Closed-Form Critical Conditions of Subharmonic Oscillations for Buck Converters

A general critical condition of subharmonic oscillation in terms of the loop gain is derived. Many closed-form critical conditions for various control schemes in terms of converter parameters are also derived. Some previously known critical conditions become special cases in the generalized framework. Given an arbitrary control scheme, a systematic procedure is proposed to derive the critical condition for that control scheme. Different control schemes share similar forms of critical conditions. For example, both V2 control and voltage mode control have the same form of critical condition. A peculiar phenomenon in average current mode control where subharmonic oscillation occurs in a window value of pole can be explained by the derived critical condition. A ripple amplitude index to predict subharmonic oscillation proposed in the past research has limited application and is shown invalid for a converter with a large pole.Comment: Submitted to an IEEE Journal on Dec. 23, 2011, and resubmitted to IEEE Transactions on Circuits and Systems-I on Feb. 14, 2012. My current six papers in arXiv have a common reviewe

Shared Equity Policy in Joint Ventures for Host Countries

This paper provides a game model for examining the host overseas investment policy and MNEs equity strategy in international joint ventures. This paper refines previous Chen & Chung’s (2008) results and considers the host policy about MNEs’ joint-venture. This paper shows foreign firms increase their technology transfer incentive because less competition from the joint-venture partner when a foreign firm holds lower shares. And the holding shares of foreign firms must be not smaller than 50 percent. The host welfare increases with foreign firms’ minority equity. The equity conflict exists in the higher technology spillover and transfer cost cases. Hence, the host governments always impose investment restrictions on MNEs in the Developing countries. Otherwise, it has more loose policy in the Developed countries.joint venture; equity policy; welfare; technology transfer; spillover

Fish play Minority Game as humans do

Previous computer simulations of the Minority Game (MG) have shown that the average agent number in the winning group (i.e., the minority group) had a maximal value such that the global gain was also maximal when an optimal amount of information was available to all agents . This property was further examined and its connection to financial markets has also been discussed . Here we report the results of an unprecedented real MG played by university staff members who clicked one of two identical buttons (A and B) on a computer screen while clocking in or out of work. We recorded the number of people who clicked button A for 1288 games, beginning on April 21, 2008 and ending on October 31, 2010, and calculated the variance among the people who clicked A as a function of time. We find that variance per person decreases to a minimum and rises to a value close to 1/4 which is the expected value when agents click buttons randomly. Our results are consistent with previous simulation results for the theoretical MG and suggest that our agents had employed more information for their strategies as their experience playing the game grew. We also carried out another experiment in which we forced 101 fish to enter one of the two symmetric chambers (A and B). We repeated the fish experiment 500 times and found that the variance of the number of fish that entered chamber A also decreased to a minimum and then increased to a saturated value, suggesting that fish have memory and can employ more strategies when facing the same situation again and again

Using Nyquist or Nyquist-Like Plot to Predict Three Typical Instabilities in DC-DC Converters

By transforming an exact stability condition, a new Nyquist-like plot is proposed to predict occurrences of three typical instabilities in DC-DC converters. The three instabilities are saddle-node bifurcation (coexistence of multiple solutions), period-doubling bifurcation (subharmonic oscillation), and Neimark bifurcation (quasi-periodic oscillation). In a single plot, it accurately predicts whether an instability occurs and what type the instability is. The plot is equivalent to the Nyquist plot, and it is a useful design tool to avoid these instabilities. Nine examples are used to illustrate the accuracy of this new plot to predict instabilities in the buck or boost converter with fixed or variable switching frequency.Comment: Submitted to an IEEE journal in 201

Quantum and Thermal Transitions Out of the Pair-Supersolid Phase of Two-Species Bosons in Lattice

We investigate two-species bosons in a two-dimensional square lattice by quantum Monte Carlo method. We show that the inter-species attraction and nearest-neighbor intra-species repulsion results in the pair-supersolid phase, where a diagonal solid order coexists with an off-diagonal pair-superfluid order. The quantum and thermal transitions out of the pair-supersolid phase are characterized. It is found that there is a direct first order transition from the pair-supersolid phase to the double-superfluid phase without an intermediate region. Furthermore, the melting of the pair-supersolid occurs in two steps. Upon heating, first the pair-superfluid is destroyed via a KT transition then the solid order melts via an Ising transitio