parallel Algorithm for the Single Function Coarsest Partition Problem on the EREW PRAM

In this paper, we derive an efficient parallel algorithm to solve the single function coarsest partition problem. This algorithm runs in O(log2n) time using O(nlogn) operations on the EREW PRAM with O(n) memory cells used. Compared with the previous PRAM algorithms that consume O(n1+ε) memory cells for some positive constant ε > 0, our algorithm consumes less memory cells without increasing the total number of operations.