Experimental investigation of a matrix receiver for a 3-mm waveband imaging system

The characteristics of a planar 8 × 8 array of a 3-mm waveband receiver antenna elements loaded with low-barrier planar Mott diodes have been studied. Experimental data on the radiation-directivity patterns (RP) and sensitivity of antenna elements in the two-dimensional array are presented. The average RP width for central elements amounts to ～35° in the E plane and ～50° in the H plane. In the operating frequency range (90–100 GHz) of the matrix receiver, the average voltage responsivity is on the order of 9000 V/W at a noise equivalent power of about 5 × 10^?12 W/Hz^1/2.     

矢量线列阵波束形成算法的左右舷分辨性能

研究矢量均匀线列阵波束形成算法的左右舷分辨性能。水听器可同步共点地测量声场的声压和质点振速,为一具有指向性的空间共点阵,从而能够解决单线阵声呐的目标左右舷模糊问题。文章分析了采用不同波束形成方法时矢量阵广义Cardiod处理和声强处理的目标左右舷分辨性能,并利用海试数据进行了验证。研究结果表明:自适应波束形成具有比常规波束形成更佳的左/右舷分辨性能,且对矢量阵处理而言,广义Cardioid处理更为稳健和实用。     

一种新型便携式制冷保温容器的试验研究

研制一种新型便携式制冷保温容器制冷系统，主要用于保存血液。确定半导体制冷核心部件的参数，如半导体制冷片的选择、容器内部结构及系统的匹配。通过性能试验进行优化，对影响半导体制冷的因素进行讨论。实验结果表明，将半导体制冷应用于保温容器是可行的，而且是有利的。该研究结果对半导体制冷技术在小型制冷保温容器中的进一步研究和应用具有一定的指导意义。     

Experimental results for improving the matrix condition using a hybrid optical system

We present preliminary experimental results for implementing the "blurred trajectories" method on three parallel optics (PO) systems. The "main" system and "auxiliary" optics were simple laboratory graded lenses attached to an iris diaphragm. When applying the blurred trajectories method we first show an improvement in the matrix condition, as the matrix condition number decreased in a range of factors of 3 to 418 relative to the main system. Following that, image restoration by weak regularization was performed so that the system matrix condition dominated the restoration process. It was shown that the restoration results of the PO are better than those of the main system and the auxiliary optics separately. In addition, the quality of the restoration follows the system's matrix condition. The improvement in the matrix condition achieved by the PO system improved the immunity to detection noise. Finally, a comparison to Wiener filtering restoration shows that it is also generally inferior to the proposed method.     

Experimental investigation of IN725 under different cooling environments using new tool holder

Heat buildup is an important issue on the cutting edge which then promotes high-temperature wear which consequently leads to poor machinability during dry machining. To improve the machinability, new tool holder designs accommodating cooling techniques have paid considerable attention toward the manufacturing domain recently. Whereas, in this paper, a new tool holder is designed and fabricated to serve for multipurpose cooling arrangements (internal cooling, external cooling) to reduce the heat buildup of the cutting edge along with the consolidated air system to clear away the chips. Initially, need of new tool holder is discussed followed by its manufacturability and machinability characteristics to a machine for nickel alloy Inconel 725. Machinability studies then are compared for dry machining, internal and external wet machining, and tool wear results are discussed. Thus, improvement in tool wear of around 70–75% and 65–72% is observed for internal wet, external wet concerning dry machining, respectively. Whereas, 15–18% (flank wear) and 6–9% (nose wear) improvement are seen for internal wet machining when compared with external wet machining. Results are best understood for internal cooling using a new tool holder.     

