Numerical Simulation on Selection of Optimal Delay Time for Precise Delay Blasting

In the traditional presplitting blasting, the presplit holes are generally uniformly initiated, which causes local damage to the retained rock mass while forming the damping ditch. In order to determine the optimal delay time of the precise delay initiation hole by hole, the finite element software ANSYS/LS-DYNA is used to build a blasting model of the concrete, which includes concrete, explosive, and air to simulate the crack forming process of the presplitting hole under various initiation modes. Four kinds of initiation modes for blasting, namely, simultaneous initiation with 0 ms, 9 ms, 12 ms, and 15 ms of delay between adjacent holes, are set up to determine the exact delay time of the best presplitting effect. The simulation results show that when the prehole detonates simultaneously, the inner hole crack penetrates the fastest, but the peak stress around the hole is up to 147.9 MPa. When interhole delayed initiation is used, although the time of interhole crack penetration is prolonged, the stress coupling is generated around the precrack and the maximum stress is obviously reduced. The maximum stress generated under the three delayed initiation conditions is only 76.8 MPa. Considering the requirement of damage control of surrounding rock mass and the rapid formation of precrack, 9 ms delay time is determined as the precise delay time of this test.

Influence of Explosion Chamber Shape on Timing Parameters of Disperser

A standardized device with a volume of 1 m3 or 20 L is used to determine explosion parameters. An explosion chamber where explosion takes place is of a spherical or cylindrical shape that suits the shape of a cubic container. In the case of a cylindrical vessel, the diameter and depth of the vessel are 1: 1. In this case, it is a spherical vessel with a volume of 365 liters. Time parameters of the disperser in the spherical vessel are compared with those of a truncated spherical vessel with a volume of 291 liters. Comparison of the measurement results showed that the optimal delay time of the explosion chamber with a volume of 291 liters is 290 ms, while the delay time of the explosion chamber with a volume of 365 liters is 350 ms.

Evaluation of the efficient application of «Iskra-T» electronic initiating devices in terms of crushing and seismic action of face blasts

The paper justifies the optimal delay time in non-synchronous fan blasting with the most optimal delay time between the holes being 15 ms. Experiments were conducted to assess the breaking conditions and seismic effects of face blasts in the underground conditions of the Rasvumchorrsky mine using the Iskra-T electronic initiating systems with delay times of 10, 15 and 20 ms. With the delay times of 10 and 15 ms there is no clear segregation of the blast stages and interference of compression waves, created by consecutively blasted charges, takes place, while their joint interaction leads to insignificant increase of the seismic effects on the mine workings. According to the results of ore drawing monitoring, the number of boulders with the above delay times did not exceed 10 pieces for the whole blasted volume for each round. With the delay time of 20 ms a clear segregation of the blast stages was obtained with the minimum number of 7 boulders per blast. In order to ensure acceptable rock mass fragmentation quality and reduce the seismic effect of blasting on the mine workings, as well as to preserve the pilot holes drilled, it is advisable to use reverse initiation with non-synchronized fan blasting with the delay time of 20 ms between the holes.

Non-Linear Chaotic Features-Based Human Activity Recognition

Human activity recognition (HAR) has vital applications in human–computer interaction, somatosensory games, and motion monitoring, etc. On the basis of the human motion accelerate sensor data, through a nonlinear analysis of the human motion time series, a novel method for HAR that is based on non-linear chaotic features is proposed in this paper. First, the C-C method and G-P algorithm are used to, respectively, compute the optimal delay time and embedding dimension. Additionally, a Reconstructed Phase Space (RPS) is formed while using time-delay embedding for the human accelerometer motion sensor data. Subsequently, a two-dimensional chaotic feature matrix is constructed, where the chaotic feature is composed of the correlation dimension and largest Lyapunov exponent (LLE) of attractor trajectory in the RPS. Next, the classification algorithms are used in order to classify and recognize the two different activity classes, i.e., basic and transitional activities. The experimental results show that the chaotic feature has a higher accuracy than traditional time and frequency domain features.

