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Natural gas foam can be used for mobility control and channel blocking during natural gas injection for enhanced oil recovery, in which stable foams need to be used at high reservoir temperature, high pressure and high water salinity conditions in field applications. In this study, the performance of methane (CH4) foams stabilized by different types of surfactants was tested using a high pressure and high temperature foam meter for surfactant screening and selection, including anionic surfactant (sodium dodecyl sulfate), non‐anionic surfactant (alkyl polyglycoside), zwitterionic surfactant (dodecyl dimethyl betaine) and cationic surfactant (dodecyl trimethyl ammonium chloride), and the results show that CH4‐SDS foam has much better performance than that of the other three surfactants. The influences of gas types (CH4, N2, and CO2), surfactant concentration, temperature (up to 110°C), pressure (up to 12.0 MPa), and the presence of polymers as foam stabilizer on foam performance was also evaluated using SDS surfactant. The experimental results show that the stability of CH4 foam is better than that of CO2 foam, while N2 foam is the most stable, and CO2 foam has the largest foam volume, which can be attributed to the strong interactions between CO2 molecules with H2O. The foaming ability and foam stability increase with the increase of the SDS concentration up to 1.0 wt% (0.035 mol/L), but a further increase of the surfactant concentration has a negative effect. The high temperature can greatly reduce the stability of CH4‐SDS foam, while the foaming ability and foam stability can be significantly enhanced at high pressure. The addition of a small amount of polyacrylamide as a foam stabilizer can significantly increase the viscosity of the bulk solution and improve the foam stability, and the higher the molecular weight of the polymer, the higher viscosity of the foam liquid film, the better foam performance. [ABSTRACT FROM AUTHOR]

Identifying and separating the signal of urbanization effects in current temperature data series is essential for accurately detecting, attributing, and projecting mean and extreme temperature change on varied spatial scales. This paper proposes a new method based on machine learning to classify the observational stations into rural stations and urban stations. Based on the classification of rural and urban stations, the global and regional land annual mean and extreme temperature indices series over 1951–2018 for all stations and rural stations were calculated, and the urbanization effects and the urbanization contribution of global land annual mean and extreme temperature indices series are quantitatively evaluated using the difference series between all stations and the rural stations. The results showed that the global land annual mean time series for mean temperature and most extreme temperature indices experienced statistically significant urbanization effects. The urbanization effects in the mean and extreme temperature indices series generally occurred after the mid-1980s, and there were significant differences of the magnitudes of urbanization effects among different regions. The urbanization effect on the trends of annual mean and extreme temperature indices series in East Asia is generally the strongest, which is consistent with the rapidly urbanization process in the region over the past decades, but it is generally small in Europe during the recent decades. [ABSTRACT FROM AUTHOR]

CO 2 foam can be used for mobility control and blocking gas breakthrough channels during CO 2 injection for enhanced oil recovery, and specially designed and formulated foam agents are needed to enhance the stability of the foams especially under reservoir conditions. In this study, the performance of CO 2 foams with various surfactants has been investigated, including amide based surfactants (e.g. coconut monoethanol amide (CMEA), lauryl diethanol amide (LDEA)), amine based surfactants (cocoacyl propyl dimethylamine (UC 11 AMPM)), sodium dodecyl sulfate (SDS) and its mixtures with the amides and amines. A visualized high pressure and high temperature foam meter and a sand-pack flooding setup were used to assess the foam's performance, along with the surface tension measurement of the surfactant solutions in the presence of CO 2. The influence of temperature, the surface tension of the aqueous solution, and SDS on CO 2 foam performance of amide and amine based surfactant were investigated. The experimental results indicate that the amide or amine based surfactant alone all show poor foam performance, while their CO 2 foam stability and their mobility control capability can be greatly enhanced at high temperature up to 100 °C with the salinity of 50000 mg/L. After adding SDS to CMEA, LDEA, or UC 11 AMPM, an excellent synergistic effect can be formed among the molecules, which can reduce the surface tensions of individual surfactant solution and enhance the stability of CO 2 foams. • The CO 2 foam performance of amine and amide based surfactants were tested at HTHP conditions. • Stable CO 2 foams can be generated by amine surfactant with SDS at temperature up to 130 °C. • The synergistic effect of amine based surfactant with SDS has been demonstrated for CO 2 foams at high temperature. [ABSTRACT FROM AUTHOR]

The sol-gel synthesis and characterization of n≥3 Aurivillius phase thin films deposited on Pt/Ti/SiO2–Si substrates is described. The number of perovskite layers, n, was increased by inserting BiFeO3 into three layered Aurivillius phase Bi4Ti3O12 to form compounds such as Bi5FeTi3O15 (n=4). 30% of the Fe3+ ions in Bi5FeTi3O15 were substituted with Mn3+ ions to form the structure Bi5Ti3Fe0.7Mn0.3O15. The electromechanical responses of the materials were investigated using piezoresponse force microscopy and the results are discussed in relation to the crystallinity of the films as measured by x-ray diffraction. [ABSTRACT FROM AUTHOR]

