Overhead Concentration Platform of Total Withdrawal Operation in Cyclic Total Reflux Batch Distillation

The total withdrawal operation is an inevitable section in cyclic total reflux batch distillation.In the operation,an interesting phenomenon "overhead concentration platform"(OCP) appears,which is defined as a period of time with high overhead concentrations when the operation is changed from total reflux to total withdrawal.The OCP phenomenon and its influential factors,such as the theoretical stage number,feed concentration,and feed composition,are examined by simulations and experiments.The experimental equipment is a column with random packings.It is shown that the number of theoretical stages influences the OCP more significantly than the other factors.

Estimation of Total Emission of VOCs Discharged by Afforesting Vegetation and Its Impacts on Ozone Concentration in Nanjing

Based on Guenther light-temperature model , annual emission of VOCs discharged by plants in Nanjing was estimated, and the impacts of VOCs discharged by afforesting vegetation in the city on ozone concentration was analyzed. The results show that annual emission of VOCs dis- charged by plants in Nanjing is about 0.004 9 Tg C. The annual emmisions of isoprene, monoterpene and other VOCs account for 18.0%, 25.9% and 56.1% of total emission of VOCs respectively. VOCs discharged by afforesting vegetation in Nanjing has the greatest impact on average con- centration of ozone in winter.

Influence of total dissolved gas-supersaturated water on silver carp(Hypophthalmichthys molitrix)

Dam discharges over spillways are the main reason for the gas-supersaturated water generated in rivers.Local aquatic organisms,especially fish,readily develop gas bubble disease(GBD) in a river with total dissolved gas supersaturation(TDGS).Sometimes,fish will die after a specific exposure period,which negatively affects the biological equilibrium.In this study,the influence of TDGS on silver carp was explored.Silver carp were exposed to gas-supersaturated water with TDGS levels of 140%,135%,130%,125%,120%,and 110%to test the impact of TDGS.Some silver carp died when the TDGS level was 120%or higher,and all the silver carp exposed to a TDGS level of 140%died within10 h.In comparison with the Chinese sucker,Prenant's schizothoracin,and rock carp,silver carp seem less sensitive to TDGS.In addition,we tested the catalase(CAT) activity in the muscles and gills of silver carp after they were exposed to gas-supersaturated water with a TDGS level of140%.The CAT activity changed with time;it increased first and then decreased until it was lower than the initial CAT activity.The results of this study can provide basic data for developing a standard for environmental evaluation.

Soil and Root Respiration Under Elevated CO_2 Concentrations During Seedling Growth of Pinus sylvestris var.sylvestriformis

The objectives of this study were to investigate the effect of higher CO2 concentrations （500 and 700 μmol mol^-1） in atmosphere on total soil respiration and the contribution of root respiration to total soil respiration during seedling growth of Pinus sylvestris vat. sylvestriformis. During the four growing seasons （May-October） from 1999 to 2003, the seedlings were exposed to elevated concentrations of CO2 in open-top chambers. The total soil respiration and contribution of root respiration were measured using an LI-6400-09 soil CO2 flux chamber on June 15 and October 8, 2003. To separate root respiration from total soil respiration, three PVC cylinders were inserted approximately 30 cm deep into the soil in each chamber. There were marked diurnal changes in air and soil temperatures on June 15. Both the total soil respiration and the soil respiration without roots showed a strong diurnal pattern, increasing from before sunrise to about 14：00 in the afternoon and then decreasing before the next sunrise. No increase in the mean total soil respiration and mean soil respiration with roots severed was observed under the elevated CO2 treatments on June 15, 2003, as compared to the open field and control chamber with ambient CO2. However, on October 8, 2003, the total soil respiration and soil respiration with roots severed in the open field were lower than those in the control and elevated CO2 chambers. The mean contribution of root respiration measured on June 15, 2003, ranged from 8.3% to 30.5% and on October 8, 2003, from 20.6% to 48.6%.

