Accumulation of Mineral Nutrients and Phytochemicals in Lettuce and Tomato Grown in High Tunnel and Open Field

High tunnel production of horticultural food crops is becoming increasingly popular and has a significant impact on their growth, productivity and nutritional quality. The present study examines the effect of high tunnel production of lettuce (Lactuca sativa cv. “Two Star” and “New Red Fire”) and tomato (Solanum lycopersicum cv. “Celebrity” and “Mountain Fresh”) on their nutritional quality relating to major nutrients and health-promoting phytochemicals. High tunnel environment increased the concentration of N (protein) in both lettuce and tomato relative to the open field cultivation. The accumulation pattern of mineral nutrients in high tunnel was similar in green-leaf and red-leaf lettuce varieties. Lettuce varieties grown in high tunnel had higher accumulation of C, S and Zn relative to those grown in open field. However, high tunnel environment suppressed the accumulation of many micronutrients such as Mg, Fe, Cu and Mn in both lettuce varieties but not in tomato. For example, accumulation of Fe was reduced by more than 80% in “Two Star” and by more than 55% in “New Red Fire” under high tunnel. It also suppressed the levels of many health-promoting phenolic compounds such as chlorogenic acid, chicoric acid, rutin and kaempferol in green-leaf lettuce and gallic acid in red-leaf lettuce. High tunnel environment improved the soil nutrient status but reduced the radiation levels (PAR, UV-A and UV-B) received by the crops. The results show that the high tunnel production has a significant impact on the nutritional quality relating to protein and mineral nutrients in both crops and health-promoting phytochemicals in lettuce.

Model test on dynamic characteristics of invert and foundation soils of high-speed railway tunnel

A dynamic model test(CL = 4) at different velocities of train,namely different loading frequencies,is carried out to study the dynamic characteristics of a high-speed railway tunnel invert and its foundation soils.Not only are the accelerations,dynamic coefficients,dynamic stresses of the invert and foundation soils emphatically analyzed,their relationship with the velocity of the train are discussed in detail.Through laboratory testing,the attenuation of vibration propagating from up the rails is obtained and the calculation formula of the speed influence coefficient of the tunnel invert is preliminarily established.The depth of the foundation soils influenced by vibration is also determined in this study.It is shown that the responses of the tunnel invert and foundation soils to vibration are slightly increased with the velocity of the train;circumferential stresses in the bottom of the invert are tensile stresses and maximum stresses appear under the foot of the rails;the dynamic soil pressures of the foundation decrease quickly with the distance away from the tunnel invert and an exponential relationship exists between them.

Stress characteristics of surrounding rocks for inner water exosmosis in high-pressure hydraulic tunnels

Seepage and stress redistribution are the main factors affecting the stability of surrounding rock in high-pressure hydraulic tunnels.In this work,the effects of the seepage field were firstly simplified as a seepage factor acting on the stress field,and the equilibrium equation of high pressure inner water exosmosis was established based on physical theory.Then,the plane strain theory was used to solve the problem of elasticity,and the analytic expression of surrounding rock stress was obtained.On the basis of criterion of Norway,the influences of seepage,pore water pressure and buried depth on the characteristics of the stress distribution of surrounding rocks were studied.The analyses show that the first water-filling plays a decisive role in the stability of the surrounding rock; the influence of seepage on the stress field around the tunnel is the greatest,and the change of the seepage factor is approximately consistent with the logarithm divergence.With the effects of the rock pore water pressure,the circumferential stress shows the exchange between large and small,but the radial stress does not.Increasing the buried depth can enhance the arching effect of the surrounding rock,thus improving the stability.

New technologies for high-risk tunnel construction in GuiyangGuangzhou high-speed railway

Based on the construction of high risk tunnels in Guiguang-Guangzhou high-speed railway, several new technologies were developed for high-risk tunnel con- struction. First, an integrated advanced geological predic- tion was developed for tunneling in karst area. Then, a new system of ventilation by involving the dedusting technol- ogy was proposed and used in the field, which received a good air quality. Finally, a method to minimize the dis- tance between the working face and the invert installation was proposed by optimizing the invert installation and adopting the micro bench method. Applying the method to the project obtained an excellent result. The achievement obtained for this study would be able to provide a valuable reference to similar projects in the future.

