1,782 research outputs found
A Linear Broadcast Indexing Scheme in Road Environments with Sensor Networks
No full textVarious broadcast schemes have been proposed to provide moving objects on the road network with efficient location-based services. However, they were mainly concerned with the implementation of a broadcast index and did not consider road network environments that moving objects change frequently. In this paper, we propose a novel bi-directional linear broadcast scheme which takes the consideration of road network characteristics. The proposed scheme splits a service area into the sensor cluster-based segments in order to process a query efficiently. The proposed scheme also performs the optimized data update based on road information collected in sensor networks by considering the frequently changed moving object environments. As a result, it can minimize the broadcast of unnecessary data. To show the superiority of our proposed scheme, we compare it with the existing broadcast scheme. Our experimental results show that our proposed scheme reduces about 13% tuning time and about 22% access latency over the existing schemes on average
Ultra-high strength WNbMoTaV high-entropy alloys with fine grain structure fabricated by powder metallurgical process
No full textAn equi-atomic WNbMoTaV high entropy alloy (HEA) with a single body-centered cubic structure (BCC) was firstly fabricated by the powder metallurgical process of mechanical alloying (MA) and spark plasma sintering (SPS). Mechanical alloying behavior, microstructure and mechanical properties of the WNbMoTaV HEA were studied systematically. During MA, a single BCC phase was formed and the average particle size and crystallite size was refined to 1.83 µm and 66.1 nm, respectively, after 6 h of MA. Afterward, the as-milled powders were subsequently sintered in the temperature range of 1500–1700 °C. The microstructure of the sintered sample exhibits a few micrometer-scale grain size and a homogeneous BCC matrix with a small amount of oxide inclusion originated from oxidation during the powder metallurgical process. The bulk sample of the WNbMoTaV HEA sintered at 1500 °C shows an ultra-high compressive yield strength of 2612 MPa with a failure strain of 8.8% at room temperature, respectively. These mechanical properties of the WNbMoTaV HEA fabricated by the powder metallurgical process were attributed to the combined effects of grain boundary strengthening, substitutional solid solution strengthening, interstitial solid solution strengthening and Orowan strengthening by the oxide inclusions. Through a Hall-Petch analysis, the Hall-Petch coefficient of the WNbMoTaV HEA was derived. The WNbMoTaV HEA fabricated via the powder metallurgical process showed the best compressive yield strength when compared with the other reported refractory HEAs processed with arc-melting and casting.
Development of semi-permanent package and performance test system for electroceutical research
No full textDrug resistance that can be occurred by various causes makes it impossible for the patient to escape from the diseases. To solve this problem, Electroceutical, which modulates the neuronal activity with electrical stimulation, has received attention. However, it is necessary to use an implantable device to deliver a precise stimulus to the target. We, therefore, developed the hermetic packaging technique for long-term animal experiments and tested the waterproof performance of the prototype with building a human tissue mimicking phantom. Finally, we have confirmed the performance of the implantable package that can operate internal components normally for over a year.2
Fabrication and mechanical properties of a light-weight refractory Al0.1CrNbVMo high entropy allowys fabricated by powder metallurgical process
No full textQuantifying uncertainties and correlations of engineering demand parameters of building structures for regional seismic loss assessment
No full textFor an accurate regional seismic loss assessment, it is essential to quantify the uncertainties and correlations of the engineering demand parameters (EDP) of the building structures. Previous studies predicted the mean EDP of each structure by a regression function of the selected intensity measure (IM), while its variability is described by the "EDP residual." The authors recently proposed a new formulation and Incremental Dynamic Analysis (IDA)-based methods to evaluate the correlation between EDP residuals. This paper proposes an IM-invariant method for estimating the variances and correlations of the EDP residuals of building structures. Based on the EDP residuals of various buildings estimated using the proposed method, primary structural characteristics affecting EDP residuals are identified. In addition, this study develops EDP estimation regression equations using predictive variables defined based on the identified structural characteristics to facilitate consideration of the EDP residual correlation in regional seismic loss assessment. Numerical examples verify the regression models and demonstrate that the proposed method can improve the accuracy of a regional loss assessment by considering the building types in the inventory.N
