2019 Vol. 17, No. 2

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2019, 17(2): 1-1.
Characterization of Cd1-xZnxTe (0≤x≤1) Nanolayers Grown by Atomic Layer Deposition on GaSb and GaAs (001) Oriented Substrates
Joel Díaz-Reyes, Roberto Saúl Castillo-Ojeda, José Eladio Flores-Mena
2019, 17(2): 97-108. doi: 10.11989/JEST.1674-862X.70929112
ZnTe, CdTe, and the ternary alloy CdZnTe are important semiconductor materials used widely for the detection of an important range of electromagnetic radiation as gamma ray and X-ray. Although, recently these materials have acquired renewed importance due to the new explored nanolayer properties of modern devices. In addition, as shown in this work they can be grown using uncomplicated synthesis techniques based on the deposition in vapour phase of the elemental precursors. This work presents the results obtained from the deposition of nanolayers of these materials using the precursor vapour on GaAs and GaSb (001) substrates. This growth technique, extensively known as atomic layer deposition (ALD), allows the layers growth with nanometric dimension. The main results presented in this work are the used growth parameters and the results of the structural characterization of the layers by the means of Raman spectroscopy measurements. Raman scattering shows the peak corresponding to longitudinal optical (LO)-ZnTe, which is weak and slightly redshift in comparison with that reported for the ZnTe bulk at 210 cm–1. For the case of the CdTe nanolayer, Raman spectra presented the LO-CdTe peak, which is indicative of the successful growth of the layer. Its weak and slightly redshift in comparison with that reported for the CdTe bulk can be related with the nanometric characteristic of this layer. The performed high-resolution X-ray diffraction (HR-XRD) measurement allows to study some important characteristics such as the crystallinity of the grown layer. In addition, the HR-XRD measurement suggests that the crystalline quality has dependence on the growth temperature.
Fabrication of Co2Fe(Al,Si) and Co2Fe(Al,Si)/MgO on Ge(111) Substrate and Its Magnetic Properties
Kohei Kataoka, Nobuki Tezuka, Masashi Matsuura, Satoshi Sugimoto
2019, 17(2): 109-115. doi: 10.11989/JEST.1674-862X.71128011
We investigated the interfacial effects on magnetic properties in Co2Fe(Al,Si)/Ge (CFAS/Ge) and CFAS/MgO/Ge systems to demonstrate the effects of the interface structure on magnetic properties. CFAS and CFAS/MgO were deposited on the i-Ge(111) substrate. In-situ reflection high energy electron diffraction (RHEED) patterns showed epitaxially grown CFAS and MgO on Ge(111). According to the X-ray diffraction (XRD) ϕ-scan of CFAS(220), we determined that the crystallographic orientation relationships were CFAS(111)<–110>//Ge(111)<–110> and CFAS(111)<–110>//MgO(111)<–110>Ge(111)<–110>. The magnetic properties were measured by the vibrating sample magnetometer (VSM) and the saturation magnetization Ms value of CFAS with 2-nm thick MgO reached the value of L21 ordered one. A uniaxial magnetic anisotropy behavior was observed both in CFAS/Ge and CFAS/MgO/Ge structures after annealing. We confirmed the behavior did not only originate from the CFAS/Ge interface but also CFAS/MgO and the ordering structure.
Energy Harvesting—Technical Analysis of Evolution, Control Strategies, and Future Aspects
MD. Shahrukh Adnan Khan, Md. Tanbhir Hoq, A. H. M. Zadidul Karim, Md. Khairul Alam, Masum Howlader, Rajprasad Kumar Rajkumar
2019, 17(2): 116-125. doi: 10.11989/JEST.1674-862X.80314201
This paper provides a technical analysis of energy harvesting (EH) in the field of power and energy sector, including different aspects of harvesting energy, individual case history, control strategies of harvesting in the field of power and energy sector together with the current trend and future aspects of it. EH is comparatively a new concept which is growing very fast since the 20th century and catching new generation research approaches. This paper not only describes the past and current scenarios of harvesting energy with radio frequency (RF) and renewables but also gives author’s own anticipation of the upcoming future trends of it by comparing the case histories.
Energy Harvesting in Cognitive Networks with Cooperative Beamforming: Power Allocation and Stability Analysis
Jin-Xin Niu, Wei Guo
2019, 17(2): 126-134. doi: 10.11989/JEST.1674-862X.6101219
Energy harvesting (EH) is a promising technology to improve both energy efficiency and spectral efficiency in cognitive radio (CR) networks. However, due to the randomness of the harvested energy and the interference constraint at the primary users (PUs), the limited transmission power of secondary users (SUs) may reduce the service rate of SUs. To solve this problem, this paper investigates a cooperative transmission method where a zero-forcing beamforming method is used in the EH based secondary network. Considering the transmission power constraint and energy causality, we derive the closed-form solution of the optimal transmission power for the secondary source and relays, which achieves the maximal stable throughput of the secondary network. Numerical results show the impact of different system parameters to the maximal stable throughput. In addition, compared with the traditional decode-and-forward (DF) scheme, the cooperative beamforming method achieves higher stable throughput under an high quality source-to-relay channel.
