Numerical simulation on phasing strategy for a gasoline engine with continuously variable intake camshaft

Intake camshaft equipped with continuously adjustable cam phasing units is applied to a 486Q gasoline engine. Phasing strategies are researched through engine cycle simulation to achieve superior engine performance. The simulation results show that at high load and low and moderate speed of the engine,phasing adjustment can lead to 6% to 8% increase in power performance because phasing advance contributes to suppressing intake backflow at IVC(intake valve closed). Cam phases obtained from numerical optimization have good agreement with engine test. At moderate load,cycle simulations show that phasing advance can increase residual gas coefficient from 9% to 20%,and reduce NO emission by 80%,BSFC(brake specific fuel consumption) by 2% at a demonstration operation. With regard to fuel economy and emissions,adjustment and optimization of intake phasing at moderate load are further verified by engine test. At low load,technical approaches to enhance combustion stability,reduce HC emission and improve cold start are investigated. The effectiveness of suppressing exhaust backflow into intake duct by phasing retard is testified by simulation. Phasing changes at the operating condition are optimally obtained by engine test for improvement of combustion stability.     

Experimental analysis of the abrasive belt follow-up grinding of Zirconium-4 alloys tubes and pipes

Abrasive belt grinding experiments of Zr-4 nuclear power tube are carried out by using three different abrasive belts with same size, and the interactive generating mechanism between abrasive and workpiece is analyzed, the main factors of material removal rate and surface roughness of Zr-4 alloys are obtained. With the help of the advanced test facilities, the abrasive grain abrasion and surface topography of the workpiece are observed. The metallographic structure and microhardness of the layer of burnt surface during Zr-4 alloys Grinding are analyzed. Some conclusions are given as follows: the material removal rate and surface roughness are mainly affected by the factors of belt speed, grinding pressure, hardness of the contact wheel and abrasive type, of which, the belt speed is the strongest factor. The adhesion wear of the Zirconium corundum and aluminium oxide abrasive grit is more serious, the most important wear form of silicon carbide is abrasion wear. With the onset of grinding burn, the mechanical properties of Zr-4 alloys are deteriorated obviously. The results provide a theoretical and experimental basis for technical optimization in the grinding of Zr-4 alloys with efficiency and high quality.     

不同灌水下限及氮素形态配比对西兰花干物质分配、产量及品质的影响

为研究不同灌水下限及氮素形态配比对西兰花干物质分配、产量及品质的影响,采用双因素随机区组设计,因素1为不同灌水下限,设3个梯度W1(田间最大持水量的80%)、W2(田间最大持水量的60%)、W3(田间最大持水量的40%);因素2为不同氮素形态配比,设3个配比N1(NO^-₃-N∶NH⁺₄-N=10∶0)、N2 (NO^-₃-N∶NH⁺₄-N=7∶3)、N3 (NO^-₃-N∶NH⁺₄-N=5∶5)。结果表明,在相同水分处理条件下,西兰花茎、花球干质量、经济产量、经济系数、Vc、水分利用效率和氮肥偏生产力均在N3处理时最高,但可溶性蛋白、硝酸盐、Cu含量最低;在相同氮素配比条件下,西兰花干质量(除花球干质量外)、产量、可溶性糖、水分利用效率和氮肥偏生产力随着灌水量的减少呈现先升高后降低的趋势,但可溶性蛋白含量降低;在N1和N2条件下,...     

超高产杂交稻剑叶的光抑制及其77K荧光光谱特性

通过对培矮64S/E32和汕优63进行高光胁迫结果表明: 与籼型杂交稻汕优63比较, 培矮64S/E32的Fv/Fm和ΦPSⅡ、PSⅡ和PSⅠ荧光强度下降的幅度以及F685/F742和F694/F742比率的变化较小。用D1蛋白合成抑制剂CAP处理时,培矮64S/E32 的Fv/Fm和qP下降程度稍高于汕优63,而用叶黄素循环抑制剂DTT处理,结果则反之。表明超高产水稻品     

低磷胁迫对磷不同利用效率玉米叶绿素荧光参数的影响

盆栽试验在高磷（+P）和低磷(－P)条件下,于四叶期测定了磷高效利用型玉米KH5和磷低效利用型玉米齐201的老叶（第2叶）和新展开叶的（第4叶）叶绿素荧光诱导动力学参数。结果表明,低磷处理使玉米叶片PSⅡ关闭程度增加、光能转换和电子传递效率降低,过剩激发能增加。基因型间比较,磷高效利用型玉米的光能转换和电子传递效率     

Effect of cooling rate on high temperature mechanical properties of weathering steel

High temperature mechanical properties are key factors which affect fracture production during deforming process of continuous casting. High temperature properties of weathering steel Q450NQR1 are tested in 3 cooling rates (1.65, 5, 10 ℃/s) using Gleeble thermo-mechanical simulator. Specimens appear austenite dynamic recrystallization at 1 050 ℃, and the ductility reaches the lowest point and the reduction of area approaches 23% at 850 ℃ in 3 cooling rates. As the cooling rate increases, the low ductility area where cracks are easy to be produced in slabs is enlarged and extended towards low temperature, and the ductility troughs are deepened. The increase of the cooling rate decreases the tensile stress and yield stress, while when the cooling rate increases to some degree, it doesn’t affect the stress. The low cooling rate decreases the film or network ferrite producing in austenite grain boundary, and the carbonitride of microalloy is enwrapped in matrix, which is helpful to improve the ductility of steel.     