Determination of elastic moduli of composite medium containing bimaterial matrix and non-uniform inclusion concentrations

Reservoir porous rocks usually consist of more than two types of matrix materials, forming a randomly heterogeneous material. The determination of the bulk modulus of such a medium is critical to the elastic wave dispersion and attenuation. The elastic moduli for a simple matrix-inclusion model are theoretically analyzed. Most of the efforts assume a uniform inclusion concentration throughout the whole single-material matrix. However, the assumption is too strict in real-world rocks. A model is developed to estimate the moduli of a heterogeneous bimaterial skeleton, i.e., the host matrix and the patchy matrix. The elastic moduli, density, and permeability of the patchy matrix differ from those of the surrounding host matrix material. Both the matrices contain dispersed particle inclusions with different concentrations. By setting the elastic constant and density of the particles to be zero, a double-porosity medium is obtained. The bulk moduli for the whole system are derived with a multi-level effective modulus method based on Hashin＇s work. The proposed model improves the elastic modulus calculation of reservoir rocks, and is used to predict the kerogen content based on the wave velocity measured in laboratory. The results show pretty good consistency between the inversed total organic carbon and the measured total organic carbon for two sets of rock samples.

The Spatial Distribution of Nitrite Concentrations in a Large Drinking Water Distribution System in Finland

Nitrite in drinking water is a potential health hazard and monitoring its concentrations in distributed water is of paramount importance. When monochloramine is used in secondary disinfection in drinking water distribution systems (DWDSs), nitrite is often formed by nitrification in the biofilm on the inner surface of distribution pipes. This article attempts to identify areas with a risk of increased nitrite concentrations as well as the main reasons leading to nitrite occurrence in a large urban DWDS in Finland using spatial inspection of obligatory monitoring data. Nitrification was found to occur throughout the study area, though nitrite was not increased everywhere. Instead, nitrite was increased close to the water treatment plants (WTPs) and was connected to fresh drinking water than stagnant drinking water. Temperature effects on nitrite concentrations were surprisingly insignificant, even though it is well known that nitrification reactions are affected by temperature. The temperature dependence of ammonium and total residual chlorine was more significant than the dependence of nitrite. The findings of this study emphasize the need to monitor nitrite concentrations close to WTPs.

Effect of Pelleted Total Mixed Ration with Different Concentrate-roughage Ratios on Production Performance and Serum Biochemical Parameters of Fattening Hainan Black Goats

[Objective] This paper was to study effects of pelleted total mixed ration with different concentrate-roughage ratios on production performance and serum biochemical parameters of fattening Hainan black goats.[Method] Thirty-six fattening Hainan black goats with the same genetic background and similar initial weight of(14.08±0.13) kg were randomly assigned into three treatments. Goats were fed with Juncao + concentrate(control group), pelleted total mixed ration I(concentrate: roughage 50 ∶50, group Ⅰ) and Ⅱ(concentrate: roughage 45∶55, group Ⅱ), respectively. The test lasted 45 d.[Result] The final weight, daily gain and feed intake of rams in experimental group Ⅰ were significantly higher than those of control group and experimental group Ⅱ(P<0.05);the final weight and daily gain of rams in experimental group Ⅰ were also markedly higher than those of experimental group Ⅱ(P<0.05);the feed/gain of rams in experimental group Ⅰ was significantly lower than those in control group and experimental group Ⅱ(P<0.05). The feed gain cost of rams in experimental group Ⅰ was markedly lower than that in experimental group Ⅱ( P<0.05), but was significantly higher than that in experimental group Ⅰ(P<0.05);the gross profit of rams in experimental group Ⅰ was significantly higher than those in control group and experimental group Ⅱ(P<0.05). Compared with control group and experimental group Ⅱ, the serum total protein and glucose lev-els in experimental group Ⅱ increased significantly(P<0.05), but the urea nitrogen content reduced(P>0.05).[Conclusion] When the concentrateroughage ratio of pelleted total mixed ration was 50∶50, the fattening effect of Hainan black goat was better, and the serum total protein and glucose levels were evidently improved.

