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1.
针对电动无人机应用于农业遥感监测时受其续航时间限制的问题,从实际应用角度出发,设计了一种续航时间长、适用于农业遥感监测的翼身融合布局的轻型电动固定翼无人机。提出了翼身融合布局轻型固定翼无人机的总体设计方法,确定了轻型固定翼无人机的结构参数,建立了物理模型并对其参数进行了优化分析。通过计算流体力学(Computational fluid dynamics,CFD)分析计算了翼身融合布局轻型固定翼无人机的气动性能,基于流固耦合模型动态分析了其飞行状态下的受力分布。结果表明,优化模型较初始设计模型的升阻比提高了2.6%,在迎角为6°、巡航速度为15.5 m/s时,所设计的翼身融合布局轻型固定翼无人机机身压力分布合理,且拥有良好的气动特性。起飞质量为1.5 kg时,无人机下表面压力最大,为143 Pa,升力主要集中在机翼前缘部分,计算所得理论续航时间为65 min,在巡航阶段最大变形量0.288 38 mm,符合飞行器工作条件,无人机结构和选用材料均满足设计和使用要求。本文设计的电动轻型固定翼农用遥感无人机在结构、材料和性能方面均适用于农业遥感监测。  相似文献   
2.
Non-edible parts of crustaceans could be a rich source of valuable bioactive compounds such as the carotenoid astaxanthin and peptides, which have well-recognized beneficial effects. These compounds are widely used in nutraceuticals and pharmaceuticals, and their market is rapidly growing, suggesting the need to find alternative sources. The aim of this work was to set up a pilot-scale protocol for the reutilization of by-products of processed shrimp, in order to address the utilization of this valuable biomass for nutraceutical and pharmaceuticals application, through the extraction of astaxanthin-enriched oil and antioxidant-rich protein hydrolysates. Astaxanthin (AST) was obtained using “green extraction methods,” such as using fish oil and different fatty acid ethyl esters as solvents and through supercritical fluid extraction (SFE), whereas bioactive peptides were obtained by protease hydrolysis. Both astaxanthin and bioactive peptides exhibited bioactive properties in vitro in cellular model systems, such as antioxidant and angiotensin I converting enzyme (ACE) inhibitory activities (IA). The results show higher astaxanthin yields in ethyl esters fatty acids (TFA) extraction and significant enrichment by short-path distillation (SPD) up to 114.80 ± 1.23 µg/mL. Peptide fractions of <3 kDa and 3–5 kDa exhibited greater antioxidant activity while the fraction 5–10 kDa exhibited a better ACE-IA. Lower-molecular-weight bioactive peptides and astaxanthin extracted using supercritical fluids showed protective effects against oxidative damage in 142BR and in 3T3 cell lines. These results suggest that “green” extraction methods allow us to obtain high-quality bioactive compounds from large volumes of shrimp waste for nutraceutical and pharmaceutical applications.  相似文献   
3.
The objective of this study was to evaluate the effects of feeding vitamin and mineral (VTM) supplement and (or) rate of gain (GAIN) during early gestation on amino acid (AA) concentrations in allantoic fluid (ALF) and amniotic fluid (AMF) and maternal serum. Seventy-two crossbred Angus heifers (initial BW = 359.5 ± 7.1 kg) were randomly assigned to one of four treatments in a 2 × 2 factorial arrangement with main effects of VTM supplement (VTM or NoVTM) and rate of gain (GAIN; low gain [LG], 0.28 kg/d, vs. moderate gain [MG], 0.79 kg/d). The VTM treatment (113 g•heifer−1•d−1, provided macro and trace minerals and vitamins A, D, and E to meet 110% of the requirements specified by the NASEM in Nutrient requirements of beef cattle. Washington, DC: The National Academies Press. doi:10.17226/19014, 2016) was initiated 71 to 148 d before artificial insemination (AI). To complete the factorial arrangement of treatments, at breeding heifers were either maintained on the basal diet (LG), or received MG diet which was implemented by adding a protein/energy supplement to the LG diet. Thirty-five gestating heifers with female fetuses were ovariohysterectomized on d 83 of gestation and maternal serum, ALF, and AMF were collected. Samples were analyzed for concentrations of neutral AA: Ala, Asn, Cys, Gln, Gly, Ile, Leu, Met, Phe, Pro, Ser, Thr, Trp, Tyr, and Val; cationic AA: Arg, His, and Lys; and anionic AA: Asp and Glu. In serum, a VTM × GAIN interaction (P = 0.02) was observed for Glu, with greater concentrations for VTM-LG than VTM-MG. Concentrations of serum Cys, Met, and Trp were greater (P ≤ 0.03) for MG than LG. In ALF, concentrations of Glu were affected by a VTM × GAIN interaction, where VTM-MG was greater (P < 0.01) than all other treatments. Further, ALF from VTM had increased (P ≤ 0.05) concentrations of His, Asp, and 12 of the 14 neutral AA; whereas GAIN affected concentrations of Arg, Cys, and Asp, with greater concentrations (P ≤ 0.05) in MG heifers. In AMF, AA concentrations were not affected (P ≥ 0.10) by VTM, GAIN, or their interaction. In conclusion, increased concentrations of AA in maternal serum and ALF of beef heifers were observed at d 83 of gestation in response to VTM supplementation and rate of gain of 0.79 kg/d, which raises important questions regarding the mechanisms responsible for AA uptake and balance between the maternal circulation and fetal fluid compartments.  相似文献   
4.
