Effect of Sludge Retention Time on Nitrite Accumulation in Real-time Control Biological Nitrogen Removal Sequencing Batch Reactor

In this study,four sequencing batch reactors(SBR),with the sludge retention time(SRT)of 5,10,20 and 40 d,were used to treat domestic wastewater,and the effect of SRT on nitrite accumulation in the biological nitrogen removal SBR was investigated.The real-time control strategy based on online parameters,such as pH,dissolved oxygen(DO)and oxidation reduction potential(ORP),was used to regulate the nitrite accumulation in SBR. The model-based simulation and experimental results showed that with the increase of SRT,longer time was needed to achieve high level of nitritation.In addition,the nitrite accumulation rate(NAR)was higher when the SRT was relatively shorter during a 112-day operation.When the SRT was 5 d,the system was unstable with the mixed liquor suspended solids(MLSS)decreased day after day.When the SRT was 40 d,the nitrification process was significantly inhibited.SRT of 10 to 20 d was more suitable in this study.The real-time control strategy combined with SRT control in SBR is an effective method for biological nitrogen removal via nitrite from wastewater.

Effects of Waterlogging Time on Rice Cd Absorption and Accumulation under Cadmium Stress

A pot experiment with exogenous cadmium was utilized to study the effects of waterlogging time on rice yield and Cd accumulationin different growth stages including top tillering stage and filling stage.The results showed that the rice yields of all flooding treatments were lower than the CK(CI).The WI,T1,T2,T3 and T4 decreased significantly by 23.7%,16.0%,15.5%,20.2%and 18.6%respectively.The Cd content of brown rice decreased with the extension of waterlogging time.And WF was the lowest,at only 3.4%of the wet irrigation of the whole growth period(WI).Under the same waterlogging condition,the Cd content in brown rice with 1 to 4 weeks of flooding treatment at the top tillering stage decreased by 27.1%(P﹤0.05),46.6%(P﹤0.05),56.0%(P﹤0.05)and 35.2%(P﹥0.05)respectively,compared with the treatment at the filling stage.And the average decrease was 41.2%.The variation tendency of Cd content in stems and leaves was similar to brown rice.The translocation efficiency of Cd from stems and leaves to rice seeds decreased with the extension of waterlogging time.The Cd enrichment factor of stems and leaves,as well as brown rice,varied greatly with different treatments.Specifically,the Cd enrichment factors in brown rice and in stems and leaves under WI were 28.0 and 17.8 times higher respectively than those under WF.The findings of this study demonstrated that flooding could inhibit the uptake and accumulation of Cd in rice,with significant positive correlation between them.The inhibition effect of flooding treatment on Cd accumulation in rice at the top tillering stage was superior to that at the filling stage.

Novel models for simulating maize growth based on thermal time and photothermal units: Applications under various mulching practices

Maize (Zea mays L.) is one of the three major food crops and an important source of carbohydrates for maintaining food security around the world.Plant height (H),stem diameter (SD),leaf area index (LAI) and dry matter (DM) are important growth parameters that influence maize production.However,the combined effect of temperature and light on maize growth is rarely considered in crop growth models.Ten maize growth models based on the modified logistic growth equation (Mlog) and the Mitscherlich growth equation (Mit) were proposed to simulate the H,SD,LAI and DM of maize under different mulching practices based on experimental data from 2015–2018.Either the accumulative growing degree-days (AGDD),helio thermal units (HTU),photothermal units (PTU) or photoperiod thermal units (PPTU,first proposed here) was used as a single driving factor in the models;or AGDD was combined with either accumulative actual solar hours (ASS),accumulative photoperiod response (APR,first proposed here) or accumulative maximum possible sunshine hours (ADL) as the dual driving factors in the models.The model performances were evaluated using seven statistical indicators and a global performance index.The results showed that the three mulching practices significantly increased the maize growth rates and the maximum values of the growth curves compared with non-mulching.Among the four single factor-driven models,the overall performance of the Mlog_(PTU)Model was the best,followed by the Mlog_(AGDD)Model.The Mlog_(PPTU)Model was better than the Mlog_(AGDD)Model in simulating SD and LAI.Among the 10 models,the overall performance of the Mlog_(AGDD–APR)Model was the best,followed by the Mlog_(AGDD–ASS)Model.Specifically,the Mlog_(AGDD–APR)Model performed the best in simulating H and LAI,while the Mlog_(AGDD–ADL)and Mlog_(AGDD–ASS)models performed the best in simulating SD and DM,respectively.In conclusion,the modified logistic growth equations with AGDD and either APR,ASS or ADL as the dual driving factors outperformed the commonly used modified logistic growth model with AGDD as a single driving factor in simulating maize growth.