结合光谱降维的IPSO-SVR水体总磷浓度预测模型

[目的]选择最优模型对水体中总磷浓度进行预测,为准确、实时、高效检测水资源状况提供支持。[方法]以2021年在长江中下游武汉—安徽地区采集的水质样本作为研究对象,首先,对采集到的长江光谱数据进行最大最小归一化和均值中心化两种预处理操作以便统一数据的范围和均值点,并使用核主成分分析(KPCA)技术对预处理后的光谱数据进行降维操作。选取方差解释率为99.6%下的6个特征向量进行后续预测模型的训练,接着在原有粒子群算法的基础上引入自适应惯性权重更新公式和遗传—模拟退火变异思想,提高算法的寻优能力。使用改进的粒子群优化算法对支持向量回归模型中的超参数组合进行寻优,对支持向量回归模型使用输出的结果进行预测模型的训练,最后使用测试集数据进行总磷浓度的预测。[结果]提出了一种结合光谱降维的改进粒子群优化算法(IPSO)结合支持向量回归(SVR)的水体总磷含量预测模型。通过和当前预测性能较好的几种机器学习模型进行精度的比较发现,该试验模型对长江水体总磷浓度进行预测时决定系数(R^(2))为0.973920,均方根差(RMSE)为0.003012,平均绝对误差(MAE)为0.002105。[结论]使用光谱数据结合降维技术、粒子群优化算法和机器学习模型的算法融合模型检测水体总磷浓度可行性强,精确度高,且拟合效果良好。

基于空间插值的长江口邻近海域春季悬浮物和叶绿素a空间分布分析

针对目前利用实测数据对长江口邻近海域水质状况进行分析研究相对偏少的情况,基于“淞航”号2018年春季航次对该海域的综合观测,利用实验室水样分析数据对船载温盐深仪(CTD)的测量数据进行校正,并对该区域2018年春季时节悬浮物(TSM)和叶绿素a(Chl-a)浓度的空间插值结果进行分析。研究结果表明:CTD观测数据与水样分析数据呈较强线性相关关系。反距离权重插值对TSM和Chl-a浓度空间分布具有整体最优的效果。TSM浓度在近岸和近海底较高,在观测区域内出现两个高值中心;Chl-a浓度在近岸海域较高,有较明显的片状高值结构,垂向上表层较高。TSM与Chl-a浓度分布在长江口南北表现出不同的特征,且两者具有一定的负相关性。长江径流、外海洋流、潮汐混合等水动力过程是影响该区域TSM和Chl-a浓度分布的主要因素。

不同绿化树种对镉的富集特征

【目的】乔木对重金属具有富集能力,但是目前对其积累特征尚不明确,一定程度上限制了乔木修复重金属污染土壤技术的推广应用。探讨5种乔木绿化树种对镉的富集特征。【方法】分析了镉污染土壤上栽植的泡桐Paulownia fortunei、楸树Catalpa bungei、悬铃木Platanus acerifolia、黑杨Populus nigra和垂柳Salix babylonica等树木不同部位对镉的富集特征,并分析了不同树种对镉的积累总量。【结果】供试树种对镉均具有一定的积累能力,单株对镉的积累量为43.01~886.28 mg·株^(-1),其中垂柳对镉的积累总量最大,达886.28 mg·株^(-1);其次是黑杨,达392.51 mg·株^(-1)。不同树种不同部位对镉的富集能力也不同,泡桐、楸树、悬铃木、黑杨和垂柳不同部位的富集系数分别为0.07~0.56、0.10~1.24、0.06~1.04、0.32~1.58、0.06~0.97。其中黑杨多数部位(除茎皮外)的富集系数均大于其他树种。所有树种根皮、茎皮和枝皮的镉质量分数均显著(P<0.05)大于其对应的根材、茎材和枝材。所有树种不同部位镉质量分数与土壤镉质量分数均呈极显著正相关(P<0.01)。【结论】乔木主要将镉积累到枝部和茎部,其中泡桐、楸树和悬铃木主要积累在枝部,黑杨和垂柳主要积累在茎部。此外,黑杨和垂柳具有较高的镉积累量,是今后镉污染土壤修复中的首选树种。

