bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymerization Kinetic Analysis of some Glycerol and Glucose Based Polymers
Authors: Rusu Gerlinde , Nitu Sabina , Rusnac Lucian , Bandur Geza 
Published: June 2015

SummaryThe present study is focused on the synthesis of polymers starting from renewable resources. The two monomers were prepared by reaction of the corresponding derivative of glycerol (2,2‐dimethyl‐1,3‐dioxolane‐4‐yl‐methyl acrylate) and glucose (3‐O‐acryloyl‐1,25,6‐di‐O‐isopropylidene‐α‐glucofuranose) with acryloyl chloride, M1 and M2. Different molar ratio were used for the copolymers synthesis (M1:M2=3:1 and 5:1). The homo and co‐polymerization processes were investigated by Differential Scanning Calorimetry (DSC). Based on DSC data the activation energies were estimated by the following methods described by: Kissinger, Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS) The thermal stabilities of the resulting polymers were evaluated from the thermo gravimetrical (TG) analysis.
Enzymatic Modification of Different Lignins Through Oxidative Coupling with Hydrophilic Compounds
Authors: Fiţigău Ionita Firuta , Boeriu Carmen Gabriela , Peter Francisc 
Published: June 2015

SummaryThe enzymatic oxidative coupling of five technical lignins from different sources and with different molecular properties, with glucosamine and the tripeptide glycil‐tyrosyl‐glycine was studied in acetone/water mixture, using laccase as catalyst. The modified lignin was isolated and the product was characterized by means of size exclusion chromatography, FT‐IR and 31P‐NMR, in order to evidence the main lignin modifications after laccase coupling reactions. An important increase of the molecular weight and significant structural modifications were observed for the product obtained after the coupling reactions of Organosolv Hardwood Lignin and Alkali pretreated Wheat straw Lignin with glucosamine and glycil‐tyrosyl‐glycine, demonstrating the achievement of the modification reactions.
Transparent electromagnetic absorber for stable angle of incidence
Authors: Hong Ic‐Pyo 
Published: June 2015

ABSTRACTIn this letter, a transparent electromagnetic absorber that provides stability for an angle of incidence and wide absorption bandwidth is presented using resistive frequency selective surface as circuit analogue structure at X‐band. The transparency of proposed structure is implemented using a transparent resistive film made of an indium‐tin‐oxide (ITO) and soda‐lime glass as dielectric spacer. Reflection loss characteristics for different angles of both TE and TM polarizations are presented through simulations. We then fabricated the proposed structure to verify the simulation results. The comparisons between the simulation and measured results show good agreements. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2023–2025, 2015
Gain enhancement of a wide‐slot antenna using dual‐layer, bandstop frequency selective surface as a substrate
Authors: Chatterjee Ayan , Parui Susanta Kumar 
Published: June 2015

ABSTRACTA technique for enhancing the gain of a conventional wide‐slot antenna over the wide frequency band using a dual‐layer, low‐profile, bandstop frequency selective surface (FSS) is presented in this article. The dual‐layer FSS exhibits transmission below −10 dB and a linear phase variation with frequency in the range of 4–7 GHz. Unit cell dimension on the order of 0.2λ is used for the FSS layers with respect to the center frequency of operation. The FSS is used as a substrate below the antenna that allows in‐phase reflection of radiated waves leading to enhancement in its gain in the broadside direction over entire operating band. An improvement of upto 3‐dBi gain is achieved over 4–6.5 GHz frequency band with a peak gain of 8.4 dBi. Spacing between the antenna and FSS layers is much less than the conventional quarter wavelength value. Simulation and measurement results are presented in each case. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2016–2020, 2015
Wideband high‐gain low‐profile dual‐polarized stacked patch antenna array with parasitic elements
Authors: Yang Tian Yang , Hong Wei , Zhang Yan 
Published: June 2015

