通信辐射源瞬态特征提取和个体识别方法

通信信号的个体识别是近年来非合作通信领域一个重要研究课题．根据瞬态信号的非线性特征,采用递归图的分析方法提取瞬态信号的起始时刻,然后采用小波变换进行特征提取,在此基础上采用遗传算法挑选出分辨能力强的特征,利用支持向量机分类器实现对通信辐射源信号的个体识别．实验结果表明该方法用较少的特征获得较高的正确识别率,正确识别率大于90％．     

融合自适应加权和局部奇异值分解的人脸识别

提出了融合自适应加权和局部奇异值分解的人脸识别方法。首先,对每个训练样本分割出人脸图像的5个特殊区域并分别进行奇异值分解,提取一些较大的奇异值构成每一区域的特征向量。然后,计算各局部块的类内距离平均值和类间距离平均值,从而得到各部分对应的权值。识别阶段,计算待识别人脸图像每一区域对所有训练样本人脸图像相应区域的隶属度,最后采用加权融合策略做出判断。基于ORL和FERET人脸数据库的实验结果表明提出的方法具有有效性和可行性。     

A slot resonators based quintuple band-notched Y-shaped planar monopole ultra-wideband antenna

A Y-shaped ultra-wideband (UWB) monopole antenna containing modified ground plane with five stop bands is presented. An inverted U-shaped slot and a C-shaped slot are placed on Y-shaped radiating patch to achieve two notched bands while three pairs of C-shaped slots are placed at different positions on modified ground plane to achieve three more notched bands. The proposed antenna is designed, fabricated and experimentally tested. The designed Y-shaped antenna has overall dimensions of 36 × 38 × 1.6 mm³ (0.34λ_l × 0.36 λ_l × 0.016 λ_l) and has impedance bandwidth 2.86–13.3 GHz at |S₁₁| < −10 dB level. Measured band notches are achieved at 3.75/5.43/7.87/8.62/9.87 GHz centre notched frequencies to eliminate worldwide interoperability for microwave access (WiMAX) band (3.45–4.0 GHz), wireless local area network (WLAN) band (5.15–5.90 GHz), X-band for satellite communication (6.77–8.00 GHz), ITU-8 band (8.3–9.1 GHz), and radio navigation (RN) band (9.3–10.6 GHz), respectively. Variation of slot parameter on individual band notch is also investigated. Omnidirectional radiation pattern for XZ-plane and dipole-like radiation pattern for YZ-plane are observed. Stable gain, variation of phase response in linear fashion and group delay <1.3 ns for whole ultra-wideband except at band notches is achieved.     

Investigation of effects of sulfur on dry reforming of biogas over nickel–iron based catalysts

The aim of this study is to maintain and increase the activity of the catalyst in the presence of H₂S with the addition of iron to the Ni catalyst. Alumina-supported monometallic iron and bimetallic nickel-iron catalysts with different weight percentages (8% Fe, 3% Ni – 3% Fe and 8% Ni – 8% Fe) were synthesized using the wet impregnation method in this study. Alumina was prepared by the sol-gel method. The activities of these synthesized catalysts in the methane dry reforming reaction were investigated at different H₂S concentrations (0 ppm, 2 ppm, and 50 ppm) with a total flow rate of 60 mL/min containing an equimolar ratio of CH₄, CO₂, and Ar at 750 °C and atmospheric pressure. To investigate the effect of sulfur compounds on the catalytic activity, the catalysts were also exposed to different gas compositions such as the mixture of H₂S + He, H₂S + CO₂ + He, and H₂S + CO₂ + CH₄ + He. In this case, FT-IR with a gas cell was used to determine the components in the gas stream at the reactor outlet. To explain catalytic performance, characterization studies were carried out using XRD, N₂ adsorption/desorption, DRIFT, SEM, TGA, and XPS analysis. All-synthesized materials showed Type-IV isotherm with a hysteresis loop corresponding to an ordered mesoporous structure. The DRIFT analysis showed a decrease in the Lewis acid sites after the addition of iron into the Ni-catalysts. In the activity test carried out in the presence of 50 ppm H₂S, it was observed that the iron-containing 8Ni–8Fe@SGA catalyst increased the sulfur resistance slightly, compared to the monometallic 8Ni@SGA catalyst. TGA analysis showed that Fe addition reduced coke deposition, as the Ni–Fe catalyst had a lower nickel crystal size than the Ni-based catalyst. FTIR analysis with a gas cell showed that sulfur in H₂S transformed to other sulfur compounds such as COS and/or SO₂ during dry reforming of biogas over alumina-supported Ni–Fe catalysts.     

