scholarly journals Experimental and Theoretical Study on Influence of Different Charging Structures on Blasting Vibration Energy

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Wenbin Gu ◽  
Zhenxiong Wang ◽  
Jianghai Chen ◽  
Jianqing Liu ◽  
Ming Lu
Keyword(s):  
Theoretical Study ◽  
Impedance Matching ◽  
Rock Fragmentation ◽  
Vibration Energy ◽  
Blasting Vibration ◽  
High Impedance ◽  
Coupling Structure ◽  
Decoupling Coefficient ◽  
Instantaneous Energy ◽  
Relationship Equation

As an important parameter in blasting design, charging structure directly influences blasting effect. Due to complex conditions of this blasting and excavating engineering in Jiangsu, China, the authors carried out comparative researches with coupling structure, air-decoupling structure, and water-decoupling structure. After collecting, comparing, and analyzing produced signals on blasting vibration, the authors summarized that when proportional distances are the same, water-decoupling structure can reduce instantaneous energy of blasting vibration more effectively with more average rock fragmentation and less harm of dust. From the perspective of impedance matching, the present paper analyzed influence of charging structure on blasting vibration energy, demonstrating that impedance matching relationship between explosive and rock changes because of different charging structures. Through deducing relationship equation that meets the impedance matching of explosive and rock under different charging structures, the research concludes that when blasting rocks with high impedance, explosive with high impedance can better transmits blasting energy. Besides, when employing decoupling charging, there exists a reasonable decoupling coefficient helping realize impedance matching of explosive and rock.

scholarly journals Impedance Enhancement of Textile Grounded Loop Antenna Using High-Impedance Surface (HIS) for Healthcare Applications

Sensors ◽  
2020 ◽  
Vol 20 (14) ◽  
pp. 3809
Author(s):  
Mohammed M. Bait-Suwailam ◽  
Isidoro I. Labiano ◽  
Akram Alomainy
Keyword(s):  
Impedance Matching ◽  
Loop Antenna ◽  
Healthcare Applications ◽  
Impédance Surface ◽  
Antenna Structure ◽  
Impedance Surface ◽  
High Impedance ◽  
Low Profile ◽  
Close Proximity ◽  
High Impedance Surface

In this paper, impedance matching enhancement of a grounded wearable low-profile loop antenna is investigated using a high-impedance surface (HIS) structure. The wearable loop antenna along with the HIS structure is maintained low-profile, making it a suitable candidate for healthcare applications. The paper starts with investigating, both numerically and experimentally, the effects of several textile parameters on the performance of the wearable loop antenna. The application of impedance enhancement of wearable grounded loop antenna with HIS structure is then demonstrated. Numerical full-wave simulations are presented and validated with measured results. Unlike the grounded wearable loop antenna alone with its degraded performance, the wearable loop antenna with HIS structure showed better matching performance improvement at the 2.45 GHz-band. The computed overall far-field properties of the wearable loop antenna with HIS structure shows good performance, with a maximum gain of 6.19 dBi. The effects of bending the wearable loop antenna structure with and without HIS structure as well as when in close proximity to a modeled human arm are also investigated, where good performance was achieved for the case of the wearable antenna with the HIS structure.

scholarly journals Automatic Measurement of Magnetron Rieke Diagrams

2019 ◽  
Author(s):  
Vladimir Bilik
Keyword(s):  
Reflection Coefficient ◽  
Anode Voltage ◽  
Block Diagram ◽  
Impedance Matching ◽  
Real Life ◽  
Automatic Measurement ◽  
Operating Conditions ◽  
Polar Diagram ◽  
Coupling Structure ◽  
Fully Automatic

A Rieke diagram [1] is a magnetron characteristic that visualizes the dependence of the generated frequency fg and the net delivered power PL on the load reflection coefficient GR. GR is defined in a specific magnetron-to-waveguide coupling structure called the standard or reference launcher (Fig. 1). The diagram is plotted as a family of isolines of constant fg and of constant PL in the polar diagram of GR. Rieke diagrams are essential in the design of applications without isolators, such as domestic or professional microwave ovens. Constructing Rieke diagrams is tedious, time-consuming and equipment-demanding [2], [3], preventing systematic studies of their dependence on operating conditions, such as anode voltage and its ripple, filament current, mounting repeatability, etc. We have devised a procedure, centering around a high-power automatic impedance matching device (autotuner), which enables fully automatic measurement and plotting of the stated dependences. A block diagram of the setup is shown in Fig. 1. The autotuner, when terminated in a match (waterload), can accomplish a task inverse to impedance matching: realizing any desired reflection coefficient GR. The measurement consists of stepping through a grid of n suitably chosen reflection coefficients GR = xR + jyR, covering a desired area of the polar diagram. Each GR is measured accurately by the autotuner, along with the corresponding fg and PL. Thus, raw data for constructing a Rieke diagram are obtained, the data consisting of a collection of n points {GR, fg, PL}i, i = 1…n, with GR, in general, irregularly scattered in the complex plane. A dedicated MATLAB routine then reads the data, sorts them out to create tabulated functions fg = f(xR, yR), PL = f(xR, yR), approximates these by a 2D spline, and uses the splines to plot smoothed isocontours for chosen constant values of fg and PL, completing thus the desired Rieke diagram construction. We will present details of this procedure as well as real-life examples. Fig. 1. Rieke diagram measurement setup. References Meredith, R. J., Engineers' Handbook of Industrial Microwave Heating, London: The IEE, 1998, 250–270. Takahashi, H., I. Namba, K. Akiyama, J. Microwave Power, 1979, 14, 261–267.Yixue, W., Z. Zhaotang, Proc. ICMMT'98, 1998, 795–798.

