Heavy Industry Share Increase Is Causing Higher Energy Consumptioni

The"11th Five-Year"plan sets the objective of reducing energy consumption per unit of GDP by 20% in five years.Readjusting industrial structure is one of the possible means to reach this goal.As for energy consumption reduction through industrial readjustment,however,present research only explores the effects of industry structural change in the six sectors such as agriculture,industry,construction,transportation and commerce,yet without considering the ramifications of sub-sector two-digit code industry structure.In this paper,we have calculated the effects of structural change in light- heavy industries on energy consumption and energy intensity from 1993 to 2005 using the factor decomposition method.As a result,we found for each percentage point gain in favour of heavy industry in the light-heavy industry mix,China’s energy consumption increases by nearly 9 million metric tons of coal equivalent.However the overall effects of structural change in light-heavy industry are less than those of sub-sector intensity factors on industrial energy intensity and energy consumption per unit of GDP.The heavy industry share gain has over recent years exerted a significant impact on industrial energy intensity.For example,78% of the abnormal increase in industrial energy intensity in 2003 could be attributed to this factor.Finally,an analytical framework for energy intensity based on this study is presented.

Optical anisotropy and the direction of polarization of exciton emissions in a semiconductor quantum dot:Effect of heavy-and light-hole mixing

The dependence of the directions of polarization of exciton emissions, fine structure splittings （FSS）, and polarization anisotropy on the light- and heavy-hole （LH-HH） mixing in semiconductor quantum dots （QDs） is investigated using a mesoscopic model. In general, all QDs have a four-fold exciton ground state. Two exciton states have directions of polarization in the growth-plane, while the other two are along the growth direction of the QD. The LH-HH mixing does affect the FSS and polarization anisotropy of bright exciton states in the growth-plane in the low symmetry QDs （e.g., C2v, CS, C1 ）, while it has no effect on the FSS and polarization anisotropy in high symmetry QDs （e.g., C3V, D2d）. When the hole ground state is pure HH or LH, the bright exciton states in the growth-plane are normal to each other. The LH-HH mixing affects the relative intensities and directions of bright exciton states in the growth-plane of the QD. The polarization anisotropy of exciton emissions in the growth-plane of the QD is independent of the phase angle of LH-HH mixing but strongly depends on the magnitude of LH-HH mixing in low symmetry QDs.

Enabling ultranarrow blue emission linewidths in colloidal alloy quantum dots by decreasing the exciton fine structure splitting and exciton–phonon coupling

The realization of colloidal alloy quantum dots(QDs)with narrow spectral linewidths requires minimization of the contributions of inhomogeneous and homogeneous broadening to the ensemble spectrum.Recently,there has been remarkable progress in eliminating the inhomogeneous contribution by controlling the size distribution of the QDs.However,considerable challenges remain in suppressing the homogeneous broadening,in terms of both intrinsic principles and rational synthetic routes.We find that ground-state exciton fine structure splitting and exciton-phonon coupling play a pivotal role in the homogeneous broadening mechanism.Here we demonstrate that the elimination of the lattice mismatch strain by using a coherent strain structure can decrease the light-heavy hole splitting,thus suppressing the asymmetric broadening of the emission on the high energy side.Besides,the improvement of the uniformity of the alloy by using a stepwise ion exchange strategy can weaken the exciton-longitudinal optical(LO)-phonon interactions,further minimizing the homogeneous broadening.As a result,the final alloy QD products exhibit a widely tunable blue emission wavelength(445-470 nm)with the narrowest ensemble photoluminescence full width at half maximum(FWHM)of 10.1-13.5 nm(or 58.4-75.3 meV).Our study provides a potential strategy for other semiconductor nanocrystals with ultranarrow spectral linewidths.