4,779 research outputs found
"Stability of Spatial Equilibrium"
This paper focuses on externalities between economic agents. We consider spatial dis- tribution of economic activities in a multiregional dynamical system, where regions may be interpreted as clubs, social subgroups, species, or strategies. Our dynamics includes gravity models and replicator dynamics as special cases. Assuming that other variables, such as prices are solved as a function of the population distribution, we analyze both interior and corner equilibria of spatial distribution in a general class of dynamics, including the replicator dynamics and the gravity model. We derive the exact conditions for stable equilibrium and give some interpretations of the stability conditions. We show that interior equilibria are stable in the presence of strong agglomeration economies, but unstable in the presence of strong congestion diseconomies.
The Home Market Effect and the Agricultural Sector
The "home market effect" (HME) is an essential topic of the new trade theory. Assuming the transport costs only for the manufacturing goods, Krugman (1980) shows that the country with bigger market size is a net exporter. The assumption of free transport of the agricultural good was shown mattering a great deal rather than being innocuous by Davis (1998). Particularly, when manufacturing and agricultural goods have identical transport costs, the HME disappears. However, we find that the homogeneous-agricultural-good assumption in Davis' model derives the discontinuity of inverse demand functions, which causes the disappearance of the HME. After establishing an analytical solvable model and assuming two differentiated agricultural goods in two countries, we find that the HME does exist even if the transport cost of the agricultural goods is positive.
Regional Specialization via Differences in Transport Costs
This paper examines a new economic geography model with multiple (three) industries and urban costs. The industries are asymmetric in their transport costs. The following results were obtained. First, if transport costs sufficiently decrease whereas commuting costs are constant, we have three stable location patterns; full dispersion, partial regional specialization, and complete regional specialization. Second, if commuting costs sufficiently decrease (resp. increase) whereas transport costs are constant, we have full agglomeration (resp. full dispersion). The cases with medium value of transport and commuting costs and with multiple (three) regions are analyzed by use of numerical simulation.
Economic Integration and Welfare: Manufacturing vs. Agricultural Markets
In the literature of new trade theory, most papers study the industrial location by imposing the assumption of free transportation in the agricultural sector. This paper explicitly incorporates arbitrary transport costs in both the manufacturing and the agricultural sectors into the Helpman-Krugman-Davis model of two countries and one production factor. The following results are obtained. First, we find a necessary and sufficient condition for the home market effect (HME) to be observed. Secondly, we find that integrating manufacturing markets has contrastive impacts on two countries to integrating agricultural markets. Our results are suggestive for the understanding of various international trade agreements.
Electromagnetic Lens-focusing Antenna Enabled Massive MIMO: Performance Improvement and Cost Reduction
Massive multiple-input multiple-output (MIMO) techniques have been recently
advanced to tremendously improve the performance of wireless communication
networks. However, the use of very large antenna arrays at the base stations
(BSs) brings new issues, such as the significantly increased hardware and
signal processing costs. In order to reap the enormous gain of massive MIMO and
yet reduce its cost to an affordable level, this paper proposes a novel system
design by integrating an electromagnetic (EM) lens with the large antenna
array, termed the EM-lens enabled MIMO. The EM lens has the capability of
focusing the power of an incident wave to a small area of the antenna array,
while the location of the focal area varies with the angle of arrival (AoA) of
the wave. Therefore, in practical scenarios where the arriving signals from
geographically separated users have different AoAs, the EM-lens enabled system
provides two new benefits, namely energy focusing and spatial interference
rejection. By taking into account the effects of imperfect channel estimation
via pilot-assisted training, in this paper we analytically show that the
average received signal-to-noise ratio (SNR) in both the single-user and
multiuser uplink transmissions can be strictly improved by the EM-lens enabled
system. Furthermore, we demonstrate that the proposed design makes it possible
to considerably reduce the hardware and signal processing costs with only
slight degradations in performance. To this end, two complexity/cost reduction
schemes are proposed, which are small-MIMO processing with parallel receiver
filtering applied over subgroups of antennas to reduce the computational
complexity, and channel covariance based antenna selection to reduce the
required number of radio frequency (RF) chains. Numerical results are provided
to corroborate our analysis.Comment: 30 pages, 9 figure
Complete analysis of hyperentangled Bell state in three degrees of freedom
We present an efficient scheme for the complete hyperentangled Bell state
analysis (HBSA) of photon system in polarization and two longitudinal momentum
degrees of freedom (DOFs). In the process of distinguishing the 64
hyperentangled Bell states in three DOFs, the weak cross-Kerr nonlinearity and
self-assisted mechanism are both utilized, which can make our scheme simple and
realizable. We also discuss the application of this complete HBSA scheme in
quantum teleportation that based on hyperentangled state in three DOFs
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