ABSTRACTTo realize wideband high‐gain dual‐polarized radiation, the proposed antenna array consists of two microstrip feeding networks and two groups, altogether 13 metal radiation patches. One group, namely four of the patches, are two‐layer stacked octagonal patches excited by feeding networks directly, and the other group of nine patches, are parasitic rectangular patches for improving both impedance bandwidth and gain level. The height of the antenna array is 7 mm (∼0.083λ0@3.55 GHz). The measured impedance bandwidths for VSWR < 1.5 at both ports are 12.6% (3.35–3.8 GHz). The isolation between the two ports is greater than 20 dB over the whole operating band. The measured gain is 16.2 dBi and the cross‐polarization level is less than −15 dB. The proposed structure possesses the features of low cost, low profile, high gain, wide band, and so forth. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2012–2016, 2015
Design of triband bandpass filter using novel hexa‐mode stub‐loaded ring resonator
Authors: Lin Lei , Wu Bian , Su Tao , Liang Chang‐hong 
Published: June 2015

ABSTRACTA novel hexa‐mode stub‐loaded ring resonator is proposed. Due to its symmetry, even‐odd‐mode method is applied to analyze the resonance characteristics. All the six modes equivalent circuits are quarter‐wavelength uniform impedance resonators (UIRs). Stub–stub coupling is introduced to split two identical modes and produce two transmission zeros (TZs). Then a triband bandpass filter operating at 1.5, 2.4, and 3.5 GHz is designed using the proposed resonator. The center frequency and bandwidth of each passband can be independently controlled. Two extra TZs were generated by the hook‐shape feedlines and a relatively wide stopband was achieved. Finally, the designed filter was fabricated and measured, and the measured results have good agreement with the simulated ones. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2005–2008, 2015
An averaged estimation of field strength into an enclosed large cavity with PCB board
Authors: Jeong In Hwan , Lee Jae W. , Cho Choon S. , Lee Young S. , Kwon Jong‐Hwa 
Published: June 2015

ABSTRACTIn this article, two analysis methods, which are called as one is the combination of coplanar strip line analysis and Baum–Liu–Tesche (BLT) equation and the other combination of PoWer Balance (PWB) method and BLT equation, are used to predict the field strength level from the plane wave outside into an large enclosure with aperture and PCB boards inside. In realistic situations, an electrically large enclosure with an aperture has a drawback in calculating the field distribution inside the cavity precisely because of multiple reflections and resonance phenomena. Commercially available software based on the previously well‐established algorithms such as finite difference time domain (FDTD), finite element method (FEM), method of moment (MOM), and so on require much time consumption to carry out the field analysis within a limitation of accuracy, especially in the regime of high frequency. However, to overcome these resource and time‐consumption problem, PWB method based on statistical theory and BLT equation applying topological method are introduced and combined to give a reasonably good field estimation result. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2029–2031, 2015
An on‐wafer embedded passive device using chip‐in‐substrate packaging technology
Authors: Liang Junge G. , Kim Eun Seong , Wang Cong , Youn Je‐Hyun , Park Min Chul , Kim Nam Young 
Published: June 2015

ABSTRACTIn this article, a new packaging technology called chip‐in‐substrate packaging (CiSP) technology, which embeds passive components such as inductors and capacitors on silicon substrates, is arranged for a three‐dimensional structure. As the parasitic capacitance of the inductors and capacitors are increased by CiSP, a lower self‐resonance frequency compared with bare chips can be avoided using a printed circuit board with low thickness and low permittivity. To verify CiSP on the circuit level, a diplexer circuit is simulated from measured components and is composed of two series LC resonators to apply a GSM band (880–960 MHz) and a DCS band (1.71–1.88 GHz). An insertion loss of 0.76 dB at 0.96 GHz for GSM and 0.772 dB at 1.71 GHz for DCS are realized by CiSP technology. Moreover, the minimum rejections of 19.1 dB at 1.71 GHz for GSM and 20.8 dB at 0.96 GHz for DCS are realized with the maximum rejections for the DCS and GSM bands of 37.6 and 33.7 dB, respectively. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2060–2067, 2015
The characteristics of a wideband ESPAR antenna using Koch fractal shaped elements
Authors: Kim Kyu‐Bo , Lee Seung‐Hwan , Choi Hak‐Keun 
Published: June 2015

