Resistive Shielding Research Articles

Simulation and analysis of the transient electromagnetic method response in double-layer water-filled goaf in coal mines

Abstract The resolution ability of the transient electromagnetic method (TEM) for double-layer water-filled goaf is affected by the low resistance shielding effect of the overlying strata. Currently, there is a lack of quantitative research on how the parameter changes of the upper water-filled goaf affect its resolution capability. In this study, through numerical and physical simulations, the relative error of the TEM response between single- and double-layer water-filled goafs was regarded as the evaluation index to analyse and summarize the resolution capability of the TEM for double-layer water-filled goaf under different burial depths, thicknesses, and areas of the upper water-filled goaf. The results are summarized as follows. (ⅰ) The resolution capability of the TEM for double-layer water-filled goaf decreased with the increasing burial depth, thickness, or area of the upper water-filled goaf. (ⅱ) The rate of decrease in resolution gradually accelerated as the burial depth increased. Conversely, as the thickness increased, the decrease rate in resolution gradually reduced. Furthermore, the resolution decreased rapidly and then tended towards a fixed value as the area increased. (ⅲ) The maximum value of the relative error curve moved towards the early stage with the increasing burial depth, resulting in a detection depth of the target body smaller than the actual value. Moreover, it moved towards the later stage with the increasing thickness or area, resulting in a detection depth of the target body greater than the actual value.

The fabrication and neutron shielding property of polyphenylene sulfide containing salicylic acid/Gd2O3 composites

A series of neutron absorbing materials with good neutron absorbing capacity, high strength and good thermal property were designed and prepared in this work. First of all, polyphenylene sulfide containing different mole content of salicylic acid (SAPPS) in the main chain was synthesized by nucleophilic substitution polymerization under high pressure. Then the composites with different content of nano Gd2O3 and modified PPS were prepared by melt blending method. The testing results indicated that the copolymers SAPPS were synthesized successfully, there was an interface interaction between nano Gd2O3 and the matrix without the need for surfactants or coupling agents. Additionally, the content of nano Gd2O3 had no obvious influence on the thermal property of the composites. While following with the increase of the content of nano Gd2O3, the tensile strength of the composites increased firstly and then decreased, when the content of nano Gd2O3 was 10 wt%, the tensile strength of 10%Gd2O3/5%SAPPS reached the maximum value of 74.9 MPa. The results of neutron shielding testing indicated that the content of nano-particles had a large effect on the neutron shielding rate of composites. The neutron shielding rate of 50%Gd2O3/5%SAPPS composite was up to 83%. All of these results indicated that the Gd2O3/5%SAPPS had potential to be applied to the high-temperature resistance and thermal shielding materials in nuclear and aerospace applications.

Review of Coveralls, Gowns, and their Use as Part of Personal Protective Equipment (PPE KIT) for Effective Protection of Healthcare Workers in India in COVID-19

Healthcare Workers (HCWs) and public health professionals are playing a pivotal role in containing COVID-19. Personal Protective Equipment (PPEs) are a critical component in the hierarchy of primary infection controls to ‘break the chain of infection’ to protect patients, HCW’s, and public. As SARS-CoV-2 is highly contagious, and vaccine and prophylactics not yet available, understanding correct PPE usage is imperative. This study aims to: understand purpose, use, and quality standards of body-coveralls and gowns and how to use PPE’s for effective protection in COVID 19 in India. Types of PPE’s in healthcare, their purposes, materials used, and properties were reviewed. Gowns and Body-coveralls classification and standards in Europe, USA and India were studied. While current stipulated test standards for coveralls in India are lower, as routine use of reusable gowns made of woven fabrics is more common in India, one could hypothesize that these coveralls provide a higher level of protection. As per current understanding of mode(s) of transmission of SARS-CoV-2 a properly fitted N95 respirator; goggles and splash resistant face shield; gloves; and single-use full body-coverall/gown preferably resistant to Synthetic Blood Penetration under pressure and made of non-woven Laminated SMS (Spunbond-Meltblown-Spunbond)_or Non Laminated SSMMS fabrics are advisable depending upon anticipated level of exposure. HCW’s should educated about transmission risks, correct principles of infection control, functional purpose of PPE’s and must be conscious that PPE’s alone will not protect them. They must follow good practices of how to wear (don) and how to remove (doff) and ensure that they do not inadvertently contaminate their clothing/skin and self-inoculate.

