Development of a novel critical nitrogen concentration-cumulative transpiration curve for optimizing nitrogen management under varying irrigation conditions in winter wheat

Accurate nitrogen(N)nutrition diagnosis is essential for improving N use efficiency in crop production.The widely used critical N(Nc)dilution curve traditionally depends solely on agronomic variables,neglecting crop water status.With three-year field experiments with winter wheat,encompassing two irrigation levels(rainfed and irrigation at jointing and anthesis)and three N levels(0,180,and 270 kg ha1),this study aims to establish a novel approach for determining the Nc dilution curve based on crop cumulative transpiration(T),providing a comprehensive analysis of the interaction between N and water availability.The Nc curves derived from both crop dry matter(DM)and T demonstrated N concentration dilution under different conditions with different parameters.The equation Nc=6.43T0.24 established a consistent relationship across varying irrigation regimes.Independent test results indicated that the nitrogen nutrition index(NNI),calculated from this curve,effectively identifies and quantifies the two sources of N deficiency:insufficient N supply in the soil and insufficient soil water concentration leading to decreased N availability for root absorption.Additionally,the NNI calculated from the Nc-DM and Nc-T curves exhibited a strong negative correlation with accumulated N deficit(Nand)and a positive correlation with relative grain yield(RGY).The NNI derived from the Nc-T curve outperformed the NNI derived from the Nc-DM curve concerning its relationship with Nand and RGY,as indicated by larger R2 values and smaller AIC.The novel Nc curve based on T serves as an effective diagnostic tool for assessing winter wheat N status,predicting grain yield,and optimizing N fertilizer management across varying irrigation conditions.These findings would provide new insights and methods to improve the simulations of water-N interaction relationship in crop growth models.

CALCULATIONS OF THE PHASE EQUILIBRIA AND CRITICAL CURVES WITH THE EQUATION OF STATE FOR BINARY MIXTURES

A rational equation of state of the perturbation type with a repulsion and attraction term has been applied to reproduce critical curves of six different binary systems up to high temperatures and pressures. A square well potential for intermolecular interaction is used. With pairwise combination rules for these potentials three adjustable parameters are needed. The experimental critical point and phase equilibrium data are compared with the values predicted using the equation of state. Good agreement is obtained for the analysis of the critical pressure composition data and molar volumes.

Calculation of Gas-Liquid Critical Curves for Binary Systems Containing Methane

The critical curves for binary systems of methane combined with nitrogen, carbon monoxide, carbon dioxide, ethane, propane, butane and water at temperatures from 125 K to 650 K and pressures from 3.5 MPa to 250 MPa were calculated by using Heilig-Franck equation of state. This equation of state contains a repulsion term and an attraction term for intermolecular interaction. With pairwise combination rules for these potentials, three adjustable parameters are needed. The results showed that the critical curves of the former six binary systems belonged to type I, and CH4＋H2O system belonged to type III. The calculated data were compared with the experimental data,which yielded good results for the pressure-temperature, pressure-composition and temperature-composition behaviors of the seven systems. Moreover, the values of the adjustable parameters were obtained from the calculation of the critical curves. They can also be used for other relevant calculation.

Shale high pressure isothermal adsorption curve and the production dynamic experiments of gas well

The high pressure static adsorption curves of shale samples from Silurian Changning-Weiyuan Longmaxi Formation were tested by using high pressure isothermal adsorption equipment.The physical modeling of depletion production was tested on single cores and multi-core series by using self-developed shale gas fluid-solid coupling experiment system.The adsorption and desorption laws were summarized and a high pressure isothermal adsorption model was established.The calculation formula of gas content was corrected,and the producing law of adsorption gas was determined.The study results show that the isothermal adsorption law of the shale reservoir under high pressure was different from the conventional low pressure.The high pressure isothermal adsorption curve had the maximum value in excess adsorption with pressure change,and the corresponding pressure was the critical desorption pressure.The high pressure isothermal curve can be used to evaluate the amount of adsorbed gas and the producing degree of adsorption gas.The high pressure isothermal adsorption model can fit and characterize the high pressure isothermal adsorption law of shale.The modified gas content calculation method can evaluate the gas content and the proportion of adsorbed gas more objectively,and is the theoretical basis of reserve assessment and production decline analysis.The producing degree of adsorption gas is closely related to the pressure,only when the reservoir pressure is lower than the critical desorption pressure,the adsorption gas can be produced effectively.In the process of gas well production,the pressure drop in the near-well area is large,the production of adsorption gas is high;away from the wellbore,the adsorption gas is low in production,or no production.

