Urban energy consumption and CO2 emissions in Beijing: current and future

This paper calculates the energy consumption and CO2 emissions of Beijing over 2005–2011 in light of the Beijing’s energy balance table and the carbon emission coefficients of IPCC. Furthermore, based on a series of energy conservation planning program issued in Beijing, the Long-range Energy Alternatives Planning System (LEAP)-BJ model is developed to study the energy consumption and CO2 emissions of Beijing’s six end-use sectors and the energy conversion sector over 2012–2030 under the BAU scenario and POL scenario. Some results are found in this research: (1) During 2005–2011, the energy consumption kept increasing, while the total CO2 emissions fluctuated obviously in 2008 and 2011. The energy structure and the industrial structure have been optimized to a certain extent. (2) If the policies are completely implemented, the POL scenario is projected to save 21.36 and 35.37 % of the total energy consumption and CO2 emissions than the BAU scenario during 2012 and 2030. (3) The POL scenario presents a more optimized energy structure compared with the BAU scenario, with the decrease of coal consumption and the increase of natural gas consumption. (4) The commerce and service sector and the energy conversion sector will become the largest contributor to energy consumption and CO2 emissions, respectively. The transport sector and the industrial sector are the two most potential sectors in energy savings and carbon reduction. In terms of subscenarios, the energy conservation in transport (TEC) is the most effective one. (5) The macroparameters, such as the GDP growth rate and the industrial structure, have great influence on the urban energy consumption and carbon emissions

Interplay between edge states and simple bulk defects in graphene nanoribbons

We study the interplay between the edge states and a single impurity in a zigzag graphene nanoribbon. We use tight-binding exact diagonalization techniques, as well as density functional theory calculations to obtain the eigenvalue spectrum, the eigenfunctions, as well the dependence of the local density of states (LDOS) on energy and position. We note that roughly half of the unperturbed eigenstates in the spectrum of the finite-size ribbon hybridize with the impurity state, and the corresponding eigenvalues are shifted with respect to their unperturbed values. The maximum shift and hybridization occur for a state whose energy is inverse proportional to the impurity potential; this energy is that of the impurity peak in the DOS spectrum. We find that the interference between the impurity and the edge gives rise to peculiar modifications of the LDOS of the nanoribbon, in particular to oscillations of the edge LDOS. These effects depend on the size of the system, and decay with the distance between the edge and the impurity.Comment: 10 pages, 15 figures, revtex

Time‐lapse photogrammetry reveals hydrological controls of fine‐scale High‐Arctic glacier surface roughness evolution

In a warming Arctic, as glacier snowlines rise, short- to medium-term increases in seasonal bare-ice extent are forecast for the next few decades. These changes will enhance the importance of turbulent energy fluxes for surface ablation and glacier mass balance. Turbulent energy exchanges at the ice surface are conditioned by its topography, or roughness, which has been hypothesized to be controlled by supraglacial hydrology at the glacier scale. However, current understanding of the dynamics in surface topography, and the role of drainage development, remains incomplete, particularly for the transition between seasonal snow cover and well-developed, weathered bare-ice. Using time-lapse photogrammetry, we report a daily timeseries of fine (millimetre)-scale supraglacial topography at a 2 m2 plot on the Lower Foxfonna glacier, Svalbard, over two 9-day periods in 2011. We show traditional kernel-based morphometric descriptions of roughness were ineffective in describing temporal change, but indicated fine-scale albedo feedbacks at depths of ~60 mm contributed to conditioning surface topography. We found profile-based and two-dimensional estimates of roughness revealed temporal change, and the aerodynamic roughness parameter, z0, showed a 22–32% decrease from ~1 mm following the exposure of bare-ice, and a subsequent 72–77% increase. Using geostatistical techniques, we identified ‘hole effect’ properties in the surface elevation semivariograms, and demonstrated that hydrological drivers control the plot-scale topography: degradation of superimposed ice reduces roughness while the inception of braided rills initiates a subsequent development and amplification of topography. Our study presents an analytical framework for future studies that interrogate the coupling between ice surface roughness and hydro-meteorological variables and seek to improve parameterizations of topographically evolving bare-ice areas

Pasture access increases dairy cow milk yield but preference for pasture is not affected by herbage allowance

A number of factors influence dairy cow preference to be indoors or at pasture. The study reported here investigated whether herbage mass and distance affects preference and if continuously housed cows exhibited behavioral and production differences compared to cows that had free access to pasture. Dairy cows (n = 16) were offered a free choice of being in cubicle housing (1.5 cubicles/cow) or at pasture with a high (3,000 ± 200 kg DM/ha) vs. low (1,800 ± 200 kg DM/ha) herbage mass. A control group (n = 16) was confined to cubicle housing for the duration of the study. Each herbage mass was offered at either a near (38 m) or far (254 m) distance in a 2 × 2 factorial crossover design to determine motivation to access pasture. Overall, dairy cows expressed a partial preference to be at pasture, spending 68.7% of their time at pasture. This was not affected (P > 0.05) by herbage mass. Both grass intake (P = 0.001) and grazing time (P = 0.039) was greater when cows were offered the high herbage mass. Neither total mixed ration intake (P > 0.05) nor milk yield (P > 0.05) was affected by herbage mass or distance. Additionally, no interaction existed between herbage mass and distance (P > 0.05). Distance affected preference: overall time on pasture was greater at the near distance (P = 0.002); however, nighttime use was not affected by distance (P = 0.184). Housed cows produced less milk than free-choice cows and this was potentially due to a combination of decreased lying time in housed cows (P < 0.001) and grass intake (1.22 kg/d) in free-choice cows. This study shows that herbage mass is not a major factor driving dairy cow preference for pasture, but distance does affect preference for pasture during the day. Additionally, there are clear production and welfare benefits for providing cows with a choice to be at pasture or cubicle housing over being continuously housed. Further research is necessary to quantify the effect of lying time on milk yields