Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 49
Filtrar
1.
J Environ Manage ; 364: 121433, 2024 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-38878574

RESUMO

Lake eutrophication caused by nitrogen and phosphorus has led to frequent harmful algal blooms (HABs), especially under the unknown challenges of climate change, which have seriously damaged human life and property. In this study, a coupled SWAT-Bayesian Network (SWAT-BN) model framework was constructed to elucidate the mechanisms between non-point source nitrogen pollution in agricultural lake watersheds and algal activities. A typical agricultural shallow lake basin, the Taihu Basin (TB), China, was chosen in this study, aiming to investigate the effectiveness of best management practices (BMPs) in controlling HABs risks in TB. By modeling total nitrogen concentration of Taihu Lake from 2007 to 2022 with four BMPs (filter strips, grassed waterway, fertilizer application reduction and no-till agriculture), the results indicated that fertilizer application reduction proved to be the most effective BMP with 0.130 of Harmful Algal Blooms Probability Reduction (HABs-PR) when reducing 40% of fertilizer, followed by filter strips with 0.01 of HABs-PR when 4815ha of filter strips were conducted, while grassed waterway and no-till agriculture showed no significant effect on preventing HABs. Furthermore, the combined practice between 40% fertilizer application reduction and 4815ha filter strips construction showed synergistic effects with HABs-PR increasing to 0.171. Precipitation and temperature data were distorted to model scenarios of extreme events. As a result, the combined approach outperformed any single BMP in terms of robustness under extreme climates. This research provides a watershed-level perspective on HABs risks mitigation and highlights the strategies to address HABs under the influence of climate change.


Assuntos
Agricultura , Teorema de Bayes , Proliferação Nociva de Algas , Lagos , Agricultura/métodos , Fertilizantes/análise , Nitrogênio/análise , China , Mudança Climática , Fósforo/análise , Eutrofização , Modelos Teóricos
2.
Int J Mol Sci ; 24(15)2023 Jul 27.
Artigo em Inglês | MEDLINE | ID: mdl-37569443

RESUMO

Binders mixed with explosives to form polymer-bonded explosives (PBXs) can reduce the sensitivity of the base explosive by improving interfacial interactions. The interface formed between the binder and matrix explosive also affects the thermal conductivity. Low thermal conductivity may result in localized heat concentration inside the PBXs, causing the detonation of the explosive. To investigate the binder-explosive interfacial interactions and thermal conductivity, PBXs with polyurethane as the binder and 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane/2,4,6-trinitrotoluene (CL-20/TNT) co-crystal as the matrix explosive were investigated through molecular dynamics (MD) simulations and reverse non-equilibrium molecular dynamics (rNEMD) simulation. The analysis of the pair correlation function revealed that there are hydrogen bonding interactions between Estane5703 and CL-20/TNT. The length of the trigger bonds was adopted as a theoretical criterion of sensitivity, and the effect of polymer binders on the sensibility of PBXs was correlated by analyzing the interfacial trigger bonds and internal trigger bonds of PBXs for the first time. The results indicated that the decrease in sensitivity of CL-20/TNT mainly comes from the CL-20/TNT contact with Estane5703. Therefore, the sensitivity of CL-20/TNT-based PBXs can be further reduced by increasing the contact area between CL-20/TNT and Estane5703. The thermal conductivity of PBXs composed of Estane5703 and CL-20/TNT (0 0 1), (0 1 0) and (1 0 0) crystal planes, respectively, were calculated through rNEMD simulations, and the results showed that only the addition of Estane5703 to the (1 0 0) crystal plane can improve the thermal conductivity of PBX100.


