A new circuit topology for continuous group delay synthesis

A new circuit topology is realized in order to synthesize group delay continuously. The circuit is based upon a new variable coupling coefficient coupled line section and a microstrip feedback loop. The new variable coupler is designed by periodically loading an edge coupled microstrip coupler. With this new design, coupling variation of more than 10 dB may be achieved. To the best of the authors knowledge, this is the first report of this type of microstrip coupler. The complete circuit consumes no do power and exhibits more than 500 ps of continuous variable true time delay. Insertion loss is better than 3 dB and return loss is better than 15 dB     

POTSOL: Model to predict extraterrestrial and clear sky solar radiation

A model was developed to predict potential and clear sky solar radiation for any latitude. The model (POTSOL) uses the fundamental geometric relationships between the earth and sun to predict the theoretical solar radiation outside the earth's atmosphere, clear sky solar radiation received at the earth's surface after accounting for atmospheric interference, and clear sky solar radiation on a panel with any tilt angle between 0° and 90° from the horizontal. The only model input parameters are latitude (PHI), clearness number (CN), and panel tilt angle (PT). The model was verified using weather data obtained from the National Climatic Center, Asheville, North Carolina for Ely, Nevada.     

HGB/TPU复合泡沫材料的制备及泡孔结构研究

采用空心玻璃微珠（HGB）填充热塑性聚氨酯（TPU）,制备了HGB/TPU复合泡沫材料。研究了硅烷偶联剂KH550对HGB的表面处理,并借助SEM探讨了不同发泡方式、发泡剂含量、HGB含量对复合泡沫材料微观形态结构的影响。结果表明：经KH550处理的HGB与TPU基体界面结合良好;通过注塑发泡得到的泡沫材料发泡效果较好;当发泡剂含量为1%、HGB含量为2%时复合泡沫材料的泡孔分布均匀,尺寸较为均一。     

Preparation,analysis, and isothermal crystallization behavior of poly[1,3‐bis(aminomethyl)cyclohexamethylene oxamide]

Poly[1,3‐bis(aminomethyl)cyclohexaneoxamide] (PBAC2) was synthesized using 1,3‐bis(aminomethyl)cyclohexane (BAC) and dibutyl oxalate (DO) via spray/solid‐state polycondensation (SSP). The structure of the synthesized polyoxamide was confirmed by ¹H‐nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy. The weight average molecular weight (M_w) of the polyoxamides prepared was 1.35 × 10⁵. The polyoxamides showed excellent thermal properties with glass transition temperature (T_g) of 150 °C, melting temperature (T_m) of 318 °C, crystallization temperature(T_c) of 253 °C, and initial degradation temperature (T_d) of 417 °C suggesting higher thermal stability than commercial polyamide 6 (T_d = 378 °C). Kinetic studies of PBAC2 predicted a two‐dimensional crystal growth. X‐ray diffraction powder diffraction suggested that the polymer has high crystallinity. A saturated water absorption of 2.8 wt % was recorded for the new polyoxamide, giving it a competitive edge for applications in civil aviation, reinforced plastics, and electronics industry where precise dimensional stability and high thermal resistance properties are a priority. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46345.     

Kinetics and Morphological Analysis of Silver Platinum Bimetallic Nanoparticles

Kinetics of a one-pot core–shell synthesis of bimetallic(BM) silver–platinum(Ag–Pt) nanoparticles(NPs) by simultaneous reduction of 1:1 mol fraction of precursors H2 Pt Cl6á6H2O and Ag NO3 in aqueous solution is reported.Kinetics analysis was done by plotting UV–visible absorptions versus reaction time with a first-order fitting. Recorded constants of Ag NPs(0.079 s~(-1)), Ag–Pt NPs 1:1(0.082 s~(-1)), and Pt NPs(0.006 s~(-1)) were obtained. The NPs suspension solutions were clear, free from Ag Cl precipitate, and had characteristic optical properties of 450 nm(Ag NPs), while there were no observable bands for Pt and BM NPs. Morphological analysis using transmission electron microscopy, energydispersive X-ray spectroscopy(EDX), and selected area electron diffraction(SAED) depicted spherical aggregates of Ag NPs, Pt NPs and core shell Pt–Ag NPs 1:1 of average size of 60, 2.5, and 20 mm, respectively. Presence of the Ag and Pt elemental composition in the nanoparticle suspensions was confirmed by EDX. SAED ring patterns revealed a single facecentered cubic crystalline nature of Ag NPs and showed typical Pt-based BMs randomly overlapped ring pattern with sharp diffraction spots.     