Absorbents based on maleic anhydride-modified cellulose fibers/diatomite for dye removal

In this work, an absorbent consisting of the maleic anhydride-modified cellulose beads combined with alkali-treated diatomite (MCDBs) was prepared in an attempt to remove basic dyes. An appropriate amount of calcium carbonate was added during the formation of MCDBs to increase the pore structure under an acidic condition. The synthesized MCDBs were characterized with FT-IR, TGA, and BET. The degree of carboxylation of MCDBs was quantified using a polyelectrolyte titration method. The removal of basic dyes such as methylene blue (MB) and methyl violet (MV) from aqueous solution was systematically investigated. The influence of pH, shaking time, and temperature on the removal process was identified. The results indicated that the MCDBs had a strong adsorption capacity toward basic dyes. The adsorption capacity increased from 51.6 to 116.6 mg/g for MB, depending on the initial concentration of the dye. A similar trend was also found for MV, i.e., adsorption increased from 30.5 to 61.1 mg/g. The experimental data fitted two kinetic models; the results demonstrated that the adsorption of MB and MV onto the MCDBs fits the pseudo-second-order model very well. The removal efficiencies of the basic dyes under the optimal conditions were up to 97.5 %. The adsorption data were also fitted using Langmuir, Freundlich, and Temkin isotherms, separately. It was found that the adsorption process for the basic dyes was better described by the Langmuir isotherm model.     

Performance measurement of decision-making units under uncertainty conditions: An approach based on double frontier analysis

Data envelopment analysis (DEA) is an approach to measure the relative efficiency of a set of decision-making units (DMUs) which uses multiple inputs to produce multiple outputs. In real world situations, due to uncertainty, DEA is sometimes faced with imprecise inputs and/or outputs. Therefore, performance measurement must often be performed under uncertainty conditions. Generally, the performance of DMUs can be evaluated from two perspectives—optimistic and pessimistic. As a result, two different evaluations are obtained for each DMU. In this article, we first obtain the efficiencies of the DMUs under evaluation from both optimistic and pessimistic views. The optimistic view evaluates each DMU with a set of the most desirable weights; the efficiencies measured by the optimistic approach are called optimistic efficiencies. The pessimistic view evaluates each DMU with a set of the most undesirable weights; the efficiencies measured by the pessimistic approach are called pessimistic efficiencies. Then it is shown that the outcomes of these two evaluations are conflicting with each other, being undoubtedly biased, unrealistic, and unconvincing. To overcome this problem, we propose a new measure of overall performance which is used for integrating the measures obtained from optimistic and pessimistic views and we will use it to identify the DMU with the best performance under uncertainty conditions. Also, we propose new fuzzy DEA models that evaluate a DMU from the pessimistic perspective in a fuzzy context. The proposed measure will be shown with two numerical examples, including the selection of a flexible manufacturing system.     

大功率白光LED加速寿命试验研究

对新型大功率GaN基蓝光芯片激发荧光粉发射白光的LED进行电流应力加速寿命测试和可靠性研究,考察白光LED主要性能参数随老化时间的变化,结果表明:经过5000多小时的老化,光通量平均降至初始值的77.5%;发光效率变化趋势与光通量变化基本一致;峰值波长没有明显的变化趋势,而相关色温随老化时间增加逐渐升高;正向导通电压也随老化时间增加而升高.实验表明样品参数型失效主要包括发光效率的降低和荧光粉转换效率的降低.     

下行床内颗粒浓度的电容层析成像测量的研究

利用电容层析成像(electrical capacitance tomography,ECT),以非侵入的方式,对下行床内气固流动情况进行测量研究。针对下行床内固体颗粒浓度低的特点,采用了SIRT图像重建算法,得到了高质量的ECT图像。在颗粒流量和流化风量变化的情况下测量了不同截面固体颗粒体积份额平均值的变化,得到了下行床内气固流动规律。实现了快速的下行床内粉粒体的ECT在线可视化测量,具有较大的工程和学术价值。     

A multi-criteria decision making analysis for feasibility of nanoparticle addition in biohydrogen production enhancement for scaling-up studies

Nanoparticles (NPs) thanks to their unique features such as large surface area, high catalytic activity and intra-cellular electron transfer ability used as an enhancement additive in biohydrogen production. Up to date, inorganic, organic and their mixtures of various NPs were produced from different input sources and synthesis methodology. The NPs properties and cost minimization are the critical factors for the scale up studies of industrial applications. Nevertheless, there have not been any study on the determination of the most efficient and feasible NPs in biohydrogen production for the scaling up the process. In this study, the NPs used for biohydrogen production enhancement over Clostridium sp. by dark fermentation were examined and these studies were evaluated to determine the most effective and feasible NPs using the two-stage TOPSIS method. As a result, iron-containing NPs (hematite, magnetite) were determined as the most effective and economical NPs for increasing the yield.     

An alternative pathway from hot dry rock to green hydrogen by organic Rankine cycle applications

Some researchers have been focused on electricity generation using thermal energy extraction from HDRs via Organic Rankine cycles. This new research topic creates a new pathway to reach green hydrogen for countries that have geothermal power such as Turkey. In this study, a well in the Nevşehir region that does not has the potential to be used in direct geothermal energy applications due to the absence of water was examined. By using the heat obtained from HDR by injected water, the estimated amount of electricity that can be produced with a single shaft binary organic Rankine cycle was revealed by calculating the thermal energy that can be obtained from the wells which have a surface temperature of 183 °C at 2900 m 2900 m depth. In the next step, the hydrolysis of water with electricity obtained from renewable energy and the hydrogen potential that can be produced were revealed. This hydrogen, which is estimated to be produced, can be fed directly to the natural gas lines or subjected to processes such as storage or industrial usage.