Assuntos
Substâncias Explosivas , Trinitrotolueno , Substâncias Explosivas/química , Simulação de Dinâmica Molecular , Polímeros/química , Condutividade Térmica , Trinitrotolueno/análise , Trinitrotolueno/química
3.
Environ Sci Technol ; 56(1): 175-184, 2022 01 04.
Artigo em Inglês | MEDLINE | ID: mdl-34898191

RESUMO

Biogenic volatile organic compound (BVOC) emissions have long been known to play vital roles in modulating the formation of ozone and secondary organic aerosols (SOAs). While early studies have evaluated their impact globally or regionally, the BVOC emissions emitted from urban green spaces (denoted as U-BVOC emissions) have been largely ignored primarily due to the failure of low-resolution land cover in resolving such processes, but also because their important contribution to urban BVOCs was previously unrecognized. In this study, by utilizing a recently released high-resolution land cover dataset, we develop the first set of emission inventories of U-BVOCs in China at spatial resolutions as high as 1 km. This new dataset resolved densely distributed U-BVOCs in urban core areas. The U-BVOC emissions in megacities could account for a large fraction of total BVOC emissions, and the good agreement of the interannual variations between the U-BVOC emissions and ozone concentrations over certain regions stresses their potentially crucial role in influencing ozone variations. The newly constructed U-BVOC emission inventory is expected to provide an improved dataset to enable the research community to re-examine the modulation of BVOCs on the formation of ozone, SOA, and atmospheric chemistry in urban environments.


Assuntos
Poluentes Atmosféricos , Ozônio , Compostos Orgânicos Voláteis , Poluentes Atmosféricos/análise , China , Ozônio/análise , Parques Recreativos
4.
Molecules ; 26(16)2021 Aug 12.
Artigo em Inglês | MEDLINE | ID: mdl-34443464

RESUMO

In order to better understand the role of binder content, molecular dynamics (MD) simulations were performed to study the interfacial interactions, sensitivity and mechanical properties of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane/2,4,6-trinitrotoluene (CL-20/TNT) based polymer-bonded explosives (PBXs) with fluorine rubber F2311. The binding energy between CL-20/TNT co-crystal (1 0 0) surface and F2311, pair correlation function, the maximum bond length of the N-NO2 trigger bond, and the mechanical properties of the PBXs were reported. From the calculated binding energy, it was found that binding energy increases with increasing F2311 content. Additionally, according to the results of pair correlation function, it turns out that H-O hydrogen bonds and H-F hydrogen bonds exist between F2311 molecules and the molecules in CL-20/TNT. The length of trigger bond in CL-20/TNT were adopted as theoretical criterion of sensitivity. The maximum bond length of the N-NO2 trigger bond decreased very significantly when the F2311 content increased from 0 to 9.2%. This indicated increasing F2311 content can reduce sensitivity and improve thermal stability. However, the maximum bond length of the N-NO2 trigger bond remained essentially unchanged when the F2311 content was further increased. Additionally, the calculated mechanical data indicated that with the increase in F2311 content, the rigidity of CL-20/TNT based PBXs was decrease, the toughness was improved.

5.
Am Heart J ; 202: 109-115, 2018 08.
Artigo em Inglês | MEDLINE | ID: mdl-29933147

RESUMO

Depression and acute coronary syndromes (ACS) are both common public health challenges. Patients with ACS often develop depression, which in turn adversely affects prognosis. Low-cost, sustainable, and effective service models that integrate depression care into the management of ACS patients to reduce depression and improve ACS outcomes are critically needed. Integrating Depression Care in ACS patients in Low Resource Hospitals in China (I-CARE) is a multicenter, randomized controlled trial to evaluate the efficacy of an 11-month integrated care (IC) intervention compared to usual care (UC) in management of ACS patients. Four thousand inpatients will be recruited and then randomized in a 1:1 ratio to an IC intervention consisting of nurse-led risk factor management, group-based counseling supplemented by individual problem-solving therapy, and antidepressant medications as needed, or to UC. The primary outcomes are depression symptoms measured by the Patient Health Questionnaire-9 at 6 and 12 months. Secondary endpoints include anxiety measured by the Generalized Anxiety Disorder-7; quality of life measured by the EQ-5D at 6 and 12 months; and major adverse events including the combined end point of all-cause death, suicide attempts, nonfatal myocardial infarction, nonfatal stroke, and all-cause rehospitalization at yearly intervals for a median follow-up of 2 years. Analyses of the cost-effectiveness and cost-utility of IC also will be performed. I-CARE trial will be the largest study to test the effectiveness of an integrated care model on depression and cardiovascular outcomes among ACS patients in resource-limited clinical settings.


