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  • Author: Cheng Yang x
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Abstract

The extra-large parachutes were different from the common parachutes because of their size and opening process. Some undesirable inflation phenomena such as canopy winding and whipping usually appeared in their pre-inflation process. However, the mechanical mechanism of these phenomena was very difficult to be explained by experimental means. In this paper, the pre-inflation process in finite mass situation of an extra-large parachute was calculated by explicit finite elements. According to the results, the pre-inflation process can be subdivided into symmetric inflation stage, undesirable inflation stage, and stable inflation stage. The canopy winding and whipping mainly occurred in the second stage. With the continuous deceleration of parachute-payload system, the top of canopy without effective constraints would appear winding and whipping under the function of inertia force. The canopy winding and whipping increased the difficulty of canopy expanding and then caused asymmetric inflation. The above undesirable phenomena had a great influence on the deceleration effect and were easy to cause the recovery failure. The actual airdrop experiments also proved that the lack of effective constraints on the canopy top will cause undesirable inflation phenomena. The conclusions in this paper can also provide a reference for extra-large parachute design and research.

Abstract

The current study is a simplification of related components of large floating roof tank and modeling for three dimensional temperature field of large floating roof tank. The heat transfer involves its transfer between the hot fluid in the oil tank, between the hot fluid and the tank wall and between the tank wall and the external environment. The mathematical model of heat transfer and flow of oil in the tank simulates the temperature field of oil in tank. Oil temperature field of large floating roof tank is obtained by numerical simulation, map the curve of central temperature dynamics with time and analyze axial and radial temperature of storage tank. It determines the distribution of low temperature storage tank location based on the thickness of the reservoir temperature. Finally, it compared the calculated results and the field test data; eventually validated the calculated results based on the experimental results.

Abstract

Introduction

This study aimed to characterise the effects of ketosis on milk yield and composition and digestive capacity in transition dairy cows.

Material and Methods

Seven ketotic and seven healthy cows were housed in individual stalls for six days. Samples of plasma, milk, refused total mixed ration, and faeces were collected, and the blood biochemical parameters, milk yield and composition, dry matter intake, and faecal dry matter (FDM) production were determined.

Results

Compared with healthy cows, the ketotic cows had significantly higher concentrations of milk fat and citrate, but lower levels of milk protein and lactose. The cows exhibited a need for acid detergent fibre in forage and better digestion of neutral detergent fibre, starch, crude protein, and phosphorus than healthy cows, but more fat and gross energy were excreted in their faeces. Ketotic cows had higher energy-corrected milk yields and lower FDM than healthy cows.

Conclusion

Lower feed intake coinciding with the requirement to maintain high milk production is considered to be the cause of ketosis in dairy cows. Ketotic cows exhibited lower dry matter fat digestion.

Abstract

The fringe projection profilometry with sinusoidal patterns based on phase-shifting algorithms is commonly distorted by the nonlinear intensity response of commercial projector. In order to solve this issue, sinusoidal width modulation is presented to generate binary sinusoidal patterns for defocusing the projection. However, the residual errors in the phase maps are usually notable for highly accurate three-dimensional shape measurements. In this paper, we propose the fringe patterns of the sinusoidal, square, and triangular periodic waveforms with seven-step phase-shifting algorithm to further improve the accuracy of three-dimensional profile reconstruction. The absolute phase values are calculated by using quality guided path unwrapping. We learn that by properly selecting fringe patterns according to the target shape, the undesired harmonics of the measured surface have negligible effect on the phase values. The experiments are presented to verify the imaging performances of three fringe patterns for different testing targets. The triangular fringe patterns are suitable for the shape measurements of complex targets with curved surfaces. The results provide a great possibility for high-accuracy shape measurement technique with wider measuring depth range.

Abstract

The characterization of surface micro-roughness is investigated by using off-specular measurements of polarized optical scattering. In the measurement system, the detection angles of optical scattering are defined by the vertical and level scattering angles. The rotating mechanism of angles is controlled by stepper motors. Waveplate and polarizer are used to adjust light polarization and detection. We conduct the optical scattering measurements by using four standard metal sheets of surface roughness. The nominal values (Ra) of standard micro-roughness are 1.6 μm, 0.8 μm, 0.4 μm, and 0.1 μm, respectively. Samples with different surface roughness are evaluated with the utilization of laser sources at three incident wavelengths. These polarized images are analyzed using a computer program to obtain the distribution of light intensity. The results show great correlation between the metal surface roughness and polarization states. This measurement system can be used to quickly and accurately distinguish between different surfaces and properties.

Abstract

Introduction

Coinfection of goose parvovirus (GPV) and duck circovirus (DuCV) occurs commonly in field cases of short beak and dwarfism syndrome (SBDS). However, whether there is synergism between the two viruses in replication and pathogenicity remains undetermined.

Material and Methods

We established a coinfection model of GPV and DuCV in Cherry Valley ducks. Tissue samples were examined histopathologically. The viral loads in tissues were detected by qPCR, and the distribution of the virus in tissues was detected by immunohistochemistry (IHC).

