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Several basic problems in plastic theory of geomaterials

Yuanxue LIU, Jiawu ZHOU, Zhongyou LI, Chen CHEN, Yingren ZHENG

《结构与土木工程前沿（英文）》 2009年第3卷第1期页码 81-84 doi: 10.1007/s11709-009-0016-3

摘要： Based on the basic mechanical properties of geomaterials, it was proven that the Drucker Postulate and the classical theory of plasticity can not be applied to geomaterials. Moreover, several basic problems of plastic theory of geomaterials were discussed. Based on the strict theoretical analysis, the following have been proven: the single yield surface model based on the classical theory of plasticity is unsuitable for geomaterials whether the rule of associated flow is applied or not; the yield surface of geomaterials is not unique, and its number is the same as the freedoms of plastic strain increment; the yield surface is not convex; and the rule of associated flow is unsuitable for geomaterials.

关键词： constitutive relation geomaterials classial plastic theory Drucker Postulate yield surface flow rule

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强度理论与实验现象

刘大斌,韩文坝,蔡冰清,韩晓东

《中国工程科学》 2007年第9卷第12期页码 44-52

摘要：用四大经典理论、莫尔强度理论和质点平衡强度理论的准则和强度条件，对单向拉压、二向拉压、纯扭转等已被认定的实验现象进行对比，对低、中碳钢重新做了纯扭转求最大屈服剪应力实验。发现质点平衡强度理论的符合率较高，13个实验中的有12个符合。尤其是拉伸—剪切使剪切破坏试验变得容易，压缩—剪切使剪切破坏试验变得困难的实验现象与质点平衡强度理论完全符合；莫尔强度理论也只有当拉伸和压缩极限强度不同时才能符合；其他强度理论都与此实验不符合。特别是当三向等应力拉伸（或压缩）时第三强度理论出现相当应力为零；三向等应力拉伸（或压

关键词：强度理论实验现象屈服现象应力状态

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The Rion-Antirion bridge—when a dream becomes reality

Jacques COMBAULT

《结构与土木工程前沿（英文）》 2011年第5卷第4期页码 415-426 doi: 10.1007/s11709-011-0130-x

摘要： Opened to traffic in August 2004, the Rion-Antirion Bridge crosses the Gulf of Corinth near Patras in western Greece. It consists of an impressive multi cable-stayed span bridge connected to the land by two approaches. An exceptional combination of physical conditions made this project quite unusual: high water depth, deep strata of weak soil, strong seismic activity and fault displacements. In addition a risk of heavy ship collision had to be taken into account. The structure has been designed in view of challenging severe earthquakes and ensuring the everyday serviceability of the link as well. To make the bridge feasible, innovative techniques had to be developed: The strength of the in situ soil has been improved by means of inclusions; the bridge deck has been suspended on its full length, and therefore isolated as much as it can be.

关键词： bridge multi cable-stayed spans soil reinforcement inclusions yield theory capacity design push-over dry dock wet dock

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PLANT DENSITY, IRRIGATION AND NITROGEN MANAGEMENT: THREE MAJOR PRACTICES IN CLOSING YIELD GAPS FOR AGRICULTURAL

《农业科学与工程前沿（英文）》 2021年第8卷第4期 doi: 10.15302/J-FASE -2020355

摘要：

Agriculture faces the dual challenges of food security and environmental sustainability. Here, we investigate current maize production at the field scale, analyze the yield gaps and impacting factors, and recommend measures for sustainably closing yield gaps. An experiment was conducted on a 3.9-ha maize seed production field in arid north-western China, managed with border and drip irrigation, respectively, in 2015 and 2016. The relative yield reached 70% in both years. However, drip irrigation saved 227 mm irrigation water during a drier growing season compared with traditional border irrigation, accounting for 44% of the maize evapotranspiration (ET). Yield variability under drip irrigation was 12.1%, lower than the 18.8% under border irrigation. Boundary line analysis indicates that a relative yield increase of 8% to 10% might be obtained by optimizing the yield-limiting factors. Plant density and soil available water content and available nitrogen were the three major factors involved. In conclusion, closing yield gaps with agricultural sustainability may be realized by optimizing agronomic, irrigation and fertilizer management, using water-saving irrigation methods and using site-specific management.