Optimum design of photoresist thickness for 90-nm critical dimension based on ArF laser lithography

In this work, a 90-nm critical dimension （CD） technological process in an ArF laser lithography system is simulated, and the swing curves of the CD linewidth changing with photoresist thickness are obtained in the absence and presence of bottom antireflection coating （BARC）. By analysing the simulation result, it can be found that in the absence of BARC the CD swing curve effect is much bigger than that in the presence of BARC. So, the BARC should be needed for the 90-nm CD manufacture. The optimum resist thickness for 90-nm CD in the presence of BARC is obtained, and the optimizing process in this work can be used for reference in practice.

Health-related quality-of-life and health-utility reporting in critical care

Mortality is a well-established patient-important outcome in critical care studies.In contrast,morbidity is less uniformly reported(given the myriad of critical care illnesses and complications of each)but may have a common end-impact on a patient’s functional capacity and health-related quality-of-life(HRQoL).Survival with a poor quality-of-life may not be acceptable depending on individual patient values and preferences.Hence,as mortality decreases within critical care,it becomes increasingly important to measure intensive care unit(ICU)survivor HRQoL.HRQoL measurements with a preference-based scoring algorithm can be converted into health utilities on a scale anchored at 0(representing death)and 1(representing full health).They can be combined with survival to calculate quality-adjusted life-years(QALY),which are one of the most widely used methods of combining morbidity and mortality into a composite outcome.Although QALYs have been use for health-technology assessment decision-making,an emerging and novel role would be to inform clinical decision-making for patients,families and healthcare providers about what expected HRQoL may be during and after ICU care.Critical care randomized control trials(RCTs)have not routinely measured or reported HRQoL(until more recently),likely due to incapacity of some patients to participate in patient-reported outcome measures.Further differences in HRQoL measurement tools can lead to non-comparable values.To this end,we propose the validation of a gold-standard HRQoL tool in critical care,specifically the EQ-5D-5L.Both combined health-utility and mortality(disaggregated)and QALYs(aggregated)can be reported,with disaggregation allowing for determination of which components are the main drivers of the QALY outcome.Increased use of HRQoL,health-utility,and QALYs in critical care RCTs has the potential to:(1)Increase the likelihood of finding important effects if they exist;(2)improve research efficiency;and(3)help inform optimal management of critically ill patients allowing for decision-making about their HRQoL,in additional to traditional health-technology assessments.

Validation of a Critical Nitrogen Curve for Summer Maize in the North China Plain

The concept of critical N concentration(N_c)has been widely used in agronomy as the basis for diagnosis of crop N status,and allows discrimination between field situations of sub-optimal and supra-optimal N supply.A critical N dilution curve of N_c=34.0W^(-0.37),where W is the aboveground biomass(Mg DM ha^(-1))and N_c the critical N concentration in aboveground dry matter(g kg^(-1)DM),was developed for spring maize in Europe.Our objectives were to validate whether this European critical N dilution curve was appropriate for summer maize production in the North China Plain(NCP)and to develop a critical N dilution curve especially for summer maize production in this region.In total 231 data points from 16 experiments were used to test the European critical N dilution curve.These observations showed that the European critical N dilution curve was unsuitable for summer maize in the NCP,especially at the early growth stage.From the data obtained,a critical N dilution curve for summer maize in the NCP was described by the equation of N_c=27.2W^(-0,27),when aboveground biomass was between 0.64 and 11.17 Mg DM ha^(-1).Based on this curve,more than 90%of the data for the N deficiency supply treatments had an N nutrition index(NNI)<1 and 92%of the data for the N excess supply treatments had an NNI>1.