氟西汀总活性成分在抑郁患者中的群体药动学研究

目的建立抑郁患者氟西汀(fluoxetine,FLX)总活性成分(total active moiety,TAM)的群体药动学(PPK)模型并研究其影响因素,为个体化用药提供参考。方法回顾性收集2020年1月-2023年12月深圳市康宁医院154例服用FLX治疗住院患者的用药情况、FLX和去甲氟西汀(norfluoxetine,NFLX)血药浓度、肝肾功能水平、血脂水平及细胞色素P4502D6酶(CYP2D6)基因型等临床资料,计算FLX和NFLX浓度之和为血浆TAM浓度,采用非线性混合效应模型法(NONMEM)建立TAM浓度PPK模型,采用拟合优度图(GOF)、正态化预测分布误差法(NPDE)和自举法(Bootstrap)对模型的稳定性和预测性能进行评估。基于最终模型的显著协变量,模拟不同人群不同剂量TAM浓度的变化情况,拟合达稳态时间并推荐给药剂量。结果154例住院患者570个血药浓度数据包括FLX(n=285)和NFLX(n=285),建立了TAM的一阶吸收和消除的一房室模型,体重(WT)是影响表观清除率(CL/F)的显著协变量,最终模型参数CL/F、表观分布容积(V/F)和吸收速率常数(Ka)的群体典型值分别为2.91 L/h、734 L和0.3 h^(-1),模型表示为:CL/F(L·h^(-1))=2.91×(WT/55)0.531,V/F(L)=734,Ka(h^(-1))=0.3(固定值)。蒙特卡洛模拟结果显示,TAM浓度达稳态时间为6~11周,给药剂量相同,体重越轻达稳时间越长,体重小于70 kg的患者,最佳给药方案为10~30 mg,大于70 kg为20~40 mg。结论成功建立了服用FLX治疗的抑郁患者TAM浓度的PPK模型,最终模型稳定可靠,低体重人群应选择较低剂量的FLX,避免药物蓄积产生不良反应。

利用衰减全反射测量微量液体的浓度

基于分光计搭建了衰减全反射光学测量平台,入射光以略大于全反射临界角入射,利用棱镜多次衰减全反射光对亮蓝溶液的浓度进行持续测量.在LabVIEW软件开发环境下搭建数据采集处理平台,实现了液体浓度的高灵敏度检测.该平台由光电二极管、信号转换调理设备、数据采集设备和计算机4部分组成,其基本任务是电压信号的产生、测量和记录,LabVIEW程序可拟合已知浓度梯度与电压信号的函数关系,实现液体浓度的灵敏检测.

基于浓度与流量突变的河流总磷通量估算

为进一步加深对流量与水质浓度突变特征的理解,探究浓度与流量突变点对通量模拟的影响,本研究基于Mann-Kendall突变检验法以及贝叶斯突变点模型,对潮河流域20多年来(1992—2014年)的径流量、总磷(TP)浓度以及二者之间关系进行突变分析,并结合LOADEST模型估算TP通量。结果表明:潮河流域径流、TP浓度整体均呈下降趋势,径流突变点发生于1998年,突变前后的平均流量分别为7.92 m^(3)·s^(-1)和2.86 m^(3)·s^(-1);TP浓度突变点发生于1993年和1996年,1992—1993年、1994—1996年和1997—2014年平均浓度分别为0.08、0.06 mg·L^(-1)和0.03 mg·L^(-1)。TP浓度-流量关系在2004年12月前后发生突变,前后两个阶段的流量阈值分别为2.36 m^(3)·s^(-1)和9.08 m^(3)·s^(-1)。突变点前,TP浓度与流量的关系是典型的流量驱动模式;突变点后二者关系会在高流量情况下转变为稀释主导模式。基于突变点识别的分段建模有助于改善LOADEST模型的模拟效果,而不同类型突变点各有优势。基于TP浓度突变点的分段模型的整体模拟效果最佳,使纳什系数从0.50提高到0.96;基于浓度-径流关系突变点的模型对关系突变后TP通量的模拟效果最佳,使纳什系数从-0.31提高到0.89。此外本研究讨论了降水及流域管理措施的可能影响。研究表明,进行水质建模及负荷模拟时,考虑水质浓度与流量及其关系的突变可在一定程度上提高模型的适用性。