Frequency comb-based microwave transfer over fiber with 7x10(-19) instability using fiber-loop optical-microwave phase detectors
No full textWe demonstrate a remote microwave/radio frequency (RF) transfer technique based on the stabilization of a fiber link using a fiber-loop optical-microwave phase detector (FLOM-PD). This method compensates for the excess phase fluctuations introduced in fiber transfer by direct phase comparison between the optical pulse train reflected from the remote site and the local microwave/RF signal using the FLOM-PD. This enables sub-fs resolution and long-term stable link stabilization while having a wide timing detection range and less of a demand in fiber dispersion compensation. The demonstrated fractional frequency instability between 2.856 GHz RF oscillators separated by a 2.3 km fiber link is 7.6 x 10(-18) and 6.5 x 10(-19) at 1000 and 82,500 s averaging times, respectively. (C) 2014 Optical Society of Americ
LearnerVoice: A Dataset of Non-Native English Learners’ Spontaneous Speech
No full textPrevalent ungrammatical expressions and disfluencies in spontaneous speech from second language (L2) learners pose unique challenges to Automatic Speech Recognition (ASR) systems. However, few datasets are tailored to L2 learner speech. We publicly release LearnerVoice, a dataset consisting of 50.04 hours of audio and transcriptions of L2 learners\u27 spontaneous speech. Our linguistic analysis reveals that transcriptions in our dataset contain L2S (L2 learner\u27s Spontaneous speech) features, consisting of ungrammatical expressions and disfluencies (e.g., filler words, word repetitions, self-repairs, false starts), significantly more than native speech datasets. Fine-tuning whisper-small.en with LearnerVoice achieves a WER of 10.26%, 44.2% lower than vanilla whisper-small.en. Furthermore, our qualitative analysis indicates that 54.2% of errors from the vanilla model on LearnerVoice are attributable to L2S features, with 48.1% of them being reduced in the fine-tuned model.Proceedings of Interspeec
Urchin-like structured magnetic hydroxyapatite for the selective separation of cerium ions from aqueous solutions
No full textIn this study, bio-inspired urchin-like structured hydroxyapatite (UHdA) and its magnetic composite (UHdA@Fe3O4) were developed for efficient and easy separation of cerium ions (Ce3+) from aquatic waste streams. UHdA and UHdA@Fe3O4 exhibited superior Ce3+ adsorption capacities of 248.39 and 230.01 mg/g-UHdA respectively, compared to a commercial HdA (141.71 mg/g-HdA) due to their hierarchical mesoporous structure and large specific surface area. The adsorption of Ce3+ to UHdA and UHdA@Fe3O4 were heterogeneous, pseudo-secondorder-kinetic, and the rate-limiting step was external mass transfer and intra-particle diffusion. Moreover, thermodynamic studies revealed that the adsorption process was spontaneous and endothermic nature. The high selectivity towards Ce3+ in multi-ionic systems is attributed to the strong affinity between strong Lewis acid (Ce3+) and base (PO43- and OH-) interactions. XRD, FTIR, and XPS analysis demonstrated that the adsorption was mainly attributable to the ion exchange of Ce3+ with Ca2+ and to surface complexation. The desorption of Ce3+ was efficiently accomplished using 0.1 M HNO3. The results suggest that UHdA and UHdA@Fe3O4 could be promising choices for the adsorption and recovery of rare earth elements.
Reliability−based topology optimization frameworks for the design of structures subjected to random excitations
No full textEmbargo set by: Seth Robbins for item 95486
Lift date: 2018-11-10T18:43:22Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemU of I Only Restriction Lifted for Item 95486 on 2018-11-11T10:15:32Z.Structural optimization aims to provide structural designs that allow for the best performance while satisfying given design constraints. Among various applications of structural optimization, topology optimization based on mathematical programming and finite element analysis has recently gained great attention in research community as well as in applied structural engineering fields. One of the most fundamental requirements on building structures is to withstand various uncertain loads such as earthquake ground motions, wind loads and ocean waves. The design of structures, therefore, needs to ensure safe and reliable operations of structures over a prolonged period of time during which they may be exposed to various randomness of excitations caused by hazardous events. As such, significant amount of time and financial resources are invested to control the dynamic response of a structure under random vibrations caused by natural hazards or operations of non-structural components. In this regard, topology optimization of structures with stochastic response constraints is of great importance and consideration in industrial applications. This thesis discusses the development of structural optimization frameworks for a wide spectrum of deterministic and probabilistic constraints in engineering and investigate numerical applications.
