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Disease-related milk losses directly affect dairy herds' profitability and the production efficiency of the dairy industry. Therefore, this study aimed to quantify phenotypic variability in milk fluctuation periods related to diseases and to explore milk fluctuation traits as indicators of disease resilience. By combining high-frequency daily milk yield data with disease records of cows that were treated and recovered from the disease, we estimated milk variability trends within a fixed period around the treatment day of each record for 5 diseases: udder health, reproductive disorders, metabolic disorders, digestive disorders, and hoof health. The average milk yield decreased rapidly from 6 to 8 d before the treatment day for all diseases, with the largest milk reduction observed on the treatment day. Additionally, we assessed the significance of milk fluctuation periods highly related to diseases by defining milk fluctuations as a period of at least 10 consecutive days in which milk yield fell below 90% of the expected milk production values at least once. We defined the development and recovery phases of milk fluctuations using 3,847 milk fluctuation periods related to disease incidences, and estimated genetic parameters of milk fluctuation traits, including milk losses, duration of the fluctuation, variation rate in daily milk yield, and standard deviation of milk deviations for each phase and their genetic correlation with several important traits. In general, the disease-related milk fluctuation periods lasted 21.19 ± 10.36 d with a milk loss of 115.54 ± 92.49 kg per lactation. Compared with the development phase, the recovery phase lasted an average of 3.3 d longer, in which cows produced 11.04 kg less milk and exhibited a slower variation rate in daily milk yield of 0.35 kg/d. There were notable differences in milk fluctuation traits depending on the disease, and greater milk losses were observed when multiple diseases occurred simultaneously. All milk fluctuation traits evaluated were heritable with heritability estimates ranging from 0.01 to 0.10, and moderate to high genetic correlations with milk yield (0.34 to 0.64), milk loss throughout the lactation (0.22 to 0.97), and resilience indicator (0.39 to 0.95). These results indicate that cows with lower milk losses and higher resilience tend to have more stable milk fluctuations, which supports the potential for breeding for more disease-resilient cows based on milk fluctuation traits. Overall, this study confirms the high effect of diseases on milk yield variability and provides insightful information about their relationship with relevant traits in Holstein cattle. Furthermore, this study shows the potential of using high-frequency automatic monitoring of milk yield to assist on breeding practices and health management in dairy cows. [ABSTRACT FROM AUTHOR]

Due to the low rigidity of the boring bar with a large length-to-diameter ratio, chatter easily occurs during deep hole boring. In this paper, an ultrasonic vibration boring bar with a length-to-diameter ratio greater than 10 is designed to suppress the chatter during the boring operation of deep holes. First, the dynamic model of the boring operation is built to guide the design of the ultrasonic vibration boring bar. Then, the optimal design of structure parameter of the ultrasonic vibration boring bar is performed by the finite element method, and then the optimized boring bar is manufactured. Finally, the vibration performance test and cutting experiments are carried out to verify the machining capability of the bar. The experimental results show that the ultrasonic vibration boring bar can reduce the cutting force by about 35%, improve the system stability, and increase the quality of the relative machined surface by about 43%, which demonstrate the feasibility of chatter suppression of the developed ultrasonic vibration boring bar. [ABSTRACT FROM AUTHOR]

As an important transmission component, the spur gear has been widely used in automobiles and various mechanical equipment. However, spur gears are usually produced by the hobbing and shaving, which inevitably reduces the service strength and service life of the gear. In this paper, the one-step punching forming process of spur gear is presented. Compared with the traditional gear machining process, the process not only avoids the destruction of the metal flow line but significantly decreases the material cost. The effect of tooth filling and equivalent strain accumulation on gear forming quality was investigated by finite element simulation. The effects of upper die punching speed, lower die preheating temperature, and friction coefficient on lower die wear during forming were studied by response surface method. The optimum process parameters of punching of spur gear were a lower die preheating temperature of 280 ℃, friction coefficient of 0.27, and upper die feed speed of 8.3 mm/s, respectively. It is predicted that about 110,000 gears can be produced before the wear failure of the lower die. On the basis of the finite element simulation results, the gear punching experiment is performed. The experimental results are in good agreement with the simulation results, and the metal flow line at the tooth is uniform and continuous, which verifies the reliability of the one-step punching process. [ABSTRACT FROM AUTHOR]

During subsequent machining of laser cladded workpiece, the stress transferred in depth direction is different from the conventional cast workpiece due to the geometrical discontinuity, resulting in the stress difference and strain discontinuity at the interface between the cladding layer and substrate. Distinguishing from the traditional finite element method model, this paper establishes a model with an inclined interface to investigate the thickness ratio, i.e., the ratio of the removal thickness in subsequent machining to cladding thickness on the machining-induced stress and strain. The results show that the maximum thickness ratio is 0.352 when the removal thickness is 0.1 mm. The change in interfacial shear stress energy dissipation due to interfacial inclination makes this result 22.8% lower than a traditional model with a horizontal interface. With the help of the presented model, the effect of removal thickness on machining-induced stress and strain evolution was investigated. The results show that an increase in the removal thickness will lead to an increase in machining-induced stress and strain. The stress difference and strain increment at the interface increase proportionally with the removal thickness, implying that variations in removal thickness will have a consequential impact on the maximum thickness ratio. Thus, the interaction of material removal thickness and thickness ratio on PEEQ increment at the interface was further analyzed. The response surface results indicate that an increase in the removal thickness leads to a corresponding increase in the maximum thickness ratio, albeit with a minor degree of influence. Therefore, the challenge of fixing the maximum thickness ratio in actual machining due to multi-step processes can be resolved through micro-adjustments. Simultaneously, in engineering applications, workpiece surface defects exhibit varying depths and require different removal amounts after cladding. This study provides further theoretical guidance for repairing and remanufacturing surface defects with diverse depths. [ABSTRACT FROM AUTHOR]

The elite bull plays an extremely important role in the genetic progression of the dairy cow population. The previous results indicated the potential positive relationship of large scrotal circumference (SC) with improved semen volume, concentration, and motility. In order to improve bull's semen quantity and quality by selection, it is necessary to estimate the genetic parameters of semen traits and their correlations with other conformation traits such as SC that could be used for an indirect selection. In this study, the genetic parameters of seven semen traits (n = 66,260) and nine conformation traits (n = 3,642) of Holstein bulls (n = 453) were estimated by using the bivariate repeatability animal model with the average information-restricted maximum likelihood (AI-REML) approach. The results showed that the estimated heritabilities of semen traits ranged from 0.06 (total number of motile sperm, TNMS) to 0.37 (percentage of abnormal sperm, PAS) and conformation traits ranged from 0.23 (pin width, PW) to 0.69 (hip height, HH). The highest genetic correlations were found between semen volume per ejaculation (SVPE), semen concentration per ejaculation (SCPE), total number of sperm (TNS), and TNMS traits that were 0.97, 0.98, 1.00, and 0.99, respectively. Phenotypic correlations between SC and SVPE, SCPE, TNS, and TNMS were 0.35, 0.35, 0.48, and 0.42, respectively. In summary, the moderate or high heritability of semen traits indicates that genetic improvement of semen quality by selection is feasible, where SC could be a useful trait for indirect selection or as correlated information to improve semen quantity and production in the practical bull breeding programs. [ABSTRACT FROM AUTHOR]