基于剪切波速的砂土液化临界公式

利用Kayen等收集的地震现场液化资料,以双曲线和幂函数为基础,提出了基于剪切波速的砂土液化临界公式。将临界公式和国内3种代表性判别方法对比分析,检验其液化判别效果。通过振动三轴液化试验,验证了液化临界公式下延至深层的适用性。结果表明:临界公式优化了判别成功率,其液化判别成功率达95%以上,非液化判别成功率可接受,同时避免在低烈度不安全而高烈度过于保守等现象。试验验证了本文临界曲线判别深度可下延至20 m以深。临界公式可作为现行规范的一种补充性和替代性的液化判别方法。

不同氮效率春玉米品种临界氮浓度稀释曲线建立与验证

采用田间定位试验,以山西省晋中地区春玉米各生育时期地上部干物质量与植株氮浓度的变化规律,建立春玉米临界氮浓度稀释曲线模型,为实现春玉米绿色增产与氮素管理提供理论依据。本研究以玉米品种‘郑单958’和‘大丰26’为试验材料,设4个施氮量处理:0 kg(N)∙hm^(−2)(N0)、120 kg(N)∙hm^(−2)(N120)、240 kg(N)∙hm^(−2)(N240)和360 kg(N)∙hm^(−2)(N360),于2014—2016年在山西农业大学东阳试验基地开展3年定位施氮试验,在春玉米拔节期(V6)、抽雄期(VT)、灌浆期(R2)和成熟期(R6)采集植株样品,分析两个春玉米品种在不同施氮量处理下地上部干物质量、籽粒产量(以下简称“产量”)和各生育时期植株氮浓度,以不同生育时期干物质累积量和植株氮浓度,建立并验证两个春玉米品种的临界氮浓度稀释曲线模型。结果表明,‘郑单958’氮素利用率高于‘大丰26’。两个春玉米品种在适宜施氮量条件下,各生育时期地上部干物质量和产量均随施氮量增加呈增加趋势,地上部干物质量在N240和N360处理间差异不显著,产量在N240处理达最大值;植物氮浓度随施氮量增加而增加,随春玉米生育进程推进与地上部干物质量呈幂指数关系。依据春玉米地上部干物质量(Md)与其对应的植株氮浓度(CN)变化关系,建立两个春玉米品种的临界氮浓度稀释曲线模型:‘郑单958’CN=30.457Md−0.292,‘大丰26’CN=33.249Md−0.333。相比‘大丰26’的模型参数,‘郑单958’的模型参数a降低8.40%,参数b降低12.31%;‘郑单958’和‘大丰26’模型均方根误差(RMSE)分别为1.71 g∙kg^(−1)和1.54 g∙kg^(−1),标准化均方根误差(n-RMSE)分别为9.25%和8.27%,表明模型稳定性较好。氮营养指数在同一生育时期随施氮量增加呈上升趋势,随生育时期推进呈先增加后降低趋势,与各生育时期的相对干物质量呈显著线性相关,与相对产量呈显著的一元二次曲线关系。本研究建立的晋中地区两个春玉米品种临界氮浓度稀释曲线模型及各生育时期氮营养指数,可用于春玉米生育时期营养状况的诊断和评估,结合施氮量与产量的关系,推荐该试验区域‘郑单958’施氮量为189.16~224.08 kg∙hm^(−2),‘大丰26’施氮量为199.72~214.67 kg∙hm^(−2)。

