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Papers by bad ri

Proceedings of The Vldb Endowment, 2009

Query optimizers rely on accurate estimations of the sizes of intermediate results. Wrong size es... more Query optimizers rely on accurate estimations of the sizes of intermediate results. Wrong size estimations can lead to overly expensive execution plans. We first define the q-error to measure deviations of size estimates from actual sizes. The q-error enables the derivation of two important results:

Ridge regression, being based on the minimization of a quadratic loss function, is sensitive to o... more Ridge regression, being based on the minimization of a quadratic loss function, is sensitive to outliers. Current proposals for robust ridge regression estimates are sensitive to "bad leverage observations", cannot be employed when the number of predictors p is larger than the number of observations n; and have a low robustness when the ratio p=n is large. In this paper a penalized regression MM estimate is proposed, in which the quadratic loss is replaced by an average of (ri=b ), where ri are the residuals and b the residual scale from an initial estimate, which is a penalized S estimate; and is a bounded function. The MM estimate can be computed for p > n and is robust for large p=n: A fast algorithm is proposed. The advantages of the proposed approach over its competitors are demonstrated through both simulated and real data.

An attractive architecture for sensor networks is to have the sensing devices mounted on small co... more An attractive architecture for sensor networks is to have the sensing devices mounted on small computers, called motes. Motes are battery-powered, and can communicate in a wireless fashion by broadcasting messages over radio frequency. In mote networks, the connectivity of a mote u can be defined by those motes that can receive messages from u with high probability and those motes from which u can receive messages with high probability. In this paper, we describe a protocol that can be triggered by any mote in a mote network in order that each mote in the network computes its connectivity. The protocol is simple and has several energy saving features. We implemented this protocol over TinyOS and discuss the results of some execution runs of this implementation.

High Speed Downlink Packet Access via geostationary Satellite (S-HSDPA). In particular, this pape... more High Speed Downlink Packet Access via geostationary Satellite (S-HSDPA). In particular, this paper surveys resource allocation constraints to be considered for S-HSDPA and investigates the performance of different scheduling schemes in the presence of a GOOD/BAD channel and their influence on the objective video quality for typical UMTS video streaming scenarios. This work has been carried out within the framework of the European SatNEx II network of excellence.

Journal of Financial Services Research, 2012

In a sample of 335 commercial banks, we do not detect a systematic effect on bank values from der... more In a sample of 335 commercial banks, we do not detect a systematic effect on bank values from derivatives use in either the high growth period of 2003–2005 or the low growth period of 2007–2009. These findings apply to all types of derivatives including credit default swaps. Our results suggest that banks take a more balanced approach and restrict their derivative activities to providing derivative services for customers and risk management. We also find that the market disciplined banks significantly for taking TARP funds, indicating that receiving TARP funds was a signal that the banks were financially distressed. Lastly, we cannot discern valuation effects resulting from derivatives use even in large and poorly capitalized banks that are more likely to take risk-shifting opportunities. Collectively, we find no compelling evidence supporting the widespread allegation that derivatives use increased banks’ speculating behaviors and significantly contributed to the loss of value during the subprime mortgage crisis.

Acta Biochimica Et Biophysica Sinica, 2005

Apoptosis, or programmed cell death, is an essential physiological process that plays a critical ... more Apoptosis, or programmed cell death, is an essential physiological process that plays a critical role in development and tissue homeostasis. The progress of apoptosis is regulated in an orderly way by a series of signal cascades under certain circumstances. The caspase-cascade system plays vital roles in the induction, transduction and amplification of intracellular apoptotic signals. Caspases, closely associated with apoptosis, are aspartate-specific cysteine proteases and members of the interleukin-1β-converting enzyme family. The activation and function of caspases, involved in the delicate caspase-cascade system, are regulated by various kinds of molecules, such as the inhibitor of apoptosis protein, Bcl-2 family proteins, calpain, and Ca 2+ . Based on the latest research, the members of the caspase family, caspase-cascade system and caspase-regulating molecules involved in apoptosis are reviewed.