Abstract: Granular and crystalline structures of resistant octenyl succinic anhydride (OSA) modified corn starch were characterized using scanning electron microscopy (SEM), optical microscopy and X-ray diffraction. As a colon-targeted delivery carrier, the releasing property of resistant OSA-modified starch was also investigated by In-vitro model. Enhanced succinylation of starch considerably increased the enzyme and acid resistibility to digestion, indicating the improvement of starch colon-targeting property as the degree of substitution (DS) increased. From In-vitro releasing assay, the resistant OSA-modified corn starch based matrix tablets could deliver bioactive components to the colon when the RS content and hydrophobicity were suitable. The relationship between the structure and In-vitro release properties of resistant OSA-modified corn starch suggests that an optimal DS and crystalline:amorphous ratio can be responsible for 5-ASA release. The matrix tablets used resistant OSA-modified corn starch with moderate DS (0.60) and V-type crystal morphology co-exist with the amorphous structure as carrier show good colon-targeted releasing properties. [Copyright &y& Elsevier]

Abstract: ZnO films were grown at low pressure in a vertical metal-organic vapor deposition (MOCVD) reactor with a rotating disk. The structural and morphological properties of the ZnO films grown at different disk rotation rate (DRR) were investigated. The growth rate increases with the increase of DRR. The ZnO film grown at the DRR of 450 revolutions per minute (rpm) has the lowest X-ray rocking curve full width at half maximum and shows the best crystalline quality and morphology. In addition, the crystalline quality and morphology are improved as the DRR increased but both are degraded when the DRR is higher than 450 rpm. These results can help improve in understanding the rotation effects on the ZnO films grown by MOCVD. [Copyright &y& Elsevier]

A variety of factors may affect the planning and design of urban infrastructure but urban population usually is the primary consideration given scaling laws between population and infrastructure. Although urban physical spatial form and infrastructure are physically attached, their allometric scaling has not been systematically addressed. In this study, we examine how five types of infrastructure, including roads, water supply pipelines, drainage pipelines, buses, and schools, affect urban spatial form characterized with landscape metrics derived for 78 large cities in China. The results suggest that urban infrastructure has scaling relations with landscape shape index (LSI), area-weighted mean perimeter-area ratio (PARA_AM), and largest patch index. Specifically, at the mean value of PARA_AM, road area increases about 2.5 times when doubling LSI. Under the same population size, cities with more fragmented spatial form need more investments in infrastructure, particularly roads and other traffic components. It is concluded that urban infrastructure experiences a super-linear quantitative relationship with landscape metrics, and a city with a more complex urban form spatially requires more infrastructure. The coefficients of the regression models show a lot of variations but the allometric scaling is meaningful for the planning and design of urban infrastructure. It will be helpful to incorporate ecological landscape metrics into urban planning and development. [ABSTRACT FROM AUTHOR]

c-axis oriented ferroelectric bismuth titanate (Bi4Ti3O12) thin films were grown on (001) strontium titanate (SrTiO3) substrates by an atomic vapor deposition technique. The ferroelectric properties of the thin films are greatly affected by the presence of various kinds of defects. Detailed x-ray diffraction data and transmission electron microscopy analysis demonstrated the presence of out-of-phase boundaries (OPBs). It is found that the OPB density changes appreciably with the amount of titanium injected during growth of the thin films. Piezo-responses of the thin films were measured by piezo-force microscopy. It is found that the in-plane piezoresponse is stronger than the out-of-plane response, due to the strong c-axis orientation of the films. [ABSTRACT FROM AUTHOR]

The valence band offset (VBO) of the wurtzite InN/ZnO heterojunction is directly determined by x-ray photoelectron spectroscopy to be 0.82±0.23 eV. The conduction band offset is deduced from the known VBO value to be 1.85∓0.23 eV, which indicates a type-I band alignment for InN/ZnO heterojunction. [ABSTRACT FROM AUTHOR]

Amine-surfactant can be converted to be cationic surfactant in water solution saturated with CO 2 , which can enhance their foaming ability and foam stability, and the foaming ability can be switched off or on by CO 2 or replacing with N 2 with heating, so the amine-surfactants have great potential for smart mobility control to gas channeling during CO 2 flooding. In this study, three alkyl propyl dimethylamines with different carbon chain length (R = 11, 17 and 22, named as UC 11 AMPM, UC 17 AMPM, and UC 22 AMPM, respectively), were investigated as CO 2 responsive foam agent, and their foam performance under static and dynamic condition was tested up to 130 °C and 10.5 MPa using a visualized foam meter and a sand-pack flooding setup. The influence of carbon chain length on bulk solution viscosity, surface activity, foaming ability, and foam quality on bulk foam stability were measured and analyzed. The experimental results indicate that the three amine surfactants all demonstrate well CO 2 responsibility and CO 2 foaming ability, and show well switchable by CO 2 and N 2 at high temperature and high pressure (HTHP) condition. With the carbon chain length increasing, the surfactant shows higher absorption on the foam films, and bulk solution has a higher viscosity, which can decrease de-foam velocity and enhance the foam stability, as a result, the surfactant shows higher mobility control ability. • The CO 2 foam performance of three amine surfactants were tested at HTHP conditions. • The influence of carbon chain length on foam performance, bulk viscosity, surface active and foam quality was analyzed. • Alkyl propyl dimethylamines have well mobility control ability to CO 2 at high temperature-tolerance (up to 130 °C). [ABSTRACT FROM AUTHOR]