山东烟区烤烟地上部临界氮稀释曲线的构建与营养诊断

为建立山东烟区烤烟地上部临界氮稀释曲线,探讨以氮素营养指数诊断烤烟氮素营养状况的可行性,优化烤烟氮素管理,田间设置6个氮肥用量,分析其对移栽后烤烟地上部干物质积累量和氮浓度的影响,并通过烤烟氮营养指数判断烟株氮素营养的丰缺情况。结果表明,随着施氮量增加,各取样时期烤烟干物质积累量均表现为先增加后稳定的趋势,不同施肥处理烤烟地上部干物质积累量差异显著;随着烤烟地上部干物质积累量的增加,不同施肥处理烤烟地上部氮浓度均逐渐降低;烤烟地上部临界氮浓度和干物质积累量符合幂函数关系,以地上部干物质积累量为驱动变量的临界氮稀释曲线为Nc=2.25×DM-0.13,其决定系数R2为0.72(p<0.05);不同氮肥处理氮营养指数(NNI)均在一定程度上呈现波动性,移栽后随时间增长呈现先上升后下降趋势,根据临界氮稀释曲线计算氮营养指数(NNI)判定烤烟氮营养状况,氮肥施用量90 kg/hm^(2)时氮营养状况较好。山东烟区烤烟地上部临界氮稀释曲线方程为Nc=2.25×DM-0.13,通过烤烟地上部临界氮稀释曲线与氮营养指数能够评价山东烟区烤烟氮营养状况,研究结果表明该试验地点适宜的氮肥施用量在90 kg/hm^(2)左右。

膜下滴灌微咸水棉花临界氮稀释曲线模型与氮肥用量推荐

为了优化膜下滴灌微咸水条件下棉花生产氮素管理,该研究于2017—2019年在新疆库尔勒市开展3 a定位施氮试验。以新陆中棉花为试验材料,设置施氮水平0(NF0)、150(NF1)、250(NF2)、300(NF3)、350(NF4)、450(NF5)kg/hm^(2),各试验处理灌水量均为487.5 mm,分析施氮量对棉花地上部干物质量、氮素累积吸收量、产量和氮肥利用效率的影响,构建了膜下滴灌微咸水棉花临界氮浓度稀释曲线模型。结果表明:棉花氮素累积吸收量随生育期进程的推进而增大,棉花临界氮浓度与最大地上部干物质量符合幂函数关系。氮肥农学利用率和表观利用率均与施氮量呈二次多项式关系,氮肥生理利用率和偏生产力均与施氮量呈线性关系。NF1、NF2和NF3处理的氮素营养指数均小于1,表明氮素营养供应不足,棉花生长受到氮素限制。NF4和NF5处理的氮素营养指数接近于1,说明棉花氮素营养状况较好,但NF5产量和氮素利用效率较低,NF4获得最高产量和较高的氮素利用效率。因此,南疆膜下滴灌微咸水棉花生育期推荐施氮量为350 kg/hm^(2)。该研究构建的临界氮浓度稀释曲线模型对田间施氮管理具有重要意义。

