Chiral structures of lander molecules on Cu(100)

Supramolecular assemblies of lander molecules (C$_{90}$H$_{98}$) on Cu(100) are investigated with low-temperature scanning tunneling microscopy. The energetically most favourable conformation of the adsorbed molecule is found to exist in two mirror symmetric enantiomers or conformers. At low coverage, the molecules align in enantiomerically pure chains along the chiral directions $[01\bar{2}],[02\bar{1}],[012]$ and $[021]$. The arrangement is proposed to be mainly governed by intermolecular van-der-Waals interaction. At higher coverages, the molecular chains arrange into chiral domains, for which a structural model is presented.Comment: to appear in Nanotechnology vol. 15 (2004

House Price Trigger and Infusion Trap

Rapid movements of house prices bring concerns about affordability when house prices go up and of crisis when they fall below their trend value. This paper reviews house prices which have the potential to deviate significant from market fundamentals in the short term, especially when supply is rigid. The paper then establishes a house price trigger model under the assumption of supply rigidity in order to explain fluctuations in house prices. The model is tested by on time series data from Hong Kong and explains that the changes of quantity demand, the level of increase and decrease in the market place, are triggers that induce fluctuations in house prices. The behaviour of developers, investors and consumers in the property market and the housing market of mainland China is also analysed using the concepts developed

Graded reflection equation algebras and integrable Kondo impurities in the one-dimensional t-J model

Integrable Kondo impurities in two cases of the one-dimensional $t-J$ model are studied by means of the boundary ${\bf Z}_2$-graded quantum inverse scattering method. The boundary $K$ matrices depending on the local magnetic moments of the impurities are presented as nontrivial realizations of the reflection equation algebras in an impurity Hilbert space. Furthermore, these models are solved by using the algebraic Bethe ansatz method and the Bethe ansatz equations are obtained.Comment: 14 pages, RevTe

CFD performance analysis of finned-tube CO2 gas coolers with various inlet air flow patterns

A detailed model of three-dimensional computational fluid dynamics (CFD) on a finned-tube CO2 gas cooler has been developed and validated. The model is then applied to investigate the effect of uniform and mal-distribution inlet airflow profiles on the coil performance. The airflow mal-distribution velocity profiles include linear-up, linear-down and parabolic while the effected coil performance parameters contain airside pressure drop, average airside heat transfer coefficient, approach temperature and coil heating capacity. The model also enables to predict the CO2 refrigerant temperature profile along the coil pipes from refrigerant inlet to outlet at different operation conditions. The simulation results reveal that different types of inlet airflow velocity profiles have significant effects on the gas cooler performance. The uniform airflow velocity profile case shows the best thermal performance of gas cooler. Compared with the cases of linear-up and parabolic air velocity profiles, the linear-down airflow profile can influence more on the coil heat transfer performance. Due to the thermal conduction between neighbour tubes through coil fins, reversed heat transfer phenomenon exists which can be detected and simulated by the CFD model. It is predicted that the linear-down airflow profile can increase greatly the reversed heat transfer phenomenon and thus lead to the highest approach temperature and the lowest heating capacity amongst these four types of airflow profiles. The research method and outcomes presented in this paper can have great potentials to optimize the performance of a CO2 gas cooler and its associated refrigeration system

Resistivity phase diagram of cuprates revisited

The phase diagram of the cuprate superconductors has posed a formidable scientific challenge for more than three decades. This challenge is perhaps best exemplified by the need to understand the normal-state charge transport as the system evolves from Mott insulator to Fermi-liquid metal with doping. Here we report a detailed analysis of the temperature (T) and doping (p) dependence of the planar resistivity of simple-tetragonal HgBa$_2$CuO$_{4+\delta}$ (Hg1201), the single-CuO$_2$-layer cuprate with the highest optimal $T_c$. The data allow us to test a recently proposed phenomenological model for the cuprate phase diagram that combines a universal transport scattering rate with spatially inhomogeneous (de)localization of the Mott-localized hole. We find that the model provides an excellent description of the data. We then extend this analysis to prior transport results for several other cuprates, including the Hall number in the overdoped part of the phase diagram, and find little compound-to-compound variation in (de)localization gap scale. The results point to a robust, universal structural origin of the inherent gap inhomogeneity that is unrelated to doping-related disorder. They are inconsistent with the notion that much of the phase diagram is controlled by a quantum critical point, and instead indicate that the unusual electronic properties exhibited by the cuprates are fundamentally related to strong nonlinearities associated with subtle nanoscale inhomogeneity.Comment: 22 pages, 5 figure

An Architecture for Accountable Anonymous Access in the Internet-of-Things Network