Missing data were frequently found in the instrumental climatic records, which hindered the statistical analyses on climate change. A novel imputation method, called Imputation Based on Decomposition of Time Series (IBDTS), was developed in this article for the climatic data with strong seasonality and spatial correlation. It was to decompose the time series into three components first, and then to predict the missing values in each component. The trend component was predicted by regression analysis, the seasonal component was predicted by spectral analysis, and the remainder component was predicted by spatial interpolation. The IBDTS imputation method showed relatively small errors in performance, and kept the real attributes of climatic series, including the amplitude and phase with the cycle period of 12 months, and the linear trend. The sensibility to station distance for the IBDTS method was relatively small. In addition, the IBDTS method had the ability to deal with the data with none of or only a few of complete series, and it was possible to be applied not only in the field of climatology but also in other fields as long as the data had the intrinsic properties of strong seasonality and spatial correlation. [ABSTRACT FROM AUTHOR]

In China and East Asia, the long-term continuous observational data at daily resolution are insufficient, and thus there is a lack of good understanding of the extreme climate variation over the last 100 years plus. In this study, the extreme temperature indices defined by ETCCDI (Expert Team on Climate Change Detection and Indices) and local meteorological administrations were analyzed for Changchun City, Northeast China, by using the daily maximum temperature (Tmax) and daily minimum temperature (Tmin) over 1909–2018. The results showed that extreme cold events, such as cold days, cold nights, frost days, icing days, and low temperature days, decreased significantly at rates of −0.41 d (10 yr)−1, −1.45 d (10 yr)−1, −2.28 d (10 yr)−1, −1.16 d (10 yr)−1 and −1.90 d (10 yr)−1, respectively. Warm nights increased significantly at a rate of 1.71 d (10 yr)−1, but warm days decreased slightly and the number of high temperature days decreased at a rate of −0.20 d (10 yr)−1. The frequency of cold surge events increased significantly at a rate of 0.25 d (10 yr)−1, occurring mainly from the mid-1950s to late-1980s. The average Tmax, average Tmin and extreme Tmin increased at rates of 0.09°C (10 yr)−1, 0.36°C (10 yr)−1 and 0.54°C (10 yr)−1, respectively; and extreme Tmax decreased significantly at a rate of −0.17°C (10 yr)−1. In 1909−2018, 1951−2018 and 1979−2018, the indices related to cold events decreased, while the trends of the indices related to warm events were different for different periods. [ABSTRACT FROM AUTHOR]

Based on the records of drought and flood in Chinese historical documents and precipitation data during the instrumental period, and by using the five-grade classification method, this study reconstructs the drought and flood grades in the Hanjiang River Basin from 1426–2017 and analyzes their spatial and temporal variation characteristics. The results show that, on the centennial scale, drought and flood variation in the basin exhibited two dry periods (early fifteenth century to early sixteenth century, early twentieth century to the present) and one four-century long wet period (early sixteenth to early twentieth centuries), with multi-decadal drought and flood fluctuations within each period. Meanwhile, the variation shows some regional differences. For example, droughts and floods both occurred at high rates in the whole river basin during the twentieth century, with the increase in droughts relatively more remarkable in the upper reaches and the increase in floods more notable in the middle and lower reaches; throughout the study period, the drought and flood variability was larger in the upper reaches, but the drought and flood frequency was higher in the middle and lower reaches. In addition, there are a few quasi-cycles of the drought and flood variability in the middle and lower reaches, which include the quasi-cycles of 2–8 years, 10–30 years, 50 years, and 80–100 years, respectively. The upper reaches are slightly different, which have the quasi-cycles of 3–5 years, 10–30 years, and 70–80 years, respectively. [ABSTRACT FROM AUTHOR]