High Speed Laser Based Intersatellite Link Systems for Harsh Environment of Space

This paper will focus on the trends for the space-based lasers, optics and terminals used in the intersatellite networks. Reviewed and evaluate the recent development in the space-based laser technologies and the critical parameters that are employed for successful high-speed intersatellite communications systems. Fiber optics and photonics technology including lasers increasingly being used in aerospace applications and many challenges are involved, since designing for aerospace is very different than for the earth environment. Satellites are much more challenging and for their intersatellite solutions have to contemplate more specific requirements such as space radiation attacks, operation in harsh environment of space and achieving weight, power requirements and reliability for space are few to consider. Therefore it is important to design a system to defend against the radiation from ionizing, gamma, and other attacks. There are numerous methods to protect them from radiation, including shielding, error correction, and using radiation resistance shielding and radiation hardening. Building laser for high speed communications network for the harsh environment of space using optical links in space has proven to be complicated task and many such schemes were tried without success in the past. Space-based optical communications using satellites in low earth orbit (LEO) and Geo-synchronous orbits (GEO) hold great promise for the proposed Internet in the Sky network of the future. However in the last few years, there has been impressive progress made to bring the concept of laser-based intersatellite systems to fruition in civilian and government-non classified projects. Laser communications offer a viable alternative to established RF communications for inter-satellite links and other applications where high performance links are a necessity. High data rate, small antenna size, narrow beam divergence, and a narrow field of view are characteristics of laser-based systems and they are just few numbers of potential advantages for system design over radio frequency communication.

Simultaneous surface scanning and stability analysis of wheeled mobile robots using a new spatial sensitive shield sensor

Abstract To achieve a complete sense of a typical mobile robot moving on the rough and unknown surfaces, a new sensitive shield attached to the robotic wheel is developed with the principle of the total resistance of a circuit. Contact point detection using the new sensitive shield empowers the wheeled-robots to scan the surface, to find the spatial stability measure and to control itself in the absence of camera and laser. The resistive circuit, whereby the sensor is developed, includes a conductive wire, a resistive wire, an impulse voltage source and an additional resistor. All these elements are assembled as an exterior sensitive shield attached to the outside of the wheel. The main advantage of the resistive shield is to determine the exact locations of the spatial contact point on the thick wheel only by means of an input data. Using the data detected from the sensitive shield, the control process can produce the accurate rotational velocities of the wheels required for pursuing a desired path. Furthermore, the results of the new sensor enhance the accuracy of the spatial stability measure. The results of this research imply how the accurate contact point detection aided by the new sensor yields a reliable approach for surface scanning and stability measure calculation.

Results of magnetotelluric survey for studying geothermal system in the Bang area, Quang Binh province