Weld extraction from real-time radiograph based on bidirectional accumulator Hough Transform

An effective approach is presented to extract welds from real-time radiographs, Firstly an algorithm based on an adaptive bidirectional threshold was proposed to segment the gradient image into ternary image, and then the bidirectional accumulator Hough Transform was developed to extract weld edges from the ternary image. Different values of the coefficient proposed in the threshold algorithm were tested, and the proposed approach was applied to extract welds from real-time radiographic images of different types of welds with defects. Results show that the proposed method is adaptive and effective to extract welds from real-time radiographs of linear welds.

Studies on the Time of Accumulation and Elimination of Alexandrium tamarense Toxins in Argopectens irradias

Using a PSP （paralytic shellfish poisoning） toxin-producing strain of4lexandrium tamarense, it studied the timing of toxin accumulation and elimination of PSP toxins in Argopectens irradias. The PSP toxicity was studied by following the standard PSP mouse bioassay developed by the Association of Official Analytical Chemists （AOAC）. Alexandrium tamarense was cultured to an average density of 1.26 × 10^4/mL for a total of about 50 L culture. The toxicity of the alga was 2.18 ×10^-6 MU/cell. The results show that PSP content increased with time in both visceral and muscle tissue during a two-week accumulation period during which scallops were fed with ,4. tamarense. The average toxin level in scallop＇s viscera was 49.4 MU/g, with an average of 10.0 MU/g in muscle tissue. This level is 2.5 times higher than the sanitation standard （4.0 MU/g of muscles）. The highest value was 61.0 MU/g in the viscera. In summary, the viscera accumulated greater concentrations of toxin than muscle tissue. Scallops that had accumulated toxins were transplanted for two weeks into a field environment containing no toxic algae. The PSP content of the scallops decreased to 7.9 MU/g viscera and 1.6 MU/g muscles two weeks after being transplanted, but did not reach the sanitation standard. Under the experimental conditions, the toxin depuration rate of shellfish toxin was 12% daily. This study worked toward the development of a sanitary shellfish industry and better management of PSP toxin-impacted shellfish in China.

Restoration of reservoir diagenesis and hydrocarbon accumulation process by calcite in-situ U-Pb dating and fluid inclusion analysis: A case study on Cretaceous Qingshuihe Formation in Gaoquan Structure, southern Junggar Basin, NW China

The complexity of diagenesis and hydrocarbon accumulation in the deep reservoirs in southern Junggar Basin restricts hydrocarbon exploration in the lower reservoir assemblage. The lithofacies and diagenesis of reservoirs in the Cretaceous Qingshuihe Formation in the Gaoquan structure of the Sikeshu Sag, southern Junggar Basin were analyzed. On this basis, the thermal history was calibrated using calcite in-situ U-Pb dating and fluid inclusion analysis to depict the hydrocarbon accumulation process in the Gaoquan structure. The results show that the Qingshuihe reservoir experienced two phases of calcite cementation and three phases of hydrocarbon charging. The calcite cements are dated to be (122.1±6.4) Ma, (14.4±1.0) Ma - (14.2±0.3) Ma. The hydrocarbon charging events occurred at around 14.2-30.0 Ma (low-mature oil), 14.2 Ma (mature oil), and 2 Ma (high-mature gas). The latter two phases of hydrocarbon charging contributed dominantly to the formation of reservoir. Due to the S-N compressive thrust activity during the late Himalayan period since 2 Ma, the traps in the Gaoquan structure were reshaped, especially the effective traps which developed in the main reservoir-forming period were decreased significantly in scale, resulting in weak hydrocarbon shows in the middle-lower part of the structure. This indicates that the effective traps in key reservoir-forming period controlled hydrocarbon enrichment and distribution in the lower reservoir assemblage. Calcite U-Pb dating combined with fluid inclusion analysis can help effectively describe the complex diagenesis and hydrocarbon accumulation process in the central-west part of the basin.

