Engineering Commons^™

Lattice Dynamics Of Orthorhombic Ndgao3, Alyssa Mock, Rafal Korlacki, Sean Knight, Megan Stokey, Alex Fritz, Vanya Darakchieva, Mathias Schubert

Department of Electrical and Computer Engineering: Faculty Publications

A complete set of infrared-active and Raman-active lattice modes is obtained from density functional theory calculations for single-crystalline centrosymmetric orthorhombic neodymium gallate. The results for infrared-active modes are compared with an analysis of the anisotropic long-wavelength properties using generalized spectroscopic ellipsometry. The frequency-dependent dielectric function tensor and dielectric loss function tensor of orthorhombic neodymium gallium oxide are reported in the spectral range of 80–1200 cm⁻¹. A combined eigendielectric displacement vector summation and dielectric displacement loss vector summation approach augmented by considerations of lattice anharmonicity is utilized to describe the experimentally determined tensor elements. All infrared-active transverse and longitudinal …

Femtosecond Photon-Mediated Plasma Enhances Photosynthesis Of Plasmonic Nanostructures And Their Sers Applications, Peng Ran, Lan Jiang, Xin Li, Bo Li, Pei Zuo, Yongfeng Lu

Department of Electrical and Computer Engineering: Faculty Publications

Laser ablation in liquid has proven to be a universal and green method to synthesize nanocrystals and fabricate functional nanostructures. This study demonstrates the superiority of femtosecond laser-mediated plasma in enhancing photoredox of metal cations for controllable fabrication of plasmonic nanostructures in liquid. Through employing upstream high energetic plasma during laser-induced microexplosions, single/three-electron photoreduction of metallic cations can readily occur without chemical reductants or capping agents. Experimental evidences demonstrate that this process exhibits higher photon utilization efficiency in yield of colloidal metal nanoparticles than direct irradiation of metallic precursors. Photogenerated hydrated electrons derived from strong ionization of silicon and water …

Manipulation Of Lipss Orientation On Silicon Surfaces Using Orthogonally Polarized Femtosecond Laser Double-Pulse Trains, Wei Liu, Lan Jiang, Weina Han, Jie Hu, Xiaowei Li, Ji Huang, Shenghua Zhan, Yongfeng Lu

Department of Electrical and Computer Engineering: Faculty Publications

Laser-induced periodic surface structures (LIPSS) provide an easy and costeffective means of fabricating gratings and have been widely studied in recent decades. To overcome the challenge of orientation controllability, we developed a feasible and efficient method for manipulating the orientation of LIPSS in real time. Specifically, we used orthogonally polarized and equal-energy femtosecond laser (50 fs, 800 nm) double-pulse trains with time delay about 1ps, total peak laser fluence about 1.0 J/cm², laser repetition frequency at 100 Hz and scanning speed at 150 μm/s to manipulate the LIPSS orientation on silicon surfaces perpendicular to the scanning direction, regardless …

Growth Of Nitride Films, Yongfeng Lu, Hossein Rabiee Golgir, Yunshen Zhou

Department of Electrical and Computer Engineering: Faculty Publications

A gallium nitride thin film can be formed on a substrate at a low temperature (e.g., not higher than 600°C .) by applying a laser to resonantly excite molecules of a first precursor that contains nitrogen, in which the laser has a wavelength that is selected to match a vibration mode and/or a vibrational rotational mode of the molecules of the first precursor. A second precursor is provided in which the excited first precursor and the second precursor react to form a nitride that is deposited on the substrate. For example, the second precursor may include gallium, and the nitride …

Fabrication Of Highly Homogeneous And Controllable Nanogratings On Silicon Via Chemical Etching-Assisted Femtosecond Laser Modification, Ji Huang, Lan Jiang, Xiaowei Li, Andong Wang, Zhi Wang, Qingsong Wang, Jie Hu, Liangti Qu, Tianhong Cui, Yongfeng Lu