Airborne ultrasonic phased arrays using ferroelectrets: a new fabrication approach

In this work, a novel procedure that considerably simplifies the fabrication process of ferroelectret-based multi-element array transducers is proposed and evaluated. Also, the potential of ferroelectrets being used as active material for aircoupled ultrasonic transducer design is demonstrated. The new construction method of multi-element transducers introduces 2 distinctive improvements. First, active ferroelectret material is not discretized into elements, and second, the need of structuring upper and/or lower electrodes in advance of the permanent polarization of the film is removed. The aperture discretization and the mechanical connection are achieved in one step using a through-thickness conductive tape. To validate the procedure, 2 linear array prototypes of 32 elements, with a pitch of 3.43 mm and a wide usable frequency range from 30 to 300 kHz, were built and evaluated using a commercial phased-array system. A low crosstalk among elements, below -30 dB, was measured by interferometry. Likewise, a homogeneous response of the array elements, with a maximum deviation of plusmn1.8 dB, was obtained. Acoustic beam steering measurements were accomplished at different deflection angles using a calibrated microphone. The ultrasonic beam parameters, namely, lateral resolution, side lobe level, grating lobes, and focus depth, were congruent with theory. Acoustic images of a single reflector were obtained using one of the array elements as the receiver. Resulting images are also in accordance with numerical simulation, demonstrating the feasibility of using these arrays in pulse-echo mode. The proposed procedure simplifies the manufacturing of multidimensional arrays with arbitrary shape elements and not uniformly distributed. Furthermore, this concept can be extended to nonflat arrays as long as the transducer substrate conforms to a developable surface.     

High-performance joining technology for aluminium matrix composites using ultrasonic-assisted brazing

High-performance aluminium matrix composite joints were fabricated using a new joining technology assisted by ultrasonic vibration. The performance of the joints was close to that of the parent materials. The microstructure and the mechanical performance were found to be systematically dependent on the volume fraction and the distribution of reinforcement particles in the bond region. The authors believe that this study can be generalised to the bonding of other ceramic-reinforced metal matrix composites.     

一种新型的OFDM智能天线

根据自适应天线阵列理论，结合给定的参考波束的误差，引入虚拟干扰的概念，对目标波束图形状进行调整，提出一种新的可以应用于任意类型天线阵列的波束综舍算法．应用提出的新算法，在主辩和旁瓣位置都可以对波束进行有效的调节．最终获得阵列的最优权矢量，能够最小化目标波束图与参考波束图间的差异．理论分析与仿真结果表明，与现有的同类算法相比，该算法能更有效地获得与参考波束基本相符的波束．应用于OFDM智能天线系统时，对不同子载波频率上信号进行单独处理，利用该算法进行波束综合，能够在整个有效频段，使所有子载波上获得基本一致的阵列输出．     

Experimental investigation of new concentration measurements using nonlinear dynamics through laser-induced thermal lens oscillation

The laser-induced thermal lens oscillation that is generated in an organic solution by Ar-ion laser irradiation was studied as a nonlinear dynamic system. The different dynamic states depend on three control parameters: laser beam power (P), depth (d) from a surface to a laser beam position, and solvent concentration. The transitions of dynamic states including several complicated states, for example, periodic, double periodic, were investigated by varying the parameters (P, d) for 27%, 30%, and 33% of tri-n-butyl phosphate solution diluted with n-dodecane. It was found that these transitions were strongly dependent on the concentration of the TBP solution. Based on this result, we also propose an application to solvent concentration measurement with a difference of 3%.     

Development trends in the sensor technology: a new BCG matrix analysis as a potential tool of technology selection for a sensor suite

This paper presents a new variant of the Boston Consulting Group matrix analysis and applies it on sensor technologies. This classifies technologies in four classes on the basis of application growth rate of technology on one axis and competence available on the other. The quadrant, with high competence and increasing application growth rate, will be the most favored one and called star. The star technologies need application-oriented research with low risk, but they need money for design and development. A new sensor suite can select these technologies if the product development time available is roughly two to three years. The quadrant with low competence but high application growth rate is the question mark. The question mark technologies need intense R&D efforts, and they involve money and high to moderate risk. These technologies can be selected if product development time available is roughly more than three years. The technologies with low or falling application growth rate, but high competence available, are cash cows. These technologies are readily available (sometimes with production agencies), need absolutely no research, and a little bit of design or application orientation. In the cases where products are immediately needed, they have to be cheaper and do not need to last long technology wise; these can be selected. Finally, the quadrant with low competence and low application growth rate is called dogs, and such technologies can be left during consideration. Time and cost frames have also been well discussed. The role of development trends in prediction of technological evolution through a new BCG matrix is a new aspect introduced in this paper. As an example, this paper applies the above analysis in the area of night vision. This analysis can broadly guide the design of future sensor suites.     