关键词： boundary line analysis irrigation method precision agriculture spatial variability yield gaps yield-limiting factors

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The effect of conservation tillage on crop yield in China

Hongwen LI,Jin HE,Huanwen GAO,Ying CHEN,Zhiqiang ZHANG

《农业科学与工程前沿（英文）》 2015年第2卷第2期页码 179-185 doi: 10.15302/J-FASE-2015058

摘要： Traditional agricultural practices have resulted in decreased soil fertility, shortage of water resources and deterioration of agricultural ecological environment, which are seriously affecting grain production. Conservation tillage (CT) research has been developed and applied in China since the 1960s and 1970s, and a series of development policies have been issued by the Chinese government. Recent research and application have shown that CT has positive effects on crop yields in China. According to the data from the Conservation Tillage Research Center (CTRC), Chinese Ministry of Agriculture (MOA), the mean crop yield increase can be at least 4% in double cropping systems in the North China Plain and 6% in single cropping systems in the dryland areas of North-east and North-west China. Crop yield increase was particularly significant in dryland areas and drought years. The mechanism for the yield increase in CT system can be attributed to enhanced soil water content and improved soil properties. Development strategies have been implemented to accelerate the adoption of CT in China.

关键词： conservation tillage crop yield soil structure development strategies

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Breeding strategies for increasing yield potential in super hybrid rice

Shihua CHENG,Xiaodeng ZHAN,Liyong CAO

《农业科学与工程前沿（英文）》 2015年第2卷第4期页码 277-282 doi: 10.15302/J-FASE-2015081

摘要： Super hybrid rice breeding is a new breeding method combining semi-dwarf breeding and heterosis breeding using germplasm and gene-environment interactions. This paper reviews the breeding strategies of super hybrid rice breeding in China, focusing on the utilization of heterosis of indica and japonica subspecies, construction of ideal plant architecture and pyramiding of disease resistant genes in restorer lines. To develop super hybrid rice, considerable effort should be made to explore genes related with high yield, good quality, resistance to pests and diseases, tolerance to stresses. Molecular breeding methods in combination with crossing techniques should be adopted in super hybrid rice breeding.

关键词： super hybrid rice breeding strategies yield potential

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Highlight yield forming and innovative technologies in tropical crops

Wenquan WANG

《农业科学与工程前沿（英文）》 2016年第3卷第4期页码 283-284 doi: 10.15302/J-FASE-2016128

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YIELD AND FRUIT QUALITY OF ALMOND, PEACH AND PLUM UNDER REGULATED DEFICIT IRRIGATION

《农业科学与工程前沿（英文）》 2021年第8卷第4期页码 583-593 doi: 10.15302/J-FASE -2020325

摘要：

The effects of regulated deficit irrigation (RDI) on the performance of almond cv. Tuono, peach cv. JH-Hall and plum cv. Stanley were assessed on the Saiss Plain (NW, Morocco) over three consecutive growing seasons (2011–2013). Irrigation treatments consisted of a control, irrigation applied to fully satisfy crop water requirements (100% ET_C), and two RDI treatments, irrigation applied to 75% ET_C (RDI-75) and 50% ET_C (RDI-50). These three treatments were applied during fruit-growth slowdown periods corresponding to Stages II and III in almond and Stage II in peach and plum. Yield and fruit quality traits were determined. The effect of RDI differed between species. Yield and fruit size were reduced significantly only in peach under RDI-50. Fruit quality improved in this species in the first year of the experiment, with an increase of sugar/acid ratio and polyphenol content. Plum quality also improved but the effects were significant only in the second and third years. Similar results were recorded in almond kernel, but their epidermal grooves were deeper under RDI-50, and this may have affected their commercial value. It is concluded that water can be saved during the fruit-growth slowdown period by up to 25% in peach and 50% in almond and plum with improvements in fruit quality without affecting total yield.

关键词： fruit quality / fruit yield / Prunus domestica / Prunus dulcis / Prunus persica / regulated deficit irrigation

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Estimating the effect of urease inhibitor on rice yield based on NDVI at key growth stages

Kailou LIU,Yazhen LI,Huiwen HU

《农业科学与工程前沿（英文）》 2014年第1卷第2期页码 150-157 doi: 10.15302/J-FASE-2014028

摘要： The effect of the urease inhibitor, N-(n-butyl) thiophosphoric triamide (NBPT) at a range of application rates on rice production was examined in a field experiment at Jinxian County, Jiangxi Province, China. The normalized difference vegetation index (NDVI) was measured at key growth stages in both early and late rice. The results showed that the grain yield increased significantly when urea was applied with NBPT, with the highest yield observed at 1.00% NBPT (wt/wt). NDVI differed with the growth stage of rice; it remained steady from the heading to the filling stage. Rice yield could be predicted from the NDVI taken at key rice growing stages, with ranging from 0.34 to 0.69 in early rice and 0.49 to 0.70 in late rice. The validation test showed that RMSE (t·hm ) values were 0.77 and 0.87 in early and late rice, respectively. Therefore, it was feasible to estimate rice yield for different amounts of urease inhibitor using NDVI.