Department of Electrical and Computer Engineering: Faculty Publications

Femtosecond laser direct writing is widely exploited in surface periodic structures processing. However, this technique still faces challenges in obtaining high surface homogeneity and flexible morphology controllability. In this study, a flexible and efficient approach has been proposed to fabricate highly homogeneous and controllable nanogratings on silicon via chemical etching-assisted femtosecond laser modification. By precisely manipulating the laser-material interaction process, alternating amorphous-crystalline nanofringes are generated when employing femtosecond laser scanning over a Si sample, with almost no material removal. Following auxiliary chemical etching, highly homogeneous nanograting structures are obtained, and the morphology of the nanogratings can be flexibly managed through …

Overview Of Extreme Manufacturing, Dongming Guo, Yongfeng Lu

Department of Electrical and Computer Engineering: Faculty Publications

Today we live in a new era of economic globalization and rapid technological growth. The advancement of both our society and standard of living require us to delve into this new world and unleash the possibilities our future. We need to broaden the horizons of our universe to discover a new realm where the future of humanity can flourish. We need to be unafraid to unveil the mysteries hidden within the depths of our oceans to unearth treasures that will benefit not only us, but the generations to come.

Effect Of Titanium And Zirconium Carbide Interphases On The Thermal Conductivity And Interfacial Heat Transfers In Copper/ Diamond Composite Materials, Clio Azina, Inaki Cornu, Jean-Francois Silvain, Yongfeng Lu, Jean-Luc Battaglia

Department of Electrical and Computer Engineering: Faculty Publications

Thermal properties of metal matrix composite materials are becoming ever more relevant with the increasing demand for thermally efficient materials. In this work, the thermal conductivity and heat transfers at the interfaces of copper matrix composite materials reinforced with diamond particles (Cu/D) are discussed. The composite materials contain either ZrC or TiC interphases and exhibit, respectively, higher and lower thermal conductivities with respect to their pure Cu/D counterparts. These thermal conductivities are accounted to the presence of strong covalent bonds and increased relative densities. The role of these interphases is also discussed regarding the phonon transmission at the interfaces.

A Novel Method Of Near-Miss Event Detection With Software Defined Radar In Improving Railyard Safety, Subharthi Banerjee, Jose Santos, Michael Hempel, Pejman Ghasemzadeh, Hamid Sharif

Department of Electrical and Computer Engineering: Faculty Publications

Railyards are one of the most challenging and complex workplace environments in any industry. Railyard workers are constantly surrounded by dangerous moving objects, in a noisy environment where distractions can easily result in accidents or casualties. Throughout the years, yards have been contributing 20–30% of the total accidents that happen in railroads. Monitoring the railyard workspace to keep personnel safe from falls, slips, being struck by large object, etc. and preventing fatal accidents can be particularly challenging due to the sheer number of factors involved, such as the need to protect a large geographical space, the inherent dynamicity of the …

Self-Organized Twist-Heterostructures Via Aligned Van Der Waals Epitaxy And Solid-State Transformations, Peter Sutter, Rina Ibragimova, Hannu-Pekka Kosma, Bruce A. Parkinson, Eli A. Sutter

Department of Electrical and Computer Engineering: Faculty Publications

Vertical van der Waals (vdW) heterostructures of 2D crystals with defined interlayer twist are of interest for band-structure engineering via twist moiré superlattice potentials. To date, twist-heterostructures have been realized by micromechanical stacking. Direct synthesis is hindered by the tendency toward equilibrium stacking without interlayer twist. Here, we demonstrate that growing a 2D crystal with fixed azimuthal alignment to the substrate followed by transformation of this intermediate enables a potentially scalable synthesis of twisted heterostructures. Microscopy during growth of ultrathin orthorhombic SnS on trigonal SnS2 shows that vdW epitaxy yields azimuthal order even for non-isotypic 2D crystals. Excess sulfur drives …

(Invited) Emerging Role Of Silicon Carbide And Gallium Nitride Based Power Electronics In Power And Transportation Sectors, Prahaladh Paniyil, Rajendra Singh

Publications

Free fuel-based energy sources (solar and wind) are pointing towards a future in which sustainable energy is affordable, abundant and deployed with high energy efficiency. Driven by advancements in the technology of lithium batteries and the availability of low-cost sustainable clean electric power, the electrification of transportation is going through fundamental disruptive transformation. Without any doubt, both power and transportation sectors will provide phenomenal growth of power electronics in the 21st century. Recently, both SiC and GaN are drawing the attention as potential replacement of Si-based power electronics. These may open some new markets where Si based power electronics cannot …

