Electromechanical Co-Simulation for Ball Screw Feed Drive System

Ball screw feed drive system is the most widely used linear drive system in the field of industrial automation. The continuous search for efficiency puts forward higher requests to the machine tool for high speed and high acceleration, which makes the feed drive system of lightweight-designed and large-size machine tools more likely to produce vibration during high-speed and high-acceleration feed operation. Electromechanical co-simulation for ball screw feed drive dynamics is an important technique for solving vibration problems occurring in the feed motion. This chapter elaborates on this technology from three aspects: modeling and simulation of dynamic characteristics of ball screw feed drive, modeling and simulation of servo control system, and the electromechanical co-simulation of ball screw feed drive system. In this chapter, the basic theoretical models, the establishment of simulation models and the comparison between simulation and experiment results of ball screw feed drive system are comprehensively introduced to provide technical references for readers

Strengthening of post-tensioned and reinforced concrete beams by bonding external steel plates

This is a preliminary study of both post-tensioned, reinforced concrete beams that were strengthened by bonding external steel plates to their soffits, and reinforced concrete beams that were strengthened by bonding plates to their sides and soffits' Four post-tensioned plated beams, in which the degrees of the prestressing forces were varied, were tested to failure. A computer program was developed to carry out parametric studies on this type of beam. The results of the analytical models were compared with the experimental test results. Thirteen plated reinforced concrete beams were tested to failure in shear. Conditions varied consisted of: the thickness of the soffit plate, the length of the side plate, the thickness of the side plate and the areas of the tensile reinforcement. The effects of these parameters on the shear strength of reinforced concrete beams and their debonding moments were investigated.Thesis (M.Eng.Sc.) -- University of Adelaide, Department of Civil Engineering, 199

The localization of single pulse in VLBI observation

In our previous work, we propose a cross spectrum based method to extract single pulse signals from RFI contaminated data, which is originated from geodetic VLBI postprocessing. This method fully utilizes fringe phase information of the cross spectrum and hence maximizes signal power, however the localization was not discussed in that work yet. As the continuation of that work, in this paper, we further study how to localize single pulses using astrometric solving method. Assuming that the burst is a point source, we derive the burst position by solving a set of linear equations given the relation between residual delay and offset to a priori position. We find that the single pulse localization results given by both astrometric solving and radio imaging are consistent within 3 sigma level. Therefore we claim that it is possible to derive the position of a single pulse with reasonable precision based on only 3 or even 2 baselines with 4 milliseconds integration. The combination of cross spectrum based detection and the localization proposed in this work then provide a thorough solution for searching single pulse in VLBI observation. According to our calculation, our pipeline gives comparable accuracy as radio imaging pipeline. Moreover, the computational cost of our pipeline is much smaller, which makes it more practical for FRB search in regular VLBI observation. The pipeline is now publicly available and we name it as "VOLKS", which is the acronym of "VLBI Observation for frb Localization Keen Searcher".Comment: 11 pages, 4 figures, 3 tables, accepted for publication in A

The Cross-sectional Return Predictability of Employment Growth:A Liquidity Risk Explanation

Employment growth (EG) is related to liquidity fundamentals of investment opportunities, firm health, and information environment and quality. This, in turn, implies that liquidity risk may play a role in explaining the relation between EG and stock returns. We find strong empirical evidence supporting the link between EG and liquidity risk. Stocks of high-EG firms are more liquid and exposed to lower liquidity risk than stocks of low-EG firms. After adjusting for liquidity risk, EG loses its power to predict returns

The Cross-sectional Return Predictability of Employment Growth:A Liquidity Risk Explanation

Employment growth (EG) is related to liquidity fundamentals of investment opportunities, firm health, and information environment and quality. This, in turn, implies that liquidity risk may play a role in explaining the relation between EG and stock returns. We find strong empirical evidence supporting the link between EG and liquidity risk. Stocks of high-EG firms are more liquid and exposed to lower liquidity risk than stocks of low-EG firms. After adjusting for liquidity risk, EG loses its power to predict returns

The Epstein-Zin model with liquidity extension

In this paper, we extend the Epstein and Zin (1989, 1991) model with liquidity risk and assess the extended model's performance against the traditional consumption pricing models. We show that liquidity is a significant risk factor, and it adds considerable explanatory power to the model. The liquidity-extended model produces both a higher cross-sectional R2 and a smaller Hansen and Jagannathan (1997) distance than the traditional consumption-based capital asset pricing model (CCAPM) and the original Epstein-Zin model. Overall, we show that liquidity is both a priced factor and a key contributor to the extended Epstein-Zin model's goodness-of-fit

Transaction costs, liquidity risk, and the CCAPM

In this paper, we make a liquidity adjustment to the consumption-based capital asset pricing model (CCAPM) and show that the liquidity-adjusted CCAPM is a generalized model of Acharya and Pedersen (2005). Using different proxies for transaction costs such as the effective trading costs measure of Hasbrouck (2009) and the bid-ask spread estimates of Corwin and Schultz (2012), we find that the liquidity-adjusted CCAPM explains a larger fraction of the cross-sectional return variations