FloWaveNet : A Generative Flow for Raw Audio

Most modern text-to-speech architectures use a WaveNet vocoder for synthesizing high-fidelity waveform audio, but there have been limitations, such as high inference time, in its practical application due to its ancestral sampling scheme. The recently suggested Parallel WaveNet and ClariNet have achieved real-time audio synthesis capability by incorporating inverse autoregressive flow for parallel sampling. However, these approaches require a two-stage training pipeline with a well-trained teacher network and can only produce natural sound by using probability distillation along with auxiliary loss terms. We propose FloWaveNet, a flow-based generative model for raw audio synthesis. FloWaveNet requires only a single-stage training procedure and a single maximum likelihood loss, without any additional auxiliary terms, and it is inherently parallel due to the characteristics of generative flow. The model can efficiently sample raw audio in real-time, with clarity comparable to previous two-stage parallel models. The code and samples for all models, including our FloWaveNet, are publicly available.Comment: 9 pages, ICML'201

Economic Effects of Environmental Taxation on Chemical Fertilizers

This paper analyzes the economic effects of environmental taxes on chemical fertilizer in producing rice. A charge of 10 percent tax on nitrogen fertilizer leads to a reduction in fertilizer use of 1.5 percent without changing rice yield, but the farm income is reduced by 0.6 percent. The tax rate of 100 percent leads to a reduction of 14.6 percent in fertilizer use, a 0.4 percent reduction in rice yield, and a 3.6 percent reduction in farm income. A significant feature of eco-taxes imposed on chemical fertilizers is their revenue potential, which could contribute to increasing government budgets for finance pollution control programs, such as education and R&D. This study provides an insight into the application of market-based instrument to achieve sustainable agricultural development.polluter-pays-principle, nonpoint pollution, environmental tax, nitrogen fertilizer, negative externalities, Environmental Economics and Policy, Q28, Q52,

A Practical Cooperative Multicell MIMO-OFDMA Network Based on Rank Coordination

An important challenge of wireless networks is to boost the cell edge performance and enable multi-stream transmissions to cell edge users. Interference mitigation techniques relying on multiple antennas and coordination among cells are nowadays heavily studied in the literature. Typical strategies in OFDMA networks include coordinated scheduling, beamforming and power control. In this paper, we propose a novel and practical type of coordination for OFDMA downlink networks relying on multiple antennas at the transmitter and the receiver. The transmission ranks, i.e.\ the number of transmitted streams, and the user scheduling in all cells are jointly optimized in order to maximize a network utility function accounting for fairness among users. A distributed coordinated scheduler motivated by an interference pricing mechanism and relying on a master-slave architecture is introduced. The proposed scheme is operated based on the user report of a recommended rank for the interfering cells accounting for the receiver interference suppression capability. It incurs a very low feedback and backhaul overhead and enables efficient link adaptation. It is moreover robust to channel measurement errors and applicable to both open-loop and closed-loop MIMO operations. A 20% cell edge performance gain over uncoordinated LTE-A system is shown through system level simulations.Comment: IEEE Transactions or Wireless Communications, Accepted for Publicatio

THREE ESSAYS ON EXCHANGE RATE ECONOMICS

A country’s economy is becoming more and more dynamic and complicated in its scale and mobility. So, the concerns of exchange rate economics have become more popular. My research interest is in international economics with its major factor, exchange rates and other macroeconomic variables. Chapter 1 presents a brief introduction of the three studies. Chapter Two investigate the role of exchange rate changes with particular attention to international capital flows. With liberalization of capital movements, international capital movements became free and unrestricted in many emerging market economies as well as developed countries. Using a Vector Auto-regressive (VAR) model for a small open economy in which the endogeneity of exchange rate changes is fully taken into account, I find that capital movements are more likely to be a cause of output fluctuations and current account deficits in developing countries than a channel of equilibrium changes. I also find that domestic currency depreciation is far more likely to be contractionary on domestic output in developing countries than in developed countries. Interestingly, the trade balance improves after depreciation regardless of its output consequence. These findings suggest that there are important differences between developed and developing economies in the way capital movements and exchange rate changes affect and are affected. Chapter Three demonstrates the dynamic relationship between the current account and the real exchange rate in response to permanent and temporary shocks using structural VAR models for seven developed countries and five developing countries. Special focus is given to the issue of the stationarity of the current account. Capital flows are also included to capture external shocks as well as potential structural breaks due to financial liberalization. I find that the results for unit root tests for the current account are ambiguous. By testing two different VAR models, each taking an opposing stance on the stationarity of the current account, I conclude that responses based on a stationary current account are a better fit to the current theoretical view than those based on a nonstationary current account process. Additionally, the real exchange rate and the current account are positively correlated under a permanent shock while two variables are negatively correlated under a monetary shock. I also find that real exchange rate is an endogenous variable, which is not closely related to the temporary factors that affect the current account in the short run. Chapter Four examines the long-run mean reverting behavior of the real exchange rates with its six different definitions for 27 economies using annual data from 1974 to 2003. I find that Purchasing Power Parity (PPP) holds better, and the half-life of the real exchange rates is shorter when the wholesale price index, rather than consumer price index, is used as price level measure. Somewhat surprisingly, there is no evidence that PPP holds better with trade-weighted real exchange rates than with bilateral ones regardless of the price index used. Strong evidence for PPP emerges only with the use of Im, Pesaran, and Shin (2003) panel tests but not with the Levine, Lin, and Chu (2002)

Genome-wide analysis to predict protein sequence variations that change phosphorylation sites or their corresponding kinases

We define phosphovariants as genetic variations that change phosphorylation sites or their interacting kinases. Considering the essential role of phosphorylation in protein functions, it is highly likely that phosphovariants change protein functions and may constitute a proportion of the mechanisms by which genetic variations cause individual differences or diseases. We categorized phosphovariants into three subtypes and developed a system that predicts them. Our method can be used to screen important polymorphisms and help to identify the mechanisms of genetic diseases