降粘型聚羧酸减水剂结构与性能研究

以不同分子量异戊烯基聚氧乙烯醚、乙烯基三乙氧基硅烷、丙烯酸为原材料,设计制备了不同侧链密度和不同主链长度结构的降粘型减水剂(V-PCE)。通过净浆排空时间、净浆流变及混凝土试验研究,评估了的V-PCE对浆体流动性能的影响。结果表明,固定侧链长度不变,随着酸醚比的增大,分子的侧链密度逐渐降低,主链长度逐渐增大,电荷密度逐渐增大;固定酸醚比,随着侧链长度增大,主链长度减小,电荷密度逐渐降低。具有较长主链、短侧链、较低侧链密度及较高电荷密度的IPEC1200AA2.50和IPEG1200AA3.00具有优异的降粘效果。

连续降雨条件下调蓄池对城市面源污染削减的模拟

目前我国水环境整治工作取得阶段性成效,点源污染问题很大程度上得到了解决,而城市面源污染的问题日益成为水环境治理的难点。为有效解决这一问题,以徐州经开区三八河流域为研究区,构建了雨水调蓄池面源污染控制的SWMM模型。通过在Control编辑模块中编辑水泵启闭的控制语言以控制调蓄池的自动排水,通过水泵曲线TYPE1类型对水泵流量大小进行设置以控制排空时间,分析了连续多年实测降雨情况下末端调蓄池的调节次数与污染物削减率。结果表明,调蓄池的调节次数和污染物削减率受其排空时间的影响相对较大,而受其运行规则的影响相对较小。在相同运行规则下,调蓄池24 h排空比48 h排空,可使调节次数的平均值分别增加11.8次(降雨24 h开泵)和12.9次(降雨48 h开泵),并可使COD和TN削减率的平均值分别提高2.28%~2.92%(降雨24 h开泵)和2.2%~2.59%(降雨48 h开泵)。

基于鲁棒软时间窗和箱种代用的铁路集装箱空箱调运优化

传统的空箱调运问题多是研究箱种之间的彼此独立性,而忽略实际运输中箱种代用的情况,针对这一普遍现象,同时考虑需求站对集装箱空箱到达有时间窗约束,以及运输走行时间不确定性会对时间窗产生影响,建立了鲁棒软时间窗和箱种代用的集装箱空箱调运模型。首先,依据走行时间不确定性特点,建立鲁棒软时间窗模型;其次,通过等价变换和对偶变换,将鲁棒软时间窗模型转换为线性规划模型,简化了模型;最后,将集装箱调运模型转换为一般的整数线性规划模型,使模型更易于求解。研究结果表明,将箱种代用引入模型,有效地配置了空箱调运,提高了运输效率,降低了运输成本;对不确定走行时间p的个数进行灵敏度分析,结果表明箱种代用和不代用情况下p都存在一个较小的上界。

利民煤矿Ⅰ030902工作面高水材料墩柱围岩控制技术研究

在工作面通过老空巷道时,工作面与老空巷道间煤柱逐渐变窄,导致空巷围岩严重变形,围岩失稳和支架压死等问题。通过理论计算、数值模拟和现场实验,确定了工作面超前支承应力范围和煤柱临界宽度以及超前加固时机。提出了高水材料墩柱支护技术对老空巷道进行围岩控制,通过建立数值模型进行模拟计算,反演高水材料墩柱支护效果,模拟得出2.5 m间距高水材料墩柱支护围岩控制效果最佳,并确定了最佳支护参数。现场监测结果显示,采用高水材料墩柱支护技术有效地控制了围岩变形,取得了良好的支护效果。

Capsule endoscopy: Improving transit time and image view

AIM： To evaluate the effect of various methods of small bowel preparation on the transit time and the quality of visualization of the entire small bowel mucosa. METHODS： Ninety-five patients underwent capsule endoscopy （CE） by easily swallowing the capsule. They were divided into three study groups according to the preparation used： group A （n = 26） by polyethylene glycol （PEG） liter or with sodium phosphate （SP） 12 h prior to the CE study; group B （n = 29） by erythromycin 1 h prior to the CE study; and group C （n = 40） without any preparation. Visualization ranged from good to satisfactory to poor. RESULTS： The gastric emptying time in the group prepared with erythromycin was shorter but without statistical significance and the small bowel transit time was unaffected. In elderly subjects prepared by PEG or SP, the gastric emptying time was significantly longer （163.7 rain, P = 0.05）. The transit times of the three sub-groups were not affected by gender or pathology. The grade of cleaning of the entire study group was 3.27±1.1. The erythromycin group presented significantly the worst quality of images （P = 0.05） compared to the other sub-groups. Age, gender, and pathology had no effect on the quality of the cleaning of the small bowel in the sub-groups. One （1.05%） case had no natural excretion. CONCLUSION： Erythromycin markedly reduces gastric emptying time, but has a negative effect on the quality of the image in the small bowel. The preparation of elderly subjects with PEG or SP has a negative effect on the small bowel transit time.