This paper presents the first results from the application of magnetotelluric method (MT) using the new equipment MTU 2000 (Canada) and analysis software to investigate the structure of geothermal area around the Bang hot water source (Quang Binh province). Results of data analysis by MT 1D and 2D models to a depth of 20 km show low resistivity zone in the southwest of Bang hot water (100°C) and allow for interpreting the structural elements of athehydro- geothermal system. This includes a very low resistivity layer at depth of 2 km suggesting a clay cap (heat resistive shield), a relatively low resistivity zone at depth ≥ 2 km reflecting fractured rocks containing geothermal fluid and hot steam. A lower resistivity body at depth of 12-14 km located about 1.5 km from the hot water source indicates the existence of a heat source or a hot mass of intrusive magma., commonly thought to be sources of typical hydro- geothermal systems potential for energy exploitation. The obtained results not only provide new information for better understanding geothermal resource in the surveyed area, but also point out the methods and technology needed to improve the effectiveness for assessing potential of geothermal resources elsewhere in Vietnam.ReferencesBản đồ Địa chất và khoáng sản Việt Nam tỷ lệ 1:1.000.000. Cục Địa chất và Khoáng sản Việt Nam xuất bản 2004. Lưu trữ Địa chất. Cumming W., 2009: Geothermal resource conceptual models using surface exploration data. In: proceedings, 34th workshop on geothermal reservoir engineering, Stanford University. Data Processing User guide. Phoenix Geophysic Ltd. 2005, 201p. Di Pippo R., 2012: Geothermal Power plant. Principles, applications, case studies. 3rd edition. Elseverdirect, 579p. Doan Van Tuyen, Tran Anh Vu, Nguyen Thi Kim Thuong, 2014: Geochemical Characteristics of Geothermal Hot Water Sources on the Territory of Vietnam. Proceeding, Thirty-Eighth Workshop on Geothermal Reservoir Engineering Stanford University, Stanford, California, February 24-26, 2014 SGP-TR-202. Duchkov A.D., Nguyen Trong Yem, Dinh Van Toan, and Trinh Viet Bac, 1992: First estimations of heat flow in northern Vietnam. Soviet Geology and Geophysics, Vol. 33, No. 5, pp 92-96. Flynn T., Quy H. H., 1997: Assessment of the geothermal resources of Socialist Republic of Vietnam. Geothermal resources Council Transactions, vol.21, 341-345. IGA report, 2013: Geothermal Exploration best practices: A Guide to resource data collection, analysis, and presentation for Geothermal projects. He Lijuan, 1999: Analysis of heat flow along a transect across the South China Sea. Geothermal Training Programme, Reports 1999, Number 5, 125-140. Hoang Huu Quy, 1998: Overview of the Geothermal potential of Vietnam. Geothermics, Vol.27, n.1, 109-115. Koenig J. et al., 1981: Evaluation of the potential for Geothermal Energy Resources in the SR of Vietnam. Berkeley, CA. Kulinich G.G., Zabolotnikov A.A, Markov Yu., 1989: Cenozoic evalution of the Earth crust and orogeny in South- Eastern Asia (Tiếng Nga). MTU2000: User guide. Phoenix Geophysic Ltd. 2000, 36p. Munoz Gerard, 2014: Exploring for Geothermal Resources with Electromagnetic Methods. Surv Geophys (2014) 35:101-122, Springer, DOI 10.1007/s10712-013-9236-0. Pellerin et al., Johnston M, Hohmann W., 1996: A numerical evaluation of electromagnetic methods in geothermal exploration. Geophysics 61(1996):121-130. Thomas Mathews, et al., 2008: Study on the sozio-economic framework for the use Geothermal energy in Vietnam. Proceedings of the 8th Asian Geothermal Symposium, Hanoi. Trần Huyên, Trương Minh, Nguyễn Tiến Bào, 1999: Về chế độ địa nhiệt ở các bể trầm tích thềm lục địa Việt Nam. Tạp chí Kinh tế Địa chất và Nguyên liệu khoáng. Cục Địa chất và Khoáng sản Việt Nam. Số 18 tháng 2 năm 1999, tr.16-25. Võ Công Nghiệp (chủ biên), 1998: Danh bạ các nguồn nước khoáng và nước nóng Việt Nam. Cục Địa chất và Khoáng sản Việt Nam. Hà Nội, 300tr. Zhdanov M., 2009: Geophysical Electromagnetic Theory and Methods. Methods in Geochemistry and Geophysics, Volume 43. ISSN: 0076-6895 Elsevier, 831pp. WinGLink User guide. Geosystem 200, 182p. www.geosystem.net.

Structure design and property evaluation of silver/stainless steel composite fabric

This study presents a fabrication method for functional commingled yarns and prepared conductive knitted fabrics for shielding electromagnetic waves and electrostatic discharge. Stainless steel filament was used as core yarn, polyethylene terephthalate filament or silver yarn was used as wrapped yarn producing polyethylene terephthalate/polyethylene terephthalate/stainless steel filament or silver/silver/stainless steel filament commingled yarns via filaments hollow spindle spinning system and then knitting into silver/stainless steel composite fabric. The effects of cycle number and metal content on air permeability, surface resistance, and electromagnetic shielding properties of resultant knitted fabrics were discussed. Besides, influences of number of layers and lamination angle on electromagnetic shielding were also investigated intensively. The result shows that, conductive composite fabrics made by silver/silver/stainless steel filament commingled yarns and 450D polyethylene terephthalate plied filaments had higher surface resistance of 3.4 Log(Ω/sq) and 5.6 Log(Ω/sq), respectively, in coursewise and walewise directions. Electromagnetic shielding varied with number of layer, lamination angle, cycle number, and metal content. When six layers of conductive knitted fabrics were laminated with 45°, electromagnetic shielding reached 15 dB at 1–3 GHz frequency. The highest air permeability, 317.6 cm3/cm2/s, occurred at single-layer conductive composite fabric.