Assuntos
Síndrome Coronariana Aguda/psicologia , Antidepressivos/uso terapêutico , Transtorno Depressivo/terapia , Síndrome Coronariana Aguda/enfermagem , Síndrome Coronariana Aguda/terapia , Ansiedade , China , Análise Custo-Benefício , Transtorno Depressivo/complicações , Transtorno Depressivo/tratamento farmacológico , Recursos em Saúde , Humanos , Medicina Integrativa , Projetos de Pesquisa
6.
Sensors (Basel) ; 18(11)2018 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-30445681

RESUMO

The Chengdu⁻Chongqing Economic Zone (CCEZ), which is located in southwestern China, is the fourth largest economic zone in China. The rapid economic development of this area has resulted in many environmental problems, including extremely high concentrations of nitrogen dioxide (NO2) and fine particulate matter (PM2.5). However, current ground observations lack spatial and temporal coverage. In this study, satellite remote sensing techniques were used to analyze the variation in NO2 and PM2.5 from 2005 to 2015 in the CCEZ. The Ozone Monitoring Instrument (OMI) and the Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol optical depth (AOD) product were used to retrieve tropospheric NO2 vertical columns and estimate ground-level PM2.5 concentrations, respectively. Geographically, high NO2 concentrations were mainly located in the northwest of Chengdu and southeast of Chongqing. However, high PM2.5 concentrations were mainly located in the center areas of the basin. The seasonal average NO2 and PM2.5 concentrations were both highest in winter and lowest in summer. The seasonal average NO2 and PM2.5 were as high as 749.33 × 1013 molecules·cm-2 and 132.39 µg·m-3 in winter 2010, respectively. Over 11 years, the annual average NO2 and PM2.5 values in the CCEZ increased initially and then decreased, with 2011 as the inflection point. In 2007, the concentration of NO2 reached its lowest value since 2005, which was 230.15 × 1013 molecules·cm-2, and in 2015, the concentration of PM2.5 reached its lowest value since 2005, which was 26.43 µg·m-3. Our study demonstrates the potential use of satellite remote sensing to compensate for the lack of ground-observed data when quantitatively analyzing the spatial⁻temporal variations in regional air quality.

8.
J Phys Chem A ; 121(36): 6732-6741, 2017 Sep 14.
Artigo em Inglês | MEDLINE | ID: mdl-28862852

RESUMO

We used crossed laser-molecular beam scattering to study the primary photodissociation channels of chloroacetaldehyde (CH2ClCHO) at 157 nm. In addition to the C-Cl bond fission primary photodissociation channel, the data evidence two other photodissociation channels: HCl photoelimination and C-C bond fission. This is the first direct evidence of the C-C bond fission channel in chloroacetaldehyde, and we found that it significantly competes with the C-Cl bond fission channel. We determined the total primary photodissociation branching fractions for C-Cl fission:HCl elimination:C-C fission to be 0.65:0.07:0.28. The branching between the primary channels suggests the presence of interesting excited state dynamics in chloroacetaldehyde. Some of the vinoxy radicals from C-Cl photofission and most of the ketene cofragments formed in HCl photoelimination have enough internal energy to undergo secondary dissociation. While our previous velocity map imaging study on the photodissociation of chloroacetaldehyde at 157 nm focused on the barrier for the unimolecular dissociation of vinoxy to H + ketene, this work shows that the HCl elimination channel contributed to the high kinetic energy portion of the m/z = 42 signal in that study.

