Extension of Haskind's relations to cylindrical wave fields in the context of an interaction theory

The Direct Matrix Method Interaction Theory (IT) proposed by Kagemoto and Yue [1] speeds up the computation of hydrodynamic coefficients for large arrays of bodies when compared to direct calculations using standard Boundary Element Method (BEM) solvers. One of the most computationally expensive parts of the matrix method is the calculation of two hydrodynamic operators, known as Diffraction Transfer Matrix (DTM) and Radiation Characteristics (RC), which describe the way an isolated geometry scatters and radiates waves, respectively. A third operator, called Force Transfer Matrix (FTM), was introduced by McNatt et al. [2] to facilitate the calculation of the forces exerted on the bodies. In this paper, a novel set of relations between the FTM and RC components is obtained using the Kochin functions specific to the cylindrical basis solutions. They extend the classical Haskind's relations, valid with incident plane waves, to the cylindrical components of the scattered and radiated fields. Moreover, an alternative demonstration of the identities is given, which does not rely on the far-field asymptotic representation of the potential. Additional expressions are provided that relate the hydrodynamic coefficients and the RC for isolated bodies as well as for arrays, and numerical checking of the derived mathematical expressions is presented. These new relations can be used to speed up calculation of the hydrodynamic operators required for the use of the IT and to test its accuracy.     

Social interactions can affect feeding behaviour of fish in tanks

Fish from the same clutch of eggs, so of the same age and family, can differ substantially in size after some time in a tank as result of social interactions. On the basis of computer simulation studies I here demonstrate that it is possible to mimic this empirical observation using the rules of the standard Dynamic Energy Budget (DEB) model, supplemented with a simple stochastic module for interaction between individuals that have identical parameters. The remarkable result is that length-at-age of two individuals in a tank where the number of food particles is kept constant closely follows von Bertalanffy growth curves with very different parameters, while in reality the individuals have identical parameters. The empirical observation demonstrates that fish are close to the supply end of the supply–demand spectrum and that age-based models for growth don't apply to supply systems. The significance of the result is discussed.     

Influence of surface forcing on near-surface and mixing layer turbulence in the tropical Indian Ocean

An autonomous upwardly-moving microstructure profiler was used to collect measurements of the rate of dissipation of turbulent kinetic energy (ε) in the tropical Indian Ocean during a single diurnal cycle, from about 50 m depth to the sea surface. This dataset is one of only a few to resolve upper ocean ε over a diurnal cycle from below the active mixing layer up to the air–sea interface. Wind speed was weak with an average value of ~5 m s⁻¹ and the wave field was swell-dominated. Within the wind and wave affected surface layer (WWSL), ε values were on the order of 10⁻⁷–10⁻⁶ W kg⁻¹ at a depth of 0.75 m and when averaged, were almost a factor of two above classical law of the wall theory, possibly indicative of an additional source of energy from the wave field. Below this depth, ε values were closer to wall layer scaling, suggesting that the work of the Reynolds stress on the wind-induced vertical shear was the major source of turbulence within this layer. No evidence of persistent elevated near-surface ε characteristic of wave-breaking conditions was found. Profiles collected during night-time displayed relatively constant ε values at depths between the WWSL and the base of the mixing layer, characteristic of mixing by convective overturning. Within the remnant layer, depth-averaged values of ε started decaying exponentially with an e-folding time of 47 min, about 30 min after the reversal of the total surface net heat flux from oceanic loss to gain.     

印度洋海—气某些特征及其海温与北半球大气环流的联系

本文根据印度洋海-气热交换和海温信息区分布特征,得出阿拉伯海是印度洋海-气相互作用的一个重要区域。并讨论了阿拉伯海海温与北半球500hPa高度场和西太平洋副热带高压的一些联系。     

Space–time opportunities for multiple agents: a constraint‐based approach

Constraint‐based models and models constructing accessibility measures mainly focus on single agents having only one available transport mode. However, numerous cases exist where multiple agents or groups of individuals with different available transport modes want to participate in a joint activity at a certain location. The aim of this paper is to provide new insights into representing and reasoning about feasible space–time opportunities for multiple agents. Relying on concepts of time geography, we propose a conceptual framework in order to determine interaction spaces for groups of individuals. Besides availability of means of transport and the locations of each individual, minimum activity duration and opening hours of opportunities are taken into account. The reasoning about space and time is visualized in three dimensions using a hybrid (CAD/GIS) system.     