Experimental investigation of a new hybrid molding process to manufacture high-performance composites

Reducing vehicle weight to reduce energy consumption and engine emissions is one of the major objectives of the automotive industry. The novel molding technology, presented in this paper, is suited to meet this demand. In this process, a thermoformed fiber-reinforced thermoplastic sheet is inserted into the mold and a long-fiber reinforced thermoplastic is injected to form a rib structure. Short cycle times make the technique an economic option for the manufacturing of hybrid high performance composites. This special integrative injection molding method optimizes efficiencies and thus energy consumption. A basic concept was realized to show the manufacture procedure. The mechanism of adhesion bonding between the long fiber thermoplastic material and the formed fabric and the influence of the main injection molding process parameters on the adhesion quality was experimentally investigated according to the Design of Experiments method. Then experimental tests were used to measure the structural properties of hybrid composites.     

Experimental and numerical investigation on ductile fracture mechanism of aluminium alloy using new modified model

In the present paper, the ductile fracture of aluminium alloy 5052P-H34 is studied by experiments and simulations. Then, the extension of the damage growth model, which captures both tension as well as shear, was employed in the present paper, and a modified Rousselier model was proposed. A stress integration algorithm based on the general backward Euler return algorithm was developed and implemented into finite element (FE) models in the ABAQUS/Explicit platform. The shear coefficient was calibrated by a FE analysis based on an inverse calibration procedure combined with the physical experiments. The predictive capability of this model was studied by comparing the experiments with the simulations, and the validity of this model was verified. The results show that the modified Rousselier model can give more accurate results for both tension and shear failure.     

MIMO capacity of antenna arrays evaluated using radio channel measurements, reverberation chamber and radiation patterns

We compare different methods of evaluating arrays for multiple-input multiple-output (MIMO) systems through calculation of the MIMO capacity of a compact antenna array for mobile or WLAN applications at 1766 MHz and comparing it to a reference array of four mono- poles. Three different methods were used: evaluation using radiation patterns and a channel model, measurements in a reverberation chamber and simultaneous measurement of radio channel data using the two arrays. We conclude that all methods give very similar relative results and that the main difference in the two arrays is the 1.3 dB lower radiation efficiency of the compact array. The channel measurements also show that the arrays provide between 80% and 90% of the capacity of a 4 times 4 MIMO system.     

Experimental and theoretical investigation of silver-coated ZnO nanorod arrays as antennas for the visible and near-IR spectral range

A new design of optical antennas consisting of zinc oxide (ZnO) nanorods covered by a thin metal film is proposed. Arrays of highly oriented ZnO nanorods perpendicular to a substrate and covered by a thin silver film have been obtained using methods of carbothermal synthesis and magnetron sputtering. The problems of electromagnetic wave diffraction on a single metal/dielectric nanovibrator (situated at the interface of dielectrics) and on a two-dimensional periodic array of these nanovibrators have been solved. The results of calculations of the electrodynamic characteristics of optical antennas with various lengths have been compared to experimental data.     

Experimental investigation of a molecular generator

Conclusions Tests have shown that above molecular generator has a highly stable frequency and good operational properties. For any given absolute frequency the resonator should be tuned with respect to variations in the ammonia gas pressure. The accuracy of the absolute frequency of a molecular generator obtained by this means and the effect of various factors on it will be further investigated.A. I. Samoilovich participated in designing our molecular generator model, he also suggested the technique and carried out the construction of the grid with long channels. M.I. Klyus took part in the construction of the generator and E. Z. Orlov in the tests described above.     