环鄱阳湖区入出湖总磷浓度与负荷变化分析

入、出湖总磷负荷变化是影响鄱阳湖富营养化状态的关键性要素。基于2009—2018年水质水量监测资料,计算环鄱阳湖区的入、出湖总磷负荷,并采用算术平均法和加权平均法分别计算总磷年平均浓度,探明其时空变化规律;运用双累积曲线法、回归分析法,分析入湖水量和入湖总磷浓度与入湖总磷负荷之间的相关关系,揭示污染负荷的主要控制因素。结果表明:①加权平均法比算术平均法更能反映环鄱阳湖区入、出湖水量、水质时空差异性,入湖总磷多年平均浓度高低排序依次为饶河区(0.123 mg/L)>信江区(0.091 mg/L)>抚河区(0.069 mg/L)>赣江区(0.063 mg/L)>修水区(0.045 mg/L)。②环鄱阳湖区各水资源分区入湖总磷负荷多年平均值为98514 t,低于湖口出湖总磷负荷年均值108442 t,这主要是由于鄱阳湖滨湖区输入、湖体内源释放以及干湿沉降等均未进行计算。③赣江区和饶河区入湖总磷年负荷多年平均值分别为45208 t和19320 t,占五河(赣江、抚河、信江、饶河、修水)总入湖负荷的比重位居前二,其中赣江区的占比达46%。④各水资源分区月入湖总磷负荷与入湖水量存在显著的相关关系,说明各分区入湖总磷负荷在很大程度上受水量控制。

从离子型稀土镁盐富集物中提取稀土工艺初探

以MgO为沉淀剂沉淀MgSO_(4)稀土浸出母液时,得到的稀土镁盐富集物REO总量较低,需要进一步除去杂质以沉淀富集稀土。以离子型稀土镁盐富集物为原料,进行碳化—酸溶—中和除杂—沉淀等工艺初步探索研究。结果表明:REO在碳化过程中的损失很少甚至可以忽略不计,有24.33%~30.9%MgO由稀土镁盐富集物转化进入碳化后液,在中和除杂过程中Fe去除率约99.5%,Al去除率约98.6%。以碳化后液为沉淀剂沉淀中和除杂后液得到碳酸稀土,经过灼烧,获得了符合《GB/T 20169—2015离子型稀土矿混合稀土氧化物》标准质量要求的稀土氧化物,该工艺总渣率为19.81%~23.22%,REO总收率平均89.43%。为了从离子型稀土镁盐富集物中提取稀土的工艺形成成套工艺技术,获取最优的工艺技术参数,有待于后续深入研究和优化。

不同乳酸菌发酵对浓缩梨汁营养物质及挥发性风味物质的影响

本研究以植物乳杆菌(Lactobacillus plantarum,LP)、嗜酸乳杆菌(Lactobacillus acidophilus,LA)、鼠李糖乳杆菌(Lactobacillus brevis,LGG)、肠膜明串珠菌(Leuconostoc mesenteroides,LM)为发酵菌种,对砀山酥梨加工产业下脚料浓缩梨汁进行发酵生产酸化剂,研究发酵过程中活性成分、抗氧化能力的变化,并采用顶空固相微萃取-气相色谱-质谱联用技术分析挥发性风味物质,以期改善其营养特性及风味品质。研究发现,四株单菌在发酵浓缩梨汁的过程中,LP单菌发酵的活菌数最多(9.7 lg CFU/mL),是最适于发酵浓缩梨汁的菌种。在混菌发酵过程中,总酸随着发酵时间的延长逐渐增加,发酵第4 d,PMF组达到最高(1.22 g/100 mL),而LPF组最低(0.82 g/100 mL)。还原糖、总酚、总黄酮以及蛋白质均随发酵逐渐降低,发酵结束时PAF组各指标均最高,分别为28 g/L、13.54 mg GAE/L、17.46 mg/L、35.39 mg/L。DPPH、ABTS+自由基清除率以及铁离子还原清除能力(FRAP)等抗氧化指标在单菌及混菌发酵中均先上升后下降,且在发酵第2 d达到最大。在不同组别混菌发酵中共检测出94种挥发性风味物质,其中OAV>1的风味物质共有20种。PAF组OAV>1的风味物质为15种,产生了更多的重要风味物质(如2-庚酮、香叶醇和芳樟醇等),对浓缩梨汁发酵酸化剂具有最为积极的影响。综上,本文研究了浓缩梨汁发酵酸化剂的乳酸菌组合,为促进梨产业副产物的高效加工利用提供了一定的理论依据。