关键词： normalized difference vegetation index (NDVI) N-(n-butyl) thiophosphoric triamide (NBPT) rice grain yield

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Lodging resistance and yield potential of winter wheat: effect of planting density and genotype

Yonggui XIAO,Jianjun LIU,Haosheng LI,Xinyou CAO,Xianchun XIA,Zhonghu HE

《农业科学与工程前沿（英文）》 2015年第2卷第2期页码 168-178 doi: 10.15302/J-FASE-2015061

摘要： Improved lodging resistance is important for achieving high yield in irrigated environments. This study was conducted to determine genotypic variation in lodging resistance and related morphological traits among winter wheat cultivars planted at two densities, and to identify key traits associated with lodging resistance. Lodging performance of 28 genotypes, including 24 released cultivars and four advanced lines, was evaluated at 250 plants per square meter and 500 plants per square meter in Shandong province during the 2008–2009 and 2009–2010 crop seasons. At the higher density, the average grain yield was 2.6% higher, even though lodging score rose by as much as 136%. The higher planting density increased lodging through increased leaf area index (LAI), plant height, center of gravity and length of basal internodes, and reduced grain weight per spike and diameter of the lower two stem internodes. LAI, center of gravity and diameter of first internodes, as the important indicators for lodging resistance, were significantly correlated with lodging score, with = 0.62, 0.59 and −0.52 ( <0.01), respectively. Plant pushing resistance was significantly associated with diameter and length of the first internodes ( = 0.71–0.77, <0.01), indicating it could be used to assess the strength of the lower stem. Higher planting density could be used to select genotypes with lodging resistance in irrigated environments. Cultivars carrying high plant density tolerance and high yield potential, such as Jimai 22 and Liangxing 66, were recommended as leading cultivars for production as well as elite crossing parents for further increasing yield potential in the Yellow and Huai Valleys Winter Wheat Zone in China.

关键词： common wheat yield potential lodging performance pushing resistance leaf area index

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Relationship between the number of tapping-induced secondary laticifer lines and rubber yield among

Yueyi CHEN,Xinsheng GAO,Xiaofei ZHANG,Weimin TIAN

《农业科学与工程前沿（英文）》 2016年第3卷第4期页码 363-367 doi: 10.15302/J-FASE-2016122

摘要： The lack of suitable early selection parameters means that traditional rubber breeding for yield is time-consuming and inefficient. Laticifer is a tissue specific for natural rubber biosynthesis and storage in rubber tree. The number of the secondary laticifers in the trunk bark tissues is positively correlated with rubber yield in the matured rubber trees that are regularly tapped. In the present study, the rubber yield from 280 of 4–5 year-old virgin trees from 7 cross combinations was compared with the number of newly differentiated secondary laticifers caused by tapping. Results showed that the number of tapping-induced lines of secondary laticifers varied in different germplasm and was positively related to the rubber yield, indicating this could be used as a suitable parameter for early evaluation of yield potential of rubber trees.

关键词： Hevea brasiliensis rubber yield breeding early evaluation tapping secondary laticifer differentiation

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PLANT DENSITY, IRRIGATION AND NITROGEN MANAGEMENT: THREE MAJOR PRACTICES IN CLOSING YIELD GAPS FOR AGRICULTURAL