Oscillatory-Plus-Transient Signal Decomposition Using TQWT and MCA
G. Ravi Shankar Reddy, Rameshwar Rao
2019, 17(2): 135-151. doi: 10.11989/JEST.1674-862X.6071911
This paper describes a method for decomposing a signal into the sum of an oscillatory component and a transient component. The process uses the tunable Q-factor wavelet transform (TQWT): The oscillatory component is modeled as a signal that can be sparsely denoted by high Q-factor TQWT; similarly, the transient component is modeled as a piecewise smooth signal that can be sparsely denoted using low Q-factor TQWT. Since the low and high Q-factor TQWT has low coherence, the morphological component analysis (MCA) can effectively decompose the signal into oscillatory and transient components. The corresponding optimization problem of MCA is resolved by the split augmented Lagrangian shrinkage algorithm (SALSA). The applications of the proposed method to speech, electroencephalo-graph (EEG), and electrocardiograph (ECG) signals are included.
Convergence of the Interior Penalty Integral Equation Domain Decomposition Method
Bo Mi, Yu Hu, Zhang Liu, Ling Qin
2019, 17(2): 152-160. doi: 10.11989/JEST.1674-862X.80504010
To solve electrically large scattering problems with limited memory, a Gauss-Seidel iteration scheme is applied to solve the interior penalty integral equation domain decomposition method. Since the original stabilization parameter in this method is frequency-dependent, the convergence of stationary iterations shows obvious dependence on frequency and slow convergence can be observed in some frequency bands. To avoid this dependence and obtain fast convergence in a wide frequency band, a frequency-independent stabilization parameter is introduced. This parameter is chosen proportionally to the average mesh length and inversely proportionally to the wavelength. Numerical examples are proposed to verify the effectiveness of the proposed approach.
Infrared Radiance Simulation and Application under Cloudy Sky Conditions Based on HIRTM
Jian-Hua Qu, Jun-Jie Yan, Mao-Nong Ran
2019, 17(2): 161-170. doi: 10.11989/JEST.1674-862X.80730010
An algorithm based on hyperspectral infrared cloudy radiative transfer model (HIRTM) is introduced and a simulation method for infrared image of the generation geostationary meteorological satellite is proposed. Based on the parameters from weather research and forecast (WRF), such as the water content, atmospheric temperature, and humidity profile, the simulation data for the advanced Himawari imager (AHI) infrared radiative (IR) channels of Himawari-8 are obtained. Simulated results based on HIRTM agree well with the observed data. Further, the movement, development, and change of the cloud are well predicated. And the simulation of IR cloud image for the weather forecast has been obtained. This paper provides an improved method for evaluation and improvement of regional numerical model for weather forecast.
No-Reference Image Quality Assessment Method Based on Visual Parameters
Yu-Hong Liu, Kai-Fu Yang, Hong-Mei Yan
2019, 17(2): 171-184. doi: 10.11989/JEST.1674-862X.70927091
Recent studies on no-reference image quality assessment (NR-IQA) methods usually learn to evaluate the image quality by regressing from human subjective scores of the training samples. This study presented an NR-IQA method based on the basic image visual parameters without using human scored image databases in learning. We demonstrated that these features comprised the most basic characteristics for constructing an image and influencing the visual quality of an image. In this paper, the definitions, computational method, and relationships among these visual metrics were described. We subsequently proposed a no-reference assessment function, which was referred to as a visual parameter measurement index (VPMI), based on the integration of these visual metrics to assess image quality. It is established that the maximum of VPMI corresponds to the best quality of the color image. We verified this method using the popular assessment database—image quality assessment database (LIVE), and the results indicated that the proposed method matched better with the subjective assessment of human vision. Compared with other image quality assessment models, it is highly competitive. VPMI has low computational complexity, which makes it promising to implement in real-time image assessment systems.
Design of Computationally Efficient Sharp FIR Filter Utilizing Modified Multistage FRM Technique for Wireless Communications Systems
Tirthadip Sinha, Jaydeb Bhaumik
2019, 17(2): 185-192. doi: 10.11989/JEST.1674-862X.70728080
Modern wireless communications gadgets demand multi-standard communications facilities with least overlap between different input radio channels. A sharp digital filter of extremely narrow transition-width with lower stop band ripples offers alias-free switching among the preferred frequency bands. A computationally competent low pass filter (LPF) structure based on the multistage frequency response masking (FRM) approach is proposed for the design of sharp finite impulse response (FIR) filters which are suitable for wireless communications applications. In comparison of basic FRM with other existing multistage FRM structures, the proposed structure has a narrow transition bandwidth and higher stop band attenuation with significant reduction in terms of the number of computational steps. A design example is incorporated to demonstrate the efficiency of the proposed approach. Simulation results establish the improvement of the proposed scheme over other recently published design strategies.