ABSTRACTThis article suggests a new 5‐element electrically steerable passive array radiators (ESPAR) antenna using a Koch fractal structure for the purpose of adding wideband characteristics to the conventional ESPAR antenna, and its characteristics were confirmed through design and fabrication. The Koch fractal ESPAR antenna with a monopole structure where two crossed boards stand vertically on a circular ground has four parasitic elements arranged around a single active element with a fixed radius and reactance is loaded on each parasitic element. It satisfied the return loss less than −15 dB from 1.7 to 2.4 GHz on the 700 MHz band and showed directivity and gain that have similar radiation patterns according to frequency. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2108–2112, 2015
Microwave backscattering of a spherical conductor coated by lossless metamaterials with an intervening air gap
Authors: Jamil Adnan G. , Rao Tenneti C. K. 
Published: June 2015

ABSTRACTA theoretical study of the electromagnetic backscattering from a lossless metamaterial (MTM) coated conducting sphere with an intervening air gap is presented in this article. The boundary‐value technique is used to obtain the normalized backscattering cross section. A comparison of backscattering characteristics is provided using different kinds of MTMs for the coating. The MTM coating combined with the added feature of an air gap (practically realized by replacing air with styrofoam) indicate that it is possible to achieve low EM backscattering over a broad range of frequencies for certain cases. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2099–2104, 2015
A bidirectional WDM‐PON‐ROF communication network architecture based on optical sextuple frequency
Authors: Li Guang , Zhang Xiao Min , Chen Yin , Huang Xu Guang 
Published: June 2015

ABSTRACTA unusual bidirectional low cost WDM‐PON‐ROF communication network architecture using optical sextuple frequency which is based on photoelectron coherent modulation through a Double‐Arm‐Mach‐Zehnder‐Modulator with a number of different wavelength characteristics is provided and analyzed theoretically. After transmitting more than 25 km in a standard single mode fiber, the clear eye‐diagram and good bit error rate are obtained for wireless signal, wired signal and upstream signal communication. In this communication network architecture, because of no laser source, the base‐station (BS) is not complicated, and because of the optical sextuple frequency signal, the ultra high frequency of the local oscillator is greatly reduced. Compared with recent schemes, the outlays of switching center and BS are greatly decreased. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2079–2083, 2015
Hybrid liquid crystal–photonic crystal fiber tunable interferometer
Authors: Poudereux David , Quintana Xabier , Corredera Pedro , Geday Morten A. , Otón José M. 
Published: June 2015

ABSTRACTTwo tunable interferometers based on photonic crystal fibers (PCF) and liquid crystals (LC) were designed and fabricated. In the first interferometer, the LC peripherally surrounds the PCF, while in the second, much more sensitive to external fields, the LC partially fills the fiber cladding holes. The devices may be applied to optical communications and sensing. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2075–2079, 2015
Comprehensive study of ultra broadband GCPW‐MS transition on thin films
Authors: El‐Gibari Mohammed , Averty Dominique , Halbwax Mathieu , Vilcot Jean‐Pierre , Li Hongwu 
Published: June 2015

AbstractBack‐to‐back GCPW‐MS‐GCPW (Grounded Coplanar Waveguide‐Microstrip lines) transitions realized on benzocyclobutene polymer thin films (20 μm) and using copper metallization are presented in this article. The achieved experimental bandwidth is 82 GHz with a remarkably lower cutoff frequency of only 1.5 GHz and insertion loss of 0.5 dB. This performance is obtained without neither making via holes in the substrate nor patterning the bottom ground plane. These transitions make easier and faster manufacturing and characterization, by means of coplanar probes, of microwave devices realized from materials in thin film and whose driving electrode is a MS line. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2041–2045, 2015
Compact MIMO antenna for LTE 2500 and UWB applications
Authors: Wu Yanjie , Long Yunliang 
Published: June 2015

ABSTRACTThis letter presents a compact multiple‐input multiple‐output (MIMO) ultrawideband (UWB) antenna, and this MIMO antenna consists of two coplanar waveguide ‐fed monopole antenna elements and an improved ground‐plane. These two antenna elements are symmetrically arranged on a FR4 substrate with dimensions 33.8 × 29 × 0.8 mm3. The improved ground‐plane has several ground stubs and windows, and they are applied as decoupling structure to improve the isolation as well as impedance matching. Simulation and measurement are used to study the antenna performance, results show that the antenna has a wide impedance bandwidth of 2.2–10.6 GHz with |S11| ≤ −9 dB, low mutual coupling of less than −12 dB and −17 dB over the range of 2.5–4.2 GHz and 5.6–10 GHz, respectively, and LTE 2500 and UWB operation bands can be covered successfully. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2046–2049, 2015
A compact spiral‐coupled directional coupler for a mobile RFID reader via integrated passive technology
Authors: Wang Cong , Jeon Hamhee , Kim Nam‐Young 
Published: June 2015