Optimal delay time to initiate anticoagulation after ischemic stroke in atrial fibrillation (START): Methodology of a pragmatic, response-adaptive, prospective randomized clinical trial

Rationale An estimated 15% of all strokes are associated with untreated atrial fibrillation. Long-term secondary stroke prevention in atrial fibrillation is anticoagulation, increasingly with non-vitamin K oral anticoagulants. The optimal time to initiate anticoagulation following an atrial fibrillation-related stroke that balances hemorrhagic conversion with recurrent stroke is not yet known. Aims To determine if there is an optimal delay time to initiate anticoagulation after atrial fibrillation-related stroke that optimizes the composite outcome of hemorrhagic conversion and recurrent ischemic stroke. Sample size estimates The study will enroll 1500 total subjects split between a mild to moderate stroke cohort (1000) and a severe stroke cohort (500). Methods and design This study is a multi-center, prospective, randomized, pragmatic, adaptive trial that randomizes subjects to four arms of time to start of anticoagulation. The four arms for mild to moderate stroke are: Day 3, Day 6, Day 10, and Day 14. The time intervals for severe stroke are: Day 6, Day 10, Day 14, and Day 21. Allocation involves a response adaptive randomization via interim analyses to favor the arms that have a better risk–benefit profile. Study outcomes The primary outcome event is the composite occurrence of an ischemic or hemorrhagic event within 30 days of the index stroke. Secondary outcomes are also collected at 30 and 90 days. Discussion The optimal timing of direct oral anticoagulants post-ischemic stroke requires prospective randomized testing. A pragmatically designed trial with adaptive allocation and randomization to multiple time intervals such as the START trial is best suited to answer this question in order to directly inform current practice on this question.

Numerical Experimentation Research in Optimizing the Signal Rate & other Related Factors on Traffic Flow

Traffic congestion is one of the current issues faced by the major cities constantly, since past few years. A well organized traffic system and its infrastructure can make a positive impact in reducing the block and thereby affecting the social strata and hence, the economy. Considering the current scenario in the city of Thiruvananthapuram, this study is conducted to forecast the optimal delay time of the signals, such as it reduces the congestion problem effectively. Similar to other cities, Thiruvananthapuram is also prone to the traffic jam in roads on a regular basis. This affects the social system immensely by consuming a large amount of time and fuel. The primal objective of this paper is to optimize the delay time provided for the vehicles that could make the system more systematic, by reducing the wastage of idle time

Unravelling the mechanisms of interference between overlapping resonances

A law that predicts quantitatively the optimal delay time between laser pulses to maximize the resonance lifetime enhancement is reported.

Researches on the Chaotic Characteristics of Fluctuating Pressure in Slit-Type Energy Dissipater

On the basis of research on energy dissipation scheme of Changheba hydropower station in model tests, the chaotic characteristics of the fluctuating pressure in the slit-type contraction section were studied with the employment of chaotic theory. According to Takens’ embedding theorem, we performed a phase space reconstruction on the measured fluctuating series, where the optimal delay time was determined with the average mutual information (AMI) method, the optimal embedding dimension was determined with the averaged false nearest neighbor (AFN) method. Calculated from the testing results, the optimal delay time was ranging from 7 to 10 while the optimal embedding dimension was ranging from 12 to 14. With the optimal embedding parameters obtained, the correlation dimension D2 and the largest Lyaponov exponent λ1 was calculated, with the obtained D2 varying from 7.626 to 8.821 and λ1 varying from 0.091 to 0.302. Conclusively, the flow characteristics on the floor were more complex than those on the sidewall, while the flow structure exhibited no essential difference. Moreover, the distribution law of correlation dimension indicated that the effects of contraction on the flow around the floor were more remarkable; however, the calculated largest Lyapunov exponent could only be served as a qualitative indicator of a chaotic system, without any instruction to the degree of chaos.

Chaotic Characteristics Identification on Terminal Departing Passenger Traffic Time Series

On the basis of actual survey of departing passengers to reach terminal, chaotic time series prediction theory was adopted for data analysis in this paper. In order to find out the self-similarity of time series, this paper divided passenger traffic into two kinds: holiday traffic and non-holiday traffic by changing interval scale. The optimal delay time and the best embedding dimension had been calculated by using time series phase space reconstruction method. To confirm whether the time series have chaotic characteristics or not, it took the largest Lyapunov exponent as determining criterion.Then the optimal time intervals of passenger traffic time series with chaotic character were determined. The study provides a theoretical basis for the application of chaos theory in passenger traffic forecast.