scholarly journals Research on the Matching of Impact Performance and Collision Coefficient of Hydraulic Rock Drill

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Yelin Li
Keyword(s):  
Stress Wave ◽  
Wave Model ◽  
Wave Theory ◽  
Collision Velocity ◽  
Impact Performance ◽  
Impact Stress ◽  
Material Condition ◽  
Rock Drill ◽  
The Impact ◽  
The Relationship

The stress wave produced by the piston impact, on the drill rod, is an important factor affecting impact performance. It is particularly important to control the stress waveform generated by the piston impact on the drill rod to meet the requirements of efficiency and component durability of some impact mechanical systems. Based on wave theory, the impact stress wave model of rock drilling is established, a dimensionless collision coefficient γ is put forward, and the matching relationship between different collision coefficients γ and stress waveforms is analysed. The length of the impact piston under the same material condition determines the change rule of the waveform. The stress waveform experimental verification is thus designed. The pressure chamber curves of different pistons in the rock drill were tested, the collision velocity of the piston was obtained, and the impact energy and impact power were calculated. The relationship between the impact performance and the collision coefficient γ is analysed. When γ is in the range of 9–11, the impact piston’s design of a high-power rock drill can be satisfied. When γ is in the range of 3∼5, it is mainly designed for low-power rock drills.

THE REDUCTION OF STRESS WAVE PROPAGATION THROUGH POROUS MATERIALS

2008 ◽  
Vol 22 (09n11) ◽  
pp. 1215-1220
Author(s):  
SOTO AKI KIDA ◽  
KEITA FUKUSHIMA ◽  
MASAYA MATSUMOTO
Keyword(s):  
Porous Medium ◽  
Porous Materials ◽  
Stress Wave ◽  
Acrylic Resin ◽  
Wave Theory ◽  
Stress Waves ◽  
Stress Wave Propagation ◽  
Impact Stress ◽  
The Impact ◽  
Impact Stress Wave

Impact stress wave propagating through porous materials is investigated in order to examine the ability of the shock absorbing effect. The specimens are modeled as the porous medium with different porous diameters made of the acrylic resin plate. When these models are impacted with different impact velocities, the impact stress waves propagating before and after the porous parts are measured using the strain gages in the experiments. As the reduction effect of the impact stress wave propagating in the porous medium, we pay attention to the maximum stresses and the duration times from the histories of the impact stress waves. One-dimensional wave theory and dynamic element method simulated this model are applied in order to explain these phenomena.

scholarly journals Research on Impact Performance of Hydraulic Rock Drill with Floating Characteristics of Double Damping System

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Yelin Li ◽  
Zeng Bin ◽  
Yi Tu
Keyword(s):  
Experimental Data ◽  
Impact Energy ◽  
Influence Factors ◽  
Characteristic Parameters ◽  
Impact Performance ◽  
Experimental Scheme ◽  
Rock Drill ◽  
Feed Force ◽  
The Impact ◽  
The Relationship

As a technological innovation of high-power hydraulic rock drill, double damping system has a very important effect on impact performance. The double damping system is a floating mechanism. The characteristics of the floating mechanism have an important influence on the impact energy, frequency, and power of the hydraulic rock drill. Based on orifice throttling theory, the static equilibrium position of a damping piston was calculated, and the characteristic parameters of the double damping system were summarized as damping flow (Qd) and feed force (Fd). According to the characterization parameters of the double damping system, an experimental scheme of the floating characteristics of the double damping system was designed, and the combined experimental data of Qd and Fd were obtained. The 40 groups of experimental data were extracted, and the relationship between the combination (Qd, Fd) and impact energy and frequency and power were analyzed. The combination (Qd, Fd) with maximum and minimum power was selected to analyze the motion law of an impact piston. The maximum drilling power was obtained at the combination (Qd = 8 L·min−1, Fd = 16.25 kN). The influence factors of the double damping system on impact performance were summarized, and the characteristics of the double damping system under optimal impact performance were obtained.

scholarly journals Negative self-appraisal mediates the relationship between mindfulness and confidence among adolescent female provincial hockey players in South Africa

