| 21. |
- Liu, Jianhua, et al.
(författare)
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Differential space-code modulation for interference suppression
- 2001
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Ingår i: IEEE Transactions on Signal Processing. - : Institute of Electrical and Electronics Engineers (IEEE). - 1053-587X .- 1941-0476. ; 49:8, s. 1786-1795
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Tidskriftsartikel (refereegranskat)abstract
- Space-time coding has been receiving much attention due to its potentials offered by fully exploiting the spatial and temporal diversities of multiple transmit and receive antennas. A differential space-time modulation (DSTM) scheme was previously proposed for demodulation without channel state information, which is attractive in fast fading channels where accurate channel estimates are difficult to obtain. However, this technique is sensitive to interference and is likely to deteriorate or even break down in a wireless environment, where interference (including intentional and unintentional jamming) signals exist. We propose a new coding and modulation scheme, referred to as the differential space-code modulation (DSCM), which is interference resistant. Our focus is on single-user communications. We show that DSCM outperforms DSTM significantly when interference is present. This advantage is achieved at the cost of a lower data rate or a wider bandwidth or a combination of both. To alleviate this problem, a high-rate DSCM (HR-DSCM) scheme is also presented, which increases the data rate considerably at the cost of a slightly higher bit-error rate (BER), while still maintaining the interference suppression capability.
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| 22. |
- Liu, Jianhua, et al.
(författare)
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High-rate differential space-code modulation for interference suppression
- 2001
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Ingår i: 2001 IEEE Third Workshop on Signal Processing Advances in Wireless Communications (SPAWC'01). Workshop Proceedings. - 0780367200 ; , s. 283-286
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Konferensbidrag (refereegranskat)abstract
- Space-time coding has been receiving much research attention recently due to the potential offered by fully exploiting spatial and temporal diversity. A differential space-time modulation (DSTM) scheme was recently proposed to perform demodulation without channel state information, which is attractive in fast fading channels where accurate channel estimates are difficult to obtain. More recently, a differential space-code modulation (DSCM) scheme, which is an improvement of DSTM for combating interference (including intentional and unintentional jamming) signals, was proposed. DSCM significantly outperforms DSTM when interference is present. This advantage, however, is achieved at the cost of a lower transmission rate, a wider bandwidth, or a combination of both. To alleviate this problem, we extend DSCM to a so-called high-rate DSCM (HR-DSCM) scheme, which increases the data rate considerably at the cost of a slightly higher bit error rate, while still maintaining the interference suppression capability.
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| 23. |
- Mansouri, Kamel, et al.
(författare)
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CoMPARA : Collaborative Modeling Project for Androgen Receptor Activity
- 2020
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Ingår i: Journal of Environmental Health Perspectives. - 0091-6765 .- 1552-9924. ; 128:2, s. 1-17
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Endocrine disrupting chemicals (EDCs) are xenobiotics that mimic the interaction of natural hormones and alter synthesis, transport, or metabolic pathways. The prospect of EDCs causing adverse health effects in humans and wildlife has led to the development of scientific and regulatory approaches for evaluating bioactivity. This need is being addressed using high-throughput screening (HTS) in vitro approaches and computational modeling.OBJECTIVES: In support of the Endocrine Disruptor Screening Program, the U.S. Environmental Protection Agency (EPA) led two worldwide consortiums to virtually screen chemicals for their potential estrogenic and androgenic activities. Here, we describe the Collaborative Modeling Project for Androgen Receptor Activity (CoMPARA) efforts, which follows the steps of the Collaborative Estrogen Receptor Activity Prediction Project (CERAPP).METHODS: The CoMPARA list of screened chemicals built on CERAPP's list of 32,464 chemicals to include additional chemicals of interest, as well as simulated ToxCast (TM) metabolites, totaling 55,450 chemical structures. Computational toxicology scientists from 25 international groups contributed 91 predictive models for binding, agonist, and antagonist activity predictions. Models were underpinned by a common training set of 1,746 chemicals compiled from a combined data set of 11 ToxCast (TM)/Tox21 HTS in vitro assays.RESULTS: The resulting models were evaluated using curated literature data extracted from different sources. To overcome the limitations of single-model approaches, CoMPARA predictions were combined into consensus models that provided averaged predictive accuracy of approximately 80% for the evaluation set.DISCUSSION: The strengths and limitations of the consensus predictions were discussed with example chemicals; then, the models were implemented into the free and open-source OPERA application to enable screening of new chemicals with a defined applicability domain and accuracy assessment. This implementation was used to screen the entire EPA DSSTox database of similar to 875,000 chemicals, and their predicted AR activities have been made available on the EPA CompTox Chemicals dashboard and National Toxicology Program's Integrated Chemical Environment.
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| 24. |
- Ouyang, Wei, et al.
