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BE-SONOS flash memory along with metal gate and high-k dielectrics in tunnel barrier and its impact on charge retention dynamics

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Journal of Semiconductors 2016年第3期37卷 42-47页

作者： Sonal Jain Deepika Gupta Vaibhav Neema Santosh Vishwakarma IET-Devi Ahilya University Indore MP India iit indore MP India

We investigate the effect of a high-k dielectric in the tunnel layer to improve the erase speed-retention trade-off. Here, the proposed stack in the tunnel layer is AlLaO_3/Hf AlO/SiO_2. These proposed materials possess low valence band offset with high permittivity to improve both the erase speed and retention time in barrier engineered silicon-oxide-nitride-oxide-silicon（BE-SONOS）. In the proposed structure Hf Al O and AlLaO_3 replace Si_3N_4 and the top SiO_2 layer in a conventional oxide/nitride/oxide（ONO） tunnel stack. Due to the lower conduction band offset（CBO） and high permittivity of the proposed material in the tunnel layer, it offers better program/erase（P/E） speed and retention time. In this work the gate length is also scaled down from 220 to 55 nm to observe the effect of high-k materials while scaling, for the same equivalent oxide thickness（EOT）. We found that the scaling down of the gate length has a negligible impact on the memory window of the devices. Hence, various investigated tunnel oxide stacks possess a good memory window with a charge retained up to 87.4%（at room temperature） after a period of ten years. We also examine the use of a metal gate instead of a polysilicon gate, which shows improved P/E speed and retention time.

关键词： high-k dielectric materials nonvolatile memory tunnel barrier retention endurance and bandgapengineered

Analysis of frequency shifting in seismic signals using Gabor-Wigner transform

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Earthquake Engineering and Engineering Vibration 2015年第4期14卷 715-724页

作者： Roshan Kumar P.Sumathi Ashok Kumar Deaprtment of Earthquake Engineering IIT Roorkee Deaprtment of Electrical Engineering IIT Roorkee

A hybrid time-frequency method known as Gabor-Wigner transform (GWT) is introduced in this paper for examining the time-frequency patterns of earthquake damaged buildings. GWT is developed by combining the Gabor transform (GT) and Wigner-Ville distribution (WVD). GT and WVD have been used separately on synthetic and recorded earthquake data to identify frequency shifting due to earthquake damages, but GT is prone to windowing effect and WVD involves ambiguity function. Hence to obtain better clarity and to remove the cross terms (frequency interference), GT and WVD are judiciously combined and the resultant GWT used to identify frequency shifting. Synthetic seismic response of an instrumented building and real-time earthquake data recorded on the building were investigated using GWT. It is found that GWT offers good accuracy for even slow variations in frequency, good time-frequency resolution, and localized response. Presented results confirm the efficacy of GWT when compared with GT and WVD used separately. Simulation results were quantified by the Renyi entropy measures and GWT shown to be an adequate technique in identifying localized response for structural damage detection.

关键词： time-frequency distribution seismic signals cross-term interference Gabor transform Wigner- Ville distribution Gabor-Wigner transform

Displacement-based seismic design of flat slab-shear wall buildings

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Earthquake Engineering and Engineering Vibration 2016年第2期15卷 209-221页

作者： Subhajit Sen Yogendra Singh Department of Earthquake Engineering IIT Roorkee

Flat slab system is becoming widely popular for multistory buildings due to its several advantages. However, the performance of flat slab buildings under earthquake loading is unsatisfactory due to their vulnerability to punching shear failure. Several national design codes provide guidelines for designing flat slab system under gravity load only. Nevertheless, flat slab buildings are also being constructed in high seismicity regions. In this paper, performance of flat slab buildings of various heights, designed for gravity load alone according to code, is evaluated under earthquake loading as per ASCE/SEI 41 methodology. Continuity of slab bottom reinforcement through column cage improves the performance of flat slab buildings to some extent, but it is observed that these flat slab systems are not adequate in high seismicity areas and need additional primary lateral load resisting systems such as shear walls. A displacement-based method is proposed to proportion shear walls as primary lateral load resisting elements to ensure satisfactory performance. The methodology is validated using design examples of flat slab buildings with various heights.

