Computing Shapley Values for Mean Width in 3-D

The Shapley value is a common tool in game theory to evaluate the importance of a player in a cooperative setting. In a geometric context, it provides a way to measure the contribution of a geometric object in a set towards some function on the set. Recently, Cabello and Chan (SoCG 2019) presented algorithms for computing Shapley values for a number of functions for point sets in the plane. More formally, a coalition game consists of a set of players $N$ and a characteristic function $v: 2^N \to \mathbb{R}$ with $v(\emptyset) = 0$. Let $\pi$ be a uniformly random permutation of $N$, and $P_N(\pi, i)$ be the set of players in $N$ that appear before player $i$ in the permutation $\pi$. The Shapley value of the game is defined to be $\phi(i) = \mathbb{E}_\pi[v(P_N(\pi, i) \cup \{i\}) - v(P_N(\pi, i))]$. More intuitively, the Shapley value represents the impact of player $i$'s appearance over all insertion orders. We present an algorithm to compute Shapley values in 3-D, where we treat points as players and use the mean width of the convex hull as the characteristic function. Our algorithm runs in $O(n^3\log^2{n})$ time and $O(n)$ space. Our approach is based on a new data structure for a variant of the dynamic convolution problem $(u, v, p)$, where we want to answer $u\cdot v$ dynamically. Our data structure supports updating $u$ at position $p$, incrementing and decrementing $p$ and rotating $v$ by $1$. We present a data structure that supports $n$ operations in $O(n\log^2{n})$ time and $O(n)$ space. Moreover, the same approach can be used to compute the Shapley values for the mean volume of the convex hull projection onto a uniformly random $(d - 2)$-subspace in $O(n^d\log^2{n})$ time and $O(n)$ space for a point set in $d$-dimensional space ($d \geq 3$)

Effects of Culture on Economic Performance and Grassland Degradation

This study uses micro-level data gathered for Tibetans and Mongolians living in the same region (Qinghai Lake area in Northwest China) and having similar religion (Buddhism) and livelihoods (livestock raising) to examine how cultural differences between these two ethnic groups affect their integration into markets, their means of livestock production, and the extent of degradation of the grassland. We find significant cultural differences between the two ethnic groups, and conclude that the impact of religious attitudes on the market orientation of herder households is the dominating force explaining a relatively high degree of grassland degradation among Mongolian households

Les effets de la culture sur les performances économiques et la dégradation des prairies

Cette étude est fondée sur des informations recueillies au cours d’enquêtes sur des Tibétains et des Mongols qui vivent dans une même région (la région du lac Qinghai dans le Nord-Ouest de la Chine), pratiquent la même religion et présentent un mode de vie similaire. Il s’agira d’examiner comment les différences culturelles entre ces deux groupes ethniques affectent leur intégration au marché, leur mode d’élevage du bétail et le niveau de dégradation des pâturages. Nous constatons des différences culturelles fondamentales entre les groupes, l’impact de l’attitude religieuse sur le rapport au marché apparaissant comme la force dominante qui explique le degré relativement élevé de dégradation des prairies parmi les ménages mongols

Les effets de la culture sur les performances économiques et la dégradation des prairies

Cette étude est fondée sur des informations recueillies au cours d’enquêtes sur des Tibétains et des Mongols qui vivent dans une même région (la région du lac Qinghai dans le Nord-Ouest de la Chine), pratiquent la même religion et présentent un mode de vie similaire. Il s’agira d’examiner comment les différences culturelles entre ces deux groupes ethniques affectent leur intégration au marché, leur mode d’élevage du bétail et le niveau de dégradation des pâturages. Nous constatons des différences culturelles fondamentales entre les groupes, l’impact de l’attitude religieuse sur le rapport au marché apparaissant comme la force dominante qui explique le degré relativement élevé de dégradation des prairies parmi les ménages mongols

Intelligent Omni-Surfaces for Full-Dimensional Wireless Communications: Principle, Technology, and Implementation

The recent development of metasurfaces has motivated their potential use for improving the performance of wireless communication networks by manipulating the propagation environment through nearly-passive sub-wavelength scattering elements arranged on a surface. However, most studies of this technology focus on reflective metasurfaces, i.e., the surface reflects the incident signals towards receivers located on the same side of the transmitter, which restricts the coverage to one side of the surface. In this article, we introduce the concept of intelligent omni-surface (IOS), which is able to serve mobile users on both sides of the surface to achieve full-dimensional communications by jointly engineering its reflective and refractive properties. The working principle of the IOS is introduced and a novel hybrid beamforming scheme is proposed for IOS-based wireless communications. Moreover, we present a prototype of IOS-based wireless communications and report experimental results. Furthermore, potential applications of the IOS to wireless communications together with relevant research challenges are discussed

theoretical approaches and empirical analysis

Non-PRIFPRI4; BJODSG

Impact of Land Institutional Factors on Farm Management and Soil Quality

Soil quality has important implications for sustainable agricultural development and food self-sufficiency in many developing countries. A decrease in soil nutrient stocks, one of the components of soil quality, necessitates more inputs and greater management skills in order to compensate for the reduction in nutrients availability. This is why the interaction of agricultural development and soil quality management attracts widespread attention from researchers. Applying plot level data on input/output, and a selected number of soil quality indicators and farm household level information, from the three villages, this paper examines the impact of land fragmentation and land tenure on soil management, the dynamic component of soil quality, crop husbandry and rice yield at plot level. A 2SLS econometric approach is applied to simultaneously estimate the interlinked relationships between these variables. From these results we conclude that land fragmentation does play a role in farm management practices and decisions. The land tenure status of a plot does not affect crop husbandry decisions on labor and herbicide use. Farmers on rented-in plots do, however, use more chemical fertilizers (phosphorus and potassium). This implies that farmers care more about short-term yields than about the built-up of long-term soil productivity. In order to sustain long-term soil productivity, measures should be taken to ensure that the prices for renting land reflect such soil investments

Impact of land fragmentation on rice producer's technical efficiency in Southeast China

PRIFPRI4; Theme 3; Subtheme 3.2; Managing natural resources; Agriculture and Rural DevelopmentDSG

Impact of land fragmentation on rice producer's technical efficiency in Southeast China [In Chinese]

PRIFPRI3; ISI; Theme 3; Subtheme 3.2; Managing natural resources; Agriculture and Rural DevelopmentDSG