A Ricardian Model with Endogenous Comparative Advantage and Endogenous Trade Policy Regimes

This paper develops a general equilibrium model with transaction costs and endogenous and exogenous comparative advantages. In the model, the governments are allowed to choose between tariff war, tariff negotiation, and laissez faire regimes. The model shows that the level of division of labor and the volume of trade increase as transaction conditions improve. In the process of moving to a high level of division of labour, a country may receive more gains from trade even if its terms of trade deteriorate. This is because an expansion of the network size of division of labour can generate productivity gains that outweigh the adverse effect of the terms of trade deterioration. When a high level of division of labor occurs in general equilibrium, if both countries play a Nash tariff game, a tariff war may break out, which can dissipate all the gains from trade. Facing this risk, all governments would prefer trade negotiations to a trade war. A Nash tariff negotiation would result in zero tariff rates. If a medium level of division of labor occurs in general equilibrium, then unilateral tariff protection and unilateral laissez faire policies would coexist. The result provides a plausible story about the evolution of trade policy regimes, and highlights the importance of trade negotiations in achieving trade liberalization.inframarginal analysis of trade theory, Ricardo model, dual structure, underdevelopment

Integrable Open Spin Chains from Flavored ABJM Theory

We compute the two-loop anomalous dimension matrix in the scalar sector of planar ${\cal N}=3$ flavored ABJM theory. Using coordinate Bethe ansatz, we obtain the reflection matrix and confirm that the boundary Yang-Baxter equations are satisfied. This establishes the integrability of this theory in the scalar sector at the two-loop order.Comment: v2, 25 pages, 2 figures, minor corrections, references adde

A single-end protection scheme for hybrid MMC HVDC grids considering the impacts of the active fault current-limiting control

In the hybrid modular multilevel converter (MMC) based high voltage direct current (HVDC) systems, the fault current can be actively suppressed by the converter itself, which endows a smaller requirement for current-limiting reactors (CLR) and a larger time margin for fault detection algorithms, comparing with the half-bridge MMC. But the robustness to fault resistance and noise disturbance of existing boundary protection schemes will be deteriorated with small CLRs. Moreover, the fast response of the fault current-limiting control will change the output DC voltage of hybrid MMC, which affects the fault characteristics and may cause mal-operation of existing protection algorithms. Thus, a single-end protection scheme considering the impacts of the active current-limiting control is proposed for the hybrid MMC based DC grids. The traveling-wave characteristics under different fault stages are analyzed to evaluate the impacts of the fault current-limiting control. In addition, a coordination protection strategy versus different fault conditions is adopted to improve reliability. Various cases in PSCAD/EMTDC are simulated to verify that the proposed method is robust to fault resistance, fault distance, power reversal, AC faults, and immune to noise

Experimental study on natural vibration frequency identification of hydraulic concrete structure using concrete piezoceramic smart module

The identification of structural modal parameter is an important link in the dynamics monitoring and diagnosis for the structural health. The passive monitoring mode of piezoceramic is used to solve the natural vibration frequency identification problem of hydraulic concrete structure. Based on self-made concrete piezoelectric smart module (CPSM), a system is developed to obtain the modal parameters of hydraulic concrete structure. The CPSM is regarded as a sensor to monitor passively the structural natural vibration frequency. The method and process are proposed to identify the natural vibration frequency of hydraulic concrete structure. Based on the physical model and numerical simulation model, the rationality and feasibility of the proposed method are verified