84,691 research outputs found
A Quadratic Generalization of the Almost Ideal and Translog Demand Systems: An Application to Food Demand in Urban China
A new demand system, the QGAITL model, nesting the quadratic almost ideal, translog and LES models as its special cases, is introduced and estimated in this paper. Employing urban household data of four major food items from Jiangsu China in 2001, empirical evidence from both in-sample evaluations and out-of-sample forecasting comparisons shows that the QGAITL is superior to its nested models, whether or not demographic effects are incorporated.Demand and Price Analysis,
Delineating Intra-Urban Spatial Connectivity Patterns by Travel-Activities: A Case Study of Beijing, China
Travel activities have been widely applied to quantify spatial interactions
between places, regions and nations. In this paper, we model the spatial
connectivities between 652 Traffic Analysis Zones (TAZs) in Beijing by a taxi
OD dataset. First, we unveil the gravitational structure of intra-urban spatial
connectivities of Beijing. On overall, the inter-TAZ interactions are well
governed by the Gravity Model , where
, are degrees of TAZ , and the distance between
them, with a goodness-of-fit around 0.8. Second, the network based analysis
well reveals the polycentric form of Beijing. Last, we detect the semantics of
inter-TAZ connectivities based on their spatiotemporal patterns. We further
find that inter-TAZ connections deviating from the Gravity Model can be well
explained by link semantics.Comment: 6 pages, 4 figure
The Gaussian Multiple Access Diamond Channel
In this paper, we study the capacity of the diamond channel. We focus on the
special case where the channel between the source node and the two relay nodes
are two separate links with finite capacities and the link from the two relay
nodes to the destination node is a Gaussian multiple access channel. We call
this model the Gaussian multiple access diamond channel. We first propose an
upper bound on the capacity. This upper bound is a single-letterization of an
-letter upper bound proposed by Traskov and Kramer, and is tighter than the
cut-set bound. As for the lower bound, we propose an achievability scheme based
on sending correlated codes through the multiple access channel with
superposition structure. We then specialize this achievable rate to the
Gaussian multiple access diamond channel. Noting the similarity between the
upper and lower bounds, we provide sufficient and necessary conditions that a
Gaussian multiple access diamond channel has to satisfy such that the proposed
upper and lower bounds meet. Thus, for a Gaussian multiple access diamond
channel that satisfies these conditions, we have found its capacity.Comment: submitted to IEEE Transactions on Information Theor
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