Time-frequency Analysis on low-resistivity Shielding Layer in TEM Soundings

The transient electromagnetic (TEM) method will be influenced by shielding effect of the low-resistivity overburden layer. By adopting the smooth pseudo Wigner-Ville distribution (SPWD), the responses simulated with a finite-difference time-domain method (FDTD) of D- and G-type models by a 2D line source and H-, A-, K- and Q-type models by a loop source are transformed to the time-frequency (T-F) plane. It is indicated that in low-resistivity, the TEM wave aggregates and will consume more energy, it transmits faster in high-resistivity layers but slower in low-resistivity ones. For A-type models widely in distribution of the North China type coalfield of our country, energy of the TEM field has been almost depleted when arriving at the bottom interface (interfaces of Ordovician limestone and coal series) during the TEM exploration in this area, influence of the low resistive shielding layer shall be taken into full consideration, and relatively longer observing time window shall be selected to ensure the detection depth and high-power instruments shall be adopted to increase the signal-noise ratio during construction design.

Modeling Single Event Crosstalk in Nanometer Technologies

With advances in CMOS technology, circuits become increasingly more sensitive to transient pulses caused by single event (SE) particles. On the other hand, coupling effects among interconnects can cause SE transients to contaminate electronically unrelated circuit paths which may increase the SE susceptibility of CMOS circuits. The coupling effects among interconnects need to be considered in single event hardening, modeling and analysis of CMOS logic gates due to technology scaling effects that increase both SE vulnerability and crosstalk effects. This work, for the first time, proposes an SE crosstalk noise estimation method for use in design automation tools. The proposed method uses an accurate 4-π model for interconnect and correctly models the effect of non-switching aggressors as well as aggressor tree branches noting the resistive shielding effect. The SE crosstalk noise expressions derived show very good results in comparison to HSPICE results. Results show that average error for noise peak is about 6.2% while allowing for very fast analysis in comparison to HSPICE.

Single event crosstalk prediction in nanometer technologies

As CMOS technology continues to scale down, circuits become increasingly more sensitive to transient pulses caused by single event (SE) particles. On the other hand, coupling effects among interconnects can cause single event transients to contaminate electronically unrelated circuit paths which may increase the SE susceptibility of CMOS circuits. The coupling effects among interconnects need to be considered in single event hardening, modeling and analysis of CMOS logic gates due to technology scaling effects that increase both SE vulnerability and crosstalk effects. This work, for the first time, proposes an SE crosstalk noise estimation method for use in design automation tools. The proposed method uses an accurate 4-? model for interconnect and correctly models the effect of non-switching aggressors as well as aggressor tree branches noting the resistive shielding effect. The SE crosstalk noise expressions derived show very good results in comparison to HSPICE results. Results show that average error for noise peak is about 5.2% while allowing for very fast analysis in comparison to HSPICE.

Accurate Prediction of Crosstalk for RC Interconnects

This work proposes an accurate crosstalk noise estimation method in the presence of multiple RC lines for use in design automation tools. The method correctly models the loading effects of non switching aggressors and aggressor tree branches using resistive shielding effect and realistic exponential input waveform. Noise peak and width expressions derived show very good results in comparison to HSPICE results. Results show that average error for noise peak is 4.1% and for the width is 6.8% while allowing for very fast analysis.

A multiline model for time-efficient estimation of crosstalk

This work proposes a novel and accurate crosstalk noise estimation method in the presence of multiple RC lines for use in design automation tools. Using the realistic exponential waveform and a reduced transfer function, the proposed model presents a complete multiline noise model by representing active and passive aggressors simultaneously on the victim line. In the model, active aggressors are easily represented by current sources and passive aggressors are accurately modeled as equivalent capacitances to victim. Each current source representing an active aggressor carries the same accuracy as the 2-π representation. Equivalent capacitances for passive aggressors, on the other hand, consider resistive shielding effect and the realistic exponential aggressor waveform. This approach allows one to obtain a general noise model that considers the effect of many active and passive aggressors and general formulas derived can easily be applied to real cases. Noise peak and width expressions are derived and results are in good agreement with HSPICE results. Results show that average error for noise peak is 4.3% and for the width is 6.9% while allowing for very fast analysis.

