国家债务适度规模研究 —基于因子增强阈值模型

本文基于国家债务适度规模假说，采用时间序列数据和因子增强阈值模型对世界有代表性国家债务适度规模的进行了测定。研究结果显示：在样本期间内，第一，在5%的显著性水平下，除西班牙外，大部分有代表性国家都不能拒绝不存在阈值效应的零假设，在10%的显著性水平下，除西班牙、希腊、印度外，其它国家不能拒绝不存在阈值效应的零假设；第二，债务规模同经济增长并不存在简单线性关系，部分验证了前文关于国家债务适度规模假说；第三，从阈值水平来看，未有阈值效应的国家中，很多都超过了60%的警戒线，如日本、美国、加拿大等，但我们的检验结果表明，这些国家债务规模并没阈值效应，即说明目前的债务水平的安全的；第四，对于中国来说，我们的结论更加验证了中国总体债务规模安全、可控，并不存在发生总体债务危机的风险；第五，同Mendoza et al.（2008）有关最优主权债务负担率区间为48%～50%的研究结论相比，我们的结论有着很大的差异，其原因在于，我们的研究充分考虑的国家的差异性，即考虑了不同国家的自身特点，同时，也将全球性因素作为考虑的因素之一

Influence of Community Factors on Water Saving in a Mega City after Implementing the Progressive Price Schemes

A progressive price scheme (PPS) has been implemented in Shanghai since 2013 in consideration of residents’ ability to pay, and charges are based on the actual water consumption of the residents, in an effort to balance the rational allocation of water resources and the goal of saving water between rich and poor families. In the current work, the effect of the PPS for water use was evaluated based on the water use of 6661 households from 14 communities in Shanghai. It was found that the PPS did not reduce household water consumption when comparing the water consumption per household both before and after the implementation of the PPS policy. To investigate the weakness of the PPS, a principal component analysis (PCA) and a hierarchical cluster analysis (HCA) were conducted to access the relationships between mean household water use and community factors such as housing price, management fees, and the number of parking sites. Moreover, a significant inverted U-shaped curve between housing price and water use was found, which demonstrates that rental households shared by several tenants were the main consumers of residential water, and they were not sensitive to the water price improvement in the PPS due to sharing water prices. Therefore, a proposal was made in this work to increase the proportion of water fee expenditure in the total household income and to use 3% as the benchmark for water affordability. Our results provided a new picture of residential water use in big cities and a method for saving and balancing urban water resources

A New High Holding Voltage Dual-Direction Scr With Optimized Segmented Topology

While silicon controlled rectifiers (SCRs) are highly robust electrostatic discharge (ESD) protection devices, they typically are not suited for high-voltage ESD protection due to their inherently low holding voltage and thus vulnerability to latch-up threat. In this letter, a new high holding voltage dual-direction SCR (NHHVDDSCR) with a small area and optimized topology is developed in a 0.18-μm CMOS technology. The results of the NHHVDDSCR and other SCR devices measured from the transmission line pulsing are compared and discussed. It is shown that the NHHVDDSCR can possess a relatively high and adjustable holding voltage, as well as an acceptable failure current for robust ESD protection of high voltage applications

Influence of Beam-to-Column Linear Stiffness Ratio on Failure Mechanism of Reinforced Concrete Moment-Resisting Frame Structures

The design philosophy of a strong-column weak-beam (SCWB), commonly used in seismic design codes for reinforced concrete (RC) moment-resisting frame structures, permits plastic deformation in beams while keeping columns elastic. SCWB frames are designed according to beam-to-column flexural capacity ratio requirements in order to ensure the beam-hinge mechanism during large earthquakes and without considering the influence of the beam-to-column stiffness ratio on the failure modes of global structures. The beam-to-column linear stiffness ratio is a comprehensive indicator of flexural stiffness, story height, and span. This study proposes limit values for different aseismic grades based on a governing equation deduced from the perspective of member ductility. The mathematical expression shows that the structural yielding mechanism strongly depends on parameters such as material strength, section size, reinforcement ratio, and axial compression ratio. The beam-hinge mechanism can be achieved if the actual beam-to-column linear stiffness ratio is smaller than the recommended limit values. Two 1/3-scale models of 3-bay, 3-story RC frames were constructed and tested under low reversed cyclic loading to verify the theoretical analysis and investigate the influence of the beam-to-column linear stiffness ratio on the structural failure patterns. A series of nonlinear dynamic analyses were conducted on the numerical models, both nonconforming and conforming to the beam-to-column linear stiffness ratio limit values. The test results indicated that seismic damage tends to occur at the columns in structures with larger beam-to-column linear stiffness ratios, which inhibits the energy dissipation. The dynamic analysis suggests that considering the beam-to-column linear stiffness ratio during the design of structures leads to a transition from a column-hinge mechanism to a beam-hinge mechanism

