The emergent network structure of the multilateral environmental agreement system

The conventional piecemeal approach to environmental treaty-making has resulted in a ‘maze’ of international agreements. However, little is known empirically about its overall structure and evolutionary dynamics. This study reveals and characterizes the evolving structure of the web of international environmental treaty law. The structure was approximated using 1001 cross-references among 747 multilateral environmental agreements concluded from 1857 to 2012. Known network analysis measures were used to answer the following questions: has a complex system of international environmental treaty law emerged? If so when, and what does it look like? What are its topological properties? To what extent is the institutional complex fragmented? The network analysis suggested that multilateral environmental agreements have self-organized into an interlocking system with a complex network structure. Furthermore, the system has defragmented as it coevolved with the increasing complexity and interconnectivity of global environmental challenges. This study demonstrates the need to approach multilateral environmental agreements in the context of a complex networked system, and recommends against assuming the overall institutional structure is fragmented. Proposals for global environmental governance reform should pay attention to this network's emergent polycentric order and complexity and to the implications of these features for the functioning of the multilateral environmental agreement system.     

The impact of highly permeable layer on hydraulic system in a coastal aquifer

This study is aimed to understand the hydraulic mechanism of coastal aquifer systems that include highly permeable layers (HPLs). These hydrologic conditions can be found in many volcanic islands that are composed of a series of lava flows discharged into sea or other standing body of water. In the first part, we developed a numerical model based on the geologic and hydrologic data obtained from the eastern Jeju Island, Korea, of which the aquifer contains clinker and hyaloclastite layers. The simulation results reproduced spatial location of fresh‐saline water interface, especially the abrupt decline of interface at the inland part and the thickness variation of transition zone along the cross‐section observed at the eastern Jeju coastal aquifer. We were able to find out that these phenomena are strongly related to the presence of the HPL. In the second part, quantitative analyses were conducted with the use of hypothetical models in order to understand the dynamic characteristics of coastal system that includes HPLs. A series of sensitivity studies were conducted to assess the effect of the horizontal length and vertical depth of HPL on the spatial location of the interface toe and the configuration of transition zone. Various case studies have shown that the seawater intruded into the inland more as the horizontal length of HPL was increased and its vertical depth was decreased. In other simulations including two HPLs, the vertical distance between these two HPLs primarily controlled the flow regime, flux variations, and the configuration of the transition zone. Finally, we performed simulations to evaluate the effect of a rising sea‐level. This study provides more understanding of how the presence of HPL controls the seawater intrusion processes, and the spatial configurations of fresh‐saline water interface at coastal aquifers. Copyright © 2012 John Wiley & Sons, Ltd.     

A steepness index unit volume flood hydrograph approach for sub‐daily flow disaggregation

The estimation of sub‐daily flows from daily flood flows is important for many hydrological and hydraulic applications. Flows during flood events often vary significantly within sub‐daily time‐scales, and failure to capture the sub‐daily flood characteristic can result in an underestimation of the instantaneous flood peaks, with possible risk of design failure. It is more common to find a longer record of daily flow series (observed or modelled using daily rainfall series) than sub‐daily flow data. This paper describes a novel approach, known as the steepness index unit volume flood hydrograph approach, for disaggregating daily flood flows into sub‐daily flows that takes advantage of the strong relationship between the standardized instantaneous flood peak and the standardized daily flood hydrograph rising‐limb steepness index. The strength of this relationship, which is considerably stronger than the relationship between the standardized flood peak and the event flood volume, is shown using data from six rivers flowing into the Gippsland Lakes in southeast Australia. The results indicate that the steepness index unit volume flood hydrograph approach can be used to disaggregate modelled daily flood flows satisfactorily, but its reliability is dependent on a model's ability to simulate the standardized daily flood hydrograph rising‐limb steepness index and the event flood volume. Copyright © 2007 John Wiley & Sons, Ltd.     

Adaptive Surface Interference Suppression for Matched-Mode Source Localization

Localizing a quiet submerged target in the presence of loud interfering surface ships is an important problem for matched-field processing (MFP) in shallow water. Typically, a data-driven interference suppression scheme is employed which requires neither prior information of the interferer's location nor filter design optimization and iterative estimation. However, the target and the interferers are usually in motion resulting in spreading or mixing of signal energies in their subspaces, thus making it difficult to determine the interference subspace dimension. In this paper, we exploit the difference in modal amplitudes for surface and submerged sources by eigenanalysis of the modal cross-spectral density matrix (CSDM). Simulation and experimental data results show that the interference subspace can be estimated adaptively and the beam output for the target is enhanced.      

Nature and Properties of sub-DLAs (absorbers with 1019 ≤ N(HI) ≤ 2 * 1020 cm-2)

Quasar absorbers provide an alternative approach to the study of galaxies. In particular, the detection of high-column density systems allow to measure the cosmological evolution of the neutral gas mass and metals in the Universe. At z <3.5, 90% of the HI mass is in damped Lyα systems (DLAs). But it has been suggested that atz > 3.5, 45% of the HI lies in systems below the traditional DLA definition (2 x 10²⁰ cm^-2), in ‘sub-DLAs’ with 10¹⁹ < N(HI) < 2 x 10²⁰ cm^-2. Here we present a sample of sub-DLAs issued from UVES archive quasar spectra. We have measured the sub-DLA number density redshift evolution and directly establish their column density distribution function. We have also undertaken a detailed metal abundance analysis of this class of absorbers to compare with the characteristics of the well studied DLAs. This revised version was published online in September 2006 with corrections to the Cover Date.     

扩展SSH Hubbard模型的晶格振动矩阵

在计及最近邻电子相互作用的扩展ＳＳＨＨｕｂｂａｒｄ模型时，得到了晶格振动矩阵，它对电子的正负自旋态对称和非对称的各类非线性元激发情形均适用。     

射电天球参考架指向维持方法讨论

依据河外射电源天球参考架的现状与建立射电天球参考架的最终目的，本文提出了以共同基本源维持参考架指向的观点。对实际资料的归算结果表明，在确保参考架指向长期稳定性方面，共同基本源指向维持模型优于ＩＥＲＳ维持模型。依据验算结果，文中同时讨论了选源标准与参考架指向稳定性的关系，指出基本源一次性变更的比例不能过高。一方面应完善选源标准；另一方面，一旦此标准发生性？上的改变时，应对在旧标准下选出的基本源进行复核，并作相应的指向调整，否则将可能造成参考架指向的跳变。     

Long-Term Soft X-Ray Variability of Active Galaxies. I. Mrk 926

We present a detailed analysis of the soft X-ray (0.1–2.4 keV) emission of the Seyfert 1 galaxy Mrk 926 in order to investigate its long-term variation. The X-ray data were obtained from the ROSAT-PSPC archives. The light curves show a gradual decrease of brightness for a time scales of 36months with the exception of a single flare event superimposed on the gradual variation of brightness. The light variations for three different energy bands and the hardness ratios were investigated to search for correlations; no correlation was confirmed. In order to compare spectral variations during the flare event with other periods, the spectral parameters were determined. Results of our analysis are discussed within the framework of the accretion disk phenomenon. This revised version was published online in July 2006 with corrections to the Cover Date.     

异心球形电容器电容的精确解

提出了导体系统电容问题求解的一种新方法，借助双球面坐标系和平行板电容公式，求出了异心球形电容器电容的解析式。此外，对另外几种类型异体系统的电容也作了讨论。