On Broadband Adaptive Beamforming in the Presence of Correlated Interferences

A novel approach of unitarily interpolated array MVDR （UIA-MVDR） is proposed, aiming at avoiding the signal cancellation caused by broadband signal-correlated interferences. UIA-MVDR belongs to the classic approaches of spectral averaging. However, it is distinguished from the conventional interpolated array MVDR （IA-MVDR） by two points： 1） It imposes a unitary constraint on the transform matrices. 2） It only optimizes the worst-case performance of array manifold approximation. As a result, the restriction on the order of Bessel function expansion is released, so that very accurate approximation can be achieved even in the case of small or middle arrays. Compared with many related approaches, UIA-MVDR destroys the correlation more completely and then achieves better performance. Its excellent performance in both correlated and uncorrelated broadband interferences suppression is confirmed via a n umber of numerical examples.     

无铁心无刷直流电机电枢制造技术研究

无铁心无刷直流电动机电枢无齿槽,采用全塑封结构,消除了齿槽效应引起的转矩波动。其电枢制造工艺复杂、要求高、难度大,需要采用新的材料和加工技术。文中对无铁心无刷直流电动机的电枢制造技术进行了研究,实践证明其工艺是可行的。     

Experimental investigation of surface flashover in vacuum using nanosecond pulses

Based on a Marx generator and a coaxial pulse forming line, an experimental investigation of surface flashover characteristics in vacuum is conducted by using nanosecond pulses of 10 ns rise time and 30 ns full width at half maximum (FWHM). Insulator dielectrics chosen for this investigation are Teflon, PMMA and Nylon. The tested factors include gas pressure, cone angle of conical frustum, diameter and length of cylindrical insulator, material and shape of electrode, and contact style between insulator and electrodes. The effects of these parameters on the surface flashover characteristics are described and analyzed in this paper. In addition, the character of flashover time lag in the nanosecond range, and surface flashover theory in vacuum charged by nanosecond pulses are also discussed.     

Observation of coupling between zero- and two-dimensional semiconductor systems based on anomalous diamagnetic effects

We report the direct observation of coupling between a single self-assembled InAs quantum dot and a wetting layer, based on strong diamagnetic shifts of many-body exciton states using magneto-photoluminescence spectroscopy. An extremely large positive diamagnetic coefficient is observed when an electron in the wetting layer combines with a hole in the quantum dot; the coefficient is nearly one order of magnitude larger than that of the exciton states confined in the quantum dots. Recombination of electrons with holes in a quantum dot of the coupled system leads to an unusual negative diamagnetic effect, which is five times stronger than that in a pure quantum dot system. This effect can be attributed to the expansion of the wavefunction of remaining electrons in the wetting layer or the spread of electrons in the excited states of the quantum dot to the wetting layer after recombination. In this case, the wavefunction extent of the final states in the quantum dot plane is much larger than that of the initial states because of the absence of holes in the quantum dot to attract electrons. The properties of emitted photons that depend on the large electron wavefunction extents in the wetting layer indicate that the coupling occurs between systems of different dimensionality, which is also verified from the results obtained by applying a magnetic field in different configurations. This study paves a new way to observe hybrid states with zero- and two-dimensional structures, which could be useful for investigating the Kondo physics and implementing spin-based solid-state quantum information processing.

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Rapid Light‐Triggered Drug Release in Liposomes Containing Small Amounts of Unsaturated and Porphyrin–Phospholipids

Prompt membrane permeabilization is a requisite for liposomes designed for local stimuli‐induced intravascular release of therapeutic payloads. Incorporation of a small amount (i.e., 5 molar percent) of an unsaturated phospholipid, such as dioleoylphosphatidylcholine (DOPC), accelerates near infrared (NIR) light‐triggered doxorubicin release in porphyrin–phospholipid (PoP) liposomes by an order of magnitude. In physiological conditions in vitro, the loaded drug can be released in a minute under NIR irradiation, while liposomes maintain serum stability otherwise. This enables rapid laser‐induced drug release using remarkably low amounts of PoP (i.e., 0.3 molar percent). Light‐triggered drug release occurs concomitantly with DOPC and cholesterol oxidation, as detected by mass spectrometry. In the presence of an oxygen scavenger or an antioxidant, light‐triggered drug release is inhibited, suggesting that the mechanism is related to singlet oxygen mediated oxidization of unsaturated lipids. Despite the irreversible modification of lipid composition, DOPC‐containing PoP liposome permeabilization is transient. Human pancreatic xenograft growth in mice is significantly delayed with a single chemophototherapy treatment following intravenous administration of 6 mg kg^?1 doxorubicin, loaded in liposomes containing small amounts of DOPC and PoP.     

淬态非晶FeSiB薄带的各向异性及其巨磁阻抗效应

采用单辊快淬法制备了Fe_(75)Si_9B_(13)非晶薄带。磁阻抗测试显示,淬态非晶FeSiB合金薄带具有显著的巨磁阻抗效应(GMI),在7 MHz频率下,纵横向最大阻抗比分别达到30%和29%。磁畴结构观察表明,薄带样品磁畴结构为具有一定的横向取向的180°条形畴,易轴与样品横向夹角约为75°。磁电阻变化与样品各向异性变化没有直接关系,相比磁阻抗,磁感抗更确切地反映了磁矩转动磁化行为和样品各向异性场的大小,易轴具有一定的横向取向以及薄带各向异性在厚度方向的空间分布是影响其GMI变化特性的原因。分析了磁电阻、磁感抗对样品巨磁阻抗效应的影响,发现,低频下,磁电阻对磁阻抗变化起主要作用,随着趋肤效应增强,样品磁感抗逐渐成为影响磁阻抗变化行为的主要方面。     

Efficient and flexible anonymization of transaction data

Transaction data are increasingly used in applications, such as marketing research and biomedical studies. Publishing these data, however, may risk privacy breaches, as they often contain personal information about individuals. Approaches to anonymizing transaction data have been proposed recently, but they may produce excessively distorted and inadequately protected solutions. This is because these approaches do not consider privacy requirements that are common in real-world applications in a realistic and flexible manner, and attempt to safeguard the data only against either identity disclosure or sensitive information inference. In this paper, we propose a new approach that overcomes these limitations. We introduce a rule-based privacy model that allows data publishers to express fine-grained protection requirements for both identity and sensitive information disclosure. Based on this model, we also develop two anonymization algorithms. Our first algorithm works in a top-down fashion, employing an efficient strategy to recursively generalize data with low information loss. Our second algorithm uses sampling and a combination of top-down and bottom-up generalization heuristics, which greatly improves scalability while maintaining low information loss. Extensive experiments show that our algorithms significantly outperform the state-of-the-art in terms of retaining data utility, while achieving good protection and scalability.