6,996 research outputs found
On orthogonal coding-based modulation
No full textIn this letter, we propose a new orthogonal coding-based modulation (OCBM) scheme, in which all available transmitting subcarriers and antennas are activated at a time instant to transmit the data constellation symbols, and the indices of the activated subcarriers and antennas are also harnessed to carry information bits. Our OCBM especially addresses a novel scheme in spatial modulation (SM) domain via employing virtual subarray, and improves the spectral efficiency compared with the existing orthogonal frequency division multiplexing (OFDM)-spread spectrum (SS), index modulation (IM)-OFDM-SS and IM-OFDM based SM (the number of transmit antennas is more than 2). In addition, our investigated detection scheme of the OCBM reduces the complexity of the receiver design by using the unique behavior of the orthogonal code, especially for the detection of the transmitted antenna index bits. Our simulated experiments have been carried out to test the performance of the proposed scheme, and demonstrate the benefits of our suggested approach
Altering tensile and crack initiation behavior in a metastable β titanium alloy via designing grain size and precipitates
No full textDoppler shift estimation for space-based AIS signals over satellite-to-ship links
No full textAs a communication system for maritime monitoring and navigation, automatic identification system (AIS) has been employed for many years, but its service range is limited in 40 nautical miles. Fortunately, an updated service navigation system named as space-based AIS has been presented in recent years, which can provide global coverage service. However, it encounters frequency offset issue caused by the relative satellites/ships motion. To cope with it, in this paper, a novel Doppler shift estimation algorithm is proposed for space-based AIS signals over satellite-to-ship wireless fading channels and non-Gaussian noise. In the estimation stage, the signals including the Doppler shift information are firstly separated from the received ones, but they are also disturbed by the noise. Then, Doppler shift is extracted from the above detached signals via the higher moments which cancel some excrescent parameters by using several flexible algebra operations, and its estimated expression is presented. Finally, numerical simulations are carried out to verify the performance of the proposed method, and simulation results demonstrate the benefits of the suggested scheme
Native p-type transparent conductive CuI via intrinsic defects
No full textThe ability of CuI to be doped p-type via the introduction of native defects has been investigated using first-principles pseudopotential calculations based on density functional theory. The Cu vacancy has a lower formation energy than any of the other native defects, which include I vacancy (V(I)), Cu interstitial (Cu(i)), I interstitial (I(i)), Cu antisite (Cu(I)), and I antisite (I(Cu)). Combined with its shallow acceptor level, it offers sufficient hole concentrations in CuI. The natural band alignments as compared to zinc-blende ZnS, ZnSe, and ZnTe have also been calculated in order to further identify the p-type dopability of CuI. It is found that CuI has a relatively high valence band maximum and conduction band minimum, which also makes it easy to dope CuI p-type in terms of the doping limit rule. In addition, the small effective mass of the light hole-about 0.303m(0)-can provide high mobility and p-type conductivity in CuI. All of these results make CuI an ideal candidate for native p-type materials (C) 2011 American Institute of Physics. [doi:10.1063/1.3633220
The Health Impact of Indoor Air Filtration in Healthy Adults and Asthmatic Children
No full textThe World Health Organization (WHO) estimated that 92% of the world’s population lived in areas with outdoor air pollution levels exceeding the WHO guidelines in 2014. Although the ultimate solution is to control emission sources, exposure reduction strategies at the individual level can address more immediate needs. As people typically spend approximately 80% of their time indoors, improvement of indoor air quality, such as using air filtration technologies, may lead to reduced total exposure. However, evidence is limited to support the effectiveness of air filtration in bringing beneficial health effects to the users. The goal of this dissertation research is to evaluate the health impact of indoor air filtration in healthy adults and asthmatic children using two randomized, double-blind, crossover trials (Aim 1 and Aim 2). Utilizing data from these two trials and other data, this dissertation also addresses two methodological questions. Aim 3 examines the relationship between free and