(författare)
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Temporal-spatial patterns of three types of pesticide loadings in a middle-high latitude agricultural watershed
- 2017
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Ingår i: Water Research. - : Elsevier. - 0043-1354 .- 1879-2448. ; 122, s. 377-386
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Tidskriftsartikel (refereegranskat)abstract
- Pesticide loadings to watersheds increase during agricultural development and may vary in accordance with different crop types and seasons. High pesticide loadings can potentially result in polluted stream water. The objective of this study was to determine the pesticide loadings and concentrations of three typical pesticides (atrazine, oxadiazon, and isoprothiolane) in river water from a middle high latitude agricultural watershed in northern China. During this study, we evaluated the watershed pesticide loss patterns for two crop types over three decades. For this purpose, we integrated data from field investigations, laboratory experiments, and modeling simulations involving a distributed hydrological solute transport model (Soil and Water Assessment Tool, SWAT). SWAT was employed to compare the temporal spatial fate and behaviors of atrazine, oxadiazon, and isoprothiolane from 1990 to 2014 in a watershed area amounting to 141.5 km(2). The results showed that the three pesticides could be detected at different locations throughout the watershed, and isoprothiolane was detected at the maximum value of 1.082 mu g/L in surface runoff of paddy land. The temporal trend for the yearly loading of atrazine decreased slightly over time, but the trends for oxadiazon and isoprothiolane increased markedly over an 18-year analysis period. In regard to the pesticide concentrations in water, atrazine was associated with the largest value of nearly 1.4 mu g/L. July and August were the found to be prime periods for pesticide loss from paddy land, and the biggest monthly loss of atrazine from dryland appeared in June. Under similar usage conditions, isoprothiolane loading from paddy fields ranked as the largest one among the three types of pesticides and reached up to 17 g/ha. Limited monitoring data were useful for validating the model, which yielded valuable temporal-spatial data on the fate of pesticides in this watershed. With the expansion of paddy rice cultivation, risks for pesticide contamination of water bodies will increase. The results of this study should be valuable for future exposure and risk assessments aimed at protecting the environment and human health.
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| 25. |
- Shen, Han-Ming, et al.
(författare)
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Enhanced thermal performance of internal Y-shaped bifurcation microchannel heat sinks with metal foams
- 2018
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Ingår i: Journal of Thermal Science and Engineering Applications. - : ASME International. - 1948-5085 .- 1948-5093. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Internal Y-shaped bifurcation has been proved to be an advantageous way on improvingthermal performance of microchannel heat sinks according to the previous research. Metal foams are known due to their predominate performance such as low-density, largesurface area, and high thermal conductivity. In this paper, different parameters of metalfoams in Y-shaped bifurcation microchannel heat sinks are designed and investigatednumerically. The effects of Reynolds number, porosity of metal foam, and the pore density(PPI) of the metal foam on the microchannel heat sinks are analyzed in detail. It is foundthat the internal Y-shaped bifurcation microchannel heat sinks with metal foam exhibitbetter heat transfer enhancement and overall thermal performance. This researchprovides broad application prospects for heat sinks with metal foam in the thermalmanagement of high power density electronic devices.
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| 26. |
- Xu, Bo, et al.
(författare)
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4-Tert-butylpyridine Free Organic Hole Transporting Materials for Stable and Efficient Planar Perovskite Solar Cells
- 2017
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Ingår i: Advanced Energy Materials. - : Wiley. - 1614-6832 .- 1614-6840. ; 7:19
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Tidskriftsartikel (refereegranskat)abstract
- 4-Tert-butylpyridine (tBP) is an important additive in triarylamine-based organic hole-transporting materials (HTMs) for improving the efficiency and steady-state performance of perovskite solar cells (PVSCs). However, the low boiling point of tBP (196 degrees C) significantly affects the long-term stability and device performance of PVSCs. Herein, the design and synthesis of a series of covalently linked Spiro[fluorene-9,9'-xanthene] (SFX)-based organic HTMs and pyridine derivatives to realize efficient and stable planar PVSCs are reported. One of the tailored HTMs, N2, N2, N7, N7-tetrakis(4-methoxyphenyl)-3', 6'bis( pyridin-4-ylmethoxy) spiro[fluorene-9,9'-xanthene]-2,7-diamine (XPP) with two para-position substituted pyridines that immobilized on the SFX core unit shows a high power conversion efficiency (PCE) of 17.2% in planar CH3NH3PbI3-based PVSCs under 100 mW cm(-2) AM 1.5G solar illumination, which is much higher than the efficiency of 5.5% that using the well-known 2,2', 7,7'-tetrakis-(N, N-di-p-methoxy-phenyl-amine) 9,9'-spirobifluorene (SpiroOMeTAD) as HTM (without tBP) under the same condition. Most importantly, the pyridine-functionalized HTM-based PVSCs without tBP as additive show much better long-term stability than that of the state-of-the-art HTM SpiroOMeTAD- based solar cells that containing tBP as additive. This is the first case that the tBP-free HTMs are demonstrated in PVSCs with high PCEs and good stability. It paves the way to develop highly efficient and stable tBP-free HTMs for PVSCs toward commercial applications.
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| 27. |
- Yang, Junyu, et al.
