Dynamic Model Construction and Control System Design for Canadian Supercritical Water-cooled Reactors

The dynamic characteristics of Canadian Supercritical Water-cooled Reactor (SCWR) are significantly different from those of CANDU reactors due to the supercritical water coolant and the once-through direct cycle coolant system. Therefore, it is necessary to study its dynamic behaviour and further design adequate control system. An accurate dynamic model is needed to describe the dynamic behaviour. Moving boundary method is applied to improve numerical accuracy and stability. In the model construction process, three regions have been considered depending on bulk and wall temperature being higher or lower than the pseudo-critical temperature. Benefits of adopting moving boundary method are illustrated in comparison with the fixed boundary method. The model is validated with both steady-state and transient simulation and can accurately predict the dynamic behaviour of the Canadian SCWR. A linear dynamic model, for dynamic analysis and control system design, is obtained through linearization on the nonlinear dynamic models derived from conservation equations. The linearized dynamic models are validated against the full order nonlinear models in both time domain and frequency domain. The open-loop dynamics are also investigated through extensive simulations. Cross-coupling analysis among inputs and outputs is examined using Relative Gain Array (RGA) and Nyquist plots, from which adequate input-output pairings are identified. Cross-coupling at different operating conditions are also evaluated to illustrate the nonlinearities. It can be concluded that the Canadian SCWR is a Multiple Input and Multiple Output (MIMO) system with strong cross-coupling and a high degree of nonlinearity. Due to the existence of strong cross-coupling, the Direct Nyquist Array (DNA) method is used to decouple the system into a diagonal dominance form via a pre-compensator. Three Single Input and Single Output (SISO) compensators are synthesized to the pre-compensated system in the frequency domain. The temperature variation induced by the disturbances at the reactor power and pressure can be significantly reduced. To deal with the nonlinearities, a gain scheduling control strategy is adopted. Different set of controllers are used at different load conditions. The control strategy is evaluated under various operating scenarios. It is shown that gain scheduling control can successfully achieve satisfactory performance for different operating conditions

Circadian rhythm disruptions: A possible link of bipolar disorder and endocrine comorbidities

Epidemiological studies have demonstrated an association between bipolar disorder (BP) and endocrine diseases. Further, circadian rhythm disruptions may be a potential common pathophysiological mechanism of both disorders. This review provides a brief overview of the molecular mechanisms of circadian rhythms, as well as roles circadian rhythms play in BP and common endocrine comorbidities such as diabetes and thyroid disease. Treatments targeting the circadian system, both pharmacological and non-pharmacological, are also discussed. The hope is to elicit new interest to the importance of circadian system in BP and offer new entry points and impetus to the development of medicine

Model predictive power control of a heat pipe cooled reactor

Heat pipe cooled reactor (HPR) has broad application prospects in deep space exploration, deep-sea submarine exploration, and other scenarios due to the small size, high inherent safety, and easy modularization and expansion. However, the HPR conducts thermal energy through evaporation and condensation of the working fluid inside the heat pipe. This feature makes the HPR a large time-delay system. If the power control system adopts the conventional PID algorithm, there will be a long settling time. Therefore, the model predictive control algorithm is proposed for the power control system to improve the control performance. The HPR linear model, which is developed by linearization of its nonlinear model, is chosen as the predictive model. The optimal control value is obtained by solving the optimization problem based on the predictive model and the electric power feedback value. The discrepancy between the predive model and the actual system response results in the presence of steady-state error. To solve this problem, an integral controller is added to eliminate the error. The appropriate control system parameters are tuned by the trial and error method. The proposed control system has satisfactory control performance, which can significantly shorten the settling time. The model predictive control can effectively overcome the influence of the large time-delay characteristic

An Experimental Study on the Basic Mechanical Properties and Compression Size Effect of Rubber Concrete with Different Substitution Rates

An experimental study was carried out on the uniaxial compression, uniaxial splitting, pure shear, and compression size effect of rubber concrete with 5 different substitution rates by applying hydraulic servo and direct shear apparatus. Then, by comparing the failure modes and ultimate strength eigenvalues of rubber concrete under different loading conditions, the following conclusions were drawn: with the increase of rubber substitution rate, the concrete specimens maintain a relatively good integrity under uniaxial compressive failure; on the contrary, the failure sections under uniaxial slitting and pure shear gradually become uneven with an increasing amount of fallen rubber particles. With the increase of specimen size, the integrity of rubber concrete after failure is gradually improved. Affected by an increased rubber substitution rate, the uniaxial compressive strength, splitting tensile strength, and shear strength of the concrete gradually decrease, while the plastic deformation capacity gradually increases. Specifically, the compressive strength is reduced by a maximum of 60.67%; the shear strength is reduced by a maximum of 49.85%; and the uniaxial splitting strength is reduced by a maximum of 58.38%. Then, we analyzed the strength relationship and the underlying mechanism among the three types of loading modes. It is found that, at the same rubber substitution rate, the compressive strength of rubber concrete gradually increases as the specimen size decreases, and the size effect on the compressive strength gradually decreases as the rubber substitution rate increases. Meanwhile, we performed qualitative and quantitative analysis on the equation describing the coupling effect of specimen size and rubber substitution rate on the compressive strength; the results suggest that the proposed equation is of a high level of applicability. Our research has a reference value for the application and promotion of rubber concrete in actual engineering projects