Input-output budgets for nitrogen in a typical purple soil sloping ploughland in Three Gorges areas

The Xinzheng watershed in Zhongxian county, Chongqing, is a typical purple soil sloping ploughland in the Three Gorges areas. In 2009, the input-output budgets in this watershed is investigated and the results indicate that the nitrogen input is 918.26 kg/(hm2·a) and the output are 569.46 kg/(hm2·a). Furthermore, chemical fertilizer nitrogen is the main input source, accounting for 57.63%, and the main output track is nitrogen in crops, accounting for 36.22%. In this small watershed, the nitrogen loss load is 258.77 kg/(hm2·a). And the primary lost nitrogen is gaseous species, which is approximately 65.11% of the total lost nitrogen. In addition, nutrient nitrogen balance index is 3.4 in this watershed and the nitrogen surplus load is 348.80 kg/(hm2·a), much higher than the risk value, indicating potential occurrence pollution in ploughland.     

不同套袋处理对‘岳苹’果实品质及着色的影响

为探讨‘岳苹’苹果的适宜果袋及摘袋后果皮色素含量的变化规律,确定摘袋后的适宜采收时间,对其设定3种套袋处理,并对不同处理果实内含物、糖、酸和果皮色素的含量进行测定。结果表明：套纸袋使‘岳苹’果实的硬度和果皮花青苷的含量分别提高7.7%和30.9%,促进果实着色,提高果实外观品质,但降低了‘岳苹’果实的风味,使果糖、蔗糖和总糖的含量分别降低了14.2%、59.7%和19.2%;套塑膜袋使‘岳苹’果实的硬度及果皮花青苷的含量分别降低了6.1%、10.0%和36.4%、35.3%;套塑膜袋摘袋使果实果糖和总糖的含量分别提高11.6%和6.8%;同时确定了‘岳苹’果实摘袋后采收的最佳时间为9~11天。     

玉米低磷响应基因ZmPAP18的表达特征与序列变异分析

紫色酸性磷酸酶(PAP)是金属磷酸酯酶家族的重要成员,在植物对低磷环境适应的过程中发挥重要作用。依据前期构建的低磷胁迫抑制消减文库,运用RT-PCR方法从耐低磷玉米自交系178中克隆了一个酸性磷酸酶基因的全长序列。该基因编码区全长1409bp,其中ORF为1371bp,编码457个氨基酸残基。经保守域分析发现,基因的推测氨基酸序列中含有紫色酸性磷酸酶所特有的5个保守基序和7个金属离子结合位点,属于紫色酸性磷酸酶类,被命名为ZmPAP18。通过实时荧光定量分析表明,ZmPAP18在根和叶中均受到低磷胁迫的诱导增强表达,且在诱导24h后表达量达到峰值;但在玉米根部的表达量高于叶片,表明ZmPAP18在玉米根部可能参与了根外磷素的活化与吸收以及无机磷由根部向其他组织的转运。此外,经序列分析发现,ZmPAP18的3’非翻译区存在一个Indel(TGTTG)位点,并在常用的14个玉米自交系中表现出丰富的多态性,为进一步开发该基因的分子标记及耐低磷种质分子改良提供了参考信息。     

Kinetics on degradation of CODcr in mustard comprehensive wastewater by electro-Fenton process

The treatment efficiency of mustard comprehensive wastewater with high salt by electro-Fenton is studied to solve the problem that microorganism is inhibited by high salt and improve the unstable performance of biological treatment. CODcr removal effect and its influencing factors in high salt wastewater by electro-Fenton process are mainly investigated, and the degradation kinetics of CODcr is analyzed. The results show that CODcr removal rate reaches 76.33 % after 120 min at the conditions that current density of 10 A/dm 2, ferrous sulfate dosage 1.0 mmol/L, electrode spacing 15 mm, pH=5, RuO2-IRO2-SnO2-TiO2/Ti quaternary as anode, titanium mesh as cathode. Kinetic analysis shows that the degradation curve of CODcr consists with the first-order response characteristics and the value of the kinetic constant is 0.0121 min -1 when COD of raw wastewater is 4 225 mg/L. By linear regression equation, kinetics model of CODcr degradation is established. The model possesses higher regression rate (R 2=99.25%) and has higher coincide degree with the experimental results.