New Correlation For Calculating Acentric Factor Of Petroleum 2 Fractions, Samir Khaled

Petroleum Engineering and Gas

A proper description of the physical properties of the petroleum fractions in hydrocarbon mixtures is 12 essential in performing reliable phase behavior calculations and compositional modeling studies. This 13 paper presents a comparison study among five different correlations used to calculate the acentric 14 factor of undefined petroleum fractions. A new correlation was developed for calculating the acentric 15 factor of undefined petroleum fractions, a function of no carbon atoms with an average error of 0.099 16 and a correlation coefficient of 0.998.

Nebraska Water Center Annual Report 2017-2018, The Nebraska Water Center

Nebraska Water Center: Administrative Materials

Contents

Introduction: Foreword • Director’s Letter by Chittaranjan Ray • Nebraska Water Center Overview and Timeline • Nebraska’s Top 10 Water Challenges

Research: Water Sciences Laboratory Overview • Nebraska Vadose Zone Program • Novel Nitrate Leaching Reduction • Ogallala Water Coordinated Agriculture Project (OWCAP) • Nebraska Water Productivity Report • USDA-NIFA Water End-User Grant • U.S. Geological Survey 104b Projects

Extension & Outreach: Bazile Groundwater Management Area • Platte River Basin Ecosystem Symposium • Testing Ag Performance Solutions (TAPS) • 2018 National Institutes for Water Resources Regional Symposium • Water Quality + Citizen Science • Nebraska Water and Natural Resources …

Impact Of Potential Engine Malfunctions On Fuel Consumption And Gaseous Emissions Of A Euro Vi Diesel Truck., Yuhan Huang, Elvin C.Y. Ng, Yat-Shing Yam, Casey K.C. Lee, Surawski C. Nic, Wai-Chuen Mok, Organ Bruce, John L. Zhou, Edward F.C. Chan

Faculty of Science & Technology (THEi)

Although new vehicles are designed to comply with specific emission regulations, their in-service performance would not necessarily achieve them due to wear-and-tear and improper maintenance, as well as tampering or failure of engine control and exhaust after-treatment systems. In addition, there is a lack of knowledge on how significantly these potential malfunctions affect vehicle performance. This study was therefore conducted to simulate the effect of various engine malfunctions on the fuel consumption and gaseous emissions of a 16-tonne Euro VI diesel truck using transient chassis dynamometer testing. The simulated malfunctions included those that would commonly occur in the intake, fuel …

Study Of Behavior Of Plastic Modified Bitumen By Incorporating Carbon Black, Ho-Fai Wong, Hao-Jue Hong, Lai-Ming Leung, Tsz-Chun Fong, Yi-Fei Shen, Tsz-Hin Lo

Faculty of Science & Technology (THEi)

In recent years, the performance of polymer modified bitumen has been widely studied. This study reports a research carried out to investigate the properties of polymer modified bitumen (PMB) by using polypropylene as modifier, carbon black as additives, to examine the optimum ratio of polypropylene to carbon black. With this objective, sample preparation using wet mixing method combining high shear mix was firstly performed. Subsequently, 18 samples were developed for the study, of which the polypropylene (PP) contents 10%, 12%, 14%, 16%, 18% and 20% with 2%, 3%, 4% of carbon black content. Afterwards, samples were characterized by standard tests …

Report From The Stem 2026 Workshop On Assessment, Evaluation, And Accreditation, Rebecca Bates, Angela Arnold, Cary Komoto, Peggy Brickman, R. Alan Cheville, Elizabeth Longley, Jose Mestre, Mihaela Sabin, James Warnock

Integrated Engineering Department Publications

A gathering of science, technology, engineering, and math (STEM) higher education stakeholders met in November 2018 to consider the relationship between innovation in education and assessment. When we talk about assessment in higher education, it is inextricably linked to both evaluation and accreditation, so all three were considered. The first question we asked was can we build a nation of learners? This starts with considering the student, first and foremost. As educators, this is a foundation of our exploration and makes our values transparent. As educators, how do we know we are having an impact? As members and implementers of …