Delayed Gastric Emptying in Anorexic Adolescents Measured with the ¹³C Octanoic Acid Breath Test

Many gastrointestinal complaints and motility disorders are described in patients suffering from different eating disorders. These have a negative impact on refeeding. This report evaluated–on admission-gastric emptying of a standardized solid meal with 13C octanoic acid breath test in anorexic adolescents. The results were compared with age and gender matched controls. Gastric emptying data were related to a subjective symptom score. 21 Anorexic girls and 3 boys (mean age: 15.6 y ± 1.3 y), body mass index (mean 15.6 kg/m2 ± 1.6 kg/m2), weight loss (mean: 22.2% ± 10.7%) were studied. T? of the gastric emptying time exceeded the P95 in 14/24 (58%) patients, classified as having delayed gastric emptying (DGE). One patient (4%) had a T? exceeding P75 and was classified as slow (SGE), whereas 9/24 (38%) patients had normal gastric emptying (NGE). In comparison to NGE, subjects with DGE had significantly higher symptom scores (p = 0.01) and more weight loss. The DGE and SGE patients lost 25.29% and 21.38% of weight respectively, whereas a weight loss of 17.64% was found in anorexics with NGE. In conclusion, gastric emptying is delayed in patients with anorexia. This is associated with more significant gastrointestinal symptoms and higher weight loss.

Spacetime Discreteness: Shedding Light on Two of the Simplest Observations in Physics

Loop quantum gravity is considered to be one of the two major candidates for a theory of quantum gravity. The most appealing aspect about this theory is it predicts that spacetime is not continuous;both space and time have a discrete nature. Simply, space is not infinitely divisible, but it has a granular structure, and time does not flow continuously like a smooth river. This paper demonstrates a review for two missed (unnoted) observations that support the discreteness of the spacetime. The content of this paper does not validate the specific model of quantized geometry of the spacetime which is predicted by the theory itself. Instead, it proves that time does not flow continuously. But it flows in certain, discrete steps, like a ticking of a clock, due to a simple observation which is absence of any possible value of time that can exist between the present and the future. Regarding space, it validates the spatial discreteness, and the existence of spatial granules (space quanta) due to a simple observation which is the existence of the origin position in a coordinates system. All of this is achieved by reviewing the concept of discreteness itself, and applied directly to the observations.

Analysis of Waste-Rock Transportation Process Performance in an Open-Pit Mine Based on Statistical Analysis of Cycle Times Data

In this paper, the performance of a waste rock transportation process in an open pit mine was assessed by using cycle time data. A computerized truck-excavator dispatch system was used to record the cycle times. The process was broken into seven steps (or components of the total cycle), durations of which were recorded for a period of 1 month, leading to N = 60,690 data points or dispatches. The open pit mine studied consisted of 12 waste types loaded by 14 excavators and hauled by 49 trucks (at a trucks-to-excavator ratio of 3.5:1) in 75 changing locations. The string-type data was coded using integers to allow a FORTRAN code to extract process performance parameters using statistical analysis. The study established a wide range of parameters including: the waste material generation rate (about 1.73 million t/month, 81% comprising waste rock), truck fill factor, f, total cycle time (Tct), production capacity, theoretical cycle time, non-productive cycle time Tnp, and cycle time performance ratio (CTPR), denoted as Tpr. The factors affecting the process performance include: truck model, excavator model, location (haul distance and road conditions) and material type. For a fixed material type and tonnage, the PDFs of the cycle time components were logarithmic in nature, capable of differentiating performance variations under different factors. It was concluded that the performance of the waste material transportation system in this mine was determined to be acceptable due to mean value of Tpr = 2.432 being closer to unity. Reduction measures were suggested to minimize the cycle time for the process bottlenecks determined from Pareto analysis (that is, full haul, empty haul and loading processes).

Investigation of Excavator Performance Factors in an Open-Pit Mine Using Loading Cycle Time

This study presents the effect of excavator model, loading operation location, shift availability and truck-shovel combination on loading cycle time and productivity of an open-pit mine. The loading cycle time was used to assess the material loading system performance which is one of the key components of the total cycle time for material transportation in an open-pit mine. Loading is among the components of cycle time during which material is being handled. The data analyzed?was?collected from a computerized dispatch system at GGM from which 62,000 loading dispatches per month involving several shifts, 14 excavators and 49 trucks were loaded. About 4465 dispatches per excavator and 1276 dispatches per truck were assessed using loading cycle time data for each dispatch for a period of four months (between August and December). Under fixed tonnage loaded and waste type (33 t of non-acid forming waste rock),?it was observed that loading cycle time depends on excavator model, location and truck being loaded. Average cycle times, PDFS?and CDFS of loading cycle time series were used to identify differences in performance under different situations. It was concluded that shift availability for excavators, loading location, excavator model and truck-shovel combinations strongly affect the productivity during loading process in an open-pit mine.