Study on Blasting Vibration Effects of Shallow Tunnel Excavation

2011 ◽  
Vol 250-253 ◽  
pp. 2366-2370 ◽  
Author(s):  
Wen Xue Gao ◽  
Wen Long Sun ◽  
Hong Liang Deng ◽  
Xi Meng Sun
Keyword(s):  
Vibration Control ◽  
Ground Surface ◽  
Rock Fragmentation ◽  
Blasting Vibration ◽  
Shallow Tunnel ◽  
Tunnel Excavation ◽  
Surface Vibration ◽  
Multi Stage ◽  
Tunnel Blasting

Based on the practice of Huolang-yu tunnel of Mixing road reconstruction, this paper studies the monitoring of ground surface vibration and the technology of controlled blasting. The results show: (1) the ground surface vibration declines from constructed position to non-excavated areas along tunnel excavation direction. (2) The vibration control of wedge cutting holes blasting is the key to reduce or eliminate shallow tunnel vibrating calamity. And the replacement of the multi-stage small wedge cutting holes to the big wedge cutting holes ameliorates blasting vibration and rock fragmentation. (3) The overall monitoring of shallow tunnel blasting vibration and the effects, and optimum of the blasting design not only reduce blasting vibration but also ensure large circulation footage.

Air-Coupled Ultrasonics

2011 ◽  
Author(s):  
Dale Chimenti ◽  
Stanislav Rokhlin ◽  
Peter Nagy
Keyword(s):  
Acoustic Impedance ◽  
Low Cost ◽  
Impedance Matching ◽  
Sound Waves ◽  
Signal Loss ◽  
Contact Mode ◽  
High Impedance ◽  
Mechanical Waves ◽  
Technological Developments ◽  
Air Coupled Ultrasonics

Ultrasonic material characterization or inspection for defects is conventionally performed using either liquid coupling (water, usually) or some type of gel or oil in contact-mode coupling. Mechanical waves can be transmitted only through some sound-supporting medium from their source (a transducer) to the object under study, and back again. Using distilled, degassed water to couple ultrasound to an object under test works quite well and has many technical advantages, including relatively low signal loss over laboratory or shop dimensions at typical frequencies, almost zero toxicity, and low cost. For many applications, the use of water is acceptable and preferred. There are, however, certain testing applications for which water can be a disadvantage. These situations include materials that are sensitive to contact with water, such as uncured graphite-epoxy composites or certain electronics. Large objects, whose total immersion is impractical, or objects for which rapid scanning is required might also be unsuitable for water coupling. Recent technological developments are beginning to permit the judicious replacement of water by a far more ubiquitous sound coupling medium—air. Ultrasonic testing in air has been investigated for more than 30 years, but recently there has been an upsurge in interest and application because of the availability of much more efficient sound-generating devices designed specifically for operation in air. In water- or direct-coupled ultrasonics, one typically employs piezoelectric transducers to generate sound waves because they are well suited to the generation of sound in water or in solids because of their high acoustic impedance. In air, however, we need just the opposite. Air is very compliant, so waves from a high-impedance source couple poorly into air. Much effort has been invested in finding suitable impedance matching materials that will render the familiar piezoelectric probe efficient in air-coupled (A-C) ultrasound. The problem, however, is nearly insurmountable because of the large acoustic impedance difference between air and quartz, for example. Quartz has an acoustic impedance of about 15 MRayl, while air’s impedance is about 425 Rayl, a ratio of about 35,000. The challenge is to find a material with an acoustic impedance that nearly equals the geometric average of these two widely disparate values.

scholarly journals Analysis of Acoustic Wave Frequency Spectrum Characters of Rock Mass under Blasting Damage Based on the HHT Method

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Haiping Yuan ◽  
Xiaole Liu ◽  
Yan Liu ◽  
Hanbing Bian ◽  
Wen Chen ◽  
...  
Keyword(s):  
Energy Spectrum ◽  
Time Lag ◽  
Three Dimensional ◽  
Blasting Vibration ◽  
Accurate Identification ◽  
Transform Method ◽  
Heisenberg Uncertainty Principle ◽  
Vibration Signals ◽  
Nonstationary Signals ◽  
Instantaneous Energy

The limitation associated with Fourier transform and wavelet analysis that they often fail to produce satisfactory resolution simultaneously in time and frequency when dealing with nonlinear and nonstationary signals is frequently encountered. Therefore, this paper aims at using the HHT (Hilbert–Huang transform) method, which is built on the basis of the EMD- (empirical mode decomposition-) based wavelet threshold denoising technique and the Hilbert transform, to analyze the blasting vibration signals in a south China lead-zinc mine. The analysis is conducted in terms of three-dimensional Hilbert spectrum, marginal spectrum, and instantaneous energy spectrum. The results indicate that the frequencies of the blasting vibration signals lie mainly within 0∼200 Hz, which consists of more than 90% of the total signal energy. At the onset of the blasting, the vibration frequency tends to be low, with the frequency that is less than 50 Hz being dominant. By using instantaneous energy spectrum, which can reveal the condition of energy release for detonator explosion, the initiation moments of detonators with 7 time-lag levels are accurately identified. This accurate identification demonstrates the superiority of the HHT method in coping with nonlinear and nonstationary signals. Additionally, the HHT method that is characterized by adaptivity, completeness, strong reconfigurability, and high accuracy provides an opportunity for reflecting signals’ change features with regard to time domain, frequency domain, and energy irrespective of the limitation of the Heisenberg uncertainty principle.

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