Experimental investigation of a bottle-sublimation cooler

A bottle-sublimation cooler is an open-cycle cooler of novel design combining the advantages of Joule–Thomson and sublimation coolers. The store of a refrigerant is bottled without heat leakages at ambient temperature. Sublimation of the refrigerant solid phase is the cold-generating process in the cooler. The cooler design and a discovered effect of the solid phase spontaneous capillary-porous structuring provide autoadjustability of the system operational characteristics. The results of experimental investigations of the stored-carbon dioxide bottle-sublimation cooler are reported in this paper. The experimental set-up and procedure of the system principal parameters measurement are covered. Temperature, thermal and overall size-mass parameters of the cooler are measured and reported. Performance specification of the cooler, which had been used for refrigerating of the IR module of a star spectrophotometer during astronomical observations, is presented.     

Experimental and numerical investigation of the interface between epoxy matrix and hemp yarn

In the present work, the adhesion between an impregnated hemp yarn and the epoxy matrix was investigated. The micromechanical tests usually used to characterise the fibre/matrix interface were adapted to the yarn/matrix interface. Single yarn composite specimens with yarn axis at 0° were manufactured and submitted to fragmentation tests to determine the experimental interfacial shear strength (IFSS). Specific single yarn composite specimens with yarn axis at 90° from the loading direction were also tested to track by digital image correlation the strain fields in the yarn, in the resin and at the yarn/matrix interface. A finite element analysis was developed and optimised to simulate the fragmentation process and provides a conservative value of IFSS.     

Experimental investigation of bridging law for single stitch fibre using Interlaminar tension test

In this study, a novel Interlaminar tension test (ITT) method was performed to experimentally investigate the bridging and fracture process of a single stitch fibre used to improve the delamination strength of composite laminates. Kevlar-29, of various thread thicknesses (44, 66, 88 and 132 tex), was used as the through-thickness stitch fibre in the ITT experiments. Key empirical force and displacement parameters, which governed the stitch fibre bridging law, were characterised and identified. Relationships of such parameters with thread thicknesses were determined. Fibre fracture load and fibre fracture energy are found to increase with increasing thread thickness. Frictional pull-out force greatly depends on the type of stitch fracture modes, which can be grouped into three categories. This paper aims to provide better physical understanding of the mechanics and mechanisms of stitch fibre fracture. By correlating critical stitch fracture parameters with stitch fibre thicknesses, the results expect to provide useful reference, which is essential and important for accurate stitch computational modeling and strength prediction of composites using stitching as the interlaminar reinforcement technique.     

Adaptive beamforming for array imaging of plate structures using lamb waves

Lamb waves are considered a promising tool for the monitoring of plate structures. Large areas of plate structures can be monitored using active arrays employing beamforming techniques. Dispersion and multiple propagating modes are issues that need to be addressed when working with Lamb waves. Previous work has mainly focused on standard delay-and-sum (DAS) beamforming while reducing the effects of multiple modes through frequency selectivity and transducer design. This paper presents a minimum variance distortionless response (MVDR) approach for Lamb waves using a uniform rectangular array (URA) and a single transmitter. Theoretically calculated dispersion curves are used to compensate for dispersion. The combination of the MVDR approach and the two-dimensional array improves the suppression of interfering Lamb modes. The proposed approach is evaluated on simulated and experimental data and compared with the standard DAS beamformer. It is shown that the MVDR algorithm performs better in terms of higher resolution and better side lobe and mode suppression capabilities. Known issues of the MVDR approach, such as signal cancellation in highly correlated environments and poor robustness, are addressed using methods that have proven effective for the purpose in other fields of active imaging.     

Ultrafiltration using polyaramide membranes — a new dimension in environmental technology

Crossflow filtration in the ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO) range with membranes made from high performance polymers (polysulfones, polyaramides etc.) is gaining relevance in many industrial applications. Membrane technologies allow not only cost and energy efficient removal of contaminants but also provide possibilities to recover valuable products from waste water streams.