A BIM-Based Study on the Sunlight Simulation in Order to Calculate Solar Energy for Sustainable Buildings with Solar Panels

With the construction industry moving rapidly toward building information modeling (BIM), pursuit of sustainability in buildings will require the use of renewable energy analysis tools in the early stages of building design, as well as establishment of BIM-compliant practices. Planning for sunlight is essential to obtain sustainable benefits from the sun in and around buildings, which process requires understanding and making allowances in building attributes that affect how sunlight can be used. This chapter presents a model for simulation of sunlight’s effect on building design under BIM technology while calculating the potential energy capacity of roof- and façade-mounted photovoltaic solar panels. For this purpose, it is suggested in the study to use statistical construction data as well as 3D digital models obtained from BIM software (Revit and THSWARE) to measure the useful sunlight duration and derivable energy of representative sample of buildings. By measuring the solar energy absorbed by the building facades, the electricity converted from solar energy and collateral savings can be calculated. Taking the cost of solar panels and feasibility of the project into consideration, this study shows using solar panels of a certain quality contributes greatly to social, economic, and environmental benefits

Recent trends in vegetation greenness in China significantly altered annual evapotranspiration and water yield

There has been growing evidence that vegetation greenness has been increasing in many parts of the northern middle and high latitudes including China during the last three to four decades. However, the effects of increasing vegetation greenness particularly afforestation on the hydrological cycle have been controversial. We used a process-based ecosystem model and a satellite-derived leaf area index (LAI) dataset to examine how the changes in vegetation greenness affected annual evapotranspiration (ET) and water yield for China over the period from 2000 to 2014. Significant trends in vegetation greenness were observed in 26.1% of China\u27s land area. We used two model simulations driven with original and detrended LAI, respectively, to assess the effects of vegetation \u27greening\u27 and \u27browning\u27 on terrestrial ET and water yield. On a per-pixel basis, vegetation greening increased annual ET and decreased water yield, while vegetation browning reduced ET and increased water yield. At the large river basin and national scales, the greening trends also had positive effects on annual ET and had negative effects on water yield. Our results showed that the effects of the changes in vegetation greenness on the hydrological cycle varied with spatial scale. Afforestation efforts perhaps should focus on southern China with larger water supply given the water crisis in northern China and the negative effects of vegetation greening on water yield. Future studies on the effects of the greenness changes on the hydrological cycle are needed to account for the feedbacks to the climate

Exceptional cavity quantum electrodynamics

An open quantum system operated at the spectral singularities where dimensionality reduces, known as exceptional points (EPs), demonstrates distinguishing behavior from the Hermitian counterpart. Based on the recently proposed microcavity with exceptional surface (ES), we report and explain the peculiar quantum dynamics in atom-photon interaction associated with EPs: cavity transparency, decoherence suppression beyond the limitation of Jaynes-Cummings (JC) system, and the population trapping of lossy cavity. An analytical description of the local density of states (LDOS) for ES microcavity is derived from an equivalent cavity quantum electrodynamics (QED) model, which goes beyond the single-excitation approximation and allows exploring the quantum effects of EPs on multiphoton process by parametrizing the extended cascaded quantum master equation. It reveals that a square Lorentzian term in LDOS induced by second-order EPs interferes with the linear Lorentzian profile, giving rise to cavity transparency for atom with special transition frequency in the weak coupling regime. This additional contribution from EPs also breaks the limit on dissipation rate of JC system bounded by bare components, resulting in the decoherence suppression with anomalously small decay rate of the Rabi oscillation and the long-time dynamics. Remarkably, we find that the cavity population can be partially trapped at EPs, achieved by forming a bound dressed state in the limiting case of vanishing atom decay. Our work unveils the exotic phenomena unique to EPs in cavity QED systems, which opens the door for controlling light-matter interaction at the quantum level through non-Hermiticity, and holds great potential in building high-performance quantum-optics devices.Comment: 11 pages, 6 figure

Hybrid Dynamic Pricing Model for Transport PPP Projects during the Residual Concession Period

Public–Private-Partnerships (PPPs) have been adopted worldwide to deliver infrastructure projects and/or provide public services. Having a reasonable concession price (operation and transfer) in place is pivotal for sustaining a win-win relationship between governments and private sectors. However, historical data have shown that the concession price of PPPs when transfer is less than satisfactory due to the changing attribute of pricing parameters, causing substantial loss of residual value (RV). Nevertheless, a rational and systematic pricing model for PPPs, especially transport PPPs, is not yet available. To this end, a hybrid dynamic pricing model for transport PPPs during the residual concession period underpinned by the case-based reasoning technique is proposed. Furthermore, using a case study of the Western Harbor Crossing tunnel in Hong Kong, the proposed model is validated to be able to account for the dynamic pricing parameters and calculate a reasonable and accurate residual concession price. The contributions of this study are twofold: (1) it highlights that a reasonable concession price beyond the operation period is significant in maintaining RV; and (2) it provides a hybrid dynamic pricing model for governments and private sectors to calibrate the current less-than-satisfactory residual concession price

