826 research outputs found
DISTRIBUTION-FUNCTIONS AND BALANCE-EQUATIONS OF DRIFTING BLOCH ELECTRONS IN AN ELECTRIC-FIELD - REPLY
No full textA study of chemical structure in "barkinite" using time-of-flight secondary ion mass spectrometry
No full textThe Late Permian coals from south China are unique in their high content of "barkinite" and elemental hydrogen, and typically produce high yields of tar. "Barkinite" has often been identified as suberinite for a long time, but now many Chinese workers have concluded that "barkinite'" is not suberinite, rather it is a distinct maceral. The term "barkinite" was formally certified and named by the State Bureau of Technical Supervision of the People's Republic of China in 1991, 1995 and 1999; however, it has not been recognized as a scientific term by international coal geologists and ICCP, and TSOP have not recognized the term, either. The petrographic characteristics of "barkinite" and suberinite show that the biggest difference between them is in the cell fillings. Therefore, in the paper, a new in situ microprobe mass chemical analytical method, time-of-flight secondary ion mass spectrometry (TOF-SIMS) was first used to study the chemical structure of cell walls and cell fillings of "barkinite". The results indicate that the chemical structures of cell fillings and cell walls are similar to each other, They are all mostly composed of aliphatic compounds (such as alkane and alkene), and followed by aromatic compounds and alkyl aromatics, in addition to minor amounts of heteroatomic compounds (such as alkoxyl and alkylamine). Based on these, we can deduce that the cell cavities of "barkinite" were mainly filled by original lipid, which were derived from cell secretion of "barkinite" itself, But suberinite is defined only as suberinized cell walls in cork tissue, and cell cavities were usually filled by secondary gelification materials (such as corpocollinite), these characteristics are quite different from those of "barkinite". The chemical characteristics of "barkinite" shown in SIMS spectra coincide with those inferred from its petrographic characteristics. The high content of hydrogen. the high tar yields and the high hydrocarbon generation potential of Late Permian coals from south China are attributed to the high aliphatic content of "barkinite". (C) 2001 Elsevier Science BN. All rights reserved.Energy & FuelsGeosciences, MultidisciplinarySCI(E)EI15ARTICLE11-84
K+ -> pi(+) nu(nu)over-bar and FCNC from nonuniversal Z(') bosons
No full textMotivated by the E787 and E949 result for K+-->pi(+)nu(nu) over bar we examine the effects of a new nonuniversal right-handed Z(') boson on flavor changing processes. We place bounds on the tree-level flavor-changing neutral current from K-(K) over bar and B-(B) over bar mixing as well as from the observed CP violation in kaon decay. We discuss the implications for K-->pinu(nu) over bar, B-->Xnu(nu) over bar and B-->tau(+)tau(-). We find that the existing bounds allow substantial enhancements in the K+-->pi(+)nu<(nu())over bar> rate, particularly through a new one-loop Z(') penguin operator.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000224275200008&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Astronomy & AstrophysicsPhysics, Particles & FieldsSCI(E)28ARTICLE5null7
Ada-XG-CatBoost: A Combined Forecasting Model for Gross Ecosystem Product (GEP) Prediction
No full textThe degradation of the ecosystem and the loss of natural capital have seriously threatened the sustainable development of human society and economy. Currently, most research on Gross Ecosystem Product (GEP) is based on statistical modeling methods, which face challenges such as high modeling difficulty, high costs, and inaccurate quantitative methods. However, machine learning models are characterized by high efficiency, fewer parameters, and higher accuracy. Despite these advantages, their application in GEP research is not widespread, particularly in the area of combined machine learning models. This paper includes both a GEP combination model and an explanatory analysis model. This paper is the first to propose a combined GEP prediction model called Ada-XGBoost-CatBoost (Ada-XG-CatBoost), which integrates the Extreme Gradient Boosting (XGBoost), Categorical Boosting (CatBoost) algorithms, and SHapley Additive exPlanations (SHAP) model. This approach overcomes the limitations of single-model evaluations and aims to address the current issues of inaccurate and incomplete GEP assessments. It provides new guidance and methods for enhancing the value of ecosystem services and achieving regional sustainable development. Based on the actual ecological data of a national city, data preprocessing and feature correlation analysis are carried out using XGBoost and CatBoost algorithms, AdaGrad optimization algorithm, and the Bayesian hyperparameter optimization method. By selecting the 11 factors that predominantly influence GEP, training the model using these selected feature datasets, and optimizing the Bayesian parameters, the error gradient is then updated to adjust the weights, achieving a combination model that minimizes errors. This approach reduces the risk of overfitting in individual models and enhances the predictive accuracy and interpretability of the model. The results indicate that the mean squared error (MSE) of the Ada-XG-CatBoost model is reduced by 65% and 70% compared to the XGBoost and CatBoost, respectively. Additionally, the mean absolute error (MAE) is reduced by 4.1% and 42.6%, respectively. Overall, the Ada-XG-CatBoost combination model has a more accurate and stable predictive performance, providing a more accurate, efficient, and reliable reference for the sustainable development of the ecological industry