Closed-Form <emphasis>RC</emphasis> and <emphasis>RLC</emphasis> Delay Models Considering Input Rise Time

The Elmore delay model is the most popular and efficient delay model used for analytical delay estimation. Closed-form delay formulas are useful for circuit design, timing-driven physical design, synthesis, and optimization. As signal rise time becomes faster and the line resistance becomes smaller from copper technology, the significance of inductance increases. Both RC and RLC delays are a strong function of signal rise time. We propose a novel and efficient delay modeling method based on nondimensionalization to consider finite input rise time as an improvement over the Elmore's approach. To further improve the accuracy of the delay model, a new correction method, effective distance correction factor (EDCF), is proposed to consider resistive shielding of downstream capacitance. EDCF can be used to correct the delays for both RC and RLC tree structures. The proposed delay modeling method was applied to a number of nets selected from an integrated circuit (IC) design, and the delay estimation results were compared with HSPICE simulations. The new delay model retains the efficiency and simplicity of the Elmore delay model with significantly improved accuracy.

Precise estimation of crosstalk in multiline circuits

With advances in VLSI technology, increasing wire density causes coupled-noise or cross-talk, which may lead to critical delays or logic malfunctions. Traditional SPICE simulators are not time-efficient estimators of crosstalk, hence alternatives are sought to ensure acceptable signal integrity in a limited design cycle time. This work proposes a novel and accurate crosstalk noise estimation method in the presence of multiple lines for use in design automation tools. It offers a complete multiline noise model, for the first time, by representing active and passive aggressors simultaneously on the victim line. In the model, active aggressors are represented by current sources and passive aggressors are accurately modelled as equivalent capacitances. Realistic exponential aggressor waveform and resistive shielding effect is all considered. This approach allows to obtain a general noise model that considers the effect of many active and passive aggressors and general formulas derived can easily be applied to real cases. Results show an average error of 4.4% for the noise peak and 6.8% for the width with respect to HSPICE while allowing for very fast analysis.

Accurate crosstalk noise modeling for early signal integrity analysis

In this paper, we propose an accurate and fast method to estimate the crosstalk noise in the presence of multiple aggressor nets for use in physical design automation tools. Since noise estimation is often part of the inner loop of optimization algorithms, very efficient closed-form solutions are needed. Previous approaches model aggressor nets one at a time, assuming that the coupling capacitance to all quiet aggressor nets are grounded. They also model the load from interconnect branches as a lumped capacitor, the value of which is the sum of interconnect and load capacitances of the branch. Finally, previous works typically use simple lumped 2-4-node circuit templates and employ a so-called dominant pole approximation to solve the template circuit. While these approximations allow for very fast analysis, they may result in significant underestimation of the noise. In this paper, we propose a new and more comprehensive fast noise estimation method. We propose a novel reduction technique for modeling quiet aggressor nets based on the concept of coupling point admittance. We also propose a reduction method to replace tree branches with effective capacitors which models the effect of resistive shielding. Furthermore, we model the simplified single aggressor net crosstalk noise problem using a 6-node template circuit and propose a new double pole approach to solve the template circuit. We have tested the proposed method on noise-prone interconnects from an industrial high-performance processor. Our results show a worst case error of 7.8% and an average error of 2.7%, while allowing for very fast analysis.

An interconnect energy model considering coupling effects

This paper presents an analytical interconnect energy model with consideration of coupling effects, including crosstalk and glitch, which are not adequately considered by the conventional (1/2) CV/sup 2/ model. The energy model introduces a new timescale parameter, called the charge time, which represents the correlation time length between two events and is considered to be the counterpart of the Elmore delay. The authors' energy model is more accurate than the (1/2) CV/sup 2/ model with the same time complexity. Experimental results show that their algorithm is several orders of magnitude faster than HSPICE with less than 5% error. In comparison, the error of the (1/2) CV/sup 2/ model can be as high as 100%. The authors further investigate the relationship between interconnect energy and signal correlation and propose a simplified model, which is even faster than their basic model. This paper also discusses ongoing issues of their model, including stability analysis, event propagation, and resistive shielding effects in interconnect energy calculation.

