确定插齿刀廓形的方法及精度分析   总被引：1，自引：0，他引：1  

赵敬云  徐珂 《拖拉机与农用运输车》2006,33(6):90-91,96

论述了由插齿刀前锥面和螺旋面方程确定的母面廓形,提出了保证插齿刀原始廓形角的3个条件,由此推出了计算廓形角的3种方法,得出了廓形角及基圆半径的计算公式,然后对3种方法的误差进行分析,计算表明第3种方法误差较小,是一种较好方法。  相似文献   

五节芒栽培糙皮侧耳的子实体质构分析   总被引：1，自引：0，他引：1  

聂国添  黄千慧  苗娟  李肖  龙莹  张磊  连玲丹  谢斌  江玉姬  谢宝贵 《食用菌学报》2016,(1):31-36

利用质构分析仪,比较分析分别以五节芒(Miscanthus floridulus)和棉籽壳为主料栽培获得的糙皮侧耳(Pleurotus ostreatus)子实体的质构指标,同时测算二者干制率和杀青率差异。结果表明,相对于常规棉籽壳培养料栽培,菌草配方栽培糙皮侧耳的菌盖咀嚼性、硬度和回复性较差,菌柄回复性、硬度、内聚性和咀嚼性较差,而且子实体的干制率和杀青率也较低。  相似文献   

高能复合酶蛋白饲料对生长育肥猪生长性能、脂肪酸组成的影响     

高侠  边连全  郭伟 《畜禽业》2006,(19):22-24

本试验探讨高能复合酶蛋白饲料对生长育肥猪生长性能、脂肪酸组成的影响。试验采用60头生长育肥猪,分为4个处理,每个处理3组,每组5头猪。研究表明:第Ⅳ组平均日增重、平均日采食量下降,与其它3组相比差异极显著(p<0.01);第四组的料重比高于其它3组,并且与第一组、第二组之间差异显著(p<0.05)。各组之间棕榈酸、硬脂酸、油酸、亚油酸的含量差异均极显著(p<0.01)。结论:高能复合酶蛋白饲料的适宜添加量为5%￣10%。  相似文献   

Satisfaction across urban consumers of smallholder-produced teak (Tectona grandis L.f.) poles in South Benin     

Augustin K.N. Aoudji  Anselme Adégbidi  Jean C. Ganglo  Valentin Agbo  Armand S.I. Yêvidé  Charles De Cannière  Philippe Lebailly 《Forest Policy and Economics》2011,13(8):642-651

The study used the expectancy-disconfirmation framework to investigate the satisfaction among urban consumers of teak pole in South Benin, so as to identify the areas where interventions are needed to secure market opportunity for smallholder forestry. A survey was conducted in five cities; and 223 household-heads were interviewed using systematic sampling, with a random start. Data were collected on socio-demographic characteristics, teak pole consumption forms, behaviour patterns, and motivations. Respondents also rated their expectations and perceptions for a set of nine attributes on a 7 points Likert scale. Hierarchical ascending cluster analysis was performed to identify consumer segments; and satisfaction level was analysed per segment, by determining the gap between expectations and perceptions, for all attributes. Four consumer segments were identified; and sociodemographic profiles differed across those segments. Competitive price was an important purchasing motivation across the identified segments. Consumers were dissatisfied with price, availability, knot frequency, bending, length, hardness, and durability of teak pole. The efforts to meet the consumer expectations should be concentrated on building farmers' capacity in silvicultural management, and ensuring the availability of good planting material. The issue of competitive price might be addressed, through the improvement of the overall efficiency in the value chain.  相似文献   

不同施肥措施对土壤硝态氮垂直分布的特征影响   总被引：16，自引：1，他引：16  

刘方春  聂俊华  刘春生  付连刚  肖秋生 《土壤通报》2005,36(1)

通过田间试验研究了冬小麦收获后NO3--N在土壤剖面中的累积状况。研究结果表明:不论是单独施用无机、生物有机肥还是无机、有机肥混施都会造成硝酸盐在土壤中的积累,但有机肥本身产生的硝酸盐累积量极微。生物有机、元机肥混施后减少了无机肥料中硝态氮深层累积。在0-100cm土层中,硝态氮的累积量呈递减趋势,在0-40cm的累积量最高。砂质土壤比牯质土壤更有利于硝态氮的深层迁移。  相似文献   

纵剖优选锯主轴调整系统结构的设计与仿真分析     

杨春梅  杨存亮  詹东  蒋婷  马岩 《林产工业》2019,46(3):9-13

针对传统板材锯切设备大多数处于半自动化状态,且存在加工精度低、出材率低、安全性差等缺点,笔者提出一种用于毛边板材裁边的纵剖优选锯设备的主轴调整系统。通过对毛边板材的裁边工艺进行分析,利用三维软件对纵剖优选锯主轴调整系统结构进行实体建模,确定了纵剖优选锯主轴调整系统的总体结构。对主轴组件上的锯片切削力和切削功率进行详细的设计计算,完成了主轴调整系统的主轴组件、锯片调整组件等结构的设计研究。根据锯片滑台最大许用应力和最大变形量对其进行有限元静力学仿真分析,通过仿真结果校核得出的锯片滑台满足设计要求。设计的纵剖优选锯主轴调整系统结构具有适用于产品多规格、高出材率、高自动化和实用性强的特点。  相似文献   