Avaliação do risco epidemiológico da carcinicultura catarinense usando como modelo a síndrome de taura e da doença da mancha branca
No full textDissertação (mestrado) - Universidade do Vale do Itajaí, Centro de Ciências Tecnológicas da Terra e do Mar. Programa de Mestrado Acadêmico em Ciência e Tecnologia Ambiental.A carcinicultura brasileira vem apresentando produtividade crescente nos últimos anos, sendo a recordista mundial, com uma projeção de 8000 kg/ha/ano em 2005. O incremento no cultivo e o impacto potencial negativo das enfermidades não podem ser negligenciados. As doenças importantes de crustáceos são infecciosas. A presença de um agente infeccioso não implica na presença da enfermidade clínica, mas a detecção da infecção na ausência da enfermidade clínica é suficiente para o caso ser declarado. Em animais aquáticos o hospedeiro e o meio ambiente influenciam de maneira significativa o grau em que uma infecção subclínica poderá tornar-se clínica, ou os animais que sobrevivem a infecção poderão tornar-se veículos do agente por toda a sua vida. A reação em cadeia da polimerase (PCR) pode ser utilizada para a amplificação enzimática de seqüências de ácidos nucléicos que estão presentes em pequeno número, como em amostras ambientais. Permitindo ações de controle e reduzindo seus efeitos negativos. Neste trabalho foram avaliados os potenciais riscos epidemiológicos advindos de falhas estruturais, barreiras e certificação sanitária. Os estabelecimentos avaliados foram os laboratórios produtores de náuplios e pós-larvas e 07 fazendas de camarões no nordeste catarinense na safra compreendida nos meses de outubro de 2002 a julho de 2003. Os modelos utilizados são as duas principais doenças de notificação obrigatória e de maior impacto econômico para o continente americano: a Síndrome de Taura (TSV) e a Doença da Mancha Branca (WSSV). Os protocolos testados para extração de RNA e DNA com resultados eficazes foram: fenol/clorofórmio # álcool isoamilico e sílica/tiocianato de guanidina e método sílica/tiocianato de guanidina e TRIZOL Reagentâ, GibcoBRL; resultado negativo foi com o protocolo DNAzol Reagentâ, GibcoBRL Para os testes de detecção do vírus TSV e WSSV foram utilizados técnicas de biologia molecular nas metodologias descritas na literatura. Não foi detectada reação positiva em nenhuma das amostras analisadas, o que não exclui a possibilidade da ocorrência dos vírus uma vez que são necessários 2 anos de testes consecutivos para ser considerada área livre
Molecular dynamics study on the structural and dynamic properties of xanthan gum in a dilute solution under the effect of temperature
No full textXanthan gum (XG) is considered one of the most industrially important polysaccharides, with applications ranging from food products such as ice creams and salad dressings to pharmaceuticals and oil well drilling fluids. The wide application of XG is due to its favourable rheological properties and its capability to resist degradation under a high shear or high temperature environment. It is generally accepted that both inter- and intramolecular interactions, including hydrogen bonding (HB), are responsible for its unique properties. To date, there is still a lack of comprehensive examination on the HB mechanism in polysaccharides. Therefore, the study proposed here was conducted using molecular dynamics (MD) simulations that are able to provide insights with an unparalleled temporal and spatial resolution. Since XG is used over a broad range of temperatures, the implications of thermal effect on the structure and molecular interactions of XG in an aqueous solution are discussed in this paper. MD simulations were run at an isobaric-isothermal condition with 1 atm target pressure and five temperatures ranging between 283K and 353K. From the simulation results, an increasingly extended conformation of XG is observed as the temperature rises, and this finding matches qualitatively with the results published in the literature. The radius of gyration, radial pair distribution functions and intramolecular HB of XG were also discussed. The outcomes of the present study may serve as a stepping stone for the future studies on polysaccharides using MD simulations.The authors would like to thank the computational resources and services provided by the National Computational Infrastructure (NCI) that is supported by the Australian Government. The financial support received from the Australian Government Research Training Program Scholarship is also greatly appreciated.Peer-reviewe