ABSTRACTThis article presents the design and implementation of a high‐performance, compact spiral‐coupled directional coupler using an advanced integrated passive device (IPD) fabrication process on a GaAs substrate for use in mobile radio frequency identification (RFID) reader applications. The IPD fabrication step is introduced specifically to enable the directional coupler, which is constructed by the transformation of the intertwined mutual inductors and air‐bridges, to have a compact size and high Q‐factor. The fabricated coupler achieves only 0.43 dB of insertion loss S21 and it exhibits the coupling S31 of 15.7 dB and the isolation S41 of 27.2 dB. This presented coupler has an extra small size of only 0.72 × 0.82 mm2 and an operational frequency of 910 MHz, which is appropriate for use in an RFID reader system. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2142–2146, 2015
Effects of Bragg reflector annealing on performance factors of FBAR‐based ultramass‐sensitive sensors
Authors: Yim Munhyuk , Lee Eunju , Kim Yeongseon , Yoon Giwan 
Published: June 2015

ABSTRACTWe present the film bulk acoustic wave resonator‐based ultramass‐sensitive (FBAR‐UMS) sensors in which their resonance characteristic improvements, mainly due to Bragg reflector (BR) annealing, favorably influence their performance factors. We fabricated two kinds of FBAR‐UMS sensors, respectively, with nonannealed and annealed BRs (namely, nonannealed and annealed sensors) and investigated the effects of BR annealing on their performance factors by comparing their resonance frequency shift (−Δfr), measured before and after each mass loading (Δm). As a result, the annealed sensors showed much larger mass‐loading effect and detectable mass range than the nonannealed ones. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2134–2137, 2015
Simple dual band‐notched UWB antenna loaded with single U‐shaped resonator
Authors: Li Hui , Kang Le , Mi Da‐Wei , Yin Ying‐Zeng 
Published: June 2015

ABSTRACTA simple dual band‐notched antenna is proposed for ultra‐wideband (UWB) applications. The basic UWB antenna, which consists of a half ring‐shaped patch and a trapezoidal ground, occupies a compact area of 25 × 25 mm2. By introducing a single U‐shaped resonator on the patch, dual band‐notched function is realized without increasing the antenna size. An additional resonance near 3 GHz can be excited by the U‐shaped resonator combined with the half ring‐shaped radiator. And the antenna impedance at 3.5 GHz is also affected which leads to a notched band. Besides, reverse currents can be produced along the resonator to produce the other notched band at 5.5 GHz. Experimental results show that the designed antenna has a wide impedance bandwidth (return loss ≤10 dB) ranging from 2.97 to 12 GHz with two rejection bands operating at 3.5 and 5.5 GHz. Meanwhile, the antenna also exhibits moderate gains and omnidirectional radiation patterns over the operating bands except at the undesired frequencies, which make it a suitable candidate for UWB applications. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2129–2134, 2015
A wideband horizontally polarized omnidirectional antenna for LTE indoor base stations
Authors: Zhu Quanjiang , Yang Shiwen , Chen Zong 
Published: June 2015

ABSTRACTA wideband horizontally polarized omnidirectional antenna is proposed for 4G LET indoor base stations. Within the band from 1.71 GHz to 2.69 GHz, the antenna achieves a return loss of greater than 14 dB. The antenna consists of four arc printed dipoles which are arranged on a circumference and fed in phase. By attaching a pair of parasitic elements around each dipole, the bandwidth of the antenna is improved significantly. Moreover, by introducing four pairs of directors, the antenna gain variation in the azimuth plane is reduced to 1 dB in the operating band, and omnidirectional radiation patterns are achieved. The measured results are in good agreement with the simulated results. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2112–2116, 2015
Wideband, hybrid rectangular water antenna for DVB‐H applications
Authors: Xing Lei , Huang Yi , Xu Qian , AlJa'afreh Saqer 
Published: June 2015