9.
Lipids Health Dis ; 16(1): 155, 2017 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-28810873

RESUMO

BACKGROUND: The evidence of adherence to statin decreasing risk of major adverse cardiovascular events (MACEs) is still lack among patients discharged with acute coronary syndrome (ACS). Our objective is to determine the relationship between six-month adherence to statins and subsequent risk of MACEs in patients discharged with ACS. METHODS: Using two prospective registry cohorts (CPACS-1 and -2), we analyzed data from 12,516 consecutive patients with ACS who were prescribed statin at hospital discharge and survived beyond 6 months without recurrent myocardial infarction (MI) or stroke. Adherence to statin was defined as good (using statin at discharge and 6 months without declined dosage) and poor adherence groups (using statin at discharge but declining dosage or stopping at 6 months). We compared the hazard ratios of all-cause mortality and MACE in subsequent 6 months between groups, using Cox-regression models, adjusting for multiple potential confounders. RESULTS: Seventy two percent of patients adhered to statin therapy at 6 months. The incident MACE in the poor adherence group was significantly higher than in good adherence group (2.7% vs. 1.8%, p = 0.002). Compared with poor adherence group, the good adherence group showed a 27% lower relative risk of MACE during the 6 month follow up (fully-adjusted hazard ratio (HR) = 0.73; 95%CI: 0.56-0.97). The protective effects of good adherence were similar in groups with different statin dose as well as groups by other baseline clinical characteristics and treatments (p > 0.05 for interaction). CONCLUSION: Our study highlights the importance of adherence to statin therapy in prevention of MACE and clinicians should aim to achieve higher dosage if tolerable. CLINICAL TRIAL REGISTRATION: CPACS2 was registered on URL: http://www.anzctr.org.au/default.aspx and unique identifier is ACTRN12609000491268 . CPACS1 was not a clinical trial and thus not registered.


Assuntos
Síndrome Coronariana Aguda/tratamento farmacológico , Inibidores de Hidroximetilglutaril-CoA Redutases/uso terapêutico , Hipolipemiantes/uso terapêutico , Adesão à Medicação/estatística & dados numéricos , Infarto do Miocárdio/prevenção & controle , Sistema de Registros , Síndrome Coronariana Aguda/complicações , Síndrome Coronariana Aguda/fisiopatologia , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Infarto do Miocárdio/etiologia , Infarto do Miocárdio/fisiopatologia , Modelos de Riscos Proporcionais , Estudos Prospectivos , Risco , Fatores de Tempo
10.
Guang Pu Xue Yu Guang Pu Fen Xi ; 36(12): 3817-24, 2016 Dec.
Artigo em Chinês | MEDLINE | ID: mdl-30234943

RESUMO

Frequent occurring of haze pollution events and high fine particulate matter (PM(2.5)) concentration in China have attracted more and more attention in the world. Satellite remote sensing can be used to characterize the air pollution. However, haze is usually misidentified as fog, thin cloud or bright surface in NASA's Moderate Resolution Imaging Spectrometer (MODIS) cloud and clear days' aerosol products, and the retrieval of its optical properties is not included in MODIS cloud detection and dark target algorithm. This approach first studies the spectral characters of cloud, fog, haze, and land cover pixels. Second, following the previous cloud detection and aerosol retrieval literatures, a threshold algorithm is developed to distinguish haze from other pixels based on MODIS multi-band apparent reflectance and brightness temperature. This algorithm is used to detect the haze distribution over North China Plain in 2008 spring and summer. Our result shows a good agreement with the true-color satellite images, which enhances MODIS's ability to monitor the severe air pollution episodes. In addition, the high AOD data from Beijing and Xiang Aerosol Robotic NETwork (AERONET) sites indicate nearly 80% haze days are detected by our approach. Finally, we analyze the errors and uncertainties in haze detection algorithm, and put forward the potential improvements.