关键词： satisfactory continuity vulnerability validated reinforcement gravity walls drift alone details

Behavior of an indigenously fabricated transferred arc plasma furnace for smelting studies

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Plasma Science and Technology 2018年第3期20卷 136-145页

作者： A K MANDAL R K DISHWAR O P SINHA Department of Metallurgical Engineering IIT(BHU)

The utilization of industrial solid waste for metal recovery requires high-temperature tools due to the presence of silica and alumina, which is reducible at high temperature. In a plasma arc furnace, transferred arc plasma furnace（TAP） can meet all requirements, but the disadvantage of this technology is the high cost. For performing experiments in the laboratory, the TAP was fabricated indigenously in a laboratory based on the different inputs provided in the literature for the furnace design and fabrication. The observed parameters such as arc length, energy consumption, graphite electrode consumption, noise level as well as lining erosion were characterized for this fabricated furnace. The nitrogen plasma increased by around 200 K（200 ℃） melt temperature and noise levels decreased by ~10 d B compared to a normal *** plasma offered 100 K（100 ℃） higher melt temperature with ~5 d B higher sound level than nitrogen plasma. Nitrogen plasma arc melting showed lower electrode and energy consumption than normal arc melting, whereas hydrogen plasma showed lower energy consumption and higher electrode consumption in comparison to nitrogen plasma. The higher plasma arc temperature resulted in a shorter meltdown time than normal arc with smoother arcing. Hydrogen plasma permitted more heats, reduced meltdown time, and lower energy consumption, but with increased graphite consumption and crucible wear. The present study showed that the fabricated arc plasma is better than the normal arc furnace with respect to temperature generation, energy consumption, and environmental friendliness. Therefore, it could be used effectively for smelting-reduction studies.

关键词： smelting transferred arc plasma furnace characterization hydrogen and nitrogen plasma hollow electrode graphite and magnesite lining

Influence of laser peening on microstructure and fatigue lives of Ti-6Al-4V

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Transactions of Nonferrous Metals Society of China 2014年第10期24卷 3111-3117页

作者： S.ANAND KUMAR R.SUNDAR S.GANESH SUNDARA RAMAN H.KUMAR R.KAUL K.RANGANATHAN S.M.OAK L.M.KUKREJA K.S.BINDRA Department of Metallurgical and Materials Engineering IIT Madras Chennai-600036 India Solid State Laser Division RRCAT Indore 452013 India Laser Material Processing Division RRCAT Indore 452013 India

The influence of low energy laser peening on fatigue lives of Ti-6Al-4V was investigated. Laser peening was carried out on Ti-6Al-4V samples. Laser peened samples were characterized by residual stress analysis, surface roughness measurements, X-ray diffraction, optical microscopy, nanoindentation hardness tests, scanning and transmission electron microscopy and fatigue testing. Laser peening resulted in the formation of nanocrystallites on the surface and near surface regions with associated increase in hardness and introduction of compressive residual stress. Owing to positive influence of nanostructured surface and compressive residual stress, fatigue lives of the laser peened samples were significantly increased compared to the unpeened samples.

关键词： Ti-6Al-4V laser peening fatigue nanostructured surface

Analyzing hydro abrasive erosion in Kaplan turbine:A case study from India

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Journal of Hydrodynamics 2016年第5期28卷 863-872页

作者： Anant Kr.RAI Arun KUMAR Alternate Hydro Energy Centre IIT Roorkee

Sediment flow through hydro turbine causes erosion of hydraulic components resulting in drop of turbine efficiency, parti- cularly in hydropower plants of the Himalayan region. The measurement of erosion and monitoring of sediment flow in turbine are major concerns in erosion study. Attempts have been made to study erosion mainly in Pelton and Francis turbines. In this study, a simple and effective method has been presented to measure erosion in a Kaplan turbine of a run-of-river scheme Chilla hydropower plant in foothills of Himalaya. Recent techniques were used to measure sediment parameters like concentration, size, shape and mineral content. A standard erosion model is applied to estimate the erosion in Kaplan turbine blade, runner chamber and draft tube cone. A calibration factor has been proposed to apply the erosion model for site specific conditions. It has been found that the outer trailing edges of the turbine blade and upper rtmner chamber are most erosion prone zones. Sediment analysis revealed that effective operation can reduce erosion in turbine components. The estimated erosion values from model are found to be consistent with measu- red values. Finally, suggestions for design improvements and effective operation of erosion affected hydropower plants are given.

