基于经济和稳定的电力系统最优运行策略

电力系统中带暂态稳定约束的最优潮流(OTS)问题是一个甚至在小规模电力系统中都难以精确处理的泛函数空间非线性优化问题,文中避开直接处理这一复杂问题,将带暂态稳定约束的潮流优化问题等价转换为欧几里德空间的优化问题,然后采用最优潮流(OPF)中常用的标准非线性规划法来解决此问题。经过转换后的OTS,在形式上和OPF有相同的变量,这样即使对于一个存在众多暂态稳定约束和多个扰动的大型电力系统,也变得容易求解。所提出的方法可以适用于任何发电机系统、控制器或者输电网络模型,不仅可以直接用于计算系统最优运行点,还可以应用于电力市场内电价的精确估价以及预防性稳定控制、电压下降问题和可用传输容量计算等领域。     

The results of 5% small-break LOCA tests and natural circulation tests at the ROSA-IV LSTF

Five 5% small-break loss-of-coolant accident (SBLOCA) experiments and two natural circulation experiments were conducted at the ROSA-IV Large Scale Test Facility (LSTF). The liquid holdup in the upflow side of steam generator (SG) U-tubes temporarily depressed the core collapsed liquid level below the bottom of core during the loop seal clearing in the cold-leg break SBLOCA tests. This phenomena was affected by the core power and core bypass but was affected little by the actuation of the high pressure injection system. Overall thermal-hydraulic phenomena in a loop seal line break test was similar to that of cold-leg break tests, however, the liquid holdup phenomena played a little role. In a hot-leg break test a temporary but rapid depression of the core liquid level was observed immediately after the initiation of accumulator injection which caused condensation and depressurization in the cold leg. The change of natural circulation flow rate with the decrease of primary system mass inventory was qualitatively the same as observed in Semiscale, LOBI and PKL. The SG effective overall heat transfer coefficient below the secondary-side collapsed liquid level was weakly dependent on the secondary side liquid level and the core power. The measured minimum heat transfer coefficient was 1.7 kW/m²K for the full secondary side mass inventory.     

Double‐Switch Series‐Resonant Cell‐Voltage Equalizer Using a Voltage Multiplier for Series‐Connected Energy Storage Cells

Series connections of energy storage cells, such as lithium‐ion cells and electric double‐layer capacitors (EDLCs), require cell‐voltage equalizers to ensure years of operation. Conventional equalizers require multiple switches, magnetic components, and/or secondary windings of a multiwinding transformer in proportion to the number of series connections, which usually makes them complex, expensive, bulky, and less extendable with increasing series connections. A double‐switch series‐resonant equalizer using a voltage multiplier is proposed in this paper. The double‐switch operation without a multiwinding transformer achieves simplified circuitry and good modularity at reduced size and cost, compared to conventional equalizers. Operational analyses were separately performed for the following two functional parts of the proposed equalizer: a series‐resonant inverter and a voltage multiplier. The mathematical analyses derived a dc‐equivalent circuit of the proposed equalizer, with which simulation analyses of even an hour's duration can be completed in an instant. Simulation analyses were separately performed for both the original and equivalent circuits. The simulation results of the derived circuit correlated well with those of the original circuit, thus verifying the derived dc‐equivalent circuit. A 5‐W prototype of the proposed equalizer was built for eight cells connected in series and an experimental equalization was performed for series‐connected EDLCs from an initially voltage‐imbalanced condition. The voltage imbalance was gradually eliminated over time, and the standard deviation in the cell voltages decreased to approximately 5 mV at the end of the experiment, thus demonstrating the equalization performance of the proposed equalizer.     

Constructing vision-driven indicators to enhance the interaction between science and society

Scientometrics - In this fast-paced modern world, science, technology, and innovation (STI) are key drivers that impact all areas of life at individual and organisational levels, deepening the...     

Synthesis of degradable network polymers containing peroxy units in the main chain or the cross-linking point

We have synthesized degradable network polymers containing readily labile peroxy bonds as the repeating units in the main chain or as the cross-linking point in the side chain. Poly(2-hydroxyethyl sorbate-alt-O₂) was obtained by the radical copolymerization of 2-hydroxyethyl sorbate with oxygen, and then cross-linked using tolylene 2,4-diisocyanate as the cross-linking agent to obtain a new type of degradable gel. We also investigated the cross-linking of conventional polymers by the reaction of the diene moieties introduced into the polymer side chain with oxygen. The hydroxy group in the side chain of poly(vinyl alcohol) (PVA) was reacted with 1-isocyanate-1,3-pentadiene in order to introduce a diene moiety into the side chain of the PVA. The dienylated PVA was reacted with oxygen in the presence of a radical initiator, leading to the formation of a gel containing a labile peroxy linkage at the cross-linking point. These gels containing peroxy units in the main chain or at the cross-linking points degraded upon heating.     

