Cooling of cultured water can resist heart failure caused by collagen deposition and necrosis of cardiac fibers under chronic heat stress in sturgeon

Background Chronic heat stress (CHS) may threaten the survival of cultivated and wild sturgeon by jeopardizing heart function. Methods Therefore, we established a heart damage model for the Siberian sturgeon (Acipenser baerii) using varying degrees of CHS (24°C and 28°C) to explore its effect on the heart structure and function, and their mutual relationship. Results Our research showed that CHS caused systemic heart failure in A. baerii, clinically manifested as severely irregular ventricles, increased myocardial fibrotic in the interstitium of cardiomyocytes, and myocardial necrosis. Echocardiographic imaging of A. baerii revealed an accelerated heart rate, incomplete ventricular contraction, decreased cardiac output, and significantly reduced pumping efficiency under CHS. Generally, the contractility of the heart decreased and the afterload increased under CHS, which is typical of high-resistance and low-output heart failure. However, cooling of cultured water (20°C) can offset the adverse effects of partial or total CHS on tissue structure and function. Conclusion Our results systematically characterized the relationship between the effects of CHS on the heart structure and heart function in sturgeon. This work provides a preliminary reference for future summer breeding pond management and protection of sturgeon.

Pulp pumping efficiency II – Designing of a pulp pump

Based on the loss model of pulp pump set up in the I part of this research, an efficient designing method is proposed by taking account of the influences of head reduction by small blade number, leakage loss via tip clearance, and erosion-corrosion wears in pumps separately. Further, a two-stage optimal designing approach was proposed to tackle the oversized design. The pump designing was performed by coupling with a CFD-based optimization procedure. An efficiency increase of near 10 % was achieved on the pump model validated in laboratory. It was proved that performance could be improved by increasing the impeller blade width and enlarging the impeller blade outlet angle. It was further shown that the erosion-corrosion wear in pulp pump was relatively lighter when compared to particle-impingement wear in slurry and sewage pump. Adoption of composite material showed potential in energy-saving in the pumping system.

Pulp pumping efficiency I – A critical review on loss and its estimation

With growing demand of paper products, the electric consumption in pulp and paper industry is increasing globally where a share of 30 % is attributed to the pulp pumping system. The efficient designing and running of pumping system are critical for energy efficiency. The incomplete information on pulp flows and the oversized designs are the major causes of low efficiency. In the first part of this research, the fiber level models and rheological properties covering a series of unit applications are examined. A loss model of pulp pump is set up by considering different factors influencing pumping performance. The efficiency improvement opportunities in pulp pumping are systematically investigated. The drag-reducing feature at low consistency pulp pumping is highlighted which will be further applied in energy optimized sizing and dimensioning of a pulp pump in the second part of this research.

A Negative Charge Pump Using Enhanced Pumping Clock for Low-Voltage DRAM

As the supply voltage decreases, there is a need for a high-speed negative charge pump circuit, for example, to produce the back-bias voltage (VBB) with high pumping efficiency at a low supply voltage (VDD). Beyond the basic negative charge pump circuit with the small area overhead, advanced schemes such as hybrid pump circuit (HCP) and cross-coupled hybrid pump circuits (CHPC) were introduced to improve the pumping efficiency and pump down speed. However, they still suffer from pumping efficiency degradation, low level |VBB|, and small pumping currents at very low VDD. A novel negative charge pump using an enhanced pumping clock is proposed. The proposed cross-coupled charge pump consists of the enhanced pumping clock generator (ECG) having a pair of inverters and PMOS latch circuit to produce an enhanced control signal with a greater amplitude, thereby working efficiently especially at low supply voltages. The proposed scheme is validated with a HSPICE simulation using the TSMC 180 nm process. The proposed scheme can be operated down to VDD = 0.4 V, and |VBB|/VDD is obtained to be 86.1% at VDD = 0.5 V and Cload = 20 nF. Compared to the state-of-the-art CHPC scheme, the pumping efficiency is larger by 35% at VDD = 0.6 V and RL = 10 KΩ, and the pumping current is 2.17 times greater at VDD = 1.2 V and VBB = 0 V, making the circuit suitable for very low supply voltage applications in DRAMs.

Research on sealing performance of oil seals with micro-dimple texture on lips

Purpose The purpose of this paper is to study the pumping efficiency of oil seals with different surface textures at different speeds, and the influence of the rotation direction of triangular texture on the sealing performance was further analyzed. Design/methodology/approach Based on the theory of elastohydrodynamic lubrication and the pumping mechanism of rotary shaft seals, establishing a numerical model of mixed lubrication in oil seal sealing area. The model is coupled with the lip surface texture parameters and the two-dimensional average Reynolds equation considering the surface roughness. Findings The results show that the application of lip surface texture technology has obvious influence on the oil film thickness, friction torque and pumping rate of oil seal. The triangular texture has the most significant effect on the increase of pump suction rate. When the rotation direction of triangular texture is 315 degrees, the pumping rate of oil seal is the largest compared with the other seven directions. Originality/value The model has a comprehensive theoretical guidance for the design of new oil seal products, which provides a certain basis for the application of surface texture technology in the field of sealing in the future. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-06-2020-0198/

Simulation of the Slip Velocity Effect in an AC Electrothermal Micropump

The principal aim of this study was to analyze the effect of slip velocity at the microchannel wall on an alternating current electrothermal (ACET) flow micropump fitted with several pairs of electrodes. Using the finite element method (FEM), the coupled momentum, energy, and Poisson equations with and without slip boundary conditions have been solved to compute the velocity, temperature, and electrical field in the microchannel. The effects of the frequency and the voltage, and the electrical and thermal conductivities, respectively, of the electrolyte solution and the substrate material, have been minutely analyzed in the presence and absence of slip velocity. The slip velocity was simulated along the microchannel walls at different values of slip length. The results revealed that the slip velocity at the wall channel has a significant impact on the flow field. The existence of slip velocity at the wall increases the shear stress and therefore enhances the pumping efficiency. It was observed that higher average pumping velocity was achieved for larger slip length. When a glass substrate was used, the effect of the presence of the slip velocity was more manifest. This study shows also that the effect of slip velocity on the flow field is very important and must be taken into consideration in an ACET micropump.