total malondialdehyde, a biomarker of oxidative stress commonly used in air pollution research, in various types of human specimens. Aim 4 evaluates the relationship between the subjective evaluation of asthma control by childhood asthma control test (C-ACT) and objective indicators of lung pathophysiology using longitudinal measurements.In Aim 1 of this dissertation, a double-blinded, randomized, crossover study was conducted to examine the cardiorespiratory health effect of a sporadic, overnight use of indoor air filtration. Seventy healthy non-smoking adults were recruited from the medical and nursing students who were living in the same dormitory building in a suburb of Shanghai, China. The participants were aged 19 to 26 years old and included 41 (59%) females. Each participant received a true and a sham indoor air filtration session in a randomized sequence. Participants and research staff that performed health assessments were blinded to this sequence until the end of the study. Each filtration session was approximately 13 hours long. True and sham filtration sessions were separated by a two-week “washout” interval. During the study period, outdoor PM2.5 concentrations ranged from 18.6 to 106.9 µg/m3, which overlapped with levels measured in Western Europe and North America. Compared to sham filtration, true filtration on average decreased indoor PM2.5 concentration by 72.4% to 10.0 µg/m3 and particle number concentration by 59.2% to 2316/cm3. For lung function measured immediately after the end of filtration, true filtration significantly lowered airway impedance at 5 Hz (Z5) by 7.1% [95% CI: 2.4%, 11.9%], airway resistance at 5 Hz (R5) by 7.4% [95% CI: 2.4%, 12.5%], and small airway resistance (R5-R20) by 20.3% [95% CI: 0.1%, 40.5%], reflecting improved airway mechanics especially for the small airways. However, no significant improvements for spirometric indicators of lung function (FEV1, FVC) were observed. True filtration also significantly lowered von Willebrand factor (VWF) by 26.9% [95% CI: 7.3%, 46.4%] 24 hours after the end of filtration, indicating reduced risk for thrombosis. Stratified analysis in male and female participants showed that true filtration significantly decreased pulse pressure by 3.3% [95% CI: 0.8%, 7.4%] in females, and significantly reduced VWF by 42.4% [95% CI: 17.4%, 67.4%] and interleukin-6 by 22.6% [95% CI: 0.4%, 44.9%] in males. Effect modification analyses indicated that filtration effects in male and female participants were not significantly different. These findings suggest that a single overnight residential air filtration, capable of reducing indoor particle concentrations substantially, can lead to improved airway mechanics and reduced thrombosis risk.Air pollution exposure is a well-established risk factor for asthma exacerbation. In individuals with asthma, indoor air filtration has only been evaluated for allergen removal in areas with low outdoor levels of PM2.5. As asthmatic individuals may be responsive to short-term changes in air pollution levels, it is not clear whether the exposures occurring outside the home environment can override the potential health benefits of residential indoor air filtration. In Aim 2 of this dissertation, I investigated the respiratory impact of residential indoor air filtration in asthmatic children living with moderate levels of outdoor PM2.5. This double-blind, randomized crossover trial recruited 43 participants (40% females) aged 5 to 13 with mild or moderate asthma. From February to April 2017, each participant used a true filtration device and a sham filtration device, respectively in their bedrooms for two weeks. A two-week washout period separated the two sessions. During the study, the average PM2.5 concentrations for outdoor, indoor with sham filtration, and indoor with true filtration were 56.5 µg/m3, 34.1µg/m3, and 14.8 µg/m3, respectively. Compared to sham filtration, on average, true filtration reduced indoor PM2.5 concentrations by 53.3%. Concomitantly, true filtration significantly decreased fractional exhaled oxide (FeNO) by 5.1 [95% CI: 0.5, 9.6] ppb, airway impedance at 5Hz (Z5) by 14.7% [3.7%, 25.8%], respiratory resistance at 5Hz (R5) by 22.4% [9.6%, 35.2%], and small airway resistance (R5-R20) by 40.6% [10.2,% 70.9%]. Peak expiratory flow (PEF) measurements were made twice daily throughout each two-week intervention session. PEF values during true filtration were 1.5% [0.7%, 2.4%] higher than the measurements during sham filtration. True filtration also introduced a non-significant increase on FEF25-75 by 5.80% [-4.09%, 15.68%]. Stratified analyses show that the participants with blood eosinophil count ≤ 500/mm3, compared to those with blood eosinophil count > 500/mm3, had a 24.3% greater increase of FEF25-75 