Deformation characteristics and safety assessment of a high-speed railway induced by undercutting metro tunnel excavation

Stratum deformation(settlement) is a challenging issue in tunnel engineering, especially when construction of metro tunnels has to undercut high-speed railway. For this purpose, we used the FLAC30 software to analyze the stratum settlement characteristics of high-speed railway at different crossing angles intersected by metro tunnel, in terms of ground settlement trough, stratum slip line and irregularity of ballastless tracks. According to the evolution of the stratum settlement at different angle regions, an optimized angle is proposed for the actual project design. In order to reduce the influence of stratum settlement on the safety of high-speed railway, an approach of safety assessment is proposed for the shield engineering undercutting high-speed railway, as per Chinese specifications using numerical results and on-site conditions. A case study is conducted for the shield tunnel section crossing the Wuhan-Guangzhou High-speed Railway between the Guangzhou North Railway Station and the Huacheng Road Station, which represents the first metro tunnel project passing below a high-speed railway in China. A series of measures is taken to ensure the safe excavation of the shield tunnel and the operation of the high-speed railway. The results can provide a technical support for performing a safety evaluation between high-speed railways and metro tunnels.

Effect of ambient wind on pressure wave generated by high-speed train entering a tunnel

Using three-dimensional, unsteady N-S equations and k-ε turbulence model, the effect of ambient wind on the pressure wave generated by a high-speed train entering a tunnel was studied via numerical simulation. Pressure changes of the train surface and tunnel wall were obtained as well as the flow field around the train. Results show that when the train runs downwind, the pressure change is smaller than that generated when there is no wind. When the train runs upwind, the pressure change is larger. The pressure change is more sensitive in the upwind condition than in the downwind condition. Compared with no wind condition, when the wind velocity is 10 m/s and 30 m/s, the pressure amplitude on the train head is reduced by 2.8% and 10.5%, respectively. The wall pressure amplitude at 400 m away from the tunnel entrance is reduced by 2.4% and 13.5%, respectively. When the wind velocity is-10 m/s and-30 m/s, the pressure amplitude on the train head increases by 3.0% and 17.7%, respectively. The wall pressure amplitude at 400 m away from the tunnel entrance increases by 3.6% and 18.6%, respectively. The pressure waveform slightly changes under ambient wind due to the influence of ambient wind on the pressure wave propagation speed.

Key technologies for construction of Jinping traffic tunnel with an extremely deep overburden and a high water pressure

Jinping traffic tunnel is one of the deepest traffic tunnels in the world with a maximum overburden of 2 375 m and the overburden over 73% of its total length is larger than 1 500 m. The tunnel is 17.5 km long and designed to provide a shortcut road between two hydropower stations： Jinping I and Jinping II of the Jinping Hydropower Project, located on Yalong River, Liangshan State, Sichuan Province, China. The tunnel is so deep that building any shafts is impossible. The construction starts from both ends （east and west ends）, and the construction length from the west end is 10 km with a blind heading. This paper deals with an overview of this project and analysis of the engineering features, as well as key technologies developed and applied during the construction, including geological prediction, rock burst prevention under a super high in-situ stress, sealing of groundwater with a high pressure and big flow rate, ventilation for a blind heading of 10 km, wet spraying of shotcrete at zones of rock burst and rich water, etc. The application of the new technologies to the construction achieved a high quality tunnel within the contract period.

TK7 High-Temperature Tunnel Kiln Computer Control System of SRIC Thailand

Based on the TK7 high-temperature tunnel kiln computer control system, this article describes the control line system, the automatic loop control which has been realized in firing zone temperature, inner and bottom pressure and flow, and logic control of kiln doors and pusher, etc. In addition, this system integrates the product information management system of magnesite brick and efficiently ensures the important process parameters. During three months performance of the control system, all parameters and energy consumption have turned out a good result.