避免建筑危害—地基基础课题的基本理论探讨

在地基基础—岩土工程的发展过程中,多种原因的理论缺失导致了不少\     

近共振地形强迫Rossby孤立波

利用扰动展开和时空伸长变换导得了包括地形强迫的非齐次ＫｄＶ方程，讨论了近共振地形强迫Ｒｏｓｓｂｙｙ孤立波的产生，及其与自由孤立波的相互作用，得到了一些有意义的结果，显示出地形对扰动具有明显的增幅作用，在某种程度上可以解释局地地形在阻塞高压形成中的作用。     

Localized multiscale energy and vorticity analysis: I. Fundamentals

A new methodology, multiscale energy and vorticity analysis (MS-EVA), is developed to investigate the inference of fundamental processes from oceanic or atmospheric data for complex dynamics which are nonlinear, time and space intermittent, and involve multiscale interactions. Based on a localized orthogonal complementary subspace decomposition through the multiscale window transform (MWT), MS-EVA is real problem-oriented and objective in nature. The development begins with an introduction of the concepts of scale and scale window and the decomposition of variables on scale windows. We then derive the evolution equations for multiscale kinetic and available potential energies and enstrophy. The phase oscillation reflected on the horizontal maps from Galilean transformation is removed with a 2D large-scale window synthesis. The resulting energetic terms are analyzed and interpreted. These terms, after being carefully classified, provide four types of processes: transport, transfer, conversion, and dissipation/diffusion. The key to this classification is the transfer–transport separation, which is made possible by looking for a special type of transfer, the so-called perfect transfer. The intricate energy source information involved in perfect transfers is differentiated through an interaction analysis.The transfer, transport, and conversion processes form the basis of dynamical interpretation for GFD problems. They redistribute energy in the phase space, physical space, and space of energy types. These processes are all referred to in a context local in space and time, and therefore can be easily applied to real ocean problems. When the dynamics of interest is on a global or duration scale, MS-EVA is reduced to a classical Reynolds-type energetics formalism.     

Is indigenous health knowledge converging to herbalism?: Healing practices among the Meru and the Maasai of the Ngarenyanyuki ward,Northern Tanzania

Globalization and cultural interaction, new lifestyles, the diffusion of “modern medicine”, the transformation of traditional religious practices and beliefs, have profoundly challenged and modified indigenous health systems. This paper questions whether due to these changes traditional healing systems are to some extent converging into “herbalism” and losing ties with their original cultural systems.By analyzing the healing practices of two communities (Maasai and Meru) in the rural ward of Ngarenyanyuki (Northern Tanzania), the paper explores how traditional and modern health knowledge circulates, changes, and evolves.Evidence from the case study shows that herbal remedies play an increasingly key role in traditional healing practices. Nevertheless, Maasai and Meru health knowledge emerges as a rich and challenging mix of evolving practices. The paper discusses these ongoing processes and inputs into the debate on health provision in African countries by underlining the need for a policy transition to more holistic healing systems which may provide highly desirable options in the current context of health reforms.     

北京地区地面沉降与地裂缝关系研究

地面沉降与地裂缝是北京平原区的主要地质灾害。本文在大量的实际资料的基础上,分析了地面沉降、地裂缝在时间、空间和活动方式上的关联,认为二者在加剧活动时间上具有同步性,在活动特征上具有相似性;但发育起点不同,分布上也存在某些不一致性。并以高丽营地裂缝为例,分析了地面沉降与地裂缝之间的相互作用,通过八仙庄地面沉降监测站分层监测结果、地下水监测孔的年水位变幅和勘察孔揭露的地层情况,计算出地裂缝两侧土层不均匀沉降差占地裂缝垂向位错量的30%。研究结果可为二者的联合防治提供理论依据。