双向地震作用下崩塌堆积体边坡动力模糊可靠性分析

考虑崩塌堆积体边坡岩土体参数随机性和模糊性,以及地震力双向性,建立一种边坡地震动力模糊可靠度计算方法,针对竖向地震力对崩塌堆积体边坡稳定可靠性的影响进行进一步研究。首先,选用动力有限元时程分析法计算出双向地震工况下崩塌堆积体边坡的响应特征,并运用模糊理论对强度参数进行模糊性处理;然后,根据Mohr-Coulumb强度准则构建边坡安全系数与可靠度的时程计算模型;最后,采用边坡地震可靠性评价新方法,通过MATLAB编写相应程序,实现计算和分析结果的快速输出。案例结果表明:新方法计算结果更加合理,对工程而言也更加安全;竖向地震作用均对崩塌堆积体边坡整体可靠性存在影响,但影响程度需根据工程实际情况进行分析。在算例工况下,竖向地震对崩塌堆积体边坡的可靠性影响很小,仅使得可靠度降低3.55%,因此,可仅考虑水平地震的影响。

基于累加式实时串并联变换算法的机械故障声学监测方法

针对基于物联网(IoT)的冲压机床故障监测问题,为了降低冲压机床故障监测的计算复杂度,并提高其低频识别的精度,提出了一种无需机器学习技术的实时性机械故障声学监测方法,即基于累加式实时串并联变换算法的机械故障声学监测方法。首先,研究了物联网场景中冲压机床声学低频分析的必要性,并给出了声学信号的表达式;然后,针对频率轴上多个周期信号重叠导致参数估计较为困难的问题,提出了一种累加式实时串并联变换算法,将输入的采样序列馈入多个具有不同输出端口的串并转换器,从累加的波形中检测出最大绝对值,并进行了比较;最后,通过样本时隙划分,将累加式实时串并联变换算法应用于机械故障监测;通过仿真和冲压机床实机测试,对累加式实时串并联变换算法和实时性机械故障声学监测方法的有效性进行了验证。研究结果表明:在无需大量信号样本的情况下,使用累加式实时串并联变换算法有利于提高低频带的识别精度;在直方图相关性方面,累加式实时串并联变换算法和Morlet小波变换具有相同的性能,且均明显优于短时傅立叶变换;同时,尽管累加式实时串并联变换算法需要的加法总数比Morlet小波变换多2.5倍,但是乘法总数减少了20447%,大幅减少了计算的复杂度。

分数卷积灰色预测模型及其在信息传播中的应用

通过构造累加生成卷积序列的离散卷积运算实现了数据序列的累加生成,并推广到分数阶卷积幂以实现分数阶累加生成。离散序列卷积运算统一了累加生成和累减生成,给定阶数即可生成相应的卷积序列。引入离散卷积运算,可以从信号处理的角度来理解累加生成。累加生成系统可视为一个线性滤波器,累加卷积序列的本质是滤波器的单位冲击响应,卷积运算对应滤波过程。在分数累加卷积序列的基础上构建了分数阶灰色预测模型。最后给出数值实验和信息传播中的实际应用案例验证理论的正确性和方法的有效性。