A bistable, self-latching inverter by the monolithic integration of resonant tunnelling diode and high electron mobility transistor

This paper reports that the structures of AlGaAs/InGaAs high electron mobility transistor （HEMT） and AlAs/GaAs resonant tunnelling diode （RTD） are epitaxially grown by molecular beam epitaxy （MBE） in turn on a GaAs substrate. An Alo.24Gao.76As chair barrier layer, which is grown adjacent to the top AlAs barrier, helps to reduce the valley current of RTD. The peak-to-valley current ratio of fabricated RTD is 4.8 and the transconductance for the 1-μm gate HEMT is 125mS/mm. A static inverter which consists of two RTDs and a HEMT is designed and fabricated. Unlike a conventional CMOS inverter, the novel inverter exhibits self-latching property.

六边形断面超高层建筑风荷载研究

为了研究六边形断面超高层建筑的静力和动力风荷载,开展了一系列刚性测压模型和多自由度气弹模型风洞试验,测量了刚性模型表面风压和气弹模型风致位移。对于静力风荷载,分析了体型系数和静风力系数的变化规律,建立了顺风向平均基底弯矩系数和平均阻力系数的经验公式。对于动力风荷载,分析了横风向荷载功率谱和均方根基底弯矩,建立了横风向广义风荷载功率谱和归一化均方根基底弯矩系数的经验公式。最后,基于多自由度气弹模型的风致振动试验结果,验证了经验公式的精确性。

水工高压隧洞钢筋混凝土衬砌裂缝开度数值模拟方法研究

水工高压隧洞常以裂缝最大宽度作为钢筋混凝土衬砌设计的控制标准,但针对大洞径、高水头隧洞的裂缝最大宽度计算,公式法存在一些局限性。许多专家学者尝试将数值模拟方法应用至衬砌裂缝宽度计算当中,但难以统筹考虑钢筋混凝土粘结滑移、裂缝开裂后的应力重分布等多重因素的影响。基于此,提出一种通过损伤模型指导布设虚拟裂缝单元以反应裂缝特征的方法,即首先利用考虑粘结滑移的混凝土损伤模型模拟钢筋混凝土联合作用下衬砌混凝土损伤随着荷载施加发展的过程,进一步对损伤集中区域增设虚拟裂缝单元以计算裂缝开展过程。经对比,采用该方法计算得到的裂缝最大宽度、发展规律与分布情况与既有文献相似,且计算收敛性好,实现了通过有限元算法精确且高效地直接得到衬砌裂缝宽度,在设计与运行安全预测方面具有较大的应用价值。

高内水压作用下透水衬砌—灌浆圈—围岩联合承载机理分析

针对混凝土衬砌在高内水压下开裂渗漏问题,将隧洞概化为透水衬砌—灌浆圈—围岩厚壁圆筒模型,通过理论推导建立了考虑外水压力的水压致裂解析方法,实现了施作衬砌—充水加压—衬砌开裂全过程模拟。研究发现衬砌施作时承受外水压力作用,渗流为向洞内溢出;内压大于外压后,钢筋应力由压转为拉;衬砌开裂后,钢筋应力急剧增大—迅速下降—缓慢增加。开裂前衬砌与围岩处于相互挤压的状态,粘结力不影响衬彻结构受力;衬彻与围岩脱离后,衬砌与围岩单独承载,其变形和受力与粘结力无关。透水衬砌—灌浆圈—围岩模型与透水衬砌—围岩模型结果规律一致,但考虑灌浆后渗漏量显著下降。

近活动断裂带长大深埋高铁隧道地应力特征分析

渝昆高铁是我国“八纵八横”重要铁路干线,铁路沿线地质环境复杂,特别是深埋长大隧道地应力复杂,隧道施工中围岩结构安全挑战严峻。采用文献调研、三维地应力反演和理论分析的方法,分析彝良—鲁甸地区2座长大深埋高铁隧道地应力分布特征。研究表明,(1)彝良、鲁甸隧道最大水平主应力呈现“北强南弱”的规律,推测为印度板块与亚欧板块碰撞产生的构造应力由高原中部向南逐渐减弱导致;(2)彝良、鲁甸隧道地应力分布表现为:彝良隧道最大水平主应力为15.6~26.8 MPa,竖向主应力为9.5~26.8 MPa;鲁甸隧道最大水平主应力10.9~15.6 MPa,竖向主应力为1.8~11.7 MPa;(3)彝良隧道侧压力系数在0.97~2.1之间,在地层浅部地应力由构造应力主导,地层深部由自重应力主导;鲁甸隧道侧压力系数在1.1~6.9之间,地应力由构造应力主导。