5.
猪活动区域多孔介质模型及其阻力系数的CFD模拟   总被引:1,自引:0,他引:1  
旨在尝试将躺卧姿势下的猪体简化成不同几何形状以求取其阻力系数,并分析它们的差异性。本研究采用校核过的CFD模型,模拟探究了简化猪模型、半椭球模型、椭球模型和半圆柱模型4种不同躺卧猪模型对猪群区域在X、Y和Z3个垂直方向上阻力系数的影响,分析了4种模型对猪栏内气流以及压力分布的影响。结果表明,椭球模型的惯性阻力系数相比半椭球模型与半圆柱模型更加接近简化猪模型,其在X、Z和Y方向上的惯性阻力系数与简化猪模型之间的相对误差分别为-4.0%、-12.2%和14.7%,并且气流与压力分布基本一致。因此,采用椭球模型代替简化猪模型进行建模计算不仅能保证准确度还能有效提高计算效率。  相似文献   
6.
水泵水轮机是抽水蓄能电站的核心部件,水泵水轮机的轴向力特性对其运行稳定性与安全性具有主要影响。作为一种典型的立式机组,为防止抬机事故的发生,机组转轮部分需要具有向下的轴向力,但在泵工况下,该轴向力容易过大,并可能引起机组下沉。采用计算流体动力学方法,研究分析抽水蓄能水泵水轮机泵工况不同流量与活动导叶开度下的轴向力特性。研究结果表明,在泵小流量、小导叶开度、高扬程的工况下,向下的轴向力较大;采用对称布置的均压管路连接转轮上冠腔体与尾水管,轴向力变为轻微向上,扬程与水力效率无显著变化,有效解决了机组泵工况向下轴向力较大的问题,机组运行的安全性与稳定性得到了显著提高。  相似文献   
7.
Objective : To investigate the association between synthetic colloids and biomarkers of acute kidney injury (AKI) in dogs with hemorrhagic shock. Design : Experimental interventional study. Setting : University. Animals : Twenty‐four healthy ex‐racing Greyhounds. Interventions : Anesthetized Greyhounds subjected to hemorrhage for 60 min were resuscitated with 20 mL/kg of fresh whole blood (FWB), 6% hydroxyethyl starch (HES) 130/0.4, 4% succinylated gelatin (GELO), or 80 mL/kg of isotonic crystalloid (CRYST) over 20 min (n = 6 per treatment). Concentrations of biomarkers of AKI were measured at baseline, end of hemorrhage, and at 40 (T60), 100 (T120), and 160 (T180) min after fluid bolus. Biomarkers included neutrophil gelatinase‐associated lipocalin in urine and serum (uNGAL; sNGAL), and urine cystatin C (uCYSC), kidney injury molecule‐1 (uKIM), clusterin (uCLUST), osteopontin, gamma‐glutamyl transferase, monocyte chemoattractant protein‐1 (uMCP), interleukin‐6, interleukin‐8, protein (uPROT), hyaluronan, and F2‐isoprostanes. Renal histology was scored for tubular injury and microvesiculation. Biomarker fold‐change from baseline was compared between groups using mixed effects models (Bonferroni–Holm corrected P<0.05). Frequencies of histology scores were compared by Fisher's exact test. Measurements and main results : In dogs treated with GELO, uNGAL fold‐change was markedly greater compared with all other groups at T60, T120, and T180 (all P<0.001), and uCYSC was greater at T60 compared with CRYST (P<0.001), and at T120 and T180 compared with all other groups (all P<0.001). Smaller, albeit significant, between‐group differences in uKIM, uCLUST, uMCP, and urine protein concentration were observed across the FWB, GELO, and HES groups, compared with CRYST. The GELO group more frequently had marked tubular microvesiculation than the other groups (P = 0.015) although tubular injury scores were comparable. Conclusion : In dogs with hemorrhagic shock, GELO was associated with greater magnitude increases in urine biomarkers of AKI and more frequent marked tubular microvesiculation, compared with FWB, CRYST, and HES.  相似文献   
8.
