LMODEL: A satellite precipitation methodology using cloud development modeling. Part I: Algorithm construction and calibration

The Lagrangian Model (LMODEL) is a new multisensor satellite rainfall monitoring methodology based on the use of a conceptual cloud-development model that is driven by geostationary satellite imagery and is locally updated using microwave-based rainfall measurements from low earth-orbiting platforms. This paper describes the cloud development model and updating procedures; the companion paper presents model validation results. The model uses single-band thermal infrared geostationary satellite imagery to characterize cloud motion, growth, and dispersal at high spatial resolution (similar to 4 km). These inputs drive a simple, linear, semi-Lagrangian, conceptual cloud mass balance model, incorporating separate representations of convective and stratiform processes. The model is locally updated against microwave satellite data using a two-stage process that scales precipitable water fluxes into the model and then updates model states using a Kalman filter. Model calibration and updating employ an empirical rainfall collocation methodology designed to compensate for the effects of measurement time difference, geolocation error, cloud parallax, and rainfall shear

"Does the Appointment of the Outside Director Increase Firm Value? The Evidence from Taiwan"

We examine the stock market reaction to the announcement of outside director appointments in Taiwan. We employ a sample of 58 outside director announcements made by Taiwan Stock Exchange listed firms during the period 1 January, 1999 to 30 June, 2003. Using this data, we can test some important hypotheses regarding the role of outside directors in conjunction with other conditions for corporate performance in affecting the stock market reactions. Our empirical findings indicate that there exists a significantly positive reaction to the announcements. The cumulative abnormal returns ---one indicator of stock market reaction measured by using the methodology of market model based event study --- reached 4.776%. We also find that the abnormal returns are positive and higher with respect to each of the following characteristics: poorer prior corporate performance, the CEO as chairman of the board, larger free cash flow and a higher degree of information asymmetry. Further, we find that the announcement effect is decreasing as number of outside directors increases. Our findings are different from existing literature, for instance, those of Lin, Pope and Young (2003) and Rosenstein and Wyatt (1990) mainly because the outside director appointment is not mandatory in Taiwan. This suggests that the announcement effects could be different across countries. The appointment appears to be more beneficial for a country with poor corporate governance mechanisms.

Joint Subcarrier Pairing and Power Allocation for OFDM Transmission with Decode-and-Forward Relaying

In this paper, a point-to-point Orthogonal Frequency Division Multiplexing (OFDM) system with a decode-and-forward (DF) relay is considered. The transmission consists of two hops. The source transmits in the first hop, and the relay transmits in the second hop. Each hop occupies one time slot. The relay is half-duplex, and capable of decoding the message on a particular subcarrier in one time slot, and re-encoding and forwarding it on a different subcarrier in the next time slot. Thus each message is transmitted on a pair of subcarriers in two hops. It is assumed that the destination is capable of combining the signals from the source and the relay pertaining to the same message. The goal is to maximize the weighted sum rate of the system by jointly optimizing subcarrier pairing and power allocation on each subcarrier in each hop. The weighting of the rates is to take into account the fact that different subcarriers may carry signals for different services. Both total and individual power constraints for the source and the relay are investigated. For the situations where the relay does not transmit on some subcarriers because doing so does not improve the weighted sum rate, we further allow the source to transmit new messages on these idle subcarriers. To the best of our knowledge, such a joint optimization inclusive of the destination combining has not been discussed in the literature. The problem is first formulated as a mixed integer programming problem. It is then transformed to a convex optimization problem by continuous relaxation, and solved in the dual domain. Based on the optimization results, algorithms to achieve feasible solutions are also proposed. Simulation results show that the proposed algorithms almost achieve the optimal weighted sum rate, and outperform the existing methods in various channel conditions.Comment: 33 pages, 11 figure