Relative Contributions Of Intracranial Pressure And Intraocular Pressure On Lamina Cribrosa Behavior, Junfei Tong, Deepta Ghate, Sachin Kedar, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

Purpose. To characterize the relative contributions of intraocular pressure (IOP) and intracranial pressure (ICP) on lamina cribrosa (LC) behavior, specifically LC depth (LCD) and LC peak strain. Methods. An axially symmetric finite element model of the posterior eye was constructed with an elongated optic nerve and retro-orbital subarachnoid space ensheathed by pia and dura mater. -e mechanical environment in LC was evaluated with ICP ranging from 5 to 15mmHg and IOP from 10 to 45 mmHg. LCD and LC peak strains at various ICP and IOP levels were estimated using full factorial experiments. Multiple linear regression analyses were …

The Endocytotic Fate Of A Mesoporous Silica Nanoparticle Supported Lipid Bylayer Crispr Delivery Vehicle, Angelea Maestas-Olguin

2019 Award Winners

No abstract provided.

Bioelectrical Circuits: Lecture 8, Jacek P. Dmochowski, Luis Cardoso

Open Educational Resources

No abstract provided.

Ce 431-106: Construction Materials Laboratory, Steve George

Civil and Environmental Engineering Syllabi

No abstract provided.

Ce 443-141: Foundation Design, Ivan Guzman

Civil and Environmental Engineering Syllabi

No abstract provided.

System Dynamics And Control, Benjamin Liaw

Open Educational Resources

Model development with applications to mechanical engineering systems. First and higher order system responses. Laplace transform, transfer functions and block diagrams. Frequency response and vibration. Introduction to feedback control. Concepts of PID control, tuning and compensation. Routh-Hurwitz stability. Control analysis and design using various graphical methods such as root locus, Bode diagram, Nyquist plot and Nichols chart. Hands-on experiments include dynamics and controls of mechanical, servo motor, fluid level/flow, pneumatic and temperature processing systems and vibration of various degree-of-freedom systems.

Bioelectrical Circuits: Lecture 9, Jacek P. Dmochowski, Luis Cardoso

Open Educational Resources

No abstract provided.

Atmospheric Pressure Plasma‐Induced Decolorisation Of Cotton Knitted Fabric Dyed With Reactive Dye, Yaohui Liu, Chester Kin-Man To, Mei‐Ki Ngai, Chi-Wai Kan, Chua Hong

Faculty of Science & Technology (THEi)

The aim of this study was to investigate the decolorisation effect of atmospheric pressure plasma treatment on knitted fabrics dyed with reactive dyes under different processing parameters, ie, air concentration, treatment duration and water content. The fabrics were dyed with reactive dye of a blue colour, and the colour depths were 0.5%, 1.5% and 3.0% on weight of fabric. The colour properties of untreated and plasma‐treated fabric samples were evaluated by means of reflectance, K/S and relative unlevelness index. The colour properties were evaluated instrumentally and quantitatively in order to study the decolorisation effect induced by atmospheric pressure plasma treatment. …

An Orthogonal Study Of Industrial Scale Colour Fading Process Of Cotton Fabric, Yaohui Liu, Chester Kin-Man To, Hiu-Yan Cheung, Chi-Wai Kan, Chua Hong

Faculty of Science & Technology (THEi)

Colour fading is now a popular process used for imparting a vintage look to textile and fashion products, which enhances market value because of the current fashion trends. This study examined a non-aqueous colour fading process with the use of oxygen plasma-induced ozone treatment. An industrial scale machine and commercially available red sulpur-dyed cotton fabric (with 0.5 %, 1.5 % and 2.5 % colour depths) were used in this study. Since the colour fading process factors are inter-related to each other, a specific experiment approach, i.e. orthogonal method, was used for obtaining the optimum conditions in an industrial scale colour …

Effect Of Limited Tension Stiffening In Rc Elements Under Cyclic Loads., Xueying Wang, Jun Shang Kuang

Faculty of Science & Technology (THEi)