Foam is of practical interest in many industrial processes, and can be used for blocking gas channeling and mobility control during the process of CO 2 storage and improved oil recovery (IOR). It is important to develop new kinds of foam agents, which can tolerate high temperature and salinity under complex reservoir conditions. It is also desirable to develop chemicals that have CO 2 -sensitivity for selective channeling blocking. CO 2 -sensitivity is referred to that injected chemical can be converted into effective foam agent in formation water with CO 2 presence. In this paper, an organic amine, octadecyl dipropylene triamine, was studied in terms of chemical mechanisms for foam generation and CO 2 -sensitivity. The chemical can be converted into a Gemini surfactant like agent to generate CO 2 foams in-situ. The effects of important influencing factors on foaming performance at reservoir conditions were evaluated, including CO 2 purity, chemical concentration, temperature, pressure and water salinity. The results indicated that the amine chemical has good CO 2 -sensitivity for generation of CO 2 foams and has exhibited extraordinary features with high temperature and salinity tolerance. CO 2 flooding assisted by this type of chemical will broaden the scope of reservoirs that can be candidates for CO 2 IOR and geo-storage. [ABSTRACT FROM AUTHOR]

Instrumental data from the pre–Industrial Revolution period are important to -understand climate change. In this paper, the observations made by the French missionary J. Amiot in present-day central Beijing during 1757–62 were processed and analyzed. The observations represent the earliest continuous dataset of meteorological records found in China that have been digitized recently. Comparisons between the Amiot annual temperature range and extreme values with modern observations showed that the observations were read at approximately 0800 and 1500 local solar time (LST) in a well-ventilated outdoor site. The daily maximum, minimum, and mean temperatures (T-max, T-min, and T-mean, respectively) during 1757–62 were determined by examining the relationship between temperature at 0800 and 1500 LST and T-max, T-min, and T-mean in modern reference series. Nearly 260 years ago, Beijing's climate was typical of an inland temperate monsoon zone with annual T-mean, annual mean T-max, and annual mean T-min being 11.5°, 17.8°, and 6.1°C, respectively; further, the temperatures did not vary considerably from the 1951–1980 temperatures, but differed evidently compared to relatively recent decades (1981–2020). The difference was larger than the magnitudes of global and regional temperature changes. Thus, climate warming since the pre–Industrial Revolution period in the urban areas of Beijing has dominantly occurred over the last four decades. Uncertainties related to the thermometer and observational conditions 260 years ago and the interpolation method used have also been discussed in this paper. [ABSTRACT FROM AUTHOR]

The intensity and direction of elevation-dependent warming (EDW) could vary in different parts of the mountain, while less attention is paid to the local EDW effect. The Tibetan Plateau (TP) and the T'ai-hang & Lvliang Mountains in Shanxi Province of China (TLMsx) were taken as cases to examine the relationship between EDW and the long-term trend of surface air temperature (SAT) lapse rate (SATLR). For the observed data, the intensity of regional EDW (I EDW) was estimated with linear regression model, while the SATLR was estimated with geographically weighted regression (GWR) model. The long-term trend of SATLR was estimated applying the modified Theil-Sen method, and the regional average SATLR trend (k SATLR ¯) was calculated and analyzed. Both observed data and simulation experiment revealed that there was not significant difference between I EDW and − k SATLR ¯ , with a little difference caused by the noise in the SAT trends. As the SATLR trend measured the difference in the surface air warming rate within 1-km vertical distance, i.e. the intensity of EDW in a small spatial scale, in the context of climate warming, it could be used to estimate the intensity of local EDW. The SATLR trend thus provided a new perspective to study the EDW effect in the future, and facilitated the quantitative analysis on the mechanisms of EDW. • Two kinds of elevation-dependent warming (EDW) effect, positive EDW and negative EDW, are found. • The regional average surface air temperature lapse rate (SATLR) trend (k SATLR ¯) was broadly opposite to that of the intensity of EDW (I EDW). • There was not significant difference between I EDW and − k SATLR ¯. [ABSTRACT FROM AUTHOR]

The aerodynamic characteristics of butterflies, especially those which can migrate overseas, have received a great deal of attention because they have larger-scale wingspans and lower flapping frequencies than other insects such as drosophilae and bees. The objective of this work is to investigate the flow structures over a simplified model of Papilio Ulysses, one kind of migratory butterflies, through hydrogen bubble visualizations, and leading-edge vortices, wing-tip vortices, separation bubbles and horseshoe vortex wake are observed. Moreover, the variations of these structures with the angle of attack are discussed in detail. A new type of leading-edge vortices which resembles the inversed Chinese character "八" is observed in the experiment. [ABSTRACT FROM AUTHOR]