基于数字图像处理的几何光学法测量液体浓度

根据全反射原理,搭建了一套测量液体浓度的实验装置。该实验装置借助数字图像处理技术对通过摄像头采集的全反射临界角进行处理,精确测量临界角,从而得到透明液体的折射率,根据拟合的液体浓度和折射率的单调函数关系,求其浓度。该实验原理简单,实验结果精确度高,在大学物理学习中培养了学生创新能力。

不同酸蚀模式与不同粘结剂在恒牙治疗中的应用比较

利用显微镜与万能拉伸试验机等设备,分析全酸蚀方法、自酸蚀方法、Gluma磷酸酸蚀法的粘接系统,在年轻恒牙治疗中的粘接残余系数、粘接强度与封闭剂脱落率。结果证明,全酸蚀方法的粘接系统在年轻恒牙治疗时的封闭剂脱落率最小;自酸蚀方法的粘接系统封闭效果最差。酸蚀时间对全酸蚀方法影响较大,缩短酸蚀时间,可提升年轻恒牙粘接强度。酸蚀时间对Gluma磷酸酸蚀法影响较小;酸蚀时间一致时,全酸蚀方法的粘接强度明显高于Gluma磷酸酸蚀法,说明全酸蚀方法的粘接系统在年轻恒牙治疗中的效果优于Gluma磷酸酸蚀法的粘接系统。酸蚀浓度对不同酸蚀方法的粘接系统在年轻恒压中治疗效果影响均较小;不同酸蚀浓度时,全酸蚀方法的粘接残余系数最高,粘接强度最强。

中高风速下海气CO_(2)交换速率影响因子探究

波浪破碎、气泡是中高风速下气体交换速率的关键因子。文章分析计算了气泡和非破碎部分的贡献,并结合热带气旋和近岸海域的特点考虑了悬浮物浓度的影响,进而评估生物在气体交换中的作用。中高风速下气泡对交换速率的贡献为55%~76%。悬浮物浓度整体贡献仅次于气泡对交换速率的贡献,为11%~19%。由悬浮物浓度增大而影响的生物碳循环过程十分重要,研究结果可为量化研究中高风速下CO_(2)气体交换提供思路。

全氟己酮和氮气混合协同灭火效能试验研究

为研究全氟己酮和氮气的气液两相流混合协同作用的灭火效能,研发了混合气体灭火浓度测试装置和基于缩尺灭火模型的两相流灭火浓度测试装置,测定了全氟己酮气体和氮气混合灭火浓度及全氟己酮经氮气雾化后的两相流灭火浓度,并通过全淹没灭火试验测试了对正庚烷火的灭火效果。结果表明,全氟己酮气体和液体雾化后的灭火浓度都与氧浓度呈线性正相关;缩尺灭火模型可准确测定液体灭火剂雾化后的灭火浓度,偏差不超过1.36%;基于氮气和全氟己酮混合后的两相流喷放方案,通过在灭火过程中同时降低保护空间氧浓度的方式,降低了全氟己酮的灭火浓度,同时还实现了大孔径喷头下的全氟己酮灭火剂低压大流量雾化和快速喷放;在100 m^(3)全淹没灭火条件下,降低灭火剂浓度及灭火剂用量达27%。