10.17159/4371 ◽  
2019 ◽  
Vol 31 (1) ◽  
pp. 1-5
Author(s):  
Stephen Walker
Keyword(s):  
Indirect Effect ◽  
Correlation Coefficients ◽  
Ordinary Least Squares ◽  
Mental Toughness ◽  
Adolescent Female ◽  
Least Squares Regression ◽  
Impact Performance ◽  
Hockey Players ◽  
The Impact ◽  
The Relationship

Introduction: Mounting evidence suggests that mindfulness is positively related to athletic performance and athlete wellbeing. However, few attempts have been made to uncover the psychological processes by which mindfulness might impact performance. Objective: To determine whether negative self-appraisal mediates the relationship between mindfulness and the confidence component of mental toughness among provincial adolescent female hockey players. Methods: Provincial adolescent female hockey players (N=486) completed measures of mindfulness, mental toughness-related confidence and negative self-appraisal. Correlation coefficients were calculated between all variables included in the study. An ordinary least-squares regression analysis was performed to test the indirect effect of negative self-appraisal on the relationship between mindfulness and confidence. Results: Negative self-appraisal exhibited an indirect effect on the relationship between mindfulness and the confidence component of mental toughness (b = .06, SE = .0, CI95 = .04, .09). A subsequent Soble test confirmed that negative self-appraisal served as a statistically significant mediator (b = .06, SE = .01, Z = 5.76, p = .001) in the model. Furthermore 78.3% of the variance in the effect of mindfulness on the confidence component of mental toughness was accounted for by negative self-appraisal. Conclusion: The effect of mindfulness on the confidence component of mental toughness among adolescent athletes is mediated by negative self-appraisal. Based on the current findings, mindfulness seems to foster confidence by lessening the impact of rigid negative appraisals of one’s performance and worth as an athlete. Keywords: mindfulness, confidence, negative self-appraisal, mediation, adolescent female athlete

scholarly journals Failure behavior of the surrounding rock of jointed rock masses in a gold mine under impact disturbance

2021 ◽  
Author(s):  
Peng Li ◽  
Yunquan Wu ◽  
Meifeng Cai
Keyword(s):  
Stress Wave ◽  
Shear Failure ◽  
Jointed Rock ◽  
Surrounding Rock ◽  
Tensile Failure ◽  
Tensile Shear ◽  
Underground Engineering ◽  
Impact Stress ◽  
The Stability ◽  
The Impact

Abstract The impact disturbance has an important influence on the safety of underground engineering openings. In this paper, based on the in-situ stress measurement and structural plane investigation, the model of jointed rock roadway was established using the discrete element method (3DEC) to study the instability and failure characteristic of roadway surrounding rock with dominant joint planes under impact disturbance and to further analyze the influence of different buried depths, impact stress wave peaks, and stress wave delays on the stability of the surrounding rock. The results show that the stability of the surrounding rock is poor, and the whole convergence deformation of the surrounding rock occurs under the impact stress wave. There are three failure modes in the surrounding rock: tensile-shear failure, tensile failure, and shear failure. Tensile-shear failure mainly occurs in a small range close to the roof and floor of the roadway and the free surfaces of the two sides, and tensile failure occurs locally, while shear failure mainly occurs along the joint plane outside this range. Moreover, the greater the buried depth and stress wave peak value, the more serious the deformation of the surrounding rock. With the increase of stress wave delay, the deformation of the surrounding rock shows complex characteristics. In addition, the impact failure mechanism of the surrounding rock in jointed rock masses was discussed. The research results have important guiding significance for the prevention and control of underground engineering cavern disasters.

scholarly journals Predictors Of Performance In An Online Financial Management Simulation

2011 ◽  
Vol 4 (6) ◽  
pp. 35 ◽  
Author(s):  
Thomas Willey ◽  
Susan Edwards ◽  
Vijay Gondhalekar
Keyword(s):  
Financial Management ◽  
Stock Price ◽  
Positive Impact ◽  
Predictive Ability ◽  
Course Performance ◽  
Impact Performance ◽  
Online Simulation ◽  
Experiential Process ◽  
The Impact ◽  
The Relationship

The purpose of our research is to investigate the factors that impact performance in a financial management simulation component of a second financial management class. We measured the impact of previous course performance, gender, age and other concurrent course components on the dependent variable. Using two different statistical techniques, we found that a students current scores on exams, case write-ups and written summary reports were the strongest predictors of performance in the online simulation. The predictive ability of this variable was complemented by the positive impact of a students age. All else equal, the higher the age, the better the performance as measured by the simulated firms stock price. These results are encouraging and we will continue this experiential process during future semesters to add additional students to our sample size to further investigate the relationship between performance in the simulation and student characteristics.