Pursuing high sensitivity and selectivity towards toxic dye molecules becomes an urgent task for sustainable development of environment. Methyl orange is a representative toxic dye containing azo structures, which is hazardous to human health even at low concentrations. At present, there are many methods for testing methyl orange, but there is no method specifically for the detection of trace methyl orange. In this work, NaBiF 4 : Yb3+/Tm3+ upconversion nanosheets (NSs) were proposed to detect toxic methyl orange (MO) dye molecule for the first time. Quantitative analysis of trace MO was achieved by recording the change of upconversion luminescence intensity of NaBiF 4 :Yb3+/Tm3+ NSs. A good regression coefficient of R = ​0.9966 was demonstrated between the quantitative trace MO and the relative intensity of NaBiF 4 : Yb3+/Tm3+ NSs. A detection limit of LOD ​= ​1.5 ​μg/mL (4.5 ​μM) was realized, revealing an excellent sensitivity for probe concentration of MO. Moreover, other dye molecules and typical metal ions such as methylene blue, 1,10 phenanthroline, rhodamine, Zr+, Cu2+, Mg2+, Ba2+, Pb2+, and Ca2+ in different solutions were also studied, showing high selectivity to the sensing of MO. This work offers an alternative strategies for detecting trace MO based on the upconversion nanomaterials and has great potential applications in environmental protection. This study offers a green synthesis strategy for NaBiF 4 : Yb3+/Tm3+ NSs and demonstrates the prepared NSs could be a promising probe for the determination of MO content in wastewater. [Display omitted] • A green synthesis process was developed using ethanol instead of the toxic ethylene glycol. • Synthesis of water-soluble NaBiF 4 : Yb3+/Tm3+ nanosheets with hexagonal phase structure. • NaBiF 4 : Yb3+/Tm3+ nanosheets shows efficient selectivity and sensitivity to pH and methyl orange. • The lower limit of detection for methyl orange was achieved to be 1.5 ​μg/mL. [ABSTRACT FROM AUTHOR]

The understanding of centennial trends of extreme temperature has been impeded due to the lack of early-year observations. In this paper, we collect and digitize the daily temperature data set of Northeast China Yingkou meteorological station since 1904. After quality control and homogenization, we analyze the changes of mean and extreme temperature in the past 114 years. The results show that mean temperature (Tmean), maximum temperature (Tmax), and minimum temperature (Tmin) all have increasing trends during 1904–2017. The increase of Tmin is the most obvious with the rate of 0.34 °C/decade. The most significant warming occurs in spring and winter with the rate of Tmean reaching 0.32 °C/decade and 0.31 °C/decade, respectively. Most of the extreme temperature indices as defined using absolute and relative thresholds of Tmax and Tmin also show significant changes, with cold events witnessing a more significant downward trend. The change is similar to that reported for global land and China for the past six decades. It is also found that the extreme highest temperature (1958) and lowest temperature (1920) records all occurred in the first half of the whole period, and the change of extreme temperature indices before 1950 is different from that of the recent decades, in particular for diurnal temperature range (DTR), which shows an opposite trend in the two time periods. [ABSTRACT FROM AUTHOR]

Aurivillius phase Bi5Ti3Fe0.7Co0.3O15 (BTF7C3O) thin films on α-quartz substrates were fabricated by a chemical solution deposition method and the room temperature ferroelectric and magnetic properties of this candidate multiferroic were compared with those of thin films of Mn3+ substituted, Bi5Ti3Fe0.7Mn0.3O15 (BTF7M3O). Vertical and lateral piezoresponse force microscopy (PFM) measurements of the films conclusively demonstrate that BTF7C3O and BTF7M3O thin films are piezoelectric and ferroelectric at room temperature, with the major polarization vector in the lateral plane of the films. No net magnetization was observed for the in-plane superconducting quantum interference device (SQUID) magnetometry measurements of BTF7M3O thin films. In contrast, SQUID measurements of the BTF7C3O films clearly demonstrated ferromagnetic behavior, with a remanent magnetization, Br, of 6.37 emu/cm3 (or 804 memu/g), remanent moment = 4.99 × 10-5 emu. The BTF7C3O films were scrutinized by x-ray diffraction, high resolution transmission electron microscopy, scanning transmission electron microscopy, and energy dispersive x-ray analysis mapping to assess the prospect of the observed multiferroic properties being intrinsic to the main phase. The results of extensive micro-structural phase analysis demonstrated that the BTF7C3O films comprised of a 3.95% Fe/Co-rich spinel phase, likely CoFe2 - xTixO4, which would account for the observed magnetic moment in the films. Additionally, x-ray magnetic circular dichroism photoemission electron microscopy (XMCD-PEEM) imaging confirmed that the majority of magnetic response arises from the Fe sites of Fe/Co-rich spinel phase inclusions. While the magnetic contribution from the main phase could not be determined by the XMCD-PEEM images, these data however imply that the Bi5Ti3Fe0.7Co0.3O15 thin films are likely not single phase multiferroics at room temperature. The PFM results presented demonstrate that the naturally 2D nanostructured Bi5Ti3Fe0.7Co0.3O15 phase is a novel ferroelectric and has potential commercial applications in high temperature piezoelectric and ferroelectric memory technologies. The implications for the conclusive demonstration of ferroelectric and ferromagnetic properties in single-phase materials of this type are discussed. [ABSTRACT FROM AUTHOR]