11.
Am Heart J ; 169(3): 349-55, 2015 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-25728724

RESUMO

BACKGROUND: Acute coronary syndromes (ACSs) are a major cause of morbidity and mortality, yet effective ACS treatments are frequently underused in clinical practice. Randomized trials including the CPACS-2 study suggest that quality improvement initiatives can increase the use of effective treatments, but whether such programs can impact hard clinical outcomes has never been demonstrated in a well-powered randomized controlled trial. DESIGN: The CPACS-3 study is a stepped-wedge cluster-randomized trial conducted in 104 remote level 2 hospitals without PCI facilities in China. All hospitalized ACS patients will be recruited consecutively over a 30-month period to an anticipated total study population of more than 25,000 patients. After a 6-month baseline period, hospitals will be randomized to 1 of 4 groups, and a 6-component quality improvement intervention will be implemented sequentially in each group every 6months. These components include the following: establishment of a quality improvement team, implementation of a clinical pathway, training of physicians and nurses, hospital performance audit and feedback, online technical support, and patient education. All patients will be followed up for 6months postdischarge. The primary outcome will be the incidence of in-hospital major adverse cardiovascular events comprising all-cause mortality, myocardial infarction or reinfarction, and nonfatal stroke. CONCLUSIONS: The CPACS-3 study will be the first large randomized trial with sufficient power to assess the effects of a multifaceted quality of care improvement initiative on hard clinical outcomes, in patients with ACS.


Assuntos
Síndrome Coronariana Aguda/terapia , Doenças Cardiovasculares/prevenção & controle , Avaliação de Resultados em Cuidados de Saúde , Melhoria de Qualidade/organização & administração , Ensaios Clínicos Controlados Aleatórios como Assunto , Síndrome Coronariana Aguda/complicações , Doenças Cardiovasculares/epidemiologia , China , Procedimentos Clínicos , Humanos , Infarto do Miocárdio/epidemiologia , Recidiva , Projetos de Pesquisa , Prevenção Secundária , Acidente Vascular Cerebral/epidemiologia
12.
Guang Pu Xue Yu Guang Pu Fen Xi ; 35(3): 739-45, 2015 Mar.
Artigo em Chinês | MEDLINE | ID: mdl-26117890

RESUMO

Biomass burning makes up an important part of both trace gases and particulate matter emissions, which can efficiently degrade air quality and reduce visibility, destabilize the global climate system at regional to global scales. Burned area is one of the primary parameters necessary to estimate emissions, and considered to be the largest source of error in the emission inventory. Satellite-based fire observations can offer a reliable source of fire occurrence data on regional and global scales, a variety of sensors have been used to detect and map fires in two general approaches: burn scar mapping and active fire detection. However, both of the two approaches have limitations. In this article, we explore the relationship between hotspot data and burned area for the Southeastern United States, where a significant amount of biomass burnings from both prescribed and wild fire took place. MODIS (Moderate resolution imaging spectrometer) data, which has high temporal-resolution, can be used to monitor ground biomass. burning in time and provided hot spot data in this study. However, pixel size of MODIS hot spot can't stand for the real ground burned area. Through analysis of the variation of vegetation band reflectance between pre- and post-burn, we extracted the burned area from Landsat-5 TM (Thematic Mapper) images by using the differential normalized burn ratio (dNBR) which is based on TM band4 (0.84 µm) and TM band 7(2.22 µm) data. We combined MODIS fire hot spot data and Landsat-5 TM burned scars data to build the burned area estimation model, results showed that the linear correlation coefficient is 0.63 and the relationships vary as a function of vegetation cover. Based on the National Land Cover Database (NLCD), we built burned area estimation model over different vegetation cover, and got effective burned area per fire pixel, values for forest, grassland, shrub, cropland and wetland are 0.69, 1.27, 0.86, 0.72 and 0.94 km2 respectively. We validated the burned area estimates by using the ground survey data from National interagency Fire Center (NIFC), our results are more close to the ground survey data than burned area from Global Fire Emissions Database (GFED) and MODIS burned area product (MCD45), which omitted many small prescribed fires. We concluded that our model can provide more accurate burned area parameters for developing fire emission inventory, and be better for estimating emissions from biomass burning.


Assuntos
Biomassa , Incêndios , Imagens de Satélites , Desastres , Modelos Teóricos , Sudeste dos Estados Unidos , Análise Espectral
13.
Guang Pu Xue Yu Guang Pu Fen Xi ; 34(3): 729-34, 2014 Mar.
Artigo em Chinês | MEDLINE | ID: mdl-25208402