Results

Coinfection of GPV and DuCV significantly inhibited growth and development of ducks, and caused atrophy and pallor of the immune organs and necrosis of the liver. GPV and DuCV synergistically amplified pathogenicity in coinfected ducks. In the early stage of infection, viral loads of both pathogens in coinfected ducks were significantly lower than those in monoinfected ducks (P < 0.05). With the development of the infection process, GPV and DuCV loads in coinfected ducks were significantly higher than those in monoinfected ducks (P < 0.05). Extended viral distribution in the liver, kidney, duodenum, spleen, and bursa of Fabricius was consistent with the viral load increases in GPV and DuCV coinfected ducks.

Conclusion

These results indicate that GPV and DuCV synergistically potentiate their replication and pathogenicity in coinfected ducks.

Abstract

Introduction: A model of fatty liver in postpartum sheep was established to measure blood paraoxonase 1 (PON1) and other biochemical indicators, which were used to predict fatty liver in sheep.

Material and Methods: Sheep were assigned into two experimental groups: a fatty liver group (T, n = 10) and a healthy control group (C, n = 5). PON1 enzyme activity towards paraoxon as a substrate was quantified spectrophotometrically. The results were analysed by t-test and pearson correlation coefficient. Disease was predicted by binary logistic analysis, and diagnostic thresholds were determined by receiver operatingcharacteristic (ROC) analysis.

Results: The activity of serum PON1 in group T was significantly decreased (P < 0.05) when compared with C group, and liver lipid content and the levels of serum BHBA, NEFA, and TG were significantly increased (P < 0.05). Thresholds were lower than 74.0 U/mL for PON1, higher than 0.97 mmol/L for β-hydroxybutyrate, higher than 1.29 mmol/L for non-esterified fatty acids, higher than 0.24 mmol/L for triglycerides, and lower than 71.35 g/L for total protein.

Conclusion: This study verified that PON1, BHBA, NEFA, TG, and TP could be used to predict the risk of fatty liver in sheep.

Abstract

Introduction: The predictive value of selected parameters in the risk of ketosis and fatty liver in dairy cows was determined.

Material and Methods: In total, 21 control and 17 ketotic Holstein Friesian cows with a β-hydroxybutyrate (BHBA) concentration of 1.20 mmol/L as a cut-off point were selected. The risk prediction thresholds for ketosis were determined by receiver operating characteristic (ROC) curve analysis.

Results: In the ketosis group, paraoxonase-1 (PON-1) activity and concentration of PON-1 and glucose (GLU) were decreased, and aminotransferase (AST) activity as well as BHBA and non-esterified fatty acid (NEFA) contents were increased. The plasma activity and concentration of PON-1 were significantly positively correlated with the level of plasma GLU. The plasma activity and concentration of PON-1 were significantly negatively correlated with the levels of AST and BHBA. According to ROC curve analysis, warning indexes of ketosis were: plasma PON-1 concentration of 46.79 nmol/L, GLU concentration of 3.04 mmol/L, AST concentration of 100 U/L, and NEFA concentration of 0.82 mmol/L.

Conclusion: This study showed that the levels of PON-1, GLU, AST, and NEFA could be used as indicators to predict the risk of ketosis in dairy cows.

Abstract

A graph G is called r-spanning cyclable if for every r distinct vertices v 1, v 2, . . . , v r of G, there exists r cycles C 1, C 2, . . . , C r in G such that v i is on C i for every i, and every vertex of G is on exactly one cycle C i. In this paper, we consider the 2-spanning cyclable problem for the generalized Petersen graph GP (n, k). We solved the problem for k ≤ 4. In addition, we provide an additional observation for general k as well as stating a conjecture.

Abstract

Background: Patients with signs/symptoms of spontaneous intracranial hemorrhage (SICH) in the emergency department (ED) generally undergo computed tomography (CT) scanning.

Objective: To assess whether D-dimer assay alone at ED admission can be used for screening non-traumatic patients with suspected ICH who do not have new onset of neurological deficits to reduce the number of CT scans.

Methods: The study included 90 non-traumatic patients who were admitted to the ED and had signs/symptoms suggestive of SICH but did not have new neurological deficits. All patients underwent non-contrast CT within 30 minutes. Three patients also underwent lumbar puncture for a definitive diagnosis. Blood D-dimer levels were measured from venous blood samples obtained in the ED. All patients were followed up for one year. The diagnosis at 3 months follow-up was used to determine whether CT was helpful.

Results: CT was not helpful for 60 patients and was necessary for 30 patients. Multivariate analysis showed that dizziness/vertigo, systolic blood pressure >120 mmHg, and positive D-dimer assay (>500 ng/ml) were significantly related to the need for CT. The results of multivariate analysis were used to perform area under the curve analysis to provide data on sensitivity, specificity, positive predictive value, and negative predictive value for these three independent factors that affect the need for CT examination. Further analysis showed that all seven patients with subarachnoid hemorrhage had a positive D-dimer assay and their median D-dimer level was significantly higher than that of patients with intracerebral hemorrhage or stroke.

Conclusions: D-dimer assay alone is inadequate in the ED for screening non-traumatic patients with suspected SICH who do not have new onset of neurological deficits to reduce the number of CT scans.