ABSTRACTIn this article, a wideband, hybrid rectangular water antenna is proposed to cover the digital video broadcasting‐handheld (DVB‐H) band. The hybrid structure combines a dielectric resonator antenna (DRA) and a monopole antenna to effectively double the available bandwidth without compromising other characteristics. With a proper design, the resonance of the DRA and the resonance from the feeding probe are combined to produce a wideband response. The proposed antenna has an extremely wide bandwidth from 464 to 1017 MHz (for S11 < −6 dB), or a fractional bandwidth of 74.6%. Both the computer simulations and measurements are conducted to validate the antenna performance. It is demonstrated that this new antenna is an promising candidate for DVB‐H applications. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2160–2164, 2015
A broadband 180° hybrid ring coupler using a microstrip‐to‐slotline inverter
Authors: Riaan Ferreira , Johan Joubert 
Published: June 2015

ABSTRACTA broadband 180° 3‐dB hybrid coupler with over 118% bandwidth. Excellent agreement between simulated and experimental results was achieved. The coupler requires simple manufacturing techniques and a single layer substrate. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2164–2168, 2015
Wideband vertical microstrip‐to‐microstrip transition with three‐pole filtering response
Authors: Yang Li , Zhu Lei , Choi Wai‐Wa , Tam Kam‐Weng 
Published: June 2015

ABSTRACTA wideband vertical microstrip‐to‐micrstrip transition is presented by utilizing the composite microstrip/slotline resonators. With the coupling between two 50‐Ω microstrip lines on top and bottom layers, respectively, and a uniform slotline resonator on the common ground plane, a proposed three‐pole wideband filtering performance for the signal transmission through different layers can be achieved. To verify the expected results, a vertical transition prototype is simulated, fabricated and measured. Good agreement between the simulation and measurement results is gained. An operating band from 3.51 to 8.25 GHz with maximum insertion loss of 1.5 dB and group delay < 0.4 ns is achieved in measurement. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2213–2216, 2015
High‐selectivity triband bandpass filter based on dual‐plane microstrip/slotline structure
Authors: Shi Li‐Yun , Wang Ning , Wu Lin‐Sheng 
Published: June 2015

ABSTRACTA compact and high‐selectivity triband bandpass filter (BPF) is proposed. The filter has a dual‐plane structure, consisting of a pair of dual‐mode open‐loop microstrip resonators and a dual‐mode slotline resonator. Using this structure, three passbands as well as five transmission zeros near the passband edges can be generated simultaneously. The triband BPF operating at 1.2 GHz (GPS application), 1.8 GHz (DCS application), and 2.4 GHz (WLAN application) is designed and fabricated. Measurement results agree well with the simulated results. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2225–2228, 2015
Limitations of suction‐controlled triaxial tests in the characterization of unsaturated soils
Authors: Zhang X. 
Published: June 2015

SummaryBehavior of unsaturated soils is influenced by many factors, and the influences of these factors are usually coupled together. Suction‐controlled triaxial (SCTX) tests are considered to allow researchers to investigate influences of individual variables on unsaturated soils under specified stress path with controls of stresses, pore water, and air pressures. In the past 50 years, SCTX testing method has been established as a standard approach to characterize constitutive behavior of unsaturated soils. Most important concepts for modern unsaturated soil mechanics were developed upon results from the SCTX tests. Among these, one of the most important contributions in the constitutive modeling of elasto‐plastic behavior for unsaturated soils is the Barcelona basic model (BBM) proposed by Alonso et al. in 1990. The BBM successfully explained many features of unsaturated soils and received extensive acceptance.However, the SCTX tests are designed based upon the divide‐and‐conquer approach in which an implicit assumption is used: soil behavior is stress‐path independent. However, it is well‐established that unsaturated soil behavior is elasto‐plastic and stress‐path dependent. It is found that the SCTX tests in fact cannot control the stress path of an unsaturated soil during loading. This incapability, in combination with complicated loading/collapse behavior of unsaturated soils, makes the SCTX tests for characterizing unsaturated soil questionable. This paper discusses the limitations of the SCTX tests in the characterization of unsaturated soils. A possible solution to the problem was proposed based on a newly developed modified state surface approach. The discussions are limited for isotropic conditions. Copyright © 2015 John Wiley & Sons, Ltd.