发动机异形活塞加工系统及其动态性能研究     

刘廷章  叶冰  卢秉恒 《农业机械学报》1998,29(2):121-125

提出了发动机非圆异形活塞裙面的一种新型车削方法,采用振动技术实现非圆截面的高频响微位移进人,采用步进电机实现中凸型线控制。这种高频车削方法的系统动态特性是影响复杂轮廓精度的主要因素,本文通过激振实验对此进行了研究,提出了相应的改进措施及补偿策略,保证了系统良好的加工性能。  相似文献   

Effects of nature sounds on the attention and physiological and psychological relaxation     

《Urban Forestry & Urban Greening》2023

This study aims to verify the effects of nature sounds on attention, and physiological and psychological relaxation. Twenty-six university students (mean age: 21.5 ± 1.9 years) participated in this study, and the experiment was conducted with one person at a time. A mixed sound of valley water and birds in a forest environment was used as the nature sound, and a road traffic sound was used as the urban sound (control). The participants performed the following steps: (1) closed their eyes and rested for 1 min; (2) opened their eyes and completed attention tasks while hearing nature or urban sounds for 1 min; (3) closed their eyes again and rested while hearing the same sound for 1 min. We used Harris and Harris grid for the attention task. We measured the participants’ oxy-hemoglobin concentration, heart rate variability, and heart rate for physiological evaluation, and used semantic differential method, and profile of mood states for psychological evaluation. As a result, ① There was no significant difference in the results of the attention task; however, the scores were slightly higher when hearing nature sound. ② The oxy-hemoglobin concentration and heart rate was lower, and parasympathetic nerve activity was enhanced when hearing nature sound than when hearing urban sound. ③ Once participants heard nature sound, they felt more comfortable, relaxed, and natural, and the negative mood state was lower, while the positive mood state was higher than urban sound. This suggests that hearing nature sounds may be an effective way to relieve stress in everyday life.  相似文献   

Suitability of tef varieties in mixed wheat flour bread matrices: A physico-chemical and nutritional approach     

《Journal of Cereal Science》2015

Wheat flour replacement from 0 to 40% by single tef flours from three Ethiopian varieties DZ-01-99 (brown grain tef), DZ-Cr-37 (white grain tef) and DZ-Cr-387 (Quncho, white grain tef) yielded a technologically viable ciabatta type composite bread with acceptable sensory properties and enhanced nutritional value, as compared to 100% refined wheat flour. Incorporation of tef flour from 30% to 40% imparted discreet negative effects in terms of decreased loaf volume and crumb resilience, and increase of crumb hardness in brown tef blended breads. Increment of crumb hardness on aging was in general much lower in tef blended breads compared to wheat bread counterparts, revealing slower firming kinetics, especially for brown tef blended breads. Blended breads with 40% white tef exhibited similar extent and variable rate of retrogradation kinetics along storage, while brown tef-blended breads retrograded slower but in higher extent than control wheat flour breads. Breads that contains 40% tef grain flour were found to contain five folds (DZ-01-99, DZ-Cr-387) to 10 folds (DZ-Cr-37) Fe, three folds Mn, twice Cu, Zn and Mg, and 1.5 times Ca, K, and P contents as compared to the contents found in 100% refined wheat grain flour breads. In addition, suitable dietary trends for lower rapidly digestible starch and starch digestion rate index were met from tef grain flour fortified breads.  相似文献   

Optimisation of rheological properties of gluten-free doughs with HPMC,psyllium and different levels of water     

《Journal of Cereal Science》2015

Hydrocolloids have traditionally been investigated as an alternative to gluten for making good quality products for coeliac patients. This study investigated the interactions between hydroxypropylmethylcellulose (HPMC) (2–4 g/100 g of flour), psyllium (0–4 g/100 g of flour) and water level (90–110 g/100 g of flour) in gluten-free breadmaking. Psyllium incorporation reduced the pasting temperature and compliance values, and increased elastic (G′) and viscous (G″) moduli values. In contrast, HPMC addition had no important effects on pasting properties and compliance values, but also increased G′ and G″ values. Psyllium inclusion reduced bread specific volume and increased bread hardness, while there were hardly differences in the bread specific volume and hardness between the percentages of HPMC studied. In addition, when the dough hydration level was increased, there was a decrease in the influence of hydrocolloids on dough rheology and specific volume and hardness of breads.  相似文献