Provisioning of mobile video streaming became reality. The next evolution step in mobile video st... more Provisioning of mobile video streaming became reality. The next evolution step in mobile video streaming is to allocate resources optimally from both the service provider and the user perspective. Therefore, it is important to determine the relation between the willingness to pay (WTP) and the delivered quality of mobile video streaming. In order to determine this relation we performed tests on subjective quality and WTP with the most frequent content types, codecs and their settings. A further analysis shows clearly a mutual dependence between subjective video quality and WTP.

Theoretical Ecology

Studies of time-invariant matrix metapopulation models indicate that metapopulation growth rate i... more Studies of time-invariant matrix metapopulation models indicate that metapopulation growth rate is usually more sensitive to the vital rates of individuals in high-quality (i.e., good) patches than in low-quality (i.e., bad) patches. This suggests that, given a choice, management efforts should focus on good rather than bad patches. Here, we examine the sensitivity of metapopulation growth rate for a two-patch matrix metapopulation model with and without stochastic disturbance and found cases where managers can more efficiently increase metapopulation growth rate by focusing efforts on the bad patch. In our model, net reproductive rate differs between the two patches so that in the absence of dispersal, one patch is high quality and the other low quality. Disturbance, when present, reduces net reproductive rate with equal frequency and intensity in both patches. The stochastic disturbance model gives qualitatively similar results to the deterministic model. In most cases, metapopulation growth rate was elastic to changes in net reproductive rate of individuals in the good patch than the bad patch. However, when the majority of individuals are located in the bad patch, metapopulation growth rate can be most elastic to net reproductive rate in the bad patch. We expand the model to include two stages and parameterize the patches using data for the softshell clam, Mya arenaria. With a two-stage demographic model, the elasticities of metapopulation growth rate to parameters in the bad patch increase, while elasticities to the same parameters in the good patch decrease. Metapopulation growth rate is most elastic to adult survival in the population of the good patch for all scenarios we examine. If the majority of the metapopulation is located in the bad patch, the elasticity to parameters of that population increase but do not surpass elasticity to parameters in the good patch. This model can be expanded to include additional patches, multiple stages, stochastic dispersal, and complex demography.

Proceedings of The Vldb Endowment, 2009

Query optimizers rely on accurate estimations of the sizes of intermediate results. Wrong size es... more Query optimizers rely on accurate estimations of the sizes of intermediate results. Wrong size estimations can lead to overly expensive execution plans. We first define the q-error to measure deviations of size estimates from actual sizes. The q-error enables the derivation of two important results:

Ridge regression, being based on the minimization of a quadratic loss function, is sensitive to o... more Ridge regression, being based on the minimization of a quadratic loss function, is sensitive to outliers. Current proposals for robust ridge regression estimates are sensitive to "bad leverage observations", cannot be employed when the number of predictors p is larger than the number of observations n; and have a low robustness when the ratio p=n is large. In this paper a penalized regression MM estimate is proposed, in which the quadratic loss is replaced by an average of (ri=b ), where ri are the residuals and b the residual scale from an initial estimate, which is a penalized S estimate; and is a bounded function. The MM estimate can be computed for p > n and is robust for large p=n: A fast algorithm is proposed. The advantages of the proposed approach over its competitors are demonstrated through both simulated and real data.

An attractive architecture for sensor networks is to have the sensing devices mounted on small co... more An attractive architecture for sensor networks is to have the sensing devices mounted on small computers, called motes. Motes are battery-powered, and can communicate in a wireless fashion by broadcasting messages over radio frequency. In mote networks, the connectivity of a mote u can be defined by those motes that can receive messages from u with high probability and those motes from which u can receive messages with high probability. In this paper, we describe a protocol that can be triggered by any mote in a mote network in order that each mote in the network computes its connectivity. The protocol is simple and has several energy saving features. We implemented this protocol over TinyOS and discuss the results of some execution runs of this implementation.

High Speed Downlink Packet Access via geostationary Satellite (S-HSDPA). In particular, this pape... more High Speed Downlink Packet Access via geostationary Satellite (S-HSDPA). In particular, this paper surveys resource allocation constraints to be considered for S-HSDPA and investigates the performance of different scheduling schemes in the presence of a GOOD/BAD channel and their influence on the objective video quality for typical UMTS video streaming scenarios. This work has been carried out within the framework of the European SatNEx II network of excellence.