(författare)
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Roll-to-Roll Slot-Die-Printed Polymer Solar Cells by Self-Assembly
- 2018
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Ingår i: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 10:26, s. 22485-22494
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Tidskriftsartikel (refereegranskat)abstract
- Extremely simplified one-step roll-to-roll slot-die-printed flexible indium tin oxide (ITO)-free polymer solar cells (PSCs) are demonstrated based on the ternary blends of electron-donor polymer thieno[3,4-b]thiophene/benzodithiophene, electron-acceptor fullerene [6,6]-phenyl-C-71-butyric acid methyl ester, and electron-extracting polymer poly[(9,9-bis(3-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN) at room temperature (RT) in ambient air. The flexible ITO-free PSC exhibits a comparable power conversion efficiency (PCE) with the device employing complicated two-step slot-die printing (5.29% vs 5.41%), which indicates that PFN molecules can migrate from the ternary nanocomposite toward the Ag cathode via vertical self-assembly during the one-step slot-die printing process in air. To confirm the migration of PFN, the morphology and elemental analysis as well as charge transport of different active layers are investigated by the in situ transient film drying process, transmission electron microscopy, atomic force microscopy, contact angle and surface energy, X-ray photoelectron spectroscopy, scanning electron microscopy, impedance spectroscopy, transient photovoltage and transient photocurrent, and laser-beam-induced current. Moreover, the good air and mechanical stability of the flexible device with a decent PCE achieved in 1 cm(2) PSCs at RT in air suggests the feasibility of energy-saving and time-saving one-step slot-die printing to large-scale roll-to-roll manufacture in the future.
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| 28. |
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| 29. |
- Yu, ChaoQing, et al.
(författare)
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Managing nitrogen to restore water quality in China
- 2019
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Ingår i: Nature. - : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 567:7749, s. 516-520
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Tidskriftsartikel (refereegranskat)abstract
- The nitrogen cycle has been radically changed by human activities(1). China consumes nearly one third of the world's nitrogen fertilizers. The excessive application of fertilizers(2,3) and increased nitrogen discharge from livestock, domestic and industrial sources have resulted in pervasive water pollution. Quantifying a nitrogen 'boundary'(4) in heterogeneous environments is important for the effective management of local water quality. Here we use a combination of water-quality observations and simulated nitrogen discharge from agricultural and other sources to estimate spatial patterns of nitrogen discharge into water bodies across China from 1955 to 2014. We find that the critical surface-water quality standard (1.0 milligrams of nitrogen per litre) was being exceeded in most provinces by the mid-1980s, and that current rates of anthropogenic nitrogen discharge (14.5 +/- 3.1 megatonnes of nitrogen per year) to fresh water are about 2.7 times the estimated 'safe' nitrogen discharge threshold (5.2 +/- 0.7 megatonnes of nitrogen per year). Current efforts to reduce pollution through wastewater treatment and by improving cropland nitrogen management can partially remedy this situation. Domestic wastewater treatment has helped to reduce net discharge by 0.7 +/- 0.1 megatonnes in 2014, but at high monetary and energy costs. Improved cropland nitrogen management could remove another 2.3 +/- 0.3 megatonnes of nitrogen per year-about 25 per cent of the excess discharge to fresh water. Successfully restoring a clean water environment in China will further require transformational changes to boost the national nutrient recycling rate from its current average of 36 per cent to about 87 per cent, which is a level typical of traditional Chinese agriculture. Although ambitious, such a high level of nitrogen recycling is technologically achievable at an estimated capital cost of approximately 100 billion US dollars and operating costs of 18-29 billion US dollars per year, and could provide co-benefits such as recycled wastewater for crop irrigation and improved environmental quality and ecosystem services.
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| 30. |
- Yue, Jincheng, et al.
(författare)
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Role of atypical temperature-responsive lattice thermal transport on the thermoelectric properties of antiperovskites Mg3XN (X = P, As, Sb, Bi)
- 2024
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Ingår i: Materials Today Physics. - : ELSEVIER. - 2542-5293. ; 41
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Tidskriftsartikel (refereegranskat)abstract
- Antiperovskite materials have garnered significant attention due to their rich array of physical properties. In this study, we undertake a theoretical exploration into the phase stabilities, and the thermal and electronic transport properties of magnesium-based antiperovskite Mg3XN (X = P, As, Sb, and Bi) based on density functional theory (DFT) calculations, aiming at designing promising thermoelectric materials. The Mg3PN and Mg3AsN possess potential lattice distortion and strong quartic anharmonicity associated with the tilting displacement of Mg6N octahedra. After phonon renormalization, the thermal conductivity of Mg3PN and Mg3AsN exhibits relatively subdued temperature responsiveness with T-0.47 and T-0.62, respectively. Of note, the thermal conductivity of Mg3BiN drops the lowest at 900 K because of its distinctive rattle-dominated flat vibrational modes and strong temperature responsiveness with T-0.96, despite having a high initial value. Moreover, the combination of multiple degeneracy pockets and lighter dispersion band edges in Mg3XN ensures high Seebeck coefficient and impressive electronic conductivity, respectively. Ultimately, Mg3BiN achieves the optimal power factor, which also guarantees its excellent thermoelectric performance with the ZT values of 1.03 and 1.01 for n-type and ptype at 900 K, respectively. Our findings shed light on the significant impact of unconventional temperatureresponsive lattice thermal conductivity on thermoelectric materials for high-temperature applications.
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