This is the author accepted manuscript. The final version is available from IEEE via the DOI in this record.With the rapid development of the Internet, more and more devices are being connected to the Internet, making up the Internet-of-Things (IoT). The accountability and privacy are two important but contradictory factors to ensure the security of IoT networks. How to provide an accountable anonymous access to IoT networks is a challenging task. Since the IoT network is largely driven by services, in this paper we propose a new and efficient architecture to achieve accountable anonymous access to IoT networks based on services. In this architecture, a self-certifying identifier is proposed to efficiently identify a service. The efficiency and overhead of the proposed architecture are evaluated by virtue of the real trace collected from an Internet service provider. The experimental results show that the proposed architecture could efficiently balance accountability and privacy with acceptable overheads.This work is partially supported by the National Key Technology Research and Development Program (No. 2017YFB0801801), the National Science and Technology Major Project of the Ministry of Science and Technology of China (No. 2017ZX03001019), and the National Natural Science Foundation of China (No. 61672490 and No. 61303241)

Thermal performance and energy savings of white and sedum-tray garden roof: A case study in a Chongqing office building

This study presents the experimental measurement of the energy consumption of three top-floor air-conditioned rooms in a typical office building in Chongqing, which is a mountainous city in the hot-summer and cold-winter zone of China, to examine the energy performance of white and sedum-tray garden roofs. The energy consumption of the three rooms was measured from September 2014 to September 2015 by monitoring the energy performance (temperature distributions of the roofs, evaporation, heat fluxes, and energy consumption) and indoor air temperature. The rooms had the same construction and appliances, except that one roof top was black, one was white, and one had a sedum-tray garden roof. This study references the International Performance Measurement and Verification Protocol (IPMVP) to calculate and compare the energy savings of the three kinds of roofs. The results indicate that the energy savings ratios of the rooms with the sedum-tray garden roof and with the white roof were 25.0% and 20.5%, respectively, as compared with the black-roofed room, in the summer; by contrast, the energy savings ratios were −9.9% and −2.7%, respectively, in the winter. Furthermore, Annual conditioning energy savings of white roof (3.9 kWh/m2) were 1.6 times the energy savings for the sedum-tray garden roof. It is evident that white roof is a preferable choice for office buildings in Chongqing. Additionally, The white roof had a reflectance of 0.58 after natural aging owing to the serious air pollution worsened its thermal performance, and the energy savings reduced by 0.033 kWh/m2·d. Evaporation was also identified to have a significant effect on the energy savings of the sedum-tray garden roof

APCN: A Scalable Architecture for Balancing Accountability and Privacy in Large-scale Content-based Networks

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record. Balancing accountability and privacy has become extremely important in cyberspace, and the Internet has evolved to be dominated by content transmission. Several research efforts have been devoted to contributing to either accountability or privacy protection, but none of them has managed to consider both factors in content-based networks. An efficient solution is therefore urgently demanded by service and content providers. However, proposing such a solution is very challenging, because the following questions need to be considered simultaneously: (1) How can the conflict between privacy and accountability be avoided? (2) How is content identified and accountability performed based on packets belonging to that content? (3) How can the scalability issue be alleviated on massive content accountability in large-scale networks? To address these questions, we propose the first scalable architecture for balancing Accountability and Privacy in large-scale Content-based Networks (APCN). In particular, an innovative method for identifying content is proposed to effectively distinguish the content issued by different senders and from different flows, enabling the accountability of a content based on any of its packets. Furthermore, a new idea with double-delegate (i.e., source and local delegates) is proposed to improve the performance and alleviate the scalability issue on content accountability in large-scale networks. Extensive NS-3 experiments with real trace are conducted to validate the efficiency of the proposed APCN. The results demonstrate that APCN outperforms existing related solutions in terms of lower round-trip time and higher cache hit rate under different network configurations.National Key R&D Program of ChinaNational Science and Technology Major Project of the Ministry of Science and Technology of ChinaNational Natural Science Foundation of Chin

The moisture distribution in wall-to-floor thermal bridges and its influence on mould growth

Moisture in building envelopes increases the energy consumption of buildings and induces mould growth, which may be amplified within the area of thermal bridges due to their different hygrothermal properties and complex structures. In this study, we aimed to (1) reveal the moisture distribution in the typical thermal bridge (i.e., wall-to-floor thermal bridge, WFTB) and its surrounding area and (2) investigate the mould growth in a building envelope that includes both a WFTB and the main part of a wall, in a humid and hot summer/cold winter region of China (Hangzhou City). The transient numerical simulations which lasted for 5 years were performed to model the moisture distribution. Simulated results indicate that the moisture distribution presents significant seasonal and spatial differences due to the WFTB. The areas where moisture accumulates have a higher risk of mould growth. The thermal insulation layer laid on the exterior surface of a WFTB can reduce the overall humidity while uneven moisture distribution may promote mould growth and water vapour condensation