Optimization potential for perception-oriented appearance classification by simulated sawing of computed tomography-scanned logs of Norway spruce     

《Wood material science & engineering》2013,8(4):319-334

Abstract

Wood, as a natural material, has favourable properties in both technical and aesthetic aspects. Due to its inherent variability, production of high-quality sawn timber demands adequate control of log conversion, which is feasible with computed tomography (CT) log scanning. Existing appearance grading rules for sawn timber might not fully reflect people's visual perception of wood surfaces, and therefore, an alternative, more perception-oriented appearance classification could be beneficial. An appearance classification of sawn timber based on partial least squares discriminant analysis (PLS-DA) of knot-pattern variables was developed and tested. Knot-pattern variables derived from images of board faces were used in training PLS-DA models against an initial classification of the board faces previously established by aid of cluster analysis. Virtual board faces obtained from simulated breakdown of 57 CT-scanned Norway spruce logs were graded according to the developed classification. Visual assessment of the grading results indicated that the classification was largely consistent with human perception of board appearance. An initial estimation of the potential to optimize log rotation, based on CT data, for the established appearance grades was derived from the simulations. Considerable potential to increase the yield of a desired appearance grade, compared to conventional log positioning, was observed.  相似文献   

拱坝坝肩抗滑承载能力极限状态材料分项系数研究   总被引：3，自引：0，他引：3  

刘国华  杨伟俊  范庆来 《中国农村水利水电》2003,(11):62-63,66

对拱坝坝肩岩体抗滑稳定中承载能力极限状态设计表达式中的材料分项系数的取值进行了分析计算与探讨，提出了分项系数取值建议，供相关规范制定时参考。可靠度分析结果表明，按建议的分项系数取值方案进行设计，可使坝肩抗滑稳定在不同设计条件下，具有较佳的可靠度及一致性。  相似文献   

Tracing Pb Pollution Penetration in Temperate Podzols     

《Land Degradation \u0026amp; Development》2017,28(8):2432-2445

We combine high‐resolution soil sampling with lead (Pb) analyses (concentrations and stable isotopes) in two temperate podzols, together with previous data obtained with selective Al and Fe dissolution techniques. We aim to assess how atmospheric Pb is incorporated into the soils during pedogenesis. Partial least squares modelling for Pb concentrations shows that the podzolization process has the largest effect on Pb concentration (80·3% of the variance). The proportion of inorganic secondary compounds, the input of fresh organic matter from the soil surface and the relative abundance of Fe versus Al are responsible for a small part of the Pb concentration variance. Lead isotopic composition (²⁰⁶Pb/²⁰⁷Pb ratios) depends on soil organic matter content either fresh/poorly humified (57·3% of the variance) or humified (24·7% of the variance). The Pb linked to inorganic compounds and the overall podzolization process play a minor role in isotopic signature (5·3 and 3·7% of the variance respectively). Soil pH appears to be the controlling variable of the different transport and retention mechanisms. The relatively low isotopic ratios observed in spodic horizons result from geogenic Pb released through the preferential dissolution of the isotopically distinct most weatherable minerals of the parent material in the eluvial horizons, which undergoes downward mobilization. An accurate knowledge of soil reactive components and formation mechanisms is essential to a correct diagnose of the scope of Pb pollution and a more effective design of remediation strategies. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Land Cover Transition in Northern Tanzania     

Issa Ouedraogo  Jennie Barron  Siza D. Tumbo  Frederic C. Kahimba 《Land Degradation \u0026amp; Development》2016,27(3):682-692

Land conversion in sub‐Saharan Africa has profound biophysical, ecological, political and social consequences for human well‐being and ecosystem services. Understanding the process of land cover changes and transitions is essential for good ecosystem management policy that would lead to improved agricultural production, human well‐being and ecosystems health. This study aimed to assess land cover transitions in a typical semi‐arid degraded agro‐ecosystems environment within the Pangani river basin in northern Tanzania. Three Landsat images spanning over 30 years were used to detect random and systematic patterns of land cover transition in a landscape dominated by crop and livestock farming. Results revealed that current land cover transition is driven by a systematic process of change dominated by the following: (i) transition from degraded land to sparse bushland (10·8%); (ii) conversion from sparse bushland to dense bushland in lowland areas (6·0%); (iii) conversion from bushland to forest (4·8%); and (iv) conversion from dense bushland to cropland in the highlands (4·5%). Agricultural lands under water harvesting technology adoption show a high degree of persistence (60–80%) between time slices. This suggests that there is a trend in land‐use change towards vegetation improvement in the catchment with a continuous increase in the adoption of water harvesting technologies for crop and livestock farming. This can be interpreted as a sign of agricultural intensification and vegetation regrowth in the catchment. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Improvement and Application on Back Propagation Network Based on Partial Least-squares Algorithm     

LIU Qiong-sun  ZHANG Yan-fen 《保鲜与加工》2007,(7):148-151

This paper proposes a novel BP network model based on nonlinear iterative partial least-squares algorithm which can fit nonlinear data. The novel BP network model can reduce iterative step number and advance learning effieieney. This paper pretreats data by nonlinear iterative partial least-squares algorithms. The weights initialization of input floor and output floor are set by applying the loading weights of dependent variable and cause variable, the member of hidden nodes are set by applying factor numbers of nonlinear iterative partial leastsquares algorithm, the connection co- efficient is set by applying the connection matrix B. Performances of the BP, PLS, and PLS-BP are analyzed and compared. The results show that the PLS-BP has better fitting and forecasting than BP and PLS.  相似文献   