新疆早熟棉花不同水分下临界氮稀释曲线的构建与验证

[目的]基于临界氮浓度(Nc),构建不同水分条件下早熟棉花氮营养指数(NNI)、氮吸收量(N_(upt))和累积氮亏缺量(N_(and))模型,为棉花氮素营养诊断提供快捷准确的方法,以提高水肥利用效率。[方法]田间试验于2021和2022年在新疆石河子市进行,供试棉花品种为当地主栽早熟品种‘新石K-18’。试验采用完全区组设计,设置4个灌溉水量(W):中度亏缺(W1,3000 m^(3)/hm^(2))、轻度亏缺(W2,3750 m^(3)/hm^(2))、正常水分(W3,4500 m^(3)/hm^(2))、水分盈余(W4,5250 m^(3)/hm^(2));5个氮素(N)水平:0、225、262.5、300、337.5 kg/hm^(2),记为N0、N1、N2、N3和N4,共20个处理。出苗后第60、75、90、105、120天,取棉株样品,分为茎、叶和铃,吐絮后棉铃又分为铃壳、棉籽、皮棉,测定干物质量和氮浓度。在吐絮期调查棉花株数、单株结铃数、单铃重,以及皮棉产量和衣分。以植株干重与含氮量构建不同水分条件下的临界氮浓度稀释曲线(Nc),采用均方根误差(root mean square error,RMSE)和标准化均方根误差(n-RMSE)对临界氮浓度稀释曲线的可靠性进行验证。基于Nc,建立棉株氮营养指数、氮吸收量、累积氮亏缺量模型,用于不同水分条件下的棉花氮素最佳用量推荐。[结果]棉花各生育期地上部干物质、棉花产量、氮含量均随灌水与施氮量的增加而增加,籽棉与皮棉产量均以W3N3处理最高,分别为5892与2747 kg/hm^(2)。W1~W4各水分条件下临界氮浓度稀释曲线R~2分别为0.999、0.912、0.952、0.974,RMSE分别为0.284、0.280、0.243和0.269,说明模型具有较高的精度。基于Nc的氮营养指数、氮吸收量与累积氮亏缺量模型,对不同水分条件滴灌棉花氮营养状况的诊断结果均表明N3 (300 kg/hm^(2))为最适施氮水平。综合棉花产量与氮含量,中度水分亏缺条件(W1)下的最佳施氮量为262.5 kg/hm^(2),轻度亏缺、正常水分和水分盈余(W2、W3和W4)条件下均为300 kg/hm^(2)。[结论]建立的滴灌棉花临界氮浓度稀释曲线和基于该模型建立的氮营养指数、氮吸收量和累积氮亏缺量模型,能够精准预测不同水分条件下滴灌棉花的氮素营养状况,为棉花氮营养诊断和高效施氮管理提供支撑。

基于贝叶斯统计的烤烟叶片临界氮稀释曲线构建

【目的】比较基于贝叶斯统计构建的烤烟叶片临界氮稀释曲线与传统方法的区别,以确定其是否可用于氮营养诊断,旨在简化和准确进行烤烟氮营养诊断。【方法】基于两年、3个氮肥用量田间试验,分析了不同氮肥施用量下移栽烤烟不同生长天数的叶片干物质积累量、氮含量。利用各取样时期最大叶片干物质重,将所有处理样本分为生长受氮限制组和不受氮限制组。然后,分别应用贝叶斯统计和传统两步法建立叶片临界氮稀释曲线,使用R语言中rjags软件包实现马尔可夫链蒙特卡洛(MCMC)算法,分析临界氮稀释曲线模型参数A1和A2的后验分布特征,分析曲线对受氮限制和不受氮限制的区分度,拟合计算叶片临界氮浓度和氮营养指数,并比较其相对于实际观测值的差异。【结果】施用氮肥显著增加了烤烟叶片干物质积累量,不同氮肥处理间差异显著,烤烟叶片氮浓度随烤烟生长进程而降低。参数A1和A2的95%后验分布分别为2.58~2.94和0.13~0.33;拟合的烤烟叶片临界氮稀释曲线不确定性水平(95%可信区间的宽度)随着叶片干物重的增加先减少后增加,曲线的不确定性水平为0.16%~0.70%。基于贝叶斯统计的烤烟叶片临界氮稀释曲线对氮限制组和非氮限制组的区分度为71%,优于传统两步法构建曲线的区分度;两种方法拟合的叶片临界氮浓度与实际临界氮浓度相关度基本一致;基于贝叶斯统计构建的曲线拟合计算的氮营养指数略大于两步法,通过两种方法拟合计算的氮营养指数呈高度线性相关,决定系数R^(2)=0.96,标准化均方根误差n-RMSE为6%,稳定度较高。【结论】基于贝叶斯统计构建的烤烟叶片临界氮稀释曲线为N_(c)=2.74×LDM^(−0.22)。贝叶斯曲线在拟合临界氮浓度的效果上,与两步法曲线差异不大,但较两步法曲线可以更好的区分生长受氮限制组与不受氮限制组,且计算的氮营养指数与两步法曲线的线性变异决定系数R2高达0.96,因此,贝叶斯曲线可更简单、准确地用于评价烤烟氮营养状况。