面向局站一体的铁路动态车流组织优化研究

针对局站一体的铁路网动态车流组织问题,基于基本运行图和编组计划,综合考虑运输企业效益和服务质量,构建基于连续型时空网络的重空车流协同优化混合整数线性规划模型。为适应车流波动,引入备选改编方案增加车流的可行时空路径,从而灵活调整开行列车的车流内容,以期实现动态车流在运行线上的合理分配。为解决大规模时空网络模型求解困难的问题,在协同优化模型的基础上进一步提出分阶段优化方法。基于路局级规模路网的案例结果表明,两种方法均能有效加速车流输送,提高运输服务质量,但分阶段优化方法的求解效率显著高于协同优化方法。

床旁超声监测严重创伤患者胃功能障碍的有效性

目的:探讨床旁超声在评估严重创伤患者胃功能障碍中的临床应用价值。方法:选取严重创伤患者(ISS评分≥16)30例。经床旁超声分别测量并记录严重创伤患者入院第1天、第3天、第5天的胃排空时间,根据其结果评估患者胃功能情况。结果:严重创伤患者第一天胃排空时间为(123.47±2.76)min,健康受试者为(33.08±1.29)min,两者比较,差异有统计学意义(P<0.05),严重创伤患者胃排空时间明显延长;严重创伤患者第1天、第3天和第5天胃排空时间分别为(123.47±2.76)min、(120.60±2.73)min、(113.52±2.89)min,经比较第1天与第5天的胃排空时间差异具有统计学意义(P<0.05),经过治疗后,患者的胃排空时间缩短;且通过对健康受试者与严重创伤患者治疗5 d后的排空时间比较,差异有统计学意义(P<0.05)。结论:严重创伤患者胃排空时间明显延长且在后续治疗过程中患者胃肠功能在缓慢改善但与健康受试者相比仍有一定差距,通过床旁超声监测可以动态监测严重创伤患者胃排空时间,进而评估胃功能变化。

重载铁路通道空车列车回送运输方案的优化

对重载运输空车调整的问题进行分析,并基于重载铁路具有空车运行方向确定、空车调整以列为单位、空车方向线路通过能力大的特点,结合重载运输装、卸车端的重空车组合、分解的货流流向需求、装卸车时间窗需求,制定大列和小列协同配合的空列车调整方案。以重载铁路一个工作日全部空车列车的总旅行时间最小为目标,建立了一个线性整数规划模型。根据模型特点,基于数学求解器编程对模型进行求解,以获得不同类型空车列车的开行方案。最后,通过一个重载运输通道的空车调配问题进行数据试验,能够在较短的时间内得出优化的空车列车的调整方案。通过实例验算,该模型能够为重载运输铁路运营企业的空车调整工作起到一定的辅助决策作用。

强化生物滴滤技术深度治理大型城镇污水处理厂恶臭气体

为了解决城镇污水处理厂恶臭污染日益严峻,以及常规除臭技术难以深度去除产生的恶臭气体的问题,以市政污水处理厂调配水井收集的H_(2)S为研究对象,研究了一种添加微生物活性促进剂的一体化生物滴滤塔除臭技术,探究其工艺影响因素,并在大量研究数据的基础上,提出相关设计参数指导建议。结果表明:1)当进口臭气风量为3000 m^(3)/h,进口处H_(2)S的质量浓度为152~304 mg/m^(3)时,空床停留时间仅为8.6 s,强化生物滴滤塔的H_(2)S去除率可达99.9%,脱硫负荷(以H_(2)S计)可达62 g/(m^(3)·h)以上;2)强化生物滴滤塔添加生物促进剂可以缩短微生物驯化周期约60%,并在极低的pH条件(pH≤1.5)下长期稳定运行;3)以城镇污水处理厂臭气进口处H_(2)S的质量浓度为180 mg/m^(3)为例,设计空床停留时间(empty bed residence time,EBRT)为17 s,强化生物滴滤塔H_(2)S去除率可达99.9%,设备整体占地面积及体积均可减少30%~50%,为生物滴滤技术的实际应用提供参考价值。

城轨底架多特征加工中的空走刀路径优化

为实现城轨底架加工效率的提升,建立了以刀具空走刀路径和换刀次数为优化目标的数学模型并改进NSGA-Ⅱ算法进行求解。首先,通过MSOS染色体对特征和刀具进行编码;其次,采用动态拥挤度排序方式和精英保留策略选择个体,保证子代种群的多样性和保留优秀个体;最后,为增加种群的多样性依据迭代次数改变变异操作。实例计算结果表明,与传统分组规划法取得的目标值相比较,采用改进NSGA-Ⅱ算法所获得的刀具空走刀路径和换刀次数最多分别减少34.2%和25%,验证了该算法在城轨底架多特征加工中的可行性和有效性,提高了生产效率。

