Ejectors are widely used as steam power cycle components to recover superfluous water vapor. However, in a system for preparing distilled water used for pharmaceutical injection, the ejector periodically deviates from the design condition owing to fluctuations in steam source pressure. In particular, when the pressure is reduced to approximately 75% of the design value, performance is significantly degraded, affecting water production efficiency. To solve this problem, a two-stage ejector with control switching strategy is proposed in this paper. The performance of a series of two-stage ejector structures with different scale ratios was analyzed, and the optimum scale ratio was determined. Furthermore, an optimal switching strategy is devised to ensure that the two-stage ejector maintains stable performance under different primary flow pressures. The numerical results indicate that the entrainment ratio of the two-stage ejector is 79.4% higher than that of the single-stage ejector when the pressure is 60% of that of the designed primary flow. Moreover, the two-stage ejector can maintain satisfactory entrainment performance when the traditional ejector enters reversed mode under 50% of the designed pressure. The experimental results show that the entrainment performance of the proposed two-stage ejector can be improved significantly when power fluid pressure is insufficient.

Multi-effect distillation with thermal vapor compression system has not been able to penetrate the market because of the low coefficient of performance. The two-stage vacuum ejector is an effective vehicle to maintain system condensing temperature, discharge non-condensable gases and improve the system performance. Improving performance of two-stage vacuum ejector relies on the understanding of the fluid dynamic phe-nomena. Unfortunately, few studies paid attention to the effect of inner fluid phase transition and non-condensable gas mass fraction on the performance of vacuum ejector. Therefore, this paper contributes to proposing a Species transport and Phase transition model to investigate the two-stage vacuum ejector numeri-cally considering the physical properties of non-condensable gases, thermodynamic transformation caused by condensation and evaporation with experimental validation. The results indicate that the entrainment perfor-mance of the ejector increases by about 14.95% when the non-condensable gases mass fraction increases from 0% to 100%. Meanwhile, with the consideration of heat and mass transfer in the phase change process, the mean error is 4.9%, which is much lower than single-phase model. Meanwhile, the internal fluid pressure, Mach number, shock waves and expansion degree can be largely influenced by the consideration of Species transport and Phase transition. The results of this paper proved that influence of non-condensable gases and phase tran-sition cannot be ignored in the design and prediction of vacuum ejector and it can contribute to ejector opti-mization and enhancing the stability and efficiency of multi-effect distillation with thermal vapor compression system.

In this paper, the influence of multicomponent and multiphase on the ejector internal flow dynamics and the ejector performance in proton exchange membrane fuel cell systems is comprehensively studied using the computational fluid dynamics technique. Mathematical and numerical models of an ejector applied for the anode recirculation in proton exchange membrane fuel cell systems are established with some consideration of the multicomponent in the secondary flow, the multiphase inside the ejector and the strongly coupled working parameters of the multiple fluid inlets. Validation is performed before the conducted simulation process by comparing the calculated mass flowrates based on the multicomponent–multiphase model and the dry gas model. It is revealed that the dry gas assumption underestimates the flow expansion process, where simulation accuracy is reduced. However, simulation accuracy is improved with a maximum deviation of less than 5% with the consideration of phase transformation, meanwhile, pressure, velocity and temperature profiles inside the ejector have been significantly influenced with the stack output power varying from 40  to  70 kW. There is an increased coverage and volume fraction of liquid water with the increases in secondary inlet humidity, temperature and primary inlet pressure. The entrainment ratio is found to increase significantly with a consideration of liquid water inside the ejector. Therefore, the condensation phenomenon and the phase transformation in the ejector employed in proton exchange membrane fuel cell systems must be considered.

The ejector is a promising candidate in recycling unconsumed hydrogen for proton exchange membrane fuel cell (PEMFC) to increase the fuel utilization. However, due to the multi-operation conditions of stack with reaction water producing, the ejector performance and out flow (i.e. the supply flow) are affected by the secondary flow state which present challenges for PEMFC stable operation and system control. In this paper, a series of numerical research were carried and the flow field distributions were obtained and analyzed to gain further understanding of supply flow pressure and humidity variation under multi-working conditions of PEMFC. Furthermore, a mathematical model for recycle loop was established to build the correlations between PEMFC working conditions and both the hydrogen recycle and supply capacity of ejector. An experimental platform was built and a series of experimental investigations were carried out for recycle system performance research after numerical and mathematical model validation. Both numerical and experimental results indicated that working conditions complexity will result the changes with more than 0.2 bar in pressure and 30% in humidity of supply flow which also could be predicted by theoretical model. It was also observed that along with the secondary flow humidity and temperature increase, the higher entrainment ratio will be achieved and less hydrogen were recycled inversely. In addition, from the research, ejector running under variable conditions may leading poor water management and proton exchange membrane damage risk is also a critical issue for hydrogen recycle application.

Inspired by the type-2 fuzzy logic (T2FL), the energy-efficient radio resource schedule mechanism is proposed to deal with the multi-radio resources management problem in MRWSNs. Firstly, three important models, including channel quality estimation (CQE) model, radio energy dissipation model and residual energy model, are established and analysed. Then using the three important factors as the input variables, the selection probability of each transceiver as output variable, the T2FL based energy-efficient radio resource schedule scheme is designed. Moreover, both experimental and simulation results indicate that the proposed schedule mechanism can effectively improve the network performance, such as throughput, energy efficiency, the success rate of data transmission, etc.