散装小麦局部环流熏蒸杀虫实仓试验   总被引：2，自引：1，他引：2  

祝超明  杨大成  杜秀琼  郜贺鹏  吴峡  王治德  张再杰  秦军  阳岭峰 《粮食储藏》2003,32(3):18-20,41

针对小麦仓中下层局部生虫，采用粮堆局部处理机环流熏蒸，分两次投药，共计熏蒸处理时间为两周。实验证明：在处理部位PH3浓度100～300ppm可以保持12天左右，粮堆中的害虫全部杀死；经检查埋入粮堆的赤拟谷盗、谷蠹和玉米象，成虫死亡率100％，对虫粮培养42天后，检查F1代为零。  相似文献   

Influence of race and post infection temperature on two components of partial resistance to wheat leaf rust in seedlings of wheat   总被引：2，自引：0，他引：2  

C. J. M. Denissen 《Euphytica》1991,58(1):13-20

Summary Components of partial resistance, infection frequency and latency period, were determined in 71 winter and spring wheat genotypes in the seedling stage, after infection with three races of leaf rust (Felix 3B, Clement B and Betuwe 85C) at three different day/night temperature regimes (24/18°C, 18/12°C and 12/6°C). The genotypes were split into two groups and two separate experiments were carried out. Five genotypes, SVP 84039, Akabozu, Banco, BH 1146 and Orso, conferred a low infection frequency and a long latency period and Westphal 12A a long latency period, indicating a relatively high level of partial resistance. The correlation coefficient between infection frequency and latency period was low. Race-specificity was not found. There was a significant temperature effect on the latency period. In the second experiment the temperature x genotype interaction was significant. Temperature-response functions of transformed data demonstrated that the latency periods of four relatively resistant genotypes, Westphal 12A, Banco, BH 1146 and Orso and of Sarno and Mirela were most sensitive to temperature. The range between the genotypes with the longest and the shortest latency period was highest at 12°C. Therefore, low temperature regimes are preferred to distinguish differences in level of partial resistance.  相似文献   

Selection for partial resistance to downy mildew in peas by means of greenhouse tests     

Rolf Stegmark 《Euphytica》1991,53(2):87-95

Summary A partially downy mildew resistant pea line was back-crossed to a susceptible cultivar with more pods per node and lower seed weight. Breeding lines with different degrees of infection in a greenhouse test were selected. These lines and the two parental lines were investigated in field trials and tested in the greenhouse for four generations. Significant genetic variation among lines was found for infection of seedlings in greenhouse tests, and infection of pods, pod set and seed weight in field-trials. Infection of seedlings in the greenhouse was correlated with infection of pods in the field. In greenhouse tests, the non-genetic variance component was large in comparison with the genetic component and a significant genotype trial interaction was found. Significant repeatability was obtained for downy mildew on seedlings and pods, number of pods per node and seed weight. An unfavourable correlation between susceptibility to downy mildew and number of pods per node was found. No single breeding line showed the ideal combination of good resistance, high number of pods per node and small seeds. However, one line showing better resistance than the susceptible parent, with smaller seeds and more pods per node than the resistant parent was found. The susceptible parent also carries some resistance factor that is not present in the resistant parent.  相似文献   

The importance of abortive stoma penetration in the partial resistance and nonhost reaction of adult barley and wheat plants to leaf rust fungi     

R. E. Niks 《Euphytica》1987,36(3):725-731

Summary Early stages of the infection process of Puccinia hordei isolate 1.2.1 and of a P. recondita f.sp. tritici isolate were studied on adult plants of four barley lines and one wheat line. Two of the barley lines are extremely susceptible to P. hordei, the other two have a very high level of partial resistance.A histological study based on a trypan blue staining indicated that stoma penetration by P. hordei isolate 1.2.1 was equally successful on the susceptible as on the partially resistant adult barley plants. Abortion of substomatal vesicles was rare in all lines. These results do not support a hypothesis that mechanisms of partial resistance in adult plants differ from those in seedlings by a substantial abortive stoma penetration.Also in the nonhost combinations wheat-P. hordei and barley-P. recondita f.sp. tritici inhibition of stoma penetration and of substomatal vesicle development appears to play a biologically insignificant role in adult plants.The proportion of stoma penetration on the leaf sheaths of two of the barley lines was as high as on the leaf blades of the flag leaf and the leaf below the flag leaf. There was no evidence for stomatal exclusion as a crucial factor in the relatively low infectibility of leaf sheaths to leaf-blade specialized rust species.  相似文献   

Field assessment of partial resistance to powdery mildew in spring barley     

J. Chr. Nørgaard Knudsen  H. H. Dalsgaard  J. Helms 《Euphytica》1986,35(1):233-243

Summary Partial resistance to powdery mildew in spring barley was evaluated in three plot types: large isolation plots, in 1.4 m² plots in chessboard design with guard plots of spring wheat and in single rows. Percentage leaf area covered by powdery mildew was scored four to six times during the season and partial resistance was characterized by the area under the disease progress curve. Varietal differences were revealed in al three plot designs, differences between the most resistant and susceptible genotypes being of a factor five. Differences between varieties decreased with decreasing plot size. The relationship between single scores of amount of powdery mildew on the upper four leaves and the area under the disease progress curve was high in all plot designs during the first two to three weeks after heading, allowing selection for the trait by one or two scorings. Differential ranking of varieties between different plot designs was observed, and is assumed to be due to increasing plot interference with reduced plot size and reduced distance between plots. A reliable selection for partial resistance could be made in large isolation plots and in 1.4 m² plots, but hardly in single rows.  相似文献