Effects of xanthan-locust bean gum mixtures on the physicochemical properties and oxidative stability of whey protein stabilised oil-in-water emulsions
No full textThe effects of xanthan gum (XG)-locust bean gum (LBG) mixtures (0.05, 0.1, 0.15, 0.2 and 0.5 wt%) on the physicochemical properties of whey protein isolate (WPI) stabilized oil-in-water (O/W) emulsions containing 20% v/v menhaden oil was investigated. The apparent viscosity of the emulsions containing XG/LBG mixtures was significantly higher (p < 0.05) than the emulsions containing either XG or LBG alone at higher concentrations of XG/LBG mixtures. Locust bean gum showed the greatest phase separation, followed by XG. Microstructure images showed depletion flocculation at lower biopolymer concentrations, and thus let led to an increase in creaming in stability and apparent viscosity of the emulsions. Addition of 0.15, 0.2 and 0.5 wt% XG/LBG mixtures greatly decreased the creaming of the emulsions. The rate of lipid oxidation for 8-week storage was significantly lower (p <0.05) in emulsions containing XG/LBG mixtures than in emulsions containing either of the biopolymer alone
Approaching nearly zero energy of PV direct air conditioners by integrating building design, load flexibility and PCM
No full textThe energy matching of PV driven air conditioners is influenced by building load demand and PV generation. Merely increasing energy performance of building or PV capacity separately may improve the energy balance on a large time resolution, the real-time energy mismatching problem is still serious. In this study, a coordinated optimization method of PV capacity, building design, and load flexibility is proposed for improving the real-time energy matching of PVAC system. Then, a methodology integrating data mining method (XG Boost) and parametric simulation was developed to identify the determinant parameters of PV system and building design, exploring feature importance and correlations. The results of XG Boost indicate that the PV capacity, shape factor, and SHGC are the most critical factors. Finally, based on the optimized building design, the PCM layer was applied to improve the real time energy matching. To achieve a goal of 90 % ZEP, the PCM capacity can be decreased by 50.4 % and 62.8 % in Guangzhou and Shanghai in the optimized building. Moreover, the PV capacity can be reduced by 23 % in Guangzhou. The findings of this study provide practical guidance for designing PVAC system coupling with building design and energy storage devices.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.Environmental & Climate Desig
Circularly Polarized Lens Antenna for Tbps Wireless Communications
No full textThe exponentially increasing demand for highspeed wireless links can be only efficiently satisfied with the development of future XG wireless communication networks, based on higher carrier signal frequencies, starting from 100 GHz. In this contribution, a circularly polarized G-band leaky-wave fed lens antenna with an integrated dielectric grid polarizer is presented, which can fulfill the challenging requirements for these future XG networks. A design is proposed in low dielectric permittivity material with a feed matching better than -10dB over a 44 % of relative bandwidth. The circularly polarized lens aperture efficiency is higher than 75% over a 35 % relative bandwidth, with an axial ratio lower than 3dB. Analytical tools have been applied to optimize the lens aperture efficiency, validating the results via full wave simulations. A lens prototype has been now fabricated and is currently being measured.Accepted author manuscriptTera-Hertz Sensin
THE EFFECTS OF OXYETHYLENE AND METHYLENE GROUPS ON THE INTERACTION BETWEEN ANIONIC AND CATIONIC SURFACTANTS
No full textThe surface tension of aqueous solutions of the 1 : 1 mixed anionic-cationic surfactant systems C8H17(OC2H4)nSO4Na-C8H17(OC2H4)3NC5H5Cl (C8EnS-C8E3Py) C8H17NC5H5Br-C8E3S (C8Py-C8E3S) CmH2m+1NC5H5Br-C8E3S (CmPy-C8E3S), where n=0, 1, 3 and m=8, 10, 12, 14, have been measured. From the surface tension-log concentration (gamma-log C) curves, the critical micelle concentration (CMC), the surface tension at the CMC, gamma(CMC), and the saturated surface adsorption of various systems were determined, and the molecular interaction parameter beta(m) and the mole fractions (x1m, x2m) of the two components in the mixed micelles were calculated. The results have shown that (1) the interaction between C8EnS and C8Py (or C8E3Py) becomes weaker as n increases, and (2) the interaction between C8E3S and C(m)Py becomes stronger as m increases. It is noted that the interaction between C8S and C8E3Py is significantly greater than that between C8E3S and C8Py. An explanation based on the electropositivity of the oxyethylene (EO) group is presented. The smaller interaction between components of the polyoxyethylenated anionic-cationic surfactants may be ascribed to the hydrophilicity and the steric hindrance effect of the EO group.Chemistry, PhysicalSCI(E)EI15ARTICLE3-4185-1906
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