Practice-Oriented System Identification Strategies for MPC of Building Thermal and HVAC Dynamics

The increasingly competitive HVAC market has made it necessary to develop technologies that exploit the economic potential in such systems to reduce energy consumption. Smart HVAC operation through optimization-based control strategies, such as model predicative control (MPC), serves as one method for achieving this goal. MPC and Economic MPC have gained significant attention due to their ability to optimally operate HVAC system in order to minimize their energy consumption and/or energy cost while maintaining desired comfort temperatures. Several research work have attempted to use system identification in order to model building thermal and HVAC dynamics. Nonetheless, empirically modeling HVAC systems in a robust and scalable manner is very challenging due to the non-convexity of the system identification optimization problem and the existence of complex actuator saturation limits. Therefore, this work develops grey-box system identification strategies that attack these challenges to enable the development of accurate empirical models of HVAC systems in practice settings. Saturation refers to the usage of the maximum or minimum HVAC capacity to track a desired temperature set-point for buildings under heating and cooling modes. The existence of significant saturation in the data collected is a common problem that poses many challenges for identifying the dynamics of HVAC systems since they can affect the quality of the collected data and result in an inaccurate identified model. Classical approaches for dealing with saturation in system identification, such as using nonlinear functions to capture the saturation behavior, are not implementable due to the complex saturation behavior associated with HVAC systems. In addition, another challenge faced in identifying HVAC and building thermal dynamics is the existence of many roots in such non-convex system identification problems. Therefore, it is desirable in industry to avoid using initial guesses that lead to local optima which result in inaccurate models. In the first part of this work, we develop an algorithm that is capable of detecting and removing saturation data from system identification experiment input-output data. This is done to extract the useful data sections that represent the cited HVAC system dynamics which are necessary to identify reliable models of the HVAC dynamics. The second part of this work develops a strategy that avoids solving system identification problems all the way to local optimality using initial guesses that lead to local optima which result in poor models. The algorithm attempts to eliminate poor initial guesses and yield initial guesses that ultimately lead to great fits of the model to the data. The parameters of the grey-box models were identified via a two-step parameter estimation approach. In the first step, the model parameters were identified using simulation prediction error method. In the second step, the model was augmented with a disturbance model and the estimation gain (i.e., Kalman gain) was identified using the standard 1-step prediction error method. The proposed strategies were applied to data collected from real building HVAC systems and have shown to successfully work in practice. The results demonstrate accurate 1-step and multi-step predictions which are necessary for the implementation of MPC

STLV-1 co-infection is correlated with an increased SFV proviral load in the peripheral blood of SFV/STLV-1 naturally infected non-human primates

Simian T-Leukemia Virus type 1 and Simian Foamy Virus infect non-human primates. While STLV-1, as HTLV-1, causes Adult T-cell Leukemia/lymphoma, SFV infection is asymptomatic. Both retroviruses can be transmitted from NHPs to humans through bites that allow contact between infected saliva and recipient blood. Because both viruses infect CD4+ T-cells, they might interfere with each other replication, and this might impact viral transmission. Impact of STLV-1 co-infection on SFV replication was analyzed in 18 SFV-positive/STLV-1-negative and 18 naturally SFV/STLV-1 co-infected Papio anubis. Even if 9 animals were found STLV-1-positive in saliva, STLV-1 PVL was much higher in the blood. SFV proviruses were detected in the saliva of all animals. Interestingly, SFV proviral load was much higher in the blood of STLV-1/SFV co-infected animals, compared to STLV-1-negative animals. Given that soluble Tax protein can enter uninfected cells, we tested its effect on foamy virus promoter and we show that Tax protein can transactivate the foamy LTR. This demonstrates that true STLV-1 co-infection or Tax only has an impact on SFV replication and may influence the ability of the virus to be zoonotically transmitted as well as its ability to promote hematological abnormalities

Background risk and quantum calculus

Abstract Infinitesimal calculus is heavily used in decision making analysis. This paper demonstrates that the application of quantum calculus in analysing preferences choice directly introduces background risk and its effects on risk-aversion, subjective probabilities and moment preferences. Quantum calculus provides another approach to the mathematical treatment of decision making, namely analysis of utility preferences

Early Reverse Transcription Is Essential for Productive Foamy Virus Infection

BACKGROUND: Although viral RNA constitutes the majority of nucleic acids packaged in virions, a late occurring step of reverse transcription leads to the presence of infectious viral cDNA in foamy virus particles. This peculiarity distinguishes them from the rest of the retroviral family. PRINCIPAL FINDINGS: To evaluate the respective contribution of these viral nucleic acids in the replication of foamy viruses, their fate was studied by real-time PCR and RT-PCR early after infection, in the presence or in the absence of AZT. We found that an early reverse transcription step, which occurs during the first hours post-entry, is absolutely required for productive infection. Remarkably, sensitivity to AZT can be counteracted by increasing the multiplicity of infection (moi). We also show that 2-LTR circular viral DNA, which appears as soon as four hours post-infection, is transcriptionally competent. CONCLUSION: Taken together, our data demonstrate that an early reverse transcription process, which takes place soon after viral entry, is indispensable for infectivity of FVs at low moi, when the amount of DNA-containing particles is not sufficient to lead to a productive infection. This study demonstrates a key role of the packaged viral RNA in the foamy virus infection, suggesting that the replication of this virus can be achieved by involving either viral DNA or RNA genome, depending on the condition of infection

A randomised phase II study of pegylated arginine deiminase (ADI-PEG 20) in Asian advanced hepatocellular carcinoma patients

[[abstract]]Background:Human hepatocellular carcinoma (HCC) cells are largely deficient of argininosuccinate synthetase and thus auxotrophic for arginine. This study aims to investigate the efficacy and pharmacodynamics of pegylated arginine deiminase (ADI-PEG 20), a systemic arginine deprivation agent, in Asian HCC patients. Methods:Patients with advanced HCC who were not candidates for local therapy were eligible and randomly assigned to receive weekly intramuscular injections of ADI-PEG 20 at doses of 160 or 320 IU m-2. The primary end point was disease-control rate (DCR). Results:Of the 71 accruals, 43.6% had failed previous systemic treatment. There were no objective responders. The DCR and the median overall survival (OS) of the intent-to-treat population were 31.0% (95% confidence interval (CI): 20.5-43.1) and 7.3 (95% CI: 4.7-9.9) months respectively. Both efficacy parameters were comparable between the two study arms. The median OS of patients with undetectable circulating arginine for more than or equal to and <4 weeks was 10.0 (95% CI: 2.1-17.9) and 5.8 (95% CI: 1.4-10.1) months respectively (P=0.251, log-rank test). The major treatment-related adverse events were grades 1-2 local and/or allergic reactions. Conclusions:ADI-PEG 20 is safe and efficacious in stabilising the progression of heavily pretreated advanced HCC in an Asian population, and deserves further exploration.British Journal of Cancer advance online publication, 31 August 2010; doi:10.1038/sj.bjc.6605856 www.bjcancer.com