Effect of Partition Wall on Heat Transfer Characteristics of a Gas-to-Gas Counterflow Microchannel Heat Exchanger

The effect of a partition wall on heat transfer characteristics of a two-stream gas-to-gas counterflow microchannel heat exchanger has been numerically investigated. The flow passages of the microchannel heat exchanger are plane channels of 100 μm in height and 20 mm in length. The material of the partition wall is assumed to be stainless steel. The computations were performed for a wide range of flow rate to investigate heat transfer characteristics of the microchannel heat exchanger. Moreover, computations for various partition wall thicknesses were conducted to investigate the effect of the wall thickness. The thickness ranged from 200 μm to 6 μm while the channel height was fixed at 100 μm. Numerical results show that heat transfer characteristics of a gas-to-gas counterflow microchannel heat exchanger are affected by partition wall thickness. Computations for various partition wall thicknesses and thermal conductivities of the partition wall were performed. The results were compared with those of a single microchannel with constant wall temperature. Applicability of the assumption of constant wall temperature was revealed.     

Experimental investigations of laminar,transitional and turbulent Gas flow in microchannels

This paper presents experimental results on flow characteristics of laminar, transitional and turbulent gas flows through microchannels. The experiments were performed for three microchannels etched into silicon wafers, capped with glass with hydraulic diameters of 69.48, 99.36 and 147.76 μm. The stagnation pressure was designated in such a way that the flow is laminar, transitional and turbulent with the outflow at atmosphere condition. The pressure was locally measured at seven locations along the channel length to determine local values of Mach number and friction factor from laminar to turbulent flow. The result shows f ? Re is a function of Mach number and is higher than incompressible value due to the compressibility effect for laminar flow. The Darcy friction factor with flow acceleration loss is higher than the Fanning friction factor for both laminar and turbulent flow. The friction factors were also compared with empirical correlations in the literature and Moody’s chart.     

Dynamic force reduction and heat transfer improvement for horizontal tubes in large-particle gas-fluidized beds

The effects of tube bank configuration on forces and heat transfer were investigated for both two-dimensional and three-dimensional gas fluidized beds. Effective dynamic forces and heat transfer coefficients were measured for several tube bank configurations, and it was found that the average forces are smaller than for a single tube. The heat transfer coefficient can be increased by providing sufficient space for particles to descend around both sides of the tube bank. The results provide useful guidelines for optimizing the configuration of tube banks to achieve high heat transfer coefficients while reducing tube erosion due to dynamic forces.     

Granulocyte-colony stimulating factor-induced proliferation of primary adult T-cell leukaemia cells

Granulocyte-colony stimulating factor (G-CSF) is known to induce proliferation and differentiation of granulocyte progenitors, and is widely used to treat neutropenia induced by intensive chemotherapy for malignant lymphoma or adult T-cell leukaemia/lymphoma (ATL). G-CSF is thought not to stimulate malignant lymphoid cells. In the present study we examined the ability of G-CSF to induce in vitro growth of primary ATL cells from 14 patients (nine acute-type, two chronic-type and three lymphoma-type), and we analysed the in vivo counts of ATL cells in patients who received G-CSF for neutropenia. FACS analysis using phycoerythrin-labelled recombinant G-CSF demonstrated that ATL cells from 11/14 patients express some G-CSF receptor (G-CSFR), with a range between 5.4% and 87.3%. Cells expressing G-CSFR also expressed CD4. Reverse polymerase chain reaction (PCR) analysis demonstrated expression of G-CSFR messenger RNA in G-CSFR expressing cells. Leukaemic cells derived from seven (four acute-type, one chronic-type and two lymphoma-type) of the 14 patients proliferated in vitro in response to G-CSF, as measured by [3H]thymidine incorporation; maximum responses were at G-CSF concentrations of 10-100 ng/ml. Nine of 14 patients receiving rG-CSF for neutropenia were analysed retrospectively for ATL cell numbers. Four patients whose primary tumour cells proliferated in response to rG-CSF in vitro showed a significant increase in ATL cell count after administration of rG-CSF (P = 0.038), whereas five patients whose leukaemic cells did not proliferate in vitro showed no significant increase in ATL cell count. G-CSF can stimulate proliferation of ATL cells which may complicate therapy for this disease.