Study of the mechanical-electrical-magnetic properties and the microstructure of three-layered cement-based absorbing boards

In this paper, a three-layered cement-based wave-absorbing board is designed and prepared by mixing wave-absorbing fillers such as nano-Si3N4, multi-layer nano graphene platelets (NGPs), nano-Ni, carbon fiber (CF) and carbon black (CB) into cement slurry. The effect of the amount of wave-absorbing fillers on the mechanical properties, resistivity and wave-absorbing reflectivity of cement slurry is studies. The microstructure of NGPs, nano-Si3N4 and the wave-absorbing board are characterized by TEM and SEM. Research shows that low content of NGPs and other wave-absorbing fillers can significantly reduce the resistivity of cement slurry and improve its mechanical strength, and dense massive crystals are precipitated in the cement hydration products. The reflectivity test reveals that in the frequency range of 2~18 GHz, the minimum reflectivity of the three-layered cement-based wave absorbing board reaches −18.8 dB, and the maximum bandwidth less than −10 dB reaches 15.3 GHz. This study can serve as reference for the preparation of new three-layered cement-based wave absorbing boards

Problematic internet gaming and non-suicidal self-injury in Chinese adolescents: Moderating and mediating roles of anxiety

Introduction: Despite consistent reports of the association between problematic internet gaming (PIG) and non-suicidal self-injury (NSSI), an increase in PIG does not necessarily lead to increased NSSI. This apparent paradox indicates the presence of other mediators and moderators in the PIG-NSSI association. This study aimed to investigate the role of anxiety as a potential moderating and mediating factor of the PIG-NSSI association in Chinese adolescents. Methods: A cross-sectional study was conducted among 10,479 Chinese adolescents (50.5% male; age range, 9–18 years). Standardized self-report questionnaires were used to assess the severity of PIG, anxiety, and NSSI. Spearman correlation and multiple linear regression were applied to examine the relationships among PIG, anxiety, and NSSI. Both moderating and mediating effects of anxiety were assessed using Hayes' methods. Results: PIG, anxiety symptoms, and NSSI significantly correlated with one another. Anxiety significantly moderated the relationship between PIG and NSSI [B = 0.002, standard error (SE) = 0.000, p < 0.001], and it partially mediated the PIG-NSSI association [B = 0.017, SE = 0.001, 95% confidence interval (CI) 0.014–0.021]. Social concern and concentration were the two dimensions of anxiety that exerted the strongest mediation effect (B = 0.017, SE = 0.002, 95% CI 0.014–0.020). Conclusions: Adolescents with PIG and high anxiety are likely to suffer more severe NSSI and may benefit from interventions to reduce anxiety symptoms

silverdissolutioninanovelleachingsystemreactionkineticsstudy

Effective silver recovery is usually restricted by either environmental pollution or high recovery costs.To tackle the issues,this study introduces a novel method for the effective recovery of silver by utilizing the alkaline sodium thiosulfate-potassium ferricyanide leaching system.The reaction kinetics of silver dissolution in this system was investigated via the rotating disk electrode technology.The influences of important parameters,including the rotation speed,sodium thiosulfate concentration,potassium ferricyanide concentration,and temperature,on the silver dissolution rate were systematically investigated.The activation energy was measured to be 17.96 kJ·mol^-1 when the silver dissolution was controlled by a diffusion process.When the silver dissolution was in the region of mixed control,the reaction orders of ferricyanide and thiosulfate were found to be 0.57 and 0.19,respectively,and the reaction orders of ferricyanide and thiosulfate were 0.55 and 0.22,respectively,when the silver dissolution was controlled by surface reaction.This study has great potential for the development of an environmentally friendly silver recovery process from end-of-life products

silverdissolutioninanovelleachingsystemreactionkineticsstudy

Effective silver recovery is usually restricted by either environmental pollution or high recovery costs. To tackle the issues, this study introduces a novel method for the effective recovery of silver by utilizing the alkaline sodium thiosulfate-potassium ferricyanide leaching system. The reaction kinetics of silver dissolution in this system was investigated via the rotating disk electrode technology. The influences of important parameters, including the rotation speed, sodium thiosulfate concentration, potassium ferricyanide concentration, and temperature, on the silver dissolution rate were systematically investigated. The activation energy was measured to be 17.96 kJmol(-1) when the silver dissolution was controlled by a diffusion process. When the silver dissolution was in the region of mixed control, the reaction orders of ferricyanide and thiosulfate were found to be 0.57 and 0.19, respectively, and the reaction orders of ferricyanide and thiosulfate were 0.55 and 0.22, respectively, when the silver dissolution was controlled by surface reaction. This study has great potential for the development of an environmentally friendly silver recovery process from end--of-life products