High temperature characteristics of GaN-based inverter is presented from room temperature (RT) to 300 degrees C, which is integrated with enhancement-mode MOSFET and depletion-mode HEMT. At 300 degrees C, the fabricated inverter operates properly at a supply voltage (V-DD) of 7 V with 6.5 V for logic voltage swing, 3.3 V for threshold voltage (V-TH), 2.4 V for logic-low noise margin (NML), and 3.4 V for logic-high noise margin (NMH). Meanwhile, the inverter exhibits small variations from RT to 300 degrees C in terms of logic voltage swing, V-TH, NML, and NMH with the maximum relative variations of 2.2%, 5.7%, 12.9%, and 4.9% in such temperature range, respectively.
The United States is now experiencing the most rapid expansion in oil and gas production in four decades, owing in large part to implementation of new extraction technologies such as horizontal drilling combined with hydraulic fracturing. The environmental impacts of this development, from its effect on water quality(1) to the influence of increased methane leakage on climate(2), have been a matter of intense debate. Air quality impacts are associated with emissions of nitrogen oxides(3,4) (NOx = NO + NO2) and volatile organic compounds(5-7) (VOCs), whose photochemistry leads to production of ozone, a secondary pollutant with negative health effects(8). Recent observations in oil-and gas-producing basins in the western United States have identified ozone mixing ratios well in excess of present air quality standards, but only during winter(9-13). Understanding winter ozone production in these regions is scientifically challenging. It occurs during cold periods of snow cover when meteorological inversions concentrate air pollutants from oil and gas activities, but when solar irradiance and absolute humidity, which are both required to initiate conventional photochemistry essential for ozone production, are at a minimum. Here, using data from a remote location in the oil and gas basin of northeastern Utah and a box model, we provide a quantitative assessment of the photochemistry that leads to these extreme winter ozone pollution events, and identify key factors that control ozone production in this unique environment. We find that ozone production occurs at lower NOx and much larger VOC concentrations than does its summertime urban counterpart, leading to carbonyl (oxygenated VOCs with a C=O moiety) photolysis as a dominant oxidant source. Extreme VOC concentrations optimize the ozone production efficiency of NOx. There is considerable potential for global growth in oil and gas extraction from shale. This analysis could help inform strategies to monitor and mitigate air quality impacts and provide broader insight into the response of winter ozone to primary pollutants.
Abstract Polystyrene-supported (PS) diarylprolinol catalysts 1?a (Ar=phenyl) and 1?b (Ar=3,5-bis(trifluoromethyl)phenyl) have been developed. Operating under site-isolation conditions, PS-1?a/1?b worked compatibly with PS-bound sulfonic acid catalyst 2 to promote deoligomerization of paraldehyde and subsequent cross-aldol reactions of the resulting acetaldehyde in one pot, affording aldol products in high yields with excellent enantioselectivities. The effect of water on the performance of the catalytic system has been studied and its optimal amount (0.5?equiv) has been determined. The dual catalytic system (1/2) allows repeated recycling and reuse (10 cycles). The potential of this methodology is demonstrated by a two-step synthesis of a phenoperidine analogue (68?% overall yield; 98?%?ee) and by the preparation of highly enantioenriched 1,3-diols 4 and 3-methylamino-1-arylpropanols 5, key intermediates in the synthesis of a variety of druglike structures.
Atmospheric modeling is an essential issue in the study of climate change. However, due to the complicated algorithmic and communication models, scientists and researchers are facing tough challenges in finding efficient solutions to solve the atmospheric equations. In this paper, we accelerate a solver for the three-dimensional Euler atmospheric equations through reconfigurable data flow engines. We first propose a hybrid design that achieves efficient resource allocation and data reuse. Furthermore, through algorithmic offsetting, fast memory table, and customizable-precision arithmetic, we map a complex Euler kernel into a single FPGA chip, which can perform 956 floating point operations per cycle. In a 1U-chassis, our CPU-DFE unit with 8 FPGA chips is 18.5 times faster and 8.3 times more power efficient than a multicore system based on two 12-core Intel E5-2697 (Ivy Bridge) CPUs, and is 6.2 times faster and 5.2 times more power efficient than a hybrid unit equipped with two 12-core Intel E5-2697 (Ivy Bridge) CPUs and three Intel Xeon Phi 5120d (MIC) cards.