by true filtration; and that the participants allergic to dust mite had smaller improvements in small airway resistance (R5 and R5-R20). These findings suggest that a two-week long intervention of indoor air filtration, capable of significantly reducing indoor PM2.5 concentrations, can lead to reduced respiratory inflammation, improved lung function (PEF) and airway mechanics in asthmatic children.Oxidative stress is a core mechanism involved in the cardiorespiratory effects of air pollution. Malondialdehyde (MDA) is a well-established marker of oxidative stress. However, most of its use in existing studies were conducted by researchers in clinical medicine and epidemiology, who were unaware that MDA is present in both unconjugated and conjugated forms. Aim 3 of this dissertation examined the relationship between free MDA (unconjugated MDA) and total MDA (the sum of both unconjugated and conjugated MDA) in various types of human biospecimens. Using bio-banked samples from multiple studies, free MDA and total MDA were measured simultaneously in nasal fluid (N=158), saliva (N=158), exhaled breath condensate (N=40), serum (N=232), and urine samples (N=429). MDA quantification was performed using an HPLC-fluorescence method with high sensitivity and specificity. Due to the right-skewed distribution of free MDA and total MDA, natural-log transformation was performed before subsequent statistical analyses. The relationship between the natural log of free and total MDA was evaluated by R2 of simple linear regression. T-test was used for comparisons of means between two groups. One-way analysis of variance was used in combination with Tukey’s test to compare the natural log of the ratio of free MDA to total MDA across various types of biospecimens. For exhaled breath condensate, serum, urine, nasal fluid and saliva samples, the R2 between free and total MDA were 0.61, 0.22, 0.59, 0.47 and 0.06, respectively; the medians of the free MDA to total MDA ratio were 48.1%, 17.4%, 9.8%, 5.1% and 3.0%, respectively. The free MDA to total MDA ratio in EBC > serum > urine > nasal fluid > saliva (PThe Childhood Asthma Control Test (C-ACT) is a validated questionnaire that provides a subjective evaluation of asthma control using collective inputs from children and their caregivers. Cross-sectional studies have identified cut-points for discerning different degrees of asthma control. However, few studies have examined whether changes in the C-ACT score are reflective of changes in airway pathophysiology in longitudinal measurements from the same individuals. In Aim 4 of this dissertation, I utilized data from four clinical visits originally conducted for Aim 2. The clinical visits were scheduled bi-weekly over a period of six weeks. Thirty-seven children aged 5 to 10 with mild or moderate asthma (43% female) took the C-ACT. The scores were 24.4 ± 2.4 (mean ± standard deviation) and ranged from 16 to 27. Linear mixed-effects models were used to examine the association between C-ACT and clinical measurements from the same participants. As a change of two points in the C-ACT score is considered as the minimal clinically important difference, I reported the change in biomarkers associated with a two-point decrease in C-ACT score. Results showed that a two-point decrease was significantly associated with a 1.7% [95% CI: 0.1%, 3.3%] decrease in FEV1, a 1.6% [0.5%, 2.8%] decrease in FVC, and a 3.8% [0.0%, 7.6%] increase in airway resistance at 5 Hz (R5). For PEF measurements conducted within two weeks before the C-ACT, a two-point decrease in C-ACT score was significantly associated with a 17.3% [95%CI: 6.8%, 27.8%] increase in the coefficient of variation, while no significant association was observed with the average PEF value (P=0.12). In contrast, within-participant measurements showed no significant associations of C-ACT with respiratory inflammation (FeNO) or any of the small airway function and mechanics parameters (FEF25-75, FEF25-75, R5-R20, X5, and Fres). When examining individual questions of the C-ACT, none of the questions answered by the caregiver were significantly associated with indicators of lung function and respiratory inflammation. In contrast, three out of the four questions answered by the child demonstrated significant or marginally significant associations with FEV1, FVC, FEF25-75, R5, and R20. This suggests that in spite of the relatively young age of the participants, their perception of disease control provides important information for asthma control assessment. Overall, the findings in Aim 4 indicate that subjective evaluation of asthma control using the C-ACT was associated with objective measurements of airway obstruction, airway restriction, respiratory resistance and the variation of airflow limitations in longitudinal measurements. However, the C-ACT is not reflective of changes in respiratory inflammation and small airway mechanics, indicating that its use should be complementary to but not a substitute for these measurements.</p