杭锦旗地区二叠系储层油气成藏期次及流体势特征

杭锦旗地区是鄂尔多斯盆地北部重要的含油气区,油气成藏期次及流体势研究有利于探究油气充注的世代以及流体势的分布特征,并进一步判定成藏期油气的运移方向。本文以什股壕区块和十里加汗区块5口井的二叠系下石盒子组盒一段储层砂岩为研究对象,基于流体包裹体分析厘定油气成藏期次,并结合流体势理论计算研究区关键成藏期的流体势并揭示油气的运移方向。研究结果显示:什股壕区块盒一段储层油气的成藏时间为132~102 Ma;十里加汗区块盒一段储层油气的成藏时间为132~101 Ma。杭锦旗北部的什股壕盒一段储层油气的流体势为18 128~22 872 J/kg;杭锦旗南部的十里加汗区块盒一段储层油气的流体势为22 975~27 153 J/kg。本文认为研究区二叠系盒一段储层油气成藏时间在早白垩世,十里加汗区块整体的流体势要高于什股壕区块,油气具备由南部向北部运移的趋势。

简短关联可编辑环签名及其区块链修正应用

关联可编辑环签名(LRRS)可提升区块链的匿名性,防止双花攻击,修正区块链数据,但其签名大小随环成员的增多而增大。针对该问题,结合已有LRRS和简短关联环签名方案,利用动态累加器对环成员的公钥进行累加计算,依据原知识证明签名(SPK)构造出新的SPK,提出简短LRRS(SLRRS)方案,基于该签名又提出新的区块链修正协议。在随机谕言机模型下,证明所提签名具有不可伪造性、匿名性、关联性。性能评估表明:随着环成员的增多,已有签名的大小在增大,而所提签名不变;同时此类签名所消耗的时间均在增多,而所提签名的时间增速较缓且最少。

青藏高原东南三江流域黄土类堆积体斜坡地震作用下的动力响应试验研究——以四川巴塘下归洼滑坡为例

青藏高原东南三江流域广泛存在堆积体斜坡,该类斜坡极易演化为滑坡灾害。以四川巴塘下归洼斜坡为例,通过振动台模型试验研究地震诱发的堆积体滑坡动力响应特征与破坏模式。试验结果表明,在地震作用初期,由于孔隙被挤密,斜坡的自振频率增大;在茂县波激励下,斜坡肩部动力响应最强烈。高幅值茂县波激励下,因斜坡整体刚度降低,放大效应减弱。Hibert谱描述了地震波在斜坡中的传播特征,向斜坡顶部传播时,地震波高频能量显著增强,地震波经过堆积层后,放大效应减弱。在足以致使堆积层滑动的强震作用下,坡表一定深度下动力响应呈现一致剧烈现象,斜坡上部会形成“脱离体”,“脱离体”在地震作用下上下颠簸运动;在临滑时,坡表出现最强烈的动力响应。斜坡的破坏模式为:地震初期,在重力和地震耦合作用下,坡表土体剥落;随地震幅值增加,坡肩与堆积层发生明显相对位移,堆积层表面出现裂缝;最终,坡脚发生明显相对位移,随后堆积层偏离基岩加速滑塌。基于地震信号特征的斜坡堆积层滑落过程可分为三阶段:(1)稳定阶段;(2)临滑阶段;(3)滑移阶段。

基于四阶相关的时分多址调制数据独特码盲识别

针对非合作通信中时分多址(TDMA)信号的独特码(UW)盲识别问题,该文首次提出分布式独特码的盲识别算法。区别于比特层的独特码识别算法,该文分别针对集中式独特码和分布式独特码,提出面向调制数据不同窗口之间相关性的波形层独特码识别算法。算法利用独特码的一致性与相关性,分两步进行,首先通过差分累积消除不同突发信号间频偏与相偏的影响,来纵向对齐各个突发信号的独特码,然后通过多层差分共轭4阶相关算法识别出独特码的位置和长度。仿真分析了不同突发个数、信噪比和有无频偏相偏情况下算法的性能,验证了波形层识别独特码的有效性,针对集中式独特码和分布式独特码,所提算法在信噪比为5 dB时均达到了95%以上的识别率,具有一定的工程应用价值。