Land surface air temperature (SAT) change is one of the core issues in monitoring and assessing regional climate change. In this study, the characteristics of SAT change over DPR Korea for the period 1918–2015 were investigated using a high-quality historical dataset. Results show that the region-averaged annual mean SAT increased 0.21 °C/decade for the period 1918–2015 on the basis of data from four stations and 0.19 °C/decade for the period 1941–2015 as estimated based on data from nine stations. Before the 1970s, Pyongyang station in the central region experienced the largest warming trend. Linear trends of seasonal mean SAT during 1941–1970 were negative for all seasons in eastern coast and for summer and autumn in western coast and northern inland areas. Since 1971, however, the annual and seasonal mean SAT trends have shifted to positive values in all regions, with winter experiencing the most rapid warming. During the period of global warming slowdown since 1998 or 2000, no significant seasonal warming trend of wintertime was detectable, and this caused the smallest winter warming for the last 45 years. Other seasons also witnessed a generally weakened warming during 1971–2015 compared to that of 1971–2000. The results of the study will help in understanding regional climate change and in assessing the impacts of climate change on economic and natural ecosystems in the country. [ABSTRACT FROM AUTHOR]

Previous observational analyses show that the land-surface diurnal temperature range (DTR) has decreased in the past 6 decades worldwide. Based on a newly developed China Meteorological Administration-Land Surface Air Temperature (CMA-LSAT) dataset, we analyzed the DTR changes between 1901 and 2014. Results indicate that the global land surface DTR significantly decreased at a rate of − 0.036 °C decade− 1 over the 1901-2014 period, mainly due to the large decrease in DTR from 1951 to 2014. For the first half of the twentieth century, most grid boxes (spatial resolution 5° × 5°) show a positive DTR trend, with the positive trends of 32.4% grid boxes being statistically significant, leading to a large and significant increase of 0.048 °C decade− 1 in DTR. However, a dramatic reversal in DTR change occurred in early 1950s, with most parts of global lands exhibiting a shift from increasing to decreasing trends. The global land average DTR decrease during 1951-2014 was − 0.054 °C decade− 1, with 45.0% grid boxes showing significant negative trends. The reverse phenomenon is more obvious in the Northern Hemisphere than that in the Southern Hemisphere. For the periods 1979-2014 and 1998-2014, the decreasing trends in DTR mainly occur in the Northern Hemisphere. The DTR in the Southern Hemisphere experienced much larger increases during the two recent periods than during the period 1951-2014. Asia, Eastern North America, and Australia exhibited widespread decreases in DTR, although the trend pattern for global DTR is generally mixed during 1979-2014 and 1998-2014. There is a good negative correlation between DTR and precipitation in the Northern Hemisphere from 1901 to 2014, with a correlation coefficient of − 0.61. The change in precipitation and number of volcanic eruptions, and the "early brightening" of Europe (Stockholm) all benefit the increase of DTR at global and regional scales in the first half of the twentieth century. [ABSTRACT FROM AUTHOR]

Abstract In-situ conversion process (ICP) can be an effective technique for the development of oil shale and ultra heavy oils, in which kerogen or heavy components will be cracked into light oils and gases via underground heating and pyrolysis, and the retorted oil can be recovered via conventional extraction techniques. Heating of targeted formation can be conducted using electrical heaters installed in vertical or horizontal wells, while a slow heating rate and lack of driving energy for oil production are the main issues of the conventional in-situ conversion process. In this study, an innovative nitrogen injection assisted in-situ conversion process (NAICP) was proposed to increase formation heating rate and improve oil production from oil shale. Reaction models of kerogen pyrolysis at elevated temperature were established, along with models for the evolution of porosity and permeability of oil shale formation during the pyrolysis process. The performance of nitrogen injection on the effectiveness of the ICP was then investigated through reservoir numerical simulation. The simulation results show that additional nitrogen injection can improve the heating rate of the oil shale formation, enhance oil production and energy efficiency in comparison with the conventional ICPs, which can be attributed to enhanced heat convection, pressurization effect and gas driving mechanism. Nitrogen injection assisted in-situ conversion process can be a promising technique for the exploitation of oil shale. Highlights • Nitrogen injection assisted in-situ process for oil shale was proposed. • The advantages of nitrogen injection assisted in-situ process were studied. • The mechanism of nitrogen injection to improve oil production performance was studied. • The effects of heating temperature and nitrogen injection rate were studied. [ABSTRACT FROM AUTHOR]

