Formulation and Application of an Economic Model Predictive Control Scheme for Thermostats

Within the last ten years, growing pressure to reduce energy consumption of buildings has led to an increased focus on the development and deployment of advanced control strategies. Heating, Ventilation, and Air-Conditioning (HVAC) constitutes the majority of the energy consumption of buildings. Model predictive control (MPC) has gained significant attention in HVAC control as it computes the control inputs for a given system by iteratively solving an optimal control problem on-line. The problem formulation accounts for the system operating objective and constraints. Several application studies of MPC applied to buildings have been reported in the literature. These studies have demonstrated the benefits of the application of MPC schemes to buildings. However, one theme that appears in some of the literature is the lamentation on the difficulty to apply MPC broadly to buildings. This is a challenging problem because the MPC system design needs to include a robust and broadly applicable system identification methodology to effectively address this problem. Moreover, in many building applications, the desired sensors measuring key variables are not available (e.g., a heat disturbance load and power consumption measurements are usually not available for residential zones controlled by a thermostat). In this work, an economic MPC scheme is developed to manipulate the temperature setpoint of a zone controlled by a thermostat. The MPC scheme is equipped with an economically-oriented objective that includes a system identification procedure, a state estimator, and a control problem formulation. The economically-oriented MPC seeks to minimize the utility bill by manipulating the setpoint to leverage the building mass as thermal energy storage while maintaining the zone temperature setpoint within a comfortable range. Given the lack of a power or HVAC load measurement in a typical thermostat, the HVAC load is approximated by a filtered version of the thermostat stage commands, which provides a normalized time-average version of the HVAC load. All the components of the resulting MPC scheme are designed in a manner to address general applicability of the resulting MPC. Simulation results are presented to demonstrate the effectiveness of the strategy

A stochastic model dissects cell states in biological transition processes

Many biological processes, including differentiation, reprogramming, and disease transformations, involve transitions of cells through distinct states. Direct, unbiased investigation of cell states and their transitions is challenging due to several factors, including limitations of single-cell assays. Here we present a stochastic model of cellular transitions that allows underlying single-cell information, including cell-state-specific parameters and rates governing transitions between states, to be estimated from genome-wide, population-averaged time-course data. The key novelty of our approach lies in specifying latent stochastic models at the single-cell level, and then aggregating these models to give a likelihood that links parameters at the single-cell level to observables at the population level. We apply our approach in the context of reprogramming to pluripotency. This yields new insights, including profiles of two intermediate cell states, that are supported by independent single-cell studies. Our model provides a general conceptual framework for the study of cell transitions, including epigenetic transformations

Sulfur Source, Rate, and Methods of Application for Polyethylene-mulched Tomato

Tomato (Lycopersicon esculentum L.) was grown with polyethylene mulch and drip irrigation on a Millhopper fine sandy soil testing very high in P and low in organic matter during two seasons to evaluate the effect of S source, rate, and application methods on plant growth and yield of fruit.  Sulfur rate of 34 and 68 kg S.ha-1 were applied with  preplant (broadcast in the bed), drip (10 weekly drip application), and  by split applications (50% preplant and 50% drip).  In split applications, S sources evaluated were ammonium sulfate and ammonium thiosulfate.  Plant height was increased with S application from 0 to 68 kg S.ha-1 in both studies. However, response on plant dry weight only occurred in spring 1999. Total marketable yield was 17.9 tons.ha-1 with 0 kg S.ha-1 and was increased linearly to 48.1 tons.ha-1 with application of 68 kg S.ha-1 in Spring 1999, but no response to S was obtained in the Spring 1998 study. Measured variables were not affected by S source and methods of application.  Increasing S application from 0  to 68 kg S.ha-1 reduced leaf and plant tissue P concentration 14 and 12% at mid season, 26 and 25% at  late season sampling times, respectively.  S application of 68 kg S.ha-1 reduced soil pH approximately 0.3 unit at the end of the season in both studies.   Key  words:  drip irrigation, sulfur,  fertigation, Lycopersicon esculentu

Transmission of vibration through gloves: effects of material thickness

It might be assumed that increasing the thickness of a glove would reduce the vibration transmitted to the hand. Three material samples from an anti-vibration glove were stacked to produce three thicknesses: 6.4, 12.8 and 19.2 mm. The dynamic stiffnesses of all three thicknesses, the apparent mass at the palm and the finger and the transmission of vibration to the palm and finger were measured. At frequencies from 20 to 350 Hz, the material reduced vibration at the palm but increased vibration at the finger. Increased thickness reduced vibration at the palm but increased vibration at the finger. The measured transmissibilities could be predicted from the material dynamic stiffness and the apparent mass of the palm and finger. Reducing the dynamic stiffness of glove material may increase or decrease the transmission of vibration, depending on the material, the frequency of vibration and the location of measurement (palm or finger). Practitioner Summary: Transmission of vibration through gloves depends on the dynamic response of the hand and the dynamic stiffness of glove material, which depends on material thickness. Measuring the transmission of vibration through gloves to the palm of the hand gives a misleading indication of the transmission of vibration to the fingers

Transmission of vibration through glove materials: effects of contact force

This study investigated effects of applied force on the apparent mass of the hand, the dynamic stiffness of glove materials, and the transmission of vibration to the hand. For 10 subjects, three glove materials, and three contact forces, apparent masses and glove transmissibilities were measured at the palm and at a finger at frequencies in the range 5 to 300 Hz. The dynamic stiffnesses of the materials were also measured. With increasing force, the dynamic stiffnesses of the materials increased, the apparent mass at the palm increased at frequencies greater than the resonance, and the apparent mass at the finger increased at low frequencies. The effects of force on transmissibilities therefore differed between materials and depended on vibration frequency, but changes in apparent mass and dynamic stiffness had predictable effects on material transmissibility. Depending on the glove material, the transmission of vibration through a glove can be increased or decreased when increasing the applied force