First, the efficient optimization framework for statics and dynamics problems is investigated. In many incidences, expensive computational cost and labor hours are so prohibitive that optimization processes become impractical or inapplicable. In order to alleviate the computational burden in dynamic topology optimization, the multiresolution topology optimization approach is adopted. Based on the polygonal finite element method and multiresolution topology optimization techniques, a method of polygonal multiresolution topology optimization for statics and dynamics problems is developed. This development provides methods to discretize complicated geometries and reduce computational cost to obtain topology results of high-resolutions.
Despite rapid technological advances, incorporating stochastic response of structures into topology optimization is considered a relatively new field of research mainly due to computational challenges. In order to overcome such technical challenges in this field, a new method is introduced for incorporating random vibration theories into topology optimization using a discrete representation method for stochastic processes. Furthermore, a novel formulation is developed for sensitivity analysis of stochastic responses in order to use gradient-based optimization algorithms for the proposed topology optimization employing the discrete representation method.
To assess the reliability of a structure subjected to random excitations, the probability of the occurrence of at least one failure event over a time interval, i.e. the first passage probability, often needs to be evaluated. In this thesis, a new method is proposed to incorporate probabilistic constraints on the first passage probability into structural design and topology optimization. To obtain the first passage probability effectively during each iteration, the failure event is described as a series system event consisting of failure events defined at discrete time points, and the system failure probability is obtained with the sequential compounding method. A new sensitivity formulation is developed employing the sequential compounding method to facilitate the use of gradient-based optimizers for the proposed method.
Finally, the conventional filter effects are investigated in reliability-based topology optimization using the elastic formulation of the ground structure method. In addition, an optimization scheme employing the discrete filter is proposed to ensure that optimized solutions satisfy the probabilistic constraints and global equilibrium. In addition, the single-loop approach is incorporated to enhance the computational efficiency of the proposed RBTO method.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2018-08-01The student, Junho Chun, accepted the attached license on 2016-07-14 at 13:46.The student, Junho Chun, submitted this Dissertation for approval on 2016-07-14 at 14:36.This Dissertation was approved for publication on 2016-07-15 at 09:10.DSpace SAF Submission Ingestion Package generated from Vireo submission #9934 on 2016-11-10 at 12:25:23Made available in DSpace on 2016-11-10T18:43:01Z (GMT). No. of bitstreams: 3
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Previous issue date: 2016-07-1
Novel Hydroxyapatite Beads for the Adsorption of Radionuclides from Decommissioned Nuclear Power Plant Sites
No full textAlthough a powdered form of hydroxyapatite (p-HdA) has been studied for the adsorption of heavy metals that contaminate the restoration sites of decommissioned nuclear power plants, most of the studies are limited in the laboratory due to the head loss and post-separation in practical applications. Herein, we fabricated a porous bead form of HdA (b-HdA) as a novel adsorbent for removing radionuclides from aqueous environments via a facile synthesis by mixing the p-HdA precursor and polyvinyl butyral (PVB) as a binder and added a sintering process for the final production of a porous structure. The spherical b-HdA with an approximate diameter of 2.0 mm was successfully fabricated. The effectiveness of the b-HdA at removing Co(II) was investigated via the adsorption equilibrium at various experimental temperatures. The b-HdA exhibited the adsorption capacity for Co(II) ions with a maximum of 7.73 and 11.35 mg/g at 293 K and 313 K, respectively. The experimental kinetic data were well described using a pseudo-second-order kinetic model, and the adsorption mechanisms of Co(II) onto the b-HdA were revealed to be a chemisorption process with intraparticle diffusion being the rate-limiting step. In addition, the competitive adsorption onto the b-HdA with the order of U(VI) > Co(II) > Ni(II) > Sr(II) > Cs(I) was also observed in the multi-radionuclides system. Considering the advantages of the size, applicability to the continuous-flow column, and the easy separation from treated water, the b-HdA can be an excellent absorbent with high potential for practical applications for removing radionuclides
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