Numerical study on wave attenuation inside and around a square array of biofouled net cages

In this study, waves propagating through a square array of 16 net cages with different levels of biofouling are numerically studied using a three-dimensional computational fluid dynamics (CFD) model. A porous-media fluid model is adopted to simulate both clean and biofouled netting of a cage array in waves. A numerical wave tank is built, and the oscillating-boundary method is adopted to generate waves. The flow motion is solved by the Navier-Stokes equations, and the free water surface is captured using the volume of fluid (VOF) method. The numerical model is validated by comparing the numerical data with corresponding experimental measurements of a net-cage model with clean netting. To analyze wave attenuation, a numerical analysis of wave elevation both inside and around the cage arrays is presented, which considers the effect of biofouling. Based on the results of the present study, the effect of biofouling on wave elevation is noticeable; the damping effect of the cage array increases with increasing level of biofouling. Furthermore, the incident angle of waves has a noticeable effect on the wave field inside and around the cage array.     

线切割与镂铣图形的CNC自动编程及虚拟加工技术研究

以AutoCAD R14为开发平台，综合运用ObjectARX SDK、Visual C^ 6.0及CNC技术，在研究了AutoCAD R14的数据结构、平面图形CNC自动编程及加工过程仿真和虚拟现实算法基础上，开发出一种适用于CNC木工镂铣、CNC线切割和CNC激光平面轨迹加工的、集CAD／CNC APT／虚拟加工功能于一体的集成技术。该技术可直接将二维AutoCAD图形快速自动转换成二维CNC加工程序，并可对所编程序进行虚拟加工实验，以检验加工的正确性和可靠性；解决了实际二维平面图形加工CAD／CAM集成及其一体化的瓶颈问题。     

Stem respiration in leafy cuttings of Prosopis juliflora during the rooting process

An oxygen electrode was used to estimate the respiration rate of basal 1 cm sections of Prosopis juliflora cuttings. The respiration rate per unit dry mass decreased linearly with increasing diameter at a rate of 0.42 nmol0₂g^–1s^–1mm^–1 between the range of 1–3 mm diameter. However, as a result of increased mass, total respiration for the whole 1 cm section of tissue increased linearly with increasing diameter. The average respiration rate of the basal 1 cm of stem tissue, measured 14 days after insertion in the propagator, was almost double that of the 1 cm section of tissue above it (1.01 nmol0₂g^–1s^–1 compared to 0.57 nmol0₂g^–1s^–1). The value of this technique as an aid to our understanding of the development of adventitious roots is discussed.     

Transient heat transfer characteristics of air-array-jet impingement with different nozzle arrangements on high-tempera-ture flat plate in small jet-to-plate distance

Numerical studies on transient heat transfer characteristics of air-array-jet impingement with a small jet-to-plate distance and a large temperature difference between nozzles and plate were presented.The dimensionless jet-to-plate distance(H/D)was 0.2,and non-dimensional nozzle-to-nozzle spacing(S/D)was 3,4,5 and 6,respectively.It is found that the quenching time is shortened at a constant total mass flow at air jet inlet m·(m·=218.21 kg/h),and the heat transfer uniformity is deterio-rated as S/D increases.However,the adding reversed-flow nozzles can shorten the quenching time of the glass plate considerably with a modest change in the heat transfer uniformity.The results at variable m·are the same as those at a fixed m·.Furthermore,the parity and arrangement of nozzles are also discussed,It is found that an odd number of nozzles is more beneficial for transient heat transfer.Based on these results,an appropriate proposal for ultra-thin glass tempering process is presented.     

Differential Cl−/Salt Tolerance and NaCl‐Induced Alternations of Tissue and Cellular Ion Fluxes in Glycine max,Glycine soja and their Hybrid Seedlings

The salt‐sensitive Glycine max N23674 cultivar, the salt‐born Glycine soja BB52 population, and their hybrid 4076 strain (F₅) selected for salt tolerance generation by generation were used as the experimental materials in this study. First, the effects of NaCl stress on seed germination, tissue damage, and time‐course ionic absorption and transportation were compared. When qualitatively compared with seed germination appearance in culture dishes, and tissue damages on roots or leaves of seedlings, or quantitatively compared with the relative salt injury rate, the inhibition on N23674 was all the most remarkable. After the exposure of 140 mm NaCl for 1 h, 4 h, 8 h, 12 h, 2 days and 4 days, the content of Cl^? gradually increased in the roots and leaves of seedlings of BB52, 4076 and 23674. Interestingly, the extents of the Cl^? rise in roots of the three experimental soybean materials were BB52 > 4076 > N23674, whereas those in leaves were just on the contrary. Secondly, by using the scanning ion‐selective electrode technique (SIET), fluxes of Na⁺ and Cl^? in roots and protoplasts isolated from roots and leaves were also investigated among the three experimental soybean materials. After 140 mm NaCl stress for 2, 4 and 6 days, and when compared with N23674, slighter net Cl^? influxes were observed in root tissue and protoplasts of roots and leaves of BB52 and 4076 seedlings, especially at the cellular protoplast level. The results indicate that with regard to the ionic effect of NaCl stress, Cl^? was the main determinant salt ion for salt tolerance in G. soja, G. max and their hybrid, and the difference in their Cl^?/salt tolerance is mainly attributed to the capacity of Cl^? restriction to the plant above‐ground parts such as leaves.     

荷电喷雾电晕电极诱导电场数值计算与分析

为深入研究电晕荷电喷雾产生电场的分布情况,针对电晕荷电喷雾中常用的多针组合式电极,采用电荷模拟法,运用matlab软件编程,对电极诱导电场进行数值计算,得出了电场中任意点的电势、场强值及其分布图。通过计算分析发现,电晕放电产生的静电场是极不均匀的;场强由电极结构参数-极径、电极尖端曲率半径、电极电压、针状电极的个数以及电极环中心距地面的垂直高度决定;雾滴从喷嘴到靶标的输运过程中,电晕电极产生的电场仅在输运初始阶段对雾滴的运动起主导作用。     

冶金因素对纯镍铸铁焊条抗热裂性能影响

研究了钛、铌，钛，钼，硅和钇镁硅铁合金对纯镍铸铁焊条抗热裂性能的影响，试验结果表明，钛，铌，钴，钇和镁在焊缝中的含量有一最佳值，综合利用这些合金元素，可显著改善纯镍铸铁焊条的抗热裂性能，其熔敷金属的机械性能可符合铁素体球墨铸铁（ＱＴ４００－１５）的要求。