自动化综采面一次采全高切顶卸压技术研究

以山西某矿1014工作面为研究对象,介绍了综采工作面综采全高技术。采空区支护巷道采用顶板卸压,采用“大变形恒阻锚索+钢带”对1014工作面进行固定,再利用深孔爆破技术沿采空区预裂顶板。爆破后对顶板进行临时和永久支护加固,最后用U型钢封堵矸石。实践证明,采用这种方法可以有效地减少煤矿的开采费用,达到煤矿的安全生产需要,并具有良好的支护效果和经济效益。

基于斜抛物线法的空钩下降能力分析研究

文中基于斜抛物线法从空钩下降的基本条件出发,将下降临界条件建立前后悬垂段钢丝绳的弧长差值及其时间增量作为浮式起重机空钩下降能力的衡量指标。通过改变挠跨比、空钩自重、钢丝绳线密度、速度曲线性能指标等参数,定量分析和考察其对空钩下降能力的影响。结果表明:悬垂段钢丝绳弧长的变化量、卷筒放绳量、放绳时间可以直观并有效地描述空钩的下降能力,适当地提高挠跨比、增加吊钩组自重或减小钢丝绳线密度会更利于空钩的下放。在较大幅度或水平跨度位置处的放绳量增加显著,空钩下降能力趋弱,据此条件所设计的吊钩组自重同时也能满足其他较小幅度或水平跨度下对空钩下放的要求。分析对比不同速度曲线影响下放绳量和放绳时间的变化,发现放绳量对加、减速度变化的敏感度较弱,以放绳时间去描述空钩的下降能力或下放效率将更为合理。

搅拌工艺对混凝土性能的影响研究

研究了普通搅拌工艺、净浆裹石搅拌工艺和基于剪切稀化的低粘度净浆裹石搅拌工艺对不同强度等级混凝土坍落度、倒置坍落度筒排空时间、压力泌水率及7 d和28 d抗压强度的影响。结果表明:基于剪切稀化效应,采用低粘度净浆裹石搅拌工艺更有利于提升C40、C50、C60混凝土拌合物的工作性能和力学性能,并且随着混凝土强度等级的提高,其性能改善更明显。相比于普通搅拌工艺,低粘度净浆裹石搅拌工艺可使C40、C50、C60混凝土坍落度分别提高12、14、15 mm;倒置坍落度排空时间分别减少2.1、2.6、3.2 s;28 d抗压强度分别提高2.7、4.6、10.1 MPa。

胶囊内镜检查对消化道转运时间的影响

目的通过胶囊内镜所获取的图像在无创、生理条件下记录胃肠转运时间,并对其影响因素进行全面分析。方法对178例连续入选的患者行胶囊内镜检查,分析年龄、性别、体质量指数等各项临床参数对消化道转运时间的影响,同时分析胶囊未完成全小肠检查的原因。结果124例患者完成全小肠检查,胶囊内镜检查中胃平均排空时间为44.5 m in,小肠平均通过时间为286 m in;年龄对小肠通过时间有影响(P<0.05),性别、体质量指数对消化道转运时间无影响(P>0.05)。年龄、小肠克罗恩病、小肠新生物为影响胶囊内镜未完成全小肠检查的因素。结论对年龄>60岁、有肠道克罗恩病史或疑诊肠道克罗恩病、怀疑小肠存在新生物的患者,行胶囊内镜检查前,应口服促肠道动力药以提高胶囊内镜检查效率。

溴酸盐的生成及控制

通过试验考察了活性炭对溴酸盐的去除效果。在溴酸盐初始浓度为137μg/L时,新投入使用的活性炭可以去除100%的溴酸盐,初始浓度为283μg/L时,活性炭空床接触时间(EBCT)大于15min时去除率为100%;使用一年的活性炭对溴酸盐的去除效果降低。新炭和旧炭出水中均含有一定数量的溴离子,旧炭对溴离子的去除效果明显降低。

基于时间窗的铁路空车调配优化模型及求解

针对以往铁路空车调配优化研究中对时效性考虑不足的现状,考虑到空车过早或过晚到达都会给铁路运输企业带来额外的费用支出,按照空车运输费用、积压库存费用及延误损失费用之和最小的原则,建立基于时间窗(规定时间段)和区段空车运输能力约束的空车供需平衡调配优化模型。以由3个空车供应站、4个空车需求站组成的铁路运输网络为例,按照线性整数规划求最小值问题,运用LINGO软件进行仿真求解,得到最优空车调配方案。