有向传感器网络中基于公平的目标覆盖最大化问题研究

以视频传感器和图像传感器为代表的有向传感器可以为安全防卫提供有效信息,已经被广泛应用于各种场景。首次提出了有向传感器网络中基于公平的目标覆盖最大化问题:在有向传感器网络中,采用具有P个确定工作方向的有向传感模型,研究基于公平的目标覆盖最大化问题,目的是激活最少的传感器,通过调度有向传感器的工作方向使目标被覆盖的最小累积覆盖时间达到最大,从而保证目标被覆盖的时间尽量均衡。首先选择最少的传感器,保证所有目标位于所选传感器的传感圆之内(该问题是NP-困难问题),为解决该问题设计了近似比为(1+lnγ)的最少传感器选择算法,其中γ=max 1≤i≤N{|s_(i)||s_(i)∈S};其次,基于最大需求优先覆盖的原则,提出了最大的无冲突目标集合选择算法。实验结果表明,该算法能有效解决有向传感器网络中基于公平的目标覆盖最大化问题。

一种基于TRT-SKT-HAF的变加速目标快速相参积累算法

在雷达高速机动目标的检测中,目标的运动特性会带来距离走动和多普勒徙动现象,不利于后续进行相参积累。传统算法为解决目标运动造成的影响,需要对目标的运动参数进行搜索,加大了计算量。针对上述问题,文中提出了一种基于慢时间序列反转变换(TRT)-二阶keystone变换(SKT)-高阶模糊函数(HAF)的变加速目标快速相参积累算法。该算法通过TRT和SKT校正距离走动,利用HAF估计目标加速度并构建相位补偿函数以校正多普勒徙动。与广义Radon-Fourier变换相比,所提方法无需进行任何参数搜索,计算复杂度减少了3个数量级。仿真结果表明,所提方法在检测门限上相比于Radon分数阶模糊函数算法降低了5 dB,在低信噪比下有更好的检测性能。

邻井气举辅助泡沫排水采气工艺起效时间探究

为了提升常规泡沫排水采气的效果,在对积液气井环空加注泡排剂的同时,使用邻井天然气对积液气井环空进行注气,即邻井气举辅助泡排新工艺。新工艺泡排剂起效时间决定关井时间和采气时率,对气井生产有重要的影响,目前行业内对此研究处于空白状态。在已有致密气井间歇泡排注剂后关井时间探究的基础上,依据注入泡排剂之后井口压力、气量和温度变化趋势来判定泡排剂下行时间和扩散时间,从而确定泡排剂的起效时间,并与常规泡排剂加注方式进行对比,分析了新工艺的优点及其原因。研究结果表明:①常规环空泡排注剂和邻井气举辅助泡沫排水采气工艺注剂后泡排剂的流动形态不一样,前者泡排剂呈“线状”,沿“静态”环空的油套管壁下行;后者泡排剂会以“液滴状”,在进入积液气井“动态”环空之后,随着邻井天然气迅速下行;②新工艺可以显著缩短泡排剂的起效时间,从8.2 h缩短至1.1 h,效率提高了86.6%,因借助注入的天然气对积液气井进行气举,排液效果更好,常规注剂不能复产的低产、低压气井借助新工艺可以正常恢复生产。为低产低压气井的排水采气提供了一种新思路,值得进一步推广应用。

汉江流域植被生长与水热的时滞累积效应

目的在全球气候变暖的背景下,研究汉江流域植被生长与气温和降水的时滞累积效应,对流域生态环境建设具有重要的意义。方法基于2001-2020年MODIS NDVI月数据和月均温、月降水数据,通过相关和时滞累积效应分析不同生态分区及植被的生长季NDVI(归一化植被指数)变化差异及其对气温和降水的响应。结果与结论(1)汉江流域生长季NDVI呈波动上升趋势,均值为0.7,与气温和降水的相关系数均值分别为0.263和0.223,正相关区域多分布于生态功能保护区和山地丘陵的植被茂密地带,负相关区域多分布于平原和盆地的栽培植被种植地带及各市人类生产生活区。(2)汉江流域生长季NDVI与气温和降水存在明显的时滞累积效应,受累积1个月滞后0个月-累积3个月滞后3个月影响的植被面积均超过了50%,气温的时滞累积效应由中间向东西两侧递减,降水则自西向东明显增加,气温的时滞累积效应对植被覆盖的促进效果大于抑制效果,降水则相反。(3)6类植被对气温和降水时滞累积的负相关性均减弱。除针叶林和阔叶林外,气温在累积6个月滞后3个月的情况下对其他类型植被覆盖的影响最大,响应程度最高的是低覆盖植被;降水在累积3个月滞后2个月的情况下对6类植被覆盖的影响最大,降水对6类植被的平均最值相关系数大小为草丛>草甸>灌丛>栽培植被>针叶林>阔叶林。