Journal of Financial Services Research, 2012

In a sample of 335 commercial banks, we do not detect a systematic effect on bank values from der... more In a sample of 335 commercial banks, we do not detect a systematic effect on bank values from derivatives use in either the high growth period of 2003–2005 or the low growth period of 2007–2009. These findings apply to all types of derivatives including credit default swaps. Our results suggest that banks take a more balanced approach and restrict their derivative activities to providing derivative services for customers and risk management. We also find that the market disciplined banks significantly for taking TARP funds, indicating that receiving TARP funds was a signal that the banks were financially distressed. Lastly, we cannot discern valuation effects resulting from derivatives use even in large and poorly capitalized banks that are more likely to take risk-shifting opportunities. Collectively, we find no compelling evidence supporting the widespread allegation that derivatives use increased banks’ speculating behaviors and significantly contributed to the loss of value during the subprime mortgage crisis.

Acta Biochimica Et Biophysica Sinica, 2005

Apoptosis, or programmed cell death, is an essential physiological process that plays a critical ... more Apoptosis, or programmed cell death, is an essential physiological process that plays a critical role in development and tissue homeostasis. The progress of apoptosis is regulated in an orderly way by a series of signal cascades under certain circumstances. The caspase-cascade system plays vital roles in the induction, transduction and amplification of intracellular apoptotic signals. Caspases, closely associated with apoptosis, are aspartate-specific cysteine proteases and members of the interleukin-1β-converting enzyme family. The activation and function of caspases, involved in the delicate caspase-cascade system, are regulated by various kinds of molecules, such as the inhibitor of apoptosis protein, Bcl-2 family proteins, calpain, and Ca 2+ . Based on the latest research, the members of the caspase family, caspase-cascade system and caspase-regulating molecules involved in apoptosis are reviewed.

Provisioning of mobile video streaming became reality. The next evolution step in mobile video st... more Provisioning of mobile video streaming became reality. The next evolution step in mobile video streaming is to allocate resources optimally from both the service provider and the user perspective. Therefore, it is important to determine the relation between the willingness to pay (WTP) and the delivered quality of mobile video streaming. In order to determine this relation we performed tests on subjective quality and WTP with the most frequent content types, codecs and their settings. A further analysis shows clearly a mutual dependence between subjective video quality and WTP.

Theoretical Ecology

Studies of time-invariant matrix metapopulation models indicate that metapopulation growth rate i... more Studies of time-invariant matrix metapopulation models indicate that metapopulation growth rate is usually more sensitive to the vital rates of individuals in high-quality (i.e., good) patches than in low-quality (i.e., bad) patches. This suggests that, given a choice, management efforts should focus on good rather than bad patches. Here, we examine the sensitivity of metapopulation growth rate for a two-patch matrix metapopulation model with and without stochastic disturbance and found cases where managers can more efficiently increase metapopulation growth rate by focusing efforts on the bad patch. In our model, net reproductive rate differs between the two patches so that in the absence of dispersal, one patch is high quality and the other low quality. Disturbance, when present, reduces net reproductive rate with equal frequency and intensity in both patches. The stochastic disturbance model gives qualitatively similar results to the deterministic model. In most cases, metapopulation growth rate was elastic to changes in net reproductive rate of individuals in the good patch than the bad patch. However, when the majority of individuals are located in the bad patch, metapopulation growth rate can be most elastic to net reproductive rate in the bad patch. We expand the model to include two stages and parameterize the patches using data for the softshell clam, Mya arenaria. With a two-stage demographic model, the elasticities of metapopulation growth rate to parameters in the bad patch increase, while elasticities to the same parameters in the good patch decrease. Metapopulation growth rate is most elastic to adult survival in the population of the good patch for all scenarios we examine. If the majority of the metapopulation is located in the bad patch, the elasticity to parameters of that population increase but do not surpass elasticity to parameters in the good patch. This model can be expanded to include additional patches, multiple stages, stochastic dispersal, and complex demography.