scholarly journals Impact of Building Design Parameters on Daylighting Metrics Using an Analysis, Prediction, and Optimization Approach Based on Statistical Learning Technique

2019 ◽  
Vol 11 (5) ◽  
pp. 1474 ◽  
Author(s):  
Jaewook Lee ◽  
Mohamed Boubekri ◽  
Feng Liang
Keyword(s):  
Statistical Learning ◽  
Building Design ◽  
Design Parameters ◽  
Optimization Approach ◽  
Impact Performance ◽  
Design Variables ◽  
Design Attributes ◽  
Learning Technique ◽  
The Impact ◽  
The Relationship

Daylighting metrics are used to predict the daylight availability within a building and assess the performance of a fenestration solution. In this process, building design parameters are inseparable from these metrics; therefore, we need to know which parameters are truly important and how they impact performance. The purpose of this study is to explore the relationship between building design attributes and existing daylighting metrics based on a new methodology we are proposing. This methodology involves statistical learning. It is an emerging methodology that helps us to analyze a large quantity of output data and the impact of a large number of design variables. In particular, we can use these statistical methodologies to analyze which features are important, which ones are not, and the type of relationships they have. Using these techniques, statistical models may be created to predict daylighting metric values for different building types and design solutions. In this article we will outline how this methodology works, and analyze the building design features that have the strongest impact on daylighting performance.

INTELLECTUAL CAPITAL AND PERFORMANCE OF NEW VENTURE HIGH-TECH FIRMS

2004 ◽  
Vol 08 (03) ◽  
pp. 297-318 ◽  
Author(s):  
NORMA JUMA ◽  
G. TYGE PAYNE
Keyword(s):  
Intellectual Capital ◽  
Strategic Alliances ◽  
Empirical Work ◽  
New Venture ◽  
High Tech ◽  
Organizational Survival ◽  
Impact Performance ◽  
And Performance ◽  
The Impact ◽  
The Relationship

Intellectual capital (IC) has been proposed as an essential factor for organizational survival and maintenance of competitive strength. However, there has been very limited consensus on what encompasses IC and how it can best be conceptualized and measured. Further, very little empirical work has specifically examined the relationship between IC and financial performance. Given these shortcomings, this paper focuses first on the impact IC has on performance and secondly on the role strategic alliances may have on this relationship. While we argue that IC will impact performance, we anticipate this relationship will be moderated by strategic alliances and other inter-firm collaborations. Findings reveal interesting relationships that suggest further effort should be placed on the conceptualization and measurement of IC, specifically regarding its relationship to firm performance.

scholarly journals Fault Diagnosis Research on Impact System of Hydraulic Rock Drill Based on Internal Mechanism Testing Method

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Yelin Li ◽  
Youxin Luo ◽  
Xiao Wu
Keyword(s):  
Fault Diagnosis ◽  
Fault Rock ◽  
Impact Performance ◽  
Rock Drill ◽  
Diagnosis Method ◽  
New Type ◽  
Internal Mechanism ◽  
Left And Right ◽  
Improved Model ◽  
The Impact

In the production and manufacturing process of hydraulic rock drill, there are small impact energy and low impact frequency, and a fault diagnosis method based on the internal mechanism testing and testing of the hydraulic rock drill is proposed. This method is used to test the change law of hydraulic oil in the rock drill, by retaining the test holes on the cylinder body and other important components of the hydraulic rock drill. At the same time, the mathematical method is used to deal with the test curve, and the influence of pressure pulsation characteristics of the front and rear chambers of the impact piston and the left and right valve chambers of the reversing valve on the impact performance of the rock drill is analyzed. Based on Newton’s law, the model of the impact piston and reversing valve is established. According to the velocity and other parameters of the impact piston, the size of the impact piston switch point is calculated. The coupling between the movement of the impact piston and the movement of the reversing valve is analyzed according to the model established. Comparing the results of the experimental data, the correctness of the fault diagnosis analysis method and model is verified. The effect of the fault rock drill and the improved model is compared, and the theoretical basis is provided for the fault diagnosis of the rock drill and the design of a new type of rock drill.

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