南京地区地源热泵系统优化及时间效应研究

地埋管换热器孔间距的合理设计是开发侵蚀堆积平原地区浅层地热能时需首先解决的问题。为了获得能供设计参考的地埋管换热器孔间距,确保地源热泵系统长期稳定运行,依托南京市秦淮区石门坎102号地源热泵试验工程,通过温度监测和数值模拟方法,研究了地埋管换热器孔间距和地源热泵系统10 a运行的时间效应,获得了南京侵蚀堆积平原地区地埋管换热器孔合理间距和运行方式。结果显示:(1)夏季工况、夏季后恢复工况、冬季工况、冬季后恢复工况的完整运行周期内,地层温度经历升温、降温、缓慢降温、基本恢复的周期性变化;(2)南京侵蚀堆积平原地区经济合理的地埋管换热器孔间距为4.0 m;(3)采取夏季制冷时间和冬季制热时间相等的运行方式,延长夏季后恢复工况,可确保地源热泵系统长期稳定运行。结果能为南京地区地埋管的设计和浅层地热能工程研究提供科学依据。

采用子阵多输入多输出的天基预警雷达强杂波抑制方法

针对天基预警雷达因其高速平台运动带来严重的距离模糊和多普勒模糊,导致杂波背景强进而降低雷达目标检测性能的问题,提出一种基于子阵级多输入多输出天基预警雷达强杂波抑制方法。构建基于子阵级多输入多输出天基雷达模型并分析远距离机动目标相参性,确定目标出现线性距离徙动和不出现多普勒频率扩散时的最大相参积累时间,以保证长时间相参积累可行性;针对多输入多输出雷达长驻留的特点采用长时间积累提高多普勒分辨率,降低一个距离-多普勒单元的杂波功率,在保证搜索效率的情况下降低该单元杂噪比,并采用3/5准则检测盲区图评估天基雷达检测性能;在强杂波背景下改善了信杂噪比,提高了目标检测概率。实验仿真表明,所提方法相比相控阵雷达可有效降低杂波背景,在单脉冲重复频率下即可达到很好的检测效果,比相控阵雷达检测性能提高约20.48%。

西湖凹陷玉泉构造油气成藏时空匹配关系研究

以地质录井资料为基础,结合流体包裹体、自生伊利石同位素等地球化学资料,运用平衡剖面、盆地模拟技术,研究玉泉构造断裂演化史、圈闭发育史、埋藏史、成岩史、生烃史、油气成藏史及其时空匹配关系。研究表明:玉泉构造经历了前挤压反转期、挤压反转早期和挤压反转晚期3个阶段,其中挤压反转早期和晚期为NWW向调节断层和圈闭发育、定型的关键阶段;花港组下段H6—H7自13.0 Ma以来油气持续充注成藏至今,储层物性较差,花港组上段为13.0~11.4 Ma和4.2 Ma至今两期油气充注成藏,且第二期为主要油气成藏期,储层物性较好,龙井组为3.4 Ma至今一期充注成藏,储层物性好。总结出玉泉构造寻找有利勘探目标的关键条件为:以花港组上段为勘探主要目的层,靠近早期发育的NNE油源断层,避开晚期NWW向调节断层,指出玉泉3井区北部、玉泉1井区北部花港组上段以及玉泉3井区NWW向断层上盘龙井组、玉泉1井区龙井组上段为有利勘探区。