为优化4层层叠式笼养鸭舍舍内环境,基于计算流体动力学(computational fluid dynamics,CFD)对鸭舍内气流场、温度场及CO_2浓度场进行模拟。将笼架简化,考虑其对气流的阻挡作用,将鸭笼及鸭只视为多孔介质。模拟结果显示,进风口为湿帘时,侧墙湿帘与端墙之间存在通风死区,风速低于0.5 m·s~(-1)。进风口为通风小窗时,鸭舍未安装通风小窗区域风速小,CO_2浓度大。改变纵墙湿帘位置对鸭舍结构进行改进,改进后气流不均匀系数降低了17%。改进通风小窗布置发现,提升通风小窗分布均匀性显著降低舍内温差;提升通风小窗安装高度将显著降低舍内CO_2浓度。该研究可为蛋鸭舍结构设计提供参考。  相似文献   
9.
BackgroundDiseases related to cerebrospinal fluid flow, such as hydrocephalus, syringomyelia, and Chiari malformation, are often found in small dogs. Although studies in human medicine have revealed a correlation with cerebrospinal fluid flow in these diseases by magnetic resonance imaging, there is little information and no standard data for normal dogs.ObjectivesThe purpose of this study was to obtain cerebrospinal fluid flow velocity data from the cerebral aqueduct and subarachnoid space at the foramen magnum in healthy beagle dogs.MethodsSix healthy beagle dogs were used in this experimental study. The dogs underwent phase-contrast and time-spatial labeling inversion pulse magnetic resonance imaging. Flow rate variations in the cerebrospinal fluid were observed using sagittal time-spatial labeling inversion pulse images. The pattern and velocity of cerebrospinal fluid flow were assessed using phase-contrast magnetic resonance imaging within the subarachnoid space at the foramen magnum level and the cerebral aqueduct.ResultsIn the ventral aspect of the subarachnoid space and cerebral aqueduct, the cerebrospinal fluid was characterized by a bidirectional flow throughout the cardiac cycle. The mean ± SD peak velocities through the ventral and dorsal aspects of the subarachnoid space and the cerebral aqueduct were 1.39 ± 0.13, 0.32 ± 0.12, and 0.76 ± 0.43 cm/s, respectively.ConclusionsNoninvasive visualization of cerebrospinal fluid flow movement with magnetic resonance imaging was feasible, and a reference dataset of cerebrospinal fluid flow peak velocities was obtained through the cervical subarachnoid space and cerebral aqueduct in healthy dogs.  相似文献   
10.
In this study, sperms collected from the right and left cauda epididymis were grouped into having canine prostatic fluid (PF) sensitization or not diluted with egg yolk Tris–fructose citrate extender, and stored at 4°C. The necessity of canine PF in cooled preservation was determined by elucidating the sperm quality after the storage. As a result, while there was no difference among all groups up to 48 hr of storage, after storage for 96 hr and more, a significantly lower sperm motility was observed in the group without being sensitized to PF than the groups with being sensitized to PF (p < .05, p < .01). Although sperm abnormality increased in all groups with increased storage time, the group without being sensitized to PF showed significantly higher sperm abnormality than did the groups with being sensitized to PF after storage for 24 hr and more (p < .01). From these findings, we concluded that PF was necessary for the cooled preservation of the canine sperm because these sperms were protected from any effects of low temperatures by being sensitized to PF.  相似文献   
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