Atomistic Simulations of Plasticity in Heterogeneous Nanocrystalline Ni Lamella

Atomistic simulations were performed on heterogeneous nanocrystalline (NC) Ni lamella made up of alternating NC and single crystalline (SC) layers to explore the effect of the heterogeneous microstructure on their mechanical response. It was found that the heterogeneous NC Ni lamella exhibit higher strength and better crack resistance than the pure NC Ni. After quantitatively analyzing the distribution of Von Mises shear strain in each sample, we found that the SC layer in heterogeneous NC Ni lamella can not only strengthen the whole sample following the conventional composite strengthening mechanism, but also homogenize the plastic strains in the NC layer and suppress the crack nucleation and propagation. The findings from this study can provide valuable insight into improving nanomaterial processing techniques, and have implications for the design of gradient or heterogeneous structures with superior properties

Lagged settlement in sandy cobble strata and earth pressure on shield tunnel

Lagged settlement is a typical accident induced by shield construction in sandy cobble strata. This paper analyzed the process and mechanism of lagged settlement, results show that all phases are in accord with the characteristics of ellipsoid theory of particle flows. Based on this theory, a method for calculating coefficient of lateral earth pressure and loosened earth pressure is proposed in this research. For the coefficient of lateral earth pressure, the boundary of loosened ellipsoid is divided into two parts, the arch zone and the excavation zone, and the lateral pressure coefficients are derived respectively according to the stress state. For loosened earth pressure on tunnel, the Terzaghi earth pressure theory and Protodyakonov earth pressure theory are adapted in different conditions according to the state of loosened cobble soil. Theories developed in this study can be applied on determination of shield excavation parameters, as well as calculation of loosened earth pressure and control of tunnel support.In Special Issue: Mathematical Methods in Civil EngineeringMaterials and Environmen

Formation of Bromate During Ferrate(VI) Oxidation of Bromide in Water

Ferrate (VI) is traditionally recognized as a safe oxidant without production of disinfection byproducts (DBPs). However, here we detected probable carcinogenic bromate (BrO 3 - ) during ferrate(VI) oxidation of bromide (Br - )-containing water, and evaluated the effects of pH, ferrate(VI) dose, initial Br - concentration, and co-existing anions on the BrO 3 - formation. BrO 3 - was produced at a moderately-weakly acidic pH condition and in the absence of phosphate that was commonly applied as a buffer and stabilizing agent in previous ferrate(VI) studies. At pH 5.0, the produced BrO 3 - was increased from 12.5 to 273.8 μg/L with the increasing initial Br - concentration from 200 to 1000 μg/L at 10 mg/L Fe(VI), corresponding to an increase in the molar conversion ([BrO 3 - ]/initial [Br - ]) from 2.3% to 10.3%, in a bicarbonate-buffered solution. As pH increased to 7.0, the BrO 3 - concentration gradually dropped. The BrO 3 - production appeared to be associated with the oxidation by high valence iron species (i.e. Fe(VI), Fe(V) and Fe(IV)). Two key intermediate products (i.e. hypobromous acid/hypobromite (HOBr/OBr - ) and hydrogen peroxide (H 2 O 2 )) relevant to the bromate formation were identified. The production of HOBr, a requisite intermediate for the ensuing bromate formation, was indirectly validated through identification of bromine-containing trihalomethanes and haloacetic acids during ferrate oxidation in a natural water, though these bromo-organic DBPs produced were insignificant. Furthermore, the inhibition effects of various anions on the formation of BrO 3 - followed chloride \u3c sulfate \u3c silicate \u3c phosphate. More H 2 O 2 was detected at higher phosphate concentration. It could reduce HOBr to Br - , thereby inhibiting the bromate formation

The impact of workplace violence on job burnout among Chinese correctional officers: the chain mediating effects of stress and insomnia

Abstract Background The risk of workplace violence and job burnout among Chinese correctional officers is high. Stress and insomnia may influence the relationship between workplace violence and job burnout; however, this influence has been rarely studied. This study aimed to explore the effect of workplace violence on job burnout among Chinese correctional officers and to assess the contribution of stress and insomnia to this effect. Methods In this study, the workplace violence scale, the Assens insomnia scale, the 21-item Depression Anxiety Stress Scale, and the Maslach Burnout Inventory-General Survey scale were used to assess the workplace violence, insomnia, stress, and job burnout experienced by the 472 correctional officers, respectively. Results The results showed that (1) workplace violence was significantly and positively predictive of job burnout, (2) workplace violence affected job burnout through the mediation of stress, (3) workplace violence affected job burnout through the mediation of insomnia, and (4) stress and insomnia played fully interlocking mediating roles in the effect of workplace violence on job burnout. Conclusion Stress and insomnia may play a full mediating role in the relationship between workplace violence and job burnout. This suggested that correctional officers may take measures to reduce stress and improve insomnia, thereby reducing their job burnout. Further research may focus on the development of effective interventions to reduce stress and improve insomnia among correctional officers