Characteristics and causes of global warming hiatus (GWH) phenomenon have received much attention in recent years. Monthly mean data of land surface air maximum temperature (Tmax), minimum temperature (Tmin), and mean temperature (Tmean) of 118 national stations since 1951 in Northeast China are used in this paper to analyze the changes of land surface air temperature in recent 64 years with an emphasis on the GWH period. The results show that (1) from 1951 to 2014, the warming trends of Tmax, Tmin, and Tmean are 0.20, 0.42, and 0.34 °C/decade respectively for the whole area, with the warming rate of Tmin about two times of Tmax, and the upward trend of Tmean obviously higher than mainland China and global averages; (2) in the period 1998-2014, the annual mean temperature consistently exhibits a cooling phenomenon in Northeast China, and the trends of Tmax, Tmin, and Tmean are −0.36, −0.14, and −0.28 °C/decade respectively; (3) in the GWH period, seasonal mean cooling mainly occurs in northern winter (DJF) and spring (MAM), but northern summer (JJA) and autumn (SON) still experience a warming, implying that the annual mean temperature decrease is controlled by the remarkable cooling of winter and spring; (4) compared to the global and mainland China averages, the hiatus phenomenon is more evident in Northeast China, and the cooling trends are more obvious in the cold season; (5) the Northeast China cooling trend occurs under the circulation background of the negative phase Arctic Oscillation (AO), and it is also closely related to strengthening of the Siberia High (SH) and the East Asian Trough (EAT), and the stronger East Asian winter monsoon (EAWM) over the GWH period. [ABSTRACT FROM AUTHOR]

The geothermal exploitations from the single-continuum (i.e. sandstone here) and dual-continuum (i.e. hot dry rock here) reservoirs using CO 2 have unique advantages and huge application potentials. However, the salt precipitation caused by the evaporation can damage the reservoir and reduce the heat mining rate. In this paper, two comprehensive simulation models are established to analyze the fluid flow, salt precipitation, and its effects on the reservoir properties and heat mining rate during the geothermal exploitation using CO 2 from the sandstone and hot dry rock reservoirs. For the sandstone reservoir, the formation water will flow back to the injection well under the actions of the gravity and the gas-liquid capillary pressure driven by evaporation, which can result in a lot of NaCl precipitating in the injection well. The salt precipitation in the sandstone reservoir can make the steady heat mining rates decrease by about 1/3. For the hot dry rock reservoir, the formation water in the matrix system can be drawn to the fracture through the fracture-matrix interface due to the capillary pressure, which complicates the distribution of the salt precipitation in the fracture system. Under the actions of the back flow in the fracture and flow exchange between fracture and matrix, the salt precipitation mainly occurs in the areas near the injection and production wells, which makes the steady heat mining rate decrease by about 1/2. Both the low-salinity water injections prior the CO 2 injection and after the salt precipitation occurred can effectively reduce the salt precipitation for the sandstone, but only the low-salinity water injection after the salt precipitation occurred can dissolve the precipitated salt and effectively recover the heat mining rate. [ABSTRACT FROM AUTHOR]

NIR phosphor-converted light-emitting diodes (pc-LEDs) are of great importance for the next-generation smart light sources, while the performances of pc-LEDs are highly dependent on the NIR phosphors. In present study, one-dimensional (1D) Ga 2 O 3 : x Cr (x = 0, 0.25%, 0.5%, 0.75%, 1.0%, 1.25%) nanofibers with diameters about 250 nm were synthesized via an electrospinning route at low temperature of 700 °C and the nanoscale size paves a way for the Ga 2 O 3 : x Cr nanofibers used in miniature electronic devices. The photoluminescence excitation (PLE) spectrum exhibits two strong absorptions in the regions of 400–500 nm and 600–700 nm, which matches exceptionally well with the commercial blue light chips. Under 440 nm excitation, nanofibrous Ga 2 O 3 : x Cr samples show a broad emission from 650 to 840 nm, and the optimized Cr3+ concentration is x = 0.5% with a peak at 730 nm and a full width at half maximum (FWHM) of 140 nm. A NIR pc-LED was fabricated by combining the Ga 2 O 3 :0.5%Cr with a commercial blue LED chip. Furthermore, the blood vessels of the hand and the clearer images of flowers and cosmetics were captured by NIR camera under illuminating of the fabricated NIR pc-LED, which demonstrates the promise of the Ga 2 O 3 : x Cr nanofibers in NIR pc-LED applications. [Display omitted] • The Ga 2 O 3 : x Cr nanofibers were synthesized via an electrospinning route at low temperature. • The relationships between the performance and morphologies of NIR Ga 2 O 3 phosphors were studied. • NIR pc-LED shows the merits of Ga 2 O 3 nanofibers in biomedicine and night vision. [ABSTRACT FROM AUTHOR]

Highlights: [•] HMT displayed an influence on the aggregation structures at different scale levels. [•] Amylose acted as the backbone of aggregation structures to provide a resistance to HMT. [•] Phosphate monoester promoted the destruction by HMT to the aggregation structures. [•] Phosphate monoester played a more significant role in changing the lamellar thickness. [ABSTRACT FROM AUTHOR]