预切缝辅助TBM滚刀破岩贯入荷载演化规律

基于全断面隧道掘进机(Tunnel Boring Machine,TBM)滚刀贯入室内模型试验,研究了3种不同破岩模式(完整岩样破岩、同轨迹破岩和异轨迹破岩)在不同围压条件下高强度花岗岩样贯入荷载演化特征,重点揭示贯入荷载-贯入度特征曲线、峰值荷载、最大跌落幅值变化规律,获取不同破岩模式在不同围压条件下TBM滚刀受力特性。结果表明:1)高围压组贯入荷载-贯入度特征曲线较低围压组先跌落,跌落幅度较小,但其对应的贯入荷载并非峰值荷载,而低围压组初次跌落荷载为峰值荷载,且跌落幅值较大;2)在中高围压10~15 MPa时,峰值荷载及贯入荷载最大跌落幅值均最小,表明此围压范围较利于TBM的掘进;3)低围压条件下选用异轨迹破岩模式较同轨迹破岩模式能更有效地降低TBM滚刀贯入荷载,但同轨迹破岩模式的岩样发生楔裂破坏,其最大跌落幅值最小,更能减少刀具所受冲击荷载,减少刀具磨损。

腕管综合征患者高频超声纹理特征及其诊断价值分析

目的 采用高频超声分析腕管综合征患者的纹理特征,并分析高频超声纹理特征对腕管综合征的诊断价值,以期为该病的诊断提供更好的方法。方法 以2021年1月—2023年12月湖州市中心医院收治的148例腕管综合征患者为病例组,纳入同期因其他因素就诊的100例非腕管综合征患者为对照组。对比2组患者高频超声纹理特征,绘制ROC曲线分析高频超声纹理特征对腕管综合征的诊断价值。结果 病例组均值、标准差、变异系数以及直方图熵均低于对照组,偏度、峰值、亮度熵以及中值均高于对照组(P<0.05);病例组像素均值比、同深度均值比、中值比、同深度中值比、Q0.5、Q0.6、Q0.7、Q0.8、Q0.9、Q1均低于对照组,Q0、Q0.05、Q0.1以及Q0.15均高于对照组(P<0.05);病例组厚度最大值、厚度中值、厚度均值、长度最大值、长度中值、长度均值、病灶面积、长轴、短轴、离心率以及病灶周长均小于对照组(P<0.05);灰阶共生矩阵、形态学特征以及一阶统计量联合诊断腕管综合征患者的AUC(0.934)显著高于单一灰阶共生矩阵AUC(0.762)、形态学特征AUC(0.884)以及一阶统计量AUC(0.753)。结论 高频超声纹理特征分析中灰阶共生矩阵、形态学特征以及一阶统计量对腕管综合征患者具有较高的诊断价值,且3种联合的诊断价值更高。