基于双量化评价指标的千米深井大采高液压支架适应性分析

针对液压支架的适应性评价缺乏量化指标的问题,以淮南矿区口孜东煤矿的千米深井软岩大采高俯斜采煤工作面的地质条件为研究对象,建立了四柱和两柱支架的“支架–推移千斤顶”承载稳定性力学模型,得到了两种架型临界载荷的一般形式及推移千斤顶参与支架力学平衡的判定准则。提出了衡量液压支架与顶板和底板适应性的双量化评价指标,指导研制了适用于该煤矿的ZZ18000/33/72D型大采高四柱液压支架,采用理论分析和数值计算对比了两种架型的适应性,并进行了现场试验。结果表明:支架与顶板的适应性指标越大及支架与底板的适应性指标越小,则支架的适应性越强;指导研制的ZZ18000/33/72D型大采高四柱支架对顶板适应性、底板比压及对安全阀的控制性等方面明显优于两柱支架,临界载荷曲线更适应该场景的顶板载荷特征。该支架与顶板和底板的适应性良好,未出现影响工作面安全和正常回采的大面积片帮及冒顶,底座也未发生陷入底板的现象。研究结果可为液压支架的适应性设计和评价提供量化参考。

基于临界氮浓度稀释曲线的内蒙古土默川平原滴灌玉米氮营养诊断

【目的】明确氮肥运筹对内蒙古土默川平原滴灌玉米产量和氮素利用效率的影响,探讨以氮营养指数为监测指标诊断土默川平原滴灌水肥一体化玉米氮营养状况的可行性。【方法】检测2022—2023年内蒙古包头市土默特右旗、呼和浩特市土默特左旗两试验地中3个施氮量(0、270、360 kg/hm^(2))和全生育期3次、5次施氮下玉米氮营养含量,采用方差分析和统计建模的方法,研究玉米的产量和氮素利用效率,分析各时期玉米冠层氮浓度和地上部生物量的变化规律并构建玉米临界氮浓度稀释曲线模型。【结果】增加施氮量和施氮次数能显著提高玉米穗数、穗粒数和千粒重进而提高产量,增加施氮次数能显著提高玉米氮素利用效率(P<0.05);施氮量从270 kg/hm^(2)增加至360 kg/hm^(2),年平均产量提高5.79%;施氮次数从3次增加至5次,年平均产量和年平均氮素利用效率分别提高3.15%、22.25%。土默川平原滴灌玉米临界氮浓度稀释曲线模型为Nc=3.36W^(-0.22),R^(2)=0.94,P<0.05,验证精度RMSE、NRMSE和MAE分别为0.40%、11.50%和0.20%,模型稳定性较好。通过模型计算,施氮量270 kg/hm^(2)时,对应适宜施氮次数为5次,分别在4叶展期、8叶展期、大喇叭口期、吐丝期和乳熟期以15∶25∶35∶15∶10的比例追施氮肥,玉米产量最优,为14.09 t/hm^(2);玉米拔节期、9叶展期、大喇叭口期、吐丝期和乳熟期需氮量范围分别为-3.42~15.29、-16.80~22.90、-26.86~62.32、-54.65~85.14和-48.18~111.80 kg/hm^(2)。【结论】适当增加施氮量和施氮次数能显著提高内蒙古土默川平原滴灌玉米产量和氮素利用效率,玉米临界氮浓度稀释曲线模型可以有效识别内蒙古土默川平原玉米拔节期到乳熟期植株氮营养状况,通过该模型还可以计算、推荐合适的施肥量,能够实现玉米生长的按需作业。

