桃品质的无损检测技术研究进展

桃果实营养物质丰富,是消费者青睐的水果之一。但桃在生长、采摘和贮藏过程中易受到损害而导致品质下降,严重影响桃的经济价值,因此桃品质检测技术对于保障果实商业价值具有至关重要的作用。传统的检测方法具有耗时长、成本高、对样品有破坏性等缺点,而基于声学特性、力学特性、介电特性、光学特性和电子鼻的无损检测方法,特别是基于光学特性的检测方法,因其无损、快速、准确的优势而发展迅速,目前在桃果实内外部品质检测中得到广泛的应用,然而目前对其优缺点及今后的发展方向缺乏系统总结。本文综述应用上述无损检测技术,尤其是基于光学特性和电子鼻的无损检测方法,评估桃果实外部品质（大小、形状、色泽、香气、表面缺陷）和内部品质（品种、糖度、可滴定酸含量、硬度、冷害、虫害等）的最新研究进展,总结分析了其在桃品质检测中存在的问题,并对桃品质无损检测研究方向进行展望,以期为桃品质无损检测技术的研究提供参考。     

高大空间辐射板导流送风的气流组织特性研究

根据贴附射流原理,本文提出一种为高大空间营造局部贴附射流条件的辐射板导流送风的方式,研究目的是在减小送风速度的条件下,使射流达到规定射程从而尽可能在降低空调能耗的情况下提高空调区的舒适性.为了说明该送风方式的优势,本文选取高大空间常用的侧墙圆喷口送风方式作为比较对象,通过对气流组织分析发现:在总送风量,送风温度相同时,...     

Study on the influence of three-grid assembly thermal deformation on breakdown times and an ion extraction process

In order to study the influence of three-grid assembly thermal deformation caused by heat accumulation on breakdown times and an ion extraction process,a hot gap test and a breakdown time test are carried out to obtain thermal deformation of the grids when the thruster is in 5 k W operation mode.Meanwhile,the fluid simulation method and particle-in-cell-Monte Carlo collision(PICMCC) method are adopted to simulate the ion extraction process according to the previous test results.The numerical calculation results are verified by the ion thruster performance test.The results show that after about 1.2 h operation,the hot gap between the screen grid and the accelerator grid reduce to 0.25–0.3 mm,while the hot gap between the accelerator grid and the decelerator grid increase from 1 mm to about 1.4 mm when the grids reach thermal equilibrium,and the hot gap is almost unchanged.In addition,the breakdown times experiment shows that 0.26 mm is the minimal safe hot gap for the grid assembly as the breakdown times improves significantly when the gap is smaller than this value.Fluid simulation results show that the plasma density of the screen grid is in the range 6?×10~(17)–6?×?10~(18) m~(13) and displays a parabolic characteristic,while the electron temperature gradually increases along the axial direction.The PIC-MCC results show that the current falling of an ion beam through a single aperture is significant.Meanwhile,the intercepted current of the accelerator grid and the decelerator grid both increase with the change in the hot gap.The ion beam current has optimal perveance status without thermal deformation,and the intercepted current of the accelerator grid and the decelerator grid are 3.65 m A and 6.26 m A,respectively.Furthermore,under the effect of thermal deformation,the ion beam current has over-perveance status,and the intercepted current of the accelerator grid and the decelerator grid are 10.46 m A and 18.24 m A,respectively.Performance test results indicate that the breakdown times increase obviously.The intercepted current of the accelerator grid and the decelerator grid increases to 13 m A and 16.5 m A,respectively,due to the change in the hot gap after 1.5 h operation.The numerical calculation results are well consistent with performance test results,and the error comes mainly from the test uncertainty of the hot gap.     

Study of the key factors affecting the triple grid lifetime of the LIPS-300 ion thruster

In order to ascertain the key factors affecting the lifetime of the triple grids in the LIPS-300 ion thruster,the thermal deformation,upstream ion density and component lifetime of the grids are simulated with finite element analysis,fluid simulation and charged-particle tracing simulation methods on the basis of a 1500 h short lifetime test.The key factor affecting the lifetime of the triple grids in the LIPS-300 ion thruster is obtained and analyzed through the test results.The results show that ion sputtering erosion of the grids in 5 kW operation mode is greater than in the case of 3 kW.In 5 kW mode,the decelerator grid shows the most serious corrosion,the accelerator grid shows moderate corrosion,and the screen grid shows the least amount of corrosion.With the serious corrosion of the grids in 5 kW operation mode,the intercept current of the acceleration and deceleration grids increases substantially.Meanwhile,the cold gap between the accelerator grid and the screen grid decreases from 1 mm to 0.7 mm,while the cold gap between the accelerator grid and the decelerator grid increases from 1 mm to 1.25 mm after 1500 h of thruster operation.At equilibrium temperature with 5 k W power,the finite element method(FEM)simulation results show that the hot gap between the screen grid and the accelerator grid reduces to 0.2 mm.Accordingly,the hot gap between the accelerator grid and the decelerator grid increases to 1.5 mm.According to the fluid method,the plasma density simulated in most regions of the discharge chamber is 1?×?10~(18)-8?×?10~(18)m~(-3).The upstream plasma density of the screen grid is in the range 6?×?10~(17)-6?×?10~(18)m~(-3)and displays a parabolic characteristic.The charged particle tracing simulation method results show that the ion beam current without the thermal deformation of triple grids has optimal perveance status.The ion sputtering rates of the accelerator grid hole and the decelerator hole are 5.5?×?10~(-14)kg s~(-1)and 4.28?×?10~(-14)kg s~(-1),respectively,while after the thermal deformation of the triple grids,the ion beam current has over-perveance status.The ion sputtering rates of the accelerator grid hole and the decelerator hole are 1.41?×?10~(-13)kg s~(-1)and 4.1?×?10~(-13)kg s~(-1),respectively.The anode current is a key factor for the triple grid lifetime in situations where the structural strength of the grids does not change with temperature variation.The average sputtering rates of the accelerator grid and the decelerator grid,which were measured during the 1500 h lifetime test in5 k W operating conditions,are 2.2?×?10~(-13)kg s~(-1)and 7.3?×?10~(-13)kg s~(-1),respectively.These results are in accordance with the simulation,and the error comes mainly from the calculation distribution of the upstream plasma density of the grids.     