RESUMO

In the present, for the characteristic of HJ-1 CCD camera, after receiving aerosol optical depth (AOD) from deep blue algorithm which was developed by Hsu et al. assisted by MODerate-resolution imaging spectroradiometer (MODIS) surface reflectance database, bidirectional reflectance distribution function (BRDF) correction with Kernel-Driven Model, and the calculation of viewing geometry with auxiliary data, a new atmospheric correction method of HJ-1 CCD was developed which can be used over vegetation, soil and so on. And, when the CCD data is processed to correct atmospheric influence, with look up table (LUT) and bilinear interpolation, atmospheric correction of HJ-1 CCD is completed quickly by grid calculation of atmospheric parameters and matrix operations of interface define language (IDL). The experiment over China North Plain on July 3rd, 2012 shows that by our method, the atmospheric influence was corrected well and quickly (one CCD image of 1 GB can be corrected in eight minutes), and the reflectance after correction over vegetation and soil was close to the spectrum of vegetation and soil. The comparison with MODIS reflectance product shows that for the advantage of high resolution, the corrected reflectance image of HJ-1 is finer than that of MODIS, and the correlation coefficient of the reflectance over typical surface is greater than 0.9. Error analysis shows that the recognition error of aerosol type leads to 0. 05 absolute error of surface reflectance in near infrared band, which is larger than that in visual bands, and the 0. 02 error of reflectance database leads to 0.01 absolute error of surface reflectance of atmospheric correction in green and red bands.

14.
Zhonghua Xin Xue Guan Bing Za Zhi ; 42(2): 156-60, 2014 Feb.
Artigo em Chinês | MEDLINE | ID: mdl-24735629

RESUMO

OBJECTIVE: To explore the current status on traditional Chinese medicine (TCM) use for hospitalized acute coronary syndrome patients in China's level 2 hospitals, and to explore associated factors of TCM use for these patients. METHODS: This survey was performed in 102 level 2 hospitals from 15 provinces or autonomous region in China. Patients admitted to these hospitals with acute coronary syndrome during September 2011 to May 2012 were eligible for this study. Information on TCM use was obtained from their medical records. Chi-square test and logistic regression analysis were used to explore the related factors of TCM use in these patients. RESULTS: We recruited 5 432 acute coronary syndrome patients in this study, TCM was applied to 3 503 patients (64.5%). Multivariable logistic regression showed that pre-hospital TCM use was positively related with in-hospital TCM use (OR = 2.08, P < 0.01) , while pre-hospital use of 4 medicines recommended by the guidelines(including aspirin/clopidogrel, ß acceptor blocker, stain and angiotensin converting enzyme inhibitor/angiotensin converting enzyme receptor blocker ), being a smoker and diagnosis of myocardial infarction rather than unstable angina at hospital discharge were negatively related with in-hospital TCM use (the ORs were 0.58, 0.78 and 0.71, respectively, all P < 0.01). The TCM use varied significantly between regions. Taking southwest region as a reference, the ORs varied between 2.98-13.37 (all P < 0.01) in eastern China, south China, central China, north China, northwest and northeast regions. CONCLUSIONS: TCM is widely used in hospitalized acute coronary syndrome patients in China's resource-constrained level 2 hospitals. Pre-hospital TCM use is positively correlated with in-hospital TCM use for these patients.


Assuntos
Síndrome Coronariana Aguda/tratamento farmacológico , Medicamentos de Ervas Chinesas/uso terapêutico , Idoso , China , Estudos Transversais , Feminino , Humanos , Pacientes Internados , Modelos Logísticos , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos
15.
ACS Omega ; 9(3): 4013-4018, 2024 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-38284042

RESUMO

Molecular dynamics (MD) simulations were performed on the energetic molecular perovskite (C6H14N2)[NH4(ClO4)3], with excellent detonation properties, thermal stability, and high specific impulse, which is a potential replacement for AP as the next generation propellants. The cohesive energy density, binding energy, pair correlation function, maximum bond length (Lmax) of the N-H trigger bond, and mechanical properties of the (C6H14N2)[NH4(ClO4)3] were reported. The calculated cohesive energy density and binding energy decrease with increasing temperature, indicating a gradual decrease in the thermal stability with temperature. In addition, H···O hydrogen bonding interactions have been found based on the results of pairwise correlation functions. The maximum length (Lmax) of the N-H trigger bond was calculated and used as a criterion to theoretically judge the impact sensitivity. The maximum bond length of the N-H trigger bond grows gradually with temperature; however, it does very slightly yet gradually above 373 K. This suggests that an increase in temperature leads to a higher impact sensitivity and lower thermal stability. However, this effect becomes less pronounced when the temperature surpasses 373 K. Moreover, the calculated mechanical data indicate that as the temperature rises, the material's stiffness, hardness, yield strength, and fracture strength all decrease. The material's ductility shows an upward trend with increasing temperature, reaching its peak at 373 K and subsequently declining as the temperature continues to rise.