Trifluoromethane (CHF3, HFC-23) is one of the hydrofluorocarbons (HFCs) regulated under the Kyoto Protocol with a global warming potential (GWP) of 14 800 (100-year). China's past, present, and future HFC-23 emissions are of considerable interest to researchers and policymakers involved in climate change. In this study, we compiled a comprehensive historical inventory (1980-2012) and a projection (2013-2050) of HFC-23 production, abatements, and emissions in China. Results show that HFC-23 production in China increased from 0.08 +/- 0.05 Gg/yr in 1980 to 15.4 +/- 2.1 Gg/yr (228 +/- 31 Tg/yr CO2-eq) in 2012, while actual HFC-23 emissions reached a peak of 10.5 +/- 1.8 Gg/yr (155 +/- 27 Tg/y CO2-eq) in 2006, and decreased to a minimum of 7.3 +/- 1.3 Gg/yr (108 +/- 19 Tg/yr CO2-eq) in 2008 and 2009. Under the examined business-as-usual (BAU) scenario, the cumulative emissions of HFC-23 in China over the period 2013-2050 are projected to be 609 Gg (9015 Tg CO2-eq which approximates China's 2012 CO2 emissions). Currently, China's annual HFC-23 emissions are much higher than those from the developed countries, while it is estimated that by year 2027, China's historic contribution to the global atmospheric burden of HFC-23 will have surpassed that of the developed nations under the BAU scenario.
To evaluate the variations in temporal and spatial distribution of biogenic volatile organic compound (BVOC) emissions in China, historical BVOC emission inventories at a spatial resolution of 36 km × 36 km for the period of 1981–2003 were developed firstly. Based on the time-varying statistical data and Vegetation Atlas of China (1:1,000,000), emissions of isoprene, 37 monoterpenes, 32 sesquiterpenes, and other volatile organic compounds (OVOCs) were estimated using MEGANv2.1 driven by WRF model. Results show China's BVOC emissions had increased by 28.01% at an annual average rate of 1.27% from 37.89 Tg in 1981 to 48.50 Tg in 2003. Emissions of isoprene, monoterpenes, sesquiterpenes, and OVOCs had increased by 41.60%, 34.78%, 41.05%, and 4.89%, respectively. With fixed meteorological variables, the estimated BVOC emissions would increase by 19.25%, resulting from the increasing of vegetation biomass during the last 23 years. On average, isoprene, monoterpenes, sesquiterpenes, and OVOCs were responsible for 52.40%, 12.73%, 2.58%, and 32.29% of the national BVOC emissions, respectively. β-pinene and α-pinene, farnesene and caryophyllene were the largest contributors to the total monoterpene and sesquiterpene emissions, respectively. The highest emissions were found over northeastern, southeastern, southwestern China, Qinling Mountain, and Hainan and Taiwan provinces. The regions with high emissions had been expanding over the years, especially in the Changbai Mountain, southern China, and southwestern forest regions. The lowest emissions in southern China occurred in 1984–1988. Almost all the provinces had experienced increasing emissions, but their contributions to the national emissions differed significantly over the past 23 years. Yunnan, Guangxi, Heilongjiang, Jiangxi, Fujian, Guangdong, and Sichuan provinces always dominated the national BVOC emissions, excluding in 1977–1981, when the three northeastern provinces had relatively lower emissions.
Housing price has increased dramatically in China during the past decade. The appreciation of house value could relax credit constraint and thus encourage entrepreneurship. However, a house serves as both an important investment channel and a prerequisite for marriage in China. The continuous high return of investment in housing and intensified marriage market competition make house purchase a priority for young people and their parents, which would crowd out entrepreneurial activities. Using two large datasets, we find that high housing price in general discourages entrepreneurial activities for urban adults. For house owners, while house value appreciation has a positive wealth effect, the ratio of mortgage over income has a negative effect. For non-owners, a higher ratio of housing price over income corresponds to a lower probability of entrepreneurship. This study highlights the negative consequences of surging housing price on entrepreneurship in developing countries.