Effect of Bimodal Grain Size Distribution on the Strain Hardening Behavior of a Medium-Entropy Alloy

The evolution of strain hardening behavior of the Fe_(50)(CoCrMnNi)_(50) medium-entropy alloy as a function of the fraction of recrystallized microstructure and the grain size was studied using the Hollomon and Ludwigson equations.The specimens under study were partially recrystallized,fully recrystallized with ultrafine-grained microstructure,and fully recrystallized with coarse grains.The yield strength decreases steadily as the fraction of recry stallized micro structure and grain size increases due to the recovery process and the Hall-Petch effect.Interestingly,the bimodal grain distribution was found to have a significant impact on strain hardening during plastic deformation.For instance,the highest ultimate tensile strength was exhibited by a 0.97 μm specimen,which was observed to contain a bimodal grain distribution.Furthermore,using the Ludwigson equation,the effect of the bimodal grain distribution was established from the behavior of K_2 and n1 curves.These curves tend to show very high values in the specimens with a bimodal grain distribution compared to those that show a homogenous grain distribution.Additionally,the bimodal grain distribution contributes to the extensive L(u|")ders strain observed in the 0.97 μm specimen,which induces a significant deviation of the Hollomon equation at lower strains.     

Bioavailability of particle‐associated nutrients as affected by internal regeneration processes in the Nyanza Gulf region of Lake Victoria

Land‐use changes have been implicated a lot in the eutrophication of many lakes while forgetting the role of internal loading as influenced by the hydrological regimes of a given lake. The phosphorus loading of Nyanza Gulf is influenced both by internal and external loading with the internal loading playing a greater role in its eutrophication. The shear on the Apatite Phosphorus (AP) rich residual rock in the western end of the gulf through strong currents across the Rusinga Channel erodes the rock into non‐apatite inorganic phosphorus (NAIP) which is readily available for primary productivity. The current suspends the phosphorus rich apatite sediment together with the reserved phosphorus within sediments to the water column. The NAIP concentration on the western end of the gulf is exceptionally high, >1500 mg kg^?1, and together with the hydrological forcing; is believed to be the driving force of Nyanza Gulf eutrophication. External loading through rivers and municipal discharges exacerbates the problem. The external loading mainly influences the inner gulf on the eastern shore while the internal loading affects mainly the western end of the gulf. Nyanza Gulf eutrophication can be managed by adopting the following measures: (i) the Mbita Causeway needs to be opened and a bridge erected in its place in order to reduce the strong current through the Rusinga Channel and the residence time within the gulf, by increasing the flushing rates; (ii) the farming communities within the basin need to be sensitized on the controlled use of fertilizers; (iii) the municipal wastes should be treated to tertiary level before discharge into the lake; and (iv) reduce erosion within the basin through re/afforestation.     

DoS detections based on association rules and frequent itemsets

To detect the DoS in networks by applying association rules mining techniques, we propose that association rules and frequent itemsets can be employed to find DoS pattern in packet streams which describe traffic and user behaviors. The method extracts information from the log analysis of submitted packets using the algo- rithm which depends on the definition of the intrusion. Large itemsets were extracted to represent the super facts to build the association analysis for the intrusion. Network data files were analysed for experiments. The analysis and experimental results are encouraging with better performance as packet frequency number increases.     

Monitoring Biosensor Activity in Living Cells with Fluorescence Lifetime Imaging Microscopy

Live-cell microscopy is now routinely used to monitor the activities of the genetically encoded biosensor proteins that are designed to directly measure specific cell signaling events inside cells, tissues, or organisms. Most fluorescent biosensor proteins rely on Förster resonance energy transfer (FRET) to report conformational changes in the protein that occur in response to signaling events, and this is commonly measured with intensity-based ratiometric imaging methods. An alternative method for monitoring the activities of the FRET-based biosensor proteins is fluorescence lifetime imaging microscopy (FLIM). FLIM measurements are made in the time domain, and are not affected by factors that commonly limit intensity measurements. In this review, we describe the use of the digital frequency domain (FD) FLIM method for the analysis of FRET signals. We illustrate the methods necessary for the calibration of the FD FLIM system, and demonstrate the analysis of data obtained from cells expressing “FRET standard” fusion proteins. We then use the FLIM-FRET approach to monitor the changes in activities of two different biosensor proteins in specific regions of single living cells. Importantly, the factors required for the accurate determination and reproducibility of lifetime measurements are described in detail.