天然气水合物生成要素影响研究

研究水合物生成影响因素有助于预测管道中的水合物生成风险,并制定相应的管道管理策略。采用PVTsim软件研究了不同组分及抑制剂对水合物生成过程的影响规律。结果表明,氮气和二氧化碳对天然气水合物生成的影响很小,可忽略不计。硫化氢对天然气水合物形成具有促进作用,增大了现场水合物堵塞事故发生的风险,对于高含硫天然气的生产处理,要注意节流、压缩等工艺部位的运行情况。随着甲醇和乙二醇质量分数占比增大,天然气水合物临界形成压力升高,水合物形成的工况范围明显缩小,可有效抑制天然气水合物形成。

基于PyroSim的不同曲率弯曲隧道火灾特性研究

为探究弯曲隧道的火灾特性,研究曲率对弯曲隧道火灾烟气蔓延的影响规律,使用火灾动力学模拟软件PyroSim,对不同曲率弯曲隧道的临界风速、温度分布、烟气蔓延规律及顶棚温度衰减规律进行研究。结果表明:在同一火源功率和火源位置的情况下,临界风速与隧道曲率呈正相关性;由于壁面沿程阻力的特殊性,弯曲隧道内高温烟气在隧道内侧的传播速度更快,并且随着火灾持续时间增加,隧道两侧烟气传播速度的差距增大;火灾的顶棚温度衰减与曲率呈正相关,给出了曲率为0.6%、0.5%、0.3%、0.25%、0.14%的顶棚温度衰减预测模型。

一种汽车用微合金非调质钢的连续冷却转变

测定了一种汽车用微合金非调质钢的过冷奥氏体连续冷却转变曲线,研究了冷却速率对相变组织及显微硬度的影响。结果表明:试验钢的临界点A c3为838℃,A c1为732℃;当冷却速率小于0.2℃/s时,试验钢的连续冷却转变产物为铁素体、珠光体和贝氏体;当冷却速率为0.2℃/s时,转变产物中出现马氏体;当冷却速率为5℃/s时,铁素体、珠光体消失,转变产物为贝氏体和马氏体;随着冷却速率的增大,马氏体含量逐渐增多,贝氏体含量逐渐减少,甚至完全消失;当冷却速率增大至20℃/s时,转变产物均为马氏体;随着冷却速率的增大,试验钢的显微硬度呈先快速增长,后增长速率变缓的趋势。

基于MIDAS NFX曲线隧道烟气分布特性数值研究

为探究不同曲率的隧道在发生火灾时对其温度分布、临界风速及烟气分布的影响,基于CFD(计算流体动力学)数值计算方法,考虑不同曲率对临界风速、温度分布、烟气分布的影响,将得到的数据进行分析拟合。文中以大连至旅顺中部通道工程某隧道为工程背景,进行烟气分布特性数值研究。通过研究表明,在通风风速和热释放率相同的条件下隧道内烟气回流长度随着曲率的增大逐渐减小,临界风速也出现相似的结论,而曲率对隧道内温度的分布情况影响较小,在通风条件下曲线型隧道火源区产生横向湍流,隧道外侧壁面烟气流动较内侧烟气流动更快。研究可为今后处理曲线型隧道火灾事故方面提供一些参考。

灯泡贯流式电站机组多水头协联优化与负荷寻优

为验证某灯泡贯流式电站机组协联关系是否存在优化空间,本文以某电站2号机组为研究对象,选取3个水头开展相对效率试验,在机组稳定性无明显突变的前提下,从机组效率及功率最大化考虑,电站在临界弃水状态附近,以追求功率最大化优化协联关系,桨叶开度以增加为主;高水头时因电站无法持续满负荷运行,以优化效率为主,低负荷工况下桨叶开度增加后相对效率同步提升,高负荷工况则降低桨叶开度以提升相对效率。此外,交叉类型的协联关系不会引起调速器协联关系计算的逻辑错误,可为同类双调机组进一步优化协联关系提供指导。