The tension capacity in cracked concrete is not well defined in existing shear models for reinforced concrete (RC) membrane elements under cyclic reversed loading, and the shear strength of RC elements is consequently overestimated due to the deviated decreasing branch of envelope of cyclic tensile stress-strain relationship. In this paper, the cyclic effect of limited tension stiffening of cracked RC elements is evaluated by proposing an analytical model named as the cyclic tension-stiffening fixed-angle truss model (CTFTM). The proposed model, based on fixed-angle theory, integrates unloading and reloading rules and accumulated damage into the limited tension-stiffening effect under cyclic loading …

Effects Of Eccentricity On Seismic Behavior Of Non-Seismically Designed Reinforced Concrete Beam-Column Joint, Ho-Fai Wong, Ying Liu, Sung-Hei Luk, Pok-Man Lee, Wing-Hei Kwong

Faculty of Science & Technology (THEi)

The staggering numbers of eccentric reinforced concrete beam-column joints without seismic design details were used in existing RC frame building due to geometrical constraints, which implied high susceptibility of the building structures to anticipated seismic risk. Three exterior RC beam-column joints were fabricated and tested, which were applied reversed cyclic loads to simulate seismic action. In this study, the effects of stirrup ratio in joints and the eccentricity which is defined as the distance between the axis of the beam and column on seismic performance are investigated. The test results provide a further understanding of the failure mode and shear …

Fragility Curves For Buildings In Hong Kong, Sung-Hei Luk, Ho-Fai Wong

Faculty of Science & Technology (THEi)

Fragility curves are the tools for evaluating the damage of structural or nonstructural components under different levels of ground excitation. It is also the necessary information for calculating the life-cycle cost of buildings during their design period. In this paper, development of fragility curves for buildings designed based on HK standard is presented. Two prototype models, which include three-storey and tenstorey reinforced concrete rigid frames, were considered. Incremental dynamic analysis was conducted under nine sets of past earthquake records with scaled peak ground accelerations. Maximum inter-storey drift ratio was selected as the damage indices and three performance levels were considered. …

Nimoal Catalysts Derived From Heptamolybdate-Intercalated Layered Double Hydroxides For Hydrodeoxygenation Of Anisole, Chuang Li, Xingzhao Zhang, Xiao Chen, Zhijian Peng, Chi-Wing Tsang, Changhai Liang

Faculty of Science & Technology (THEi)

The catalytic performance of NiMoAl catalysts derived from layered double hydroxide (LDH) precursors with molybdenum species incorporated into the interlayers was investigated for the hydrodeoxygenation (HDO) of anisole as a model compound of the lignin. The results showed that high dispersion of small Ni nanoparticles with 2–5 nm due to the pinning effect of Mo from Mo7O246− intercalated the LDHs. Due to presence of the oxygen vacancy sites on the molybdenum oxide, the NiMoAl catalysts exhibit higher conversion of anisole than the corresponding NiAl catalyst. The activity for hydrodeoxygenation was enhanced with the increased content of molybdenum species, which can …

Assessing Impact And Blast Resilience Of Polymer Coated Cementitious Materials, Murtaza Nalwala, Gabriel Nsengiyumva, Yong-Rak Kim

UCARE: Research Products

RESEARCH MOTIVATION The bridge piers are highly vulnerable to the impact and blast loads. The position in which they are constructed makes it difficult to install protective devices around them. By the current AASHTO standard, it is possible to under-design bridge piers for commercial vehicle impacts and other events such as blast.

OBJECTIVE To improve impact and blast resilience of bridge piers using polymeric coatings.

CONCLUSION Polymer coating of Portland cement concrete can be achieved with a good bonding. ü The polymeric coating seem to improve impact resilience of Portland cement concrete by increasing absorbed impact energy (i.e., area underneath …

A Regulated Charge Pump With Extremely Low Output Ripple, Mir Mohammad Navidi, David W. Graham

Faculty & Staff Scholarship

Abstract: In this paper, we present a regulated charge pump with extremely low output ripple (mV) that can be used for accurate programming of nonvolatile memory. We present a technique to include a low-drop-out regulator inside the charge-pump regulation loop to reduce the ripple. This charge pump was fabricated in a 0.35 µm standard CMOS process. The die area of this charge pump is 0.163 mm2 . While operating from a 2.5 V supply, this charge pump generates regulated voltages up to 10 V.