关键词： turbine sediment erosion measurement IEC 62364 hydropower

Understanding the Mechanism of Nanoparticle Formation in a Wire Explosion Process by Adopting the Optical Emission Technique

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Plasma Science and Technology 2013年第6期15卷 562-569页

作者： B.DEBALINA M.KAMARAJ S.R.CHAKRAVARTHI N.J.VASA R.SARATHI Dept.of Metallurgical and Materials Engg. IIT MadrasChennai 600036India Dept.of Aerospace Engg. IIT MadrasChennai 600036India Dept.of Engineering Design IIT MadrasChennai 600036India Dept.of Electrical Engg. IIT MadrasChennai 600036India

In the present study nano-tungsten carbide particles were generated in a wire explosion *** plasma generated during the wire explosion process was analyzed using optical emission spectroscopy（OES）.The impact of ambient pressure on the plasma temperature,electron density and plasma lifetime was *** variations of the plasma produced under different experimental conditions were *** produced nanoparticles were characterized through wide angle X-ray diffraction（WAXD） and transmission electron microscopy（TEM） studies. Particles produced with a negative DC charging voltage had a larger mean size when compared to a positive charging *** dependence on the plasma duration was observed where plasma was sustained for a longer duration with a negative DC charging voltage.

关键词： optical emission wire explosion tungsten carbide life time nano particle

Estimating statistics of sky brightness using radio interferometric observations

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Research in Astronomy and Astrophysics 2019年第4期19卷 119-136页

作者： Prasun Dutta Meera Nandakumar Department of Physics IIT (BHU) Varanasi

Radio interferometers are used to construct high resolution images of the sky at radio frequencies and are the key instruments for accessing the statistical properties of the evolution of neutral hydrogen over cosmic time. Here we use simulated observations of the model sky to assess the efficacy of different estimators of the large-scale structure and power spectrum of the sky brightness distribution. We find that while the large-scale distribution can be reasonably estimated using the reconstructed image from interferometric data, estimates of the power spectrum of the intensity fluctuations calculated from the image are generally biased. This bias is found to be more pronounced for diffuse emission. The visibility based power spectrum estimator, however, gives an unbiased estimate of the true power spectrum. This work demonstrates that for an observation with diffuse emission the reconstructed image can be used to estimate the large-scale distribution of the intensity, while to estimate the power spectrum, visibility based methods should be *** the upcoming experiments aimed at measuring the evolution of the power spectrum of the neutral hydrogen distribution, this is a very important result.

关键词： instrumentation:interferometers methods:data analysis techniques:interferometric

Neutral and metallic *** and semiconducting surface layer in acceptor doped CeO_(2)

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International Journal of Minerals,Metallurgy and Materials 2024年第4期31卷 795-802页

作者： Ilan Riess Physics Department Technion IITHaifa 3200003Israel

The monomolecular surface layer of acceptor doped CeO_(2) may become neutral and metallic or charged and *** is revealed in the theoretical analysis of the oxygen pressure dependence of the surface defects concentration in acceptor doped ceria with two different dopant types and operated under different oxygen *** published experimental data for highly reduced Sm0.2Ce0.8O1.9-x(SDC)containing a fixed valence dopant Sm3+are very different from those published for Pr0.1Ce0.9O_(2)-x(PCO) with the variable valence dopant Pr4+/Pr3+being reduced under milder *** theoretical analysis of these experimental results fits very well the experimental results of SDC and *** leads to the following predictions:the highly reduced surface of SDC is metallic and neutral,the metallic surface electron density of state is gs=0.9×10^(38)J-1·m^(-2)(1.4×1015eV^(-1)·cm^(-2)),the electron effective mass is meff,s=3.3me,and the phase diagram of the reduced surface has theα(fcc)structure as in the *** PCO a double layer is predicted to be formed between the surface and the bulk with the surface being negatively charged and *** surface of PCO maintains high Pr^(3+) defect concentration as well as relative high oxygen vacancy concentration at oxygen pressures higher than in the *** reasons for the difference between a metallic and semiconducting surface layer of acceptor doped CeO_(2) are reviewed,as well as the key theoretical considerations applied in coping with this *** that we make use of the experimental data and theoretical analysis available for acceptor doped ceria.

关键词： CeO_(2) surface defects metallic surface oxide reduction Sm doped CeO_(2) Pr doped CeO_(2)