以白沙洲大道改造工程为例分析现状快速路改造的设计要点

以白沙洲大道改造工程设计为例,提出快速路改造的总体设计和桥梁设计要点。对于现状快速路,为提高主线的连续性和独立性,总体方案宜将现状地面段改造为高架段,同步将现状枢纽型“低接高”立交改造为“高接高”立交,使主线系统和地面辅道系统的影响降到最低;在一些重要主干路口,结合主线改造,通过增设平行上/下桥匝道形成简易菱形立交,实现主线高架与辅道到发交通的快速联系;从总体方案考虑,增设声屏障;从对交通影响最小考虑,主线桥梁上部结构宜采用钢-混组合梁。帮宽桥根据地面绿化带布置,下部结构采用分离式柱式墩和带牛腿的偏心柱式墩,上部结构宜采用钢箱梁,帮宽桥与既有桥之间设置0.02 m的沉降缝。设计经验的总结为同类型设计提供了参考和借鉴。     

云南东川铜矿带碳、氧同位素特征及成矿机制讨论

东川铜矿带地处云南东川盆地,属于沉积岩容矿层状铜矿带,发育有稀矿山式铁铜矿体、东川式铜矿体、桃园式铜矿体等多类型铜矿体。为探讨东川铜矿带的成矿机制,本文通过对东川铜矿带各类型矿体的碳、氧同位素分析,结合前人研究成果,发现相对于赋矿白云岩,稀矿山式、东川式、桃园式铜矿体的白云石δ¹³C值呈降低的趋势,东川式铜矿体的包裹体δ¹³C值为-16.40‰～-0.20‰,桃园式铜矿体的包裹体δ¹³C值为-18.40‰～-4.20‰,包裹体中的δ¹³C值呈现明显的低值。碳、氧同位素特征说明成矿流体的碳源主要来自于海相碳酸盐的溶解作用,其次来自于有机质的氧化作用和脱羟基作用,有机质亦参与了成矿作用。含矿卤水运移到具还原性质的落雪组白云岩和黑山组炭质板岩中,与含有机质地层和含有机质流体发生氧化还原反应,形成多层位的层控铜矿床,东川铜矿带成矿机制为盆地卤水交代成矿。     

洛马公司成功地进行了UFCS和HIMARS的弹架接口试验

由洛马公司研发的装备了通用火控系统(UFCS)的高机动性火箭炮系统(HIMARS)于2008年3月20日在白沙导弹靶场成功地发射了陆军战术导弹系统(ATACMS)。导弹按预定弹道飞行,击中了75km处的目标。这是首次从装备了UFCS的HIMARS发射架上发射ATACMS,也是新型AT-ACMS的第二次后继生产发射试验。新型ATACMS导弹可以沿垂直弹道攻击目标,以减少打击城市目标时的附带损伤。这次靶试成功地验证了新型UFCS弹架接口。这种接口是在现有火控系统的基础上改进的,它可以实现多管发射。目前新型UFCS已完成研发、验证和审批,正在交付用于HIMARS。该系统还将装备英国正在计划中的轻型火箭炮武器系统。洛马公司成功地进行了UFCS和HIMARS的弹架接口试验@尚绍华 @王蒙     

高粘度液体爆炸分散实验研究

在无约束空间中.采用不同比药量(炸药量与装填液体之比)对不同粘度的高粘度液体进行了爆炸分散实验.讨论了液体粘度、比药量对爆炸分散后液体粒径分布的影响以及对初始云团半径的影响.实验结果表明,液体粘度和分散药量对爆炸分散后液体粒径大小的分布,以及初始云团半径的形成有显著的影响.粘度越大,爆炸分散后形成的颗粒平均直径越大,分散越不均匀,颗粒的形状越不规则;比药量越大,液体分散效果越好,初始云团形成的速度越快,且初始云团半径也越大.     

二色补血草根中几种金属元素含量分析

采用微波消解-原子吸收光谱法对二色补血草根中K、Ca、Na、Mg、Zn、Fe、Cu和Mn八种金属元素含量进行了分析测定。结果表明,各元素平均回收率(n=7)在89%~96%之间能达到分析要求。八种金属元素在根中含量丰富,顺序为KNaMgCaFeZnCuMn。对金属元素含量的测定有助于阐明二色补血草的药用机理。     

核酸适配体技术在霉菌毒素检测中的应用

近年来,食品和饲料中的霉菌毒素污染对畜产品安全和人类健康构成严重威胁,带来了巨大的经济损失。对霉菌毒素检测技术的开发成为食品安全领域重要的研究内容。核酸适配体是指利用指数富集系统进化技术(SELEX)体外筛选得到的一类能够特异性地识别目标物的寡核苷酸序列,具有筛选程序简单,易于合成,性能稳定等优点,目前在食品安全检测、环境污染物监测以及临床诊断方面展现良好的应用前景。本文在介绍核酸适配体及其应用优势的基础上,综述目前筛选到的霉菌毒素适配体,以及核酸适配体技术在霉菌毒素检测中的应用与发展趋势。