A novel approach of mechanical chemical grinding
No full textIn this study, two diamond wheels are newly developed. A novel approach of mechanical chemical grinding (MCG) is proposed using the diamond wheel (C2) with ceria (CeO2) developed. A uniform wear layer of 48 nm in thickness is obtained on a silicon (Si) wafer ground by the C2 at a feed rate of 12 mu m/min, which is less than one third that formed by a conventional diamond wheel with mesh size of 5000. The uniform wear layer consists of a 40 nm amorphous layer at the top and an 8 nm damage crystalline layer beneath. Si, silica (SiO2) and SiOx are identified on all the ground Si wafers by energy dispersive spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy and Raman spectra. Only CeO2 and diamond are confirmed by XRD on the C2, indicating the perfect vitrified effect. CeO2, diamond and amorphous carbon are discerned by Raman spectra on the C2 at 466,1332 and 1430 cm(-1), respectively. (C) 2017 Elsevier B.V. All rights reserved
Youthhood
No full textTESTING-GROUND issue 03, Youthhood, examines worlds through youthful eyes, makes evident young ambitions, and questions how we can better empower young people to design cities, landscapes, and a planet that works for them. The issue includes contributions from: Carmel Keren, Jude Daniel Smith, Claire Edwards, Kazeem Kuteyi, Emmanuel Adarkwah, Reza Nik, Dan Cui, Kristofer Cullum-Fernandez, Fida Sassi, Simeon Shtebunaev, Daze Aghaji, Averill Dimabuyu, Sarri Elfaitouri, Rebecca McDonald-Balfour, and Ed Wall.
Rebecca McDonald-Balfour (Author), Jude Daniel Smith (Author), Daze Aghaji (Author), Carmel Keran (Author), Alexis Liu (Author), Dan Cui (Author), Kristofer Cullum-Fernandez (Author), Fida Sassi (Author), Averill Dimabuyu (Author), Ed
Impact damage of composite laminates with high-speed waterjet
No full textRain erosion may cause substantial damage to aircrafts during supersonic flight. Such event is investigated here via high-speed waterjet impact on composite laminates. An experimental setup is developed to produce waterjets with the speed up to 700m/s and a finite element model of the waterjet-composite impact event is established. The consistency of experiment and simulation results validates the adopted numerical methods. The distribution of the water-hammer pressure is non-uniform and the maximum pressure occurs near the contact periphery when the water is about to eject laterally. After a high-speed (300∼560m/s) waterjet impacts a composite laminate, the impacted surface depression is observed, and the typical surface damage presents a central region with no visible surface damage surrounded by a faded “failure ring” with resin removal, matrix cracking and minor fiber fracture. Delamination occurs at the interfaces of adjacent layers with unequal dimensions and longitudinal matrix cracking appears on the back surface. Both the velocity and the diameter of waterjets are crucial factors on CFRP damage extents. Water-hammer pressure, the stagnation pressure and propagation of stress waves are failure mechanisms for most matrix damage in CFRP impacted by waterjets.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Structural Integrity & Composite
Sampling and Reconstruction of Signals on Product Graphs
No full textIn this paper, we consider the problem of subsampling and reconstruction of signals that reside on the vertices of a product graph, such as sensor network time series, genomic signals, or product ratings in a social network. Specifically, we leverage the product structure of the underlying domain and sample nodes from the graph factors. The proposed scheme is particularly useful for processing signals on large-scale product graphs. The sampling sets are designed using a low-complexity greedy algorithm and can be proven to be near-optimal. To illustrate the developed theory, numerical experiments based on real datasets are provided for sampling 3D dynamic point clouds and for active learning in recommender systems.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Signal Processing System
Ban dao ti yi zhi jie gou zai guang cui hua he guang dian cui hua zhong de yan jiu
No full textLi, Qian = 半導體异质结构在光催化和光電催化中的研究 / 李乾.Thesis Ph.D. Chinese University of Hong Kong 2015.Includes bibliographical references (leaves 145-162).Abstracts also in Chinese.Title from PDF title page (viewed on 30, December, 2016).Li, Qian = Ban dao ti yi zhi jie gou zai guang cui hua he guang dian cui hua zhong de yan jiu / Li Qian
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