16.
Heliyon ; 10(10): e30710, 2024 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-38765023

RESUMO

In this paper, in order to establish the energy separation mechanism of the vortex tube, the hydrodynamic behavior of the compressible fluid in the asymmetric cavity space is investigated, and a numerical model of the trajectory deflection behavior is deduced and established; in order to form the optimal design method of the structural parameters of the vortex tube, the force situation of the fluid microelements entering different regions of the vortex chamber of the vortex tube is analyzed, and the trajectory deflection equations are corrected by combining with the expansion behavior of the fluid and the characterizing equations of vortex strength, transportability, and vortex initiation characteristics are given. The characterization equations of vortex strength, transportability and vortex initiation characteristics are given, and the numerical simulation of their influence parameters is carried out; in order to realize the prediction of the vortex tube performance of a given structure, the multifactor Pearson thermodynamic map is used to correlate and analyze the experimental data of vortex tubes reported publicly in the past years, and the polynomial regression equations are designed and established for the prediction of the vortex tube's energy separation effect and the confidence level and the degree of coincidence of the prediction results are examined. The confidence level and degree of agreement of the prediction results were examined. It is found that: the trajectory deflection motion of the compressible fluid in the asymmetric cavity space is the result of the combined effect of structural air pressure bias and the expansion behavior of the incident fluid; in order to improve the vortex strength in the vortex tube, the vortex initiation chamber space should be as small as possible; the increase of the diameters of the hot-end pipe and the cold-end pipe is conducive to the enhancement of vortex strength, but at the same time, it weakens the vortex transport in the heat pipe; the vortex initiation chamber size has a negative correlation with the hot-end temperature rise, and the inlet fluid pressure has a The negative correlation between the size of the vortex chamber and the temperature rise at the hot end, the positive correlation between the increase of inlet fluid pressure and the resulting temperature rise, and the strong correlation between the inlet fluid pressure and the friction coefficient on the effect of energy separation; the predictive equations for the effect of energy separation obtained by the fitting are in good agreement with the real situation.

17.
Foods ; 12(3)2023 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-36766065

RESUMO

More than half of the people on Earth get their calories, proteins, and minerals from rice grains. Staple increases in the quantity and quality of rice grains are key to ending hunger and malnutrition. Rice production, however, is vulnerable to climate change, and the climate on Earth is becoming more fluctuating with the atmospheric change induced by human activities. As a result, the impacts of climate change on rice grain (ICCRG) have sparked widespread concern. In order to reveal the development and the trend in the study on the ICCRG, a bibliometric analysis was conducted. The results showed that both the model simulations and the field experiment-based observations, as reflected by APSIM (the Agricultural Production Systems sIMulator) and free-air carbon dioxide (CO2) enrichment, are of concern to researchers worldwide, especially in China, India, the United States, and Japan. Different types of warming include short-term, nighttime, soil and water, and canopy, and their interactions with other climate factors, such as CO2, or agronomic factors, such as nitrogen level, are also of concern to researchers. Spatiotemporal variations in changing weather and regional adaptations from developed and developing countries are challenging the evaluation of ICCRG from an economic perspective. In order to improve the efficacy of breeding adaptable cultivars and developing agronomic management, interdisciplinary studies integrating molecular biology, plant physiology, agronomy, food chemistry, ecology, and socioeconomics are needed.