Unpacking the context of Value for Money assessment in global markets: a procurement option framework for Public Private Partnerships

Purpose: The unprecedented COVID-19 pandemic has further constrained the budgets of governments worldwide for delivering their much-needed infrastructure. Consequently, Public-Private Partnerships (PPPs), with the private sector’s investment and ingenuity, would appear to be an increasingly popular alternative. Value for money (VfM) has become the major criterion for evaluating PPPs against the traditional public sector procurement, and however is plagued with controversy. Hence, it is important that governments compare and contrast their practice with similar and disparate bodies to engender best practice. This paper, therefore, aims to understand governments’ evaluation context and provide a cross-continental comparison on their VfM assessment. Design/ methodology/ approach: Faced with different domestic contexts (e.g., aging infrastructure, population growth, and competing demands on finance), various governments tend to adopt different emphases when undertaking the VfM assessment. In line with the theory of boundary spanning, a cross continental comparison is conducted between three of the most noticeable PPP markets (i.e., the United Kingdom - UK, Australia and China) about their VfM assessment. The institutional level is interpreted by a social, economic and political framework, and the methodological level is elucidated through a qualitative and quantitative VfM assessment. Findings: There are individual institutional characteristics that have shaped the way each country assesses VfM. For the methodological level, we identify that: (1) these global markets use a public sector comparator as the benchmark in VfM assessment; (2) ambiguous qualitative assessment is conducted only against PPPs to strengthen their policy development; (3) Australia’s priority is in service provision whereas that of the UK and China is project finance and production; and (4) all markets are seeking an amelioration of existing controversial VfM assessments so that purported VfM relates to project lifecycles. Therefore, an option framework is proposed to make headway towards a sensible selection of infrastructure procurement approaches in the post COVID-19 era. Originality/ value: This study addresses a current void of enhancing the decision-making process for using PPPs within today’s changing environment and then opens up an avenue for future empirical research to examine the option framework and ensuing VfM decisions. Practically, it presents a holistic VfM landscape for public sector procurers that aim to engage with PPPs for their infrastructure interventions

Comparative Study on Properties of Polylactic Acid Nanocomposites with Cellulose and Chitin Nanofibers Extracted from Different Raw Materials

Polylactic acid (PLA) was reinforced with ultralong cellulose and chitin nanofibers extracted from four raw materials by extrusion. The mechanical, rheological, thermal, and viscoelastic performances of four nanocomposites were comparatively studied in detail. The results showed that fibrillation of poplar was much easier than that of cotton, and fibrillation of crab shell was relatively hard as compared to prawn shell. The poplar CNFs/PLA composite exhibited the best mechanical properties among four nanocomposites due to the highest aspect ratio of nanofibers, while both the cotton CNFs/PLA composite and the crab shell CHNFs/PLA composite had low mechanical strength due to the relatively low aspect ratio. FE-SEM images showed that the ultralong nanofibers were uniformly dispersed in PLA matrix for all four samples with the water preblending method. The CTE values of the nanocomposites with 40 wt% nanofibers extracted from poplar, cotton, crab shell, and prawn shell were 69.5 × 10−6 K−1, 79.6 × 10−6 K−1, 77.2 × 10−6 K−1, and 75.3 × 10−6 K−1, respectively. All the results indicated that the aspect ratio of the nanofibers has a great influence on the performance of the composites, irrespective of the composites prepared by cellulose or chitin

Strain hardening of as-extruded Mg-xZn (x = 1, 2, 3 and 4 wt%) alloys

The influence of Zn on the strain hardening of as-extruded Mg-xZn (x = 1, 2, 3 and 4 wt%) magnesium alloys was investigated using uniaxial tensile tests at 10 s at room temperature. The strain hardening rate, the strain hardening exponent and the hardening capacity were obtained from true plastic stress-strain curves. There were almost no second phases in the as-extruded Mg-Zn magnesium alloys. Average grain sizes of the four as-extruded alloys were about 17.8 μm. With increasing Zn content from 1 to 4 wt%, the strain hardening rate increased from 2850 MPa to 6810 MPa at (σ-σ) = 60 MPa, the strain hardening exponent n increased from 0.160 to 0.203, and the hardening capacity, Hc increased from 1.17 to 2.34. The difference in strain hardening response of these Mg-Zn alloys might be mainly caused by weaker basal texture and more solute atoms in the α-Mg matrix with higher Zn content