Xiuwei GUO, Manoj Kumar SHUKLA, Di WU, Shichao CHEN, Donghao LI, Taisheng DU

《农业科学与工程前沿（英文）》 2021年第8卷第4期页码 525-544 doi: 10.15302/J-FASE-2020355

摘要： Agriculture faces the dual challenges of food security and environmental sustainability. Here, we investigate current maize production at the field scale, analyze the yield gaps and impacting factors, and recommend measures for sustainably closing yield gaps. An experiment was conducted on a 3.9-ha maize seed production field in arid north-west China, managed with border and drip irrigation, respectively, in 2015 and 2016. The relative yield reached 70% in both years. However, drip irrigation saved 227 mm irrigation water during a drier growing season compared with traditional border irrigation, accounting for 44% of the maize evapotranspiration (ET). Yield variability under drip irrigation was 12.1%, lower than the 18.8% under border irrigation. Boundary line analysis indicates that a relative yield increase of 8% to 10% might be obtained by optimizing the yield-limiting factors. Plant density and soil available water content and available nitrogen were the three major factors involved. In conclusion, closing yield gaps with agricultural sustainability may be realized by optimizing agronomic, irrigation and fertilizer management, using water-saving irrigation methods and using site-specific management.

关键词： boundary line analysis irrigation method precision agriculture spatial variability yield gaps yield-limiting factors

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Genomics approaches to unlock the high yield potential of cassava, a tropical model plant

Shengkui ZHANG,Ping’an MA,Haiyan WANG,Cheng LU,Xin CHEN,Zhiqiang XIA,Meiling ZOU,Xinchen ZHOU,Wenquan WANG

《农业科学与工程前沿（英文）》 2014年第1卷第4期页码 259-266 doi: 10.15302/J-FASE-2014043

摘要： Cassava, a tropical food, feed and biofuel crop, has great capacity for biomass accumulation and an extraordinary efficiency in water use and mineral nutrition, which makes it highly suitable as a model plant for tropical crops. However, the understanding of the metabolism and genomics of this important crop is limited. The recent breakthroughs in the genomics of cassava, including whole-genome sequencing and transcriptome analysis, as well as advances in the biology of photosynthesis, starch biosynthesis, adaptation to drought and high temperature, and resistance to virus and bacterial diseases, are reviewed here. Many of the new developments have come from comparative analyses between a wild ancestor and existing cultivars. Finally, the current challenges and future potential of cassava as a model plant are discussed.

关键词： cassava genomics yield potential adaptability tropical model

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iron-molybdate catalysts with various metal oxides by a mechanochemical method: enhanced formaldehyde yield

Xue Liu, Lingtao Kong, Shengtao Xu, Chaofan Liu, Fengyun Ma

《化学科学与工程前沿（英文）》 2021年第15卷第5期页码 1099-1110 doi: 10.1007/s11705-020-2008-8

摘要： A mechanochemical method was employed to prepare modified iron molybdate catalysts with various metal salts as precursors. The physicochemical properties of the iron molybdate catalysts were characterized, and their performances in catalyzing the reaction from methanol to formaldehyde (HCHO) were evaluated. Iron molybdate catalysts doped with Co(NO ) ·6H O and Al(NO ) ·9H O resulted in high HCHO yields. Compared with a commercial catalyst, the HCHO yields in the reaction with the modified catalyst at an optimal Co/Mo molar ratio reached 97.37%. According to chemical state analysis, the formation of CoO and the efficient decrease in the MoO sublimation rate could be important factors enhancing the HCHO yield in reactions catalyzed with iron molybdate doped with different Co/Mo mole ratios.

关键词： iron molybdate catalyst metal oxides methanol to formaldehyde Co/Mo ratio formaldehyde yield

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Electrorheological damper for the ultra-precision air bearing stage

ZHU Yu, JIA Songtao, CHEN Yaying, LI Guang

《机械工程前沿（英文）》 2008年第3卷第2期页码 158-163 doi: 10.1007/s11465-008-0031-4

摘要： This paper illustrates how the electrorheological damper substantially improves the performance of the ultra-precision air bearing stage. Smart materials such as electrorheological fluids have attracted many researchers’ attention because of their resistance changeable performance in different electric fields. Meanwhile, the ultra-precision air bearing stage driven by the linear-motor is characterized by zero mechanical damping and poor anti-disturbance. To solve this problem and consider the characteristics of electrorheological fluids, an electrorheological damper is proposed in this paper. The electrorheological damper’s characteristics in high electric fields are obtained based on the Eyring constitutive model, which smoothly transits from the pre-yield to post-yield region. To enhance the performance of the electrorheological damper, which takes effect only when the stage is going to decelerate or position, the on-off and sliding mode control methods design and optimize the controller. The results prove that by using the advanced sliding mode control method, the characteristics of the ultra-precision air bearing stage can be effectively improved through the introduction of the electrorheological damper.

关键词： post-yield linear-motor advanced sliding pre-yield position