18.
Environ Sci Pollut Res Int ; 30(46): 102231-102243, 2023 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-37665441

RESUMO

Global warming is currently an area of concern. Human activities are the leading cause of urban greenhouse gas intensification. Inversing the spatial distribution of carbon emissions at microscopic scales such as communities or controlling detailed planning plots can capture the critical emission areas of carbon emissions, thus providing scientific guidance for intracity low-carbon development planning. Using the Sino-Singapore Tianjin Eco-city as an example, this paper uses night-light images and statistical yearbooks to perform linear fitting within the Beijing-Tianjin-Hebei city-county region and then uses fine-scale data such as points of interest, road networks, and mobile signaling data to construct spatial characteristic indicators of carbon emissions distribution and assign weights to each indicator through the analytic hierarchy process. As a result, the spatial distribution of carbon emissions based on detailed control planning plots is calculated. The results show that among the selected indicators, the population distribution significantly influences carbon emissions, with a weight of 0.384. The spatial distribution of carbon emissions is relatively distinctive. The primary carbon emissions are from the Sino-Singapore Cooperation Zone due to its rapid urban construction and development. In contrast, carbon emissions from other areas are sparse, as there is mostly unused land under construction.

19.
Res Sq ; 2023 Dec 12.
Artigo em Inglês | MEDLINE | ID: mdl-38168284

RESUMO

Ambient PM2.5 pollution is recognized as a leading environmental risk factor, causing significant mortality and morbidity in China. However, the specific contributions of individual PM2.5 constituents remain unclear, primarily due to the lack of a comprehensive ground monitoring network for constituents. This issue is particularly critical for carbonaceous species such as organic carbon (OC) and elemental carbon (EC), which are known for their significant health impacts, and understanding the OC/EC ratio is crucial for identifying pollution sources. To address this, we developed a Super Learner model integrating Multi-angle Imaging SpectroRadiometer (MISR) retrievals to predict daily OC concentrations across China from 2003 to 2019 at a 10-km spatial resolution. Our model demonstrates robust predictive accuracy, as evidenced by a random cross-validation R2 of 0.84 and an RMSE of 4.9 µg/m3, at the daily level. Although MISR is a polar-orbiting instrument, its fractional aerosol data make a significant contribution to the OC exposure model. We then use the model to explore the spatiotemporal distributions of OC and further calculate the EC/OC ratio in China. We compared regional pollution discrepancies and source contributions of carbonaceous pollution over three selected regions: Beijing-Tianjin-Hebei, Fenwei Plain, and Yunnan Province. Our model observes that OC levels are elevated in Northern China due to industrial operations and central heating during the heating season, while in Yunnan, OC pollution is mainly contributed by local forest fires during fire seasons. Additionally, we found that OC pollution in China is likely influenced by climate phenomena such as the El Niño-Southern Oscillation. Considering that climate change is increasing the severity of OC concentrations with more frequent fire events, and its influence on OC formation and dispersion, we suggest emphasizing the role of climate change in future OC pollution control policies. We believe this study will contribute to future epidemiological studies on OC, aiding in refining public health guidelines and enhancing air quality management in China.

20.
Guang Pu Xue Yu Guang Pu Fen Xi ; 32(3): 775-80, 2012 Mar.
Artigo em Chinês | MEDLINE | ID: mdl-22582651

RESUMO

With the urbanizing in China, haze days occur frequently, which have largely impacted air quality. In the present paper, based on haze physical properties, haze optical properties were calculated by Mie theory and apparent reflectance of haze in Environment Satellite 1 (HJ-1) channels was simulated by Radiative Transfer (RT) 3. Simulated results show that it is reasonable to extract the haze from apparent reflectance in the first and second channels. By Deep Blue algorithm, Haze Optical Depth (HOD) was retrieved from HJ-1 data supported by reflectance database from MODIS product. From HJ-1 data in 2009 over Beijing area, the haze days were monitored and validated by AERONET/PHOTONS Beijing site. The validation shows that the correlation coefficient of HOD is greater than 0.9, but HOD from HJ-1 is greater than that from ground-based measurements. The discussions show that the error from reflectance database is less than 0.1 and radiance resolution of HJ-1 needs to advance for haze monitoring.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA