Companion robots for older adults: Rodgers’ evolutionary concept analysis approach

Intelligent Service Robotics - This study aims to analyze the concept of companion robots for older adults from the perspective of nursing. This study employed a concept analysis. The literature...     

Analysis and improvement of performance of MC-CDMA system withnonlinear amplifier

A multicode CDMA system with nonlinear amplifier is analysed for uncoded BER and a simulation carried out to evaluate the coded BER performance. The adaptive predistorter is shown to significantly reduce the nonlinear effect of the amplifier     

Correlations of control parameters determining pressure distributions in a vertical exhaust shaft

The pressure distribution in a vertical exhaust shaft is important in determining the ventilation performances of local exhaust hoods in high-rise buildings. Uneven pressure distribution can cause insufficient exhaust airflows from hood fans, and can cause excessive exfiltration resulting in unwanted noise through any gap openings. There are various system parameters that affect the pressure distribution in a vertical shaft, such as building height, shaft size, roof fan characteristics, concurrent hood fan usage, and outdoor temperature. The objective of this study is to quantify and investigate the effects of these parameters numerically on the overall ventilation performance of a vertical shaft. In order to achieve this goal, specialized simulation software has been developed, which implements the principles of fluid dynamics in vertical air columns with horizontal branches. Simulation results have been obtained based on a model of a 25-story apartment building, according to the experimental design method. Analysis of the variance has been conducted to investigate any correlations between the parameters. The results show that the deviation of the pressure distribution based on a slight negative value (i.e. −30 Pa or −40 Pa) has a strong correlation with the maximum pressure in the shaft. This indicates the possibility of using the pressure deviation as a single objective parameter, which represents both the insufficiency and unevenness of the pressure distribution throughout the shaft. Roof fan rpm and inlet damper opening can be used as operational parameters, and the pressure and pressure gradient at the top-most level, and outside temperature can be used as sensing parameters for pressure control in a vertical shaft.     

Dynamics modeling of a gas engine-driven heat pump in cooling mode

The present study has been conducted to simulate dynamics of a gas engine-driven heat pump (GHp) for design of control algorithm. The dynamics modeling of a GHp was based on conservation laws of mass and energy. For automatic control of refrigerant pressures, actuators such as engine speed, outdoor fans, coolant three-way valves and liquid injection valves were pI or p controlled. The simulation results were found to be realistic enough to apply for control algorithm design. The model can be applied to build a virtual real-time GHp system so that it interfaces with a real controller in purpose of prototyping control algorithm.     

Tracer gas experiment for local mean ages of air from individual supply inlets in a space with multiple inlets

We investigate the supply characteristics of incoming air via individual inlets in a ventilated space with multiple inlets. Theoretical considerations are given to determine the relations between the local mean age (LMA) of the total supply air and the individual LMA of each supply air inlet. Tracer gas experiments are conducted in a simplified livestock model with two supply inlets and one exhaust outlet. Transient concentration responses at internal points are measured after tracer gas injection one inlet at a time, and for simultaneous tracer injection at both inlets. The spatial distributions of LMAs and steady concentrations are obtained by tracer injections from each supply inlet, which demonstrate the supply characteristics of the individual inlets in the space. We have found that the overall LMA is the weighted average of the LMA by each inlet, and the weighting factor for the average is the corresponding steady state concentration at a given point. Experiments repeated for various airflow rates show that the nondimensional steady concentrations remain nearly constant regardless of the total airflow rate, but are greatly influenced by the airflow ratio between inlets. The local mean ages are found to increase proportionally with respect to the nominal time constant. Experimental procedures and results are verified by the fact that the total LMA measured at the exhaust is in good agreement with the theoretical nominal time constant of the space.