With the increasing popularity of the heat meter readings for district heating apartments in China, the analysis of the generated big data is becoming a critical problem. With the nonlinear of the district heating household dataset, this archive describes a kernel Gaussian mixture cluster (KGMC) based data mining algorithm within which the original data in low-dimensional space are projected into the high-dimensional space to do clustering and identify anomalies. At the meantime, this article adopts Gaussian kernel function to prevent the curse of dimensionality. According to the implementation of the experiment with Spark, the data from 18 zones of 17,000 apartments belonging to 6 substations have been studied and four kinds of anomalies have been identified. With the detection and correction of abnormal actions, 5.4% of the demand of heat will be proactively reduced in heating areas in China. Meanwhile, with the comparison, the proposed KGMC can outperform K-means and Gaussian Mixture Model (GMM) methods in terms of detection rate (DR) and false positive rate (FPR).

ABSTRACT Multi-radio wireless sensor networks (MRWSNs) are receiving increasing attentions as an effective means to reduce interference, increase throughput and achieve the path redundancy, reliability and connectivity. One essential performance topic is how to effectively utilize channel diversity and achieve the parallel communication. In this paper, we propose a multi-radio multi-channel-hopping scheme (MRMCHS) based on the pseudo-random hopping sequence. It independently calculates the distinct channel hopping sequences of m RF transceivers equipped at a same node and ensures each channel to be visited once and only once in a cycle. Furthermore, corresponding multi-radio parallel communication mechanism (MRPCM) is designed to reduce communication delay and improve network throughput. Both simulation and experiment results demonstrate that the proposed mechanisms outperform other protocols, in terms of system throughput, average delay and energy consumption.

A simplified and accurate hybrid model is proposed to analyze, evaluate, and predict space heating energy consumption and indoor temperature in residential buildings connected to district heating systems. With classical engineering equations of thermodynamic laws, this method uses physical and empirical modeling to describe heat exchangers in real-time. Furthermore, the model has optimized the cost of computation and enhanced the prediction accuracy. It is revealed this method can accurately predict the residential heat load and indoor temperature with the maximum error of +/- 10%. The architectural parameter, outdoor temperature, and wind velocity have decisive effects on the heat energy demand.

Multi-Radio technology is regarded as a promising way to improve the performance of Wireless Sensor Networks (WSNs) that is widely applied in some real-time application, such as industrial control, earthquake monitoring, etc. In order to meet the harsh real-time performance requirement of Multi-Radio WSNs (MRWSNs) based real-time control/monitoring system, it is critical to conduct the analysis of fast communication delay for the periodic real-time tasks in MRWSNs In this paper, two types of packets, including carry-in packet which causes channel conflict delay and non-carry-in packets which cause channel contention delay, are independently analysed and then are combined together to obtain the upper bound of communication delay under the constrained condition. Subsequently, the basic delay analysis based the improved upper bound of communication delay is derived. Both experiment and simulation results demonstrate that the delay analysis can efficiently estimate the delay time of the transferred packet as well as provide a secured and tight upper bound of communication delay in MRWSNs.

In this paper, a simple yet accurate model is proposed for real-time control and optimization of two-phase flow plate heat exchanger (PHE). The model is derived with selected controllable or measurable I/O parameters and heat mass transfer equations by mechanism analysis. The linear and nonlinear least-squares methods are adopted to identify unknown or empirical parameters to reduce the error of evaluation and prediction in applications. The modeling approach takes advantages of both mechanism and empirical model, which has the effectiveness that the unreachable parameters are eliminated while the computation is reduced with wide operating range. Validation was carried out in a substation in a district heating system, and the testing results showed that the proposed model can predict the performance of the PHE with a maximum error less than ±8% that satisfied the requirements of real-time control and optimization in applications.

The study was performed in 36 Chinese patients with Enterovirus 71 (EV71) encephalitis and 141 patients with EV71-related hand, foot and mouth disease (HFMD) without encephalitis. Genotyping was determined by polymerase chain reaction- restriction fragment length polymorphism. Patients with EV71 encephalitis had a significantly higher frequency of interleukin-8 (IL-8)-251TT genotype than patients with EV71-related HFMD without encephalitis (55.6% vs 31.2%, p = 0.023). The frequency of IL-8-251T alleles was significantly higher among patients with EV71 encephalitis than in patients with EV71-related HFMD without encephalitis (72.2% vs 58.9%, odds ratio 1.8, 95% confidence interval 1.0-3.2, p = 0.038). There were significant differences in gender, age, fever days, white blood cell count, C-reactive protein and blood glucose concentration and IL-8 levels among genotypes of IL-8-251A/T in EV71-infected patients, but no significant differences in alanine or aspartate aminotransferase, creatine kinase-myocardial isozyme and cerebrospinal fluid in patients with EV71 encephalitis. These findings suggest that the IL-8-251T allele is associated with susceptibility to EV71 encephalitis in Chinese patients.