RC delay metrics for performance optimization

For performance optimization tasks such as floorplanning, placement, buffer insertion, wire sizing, and global routing, the Elmore resistance-capacitance (RC) delay metric remains popular due to its simple closed form expression, fast computation speed, and fidelity with respect to simulation. More accurate delay computation methods are typically central processing unit intensive and/or difficult to implement. To bridge this gap between accuracy and efficiency/simplicity, we propose two new RC delay metrics called delay via two moments (D2M) and capacitance metric (ECM), which are virtually as simple and fast as the Elmore metric, but more accurate. D2M uses two moments of the impulse response in a simple formula that has high accuracy at the far end of RC lines. ECM captures resistive shielding effects by modeling the downstream capacitance by an effective capacitance. In contrast, the Elmore metric models this as a lumped capacitance, thereby ignoring resistive shielding. Although not as accurate as D2M, ECM yields consistent performance and may be well-suited to optimization due to its Elmore-like recursive construction.

Modeling the "Effective capacitance" for the RC interconnect of CMOS gates

With finer line widths and faster switching speeds, the resistance of on-chip metal interconnect is having a dominant impact on the timing behavior of logic gates. Specifically, the gates are switching faster and the interconnect delays are getting longer due to scaling. This results in a trend in which the RC interconnect delay is beginning to comprise a larger portion of the overall logic stage delay. This shift in relative delay dominance from the gate to the RC interconnect is increased by resistance shielding. That is, as the gate "resistance" gets smaller and the metal resistance gets larger, the gate no longer "sees" the total net capacitance and the gate delay may be significantly less than expected. This trend complicates the timing analysis of digital circuits, which relies upon simple, empirical gate delay equations for efficiency. In this paper, we develop an analytical expression for the "effective load capacitance" of a pc interconnect. In addition, when there is significant shielding, the response waveforms at the gate output may have a large exponential tail. We show that this waveform tail can strongly influence the delay of the RC interconnect. Therefore, we propose an extension of the effective capacitance equation that captures the complete waveform response accurately, with a two-piece gate-output-waveform approximation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

On the Latitudinal Variation of Magnetotelluric Source Field in the Equatorial Region of India.

The equatorial electrojet through the southern peninsular India could be considered as one of the possible features responsible for non-uniformity in the magnetotelluric (MT) source field. The present study aims at examining the nature of such a non-uniformity in the equatorial region of India. A special field experiment was designed to facilitate simultaneous measurement of magnetic pulsation signals at pairs of mobile stations along a meridian from Kanyakumari to Hyderabad. The latitudinal variation in the strength of the MT source field shows an enhancement of signal amplitude by a factor of 2 to 3 right under the jet during 10-14Hr LT and a gradual decrease away from the dip equator. On the other hand, the signal strength is found to decrease towards the dip equator during 16-18Hrs LT. The results indicate that the source field effects may have to be taken into consideration when MT surveys for periods greater than 100sec., are carried out in the daytime in this region, particularly in the high resistive shield areas exposing the Archaean basement.

The inversion of time‐domain airborne electromagnetic data using the plate model

Airborne electromagnetic (EM) methods were developed in the early 1950s, mostly by Canadian mining exploration companies as a means of economically carrying out prospecting for sulfide deposits associated with volcanics in resistive shield areas. Present interpretation techniques are based on the use of nomograms but the approach is easily amenable to digital processing. For highly accurate interpretation, however, it is necessary to develop quantitative interpretation techniques that can make full use of all the data available. Inverse theory has been used for interpretation with great success in most geophysical disciplines; however, in airborne EM surveying, inversion has only been used for the interpretation of airborne EM data using half‐space and one‐layer models. By introducing some approximations to the rectangular thin‐plate model, it is now possible to apply inverse theory to the interpretation of time‐domain EM data. This approach provides estimates of the parameter errors, the correlation matrix, and a means of assessing the validity of the model. Synthetic profile data are used to demonstrate the validity of the method. The results of the inversion of real anomalies are compared with ground geophysical survey interpretation and drillhole data. The inversion results agree with the known geology of the area and the ground geophysical survey interpretation.