跨坐式单轨大坡度隧道大功率火灾排烟方案研究

[目的]跨坐式单轨隧道因火灾功率增大,坡度增陡,导致火灾临界风速增大,排烟设备配置增加,需对跨坐式单轨大坡度隧道和大功率火灾下的排烟方案进行研究。[方法]建立1∶20缩尺模型试验平台,计算不同火源热释放率和不同坡度下的隧道临界风速。采用SES(地铁环境模拟)软件建立跨坐式单轨隧道火灾一维数值计算模型,计算不同坡度隧道所需排烟设备配置。[结果及结论]根据模型试验得到跨坐式单轨隧道在20 MW大功率火灾下的临界风速值:坡度为-6%、-3%、0%、3%、6%时,对应火灾临界风速分别为3.55 m/s、3.33 m/s、2.91 m/s、2.57 m/s、2.46 m/s;车站隧道风机配置风量与坡度呈线性相关:坡度为0%时,单台隧道风机风量约75 m^(3)/s;坡度为-6%时,单台隧道风机风量约110 m^(3)/s;坡度为6%时,单台隧道风机风量约46 m^(3)/s。针对洞口隧道,洞口处射流风机配置可通过车站隧道风机结合隧道坡度反算得到;针对大坡度隧道、大功率火灾,向上坡和向下坡排烟时对应的设备配置差异较大,提出优先选用向上坡排烟的方案,以减少设备投资。

大深宽比矩形高层建筑表面脉动风压非高斯特性

为探究大深宽比矩形高层建筑表面脉动风压的非高斯特性,本文对深宽比为1/9~9的矩形高层建筑进行了同步测压风洞试验。基于试验结果,分析了建筑表面风压的三阶和四阶统计矩分布特性,对高层建筑各立面风压进行高斯与非高斯分布的分区;研究了风压的空间相关系数与非高斯性强度的关系,提出了一种新的估算建筑侧风面平均再附长度的计算方法。结果表明:在建筑侧风面上,脉动风压服从高斯还是非高斯分布取决于测点到迎风前缘的距离;除了以往文献指出的迎风面角部、侧风面分离区和背风面风压呈现非高斯性外,再附区后面的风压也呈现出高度的非高斯性;本文提出的相关系数法在计算平均再附长度时具有良好的准确性,利用该方法获得了矩形高层建筑侧风面的平均再附长度沿高度的变化呈抛物线形状。

400 km/h及以上速度下列车通过隧道时列车表面压力特征研究

[目的]为了保障400 km/h及以上速度列车穿越隧道时的行车安全,提升乘客舒适性,需采用数值模拟方法,对列车通过隧道时的列车表面压力特征进行研究。[方法]介绍了一维流动理论和广义黎曼变量特征线法,通过动模型试验对其进行了验证。探究了不同列车运行速度、不同隧道长度对8辆编组列车通过隧道时的列车表面压力影响规律,并分析了不同列车表面压力的分布特征。[结果及结论]当列车运行速度为400 km/h,隧道长度为0.7 km时,列车表面的最大正压值、最大压力幅值、最大负压值均达到峰值;当隧道长度超过0.7 km后,最大正压值基本不随隧道长度的增加而变化,最大负压值和最大压力幅值均随着隧道长度的增大而逐渐减小。在不同列车运行速度下,列车表压力值均随列车运行速度的增加而逐渐增加。列车运行速度为400 km/h时的同一列车不同部位表面的最大正压值和最大压力幅值均表现为头车>中间车>尾车,最大负压值则表现为头车<中间车<尾车。列车表面最大正压值、最大负压值和最大压力幅值在数值上均表现为随着测点距车头鼻尖的距离的增大而逐渐减小。

基于爆破法的某高速铁路隧道开挖施工技术

为研究基于爆破法的某高速铁路隧道开挖施工技术,以沪渝蓉高铁武宜段WYZQ-5标白果树1号隧道为项目背景,首先,根据该隧道的工程情况,给出了基于爆破法施工的总体施工方案。其次,对隧道爆破施工中的隧道掌子面孔位布置、装填炸药、连线起爆、爆破效果控制,以及爆破施工控制关键施工技术进行了详细研究。最后,从施工安全角度探究了高速铁路隧道爆破施工安全问题,并给出了相关施工安全控制措施。

营业线高铁隧道套衬施工安全技术应用

依托贵广铁路提质改造工程隧道增设套衬施工为例,阐述了贵广铁路提质改造工程隧道增设套衬施工安全技术的实施应用,隧道结构稳定性和耐久性得到显著增强,减少隧道拱顶开裂、掉块、空鼓、渗漏水等病害产生,达到了安全可靠的整治效果,为类似的营业线高铁隧道缺陷与病害整治积累施工实践经验,提供安全技术参考实例,有较强的施工指导性。