In-situ upgrading (ISU) via downhole heating is an innovative and efficient technique for oil shale and ultra heavy oil recovery. However, low heat transfer in the ISU process can limit its application in large scale. Therefore, efficient air injection assisted ISU process (AAISU) was proposed. In this study, reservoir stimulation of the AAISU process was performed to investigate the effect of air injection on heat transfer, oil production performance and energy conversion efficiency, as compared to the original ISU process. The influences of important engineering aspects were investigated, including well pattern, well distance, heating temperature and air injection rate for the field application of the AAISU technique. The reservoir stimulation results indicate that heat transfer rate can be significantly accelerated by air injection, and the average reservoir temperature during the AAISU can be increased to 250 °C after one year, in comparison with that of 116 °C in the ISU process. The contribution of air injection on the total heat transfer can be approached to 60%. Air injection can also enhance oil recovery and improve the energy efficiency. Heating temperature and air injection rate also have significant impact on the performance of the AAISU process. For a 15 m × 15 m × 10 m geo-model, increase of the heating temperature from 250 °C to 350 °C and air injection rate from 500 m3/day to 1000 m3/day can result in improved energy efficiency. However, heating temperature above 350 °C and the air injection rate over 1000 m3/day can led to a decreased energy efficiency, due to higher energy consumption on electrical heating and high rate of air injection. • Air injection assisted in situ upgrading process (AAISU) of ultra heavy oils was proposed. • The effect of air injection on heat transfer was studied. • The influence of well pattern and well distance on the AAISU was investigated. • The influence of heating temperature and air injection rate on the AAISU process was evaluated. [ABSTRACT FROM AUTHOR]

• The SrAl2O4:Eu/Yb nanofibers were fabricated via a facile electrospinning method. • The optical emission modulation is attributed to the valence of Eu. • Tuning the valence of Eu lies on adjusting the annealing routes. • The tailoring of single UC, DC and dual-mode UC/DC optical emission could be realized. ga1 One-dimensional Eu/Yb co-doped SrAl 2 O 4 nanofibers were successfully synthesized via an electrospinning technique. The morphologies, crystal structures, and chemical valences were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), respectively. The results revealed that the valence of Eu ions was primary trivalent (Eu3+) after annealing in oxygen ambient (air), and the red up-conversion (UC) luminescence was observed which was derived from 5D 0–2 to ground state 7F J (J = 0–6) of Eu3+ ions. While they evolved to bivalent (Eu2+) after annealing in a reduced (H 2 /Ar) ambient, showing green down-conversion (DC) luminescence under the exposure of 365 nm, which was ascribed to Eu2+ 4 f -5 d allowed transition. The mixed valence of Eu2+/Eu3+ could be realized through a partially oxidation in air again, strikingly, resulting in dual-mode UC and DC. Herein, we demonstrate the tunable dual-mode UC and DC emission performance in SrAl 2 O 4 : Eu/Yb nanofibers through selective annealing processes. Consequently, the synthesized SrAl 2 O 4 : Eu/Yb nanofibers may offer potentials applications towards multifunctional luminescent occasion. [ABSTRACT FROM AUTHOR]

• Air injection assisted in situ upgrading process (ISU) of ultra heavy oils was proposed. • The effect of air injection on heat transfer was studied. • The influence of low temperature oxidation on oil cracking was investigated. • The benefit of air injection on energy efficiency of the ISU process was evaluated. In situ upgrading (ISU) via underground heating and thermal cracking is regarded as an effective technique for exploiting ultra heavy oils, in which the heavy oil components can be cracked into light oils and gases for production. However, the slow heating rate via conduction from wellbore to oil formation is the main issue concerned in the conventional ISU process. Herein, an air injection assisted ISU technique (AAISU) is proposed to improve heat transfer by gas convection and along with the thermal effect of oil oxidation due to the oxygen in the injected air. Air injection can also provide extra energy for oil production and reservoir pressure maintenance. To illustrate the advantage of the proposed AAISU technique, thermal cracking experiments of ultra heavy oil samples in the presence of air under high pressure were conducted to investigate the reaction mechanisms and to establish the kinetics models of the oxidation and cracking reactions. Moreover, reservoir numerical simulation studies are performed to evaluate the effects of air injection during the ISU process. The experiment results indicate that the ultra heavy oil can be effectively cracked into gases, light oils and coke-like substances in the presence of air at temperature over 350 °C. The activation energy of the thermal cracking derived is around 248 kJ/mol. The numerical simulation results show that the heat transfer rate can be effectively enhanced by air injection because of the heat convection of the air flow and the thermal effect of the low temperature oxidation reactions of oil components. The total oil recovery factor can be increased via air injection with improved energy conversion efficiency from 6.51 GJ/GJ to 8.42 GJ/GJ. [ABSTRACT FROM AUTHOR]

Ultrathin BiFeO3 films are deposited by liquid injection metal-organic chemical vapor deposition on SrTiO3 substrates using a toluene solution of Bi(thd)3 and Fe(thd)3 (thd: 2,2,6,6-tetramethyl-3,5-heptanedionate). [ABSTRACT FROM AUTHOR]